JP7695782B2 - secondary battery - Google Patents

Description

The present invention relates to a secondary battery.

In recent years, there has been a strong desire to reduce carbon dioxide emissions in order to combat global warming. In the automotive industry, there is hope that the introduction of electric vehicles (EVs) and hybrid electric vehicles (HEVs) will help reduce carbon dioxide emissions, and there has been active development of non-aqueous electrolyte secondary batteries, such as motor drive secondary batteries, which hold the key to putting these into practical use.

Secondary batteries for driving motors are required to have extremely high output characteristics and high energy compared to consumer lithium-ion secondary batteries used in mobile phones, laptops, etc. Therefore, lithium-ion secondary batteries, which have the highest theoretical energy of all practical batteries, have attracted attention and are currently being developed at a rapid pace.

The currently widely used lithium-ion secondary batteries use a flammable organic electrolyte as the electrolyte. These liquid-based lithium-ion secondary batteries require stricter safety measures against leakage, short circuits, overcharging, etc. than other batteries.

In recent years, therefore, research and development of all-solid-state batteries, such as all-solid-state lithium-ion secondary batteries that use oxide- or sulfide-based solid electrolytes, has been actively conducted. A solid electrolyte is a material that is mainly composed of an ion conductor that can conduct ions in a solid state. For this reason, in principle, all-solid-state lithium-ion secondary batteries do not cause various problems caused by flammable organic electrolytes, as in conventional liquid-based lithium-ion secondary batteries. In addition, in general, the use of a high-potential, large-capacity positive electrode material and a large-capacity negative electrode material can significantly improve the output density and energy density of the battery. All-solid-state lithium-ion secondary batteries that use elemental sulfur (S) or sulfide-based materials as the positive electrode active material are promising candidates.

In a lithium-ion secondary battery, the negative electrode potential decreases as the charging proceeds. When the negative electrode potential decreases below 0 V (vs. Li/Li+), metallic lithium precipitates at the negative electrode, forming dendrite crystals (this phenomenon is also called the electrodeposition of metallic lithium). In particular, in an all-solid-state battery using metallic lithium or a lithium-containing alloy as the negative electrode active material, the electrodeposition of metallic lithium is the charging reaction itself. Here, if excessive electrodeposition of metallic lithium occurs in an all-solid-state battery and the precipitated dendrite reaches the positive electrode active material layer, an internal short circuit of the battery may occur. Such electrodeposition of metallic lithium is likely to occur at the end (edge) of the battery, and short circuits due to the growth of dendrites are also likely to occur along the side of the end of the battery.

For the purpose of preventing the electrolytic deposition of metallic lithium in all-solid-state batteries and the resulting internal short circuit of the battery, for example, Patent Document 1 discloses a technology in which the negative electrode is made slightly smaller than the outer periphery of the solid electrolyte layer, thereby cutting off the supply of electrons to the negative electrode and preventing the electrolytic deposition of metallic lithium at the ends of the battery.

JP 2016-12495 A

However, even with the technology described in Patent Document 1, there was still room for improvement.

The present invention aims to provide a means for preventing the electrolytic deposition of lithium at the ends of a secondary battery having a lithium-containing negative electrode and a solid electrolyte layer, and the resulting growth of dendrites and the occurrence of internal short circuits in the battery.

The present inventors have conducted extensive research to solve the above problems. As a result, they have found that in a secondary battery including metallic lithium or a lithium-containing alloy as the negative electrode active material and having a solid electrolyte layer, the above problems can be solved by providing a low-reactivity region in at least a portion of the outer periphery of the interface between the negative electrode active material layer and the solid electrolyte layer, in which the ratio of the lithium ion partial molar volume of the solid electrolyte layer to the lithium partial molar volume of the negative electrode active material layer is larger than that of the inside of the outer periphery at the interface, and have completed the present invention.

That is, according to one embodiment of the present invention, a secondary battery is provided that includes a power generating element having a positive electrode in which a positive electrode active material layer containing a positive electrode active material is disposed on the surface of a positive electrode current collector, a negative electrode in which a negative electrode active material layer containing a negative electrode active material including metallic lithium or a lithium-containing alloy is disposed on the surface of a negative electrode current collector, and a solid electrolyte layer containing a solid electrolyte is interposed between the positive electrode active material layer and the negative electrode active material layer. The secondary battery is characterized in that a low-reactivity region exists in at least a part of the outer periphery of the interface between the negative electrode active material layer and the solid electrolyte layer, in which the ratio of the lithium ion partial molar volume of the solid electrolyte layer to the lithium partial molar volume of the negative electrode active material layer is larger than that inside the outer periphery at the interface.

In the secondary battery according to the present invention, the reactivity of lithium at the interface corresponding to the low reactivity region of the outer peripheral edge is lower than that inside the outer peripheral edge. Therefore, according to the present invention, in a secondary battery having a lithium-containing negative electrode and a solid electrolyte layer, it is possible to effectively prevent the electrolytic deposition of lithium at the ends of the battery and the resulting growth of dendrites and the occurrence of internal short circuits in the battery.

FIG. 1 is a perspective view showing the appearance of a flat laminated battery which is one embodiment of an all-solid-state battery according to the present invention. FIG. 2 is a cross-sectional view taken along line 2-2 shown in FIG. FIG. 3 is an enlarged cross-sectional view of a unit cell layer constituting the power generating element of the stacked battery shown in FIGS. FIG. 4 is an enlarged cross-sectional view showing a modification of the unit cell layer shown in FIG. FIG. 5 is an enlarged cross-sectional view showing another modified example of the unit cell layer shown in FIG.

One aspect of the present invention is a secondary battery that includes a power generating element having a positive electrode in which a positive electrode active material layer containing a positive electrode active material is disposed on the surface of a positive electrode current collector, a negative electrode in which a negative electrode active material layer containing a negative electrode active material including metallic lithium or a lithium-containing alloy is disposed on the surface of a negative electrode current collector, and a solid electrolyte layer that is interposed between the positive electrode active material layer and the negative electrode active material layer and contains a solid electrolyte, and in at least a part of the outer periphery of the interface between the negative electrode active material layer and the solid electrolyte layer, there is a low-reactivity region in which the ratio of the lithium ion partial molar volume of the solid electrolyte layer to the lithium partial molar volume of the negative electrode active material layer is larger than that inside the outer periphery at the interface.

The following describes the above-mentioned embodiment of the present invention with reference to the drawings. However, the technical scope of the present invention should be determined based on the claims and is not limited to the following embodiment. Note that the dimensional ratios in the drawings are exaggerated for the convenience of explanation and may differ from the actual ratios.

Figure 1 is a perspective view showing the appearance of a flat-layered all-solid-state battery, which is one embodiment of the secondary battery according to the present invention. Figure 2 is a cross-sectional view taken along line 2-2 in Figure 1. The layered structure allows the battery to be compact and have a high capacity. In this specification, the flat-layered non-bipolar all-solid-state lithium-ion secondary battery shown in Figures 1 and 2 (hereinafter also simply referred to as a "layered battery") will be described in detail as an example. However, when viewed from the perspective of the internal electrical connection form (electrode structure) of the all-solid-state battery according to this embodiment, it can be applied to both non-bipolar (internal parallel connection type) batteries and bipolar (internal series connection type) batteries.

As shown in FIG. 2, the stacked battery 10 has a flat rectangular shape, and a positive electrode current collector 25 and a negative electrode current collector 27 are pulled out from both sides of the stacked battery 10 to extract power. The power generating element 21 is wrapped in the battery exterior material (laminate film 29) of the stacked battery 10, and its periphery is heat-sealed, and the power generating element 21 is sealed with the positive electrode current collector 25 and the negative electrode current collector 27 pulled out to the outside.

The all-solid-state battery according to this embodiment is not limited to a laminated flat shape. A wound all-solid-state battery may be cylindrical, or may be a cylindrical shape that has been deformed to have a rectangular flat shape, and is not particularly limited. The cylindrical shape may be a laminate film or a conventional cylindrical can (metal can) as the exterior material, and is not particularly limited. Preferably, the power generating element is housed inside a laminate film containing aluminum. This form can achieve weight reduction.

Also, there is no particular restriction on the removal of the current collectors (25, 27) shown in FIG. 1. The positive and negative current collectors 25 and 27 may be pulled out from the same side, or the positive and negative current collectors 25 and 27 may each be divided into multiple pieces and removed from each side, and are not limited to those shown in FIG. 1 and FIG. 2. Also, in a wound type lithium ion battery, the terminals may be formed using, for example, a cylindrical can (metal can) instead of tabs.

As shown in FIG. 2, the stacked battery 10 of this embodiment has a structure in which a flat, approximately rectangular power generating element 21, in which a charge/discharge reaction actually proceeds, is sealed inside a laminate film 29, which is a battery exterior material. Here, the power generating element 21 has a structure in which a positive electrode, a solid electrolyte layer 17, and a negative electrode are laminated. In this embodiment, the solid electrolyte layer 17 contains LGPS (Li ₁₀ GeP ₂ S ₁₂ ), which is a type of sulfide solid electrolyte. The positive electrode has a structure in which a positive electrode active material layer 13 containing a positive electrode active material is arranged on both sides of a positive electrode collector 11. The negative electrode has a structure in which a negative electrode active material layer 15 containing a negative electrode active material (here, metallic lithium) is arranged on both sides of a negative electrode collector 12. Specifically, the positive electrode, the solid electrolyte layer, and the negative electrode are laminated in this order so that one positive electrode active material layer 13 and the adjacent negative electrode active material layer 15 face each other through the solid electrolyte layer 17. As a result, the adjacent positive electrode, solid electrolyte layer, and negative electrode constitute one single cell layer 19. Therefore, it can be said that the stacked battery 10 shown in Fig. 2 has a configuration in which a plurality of single cell layers 19 are stacked and electrically connected in parallel.

As shown in FIG. 2, the outermost positive electrode collectors located on both outermost layers of the power generating element 21 each have a positive electrode active material layer 13 disposed on only one side, but active material layers may be provided on both sides. In other words, instead of using a collector dedicated to the outermost layer with an active material layer provided on only one side, a collector with active material layers on both sides may be used as the outermost layer collector as is.

The positive electrode collector 11 and the negative electrode collector 12 are respectively attached with a positive electrode collector plate (tab) 25 and a negative electrode collector plate (tab) 27 that are electrically connected to each electrode (positive electrode and negative electrode), and are structured so as to be sandwiched between the ends of the laminate film 29, which is the battery exterior material, and are led out of the laminate film 29. The positive electrode collector plate 25 and the negative electrode collector plate 27 may be attached to the positive electrode collector 11 and the negative electrode collector 12 of each electrode by ultrasonic welding, resistance welding, or the like, respectively, via a positive electrode lead and a negative electrode lead (not shown) as necessary.

Figure 3 is an enlarged cross-sectional view of the single cell layer 19 that constitutes the power generating element 21 of the stacked battery 10 shown in Figures 1 and 2.

In this embodiment, as shown in FIG. 3, a region 15a is provided around the entire outer edge P of the interface between the negative electrode active material layer 15 and the solid electrolyte layer 17, in which the lithium partial molar volume in the region of the negative electrode active material layer 15 on the solid electrolyte layer 17 side corresponding to the outer edge P is smaller than that in the region of the negative electrode active material layer 15 corresponding to the inside of the outer edge P. Specifically, this region 15a is formed by disposing gold in place of metallic lithium.

In the present embodiment shown in FIG. 3, a region 17a is provided around the entire outer peripheral portion P of the interface between the negative electrode active material layer 15 and the solid electrolyte layer 17, in which the lithium ion partial molar volume in the region of the solid electrolyte layer 17 on the negative electrode active material layer 15 side corresponding to the outer peripheral portion P is larger than that in the region of the solid electrolyte layer 17 corresponding to the inside of the outer peripheral portion P. Specifically, this region 17a is formed by disposing a mixture of oxymethylene-bonded PEG400 and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) instead of LGPS.

3, the region 15a in the negative electrode active material layer 15 and the region 17a in the solid electrolyte layer 17 are adjacent to each other over the entire circumference of the outer peripheral portion P of the interface between the negative electrode active material layer 15 and the solid electrolyte layer 17. As a result, in the embodiment shown in FIG. 3, a region exists over the entire circumference of the outer peripheral portion P of the interface between the negative electrode active material layer 15 and the solid electrolyte layer 17 in which the ratio of the lithium ion partial molar volume of the solid electrolyte layer 17 to the lithium partial molar volume of the negative electrode active material layer 15 is larger than that inside the outer peripheral portion P at the interface. In such a region existing in the outer peripheral portion P of the interface, the reactivity of lithium at the interface is lower than that inside the outer peripheral portion P. Therefore, in this specification, such a region is referred to as a "low reactivity region". Due to the relationship of the reactivity of lithium at such an interface, according to the present invention, in a secondary battery having a lithium-containing negative electrode and a solid electrolyte layer, it is possible to effectively prevent the electrodeposition of lithium at the end of the battery and the resulting growth of dendrites and the occurrence of an internal short circuit in the battery. The mechanism by which this effect occurs is explained below.

According to the literature (C. Monroe, J. Newman, Journal of the Electrochemical Society, 152 (2) A396-A404 (2005)), the electrochemical reaction equation that can be thermodynamically interpreted for a secondary battery with a lithium-containing negative electrode is expressed as the following Equation 1.

In Equation 1, i _BV represents the reactivity of lithium at the interface, and Δμ _e- represents the electrochemical potential of lithium at the interface. As is clear from Equation 1, the reactivity of lithium at the interface is positively correlated with the electrochemical potential of lithium at the interface. Here, the electrochemical potential of lithium at the interface, Δμ _e-, is expressed by Equation 2 below.

Therefore, according to Equation 2, it can be said that a region where the ratio of the lithium ion partial molar volume of the solid electrolyte layer 17 to the lithium partial molar volume of the negative electrode active material layer 15 is larger than that inside the outer peripheral portion at the interface is a region where the value of the electrochemical potential Δμ _e− of lithium at the interface is smaller than that inside the outer peripheral portion. In other words, it can be said that this region is a region where the reactivity (i _BV ) of lithium at the interface is lower (i.e., a low-reactivity region). In the present invention, in a secondary battery having a lithium-containing negative electrode and a solid electrolyte layer, such a low-reactivity region exists at the end (outer peripheral portion) of the battery, and thus it is possible to effectively prevent the electrodeposition of lithium at the end (outer peripheral portion) and the growth of dendrites caused thereby and the occurrence of an internal short circuit in the battery.

The value of the lithium partial molar volume of the negative electrode active material layer 15 and the value of the lithium ion partial molar volume of the solid electrolyte layer 17 can be measured by appropriately referring to conventionally known knowledge. For example, the lithium partial molar volume is discussed in detail in the literature (Koerver, R. et al., Chemo-Mechanical Expansion of Lithium Electrode Materials-On the Route to Mechanically Optimized All-Solid-State Batteries. Energy Environ. Sci. 2018, 11, 2142-2158).

In the embodiment shown in FIG. 3, the low-reactivity region is configured to exist over the entire outer peripheral portion of the negative electrode active material layer 15 and the solid electrolyte layer 17, but is not limited to this form. For example, even if the low-reactivity region exists only in a part of the outer peripheral portion, it is included in the technical scope of the present invention as long as the region satisfies the definition of the low-reactivity region described above. In the embodiment shown in FIG. 3, the outer peripheral portion P is provided to include the ends of the negative electrode active material layer 15 and the solid electrolyte layer 17, but in some cases it may be provided slightly inside the ends. However, from the viewpoint of effectively preventing the electrolytic deposition of metallic lithium at the ends and the growth of dendrites caused by this and the occurrence of internal short circuits in the battery, the outer peripheral portion P is provided to include the ends of the negative electrode active material layer 15 and the solid electrolyte layer 17. Furthermore, the width at which the outer peripheral portion P is provided as viewed from the ends of the negative electrode active material layer 15 and the solid electrolyte layer 17 (the length of the outer peripheral portion P shown in FIG. 3) is not particularly limited, and it is sufficient that the width is provided to obtain the effects of the present invention. As an example, the width of the outer peripheral edge portion P (the length of the outer peripheral edge portion P shown in FIG. 3) is preferably 1 mm to 5 cm, more preferably 3 mm to 3 cm, and even more preferably 5 mm to 2 cm.

In the embodiment shown in FIG. 3, the lithium ion partial molar volume and the lithium partial molar volume at the outer periphery of both the negative electrode active material layer 15 and the solid electrolyte layer 17 are controlled to form a low-reactivity region, but this is not limited to this form. For example, only one of these may be controlled as shown in FIG. 4 and FIG. 5.

Figure 4 is an enlarged cross-sectional view showing a modified example of the cell layer shown in Figure 3. Also, Figure 5 is an enlarged cross-sectional view showing another modified example of the cell layer shown in Figure 3.

In the embodiment shown in FIG. 4, similarly to the embodiment shown in FIG. 3, a region 15a is provided around the entire periphery of the outer periphery of the interface between the negative electrode active material layer 15 and the solid electrolyte layer 17, in which the lithium partial molar volume in the region of the negative electrode active material layer 15 on the solid electrolyte layer 17 side corresponding to the outer periphery is smaller than the region of the negative electrode active material layer 15 corresponding to the inside of the outer periphery. In contrast, no control is performed on the outer periphery of the solid electrolyte layer 17 to change the lithium ion partial molar volume. That is, in the embodiment shown in FIG. 4, the constituent material of the negative electrode active material layer 15 is the same in the region corresponding to the outer periphery and the region corresponding to the inside of the outer periphery. It can be said that the embodiment shown in FIG. 4 having such a configuration also has a low reactivity region similar to that of the embodiment shown in FIG. 3. In the embodiment shown in FIG. 3, the region 15a is formed by disposing gold instead of metallic lithium, but the lithium partial molar volume of the negative electrode active material layer 15 corresponding to the outer periphery may be controlled by other methods. For example, if the lithium concentration in the region 15a is reduced, it is possible to provide the region 15a using a metal other than gold. Region 15a may also be provided by arranging materials that have the same composition except for the lithium content.

In the embodiment shown in FIG. 5, similarly to the embodiment shown in FIG. 3, a region 17a is provided around the entire periphery of the outer periphery of the interface between the negative electrode active material layer 15 and the solid electrolyte layer 17, in which the lithium ion partial molar volume in the region of the solid electrolyte layer 17 on the negative electrode active material layer 15 side corresponding to the outer periphery is larger than the region corresponding to the inside of the outer periphery of the solid electrolyte layer 17. In contrast, no control is performed to change the lithium partial molar volume for the outer periphery of the negative electrode active material layer 15. That is, in the embodiment shown in FIG. 5, the constituent material of the negative electrode active material layer 15 is the same in the region corresponding to the outer periphery and the region corresponding to the inside of the outer periphery. It can be said that the embodiment shown in FIG. 5 having such a configuration also has a low reactivity region similar to that of the embodiment shown in FIG. 3. In the embodiment shown in FIG. 3, the region 17a is formed by disposing a mixture of oxymethylene-bonded PEG400 and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) instead of LGPS, but the lithium ion partial molar volume of the solid electrolyte layer 17 corresponding to the outer periphery may be controlled by other methods. For example, if the lithium ion concentration in the region 17a is reduced, it is possible to provide the region 17a by using a lithium salt and a diluent other than the above-mentioned materials.

The main components of the secondary battery according to this embodiment are described below.

[Current collector]
The current collector has a function of mediating the movement of electrons from one surface in contact with the positive electrode active material layer to the other surface in contact with the negative electrode active material layer. There is no particular limitation on the material constituting the current collector. For example, metals and conductive resins can be used as the material constituting the current collector.

Specific examples of metals include aluminum, nickel, iron, stainless steel, titanium, and copper. In addition, clad materials of nickel and aluminum, clad materials of copper and aluminum, and the like may be used. Also, a foil in which a metal surface is coated with aluminum may be used. Among these, aluminum, stainless steel, copper, and nickel are preferred from the viewpoints of electronic conductivity, battery operating potential, and adhesion of the negative electrode active material to the current collector by sputtering.

The latter conductive resin includes a resin in which a conductive filler is added as necessary to a non-conductive polymeric material.

Examples of non-conductive polymeric materials include polyethylene (PE; high density polyethylene (HDPE), low density polyethylene (LDPE), etc.), polypropylene (PP), polyethylene terephthalate (PET), polyethernitrile (PEN), polyimide (PI), polyamideimide (PAI), polyamide (PA), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polyvinylidene fluoride (PVdF), or polystyrene (PS). Such non-conductive polymeric materials may have excellent electric potential resistance or solvent resistance.

A conductive filler can be added to the conductive polymer material or non-conductive polymer material as necessary. In particular, when the resin that serves as the base material of the collector is made of only a non-conductive polymer, a conductive filler is necessarily required to impart conductivity to the resin.

The conductive filler can be used without any particular restriction as long as it is a material having electrical conductivity. For example, metals and conductive carbon can be mentioned as materials having excellent electrical conductivity, potential resistance, or lithium ion blocking properties. There are no particular restrictions on the metal, but it is preferable that it contains at least one metal selected from the group consisting of Ni, Ti, Al, Cu, Pt, Fe, Cr, Sn, Zn, In, and Sb, or an alloy or metal oxide containing these metals. There are also no particular restrictions on the conductive carbon. It is preferable that it contains at least one selected from the group consisting of acetylene black, Vulcan (registered trademark), Black Pearl (registered trademark), carbon nanofiber, Ketjen Black (registered trademark), carbon nanotube, carbon nanohorn, carbon nanoballoon, and fullerene.

There are no particular restrictions on the amount of conductive filler added, so long as it is an amount that can impart sufficient conductivity to the current collector, and it is generally 5 to 80% by mass relative to the total mass of the current collector (100% by mass).

The current collector may be a single layer structure made of a single material, or may be a laminate structure made of an appropriate combination of layers made of these materials. From the viewpoint of reducing the weight of the current collector, it is preferable that the current collector contains at least a conductive resin layer made of a resin having electrical conductivity. Also, from the viewpoint of blocking the movement of lithium ions between the layers of the single cells, a metal layer may be provided on part of the current collector.

[Negative electrode active material layer]
The negative electrode active material layer includes a negative electrode active material. In the present invention, the negative electrode active material essentially includes metallic lithium (Li) or a lithium-containing alloy. The type of these negative electrode active materials is not particularly limited, but the lithium-containing alloy may be, for example, an alloy of lithium and at least one material that can be alloyed with lithium. Here, examples of materials that can be alloyed with lithium include Si, Au, In, Ge, Sn, Pb, Al, Zn, H, Ca, Sr, Ba, Ru, Rh, Ir, Pd, Pt, Ag, Cd, Hg, Ga, Tl, C, N, Sb, Bi, O, S, Se, Te, Cl, etc. Among these, from the viewpoint of being able to configure a battery with excellent capacity and energy density, the material that can be alloyed with lithium preferably includes at least one element selected from the group consisting of Si, Au, In, Ge, Sn, Pb, Al, and Zn, and more preferably includes Si, Au, or In. In some cases, two or more kinds of negative electrode active materials may be used in combination. Of course, negative electrode active materials other than those mentioned above may be used as long as they essentially contain metallic lithium or a lithium-containing alloy.

The shape of the negative electrode active material may be, for example, particulate (spherical, fibrous), thin film, etc., but is preferably thin film. When the negative electrode active material is particulate, its average particle size (D ₅₀ ) is, for example, preferably in the range of 1 nm to 100 μm, more preferably in the range of 10 nm to 50 μm, even more preferably in the range of 100 nm to 20 μm, and particularly preferably in the range of 1 to 20 μm. In this specification, the average particle size (D ₅₀ ) of the active material can be measured by a laser diffraction scattering method.

The content of the negative electrode active material in the negative electrode active material layer is not particularly limited, but is preferably within the range of 40 to 100 mass %, and more preferably within the range of 50 to 100 mass %.

The negative electrode active material layer may further include a solid electrolyte. When the negative electrode active material layer includes a solid electrolyte, the ionic conductivity of the negative electrode active material layer can be improved. Examples of the solid electrolyte include a sulfide solid electrolyte and an oxide solid electrolyte, and a sulfide solid electrolyte is preferable.

Examples of the sulfide solid electrolyte include LiI-Li ₂ S-SiS ₂ , LiI-Li ₂ SP ₂ O ₅ , LiI-Li ₃ PO ₄ -P ₂ S ₅ , Li ₂ S-P ₂ S ₅ , LiI-Li ₃ PS ₄ , LiI-LiBr-Li ₃ PS _4, Li ₃ PS _4, Li ₂ S-P ₂ S ₅ , Li ₂ S-P ₂ S ₅ -LiI, Li ₂ S-P ₂ S ₅ -Li ₂ O, Li ₂ S-P ₂ S ₅ -Li ₂ O-LiI, Li ₂ S-SiS ₂ , Li ₂ S-SiS ₂ -LiI, Li ₂ S-SiS ₂ -LiBr, Li ₂ S-SiS ₂ -LiCl, Li ₂ S-SiS ₂ -B ₂ S ₃ -LiI, Li ₂ S-SiS ₂ -P ₂ S ₅ -LiI, Li ₂ S-B ₂ S ₃ , Li ₂ S-P ₂ S ₅ -Z _m S _n (where m and n are positive numbers, and Z is Ge, Zn, or Ga), Li ₂ S-GeS ₂ , Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Li ₂ S-SiS ₂ -Li _x MO _y (wherein x and y are positive numbers, and M is any one of P, Si, Ge, B, Al, Ga, and In). Note that the description "Li ₂ S-P ₂ S ₅ " means a sulfide solid electrolyte obtained by using a raw material composition containing Li ₂ S and P ₂ S ₅ , and the same applies to other descriptions.

The sulfide solid electrolyte may have, for example, a Li ₃ PS ₄ skeleton, a Li ₄ P ₂ S ₇ skeleton, or a Li ₄ P ₂ S ₆ skeleton. Examples of sulfide solid electrolytes having a Li ₃ PS ₄ skeleton include LiI-Li ₃ PS ₄ , LiI-LiBr-Li ₃ PS _{4, and} Li ₃ PS _4. Examples of sulfide solid electrolytes having a Li ₄ P ₂ S ₇ skeleton include Li-P-S solid electrolytes called LPS (for example, Li ₇ P ₃ S ₁₁ ). Examples of sulfide solid electrolytes include LGPS represented by Li _(4-x) Ge _(1-x) P _x S ₄ (x satisfies 0<x<1). In particular, the sulfide solid electrolyte contained in the active material layer is preferably a sulfide solid electrolyte containing P element, and more preferably a material containing Li ₂ S-P ₂ S ₅ as a main component. Furthermore, the sulfide solid electrolyte may contain a halogen (F, Cl, Br, I). In a preferred embodiment, the sulfide solid electrolyte contains Li ₆ PS ₅ X (wherein X is Cl, Br or I, preferably Cl).

Furthermore, when the sulfide solid electrolyte is a Li ₂ S-P ₂ S ₅ system, the ratio of Li ₂ S and P ₂ S ₅ , in terms of molar ratio, is preferably within the range of Li ₂ S:P ₂ S ₅ =50:50 to 100:0, and in particular, Li ₂ S:P ₂ S ₅ =70:30 to 80:20.

The sulfide solid electrolyte may be sulfide glass, crystallized sulfide glass, or a crystalline material obtained by a solid phase method. The sulfide glass can be obtained, for example, by performing mechanical milling (ball mill, etc.) on the raw material composition. The crystallized sulfide glass can be obtained, for example, by heat treating the sulfide glass at a temperature equal to or higher than the crystallization temperature. The ion conductivity (for example, Li ion conductivity) of the sulfide solid electrolyte at room temperature (25° C.) is preferably, for example, 1×10 ⁻⁵ S/cm or more, and more preferably 1×10 ⁻⁴ S/cm or more. The value of the ion conductivity of the solid electrolyte can be measured by an AC impedance method.

Examples of oxide solid electrolytes include compounds having a NASICON structure. Examples of compounds having a NASICON structure include compounds (LAGP) represented by the general formula Li _1+x Al _x Ge _2-x (PO ₄ ) ₃ (0≦x≦2), and compounds (LATP) represented by the general formula Li _1+x Al _x Ti _2-x (PO ₄ ) ₃ (0≦x≦2). Other examples of oxide solid electrolytes include LiLaTiO (e.g., Li _0.34 La _0.51 TiO ₃ ), LiPON (e.g., Li _2.9 PO _3.3 N _0.46 ), and LiLaZrO (e.g., Li ₇ La ₃ Zr ₂ O ₁₂ ).

The shape of the solid electrolyte may be, for example, a particulate shape such as a true sphere or an oval sphere, a thin film shape, etc. When the solid electrolyte is particulate, its average particle size ( _D50 ) is not particularly limited, but is preferably 40 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less. On the other hand, the average particle size ( _D50 ) is preferably 0.01 μm or more, and more preferably 0.1 μm or more.

The content of the solid electrolyte in the negative electrode active material layer is, for example, preferably in the range of 0 to 60 mass %, and more preferably in the range of 0 to 50 mass %.

The negative electrode active material layer may further contain at least one of a conductive additive and a binder in addition to the above-mentioned negative electrode active material and solid electrolyte.

Examples of conductive assistants include, but are not limited to, metals such as aluminum, stainless steel (SUS), silver, gold, copper, and titanium, alloys or metal oxides containing these metals, carbon fibers (specifically, vapor-grown carbon fibers (VGCF), polyacrylonitrile-based carbon fibers, pitch-based carbon fibers, rayon-based carbon fibers, activated carbon fibers, etc.), carbon nanotubes (CNT), and carbon black (specifically, acetylene black, Ketjen Black (registered trademark), furnace black, channel black, thermal lamp black, etc.). In addition, particulate ceramic materials and resin materials coated with the above-mentioned metal materials by plating or the like can also be used as conductive assistants. Among these conductive assistants, from the viewpoint of electrical stability, it is preferable to include at least one selected from the group consisting of aluminum, stainless steel, silver, gold, copper, titanium, and carbon, more preferably to include at least one selected from the group consisting of aluminum, stainless steel, silver, gold, and carbon, and even more preferably to include at least one carbon. These conductive assistants may be used alone or in combination of two or more.

The conductive assistant is preferably particulate or fibrous. When the conductive assistant is particulate, the shape of the particles is not particularly limited, and may be any shape, such as powder, sphere, rod, needle, plate, column, irregular shape, scale, spindle shape, etc.

When the conductive assistant is particulate, the average particle diameter (primary particle diameter) is not particularly limited, but is preferably 0.01 to 10 μm from the viewpoint of the electrical properties of the battery. In this specification, the "particle diameter of the conductive assistant" means the maximum distance L between any two points on the contour line of the conductive assistant. The value of the "average particle diameter of the conductive assistant" is calculated as the average particle diameter of particles observed in several to several tens of fields of view using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

When the negative electrode active material layer contains a conductive assistant, the content of the conductive assistant in the negative electrode active material layer is not particularly limited, but is preferably 0 to 10 mass %, more preferably 2 to 8 mass %, and even more preferably 4 to 7 mass %, relative to the total mass of the negative electrode active material layer. Within such a range, it is possible to form a stronger electron conduction path in the negative electrode active material layer, which can effectively contribute to improving the battery characteristics.

On the other hand, binders are not particularly limited, but examples include the following materials:

Thermoplastic polymers such as polybutylene terephthalate, polyethylene terephthalate, polyvinylidene fluoride (PVDF) (including compounds in which hydrogen atoms are replaced by other halogen elements), polyethylene, polypropylene, polymethylpentene, polybutene, polyether nitrile, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene-butadiene rubber (SBR), ethylene-propylene-diene copolymer, styrene-butadiene-styrene block copolymer and its hydrogenated product, styrene-isoprene-styrene block copolymer and its hydrogenated product, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene Fluorine resins such as ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride (PVF), etc., vinylidene fluoride-hexafluoropropylene fluororubber (VDF-HFP fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene fluororubber (VDF-HFP-TFE fluororubber), vinylidene fluoride-pentafluoropropylene fluororubber (VDF-PFP fluororubber), vinylidene fluoride-pentafluoropropylene fluororubber (VDF-PFP fluororubber), etc. Examples of the fluororubber include vinylidene fluoride-based fluororubbers such as vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-PFP-TFE-based fluororubber), vinylidene fluoride-perfluoromethylvinyl ether-tetrafluoroethylene-based fluororubber (VDF-PFMVE-TFE-based fluororubber), and vinylidene fluoride-chlorotrifluoroethylene-based fluororubber (VDF-CTFE-based fluororubber), and epoxy resins. Among these, polyimide, styrene-butadiene rubber, carboxymethyl cellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are more preferable.

The thickness of the negative electrode active material layer varies depending on the configuration of the intended all-solid-state battery, but is preferably within the range of 0.1 to 1000 μm, for example.

[Cathode active material layer]
The positive electrode active material layer includes a positive electrode active material. The type of the positive electrode active material is not particularly limited, but sulfur element (S ₈ ) or a reduction product of sulfur containing lithium (any of the compounds Li ₂ S ₈ to Li ₂ S) is preferably used. Here, for example, sulfur element (S ₈ ) has an extremely large theoretical capacity of about 1670 mAh/g, and has the advantage of being low cost and abundant in resources. In this case, when the all-solid-state battery is provided in a charged state, the positive electrode active material includes sulfur element (S ₈ ). In addition, when the all-solid-state battery is provided in a discharged state, the positive electrode active material includes a reduction product of sulfur containing lithium (any of the compounds Li ₂ S ₈ to Li ₂ S described above).

The positive electrode active material layer may contain a positive electrode active material other than the above-mentioned elemental sulfur (S ₈ ) or the reduction product of sulfur containing lithium (any of the above-mentioned compounds Li ₂ S ₈ to Li ₂ S). However, the ratio of the elemental sulfur or the reduction product of sulfur containing lithium to the positive electrode active material contained in the positive electrode active material layer is preferably 50 to 100 mass%, more preferably 80 to 100 mass%, even more preferably 90 to 100 mass%, still more preferably 95 to 100 mass%, particularly preferably 98 to 100 mass%, and most preferably 100 mass%.

Examples of positive electrode active materials other than elemental sulfur or reduction products of sulfur containing lithium include disulfide compounds, sulfur-modified polyacrylonitriles typified by the compounds described in WO 2010/044437, sulfur-modified polyisoprene, rubeanic acid (dithiooxamide), polycarbon sulfide, etc. In addition, inorganic sulfur compounds such as S-carbon composites, TiS ₂ , TiS ₃ , TiS ₄ , NiS, NiS ₂ , CuS, FeS ₂ , MoS ₂ , and MoS ₃ can also be used. Further, examples of the positive electrode active material that does not contain sulfur include layered rock salt type active materials such as LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , and Li(Ni-Mn-Co)O ₂ , spinel type active materials such as LiMn ₂ O ₄ and LiNi _0.5 Mn _1.5 O ₄ , olivine type active materials such as LiFePO ₄ and LiMnPO ₄ , and Si-containing active materials such as Li ₂ FeSiO ₄ and Li ₂ MnSiO ₄ . Examples of oxide active materials other than the above include Li ₄ Ti ₅ O ₁₂ . In some cases, two or more positive electrode active materials may be used in combination. Of course, positive electrode active materials other than the above may be used.

The shape of the positive electrode active material may be, for example, particulate (spherical, fibrous), thin film, etc. When the positive electrode active material is particulate, the average particle size (D ₅₀ ) is, for example, preferably in the range of 1 nm to 100 μm, more preferably in the range of 10 nm to 50 μm, even more preferably in the range of 100 nm to 20 μm, and particularly preferably in the range of 1 to 20 μm. In this specification, the average particle size (D ₅₀ ) of the active material can be measured by a laser diffraction scattering method.

The content of the positive electrode active material in the positive electrode active material layer is not particularly limited, but is preferably within the range of 40 to 99% by mass, and more preferably within the range of 50 to 90% by mass.

The positive electrode active material layer may also further contain a conductive additive and/or a binder, similar to the negative electrode active material layer.

[Solid electrolyte layer]
The solid electrolyte layer of the all-solid-state battery according to this embodiment contains a solid electrolyte as a main component and is a layer interposed between the above-mentioned positive electrode active material layer and the above-mentioned negative electrode active material layer. In addition, the solid electrolyte layer of the all-solid-state battery according to this embodiment preferably contains a sulfide solid electrolyte as an essential component from the viewpoint of excellent ion conductivity and durability, and in this case, other solid electrolytes may be included. However, the ratio of the sulfide solid electrolyte to the solid electrolyte contained in the solid electrolyte layer is preferably 50 to 100 mass%, more preferably 80 to 100 mass%, even more preferably 90 to 100 mass%, even more preferably 95 to 100 mass%, particularly preferably 98 to 100 mass%, and most preferably 100 mass%. The specific form of the sulfide solid electrolyte and other solid electrolytes contained in the solid electrolyte layer is the same as that described above, so a detailed description will be omitted here.

The content of the solid electrolyte in the solid electrolyte layer is, for example, preferably in the range of 10 to 100 mass%, more preferably in the range of 50 to 100 mass%, and even more preferably in the range of 90 to 100 mass%.

The solid electrolyte layer may further contain a binder in addition to the solid electrolyte described above. The specific form of the binder that may be contained in the solid electrolyte layer is the same as that described above, so a detailed description is omitted here.

The thickness of the solid electrolyte layer varies depending on the configuration of the intended all-solid-state battery, but is preferably within the range of 1 to 1000 μm, and more preferably within the range of 10 to 300 μm.

[Positive and negative current collector plates]
The material constituting the current collector plate (25, 27) is not particularly limited, and a known highly conductive material conventionally used as a current collector plate for a secondary battery can be used. As the material constituting the current collector plate, for example, a metal material such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof is preferable. From the viewpoint of light weight, corrosion resistance, and high conductivity, aluminum and copper are more preferable, and aluminum is particularly preferable. The same material may be used for the positive electrode current collector plate 25 and the negative electrode current collector plate 27, or different materials may be used.

[Positive and negative electrode leads]
Although not shown, the current collectors (11, 12) and the current collectors (25, 27) may be electrically connected via positive and negative electrode leads. As the materials for the positive and negative electrode leads, materials used in known lithium ion secondary batteries may be similarly adopted. It is preferable that the part removed from the exterior is covered with a heat-resistant insulating heat shrink tube or the like so as not to come into contact with peripheral devices or wiring, causing leakage and affecting products (e.g., automobile parts, particularly electronic devices, etc.).

[Battery exterior material]
As the battery exterior material, a known metal can case can be used, and a bag-shaped case using a laminate film 29 containing aluminum, which can cover the power generating element as shown in Figures 1 and 2, can be used. The laminate film can be, for example, a three-layer laminate film formed by laminating PP, aluminum, and nylon in this order, but is not limited thereto. A laminate film is preferable from the viewpoint of being excellent in high output and cooling performance and being suitable for use in batteries for large equipment for EVs and HEVs. In addition, since the group pressure applied from the outside to the power generating element can be easily adjusted, a laminate film containing aluminum is more preferable as the exterior body.

The stacked battery according to the embodiment shown in FIG. 2 has a configuration in which multiple single cell layers are connected in parallel, and as a result has high capacity and excellent cycle durability. Therefore, the stacked battery according to this embodiment is suitable for use as a power source for driving EVs and HEVs.

Although one embodiment of a secondary battery has been described above, the present invention is not limited to the configuration described in the above embodiment, and can be modified as appropriate based on the claims.

For example, the type of battery to which the secondary battery of the present invention can be applied includes a bipolar battery that includes a bipolar electrode having a positive electrode active material layer electrically bonded to one surface of a current collector and a negative electrode active material layer electrically bonded to the opposite surface of the current collector.

The secondary battery according to this embodiment does not have to be an all-solid-state type. That is, the solid electrolyte layer may further contain a conventionally known liquid electrolyte (electrolytic solution). There is no particular limit to the amount of liquid electrolyte (electrolytic solution) that can be contained in the solid electrolyte layer, but it is preferable that the amount is such that the shape of the solid electrolyte layer formed by the solid electrolyte is maintained and leakage of the liquid electrolyte (electrolytic solution) does not occur.

The liquid electrolyte (electrolyte) that can be used has a form in which a lithium salt is dissolved in an organic solvent. Examples of organic solvents that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propionate (MP), methyl acetate (MA), methyl formate (MF), 4-methyldioxolane (4MeDOL), dioxolane (DOL), 2-methyltetrahydrofuran (2MeTHF), tetrahydrofuran (THF), dimethoxyethane (DME), propylene carbonate (PC), butylene carbonate (BC), dimethyl sulfoxide (DMSO), and γ-butyrolactone (GBL). Among these, from the viewpoint of further improving the rapid charging characteristics and output characteristics, the organic solvent is preferably a chain carbonate, more preferably at least one selected from the group consisting of diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC), and more preferably selected from ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC).

Examples of the lithium salt include Li( _FSO2 ) _2N (lithium bis(fluorosulfonyl)imide; _LiFSI ), _Li ( _C2F5SO2 ) _2N , _LiPF6 , _LiBF4 , _LiClO4 , _LiAsF6 , and _LiCF3SO3 . Among _these , the lithium salt is preferably Li( _FSO2 ) _2N (LiFSI) from the viewpoints of battery output and charge/discharge cycle characteristics.

The liquid electrolyte (electrolyte) may further contain additives other than the above-mentioned components. Specific examples of such compounds include, for example, ethylene carbonate, vinylene carbonate, methylvinylene carbonate, dimethylvinylene carbonate, phenylvinylene carbonate, diphenylvinylene carbonate, ethylvinylene carbonate, diethylvinylene carbonate, vinylethylene carbonate, 1,2-divinylethylene carbonate, 1-methyl-1-vinylethylene carbonate, 1-methyl-2-vinylethylene carbonate, 1-ethyl-1-vinylethylene carbonate, 1-ethyl-2-vinylethylene carbonate, and 1-ethyl-2-vinylethylene carbonate. Examples of the additives include ethylene carbonate, vinyl vinylene carbonate, allyl ethylene carbonate, vinyloxymethyl ethylene carbonate, allyloxymethyl ethylene carbonate, acryloxymethyl ethylene carbonate, methacryloxymethyl ethylene carbonate, ethynyl ethylene carbonate, propargyl ethylene carbonate, ethynyloxymethyl ethylene carbonate, propargyloxyethylene carbonate, methylene ethylene carbonate, and 1,1-dimethyl-2-methylene ethylene carbonate. These additives may be used alone or in combination of two or more. The amount of additive used in the electrolyte can be adjusted as appropriate.

[Battery pack]
A battery pack is a device that consists of multiple batteries connected together. More specifically, it is a device that uses at least two batteries and is connected in series or parallel or both. By connecting them in series or parallel, it is possible to freely adjust the capacity and voltage.

A small, removable battery pack can be formed by connecting multiple batteries in series or in parallel. Then, multiple such small, removable battery packs can be connected in series or in parallel to form a large-capacity, high-output battery pack suitable for vehicle drive power sources and auxiliary power sources that require high volumetric energy density and high volumetric output density. How many batteries are connected to form a battery pack, and how many stages of small battery packs are stacked to form a large-capacity battery pack, can be determined based on the battery capacity and output of the vehicle (electric vehicle) in which it is to be installed.

[vehicle]
The secondary battery according to the present invention maintains its discharge capacity even after long-term use and has good cycle characteristics. Furthermore, it has a high volumetric energy density. In vehicle applications such as electric vehicles, hybrid electric vehicles, fuel cell vehicles, and hybrid fuel cell vehicles, higher capacity, larger size, and longer life are required compared to electric and portable electronic device applications. Therefore, the nonaqueous electrolyte secondary battery can be suitably used as a power source for vehicles, for example, a power source for driving a vehicle or an auxiliary power source.

Specifically, the battery or a battery pack consisting of a combination of multiple batteries can be mounted on a vehicle. In the present invention, a long-life battery with excellent long-term reliability and output characteristics can be constructed, so that by mounting such a battery, a plug-in hybrid electric vehicle with a long EV driving distance or an electric vehicle with a long driving distance per charge can be constructed. For example, if the battery or a battery pack consisting of a combination of multiple batteries is used in a hybrid vehicle, a fuel cell vehicle, or an electric vehicle (all of which include four-wheeled vehicles (commercial vehicles such as passenger cars, trucks, and buses, and light vehicles, etc.), as well as two-wheeled vehicles (motorcycles) and three-wheeled vehicles), it will become a vehicle with a long life and high reliability. However, the use is not limited to automobiles, and it can be applied to various power sources of other vehicles, such as mobile bodies such as trains, and can also be used as a mounted power source for uninterruptible power supplies, etc.

[Example 1]
(Preparation of solid electrolyte layer)
80 mg of sulfide solid electrolyte (Li ₁₀ GeP ₂ S ₁₂ ; LGPS) was weighed out, placed in an SLD sleeve (Φ10), clamped at both ends with hard Cr-plated SLD pins, and pressed at room temperature at a pressure of 390 MPa for 1 minute to obtain an electrolyte pellet.

Next, an SLD sleeve (Φ8) having a smaller diameter than the SLD sleeve was inserted into one end of the electrolyte pellet, _and 12.8 mg _of sulfide solid electrolyte ( _Li10GeP2S12 ) was weighed out and inserted into the Φ8 sleeve. Pressing was performed for 1 minute in the same manner as above to obtain an electrolyte pellet whose outer periphery on one end was thinner than the inside of the outer periphery.

Next, the Φ8 sleeve was removed, and 7.2 mg of a mixture of oxymethylene-bonded PEG400 and solid electrolyte (lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)) (the mixture ratio was controlled so that the molar ratio (Li/O) of the lithium atoms contained in the solid electrolyte to the oxygen atoms contained in the oxymethylene-bonded PEG400 was 1/15) was weighed and placed in the recess on the outer periphery of one end of the electrolyte pellet obtained above, and both ends were again clamped with hard Cr-plated SLD pins and pressed at room temperature for 1 minute at a pressure of 390 MPa to produce an electrolyte pellet (the solid electrolyte layer of this example).

(Preparation of negative electrode active material layer)
A shield plate was placed on the exposed part of the solid electrolyte (LGPS) on the side where LiTFSI was placed on the outer periphery of the solid electrolyte layer prepared above, and gold was vapor-deposited on the part corresponding to the outer periphery by vacuum vapor deposition. The shield plate was then removed, and metallic lithium was vapor-deposited on the exposed surface of the solid electrolyte layer and the front surface of the gold vapor deposition surface by vacuum vapor deposition. Thereafter, both ends of the obtained laminate were sandwiched between hard Cr-plated SLD pins, and pressed at 60° C. for 3 hours at a pressure of 20 MPa to obtain a laminate of the solid electrolyte layer and the negative electrode active material layer of this embodiment (having the configuration shown in FIG. 3).

[Example 2]
First, a solid electrolyte layer of this example was prepared having a uniform composition of LGPS without providing a region using a mixture of oxymethylene-bonded PEG400 and a solid electrolyte (LiTFSI).

Next, gold and lithium were vapor-deposited onto one end of the solid electrolyte layer in the same manner as in Example 1 described above, to obtain a laminate of the solid electrolyte layer and the negative electrode active material layer of this example (having the configuration shown in Figure 4).

[Example 3]
First, a solid electrolyte layer of this example was produced using a method similar to that of Example 1 described above, in which a region using a mixture of oxymethylene-bonded PEG400 and a solid electrolyte (LiTFSI) exists on the outer periphery.

Next, the negative electrode active material layer of this example, which has a uniform composition consisting of metallic lithium, was produced without vapor deposition of gold, to obtain a laminate of the solid electrolyte layer and the negative electrode active material layer of this example (having the configuration shown in Figure 5).

10 All-solid-state lithium ion secondary battery,
11 positive electrode current collector,
12 negative electrode current collector,
13 positive electrode active material layer,
15 negative electrode active material layer,
15a: a region in which the lithium partial molar volume in a region on the solid electrolyte layer side of the negative electrode active material layer corresponding to the outer peripheral edge portion is smaller than that in a region corresponding to the inside of the outer peripheral edge portion of the negative electrode active material layer;
17 electrolyte layer,
17a: a region in which the partial molar volume of lithium ions in a region of the solid electrolyte layer on the negative electrode active material layer side corresponding to the outer peripheral edge portion is larger than that in a region of the solid electrolyte layer corresponding to the inside of the outer peripheral edge portion;
19 cell layer,
21 power generating element,
25 Positive electrode current collector (positive electrode tab),
27 negative electrode current collector (negative electrode tab),
29 Laminate film,
P: The outer peripheral edge portion of the interface between the negative electrode active material layer and the solid electrolyte layer.

Claims (5)

a positive electrode having a positive electrode active material layer containing a positive electrode active material disposed on a surface of a positive electrode current collector;
a negative electrode including a negative electrode active material layer disposed on a surface of a negative electrode current collector, the negative electrode active material layer including a negative electrode active material including metallic lithium or a lithium-containing alloy;
a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer and including a solid electrolyte;
A power generating element having
a low-reactivity region is present in at least a part of an outer periphery of the interface between the negative electrode active material layer and the solid electrolyte layer, the low-reactivity region having a larger ratio of a lithium ion partial molar volume of the solid electrolyte layer to a lithium partial molar volume of the negative electrode active material layer compared to an inside of the outer periphery at the interface, the ratio not extending to an end face of the negative electrode active material layer ;
a partial molar volume of lithium ions in a region of the solid electrolyte layer corresponding to the outer peripheral edge portion is larger than a region of the solid electrolyte layer corresponding to an inside of the outer peripheral edge portion;
a partial molar volume of lithium in a region of the negative electrode active material layer corresponding to the outer peripheral edge portion is smaller than a region of the negative electrode active material layer corresponding to an inside of the outer peripheral edge portion . a positive electrode having a positive electrode active material layer containing a positive electrode active material disposed on a surface of a positive electrode current collector;
a negative electrode including a negative electrode active material layer disposed on a surface of a negative electrode current collector, the negative electrode active material layer including a negative electrode active material including metallic lithium or a lithium-containing alloy;
a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer and including a solid electrolyte;
A power generating element having
a low-reactivity region is present in at least a part of an outer periphery of the interface between the negative electrode active material layer and the solid electrolyte layer, in which a ratio of a partial molar volume of lithium ions in the solid electrolyte layer to a partial molar volume of lithium in the negative electrode active material layer is larger than that of an inside of the outer periphery at the interface;
a constituent material of the negative electrode active material layer is the same in a region corresponding to the outer peripheral edge portion and a region corresponding to the inside of the outer peripheral edge portion,
a partial molar volume of lithium ions in a region of the solid electrolyte layer corresponding to the outer peripheral edge is larger than a region of the solid electrolyte layer corresponding to an inside of the outer peripheral edge, and the region of the solid electrolyte layer corresponding to the outer peripheral edge contains a lithium salt and a diluent . a positive electrode having a positive electrode active material layer containing a positive electrode active material disposed on a surface of a positive electrode current collector;
a negative electrode including a negative electrode active material layer disposed on a surface of a negative electrode current collector, the negative electrode active material layer including a negative electrode active material including metallic lithium or a lithium-containing alloy;
a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer and including a solid electrolyte;
A power generating element having
a low-reactivity region is present in at least a part of an outer periphery of the interface between the negative electrode active material layer and the solid electrolyte layer, the low-reactivity region having a larger ratio of a lithium ion partial molar volume of the solid electrolyte layer to a lithium partial molar volume of the negative electrode active material layer compared to an inside of the outer periphery at the interface, the ratio not extending to an end face of the negative electrode active material layer;
a constituent material of the solid electrolyte layer is the same in a region corresponding to the outer peripheral edge portion and a region corresponding to an inside of the outer peripheral edge portion;
a partial molar volume of lithium in a region of the negative electrode active material layer corresponding to the outer peripheral edge portion is smaller than a region of the negative electrode active material layer corresponding to an inside of the outer peripheral edge portion. The secondary battery according to any one of claims 1 to 3, wherein the solid electrolyte includes a sulfide solid electrolyte. The secondary battery according to any one of claims 1 to 4, which is an all-solid-state lithium-ion secondary battery.