JP7666403B2 - battery - Google Patents

Description

This disclosure relates to batteries.

Patent Document 1 discloses a bipolar battery that is characterized by having a battery element formed by alternately stacking a predetermined number of bipolar electrodes, each of which has a positive electrode layer formed on one surface of a current collector and a negative electrode layer formed on the other surface, and electrolyte layers that perform ion exchange between the bipolar electrodes, and a stack thickness absorbing member that is interposed between the battery elements to absorb distortion in the stacking direction.

Patent Document 2 discloses a lithium ion secondary battery that has a positive electrode and a negative electrode on either side of a solid electrolyte, and current collectors on the outside of the positive electrode and the negative electrode, respectively, and that is characterized in that at least one of the current collectors contains a viscoelastic material.

JP 2007-26734 A JP 2009-181874 A

For example, solid-state lithium-ion batteries, more specifically, solid-state lithium-ion batteries that use metallic lithium as the negative electrode active material, may expand and contract during charging and discharging. Such expansion and contraction of the battery may cause separation between the battery components, such as the current collector layer and the electrode layer, and as a result, the charge and discharge capacity may decrease when the battery is repeatedly charged and discharged.

The present disclosure aims to provide a battery that can suppress the decrease in charge/discharge capacity due to repeated charging and discharging.

The present inventors have found that the above object can be achieved by the following means:
Aspect 1
The battery includes a battery element in which a positive electrode current collector layer, a power generating element, and a negative electrode current collector layer are laminated in this order, and an elastic spacer is laminated in the lamination direction of the battery element,
The power generating element expands and contracts in the stacking direction as the element is charged and discharged,
The elastic spacer contains fibers and has voids.
battery.
Aspect 2
With respect to the stacking direction, the power generating element has a positive electrode layer, a solid electrolyte layer, and a negative electrode layer stacked in this order at least in a charged state.
2. The battery of embodiment 1.
Aspect 3
3. The battery according to claim 2, wherein the negative electrode layer contains lithium as a negative electrode active material that is deposited between the solid electrolyte layer and the negative electrode current collector layer in a charged state.
Aspect 4
Aspect 4. The battery of any one of aspects 1-3, wherein the fibers are carbon fibers.
Aspect 5
The battery according to any one of aspects 1 to 4, wherein the elastic spacer is a compression molded body of the fiber.
Aspect 6
The battery according to any one of aspects 1 to 5, wherein the ratio of the fibers to the solid content of the elastic spacer is 90 volume % or more.
Aspect 7
The battery according to any one of the preceding claims, wherein the porosity of the elastic spacer is 60 to 80%.
Aspect 8
The battery of any one of the preceding aspects, wherein the elastic spacer has an elastic range of 0.1 or more.
Aspect 9
The battery of any one of the preceding aspects, which is a lithium ion battery.

This disclosure provides a battery that can suppress the decrease in charge/discharge capacity due to repeated charging and discharging.

FIG. 1 is a schematic diagram of a solid-state battery 1 according to a first embodiment of the present disclosure. FIG. 2 is a top view of the test all-solid-state battery 2. FIG. 3 is a cross-sectional side view of the test all-solid-state battery 2 in a discharged state. FIG. 4 is a cross-sectional side view of the test all-solid-state battery 2 in a charged state. FIG. 5 is a schematic diagram showing a measurement device 3 for measuring the pressure during charging and discharging of a test all-solid-state battery 2.

The following describes in detail the embodiments of the present disclosure. Note that the present disclosure is not limited to the following embodiments, and can be modified in various ways within the scope of the disclosure.

The battery disclosed herein has a battery element in which a positive electrode current collector layer, a power generating element, and a negative electrode current collector layer are stacked in this order, and an elastic spacer stacked in the stacking direction of the battery element, the power generating element expands and contracts in the stacking direction as the battery element is charged and discharged, and the elastic spacer contains fibers and has voids.

In general, in batteries that have power generating elements that expand and contract in the stacking direction as they are charged and discharged, deformation of the power generating elements caused by repeated charging and discharging can cause irreversible deformation of the components that make up the battery and peeling between components. Such deformation and peeling of components can result in a decrease in charge and discharge capacity due to, for example, an increase in internal resistance.

In order to prevent the above problems, i.e., deformation and peeling of battery components, it is possible to arrange an elastic member in the direction in which the power generating element expands and contracts. However, if rubber is used as the elastic member, the internal pressure of the battery increases when the power generating element expands, and a sturdy container is required to withstand that pressure, resulting in a decrease in the energy density of the battery. Furthermore, if a spring, such as a disc spring, is used as the elastic member, the volume of the spring itself and the need for a spacer decrease the energy density of the battery.

In contrast, the battery of the present disclosure has an elastic spacer arranged in the direction in which the power generating element expands and contracts, and the elastic spacer contains fibers and has voids. Such an elastic spacer can apply pressure uniformly to the surface of the power generating element in the stacking direction, and has a relatively wide elastic range. Therefore, it can elastically deform in response to the expansion and contraction of the power generating element due to repeated charging and discharging, while suppressing the problems that arise when rubber or springs are used.

An example of a battery having a power generating element that expands and contracts in the stacking direction with charging and discharging is a lithium ion battery. Among lithium ion batteries, lithium ion batteries that use an alloy-based active material as the negative electrode active material, or lithium ion batteries in which metallic lithium precipitates between the solid electrolyte layer and the negative electrode current collector layer during discharging, have particularly large expansion and contraction of the power generating element with charging and discharging, and are particularly useful when the battery disclosed herein is one of these batteries.

Elastic spacer
The elastic spacer is laminated in the lamination direction of the battery elements, that is, the elastic spacer is laminated on at least one surface of the positive electrode current collector layer or the negative electrode current collector layer of the battery elements.

The elastic spacer contains fibers and has voids. The fibers may be conductive. That is, the elastic spacer may be a conductive elastic spacer.

Examples of fibers include carbon fibers and metal fibers. Metal fibers may be, for example, stainless steel (SUS), nickel, titanium, copper, or aluminum coated on a core material. Of these, carbon fibers are preferred. Carbon fibers have a relatively high elastic modulus, and are therefore particularly useful when the power generating element expands and contracts to a large extent. In addition, because carbon fibers are very fine, elastic spacers containing carbon fibers are useful because they can apply pressure particularly uniformly to a surface.

The elastic spacer may be, for example, a compression molded fiber body.

From the viewpoint of improving the elasticity of the elastic spacer, it is preferable that the ratio of fibers in the solid content of the elastic spacer is 90% by volume or more. The remainder may be, for example, a binder for bonding the fibers together to form the elastic spacer.

The proportion of fibers in the solid content of the elastic spacer may be 90% by volume or more, 95% by volume or more, 97% by volume or more, or 99% by volume or more.

In addition, from the viewpoint of increasing the elastic range of the elastic spacer, it is preferable that the porosity of the elastic spacer is large, specifically, 60 to 80%.

The porosity of the elastic spacer may be 60% or more, 65% or more, or 70% or more, and may be 80% or less, 75% or less, or 70% or less.

In addition, from the viewpoint of improving the reversibility of the elastic spacer, it is preferable that the elastic range of the elastic spacer is 0.1 or more.

The elastic range of the elastic spacer may be 0.1 or more, 0.2 or more, 0.3 or more, or 0.4 or more.

Battery element
The battery element is formed by laminating a positive electrode current collector layer, a power generating element, and a negative electrode current collector layer in this order.

<Positive electrode current collector layer>
The material used for the positive electrode current collector layer is not particularly limited, and any material that can be used for an all-solid-state battery can be appropriately used.

For example, the material used for the positive electrode current collector layer may be, but is not limited to, stainless steel (SUS), aluminum, copper, nickel, iron, titanium, or carbon. In particular, it is preferable that the material for the positive electrode current collector layer is aluminum.

The shape of the positive electrode current collector layer is not particularly limited, and examples include foil, plate, and mesh shapes. Of these, foil shapes are preferred.

<Power generation elements>
The power generating element expands and contracts in the stacking direction as the power generating element is charged and discharged. Although not particularly limited, the expansion and contraction of the power generating element can be caused by, for example, the expansion and contraction of the active material accompanying the absorption/release of lithium in the active material accompanying the charge/discharge, or the precipitation of metallic lithium between the solid electrolyte layer and the negative electrode current collector layer.

Regarding the stacking direction of the battery disclosed herein, the power generating element is stacked in this order, at least in the charged state, with a positive electrode layer, a solid electrolyte layer, and a negative electrode layer.

(Positive electrode layer)
The positive electrode layer contains a positive electrode active material and, optionally, a solid electrolyte, a conductive additive, and a binder.

The material of the positive electrode active material is not particularly limited. For example, the positive electrode active material may be, but is not limited to, lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), lithium manganese oxide (LiMn ₂ O ₄ ), LiCo _1/3 Ni _1/3 Mn _1/3 O 2 , or a different element-substituted Li-Mn spinel having a composition represented by Li _{1 +x} Mn _2-x-y M _y O ₄ (M is one or more metal elements selected from Al, Mg, Co, Fe, Ni, and Zn).

The solid electrolyte may be any of those described in "Solid electrolyte layer" below.

The conductive additive is not particularly limited. For example, the conductive additive may be a carbon material such as VGCF (Vapor Grown Carbon Fiber) and carbon nanofiber, or a metal material, but is not limited thereto.

The binder is not particularly limited. For example, the binder may be a material such as polyvinylidene fluoride (PVdF), butadiene rubber (BR), polytetrafluoroethylene (PTFE), or styrene butadiene rubber (SBR), or a combination thereof, but is not limited thereto.

(Solid electrolyte layer)
The solid electrolyte layer includes at least a solid electrolyte. The solid electrolyte layer may include a binder or the like as necessary in addition to the solid electrolyte. For the binder, the above description of "(positive electrode active material layer)" can be referred to.

The material of the solid electrolyte is not particularly limited, and any material that can be used as a solid electrolyte in an all-solid-state battery can be used. For example, the solid electrolyte may be, but is not limited to, a sulfide solid electrolyte, an oxide solid electrolyte, or a polymer electrolyte.

Examples of sulfide solid electrolytes include, but are not limited to, sulfide-based amorphous solid electrolytes, sulfide-based crystalline solid electrolytes, and argyrodite-type solid electrolytes. Specific examples of sulfide solid electrolytes include Li ₂ S-P ₂ S ₅ system (Li ₇ P ₃ S ₁₁ , Li ₃ PS ₄ , Li ₈ P ₂ S ₉ , etc.), Li ₂ S-SiS ₂ , LiI-Li ₂ S-SiS ₂ , LiI-Li ₂ S-P ₂ S ₅ , LiI-LiBr-Li ₂ S-P ₂ S ₅ , Li ₂ S-P ₂ S ₅ -GeS ₂ (Li ₁₃ GeP ₃ S ₁₆ , Li ₁₀ GeP ₂ S ₁₂ , etc.), LiI-Li ₂ S-P ₂ O ₅ , LiI-Li ₃ PO ₄ -P ₂ S ₅ , Li _7-x PS _6-x Cl _x , etc.; or combinations thereof.

Examples of oxide solid electrolytes include _, but _are not _limited to, _{Li7La3Zr2O12 ,} Li7 _{-xLa3Zr1 -} xNbxO12, Li7-3xLa3Zr2AlxO12, _{Li3xLa2/ 3 - xTiO3 , Li1+ xAlxTi2 - x ( PO4 )3, Li1+xAlxGe2-x(PO4)3 , Li3PO4 , or Li3 + xPO4 - xNx ( LiPON ) .}

The sulfide solid electrolyte and the oxide solid electrolyte may be glass or crystallized glass (glass ceramic).

Polymer electrolytes include, but are not limited to, polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof.

(Negative electrode layer)
The negative electrode layer contains a negative electrode active material and an optional solid electrolyte, a conductive additive, and a binder. Alternatively, the negative electrode layer may be a layer containing metallic lithium as a negative electrode active material that is deposited between the solid electrolyte layer and the negative electrode current collector layer in a charged state, and in this case, the negative electrode layer may disappear in a discharged state of the battery.

The material of the negative electrode active material is not particularly limited, and may be metallic lithium, or a material capable of absorbing and releasing metal ions such as lithium ions. Examples of materials capable of absorbing and releasing metal ions such as lithium ions include, but are not limited to, alloy-based negative electrode active materials and carbon materials.

The alloy-based negative electrode active material is not particularly limited, and examples thereof include Si alloy-based negative electrode active materials and Sn alloy-based negative electrode active materials. Examples of the Si alloy-based negative electrode active material include silicon, silicon oxide, silicon carbide, silicon nitride, and solid solutions thereof. The Si alloy-based negative electrode active material may also include elements other than silicon, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, Ti, and the like. The Sn alloy-based negative electrode active material may also include tin, tin oxide, tin nitride, and solid solutions thereof. The Sn alloy-based negative electrode active material may also include elements other than tin, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Ti, Si, and the like. Among these, the Si alloy-based negative electrode active material is preferred.

The carbon material is not particularly limited, but examples include hard carbon, soft carbon, graphite, etc.

<Negative electrode current collector layer>
The material and shape of the negative electrode current collector layer are not particularly limited, and the materials and shapes described in the above "Positive electrode current collector layer" may be used. In particular, the material of the negative electrode current collector layer is preferably copper. The shape is preferably a foil.

Example 1 and Comparative Examples 1 and 2
Example 1
Vapor grown carbon fiber (VGCF) as fiber and polyvinylidene fluoride (PVdF) as binder were stirred in butyl butyrate and dried to obtain a powder. 30 mg of the powder was placed in a metal cylinder and compression molded at 6 ton/ ^cm2 to form an elastic spacer.

A resin ring made of polyether ether ketone (PEEK) was placed in a ceramic cylinder. Next, a negative electrode current collector layer, a solid electrolyte layer, a positive electrode active material layer containing LiNi _1/3 Co _1/3 Mn _1/3 O ₂ as a positive electrode active material, and a positive electrode current collector layer were laminated in this order inside the resin ring, and uniaxially pressed to produce an all-solid-state battery inside the resin ring.

The solid-state battery was then punched out from the ceramic cylinder along with the resin ring.

The all-solid-state battery 2 used in the test had a configuration as shown in Figures 2 to 4. Figure 2 is a top view of the all-solid-state battery 2. Figure 3 is a cross-sectional side view of the all-solid-state battery 2 in a discharged state. Also, Figure 4 is a cross-sectional side view of the all-solid-state battery 2 in a charged state.

As shown in Figures 2 and 3, the all-solid-state battery 2 in a discharged state has a structure in which a positive electrode collector layer 10, a positive electrode active material layer 21, a solid electrolyte layer 22, and a negative electrode collector layer 30 are laminated in this order inside a resin ring 50. As shown in Figure 4, when the all-solid-state battery 2 is charged, metallic lithium is precipitated between the solid electrolyte layer 22 and the negative electrode collector layer 30, forming a negative electrode active material layer 23. In the all-solid-state battery 2, the negative electrode active material layer 23 disappears when the battery is discharged and is formed when the battery is charged.

As shown in the measuring device 3 in FIG. 5, a pin 100 was placed on top of the all-solid-state battery 2, and the elastic spacer 40 and pin 110 prepared above were placed on the bottom, and the batteries were held down at 0.2 N·m using screws. A load cell 120 was placed on the top pin 100, and a dynamic strain gauge 130 and a data logger 140 were connected to the load cell 120, allowing pressure to be measured.

The charge/discharge test was performed by placing the measurement device 3 with the all-solid-state battery 2 placed in a thermostatic chamber at 60° C., at a current value of 1.8 mA/cm ² and a voltage range of 3.0 to 4.2 V, using a charge/discharge device HJ1001SD8 manufactured by Hokuto Denko Corporation.

Comparative Examples 1 and 2
A charge/discharge test was carried out in the same manner as in Example 1, except that a disc spring and rubber were used instead of the elastic spacer.

<result>
The pressure before the charge/discharge test, the maximum pressure during the charge/discharge test, and the discharge capacity of the all-solid-state battery in each example are shown in Table 1.

As shown in Table 1, in Example 1, which used an elastic spacer, the maximum pressure in the charge/discharge test was 3 MPa, and in Comparative Examples 1 and 2, which used disc springs and rubber, the maximum pressures were 14 MPa and 10 MPa, respectively.

REFERENCE SIGNS LIST 1 Solid-state battery 10 Positive electrode current collector layer 20 Power generating element 21 Positive electrode active material layer 22 Solid electrolyte layer 23 Negative electrode active material layer 30 Negative electrode current collector layer 40 Elastic spacer 2 All-solid-state battery 50 Resin ring 3 Measuring device 100 Pin 110 Pin 120 Load cell 130 Dynamic strain gauge 140 Data logger

Claims (7)

The battery includes a battery element in which a positive electrode current collector layer, a power generating element, and a negative electrode current collector layer are laminated in this order, and an elastic spacer is laminated in the lamination direction of the battery element,
The power generating element expands and contracts in the stacking direction as the element is charged and discharged,
The elastic spacer contains fibers and has voids,
With respect to the stacking direction, the power generating element has a positive electrode layer, a solid electrolyte layer, and a negative electrode layer stacked in this order at least in a charged state ,
The elastic spacer is laminated on at least one surface of the battery element.
battery. The battery according to claim 1, wherein the negative electrode layer contains lithium as a negative electrode active material that is deposited between the solid electrolyte layer and the negative electrode current collector layer in a charged state. The battery according to claim 1 or 2, wherein the fibers are carbon fibers. The battery according to claim 1 or 2, wherein the elastic spacer is a compression molded body of the fiber. The battery according to claim 1 or 2, wherein the ratio of the fibers to the solid content of the elastic spacer is 90% by volume or more. The battery according to claim 1 or 2, wherein the porosity of the elastic spacer is 60 to 80%. The battery according to claim 1 or 2, which is a lithium ion battery.

Images