JP6783504B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

The present invention relates to a non-aqueous electrolyte secondary battery.

In recent years, secondary batteries such as lithium ion secondary batteries and nickel-metal hydride batteries are preferably used as a power source for mounting on vehicles or a power source for personal computers and mobile terminals. In particular, since a lithium ion secondary battery is lightweight and has a high energy density, it is becoming more important as a high output power source for mounting on a vehicle or a power source for a power storage system. As one of these types of batteries, a battery structure including an electrode body in which a positive electrode and a negative electrode are superposed via a separator is known. The positive electrode generally has a structure in which a positive electrode active material layer containing a positive electrode active material is held on a positive electrode current collector, and the positive electrode active material includes a lithium element and a transition metal element. The oxide (lithium transition metal composite oxide) contained in is widely used (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2013-152866

By the way, the present inventor considers using a positive electrode active material in which a small amount of dissimilar metal elements such as tungsten (W) and molybdenum (Mo) are added to a lithium transition metal composite oxide in order to improve battery performance. .. However, when a positive electrode active material in which a small amount of a trace amount of additive element is added to a lithium transition metal composite oxide is used, an event was found in which the trace amount of the additive element is locally eluted at both ends of the positive electrode active material layer in the width direction. .. Local elution of trace added elements in this way can cause deterioration of battery performance (for example, battery capacity). Therefore, it is desired to suppress the event that the trace additive element is locally eluted at the end of the positive electrode active material layer as little as possible. An object of the present invention is to solve the above problems.

In the non-aqueous electrolyte secondary battery proposed here, the positive electrode, the negative electrode, and the separator having a structure in which the positive electrode active material layer containing the positive electrode active material is held by the positive electrode current collector have their width directions aligned with each other. It includes an overlapping electrode body, a battery case accommodating the electrode body, and an electrolytic solution injected into the battery case. The positive electrode active material layer includes a non-additive element-containing region using a positive electrode active material made of a lithium transition metal composite oxide represented by the general formula LiMeO ₂ (where Me is at least one transition metal element). It has an additive element-containing region using a positive electrode active material in which a part of the Me site of the LiMeO ₂ is replaced with a trace additive element M. The non-additive element-containing region is provided at least at both ends of the positive electrode active material layer in the width direction. According to such a configuration, since the trace additive element M is not added to both ends of the positive electrode active material layer in the width direction, it is unlikely that the trace additive element M is eluted from the end. Therefore, the situation where the battery performance (for example, the battery capacity) is deteriorated due to the elution of the trace additive element M from the end portion is eliminated.

FIG. 1 is a diagram showing an example of the structure of a lithium ion secondary battery. FIG. 2 is a diagram showing a wound electrode body of a lithium ion secondary battery. FIG. 3 is a cross-sectional view showing a section III-III in FIG. FIG. 4 is a cross-sectional view showing a laminated structure of a positive electrode sheet and a negative electrode sheet of a wound electrode body of a lithium ion secondary battery according to an embodiment of the present invention.

Hereinafter, the secondary battery according to the embodiment of the present invention will be described with reference to the drawings. Here, the secondary battery will be described by taking a lithium ion secondary battery as an example. Members and parts that perform the same action are appropriately designated by the same reference numerals. In addition, each drawing is drawn schematically and does not necessarily reflect the actual product. In addition, each drawing shows only one example, and each drawing does not limit the present invention unless otherwise specified.

In the present specification, the “secondary battery” generally refers to a battery that can be recharged repeatedly, and includes a so-called storage battery such as a lithium ion secondary battery and a nickel hydrogen battery. Further, in the present specification, the "lithium ion secondary battery" refers to a secondary battery that uses lithium ions as a charge carrier and realizes charging and discharging by the transfer of charges accompanying the lithium ions between the positive and negative electrodes. Hereinafter, the case where the present invention is applied to a lithium ion secondary battery will be described, but it is not intended to limit the application target of the present invention.

FIG. 1 shows a lithium ion secondary battery 100. As shown in FIG. 1, the lithium ion secondary battery 100 includes a wound electrode body 200 and a battery case 300. Further, FIG. 2 is a diagram showing a wound electrode body 200. FIG. 3 shows a cross section III-III in FIG.

The lithium ion secondary battery 100 according to an embodiment of the present invention is configured in a flat rectangular battery case (that is, an outer container) 300 as shown in FIG. As shown in FIG. 2, in the lithium ion secondary battery 100, a flat wound electrode body 200 is housed in a battery case 300 together with a liquid electrolyte (electrolyte solution) (not shown).

As shown in FIG. 2, the wound electrode body 200 includes a long sheet-shaped positive electrode (positive electrode sheet 220) and a long sheet-shaped negative electrode (negative electrode sheet 240) similar to the positive electrode sheet 220. It is provided with a long sheet-shaped separator (separator 262,264).

The positive electrode sheet 220 includes a band-shaped positive electrode current collector 221 and a positive electrode active material layer 223. For the positive electrode current collector 221, for example, a metal foil suitable for the positive electrode can be preferably used. In this embodiment, a strip-shaped aluminum foil having a thickness of about 15 μm is used as the positive electrode current collector 221. The positive electrode sheet 220 is an uncoated portion in which the positive electrode current collector 221 is exposed without forming the positive electrode active material layer 223 at one end in the width direction orthogonal to the longitudinal direction of the positive electrode current collector 221. 222 is provided. Further, a positive electrode active material layer 223 is formed at the other end so that an uncoated portion 222 is not substantially provided. In the illustrated example, the positive electrode active material layer 223 is held on both sides of the positive electrode current collector 221 except for the uncoated portion 222 set on the positive electrode current collector 221. The positive electrode active material layer 223 contains a positive electrode active material, a conductive material, and a binder.

Positive electrode active materials include LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (lithium nickel cobalt manganese composite oxide), LiNiO ₂ (lithium nickel composite oxide), LiCoO ₂ (lithium cobalt composite oxide), etc. A lithium transition metal composite oxide having a layered structure represented by the general formula LiMeO ₂ (Me contains at least one of transition metal elements such as Ni, Co, and Mn), and the Me site of LiMeO ₂ . A positive electrode active material in which a part of the above is replaced with a trace additive element M is preferably used.

The trace addition element M may be one or more of a transition metal element and a main group metal element (including a metalloid element). For example, Group 1 (alkali metals such as sodium), Group 2 (alkaline earth metals such as magnesium and calcium), Group 3 (transition metals such as lanthanum) and Group 4 (transition metals such as titanium and zirconium) in the periodic table. Group 5 (transition metals such as niobium), Group 6 (transition metals such as chromium and tungsten), Group 7 (transition metals such as titanium and zirconium), Group 8 (transition metals such as iron), Group 9 (logium, etc.) (Transition metal of), group 10 (transition metal such as palladium and platinum), group 11 (transition metal such as copper), group 12 (metal such as zinc) and group 13 (metal such as aluminum). Metal elements can be mentioned. Typical examples are W, Zr, Mo, Mg, Ca, Na, Fe, Cr, Zn, Si, Sn, Nb and Al. In particular, it is preferably an oxide containing W as an additive element. Such a trace addition element M can be added at a ratio (addition amount) of 20 mol% or less, preferably 10 mol% or less, of the constituent transition metal element (that is, Me) of LiMeO ₂ . Further, the trace amount added element M is 0.1% by mass to 5% by mass (for example, 0.5% by mass to 3% by mass, for example, 1% by mass) when the total mass of the positive electrode active material is 100% by mass. It can be added in proportion (addition amount). By using the positive electrode active material to which a small amount of the trace amount of the element M is added, the conductivity of the positive electrode can be improved. Therefore, a battery constructed using such a positive electrode can realize excellent output characteristics and cycle characteristics.

In addition to the above-mentioned positive electrode active material, the positive electrode active material layer 223 can contain a conductive material such as acetylene black (AB) and a binder such as polyvinylidene fluoride (PVDF) and styrene butadiene rubber (SBR). The thickness of the positive electrode sheet 220 is not particularly limited, but is, for example, 150 μm or less, preferably 130 μm or less, and more preferably 110 μm or less. By using such a thin positive electrode sheet 220, the effects of the techniques disclosed herein can be better exerted. Details of the positive electrode active material layer 223 will be described later.

As shown in FIG. 2, the negative electrode sheet 240 includes a band-shaped negative electrode current collector 241 and a negative electrode active material layer 243. For the negative electrode current collector 241, for example, a metal foil suitable for the negative electrode can be preferably used. In this embodiment, a strip-shaped copper foil having a thickness of about 10 μm is used for the negative electrode current collector 241. The negative electrode sheet 240 is an uncoated portion in which the negative electrode current collector 241 is exposed without forming the negative electrode active material layer 243 at one end in the width direction orthogonal to the longitudinal direction of the negative electrode current collector 241. 242 is provided. Further, the negative electrode active material layer 243 is formed so that the uncoated portion 242 is not substantially provided at the other end portion. The negative electrode active material layer 243 is held on both sides of the negative electrode current collector 241 except for the uncoated portion 242 set in the negative electrode current collector 241. The negative electrode active material layer 243 contains a negative electrode active material, a thickener, a binder, and the like.

As the negative electrode active material, one or more of the substances conventionally used in lithium ion secondary batteries can be used without particular limitation. Preferable examples include carbon-based materials such as graphite carbon and amorphous carbon, lithium transition metal oxides, lithium transition metal nitrides and the like. Further, in addition to the negative electrode active material, a binder such as polyvinylidene fluoride (PVDF) or styrene butadiene rubber (SBR) or a thickener such as carboxymethyl cellulose (CMC) can be added.

As shown in FIGS. 2 and 3, the separators 262 and 264 are members that separate the positive electrode sheet 220 and the negative electrode sheet 240. In this example, the separators 262 and 264 are made of a strip-shaped sheet material having a plurality of minute holes and having a predetermined width. For the separators 262 and 264, for example, a single-layer structure separator or a laminated structure separator made of a porous polyolefin resin can be used. In this example, as shown in FIGS. 2 and 3, the width b1 of the negative electrode active material layer 243 is slightly wider than the width a1 of the positive electrode active material layer 223. Further, the widths c1 and c2 of the separators 262 and 264 are slightly wider than the width b1 of the negative electrode active material layer 243 (c1, c2> b1> a1).

The wound electrode body 200 is an electrode body in which the positive electrode sheet 220 and the negative electrode sheet 240 are overlapped and wound while the separators 262 and 264 are interposed between the positive electrode active material layer 223 and the negative electrode active material layer 243. is there. In this embodiment, as shown in FIGS. 2 and 3, the positive electrode sheet 220, the negative electrode sheet 240, and the separators 262 and 264 have the positive electrode sheet 220, the separator 262, the negative electrode sheet 240, and the separator in the same width direction. They are stacked in the order of 264. In this embodiment, the negative electrode current collector 241 and the positive electrode current collector 221 have uncoated portions 242 and 222 protruding to the opposite sides in the width direction of the wound electrode body 200 for the purpose of improving the current collecting property. It is piled up so as to do. The stacked sheet material (for example, the positive electrode sheet 220) is wound around the winding axis WL set in the width direction.

The winding electrode body 200 is housed in the battery case 300 in a state of being flatly pushed and bent in one direction orthogonal to the winding axis WL. Further, in the wound electrode body 200, in the width direction of the separators 262 and 264, the uncoated portion 222 of the positive electrode sheet 220 and the uncoated portion 242 of the negative electrode sheet 240 protrude from each other on opposite sides. Of these, the positive electrode terminal 420 is fixed to the uncoated portion 222 of the positive electrode current collector 221 and the negative electrode terminal 440 is fixed to the uncoated portion 242 of the negative electrode current collector 241.

As the electrolytic solution (non-aqueous electrolytic solution), the same non-aqueous electrolytic solution conventionally used for lithium ion secondary batteries can be used without particular limitation. Such a non-aqueous electrolyte typically has a composition in which a suitable non-aqueous solvent contains a supporting salt. As the non-aqueous solvent, for example, one or more selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and the like can be used. Further, as the supporting salt, for example, a lithium salt such as LiPF ₆ can be used.

Hereinafter, the positive electrode active material layer 223 of the lithium ion secondary battery 100 will be described in more detail. FIG. 4 schematically shows a cross section obtained by cutting the positive electrode sheet 220, the separator 262, and the negative electrode sheet 240 stacked in the wound electrode body 200 in the width direction (for example, the width direction of the positive electrode sheet 220).

As shown in FIG. 4, the above-mentioned lithium ion secondary battery 100 has a positive electrode 220 having a structure in which a positive electrode active material layer 223 containing a positive electrode active material is held by a positive electrode current collector 221, a negative electrode 240, and a separator 262. The electrodes 200 are provided so as to be overlapped with each other in the same width direction. In such an electrode body 200, the end portions 223E on both sides of the positive electrode active material layer 223 in the width direction are exposed on the side surface 200A (see FIG. 2) of the electrode body 200 in the side view (that is, when viewed from both sides in the width direction). ..

The present inventor of the lithium ion secondary battery 100 in this form has a positive electrode active material in which a part of the Me sites of LiMeO ₂ described above is replaced with a trace additive element M (that is, a positive electrode active material to which a trace additive element M is added). We found an event in which the trace additive element M was eluted at the ends 223E on both sides of the positive electrode active material layer 223 in the width direction. It is not necessary to clarify the reason why the trace additive element M is eluted at the end portion 223E of the positive electrode active material layer 223, but the following can be considered, for example. That is, gas (for example, oxygen) exists at both ends of the electrode body 200 in the width direction. Therefore, both ends of the electrode body 200 in the width direction are in contact with the gas, and the gas draws out lithium ions from the ends 243E on both sides of the negative electrode active material layer 243 in the width direction during charging. Therefore, at the end portion 243E of the negative electrode active material layer 243, the potential may rise locally during charging. In this case, it is considered that the potential may rise locally in the end portion 223E of the positive electrode active material layer 223, which is close to the end portion 243E of the negative electrode active material layer 243, in an attempt to maintain the voltage. As described above, when the potential of the end portion 223E of the positive electrode active material layer 223 rises locally, it may cause elution of the trace additive element M contained in the positive electrode active material.

Based on the above findings, the present inventor used a positive electrode active material to which the trace additive element M was not added at the ends 223E on both sides of the positive electrode active material layer 223 in which the trace additive element M was easily eluted. In addition, it was decided to use the positive electrode active material to which the trace additive element M was added in the other parts. That is, the positive electrode active material layer 223 disclosed here has an additive element-containing region R1 and a non-additive element-containing region R2, as shown in FIG.

The additive element-containing region R1 is provided in the intermediate portion 223C excluding the end portions 223E on both sides in the width direction of the positive electrode active material layer 223. In the additive element-containing region R1, as the positive electrode active material, a substance in which a part of the Me site of LiMeO ₂ is replaced with a trace additive element M is used. By using the positive electrode active material in which a part of the Mesite is replaced with the trace additive element M in this way, the conductivity of the positive electrode can be improved. Therefore, a battery constructed using such a positive electrode can realize excellent output characteristics and cycle characteristics.

The non-additive element-containing region R2 is provided at the ends 223E on both sides of the positive electrode active material layer 223 in the width direction. In the non-additive element-containing region R2, LiMeO ₂ is used as the positive electrode active material. That is, in the positive electrode active material layer 223, the trace additive element M is not added to the end portions 223E on both sides in the width direction, and the trace additive element M is added to the other regions.

In the lithium ion secondary battery 100 disclosed here, the positive electrode active material layer 223 has a non-additive element-containing region R2 in which the trace additive element M is not added to the end portions 223E on both sides in the width direction. Therefore, even if the potential locally rises at the ends 223E on both sides of the positive electrode active material layer 223 in the width direction during charging, it is unlikely that the trace additive element M is eluted from the ends 223E. Therefore, the phenomenon that the battery performance (for example, the battery capacity) deteriorates due to the elution of the trace additive element M from the end portion 223E is alleviated.

As the positive electrode active material layer 223 disclosed here, as shown in FIG. 4, when the total width of the positive electrode active material layer 223 along the width direction is 100%, the total width of the non-additive element-containing region R2 ( The ratio of W1 + W2) is preferably about 3% or more (further, 3.8% or more, particularly 4% or more). By providing the non-additive element-containing region R2 with such a width ratio, elution of the trace additive element M can be avoided more effectively. On the other hand, if the ratio of the above width (W1 + W2) is too large, the ratio of the positive electrode active material to which the trace additive element M is added decreases relatively. Therefore, the effect of improving the battery performance by adding the trace additive element M to the positive electrode active material is achieved. (For example, the effect of improving electron conductivity) may be insufficient. From the viewpoint of performance improvement by adding the trace addition element M, the ratio of the width (W1 + W2) is preferably 10% or less, more preferably 7.8% or less, and particularly preferably 6% or less. .. For example, from the viewpoint that the positive electrode active material layer 223 having the above width (W1 + W2) ratio of 3.8% to 7.8% achieves both performance improvement by addition of the trace addition element M and suppression of elution of the trace addition element M. Appropriate from.

The positive electrode active material layer 223 may be formed based on a different mixture (paste-like positive electrode active material layer forming composition) in the additive element-containing region R1 and the non-additive element-containing region R2. For example, it is preferable to prepare a first mixture for forming the additive element-containing region R1 and a second mixture for forming the non-additive element-containing region R2. In this embodiment, the second mixture contains a positive electrode active material composed of a lithium transition metal composite oxide represented by LiMeO ₂ . On the other hand, the first mixture contains a positive electrode active material in which a part of the Me site of LiMeO ₂ is replaced with a trace additive element M. A part of the positive electrode active material layer 223 is formed on the surface of the positive electrode current collector 221 by applying the first mixture to the portion of the positive electrode current collector 221 where the additive element-containing region R1 is formed and drying the mixture. A part of this becomes the additive element-containing region R1 of the positive electrode active material layer 223. Further, when the second mixture is applied in a band shape to the remaining portion of the positive electrode current collector 221 in the longitudinal direction and dried to form the remaining portion of the positive electrode active material layer 223 on the surface of the positive electrode current collector 221. Good. The remaining portion becomes the non-additive element-containing region R2 of the positive electrode active material layer 223.

≪Test Example 1≫
The present inventor conducted a test to evaluate the action and effect of the positive electrode sheet 220. In the lithium ion secondary battery used in such a test, as shown in FIGS. 1 to 4, a positive electrode sheet 220 in which positive electrode active material layers 223 are formed on both sides of the positive electrode current collector 221 and a negative electrode current collector 241 A negative electrode sheet 240 having a negative electrode active material layer 243 formed on both sides of the negative electrode sheet 240 is provided. Non-additive element-containing regions R2 using LiNi _1/3 Co _1/3 Mn _1/3 O ₂ as the positive electrode active material are provided at the ends 223E on both sides of the positive electrode active material layer 223 in the width direction. On the other hand, in the intermediate portion 223C of the positive electrode active material layer 223 excluding the end portion 223E, a part of the transition metal element (NiCoMn) site of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ is tungsten (W). The additive element-containing region R1 using the W-added positive electrode active material substituted with) is provided. The amount of W added to the positive electrode active material in the additive element-containing region R1 was set to a ratio of 1% by mass with respect to the total mass of the positive electrode active material.

The mixture used to form the positive electrode active material layer 223 is a positive electrode active material, acetylene black (AB) as a conductive material, and polyvinylidene fluoride (PVdF) as a binder in a mass ratio of 90: 8: 2. -A mixture in methylpyrrolidone (NMP) was used.

Here, the positive electrode active material layer 223 was formed in the additive element-containing region R1 and the non-additive element-containing region R2 based on different mixtures. That is, a first mixture for forming the additive element-containing region R1 and a second mixture for forming the non-additive element-containing region R2 were prepared. The first mixture contains the above-mentioned W-added positive electrode active material, and the second mixture contains the above-mentioned W-free positive electrode active material. By applying the first mixture to the portion of the aluminum foil as the positive electrode current collector 221 where the additive element-containing region R1 is formed on both sides and drying, the positive electrode active material layer 223 is formed on both sides of the positive electrode current collector 221. Formed a part. Further, the second mixture was applied in a band shape to the remaining portion of the positive electrode current collector 221 in the longitudinal direction and dried to form the remaining portion of the positive electrode active material layer 223 on the surface of the positive electrode current collector 221. ..

≪Samples 1-5≫
Here, when the total width of the positive electrode active material layer 223 is 100%, five samples having different ratios of the total width (W1 + W2) of the non-additive element-containing region R2 of the positive electrode active material layer 223 were prepared (FIG. 4). reference). Samples 1 to 5 had the same configuration except for the ratio of such widths (W1 + W2).

≪Negative electrode sheet≫
The negative electrode sheet 240 was produced as follows. Graphite powder as a negative electrode active material, styrene-butadiene copolymer (SBR) as a binder, and carboxymethyl cellulose as a thickener are mixed in water at a mass ratio of 98: 1: 1 to prepare a negative electrode mixture. Was applied to both sides of a long sheet-shaped copper foil (negative electrode current collector) in a strip shape and dried to prepare a negative electrode sheet 240 having negative electrode active material layers 243 on both sides of the negative electrode current collector 241. ..

≪Lithium-ion secondary battery≫
A wound body is produced by winding the positive electrode sheet 220 and the negative electrode sheet 240 via two separators 262 and 264, and the wound body is crushed from the lateral direction to form a flat wound electrode body. 200 was made. The wound electrode body 200 thus obtained is housed in a battery case (here, a square shape is used) 300 together with a non-aqueous electrolyte (non-aqueous electrolyte solution), and the opening of the battery case 300 is airtightly sealed. did. Here, as the separators 262 and 264, a porous film having a three-layer structure of polypropylene (PP), polyethylene (PE) and polypropylene (PP) was used. Further, an electrolytic solution in which ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate were blended in a volume ratio of 3: 4: 3 and LiPF ₆ was dissolved in 1 mol / L was used.

≪Measurement of initial capacity≫
Each of the test lithium ion secondary batteries obtained in each of the samples 1 to 5 was charged to a voltage of 4.1 V at a current value of 1 C under a temperature condition of 25 ° C. After a 5-minute pause, the charged battery was discharged to a voltage of 3.0 V at a current value of 1 C at 25 ° C. Then, after a 5-minute pause, the battery was charged with a current value of 1 C to a voltage of 4.1 V, and then charged with a constant voltage method until the current value decreased to 0.1 C. The charged battery was discharged at 25 ° C. at a current value of 1 C to a voltage of 3.0 V, and then discharged by a constant voltage method until the current value was reduced to 0.1 C. The discharge capacity at this time was defined as the initial capacity (rated capacity).

≪Capacity retention rate after 25 ℃ pulse cycle≫
After adjusting each of the test lithium-ion secondary batteries of each sample to a state of charge (SOC 50%) of about 50% of the initial capacity, CC discharge and 20C for 100 seconds at 20C under a temperature condition of 25 ° C. The charge / discharge cycle of performing CC charging for 100 seconds was repeated 1000 times in succession. Then, the battery capacity after the 25 ° C. pulse cycle is measured under the same conditions as the initial capacity, and from [(Battery capacity after the 25 ° C. pulse cycle) / (Initial capacity)] × 100 (%), after the 25 ° C. pulse cycle. The capacity retention rate was calculated.

≪Evaluation of each sample≫
The results of the above tests are shown in Table 1 for each sample.

As shown in Table 1, in Sample 1, the positive electrode active material with W added is used in the entire area of the positive electrode active material layer 223 (that is, there is no non-additive element-containing region R2). In such sample 1, the 25 ° C. capacity retention rate was 96.8%. On the other hand, in Samples 2 to 5, the positive electrode active material with W added to the intermediate portion 223C of the positive electrode active material layer 223 was used, and the positive electrode without W added to the end portions 223E on both sides in the width direction of the positive electrode active material layer 223. Active materials are used. For these samples 2 to 5, the capacity retention rate after the cycle was 97.3% or more, which was extremely high durability performance as compared with sample 1. From this result, by using the positive electrode active material with W added to the intermediate portion 223C of the positive electrode active material layer 223 and using the positive electrode active material without W added to the end portions 223E on both sides in the width direction of the positive electrode active material layer 223. , It was confirmed that the capacity retention rate was improved after the 25 ° C. pulse cycle.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above.

Preferable application of the technique disclosed herein is not limited to the above-mentioned winding type electrode body. For example, the positive electrode current collector 221 and the negative electrode current collector 241 are each a rectangular sheet material, and the positive electrode current collector 221 and the negative electrode current collector 241 have their respective width directions (for example, longitudinal directions) aligned with each other. , The positive electrode active material layer 223 and the negative electrode active material layer 243 may be a laminated electrode body in which the positive electrode active material layer 223 and the negative electrode active material layer 243 are alternately laminated so as to face each other with a separator interposed therebetween. Even in such a case, the above-mentioned effect can be obtained. In this case, the non-additive element-containing region R2 may be provided not only at the ends on both sides of the positive electrode active material layer 223 in the longitudinal direction (width direction) but also at the ends on both sides in the lateral direction. In this way, by configuring all the open ends of the positive electrode active material layer 223 (that is, the ends exposed on the side surfaces of the laminated electrode body), the trace additive elements are not added, the elution of the trace additive elements can be further enhanced. Can be avoided well. The shapes of the positive electrode current collector 221 and the negative electrode current collector 241 are not limited to a rectangle, and a square shape having four sides having the same length may be adopted. In this case, the longitudinal direction is understood as a direction along any one side.

100 Lithium ion secondary battery 200 Winding electrode body 220 Positive electrode sheet 221 Positive electrode current collector 223 Positive electrode active material layer 223C Intermediate part of positive electrode active material layer 223E Both ends in the width direction of the positive electrode active material layer 240 Negative electrode sheet 262,264 Separator R1 Additive element-containing region R2 Non-additive element-containing region

Claims (1)

A positive electrode having a structure in which a positive electrode active material layer containing a positive electrode active material is held by a positive electrode current collector, a negative electrode, and an electrode body in which a separator overlaps with each other in the same width direction.
A battery case containing the electrode body and
The battery case is provided with an electrolytic solution injected into the battery case.
The positive electrode active material layer is
A non-additive element-containing region using a positive electrode active material composed of a lithium transition metal composite oxide represented by the general formula LiMeO ₂ (where Me is at least one transition metal element).
It has an additive element-containing region using a positive electrode active material in which a part of the Me site of LiMeO ₂ is replaced with a trace additive element M.
The non-additive element-containing region is provided at least at both ends of the positive electrode active material layer in the width direction.
The trace additive element M is tungsten,
Here, assuming that the total width of the positive electrode active material layer along the width direction is 100%, the total width of the non-additive element-containing region along the width direction is 3% or more and 7.8% or less. A non-aqueous electrolyte secondary battery characterized by.

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