Non-aqueous electrolyte secondary battery

Abstract

The present technology provides a non-aqueous electrolyte secondary battery. The electrode body includes a stack. The stack includes a positive electrode plate, a separator and a negative electrode plate. The positive electrode plate, the separator and the negative electrode plate each have a strip-shaped planar shape. The stack is wound into a spiral shape. In a cross section of the stack that is orthogonal to the winding axis, the electrode body includes a first curved portion, a flat portion and a second curved portion. The positive electrode plate ends winding in the second curved portion. The winding end position of the positive electrode plate exceeds the vertex of the second curved portion. The negative electrode plate includes a negative electrode substrate and a negative electrode active material layer. On both sides of the negative electrode plate in the width direction, the negative electrode substrate includes an exposed portion.

Description

Technical Field

[0001] The present technology relates to a non-aqueous electrolyte secondary battery. Background Art

[0002] Japanese Patent Application Laid-Open No. 2015-220216 discloses that an aging step is performed to prevent elution of metal in a positive electrode active material. Summary of the invention

[0003] Generally speaking, the manufacturing method of a non-aqueous electrolyte secondary battery (hereinafter, may be referred to as a "battery") includes an assembly process, a liquid injection process and a sealing process. An electrode body is formed in the assembly process. The electrode body may be a wound type. The electrode body may be housed in an outer body. In the liquid injection process, an electrolyte is injected into the outer body. In the sealing process, the outer body is sealed. The liquid injection process and the sealing process are performed in a low-moisture atmosphere. This is because the battery performance may be reduced due to the mixing of water into the battery.

[0004] In the past, a nitrogen atmosphere was used as a low-moisture atmosphere. A nitrogen atmosphere is a low-moisture atmosphere and also an extremely low-oxygen atmosphere. For example, from the perspective of manufacturing cost, it is expected that the liquid injection process and the sealing process can also be performed in an oxygen-containing atmosphere.

[0005] For example, the use of a dry air atmosphere can be considered. The dry air atmosphere can be a low-moisture atmosphere and an oxygen-containing atmosphere. However, if the liquid injection process and the sealing process are performed in an oxygen-containing atmosphere, there is a tendency that the occurrence rate of voltage failure increases.

[0006] The purpose of this technology is to reduce the occurrence rate of voltage failure.

[0007] The structure and effects of the present technology are described below. However, the mechanism of action in this specification includes assumptions. The mechanism of action does not limit the scope of the present technology.

[0008] [1] A non-aqueous electrolyte secondary battery includes an outer casing, an electrode assembly, and an electrolyte solution.

[0009] The outer casing contains the electrode body and the electrolyte. The outer casing includes a container and an external terminal. The container includes a bottom, a top, and a side wall. The side wall connects the bottom and the top. The external terminal is installed on the top.

[0010] The electrode body includes a stack. The stack includes a positive electrode plate, a separator and a negative electrode plate. The positive electrode plate, the separator and the negative electrode plate each have a strip-shaped planar shape. The positive electrode plate, the separator and the negative electrode plate are stacked. The separator separates the positive electrode plate from the negative electrode plate. The stack is wound into a spiral shape. In a cross section of the stack that is orthogonal to the winding axis, the electrode body includes a first curved portion, a flat portion and a second curved portion. In the first curved portion and the second curved portion, the stack is curved. In the flat portion, the stack is flat. In the direction connecting the bottom and the top of the container, the second curved portion is closer to the bottom than the first curved portion. The flat portion connects the first curved portion to the second curved portion.

[0011] The positive electrode plate is wound up in the second curved portion and ends at a position beyond the apex of the second curved portion. The positive electrode plate contains a transition metal oxide.

[0012] The negative electrode plate includes a negative electrode substrate and a negative electrode active material layer. The negative electrode active material layer is disposed on the surface of the negative electrode substrate. The negative electrode substrate includes an exposed portion on both sides of the width direction of the negative electrode plate. The exposed portion protrudes outwardly compared to the end face of the negative electrode active material layer.

[0013] According to the new findings of the present technology, the mechanism of voltage failure in an oxygen-containing atmosphere can be described as follows.

[0014] Figure 1 This is a first schematic cross-sectional view showing an electrode body in a reference embodiment.

[0015] The electrode body 220 is a wound type and includes a first curved portion Rp1 , a flat portion Fp, and a second curved portion Rp2 .

[0016] Figure 2 It is a second schematic cross-sectional view showing the electrode body in the reference form.

[0017] exist Figure 2 , the electrode body 220 is shown as viewed from a line of sight parallel to the Y-axis. Figure 2 The electrode body 220 is in a discharged state.

[0018] Figure 3 It is a third schematic cross-sectional view showing the electrode body in the reference form.

[0019] Figure 3The electrode body 220 is in a charged state. The negative electrode plate 222 is fixed at one end in the X-axis direction through current collection processing. The negative electrode plate 222 may expand during charging. Due to the expansion of the negative electrode plate 222, the electrode body 220 may have winding relaxation in the portion where the negative electrode plate 222 is not fixed. The winding relaxation may be significant in region IV. Region IV is included in the outermost periphery. Due to the winding relaxation, a gap is formed between the electrodes. Due to the formation of the gap, the surrounding oxygen (O2) may come into contact with the negative electrode plate 222.

[0020] Figure 4 This is a conceptual diagram showing the mechanism of occurrence of voltage failure.

[0021] exist Figure 4 It is shown in Figures 1 to 3 The positional relationship between the positive electrode plate 221 and the negative electrode plate 222 in the region IV in FIG. The negative electrode plate 222 includes a negative electrode substrate 222c, a negative electrode active material layer 222a, and a negative electrode active material layer 222b. The positive electrode plate 221 includes a positive electrode substrate 221c, a positive electrode active material layer 221a, and a positive electrode active material layer 221b. The negative electrode active material layer 222a (inner peripheral side) is opposite to the positive electrode active material layer 221b (outer peripheral side). The negative electrode active material layer 222b (outer peripheral side) is not opposite to the positive electrode active material layers 221a and 221b. The negative electrode active material layer 222b (outer peripheral side) is, for example, a "non-opposing portion".

[0022] By performing the injection process and the sealing process in an oxygen-containing atmosphere, the battery can be provided with an oxygen-containing atmosphere. The electrolyte 230 penetrates into the negative electrode active material layer 222b. (i) Since oxygen (O2) contacts the negative electrode active material layer 222b, lithium ions (Li + ) may be consumed. As a result, Li + (ii) In order to alleviate the concentration gradient of Li + The concentration gradient of Li + It is possible to diffuse from the negative electrode active material layer 222a side to the negative electrode active material layer 222b side. Hereinafter, in this specification, this phenomenon is also described as "Li + (iii) In order to compensate for the Li + The positive electrode active material layer 221b supplies Li to the negative electrode active material layer 222a. + As a result, the potential of the positive electrode active material layer 221b may increase locally. (iv) Due to the increase in potential, transition metals may be dissolved from the transition metal oxide contained in the positive electrode active material layer 221b into the electrolyte. The dissolved transition metals may precipitate on the surface of the negative electrode active material layer 222a. Due to the precipitation of transition metals, voltage failure may occur.

[0023] Figure 5 This is a schematic cross-sectional view showing an electrode body in an embodiment of the present technology.

[0024] In the present technology, the occurrence rate of voltage failure can be reduced by the winding end position of the positive electrode plate 121 and the exposed portion of the negative electrode substrate 122 c .

[0025] In the aforementioned reference form, the positive electrode plate 221 is wound at the flat portion Fp (see Figure 1 ). In the present technology, the positive electrode plate 121 is wound up in the second curved portion Rp2. The winding end position of the positive electrode plate 121 exceeds the apex of the second curved portion Rp2. Therefore, it can be considered that a tension Ts is applied to the region VI. By applying the tension Ts, it can be expected that the winding slack is reduced.

[0026] Figure 6 This is a conceptual diagram showing the function of the exposed portion of the negative electrode substrate.

[0027] exist Figure 6 It is shown in Figure 5 The positional relationship between the positive electrode plate 121 and the negative electrode plate 122 in the region VI. In the present technology, the negative electrode substrate 122c includes exposed portions (first exposed portion Ep1 and second exposed portion Ep2) on both sides in the width direction (X-axis direction). The second exposed portion Ep2 can be located in the region VI. The second exposed portion Ep2 extends outward compared to the end faces of the negative electrode active material layers 122a and 122b. The second exposed portion Ep2 can physically hinder the Li + Therefore, it is considered that a series of reactions leading to the precipitation of transition metals may be hindered.

[0028] By the synergy of the above-mentioned actions, the present technology can be expected to reduce the occurrence rate of voltage failure.

[0029] [2] The length of the exposed portion may be greater than the thickness of the negative electrode active material layer, for example.

[0030] By making the exposed portion longer than the thickness of the negative electrode active material layer, it is expected that Li + Diffusion to non-opposing parts (refer to Figure 4 ).

[0031] [3] The length of the exposed portion may be, for example, 0.8 mm or more.

[0032] By making the exposed portion 0.8 mm or more, it is expected that Li is less likely to be generated. + Diffusion to non-opposed parts.

[0033] [4] The container is sealed. The gas in the container may have an oxygen concentration of 1% to 21% by mole.

[0034] In the battery of the present technology, even if the atmosphere in the container is oxygen-containing, it can be expected that voltage failure is unlikely to occur.

[0035] The foregoing and other objects, features, aspects and advantages of the present technology will become apparent from the following detailed description of the present technology when read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a first schematic cross-sectional view showing an electrode body in a reference embodiment.

[0037] Figure 2 It is a second schematic cross-sectional view showing the electrode body in the reference form.

[0038] Figure 3 It is a third schematic cross-sectional view showing the electrode body in the reference form.

[0039] Figure 4 This is a conceptual diagram showing the mechanism of occurrence of voltage failure.

[0040] Figure 5 This is a schematic cross-sectional view showing an electrode body in an embodiment of the present technology.

[0041] Figure 6 This is a conceptual diagram showing the function of the exposed portion of the negative electrode substrate.

[0042] Figure 7 This is a schematic diagram showing an example of a non-aqueous electrolyte secondary battery in an embodiment of the present technology.

[0043] Figure 8 This is a schematic diagram of an electrode body in an embodiment of the present technology. DETAILED DESCRIPTION

[0044] The following describes an embodiment of the present technology (also described as "the present embodiment" in this specification). However, the following description does not limit the scope of the present technology. For example, the description related to the effects in this specification does not limit the scope of the present technology within the entire range in which the effects can be exerted.

[0045] <Definitions of Terms, etc.>

[0046] In this specification, the descriptions such as “comprise, include”, “have” and their variations [such as “be composed of”, “encompass, involve”, “contain”, “carry, support”, “hold”, etc.] are open forms. For the open form, in addition to the essential elements, additional elements may be included, or additional elements may not be included. The description such as “consist of” is a closed form. The description such as “consist essentially of” is a semi-closed form. For the semi-closed form, in addition to the essential elements, additional elements may be further included within the scope that does not hinder the purpose of the present technology. For example, elements that are generally envisioned in the field to which the present technology belongs (such as unavoidable impurities, etc.) may also be included as additional elements.

[0047] In this specification, expressions such as “may” and “can” are not used in an obligatory sense, that is, “must”, but are used in a permissive sense, that is, “have the possibility of”.

[0048] In this specification, elements expressed in singular form (a, an, the) also include plural forms unless otherwise specified. For example, "particle" refers not only to "one particle" but also to "a collection of particles (powder, powder, particle group)".

[0049] In this specification, for example, for numerical ranges such as "0.8 mm to 2.0 mm" and "0.8 to 2.0 mm", unless otherwise specified, the upper limit and lower limit are included. That is, "0.8 mm to 2.0 mm" and "0.8 to 2.0 mm" both represent a numerical range of "above 0.8 mm and below 2.0 mm". In addition, a numerical value arbitrarily selected from the numerical range may be set as a new upper limit and lower limit. For example, a new numerical range may be set by arbitrarily combining the numerical values ​​within the numerical range with the numerical values ​​recorded in other parts, tables, figures, etc. in this specification.

[0050] In this specification, all numerical values ​​are modified by the term "about". The term "about" may refer to, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​are approximate values ​​that may vary depending on the use form of the present technology. All numerical values ​​are shown with significant figures. All measured values, etc., may be processed by rounding off based on the number of significant figures. All numerical values, for example, may include errors associated with detection limits, etc.

[0051] In this specification, when a compound is expressed by a stoichiometric composition formula such as "LiCoO2", the stoichiometric composition formula is only a representative example. The composition ratio may also be non-stoichiometric. For example, when lithium cobalt oxide is expressed as "LiCoO2", unless otherwise specified, lithium cobalt oxide is not limited to a composition ratio of "Li / Co / O=1 / 1 / 2", and may contain Li, Co and O in any composition ratio. In addition, doping and substitution based on trace elements may also be allowed.

[0052] The geometric terms in this specification (such as "parallel", "vertical", "orthogonal", etc.) should not be understood as strictly meaning. For example, "parallel" may be slightly offset from "parallel" in the strict sense. The geometric terms in this specification may include tolerances, errors, etc. in design, operation, and manufacturing. The dimensional relationship in each figure is sometimes inconsistent with the actual dimensional relationship. In order to facilitate the understanding of this technology, there are cases where the dimensional relationship (length, width, thickness, etc.) in each figure is changed. In addition, there are cases where a part of the structure is omitted.

[0053] In this specification, “the direction connecting the bottom and the top of the container ( Figure 1 , 7 The "Z-axis direction (such as the vertical direction)" is also recorded as the "height direction". However, the relationship between the height direction and the vertical direction is arbitrary. The height direction may be parallel to the vertical direction or may not be parallel to the vertical direction.

[0054] <Non-aqueous electrolyte secondary battery>

[0055] Figure 7 This is a schematic diagram showing an example of a non-aqueous electrolyte secondary battery in an embodiment of the present technology.

[0056] The battery 100 can be used for any purpose. For example, the battery 100 can also be used as a main power source or a power auxiliary power source in an electric vehicle or the like. Alternatively, a battery module or a battery pack can be formed by connecting a plurality of batteries 100. The battery 100 can also have a rated capacity of, for example, 1 to 200 Ah.

[0057] "Exterior Body"

[0058] The battery 100 includes an outer casing 110. The outer casing 110 contains an electrode body 120. The outer casing 110 is square (rectangular). The outer casing 110 includes a container 111 and an external terminal 112. The container 111 may be made of metal, for example. The container 111 may be made of aluminum (Al) alloy, for example. The container 111 includes a bottom 111a, a top 111b, and a side wall 111c. The side wall 111c connects the bottom 111a and the top 111b.

[0059] The container 111 is sealed. The container 111 may contain an oxygen-containing atmosphere. For example, the gas in the container 111 may have an oxygen concentration of 1 to 21% or 5 to 15% by mole fraction (mass fraction). The oxygen concentration may be measured by gas chromatography. The oxygen concentration may be measured three or more times. The arithmetic average of the results of three or more times may be used.

[0060] For example, by sealing the container 111 under a dry air atmosphere, the container 111 can be made into an oxygen-containing atmosphere. The dry air atmosphere can also have an oxygen concentration equivalent to that of the atmosphere. The dry air atmosphere can also have an oxygen partial pressure of 160 mmHg, for example. For example, when the container 111 is sealed under a nitrogen atmosphere, the oxygen concentration of the gas in the container 111 can be less than 1 ppm by mole fraction. In addition, the oxygen concentration in the container 111 can be lower than the oxygen concentration in the dry air atmosphere. This is because various gases may be generated in the container 111 due to the decomposition of the electrolyte, etc.

[0061] The external terminal 112 is mounted on the top 111b. The external terminal 112 includes a positive terminal 112a and a negative terminal 112b. The positive electrode collector plate 113a connects the positive terminal 112a to the electrode body 120. Each of the positive terminal 112a and the positive electrode collector plate 113a may be made of, for example, Al. The negative electrode collector plate 113b connects the negative terminal 112b to the electrode body 120. Each of the negative terminal 112b and the negative electrode collector plate 113b may be made of, for example, copper (Cu), nickel (Ni), etc.

[0062] Electrode

[0063] The battery 100 includes an electrode body 120 . The battery 100 may include a single electrode body 120 or a plurality of electrode bodies 120 . That is, the exterior body 110 may accommodate a plurality of electrode bodies 120 .

[0064] Figure 8 This is a schematic diagram of an electrode body in an embodiment of the present technology.

[0065] The electrode body 120 includes a stack 125. The stack 125 includes a positive electrode plate 121, a separator 123, and a negative electrode plate 122. The stack 125 may also include a single separator 123. The stack 125 may also include, for example, two separators 123. The positive electrode plate 121, the separator 123, and the negative electrode plate 122 each have a strip-shaped planar shape. The positive electrode plate 121, the separator 123, and the negative electrode plate 122 are stacked. For example, the separator 123, the positive electrode plate 121, the separator 123, and the negative electrode plate 122 may be stacked in sequence. At least a portion of the separator 123 is sandwiched between the positive electrode plate 121 and the negative electrode plate 122. The separator 123 separates the positive electrode plate 121 from the negative electrode plate 122.

[0066] exist Figure 5 , a cross section of the stack 125 perpendicular to the winding axis is shown. The stack 125 is wound in a spiral shape. For example, the electrode body 120 may be formed by forming the stack 125 wound in a cylindrical shape into a flat shape. Alternatively, the stack 125 may be wound in a flat shape. The terminal of the stack 125 is fixed, for example, by an adhesive tape 126 or the like.

[0067] Figure 5 The Z-axis direction is equivalent to the height direction. The "height direction" is a direction connecting the bottom 111a and the top 111b of the container 111. In the height direction, the electrode body 120 includes a first curved portion Rp1, a flat portion Fp and a second curved portion Rp2. In the flat portion Fp, the stack 125 is flat. In the first curved portion Rp1 and the second curved portion Rp2, the stack 125 is curved. It is also possible that in the first curved portion Rp1 and the second curved portion Rp2, the stack 125 describes an arc. For example, it is also possible that when the outer shapes of the first curved portion Rp1 and the second curved portion Rp2 describe an arc, the radius r of the circle and the thickness d of the electrode body 120 satisfy the relationship "2r≈d".

[0068] In the height direction, the second curved portion Rp2 is closer to the bottom portion 111a than the first curved portion Rp1 (see Figure 7 The flat portion Fp is sandwiched between the first curved portion Rp1 and the second curved portion Rp2. The flat portion Fp connects the first curved portion Rp1 and the second curved portion Rp2.

[0069] (Positive plate)

[0070] The positive electrode plate 121 is a strip-shaped sheet. The positive electrode plate 121 is wound up in the second curved portion Rp2 (see Figure 5). The winding end position of the positive electrode plate 121 exceeds the vertex of the second curved portion Rp2. The "vertex" refers to the point in the second curved portion Rp2 that protrudes most toward the bottom 111a. By winding the positive electrode plate 121 to a state where it crosses the vertex of the second curved portion Rp2, it is expected that a tension Ts is applied to the first curved portion Rp1. By applying the tension Ts, it is expected that the winding slack is reduced.

[0071] For example, the greater the dynamic friction coefficient between the positive electrode plate 121 and the separator 123, the more the winding slack can be expected to be reduced. The dynamic friction coefficient between the positive electrode plate 121 and the separator 123 may be, for example, 0.50 to 1.00. The "dynamic friction coefficient" in this specification can be measured according to "JIS K 7125".

[0072] The positive electrode plate 121 includes a positive electrode substrate 121c, a positive electrode active material layer 121a, and a positive electrode active material layer 121b. The positive electrode active material layer 121a and the positive electrode active material layer 121b are respectively arranged on the surface of the positive electrode substrate 121c. The positive electrode active material layer 121a (inner peripheral side) and the positive electrode active material layer 121b (outer peripheral side) are in a front-back relationship (refer to Figure 6 ).

[0073] The positive electrode substrate 121c may also have a thickness of 10 to 30 μm, for example. The positive electrode substrate 121c may also be, for example, Al foil, etc. The positive electrode active material layers 121a and 121b may also have a thickness of 10 to 200 μm, for example. The positive electrode active material layers 121a and 121b may also contain positive electrode active materials. The positive electrode active material layers 121a and 121b may also further contain, for example, conductive materials and binders, etc. For example, the positive electrode active material layers 121a and 121b may also be substantially composed of 0.1 to 10% binder, 0.1 to 10% conductive material and the remaining positive electrode active material by mass fraction. The conductive material may contain any component. The conductive material may also contain, for example, carbon black, etc. The binder may contain any component. The binder may also contain, for example, polyvinylidene fluoride (PVdF), etc.

[0074] The positive electrode active material includes a transition metal oxide. That is, the positive electrode plate 121 includes a transition metal oxide. The positive electrode active material may include, for example, at least one selected from the group consisting of LiCoO2, LiNiO2, LiMnO2, LiMn2O4, Li(NiCoMn)O2, and Li(NiCoAl)O2.

[0075] The positive electrode active material can also be represented by the following formula, for example.

[0076] Li 1-a Ni x Co y Mn1-x-y O2.

[0077] In the above formula, "a" satisfies the relationship of "-0.3≤a≤0.3". "x" satisfies the relationship of "0≤x≤1". "x" may also satisfy the relationship of "0.5≤x≤0.9", for example. "y" satisfies the relationship of "0≤y≤1". "y" may also satisfy the relationship of "0.1≤y≤0.5", for example.

[0078] (Negative plate)

[0079] The negative electrode plate 122 is a strip-shaped sheet. The negative electrode plate 122 is wound around the flat portion Fp (see Figure 5 The negative electrode plate 122 may also be wound up in the second curved portion Rp2 immediately before the flat portion Fp. However, the winding end position of the negative electrode plate 122 is closer to the terminal end (adhesive tape 126) of the stack 125 than the winding end position of the positive electrode plate 121.

[0080] For example, the greater the dynamic friction coefficient between the negative electrode plate 122 and the separator 123 is, the more reduction in winding slack can be expected. The dynamic friction coefficient between the negative electrode plate 122 and the separator 123 may be, for example, 0.40 to 0.80.

[0081] The negative electrode plate 122 includes a negative electrode substrate 122c, a negative electrode active material layer 122a, and a negative electrode active material layer 122b. The negative electrode active material layer 122a and the negative electrode active material layer 122b are respectively arranged on the surface of the negative electrode substrate 122c. The negative electrode active material layer 122a (inner side) and the negative electrode active material layer 122b (outer side) are in a front-back relationship (refer to Figure 6 ).

[0082] The negative electrode substrate 122c may have a thickness of, for example, 5 to 30 μm. The negative electrode substrate 122c may be, for example, Cu foil or the like. The negative electrode substrate 122c includes exposed portions (a first exposed portion Ep1 and a second exposed portion Ep2) on both sides in the width direction (X-axis direction). Each of the first exposed portion Ep1 and the second exposed portion Ep2 protrudes outward compared to the end faces of the negative electrode active material layers 122a and 122b. In addition, the "end faces of the negative electrode active material layers 122a and 122b" may be inclined or not smooth.

[0083] The negative electrode collector plate 113b is joined to the first exposed portion Ep1. Therefore, the length of the first exposed portion Ep1 can be, for example, several mm to several cm. "Length" refers to the dimension in the X-axis direction. The first exposed portion Ep1 can have a sufficient length. By joining the negative electrode collector plate 113b, the gaps between the negative electrode substrates 122c can be closed. Moreover, by joining the negative electrode collector plate 113b, the negative electrode plate 122 can be partially fixed. Therefore, it can be considered that it is difficult to generate Li on the first exposed portion Ep1 side. + Diffusion to non-opposed parts.

[0084] In the X-axis direction, the second exposed portion Ep2 is located on the opposite side of the first exposed portion Ep1. The second exposed portion Ep2 side is not substantially fixed. It can be considered that when the second exposed portion Ep2 is not provided, Li + Diffusion to non-opposed parts.

[0085] The second exposed portion Ep2 in this embodiment can physically prevent Li + The length of the second exposed portion Ep2 may be, for example, greater than the thickness of the negative electrode active material layers 122a and 122b. By making the second exposed portion Ep2 longer than the thickness of the negative electrode active material layers 122a and 122b, it is expected that Li + Diffusion to non-opposed parts.

[0086] It can be considered that the longer the second exposed portion Ep2 is, the more it can hinder Li + Diffusion to the non-opposing portion. The length of the second exposed portion Ep2 may be, for example, greater than 0.8 mm. However, if the second exposed portion Ep2 is too long, for example, it may impose restrictions on the joining position of the positive electrode collector plate 113a. The length of the second exposed portion Ep2 may be, for example, less than 2.0 mm.

[0087] The negative electrode active material layers 122a and 122b may have a thickness of 10 to 200 μm, for example. The negative electrode active material layers 122a and 122b contain negative electrode active materials. The negative electrode active material layers 122a and 122b may further contain a binder, etc. For example, the negative electrode active material layers 122a and 122b may be substantially composed of 0.1 to 10% of a binder and the remainder of the negative electrode active material by mass fraction. The binder may contain any component. The binder may also contain, for example, at least one selected from the group consisting of carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR).

[0088] The negative electrode active material may contain any component. For example, the negative electrode active material may contain graphite, soft carbon, hard carbon, silicon, silicon oxide, silicon-based alloy, tin, tin oxide, tin-based alloy, and Li4Ti5O 12At least one selected from the group consisting of.

[0089] 《Precipitation of transition metals》

[0090] By hindering Li + The diffusion to the non-opposing portion can reduce the amount of transition metal precipitated on the negative electrode plate 122. The amount of transition metal precipitated can be quantified by XRF (X-ray fluorescence).

[0091] The range from the winding end position of the negative electrode plate 122 to the position of one turn of the negative electrode plate 122 is cut out as a sample piece from the outermost circumference of the electrode body 120. The sample piece may have a plane size of, for example, 110 mm×100 mm. The XRF measurement conditions may be as follows.

[0092] Scan size: 4mm×7mm

[0093] Image size: 80×140 pixels

[0094] The size of a point: 50μm / pixel

[0095] Measurement time for one point: 20.00ms

[0096] Added frames: 3

[0097] Mapping time: 13.4min

[0098] Tube voltage: 45kV

[0099] Tube current: 900μA

[0100] Filter: OFF

[0101] Collimator: No

[0102] When multiple transition metals are detected, the precipitation amount means the total amount of each transition metal. The precipitation amount may be, for example, less than 100 cps. The precipitation amount may be, for example, 1 to 90 cps or 83 to 90 cps.

[0103] 《Spacers》

[0104] The spacer 123 is a porous sheet. The spacer 123 is electrically insulating. The spacer 123 may include, for example, a polyolefin resin, etc. The spacer 123 may be substantially composed of a polyolefin resin, for example. The polyolefin resin may include, for example, at least one selected from the group consisting of polyethylene (PE) and polypropylene (PP). The spacer 123 may have, for example, a single-layer structure. The spacer 123 may be substantially composed of a PE layer, for example. The spacer 123 may have, for example, a multi-layer structure. The spacer 123 may be formed by stacking a PP layer, a PE layer, and a PP layer in sequence. It is also possible that, for example, a heat-resistant layer (ceramic particle layer) is formed on the surface of the spacer 123.

[0105] Electrolyte

[0106] At least a portion of the electrolyte is impregnated in the electrode body 120 . A portion of the electrolyte may be stored in the bottom 111 a of the container 111 .

[0107] The electrolyte contains a solvent and a supporting electrolyte. The solvent is aprotic. The solvent may contain any component. For example, the solvent may also contain at least one selected from the group consisting of vinylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC). The supporting electrolyte is dissolved in the solvent. The supporting electrolyte may also contain LiPF6, etc. The supporting electrolyte may also have a molar concentration of 0.5 to 2.0 mol / L, for example. In addition to the solvent and the supporting electrolyte, the electrolyte may further contain any additives.

[0108] Example

[0109] Hereinafter, an embodiment of the present technology (also described as "the present embodiment" in this specification) will be described. However, the following description does not limit the scope of the present technology.

[0110] <Manufacturing of non-aqueous electrolyte secondary batteries>

[0111] Test cells No. 1 to 7 were manufactured (see Table 1 below). In the manufacturing process of test cells No. 1 to 6, the injection process and the sealing process were carried out in a dry air atmosphere (oxygen partial pressure of 160 mmHg). In the manufacturing process of test cell No. 7, the injection process and the sealing process were carried out in a nitrogen atmosphere (oxygen concentration of 1 ppm or less).

[0112] <Evaluation>

[0113] The amount of transition metal precipitation on the negative electrode plate was measured by XRF. The positive electrode active material in this embodiment contains Li(NiCoMn)O2. Therefore, three transition metals (Ni, Co, Mn) were detected from the negative electrode plate. The "amount of transition metal precipitation" in the following Table 1 is the total amount of Ni, Co and Mn.

[0114] After manufacturing the test battery, the rate of occurrence of voltage failure was determined. The rate of occurrence of voltage failure was determined by dividing the number of failures by the number of manufactured batteries.

[0115]

[0116] <Results>

[0117] In Table 1 above, it can be seen that the occurrence rate of voltage failure increases as the amount of transition metal deposition increases.

[0118] For the test cells (No. 1 to 3) in which the winding end position of the positive electrode plate was located in the second curved portion, the amount of transition metal precipitation tended to be smaller than that of the test cells (No. 4 to 6) in which the winding end position of the positive electrode plate was located in the flat portion. This is believed to be because winding slack is less likely to occur.

[0119] The amount of transition metal precipitation tends to decrease when the length of the second exposed portion exceeds 0 mm. In the test cells (No. 1 and 2) where the winding end position of the positive electrode plate is located within the second bend and the length of the second exposed portion exceeds 0 mm, the amount of transition metal precipitation decreases significantly.

[0120] <Note>

[0121] The present technology also provides a method for manufacturing a non-aqueous electrolyte secondary battery.

[0122] [5] A method for producing a non-aqueous electrolyte secondary battery comprises the following (a) to (d).

[0123] (a) The electrode assembly described in the above [1] is assembled.

[0124] (b) The electrode assembly is housed in the outer casing.

[0125] (c) Injecting electrolyte into the outer package under an oxygen-containing atmosphere.

[0126] (d) The outer casing is sealed in an oxygen-containing atmosphere to produce a nonaqueous electrolyte secondary battery.

[0127] [6] The oxygen-containing atmosphere may be, for example, a dry air atmosphere. The dry air atmosphere may have a dew point temperature of, for example, -80 to 0°C or -70 to -20°C.

[0128] The present embodiment and the present example are illustrative in all respects. The present embodiment and the present example are not restrictive. The scope of the present technology includes all changes within the meaning and scope equivalent to the claims. For example, it is also intended from the beginning to include the following scheme: extracting any structure from the present embodiment and the present example and combining them arbitrarily.

Claims

1. A non-aqueous electrolyte secondary battery, characterized in that: The non-aqueous electrolyte secondary battery comprises an outer casing, an electrode body and an electrolyte solution. The outer casing contains the electrode body and the electrolyte solution. The outer package includes a container and an external terminal, The container comprises a bottom, a top and side walls, The side wall connects the bottom with the top, The external terminal is mounted on the top. The electrode body includes a laminated body, The stacked body comprises a positive electrode plate, a separator and a negative electrode plate, The positive electrode plate, the separator, and the negative electrode plate each have a strip-shaped planar shape. The positive electrode plate, the separator, and the negative electrode plate are stacked. The separator separates the positive electrode plate from the negative electrode plate. The stacked body is wound into a spiral shape, In a cross section of the stacked body orthogonal to the winding axis, the electrode body includes a first curved portion, a flat portion, and a second curved portion. In the first curved portion and the second curved portion, the stacked body is curved. In the flat portion, the laminate is flat, In a direction connecting the bottom and the top of the container, the second curved portion is closer to the bottom than the first curved portion, The flat portion connects the first curved portion and the second curved portion. The positive electrode plate is wound up in the second bent portion. The winding end position of the positive electrode plate exceeds the apex of the second curved portion, The positive electrode plate comprises a transition metal oxide, The negative electrode plate comprises a negative electrode substrate and a negative electrode active material layer. The negative electrode active material layer is disposed on the surface of the negative electrode substrate. The negative electrode substrate includes a first exposed portion and a second exposed portion on both sides in the width direction of the negative electrode plate. The first exposed portion and the second exposed portion each protrude outward from an end surface of the negative electrode active material layer. The first exposed portion is joined to and fixed to the negative electrode collector plate. The second exposed portion is located on the opposite side of the first exposed portion and protrudes outward from an end surface of the negative electrode active material layer disposed on any surface of the negative electrode substrate in the width direction of the negative electrode plate. The length of the second exposed portion is 2.0 mm or less.

2. The nonaqueous electrolyte secondary battery according to claim 1, characterized in that: The length of the second exposed portion is longer than the thickness of the negative electrode active material layer.

3. The non-aqueous electrolyte secondary battery according to claim 2, characterized in that: The length of the second exposed portion is greater than or equal to 0.8 mm.

4. The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, characterized in that The container is sealed, The gas in the container has an oxygen concentration of 1% or more and 21% or less by mole fraction.

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