Non-aqueous electrolyte secondary battery

Abstract

The present technology provides a nonaqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery includes an exterior body, an electrode body, and an electrolyte solution. In a cross section of the laminate orthogonal to a winding axis, the electrode body has a profile line of a rounded rectangular shape. The profile line is composed of a first arc-shaped portion, a straight line portion, and a second arc-shaped portion. The profile line has a height ratio (R1=H0 / H1) of 1.20-1.35. H0 represents a distance between two points farthest apart on the profile line. H1 represents an average length of two line segments. A separator includes a first main surface and a second main surface. The first main surface is in contact with a negative electrode plate. A first dynamic friction coefficient between the first main surface and the negative electrode plate is 0.52-0.66.

Description

Technical Field

[0001] This technology relates to non-aqueous electrolyte secondary batteries. Background Technology

[0002] International Publication No. 2007 / 037145 discloses a porous layer with excellent permeability to non-aqueous electrolyte disposed between the negative electrode and the spacer. Summary of the Invention

[0003] Generally, a non-aqueous electrolyte secondary battery (hereinafter referred to as a "battery") includes an electrode body. The electrode body comprises a stack. The stack is formed by stacking a positive electrode plate, a spacer, and a negative electrode plate. The electrode body can be of a wound type. That is, the electrode body can be formed by winding the stack into a spiral shape. Wound electrode bodies are sometimes also formed into a flat shape. By forming the electrode body into a flat shape, the electrode body includes a flat portion and a curved portion. The stack is flat in the flat portion. The stack is curved in the curved portion.

[0004] The electrolyte is immersed in the electrode body. The electrolyte may permeate into the voids within the electrode body (e.g., the gaps between electrodes). The electrode body may expand during charging and contract during discharging. This can be considered primarily due to the expansion of the negative electrode plate during charging and its contraction during discharging. During charging, the voids within the electrode body may decrease as the electrode body expands. Due to the reduction in voids, electrolyte may drain from the electrode body. During discharging, the voids within the electrode body may increase as the electrode body contracts. Due to the increase in voids, electrolyte around the electrode body may be absorbed by the electrode body. However, there is a tendency for the amount of electrolyte absorbed during discharging to be less than the amount drained during charging. Therefore, if the battery is used for a long period, the electrolyte may deplete within the electrode body. Due to electrolyte depletion, there is a possibility of lithium (Li) deposition, for example.

[0005] The purpose of this technology is to reduce the precipitation of Li associated with long-term use.

[0006] The structure and effects of this technology are described below. However, the mechanism of action in this specification is speculative and does not limit the scope of this technology.

[0007] 1. A non-aqueous electrolyte secondary battery comprises an outer casing, electrode bodies, and an electrolyte. The outer casing houses the electrode bodies and the electrolyte. The electrode bodies comprise a stack. The stack comprises a positive electrode plate, a spacer, and a negative electrode plate. The spacer separates the positive and negative electrode plates. The stack is wound into a vortex shape.

[0008] In a cross-section orthogonal to the winding axis of the laminate, the electrode body has a rounded rectangular outline. The outline consists of a first arcuate portion, a straight portion, and a second arcuate portion. The straight portion consists of two line segments. The straight portion connects the first arcuate portion and the second arcuate portion. The outline has a height ratio of 1.20 to 1.35.

[0009] The height ratio is determined by the following formula (α):

[0010] R1 = H0 / H1…(α).

[0011] In the above equation (α), R1 represents the height ratio. H0 represents the distance between the two furthest points on the contour line. H1 represents the average length of the two line segments.

[0012] The spacer includes a first main surface and a second main surface. The first main surface is in contact with the negative electrode plate. The first coefficient of kinetic friction between the first main surface and the negative electrode plate is 0.52 to 0.66.

[0013] In this technology, by keeping the "height ratio (R1)" and the "first coefficient of kinetic friction" within a specific range, the precipitation of Li associated with long-term use can be reduced.

[0014] The electrode body is wound. The electrode body is flat. In a cross-section orthogonal to the winding axis, the outline of the electrode body is a rounded rectangle. The line segment connecting the two furthest points on the outline is also referred to as the major axis. The direction parallel to the major axis is also referred to as the "height direction." The dimension in the height direction is also referred to as the "height dimension." Furthermore, the height direction is merely a designation. The relationship between the height direction and the vertical direction is arbitrary.

[0015] The length of the major axis of the contour line is the "height dimension (H0) of the electrode body". The straight portion of the contour line consists of two line segments. The straight portion is the contour line of the flat portion of the electrode body. The part sandwiched between the two line segments corresponds to the flat portion. The average length of the two line segments is the "height dimension (H1) of the flat portion". The height dimension (H0) of the electrode body is the sum of the height dimension (H1) of the flat portion and the height dimension (H2) of the curved portion (see reference). Figure 4 The larger the height ratio (R1 = H0 / H1), the smaller the proportion of flat parts in the electrode body. In other words, the larger the height ratio, the larger the proportion of curved parts in the electrode body.

[0016] Compared to the flat portion, the gap between electrodes tends to be wider in the curved portion. During charging, a higher pressure is applied to the electrolyte in the flat portion. This can be attributed to the narrower gap between the electrodes. A portion of the electrolyte squeezed out from the flat portion is forced into the curved portion where the pressure is relatively lower. By making the height ratio larger (i.e., by making the curved portion larger), there is a tendency to increase the amount of electrolyte that can accumulate in the curved portion during charging (hereinafter also referred to as "accumulation amount"). By having a moderate accumulation amount in the curved portion, it is possible to make the curved portion have a buffering function during charging. That is, by temporarily retaining the electrolyte squeezed out from the flat portion in the curved portion, it is expected to reduce the amount of electrolyte discharged from the electrode body. As a result, it is expected to alleviate the depletion of electrolyte in the electrode body. However, if the accumulation amount is too large, it may promote the precipitation of Li, etc. That is, since the electrolyte tends to remain in the curved portion, the distribution of electrolyte in the electrode body may become uneven. As a result, the electrode reaction may become uneven, and Li may be deposited locally. When the height ratio is 1.20 to 1.35, the curved portion can have a moderate accumulation.

[0017] The first kinetic friction coefficient can be considered to reflect the permeability of the electrolyte between the spacer and the negative electrode plate. The spacer is porous. The surface of the spacer may have minute irregularities. The surface of the negative electrode plate may also have minute irregularities. It can be assumed that due to the increased surface irregularities of the negative electrode plate, the frictional force between the spacer and the negative electrode plate increases, and the first kinetic friction coefficient increases. It can be assumed that due to the increased surface irregularities of the negative electrode plate, a gap caused by the irregularities will form between the spacer and the negative electrode plate. This gap may become a permeation path for the electrolyte. There is a tendency that the larger the first kinetic friction coefficient, the higher the permeability of the electrolyte between the spacer and the negative electrode plate. By increasing the permeability of the electrolyte between the spacer and the negative electrode plate, it can be expected that the electrolyte will easily return to the interior of the electrode body when it absorbs electrolyte. As a result, it can be expected to reduce Li deposition. This can be assumed that this is because it is difficult for the electrolyte distribution within the electrode body to become uneven. However, excessively high electrolyte permeability may actually promote Li deposition. That is, due to excessive electrolyte permeability, there is a possibility that the electrolyte may easily flow out of the electrode body. This outflow may accelerate electrolyte depletion. When the first coefficient of kinetic friction is 0.52 to 0.66, the electrolyte can exhibit moderate permeability between the spacer and the negative electrode plate.

[0018] Through the synergy of the above effects, it is expected that the precipitation of Li associated with long-term use can be reduced in this technology.

[0019] 2. The negative electrode plate includes a negative electrode active material layer. The negative electrode active material layer is in contact with the first main surface. The negative electrode active material layer contains negative electrode active material particles. The negative electrode active material particles may also have a median sphericity of 0.60 to 0.85.

[0020] A higher median roundness indicates that the negative electrode active material particles are closer to a sphere. The undulations on the surface of the negative electrode plate correspond to the grooves between adjacent particles. By making the negative electrode active material particles moderately round, there is a tendency for the grooves to become deeper. Conversely, when the median roundness is low, the negative electrode active material particles tend to be arranged horizontally in the planar direction of the negative electrode plate during compression molding of the negative electrode plate or electrode body. "Planar direction" refers to the direction orthogonal to the thickness direction of the negative electrode plate. If the negative electrode active material particles are horizontally arranged in the planar direction, there is a tendency for the grooves between adjacent particles to become shallower. When the median roundness is between 0.60 and 0.85, moderate undulations can be formed on the surface of the negative electrode plate. By making the surface of the negative electrode plate moderately undulating, a first coefficient of kinetic friction of 0.52 to 0.66 can be easily obtained.

[0021] 3. The negative electrode active material layer has a strip-shaped planar shape. Alternatively, the electrode body may have an aspect ratio of 2.0 to 2.5.

[0022] The aspect ratio is determined by the following formula (β):

[0023] R2 = W / H1…(β).

[0024] In the above formula (β), R2 represents the aspect ratio. W represents the length of the negative electrode active material layer in the width direction. H1 represents the average length of the two line segments.

[0025] The width direction of the negative electrode active material layer corresponds to the width direction of the electrode body. The width direction of the electrode body can be parallel to the winding shaft. The electrolyte can be discharged from the electrode body from both ends in the width direction. These two ends in the width direction can be considered as the electrolyte outlets.

[0026] The length of the negative electrode active material layer in the width direction is called the "width dimension (W) of the flat portion". In the outline of the electrode body, the length of the straight portion (the average length of the two line segments) is called the "height dimension (H1) of the flat portion". Therefore, the aspect ratio (R2) can also be considered as the aspect ratio of the flat portion.

[0027] A larger aspect ratio (R²) means that, when viewed from the center of the flat section, the center of the flat section is relatively closer to the curved section (buffer) compared to the two ends (outlets) in the width direction. Therefore, the amount of electrolyte moving towards the buffer can be relatively greater than the amount moving towards the outlet. When the aspect ratio (R²) is 2.0 to 2.5, there is a tendency for electrolyte depletion, which is associated with long-term use, to be reduced. This can be attributed to the difficulty in electrolyte flowing out of the electrode body.

[0028] 4. The second main surface is in contact with the positive electrode plate. Alternatively, the second coefficient of kinetic friction between the second main surface and the positive electrode plate can be 0.70 to 0.85.

[0029] The second coefficient of kinetic friction can be considered to reflect the surface roughness of the positive electrode plate. A larger second coefficient of kinetic friction indicates greater surface roughness of the positive electrode plate. By increasing the surface roughness of the positive electrode plate, a gap can be formed between the positive electrode plate and the spacer. This gap can also serve as a penetration path for the electrolyte. When the second coefficient of kinetic friction is between 0.70 and 0.85, a smaller initial resistance can be expected. Furthermore, a smaller rate of increase in resistance after charge-discharge cycles can also be expected. This can be attributed to the ability to distribute appropriate amounts of electrolyte separately onto the surfaces of the positive and negative electrodes.

[0030] 5. Alternatively, the electrolyte may contain methyl propionate.

[0031] Electrolytes containing methyl propionate (MP) can have low viscosity. By making the electrolyte low in viscosity, the distribution of the electrolyte within the electrode body tends to become more uniform. This can be attributed to improved electrolyte penetration. Furthermore, by including MP in the electrolyte, improvements in initial resistance and the rate of increase in resistance after charge-discharge cycles can be expected.

[0032] The above and other objects, features, aspects and advantages of this technology will become clear from the following detailed description relating to this technology, which is understood in conjunction with the accompanying drawings. Attached Figure Description

[0033] Figure 1 This is a schematic diagram illustrating an example of the structure of a non-aqueous electrolyte secondary battery according to this embodiment.

[0034] Figure 2 This is a schematic diagram illustrating an example of the structure of the electrode body in this embodiment.

[0035] Figure 3 This is a schematic cross-sectional view showing an example of the structure of the electrode body in this embodiment.

[0036] Figure 4 This is a schematic diagram showing an example of the outline of the electrode body in this embodiment.

[0037] Figure 5 This is a schematic diagram illustrating the method for determining the coefficient of kinetic friction.

[0038] Figure 6 This is a chart showing an example of the measurement results for the first coefficient of kinetic friction. Detailed Implementation

[0039] Hereinafter, embodiments of the present technology (also referred to as "this embodiment" in this specification) will be described. However, the following description does not limit the scope of the present technology. For example, the scope of the present technology is not limited to all aspects in which the effects can be achieved, as the description relates to the effects described in this specification is not intended to limit the scope of the present technology.

[0040] <Definitions of terms, etc.>

[0041] In this specification, expressions such as "comprise," "include," "have," and their variations (e.g., "be composed of," "encompass," "involve," "contain," "carry," "support," "hold," etc.) are open-ended. Open-ended expressions may include additional elements in addition to essential elements, or they may not include additional elements. Expressions such as "consist of" are closed-ended. Expressions such as "consist essentially of" are semi-closed-ended. Semi-closed-ended expressions may further include additional elements in addition to essential elements, without hindering the purpose of this technology. For example, elements commonly conceived in the art to which this technology pertains (e.g., unavoidable impurities) may also be included as additional elements.

[0042] In this specification, expressions such as "may" and "can" are not used in an obligatory sense, meaning "must," but rather in an permissive sense, meaning "possibility of having."

[0043] In this specification, unless otherwise specified, elements expressed in the singular form (a, an, the) also include the plural form. For example, "particle" can mean not only "a single particle" but also "an aggregate of particles (powder, granules, granules)".

[0044] In this specification, unless otherwise specified, numerical ranges such as "1μm to 10μm" and "1 to 10μm" include both upper and lower limits. That is, "1μm to 10μm" and "1 to 10μm" both represent a numerical range "above 1μm and below 10μm". Alternatively, new upper and lower limits can be set from any value selected within the numerical range. For example, a new numerical range can be set by arbitrarily combining values ​​within the range with values ​​described in other parts of this specification, tables, figures, etc.

[0045] In this specification, all numerical values ​​are described using the term "approximately." "Approximately" may refer to, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​are approximate values ​​that may vary depending on the application of this technology. All numerical values ​​are displayed with significant figures. All measured values ​​may be rounded based on the number of significant figures. All numerical values ​​may include errors associated with the detection limits of the measuring device.

[0046] Geometric terms used in this specification (such as "parallel," "perpendicular," "orthogonal," etc.) should not be interpreted in a strict sense. For example, "parallel" may deviate slightly from the strict meaning of "parallel." Geometric terms used in this specification may include tolerances and errors in design, operation, manufacturing, etc. Dimensional relationships in the drawings may sometimes differ from actual dimensional relationships. To aid in understanding this technology, dimensional relationships (length, width, thickness, etc.) in the drawings may have been altered. Furthermore, some structural elements may have been omitted.

[0047] In this specification, when a compound is expressed by a stoichiometric formula such as "LiCoO2", the stoichiometric formula is merely a representative example. The composition ratio can 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 can contain Li, Co, and O in any composition ratio. Furthermore, doping or substitution based on trace elements is also permissible.

[0048] <Non-aqueous electrolyte secondary battery>

[0049] Figure 1 This is a schematic diagram illustrating an example of the structure of a non-aqueous electrolyte secondary battery according to this embodiment.

[0050] The battery 100 can be used for any purpose. For example, it can be used as a main power source or auxiliary power source in electric vehicles. Alternatively, multiple batteries 100 can be connected to form a battery module or battery pack. The battery 100 can also have a rated capacity of, for example, 1 to 200 Ah.

[0051] The battery 100 includes an outer casing 90. The outer casing 90 houses the electrode body 50 and the electrolyte (not shown). That is, the battery 100 includes the electrode body 50 and the electrolyte. For example, a portion of the electrolyte may be deposited at the bottom of the outer casing 90. A portion of the electrode body 50 may also be immersed in the electrolyte. The electrode body 50 may also be held, for example, in a pouch-like support (not shown).

[0052] The outer casing 90 can have any shape. For example, the outer casing 90 can be a shell made of aluminum (Al) alloy. For example, the outer casing 90 can also be a bag made of Al laminate.

[0053] The outer casing 90 may also be square (flat cuboid shape). The outer casing 90 may also include a sealing plate 91 and an outer container 92. The sealing plate 91 blocks the opening of the outer container 92. For example, the sealing plate 91 and the outer container 92 may be joined by laser processing or the like.

[0054] Alternatively, a positive terminal 81 and a negative terminal 82 may be provided on the sealing plate 91. Alternatively, the sealing plate 91 may also be provided with an injection port (not shown), a gas vent valve (not shown), etc. Electrolyte can be injected into the interior of the outer casing 90 through the injection port. The injection port can be sealed, for example, by a sealing plug. The positive current collector 71 connects the positive terminal 81 to the electrode body 50. The positive current collector 71 may be, for example, an Al plate. The negative current collector 72 connects the negative terminal 82 to the electrode body 50. The negative current collector 72 may be, for example, a copper (Cu) plate.

[0055] Figure 2 This is a schematic diagram illustrating an example of the structure of the electrode body in this embodiment.

[0056] Electrode body 50 includes a laminate 40. Electrode body 50 may also be substantially composed of a laminate 40. Laminate 40 includes a positive electrode plate 10, a spacer 30, and a negative electrode plate 20. At least a portion of the spacer 30 is sandwiched between the positive electrode plate 10 and the negative electrode plate 20. The spacer 30 separates the positive electrode plate 10 and the negative electrode plate 20. Laminate 40 may also include a single spacer 30. Laminate 40 may also include two spacers 30. For example, the positive electrode plate 10 may be held by two spacers 30. For example, the negative electrode plate 20 may also be held by two spacers 30. Laminate 40 may also be formed, for example, by sequentially stacking spacers 30 (first spacer), negative electrode plate 20, spacers 30 (second spacer), and positive electrode plate 10. Each of the positive electrode plate 10, negative electrode plate 20, and spacer 30 may, for example, have a strip-shaped planar shape.

[0057] The electrode body 50 is of the wound type. That is, the laminate 40 is wound into a spiral shape. For example, the laminate 40 can also be wound into a cylindrical core to form a cylindrical wound body. The cylindrical wound body can also be compressed radially to form a flat electrode body 50. For example, the height ratio (R1) described later can be adjusted according to the diameter of the core, etc. For example, there is a tendency that the smaller the diameter of the core, the larger the height ratio (R1).

[0058] Figure 3 This is a schematic cross-sectional view showing an example of the structure of the electrode body in this embodiment.

[0059] exist Figure 3 The diagram shows a cross-section orthogonal to the winding axis. The electrode body 50 includes a flat portion 51 and a bent portion 52. In the flat portion 51, the laminate 40 is flat. In the bent portion 52, the laminate 40 is bent. The flat portion 51 is held by two bent portions 52. The flat portion 51 connects the two bent portions 52. Compared to the flat portion 51, the bent portion 52 tends to have a wider gap between the electrodes.

[0060] The flat portion 51 may be the part pressed by the molding die during molding. The curved portion 52 may be the part that does not contact the molding die during molding. At the outermost periphery of the electrode body 50, the thickness of the spacer 30 at the flat portion 51 may be thinner than the thickness of the spacer 30 at the curved portion 52. For example, the boundary between the flat portion 51 and the curved portion 52 can be determined based on the variation in the thickness of the outermost spacer 30.

[0061] (Number of layers)

[0062] The number of layers of each component is expressed in the radial direction of the electrode body 50 (e.g., Figure 3The number of times a straight line traversing the electrode body 50 in the Y-axis direction intersects the target component. The positive electrode plate 10 may, for example, have 60 to 80 layers. The negative electrode plate 20 may, for example, have 60 to 80 layers. The spacer 30 may, for example, have 120 to 160 layers.

[0063] (Height ratio)

[0064] Figure 4 This is a schematic diagram showing an example of the outline of the electrode body in this embodiment.

[0065] exist Figure 4 It shows Figure 3 The outline of the electrode body 50. The electrode body 50 has a rectangular outline L0 with rounded corners. The outline L0 is composed of a first arc-shaped portion L1, a straight portion L3 and a second arc-shaped portion L2.

[0066] Each of the first arc-shaped portion L1 and the second arc-shaped portion L2 is the outline of the curved portion 52. Each of the first arc-shaped portion L1 and the second arc-shaped portion L2 is depicted as an arc. Each of the first arc-shaped portion L1 and the second arc-shaped portion L2 can be a circular arc, an elliptical arc, a semi-circular arc, or a semi-elliptical arc.

[0067] The straight section L3 is the outline of the flat section 51. The straight section L3 is composed of two line segments. Each of the two line segments connects the first arc-shaped section L1 and the second arc-shaped section L2.

[0068] The contour line L0 has a height ratio (R1) of 1.20 to 1.35 (refer to formula (α) above). The height ratio (R1) is the ratio of the length of the major axis (H0) to the average length (H1) of the two line segments. The average length (H1) is the arithmetic mean of the lengths of the two line segments constituting the straight section L3. The length of the major axis (H0) is the distance between the two farthest points on the contour line L0. That is, the length of the major axis (H0) is the distance between the front end of the first arc-shaped section L1 and the front end of the second arc-shaped section L2. The front end refers to the most prominent part in the height direction (Z-axis direction). The length of each part can be measured, for example, by a vernier caliper. For example, a digital vernier caliper (constant pressure type) manufactured by Mitutoyo or an equivalent product can also be used. The length of each part can also be measured, for example, by an image dimension measuring device.

[0069] When the height ratio (R1) is 1.20 to 1.35, it is expected that the precipitation of Li associated with long-term use can be reduced. This can be attributed to the fact that the curved portion 52 can function as a buffer for the electrolyte. The profile L0 can, for example, have a height ratio (R1) of 1.21 to 1.30, 1.22 to 1.28, or 1.22 to 1.26. The profile L0 can, for example, have a height ratio (R1) of 1.20 to 1.24 or 1.24 to 1.35.

[0070] Spacer

[0071] The spacer 30 is a porous sheet. The spacer 30 may, for example, have a thickness of 10–30 μm. The spacer 30 may, for example, have an air permeability of 100–400 s / 100 mL. In this specification, “air permeability” refers to “air resistance” as defined in JIS P 8117:2009. Air permeability is determined using the Göttingen test method.

[0072] The spacer 30 is electrically insulating. The spacer 30 may, for example, comprise a porous resin layer. The spacer 30 may, for example, be substantially composed of a porous resin layer. The porous resin layer may, for example, comprise polyolefins. The porous resin layer may, for example, comprise at least one selected from the group consisting of polyethylene (PE) and polypropylene (PP). The spacer 30 may, for example, have a single-layer structure. The spacer 30 may, for example, be substantially composed of a PE layer. The spacer 30 may, for example, have a multi-layer structure. The spacer 30 may, for example, be formed by sequentially stacking a PP layer, a PE layer, and another PP layer. Alternatively, the spacer 30 may also comprise a porous ceramic layer in addition to the porous resin layer. For example, the porous ceramic layer may substantially consist of 1 to 10% binder and the remainder ceramic particles by mass fraction. The porous ceramic layer may, for example, be disposed on the outermost surface of the spacer 30.

[0073] (Coefficient of kinetic friction)

[0074] Figure 5 This is a schematic diagram illustrating the method for determining the coefficient of kinetic friction.

[0075] The spacer 30 includes a first main surface 31 and a second main surface 32. The first main surface 31 is the contact surface that contacts the negative electrode plate 20. In the electrode body 50, the first main surface 31 contacts the negative electrode active material layer 22. The second main surface 32 is the opposite surface of the first main surface 31. The second main surface 32 is the contact surface that contacts the positive electrode plate 10. In the electrode body 50, the second main surface 32 contacts the positive electrode active material layer 12.

[0076] The first dynamic friction coefficient between the first main surface 31 and the negative electrode plate 20 is 0.52 to 0.66. It can be considered that the first dynamic friction coefficient reflects the permeability of the electrolyte between the spacer 30 and the negative electrode plate 20. When the first dynamic friction coefficient is 0.52 to 0.66, the deposition of Li associated with long-term use can be reduced. This can be considered as the electrolyte exhibiting moderate permeability. The first dynamic friction coefficient can, for example, be 0.54 to 0.64, 0.56 to 0.62, or 0.58 to 0.60. The first dynamic friction coefficient can, for example, be 0.52 to 0.56 or 0.56 to 0.66.

[0077] The second dynamic friction coefficient between the second main surface 32 and the positive electrode plate 10 can, for example, be 0.70 to 0.85. It can be considered that the second dynamic friction coefficient reflects the permeability of the electrolyte between the spacer 30 and the positive electrode plate 10. When the second dynamic friction coefficient is 0.70 to 0.85, a smaller initial resistance can be expected. Furthermore, a smaller rate of increase in resistance after charge-discharge cycles can also be expected. The second dynamic friction coefficient can, for example, be 0.72 to 0.83, 0.74 to 0.81, or 0.76 to 0.79. The second dynamic friction coefficient can, for example, be 0.70 to 0.72 or 0.72 to 0.85.

[0078] The coefficient of kinetic friction can be determined by the following steps.

[0079] Prepare battery 100. Completely discharge battery 100. Open battery 100 (outer casing 90) in a drying oven. Recover electrode body 50 from battery 100. By disassembling electrode body 50, recover positive electrode plate 10, spacer 30, and negative electrode plate 20. Cut a first sample sheet from negative electrode plate 20. The first sample sheet can be cut from the portion of negative electrode active material layer 22 that has not been peeled from negative electrode substrate 21. For example, the first sample sheet can be cut from the portion corresponding to the bend 52.

[0080] A second sample sheet is cut from the positive electrode plate 10. The second sample sheet is cut from the portion of the positive electrode active material layer 12 that has not been peeled off from the positive electrode substrate 11. For example, the second sample sheet can be cut from the portion corresponding to the bend 52.

[0081] The third sample piece is cut from the spacer 30. The third sample piece is cut from the portion of the fine pore that is not filled with positive and negative active material particles. For example, the third sample piece can be cut from the portion corresponding to the bend 52.

[0082] The electrolyte adhering to each sample piece was rinsed with dimethyl carbonate (DMC). Each sample piece was then dried in a drying oven. After drying, each sample piece was removed from the drying oven.

[0083] Prepare the experimental setup (refer to) Figure 5 The testing apparatus is based on JIS K 7125:1999. The third sample piece (spacer 30) is cut to a planar dimension of 80mm × 200mm, for example. The object material 202 is fixed to the surface of the test bench 201. The object material 202 can be fixed, for example, by adhesive tape. The object material 202 is the first sample piece (negative electrode plate 20). The object material 202 has a sufficiently large planar dimension compared to the third sample piece. The third sample piece is positioned on the object material 202 in such a way that it contacts the first main surface 31. A sliding piece 203 is positioned on the third sample piece. At this time, the first sample piece (negative electrode plate 20) and the third sample piece (spacer 30) are positioned opposite each other so that at least the portion cut from the bending portion 52 is pressed. The sliding piece 203 has a planar dimension of 63mm × 63mm. The bottom surface of the sliding piece 203 (the contact surface with the third sample piece) is covered, for example, with felt. The mass of the sliding plate 203 is 200g ± 2g. The third sample piece is pulled parallel to the friction surface. The test speed is 100mm / min ± 10mm / min. The test force required to move the third sample piece at the test speed is measured. The test force can be measured using a force sensor (not shown). Furthermore, the dimensions of the first to third sample pieces in this specification are examples. The dimensions of the first to third sample pieces can be appropriately set based on the dimensions of the electrode plate, spacer 30, electrode body 50, bending portion 52, etc. It can be considered that by making the first to third sample pieces at least larger than the sliding plate 203, the coefficient of friction can be measured.

[0084] Figure 6 This is a chart showing an example of the measurement results for the first coefficient of kinetic friction.

[0085] The test force is plotted relative to the displacement of the third specimen. Initially, the test force increases linearly. It then reaches its maximum value and gradually decreases afterward.

[0086] The coefficient of kinetic friction is obtained by the following equation (γ):

[0087] μ D =F D / F p …(γ).

[0088] In the above equation (γ), μ D F represents the coefficient of kinetic friction. D This represents the average test force over a displacement range of 10–30 mm. F p This represents the normal force (1.96 N) generated due to the mass of the sliding plate 203. The first coefficient of kinetic friction was measured five times. The arithmetic mean of the five measurements was used.

[0089] In addition to changing the object material 202 to the second sample sheet (positive electrode plate 10) and placing the third sample sheet (spacer 30) on the object material 202 in such a way that the object material 202 is in contact with the second main surface 32, the second dynamic friction coefficient can be measured in the same way as the first dynamic friction coefficient.

[0090] Negative electrode plate

[0091] The negative electrode plate 20 includes a negative electrode active material layer 22 (see reference). Figure 2 The negative electrode plate 20 may also be substantially composed of a negative electrode active material layer 22. Alternatively, the negative electrode plate 20 may also include a negative electrode substrate 21. For example, the negative electrode active material layer 22 may be disposed on the surface of the negative electrode substrate 21. The negative electrode active material layer 22 may be disposed only on one side of the negative electrode substrate 21. The negative electrode active material layer 22 may be disposed on both the outer and inner sides of the negative electrode substrate 21. The negative electrode substrate 21 is a conductive sheet. The negative electrode substrate 21 may, for example, comprise pure Cu foil, Cu alloy foil, etc. The negative electrode substrate 21 may, for example, have a thickness of 5–30 μm. Alternatively, in the width direction of the negative electrode plate 20 (… Figure 2 Along the Y-axis direction, the negative electrode substrate 21 is exposed at one end. The negative electrode current collector 72 (see reference 1) can be joined to the exposed portion of the negative electrode substrate 21. Figure 1 ).

[0092] The negative electrode active material layer 22 can have a thickness of either 10–150 μm or 50–100 μm. The negative electrode active material layer 22 can have a thickness of either 0.5–2.0 g / cm³. 3 Its density can also be 1.0–1.5 g / cm³. 3 The density is calculated by dividing the mass of the negative electrode active material layer 22 by its apparent volume. The apparent volume includes the volume of voids within the negative electrode active material layer 22.

[0093] Aspect Ratio

[0094] The negative electrode active material layer 22 has a strip-shaped planar shape (see reference). Figure 2 The electrode body 50 may, for example, have an aspect ratio of 2.0 to 2.5. The aspect ratio (R2) is the ratio of the width dimension (W) of the flat portion 51 to the height dimension (H1) of the flat portion 51 (see reference). Figure 2 , 4The width dimension (W) corresponds to the length in the width direction of the negative electrode active material layer 22. When the aspect ratio (R2) is 2.0 to 2.5, there is a tendency to reduce electrolyte depletion associated with long-term use. The aspect ratio (R2) can be, for example, 2.1 to 2.4 or 2.2 to 2.4. The aspect ratio (R2) can be, for example, 2.0 to 2.1 or 2.1 to 2.5.

[0095] (Negative electrode active material particles)

[0096] The negative electrode active material layer 22 is in contact with the first main surface 31 of the spacer 30. The negative electrode active material layer 22 comprises negative electrode active material particles. The negative electrode active material layer 22 may also be substantially composed of negative electrode active material particles. The negative electrode active material particles may, for example, comprise materials derived from natural graphite, artificial graphite, silicon, silicon oxide, tin, tin oxide, and Li4Ti5O. 12 At least one selected from the group comprising the negative electrode active material particles. The negative electrode active material particles may also be, for example, composite particles. The negative electrode active material particles may also include, for example, substrate particles and a coating. The coating may cover the surface of the substrate particles. The substrate particles may also include, for example, natural graphite. The coating may also include, for example, amorphous carbon.

[0097] The negative electrode active material particles can have any shape. For example, they can be spherical, blocky, or sheet-like. They can also be spherical graphite. The shape of the negative electrode active material particles can be reflected in the surface irregularities of the negative electrode active material layer 22. In the compressed negative electrode active material layer 22, because the negative electrode active material particles have an approximately spherical shape, there is a tendency for the grooves between the particles to deepen. As a result, a larger first coefficient of kinetic friction can be expected. The shape of the negative electrode active material particles in the compressed negative electrode active material layer 22 can be evaluated, for example, by their roundness.

[0098] (Roundness)

[0099] Roundness can be determined through the following steps: A test piece of specified size is cut from the compressed negative electrode plate 20. The test piece is embedded in a resin material. A cross-sectional sample of the negative electrode active material layer 22 is prepared by cutting the embedded test piece. The cross-sectional sample includes a section perpendicular to the surface of the negative electrode active material layer 22. The cross-sectional sample is cleaned (ion milling). After cleaning, a cross-sectional SEM image is obtained by observing the cross-sectional sample using a SEM (scanning electron microscope). Thirty negative electrode active material particles are randomly extracted from the cross-sectional SEM image. The roundness of the 30 negative electrode active material particles is determined. The median of the 30 roundness values ​​is calculated.

[0100] The roundness of each particle is determined by the following formula (δ):

[0101] C = 4πS / P 2 …(δ).

[0102] In the above formula (δ), "C" represents roundness. "S" represents the area of ​​the cross-sectional image of the particle. "P" represents the perimeter (length of the outline) of the cross-sectional image of the particle. The roundness of a perfect circle is 1.

[0103] The median value of roundness can be, for example, 0.60 to 0.85. When the median value of roundness is 0.60 to 0.85, it is expected that a moderate undulation can be formed on the surface of the negative electrode active material layer 22. The median value of roundness can be, for example, 0.65 to 0.80 or 0.70 to 0.80. The median value of roundness can be, for example, 0.60 to 0.76 or 0.76 to 0.85.

[0104] (Particle size)

[0105] The negative electrode active material particles can have a D50 of 5–20 μm, 9.5–15 μm, or 10–12 μm. In this specification, "D50" is defined as the particle size at which the cumulative frequency from the smallest particle size in the volumetric particle size distribution reaches 50%. The volumetric particle size distribution can be determined using a laser diffraction particle size distribution measuring device. For example, a laser diffraction particle size distribution measuring device manufactured by Shimadzu Corporation, such as the "product name SALD-2200," or an equivalent product, can be used.

[0106] The negative electrode active material particles can have an arithmetic mean diameter of, for example, 5–20 μm, 9.5–15 μm, or 10–12 μm. The "arithmetic mean diameter" in this specification can be measured in the compressed negative electrode active material layer 22. The diameters of 30 negative electrode active material particles were measured in the cross-sectional SEM image described above. The diameter of each negative electrode active material particle represents the distance between the two furthest points on the particle's outline. The arithmetic mean of the 30 diameters is considered the arithmetic mean diameter. Depending on the manufacturing method of the negative electrode plate 20, there are cases where a difference exists between D50 and the arithmetic mean diameter, and cases where D50 and the arithmetic mean diameter are substantially the same.

[0107] (Any ingredients)

[0108] Alternatively, the negative electrode active material layer 22 may include conductive materials, binders, etc., in addition to the negative electrode active material particles. For example, the negative electrode active material layer 22 may substantially consist of 0-10% conductive material, 0.1-10% binder, and the remainder negative electrode active material particles by mass fraction. The conductive material may contain any components. For example, the conductive material may include carbon black, carbon nanotubes, etc. The binder may contain any components. For example, the binder may contain at least one selected from the group consisting of carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR).

[0109] Positive electrode plate

[0110] The positive electrode plate 10 may also include, for example, a positive electrode substrate 11 and a positive electrode active material layer 12 (see reference). Figure 2 The positive electrode substrate 11 is a conductive sheet. The positive electrode substrate 11 may, for example, comprise pure Al foil, Al alloy foil, etc. The positive electrode substrate 11 may, for example, have a thickness of 10–30 μm. Alternatively, the thickness may be such that, in the width direction of the positive electrode plate 10 (… Figure 2 Along the Y-axis direction, the positive electrode substrate 11 is exposed at one end. The positive electrode current collector 71 (see reference 1) can be joined to the exposed portion of the positive electrode substrate 11. Figure 1 ).

[0111] The positive electrode active material layer 12 may be disposed on only one side of the positive electrode substrate 11. Alternatively, the positive electrode active material layer 12 may be disposed on both the front and back sides of the positive electrode substrate 11. For example, the positive electrode active material layer 12 may have a thickness of 10 to 150 μm or a thickness of 50 to 100 μm.

[0112] The positive electrode active material layer 12 is in contact with the second main surface 32 of the spacer 30. The positive electrode active material layer 12 contains positive electrode active material particles. The positive electrode active material particles may, for example, have an arithmetic mean diameter of 1 to 30 μm. The positive electrode active material particles may contain any composition. For example, the positive electrode active material particles may also contain at least one selected from the group consisting of LiCoO2, LiNiO2, LiMnO2, LiMn2O4, Li(NiCoMn)O2, Li(NiCoAl)O2, and LiFePO4. For example, in the composition formula such as "Li(NiCoMn)O2", the sum of the composition ratios within parentheses is 1. That is, satisfying "C Ni +C Co +C Mn The relationship is "=1". For example, "C" Ni "" indicates the composition ratio of Ni. The sum of the composition ratios only needs to be 1, and the composition ratio of each component is arbitrary.

[0113] Alternatively, the positive electrode active material layer 12 may include, in addition to the positive electrode active material particles, conductive materials, binders, etc. For example, the positive electrode active material layer 12 may substantially consist of 0.1–10% conductive material, 0.1–10% binder, and the remainder positive electrode active material particles by mass fraction. The conductive material may include, for example, acetylene black. The binder may contain any components. The binder may include, for example, polyvinylidene fluoride (PVdF).

[0114] Electrolyte

[0115] The electrolyte is a liquid electrolyte. The electrolyte comprises a solvent and a supporting electrolyte. The solvent is aprotic. The solvent may contain any components. For example, the solvent may also contain at least one selected from the group consisting of carbonates, carboxylic esters, ethers, and lactones. For example, the solvent may also be substantially composed of carbonates. For example, the solvent may also contain both carbonates and carboxylic esters. The amount of carboxylic ester incorporated may, for example, be 0.1 to 50 parts by volume, 1 to 10 parts by volume, or 1 to 5 parts by volume relative to 100 parts by volume of carbonate.

[0116] Carbonates may also include, for example, at least one selected from the group consisting of vinylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC).

[0117] The carboxylic acid ester may also include at least one selected from the group consisting of methyl formate (MF), methyl acetate (MA), and methyl propionate (MP). That is, the electrolyte may also contain MP. An electrolyte containing MP can have a low viscosity. By including MP in the electrolyte, there is a tendency for the distribution of the electrolyte within the electrode body 50 to become more uniform. Furthermore, by including MP in the electrolyte, it is expected that the initial resistance and the rate of increase in resistance after charge-discharge cycles can be improved.

[0118] Ethers may also include, for example, 1,2-dimethoxyethane (DME), 1,4-dioxane (DOX), tetrahydrofuran (THF), etc. Lactones may also include, for example, γ-butyrolactone (GBL), δ-valerolactone, etc.

[0119] The supporting electrolyte is soluble in a solvent. The supporting electrolyte may, for example, contain at least one selected from the group consisting of LiPF6, LiBF4, and LiN(FSO2)2. The supporting electrolyte may, for example, have a molar concentration of either 0.5–2.0 mol / L or 0.8–1.2 mol / L.

[0120] Alternatively, the electrolyte may contain any additives in addition to the solvent and supporting electrolyte. For example, the electrolyte may contain 0.01 to 5% additives by mass fraction. The additives may include at least one selected from the group consisting of vinylene carbonate (VC), lithium difluorophosphate (LiPO2F2), lithium fluorosulfonate (FSO3Li), and lithium bis(oxalatoborate) (LiBOB).

[0121] Example

[0122] The following describes embodiments of the present technology (also referred to as "the present embodiments" in this specification). However, the following description does not limit the scope of the present technology.

[0123] <Battery Manufacturing>

[0124] Manufacture the test cells (non-aqueous electrolyte secondary cells) No. 1 to 14 as follows.

[0125] The design dimensions of each part are as follows.

[0126] Design dimensions, etc.

[0127] Rated capacity: 4Ah

[0128] Material of the outer casing: Al alloy

[0129] External dimensions of the casing: Width 120mm × Depth 12.5mm × Height 65mm

[0130] Electrode body dimensions: Width 116mm × Depth 10.5mm × Height 58mm

[0131] Positive electrode plate: 105mm in width

[0132] Positive electrode active material layer: width dimension 90mm

[0133] Number of positive electrode layers: 66

[0134] Negative electrode plate: Width 107mm

[0135] Negative electrode active material layer: width dimension 95mm

[0136] Number of layers in the negative electrode: 68

[0137] Spacer: Width: 100mm

[0138] In this embodiment, the width dimension is represented as... Figure 1 The dimension along the X-axis. Depth dimension represents... Figure 2 The dimension along the Y-axis. Height dimension indicates... Figure 1 The dimensions in the Z-axis direction, etc.

[0139] Manufacturing of the Positive Electrode Plate

[0140] Prepare the following materials.

[0141] Positive electrode active material particles: Li(NiCoMn)O2

[0142] Conductive material: Acetylene black

[0143] Adhesive: PVdF

[0144] Dispersion medium: N-methyl-2-pyrrolidone

[0145] Positive electrode substrate: Al alloy foil

[0146] A positive electrode slurry is prepared by mixing positive electrode active material particles, conductive materials, binders, and dispersion media. The positive electrode slurry is then coated onto both sides of a positive electrode substrate and dried to form a positive electrode active material layer. This process is followed by the manufacture of a positive electrode raw sheet. The raw sheet is then compressed. Finally, the compressed raw sheet is cut into strips to produce a positive electrode plate.

[0147] The width of the positive electrode plate is 105 mm. The width of the positive electrode active material layer is 90 mm. At one end of the positive electrode plate in the width direction, 15 mm of the positive electrode substrate is exposed.

[0148] Manufacturing of Negative Electrode Plates

[0149] Prepare the following materials.

[0150] Negative electrode active material particles: spherical natural graphite

[0151] Adhesives: CMC, SBR

[0152] Dispersion medium: water

[0153] Negative electrode substrate: Cu alloy foil

[0154] The D50 of the negative electrode active material particles was determined. The D50 is shown in Tables 1 and 2 below.

[0155] A negative electrode slurry is prepared by mixing negative electrode active material particles, a binder, and a dispersion medium. The negative electrode slurry is then coated onto both sides of a negative electrode substrate and dried to form a negative electrode active material layer. This process is followed by the manufacture of a negative electrode blank. The negative electrode blank is then compressed. Finally, the compressed negative electrode blank is cut into strips to manufacture a negative electrode plate.

[0156] The width of the negative electrode plate is 107 mm. The width of the negative electrode active material layer is 95 mm. At one end of the negative electrode plate in the width direction, 12 mm of the negative electrode substrate is exposed.

[0157] In the negative electrode plate, the median sphericity of the negative electrode active material particles is determined by the aforementioned steps. The median sphericity values ​​are shown in Tables 1 and 2 below.

[0158] Preparation of Spacers

[0159] Prepare the spacer. The spacer is composed of a porous resin layer. The porous resin layer is composed of polyolefin.

[0160] The Formation of Electrodes

[0161] A laminate is formed by sequentially stacking spacers, a positive electrode plate, another spacer, and a negative electrode plate. A cylindrical wound body is formed by winding the laminate around a core. The wound body is flattened in a direction orthogonal to the winding axis, thus forming an electrode body. In this embodiment, the height ratio (R1) is adjusted according to the diameter of the core.

[0162] The height ratio (R1) and aspect ratio (R2) are determined by measuring the dimensions of each part within the electrode body. The height ratio (R1) and aspect ratio (R2) are shown in Tables 1 and 2 below.

[0163] (Electrolyte injection)

[0164] Electrodes are housed in an outer casing. Electrolyte is injected into the outer casing. After injection, the electrolyte thoroughly impregnates the electrodes. After impregnation, a predetermined amount of charging is performed. Gas generated from the electrodes during charging is expelled from the outer casing. After gas expulsion, the outer casing is sealed. The battery is manufactured using these steps. In the test batteries No. 1 to 13, an electrolyte containing the following components was used.

[0165] Solvent: "EC / EMC / DMC = 30 / 35 / 35 (volume ratio)"

[0166] Supported electrolyte: LiPF6 (1 mol / L)

[0167] Additive: Vitamin C (0.3% by mass)

[0168] In the test battery No. 14, an electrolyte containing the following components was used.

[0169] Solvent: "EC / EMC / DMC / MP = 28 / 34 / 35 / 3 (volume ratio)"

[0170] Supported electrolyte: LiPF6 (1 mol / L)

[0171] Additive: Vitamin C (0.3% by mass)

[0172] Evaluation of Penetration

[0173] The battery was prepared after being left to stand for 2.0 hours following electrolyte injection. The electrode body was recovered by opening the battery in a drying oven. The electrode body was disassembled from its outermost periphery. Each time one layer of the stack was disassembled, the spacers were visually inspected to confirm whether they were wetted by the electrolyte. The wetted and unwetted portions were distinguished by their different surface colors.

[0174] While extending the settling time after electrolyte injection at 0.5-hour intervals, the extent to which the spacer was wetted was observed. The values ​​shown in the "Electrolyte Penetration Immersion Time" section of Tables 1 and 2 below indicate the time required to confirm that the spacer was wetted throughout its entire circumference. It can be assumed that the shorter the immersion time, the better the electrolyte penetration.

[0175] Coefficient of Friction

[0176] After the battery is completed, the electrode body is recovered by opening the battery in a drying chamber. Following the aforementioned steps, the first and second coefficients of kinetic friction are measured. The first and second coefficients of kinetic friction are shown in Tables 1 and 2 below.

[0177] Initial Resistance

[0178] At a temperature of 25°C, the battery's state of charge (SOC) was adjusted to 50% using constant current-constant voltage (CC-CV) charging. The constant current (CC) charging current was 1 It. The total charging time was 1.5 hours. "1 It" is defined as the current required to fully charge the battery to its rated capacity within one hour. At 50% SOC, the battery voltage was 3.69V. After adjusting the SOC, with a 30-minute pause, the battery was discharged for 10 seconds at a current of 180A. The initial discharge resistance (initial resistance) was calculated using the following formula.

[0179] r=(V0-V 10 ) / 180

[0180] In the above formula, r represents the discharge resistance. V0 represents the voltage at the start of discharge. 10 This indicates the voltage 10 seconds after the start of discharge. Furthermore, the initial resistances in Tables 1 and 2 below are relative values. The initial resistance of No. 1 is defined as 100.

[0181] Rate of increase in resistance

[0182] After measuring the initial resistance, the battery's state of charge (SOC) was adjusted to 80% using CC-CV charging at 25°C. The current during CC charging was 1 It. The total charging time was 1.5 hours. After adjusting the SOC, a cycle test was conducted at 25°C. That is, the following discharge and charge cycles were alternately repeated over 1200 hours.

[0183] Discharge: Current = 1 It, discharge capacity = equivalent to 20% of SOC capacity.

[0184] Charging: Current = 1 It, Charging capacity = equivalent to 20% of SOC capacity.

[0185] After the cyclic test, the discharge resistance (post-cycle resistance) was measured in the same manner as the initial resistance. The rate of increase in resistance (percentage) was obtained by dividing the post-cycle resistance by the initial resistance. The rate of increase in resistance is shown in Tables 1 and 2 below.

[0186] Li precipitation

[0187] After the cycle test, the electrode body was recovered by opening the battery in a drying oven. The electrode body was disassembled from the outermost periphery. Each time a layer of the stack was disassembled, Li was visually checked to confirm whether Li was deposited on the surface of the negative electrode plate. The areas with Li deposits and those without Li deposits were distinguished by the difference in surface color. In the "Li Deposition" section of Tables 1 and 2 below, "OK" indicates that no Li deposition was confirmed throughout the entire cycle. "NG" indicates that Li deposition was confirmed in a localized area.

[0188]

[0189] <Results>

[0190] In Tables 1 and 2 above, when the height ratio (R1) is 1.20–1.35 and the first coefficient of kinetic friction is 0.52–0.66, a tendency to reduce Li deposition after cyclic testing can be observed (refer to Nos. 1–9). This can be attributed to the difficulty in causing electrolyte depletion in the electrode body and the ease with which the electrolyte distribution within the electrode body becomes uniform.

[0191] When the height ratio (R1) is 1.20–1.35 and the first coefficient of kinetic friction is 0.52–0.66, a tendency for the rate of increase in resistance to decrease can also be observed. This can be attributed to the fact that by increasing the amount of electrolyte movement, it is easier to stir the electrolyte, thus making it less likely for the electrolyte concentration to become uneven.

[0192] When the height ratio (R1) is 1.20–1.35 and the first coefficient of kinetic friction is 0.52–0.66, a tendency for shorter immersion time can also be observed. This can be attributed to the easier penetration of the electrolyte into the electrode body and the easier detachment of air bubbles from it, thus shortening the immersion time. Increased productivity can be expected through this reduction in immersion time.

[0193] In Tables 1 and 2 above, when the second coefficient of kinetic friction is 0.70 to 0.85, a tendency for the initial resistance to decrease can be observed (see Nos. 10 to 13). Furthermore, a tendency for the rate of increase in resistance to decrease can also be observed. Additionally, by including MP in the electrolyte, a tendency for improvement in both the initial resistance and the rate of increase in resistance can be observed (see Nos. 10 and 14).

[0194] This embodiment and example are illustrative in all respects. This embodiment and example are not restrictive. The scope of this technology includes all modifications within the same meaning and scope as the claims. For example, it is also intended from the outset to include extracting arbitrary structures from this embodiment and example and combining them arbitrarily.

Claims

1. A non-aqueous electrolyte secondary battery, characterized in that, The non-aqueous electrolyte secondary battery includes an outer casing, electrode components, and an electrolyte. The outer casing houses the electrode body and the electrolyte. The electrode body comprises a stack. The laminate includes a positive electrode plate, a spacer, and a negative electrode plate. The spacer separates the positive electrode plate from the negative electrode plate. The stacked body is coiled into a vortex shape. In a cross-section orthogonal to the winding axis of the laminate, the electrode body has a rounded rectangular outline. The outline is composed of a first arc-shaped portion, a straight portion, and a second arc-shaped portion. The straight section is composed of two line segments. The straight section connects the first arc-shaped section and the second arc-shaped section. The outline has a height ratio of 1.20 to 1.

35. The height ratio is calculated using formula (α): R1=H0 / H1 …(α) In the above equation (α), R1 represents the height ratio. H0 represents the distance between the two furthest points on the outline. H1 represents the average length of the two line segments. The spacer includes a first main surface and a second main surface. The first main surface is in contact with the negative electrode plate. The coefficient of kinetic friction between the first main surface and the negative electrode plate is 0.52 to 0.

66. The first coefficient of kinetic friction is obtained by equation (γ): m D =F D / F p …(c), In the above formula (γ), μ D Indicates the first coefficient of kinetic friction. F D This represents the average test force within a displacement range of 10~30mm. F p This represents the normal force generated due to the mass of the sliding plate. The negative electrode plate contains a layer of negative electrode active material. The negative electrode active material layer has a strip-shaped planar shape. The electrode body has an aspect ratio of 2.0 to 2.

5. The aspect ratio is calculated using formula (β): R2=W / H1…(β) In the above formula (β), R2 represents the aspect ratio. W represents the length of the negative electrode active material layer in the width direction. H1 represents the average length of the two line segments.

2. The non-aqueous electrolyte secondary battery according to claim 1, characterized in that, The negative electrode active material layer is in contact with the first main surface. The negative electrode active material layer contains negative electrode active material particles. The negative electrode active material particles have a median sphericity of 0.60 to 0.

85. Regarding the median of the roundness, the median of the roundness is obtained by randomly extracting 30 negative electrode active material particles from the cross-sectional SEM image and measuring the roundness of these 30 negative electrode active material particles.

3. The non-aqueous electrolyte secondary battery according to claim 1 or 2, characterized in that, The second main surface is in contact with the positive electrode plate. The second coefficient of kinetic friction between the second main surface and the positive electrode plate is 0.70 to 0.

85.

4. The non-aqueous electrolyte secondary battery according to claim 1 or 2, characterized in that, The electrolyte contains methyl propionate.

5. The non-aqueous electrolyte secondary battery according to claim 3, characterized in that, The electrolyte contains methyl propionate.

Images