Non-aqueous electrolyte secondary battery

Abstract

To provide a non-aqueous electrolyte secondary battery in which the initial cycle capacity maintenance rate is high and the cycle capacitance maintenance rate after a storage durability test is prevented from dropping.SOLUTION: A positive electrode active material layer includes a positive electrode active material represented by the formula (1): Li(1+x)NiyTizMe(1-y-z)O2. When the specific surface area of a negative electrode active material layer is represented by S(m2 / g), the relational expression (a): 10x+2<S is satisfied.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a non-aqueous electrolyte secondary battery.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2011-113825 (Patent Document 1) proposes a positive electrode material for a lithium-ion secondary battery having a high nickel content.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a lithium composite oxide having a high nickel content is used for the positive electrode active material layer, although the non-aqueous electrolyte secondary battery (hereinafter also referred to as a battery) can have a higher capacity, side reactions in the negative electrode and the positive electrode and capacity deterioration of the positive electrode active material tend to occur easily in the storage durability test. Due to the above side reactions, the capacity-potential curves (hereinafter also referred to as the positive electrode single-pole curve and the negative electrode single-pole curve, respectively) in the positive electrode and the negative electrode may shift (FIGS. 1, 2, and 3). When the sum of the shift amount of the positive electrode single-pole curve (hereinafter also referred to as the positive electrode shift amount) and the capacity deterioration of the positive electrode active material becomes larger than the shift amount of the negative electrode single-pole curve (hereinafter also referred to as the negative electrode shift amount), the reserve capacity of the negative electrode decreases, and as a result, lithium (Li) precipitates on the negative electrode, and the cycle capacity retention rate tends to decrease easily.

[0005] An object of the present disclosure is to provide a non-aqueous electrolyte secondary battery having a high initial cycle capacity retention rate and suppressing a decrease in the cycle capacity retention rate after a storage durability test.

Means for Solving the Problems

[0006] The present invention provides the following non-aqueous electrolyte secondary battery. [1] including an electrode body, The electrode body includes a positive electrode plate and a negative electrode plate, The positive electrode plate includes a positive electrode active material layer, The negative electrode plate includes a negative electrode active material layer, The positive electrode active material layer has the formula (1): Li (1+x) Ni y Ti z Me (1-y-z) O2 [In formula (1), Me includes two or more selected from the group consisting of Mn, Co, and Al, satisfies the relationships of 0 < x < 0.1, 0.8 < y < 0.85, and 0 ≤ z < 0.03] and includes a positive electrode active material represented by The negative electrode active material layer includes a negative electrode active material, The negative electrode active material includes graphite, When the specific surface area of the negative electrode active material layer is S (m 2 / g), the following relational expression: (a) 10x + 2 < S A non-aqueous electrolyte secondary battery that satisfies [2] The non-aqueous electrolyte secondary battery according to [1], further satisfying (b) S < 10x + 3.4. [3] The non-aqueous electrolyte secondary battery according to [1] or [2], wherein the graphite content in the negative electrode active material is 99% by mass or more. [4] The non-aqueous electrolyte secondary battery according to any one of [1] to [3], wherein in formula (1), the relationship of 0.01 < z < 0.03 is satisfied.

Advantages of the Invention

[0007] According to the present disclosure, it becomes possible to provide a non-aqueous electrolyte secondary battery having a high initial cycle capacity retention rate and suppressing a decrease in the cycle capacity retention rate after a storage durability test.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

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Figure 4

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Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. In all the following drawings, the scale is appropriately adjusted for easy understanding of each component, and the scale of each component shown in the drawings does not necessarily match the scale of the actual component. In the description of each of the following embodiments, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

[0010] <Non-aqueous electrolyte secondary battery> FIG. 4 is a schematic diagram showing an example of the configuration of the battery in the present embodiment. The battery 100 can be used for any application. The battery 100 may be used as a main power source or a power assist power source in, for example, an electric vehicle. A battery module or a battery pack may be formed by connecting a plurality of batteries 100.

[0011] The battery 100 includes an exterior body 90. The exterior body 90 is rectangular (flat cuboid shape). However, the rectangular shape is just an example. The exterior body 90 can have any form. The exterior body 90 may be, for example, cylindrical or pouch-shaped. The exterior body 90 may be made of, for example, an Al alloy. The exterior body 90 houses the electrode body 50 and an electrolytic solution (not shown). The exterior body 90 may include, for example, a sealing plate 91 and an exterior can 92. The sealing plate 91 closes the opening of the exterior can 92. For example, the sealing plate 91 and the exterior can 92 may be joined by laser welding.

[0012] A positive electrode terminal 81 and a negative electrode terminal 82 are provided on the sealing plate 91. A filling port and a gas discharge valve may be further provided on the sealing plate 91. The electrolytic solution can be injected into the interior of the exterior body 90 through the filling port. The electrode body 50 is connected to the positive electrode terminal 81 by a positive electrode current collector member 71. The positive electrode current collector member 71 may be, for example, an Al plate or the like. The electrode body 50 is connected to the negative electrode terminal 82 by a negative electrode current collector member 72. The negative electrode current collector member 72 may be, for example, a Cu plate or the like.

[0013] FIG. 5 is a schematic diagram showing an example of the configuration of the electrode body in the present embodiment. The electrode body 50 is of a wound type. The electrode body 50 includes a positive electrode plate 10, a separator 30, and a negative electrode plate 20. That is, the battery 100 includes a positive electrode plate 10, a negative electrode plate 20, and an electrolytic solution. The positive electrode plate 10, the separator 30, and the negative electrode plate 20 are all strip-shaped sheets. The electrode body 50 may include a plurality of separators 30. The electrode body 50 is formed by laminating the positive electrode plate 10, the separator 30, and the negative electrode plate 20 in this order and winding them in a spiral shape. One of the positive electrode plate 10 or the negative electrode plate 20 may be sandwiched between the separators 30. Both the positive electrode plate 10 and the negative electrode plate 20 may be sandwiched between the separators 30. The electrode body 50 may be formed into a flat shape after winding. Note that the wound type is an example. The electrode body 50 may be, for example, of a stacked type.

[0014] (Positive electrode plate) The positive electrode plate 10 includes a positive electrode substrate 11 and a positive electrode active material layer 12. The positive electrode substrate 11 is a conductive sheet. The positive electrode substrate 11 may be, for example, an Al alloy foil or the like. The positive electrode substrate 11 may have a thickness of, for example, 10 μm to 30 μm. The positive electrode active material layer 12 is disposed on the surface of the positive electrode substrate 11. The positive electrode active material layer 12 may be disposed on only one side of the positive electrode substrate 11, for example. The positive electrode active material layer 12 may be disposed on both the front and back surfaces of the positive electrode substrate 11, for example. In the width direction of the positive electrode plate 10 (the X-axis direction in FIG. 2), the positive electrode substrate 11 may be exposed at one end. A positive electrode current collector member 71 may be joined to the exposed portion of the positive electrode substrate 11.

[0015] For example, an intermediate layer (not shown) may be formed between the positive electrode active material layer 12 and the positive electrode substrate 11. In the present embodiment, even when there is an intermediate layer, the positive electrode active material layer 12 is regarded as being disposed on the surface of the positive electrode substrate 11. The intermediate layer may be thinner than the positive electrode active material layer 12. The intermediate layer may have a thickness of, for example, 0.1 μm to 10 μm. The intermediate layer may contain, for example, a conductive material, an insulating material, or the like.

[0016] (Positive electrode active material layer) The positive electrode active material layer 12 contains a positive electrode active material. The positive electrode active material is represented by the following formula (1): Li (1+x) Ni y Ti z Me (1-y-z) O2 [In formula (1), Me contains two or more selected from the group consisting of Mn, Co, and Al, satisfies the relationships of 0 < x < 0.1, 0.8 < y < 0.85, and 0 ≦ z < 0.03] and includes a layered metal oxide represented by

[0017] The layered metal oxide represented by formula (1) may satisfy, for example, the relationships of 0 < x < 0.2, 0.8 < y < 0.84, and 0.01 < z < 0.03.

[0018] The layered metal oxide represented by formula (1) may contain at least one selected from the group consisting of Zr, B, Mg, Fe, Cu, Zn, Sn, Na, K, Ba, Sr, Ca, W, Mo, Nb, Si, V, Cr, and Ge.

[0019] The positive electrode active material is a particle group. The particle group can include a first positive electrode active material particle group and a second positive electrode active material particle group. The first positive electrode active material particle group consists of a plurality of first positive electrode active material particles. The second positive electrode active material particle group consists of a plurality of second positive electrode active material particles. The first positive electrode active material particles and the second positive electrode active material particles can have any shape. The first positive electrode active material particles and the second positive electrode active material particles may be, for example, spherical, columnar, massive, etc.

[0020] The plurality of first positive electrode active material particles may have, for example, an average particle diameter (D50) of 10 μm to 20 μm. The plurality of second positive electrode active material particles may have, for example, an average particle diameter (D50) of 0.5 μm to 9 μm. The average particle diameter (D50) in this specification is the particle diameter at which the cumulative frequency from the smaller particle diameter in the volume-based particle size distribution reaches 50%. The volume-based particle size distribution can be measured by a laser diffraction particle size distribution measuring device.

[0021] The first positive electrode active material particles and the second positive electrode active material particles each independently contain a positive electrode active material represented by formula (1). The first positive electrode active material particles and the second positive electrode active material particles may each independently have an arbitrary crystal structure. The first positive electrode active material particles and the second positive electrode active material particles may each independently have, for example, a layered structure, a spinel structure, an olivine structure, or the like. The first positive electrode active material particles and the second positive electrode active material particles may have substantially the same chemical composition. The first positive electrode active material particles and the second positive electrode active material particles may have different chemical compositions from each other.

[0022] As long as the positive electrode active material layer 12 contains a positive electrode active material, it may further contain additional components. In addition to the positive electrode active material, the positive electrode active material layer 12 may contain, for example, a conductive material and a binder. The conductive material may contain any component. The conductive material may contain, for example, at least one selected from the group consisting of carbon black, graphite, vapor-grown carbon fiber (VGCF), carbon nanotube (CNT), and graphene flakes. The blending amount of the conductive material may be, for example, from 0.1 part by mass to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material. The binder may contain any component. The binder may contain, for example, at least one selected from the group consisting of polyvinylidene fluoride (PVdF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), polytetrafluoroethylene (PTFE), and polyacrylic acid (PAA). The blending amount of the binder may be, for example, from 0.1 part by mass to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material. The positive electrode active material layer 12 may contain, for example, by mass fraction, 80% to 99% of the positive electrode active material, 0.1% to 10% of the conductive material, and the balance of the binder.

[0023] The positive electrode active material layer 12 may have a thickness of, for example, 10 μm to 200 μm. The positive electrode active material layer 12 may have a thickness of, for example, 50 μm to 150 μm. The positive electrode active material layer 12 may have a thickness of, for example, 50 μm to 100 μm.

[0024] The positive electrode active material layer 12 may have a high density. The positive electrode active material layer 12 may have a density, for example, of from 3.3 g / cm 3 to 3.9 g / cm 3 The positive electrode active material layer 12 may have a density, for example, of from 3.4 g / cm 3 to 3.7 g / cm 3 The positive electrode active material layer 12 may have a density, for example, of from 3.4 g / cm 3 to 3.6 g / cm 3 The density of the active material layer in this specification indicates the apparent density.

[0025] The positive electrode plate 10 is manufactured by forming the positive electrode active material layer 12 by applying a positive electrode slurry to the surface of the positive electrode substrate 11, then rolling the positive electrode active material layer 12 and the positive electrode substrate 11 to produce a raw sheet, and then cutting it to a predetermined planar size according to the specifications of the battery 100. The positive electrode slurry is prepared by mixing a positive electrode active material and additional components.

[0026] (Negative electrode plate) The negative electrode plate 20 may include, for example, a negative electrode substrate 21 and a negative electrode active material layer 22. The negative electrode substrate 21 is a conductive sheet. The negative electrode substrate 21 may be, for example, a Cu alloy foil or the like. The negative electrode substrate 21 may have a thickness of, for example, from 5 μm to 30 μm. 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 on only one side of the negative electrode substrate 21, for example. The negative electrode active material layer 22 may be disposed on both the front and back surfaces of the negative electrode substrate 21, for example. In the width direction (X-axis direction in FIG. 2) of the negative electrode plate 20, the negative electrode substrate 21 may be exposed at one end. A negative electrode current collector member 72 may be joined to the exposed portion of the negative electrode substrate 21.

[0027] (Negative electrode active material layer) The negative electrode active material layer 22 contains a negative electrode active material. The negative electrode active material may contain any component. The negative electrode active material may contain, for example, at least one selected from the group consisting of graphite, soft carbon, hard carbon, silicon, silicon oxide, silicon-based alloy, tin, tin oxide, tin-based alloy, and lithium titanium composite oxide. The graphite may be natural graphite or artificial graphite.

[0028] In addition to the negative electrode active material, the negative electrode active material layer 22 may further contain, for example, a binder or the like as other components. The negative electrode active material layer 22 may contain, for example, by mass fraction, 95% to 99.5% of the negative electrode active material and the balance of the binder. The binder may contain any component. The binder may contain at least one selected from the group consisting of, for example, carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR). When the negative electrode active material layer 22 contains graphite, the graphite content in the negative electrode active material is preferably 99% by mass or more. The specific surface area of the negative electrode active material is, for example, 0.5 to 5 m 2 / g.

[0029] The specific surface area of the negative electrode active material layer 22 may be, for example, 2 or more, may be 2 or more and 4.5 or less, and may be 2 or more and 4 or less. The specific surface area S of the negative electrode active material layer 22 is the specific surface area of the negative electrode active material layer of the negative electrode plate taken out from the battery after activation. The specific surface area S of the negative electrode active material layer 22 is measured according to the method described in the column of the following examples.

[0030] The negative electrode active material layer 22 may have a thickness of, for example, 10 μm to 200 μm.

[0031] The negative electrode active material layer 22 may have a high density. The negative electrode active material layer 22 may have a density of, for example, 1.0 g / cm 3 to 2.0 g / cm 3 The negative electrode active material layer 22 may have a density of, for example, 1.2 g / cm 3 to 1.7 g / cm 3 The negative electrode active material layer 22 may have a density of, for example, 1.3 g / cm 3 to 1.6 g / cm 3It may have a density of

[0032] The negative electrode plate 20 is manufactured by forming a negative electrode active material layer 22 by applying a negative electrode slurry to the surface of a negative electrode substrate 21, then rolling the negative electrode active material layer 22 and the negative electrode substrate 21 to produce a raw sheet, and then cutting it to a predetermined planar size according to the specifications of the battery 100. The negative electrode slurry is prepared by mixing a negative electrode active material and other components.

[0033] [Relational expression (a)] It was found that the cycle capacity retention rate is correlated with the reserve capacity of the negative electrode (Fig. 6). The total of the positive electrode shift amount y1 (Ah / m 2 ) and the capacity degradation amount of the positive electrode active material (Ah / m 2 ) is larger than the negative electrode shift amount y2 (Ah / m 2 ), the reserve capacity of the negative electrode (Ah / m 2 ) tends to decrease easily. The negative electrode shift amount y2 tends to decrease when the irreversible Li amount of the negative electrode decreases, and the irreversible Li amount of the negative electrode tends to depend on the specific surface area of the negative electrode active material layer (Fig. 7). On the other hand, as a result of the research by the present inventor, it was found that the positive electrode shift amount y1 has a strong correlation with the Li / M (=1 + x) ratio in the positive electrode active material (M is the total of metals other than Li in the positive electrode active material) (Fig. 8). Therefore, as a result of examining the control of the specific surface area of the negative electrode active material layer according to the Li / M ratio of the positive electrode active material, when the specific surface area of the negative electrode active material layer 22 is S, the following relational expression: (a) 10x + 2 < S By satisfying this, it was found that the initial cycle capacity retention rate can be increased and the decrease in the cycle capacity retention rate can be suppressed in the durability test.

[0034] The relational expression (a) is obtained by applying the x-S straight line, which is determined such that the relationship of the positive electrode shift amount y1 < the negative electrode shift amount y2 is at least satisfied, from the approximate straight line (Figure 7) obtained by plotting the irreversible Li amount of the negative electrode by the storage durability test against the specific surface area of the negative electrode active material layer and the approximate straight line (Figure 8) obtained by plotting the positive electrode shift amount y1 against x, so that the decrease in the cycle capacity retention rate is suppressed (satisfying the cycle capacity retention rate ≥ 95%) (Figure 9). In the relational expression (a), x is defined as in the above formula (1). The specific surface area S of the negative electrode active material layer 22 is measured according to the method described in the column of the examples below.

[0035] [Relational expression (b)] The battery satisfies the following relational expression: (b) S < 10x + 3.4 It can further satisfy. By the battery satisfying the relational expression (b), the precipitation of lithium is suppressed after the durability test, and as a result, it has been found that the decrease in the capacity retention rate in the storage durability test is likely to be suppressed. By the battery satisfying the relational expressions (a) and (b), the decrease in the cycle capacity retention rate is suppressed even after the durability test, and there is a tendency that the decrease in the capacity retention rate in the durability test is likely to be suppressed.

[0036] The relational expression (b) is obtained by applying the x-S straight line obtained as described above so that the decrease in the capacity retention rate in the storage durability test is suppressed (satisfying the capacity retention rate ≥ 95% after 120 days) (Figure 10).

[0037] (Opposite capacity ratio) The opposite capacity ratio (the ratio of the negative electrode capacity to the positive electrode capacity) may be, for example, 1.00 to 1.15, preferably 1.04 to 1.10. The negative electrode capacity is calculated by multiplying the total mass of the negative electrode active material contained in the negative electrode active material layer 22 by the specific capacity of the negative electrode active material. The positive electrode capacity is calculated by multiplying the total mass of the positive electrode active material contained in the positive electrode active material layer 12 by the specific capacity of the positive electrode active material.

[0038] (Separator) At least a part of the separator 30 is interposed between the positive electrode plate 10 and the negative electrode plate 20. The separator 30 separates the positive electrode plate 10 and the negative electrode plate 20. The separator 30 may have a thickness of, for example, from 10 μm to 30 μm.

[0039] The separator 30 is a porous sheet. The separator 30 allows the electrolyte to permeate. The separator 30 may have an air permeability of, for example, from 100 s / 100 mL to 400 s / 100 mL. The "air permeability" in this specification indicates the "Air Resistance" defined in "JIS P 8117:2009". The air permeability is measured by the Gurley test method.

[0040] The separator 30 is electrically insulating. The separator 30 may contain, for example, a polyolefin-based resin or the like. The separator 30 may be composed of, for example, substantially a polyolefin-based resin. The polyolefin-based resin may contain at least one selected from the group consisting of, for example, polyethylene (PE) and polypropylene (PP). The separator 30 may have, for example, a single-layer structure. The separator 30 may be composed of, for example, substantially a PE layer. The separator 30 may have, for example, a multilayer structure. The separator 30 may be formed, for example, by laminating a PP layer, a PE layer, and a PP layer in this order. A heat-resistant layer or the like may be formed on the surface of the separator 30.

[0041] (Electrolyte) The electrolyte contains a solvent and a supporting electrolyte. The solvent is aprotic. The solvent may contain any component. The solvent may contain, for example, at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), 1,2-dimethoxyethane (DME), methyl formate (MF), methyl acetate (MA), methyl propionate (MP), and γ-butyrolactone (GBL).

[0042] The supporting electrolyte is dissolved in the solvent. The supporting electrolyte may include at least one selected from the group consisting of, for example, LiPF6, LiBF4, and LiN(FSO2)2. The supporting electrolyte may have a molar concentration of, for example, from 0.5 mol / L to 2.0 mol / L. The supporting electrolyte may have a molar concentration of, for example, from 0.8 mol / L to 1.2 mol / L.

[0043] The electrolytic solution may further contain an optional additive. For example, the electrolytic solution may contain an additive in a mass fraction of from 0.01% to 5%. The additive may include at least one selected from the group consisting of, for example, vinylene carbonate (VC), lithium difluorophosphate (LiPO2F2), lithium fluorosulfonate (FSO3Li), and lithium bis(oxalato)borate (LiBOB).

[0044] <Method for manufacturing a battery> The method for manufacturing a battery in the present embodiment includes a step (A) of inserting an electrode body into an exterior body, a step (B) of injecting an electrolytic solution, and an activation step (C).

[0045] In the step (A) of inserting the electrode body into the exterior body, the electrode body 50 is housed in the exterior body 90. The electrode body 50 can be connected to the positive electrode terminal 81 by the positive electrode current collector member 71. The electrode body 50 can be connected to the negative electrode terminal 82 by, for example, the negative electrode current collector member 72.

[0046] In the step (B) of injecting the electrolytic solution, the electrolytic solution is injected into the exterior body 90. The electrolytic solution is impregnated into the electrode body 50. After the injection of the electrolytic solution, the exterior body 90 is sealed.

[0047] In the activation step (C), the battery 100 is activated. For example, the battery 100 is charged in a constant current-constant voltage (CC-CV) mode, and after a predetermined time has elapsed, it is discharged in a constant current (CC-CV) mode. More specifically, in a temperature environment of 25°C, with a current of 0.2 mA / cm 2 the positive electrode potential becomes 4.30 V (vs. Li +Until reaching (vs. Li), charge is carried out in a constant current mode, and subsequently, until the current reaches 0.04 mA / cm 2 charge is carried out in a constant voltage mode until reaching. Thereafter, with a 10-minute pause in between, at a current of 0.2 mA / cm 2 the positive electrode potential is discharged in a constant current mode until reaching 2.5 V (vs. Li + / Li).

[0048] From the above, the battery 100 is manufactured. The manufactured battery 100 suppresses the increase in internal resistance and has good fusibility by satisfying the relational expressions (a) and (b) as described above.

[0049] The battery can have a cycle capacity retention rate of 95% or more. Also, the battery can have a cycle capacity retention rate of 95% or more even after the storage durability test. When the cycle capacity retention rate is 95% or more even after the storage durability test, the battery can have good cycle characteristics. Further, the battery can have a capacity retention rate of 95% or more after a 120-day storage durability test. When the capacity retention rate is 95% or more even after a 120-day storage durability test, the battery can have good storage durability characteristics.

[0050] Hereinafter, embodiments of the present technology will be described. However, the following description does not limit the scope of the present technology.

Embodiment

[0051] <Example 1> (Manufacture of positive electrode plate) Lithium nickel composite oxide (Li 1.03 Ni 0.82 Co 0.05 Mn 0.11By mixing large particles and small particles composed of O2), a mixed powder of the positive electrode active material was prepared. The mixing ratio was "large particles / small particles = 6 / 4 (mass ratio)". The D50 of the large particles was 17 μm, and the D50 of the small particles was 4 μm. By mixing 97.6 parts by mass of the mixed powder, 1.5 parts by mass of a conductive material (carbon black), 0.9 parts by mass of a binder (PVdF), and a predetermined amount of a dispersion medium (N-methyl-2-pyrrolidone), a positive electrode slurry was prepared. The positive electrode slurry was applied to the surface of a positive electrode substrate (Al foil) at a coating amount of 350 (g / m 2 ) and dried, whereby a positive electrode active material layer was formed. The positive electrode active material layer was compressed by a rolling machine. Thus, a positive electrode raw sheet having a density of the positive electrode active material layer of 3.5 (g / cc) was manufactured. The positive electrode raw sheet was cut into a predetermined size to manufacture a positive electrode plate. A tab terminal (Al thin plate) was joined to the positive electrode plate.

[0052] (Manufacture of negative electrode plate) By mixing 98 parts by mass of a negative electrode active material (natural graphite, D50 = 17 μm, specific surface area = 1.2 m 2 / g), 1 part by mass of CMC, 1 part by mass of SBR, and a predetermined amount of a dispersion medium (water), a negative electrode slurry was prepared. The negative electrode slurry was applied to the surface of a negative electrode substrate (Cu foil) at a coating amount of 225 (g / m 2 ) and dried, whereby a negative electrode active material layer having a specific surface area S of 4 (m 2 / g) was formed. The negative electrode active material layer was compressed by a rolling machine. Thus, a negative electrode raw sheet having a density of the negative electrode active material layer of 1.5 (g / cc) was manufactured. The negative electrode raw sheet was cut into a predetermined size to manufacture a negative electrode plate. A tab terminal (Ni thin plate) was joined to the negative electrode plate.

[0053] (Assembly) As a separator, a porous sheet made of polyolefin was prepared. The positive electrode plate, the separator, and the negative electrode plate were laminated so that the separator was interposed between the positive electrode plate and the negative electrode plate. By winding this, a wound electrode body was formed. As an exterior body, a pouch made of an Al laminate film was prepared. The electrode body was housed in the exterior body.

[0054] (Electrolyte Injection) The electrolyte was prepared. The electrolyte contained the following components. The electrolyte was injected into the package in an amount of 2 (g / Ah). The package was sealed. Thus, the test cell was manufactured.

[0055] Solvent: EC / EMC = 3 / 7 (volume ratio) Supporting electrolyte: LiPF6 (1 mol / L) Additive: LiBOB (0.5% by mass fraction)

[0056] (Activation) Under a temperature environment of 25°C, initial charge and discharge were performed. With a current of 0.2 mA / cm 2 until the positive electrode potential reached 4.30 V (vs. Li + / Li), the test cell was charged in a constant current mode. Subsequently, until the current reached 0.04 mA / cm 2 , the test cell was charged in a constant voltage mode. Thereby, the initial charge capacity was measured. With a 10-minute pause in between, with a current of 0.2 mA / cm 2 until the positive electrode potential reached 2.5 V (vs. Li + / Li), the test cell was discharged in a constant current mode. Thereby, the initial discharge capacity was measured.

[0057] (Measurement of Capacity Retention Rate) Regarding the test cell after activation, the cell capacity was measured under the following conditions in a temperature environment of 25°C before and after the cycle test. Constant current (CC) charge: CC current: 0.05C, 4.2V cut-off Constant current (CC) discharge: CC discharge: 0.05C, 3.0V cut-off The capacity retention rate was calculated according to the following formula: Capacity retention rate = (Cell capacity after cycle test / Cell capacity before cycle test) × 100 (%) was calculated according to. The cycle durability test was conducted under the following conditions. Temperature: 25°C Number of cycles: 100 cycle Constant current - constant voltage (CC - CV) charging: CC current = 1C, CV voltage = 4.2V, 0.05C cut-off Rest: 1 minute Constant current (CC) discharge: CC current = 1C, 3.0V cut-off Rest: 10 minutes The capacity retention rate was also measured in the same manner for the test cells after the storage durability test described below (after 120 days). The results are shown in Table 1.

[0058] <Storage durability test> After the test cell after activation was charged at a constant current (CC) (current = 0.05C, 4.2V cut-off), it was stored in a 60°C constant temperature bath for 120 days. The cell capacities before the storage durability test and on the 30th, 60th, 90th, and 120th days of storage were measured under the following conditions in a temperature environment of 25°C. Constant current (CC) charging: CC current: 0.05C, 4.2V cut-off Constant current (CC) discharge: CC discharge: 0.05C, 3.0V cut-off The capacity retention rate is calculated by the following formula: Capacity retention rate = (Cell capacity at each storage day / Cell capacity before the storage durability test) × 100 (%) It was calculated according to. The results are shown in Table 1.

[0059] <Specific surface area> The BET specific surface area of the negative electrode plate taken out from the electrode body after the initial charge and discharge was measured by the nitrogen adsorption method.

[0060] <Measurement of charging capacity and discharging capacity of a single electrode> The test cell after activation was charged and discharged under the following conditions in a temperature environment of 25°C. Constant current (CC) charging: CC current: 0.05C, 4.2V cut-off Constant current (CC) discharge: CC discharge: 0.05C, 3.0V cut-off After charging and discharging, the test cell was disassembled, the positive electrode plate and the negative electrode plate were taken out, and a single electrode cell of the positive electrode plate - counter electrode Li foil (hereinafter referred to as the positive electrode cell) and a single electrode cell of the negative electrode plate - counter electrode Li foil (hereinafter referred to as the negative electrode cell) were fabricated. The electrolyte was EC / EMC = 3 / 7_LiPF6: 1 mol / l. Next, the remaining discharge capacity of the positive electrode of the positive electrode cell was measured by constant current (CC) discharge (CC current = 0.05C, 2.5V cut-off), and then the positive electrode capacity was measured under the following conditions. Constant current (CC) charge: CC current = 0.05C, 4.3V cut-off Rest: 10 minutes Constant current (CC) discharge: CC current = 0.05C, 2.5V cut-off Subsequently, the remaining discharge capacity of the negative electrode of the negative electrode cell was measured by constant current (CC) charge (CC current = 0.05C, 2.0V cut-off), and then the positive electrode capacity was measured under the following conditions. Constant current (CC) discharge: CC current = 0.05C, 0.001V cut-off Rest: 10 minutes Constant current (CC) charge: CC current = 0.05C, 2.0V cut-off Similarly, the charging capacity and discharging capacity of the single electrode were measured for the test cell after the storage durability test (after 120 days). The initial charging capacity and discharging capacity of the single electrode are shown in Table 1.

[0061] <Li-ICP measurement> The activated test cell was charged and discharged under the following conditions in a temperature environment of 25°C. Constant current (CC) charge: CC current: 0.05C, 4.2V cut-off Constant current (CC) discharge: CC discharge: 0.05C, 3.0V cut-off After charging and discharging, the test cell was disassembled, and a negative electrode plate of 10 cm 2 was cut out. The negative electrode active material layer was peeled off in 10 ml of water, 10 ml of hydrochloric acid was added, and then it was treated at 80°C for 30 minutes. The obtained aqueous solution was filtered, water was added to the filter paper deposit, and the adhered part was also recovered. The recovered aqueous solution was adjusted to 100 ml. B-ICP measurement was performed, and the Li amount was determined by the external calibration curve method. Similarly, the Li amount was determined for the test cell after the storage durability test (after 120 days).

[0062] <Positive electrode shift amount, negative electrode shift amount, reserve capacity, positive electrode - negative electrode deviation amount> Positive electrode shift amount (Ah / m 2) is obtained as the amount obtained by subtracting the difference between the positive electrode - negative electrode shift amount (Ah / m 2 ) after the storage durability test and the initial positive electrode - negative electrode shift amount (Ah / m 2 ) from the negative electrode shift amount (Ah / m 2 ). The negative electrode shift amount (Ah / m 2 ) is obtained as the amount obtained by subtracting the difference between the amount of Li in the negative electrode (Ah / m 2 ) and the negative electrode residual discharge amount (Ah / m 2 ) after the storage durability test from the difference between the initial amount of Li in the negative electrode (Ah / m 2 ) and the negative electrode residual discharge amount (Ah / m 2 ). The reserve capacity (Ah / m 2 ) is obtained as the amount obtained by subtracting the cell capacity (Ah / m 2 ) and the negative electrode residual discharge amount (Ah / m 2 2 ) from the negative electrode discharge capacity (Ah / m). The positive electrode - negative electrode shift amount (Ah / m 2 ) is obtained as the amount obtained by subtracting the negative electrode residual discharge amount (Ah / m 2 ) from the positive electrode residual discharge amount (Ah / m 2 ).

[0063] <Examples 2 to 7 and Comparative Examples 1 to 5> As shown in Table 1, test cells were manufactured in the same manner as in Example 1, except that the composition ratio of the positive electrode active material, the type of the negative electrode active material, the ratio when the negative electrode active material is a mixture, the specific surface area of the negative electrode active material, and the specific surface area of the negative electrode active material layer were changed. The results are shown in Table 1.

[0064]

Table 1

[0065] In Examples 1 to 7 according to the present disclosure, the initial cycle capacity retention rate was 95% or more, and the cycle capacity retention rate was also 95% or more even after the storage durability test. Further, in Examples 2 to 7, the capacity retention rate after the storage durability test was 95% or more. On the other hand, in Comparative Examples 1 to 2, although the initial cycle capacity retention rate was 95% or more, the cycle capacity retention rate decreased after the storage durability test. Also, in Comparative Examples 3 to 5, the initial cycle capacity retention rate was low, and the cycle capacity retention rate decreased after the storage durability test.

Description of Reference Numerals

[0066] 10 Positive electrode plate, 11 Positive electrode base material, 12 Positive electrode active material layer, 13, 23 Tab, 20 Negative electrode plate, 21 Negative electrode base material, 22 Negative electrode active material layer, 30 Separator, 50 Electrode body, 71 Positive electrode current collector member, 72 Negative electrode current collector member, 81 Positive electrode terminal, 82 Negative electrode terminal, 90 Outer package, 91 Sealing plate, 92 Outer can, 100 Battery.

Claims

1. comprising an electrode body, said electrode body comprising a positive electrode plate and a negative electrode plate, said positive electrode plate comprising a positive electrode active material layer, said negative electrode plate comprising a negative electrode active material layer, said positive electrode active material layer having the formula (1): Li （１＋ｘ） Ni ｙ Ti ｚ Me （１－ｙ－ｚ） O ２ [In formula (1), Me comprises two or more selected from the group consisting of Mn, Co and Al, satisfying the relationships 0 < x < 0.1, 0.8 < y < 0.85 and 0 ≤ z < 0.03] and containing a positive electrode active material represented by said negative electrode active material layer containing a negative electrode active material, said negative electrode active material containing graphite, when the specific surface area of said negative electrode active material layer is S (m ２ / g), the following relational expression: (a) 10x + 2 < S A non-aqueous electrolyte secondary battery satisfying.

2. (b) The non-aqueous electrolyte secondary battery according to claim 1, further satisfying S < 10x + 3.

4.

3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the graphite content in said negative electrode active material is 99% by mass or more.

4. The non-aqueous electrolyte secondary battery according to claim 1, wherein in formula (1), the relationship 0.01 < z < 0.03 is satisfied.

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