Electrode, secondary battery, and battery pack

Abstract

According to an embodiment, there is provided an electrode comprising an active material, the active material containing an oxide represented by the general formula Li x Ni 1‑a‑b‑ c Co a Mn b M c O2 (in the formula, x, a, b, and c are 0.9≤x≤1.25, 0.05≤a≤0.5, 0.03≤b≤0.5, 0≤c≤0.2, and M contains one or more metal elements other than Ni, Co, and Mn). The electrode satisfies the following formula (1). 0.001 In the formula (1), A is a pore volume (mL / g) of pores having a pore diameter of 0.01 μm or more and 0.3 μm or less in a pore size distribution of the electrode based on a mercury intrusion method, and B is a pore volume (mL / g) of pores having a pore diameter of more than 0.3 μm and 1 μm or less in the pore size distribution of the electrode based on the mercury intrusion method.

Description

Technical Field

[0001] Embodiments of the present invention relate to electrodes, secondary batteries, and battery packs. Background Technology

[0002] With the increasing capacity of lithium-ion batteries in recent years, there is a demand for higher energy density. Nickel-cobalt-manganese composite oxides, lithium iron phosphate, and lithium manganese oxide are known as positive electrode active materials for lithium-ion batteries. One method to further increase the capacity of batteries using nickel-cobalt-manganese composite oxides in the positive electrode is to increase the nickel content.

[0003] In batteries with a cathode containing a nickel-cobalt-manganese composite oxide as the active material, a large amount of gas is generated during charge-discharge cycles under a wide range of states of charge (SOC) conditions, resulting in degradation of the active material. In particular, the amount of gas generated increases significantly when using a nickel-cobalt-manganese composite oxide with a high nickel ratio, thus presenting a challenge of balancing high battery capacity with the suppression of gas generation.

[0004] Existing technical documents Patent documents Patent Document 1: International Publication No. WO2011-108106 Patent Document 2: Japanese Patent Application Publication No. 2012-54135 Patent Document 3: Japanese Patent Application Publication No. 10-255763 Summary of the Invention

[0005] The problem that the invention aims to solve The purpose of this invention is to provide an electrode that can suppress gas generation while increasing battery capacity, a secondary battery having the electrode, and a battery pack.

[0006] Methods for solving problems According to an embodiment, an electrode is provided comprising an active material, said active material containing a component of the general formula Li. x Ni 1-a-b-c Co a Mn b M c O2 (where x, a, b, and c are 0.9≤x≤1.25, 0.05≤a≤0.5, 0.03≤b≤0.5, and 0≤c≤0.2, and M contains one or more metallic elements other than Ni, Co, and Mn) represents an oxide.

[0007] The electrodes satisfy the following equation (1).

[0008] 0.001<B / (A+B)≤0.09 (1).

[0009] In equation (1), A is the pore volume (mL / g) of the electrode with a pore size of 0.01 μm or more and 0.3 μm or less, based on the mercury indentation method, and B is the pore volume (mL / g) of the electrode with a pore size of 0.3 μm or more and 1 μm or less, based on the mercury indentation method.

[0010] According to other embodiments, a secondary battery comprising a positive electrode, a negative electrode, and an electrolyte is provided. The positive electrode comprises the electrode of the embodiment.

[0011] According to other embodiments, a battery pack is provided. The battery pack includes the aforementioned secondary battery. Attached Figure Description

[0012] Figure 1 This is a top view that roughly represents an example of an electrode.

[0013] Figure 2 It is a cross-section obtained by cutting the battery along the thickness direction in one embodiment.

[0014] Figure 3 yes Figure 2 An enlarged sectional view of part E.

[0015] Figure 4 This is a partial cutaway perspective view of a battery in another embodiment.

[0016] Figure 5 This is an exploded perspective view of a battery pack as an example of an implementation method.

[0017] Figure 6 It means Figure 5 The diagram shows a block diagram of the battery pack circuit.

[0018] Figure 7 This is a diagram illustrating an example of the pore size distribution of the electrodes of the embodiments and comparative examples based on the mercury infiltration method. Detailed Implementation

[0019] Hereinafter, embodiments will be described with reference to the accompanying drawings. Furthermore, common components are labeled with the same symbols throughout the embodiments, and repeated descriptions are omitted.

[0020] Furthermore, the figures are schematic diagrams used to facilitate the explanation and understanding of the embodiments. Their shapes, sizes, proportions, etc., may differ from the actual devices, but they can be appropriately modified by referring to the following description and known techniques.

[0021] (First Implementation) The first embodiment relates to an electrode. The electrode comprises a material of the general formula Li x Ni1-a-b-c Co a Mn b M c O2 represents the active material of the oxide. In the general formula, x, a, b, and c are 0.9≤x≤1.25, 0.05≤a≤0.5, 0.03≤b≤0.5, and 0≤c≤0.2. M contains one or more metallic elements other than Ni, Co, and Mn. The electrode satisfies the following equation (1).

[0022] 0.001<B / (A+B)≤0.09 (1) In equation (1), A is the pore volume (mL / g) of the electrode in the range of pore size greater than 0.01 μm and less than 0.3 μm based on the mercury intrusion method, and B is the pore volume (mL / g) of the electrode in the range of pore size greater than 0.3 μm and less than 1 μm based on the mercury intrusion method. Here, in the pore size distribution based on the mercury intrusion method, the horizontal axis is the pore size (μm), and the vertical axis is the Log differential pore volume (mL / g). The method for determining the pore size distribution based on the mercury intrusion method is described below.

[0023] The electrode according to the embodiment can also reduce gas generation during charge-discharge cycles. The mechanism by which the gas generation suppression effect is obtained is not yet clear, but it is speculated as follows.

[0024] The electrode described in this embodiment can be used, for example, in a non-aqueous electrolyte secondary battery such as a lithium secondary battery. As an example of a secondary battery, there is one that includes an electrolyte containing a solvent. In this electrolyte, Li ions (Li... + Diffusion can occur with a shell (also known as a solvated structure) having a Stokes radius larger than that of the solvent molecule. Pores with a diameter greater than 0.3 μm and less than 1 μm facilitate the diffusion of solvated Li ions within the electrode. Conversely, electrodes with pores having a diameter greater than 0.01 μm and less than 0.3 μm are more likely to achieve high density. Therefore, pores with a diameter greater than 0.01 μm and less than 0.3 μm contribute to high capacity in the electrode.

[0025] By making the value of B / (A+B) greater than 0.001, it is possible to promote the entry of solvated Li ions into the pores and the diffusion of Li ions. On the other hand, increasing the value of B / (A+B) may hinder the contact between the active material and the conductive agent. If the contact between the active material and the conductive agent becomes insufficient, current concentration is likely to occur. By making the value of B / (A+B) greater than 0.001 and less than 0.09, it is possible to ensure the contact between the active material and the conductive agent and promote the entry of solvated Li ions into the pores and the diffusion of Li ions. As a result, the electrode can react approximately uniformly without unevenness during charge and discharge, thus suppressing gas generation during charge and discharge cycles. Therefore, charge and discharge cycle life can be improved.

[0026] Therefore, by making the value of B / (A+B) greater than 0.001 and less than 0.09, a high-capacity electrode with low gas generation can be achieved. The value of B / (A+B) can be greater than 0.001 and less than 0.025. If it is within this range, the amount of gas generated can be further reduced. Therefore, the charge-discharge cycle life can be improved.

[0027] The electrodes will be described in detail below.

[0028] The electrode has pores with a pore diameter ranging from 0.01 μm to 1 μm. The electrode may have only pores with a pore diameter ranging from 0.01 μm to 1 μm, or it may have pores with a size deviating from this range. In the electrode, for example, the ratio of the pore volume (mL / g) represented by (A+B) in the above formula (1) to the pore volume (mL / g) of pores with a pore diameter ranging from 0.01 μm to 60 μm based on the mercury infiltration method (hereinafter referred to as pore volume C) may be 80% or more. In the electrode in which the ratio of pore volume (A+B) to pore volume C is 80% or more, the pores with a pore diameter ranging from 0.01 μm to 1 μm occupy most of the pores with a pore diameter ranging from 0.01 μm to 60 μm, thus easily obtaining the gas generation suppression effect specific to formula (1). Furthermore, the pores of the electrode with a 100% ratio have a pore diameter in the range of 0.01 μm or more and 1 μm or less. The ratio can be in the range of 80% or more and 100% or less, but the upper limit of the ratio is preferably set to 90%. By making the ratio 80% or more and 90% or less, the ratio of pores with a pore diameter in the range of 0.01 μm or more and 1 μm or less to pores with a pore diameter exceeding 1 μm can be appropriately achieved. As a result, the diffuseability of Li ions can be further improved, thereby increasing the uniformity of the charge-discharge reaction in the electrode, and thus further reducing the amount of gas generated during charge-discharge cycles.

[0029] In the pore size distribution based on mercury infiltration, the electrode can have at least one peak in the range of pore size ≥ 0.1 μm and ≤ 0.3 μm. Preferably, the at least one peak includes a peak with the maximum height. Here, when the pore volume (mL / g) in the range of pore size ≥ 0.003 μm and ≤ 0.005 μm is set as the minimum pore volume, the peak has a pore volume exceeding this minimum pore volume. The peak with the maximum height is the peak whose apex is the maximum value of the Log differential pore volume in the range of pore size ≥ 0.01 μm and ≤ 1 μm.

[0030] By having a peak with the highest height in the range of pore size greater than 0.1 μm and less than 0.3 μm, more pores with pore sizes in the range of 0.1 μm and less than 0.3 μm can exist than pores with pore sizes outside this range. As a result, the gas generation suppression effect of equation (1) can be further improved.

[0031] An electrode may have a current collector and an electrode composite layer (including an active material layer). The electrode can be either a positive electrode or a negative electrode.

[0032] The current collector may, for example, have a first surface and a second surface that is the back side of the first surface. The current collector may, for example, be strip-shaped or sheet-shaped.

[0033] The current collector is preferably aluminum foil or an aluminum alloy foil containing aluminum and one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu and Si.

[0034] The active material layer can be formed on both the first and second surfaces of the current collector. Alternatively, the active material layer can be formed on either the first or second surface of the current collector. The current collector may include portions on neither the first nor the second surface that bear the active material layer. These portions can function, for example, as electrode tabs or electrode leads.

[0035] The layer containing the active substance can possess the active substance. The active substance comprises substances of the general formula Li. x Ni 1-a-b-c Co a Mn b M c O2 represents the oxide (hereinafter referred to as the first oxide). The first oxide can also be called lithium-containing nickel-cobalt-manganese oxide or lithium-nickel-cobalt-manganese composite oxide. Lithium-containing nickel-cobalt-manganese oxide can have a layered structure. In the general formula, x, a, b, and c are 0.9≤x≤1.25, 0.05≤a≤0.5, 0.03≤b≤0.5, and 0≤c≤0.2. M contains one or more metallic elements other than Ni, Co, and Mn. The reasons for limiting x, a, b, and c to the above ranges are explained below.

[0036] The value of x can vary within a range of 0.9 to 1.25. By setting x to 0.9 or higher, the active material can maintain a stable crystal structure. Conversely, by setting x to 1.25 or lower, the discharge capacity can be increased.

[0037] By making the value of (1-abc) above 0.49, a high-capacity active material can be obtained, thus improving the energy density of the battery. Furthermore, by making the value of (1-abc) below 0.9, the reduction in the structural and thermal stability of the active material can be prevented, thus ensuring good battery safety and lifespan characteristics.

[0038] Practical battery performance can be obtained by setting a value of 0.05 or higher and 0.5 or lower.

[0039] Practical battery performance can be obtained by setting b to above 0.03 and below 0.5.

[0040] M only needs to contain one or more metallic elements other than Ni, Co, and Mn. For example, M can contain one or more elements selected from Mg, Ca, Al, Ti, V, Cr, Sr, Zr, Nb, Mo, and W.

[0041] As explained above, first oxides can achieve batteries with excellent energy density, lifespan performance, and safety. On the other hand, first oxides have problems with gas generation during charging and discharging. By making the electrode containing first oxide as the active material satisfy equation (1), gas generation during charging and discharging can be suppressed, thus obtaining batteries with excellent energy density, lifespan performance, and safety.

[0042] In the first oxide, the preferred range of (1-abc) is 0.6 ≤ (1-abc) ≤ 0.9. By setting the value of (1-abc) to this range, the energy density of the active material can be increased, thus increasing the energy density of the electrode, but gas is easily generated during charge-discharge cycles. A fine pore size distribution satisfying equation (1) has a high effect on suppressing gas generation when the molar ratio of Ni (1-abc) is set to 0.6 or more and 0.9 or less. Therefore, by making the molar ratio of Ni (1-abc) in the first oxide 0.6 or more and 0.9 or less, it is possible to reduce the amount of gas generated during charge-discharge cycles while achieving high energy density.

[0043] The first oxide can have a particle form. The particles of the first oxide can be, for example, single crystal particles, aggregates of single crystal particles, or aggregates of polycrystalline particles. The particles of the first oxide can be a mixture of single crystal particles and aggregates of single crystal particles. Single crystal particles are also called primary particles. Aggregates of single crystal particles are also called secondary particles. Examples of aggregates of single crystal particles include aggregates formed by the aggregation of single crystal particles, aggregates formed by the bonding of aggregated particles through sintering or the like, and aggregates formed by the fusion and bonding of aggregated particles. Aggregates of single crystal particles may or may not have boundaries between particles. The particles of the first oxide preferably include aggregates of single crystal particles. By including aggregates of single crystal particles in the particles of the first oxide, when the particles of the first oxide repeatedly undergo Li ion insertion and extraction reactions during charge-discharge cycles, the breakage of the particles of the first oxide and the generation of new fine pores in the electrode can be suppressed. As a result, even with repeated charge-discharge cycles, the fine pore size distribution that satisfies equation (1) can be maintained, thus suppressing gas generation during long cycles.

[0044] The shape of the first oxide particles can be, for example, granular, fibrous, or scaly.

[0045] The active material may include other active materials besides the first oxide. The proportion of the first oxide in the active material may, for example, be 70% by mass or more and 100% by mass or less. Examples of other active materials include manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, and lithium manganese composite oxides (e.g., Li). x Mn2O4 or Li x MnO2; 0 < x ≤ 1), lithium-nickel composite oxides (e.g., Li) x NiO2; 0 < x ≤ 1), lithium-cobalt composite oxides (e.g., Li) x CoO2; 0 < x ≤ 1), lithium nickel cobalt composite oxides (e.g., Li) x Ni 1-y Co y O2; 0 < x ≤ 1, 0 < y < 1), lithium manganese cobalt composite oxides (e.g., Li) x Mn y Co 1-y O2; 0 < x ≤ 1, 0 < y < 1), lithium manganese nickel composite oxides with spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≤ 1, 0 < y < 2), lithium phosphates with olivine structures (e.g., Li) x FePO4; 0 < x ≤ 1, Li x Fe 1-y Mn y PO4; 0<x≤1, 0<y≤1, Lix CoPO4; 0 < x ≤ 1), ferric sulfate (Fe2(SO4)3), vanadium oxides (e.g., V2O5).

[0046] One of the compounds listed above can be used alone as the active substance. Alternatively, a mixture of two or more of the compounds listed above can be used as the active substance.

[0047] The average particle size of the active material can be set to be greater than 1 μm and less than 10 μm.

[0048] The active material layer may also contain conductive agents and binders as needed.

[0049] The conductive agent that the electrode may contain can improve current collection performance and suppress the contact resistance between the active material and the current collector. Examples of conductive agents include carbonaceous materials such as acetylene black, carbon black, graphite, carbon nanofibers, and carbon nanotubes. One or more of these carbonaceous materials can be used alone.

[0050] Adhesives can bind active materials, conductive agents, and current collectors together. Examples of adhesives include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, styrene-butadiene rubber, acrylic resins or their copolymers, polyacrylic acid, and polyacrylonitrile.

[0051] The proportion of active material in the electrode composite layer (including the active material layer) can be set to, for example, 80% by mass or more and 95% by mass or less.

[0052] The proportion of the conductive agent in the electrode composite layer (including the active material layer) can be set, for example, to 3% by mass or more and 18% by mass or less. The aforementioned effects can be achieved by using a conductive agent content of 3% by mass or more. By using a conductive agent content of 18% by mass or less, the decomposition of electrolytes on the surface of the conductive agent under high-temperature storage can be reduced.

[0053] The proportion of binder in the electrode composite layer (including the active material layer) can be set, for example, to 2% by mass or more and 17% by mass or less. By using a binder amount of 2% by mass or more, sufficient electrode strength can be obtained. By using a binder amount of 17% by mass or less, the amount of insulating material (i.e., binder) in the electrode can be reduced, thereby reducing internal resistance.

[0054] Electrodes can be fabricated, for example, by the following method. First, a portion of the active material, conductive agent, binder, and solvent are added to a stirrer and stirred with stirring blades. This step is called the first stirring step. The first stirring step is carried out when the solid component ratio of the slurry (mixture) is high, so the viscosity of the slurry increases, and the stirring torque value increases as stirring continues. The maximum value of the stirring torque value is set as T1. If stirring continues further, the added material is broken down, so the stirring torque value decreases. The stirring torque value at this time is set as T2. In this stage, the remaining solvent is added to the stirrer and stirred further with stirring blades. This step is called the second stirring step. The second stirring step ends when the viscosity of the slurry reaches a specified value. The ratio (%) of the stirring torque value T2 to the maximum value T1 of the stirring torque is taken as the reduction rate (%) of the stirring torque. By setting the reduction rate of the stirring torque to 85% or less, the stirring based on the first stirring step becomes sufficient, so that the active material, conductive agent, and binder can be uniformly dispersed. As a result, an active material layer that satisfies equation (1) can be formed. The lower limit of the rate of reduction of stirring torque can be set, for example, to 75%.

[0055] The slurry obtained through the second stirring step is coated onto one or both surfaces of the current collector, and the coating is dried. Then, the dried coating is pressed. In this way, an electrode is obtained having a current collector and an electrode composite layer (containing an active material layer) formed on one or both surfaces of the current collector, satisfying equation (1). It should be noted that the value represented by B / (A+B) can be set to a specified range, for example, by adjusting the electrode material such as the active material, the solid component ratio of the slurry in the first stirring step, the reduction rate of stirring torque, etc. On the other hand, the ratio of pore volume (A+B) to pore volume C can be set to a specified range, for example, by adjusting the solid component ratio of the slurry in the second stirring step, etc. When the solid component ratio of the slurry in the second stirring step is high, the viscosity of the slurry increases. When the viscosity of the slurry is high, the unevenness of the surface of the slurry layer coated on the current collector is less likely to be destroyed, and drying is performed in a rougher state on the surface of the slurry layer. As a result, the surface unevenness of the electrode composite layer increases, thus reducing the ratio of pore volume (A+B) to pore volume C. On the other hand, if the solid content of the slurry in the second mixing step is low, the viscosity of the slurry will be low. When the viscosity of the slurry is low, the unevenness of the surface of the slurry layer on the current collector is destroyed, and the surface of the slurry layer becomes smoother before drying. As a result, the unevenness of the surface of the electrode composite layer is reduced, thus increasing the ratio of pore volume (A+B) to pore volume C.

[0056] Figure 1 This is a partial cutaway top view that schematically illustrates an example of an electrode involved in the embodiment. Here, as an example of an electrode, a positive electrode is illustrated.

[0057] Figure 1 The illustrated positive electrode 3 includes a positive current collector 3a and a layer 3b containing a positive active material disposed on the surface of the positive current collector 3a. The layer 3b containing the positive active material is supported on the main surface of the positive current collector 3a. Additionally, the positive current collector 3a includes a portion on its surface where the layer 3b containing the positive active material is not disposed. This portion functions, for example, as a positive current collector tab 3c. In the illustrated example, the positive current collector tab 3c is a narrow portion with a width narrower than the layer 3b containing the positive active material. The width of the positive current collector tab 3c can be narrower than the width of the layer 3b containing the positive active material, or it can be the same as the width of the layer 3b containing the positive active material. Alternatively, instead of the positive current collector tab 3c being part of the positive current collector 3a, a separate conductive component can be electrically connected to the positive electrode 3 and used as an electrode current collector tab (positive current collector tab).

[0058] The following describes the methods for determining the pore size distribution and the composition of active substances.

[0059] <Electrode Removal> When the electrode for the test object is assembled in a battery, it is removed from the battery as the electrode for the test sample as described below. The battery is discharged, and the electrode is removed by disassembly in an argon-atmospheric glove box. The electrode is then cleaned with diethyl carbonate and dried under vacuum. This yields the test sample.

[0060] Electrodes obtained by the above method can be used as samples. The pore size distribution measurement apparatus used is the Autopore 9520 model manufactured by Shimadzu Corporation. During measurement, the sample was cut to approximately 25 mm wide, folded, placed in the standard unit, and inserted into the measurement chamber. Measurements were performed under an initial pressure of 20 kPa (equivalent to approximately 3 psia, pore diameter approximately 60 μm) and a final pressure of 414,000 kPa (equivalent to approximately 60,000 psia, pore diameter approximately 0.003 μm). Furthermore, in the pore size distribution based on the mercury infiltration method, not only pores containing the active material layer but also pores of the electrode current collector appeared. However, the pore size of the current collector is sufficiently small compared to the pore size containing the active material layer, and its proportion is also small, therefore it can be ignored. The pore volume was calculated based on the obtained pore size distribution curve. Figure 7 An example of a graph showing the distribution of fine pore size.

[0061] <Confirmation of Lithium-Containing Nickel-Cobalt-Manganese Oxides> The active material contained in the identification electrode described below can be used to confirm whether it contains lithium nickel cobalt manganese oxide.

[0062] As described above, after cleaning and drying the electrodes removed from the battery, the resulting electrodes are attached to a glass sample plate. At this time, care should be taken to use double-sided tape or similar materials to prevent the electrodes from peeling or lifting. If necessary, the electrodes can also be cut to a size suitable for attachment to the glass sample plate. Additionally, Si standard samples can be added to the electrodes for peak position correction.

[0063] Next, a glass plate with electrodes attached is placed in a powder X-ray diffraction (XRD) apparatus, and a diffraction pattern is obtained using Cu-Kα rays. By using Cu-Kα rays as the radiation source and varying 2θ within the measurement range of 5 to 90°, X-ray diffraction patterns can be obtained.

[0064] For example, the SmartLab device manufactured by Rigaku Corporation was used as the apparatus for powder X-ray diffraction. The measurement conditions are as follows: X-ray source: Cu target Output: 45kV, 200mA Slatter slit: both incident and received light angles are 5°. Step size: 0.02 deg Scanning speed: 20 deg / minute Semiconductor detector: D / teX Ultra 250 Sample plate holder: Flat glass sample plate holder (0.5mm thick) Measurement range: 5°≤2θ≤90°.

[0065] In order to obtain the same measurement results as described above when using other equipment, measurements were performed using standard Si powder for powder X-ray diffraction. Under conditions that yielded peak intensities and peak positions consistent with those obtained by the aforementioned equipment, the sample was measured.

[0066] When the active material of the test object contains lithium nickel cobalt manganese oxide, X-ray diffraction can be used to confirm that the X-ray diffraction pattern belongs to space group R3-m.

[0067] Next, the sample containing the active material is observed using a scanning electron microscope (SEM). During SEM observation, to prevent the sample removed from the battery from contacting the atmosphere, it is preferable to treat it under an inactive atmosphere such as argon or nitrogen.

[0068] In a 3000x SEM image, several particles with morphologies of primary or secondary particles that are identifiable within the field of view are selected. Selection is performed to maximize the particle size distribution. For the observed active material particles, energy-dispersive X-ray spectroscopy (EDX) is used to determine the types and composition of the constituent elements. This allows for the determination of the types and amounts of elements other than Li contained in each selected particle. The same procedure is performed on multiple active material particles to determine their mixing state.

[0069] Next, for example, the composite layer (containing the active material layer) is separated from the current collector using a scraper to obtain a powdered electrode composite sample containing the active material. The collected powdered sample is washed with acetone and dried. The obtained powder is dissolved in hydrochloric acid, the conductive agent is filtered out, and then diluted with deionized water to prepare the sample for measurement. The metal content in the sample is calculated using inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0070] When there are multiple active substances, their mass ratio is estimated by the ratio of the inherent elements in each active substance. The ratio of the inherent elements to the mass of the active substance is determined by the composition of the constituent elements obtained by energy-dispersive X-ray spectrophotometry.

[0071] This allows for the identification of active substances contained in the electrode.

[0072] <Methods for Identifying Single-Crystal Particles> Whether an active substance is a single-crystal particle can be confirmed, for example, by analyzing electron beam diffraction images obtained using a transmission electron microscope (TEM).

[0073] The electrode according to the first embodiment described above comprises an active material, said active material containing a component of the general formula Li x Ni 1-a-b-c Co a Mn b M c O2 (where x, a, b, and c are oxides of 0.9≤x≤1.25, 0.05≤a≤0.5, 0.03≤b≤0.5, and 0≤c≤0.2; M includes one or more metallic elements other than Ni, Co, and Mn) is used. Additionally, the electrode satisfies equation (1).

[0074] 0.001<B / (A+B)≤0.09 (1) Based on the aforementioned electrodes, capacity can be increased and gas generation during charge-discharge cycles can be reduced. Therefore, charge-discharge cycle life can be improved.

[0075] (Second Implementation) According to a second embodiment, a battery comprising a positive electrode, a negative electrode, and an electrolyte is provided. At least one of the positive or negative electrode is an electrode of the embodiment.

[0076] Examples of batteries used in implementation methods include secondary batteries such as lithium-ion batteries. Secondary batteries include non-aqueous electrolyte secondary batteries containing a non-aqueous electrolyte.

[0077] The battery may include a separator or an outer packaging component, or both. A positive electrode, a negative electrode, and a separator can form an electrode assembly. An electrolyte can be held within the electrode assembly. Furthermore, the battery may further include an outer packaging component that houses the electrode assembly and the electrolyte. Moreover, the battery may further include a positive terminal electrically connected to the positive electrode and a negative terminal electrically connected to the negative electrode. At least a portion of the positive terminal and at least a portion of the negative terminal may extend outwards from the outer packaging component.

[0078] (positive electrode) The positive electrode may have a positive current collector and a positive composite material layer (including a positive active material layer).

[0079] The positive electrode can be the electrode of the first embodiment.

[0080] (negative electrode) The negative electrode may comprise a negative current collector and a negative electrode composite layer (containing a negative electrode active material layer). The negative electrode composite layer (containing the negative electrode active material layer) may, for example, be formed on one side or both sides of the current collector. The current collector may, for example, be strip-shaped or sheet-shaped. The negative electrode composite layer (containing the negative electrode active material layer) may comprise a negative electrode active material and any conductive agent and binder.

[0081] Examples of negative electrode active materials include metal oxides, carbonaceous materials, and metal compounds. There can be one or more types of negative electrode active materials.

[0082] Examples of carbonaceous materials include natural graphite, synthetic graphite, coke, vapor-grown carbon fibers, mesophase pitch-based carbon fibers, spherical carbon, and resin-sintered carbon. More preferred carbonaceous materials include vapor-grown carbon fibers, mesophase pitch-based carbon fibers, and spherical carbon. The preferred carbonaceous material is based on the crystal plane distance d of the (002) plane as determined by X-ray diffraction. 002 It is below 0.34nm.

[0083] As metal compounds, metal sulfides and metal nitrides can be used. As metal sulfides, examples include titanium sulfide such as TiS₂, molybdenum sulfide such as MoS₂, and compounds such as FeS, FeS₂, and Li. x Iron sulfide such as FeS2. As metal nitrides, lithium cobalt nitrides (e.g., Li) can be used, for example. s Co t N, 0<s<4, 0<t<0.5).

[0084] Examples of metal oxides include titanium oxides. Examples of titanium oxides include lithium titanium oxides (lithium-titanium composite oxides) and niobium titanium oxides (niobium-titanium composite oxides). Preferably, the titanium oxide contains lithium titanium composite oxides. Electrodes containing such titanium oxides as lithium titanium composite oxides can exhibit a redox potential of 0.4V (vs. Li / Li) relative to lithium. + The Li intercalation potential is above 1000, thus preventing the deposition of metallic lithium on the electrode surface during repeated high-current input / output operations. The titanium oxide is particularly preferably a lithium-titanium composite oxide having a spinel-type crystal structure. Specific examples of such spinel-type lithium-titanium composite oxides include those made of Li... 4+a Ti5O 12 Lithium titanate with a spinel structure, whose value of subscript a varies with charge and discharge in the range of 0 ≤ a ≤ 3.

[0085] Examples of niobium-containing titanium oxides include monoclinic niobium-containing titanium oxides. Examples of monoclinic niobium-containing titanium oxides include Nb₂TiO₇, Nb₂Ti₂O₉, and Nb₂TiO₇. 10 Ti2O 29 、Nb 14 TiO 37 、Nb 24 TiO 62 .

[0086] The form of active substances can be, for example, particles, fibers, etc. Active substance particles can be primary particles, secondary particles, or a mixture of primary and secondary particles. Examples of secondary particles include aggregates of primary particles.

[0087] The active material may include further active materials other than the aforementioned titanium oxide. For convenience, the active material containing the aforementioned titanium oxide is sometimes referred to as the "first active material," and the further active materials other than this are referred to as the "second active material." When a second active material is included in addition to the first active material, it is preferable to use a material capable of exhibiting 0.4V (vs. Li / Li) as the second active material. +An active material with a Li intercalation potential of 5% or higher. When a second active material is included, the mass ratio of the second active material to the first active material is preferably 5% or more and 40% or less by mass, more preferably 10% or more and 30% or less by mass.

[0088] Conductive agents can improve current collection performance and suppress contact resistance between the active material and the current collector. Examples of conductive agents include carbonaceous materials such as acetylene black, carbon black, graphite, carbon nanofibers, and carbon nanotubes. These carbonaceous materials can be used alone or in combination.

[0089] Adhesives can bind active materials, conductive agents, and current collectors together. Examples of adhesives include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubbers, styrene-butadiene rubber, acrylic resins and their copolymers, polyacrylic acid, and polyacrylonitrile.

[0090] The proportion of negative electrode active material in the negative electrode composite layer (including the negative electrode active material layer) can be set to, for example, 70% or more by mass and 97.5% or less by mass.

[0091] The proportion of the conductive agent in the negative electrode composite layer (including the negative electrode active material layer) can be set to, for example, 2% by mass or more and 20% by mass or less. By making the amount of conductive agent 2% by mass or more, the current-collecting performance of the composite layer (including the active material layer) can be improved, and excellent high-current performance and low-temperature performance are expected. On the other hand, from the viewpoint of high capacity, the amount of conductive agent is preferably 20% by mass or less.

[0092] The proportion of binder in the negative electrode composite layer (including the negative electrode active material layer) can be set to, for example, 0.5% by mass or more and 10% by mass or less. By making the amount of binder 0.5% by mass or more, the adhesion between the composite layer (including the active material layer) and the current collector becomes sufficient, and excellent high-temperature storage performance can be expected. On the other hand, from the viewpoint of high capacity, the amount of binder is preferably 10% by mass or less.

[0093] The current collector can be a type suitable for the negative electrode active material. For example, the negative electrode current collector may contain at least one element selected from copper, nickel, and aluminum. Examples of the negative electrode current collector's form include foils and porous bodies. When the negative electrode active material contains titanium oxide, the negative electrode current collector is preferably formed from aluminum foil or an aluminum alloy foil containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, and Si. The thickness of the current collector is preferably 20 μm or less, more preferably 15 μm or less.

[0094] (Diaphragm) A diaphragm can be disposed, for example, between the positive and negative electrodes. The diaphragm may include a portion that contacts or is opposite only one of the positive or negative electrodes.

[0095] The membrane is not particularly limited; for example, microporous membranes, woven or nonwoven fabrics, or laminates of the same or different materials can be used. Examples of materials that can form the membrane include polyethylene, polypropylene, ethylene-propylene copolymers, ethylene-butene copolymers, and cellulose.

[0096] (Non-aqueous electrolyte) Examples of electrolytes include non-aqueous electrolytes. For example, liquid or gel-like non-aqueous electrolytes can be used as non-aqueous electrolytes.

[0097] Liquid non-aqueous electrolytes can be prepared by dissolving the electrolyte in an organic solvent. The preferred electrolyte concentration is in the range of 0.5–3 mol / L. Gel-like non-aqueous electrolytes can be prepared by compounding the liquid electrolyte with a polymer material.

[0098] Examples of electrolytes include lithium salts such as lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), and lithium bis(trifluoromethanesulfonyl)imide [LiN(CF3SO2)2]. One of these electrolytes can be used alone, or two or more can be used in combination. LiPF6 is preferably included in the electrolyte.

[0099] Examples of organic solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate; chain carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC); cyclic ethers such as tetrahydrofuran (THF), 2-methyltetrahydrofuran (2MeTHF), and dioxane (DOX); chain ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); acetonitrile (AN), γ-butyrolactone (GBL), and sulfolane (SL). One of these solvents can be used alone, or two or more can be used in combination as organic solvents.

[0100] More preferred examples of organic solvents include mixed solvents composed of two or more selected from propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (MEC). By using such mixed solvents, non-aqueous electrolyte batteries with excellent charge-discharge cycle characteristics can be obtained. Additionally, additives can be added to the non-aqueous electrolyte.

[0101] (Outer packaging components) As an outer packaging component, for example, a laminated film bag or a metal container can be used.

[0102] As for the shape, there are no particular limitations, and examples include flat, square, cylindrical, coin-shaped, button-shaped, sheet-shaped, and stacked types. In addition, of course, besides small batteries installed in portable electronic devices, it can also be large batteries installed in two-wheeled to four-wheeled vehicles.

[0103] As a laminated film, for example, a multilayer film in which a metal layer is sandwiched between resin films can be used. Alternatively, a multilayer film consisting of a metal layer and a resin layer covering the metal layer can also be used.

[0104] For lightweight purposes, aluminum foil or aluminum alloy foil is preferred as the metal layer. The resin film can be made of polymeric materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The laminated film can be sealed and formed into the shape of an outer packaging component by heat-melt bonding. The wall thickness of the laminated film is preferably 0.2 mm or less.

[0105] The metal container can be formed of aluminum or an aluminum alloy. The aluminum alloy preferably contains elements such as magnesium, zinc, and silicon. On the other hand, the content of transition metals such as iron, copper, nickel, and chromium is preferably less than 100 ppm. This significantly improves long-term reliability and heat dissipation under high-temperature environments. The wall thickness of the metal container is preferably less than 0.5 mm, and more preferably less than 0.2 mm. The metal container can also function as either a positive or negative terminal.

[0106] (Positive extreme) The positive terminal is preferably made of a material that is electrically stable and conductive in a range of 3.0V to 4.5V relative to the redox potential of lithium. The positive terminal is preferably made of aluminum or an aluminum alloy containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, and Si. To reduce the contact resistance with the positive current collector, the positive terminal is preferably made of the same material as the positive current collector. Furthermore, the positive terminal and the positive current collector, such as a positive lead, can be connected via a positive current collector tab. The positive current collector tab is preferably made of the same material as both the positive terminal and the positive current collector.

[0107] (Negative extreme) The negative terminal is preferably made of a material that is electrically stable and conductive in a potential range of 0.8V to 3.0V relative to the redox potential of lithium. The negative terminal is preferably made of aluminum or an aluminum alloy containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, and Si. To reduce the contact resistance with the negative current collector, the negative terminal is preferably made of the same material as the negative current collector. Furthermore, the negative terminal and the negative current collector, for example, a negative lead, can be connected via a negative current collector tab. The negative current collector tab is preferably made of the same material as both the negative terminal and the negative current collector.

[0108] Reference Figure 2 and Figure 3 An example of a battery according to an embodiment will be described. Figure 2 The flat battery shown comprises a flat, wound electrode assembly 1, an outer packaging component 2, a positive terminal 7, a negative terminal 6, and an electrolyte (not shown). The outer packaging component 2 is a bag-shaped outer packaging component formed by lamination. The wound electrode assembly 1 is housed within the outer packaging component 2. Figure 3 As shown, the wound electrode assembly 1 includes a positive electrode 3, a negative electrode 4, and a separator 5. It is formed by winding a stack of layers arranged in the order of negative electrode 4, separator 5, positive electrode 3, and separator 5 from the outside into a spiral shape and then pressing it into shape.

[0109] The positive electrode 3 includes a positive current collector 3a and a layer 3b containing positive active material. The layer 3b contains positive active material. The layer 3b is formed on both sides of the positive current collector 3a. The negative electrode 4 includes a negative current collector 4a and a layer 4b containing negative active material. The layer 4b contains negative active material. In the outermost part of the negative electrode 4, the layer 4b is formed only on one side of the inner surface of the negative current collector 4a. In other parts of the negative electrode 4, the layer 4b is formed on both sides of the negative current collector 4a.

[0110] like Figure 3 As shown, near the outer periphery of the wound electrode assembly 1, the positive terminal 7 is connected to the positive electrode 3. Additionally, the negative terminal 6 is connected to the outermost negative electrode 4. The positive terminal 7 and the negative terminal 6 extend outwards through the opening in the outer packaging component 2.

[0111] Batteries are not limited to those mentioned above. Figure 2 and Figure 3 The configuration shown could be, for example, Figure 4 The structure shown.

[0112] exist Figure 4In the square battery shown, the wound electrode assembly 11 is housed within a bottomed rectangular cylindrical metal container 12, which serves as the outer packaging component. A rectangular cap 13 is welded to the opening of the container 12. The flat wound electrode assembly 11 may, for example, have the same shape as the referenced... Figure 2 and Figure 3 The winding electrode assembly 1 described above has the same configuration.

[0113] One end of the negative electrode tab 14 is electrically connected to the negative current collector, and the other end is electrically connected to the negative terminal 15. The negative terminal 15 is fixed to the rectangular cover 13 by an airtight seal sandwiching the glass material 16. One end of the positive electrode tab 17 is electrically connected to the positive current collector, and the other end is electrically connected to the positive terminal 18 fixed to the rectangular cover 13.

[0114] The negative electrode tab 14 is made of materials such as copper, nickel, aluminum, or aluminum alloys containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, and Si. In order to reduce the contact resistance with the negative current collector, the negative electrode tab 14 is preferably made of the same material as the negative current collector.

[0115] The positive electrode tab 17 is made of materials such as aluminum or aluminum alloys containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, and Si. In order to reduce the contact resistance with the positive current collector, the positive electrode tab 17 is preferably made of the same material as the positive current collector.

[0116] It should be noted that the battery shown in the figure uses a wound electrode assembly formed by winding the separator together with the positive and negative electrodes, but the structure of the electrode assembly is not particularly limited. For example, a stacked electrode assembly can be used, which is formed by bending the separator and alternately arranging the positive and negative electrodes at the folded parts, or a stacked electrode assembly in which the positive and negative electrodes are alternately arranged while sandwiching the separator in between.

[0117] The battery according to the first embodiment includes the electrode of the first embodiment as at least one of the positive or negative electrode. Therefore, it is possible to increase the battery capacity and reduce the amount of gas generated during charge-discharge cycles.

[0118] (Third implementation method) According to a third embodiment, a battery pack is provided. The battery pack includes the battery described in the embodiment.

[0119] The battery pack of this embodiment may include one or more batteries (single cells) as described in the previously described embodiments. The multiple batteries included in the battery pack may also be electrically connected in series or parallel to form a battery pack. The battery pack may contain multiple battery packs.

[0120] Next, an example of a battery pack according to the embodiments will be described with reference to the accompanying drawings.

[0121] Figure 5 This is an exploded perspective view of a battery pack as an example of an implementation method. Figure 6 It means Figure 5 A block diagram of the battery pack circuit.

[0122] Figure 5 and Figure 6 The battery pack 20 shown includes multiple individual cells 21. Each individual cell 21 can be a reference cell. Figure 2 A flat battery as an example of the described implementation method.

[0123] Multiple individual cells 21 are stacked in such a way that the outwardly extending negative terminals 51 and positive terminals 61 are aligned in the same direction, and then bound together with adhesive tape 22 to form a battery pack 23. These individual cells 21 are as follows... Figure 6 They are electrically connected in series as shown.

[0124] The printed circuit board 24 is arranged opposite to the sides extending from the negative terminal 51 and the positive terminal 61 of the single battery 21. For example... Figure 6 As shown, a thermistor 25, a protection circuit 26, and a power-on terminal 27 for supplying power to external devices are mounted on the printed circuit board 24. In addition, an insulating plate (not shown) is installed on the surface of the printed circuit board 24 opposite to the battery pack 23 to prevent unnecessary connections with the wiring of the battery pack 23.

[0125] The positive terminal lead 28 is connected to the bottom positive terminal 61 of the battery pack 23, and its tip is inserted into the positive terminal connector 29 of the printed circuit board 24 for electrical connection. The negative terminal lead 30 is connected to the top negative terminal 51 of the battery pack 23, and its tip is inserted into the negative terminal connector 31 of the printed circuit board 24 for electrical connection. These connectors 29 and 31 are connected to the protection circuit 26 through wirings 32 and 33 formed on the printed circuit board 24.

[0126] Thermistor 25 detects the temperature of the individual cell 21 and sends its detection signal to protection circuit 26. Protection circuit 26 can disconnect the positive wiring 34a and negative wiring 34b between protection circuit 26 and the power-on terminal 27 for powering external devices under specified conditions. An example of the specified conditions is when the detection temperature of thermistor 25 reaches or exceeds a specified temperature. Other examples of the specified conditions include, for example, detecting overcharging, over-discharging, or overcurrent in the individual cell 21. This overcharging detection is performed on each individual cell 21 or the entire battery pack 23. When detecting each individual cell 21, the battery voltage, positive electrode potential, or negative electrode potential can be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each individual cell 21. Figure 5and Figure 6 In the case of battery pack 20, wiring 35 for voltage detection is connected to each individual battery 21. The detection signal is sent to protection circuit 26 through these wirings 35.

[0127] Protective sheets 36 made of rubber or resin are respectively disposed on the three sides of the battery pack 23, excluding the protruding sides of the positive terminal 61 and the negative terminal 51.

[0128] The battery pack 23, along with the protective sheets 36 and the printed circuit board 24, is housed within the storage container 37. Specifically, the protective sheets 36 are disposed on the two inner sides along the long side and the inner side along the short side of the storage container 37, and the printed circuit board 24 is disposed on the inner side opposite to the short side. The battery pack 23 is located within the space enclosed by the protective sheets 36 and the printed circuit board 24. A cover 38 is mounted on top of the storage container 37.

[0129] Alternatively, heat-shrinkable tape can be used instead of adhesive tape 22 to secure the battery pack 23. In this case, protective sheets are placed on both sides of the battery pack, and after wrapping the heat-shrinkable tape around them, the tape shrinks to secure the battery pack.

[0130] Figure 5 and Figure 6 The diagram shows a configuration where individual cells 21 are connected in series, but they can also be connected in parallel to increase battery capacity. Furthermore, assembled battery packs can also be connected in series and / or in parallel.

[0131] Furthermore, the form factor of this battery pack can be adapted to different applications. The preferred applications are those where good cycle performance is desired when drawing high currents. Specific applications include powering digital cameras, two- to four-wheeled hybrid electric vehicles, two- to four-wheeled electric vehicles, and electric bicycles. This battery pack is particularly suitable for automotive applications.

[0132] The battery pack according to the second embodiment includes the battery according to the first embodiment. Therefore, this battery pack can increase capacity and reduce the amount of gas generated during charge-discharge cycles.

[0133] [Example] The following describes the embodiments, but the present invention is not limited to the embodiments described below as long as it does not depart from the spirit of the present invention.

[0134] (Example 1) In Example 1, the non-aqueous electrolyte battery of Example 1 was fabricated through the following steps.

[0135] <Method for making the positive electrode> As the positive electrode active material, it is prepared to be derived from the general formula Li x Ni 1-a-b-c Co a Mn b M c (where x is 0.98, 1-abc is 0.80, a is 0.10 and b is 0.10, and c is 0) represents an aggregate of single-crystal particles of lithium nickel cobalt manganese composite oxide.

[0136] A positive electrode active material, polyvinylidene fluoride (PVDF) as a binder, and acetylene black as a conductive agent were prepared in a mixing ratio of 100 parts by mass (93% by mass): 2 parts by mass (2% by mass): 5 parts by mass (5% by mass). The positive electrode active material, binder, conductive agent, and N-methylpyrrolidone (NMP) were added to a planetary mixer. The solid content ratios of all added materials are shown in Table 2. All added materials were stirred in the planetary mixer for the first stirring process. During stirring, the operating current of the stirring blades was monitored as the stirring torque. After the operating current of the stirring blades increased from the start of stirring to the maximum current value (5.9 A), stirring was continued for another 50 minutes to obtain an intermediate slurry. The operating current value of the stirring blades at this point (4.9 A) was taken as the stirring torque value T2. The reduction rate (%) of the stirring torque was calculated based on the ratio (%) of the stirring torque value T2 to the maximum stirring torque T1 (maximum current value), and the result was 83%.

[0137] Next, N-methylpyrrolidone (NMP) is added to the intermediate slurry, and the solid component ratio of the total materials (referred to as the second stirring solid component ratio) is set to 64% by mass. The mixture is then stirred using a planetary mixer to perform the second stirring process, resulting in a slurry.

[0138] The slurry is coated onto both sides of a current collector formed from aluminum foil, and the coating is allowed to dry. The dried coating is then subjected to a roll forming process. This produces a current collector with an electrode density (excluding the current collector) of 3.3 g / cm³ formed on both sides of the current collector. 3 The positive electrode contains a layer of positive active material.

[0139] <Method for making the negative electrode> As the negative electrode active material, Li4Ti5O is prepared. 12Lithium titanate with a spinel structure is represented. A slurry is prepared by mixing a negative electrode active material, polyvinylidene fluoride as a binder, graphite as a conductive agent, and N-methylpyrrolidone (NMP) as a solvent. The mixing ratio of the negative electrode active material, binder, and conductive agent is set at 100 parts by mass (94% by mass): 2 parts by mass (2% by mass): 4 parts by mass (4% by mass). The resulting slurry is coated onto an aluminum foil serving as a current collector, and after drying, the electrode density (excluding the current collector) is 2.2 g / cm³. 3 The negative electrode is obtained by pressing and molding in a certain way.

[0140] <Electrode Assembly Fabrication> The positive and negative electrodes prepared as described above are stacked with a cellulose membrane sandwiched between them to obtain a stacked electrode assembly. The positive and negative terminals are then connected to this electrode assembly.

[0141] <Preparation of Liquid Non-Aqueous Electrolytes> A mixed solvent of propylene carbonate and diethyl carbonate (volume ratio 1:2) was prepared. Lithium hexafluorophosphate (LiPF6) was dissolved in this solvent at a concentration of 13.3% by mass. Thus, a liquid non-aqueous electrolyte was prepared.

[0142] Assembly The electrode assembly and liquid non-aqueous electrolyte prepared as described above are placed in a metal container and sealed to obtain a non-aqueous electrolyte secondary battery.

[0143] (Examples 2-8 and Comparative Examples 1, 2) The solid component ratio of the intermediate slurry in the first stirring step, the reduction rate of stirring torque in the first stirring step, and the solid component ratio of the second stirring step are set as shown in Table 2 below. Otherwise, a non-aqueous electrolyte secondary battery is manufactured by the same method as in Example 1.

[0144] (Example 9) As the positive electrode active material, it is prepared to be derived from the general formula Li x Ni 1-a-b-c Co a Mn b M c (where x is 0.98, 1-abc is 0.80, a is 0.10 and b is 0.10, and c is 0) represents an aggregate of polycrystalline particles of lithium nickel cobalt manganese composite oxide. Furthermore, the solid composition ratio of the intermediate slurry in the first stirring step, the reduction rate of stirring torque in the first stirring step, and the solid composition ratio of the second stirring step are set as shown in Table 2 below. Otherwise, a non-aqueous electrolyte secondary battery is manufactured using the same method as in Example 1.

[0145] The pore size distribution of the positive electrodes of the examples and comparative examples based on mercury infiltration was determined using the method described above. For the obtained pore size distribution, the pore volume A (mL / g) in the range of pore size ≥ 0.01 μm and ≤ 0.3 μm, the pore volume B (mL / g) in the range of pore size > 0.3 μm and ≤ 1 μm, B / (A+B), the percentage (%) of the pore volume (A+B) (mL / g) in the range of pore size ≥ 0.01 μm and ≤ 60 μm, and the pore size (μm) at the peak of the largest peak are shown in Table 1.

[0146] The following steps were used to evaluate the various non-aqueous electrolyte secondary batteries fabricated in the embodiments and comparative examples.

[0147] <Determination of 1C Discharge Capacity> For rechargeable batteries, follow these steps to confirm the 1C discharge capacity: First, charge the rechargeable battery at 1C with a constant current (CC charging) until the battery voltage reaches 2.75V, then charge it at 2.75V with a constant voltage (CV charging) for 2 hours. To confirm the 1C discharge capacity, discharge the rechargeable battery at a constant current of 1C until the battery voltage reaches 1.5V; the discharge capacity during this discharge is taken as the 1C discharge capacity.

[0148] <Cyclic Test> The secondary battery, whose 1C discharge capacity was determined according to the above steps, was charged and discharged at a 3C current in a constant temperature bath at 75°C. After 600 cycles, the battery was removed, and its capacity was confirmed at 25°C. The amount of gas generated was calculated as shown in Table 1.

[0149] As clearly shown in Tables 1 and 2, the electrodes of Examples 1-9 generate less gas during charge-discharge cycles compared to the electrodes of Comparative Examples 1 and 2. When comparing Examples 2, 7, and 8 with the same B / (A+B) value, the electrode of Example 2, where the proportion of pore volume (A+B) in pore volume C is 80% or more and 90% or less, generates less gas during charge-discharge cycles compared to the electrodes of Examples 7 and 8, where the proportion is less than 80% or greater than 90%.

[0150] By comparing Examples 2 and 9, which have the same composition and pore volume A, B, and C of lithium nickel cobalt manganese composite oxide, it can be seen that the electrode of Example 2, which uses an aggregate of single crystal particles of lithium nickel cobalt manganese composite oxide, produces less gas during charge-discharge cycles compared to the electrode of Example 9, which uses an aggregate of polycrystalline particles of lithium nickel cobalt manganese composite oxide.

[0151] The pore size distribution of the electrodes (positive electrodes) of Examples 1-3 and Comparative Examples 1 and 2 is shown in the figure. Figure 7 . Figure 7 In the pore size distribution shown, the horizontal axis represents the pore size diameter (μm), and the vertical axis represents the Log differential intrusion volume (mL / g). Figure 7 The pore size distribution of the electrode (positive electrode) of the reference example is also described. The positive electrode of the reference example has the same composition as the positive electrode of Example 1. In addition, the pore volume A of the positive electrode of the reference example is 0.0645 (mL / g), the pore volume B is 0.0145 (mL / g), B / (A+B) is 0.184, the proportion (%) of the pore volume (A+B) (mL / g) in the pore volume C (mL / g) is 89, and the pore size of the peak of the largest peak is 0.25 (μm). The electrodes of Comparative Examples 1-2 and the reference example, like those of Examples 1-6, have peaks in the range of pore size of 0.1 μm or more and 0.3 μm or less. A comparison of the pore size distribution of the electrode in the reference example with that in the electrode in Comparative Example 2 shows that the pore volume in the range of pore size from 0.3 μm to 1 μm is larger than that in Comparative Example 2, and the value of B / (A+B) of the electrode in the reference example is larger than that in Comparative Example 2.

[0152] (Example 10) As the positive electrode active material, it is prepared to be derived from the general formula Li x Ni 1-a-b-c Co a Mn b M c (where x is 0.98, 1-abc is 0.50, a is 0.20 and b is 0.30, and c is 0) represents an aggregate of single-crystal particles of lithium nickel cobalt manganese composite oxide. The positive electrode was fabricated in the same manner as in Example 2, except that the positive electrode active material was used.

[0153] Except for using the obtained positive electrode, a non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 1.

[0154] (Comparative Example 3) Except that an aggregate of single-crystal particles of lithium nickel cobalt manganese composite oxide with the same composition as in Example 10 was used as the positive electrode active material, the positive electrode was fabricated in the same manner as in Comparative Example 1.

[0155] Except for using the obtained positive electrode, a non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 1.

[0156] The 1C discharge capacity and cycle test were performed on the secondary batteries of Example 10 and Comparative Example 3, and the amount of gas generated was measured. The amount of gas generated by the secondary battery of Comparative Example 3 was set to 100% to represent the amount of gas generated by the secondary battery of Example 10, and the results are shown in Table 3. Furthermore, the amount of gas generated by the secondary battery of Comparative Example 1 was set to 100% to represent the amount of gas generated by the secondary battery of Example 2, and the results are shown in Table 3.

[0157] The following information can be obtained from Table 3. The molar ratio (1-abc) of Ni in the oxides of the electrodes of Example 2 and Comparative Example 1 satisfies 0.6 ≤ (1-abc) ≤ 0.9. A comparison between Example 2 and Comparative Example 1 shows that the gas generation amount of the electrode of Example 2, where B / (A+B) is greater than 0.001 and less than 0.09, is 40% less than that of the electrode of Comparative Example 1, where B / (A+B) deviates from the above range.

[0158] On the other hand, the molar ratio (1-abc) of Ni in the oxides of the electrodes of Example 10 and Comparative Example 3 is 0.5. It is clear from the comparison between Example 10 and Comparative Example 3 that the amount of gas generated by the electrode of Example 10, where B / (A+B) is greater than 0.001 and less than 0.09, is less than that of the electrode of Comparative Example 3, where B / (A+B) deviates from the above range, but the reduction rate of gas generation in Example 2 is greater.

[0159] According to one or more embodiments and examples described above, it includes components containing the general formula Li x Ni 1-a-b- c Co a Mn b M c O2 (where x, a, b, and c are active materials of oxides represented by 0.9≤x≤1.25, 0.05≤a≤0.5, 0.03≤b≤0.5, and 0≤c≤0.2; M includes one or more metallic elements other than Ni, Co, and Mn) Furthermore, the electrode satisfies equation (1). Based on this electrode, capacity can be increased, and the amount of gas generated during charge-discharge cycles can be reduced. Therefore, charge-discharge cycle life can be improved.

[0160] 0.001<B / (A+B)≤0.09 (1) In equation (1), A is the pore volume (mL / g) of the electrode with a pore size of 0.01 μm or more and 0.3 μm or less, based on the mercury indentation method, and B is the pore volume (mL / g) of the electrode with a pore size of 0.3 μm or more and 1 μm or less, based on the mercury indentation method.

[0161] The invention with embodiments described below.

[0162] <1> An electrode comprising an active material, said active material containing a component of the general formula Li x Ni 1-a-b-c Co a Mn b M c O2 (where x, a, b, and c are 0.9≤x≤1.25, 0.05≤a≤0.5, 0.03≤b≤0.5, 0≤c≤0.2, and M contains one or more metallic elements other than Ni, Co, and Mn) represents an oxide, and the electrode satisfies the following equation (1). 0.001<B / (A+B)≤0.09 (1) In equation (1), A is the pore volume (mL / g) of the electrode with a pore diameter of 0.01 μm or more and 0.3 μm or less, based on the mercury indentation method, and B is the pore volume (mL / g) of the electrode with a pore diameter greater than 0.3 μm and less than 1 μm.

[0163] <2> according to <1> The electrode, wherein the active material comprises an aggregate of single-crystal particles of the oxide.

[0164] <3> according to <1> or <2> The electrode wherein the value of (1-abc) in the general formula of the oxide is 0.6 ≤ (1-abc) ≤ 0.9.

[0165] <4> according to <1> ~ <3> In any one of the electrodes, the pore volume (mL / g) represented by (A+B) in formula (1) is 80% or more relative to the pore volume (mL / g) in the range of pore diameters of 0.01 μm or more and 60 μm or less.

[0166] <5> according to <1> ~ <4> The electrode described in any one of the above is a positive electrode for a lithium secondary battery.

[0167] <6> A secondary battery comprising a positive electrode, a negative electrode, and an electrolyte. The positive electrode is <1> ~ <5> The electrode as described in any one of the following.

[0168] <7> according to <6> The secondary battery, wherein the negative electrode comprises lithium-containing titanium oxide.

[0169] <8> A battery pack having <6> or <7> The aforementioned secondary battery.

[0170] Several embodiments of the present invention have been described, but these embodiments are given by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the scope of the invention as set forth in the claims and their equivalents.

[0171] Explanation of reference numerals in the attached figures 1…Electrode assembly, 2…Outer packaging component, 3…Positive electrode, 3a…Positive current collector, 3b…Layer containing positive active material, 3c…Positive current collector tab, 4…Negative electrode, 4a…Negative current collector, 4b…Layer containing negative active material, 5…Separator, 6…Negative terminal, 7…Positive terminal, 11…Electrode assembly, 12…Container, 13…Rectangular cover, 14…Negative electrode tab, 16…Glass material, 17…Positive electrode tab, 18…Positive terminal, 20…Battery pack, 21…Single cell, 22…Adhesive 23… Battery pack, 24… Printed circuit board, 25… Thermistor, 26… Protection circuit, 27… Power supply terminal for powering external devices, 28… Positive side lead, 29… Positive side connector, 30… Negative side lead, 31… Negative side connector, 32… Wiring, 33… Wiring, 34a… Positive side wiring, 34b… Negative side wiring, 35… Wiring, 36… Protective sheet, 37… Storage container, 38… Lid, 51… Negative terminal, 61… Positive terminal.

Claims

1. An electrode comprising an active material, said active material containing a component of the general formula Li x Ni 1-a-b-c Co a Mn b M c O2 (where x, a, b, and c are 0.9≤x≤1.25, 0.05≤a≤0.5, 0.03≤b≤0.5, 0≤c≤0.2, and M contains one or more metallic elements other than Ni, Co, and Mn) represents an oxide, and the electrode satisfies the following equation (1). 0.001<B / (A+B)≤0.09 (1) in, In equation (1), A is the pore volume (mL / g) of the electrode with a pore size of 0.01 μm or more and 0.3 μm or less, based on the mercury indentation method, and B is the pore volume (mL / g) of the electrode with a pore size greater than 0.3 μm and less than 1 μm.

2. The electrode according to claim 1, wherein, The active material comprises an aggregate of single-crystal particles of the oxide.

3. The electrode according to claim 1, wherein, The value of (1-abc) in the general formula of the oxide is 0.6 ≤ (1-abc) ≤ 0.

9.

4. The electrode according to claim 1, wherein, The pore volume (mL / g) represented by (A+B) in formula (1) is more than 80% of the pore volume (mL / g) in the range of pore diameters of 0.01μm or more and 60μm or less.

5. The electrode according to claim 1 is a positive electrode for a lithium secondary battery.

6. A secondary battery comprising a positive electrode, a negative electrode, and an electrolyte. The positive electrode is the electrode according to any one of claims 1 to 5.

7. The secondary battery according to claim 6, wherein, The negative electrode contains lithium-containing titanium oxide.

8. A battery pack comprising the secondary battery of claim 6.

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