Cathode layer and lithium ion battery

Abstract

[Problem] The present disclosure is primarily intended to provide a positive electrode layer capable of suppressing capacity degradation due to charging and discharging of a lithium-ion battery. [Solution] In the present disclosure, the problem is solved by providing a positive electrode layer used in a lithium-ion battery, wherein the positive electrode layer comprises a positive electrode active material and an oxygen absorption and release material, wherein the positive electrode active material has crystalline primary particles containing Li, TM (TM is a transition metal), and O, and the oxygen absorption and release material is an oxide containing at least one of Ce and Zr, and the content of the oxygen absorption and release material in the positive electrode layer is greater than 0.5 weight% and less than 7 weight%.

Description

Technology Field

[0001] The present disclosure relates to a positive electrode layer for a lithium-ion battery and a lithium-ion battery. Background Technology

[0002] Positive electrode active materials containing nickel-based lithium metal composite oxides are widely used (e.g., Patent Documents 1 to 3). Prior art literature

[0003] Japanese Patent Publication No. 2023-104990, Japanese Patent Publication No. 2014-72072, Japanese Patent Publication No. 2004-311408 The problem to be solved

[0004] When charging a positive electrode active material containing a lithium metal composite oxide, lithium ions may be drawn out of the positive electrode active material, and oxygen within the positive electrode active material may be released. As a result, degradation of the positive electrode active material may occur during charging and discharging of the battery, and the reversible capacity of the battery may decrease. In particular, when charging and discharging including a high potential region of, for example, 4.1V or higher is performed, the reversible capacity is prone to decrease. Patent Document 1 describes that structural stabilization can be achieved even in a high potential region of 4.1V or higher by mixing large particles and small particles in a predetermined ratio, but there is room for improvement in suppressing the decrease in capacity.

[0005] The present disclosure is made in consideration of the above problem and has the primary objective of providing a positive electrode layer for a lithium-ion battery capable of suppressing capacity degradation due to charging and discharging of the battery. means of solving the problem

[0006] [1]

[0007] As a positive electrode layer used in lithium-ion batteries,

[0008] The above positive electrode layer comprises a positive electrode active material and an oxygen absorption and release material, and

[0009] The above positive electrode active material has crystalline primary particles containing Li, TM (TM is a transition metal), and O, and

[0010] The above oxygen absorption and release material is an oxide containing at least one of the elements Ce and Zr, and

[0011] A positive electrode layer in which the content of the oxygen-absorbing and emitting material in the positive electrode layer is greater than 0.5 weight% and less than 7 weight%.

[0012] [2]

[0013] The above oxygen absorption and release material is CeO2, ZrO2, and Ce p Zr 1-p O2(0 <p<1) 중 적어도 1종인, [1]에 기재된 정극층.

[0014] [3]

[0015] The positive electrode layer described in [1] or [2], wherein the content of the oxygen-absorbing and releasing material in the positive electrode layer is 1% by weight or more and 5% by weight or less.

[0016] [4]

[0017] The above primary particle is a positive electrode layer described in any one of [1] to [3], comprising at least Ni as the above TM.

[0018] [5]

[0019] The primary particle above is a positive electrode layer described in any one of [1] to [4], containing at least one of Co and Mn as the TM.

[0020] [6]

[0021] The positive electrode layer described in [4], wherein the molar ratio of Ni to the above TM is 0.5 or greater.

[0022] [7]

[0023] The positive electrode active material is a positive electrode layer described in any one of [1] to [6], comprising a single-crystal active material composed of the primary particles.

[0024] [8]

[0025] The positive electrode layer described in [7], wherein the particle size of the primary particles constituting the above single-crystal active material is 0.5 μm or larger.

[0026] [9]

[0027] The proportion of the single-crystal active material in the above positive electrode active material is 50% by weight or more, as described in [7] or [8].

[0028]

[10]

[0029] The above primary particle is a positive electrode layer described in any one of [1] to [9] having a layered rock salt-type crystal structure.

[0030]

[11]

[0031] The above primary particle is Li x Ni a Co b Mn c O y A positive electrode layer described in any one of [1] to

[10] having a composition represented by (wherein 0.1≤x≤1.5, 0.5≤a≤1.0, 0≤b≤0.3, 0≤c≤0.3, a+b+c=1.0, 1.5≤y≤2.1).

[0032]

[12]

[0033] A lithium-ion battery comprising a positive electrode layer as described in any one of [1] to

[11] . Effects of the invention

[0034] According to the present disclosure, a positive electrode layer for a lithium-ion battery can be provided that is capable of suppressing capacity degradation due to charging and discharging of the battery. Brief explanation of the drawing

[0035] FIG. 1 is a schematic diagram illustrating a positive electrode active material and an oxygen absorption and release material according to the present disclosure. FIG. 2 is a schematic cross-sectional view illustrating a lithium-ion battery according to the present disclosure. FIG. 3 is a schematic cross-sectional view illustrating a lithium-ion battery according to the present disclosure. Specific details for implementing the invention

[0036] The present disclosure will be described in detail below with reference to the drawings. Each drawing shown below is illustrative, and the size and shape of each part may be exaggerated to facilitate understanding.

[0037] A. Positive polar layer

[0038] The positive electrode layer in the present disclosure is a positive electrode layer used in a lithium-ion battery, wherein the positive electrode layer comprises a positive electrode active material and an oxygen absorption and release material, wherein the positive electrode active material has crystalline primary particles containing Li, TM (TM is a transition metal) and O, and the oxygen absorption and release material is an oxide containing at least one of Ce and Zr, and the content of the oxygen absorption and release material in the positive electrode layer is greater than 0.5 weight% and less than 7 weight%.

[0039] FIG. 1 is a schematic diagram illustrating a positive electrode active material and an oxygen absorption and release material according to the present disclosure. The positive electrode layer has a positive electrode active material (10) having crystalline primary particles (P) containing Li, TM (TM is a transition metal) and O, as illustrated in FIG. 1, and an oxygen absorption and release material (11). Additionally, the primary particles (P) shown in FIG. 1 constitute a single-crystal active material.

[0040] As described above, in positive electrode active materials containing lithium metal composite oxides, lithium ions may be drawn out from the positive electrode active material during charging, and oxygen within the positive electrode active material may be released. While positive electrode active materials containing Ni are expected to increase discharge capacity, such oxygen release becomes significant. Furthermore, it is known that when a battery containing a layered rock salt-type positive electrode active material containing Ni is charged, lithium ions are drawn out from the positive electrode active material, causing the crystal structure to contract in the c-axis direction.

[0041] In this regard, the present disclosure includes an oxygen-absorbing and releasing material in an amount within a predetermined range, so that the oxygen-absorbing and releasing material absorbs oxygen released from the positive electrode active material during charging. Additionally, during discharging, the oxygen-absorbing and releasing material releases oxygen and returns it to the positive electrode active material. Accordingly, the degradation of the positive electrode active material due to charging and discharging of the battery can be suppressed, thereby suppressing capacity degradation. In particular, capacity degradation can be suppressed even when charging and discharging including a high potential region is performed. If the content of the oxygen-absorbing and releasing material is excessively low, the degradation of the positive electrode active material due to charging and discharging cannot be suppressed, and thus capacity degradation cannot be suppressed. On the other hand, if the content of the oxygen-absorbing and releasing material is excessively high, the content of the positive electrode active material becomes relatively low, and sufficient battery capacity cannot be obtained.

[0042] The positive polar layer is explained in detail below.

[0043] 1. Positive electrode active material

[0044] The positive electrode active material in the present disclosure has crystalline primary particles containing Li, TM (TM is a transition metal), and O.

[0045] The primary particle contains Li, TM (TM is a transition metal), and O. The primary particle may contain one type of transition metal, two types of transition metals, three types of transition metals, or four or more types of transition metals.

[0046] Transition metals are metals belonging to groups 3 through 11 of the periodic table. Transition metals included in the primary particles may be metals belonging to the 3rd, 4th, or 5th periods. Examples of transition metals include Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, La, and W.

[0047] It is preferable that the primary particles contain at least Ni as TM. This is because a positive electrode active material with good capacitance characteristics is obtained. The molar ratio of Ni to TM (all transition metals included in the primary particles) is, for example, 0.25 or higher, and may be 0.33 or higher, 0.50 or higher, 0.70 or higher, or 0.80 or higher. By increasing the proportion of Ni, the capacitance characteristics are improved.

[0048] It is preferable that the primary particle contains at least one of Co and Mn as TM.

[0049] The primary particle may contain Co as a TM, or it may not contain Co. The molar ratio of Co to TM (all transition metals included in the primary particle) may be, for example, 0 or greater, 0.05 or greater, or 0.10 or greater. Meanwhile, the molar ratio of Co to TM may be, for example, 0.40 or less, or 0.20 or less.

[0050] The primary particle may contain Mn as TM, or it may not contain Mn. The molar ratio of Mn to TM (all transition metals included in the primary particle) may be, for example, 0 or greater, 0.05 or greater, or 0.10 or greater. Meanwhile, the molar ratio of Mn to TM may be, for example, 0.40 or less, or 0.20 or less.

[0051] It is preferable that the primary particle contains at least one of Ni, Co, and Mn as a TM. The molar ratio of the total of Ni, Co, and Mn to the TM (all transition metals included in the primary particle) is, for example, 0.80 or higher, may be 0.90 or higher, or 0.95 or higher. In addition, the "total of Ni, Co, and Mn" includes cases where the ratio of one or two types of Ni, Co, and Mn is 0.

[0052] The primary particles are, in addition to Li and TM, other metal M other than Li and TM. 1 It may contain (including metalloids). Other metal M 1 Examples include metals belonging to groups 12 to 14 of the periodic table. Examples of metals belonging to groups 12 to 14 include Zn, Al, Si, Ga, Ge, In, and Sn.

[0053] The composition of the primary particle is not particularly limited, but, for example, general formula Li x Ni a Co b Mn c O y It may be a composition represented as (0.1≤x≤1.5, 0.5≤a≤1.0, 0≤b≤0.3, 0≤c≤0.3, a+b+c=1.0, 1.5≤y≤2.1).

[0054] The above x represents the molar ratio of Li to the sum of Ni, Co, and Mn, and is typically 0.1 or higher, may be 0.4 or higher, may be 0.6 or higher, may be 0.8 or higher, may be 1.0 or higher, or may be 1.05 or higher. Meanwhile, the above x is typically 1.5 or lower, may be 1.4 or lower, or may be 1.2 or lower.

[0055] The above y represents the molar ratio of O to the sum of Ni, Co, and Mn, and is typically 1.5 or higher, and may be 1.6 or higher, 1.7 or higher, 1.8 or higher, or 1.9 or higher. Meanwhile, the above y is typically 2.1 or lower, and may be 2.0 or lower.

[0056] The above a represents the molar ratio of Ni to the sum of Ni, Co, and Mn, and is typically 0.50 or higher, and may be 0.6 or higher, 0.7 or higher, 0.8 or higher, or 0.85 or higher. Meanwhile, the above a is typically 1.0 or lower, and may be 0.9 or lower.

[0057] The above b represents the molar ratio of Co to the sum of Ni, Co, and Mn, and is typically 0 or greater, and may be 0.01 or greater, 0.02 or greater, 0.03 or greater, 0.04 or greater, 0.05 or greater, 0.06 or greater, 0.07 or greater, or 0.075 or greater. Meanwhile, the above b is typically 0.30 or less, and may be 0.25 or less, 0.20 or less, 0.15 or less, 0.10 or less, 0.09 or less, or 0.08 or less.

[0058] The above c represents the molar ratio of Mn to the sum of Ni, Co, and Mn, and is typically 0 or greater, and may be 0.01 or greater, 0.02 or greater, 0.03 or greater, 0.04 or greater, 0.05 or greater, 0.06 or greater, 0.07 or greater, or 0.075 or greater. Meanwhile, the above c is typically 0.30 or less, and may be 0.25 or less, 0.20 or less, 0.15 or less, 0.10 or less, 0.09 or less, or 0.08 or less.

[0059] Among the above equations, the molar ratio of Ni a, the molar ratio of Co b, and the molar ratio of Mn c satisfy the relationship a+b+c=1.0.

[0060] The positive electrode active material in the present disclosure is, for example, LiNi 0.90 Mn 0.10 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.5 Co 0.4 Mn 0.1 O2, LiNi 0.5 Co 0.1 Mn 0.4O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.6 Co 0.3 Mn 0.1 O2, LiNi 0.6 Co 0.1 Mn 0.3 O2, LiNi 0.7 Co 0.1 Mn 0.2 O2, LiNi 0.7 Co 0.2 Mn 0.1 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, or, LiNi 0.9 Co 0.05 Mn 0.05 It has a composition that appears as O2.

[0061] In the present disclosure, the composition of the positive electrode active material can be determined, for example, by dissolving the positive electrode active material in acid and measuring it by ICP emission spectroscopy (ICP-OES).

[0062] As for the crystal structure of the primary particle, examples include the layered rock salt type and the spinel type, and the layered rock salt type is preferred. The crystal structure of the layered rock salt type is typically attributed to the space group R-3m.

[0063] The positive electrode active material in the present disclosure typically comprises a single-crystal active material composed of the primary particles. A single-crystal active material refers to a material that is not a so-called polycrystalline active material (an active material in which a large number of primary particles are aggregated without gaps). A single-crystal active material typically exists as a single independent particle without being aggregated. It is preferable that grain boundaries are not detected in the single-crystal active material under SEM observation (magnification: approximately 10,000 to 30,000 times). A single-crystal active material has the advantage of exhibiting less degradation over time compared to a polycrystalline active material.

[0064] The particle size of the primary particle is, for example, 0.5 μm or larger, and may be 0.6 μm or larger, 0.8 μm or larger, or 1.0 μm or larger. If the particle size of the primary particle is excessively small, the particle may not grow sufficiently, making it difficult to produce as a single crystal. On the other hand, the particle size of the primary particle is, for example, 10 μm or smaller, and may be 5 μm or smaller. The particle size of the primary particle is determined as the longest diameter in a cross-sectional image obtained by a scanning electron microscope (SEM).

[0065] The external shape of the primary particle is, for example, a polyhedral shape. The external shape of the primary particle may be, for example, a hexahedral shape, an octahedral shape, etc.

[0066] The positive electrode active material in the present disclosure may include secondary particles, but may not include them. Secondary particles refer to polycrystalline active materials in which a plurality of primary particles are aggregated without gaps. In these secondary particles, oxygen released from primary particles present within the primary particles constituting the secondary particles is difficult to absorb by the oxygen absorption and release material, and deterioration within the secondary particles is difficult to suppress. In contrast, oxygen released from a single-crystal active material is easily absorbed by the oxygen absorption and release material, and oxygen released from the oxygen absorption and release material is easily introduced into the single-crystal active material. For this reason, by including a single-crystal active material in the positive electrode active material, the effect of the oxygen absorption and release material is fully exerted. The proportion of the single-crystal active material in the positive electrode active material is, for example, 50 wt% or more, and may be 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more. Meanwhile, the proportion of single-crystal active material in the positive electrode active material is, for example, 100 weight% or less.

[0067] The content of the positive electrode active material in the positive electrode layer is, for example, 20 wt% or more, and may be 30 wt% or more, 40 wt% or more, 50 wt% or more, 60 wt% or more, or 70 wt% or more. If the content of the positive electrode active material is excessively low, there is a possibility that sufficient energy density may not be obtained. On the other hand, the content of the positive electrode active material is, for example, 95 wt% or less, and may be 90 wt% or less, or 80 wt% or less. If the content of the positive electrode active material is excessively high, there is a possibility that the ionic conductivity and electronic conductivity in the positive electrode layer may decrease relatively. The content of the positive electrode active material in the positive electrode layer refers to the content of the positive electrode active material when the total solid content of the positive electrode layer is 100 wt%.

[0068] Method for manufacturing positive electrode active material

[0069] The positive electrode active material in the present disclosure can be manufactured by performing a process of synthesizing a transition metal hydroxide, a calcination process in which a mixture of the transition metal hydroxide, a Li source, and a room temperature molten salt (flux) is subjected to heat treatment, and a grinding process in which the calcined product is ground.

[0070] (a) Transition metal hydroxide synthesis process

[0071] Transition metal hydroxides are precursors of positive electrode active materials. Transition metal hydroxides may be obtained as precipitates by crystallization after dissolving multiple types of transition metal compounds in a solvent.

[0072] The method for synthesizing transition metal hydroxides is not particularly limited, but the following methods may be used as examples. First, an aqueous solution of the raw material for the transition metal hydroxide is prepared. As a method for preparing the aqueous solution of the raw material, for example, a method of dissolving a water-soluble transition metal compound in water may be used. Examples of transition metal compounds include metal salts such as sulfates and nitrates. Examples of Ni sources include NiSO4 and Ni(NO3)2. Examples of Co sources include CoSO4, Co(NO3)2, and Co(NO3)3. Examples of Mn sources include MnSO4 and Mn(NO3)2. The composition of the aqueous solution of the raw material is appropriately adjusted to suit the desired positive electrode active material.

[0073] Next, a certain amount of an aqueous NH3 solution is added to a reaction vessel, and while stirring with a stirrer or the like, nitrogen is substituted to create a non-oxidizing atmosphere. Subsequently, an aqueous sodium hydroxide solution is added to the reaction vessel to maintain the pH at an alkaline level, and while controlling the temperature, the above-mentioned raw material solution is dropped into the reaction vessel to form a reaction solution. By adjusting the pH of the reaction solution, a precipitate (precipitate) of a transition metal hydroxide can be formed.

[0074] After the precipitation reaction is finished, a false sintering is performed. The conditions for the sintering are, for example, that the temperature is 120°C or higher and 220°C or lower, the time is, for example, 4 hours or higher and 10 hours or lower, and the pressure is, for example, 0.2 MPa or higher and 1.0 MPa or lower.

[0075] After plasticizing, the material is washed with water, filtered to remove the transition metal hydroxide, and then subjected to drying treatment. The drying temperature is, for example, 100°C or higher and 150°C or lower. The drying time is, for example, 8 hours or higher and 24 hours or lower.

[0076] (b) Sintering process

[0077] A mixture is obtained by mixing the obtained transition metal hydroxide, a Li source, and a room temperature molten salt (flux). The Li source is a lithium compound, and for example, at least one selected from lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium oxide, and lithium chloride may be cited. In the present disclosure, the single-crystal active material described above is obtained by adding a room temperature molten salt to the Li source during calcination. The method of mixing the transition metal hydroxide, the Li source, and the room temperature molten salt is optional. For example, mixing may be performed using a mortar and pestle. As the room temperature molten salt, a lithium compound of the same type as the Li source may be used. In this case, by mixing the amount of lithium in the lithium compound in excess of the total amount of each transition metal species of the transition metal hydroxide, the excess lithium compound forms a molten salt, thereby promoting the single crystallization of the positive electrode active material. In the present disclosure, the mixture may contain lithium hydroxide as a Li source and a room temperature molten salt.

[0078] The ratio of the Li source to the transition metal hydroxide in the mixture is such that the ratio (molar ratio) of lithium and transition metal species to the total amount of lithium and transition metal species (e.g., Ni, Co, Mn) in the positive electrode active material is equivalent, for example, to the ratio (molar ratio) of the lithium source and transition metal species to the total amount of each transition metal species in the lithium source and transition metal hydroxide in the mixture. The ratio of the room temperature molten salt (flux) in the mixture is preferably such that the ratio (molar ratio) of Li in the room temperature molten salt to the total amount of transition metal species contained in the transition metal hydroxide is, for example, 0.1 or more, 0.5 or more, or 0.6 or more. The ratio (molar ratio) of Li contained in the Li source and molten salt to the total amount of transition metal species contained in the transition metal hydroxide is, for example, 1.1 or more, 1.5 or more, or 1.6 or more. Meanwhile, the ratio (molar ratio) of Li contained in the Li source and molten salt to the total amount of transition metal species contained in the transition metal hydroxide is, for example, 2.0 or less, and may be 1.8 or less. The mixing method is not particularly limited, and known methods may be adopted.

[0079] Next, heat treatment is performed on the mixture. Any heat treatment furnace may be used for the heat treatment. For example, a muffle furnace, an electric furnace, etc. may be used. The treatment temperature (firing temperature) is, for example, 650°C or higher and 1100°C or lower, and may be, for example, 700°C or higher and 900°C or lower. The treatment time (firing time) is, for example, 5 hours or higher and 15 hours or lower, and may be, for example, 8 hours or higher and 12 hours or lower.

[0080] Next, the calcined product is ground to a predetermined particle size, for example, an average particle size of 0.2 μm or less. This grinding may be performed using an agate mortar. Next, the ground product is dispersed in pure water and washed by stirring. The slurry after washing is filtered, rinsed, and vacuum dried.

[0081] The obtained dry powder may be post-annealed (re-fired). Post-annealing is performed under an oxygen atmosphere. The firing temperature during post-annealing is, for example, 500°C or higher and 800°C or lower, and the firing time is, for example, 1 hour or higher and 5 hours or lower.

[0082] (c) Grinding process

[0083] Next, the calcined material is crushed to a predetermined particle size. This crushing may be performed using an agate mortar and pestle or using a mill such as a laboratory mill. After crushing, additional processes such as classification and granulation may be performed. By the above, a positive electrode active material containing a single-crystal active material having a predetermined composition is obtained.

[0084] 2. Oxygen absorption and release material

[0085] The positive electrode layer in the present disclosure has an oxygen-absorbing and emitting material. As shown in FIG. 1, the oxygen-absorbing and emitting material (11) is preferably attached to at least a portion of the surface of the primary particle (P). The oxygen-absorbing and emitting material is an oxide containing at least one of the elements Ce and Zr. The oxygen-absorbing and emitting material may contain one or more additive elements. The additive elements are metal elements other than Ce and Zr, such as Ti, Y, Nd, La, etc.

[0086] As oxygen-absorbing and releasing materials, CeO2, ZrO2, and complex oxides of Ce and Zr (Ce p Zr 1-p O2(0 <p<1)), Ce와 Zr과 첨가 원소와의 복합 산화물을 들 수 있고, 그 중에서도, CeO2, ZrO2및 Ce p Zr 1-p O2 is desirable. Ce p Zr 1-pIn O2, p represents the proportion of the element Ce, and 0 <p<1.0이며, 0.4<p<1.0이어도 되고, 0.5≤p≤0.9여도 된다. 이들의 산소 흡장 방출재는, 1종 단독으로 이용해도 되고, 2종 이상을 조합하여 이용해도 된다.

[0087] Furthermore, in the embodiments described below, CeO2 is used as the oxygen absorption and release material, but ZrO2, which is a composite oxide of Ce and Zr and is already known as a conventional oxygen absorption and release material, and CeO2 are used. p Zr 1-p O2(0 <p<1), Ce와 Zr과 첨가 원소와의 복합 산화물이면, 마찬가지의 효과가 얻어진다고 추찰된다.

[0088] In the present disclosure, the content of the oxygen-absorbing and releasing material in the positive electrode layer is typically greater than 0.5 wt%, and may be 0.6 wt% or more, 0.8 wt% or more, 1 wt% or more, or 3 wt% or more. If the content of the oxygen-absorbing and releasing material in the positive electrode layer is excessively low, the deterioration of the positive electrode active material cannot be suppressed, and thus the decrease in capacity due to charging and discharging cannot be suppressed. On the other hand, the content of the oxygen-absorbing and releasing material in the positive electrode layer is typically less than 7 wt%, may be 5 wt% or less, or 3 wt% or less. If the content of the oxygen-absorbing and releasing material in the positive electrode layer is excessively high, the content of the positive electrode active material becomes relatively low, and sufficient battery capacity cannot be obtained. The content of the oxygen-absorbing and releasing material in the positive electrode layer refers to the content of the oxygen-absorbing and releasing material when the total solid content of the positive electrode layer is 100 wt%.

[0089] The oxygen-absorbing and emitting material is, for example, in the form of particles. The particle size of the oxygen-absorbing and emitting material may, for example, be 10 μm or less, 1 μm or less, 0.4 μm or less, 0.3 μm or less, 0.1 μm or less, or 0.05 μm or less. On the other hand, the particle size of the oxygen-absorbing and emitting material may be 0.01 μm or more. The particle size of the oxygen-absorbing and emitting material is, for example, smaller than the particle size of the primary particles. In addition, the oxygen-absorbing and emitting material may exist as an aggregate of fine particles. The above particle size may be the particle size of the primary particles of the oxygen-absorbing and emitting material or the particle size of the aggregate.

[0090] As shown in FIG. 1, it is preferable that the oxygen-absorbing and emitting material (11) be attached to at least a portion of the surface of the primary particle (10). Additionally, the positive electrode layer (1) may have an oxygen-absorbing and emitting material (11) that is not attached to the surface of the primary particle (10). Whether the positive electrode layer contains the oxygen-absorbing and emitting material can be confirmed by scanning electron microscopy and an energy-dispersive X-ray analysis device.

[0091] Methods for obtaining a positive electrode layer containing an oxygen-absorbing and releasing agent and a positive electrode active material include, for example, mixing the oxygen-absorbing and releasing agent with the positive electrode active material before post-annealing in the manufacturing process of the positive electrode active material, or mixing the oxygen-absorbing and releasing agent with another positive electrode layer material during the formation of the positive electrode layer. Among these, the method of mixing with another positive electrode layer material during the formation of the positive electrode layer is preferred. This is because post-annealing in the manufacturing process of the positive electrode active material is often performed under an oxygen atmosphere, and the oxygen-absorbing and releasing agent absorbs oxygen during post-annealing, thereby reducing the effect of the oxygen-absorbing and releasing agent.

[0092] 3. Positive polar layer

[0093] The positive electrode layer comprises the positive electrode active material and the oxygen absorption and release material described above, and may additionally include a conductive material and a binder, etc., as necessary. The positive electrode layer may contain an electrolyte. The electrolyte is, for example, the electrolyte solution described below. Meanwhile, the positive electrode layer may contain a solid electrolyte.

[0094] Examples of conductive materials include graphite, acetylene black (AB), Ketjen black (registered trademark), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNT), and graphene flakes (GF). The content of the conductive material in the positive electrode layer may be, for example, 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the positive electrode active material.

[0095] Examples of binders include polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polytetrafluoroethylene (PTFE), carboxymethylcellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ether, and derivatives thereof. The content of the binder in the positive electrode layer may be, for example, 0.1 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the positive electrode active material.

[0096] The thickness of the positive electrode layer may be, for example, 0.1 μm or more and 1000 μm or less, 1 μm or more and 500 μm or less, or 30 μm or more and 100 μm or less.

[0097] A positive electrode layer can be formed by the following method. For example, a positive electrode active material containing primary particles, an oxygen absorption and release agent, and a solvent are mixed to obtain a slurry for the positive electrode layer, and a coating treatment is performed to coat the slurry for the positive electrode layer onto a positive electrode current collector. As described above, the oxygen absorption and release agent may be mixed before post-annealing in the manufacturing process of the positive electrode active material. Subsequently, the positive electrode layer is formed by performing a drying treatment and a pressing treatment as necessary. Examples of pressing treatments include a roller press and a flat plate press.

[0098] Examples of solvents include N-methylpyrrolidone (NMP), tetralin, diisobutyl ketone, butyl butyrate, mesitylene, heptane, dibutyl ether, decane, dodecane, isodecane, and toluene. These solvents may be used individually or in combination of two or more.

[0099] B. Lithium-ion battery

[0100] The lithium-ion battery in the present disclosure includes a positive electrode layer for the lithium-ion battery described above. That is, in the present disclosure, a battery is provided in which a positive electrode layer, an electrolyte layer, and a negative electrode layer are stacked in this order, and the positive electrode layer is the positive electrode layer described above. FIG. 2 is a schematic cross-sectional view illustrating a lithium-ion battery in the present disclosure. The lithium-ion battery (50) shown in FIG. 2 comprises a negative electrode current collector (5), a negative electrode layer (4), an electrolyte layer (3), a positive electrode layer (1), and a positive electrode current collector (2), arranged in the thickness direction (D T Following this order, the negative electrode current collector (5) and the negative electrode layer (4) form the negative electrode (AN), and the positive electrode layer (1) and the positive electrode current collector (2) form the positive electrode (CA).

[0101] According to the present disclosure, since the lithium-ion battery has the positive electrode layer described above, the decrease in capacity due to charging and discharging of the battery can be suppressed.

[0102] 1. Positive polar layer

[0103] As for the positive polar layer, it is the same as the content described in “A. Positive Polar Layer”.

[0104] 2. Pole layer

[0105] The negative electrode layer comprises at least a negative electrode active material and, if necessary, may contain at least one of an electrolyte, a conductive material, and a binder. Examples of negative electrode active materials include silicon-based active materials such as Si and Si alloys, tin and tin alloys, and silicon oxide; carbon-based active materials such as graphite or hard carbon; various oxide-based active materials such as lithium titanate; metallic lithium and lithium alloys.

[0106] The negative electrode active material may, for example, be in the form of particles or in the form of sheets. The average particle size of the particles of the negative electrode active material may, for example, be 1 μm or more. The average particle size of the negative electrode active material may, for example, be 30 μm or less.

[0107] Regarding the conductive material, binder, and electrolyte used in the negative electrode layer, the same as those described for the positive electrode layer can be cited.

[0108] 3. Electrolyte layer

[0109] The electrolyte layer is a layer formed between the positive electrode layer and the negative electrode layer, and contains at least an electrolyte. The electrolyte is, for example, a liquid electrolyte (electrolyte).

[0110] An example of an electrolyte is a non-aqueous electrolyte. A non-aqueous electrolyte contains, for example, a lithium salt and a non-aqueous solvent. Examples of lithium salts include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, and LiAsF6; and organic lithium salts such as LiCF3SO3, LiN(SO2CF3)2, LiN(SO2C2F5)2, and LiC(SO2CF3)3.

[0111] Examples of non-aqueous solvents include carbonate-based solvents such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethylmethyl carbonate (EMC). The non-aqueous solvent may be a mixture of cyclic carbonates such as EC and PC, which have high dielectric constant and high viscosity, and chain carbonates such as DMC, DEC, and EMC, which have low dielectric constant and low viscosity. The concentration of the lithium salt in the non-aqueous electrolyte is, for example, 0.3 M or more and 5 M or less. In addition, the non-aqueous electrolyte may contain an ionic liquid. Examples of ionic liquids include sulfonium salts, ammonium salts, pyridinium salts, piperidinium salts, pyrrolidinium salts, morpholium salts, phosphonium salts, and imidazolium salts.

[0112] Another example of an electrolyte is an aqueous electrolyte. An aqueous electrolyte is an electrolyte that contains water as the main component of the solvent. The ratio of water to all solvents is, for example, 50 mass% or more, and may be 70 mass% or more. Examples of lithium salts used in aqueous electrolytes include imide-based electrolytes such as lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide. The concentration of the lithium salt in the aqueous electrolyte is, for example, 1 M or more and 25 M or less.

[0113] The electrolyte layer may be provided with a separator impregnated with the electrolyte described above. By providing a separator, the occurrence of an internal short circuit can be suppressed. The separator is, for example, a porous membrane. Examples of materials for the separator include resins such as polyethylene, polypropylene, polyester, polyvinyl alcohol, cellulose, and polyamide. In addition, the electrolyte layer may contain a solid electrolyte. Examples of solid electrolytes include organic electrolytes such as polymer electrolytes and gel electrolytes; and inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, and halide solid electrolytes.

[0114] 4. Entire House of Straight Dramas

[0115] Examples of materials for the positive electrode current collector include SUS, Cr, Au, Pt, Zn, aluminum, copper, nickel, iron, titanium, and carbon. The thickness of the positive electrode current collector is, for example, 0.1 μm or more and 100 μm or less. Examples of shapes for the positive electrode current collector include thin shapes, mesh shapes, and porous shapes. The shape of the positive electrode current collector when viewed from a planar perspective is not particularly limited, but examples include circular shapes, elliptical shapes, rectangular shapes, and any polygonal shapes. The positive electrode current collector may be configured with a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer disposed on its surface.

[0116] 5. Bu-geuk entire house

[0117] Examples of materials for the negative electrode current collector include SUS, aluminum, copper, nickel, iron, titanium, and carbon. Additionally, the thickness of the negative electrode current collector varies depending on the shape, but is, for example, 1 μm or more and 50 μm or less. The shape of the negative electrode current collector may be, for example, a thin film shape and a plate shape. The shape of the negative electrode current collector when viewed from a planar perspective is not particularly limited, but examples include a circular shape, an elliptical shape, a rectangular shape, and any polygonal shape. The negative electrode current collector may be configured with a buffer layer, an elastic layer, or a PTC thermistor layer disposed on its surface.

[0118] 6. Lithium-ion battery

[0119] The battery in the present disclosure may have an outer body that houses power generation elements (positive electrode layer, electrolyte layer, negative electrode layer). Examples of the outer body include a case-type outer body and a laminate-type outer body.

[0120] The lithium-ion battery in the present disclosure is typically a secondary battery. When a set of a positive electrode layer, an electrolyte layer, and a negative electrode layer is used as a power generation unit, the lithium-ion battery in the present disclosure may be a single cell having only one power generation unit, or a stacked battery having two or more units. The stacked battery may be a monopolar stacked battery (a stacked battery connected in parallel) or a bipolar stacked battery (a stacked battery connected in series).

[0121] FIG. 3 is a schematic cross-sectional view illustrating the case where the lithium-ion battery in the present disclosure is a bipolar battery. The lithium-ion battery (50) shown in FIG. 3 has a plurality of stacked power generation units (P). Each power generation unit (P) has a positive electrode layer (1), a negative electrode layer (4), and an electrolyte layer (3) disposed between the positive electrode layer (1) and the negative electrode layer (4). The lithium-ion battery (50) shown in FIG. 3 has bipolar electrodes (BP) (BP1 to BP29) as electrodes. Additionally, the lithium-ion battery (50) has a positive electrode end electrode (CA) and a negative electrode end electrode (AN). The bipolar electrode (BP) has a current collector (6), a positive electrode layer (1), and a negative electrode layer (4). The positive electrode layer (1) is disposed on one side of the current collector (6), and the negative electrode layer (4) is disposed on the other side of the current collector (6). The positive electrode end electrode (CA) has the current collector (6) and the positive electrode layer (1). This positive electrode layer (1) is disposed on one side of the current collector (6). The negative electrode end electrode (AN) has the current collector (6) and the negative electrode layer (4). This negative electrode layer (4) is disposed on one side of the current collector (6).

[0122] The lithium-ion battery (50) in the present disclosure may have only one bipolar electrode (BP) or two or more. Meanwhile, the battery in the present disclosure may not have a bipolar electrode.

[0123] The applications of lithium-ion batteries are not particularly limited, but examples include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline vehicles, and diesel vehicles. In particular, it is desirable to use them as power sources for driving hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or battery electric vehicles (BEVs). Additionally, the batteries may be used as power sources for mobile bodies other than vehicles (e.g., railways, ships, aircraft) or as power sources for electrical products such as information processing devices.

[0124] Furthermore, the present disclosure is not limited to the above embodiments. The above embodiments are examples, and any configuration having substantially the same structure and the same functional effect as the technical concept described in the claims of the present disclosure is included within the technical scope of the present disclosure.

[0125] [Example]

[0126] (Comparative Example 1)

[0127] [Synthesis of Positive Electrode Active Material]

[0128] By the method shown below, LiNi 0.90 Co 0.05 Mn 0.05 A positive electrode active material having a composition that appears as O2 was obtained.

[0129] <Preparation of Aqueous Solution of Raw Materials>

[0130] First, a raw material aqueous solution was prepared by dissolving NiSO4, CoSO4, and MnSO4 in ion-exchanged water. The ratio (molar ratio) of Ni, Co, and Mn in the raw material aqueous solution was adjusted so that Ni:Co:Mn was 90:5:5. The concentration of the raw material aqueous solution (moles of raw material (total solute) relative to the raw material aqueous solution) was set to 0.2 mol%.

[0131] Dehydration and Plasticity

[0132] A predetermined amount of an aqueous NH3 solution was added to a reaction vessel, and nitrogen was purged while stirring the inside of the reaction vessel with a stirrer. NaOH was added to the reaction vessel to adjust the pH of the aqueous solution to alkaline. Transition metal hydroxides were precipitated by dropping the raw material solution while maintaining a constant pH inside the reaction vessel and controlling the temperature. After the precipitation reaction was completed, dehydration and plasticization were performed on the precipitate under the following temperature and pressure conditions.

[0133] · Temperature: 120℃

[0134] · Time: 8 hours

[0135] · Pressure: 0.2 MPa

[0136] Precursor Recovery

[0137] After plasticization, the precipitate was washed with water. The washed material was filtered to extract the transition metal hydroxide. Subsequently, it was dried at 110°C for 12 hours to evaporate the moisture (dry material). Accordingly, a precursor was prepared.

[0138] <li 원료의 혼합>

[0139] The obtained precursor (transition metal hydroxide) and the lithium compound (LiOH) as a Li source were mixed in a mortar and pestle such that the ratio (molar ratio) of Li to the total amount of transition metal species contained in the transition metal hydroxide was 1.0. In addition, the lithium compound (LiOH) as a molten salt was mixed such that the ratio (molar ratio) of Li to the total amount of transition metal species contained in the transition metal hydroxide was 0.6. That is, the total amount of LiOH added was set so that the ratio (molar ratio) of Li contained in LiOH to the total amount of transition metal species contained in the transition metal hydroxide was 1.6. Accordingly, during calcination, the excess lithium compound forms a molten salt, thereby promoting the single crystallization of the positive electrode active material.

[0140] <Small>

[0141] Heat treatment (calcination) was performed on the mixture. It was calcined in a muffle furnace at 780°C for 12 hours (calcination process). Subsequently, the calcined material was crushed in an agate mortar to a particle size of 0.2 mm or less, dispersed in 500 mL of pure water, and vigorously stirred for 1 minute to obtain a slurry. The slurry was filtered through a Buchner lot and filter paper, rinsed with 500 mL of pure water, and the resulting cake was vacuum dried at 90°C. The obtained dried powder was calcined at 500°C for 3 hours under oxygen circulation (post-annealing). The calcined material was ground in an agate mortar to a predetermined particle size (grinding). Accordingly, LiNi 0.90 Co 0.05 Mn 0.05 A positive electrode active material having a composition that appears as O2 was obtained.

[0142] [Production of a Straight Play]

[0143] A slurry for a positive electrode layer, comprising the above particles as a positive electrode active material and N-methylpyrrolidone (NMP) as a solvent, was coated onto a metal foil serving as a positive electrode current collector using a film applicator equipped with a film thickness adjustment function (All Good Co., Ltd.). After coating, a drying treatment was performed for 5 minutes using an 80°C hot plate to evaporate the NMP solvent, thereby forming a positive electrode layer on the positive electrode current collector. Accordingly, a positive electrode having a positive electrode current collector and a positive electrode layer was obtained.

[0144] [Battery Production]

[0145] A negative electrode composite paste containing natural graphite, which is the negative electrode active material, was coated onto the surface of a metal foil, which is the negative electrode current collector, using a film applicator equipped with a film thickness adjustment function (manufactured by All Good Co., Ltd.). Afterwards, a negative electrode having a negative electrode layer on the negative electrode current collector was fabricated by drying it in a dryer at 80°C for 5 minutes. A 1M LiPF6 solution was prepared as the electrolyte, containing LiPF6 as the electrolyte and ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) as solvents in a ratio of EC / DMC / EMC = 3 / 4 / 3 vol%. The positive electrode, separator, and negative electrode were laminated, and the electrolyte was impregnated into the separator to fabricate a small laminate cell in which a power generation element is housed in a pouch made of an Al laminate film.

[0146] (Example 1)

[0147] In the manufacturing process of the positive electrode active material, the positive electrode active material was manufactured in the same manner as Comparative Example 1, except that CeO2 (manufactured by Nanotech Co.) was mixed into the dry powder prior to post-annealing (re-calcination) using an agate mortar to a concentration of 3% by weight relative to the positive electrode layer, and LiNi 0.90 Co 0.05 Mn 0.05 A mixture of a positive electrode active material having a composition appearing as O2 and CeO2 was obtained. The obtained mixture was dispersed on a carbon tape and observed using a scanning electron microscope; as shown in FIG. 1, it was confirmed that an oxygen absorption-releasing agent (11) was attached to the surface of the primary particles (10) constituting the single-crystal active material. Additionally, elemental mapping of Ni and Ce was performed using an energy-dispersive X-ray analysis device (EDX). As a result, it was confirmed that the oxygen absorption-releasing agent (Ce) was mainly attached to the surface of the positive electrode active material (Ni). A slurry for a positive electrode layer containing the obtained mixture and an NMP solvent was coated onto a metal foil serving as a positive electrode current collector using a film applicator (AllGood Co., Ltd.) equipped with a film thickness adjustment function, and a drying treatment was performed to obtain a positive electrode having a positive electrode current collector and a positive electrode layer. A laminated cell was obtained in the same manner as Comparative Example 1, except that the obtained positive electrode layer was used.

[0148] (Examples 2–4, Comparative Examples 2–3)

[0149] LiNi 0.90 Co 0.05 Mn 0.05 After obtaining a positive electrode active material having a composition represented as O2, CeO2 (manufactured by Nanotech Co.) was mixed with the positive electrode active material and an NMP solvent to prepare a slurry for the positive electrode layer such that the CeO2 content in the positive electrode layer is the content shown in Table 1. A laminated cell was obtained in the same manner as in Example 1, except that the obtained slurry for the positive electrode layer was used.

[0150] [evaluation]

[0151] In the laminated cell, a cycle test was conducted under the following conditions.

[0152] Ambient temperature: 60℃

[0153] Cycle count: 100

[0154] Current rate: 0.3C

[0155] Voltage range: 4.25V to 2.5V

[0156] In the initial capacity test based on the cycle test results, the initial discharge capacity per 1g of positive electrode active material (unit: mAhg) is obtained by dividing the electrical capacity (mAh) obtained during the discharge process of the first charge-discharge cycle by the weight (unit: g) of the positive electrode active material included in the electrode within the laminated cell. -1 ) was calculated. Likewise, the discharge capacity (mAhg after 100 cycles) -1 ) was calculated. In addition, the degree of deterioration rate was calculated when Comparative Example 1 was set to 1. The results are shown in Table 1.

[0157] Degree of degradation rate of each example or comparative example = (Initial discharge capacity - Discharge capacity after 100 cycles) / (Initial discharge capacity of Comparative Example 1 - Discharge capacity of Comparative Example 1 after 100 cycles)

[0158]

[0159] As shown in Table 1, it was confirmed that a battery having a positive electrode layer containing an oxygen-absorbing and releasing material in a predetermined ratio suppresses capacity degradation after 100 cycles (Examples 1 to 4). In both Example 1 and Example 2, the content of the oxygen-absorbing and releasing material in the positive electrode layer was 3 wt%, but the capacity degradation rate was lower in Example 2. This suggests that the oxygen-absorbing and releasing material in Example 1 absorbed oxygen during post-annealing in an oxygen atmosphere, so the oxygen absorption and release effect during battery charging and discharging was lower than in Example 2. Explanation of the symbols

[0160] 1… Straight pole 2… The entire house of a serious drama 3… Electrolyte layer 4… Poor polarity 5… Buguk entire house 10… positive electrode active material 11… Oxygen absorption and release material 50… lithium-ion battery

Claims

Claim 1 A positive electrode layer used in a lithium-ion battery, wherein the positive electrode layer comprises a positive electrode active material and an oxygen absorption and release material, wherein the positive electrode active material has crystalline primary particles containing Li, TM (TM is a transition metal) and O, and the oxygen absorption and release material is an oxide containing at least one of Ce and Zr, and wherein the content of the oxygen absorption and release material in the positive electrode layer is greater than 0.5 weight% and less than 7 weight%. Claim 2 In claim 1, the oxygen absorption and release material is CeO2, ZrO2, and Ce p Zr 1-p O2(0 <p<1) 중 적어도 1종인, 정극층. Claim 3 A positive electrode layer according to claim 1, wherein the content of the oxygen-absorbing and emitting material in the positive electrode layer is 1% by weight or more and 5% by weight or less. Claim 4 In claim 1, the primary particle is a positive electrode layer comprising at least Ni as the TM. Claim 5 In claim 4, the primary particle is a positive electrode layer containing at least one of Co and Mn as the TM. Claim 6 In claim 4, the positive electrode layer, wherein the molar ratio of Ni to TM is 0.5 or higher. Claim 7 In claim 1, the positive electrode active material comprises a positive electrode layer including a single-crystal active material composed of the primary particles. Claim 8 In claim 7, the positive electrode layer, wherein the particle size of the primary particles constituting the single-crystal active material is 0.5 μm or more. Claim 9 In claim 7, the ratio of the single-crystal active material in the positive electrode active material is 50 weight% or more, in the positive electrode layer. Claim 10 In claim 1, the primary particle is a positive electrode layer having a layered rock salt-type crystal structure. Claim 11 In claim 1, the primary particle is Li x Ni a Co b Mn c O y A positive polar layer having a composition represented by (wherein 0.1≤x≤1.5, 0.5≤a≤1.0, 0≤b≤0.3, 0≤c≤0.3, a+b+c=1.0, 1.5≤y≤2.1). Claim 12 A lithium-ion battery comprising a positive electrode layer described in any one of claims 1 to 11.

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