Positive electrode plate and non-aqueous electrolyte secondary battery

Abstract

The invention relates to a positive electrode plate and a nonaqueous electrolyte secondary battery. The positive electrode plate includes: a first active material which is a lithium transition metal composite oxide; and a second active material that is a lithium transition metal composite oxide and that has a smaller average particle diameter (D50) than the first active material. The crystallite size of the second active material is 800 nm or more. The ratio (Li / M) of the number of moles of lithium (Li) in the first active material to the total number of moles of the transition metal (M) is 1.05 or more. The ratio (Li / M) of the number of moles of lithium (Li) in the second active material to the total number of moles of the transition metal (M) is 1.04 or less.

Description

Technical Field The present invention relates to a positive electrode plate and a non-aqueous electrolyte secondary battery. Background Art In non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries, as the positive electrode active material contained in the active material layer of the positive electrode plate, it is known to use a lithium transition metal composite oxide as a composite oxide of lithium and transition metals. Japanese Patent Publication No. 2021-518049, Japanese Patent Publication No. 2011-113825 and International Publication No. 2021 / 065162 disclose that by using a positive electrode plate of two or more lithium transition metal composite oxides with different particle sizes, the capacity and output can be improved. Summary of the invention In a non-aqueous electrolyte secondary battery, when the charge capacity is increased, the thermal stability may be reduced. Therefore, a non-aqueous electrolyte secondary battery that achieves both a high charge capacity and excellent thermal stability is required. An object of the present disclosure is to provide a positive electrode plate capable of achieving both high charge capacity and excellent thermal stability, and a nonaqueous electrolyte secondary battery including the same.

[0001] A positive electrode plate, comprising: a first active material, which is a lithium transition metal composite oxide; and a second active material, which has a smaller average particle size (D50) than the first active material and is a lithium transition metal composite oxide, wherein the crystallite size of the second active material is greater than 800 nm, the ratio of the molar number of lithium (Li) in the first active material to the total molar number of transition metals (M) (Li / M) is greater than 1.05, and the ratio of the molar number of lithium (Li) in the second active material to the total molar number of transition metals (M) (Li / M) is less than 1.04.

[0002] The positive electrode plate according to [1], wherein a ratio (Li / M) of the number of moles of lithium (Li) to the total number of moles of transition metals (M) in the first active material is 1.12 or less.

[0003] The positive electrode plate according to [1] or [2], wherein a ratio (Li / M) of the number of moles of lithium (Li) to the total number of moles of transition metals (M) in the second active material is 0.98 or more.

[0004] The positive electrode plate according to any one of [1] to [3], wherein a ratio (Li / M) of the number of moles of lithium (Li) to the total number of moles of transition metals (M) in the second active material is 1.01 or more.

[0005] The positive electrode plate according to any one of [1] to [4], wherein a mass ratio of the first active material to the second active material (first active material / second active material) is 5 / 5 or more and 8 / 2 or less.

[0006] The positive electrode plate according to any one of [1] to [5], wherein an average particle size (D50) of the first active material is 12 μm or more and 20 μm or less.

[0007] The positive electrode plate according to any one of [1] to [6], wherein an average particle size (D50) of the second active material is 2 μm or more and 8 μm or less.

[0008] The positive electrode plate according to any one of [1] to [7], wherein the first active material and the second active material each contain 80 mol % or more of nickel (Ni) based on the total amount of transition metals.

[0009] The positive electrode plate according to any one of [1] to [8], wherein the second active material is at least one of a single particle and a secondary particle in which three or less primary particles are aggregated.

[0010] A nonaqueous electrolyte secondary battery includes: an electrode body having a positive electrode plate according to any one of [1] to [9], a negative electrode plate, and a separator between the positive electrode plate and the negative electrode plate; and an electrolyte solution. The above and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 The charge capacity and 4.1 V vs. Li / Li when charging the test battery cell (r1) having the positive electrode plate (r1) formed using the first active material + A graph in which the ratio of the capacity at the above potentials is plotted against the ratio (Li / M) of the number of moles of lithium (Li) to the total number of moles of transition metals (M) in the first active material. Figure 2 The charge capacity and 4.1 V vs. Li / Li when charging the test battery cell (r2) having the positive electrode plate (r2) formed using the second active material + A graph in which the ratio of the capacity at the above potentials is plotted against the ratio (Li / M) of the number of moles of lithium (Li) to the total number of moles of transition metals (M) in the second active material. DETAILED DESCRIPTION (Positive plate) The positive electrode plate of this embodiment can be used in a non-aqueous electrolyte secondary battery (hereinafter also referred to as a "secondary battery"). The positive electrode plate includes: a first active material, which is a lithium transition metal composite oxide; and a second active material, which has a smaller average particle size (D50) than the first active material and is a lithium transition metal composite oxide. The crystallite size of the second active material is 800 nm or more. The lithium transition metal composite oxide is an oxide containing lithium and a transition metal. As the transition metal contained in the lithium transition metal composite oxide, one or more selected from nickel (Ni), manganese (Mn), cobalt (Co), aluminum (Al), and titanium (Ti) can be listed, preferably one or more selected from Ni, Mn, Co, and Al, more preferably one or more selected from Ni, Mn, and Co. The above-mentioned transition metal preferably includes Ni, Mn, and Co, and may include Ni, Mn, Co, and Al. Relative to the total amount of transition metals, the first active material and the second active material each independently contain preferably 80 mol% or more of Ni, more preferably contain 80 mol% or more and 98 mol% or less of Ni, may contain 81 mol% or more and 95 mol% or less of Ni, may contain 82 mol% or more and 90 mol% or less of Ni. By using the first active material and the second active material having a Ni content within the above range, a high capacity of the secondary battery can be achieved. The ratio (Li / M) of the number of moles of Li in the first active material to the total number of moles of transition metals (M) is 1.05 or more, may be 1.07 or more, and may be 1.09 or more. The above ratio (Li / M) in the first active material is preferably 1.05 or more and 1.12 or less, may be 1.05 or more and 1.10 or less, may be 1.07 or more and 1.10 or less, and may be 1.07 or more and 1.09 or less. The ratio (Li / M) of the number of moles of Li in the second active material to the total number of moles of transition metals (M) is 1.04 or less, can be 1.03 or less, and can be 1.02 or less. The above ratio (Li / M) in the second active material is preferably 0.98 or more and 1.04 or less, can be 1.00 or more and 1.04 or less, more preferably 1.01 or more and 1.04 or less, and can be 1.02 or more and 1.03 or less. The composition of the first active material and the second active material (lithium transition metal composite oxide) can be obtained by high-frequency inductively coupled plasma (ICP) emission analysis. As described in the manufacturing example of the embodiment described later, if the above ratio (Li / M) in the first active material is less than 1.05, the total capacity of the test battery cell (r1) having the positive electrode plate (r1) formed using the first active material when charged is 4.1Vvs.Li / Li + The ratio of the capacity at the potential above this value becomes larger ( Figure 1 and Table 1). On the other hand, if the above ratio (Li / M) in the first active material becomes greater than 1.05, the above capacity ratio tends to converge and the change tends to become smaller ( Figure 1 and Table 1). It is considered that if the 4.1Vvs.Li / Li +If the ratio of the capacity at the potential above increases, the stability of the structure of the lithium transition metal composite oxide constituting the first active material decreases, and the lithium transition metal composite oxide is prone to phase change. As a result, it is inferred that the potential during charging of the secondary battery is prone to rise, and the ratio of the capacity at this potential increases. The ratio of the above capacity is an indicator of the thermal stability of the test battery cell (r1), and the smaller the ratio of the capacity, the better the thermal stability. Therefore, whether the above ratio (Li / M) of the first active material is above 1.05, it can be said that the impact on the thermal stability of the secondary battery is large. If the ratio (Li / M) in the second active material is 1.04 or less, the charge capacity per unit mass of the second active material can be increased when charging the test battery cell (r2) having the positive electrode plate (r2) formed using the second active material (the manufacturing example of the embodiment described later, Figure 2 and Table 2). On the other hand, if the above ratio (Li / M) in the second active material is higher than 1.04, the charge capacity tends to be greatly reduced ( Figure 2 and Table 2). Therefore, it can be said that whether the above ratio (Li / M) of the second active material is 1.04 or less has a great influence on the size of the charge capacity of the secondary battery. Therefore, by using the first active material having the ratio (Li / M) of 1.05 or more and the second active material having the ratio (Li / M) of 1.04 or less to obtain a positive electrode plate, a secondary battery with a high capacity that has both excellent thermal stability and charge capacity can be easily obtained. As the first active material and the second active material, when a lithium transition metal composite oxide having a Ni content of 80 mol% or more relative to the total amount of the above-mentioned transition metal is used, the high capacity of the secondary battery can be achieved. On the other hand, since the resistance of the positive plate becomes smaller, the potential of the secondary battery is likely to rise and the thermal stability is likely to decrease. Therefore, from the viewpoint of both excellent thermal stability and high capacity of the charge capacity, when using a first active material and a second active material having a large Ni content in the transition metal, it is particularly preferred to use a lithium transition metal composite oxide having a ratio (Li / M) in the above-mentioned range. The crystallite size of the second active material can be as long as it is 800nm ​​or more, and can be 850nm or more, or 900nm or more. The crystallite size of the second active material can be 800nm ​​or more and 2000nm or less, 800nm ​​or more and 1500nm or less, 850nm or more and 1200nm or less, or 900nm or more and 1100nm or less. When the second active material is a single particle, the crystallite size of the second active material is the size of the crystallites contained in the single particle, and when the second active material is a secondary particle, it is the size of the crystallites contained in the primary particles constituting the secondary particles. The crystallite size can be measured by X-ray diffraction. When the crystallite size of the second active material is within the above range, the storage durability of the secondary battery can be improved. In the positive plate, even when a second active material having the above crystallite size is used, a lithium transition metal composite oxide having a ratio (Li / M) in the above range is used as the first particle and the second particle. Therefore, by using this positive electrode plate, a secondary battery having both excellent thermal stability and a high-capacity charge capacity can be obtained. The average particle size (D50) of the first active material (hereinafter also referred to as "D50") is not particularly limited as long as it is larger than the D50 of the second active material. The D50 of the first active material is preferably greater than 12 μm and less than 20 μm, may be greater than 14 μm and less than 19 μm, and may be greater than 15 μm and less than 18 μm. By having the D50 of the first active material within the above range, it is easy to obtain a high-capacity secondary battery that takes into account both excellent thermal stability and charging capacity. With respect to the D50 of the first active material, when the first active material is a secondary particle, it is based on the particle size of the secondary particle. The average particle size (D50) in this specification is the particle size at which the accumulation of frequencies from the smaller particle size side in the volume-based particle size distribution becomes 50%. The volume-based particle size distribution can be measured using a laser diffraction particle size distribution measuring device. The D50 of the second active material is not particularly limited as long as it is smaller than the D50 of the first active material. The D50 of the second active material is preferably greater than 2 μm and less than 8 μm, may be greater than 2 μm and less than 6 μm, and may be greater than 4 μm and less than 6 μm. By having the D50 of the second active material be within the above range, it is easy to obtain a high-capacity secondary battery that takes into account both excellent thermal stability and charging capacity. With respect to the D50 of the second active material, when the second active material is a single particle, it is based on the particle size of the single particle, and when the second active material is a secondary particle, it is based on the particle size of the secondary particle. The first active material is preferably a secondary particle (aggregated particle) in which primary particles are aggregated, and the number of primary particles contained in the secondary particles is, for example, greater than 100. When both the first active material and the second active material are secondary particles, the number of primary particles contained in one first active material is preferably greater than the number of primary particles contained in one second active material. The second active material is preferably at least one of a single particle and a secondary particle aggregated with less than 3 primary particles, and may be at least one of a single particle or a secondary particle aggregated with 2 primary particles. The second active material may include a single particle and a secondary particle aggregated with less than 3 primary particles. Thus, it is easy to obtain a secondary battery with high capacity that takes into account excellent thermal stability and charging capacity. The particle size of the single particle or primary particle constituting the second active material may be greater than 0.7 μm, may be greater than 0.8 μm, may be greater than 1 μm, for example, may be greater than 0.7 μm and less than 8 μm, may be greater than 0.8 μm and less than 6 μm. The mass ratio of the first active material to the second active material contained in the positive plate (first active material / second active material) is preferably 5 / 5 or more and 8 / 2 or less, 5 / 5 or more and 7 / 3 or less, or 6 / 4 or more and 7 / 3 or less. By making the mass ratio (first active material / second active material) within the above range, the filling property of the first active material and the second active material in the positive plate can be improved, thereby improving the output and capacity of the secondary battery. The positive electrode plate can have an active material layer including a first active material and a second active material, and the active material layer can be formed on a positive electrode current collector. The positive electrode current collector is, for example, a metal foil made of aluminum material such as aluminum and aluminum alloy. The positive electrode plate can have a tab formed of aluminum material. The active material layer may include other positive electrode active materials in addition to the first active material and the second active material, and may include a conductive material, a binder, etc. In the total amount of the positive electrode active material contained in the active material layer, the content of the first active material and the second active material is preferably 95% by mass or more and 100% by mass or less, more preferably 95% by mass or more and 99% by mass or less, and may be 96% by mass or more and 98% by mass or less. Conductive materials include, for example, carbon materials. Carbon materials include, for example, one or more selected from fibrous carbon, carbon black (acetylene black, Ketjen black, etc.), coke, and activated carbon. As fibrous carbon, carbon nanotubes (CNTs) may be listed. CNTs may be single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes such as double-walled carbon nanotubes (DWCNTs). Examples of the binder include one or more selected from the group consisting of styrene butadiene rubber (SBR), polyvinylidene fluoride (PVdF), and polytetrafluoroethylene (PTFE). The positive electrode plate can be manufactured, for example, by forming an active material layer containing a first active material and a second active material on a positive electrode collector. The active material layer can be formed by applying a slurry containing the first active material and the second active material on the positive electrode collector, drying, and compressing. The slurry can further contain a conductive material, a binder, a solvent such as N-methyl-2-pyrrolidone (NMP), and the like. (Non-aqueous electrolyte secondary battery) The secondary battery may include: an electrode body having the above-mentioned positive electrode plate, negative electrode plate, and a separator existing between the positive electrode plate and the negative electrode plate; and an electrolyte. The secondary battery may further include a battery case accommodating the electrode body and the electrolyte. The electrode body may be a stacked electrode body composed of a stacked body in which a positive electrode plate, a negative electrode plate, and a separator are stacked, or may be a wound electrode body in which a stacked body is wound. The stacked electrode body may have a quadrilateral shape when viewed from above, preferably a square or a rectangle, and more preferably a rectangle. The wound electrode body may be a flat wound electrode body that is pressed after the stack is wound. The negative electrode plate may include a negative electrode collector and a negative electrode active material layer formed on the negative electrode collector. The negative electrode collector is, for example, a metal foil made of a copper material such as copper and a copper alloy. The negative electrode active material layer includes a negative electrode active material and may further include one or both of a conductive material and a binder. As negative electrode active materials, carbon-based active materials containing carbon (C) atoms such as graphite can be listed; metal-based active materials containing metal elements such as metal single substances or metal oxides containing elements selected from silicon (Si), tin (Sn), antimony (Sb), bismuth (Bi), titanium (Ti), and germanium (Ge) can be listed. As conductive materials, carbon materials such as fibrous carbon, carbon black (such as acetylene black, Ketjen black), coke, and activated carbon can be listed. Fibrous carbon can list the examples described above. As binders, cellulose-based binders such as carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), etc. can be listed. As the separator, a porous sheet (film, nonwoven fabric, etc.) composed of a resin such as polyethylene, polypropylene, polyester, cellulose, polyamide, etc. can be cited. The porous sheet can be a single-layer structure or a multilayer structure of two or more layers. The separator can have a functional layer on the surface of the porous sheet. The functional layer can include at least one of a heat-resistant layer and an adhesive layer for bonding to the positive electrode plate and the negative electrode plate. As electrolyte, non-aqueous electrolyte can be listed, for example, electrolyte containing supporting salt in non-aqueous solvents such as organic solvents can be listed. As non-aqueous solvent, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) etc. can be listed. Electrolyte can include one or more non-aqueous solvents among these. As supporting salt, for example, lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6) and lithium borofluoride (LiBF4) etc. can be listed. Electrolyte can include one or more supporting salt among these. Electrolyte can further include additives such as vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate. The battery case is preferably made of metal, and can be formed using, for example, aluminum, an aluminum alloy, iron, or an iron alloy. Example The present disclosure will be described in more detail below with reference to Examples and Comparative Examples. [Analysis of Compositions of the First Active Material and the Second Active Material] The compositions of the first active material and the second active material were analyzed by high-frequency inductively coupled plasma (ICP) emission analysis. [Measurement of Average Particle Size (D50) of First Active Material and Second Active Material] The average particle diameter (D50) of the first active material and the second active material was measured using a laser diffraction particle size distribution analyzer ("Masterizer-3000", manufactured by Malvern Panalytica l). [Determination of crystallite size] The crystallite size of the second active material was calculated from the peak intensity of the (104) plane using an X-ray diffraction apparatus ("SmartLab", manufactured by Rigaku Corporation). [Production Example 1] (Preparation of the First Active Material) By 0.80 Co 0.05 Mn 0.15 A transition metal compound represented by (OH)2 and LiOH are mixed and sintered to obtain a first active material, which is a lithium transition metal composite oxide, and the ratio of the molar number of Li to the total molar number of the transition metal (M) (Li / M) is 1.05, and the average particle size (D50) is 17.2μm. The first active materials are obtained by mixing NiCoMn composite hydroxide and lithium compound and calcining at 700-1000° C., wherein the first active materials are lithium transition metal composite oxides, and the ratio of the mole number of Li to the total mole number of transition metal (M) (Li / M) is 1.03, 1.07, 1.09 and 1.12. The average particle size of the first active materials is within the range of 12 μm or more and 20 μm or less. (Production of positive electrode plate (r1)) Using the first active material having the above-obtained ratio (Li / M), respectively, the positive electrode plate (r1) is prepared by the following steps. First, 97.5 parts by mass of the first active material, 1.5 parts by mass of carbon black as a conductive material, and 1.0 parts by mass of polyvinylidene fluoride (PVdF) as a binder are mixed, and then an appropriate amount of N-methyl-2-pyrrolidone (NMP) is added to obtain a slurry. The slurry is applied to aluminum foil as a positive electrode collector and dried, and rolled to a specified thickness using a calendering roller. Thus, a density of 3.30 g / cm is formed on the aluminum foil. 3 The positive electrode active material layer is formed to obtain a positive electrode original sheet (r1). The positive electrode original sheet (r1) is cut into a predetermined size and an electrode tab formed of aluminum is installed to obtain a positive electrode (r1). (Preparation of Electrolyte) In a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) as non-aqueous solvents in a ratio of EC:EMC=30:70 (volume ratio), lithium hexafluorophosphate (LiPF6) as a supporting salt is added in a concentration of 1 mol / L relative to 1 L of the mixed solvent, and vinylene carbonate (VC) is added in a content of 0.3 mass % relative to the total mass of the mixed solvent to prepare an electrolyte solution. (Production of Test Battery Cell (r1)) The positive electrode plates (r1) obtained above were respectively used to prepare test battery cells (r1) by the following steps. The positive electrode plates (r1) and the lithium metal plates as the counter electrodes of the positive electrode plates (r1) were stacked via a polyolefin separator to obtain a stacked electrode body. The stacked electrode body was placed in a battery case composed of aluminum laminate sheets, and the electrolyte prepared above was injected, and then the opening was sealed to obtain a test battery cell (r1). For each test battery cell (r1), a current density of 0.2 mA / cm was applied at a temperature of 25°C. 2 Perform constant current charging until it reaches 4.3Vvs.Li / Li + The potential is then 4.3 V vs. Li / Li + The potential was charged at a constant voltage until it reached 0.04 mA / cm 2The current density of the first active material was used to measure the charge capacity per unit mass [mAh / g]. In addition, the 4.1Vvs.Li / Li ratio of the test battery cell (r1) to the overall capacity of the test battery cell (r1) during charging was calculated. + The results are shown in Figure 1 and Table 1. Figure 1 The results shown in Table 1 are plotted as follows: the charge capacity [mAh / g] and 4.1 V vs. Li / Li when charging the test battery cell (r1) having the positive electrode plate (r1) formed using the first active material. + The capacity ratio [%] at the above potential is plotted against the ratio (Li / M) of the number of moles of lithium (Li) in the first active material to the total number of moles of transition metals (M). Figure 1 As shown in the graph and Table 1, when the ratio (Li / M) of the first active material is less than 1.05, the total capacity of the test battery cell (r1) when charged is 4.1Vvs.Li / Li. + The ratio of the capacity at a potential above this value becomes larger. [Table 1] [Production Example 2] (Manufacturing of Second Active Material) By 0.83 Co 0.12 Mn 0.05 The transition metal compound represented by (OH)2 and LiOH are mixed and calcined to obtain a second active material, which is a lithium transition metal composite oxide, and the ratio of the molar number of Li to the total molar number of the transition metal (M) (Li / M) is 1.01. The average particle size (D50) of the second active material is 5.9 μm, and the crystallite size is 965 nm. The second active material is obtained by mixing a NiCoMn composite hydroxide and a lithium compound and calcining at 700 to 1000° C. The second active materials are lithium transition metal composite oxides, and the ratio of the mole number of Li to the total mole number of transition metals (M) (Li / M) is 0.98, 1.00, 1.04, 1.07 and 1.10. The average particle size of the second active materials is within the range of 2 μm or more and 8 μm or less, and the crystallite size is within the range of 800 nm or more. (Production of positive electrode plate (r2)) The positive electrode plate (r2) was obtained by following the steps described in the preparation of the positive electrode plate (r1) except that the second active material was used instead of the first active material. (Production of Test Battery Cell (r2)) The test cell (r2) was obtained by following the procedure described in the preparation of the test cell (r1) except that the positive electrode plate (r2) was used instead of the positive electrode plate (r1). The test cell (r2) was charged at a constant current and a constant voltage in the same manner as the test cell (r1) to measure the charge capacity per unit mass of the second active material [mAh / g]. In addition, the 4.1V vs. Li / Li ratio of the test cell (r2) to the overall capacity of the test cell (r2) was calculated. + The results are shown in Figure 2 and Table 2. Figure 2 The results shown in Table 2 are plotted as follows: the charge capacity [mAh / g] and 4.1 V vs. Li / Li when charging the test battery cell (r2) having the positive electrode plate (r2) formed using the second active material. + The capacity ratio [%] at the above potential is plotted against the ratio (Li / M) of the number of moles of lithium (Li) in the second active material to the total number of moles of transition metals (M). Figure 2 As can be seen from the graph and Table 2, when the ratio (Li / M) of the first active material is greater than 1.04, the charge capacity when charging the test cell (r2) is significantly reduced. [Table 2] [Examples 1 to 3, Comparative Examples 1 to 3] (Production of positive electrode plate) A positive electrode active material was prepared by mixing a first active material and a second active material having a ratio (Li / M) shown in Table 3 at a first active material: second active material = 6:4 (mass ratio). A positive electrode plate was obtained by the steps described in the preparation of positive electrode plate (r1) except that the positive electrode active material was used instead of the first active material. (Fabrication of non-aqueous electrolyte secondary battery) A nonaqueous electrolyte secondary battery was obtained by following the procedure described in the preparation of the test cell (r1) except that the positive electrode plate obtained above was used instead of the positive electrode plate (r1). For the non-aqueous electrolyte secondary battery, constant current charging and constant voltage charging were performed in the same manner as for the test battery cell (r1), and the charge capacity per unit mass of the positive electrode active material [mAh / g] was measured. In addition, when charging the non-aqueous electrolyte secondary battery, 4.1Vvs.Li / Li + The results are shown in Table 3. [Table 3] As shown in Table 3, it can be seen that using a positive electrode plate containing a first active material having a ratio (Li / M) of 1.05 or more and a second active material having a ratio (Li / M) of 1.04 or less can obtain a non-aqueous electrolyte secondary battery that achieves both high charge capacity and excellent thermal stability. [Evaluation of filling properties] The first active material having a ratio (Li / M) of 1.05 and the second active material having a ratio (Li / M) of 1.01 were mixed at the mass ratio shown in Table 4, and the density when pressed at a pressure of 200 Pa was measured. The results are shown in Table 4. [Table 4] As shown in Table 4, when the first particle / second particle (mass ratio) is in the range of 5 / 5 or more and 8 / 2 or less, the density can be made 3.40 g / cm 3 As described above, good filling properties can be obtained. Although the embodiments of the present invention have been described, the embodiments disclosed this time should be considered to be illustrative in all aspects and not restrictive. The scope of the present invention is indicated by the claims, and it is intended to include all modifications within the meaning and scope equivalent to the claims.

Claims

1. A positive electrode plate comprising: a first active material, which is a lithium transition metal composite oxide; and a second active material, which has a smaller average particle size D50 than the first active material and is a lithium transition metal composite oxide, wherein: The crystallite size of the second active material is greater than 800 nm, the ratio of the molar number of lithium (Li) in the first active material to the total molar number of transition metals (M) (Li / M) is greater than 1.05, and the ratio of the molar number of lithium (Li) in the second active material to the total molar number of transition metals (M) (Li / M) is less than 1.

04.

2. The positive electrode plate according to claim 1, wherein: The ratio (Li / M) of the number of moles of lithium (Li) to the total number of moles of transition metals (M) in the first active material is 1.12 or less.

3. The positive electrode plate according to claim 1, wherein: The ratio (Li / M) of the number of moles of lithium (Li) to the total number of moles of transition metals (M) in the second active material is 0.98 or more.

4. The positive electrode plate according to claim 1, wherein: The ratio (Li / M) of the number of moles of lithium (Li) to the total number of moles of transition metals (M) in the second active material is 1.01 or more.

5. The positive electrode plate according to claim 1, wherein: A mass ratio of the first active material to the second active material (first active material / second active material) is 5 / 5 or more and 8 / 2 or less.

6. The positive electrode plate according to claim 1, wherein: The first active material has an average particle size D50 of 12 μm or more and 20 μm or less.

7. The positive electrode plate according to claim 1, wherein: The average particle size D50 of the second active material is greater than or equal to 2 μm and less than or equal to 8 μm.

8. The positive electrode plate according to claim 1, wherein: The first active material and the second active material each contain 80 mol % or more of nickel (Ni) based on the total amount of transition metals.

9. The positive electrode plate according to claim 1, wherein: The second active material is at least one of a single particle and a secondary particle in which three or less primary particles are aggregated. 10 . A non-aqueous electrolyte secondary battery comprising: an electrode body having a positive electrode plate according to claim 1 , a negative electrode plate, and a separator between the positive electrode plate and the negative electrode plate; and an electrolyte solution.

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