Multi-component positive electrode material and manufacturing method thereof, positive electrode sheet, and lithium-ion battery

Abstract

By arranging the internal crystal grains of the multi-component positive electrode material of the present invention in an irregular, non-radial and disordered manner, the multi-component positive electrode material has high powder compaction density and processability, and the positive electrode pieces containing the multi-component positive electrode material can easily withstand large rolling pressure, making the electrode pieces less likely to break. [Solution] The present invention relates to the technical field of lithium ion batteries, and in particular to a multi-component positive electrode material and its manufacturing method, a positive electrode sheet, and a lithium ion battery. The multi-component positive electrode material includes secondary particles formed by aggregation of primary particles. The ratio of the total cross-sectional area of ​​the primary particles having five or more grain boundaries to the cross-sectional area of ​​the secondary particles is ≥ 3:4, and the porosity of the secondary particles on the cross section is ≤ 2%. The grain boundary is defined as the outline of the interface between primary particles with the same structure but different orientations on the cross section of the secondary particle, and the length of the grain boundary is ≥ 0.1 μm.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to a patent application filed in China on October 25, 2023 (application number 202311394203.9), the entire disclosure of which is incorporated herein by reference.

[0002] The present invention relates to the technical field of lithium ion batteries, and in particular to a multi-component positive electrode material and a method for producing the same, a positive electrode sheet including the multi-component positive electrode material, and a lithium ion battery including the positive electrode sheet. [Background technology]

[0003] Lithium-ion batteries are mainly divided into cylindrical, rectangular and pouch-shaped in terms of shape. Lithium-ion batteries have a wide range of applications, from small consumer electronics to power tools, and even as power batteries with energy storage functions. The rapid increase in lithium-ion battery production and the dramatic advances in production technology are precisely due to strong market demand.

[0004] The manufacturing process for lithium-ion batteries is complex, typically involving paste homogenization, coating, rolling, cutting, liquid injection, and winding of the cathode material. Maintaining sufficient stability of the cathode material throughout the various manufacturing steps is crucial. During the actual production of lithium batteries, manufacturers increase the amount of cathode material or apply greater pressure during the rolling process to improve the energy density of lithium-ion batteries. However, excessive pressure can easily cause the cathode sheet to fracture, resulting in scrapped electrode pieces and ultimately a high battery reject rate. From the perspective of cathode material performance, the occurrence of electrode fragment fracture is closely related to the structure of the cathode material itself.

[0005] Generally, when designing a positive electrode material, in order to improve cycling performance, the positive electrode material is intentionally designed to have a radial distribution of material on the cross section, but when using a large rolling pressure during the process of making a battery pole piece to obtain sufficient energy density, the pressure applied to the positive electrode material is transmitted along the radial direction to the positive electrode aluminum foil electrode piece, and after spreading in the same direction, it is easy to cause breakage of the electrode piece, thereby significantly reducing the defective rate of battery pole pieces. This phenomenon also affects the electrical performance of the battery, especially safety performance, high temperature stability and cycling performance, and cannot meet the high safety requirements of electric vehicle batteries. Summary of the Invention [Problem to be solved by the invention]

[0006] To solve the problems of existing battery pole pieces being prone to fracture and unable to withstand high rolling pressure, resulting in poor safety performance, high-temperature stability, and cycling performance in assembled batteries, the present invention proposes a multi-component positive electrode material, a manufacturing method thereof, a positive electrode sheet, and a lithium-ion battery. By arranging the internal crystal grains of the multi-component positive electrode material in an irregular, non-radial, and disordered manner, the multi-component positive electrode material has high powder compaction and processability, and positive electrode pieces containing the multi-component positive electrode material are able to withstand high rolling pressure and are less likely to fracture. [Means for solving the problem]

[0007] To achieve the above object, a first aspect of the present invention provides a multi-component positive electrode material, which includes secondary particles formed by aggregation of primary particles, the ratio of the total cross-sectional area of ​​the primary particles having five or more grain boundaries to the cross-sectional area of ​​the secondary particles being ≥ 3:4, and the cross-sectional porosity of the secondary particles being ≤ 2%.

[0008] A grain boundary is defined as the boundary line of the interface between primary particles with the same structure and different orientations on the cross section of a secondary particle, and the length of said grain boundary is ≧0.1 μm.

[0009] In the present invention, unless otherwise specified, the cross section of the secondary particles refers to a cross section that has undergone ion milling, and preferably has undergone ion milling and a cross section diameter that is equal to or smaller than the DB diameter of the secondary particles. 50 Refers to a cross section equal to the granule.

[0010] In the present invention, the method for obtaining the cross section of the secondary grains used to determine the number of grain boundaries is as follows.

[0011] S1, Sample preparation, a, each approximately 2 × 4 cm 2 of aluminum foil and 1.5 x 1.5 cm 2 (b) A silicon foil was pre-cut, and the aluminum foil was folded in half, flattening both sides and leaving a gap in the center for the sample. (b) The conductive adhesive was added to the positive electrode material powder and mixed evenly. The mixture was then used to fill the pre-void in the aluminum foil. The aluminum foil was then placed on a platform, and the periphery of the sample was compressed using a flat plate. The middle of the sample was then gently pressed to obtain a pre-treated sample. The side of the pre-treated sample that touched the platform was designated the front, and the pressed side was designated the back. (c) The pre-treated sample was dried at 100°C for 60 minutes. After drying, the pre-treated sample was removed, and the excess aluminum foil without the sample was cut away. The sample was then cut vertically from the back at a sufficient area of ​​the sample. d. Take the silicon wafer and glue the back of the cut pre-treated sample to the silicon wafer, so that the relatively flat front of the sample is in close contact with the backing plate and can face the ion beam. When glued, ensure that the cross section of the aluminum foil protrudes from the edge of the silicon wafer or is at the same height as it, for example, protruding by 60 μm or more, to obtain the sample to be measured.

[0012] For S2, measurement, conductive tape is attached to the sides of the sample stage, and the sample to be measured is fixed on the sample stage, with the top edge of the sample elevated approximately 1–3 mm above the sample stage. Next, ion milling is performed on the sample on the sample stage. After ion milling is complete, a liquid conductive adhesive is applied to the gap between the silicon flake in the sample and the sample to improve conductivity. Finally, the processed sample stage is placed on the dedicated sample stage support frame of the electron microscope, and the sample stage is firmly fixed in place using an internal hex wrench. A cross-section sample is then obtained through electron microscope observation. The ion mill used in this study is a Hitachi IM4000PLUS ion mill. The ion milling conditions are listed in Table 1. [Table 1]

[0013] DB of secondary particles on the ion milling cross section obtained based on the above method 50 Granules with a cross-sectional diameter equal to 1000 nm were selected for observation because this cross section is more representative of the cross section passing through or approaching the sphere's center. To perform ion milling, first adjust the ion mill's STAGE CONT to C4 mode, set the operating time to 40 min, set the acceleration voltage to 6 kV, adjust the discharge voltage to maximum, and adjust the airflow to 0.09 cm3 / min. The electron microscope's test conditions were set to low-voltage backscattering mode, voltage = 1 kV, WD = 2.5 mm, and magnification = 10 k.

[0014] Preferably, the powder compaction density of the multi-component positive electrode material is ≥ 3.4 g / cm 3 is.

[0015] Preferably, the total residual alkali content of the multi-component positive electrode material satisfies m(Li2CO3)+m(LiOH)<6000 ppm.

[0016] A second aspect of the present invention provides a method for manufacturing a multi-element positive electrode material, the method comprising the steps of:

[0017] (1) A precursor having the composition shown in Formula II is mixed with a lithium source to obtain a mixture I, and the precursor is formed by aggregation of primary particles, and the primary particles on the cross section of the precursor are distributed non-radially.

[0018] (2) The mixture I is first sintered in an oxygen-containing atmosphere to obtain a semi-finished product, and the first sintering satisfies the following conditions: the temperature is increased to T1 at a temperature increase rate V1, the temperature is kept constant for t1, and then the temperature is increased to T2 at a temperature increase rate V2, and the temperature is kept constant for t2.

[0019] (3) Mixing the semi-finished product with an optional G-containing coating agent to obtain Mixture II.

[0020] (4) Sinter the semi-finished product or mixture II a second time in an oxygen-containing atmosphere to obtain a multi-element positive electrode material. (NiαCoβMnγMδ)(OH)2(II)

[0021] Formula II includes the following: 0.3≦α<1, 0<β<0.5, 0<γ<0.5, 0≦δ≦0.05, and α+β+γ+δ=1; M and G are each independently selected from at least one of Mg, Ti, W, V, Ta, Zr, La, Ce, Er, Sr, Si, B, Al, Co, and Y.

[0022] Preferably, the precursor is prepared by the following method: in an inert atmosphere, a mixed metal salt solution containing a nickel source, a cobalt source, a manganese source, and an optional M-containing dopant is contacted with a precipitating agent, a complexing agent, and a dispersing agent to co-precipitate, and the obtained co-precipitated reaction product is sequentially washed and dried to obtain the precursor.

[0023] Preferably, the co-precipitation reaction is carried out under the following conditions: the temperature is kept at 40 to 80° C., the pH value is set at 10 to 13, and the stirring speed is kept at 200 to 550 rpm.

[0024] Preferably, in step (2), the initial sintering is performed by setting the heating rate V1 to 1-6°C / min, preferably 1-3°C / min, more preferably 1-2°C / min, T1 to 400-760°C, preferably 500-750°C, the warming time t1 to 2-6 hours, preferably 3-5 hours, the heating rate V2 to 1-6°C / min, preferably 1-3°C / min, T2 to 710-950°C, preferably 710-920°C, and the warming time t2 to 5-13 hours, preferably 6-12 hours.

[0025] A third aspect of the present invention provides a positive electrode sheet, the active material layer of which comprises the multi-component positive electrode material proposed in the first aspect or the multi-component positive electrode material prepared according to the preparation method proposed in the second aspect.

[0026] A fourth aspect of the present invention proposes a lithium ion battery, comprising the positive electrode sheet proposed in the third aspect. [Effects of the Invention]

[0027] The present invention has the following beneficial effects compared to the current technology.

[0028] (1) The multi-component positive electrode material proposed in the present invention has a ratio of the total cross-sectional area of ​​primary particles having five or more grain boundaries to the cross-sectional area of ​​secondary particles of ≥ 3:4, the length of the grain boundaries is limited to ≥ 0.1 μm, and the porosity of the secondary particles on their cross sections is limited to ≤ 2%. As a result, most of the primary particles constituting the primary particles are closely arranged and have many grain boundaries. It can also be seen that most of the cross sections of the primary particles of the present invention are polygonal on the cross sections of the secondary particles. Based on the closely arranged primary particles with polygonal cross sections, the multi-component positive electrode material of the present invention disperses and conducts the applied pressure along multidirectional interfaces under extreme compaction, meaning that the internal primary particles are less susceptible to creep deformation and breakage under pressure. When a multi-component positive electrode material with this structure is applied to a positive electrode sheet, electrode fragment fracture can be reduced, resulting in high powder compaction and processability.

[0029] (2) The method proposed in this invention utilizes a precursor with randomly arranged internal particles and optimizes the initial sintering process to produce a multi-component positive electrode material with similarly randomly arranged internal particles. Specifically, the co-precipitation reaction conditions are controlled to maintain random growth of crystalline species, resulting in a precursor with non-radial and randomly distributed primary particles, which meets the requirements. When the precursor is thoroughly mixed with a lithium source, the lithium source reacts slowly and completely with the precursor according to the dual-platform heat-retention sintering process curve, further coating the obtained semi-finished product, and finally obtaining a multi-component positive electrode material with fully grown and randomly arranged granules.

[0030] (3) When the multi-component positive electrode material proposed in the present invention is applied to a positive electrode sheet and contains a specific dopant element M, the dopant element M is distributed at the interface and is in an amorphous state. When pressure is applied, the specific dopant element M can act as a lubricant, making the secondary particles less likely to break and only causing relative displacement, thereby reducing the risk of electrode fragment fracture. Furthermore, the electrical properties of the material are not affected, making it easier to withstand high rolling pressure and ensuring that electrode fragment fracture is less likely to occur. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is an SEM image of a cross section of precursor S1 produced in Production Example 1. [Figure 2] 1 is an SEM image of a cross section of precursor DS1 produced in Comparative Production Example 1. [Figure 3] 1 is a SEM image of a cross section of the multi-component positive electrode material P3 prepared in Example 3. [Figure 4] 1 is a SEM image of a cross section of the multi-component positive electrode material DP3 produced in Comparative Example 3. [Figure 5] FIG. 10 is a cross-sectional view of the multi-component positive electrode material P4 produced in Example 4 by ion milling. [Figure 6] FIG. 1 is a cross-sectional view of the multi-component positive electrode material DP1 produced in Comparative Example 1 by ion milling. [Figure 7]1 is an SEM image of a single folded cross section of a positive electrode sheet made of the multi-component positive electrode material P1 of Example 1. [Figure 8] 1 is an SEM image of a double-folded cross section of a positive electrode sheet made of the multi-component positive electrode material P1 of Example 1. [Figure 9] 1 is an SEM image of a single folded cross section of a positive electrode sheet made of the multi-component positive electrode material DP1 of Comparative Example 1. [Figure 10] 1 is a SEM image of a double cross section of a positive electrode sheet made of the multi-component positive electrode material DP1 of Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0032] The endpoints and any values ​​of the ranges set forth herein should not be understood to be limiting to the ranges or values, but rather to include ranges or values ​​close to the ranges or values. In the case of numerical ranges, the endpoints of each range may be combined, or the endpoints of each range may be combined with individual point values, or the individual point values ​​may be combined to obtain one or more new numerical ranges, which are considered to be disclosed herein.

[0033] A first aspect of the present invention provides a multi-component positive electrode material, which includes secondary particles formed by aggregation of primary particles, where the ratio of the total cross-sectional area of ​​the primary particles having five or more grain boundaries to the cross-sectional area of ​​the secondary particles is ≥ 3:4, and the cross-sectional porosity of the secondary particles is ≤ 2%.

[0034] A grain boundary is defined as the boundary line of the interface between primary particles with the same structure and different orientations on the cross section of a secondary particle, and the length of said grain boundary is ≧0.1 μm.

[0035] In the present invention, unless otherwise specified, the cross section of the secondary particles refers to a cross section that has undergone ion milling, and preferably has undergone ion milling and a cross section diameter that is equal to or smaller than the DB diameter of the secondary particles. 50It refers to a cross section that is equal to the granules. When the grain boundaries satisfy the above conditions, the grain boundaries between the primary particles are arranged radially and randomly on the cross section of the secondary particles, and the primary particles are arranged staggered like canines on the cross section of the secondary particles, so that the secondary particles undergo creep deformation under extreme compaction and are less likely to break. Therefore, when the multi-component positive electrode material is applied to the positive electrode sheet, the electrode fragment fracture can be reduced.

[0036] In some embodiments of the present invention, preferably, the number of grain boundaries having a length of ≦1.5 μm accounts for 70% or more of the total number of grain boundaries, more preferably, the number of grain boundaries having a length of ≦1.2 μm accounts for 70% or more of the total number of grain boundaries, and even more preferably, the number of grain boundaries having a length selected from 0.2-1.2 μm accounts for 80% or more of the total number of grain boundaries.

[0037] In the present invention, the number of grain boundaries with a length of ≦1.5 μm accounting for 70% or more of the total number of grain boundaries refers to the contour lines of interfaces between primary particles with the same structure but different orientations on the cross section of the secondary particle. The total number of grain boundaries with a contour line length of 0.1 μm ≦ ≦ 1.5 μm and a contour line length ≧ 0.1 μm accounts for 70% or more. In other words, the total number of grain boundaries with a grain boundary length of 0.1 μm ≦ ≦ 1.5 μm and a grain boundary length ≧ 0.1 μm accounts for 70% or more.

[0038] Similarly, when the number of grain boundaries with a length ≦1.2 μm accounts for 70% or more of the total number of grain boundaries, this corresponds to the total number of grain boundaries with a length of 0.1 μm≦grain boundary length ≦1.2 μm and a length of ≧0.1 μm accounting for 70% or more. When the number of grain boundaries with a length selected from the range of 0.2-1.2 μm accounts for 80% or more of the total number of grain boundaries, this corresponds to the total number of grain boundaries with a length of 0.2 μm≦grain boundary length ≦1.2 μm and a length of ≧0.1 μm accounting for 80% or more.

[0039] In some embodiments of the present invention, the grain boundary density of the secondary particles is preferably ≧1.8. For example, the grain boundary density is 1.8, 2, 2.2, 2.5, 2.8, 3, or any value within a range between any two values, preferably 2-3. The grain boundary density = number of interfaces between primary particles on a cross section of the secondary particle / number of primary particles on a cross section of the secondary particle.

[0040] In the present invention, when the length and ratio of grain boundaries, as well as the grain boundary density, meet the above-mentioned conditions, particularly when the preferable conditions are met, the primary particles of the multi-component positive electrode material exhibit a clearly disordered distribution, and in addition, the positive electrode active material granules are not broken apart during charging and discharging, and sufficient cycling characteristics are maintained.

[0041] In some embodiments of the present invention, the average length ratio of the primary particles is preferably ≦1.5. For example, the average length ratio may be 0.8, 0.9, 1, 1.02, 1.05, 1.08, 1.1, 1.3, 1.5, or any value within a range between any two values, preferably 1-1.5, and more preferably 1-1.1. When the above condition is met, the primary particles have a small average length ratio, which is convenient for stacking with each other and increases the density of the primary particles among the secondary particles.

[0042] In the present invention, the concept of the major axis ratio is the same as the length-to-width ratio, i.e., the ratio between the maximum diameter passing through the interior of a granule and the maximum diameter perpendicular to it, and this parameter is used to describe the morphology of a granule and thereby determine whether the morphology is close to a regular shape. The average major axis ratio of the present invention refers to the average value of the major axis ratios of all primary particles in the cross section of a secondary particle.

[0043] In some embodiments of the present invention, it is more preferable that the number of the primary particles having a major axis ratio selected from 0.9 to 1.1 is 70% or more. If the above condition is satisfied, the primary particles are less likely to be guided into a radial arrangement when they aggregate to form secondary particles, and the secondary particles are less likely to be deformed and crushed due to the stacked shape being easily changed under the action of pressure.

[0044] In some embodiments of the present invention, the average particle size DB of the secondary particles is preferably 50 and the average particle size DA of the primary particles 50 , 10≦DB 50 / DA 50 ≦40. For example, DB 50 / DA 50is 10, 15, 20, 25, 30, 35, 40, and any value in the range between any two values. 50 and DB 50 When satisfies the above formula, the secondary particles are composed of an appropriate amount of primary particles and are firmly bonded to each other, which is convenient for increasing the strength of the secondary particles, and in addition, has good electrical properties.

[0045] In the present invention, the secondary particles are spherical or approximately spherical. Preferably, the average particle size of the secondary particles is 50 is selected from 6-14 μm, for example, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, and any value in the range between any two values, preferably 8-12 μm.

[0046] In some embodiments of the present invention, the average particle size of the primary particles, DA 50 is selected from 0.1-1.5 μm. For example, DA 50 is 0.1 μm, 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, or any value within a range between any two values, preferably 0.2-1.2 μm. 50 When the average particle size of the primary particles in the multi-component positive electrode material is within the above range, the primary particles have a small average particle size and a compact density, which helps to form a stable structure, reduces internal stress during charging and discharging of the battery, and eases the formation of microcracks.

[0047] In some embodiments of the present invention, the multi-element positive electrode material preferably has the composition shown in Formula I: Li a (Ni x Co y Mn z M b )G c O2(I)

[0048] In formula I, 1 ≦ a ≦ 1.2, 0 ≦ b ≦ 0.05, 0 ≦ c ≦ 0.05, 0.3 ≦ x < 1, 0 < y < 0.5, 0 < z < 0.5, and x + y + z + b = 1, and M and G are each independently selected from at least one of Mg, Ti, W, V, Ta, Zr, La, Ce, Er, Sr, Si, B, Al, Co, and Y.

[0049] In some embodiments of the present invention, preferably, in formula I, 1 ≦ a ≦ 1.1, 0 < b ≦ 0.02, 0 < c ≦ 0.02, 0.4 ≦ x ≦ 0.95, 0.01 ≦ y ≦ 0.2, 0.01 ≦ z ≦ 0.3, M is selected from at least one of Mg, Ti, W, V, Ta, Zr, La, Ce, Er, Sr, Si, Al, Co, and Y, and G is selected from at least one of Mg, Ti, W, Zr, Ce, Er, Si, B, and Al.

[0050] In some embodiments of the present invention, preferably, in formula I, 0.0001 ≦ b ≦ 0.02, 0.0001 ≦ c ≦ 0.02, M is selected from at least one of W, Zr, La, and Y, and G is selected from at least one of B, Ti, W, Si, and Al.

[0051] In some embodiments of the present invention, preferably, in the XRD pattern, the full width at half maximum FWHM of the characteristic diffraction peak of the multi-component cathode material on the (104) crystal plane (104) is selected from 0.2 - 0.24, for example, 0.2, 0.22, 0.23, 0.24, and any value within the range between any two values, and preferably, it is 0.22 - 0.24.

[0052] In the present invention, on the one hand, the full width at half maximum FWHM of the characteristic diffraction peak of the (104) crystal plane (104)When the above conditions are satisfied, the multi-component cathode material has better crystal performance and cycling performance, and the particles can achieve complete growth, so that there are more grain boundaries in the primary particles, and the crystal arrangement based on the grain boundaries is very irregular, and the crystal planes are jagged like teeth and mesh with each other. Therefore, under normal pressure, the multi-component cathode material can have a stable structure. In addition, because the strength at the grain boundaries is relatively low, the secondary particles undergo creep deformation under high pressure, thereby reducing the pressure of the primary particles applied to the aluminum foil and reducing electrode sheet crushing. On the other hand, the full width at half maximum FWHM of the characteristic diffraction peak of the (104) crystal plane (104) When the above conditions are satisfied, the adhesion between secondary particles decreases, so the tap density of the multi-component cathode material increases and electrode sheet crushing is further reduced.

[0053] In some embodiments of the present invention, preferably, the multi-component cathode material has a single α-NaFeO₂-type layered structure.

[0054] In some embodiments of the present invention, preferably, the tap density of the multi-component cathode material is ≧3.4 g / cm 3 ³. The multi-component cathode material proposed in the present invention has a high powder tap density, so the energy density of the lithium battery can be increased to a certain extent.

[0055] In some embodiments of the present invention, preferably, the total residual alkali content of the multi-component cathode material satisfies m(Li₂CO₃)+m(LiOH)<6000 ppm. More preferably, the total residual alkali content of the multi-component cathode material further satisfies the conditions that m(Li₂CO₃)<m(LiOH) and both m(Li₂CO₃) and m(LiOH) are less than 3000 ppm.

[0056] In the present invention, when the total residual alkali content of the multi-component positive electrode material satisfies the above conditions, the crystal lattice structure of the obtained multi-component positive electrode material is stable and complete, thereby significantly enhancing the structural stability, capacity performance, and safety performance of the multi-component positive electrode material, and thereby improving the cycling stability of the multi-component positive electrode material. Furthermore, a reduced residual alkali content reduces intergranular adhesion, increases the compaction degree of the material, and further reduces the likelihood of electrode fragment fracture.

[0057] A second aspect of the present invention provides a method for manufacturing a multi-element positive electrode material, the method comprising the steps of:

[0058] (1) A precursor having the composition shown in Formula II is mixed with a lithium source to obtain a mixture I, and the precursor is formed by aggregation of primary particles, and the primary particles on the cross section of the precursor are distributed non-radially.

[0059] (2) The mixture I is first sintered in an oxygen-containing atmosphere to obtain a semi-finished product, and the first sintering satisfies the following conditions: the temperature is increased to T1 at a temperature increase rate V1, the temperature is kept constant for t1, and then the temperature is increased to T2 at a temperature increase rate V2, and the temperature is kept constant for t2.

[0060] (3) Mixing the semi-finished product with an optional G-containing coating agent to obtain Mixture II.

[0061] (4) Sintering the semi-finished product or the mixture II for the second time in an oxygen-containing atmosphere to obtain a multi-element positive electrode material. (NiαCoβMnγMδ)(OH)2(II)

[0062] Formula II includes the following: 0.3≦α<1, 0<β<0.5, 0<γ<0.5, 0≦δ≦0.05, and α+β+γ+δ=1; M and G are each independently selected from at least one of Mg, Ti, W, V, Ta, Zr, La, Ce, Er, Sr, Si, B, Al, Co, and Y.

[0063] In some embodiments of the present invention, preferably, for Formula II, 0.4≦α≦0.95, 0.01≦β≦0.2, 0.01≦γ≦0.3, 0<δ≦0.02, and α+β+γ+δ=1, and M is selected from at least one of Mg, Ti, W, V, Ta, Zr, La, Ce, Er, Sr, Si, Al, Co, and Y. Preferably, for Formula II, 0.0001≦δ≦0.02, and M is selected from at least one of W, Zr, La, and Y.

[0064] According to research, we have found that adding a specific dopant M to a positive electrode material helps to ensure a disordered distribution of primary particles, and the dopant M is distributed at the interface and remains amorphous. When pressure is applied, the dopant M can act as a lubricant, preventing the secondary particles from breaking and only causing relative displacement, thereby reducing the risk of electrode fragment fracture and ensuring that the electrical properties of the material are not affected. Compared with adding an M-containing dopant during raw material blending, adding an M-containing dopant during the wet co-precipitation synthesis process to prepare the precursor not only stabilizes the internal structure of the material and improves the cycle life of ternary materials, especially high-nickel ternary materials, but also allows the dopant M to be more evenly distributed within the positive electrode material, which helps to ensure a disordered distribution of primary particles.

[0065] Furthermore, in the present invention, the sintering process is further optimized, and a two-stage initial sintering process is used to slowly and completely react the lithium source with the precursor, and the obtained semi-finished product is further coated, and finally a multi-element positive electrode material with fully grown and randomly arranged granules is obtained.

[0066] In some embodiments of the present invention, the precursor D 50 is selected from 8-14 μm, and the specific surface area of ​​the precursor is 3-7 m 2 / g.

[0067] In some embodiments of the present invention, the dosage of the precursor and the lithium source preferably satisfies n(Ni+Co+Mn+M):n(Li)=1:1-1.2, and preferably n(Ni+Co+Mn+M):n(Li)=1:1-1.1.

[0068] In some embodiments of the present invention, the precursor is preferably prepared by the following method: in an inert atmosphere, a mixed metal salt solution containing a nickel source, a cobalt source, a manganese source, and an optional M-containing dopant is contacted with a precipitating agent, a complexing agent, and a dispersing agent to co-precipitate, and the obtained co-precipitated reaction product is sequentially washed and dried to obtain the precursor.

[0069] In the present invention, unless otherwise specified, the inert atmosphere includes, but is not limited to, a nitrogen atmosphere, an argon atmosphere, and the like.

[0070] In some embodiments of the present invention, the co-precipitation reaction is preferably carried out at a temperature of 40 to 80°C, a pH of 10 to 13, and a stirring speed of 200 to 550 rpm. More preferably, the co-precipitation reaction is carried out at a temperature of 50 to 70°C, a pH of 11 to 12.5, and a stirring speed of 350 to 500 rpm.

[0071] In the present invention, by controlling the conditions of the co-precipitation reaction, especially by adding the doping element M, the pH value and the stirring speed are kept within a specified range, thereby maintaining the disordered growth of the crystal seeds, making the primary particles non-radially and disorderly distributed, and obtaining the precursors with irregularly arranged internal particles.

[0072] In some embodiments of the present invention, preferably, the dosages of the nickel source, the cobalt source, the manganese source, and the dopant in the mixed metal salt solution satisfy n(Ni):n(Co):n(Mn):n(M), where 0.3 ≤ n(Ni) < 1, 0 < n(Co) < 0.5, 0 < n(Mn) < 0.5, and 0 ≤ n(M) ≤ 0.05. More preferably, they satisfy 0.4 ≤ n(Ni) ≤ 0.95, 0.01 ≤ n(Co) ≤ 0.2, 0.01 ≤ n(Mn) ≤ 0.3, and 0 < n(M) ≤ 0.02. Even more preferably, they satisfy 0.0001 ≤ n(M) ≤ 0.02.

[0073] In some embodiments of the present invention, preferably, in terms of metal element conversion, the concentration of the mixed metal salt solution is 1 - 3 mol / L.

[0074] In some embodiments of the present invention, preferably, the nickel source, the cobalt source, the manganese source, and the dopant are each independently selected from at least one of sulfates, chlorides, nitrates, and acetates. In the present invention, the nickel source is selected from at least one of nickel sulfate, nickel chloride, nickel nitrate, and nickel acetate; the cobalt source is selected from at least one of cobalt sulfate, cobalt chloride, cobalt nitrate, and cobalt acetate; and the manganese source is selected from at least one of manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate.

[0075] In some embodiments of the present invention, preferably, the dopant is selected from soluble salts containing M, and preferably selected from at least one of sulfates, chlorides, hydroxides, and carbonates containing M.

[0076] In one specific embodiment of the present invention, the dopant is selected from at least one of sulfates, chlorides, hydroxides and carbonates of Mg, Ti, W, V, Ta, Zr, La, Ce, Er, Sr, Si, B, Al, Co and Y, preferably selected from at least one of sulfates, chlorides, hydroxides and carbonates of Mg, Ti, W, V, Ta, Zr, La, Ce, Er, Sr, Si, Al, Co and Y, more preferably selected from at least one of sulfates, chlorides, hydroxides and carbonates of W, Zr, La and Y.

[0077] In one specific embodiment of the present invention, the precipitating agent is selected from NaOH and / or KOH, the complexing agent is selected from at least one of aqueous ammonia, disodium ethylenediaminetetraacetate, ammonium nitrate, ammonium chloride, and ammonium sulfate, and the dispersing agent is selected from at least one of polyethylene glycol (PEG), polyvinyl alcohol (PVA), and polyglycerol.

[0078] In one embodiment of the present invention, the precipitating agent, the complexing agent, and the dispersing agent are each independently present in the form of an aqueous solution, more preferably, the concentration of the precipitating agent solution is 2-15 mol / L, the concentration of the complexing agent solution is 1-15 mol / L, and the concentration of the dispersing agent solution is 1-200 g / L.

[0079] In the present invention, the washing is intended to remove substances remaining on the surface of the co-precipitation reaction product, and the drying is intended to remove moisture remaining on the surface of the co-precipitation reaction product. Preferably, the drying temperature is set to 105 to 130°C.

[0080] In some embodiments of the present invention, the initial sintering in step (2) preferably satisfies the following conditions: the heating rate V1 is 1-6°C / min, preferably 1-3°C / min, more preferably 1-2°C / min; T1 is 400-760°C, preferably 500-750°C; the warming time t1 is 2-6 hours, preferably 3-5 hours; the heating rate V2 is 1-6°C / min, preferably 1-3°C / min; T2 is 710-950°C, preferably 710-920°C; and the warming time t2 is 5-13 hours, preferably 6-12 hours.

[0081] In the present invention, a dual-platform sintering process is used to prepare a multi-component positive electrode material, which has the advantages of low residual alkalinity, a disordered internal structure, and a stable structure. That is, in step (2), by setting appropriate heating rates (V1 and V2), holding temperatures (T1 and T2), and holding times (t1 and t2), the material is subjected to a dual-platform sintering process, so that the lithium source completely reacts with the precursor, the primary particles grow larger, and then grow along various crystallographic directions, resulting in a pressure-resistant, cohesive positive electrode material with a disordered internal structure.

[0082] In some embodiments of the present invention, preferably, when the nickel content in the precursor is ≥ 60 mol %, calculated as metal element, the oxygen concentration in the oxygen-containing atmosphere is ≥ 92 vol %, such that a sufficient oxygen concentration reduces the degree of mixing of nickel with lithium ions when the nickel content is high, thereby reducing the amount of residual alkali in the material.

[0083] In some embodiments of the present invention, the product of the initial sintering is preferably cooled to room temperature and crushed to obtain a semi-finished product, wherein the crushing means includes one or more of a jaw crusher, a roll pair, a colloid mill, a mechanical grinder, and a jet mill.

[0084] In some embodiments of the present invention, preferably, in step (3), the dosages of the semi-finished product and the coating agent satisfy n(Ni + Co + Mn + M):n(G) = 1:n(G), where 0 ≦ n(G) ≦ 0.05, preferably 0 < n(G) ≦ 0.02, and more preferably 0.0001 ≦ n(G) ≦ 0.02.

[0085] In some embodiments of the present invention, preferably, the coating agent is selected from at least one of oxides, hydroxides, and carbonates containing G, preferably selected from at least one of oxides, hydroxides, and carbonates containing Mg, Ti, W, Zr, Ce, Er, Si, B, and Al, and more preferably selected from at least one of oxides, hydroxides, and carbonates containing B, Ti, W, Si, and Al.

[0086] In some embodiments of the present invention, preferably, in step (4), the secondary sintering is suitable for the condition of suppressing the temperature T3 to 300 - 800 °C, preferably 400 - 700 °C, and setting the time t3 to 4 - 10 h, preferably 5 - 8 h.

[0087] In the present invention, the multi-component cathode material manufactured according to the manufacturing method has the composition shown in Formula I. Li a (Ni x Co y Mn z M b )G c O2 (I)

[0088] In Formula I, 1 ≦ a ≦ 1.2, 0 ≦ b ≦ 0.05, 0 ≦ c ≦ 0.05, 0.3 ≦ x < 1, 0 < y < 0.5, 0 < z < 0.5, and x + y + z + b = 1. M and G are each independently selected from at least one of Mg, Ti, W, V, Ta, Zr, La, Ce, Er, Sr, Si, B, Al, Co, and Y.

[0089] In some embodiments of the present invention, preferably, in Formula I, 1 ≦ a ≦ 1.1, 0 < b ≦ 0.02, 0 < c ≦ 0.02, 0.4 ≦ x ≦ 0.95, 0.01 ≦ y ≦ 0.2, 0.01 ≦ z ≦ 0.3, M is selected from at least one of Mg, Ti, W, V, Ta, Zr, La, Ce, Er, Sr, Si, Al, Co, and Y, and G is selected from at least one of Mg, Ti, W, Zr, Ce, Er, Si, B, and Al.

[0090] In some embodiments of the present invention, more preferably, in Formula I, 0.0001 ≦ b ≦ 0.02, 0.0001 ≦ c ≦ 0.02, M is selected from at least one of W, Zr, La, and Y, and G is selected from at least one of B, Ti, W, Si, and Al.

[0091] The third aspect of the present invention proposes a positive electrode sheet. The active material layer of the positive electrode sheet includes the multi-component positive electrode material proposed in the first aspect or the multi-component positive electrode material manufactured according to the manufacturing method proposed in the second aspect.

[0092] In the present invention, unless otherwise specified, the positive electrode sheet includes a positive electrode current collector and an active material layer placed on the positive electrode current collector.

[0093] In some embodiments of the present invention, the active material layer not only includes the multi-component positive electrode material but also includes a conductive agent, an adhesive, and a dispersant.

[0094] In one specific embodiment of the present invention, the manufacturing method of the positive electrode sheet is as follows. The multi-component positive electrode material, SuperP, CNT, and polyvinylidene fluoride (PVDF) are completely mixed with an appropriate amount of N-methylpyrrolidone (NMP) according to a mass ratio of 97:1:0.8:1.2 to form a uniform paste. Subsequently, the slurry is applied to an aluminum foil. After undergoing a drying process, it is cut into an electrode sheet of 112 mm × 40 mm using a die cutter, and the loading amount of the multi-component positive electrode material is 380 ± 2 g / m 2 is.

[0095] In the present invention, the method for determining whether the electrode pieces are broken is as follows: The prepared positive electrode sheet is baked in a vacuum drying box at 125°C for more than 8 hours, and then rolling pressure is applied to the positive electrode sheet twice to reach the corresponding degree of compaction. Next, a fixed weight plate is used to compress and fold the electrode pieces. Finally, an LED point light source is used to observe the light transmittance. The thickness and length of the positive electrode sheet before and after rolling pressure are recorded, and the thickness compression ratio and elongation ratio of the positive electrode sheet before and after rolling pressure are calculated. The positive electrode sheet is compressed to different degrees of compaction, and the electrode pieces are folded once, twice, three times, and four times according to the different degrees of compaction. The light transmittance is observed, and the result indicates whether the electrode pieces are broken.

[0096] In addition to determining whether the electrode pieces are broken by the above method, the present invention also uses the same formulation of the multi-element positive electrode material to prepare battery electrode pieces, and then applies a certain pressure to the electrode pieces, and then uses SEM to observe the cross section of the battery electrode pieces, and determines whether the electrode pieces are broken according to the cross section.

[0097] In some embodiments of the present invention, the ultimate compaction density of the positive electrode sheet is preferably 3.2-3.8 g / cm 3 For example, 3.2 g / cm 3 , 3.3g / cm 3 , 3.5g / cm 3 , 3.6g / cm 3 , 3.7g / cm 3 , 3.8g / cm 3 , as well as any value in the range between any two values, preferably 3.3-3.7 g / cm 3 is.

[0098] In some embodiments of the present invention, the thickness compression ratio of the positive electrode sheet is preferably selected from the range of 25 to 45%, for example, 25%, 30%, 32%, 35%, 38%, 40%, 45%, and any value within a range between any two values, preferably 30-40%.

[0099] In some embodiments of the present invention, the elongation ratio of the positive electrode sheet is preferably selected from the range of 1.2-3%, for example, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 3%, and any value within a range between any two values, preferably 1.5-2.5%.

[0100] In the present invention, the positive electrode sheet manufactured using the multi-component positive electrode material can withstand a larger rolling pressure and is less likely to be crushed.

[0101] A fourth aspect of the present invention proposes a lithium ion battery, comprising the positive electrode sheet proposed in the third aspect.

[0102] The present invention will now be described in more detail through examples.

[0103] (1) The composition of precursor and multi-element cathode materials is measured using the ICP method. The equipment used is a PE Optima 7000DV. The test is conducted by completely dissolving 0.1g of sample in a mixed acid solution of 3mL of HNO3 and 9mL of HCl, and then diluting it to 250mL.

[0104] (2) Obtaining the cross section of the secondary particle. In the present invention, the cross section of the secondary particle is obtained in two ways. First, as shown in Figures 1-4, the cross section is obtained by referring to the SEM image of the cross section as follows: a small amount of the material to be tested is placed on a glass plate, and another glass plate is used to press the material, and a cross section pressed away from the center of the secondary particle is selected. This cross section is then observed using a scanning electron microscope to obtain the cross section of the secondary particle according to the present invention. This method is convenient for three-dimensional observation.

[0105] Second, referring to ion milled cross sections, as shown in Figures 5-6, cross sections acquired according to this method are useful for clearly defining the grain boundaries mentioned herein. The method for acquiring the cross sections is as follows.

[0106] S1, Sample preparation, a, each approximately 2 × 4 cm2 of aluminum foil and 1.5 x 1.5 cm 2 (b) A silicon foil was pre-cut, and the aluminum foil was folded in half, flattening both sides and leaving a gap in the center for the sample. (b) The conductive adhesive was added to the positive electrode material powder and mixed evenly. The mixture was then used to fill the pre-void in the aluminum foil. The aluminum foil was then placed on a platform, and a flat plate was used to compress the periphery of the sample. The middle of the sample was then gently pressed to obtain a pre-treated sample. The side of the pre-treated sample that touched the platform was designated the front, and the pressed side was designated the back. (c) The pre-treated sample was dried at 100°C for 60 minutes. After drying, the pre-treated sample was removed, and the excess aluminum foil without the sample was cut away. The sample was then cut vertically from the back at a sufficient area of ​​the sample. d. Take the silicon wafer and glue the back of the cut pre-treated sample to the silicon wafer, so that the relatively flat front of the sample is in close contact with the backing plate and can face the ion beam. When glued, ensure that the cross section of the aluminum foil protrudes from the edge of the silicon wafer or is flush with it, for example, protruding by 60 μm or more, to obtain the sample to be measured.

[0107] For S2, measurement, conductive tape is attached to the sides of the sample stage, and the sample to be measured is fixed on the sample stage, with the top edge of the sample elevated approximately 1–3 mm above the sample stage. Next, ion milling is performed on the sample on the sample stage. After ion milling is complete, a liquid conductive adhesive is applied to the gap between the silicon flake in the sample and the sample to improve conductivity. Finally, the processed sample stage is placed on the dedicated sample stage support frame of the electron microscope, and the sample stage is firmly fixed in place using an internal hex wrench. A cross-section sample is then obtained through electron microscope observation. The ion mill used in this study is a Hitachi IM4000PLUS ion mill. The ion milling conditions are listed in Table 1. [Table 1]

[0108] From the ion milling cross-section obtained using the above method, granules with a cross-sectional diameter of 8-12 μm were sieved out for observation, in accordance with the average particle size of the secondary particles defined in this invention, because such cross-sections serve as more representative examples of cross-sections passing through or approaching the center of a sphere. To perform the ion milling process, first adjust the ion mill's STAGE CONT to C4 mode, set the operating time to 40 min, the acceleration voltage to 6 kV, the discharge voltage to maximum, and the airflow to 0.09 cm3 / min. The electron microscope test conditions were set to low-voltage backscattering mode, voltage = 1 kV, WD = 2.5 mm, and magnification = 10 k.

[0109] (3) Regarding the measurement criteria for grain boundaries, in the present invention, the grain boundaries are determined based on ion milling cross-sectional views, and the grain boundaries are defined as the contour lines of the interfaces between primary particles with the same structure and different orientations on the cross-section of secondary particles, and the length of the grain boundaries is ≧0.1 μm.

[0110] (4) Morphological tests are carried out using a Hitachi S-4800 scanning electron microscope.

[0111] (5) Particle size DA 50 and DB 50 The test is carried out using a laser particle size analyzer, model Mastersize2000, manufactured by Malvern.

[0112] (6) For compaction density, a test is carried out using a BT-30 tap density analyzer manufactured by Hyakutoku Co., Ltd.

[0113] The compositions and physical property parameters of the precursors prepared in Preparation Examples 1-5 and Comparative Preparation Examples 1-4 are shown in Table 2.

[0114] Manufacturing Example 1 A 2 mol / L mixed metal salt solution is blended, and the molar ratio of nickel sulfate, cobalt sulfate, manganese sulfate, and yttrium sulfate in the mixed metal salt solution, in terms of metal elements, is 0.5:0.2:0.2985:0.0015. 3 mol / L NaOH solution is blended, 3 mol / L ammonia water is blended, and 10 g / L PVA dispersant aqueous solution is blended.

[0115] Under nitrogen atmosphere, the above solution is injected into the reactor in parallel flow to carry out co-precipitation reaction, the reaction temperature is kept at 50°C, the reaction pH value is set to 11.2, the stirring speed is set to 350 rpm, and after washing, drying at 120°C and sieving, precursor S1 is obtained.

[0116] The SEM of the cross section of the precursor S1 is shown in FIG. 1, which shows that the precursor is formed by aggregation of primary particles, and the primary particles on the cross section of the precursor are randomly distributed.

[0117] Manufacturing Example 2 The dopant was replaced with zirconium chloride, A 2 mol / L mixed metal salt solution is formulated, and the molar ratio of nickel sulfate, cobalt sulfate, manganese sulfate, and zirconium chloride in the mixed metal salt solution is 0.6:0.2:0.1985:0.0015 in terms of metal elements; The method differs from Preparation Example 1 in that the stirring speed is changed to 450 rpm and the dispersant is changed to a 10 g / L PEG1000 dispersant aqueous solution, but other conditions are the same to obtain precursor S2.

[0118] A SEM image of the cross section of the precursor S2 resembles FIG.

[0119] Manufacturing Example 3 The dopant was replaced with lanthanum nitrate. A 2 mol / L mixed metal salt solution is formulated, and the molar ratio of nickel sulfate, cobalt sulfate, manganese sulfate, and lanthanum nitrate in the mixed metal salt solution is 0.81:0.09:0.0985:0.0015 in terms of metal elements; Change the ammonia concentration to 4 mol / L, The co-precipitation reaction differs from that of Preparation Example 1 in that the reaction temperature is set to 55°C, the reaction pH is set to 11.7, and the stirring speed is set to 450 rpm, but the other conditions are the same to obtain precursor S3.

[0120] A SEM image of the cross section of the precursor S3 resembles FIG.

[0121] Manufacturing Example 4 The dopants were replaced with sodium tungsten and yttrium sulfate. A 2 mol / L mixed metal salt solution is formulated, and the molar ratio of nickel sulfate, cobalt sulfate, manganese sulfate, sodium tungstate, and yttrium sulfate in the mixed metal salt solution is 0.95:0.02:0.02:0.0275:0.001:0.0015 in terms of metal elements; Change the concentration of NaOH to 4 mol / L, The dispersant was replaced with a 10g / L PEG1000 dispersant solution. The coprecipitation reaction differs from that of Preparation Example 1 in that the reaction pH is set to 12.1 and the stirring speed is reduced to 400 rpm, but the other conditions are the same to obtain precursor S4.

[0122] A SEM image of the cross section of the precursor S4 resembles FIG.

[0123] Manufacturing Example 5 Precursor S5 is obtained under the same conditions as in Preparation Example 4 except that no dopants (sodium tungsten and yttrium sulfate) are added, and a 2 mol / L mixed metal salt solution is compounded, and the molar ratio of nickel sulfate, cobalt sulfate, and manganese sulfate in the mixed metal salt solution is 0.95:0.02:0.03, respectively, in terms of metal elements.

[0124] Comparative Manufacturing Example 1 A SEM image of the cross section of the precursor S5 resembles FIG.

[0125] No dopant (yttrium sulfate) is added, and a 2 mol / L mixed metal salt solution is formulated, and the molar ratio of nickel sulfate, cobalt sulfate, and manganese sulfate in the mixed metal salt solution is 50:20:30 in terms of metal elements; The coprecipitation reaction differs from that in Preparation Example 1 in that the reaction temperature is set to 60°C, the reaction pH is set to 11.7, and the stirring speed is set to 800 rpm, but the other conditions are the same to obtain precursor DS1.

[0126] The SEM image of the cross section of the precursor DS1 is similar to Figure 2. According to Figure 2, the precursor DS1 is formed by the aggregation of primary particles, and the primary particles on the cross section of the precursor DS1 are distributed radially.

[0127] Comparative Manufacturing Example 2 No dopant (zirconium chloride) is added, and a 2 mol / L mixed metal salt solution is blended, and the molar ratio of nickel sulfate, cobalt sulfate, and manganese oxide in the mixed metal salt solution is 60:20:20 in terms of metal elements; The concentration of the NaOH solution was changed to 2 mol / L, and the concentration of the ammonia water was changed to 2 mol / L. The coprecipitation reaction differs from that in Preparation Example 2 in that the reaction temperature is set to 55°C, the reaction pH is set to 13.2, and the stirring speed is set to 450 rpm, but the other conditions are the same to obtain precursor DS2.

[0128] A cross-sectional SEM image of the precursor DS2 resembles FIG.

[0129] Comparative Manufacturing Example 3 No dopant (lanthanum nitrate) is added, and a 2 mol / L mixed metal salt solution is formulated, and the molar ratio of nickel sulfate, cobalt sulfate, and manganese sulfate in the mixed metal salt solution is 81:9:10 in terms of metal elements; The coprecipitation reaction differs from that in Preparation Example 3 in that the reaction temperature is set to 58°C, the reaction pH is set to 13.2, and the stirring speed is set to 800 rpm, but the other conditions are the same to obtain precursor DS3.

[0130] A cross-sectional SEM image of the precursor DS3 resembles FIG.

[0131] Comparative Manufacturing Example 4 No dopants (sodium tungsten and yttrium sulfate) are added, and a 2 mol / L mixed metal salt solution is formulated, and the molar ratio of nickel sulfate, cobalt sulfate, and manganese sulfate in the mixed metal salt solution is 95:2:3 in terms of metal elements; The dispersant was replaced with a 10 g / L aqueous solution of polyglycerol dispersant. The coprecipitation reaction differs from that in Preparation Example 4 in that the reaction temperature is set to 60°C, the reaction pH is set to 11.7, and the stirring speed is set to 600 rpm, but the other conditions are the same to obtain precursor DS4.

[0132] A cross-sectional SEM image of the precursor DS4 resembles FIG. [Table 2]

[0133] JPEG2026501530000005.jpg92170

[0134] JPEG2026501530000006.jpg91170

[0135] According to Table 2, compared to Comparative Preparations 1-4, Preparations 1-5 satisfy the following conditions for the co-precipitation reaction: temperature 40-80°C, pH 10-13, and stirring speed 200-550 rpm. In particular, when combined with the type of doping element M, the precursor satisfying Formula II is formed by the aggregation of primary particles, and the primary particles on the cross section of the precursor DS1 are distributed non-radially.

[0136] The process parameters of Examples 1-5 and Comparative Examples 1-8 are shown in Table 3, and the compositions and physical property parameters of the manufactured multi-element positive electrode materials are shown in Table 4.

[0137] Example 1 (1) Precursor S1 obtained in Preparation Example 1 is mixed with lithium carbonate under the condition that the amount of precursor S1 and lithium carbonate satisfies n(Ni+Co+Mn+Y):n(Li)=1:1.05 to obtain mixture I.

[0138] (2) In an air atmosphere, the mixture I is first sintered according to the following conditions: the temperature is increased to T1=730°C at a rate of V1=5°C / min, the constant temperature is maintained for t1=3 hours, the temperature is then increased to T2=920°C at a rate of V2=5°C / min, and the constant temperature is maintained for t2=9 hours. The reaction product is then cooled to room temperature, crushed in a crusher, and then sieved to obtain a semi-finished product with a disordered internal structure.

[0139] (3) Mix the semi-finished product with MgO according to the condition that the dosage of the semi-finished product and MgO satisfies n(Ni+Co+Mn+Y):n(Mg)=1:0.0012 to obtain a uniformly coated mixture II.

[0140] (4) The mixture II is sintered for the second time in an air atmosphere (the temperature is controlled to 700°C and the time is set to 6 hours) to obtain a multi-element positive electrode material P1.

[0141] Example 2 In step (1), the precursor was replaced with precursor S2 prepared in Preparation Example 2, and the amounts of precursor S2 and lithium carbonate satisfied the relationship n(Ni+Co+Mn+Zr):n(Li)=1:1.06; In step (2), the atmosphere for the initial sintering is changed to an oxygen atmosphere, and the oxygen content is kept at ≥ 92V%; The initial sintering was carried out by increasing the temperature to T1 = 710 ° C at a heating rate of V1 = 4 ° C / min, maintaining the constant temperature for t1 = 3 h, and then increasing the temperature to T2 = 860 ° C at a heating rate of V2 = 4 ° C / min, maintaining the constant temperature for t2 = 10 h. Step (3) is to replace the coating material with Al2O3, and the dosage of the semi-finished product and Al2O3 satisfies n(Ni+Co+Mn+Zr):n(Al)=1:0.001; This differs from the method of Example 1 in that, under the same conditions as above, a multi-component positive electrode material P2 is obtained.

[0142] Example 3 In step (1), the precursor was replaced with precursor S3 prepared in Preparation Example 3, and the amounts of precursor S3 and lithium hydroxide satisfied the relationship n(Ni+Co+Mn+La):n(Li)=1:1.02; In step (2), the atmosphere for the initial sintering is changed to an oxygen atmosphere, and the oxygen content is kept at ≥ 95V%; The initial sintering was carried out by increasing the temperature to T1 = 600°C at a heating rate of V1 = 2°C / min, maintaining the temperature at that temperature for t1 = 4 hours, and then increasing the temperature to T2 = 785°C at a heating rate of V2 = 2°C / min, and maintaining the temperature at that temperature for t2 = 8 hours. Step (3) is to replace the coating agent with CeO2, and the dosage of the semi-finished product and CeO2 satisfies n(Ni+Co+Mn+La):n(Ce)=1:0.0008; In step (4), the temperature of the secondary sintering is changed to 500°C. This differs from the method of Example 1 in that, under the same conditions as above, a multi-component positive electrode material P3 is obtained.

[0143] The SEM image of the cross section of the multi-component positive electrode material P3 is shown in Figure 3. According to Figure 3, the internal grains of the multi-component positive electrode material P3 grow in a disordered and non-radial manner.

[0144] Example 4 In step (1), the precursor was replaced with precursor S4 prepared in Preparation Example 4, and the amounts of precursor S4 and lithium hydroxide satisfied the relationship n(Ni+Co+Mn+W+Y):n(Li)=1:1.03; In step (2), the atmosphere for the initial sintering is changed to an oxygen atmosphere, and the oxygen content is kept at ≥ 95V%; The initial sintering was carried out by increasing the temperature to T1 = 600°C at a rate of V1 = 2°C / min, maintaining the temperature at this level for t1 = 4 hours, and then increasing the temperature to T2 = 725°C at a rate of V2 = 2°C / min, maintaining the temperature at this level for t2 = 8 hours. Step (3) is to replace the coating agent with B2O3, and the dosage of the semi-finished product and B2O3 satisfies n(Ni+Co+Mn+W+Y):n(B)=1:0.001; In step (4), the temperature of the secondary sintering is changed to 250°C. This differs from the method of Example 1 in that, under the same conditions as above, a multi-component positive electrode material P4 is obtained.

[0145] The ion milled cross section of the multi-component positive electrode material P4 is shown in Figure 5. As shown in Figure 5, the internal grains of the multi-component positive electrode material P4 grow in a disordered and non-radial manner.

[0146] Example 5 In step (1), the precursor was replaced with precursor S5 prepared in Preparation Example 5, and the dopant was replaced with tungsten oxide and yttrium oxide. This differs from the method of Example 4 in that the amounts of precursor S5, tungsten oxide, yttrium oxide, and lithium hydroxide were n(Ni):n(Co):n(Mn):n(W):n(Y):n(Li)=0.95:0.02:0.0275:0.001:0.0015:1.03, but other conditions were the same. This yielded multi-component positive electrode material P5.

[0147] Comparative Example 1 Step (1) differs from the method of Example 1 in that the precursor is replaced with the precursor DS1 prepared in Comparative Preparation Example 1, but other conditions are the same to obtain a multi-element positive electrode material DP1.

[0148] The ion milling cross section of the multi-component positive electrode material DP1 is shown in Figure 6. As shown in Figure 6, the internal grains of the multi-component positive electrode material DP1 grow radially.

[0149] Comparative Example 2 Step (1) differs from the method of Example 2 in that the precursor is replaced with the precursor DS2 prepared in Comparative Preparation Example 2, but other conditions are the same to obtain a multi-element positive electrode material DP2.

[0150] Comparative Example 3 Step (1) differs from the method of Example 3 in that the precursor is replaced with the precursor DS3 prepared in Comparative Preparation Example 3, but other conditions are the same to obtain a multi-element positive electrode material DP3.

[0151] The SEM image of the cross section of the multi-component positive electrode material DP3 is shown in Figure 4. As shown in Figure 4, the internal grains of the multi-component positive electrode material DP3 grow radially.

[0152] Comparative Example 4 Step (1) differs from the method of Example 4 in that the precursor is replaced with the precursor DS4 prepared in Comparative Preparation Example 4, but other conditions are the same to obtain a multi-element positive electrode material DP4.

[0153] Comparative Example 5 The method differs from that of Example 1 in that t1 is changed to 0h in step (2), but other conditions are the same to obtain a multi-element positive electrode material DP5.

[0154] Comparative Example 6 In step (2), the initial sintering is performed by increasing the temperature to T1=710°C at a heating rate of V1=7°C / min, maintaining the constant temperature for t1=3 hours, and then increasing the temperature to T2=860°C at a heating rate of V2=7°C / min, maintaining the constant temperature for t2=10 hours, which is different from the method in Example 2. However, the other conditions are the same, and a multi-component positive electrode material DP6 is obtained.

[0155] Comparative Example 7 In step (2), the atmosphere for the first and second sintering was changed to an oxygen atmosphere with an oxygen content of 85V%. This was different from the method in Example 3, but the other conditions were the same to obtain a multi-component positive electrode material DP7.

[0156] Comparative Example 8 In step (2), the initial sintering is performed by increasing the temperature to T1=600°C at a heating rate of V1=7°C / min, then increasing the temperature to T2=725°C at a heating rate of V2=7°C / min, and maintaining the temperature at this rate for t2=7 hours, which is different from the method in Example 4. However, the other conditions are the same, and a multi-component positive electrode material DP8 is obtained. [Table 3]

[0157] JPEG2026501530000008.jpg142170

[0158] JPEG2026501530000009.jpg140170 [Table 4]

[0159] JPEG2026501530000011.jpg107170Note: 4-If the ratio of the total cross-sectional area of ​​primary particles having 5 or more grain boundaries to the cross-sectional area of ​​secondary particles is ≧3:4, mark with √, otherwise mark with ×. 5-Porosity on the cross section of secondary particles. 6-Grain boundary density of secondary particles = number of interfaces between primary particles on the cross section of the secondary particle / number of primary particles on the cross section of the secondary particle. 7-Ratio of the number of grain boundaries with a length ≦1.5 μm to the total number of grain boundaries. 8-Proportion of the number of primary particles with a major axis ratio selected from 0.9 to 1.1.

[0160] JPEG2026501530000012.jpg98170

[0161] According to the data in Tables 2-4, Examples 1-5, compared to Comparative Examples 1-8, utilize the manufacturing method proposed by the present invention to produce multi-element positive electrode materials with the advantages of internal grains growing non-radially, high compaction, and electrode pieces being less likely to break. In Examples 1-4, the powder compaction of the materials manufactured using the dual-platform insulation method with non-radial doped precursors is significantly higher than that of the positive electrode materials of Comparative Examples 1-8 manufactured using the same method with radially distributed precursors. The compaction of the material of Example 5, which was manufactured by adding doping element M during the manufacturing process without using doping element M during the precursor stage, is slightly lower than that of the material of Example 4, which was manufactured using doping element M during the precursor stage.

[0162] Moreover, the materials produced according to the heating rates V1 and V2 (Comparative Example 6) being too high, the Ni content being high, and the oxygen concentration being insufficient for the first sintering (Comparative Example 7), as well as the first sintering using a single platform (Comparative Examples 8 and 5), have obviously high alkali contents and correspondingly low compaction degrees, which make the electrode pieces prone to fracture when compacting.

[0163] Test Example 1 The positive electrode sheets manufactured using the multi-component positive electrode materials of the above examples and comparative examples were subjected to ultimate compaction and crushing tests. The test results are shown in Table 5.

[0164] Regarding the manufacturing method of the positive electrode sheet, the multi-component positive electrode material, SP, CNT, and polyvinylidene fluoride (PVDF) were thoroughly mixed with an appropriate amount of N-methylpyrrolidone (NMP) in a mass ratio of 97:1:0.8:1.2 to form a uniform paste. The slurry was then applied to an aluminum foil, dried, and cut into 112 mm × 40 mm electrode pieces using a die-cutting machine. The multi-component positive electrode material loading was 380±2 g / m. 2 is.

[0165] To determine whether the electrode pieces were broken, the fabricated positive electrode sheet was baked in a vacuum drying oven at 125°C for more than 8 hours, then rolled twice to achieve the appropriate degree of compaction. A fixed weight plate was then used to compress and fold the electrode pieces. Finally, an LED point light source was used to observe the light transmittance. The thickness and length of the positive electrode sheet before and after rolling were recorded, and the thickness compression ratio and elongation ratio of the positive electrode sheet before and after rolling were calculated. The positive electrode sheet was compressed to different degrees of compaction, and the electrode pieces were folded once, twice, three times, and four times according to the different degrees of compaction. The light transmittance was then observed, and the electrode piece fracture status was determined based on whether light was transmitted. [Table 5]

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[0167] JPEG2026501530000015.jpg70170

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[0172] JPEG2026501530000020.jpg234170

[0173] JPEG2026501530000021.jpg225170 Note: ~Do not perform test examples after light transmission under these conditions.

[0174] According to the data in Table 5, when the positive electrode sheet made of the multi-component positive electrode material P1 of Example 1 is subjected to ultimate compaction, the ultimate compaction density corresponding to the single fold and double fold when it is not possible to make the sheet opaque is 3.64 g / cm. 3 and 3.57 g / cm 3 (Taking Example 1 as an example, the ultimate compaction density corresponding to the positive electrode sheet A2 corresponding to the time when the first single fold does not allow light to pass through, and the ultimate compaction density corresponding to the positive electrode sheet A4 corresponding to the time when the first double fold does not allow light to pass through.) When the positive electrode sheet made of the multi-component positive electrode material P2 of Example 2 is subjected to ultimate compaction, the ultimate compaction density corresponding to the time when the first single fold and the second double fold do not allow light to pass through is 3.66 g / cm. 3 and 3.62 g / cm 3 The positive electrode sheet made of the multi-component positive electrode material P3 in Example 3 was subjected to ultimate compaction, and the ultimate compaction densities corresponding to the single and double folds at which light could not be transmitted were 3.77 g / cm. 3 and 3.59 g / cm 3 The positive electrode sheet made of the multi-component positive electrode material P4 in Example 4 was subjected to ultimate compaction, and the ultimate compaction densities corresponding to the single and double folds at which light could not be transmitted were 3.71 g / cm. 3 and 3.57 g / cm 3 The ultimate compaction degree of these materials is higher than the results of the corresponding comparative examples.

[0175] In the SEM images of the cross section of the positive electrode sheet made of the multi-component positive electrode material P1 of Example 1 after extreme compaction, as shown in Figures 7 (single fold) and 8 (double fold), the secondary particles are easily softened under the action of high extreme compaction, which corresponds to removing some of the rolling pressure, thereby reducing the pressure applied by the secondary particles to the aluminum foil electrode pieces and reducing the breakage of the electrode pieces, and in addition, the electrical properties of the battery may still better meet the usage requirements.

[0176] In the SEM images of the cross section of the positive electrode sheet made of the multi-component positive electrode material DP1 of Comparative Example 1 after extreme compaction, as shown in Figures 9 (single fold) and 10 (double fold), even when extreme compaction is applied to the secondary particles, the radial distribution of the internal structure of the multi-component positive electrode material DP1 leads to deformation of the secondary particles, and the pressure applied thereto is directly transmitted to the aluminum foil, causing the aluminum foil to split.

[0177] Although the preferred embodiments of the present invention have been described in detail above, they are not limited to the present invention. Within the scope of the technical concept of the present invention, it is possible to carry out simple modifications to the technical means of the present invention and combine various technical features in other suitable ways, and such simple modifications and combinations should also be considered as the contents disclosed in the present invention, and all are included in the protection scope of the present invention.

Claims

1. Secondary particles formed by aggregation of primary particles, The ratio of the total cross-sectional area of primary particles having 5 or more grain boundaries to the cross-sectional area of the secondary particles is ≧3:4, and the porosity in the cross-section of the secondary particles is ≦2%, The grain boundary is defined as the contour line of the interface between primary particles having the same structure and different directions in the cross-section of the secondary particle, and the length of the grain boundary is ≧0.1 μm, A multi-component positive electrode material characterized by the above.

2. The number of grain boundaries with a length of ≦1.5 μm accounts for 70% or more of the total number of grain boundaries, Preferably, the number of grain boundaries with a length of ≦1.2 μm accounts for 70% or more of the total number of grain boundaries, More preferably, the number of grain boundaries with a length selected from 0.2 - 1.2 μm accounts for 80% or more of the total number of grain boundaries, The multi-component positive electrode material according to Claim 1, characterized by the above.

3. The grain boundary density of the secondary particle is ≧1.8, preferably selected from 2 - 3, The grain boundary density is defined as the number of interfaces between primary particles in the cross-section of the secondary particle / the number of primary particles in the cross-section of the secondary particle, The multi-component positive electrode material according to Claim 1 or 2, characterized by the above.

4. The average aspect ratio of the primary particles is ≦1.5, preferably selected from 1 - 1.5, more preferably selected from 1 - 1.1, Preferably, the number of primary particles with an aspect ratio selected from 0.9 - 1.1 accounts for ≧70%, and the multi-component positive electrode material according to any one of Claims 1 - 3 is characterized by the above.

5. The average particle size DB of the secondary particles 50 and the average particle size DA of the primary particles 50 is 10≦DB 50 / DA 50 ≦40, and / or The average particle size DB of the secondary particles 50 is selected from 6-14 μm, preferably 8-12 μm, and / or The average particle diameter DA of the primary particles 50 is selected from 0.1-1.5 μm, preferably 0.2-1.2 μm; The multi-component positive electrode material according to any one of Claims 1 - 4, characterized by the above.

6. Having the composition shown in Formula I, Li a (Ni x Co y Mr z M b )G c O 2 (I) Here, 1≦a≦1.2, 0≦b≦0.05, 0≦c≦0.05, 0.3≦x<1, 0<y<0.5, 0<z<0.5, and x + y + z + b = 1, M and G are each independently selected from at least one of Mg, Ti, W, V, Ta, Zr, La, Ce, Er, Sr, Si, B, Al, Co, and Y, Preferably, in Formula I, 1≦a≦1.1, 0 < b≦0.02, 0 < c≦0.02, 0.4≦x≦0.95, 0.01≦y≦0.2, 0.01≦z≦0.3, M is selected from at least one of Mg, Ti, W, V, Ta, Zr, La, Ce, Er, Sr, Si, Al, Co, and Y, and G is selected from at least one of Mg, Ti, W, Zr, Ce, Er, Si, B, and Al, More preferably, Formula I includes: 0.0001≦b≦0.02, 0.0001≦c≦0.02; M is selected from at least one of W, Zr, La, and Y; and G is selected from at least one of B, Ti, W, Si, and Al.

6. The multi-element positive electrode material according to claim 1, wherein the multi-element positive electrode material is a polycrystalline silicon dioxide.

7. The XRD pattern has a characteristic diffraction peak of the (104) crystal plane, and the half-peak width FWHM of the characteristic diffraction peak of the (104) crystal plane (104) is selected from 0.2-0.24, 7. The multi-element positive electrode material according to claim 1, wherein the multi-element positive electrode material is a polycrystalline silicon dioxide.

8. Single α-NaFeO 2 8. The multi-component positive electrode material according to claim 1, characterized in that it has a layered structure.

9. Powder compaction density ≥ 3.4g / cm 3 9. The multi-component positive electrode material according to claim 1, wherein

10. The total residual alkali content is m(Li 2 CO 3 ) + m(LiOH) < 6000 ppm, and / or The total residual alkali content is m(Li 2 CO 3 ) < m(LiOH), and further satisfies the condition that both m(Li 2 CO 3 ) and m(LiOH) are less than 3000 ppm.

10. The multi-element positive electrode material according to claim 1, wherein the multi-element positive electrode material is a polycrystalline silicon dioxide.

11. (1) mixing a precursor having a composition shown in formula II with a lithium source to obtain a mixture I, and forming the precursor by agglomeration of primary particles, and the primary particles in the cross section of the precursor are distributed non-radially; (NiαCoβMnγMδ)(OH) 2 (II) (2) first sintering the mixture I in an oxygen-containing atmosphere to obtain a semi-finished product, the first sintering conditions including: increasing the temperature to T1 at a temperature increase rate V1, maintaining the temperature at a constant value t1, and then increasing the temperature to T2 at a temperature increase rate V2, and maintaining the temperature at a constant value t2; (3) mixing the semi-finished product with an optional G-containing coating agent to obtain mixture II; (4) sintering the semi-finished product or mixture II for a second time in an oxygen-containing atmosphere to obtain a multi-component positive electrode material; wherein 0.3≦α<1, 0<β<0.5, 0<γ<0.5, 0≦δ≦0.05, and α+β+γ+δ=1; M and G are each independently selected from at least one of Mg, Ti, W, V, Ta, Zr, La, Ce, Er, Sr, Si, B, Al, Co, and Y; A method for producing a multi-element positive electrode material.

12. In step (1), the precursor D 50 12. The method according to claim 11, wherein the thickness is selected from the range of 8-14 μm.

13. The specific surface area of ​​the precursor is 3-7m 2 13. The method according to claim 11, wherein the amount of the hydroxyl group is selected from the group consisting of hydroxyl groups and hydroxyl groups.

14. The dosage of the precursor and the lithium source satisfies n(Ni+Co+Mn+M):n(Li)=1:1-1.2, preferably n(Ni+Co+Mn+M):n(Li)=1:1-1.1; 14. The method according to any one of claims 11 to 13, characterized in that

15. obtaining the precursor by contacting a mixed metal salt solution containing a nickel source, a cobalt source, a manganese source, and an optional M-containing dopant with a precipitating agent, a complexing agent, and a dispersing agent in an inert atmosphere to co-precipitate the precursor, and sequentially washing and drying the obtained co-precipitation reaction product; Preferably, the conditions for the coprecipitation include that the temperature is selected from 40 to 80°C, the pH value is 10 to 13, and the stirring rotation speed is selected from 200 to 550 rpm. More preferably, the conditions for the coprecipitation include that the temperature is selected from 50 to 70°C, the pH value is 11 to 12.5, and the stirring rotation speed is selected from 350 to 500 rpm. The manufacturing method according to any one of claims 11-14, characterized in that.

16. In the mixed metal salt solution, the dosages of the nickel source, cobalt source, manganese source and dopant are n(Ni):n(Co):n(Mn):n(M), satisfying 0.3≦n(Ni)<1, 0<n(Co)<0.5, 0<n(Mn)<0.5, 0≦n(M)≦0.

05. Preferably, it satisfies 0.4≦n(Ni)≦0.95, 0.01≦n(Co)≦0.2, 0.01≦n(Mn)≦0.3, 0<n(M)≦0.

02. More preferably, it satisfies 0.0001≦n(M)≦0.

02. The manufacturing method according to claim 15, characterized in that.

17. In step (2), the conditions for the first sintering are The heating rate V1 is selected from 1-6°C / min, preferably selected from 1-3°C / min, more preferably selected from 1-2°C / min, T1 is selected from 400-760°C, preferably selected from 500-750°C, and the heat preservation time t1 is selected from 2-6 h, preferably selected from 3-5 h. The heating rate V2 is selected from 1-6°C / min, preferably selected from 1-3°C / min, T2 is selected from 710-950°C, preferably selected from 710-920°C, and the heat preservation time t2 is selected from 5-13 h, preferably selected from 6-12 h. The manufacturing method according to any one of claims 11-16, characterized in that.

18. When the nickel content in the precursor in terms of metal element conversion is ≧60 mol%, the oxygen concentration in the oxygen-containing atmosphere is ≧92 vol.%. The manufacturing method according to any one of claims 11-17, characterized in that.

19. The manufacturing method according to any one of claims 11-18, characterized in that the product of the first sintering is cooled to room temperature and crushed to obtain the semi-finished product.

20. In step (3), the dosages of the semi-finished product and the coating agent satisfy n(Ni + Co + Mn + M):n(G)=1:n(G), where 0≦n(G)≦0.05, preferably 0 < n(G)≦0.02, and more preferably 0.0001≦n(G)≦0.

02. The manufacturing method according to any one of claims 11 - 19, characterized in that.

21. The coating agent is selected from at least one of oxides, hydroxides, and carbonates containing G. Preferably, it is selected from at least one of oxides, hydroxides, and carbonates containing Mg, Ti, W, Zr, Ce, Er, Si, B, and Al. More preferably, it is selected from at least one of oxides, hydroxides, and carbonates containing B, Ti, W, Si, and Al. The manufacturing method according to any one of claims 11 - 20, characterized in that.

22. In step (4), the conditions of the second sintering are that the temperature T3 is selected from 300 - 800°C, preferably from 400 - 700°C, and the time t3 is selected from 4 - 10 h, preferably from 5 - 8 h. The manufacturing method according to any one of claims 11 - 21, characterized in that.

23. In step (4), the multi-component cathode material has the composition shown in Formula I. Li a (Ni x Co y Mr z M b )G c O 2 (I) Here, 1≦a≦1.2, 0≦b≦0.05, 0≦c≦0.05, 0.3≦x<1, 0<y<0.5, 0<z<0.5, and x + y + z + b = 1. M and G are each independently selected from at least one of Mg, Ti, W, V, Ta, Zr, La, Ce, Er, Sr, Si, B, Al, Co, and Y. Preferably, in Formula I, 1≦a≦1.1, 0 < b≦0.02, 0 < c≦0.02, 0.4≦x≦0.95, 0.01≦y≦0.2, 0.01≦z≦0.

3. M is selected from at least one of Mg, Ti, W, V, Ta, Zr, La, Ce, Er, Sr, Si, Al, Co, and Y. G is selected from at least one of Mg, Ti, W, Zr, Ce, Er, Si, B, and Al. More preferably, in Formula I, 0.0001≦b≦0.02, 0.0001≦c≦0.

02. M is selected from at least one of W, Zr, La, and Y. G is selected from at least one of B, Ti, W, Si, and Al. The manufacturing method according to any one of claims 11 - 22, characterized in that.

24. The active material layer comprises a multi-element positive electrode material according to any one of claims 1-10 or a multi-element positive electrode material produced according to the method of production according to any one of claims 11-23. A positive electrode sheet characterized by:

25. The loading of the multi-component positive electrode material is 380±2 g / m 2 25. The positive electrode sheet according to claim 24, wherein

26. Ultimate compaction density is 3.2-3.8g / cm 3 Preferably, 3.3-3.7 g / cm 3 26. The positive electrode sheet according to claim 24, wherein

27. The positive electrode sheet according to any one of claims 24 to 26, characterized in that the thickness compression ratio is selected from 25 to 45%, preferably 30-40%.

28. 28. The positive electrode sheet according to any one of claims 24 to 27, characterized in that the elongation ratio is selected from the range of 1.2-3%, preferably 1.5-2.5%.

29. A lithium ion battery comprising the positive electrode sheet according to any one of claims 24 to 28.

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