Positive electrode piece and method for manufacturing the same, lithium-ion battery

Abstract

In the field of lithium-ion batteries, the present invention specifically provides a positive electrode piece and a method for manufacturing the same. The lithium-ion battery comprising the positive electrode piece comprises a positive electrode active material layer, the positive electrode active material layer comprises a positive electrode material, a negative thermal expansion material, a conductive agent, and a binder, the characteristic value J of the positive electrode piece satisfies 0.001 ≤ J ≤ 0.005, and J = R(F) / ρ, where R(F) represents the peak intensity ratio of the main peak (F) of the negative thermal expansion material and the (003) characteristic peak of the positive electrode material in the XRD spectrum of the positive electrode piece, and ρ is the surface density (mg / cm³) of the positive electrode piece. 2 The provided positive electrode piece simultaneously possesses low volume expansion, high structural stability, and high temperature stability, and at the same time, the lithium-ion battery containing this positive electrode piece combines excellent capacity performance, multiplier performance, cycle performance, and energy density.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, specifically to a positive electrode sheet and a method for manufacturing the same, and a lithium-ion battery including the positive electrode sheet.

Background Art

[0002] Lithium-ion batteries are new type of green secondary batteries that were successfully developed in the 1990s. In recent years, with the pursuit of green energy by people, they have achieved prosperous development, and their application fields have continuously expanded from the initial small digital devices to power tools, electric vehicles, and energy storage power plants, etc. How to achieve high energy density, high voltage, long cycle life, and high safety of lithium-ion batteries has become an important goal in this field.

[0003] The positive electrode sheet has an important influence on the performance of lithium-ion batteries and includes a positive electrode current collector and a positive electrode active material layer provided on the surface of the current collector. The positive electrode active material layer is a thin film formed by coating a positive electrode active material on the surface of the current collector, and is composed of a lithium-containing layered compound positive electrode material, a conductive agent, and a binder, with the positive electrode material as the main component. The positive electrode active material layer must have high conductivity and high durability. For the positive electrode material, during the charge and discharge process, the insertion and release of lithium ions cause changes in the cell volume, which affects the contact between positive electrode particles. At the same time, heat is generated during the charge and discharge cycle process of the lithium-ion battery, resulting in stress and deformation due to thermal expansion and contraction of the current collector and the positive electrode active material layer, causing phenomena such as pole piece deformation, positive electrode particle fracture, and destruction of the contact between the positive electrode and the current collector, leading to a continuous decline in the battery discharge performance, accelerating the attenuation of the battery cycle life, and causing safety risks.

[0004] Patent Document 1 utilizes the negative thermal expansion property of scandium fluoride (ScF3 phase) to enhance the high-temperature stability of the material. However, when a scandium fluoride coating is applied to the surface of the positive electrode material, the coating layer reduces the lithium ion transfer performance on the surface of the positive electrode material, affecting the capacity performance after the electrode piece is fabricated in accordance with the positive electrode material, significantly reducing the capacity of the lithium battery, and further negatively affecting the magnification and energy density. Therefore, from the viewpoint of optimizing the performance of the electrode piece, it is necessary to improve electrical performance by utilizing the good properties of the negative thermal expansion material.

[0005] Therefore, providing a positive electrode piece that possesses good high-temperature stability and good electrochemical properties such as capacity, magnification, and cycle is of great importance. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Chinese Patent Publication No. 109728275 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The present invention aims to overcome the above-mentioned technical problems by providing a positive electrode piece, a method for manufacturing the same, and a lithium-ion battery, wherein the positive electrode piece has low volume expansion, high structural stability, and high temperature stability, and at the same time, the lithium-ion battery containing the positive electrode piece has excellent capacity performance, multiplier performance, cycle performance, and energy density. [Means for solving the problem]

[0008] To achieve the above objective, a first aspect of the present invention provides a positive electrode piece, the positive electrode piece comprising a positive electrode active material layer, the positive electrode active material layer comprising a positive electrode material, a negative thermal expansion material, a conductive agent, and a binder. The characteristic value J of the positive electrode piece satisfies 0.001 ≤ J ≤ 0.005. Let J = R(F) / ρ, where R(F) is the peak intensity ratio of the main peak (F) of the negative thermal expansion material and the (003) characteristic peak of the positive electrode material in the XRD spectrum of the positive electrode piece, and ρ is the surface density (mg / cm³) of the positive electrode piece. 2 ) indicates.

[0009] The inventors of this invention have found through research that when a negative thermal expansion material is added to the positive electrode active material layer, the negative thermal expansion material can absorb heat in situ during the positive electrode material cycle process, reducing its volume and providing space for the volume expansion of the positive electrode active material. This is advantageous for stress relaxation and avoiding material deformation. At the same time, by compounding the negative thermal expansion material with the positive electrode material in the positive electrode active material layer, the negative thermal expansion material maintains its original material structure and is uniformly distributed within the positive electrode active material layer. By forming interparticle contact with the positive electrode material, the negative thermal expansion material ensures at the positive electrode piece level that it can optimally neutralize the volume expansion of the positive electrode active material layer caused by the thermal expansion of the positive electrode material during the charge-discharge cycle process. Since the lattice parameters of positive electrode materials (especially nickel-cobalt-manganate lithium positive electrode materials) change within a certain range due to different doping modifications, the heat generation during charge-discharge after application to an electrode piece also differs accordingly.

[0010] At the same time, when processing positive electrode pieces with the same mixing ratio using the same positive electrode material, the density of the coated surface differs, resulting in differences in the internal resistance of the electrode pieces. Consequently, the heat generation of the electrode pieces during the charge-discharge cycle process also differs.

[0011] Therefore, the present invention realizes a positive electrode piece having a positive electrode material blended with a negative thermal expansion material by rationally controlling the characteristic value J of the positive electrode piece, that is, by rationally controlling the composition of the positive electrode active material layer in the positive electrode piece, without affecting the lithium ion transfer performance and conductivity performance, and at the same time effectively mitigating deformation caused by volume expansion due to heat absorption during the charge-discharge cycle process of the positive electrode piece.

[0012] A second aspect of the present invention provides a method for manufacturing a positive electrode piece, the manufacturing method being: (1) A step of mixing positive electrode material, negative thermal expansion material, conductive agent, binder and solvent to obtain a positive electrode slurry, (2) The steps include applying the positive electrode slurry to the surface of the positive electrode current collector, drying, and roll pressing in sequence to place a positive electrode active material layer on the surface of the positive electrode current collector and obtain a positive electrode piece, The positive electrode material is a lithium-containing layered compound, and the negative thermal expansion material has the composition shown in formula II, Q a Q' b O c (II) Let a, b, and c be independently selected from natural numbers between 1 and 15, and Q and Q' be independently selected from at least one element among Zr, W, Hf, Al, Sc, In, Y, Mo, V, Sn, Ti, and P, and Q and Q' are different elements.

[0013] A third aspect of the present invention provides a lithium-ion battery, the lithium-ion battery comprising a positive electrode piece according to the first aspect, or a positive electrode piece manufactured by a manufacturing method according to the second aspect. [Effects of the Invention]

[0014] Compared to conventional technologies, the present invention has the following advantages. (1) The positive electrode piece according to the present invention incorporates a negative thermal expansion material into the positive electrode piece and combines specific characteristic values ​​J, assuming that the transfer of lithium ions from the bulk phase to the surface of the positive electrode material in the positive electrode active material layer is not limited, thereby achieving good magnification performance and capacity. At the same time, the combination of the negative thermal expansion material and the positive electrode material suppresses the expansion of the positive electrode piece during the cycle process, avoiding the effect of the expansion of the positive electrode piece on electrical performance, improving the structural stability, thermal stability and cycle life of the positive electrode piece, and simultaneously improving the safety of the battery. (2) The positive electrode piece according to the present invention can improve high-magnification performance to some extent by adding a specific amount of negative thermal expansion material, which not only has little effect on the discharge capacity but also improves high-magnification performance to some extent. This is because, at high magnification and high current, the volumetric thermal expansion effect of the positive electrode material is partially neutralized by the volumetric contraction of the negative thermal expansion material. (3) The manufacturing method according to the present invention has advantages such as a simple process, a green and pollution-free manufacturing process, and low production costs, making it convenient for large-scale industrial production. (4) The positive electrode piece according to the present invention is applied to a lithium-ion battery and effectively improves the electrochemical performance of the lithium-ion battery, particularly its capacity performance, magnification performance, and cycle performance. [Brief explanation of the drawing]

[0015] [Figure 1] This is the XRD spectrum of the positive electrode piece S1 manufactured in Example 1. [Modes for carrying out the invention]

[0016] The endpoints and any values ​​of the ranges disclosed herein should be understood to include values ​​close to such exact ranges or values, and not to be limited to such exact ranges or values. In the case of numerical ranges, the intervals between the endpoint values ​​of each range, between the endpoint values ​​of each range and individual point values, and between individual point values ​​combine to obtain one or more new numerical ranges, and these numerical ranges shall be deemed to be specifically disclosed in the specification.

[0017] A first aspect of the present invention provides a positive electrode piece, the positive electrode piece comprising a positive electrode active material layer, the positive electrode active material layer comprising a positive electrode material, a negative thermal expansion material, a conductive agent and a binder, The characteristic value J of the positive electrode piece satisfies 0.001 ≤ J ≤ 0.005. Let J = R(F) / ρ, where R(F) is the peak intensity ratio of the main peak (F) of the negative thermal expansion material and the (003) characteristic peak of the positive electrode material in the XRD spectrum of the positive electrode piece, and ρ is the surface density (mg / cm³) of the positive electrode piece. 2 )

[0018] In this invention, the range of J=R(F) / ρ is selected from 0.001-0.005, and the unit of the surface density ρ of the positive electrode piece is mg / cm³. 2In this case, the numerical relative ratio relationship between R(F) and ρ is limited. That is, once the value of either R(F) or ρ of the positive electrode piece is determined, the other parameter must be set within an appropriate range, thereby enabling the creation of the positive electrode piece according to the present invention.

[0019] In the present invention, unless otherwise specified, the positive electrode piece further comprises a positive electrode current collector, and the positive electrode active material layer is provided on the surface of the positive electrode current collector. In the present invention, the positive electrode current collector includes, but is not limited to, aluminum foil.

[0020] In some embodiments of the present invention, the characteristic value J of the positive electrode piece satisfies 0.001 ≤ J ≤ 0.005 and is any value within the range of, for example, 0.001, 0.00125, 0.0015, 0.0018, 0.002, 0.0023, 0.0025, 0.003, 0.0035, 0.004, 0.005, and any two numerical values, preferably 0.00125 ≤ J ≤ 0.004.

[0021] In this invention, by rationally controlling the characteristic value J of the positive electrode piece, it is ensured that the transfer of lithium ions from the bulk phase to the surface of the positive electrode material in the positive electrode active material layer is not restricted, thereby achieving good magnification performance and capacity. At the same time, by combining the negative thermal expansion material and the positive electrode material, the expansion of the positive electrode piece is suppressed during the cycle process, avoiding the effect of the positive electrode piece expansion on electrical performance, improving the high-temperature stability and cycle life of the positive electrode piece, and simultaneously improving the safety of the battery.

[0022] In some embodiments of the present invention, R(F) = I(F) / I(003), where I(F) and I(003) represent the peak intensities of the main peak (F) of the negative thermal expansion material and the (003) characteristic peak of the positive electrode material in the XRD spectrum of the positive electrode piece, respectively.

[0023] In the present invention, unless otherwise specified, I(003) represents the peak intensity of the characteristic (003) peak of the positive electrode material around 2θ = 18° ± 2, and I(F) represents the peak intensity of the main (F) peak of the negative thermal expansion material.

[0024] In this invention, the high-temperature performance and cycle stability of the electrode piece can be improved by adjusting and controlling the peak intensity ratio R(F) value between the main peak I(F) of the negative thermal expansion material in the positive electrode piece and the peak intensity of the positive electrode material I(003). If the R(F) value is low, it indicates that the negative thermal expansion material cannot maintain its original crystal structure in the processed positive electrode piece, and its thermal contraction and cold expansion performance cannot be properly exhibited. However, if the R(F) value is too high, it indicates that too much negative thermal expansion material has been added, which affects the capacity performance of the positive electrode piece.

[0025] In some embodiments of the present invention, preferably 0.005 ≤ R(F) ≤ 0.1, for example, any value within the range of 0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.08, 0.1 and any two numerical values, and more preferably 0.02 ≤ R(F) ≤ 0.05.

[0026] In the present invention, an R(F) value that satisfies the above range, and a particularly preferred range, indicates that the applied negative thermal expansion material has good crystallinity and can maintain its structure in the electrode piece. As a result, a characteristic peak (F) appears in the XRD diffraction spectrum, while the ratio indicating that the negative thermal expansion material can exert a negative thermal expansion effect in the cathode material active layer can exhibit an optimal effect according to the electrode piece process.

[0027] In this invention, the surface density parameter of the positive electrode piece affects the performance of the positive electrode piece. The smaller the surface density of the positive electrode piece, the thinner the positive electrode piece becomes, the lower the internal resistance of the battery, and in charge-discharge cycles, the lithium-ion battery is constantly embedded, and the changes to the electrode piece structure when it escapes are also small, which is advantageous for lithium-ion movement, and at the same time the thermal expansion of the electrode piece is also small. The larger the surface density of the positive electrode piece, the longer the movement path of the lithium-ion battery becomes, the higher the internal resistance of the battery, and the greater the thermal expansion of the electrode piece.

[0028] In the present invention, if the areal density ρ of the positive electrode sheet is too low, it means that the active material for rapid charging in the battery is very little, the gram capacity of the positive electrode sheet is low, and the positive electrode active particles are likely to crack during the processing of the positive electrode sheet, which will affect the battery life. If the areal density ρ of the positive electrode sheet is too high, it will not only affect the stability of the positive electrode active material layer and the surface quality of the positive electrode sheet, but also increase the charge transfer impedance, increase the polarization degree, increase the internal resistance of the battery, reduce the discharge specific capacity, and affect the rate performance and cycle life. Therefore, reasonably controlling the areal density of the positive electrode sheet has important significance for battery performance.

[0029] In some embodiments of the present invention, preferably, the areal density of the positive electrode sheet is 8 mg / cm 2 ≦ρ≦25 mg / cm 2 satisfies, for example, 8 mg / cm 2 , 10 mg / cm 2 , 12 mg / cm 2 , 14 mg / cm 2 , 16 mg / cm 2 , 20 mg / cm 2 , 25 mg / cm 2 , and any value within the range consisting of any two numerical values, preferably 10 mg / cm 2 ≦ρ≦16 mg / cm 2 .

[0030] In the present invention, unless otherwise specified, the areal density ρ of the positive electrode sheet refers to the coating weight of the positive electrode active material layer per unit area of the battery electrode sheet. As a parameter, the areal density ρ of the positive electrode sheet is measured by the following method, and the areal density ρ = the coating weight m of the positive electrode active material layer / the coating area S. The coating weight m of the positive electrode active material layer is obtained by weighing the weight of the positive electrode sheet after coating and the weight of the positive electrode current collector (aluminum foil), and calculating the difference between the two. The coating area S is the area of the positive electrode current collector corresponding to the positive electrode sheet, that is, the area of the circular aluminum foil, which can be calculated from the diameter of the aluminum foil.

[0031] In this invention, the crystal structure of the cathode material has strong orientation, so in the XRD spectrum, it appears as independent and distinct diffraction peaks within a certain angular range. For example, the (003) characteristic peak and the (101) characteristic peak of the cathode material correspond to 2θ = 18° ± 2 and 2θ = 37° ± 2, respectively, and no peaks of other cathode materials appear between the two peaks.

[0032] In some embodiments of the present invention, preferably, in the XRD spectrum of the positive electrode piece, the positive electrode material has a (003) characteristic peak and a (101) characteristic peak at positions 2θ=18°±2 and 2θ=37°±2, respectively.

[0033] In the present invention, in a positive electrode active material layer modified with a negative thermal expansion material, the negative thermal expansion material existing as the original crystal structure exhibits a diagram corresponding to the XRD diffraction spectrum of the positive electrode piece, and this diagram appears between the (003) characteristic peak and the (101) characteristic peak of the positive electrode material. Among the one or more characteristic peaks of the negative thermal expansion material that may appear within this interval, the peak with the highest peak intensity is defined as the principal peak (F), and the peak intensity of that XRD principal peak is defined as I(F).

[0034] In some embodiments of the present invention, preferably, in the XRD spectrum of the positive electrode piece, the main peak (F) of the negative thermal expansion material lies between the (003) characteristic peak and the (101) characteristic peak of the positive electrode material. When these characteristics are met, the negative thermal expansion material incorporated into the positive electrode piece maintains its original structure and exhibits good negative thermal expansion performance.

[0035] In one specific embodiment of the present invention, in the XRD spectrum of the positive electrode piece, the diffraction peak of the negative thermal expansion material, particularly the principal peak (F), is distributed between the midpoint of the (003) characteristic peak and the (101) characteristic peak of the positive electrode material, i.e., between 2θ=18° and 2θ=37°.

[0036] In some embodiments of the present invention, preferably, the average particle size D of the negative thermal expansion material 50 (F) is D 50 (F)≦0.42D50 satisfies D 50 is the average particle size (μm) of the positive electrode material. In the present invention, an appropriate D 50 (F) By selecting a negative thermal expansion material, it helps to fill the gaps between the positive electrode materials in the positive electrode sheet and better exert its function.

[0037] In some embodiments of the present invention, preferably, the average particle size D of the positive electrode material 50 is selected from 1 - 20 μm, for example, 1 μm, 2 μm, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, and any value within the range consisting of any two numerical values, and preferably 1 - 10 μm.

[0038] In some embodiments of the present invention, preferably, the average particle size D of the negative thermal expansion material 50 (F) is selected from 0.1 - 10 μm, for example, 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 5 μm, 10 μm, and any value within the range consisting of any two numerical values, and preferably 0.1 - 3 μm.

[0039] In some embodiments of the present invention, preferably, the positive electrode material is a lithium-containing layered compound.

[0040] In the present invention, there is a wide selection range for the type of the positive electrode material. Preferably, the positive electrode material has a composition shown in Formula I, Li 1+α Ni x Co y Mn z M m M′ n O2 (I), where -0.5 ≤ α ≤ 0.4, 0 < x < 1, 0 ≤ y < 1, 0 ≤ z < 1, 0 ≤ m ≤ 0.1, 0 ≤ n ≤ 0.1, and x + y + z + m + n = 1, and M and M′ are each independently selected from at least one element among Al, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, La, Ce, Er, Mg, Sr, Ba, P, and B.

[0041] In some specific embodiments of the present invention, in Formula I, -0.5 ≤ α ≤ 0.4, for example, -0.5, -0.2, -0.1, 0, 0.02, 0.03, 0.05, 0.1, 0.2, 0.4, and any value within the range consisting of any two numerical values, preferably 0 ≤ α ≤ 0.1.

[0042] In some specific embodiments of the present invention, in Formula I, 0 < x < 1, for example, 0.2, 0.5, 0.6, 0.7, 0.8, 0.83, 0.9, 0.95, and any value within the range consisting of any two numerical values, preferably 0.6 ≤ x ≤ 0.9.

[0043] In some specific embodiments of the present invention, in Formula I, 0 ≤ y < 1, for example, 0, 0.01, 0.05, 0.1, 0.11, 0.15, 0.2, 0.3, 0.4, and any value within the range consisting of any two numerical values, preferably 0.01 ≤ y ≤ 0.2.

[0044] In some specific embodiments of the present invention, in Formula I, 0 ≤ z < 1, for example, 0, 0.01, 0.05, 0.08, 0.1, 0.15, 0.2, 0.25, 0.3, 0.4, and any value within the range consisting of any two numerical values, preferably 0.01 ≤ z ≤ 0.3.

[0045] In some specific embodiments of the present invention, in Formula I, 0 ≤ m ≤ 0.1, for example, 0, 0.001, 0.002, 0.005, 0.01, 0.018, 0.05, 0.06, 0.08, 0.1, and any value within the range consisting of any two numerical values, 0 ≤ n ≤ 0.1, for example, 0, 0.001, 0.002, 0.005, 0.01, 0.018, 0.05, 0.06, 0.08, 0.1, and any value within the range consisting of any two numerical values, preferably, 0.001 ≤ m + n ≤ 0.1, for example, 0.001, 0.006, 0.01, 0.02, 0.05, 0.06, 0.08, 0.09, 0.1, and any value within the range consisting of any two numerical values.

[0046] In some specific embodiments of the present invention, in formula I, M and M' are each independently selected from at least one element among Al, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, La, Ce, Er, Mg, Sr, Ba, P, and B, preferably M and M' are different elements, and more preferably M is selected from at least one element among Al, Y, Ti, Zr, La, Sr, and B, and M' is selected from at least one element among Nb, Mo, W, and P.

[0047] In one specific embodiment of the present invention, the positive electrode material is Li 1.02 Ni 0.9 Co 0.05 Mn 0.05 O2, Li 1.03 Ni 0.83 Co 0.11 Mn 0.06 O2, Li 1.03 Ni 0.6 Co 0.1 Mn 0.3 O2, Li 1.02 Ni 0.9 Co 0.05 Mn 0.05 Al 0.018 W 0.002 O2, Li 1.03 Ni 0.83 Co 0.104 Mn 0.06 Zr 0.005 Nb 0.001 This includes, but is not limited to, O2, etc.

[0048] In some embodiments of the present invention, preferably, the negative thermal expansion material has the composition shown in formula II, and Q a Q' b O c (II) Let a, b, and c be independently selected from natural numbers between 1 and 15, and Q and Q' be independently selected from at least one element among Zr, W, Hf, Al, Sc, In, Y, Mo, V, Sn, Ti, and P, and Q and Q' be different elements.

[0049] In some embodiments of the present invention, more preferably, the negative thermal expansion material is selected from at least one of tungstates, molybdates, vanadates, and pyrophosphates.

[0050] In one specific embodiment of the present invention, when the negative thermal expansion material is selected from tungstates, the tungstate is ZrW2O8, HfW2O8, Al2W3O 12 ,Sc2W3O 12 In2W3O 12 Y2W3O 12 This includes, but is not limited to, the following.

[0051] In one specific embodiment of the present invention, when the negative thermal expansion material is selected from molybdate salts, the molybdate salt includes, but is not limited to, ZrMo2O8, HfMo2O8, etc.

[0052] In one specific embodiment of the present invention, when the negative thermal expansion material is selected from vanadates, the vanadates include, but are not limited to, ZrV2O7, HfV2O7, SnV2O7, TiV2O7, etc.

[0053] In one specific embodiment of the present invention, when the negative thermal expansion material is selected from pyrophosphates, the pyrophosphate includes, but is not limited to, ZrP2O7, HfP2O7, SnP2O7, and TiP2O7.

[0054] In some embodiments of the present invention, the thickness of the positive electrode active material layer is preferably 20-85 μm, for example, any value within the range of 20 μm, 25 μm, 30 μm, 40 μm, 50 μm, 60 μm, 75 μm, 85 μm, and any two numbers, preferably 25-60 μm.

[0055] In this invention, with respect to the positive electrode piece, the thickness of the positive electrode active material layer is related to the properties, weight, and roll press pressure of the coated active material. The active material refers to a mixture formed from a positive electrode material, a negative thermal expansion material, a conductive agent, and a binder. If the coating weight of the active material is large, the compaction performance of the positive electrode piece is low, and the roll press pressure during the processing is small, the thickness of the active material layer increases, increasing the number of charge transport paths, which negatively affects charge transport, causes an increase in impedance, and makes the thermal effect during the charge-discharge process even more pronounced, negatively impacting the cycle.

[0056] In this invention, in order to achieve optimal electrical performance of the positive electrode piece, if a negative thermal expansion material is present in the positive electrode piece, it is also necessary to match the surface density of the positive electrode piece. If the surface density of the positive electrode piece is low and the content of the positive electrode material is small, the amount of heat generated is low and the processing performance of the positive electrode piece is low, and it is necessary to reduce the content of the negative thermal expansion material in the positive electrode piece to match the thermal expansion due to heat absorption of the positive electrode active material layer on the electrode piece. If the surface density of the positive electrode piece is high and the content of the positive electrode material is large, the amount of heat generated is large, and it is necessary to completely maintain the crystal structure of the negative thermal expansion material in the positive electrode piece during the processing process, and more negative thermal expansion material is required to neutralize the volume expansion during the charging and discharging process of the electrode piece.

[0057] In some embodiments of the present invention, preferably, the content of the positive electrode material is 85.5-94.52 wt%, preferably 90-94.5 wt%, based on the total weight of the positive electrode active material layer, and the content of the negative thermal expansion material is 0.48-9.5 wt%, preferably 0.5-5 wt%.

[0058] In some embodiments of the present invention, more preferably, the content of the conductive agent is 2-4 wt%, preferably 2.5-3.5 wt%, and the content of the binder is 1-3 wt%, preferably 1.5-2.5 wt%, based on the total weight of the positive electrode active material layer.

[0059] In the present invention, the conductive agent includes, but is not limited to, acetylene black, carbon fiber, carbon nanotubes, graphite, Kochen black, etc., and the binder includes, but is not limited to, PVDF, etc.

[0060] The positive electrode piece according to the present invention has the characteristic of low internal resistance, and when an impedance test is performed on the positive electrode piece, the measured initial discharge impedance value of the positive electrode piece R(d) ≤ 20Ω, preferably R(d) ≤ 18Ω.

[0061] A second aspect of the present invention provides a method for manufacturing a positive electrode piece, the manufacturing method being: (1) A step of mixing positive electrode material, negative thermal expansion material, conductive agent, binder and solvent to obtain a positive electrode slurry, (2) The steps include applying the positive electrode slurry to the surface of the positive electrode current collector, drying, and roll pressing in sequence to place a positive electrode active material layer on the surface of the positive electrode current collector and obtain a positive electrode piece, The positive electrode material is a lithium-containing layered compound, and the negative thermal expansion material has the composition shown in formula II, Q a Q' b O c (II) Let a, b, and c be independently selected from natural numbers between 1 and 15, and Q and Q' be independently selected from at least one element among Zr, W, Hf, Al, Sc, In, Y, Mo, V, Sn, Ti, and P, and Q and Q' be different elements.

[0062] In some embodiments of the present invention, preferably in step (1), the mass ratio of the positive electrode material, negative thermal expansion material, conductive agent, and binder is (85.5-94.52):(0.48-9.5):(2-4):(1-3), and preferably (90-94.5):(0.5-5):(2.5-3.5):(1.5-2.5).

[0063] In some embodiments of the present invention, preferably in step (1), the positive electrode material has a composition shown in formula I, and Li 1+α Ni x Co y Mn z Mm M′ n Denoted as O2(I), where -0.5 ≤ α ≤ 0.4, 0 < x < 1, 0 ≤ y < 1, 0 ≤ z < 1, 0 ≤ m ≤ 0.1, 0 ≤ n ≤ 0.1, and x + y + z + m + n = 1. M and M′ are each independently selected from at least one element among Al, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, La, Ce, Er, Mg, Sr, Ba, P, and B.

[0064] In some embodiments of the present invention, preferably, in Formula I, 0 ≤ α ≤ 0.1, 0.6 ≤ x ≤ 0.9, 0.01 ≤ y ≤ 0.2, 0.01 ≤ z ≤ 0.3. m and n are not both 0 at the same time, and 0.001 ≤ m + n ≤ 0.1.

[0065] In some embodiments of the present invention, preferably, in Formula I, the elements M and M′ are different. More preferably, in Formula I, M is selected from at least one element among Al, Y, Ti, Zr, La, Sr, and B, and M′ is selected from at least one element among Nb, Mo, W, and P.

[0066] In some embodiments of the present invention, preferably, in step (1), the average particle size D 50 (F) of the negative thermal expansion material satisfies D 50 (F) ≤ 0.42D 50 , where D 50 is the average particle size (μm) of the positive electrode material. More preferably, the average particle size D 50 of the positive electrode material is selected from 1 - 20 μm, preferably 1 - 10 μm, and the average particle size D 50 (F) of the negative thermal expansion material is selected from 0.1 - 10 μm, preferably 0.1 - 3 μm.

[0067] In the present invention, in step (1), the solvent may be any one that can uniformly mix the positive electrode material, negative thermal expansion material, conductive agent, and binder. The solvent includes, but is not limited to, NMP, methanol, ethanol, etc.

[0068] In some embodiments of the present invention, preferably in step (1), the mixing conditions are a temperature of 15-40°C, preferably 20-30°C, a time of 10-120 min, preferably 20-60 min, and a rotational speed of 500-2000 rpm, preferably 800-1500 rpm.

[0069] In some embodiments of the present invention, the solid content of the positive electrode slurry is preferably 40-60 wt%.

[0070] In the present invention, in step (2), the coating refers to uniformly coating the positive electrode slurry onto the surface of the positive electrode current collector to form a positive electrode slurry coating layer, and the drying refers to removing the solvent in the positive electrode slurry coating layer to form a positive electrode active material layer. Preferably, the drying refers to removing the positive electrode slurry, and the drying temperature is 80-150°C, preferably 120-150°C.

[0071] In some embodiments of the present invention, the pressure P of the roll press is preferably selected from 5 to 20T. In the present invention, the roll press operation is generally performed in a roll press apparatus to cut the roll press product and obtain a positive electrode piece.

[0072] The method for manufacturing positive electrode pieces according to the present invention balances the volume expansion of materials during the charge-discharge process by mixing a negative thermal expansion material between positive electrode material particles, thereby improving the stability of the electrode piece cycle. Specifically, the type of positive electrode material, the amount added, and D 50 , the type of negative thermal expansion material, the amount added and D 50 (F) and the pressure P of the roll press are adjusted and controlled to adjust the characteristic value J of the positive electrode piece, thereby providing the positive electrode piece with low volume expansion, high structural stability and high temperature stability simultaneously.

[0073] A third aspect of the present invention provides a lithium-ion battery comprising a positive electrode piece according to the first aspect, or a positive electrode piece manufactured by a manufacturing method according to the second aspect.

[0074] In one specific embodiment of the present invention, the lithium-ion battery includes a positive electrode piece, a negative electrode piece, a separator provided between the positive electrode piece and the negative electrode piece, and an electrolyte.

[0075] The present invention will be described in detail below through the examples provided.

[0076] Table 1 shows the process parameters for manufacturing the positive electrode pieces in both the examples and comparative examples, as well as the physical property parameters of the manufactured positive electrode pieces.

[0077] Example 1 (1) Cathode material (Li 1.02 Ni 0.9 Co 0.05 Mn 0.05 O2, D 50 (It is 3.5 μm), negative thermal expansion material (ZrW2O8, D 50 (F is 0.4 μm), a conductive agent (acetylene black), a binder (PVDF), and a solvent (NMP) are mixed (temperature 25°C, rotation speed 1000 rpm, time 40 min) to obtain a positive electrode slurry with a solid content of 40 wt%, The mass ratio of the positive electrode material, negative thermal expansion material, conductive agent, and binder is 91.2:3.8:3:2. (2) The positive electrode slurry is applied to the surface of the positive electrode current collector aluminum foil to form a positive electrode slurry coating layer on the surface of the aluminum foil. After drying at 135°C, a roll press (pressure 15T) is performed using a roll press device to form a positive electrode active material layer on the surface of the aluminum foil, thereby obtaining a positive electrode piece S1.

[0078] The XRD spectrum of the positive electrode piece S1 is shown in Figure 1. As can be seen from Figure 1, the positive electrode material has 2θ = 18 ° and 2θ=37 ° The negative thermal expansion material has a (003) characteristic peak and a (101) characteristic peak at the position, and the main peak (F) of the negative thermal expansion material is located between the (003) characteristic peak and the (101) characteristic peak of the positive electrode material.

[0079] Examples 2-6 The difference, following the method of Example 1, is: In step (1), based on the data in Table 1, the mass ratios of the above positive electrode material, negative thermal expansion material, conductive agent, and binder are adjusted respectively, with other conditions being the same, and positive electrode sheets S2 - S6 are obtained respectively.

[0080] Examples 7 - 11 According to the method of Example 1, the differences are that in step (1), based on the data in Table 1, the type of the above positive electrode material and D 50 , the type of the negative thermal expansion material and D 50 (F), and the mass ratios of the above positive electrode material, negative thermal expansion material, conductive agent, and binder are adjusted respectively, in step (2), based on the data in Table 1, the pressure of the roll press is adjusted respectively, with other conditions being the same, and positive electrode sheets S7 - S11 are obtained respectively.

[0081] Example 12 According to the method of Example 1, the differences are that in step (1), based on the data in Table 1, the type of the above positive electrode material and D 50 , and the mass ratios of the above positive electrode material, negative thermal expansion material, conductive agent, and binder are adjusted, in step (2), based on the data in Table 1, the pressure of the roll press is adjusted, with other conditions being the same, and positive electrode sheet S12 is obtained.

[0082] Example 13 According to the method of Example 12, the differences are that in step (1), based on the data in Table 1, the D 50 (F) of the above negative thermal expansion material is adjusted, with other conditions being the same, and positive electrode sheet S13 is obtained.

[0083] Example 14 According to the method of Example 1, the differences are that in step (1), based on the data in Table 1, the type of the above positive electrode material is adjusted, Under similar conditions, the positive electrode piece S14 is obtained.

[0084] Example 15 The difference, according to the method of Example 14, is that Step (2) involves adjusting the pressure of the roll press based on the data in Table 1. Under similar conditions, the positive electrode piece S15 is obtained.

[0085] Example 16 The difference, according to the method of Example 14, is that Step (1) involves adjusting the type of negative thermal expansion material based on the data in Table 1. Under similar conditions, a positive electrode piece S16 is obtained in each case.

[0086] Example 17 The difference, according to the method of Example 17, is that This involves adjusting the type of positive electrode material based on the data in Table 1. Under similar conditions, the positive electrode piece S17 is obtained.

[0087] Comparative Example 1 The difference, following the method of Example 1, is: Step (1) involves adjusting the mass ratio of the positive electrode material, negative thermal expansion material, conductive agent, and binder based on the data in Table 1. Under similar conditions, the positive electrode piece DS1 is obtained.

[0088] Comparative Example 2 The difference, following the method of Example 1, is: Step (1) is based on the data in Table 1. 50 (F)>0.42D 50 To that end, D of the negative thermal expansion material 50 This involves adjusting (F), Under similar conditions, the positive electrode piece DS2 is obtained.

[0089] Comparative Example 3 The difference, following the method of Example 1, is: Step (2) involves adjusting the pressure of the roll press to 4T based on the data in Table 1 and replacing it. Under similar conditions, the positive electrode piece DS3 is obtained.

[0090] [Table 1-1]

[0091] [Table 1-2]

[0092] [Table 1-3]

[0093] Test example The positive electrode pieces manufactured in the above examples and comparative examples were evaluated and measured using a 2025 type button cell battery, and the assembly process was specifically as follows. Battery Assembly: The positive electrode, separator, negative electrode, and electrolyte were assembled into 2025-type button-cell batteries in a gas glove box filled with argon gas containing less than 5 ppm of both water and oxygen, and left to stand for 6 hours. A 16 mm diameter, 0.5 mm thick metallic lithium piece was used for the negative electrode, a 25 μm thick porous polyethylene membrane (Celgard 2325) was used for the separator, and the electrolyte was an equal mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) containing 1 mol / L of LiPF6.

[0094] Electrochemical performance tests were conducted on the 2025 type button batteries assembled in the above examples and comparative examples using the Shenzhen Xinwell battery test system, and the test results are shown in Tables 1 and 2. (1) Initial impedance test method: A button cell battery was charged to a constant capacity at 25°C and 0.1C (when the nickel content of the positive electrode material in the positive electrode piece is ≥80 mol%, the charge / discharge current density at 0.1C during the test is 20 mA / g, and when the nickel content of the positive electrode material in the positive electrode piece is <80 mol%, the charge / discharge current density at 0.1C during the test is 18 mA / g), left for 10 minutes, then charged to 4.35V with a constant current and voltage of 0.33C, left for 10 minutes, then discharged to 3.0V with a constant current of 0.33C, left for 10 minutes, and the charged battery was again charged and discharged to 50% DOD, left for 3 minutes, then discharged for 18s with a constant current of 1C, and the voltage and current before and after the discharge process were recorded and the impedance value was calculated. (2) 0.1C initial charge-discharge ratio capacity and initial charge-discharge efficiency test: At 25°C, a button cell battery was subjected to a charge-discharge test at 0.1C. If the nickel content of the positive electrode material in the positive electrode piece was ≥80 mol%, the charge-discharge current density at 0.1C during the test was 20 mA / g, and the charge-discharge voltage range was controlled to 3-4.3V. If the nickel content of the positive electrode material in the positive electrode piece was <80 mol%, the charge-discharge current density at 0.1C during the test was 18 mA / g, and the charge-discharge voltage range was controlled to 3.0-4.4V. (3) Cycle performance test: The charge / discharge voltage range is controlled to 3-4.3V, and the button cell battery is charged and discharged twice at 0.1C at a constant temperature of 45°C, and then charged and discharged 80 times at 1C. (4) Magnification performance test: The charge / discharge voltage range is controlled to 3.0-4.3V, and at 25°C, the button cell is charged and discharged twice at 0.1C, then charged and discharged once each at 0.2C, 0.33C, 0.5C, 1C, and 2C. The magnification performance of the multi-component cathode material is evaluated by the ratio of the initial discharge ratio capacity at 0.1C to the discharge ratio capacity at 2C. The initial discharge ratio capacity at 0.1C is the discharge ratio capacity of the button cell after the first cycle, and the discharge ratio capacity at 2C is the discharge ratio capacity of the button cell after the seventh cycle.

[0095] [Table 2]

[0096] As can be seen from the data in Table 1-2, Example 1-17 differs from Comparative Example 1-3 in the type of positive electrode material and D 50 , Types of negative thermal expansion materials and D 50 (F) The mass ratio of the positive electrode material to the negative thermal expansion material, the roll press pressure, the peak intensity ratio R(F) of the obtained positive electrode piece, the surface density ρ, and the characteristic value J are adjusted and controlled within a preferred range to ensure that the layered active material in the positive electrode piece exhibits good electrical performance, with good lithium ion escape and embedding ability and good capacity multiplication performance. At the same time, by adding the negative thermal expansion material to the electrode piece, the volume expansion of the electrode piece during the charge and discharge process can be neutralized, thereby weakening the volume expansion of the electrode piece during the charge and discharge process and avoiding the adverse effect of the volume expansion of the electrode piece on battery performance. As a result, the battery has good cycle performance, and ultimately the battery can have overall performance with high capacity, good multiplication, and good cycle life.

[0097] Comparative Example 1 showed that the amount of negative thermal expansion material used was small, the resulting positive electrode piece R(F) value was very small, the surface density ρ of the positive electrode piece was large, the corresponding electrode piece characteristic value J was small, the proportion of negative thermal expansion material that can exert a negative thermal expansion effect on the positive electrode piece was small, the negative thermal expansion material did not adequately counteract the volume change of the positive electrode material during the charge and discharge process, and a large surface density ρ increased the internal resistance of the battery, decreased the discharge ratio capacity, affected the multiplier performance and cycle life, and the volume expansion and thermal effect of the positive electrode particles during the charge and discharge process was high, resulting in a deterioration of the cycle performance of the electrode piece.

[0098] The negative thermal expansion material D used in Comparative Example 2 50 (F) is too large, the negative thermal expansion material does not match the positive electrode material, the pole segment R(F) value is small, and the pole segment surface density ρ is appropriate, but the corresponding pole segment characteristic value J is small, and although a certain amount of negative thermal expansion material is added during the pole segment manufacturing process, the negative thermal expansion material does not match the positive electrode material, so after the pole segment is manufactured, the two cannot work together, the pole segment capacity is reduced, and at the same time the negative thermal expansion material cannot neutralize the thermal effect, which affects the magnification and cycle performance.

[0099] In Comparative Example 3, the electrode pieces obtained after processing were too thick, had too high a surface density, and their J-value deviated from the optimal range. As a result, the material exhibiting negative thermal expansion in the positive electrode material active layer could not adequately perform its neutralization action during the cycle process, leading to a deterioration in electrode piece performance.

[0100] Examples 1-13 show the electrical performance of electrode pieces fabricated using a preferred design. As can be seen, when electrode pieces are fabricated for different positive electrode materials and negative thermal expansion materials, under the premise that the required characteristic values ​​of the electrode pieces are met, the battery exhibits good magnification and cycle performance. In Example 11, however, the amount of negative thermal expansion material added was relatively high, causing the characteristic value J of the electrode piece to deviate from the preferred range, resulting in a certain degree of decrease in electrical performance.

[0101] Examples 14-15 and 17 use a preferred cathode material and apply it to the cathode piece. By using a ternary cathode material with M and M' modified elements introduced, the stability of the cathode material itself is improved. At the same time, by controlling the processing conditions, the resulting cathode piece satisfies the characteristic values ​​of the electrode piece, thereby improving cycle performance. In contrast, Example 16 uses an undesirable negative thermal expansion material, causing its characteristic value J to deviate from the preferred range, resulting in a decrease in electrode piece magnification and cycle performance.

[0102] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, several simple modifications can be made to the technical solutions of the present invention, including combining each technical feature in other appropriate ways, and these simple modifications and combinations should also be considered as part of the disclosure of the present invention and all fall within the scope of protection of the present invention.

[0103] (Cross-reference of related applications) This invention claims priority and interest in patent application number 202311735942.X, submitted to the China National Intellectual Property Administration on December 15, 2023, and its entire contents are incorporated herein by reference.

Claims

1. A positive electrode piece, wherein the positive electrode piece includes a positive electrode active material layer, and the positive electrode active material layer includes a positive electrode material, a negative thermal expansion material, a conductive agent, and a binder. The characteristic value J of the positive electrode piece satisfies 0.001 ≤ J ≤ 0.

005. Let J = R(F) / ρ, where R(F) is the peak intensity ratio of the main peak (F) of the negative thermal expansion material and the (003) characteristic peak of the positive electrode material in the XRD spectrum of the positive electrode piece, and ρ is the surface density (mg / cm³) of the positive electrode piece. ２ A positive electrode piece characterized by exhibiting the following characteristics.

2. The positive electrode piece according to claim 1, wherein the characteristic value J of the positive electrode piece satisfies 0.00125 ≤ J ≤ 0.

004.

3. The positive electrode piece according to claim 1 or 2, wherein R(F) = I(F) / I(003), where I(F) and I(003) represent the peak intensities of the main peak (F) of the negative thermal expansion material and the (003) characteristic peak of the positive electrode piece in the XRD spectrum of the positive electrode piece, respectively.

4. The positive electrode piece according to claim 3, wherein 0.005 ≤ R(F) ≤ 0.1, preferably 0.02 ≤ R(F) ≤ 0.

05.

5. The surface density of the positive electrode piece is 8 mg / cm². ２ ≤ρ ≤ 25 mg / cm ２ The following conditions must be met, preferably 10 mg / cm³ ２ ≤ρ ≤ 16 mg / cm ２ The positive electrode piece according to any one of claims 1 to 4.

6. In the XRD spectrum of the positive electrode piece, the positive electrode material is 2θ = 18 ° ±2 and 2θ = 37 ° A positive electrode piece according to any one of claims 1-5, having a (003) characteristic peak and a (101) characteristic peak at ±2 positions.

7. The positive electrode piece according to any one of claims 1-6, wherein in the XRD spectrum of the positive electrode piece, the main peak (F) of the negative thermal expansion material is located between the (003) characteristic peak and the (101) characteristic peak of the positive electrode piece.

8. The average particle size D of the negative thermal expansion material ５０ (F) is such that D ５０ (F) ≤ 0.42D ５０ is satisfied, and D ５０ is the average particle size (μm) of the positive electrode material. The positive electrode sheet according to any one of claims 1 to 7

9. The average particle size D of the aforementioned positive electrode material ５０ The positive electrode piece according to any one of claims 1 to 8, wherein the thickness is selected from 1 to 20 μm, preferably 1 to 10 μm.

10. The average particle size D of the negative thermal expansion material ５０ The positive electrode piece according to any one of claims 1 to 9, wherein (F) is selected from 0.1 to 10 μm, preferably from 0.1 to 3 μm.

11. The positive electrode piece according to any one of claims 1 to 10, wherein the positive electrode material is a lithium-containing layered compound.

12. The positive electrode material has the composition shown in formula I, Li １＋α Ni ｘ Co ｙ Mn ｚ M ｍ M′ ｎ O ２ (I) -0.5 ≤ α ≤ 0.4, 0 < x < 1, 0 ≤ y < 1, 0 ≤ z < 1, 0 ≤ m ≤ 0.1, 0 ≤ n ≤ 0.1, x + y + z + m + n = 1, and M and M' are each independently selected from at least one element among Al, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, La, Ce, Er, Mg, Sr, Ba, P, and B. Preferably, in equation I, 0 ≤ α ≤ 0.1, 0.6 ≤ x ≤ 0.9, 0.01 ≤ y ≤ 0.2, 0.01 ≤ z ≤ 0.3, and m and n are not simultaneously 0, and 0.001 ≤ m + n ≤ 0.

1. Preferably, in formula I, elements M and M' are different. More preferably, in formula I, M is selected from at least one element among Al, Y, Ti, Zr, La, Sr, and B, and M' is selected from at least one element among Nb, Mo, W, and P, the positive electrode piece according to any one of claims 1-11.

13. The negative thermal expansion material has the composition shown in formula II, 1 ａ Q' ｂ O ｃ (II) The positive electrode piece according to any one of claims 1 to 12, wherein a, b, and c are each independently selected from natural numbers between 1 and 15, and Q and Q' are each independently selected from at least one element among Zr, W, Hf, Al, Sc, In, Y, Mo, V, Sn, Ti, and P, and the elements Q and Q' are different.

14. The negative thermal expansion material is selected from at least one of tungstate, molybdate, vanadate, and pyrophosphate. Preferably, the negative thermal expansion material is ZrW ２ O ８ , HfW ２ O ８ Al ２ W ３ O １２ , Sc ２ W ３ O １２ In ２ W ３ O １２ , Y ２ W ３ O １２ , ZrMo ２ O ８ , HfMo ２ O ８ ZrV ２ O ７ , HfV ２ O ７ SnV ２ O ７ TiV ２ O ７ , ZrP ２ O ７ HfP ２ O ７ SnP ２ O ７ and TiP ２ O ７ A positive electrode piece according to any one of claims 1-13, selected from at least one of the above.

15. The positive electrode piece according to any one of claims 1 to 14, wherein the thickness of the positive electrode active material layer is 20-85 μm, preferably 25-60 μm.

16. A positive electrode piece according to any one of claims 1 to 15, wherein, based on the total weight of the positive electrode active material layer, the content of the positive electrode material is 85.5-94.52 wt%, preferably 90-94.5 wt%, and the content of the negative thermal expansion material is 0.48-9.5 wt%, preferably 0.5-5 wt%.

17. The positive electrode piece according to any one of claims 1 to 16, wherein, based on the total weight of the positive electrode active material layer, the content of the conductive agent is 2-4 wt%, preferably 2.5-3.5 wt%, and the content of the binder is 1-3 wt%, preferably 1.5-2.5 wt%.

18. The positive electrode piece according to any one of claims 1-17, wherein the initial discharge impedance value R(d) of the positive electrode piece is ≤ 20 Ω, preferably R(d) ≤ 18 Ω.

19. A method for manufacturing a positive electrode piece, (1) A step of mixing positive electrode material, negative thermal expansion material, conductive agent, binder and solvent to obtain a positive electrode slurry, (2) The process includes the steps of applying the positive electrode slurry to the surface of the positive electrode current collector, drying it, and then rolling it to place a positive electrode active material layer on the surface of the positive electrode current collector to obtain a positive electrode piece, The positive electrode material is a lithium-containing layered compound, and the negative thermal expansion material has the composition shown in formula II. 1 ａ Q' ｂ O ｃ (II) A method for manufacturing a positive electrode piece, characterized in that a, b, and c are each independently selected from natural numbers between 1 and 15, Q and Q' are each independently selected from at least one element among Zr, W, Hf, Al, Sc, In, Y, Mo, V, Sn, Ti, and P, and Q and Q' are different elements.

20. In step (1), The manufacturing method according to claim 19, wherein the mass ratio of the positive electrode material, negative thermal expansion material, conductive agent, and binder is (85.5-94.52):(0.48-9.5):(2-4):(1-3), and preferably (90-94.5):(0.5-5):(2.5-3.5):(1.5-2.5).

21. The positive electrode material has the composition shown in formula I, Li １＋α Ni ｘ Co ｙ Mn ｚ M ｍ M′ ｎ O ２ (I) -0.5 ≤ α ≤ 0.4, 0 < x < 1, 0 ≤ y < 1, 0 ≤ z < 1, 0 ≤ m ≤ 0.1, 0 ≤ n ≤ 0.1, x + y + z + m + n = 1, and M and M' are each independently selected from at least one element among Al, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, La, Ce, Er, Mg, Sr, Ba, P, and B. Preferably, in formula I, 0 ≤ α ≤ 0.1, 0.6 ≤ x ≤ 0.9, 0.01 ≤ y ≤ 0.2, 0.01 ≤ z ≤ 0.3, m and n are not both 0, and 0.001 ≤ m + n ≤ 0.1, preferably, in formula I, M and M' are different elements, and more preferably, in formula I, M is selected from at least one element among Al, Y, Ti, Zr, La, Sr and B, and M' is selected from at least one element among Nb, Mo, W and P, the manufacturing method according to claim 19 or 20.

22. The average particle size D of the negative thermal expansion material ５０ (F) is D ５０ (F) ≤ 0.42D ５０ Satisfying D ５０ The manufacturing method according to any one of claims 19-21, wherein is the average particle size (μm) of the positive electrode material.

23. The average particle size D of the aforementioned positive electrode material ５０ The manufacturing method according to any one of claims 19-22, wherein the particle is selected from 1-20 μm, preferably 1-10 μm.

24. The average particle size D of the negative thermal expansion material ５０ The manufacturing method according to any one of claims 19-23, wherein (F) is selected from 0.1-10 μm, preferably from 0.1-3 μm.

25. The manufacturing method according to any one of claims 19-24, wherein the mixing conditions include a temperature of 15-40°C, preferably 20-30°C, a time of 10-120 min, preferably 20-60 min, and a rotational speed of 500-2000 rpm, preferably 800-1500 rpm.

26. The manufacturing method according to any one of claims 19 to 25, wherein in step (2), the drying temperature is 80-150°C, preferably 120-150°C.

27. The manufacturing method according to any one of claims 19-26, wherein the pressure P of the roll press is selected from 5T < P < 20T.

28. The manufacturing method according to any one of claims 19-27, wherein in step (1), the mass ratio of the positive electrode material, negative thermal expansion material, conductive agent, and binder is (90-94.5):(0.5-5):(2.5-3.5):(1.5-2.5).

29. A lithium-ion battery characterized by comprising a positive electrode piece according to any one of claims 1 to 18, or a positive electrode piece manufactured by the manufacturing method according to any one of claims 19 to 28.

Images