Lithium-rich manganese-based positive electrode material and preparation method therefor, positive electrode sheet, battery and electronic equipment

Abstract

A lithium-rich manganese-based positive electrode material and a preparation method therefor, a positive electrode sheet, a battery and electronic equipment. The lithium-rich manganese-based positive electrode material comprises first particles and second particles, wherein the first particles satisfy chemical formula (1), and the second particles satisfy chemical formula (2): aLi2O·bLi2MnO3·cLiXαX'βO2 (1)，and xLi2O·yLi2MnO3·zLiYγY'δO2 (2); in formula (1), -0.1≤a≤0, 0<b≤0.4, b+a>0, and b+c-a=1; in formula (2), 0≤x≤0.1, 0.4<y<1, and x+y+z=1; in formula (1) and formula (2), X and Y each independently comprise at least one of Ni and Co, X' and Y' each independently comprise at least one of Mn, Al, Na, Mg, B, Ti, Y, Zr, Nb, Sn, La, Ce, Ta and W, 0≤β≤0.5≤α≤1, 0≤δ≤0.5≤γ≤1, α+β=1, and γ+δ=1; the lithium-oxygen ratio RA of the first particles is equal to (2a+2b+c) / (a+3b+2c), and satisfies: 1 / 2<RA<7 / 12; and the lithium-oxygen ratio RB of the second particles is equal to (2x+2y+z) / (x+3y+2z), and satisfies: RA<RB<5 / 7. The lithium-rich manganese-based positive electrode material has relatively high long-cycle stability.

Description

Lithium-rich manganese-based positive electrode material and preparation method thereof, positive electrode sheet, battery and electronic device

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 25, 2023, with application number 202311794377.4 and invention name “Lithium-rich manganese-based positive electrode material and preparation method thereof, positive electrode sheet, battery and electronic device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of electrochemical technology, and in particular to a lithium-rich manganese-based positive electrode material and a preparation method thereof, a positive electrode sheet, a battery, and an electronic device. Background Art

[0003] Secondary batteries, represented by lithium-ion batteries, boast advantages such as high operating voltage, high energy density, excellent safety, and no memory effect. They have achieved tremendous success in portable electronic devices, electric vehicles, and hybrid electric vehicles. Among conventional secondary batteries, lithium-rich manganese-based laminated cathode materials have attracted widespread attention due to their high specific capacity exceeding 250 mAh / g, high operating voltage of 4.8 V, and low cost. However, current lithium-rich manganese-based laminated cathode materials suffer from severe capacity and voltage decay during long-term cycling, resulting in poor long-term cycling stability.

[0004] Summary of the Invention

[0005] Based on this, the present application provides a lithium-rich manganese-based positive electrode material with high long-cycle stability and its preparation method, positive electrode plate, battery and electronic equipment.

[0006] The first aspect of the present application provides a lithium-rich manganese-based positive electrode material, comprising a first particle and a second particle, wherein the first particle satisfies the chemical formula (1) and the second particle satisfies the chemical formula (2): aLi2O·bLi2MnO3·cLiX α X' β O2 (1), xLi2O·yLi2MnO3·zLiY γ Y' δ O2 (2),

[0007] In formula (1), -0.1≤a≤0, 0<b≤0.4,b+a> 0, b+ca=1;

[0008] In formula (2), 0≤x≤0.1, 0.4≤y<1, x+y+z=1;

[0009] In formula (1) and formula (2), X and Y each independently include at least one of Ni and Co, X' and Y' each independently include at least one of Mn, Al, Na, Mg, B, Ti, Y, Zr, Nb, Sn, La, Ce, Ta, and W, and 0≤β≤0.5≤α≤1, 0≤δ≤0.5≤γ≤1, α+β=1, γ+δ=1;

[0010] The lithium-oxygen ratio R of the first particle A =(2a+2b+c) / (a+3b+2c), and satisfies: 1 / 2 <R A <7 / 12;

[0011] The lithium-oxygen ratio R of the second particle B =(2x+2y+z) / (x+3y+2z), and satisfies: R A <R B <5 / 7.

[0012] In some embodiments of the present application, in the lithium-rich manganese-based positive electrode material, the mass percentages of the first particles and the second particles are w A and w B The molar masses of the first particle and the second particle are M A and M B The lithium-oxygen ratio of the lithium-rich manganese-based positive electrode material is R=(R A w A M B +R B w B M A ) / (w A M B +w B M A ), and 0.5 <R≤0.6。

[0013] In some embodiments of the present application, the second particle includes a core and a shell covering at least a portion of the surface of the core, the core satisfies the chemical formula (2), and the shell comprises a conductive carbon material;

[0014] Optionally, the specific surface area of ​​the core is 0.1m 2 / g~3m 2 / g;

[0015] Optionally, the mass percentage of the conductive carbon material in the second particles is 0.1% to 5%;

[0016] Optionally, the conductive carbon material includes one or more of acetylene black, Ketjen black, conductive graphite, carbon fiber, graphene, multi-walled carbon nanotubes and single-walled carbon nanotubes.

[0017] In some embodiments of the present application, the first particles and the second particles each independently comprise a primary particle;

[0018] Optionally, the average particle size D' of the primary particles of the first particles is A The average particle size D' of the primary particles of the second particles B Satisfaction between: D' A <D’ B <2μm;

[0019] Optionally, the volume median particle size Dv501 of the first particles is 3 μm to 16 μm, and the volume median particle size Dv502 of the second particles is 2 μm to 7 μm;

[0020] Optionally, the specific surface area of ​​the first particles is 1m 2 / g~5m 2 / g, the specific surface area of ​​the second particles is 0.1m 2 / g~20m 2 / g.

[0021] In some embodiments of the present application, at least one of the following conditions is met:

[0022] (1) The volume median particle size Dv50 of the lithium-rich manganese-based positive electrode material is 3 μm to 16 μm;

[0023] (2) The specific surface area of ​​the lithium-rich manganese-based positive electrode material is 1m 2 / g~5m 2 / g;

[0024] (3) The water content in the lithium-rich manganese-based positive electrode material is less than 500 ppm;

[0025] (4) The LiOH content in the lithium-rich manganese-based positive electrode material is less than 3000 ppm;

[0026] (5) The Li2CO3 content in the lithium-rich manganese-based positive electrode material is less than 3000ppm.

[0027] The second aspect of the present application provides a method for preparing a lithium-rich manganese-based positive electrode material, comprising:

[0028] The first particles are mixed with the second particles to prepare the lithium-rich manganese-based positive electrode material, wherein the first particles satisfy the chemical formula (1) and the second particles satisfy the chemical formula (2): aLi2O·bLi2MnO3·cLiX α X' β O2 (1), xLi2O·yLi2MnO3·zLiY γ Y' δO2 (2),

[0029] In formula (1), -0.1≤a≤0, 0<b≤0.4,b+a> 0, b+ca=1;

[0030] In formula (2), 0≤x≤0.1, 0.4 <y<1,x+y+z=1;

[0031] In formula (1) and formula (2), X and Y each independently include at least one of Ni and Co, X' and Y' each independently include at least one of Mn, Al, Na, Mg, B, Ti, Y, Zr, Nb, Sn, La, Ce, Ta, and W, and 0≤β≤0.5≤α≤1, 0≤δ≤0.5≤γ≤1, α+β=1, γ+δ=1;

[0032] The lithium-oxygen ratio R of the first particle A =(2a+2b+c) / (a+3b+2c), and satisfies: 1 / 2 <R A <7 / 12;

[0033] The lithium-oxygen ratio R of the second particle B =(2x+2y+z) / (x+3y+2z), and satisfies: R A <R B <5 / 7.

[0034] In some embodiments of the present application, the mass percentage of the first particles is w A , and 60% ≤ w A <100%, the mass percentage of the second particles is w B , and 0 <w B ≤40%.

[0035] In some embodiments of the present application, the method for preparing the first particles comprises:

[0036] Performing a first sintering treatment on a first mixture containing a first precursor and a first lithium source to prepare the first particles, wherein the first precursor contains manganese element, X element and X' element;

[0037] Optionally, the first sintering process includes:

[0038] Heating the first mixture to 300°C to 600°C at a heating rate of 1°C / min to 10°C / min, keeping the temperature for 2h to 8h, then heating the mixture to 750°C to 1000°C at a heating rate of 1°C / min to 10°C / min, and keeping the temperature for 8h to 20h;

[0039] Optionally, the first precursor includes at least one of a carbonate, a hydroxide and an oxide containing manganese, an X element and an X' element;

[0040] Optionally, the first lithium source includes one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium chloride, lithium oxide and lithium peroxide;

[0041] Optionally, the ratio of the molar number of lithium element in the first lithium source to the total molar number of metal elements in the first precursor is 1.0 to 1.45:1;

[0042] Optionally, the specific surface area of ​​the first precursor is 10m 2 / g~100m 2 / g;

[0043] Optionally, the median particle size D501 of the first precursor is 3 μm to 16 μm.

[0044] In some embodiments of the present application, the method for preparing the second particles comprises:

[0045] performing a second sintering treatment on a second mixture containing a second precursor and a second lithium source to obtain a sintered product, wherein the second precursor contains manganese element, Y element and Y' element;

[0046] performing a coating treatment on the sintered product to prepare the second particles;

[0047] Optionally, the second sintering process includes:

[0048] The second mixture is heated to 300°C to 600°C at a heating rate of 1°C / min to 10°C / min, kept at this temperature for 2h to 8h, then heated to 900°C to 1200°C at a heating rate of 1°C / min to 10°C / min, kept at this temperature for 1h to 5h, then cooled to 700°C to 900°C, and kept at this temperature for 6h to 15h;

[0049] Optionally, the second precursor includes at least one of a carbonate, a hydroxide and an oxide containing manganese, Y and Y' elements;

[0050] Optionally, the second lithium source includes one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium chloride, lithium oxide and lithium peroxide;

[0051] Optionally, the ratio of the molar number of lithium element in the second lithium source to the total molar number of metal elements in the second precursor is 1.4 to 2.25:1;

[0052] Optionally, the specific surface area of ​​the first precursor is 5m 2 / g~50m 2 / g;

[0053] Optionally, the median particle size D502 of the first precursor is 1.5 μm to 8 μm.

[0054] In some embodiments of the present application, the coating process includes:

[0055] mixing the sintered product with a conductive carbon material;

[0056] Optionally, the mass ratio of the conductive carbon material to the sintered product is (0.1-3):100;

[0057] Optionally, the conductive carbon material includes one or more of acetylene black, Ketjen black, conductive graphite, carbon fiber, graphene, multi-walled carbon nanotubes and single-walled carbon nanotubes.

[0058] The third aspect of the present application provides a positive electrode plate, comprising the lithium-rich manganese-based positive electrode material described in the first aspect of the present application or the lithium-rich manganese-based positive electrode material prepared by the method described in the second aspect of the present application.

[0059] The fourth aspect of the present application provides a battery, comprising the positive electrode sheet described in the third aspect of the present application.

[0060] The fifth aspect of the present application provides an electronic device comprising the battery described in the fourth aspect of the present application.

[0061] The electronic device of the present application includes the battery provided by the present application, and thus has at least the same advantages as the battery.

[0062] The present application provides a lithium-rich manganese-based positive electrode material. The first particles and the second particles satisfy the above conditions. It is not intended to be limited by any theory. The inventors found that by increasing the lithium-oxygen ratio of the first particle to R A The first particle is designed with a relatively low Li2O / Li2MnO3 composition, which can effectively reduce the first-cycle irreversible capacity loss of the material as a whole; the second particle is designed with a higher Li2O / Li2MnO3 composition than the first particle, and the lithium-oxygen ratio of the second particle is R B The lithium-oxygen ratio R of the first particle A Satisfying the above relationship allows the second particles to act as a capacity "sustained release agent" to continuously compensate for capacity loss during long cycles. In this way, the synergistic cooperation between the first and second particles can effectively improve the long-term cycling performance of lithium-rich manganese-based positive electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] FIG1 is a scanning electron microscope (SEM) image of the lithium-rich manganese-based cathode material of Example 1;

[0064] FIG2 is a particle size distribution (PSD) diagram of the lithium-rich manganese-based positive electrode material of Example 1. DETAILED DESCRIPTION

[0065] To facilitate understanding of the present application, the present application will be described in more detail below. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of the present application.

[0066] For simplicity, this application only explicitly discloses certain numerical ranges. However, any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and similarly, any upper limit may be combined with any other upper limit to form an unspecified range. In addition, although not explicitly stated, each point or individual value between the endpoints of a range is included in the range. Thus, each point or individual value may serve as its own lower limit or upper limit and be combined with any other point or individual value, or with other lower limits or upper limits, to form an unspecified range.

[0067] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. It should be noted that, unless otherwise stated, the term "and / or" used herein includes any and all combinations of one or more related listed items, and "above" and "below" are inclusive of the number, and the meaning of "a variety" in "one or more" is more than two.

[0068] The above disclosure of the present application is not intended to describe every disclosed embodiment or every implementation in the present application. The following description more specifically illustrates exemplary embodiments. In many places throughout the application, guidance is provided through a series of examples, which can be used in various combinations. In each example, the enumeration is intended only as a representative group and should not be construed as exhaustive.

[0069] During the research process, the inventors discovered that the high specific capacity of the lithium-rich manganese-based layered positive electrode material comes from the redox of oxygen ions during the activation of the Li2MnO3 component during the first charge, and the oxygen precipitation caused by the redox of oxygen ions also leads to a large irreversible capacity loss in the first cycle. The irreversible migration of transition metal ions during the subsequent charge and discharge process will cause the crystal structure of the material to change from layered to spinel structure, resulting in severe energy attenuation. At the same time, as the content of the Li2MnO3 component in the lithium-rich manganese-based layered positive electrode material increases, the ionic / electronic conductivity of the material decreases, resulting in a large impedance, which will further deteriorate the rate performance and cycle performance of the material.

[0070] In order to solve the aforementioned technical problems, the inventors proposed the following technical solutions of this application.

[0071] The first aspect of the present application provides a lithium-rich manganese-based positive electrode material, comprising a first particle and a second particle, wherein the first particle satisfies the chemical formula (1) and the second particle satisfies the chemical formula (2): aLi2O·bLi2MnO3·cLiX α X' β O2 (1), xLi2O·yLi2MnO3·zLiY γ Y' δ O2 (2),

[0072] In formula (1), -0.1≤a≤0, 0<b≤0.4,b+a> 0, b+ca=1;

[0073] In formula (2), 0≤x≤0.1, 0.4≤y<1, x+y+z=1;

[0074] In formula (1) and formula (2), X and Y each independently include at least one of Ni and Co, X' and Y' each independently include at least one of Mn, Al, Na, Mg, B, Ti, Y, Zr, Nb, Sn, La, Ce, Ta, and W, and 0≤β≤0.5≤α≤1, 0≤δ≤0.5≤γ≤1, α+β=1, γ+δ=1;

[0075] The lithium-oxygen ratio R of the first particle A =(2a+2b+c) / (a+3b+2c), and satisfies: 1 / 2 <R A <7 / 12;

[0076] The lithium-oxygen ratio R of the second particle B =(2x+2y+z) / (x+3y+2z), and satisfies: R A <R B <5 / 7.

[0077] It should be noted that in the above chemical formula (1), the Li2MnO3 component completes electrochemical activation in part through the reaction path of Li2MnO3→Li2O+MnO2 during the electrochemical activation process, but the reversibility of the reaction path is poor. Therefore, the component is adjusted in the form of "Li2O" defects (a takes a negative value) in the chemical formula to improve the reversibility of the electrochemical reaction of the first particle as a whole.

[0078] In some embodiments, -0.1≤a≤0. Alternatively, a may be -0.02, 0, -0.1, or any range thereof.

[0079] In some embodiments, 0 < b ≤ 0.4. Optionally, b can be 0.3, 0.35, 0.4, or within the range composed of any of the above values.

[0080] In some embodiments, 0 ≤ x ≤ 0.1. Optionally, x can be 0, 0.1, 0.05, or within the range composed of any of the above values.

[0081] In some embodiments, 0.4 ≤ y < 1. Optionally, y can be 0.4, 0.5, 0.6, 0.7, 0.95, or within the range composed of any of the above values.

[0082] The first and second particles of the lithium-rich manganese-based cathode material provided in this application that meet the above conditions are not intended to be limited by any theory. The inventors found during the research process that in the lithium-rich manganese-based material, the extraction of lithium ions is charge-compensated by the redox of oxygen ions, but the reversibility of the anion redox reaction is lower than that of traditional transition metal elements (such as Ni 2+ / 3+ / 4+ or Co 3+ / 4+ etc.). Therefore, the Li / O ratio in the lithium-rich manganese-based material has a greater impact on the specific capacity and electrochemical reversibility of this material, and when the Li / O ratio is not within a suitable range, it will show rapid energy decay. And the inventors further found that during the initial cycling process of the first and second particles of the lithium-rich manganese-based cathode material of this application, they are activated by losing lattice oxygen from the structure. Since highly reactive O-O dimers or oxygen are generated after the oxidation of lattice oxygen, the reaction products can react with the electrolyte and decompose, which will lead to irreversible capacity loss and low initial Coulomb efficiency.

[0083] Accordingly, in this application, by adjusting the lithium-oxygen ratio R A of the first particle to the above range, that is, the first particle adopts a relatively low Li2O / Li2MnO3 component design, the oxidation of lattice oxygen can be reduced, thereby effectively reducing the irreversible capacity loss of the material in the first cycle as a whole. The second particle adopts a relatively higher Li2O / Li2MnO3 component design than the first particle, and makes the lithium-oxygen ratio R B of the second particle and the lithium-oxygen ratio R A of the first particle satisfy the above relationship, which can achieve gradual activation and gradual release of lithium ions during the cycling process, so that the second particle serves as a capacity "slow release agent" to continuously compensate for the capacity loss during the long cycling process. Thus, through the synergistic cooperation between the first particle and the second particle, the long cycling performance of the lithium-rich manganese-based cathode material can be effectively improved.

[0084] In some embodiments, in the lithium-rich manganese-based cathode material, the mass percentages of the first particle and the second particle are w A and w B, the molar masses of the first particles and the second particles are M A and M B , and the lithium-oxygen ratio R of the lithium-rich manganese-based cathode material is R = (R A w A M B + R B w B M A ) / (w A M B + w B M A ), and 0.5 < R ≤ 0.6, preferably 0.55 ≤ R ≤ 0.6.

[0085] The mass percentages w A and w B of the first particles and the second particles in the lithium-rich manganese-based cathode material, and the lithium-oxygen ratio R of the lithium-rich manganese-based cathode material satisfy the above relationship, which is beneficial to further enhancing the cooperation between the first particles and the second particles and further enhancing the long-cycle stability of the lithium-rich manganese-based cathode material.

[0086] In some embodiments, the second particle includes a core and a shell covering at least a part of the surface of the core, the core satisfies the chemical formula (2), and the shell contains a conductive carbon material.

[0087] The lithium-oxygen ratio R B of the second particle is relatively higher, that is, the second particle has a relatively higher Li2O / Li2MnO3 component, which will affect the extraction of lithium ions and reduce the rate performance. Therefore, by coating a shell containing a conductive carbon material on the surface of the core of the second particle, the electron transport ability can be effectively improved, and the rate performance of the lithium-rich manganese-based cathode material can be improved.

[0088] In some embodiments, the specific surface area of the core is 0.1 m 2 / g to 3 m 2 / g. For example, the specific surface area can be 0.1 m 2 / g, 0.5 m 2 / g, 0.8 m 2 / g, 1 m 2 / g, 1.5 m 2 / g, 2 m 2 / g, 2.5 m 2 / g, 3 m 2 / g or within the range composed of any of the above values.

[0089] The specific surface area of ​​the inner core is within the above range, which can control the reactivity of the second particles, enhance the effect of the capacity "sustained release agent" during long cycles, and reduce the side reactions at the interface between the second particles with a high lithium-oxygen ratio (Li / O) and the electrolyte, thereby inhibiting oxygen release.

[0090] In some embodiments, the mass percentage of the conductive carbon material in the second particles is 0.1% to 5%. For example, the mass percentage can be 0.1%, 0.5%, 0.7%, 1%, 2%, 3%, 4%, 5%, or any range thereof.

[0091] The mass percentage of the conductive carbon material in the second particles is within the above range, which is beneficial to further improve the electron transport capacity of the second particles and further improve the rate performance of the lithium-rich manganese-based positive electrode material.

[0092] In some embodiments, the conductive carbon material includes, but is not limited to, one or more of acetylene black, Ketjen black, conductive graphite, carbon fiber, graphene, multi-walled carbon nanotubes, and single-walled carbon nanotubes.

[0093] In some embodiments, the first particle and the second particle each comprise a primary particle.

[0094] It should be noted that the “primary particles” mentioned in this application refer to particles that have not agglomerated during the formation process and whose particle size is close to that of crystal grains.

[0095] In some embodiments, the average particle size D' of the primary particles of the first particles is A The average particle size D' of the primary particles of the second particles B Satisfaction between: D' A <D’ B <2μm.

[0096] In the present application, the particle size of the primary particles can be obtained by measuring the size using a scanning electron microscope (SEM).

[0097] D' A With D' B The above relationship is satisfied, and a suitable combination of particle sizes between the first particles and the second particles can be achieved, thereby further improving the long-cycle performance of the material.

[0098] In some embodiments, the volume median particle size Dv501 of the first particles is 3 μm to 16 μm, and the volume median particle size Dv502 of the second particles is 2 μm to 7 μm.

[0099] In some embodiments, the specific surface area of ​​the first particles is 1 m 2 / g~5m 2 / g, the specific surface area of ​​the second particles is 0.1m 2 / g~20m 2 / g.

[0100] The volume median particle size and specific surface area distribution of the first particles and the second particles are within the above ranges. At the same time, combined with the aforementioned lithium-oxygen ratio design of the first particles and the second particles, the capacity and long-cycle stability of the material can be further effectively improved.

[0101] In this application, the core of the second particle has a larger primary particle size and a smaller specific surface area than the first particle, resulting in lower electrochemical activity. The relatively higher Li2O / Li2MnO3 composition of the second particle, combined with the morphological characteristics of the second particle, can achieve gradual activation during cycling and release lithium ions, reducing active lithium loss in the battery system.

[0102] In some embodiments, the volume median particle size Dv50 of the lithium-rich manganese-based positive electrode material is 3 μm to 16 μm.

[0103] In some embodiments, the specific surface area of ​​the lithium-rich manganese-based positive electrode material is 1 m 2 / g~5m 2 / g.

[0104] In some embodiments, the water content in the lithium-rich manganese-based positive electrode material is less than 500 ppm.

[0105] Controlling the water content in lithium-rich manganese-based positive electrode materials helps avoid side reactions between the electrolyte and the electrode, reducing electrolyte decomposition and HF generation.

[0106] In some embodiments, the LiOH content in the lithium-rich manganese-based positive electrode material is less than 3000 ppm.

[0107] In some embodiments, the Li2CO3 content in the lithium-rich manganese-based positive electrode material is less than 3000 ppm.

[0108] Controlling the content of LiOH and Li2CO3 in lithium-rich manganese-based positive electrode materials can improve the processability of electrode slurry and reduce gas production in the battery.

[0109] The second aspect of the present application provides a method for preparing the lithium-rich manganese-based positive electrode material according to the first aspect of the present application, which may include the following steps:

[0110] S1. Mixing first particles with second particles to prepare the lithium-rich manganese-based positive electrode material, wherein the first particles satisfy chemical formula (1) and the second particles satisfy chemical formula (2): aLi2O·bLi2MnO3·cLiX α X' βO2 (1), xLi2O·yLi2MnO3·zLiY γ Y' δ O2 (2),

[0111] In formula (1), -0.1≤a≤0, 0<b≤0.4,b+a> 0, b+ca=1;

[0112] In formula (2), 0≤x≤0.1, 0.4 <y<1,x+y+z=1;

[0113] In formula (1) and formula (2), X and Y each independently include at least one of Ni and Co, X' and Y' each independently include at least one of Mn, Al, Na, Mg, B, Ti, Y, Zr, Nb, Sn, La, Ce, Ta, and W, and 0≤β≤0.5≤α≤1, 0≤δ≤0.5≤γ≤1, α+β=1, γ+δ=1;

[0114] The lithium-oxygen ratio R of the first particle A =(2a+2b+c) / (a+3b+2c), and satisfies: 1 / 2 <R A <7 / 12;

[0115] The lithium-oxygen ratio R of the second particle B =(2x+2y+z) / (x+3y+2z), and satisfies: R A <R B <5 / 7.

[0116] In some embodiments, the mass percentage of the first particles is w A , 60%≤w A <100%; the mass percentage of the second particle is w B , 0 <w B ≤40%.

[0117] The preparation method provided in the present application is to mix the first particles and the second particles that meet the above conditions and optimize the mixing ratio of the two particles, that is, to control the mass percentage ratio of the two particles within an appropriate range, so as to effectively exert the synergistic effect between the two particles and achieve an effective improvement in the long-cycle performance of the lithium-rich manganese-based positive electrode material.

[0118] In some embodiments, the method for preparing the first particles comprises:

[0119] S10, performing a first sintering treatment on a first mixture containing a first precursor and a first lithium source to prepare the first particles, wherein the first precursor contains manganese element, X element and X' element.

[0120] In some embodiments, the first sintering process may include:

[0121] The first mixture is heated to 300°C to 600°C at a heating rate of 1°C / min to 10°C / min, kept warm for 2h to 8h, then heated to 750°C to 1000°C at a heating rate of 1°C / min to 10°C / min, and kept warm for 8h to 20h.

[0122] During the first sintering process, low temperature is used first, followed by high temperature sintering, which allows the particles to grow first. This is when the first lithium source melts and penetrates into the first precursor particles, undergoing a preliminary reaction and growing into small primary particles. This is followed by full fusion, where the first lithium source decomposes to generate Li2O, which further reacts with the small primary particles, fusing them into large particles. This results in a complete and structurally stable crystal structure for the prepared lithium-rich manganese-based cathode material.

[0123] In some embodiments, the first precursor includes at least one of a carbonate, a hydroxide, and an oxide containing manganese, an X element, and an X′ element.

[0124] In some embodiments, the first lithium source includes, but is not limited to, one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium chloride, lithium oxide, and lithium peroxide.

[0125] In some embodiments, the ratio of the molar number of lithium element in the first lithium source to the total molar number of metal elements in the first precursor is 1.0 to 1.45:1.

[0126] In some embodiments, the specific surface area of ​​the first precursor is 10m 2 / g~100m 2 / g.

[0127] In some embodiments, the median particle size D501 of the first precursor is 3 μm to 16 μm.

[0128] In some embodiments, the method for preparing the second particles comprises:

[0129] S20, performing a second sintering treatment on a second mixture containing a second precursor and a second lithium source to obtain a sintered product, wherein the second precursor contains manganese element, Y element and Y' element;

[0130] S30, coating the sintered product to prepare the second particles.

[0131] In some embodiments, the second sintering process may include:

[0132] The second mixture is heated to 300°C to 600°C at a heating rate of 1°C / min to 10°C / min, kept warm for 2h to 8h, then heated to 900°C to 1200°C at a heating rate of 1°C / min to 10°C / min, kept warm for 1h to 5h, then cooled to 700°C to 900°C, and kept warm for 6h to 15h.

[0133] During the second sintering process, the process is first performed at a low temperature, then at a high temperature, and finally at a low temperature again. This allows the particles to grow first, that is, the second lithium source melts and penetrates into the interior of the second precursor particles, undergoing a preliminary reaction and growing into small primary particles. This is then fully fused, that is, the second lithium source decomposes to generate Li2O, which further reacts with the small primary particles to fuse them into large particles. Finally, the elements are homogenized at a low temperature, thereby making the crystals of the prepared lithium-rich manganese-based cathode material tend to be complete and the structure stable.

[0134] In some embodiments, the second precursor includes at least one of a carbonate, a hydroxide, and an oxide containing a manganese element, a Y element, and a Y′ element.

[0135] In some embodiments, the second lithium source includes, but is not limited to, one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium chloride, lithium oxide, and lithium peroxide.

[0136] In some embodiments, the ratio of the molar number of lithium element in the second lithium source to the total molar number of metal elements in the second precursor is 1.4 to 2.25:1.

[0137] In some embodiments, the specific surface area of ​​the second precursor is 5m 2 / g~50m 2 / g.

[0138] In some embodiments, the median particle size D502 of the second precursor is 1.5 μm to 8 μm.

[0139] It should be noted that the present application provides a lithium-rich manganese-based positive electrode material in which the lithium-oxygen ratio of the first particle and the second particle is R A and R B The acquisition can be achieved by designing the components of the first precursor and the second precursor, and regulating the ratio of the total molar number of the lithium element in the lithium source to the total molar number of the metal element in the precursor.

[0140] In some embodiments, the coating process may include: mixing the sintered product with a conductive carbon material.

[0141] In some embodiments, the mass ratio of the conductive carbon material to the sintered product is (0.1-3):100.

[0142] In some embodiments, the conductive carbon material includes one or more of acetylene black, Ketjen black, conductive graphite, carbon fiber, graphene, multi-walled carbon nanotubes, and single-walled carbon nanotubes.

[0143] In some embodiments, the mixing method of mixing the sintered product with the conductive carbon material includes at least one of mechanical mixing and liquid phase mixing.

[0144] In some embodiments, after the sintered product is mixed with the conductive carbon material, a post-processing step is further included: the mixed mixture is subjected to at least one of stirring, drying and screening.

[0145] As a non-limiting example, liquid phase mixing may include: adding polyvinyl pyrrolidone (PVP) to ethylene glycol to fully dissolve it, preparing an ethylene glycol solution of PVP, and making the mass proportion of PVP in the solution 0.1wt.% to 5wt.%, then adding the conductive carbon material, stirring and dispersing for 30min to 240min. After that, the sintered product is added and continued to be stirred and dispersed for 5min to 60min to prepare a mixed solution, and making the mass proportion of the sintered product relative to the ethylene glycol be 20wt.% to 60wt.%, and then vacuum filtering to obtain a filter cake material, washing the filter cake material with anhydrous ethanol solution 2 to 5 times, and then vacuum drying at a temperature of 80°C to 300°C, and sieving to obtain second particles.

[0146] The third aspect of the present application provides a positive electrode plate, comprising the lithium-rich manganese-based positive electrode material described in the first aspect of the present application or the lithium-rich manganese-based positive electrode material prepared by the method described in the second aspect of the present application.

[0147] The fourth aspect of the present application provides a battery, comprising the positive electrode sheet described in the third aspect of the present application.

[0148] In some embodiments, the battery further comprises a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, lithium ions are intercalated and released between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0149] The fifth aspect of the present application provides an electronic device comprising the battery described in the fourth aspect of the present application.

[0150] In some embodiments, the type of electronic device is not particularly limited and can be any electronic device known in the art. For example, the electronic device can include, but is not limited to, power tools, electric vehicles, laptop computers, pen-based computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, and the like.

[0151] Example

[0152] The following are specific examples, which describe the present disclosure in more detail. These examples are intended for illustrative purposes only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing. The instruments used in the examples are also commercially available.

[0153] Example 1

[0154] (1) Preparation of first particles:

[0155] S1: 1000g of Ni 0.35 Mn 0.65 (OH)2 precursor (specific surface area 32.0m 2 / g, D50=10.0μm), 524.75g of lithium carbonate, 7.00g of Co(OH)2, 1.92g of Al2O3, and 3.01g of TiO2 were mixed uniformly in a high-speed mixer, and the molar ratio of Li to the total of Ni / Co / Mn metal ions was 1.28:1 to obtain a mixture A.

[0156] S2: Mixture A was calcined in air in stages, wherein the first stage was calcined at 550°C for 6 h with a heating rate of 3°C / min; the second stage was calcined at 850°C for 16 h with a heating rate of 3°C / min to obtain calcined product S. A .

[0157] S3: The calcined product S A The first particles M were obtained by mechanical grinding and 325 mesh screening. A , the molecular formula is -0.02Li2O·0.3Li2MnO3·0.68LiNi 0.49 Co 0.01 Mn 0.49 Al 0.005 Ti 0.005 O2, D50 = 9.8 μm, specific surface area is 2.82 m 2 / g.

[0158] (2) Preparation of the second granule:

[0159] S1: 1000g of Ni 0.25 Co 0.10 Mn 0.65 (OH)2 precursor (specific surface area 15.5m 2 / g, D50=3.5μm), 618.96g of lithium carbonate, 3.01g of TiO2, and 8.73g of WO3 were mixed uniformly in a high-speed mixer, and the molar ratio of Li to the total of Ni / Co / Mn metal ions was 1.51:1 to obtain a mixture B.

[0160] S2: Mixture B was calcined in air in stages, wherein the first stage was calcined at 550°C for 6 h with a heating rate of 3°C / min; the second stage was calcined at 1050°C for 2 h with a heating rate of 4°C / min; the third stage was calcined at 860°C for 10 h to obtain the calcined product S. B ; S B The sintered product P was obtained by crushing with air jet mill and sieving with 325 mesh. B , which is the core of the second particle, has the molecular formula 0.5Li2MnO3·0.5LiNi 0.49 Co 0.2 Mn 0.3 Ti 0.005 W 0.005 O2, D50 = 3.1 μm, specific surface area is 0.65 m 2 / g.

[0161] S3: Add 10g of polyvinyl pyrrolidone (PVP) to 1L of ethylene glycol and dissolve it completely. Then add 10g of conductive graphite and stir and disperse it for 60min. Then add 1000g of sintered product PVP. B After that, the stirring and dispersion was continued for 20 minutes, and then vacuum filtration was performed to obtain a filter cake. The filter cake was washed with anhydrous ethanol solution for 3 times to obtain a coated product, which was then vacuum dried at 120°C and sieved to obtain the second particle M. B .

[0162] (3) The first particles and the second particles are uniformly mixed in a mass ratio of 80:20 to obtain a lithium-rich manganese-based positive electrode material.

[0163] Example 2

[0164] (1) Preparation of first particles:

[0165] S1: 1000g of Ni 0.325 Co 0.325 Mn 0.35 (OH)2 precursor (specific surface area 11.5m 2 / g, D50=16.0μm), 312.30g of LiOH·H2O and 275.10g of lithium carbonate were mixed uniformly in a high-speed mixer, and the molar ratio of Li to the total of Ni / Co / Mn metal ions was 1.36:1 to obtain a mixture A.

[0166] S2: Mixture A was calcined in air in stages, wherein the first stage was calcined at 300°C for 8 h with a heating rate of 5°C / min; the second stage was calcined at 750°C for 20 h with a heating rate of 5°C / min to obtain calcined product S. A .

[0167] S3: The calcined product S A The first particles M were obtained by mechanical grinding and 325 mesh screening. A , the molecular formula is 0.35Li2MnO3·0.65LiNi 0.5 Co 0.5 O2, D50 = 15.58 μm, specific surface area is 1.22 m 2 / g.

[0168] (2) Preparation of the second granule:

[0169] S1: 1000g of Ni 0.30 Co 0.10 Mn 0.60 (OH)2 precursor (specific surface area 5.6m 2 / g, D50=1.5μm), 612.78g of lithium carbonate, 1.48g of Na2CO3, 1.12g of MgO, 0.98g of B2O3, and 3.42g of ZrO2 were mixed uniformly in a high-speed mixer, and the molar ratio of Li to the total Ni / Co / Mn metal ions was 1.52:1 to obtain a mixture B.

[0170] S2: Mixture B was calcined in air in stages, wherein the first stage was calcined at 600°C for 8 h with a heating rate of 3°C / min; the second stage was calcined at 1200°C for 1 h with a heating rate of 10°C / min; the third stage was calcined at 900°C for 15 h to obtain calcined product S B ; S B The sintered product P was obtained by crushing with air jet mill and sieving with 325 mesh. B , which is the core of the second particle, has the molecular formula 0.5Li2MnO3·0.5LiNi 0.59 Co 0.195 Mn 0.195 Na 0.005 Mg 0.005 B 0.005 Zr 0.005 O2, D50 = 1.65 μm, specific surface area is 0.35 m2 / g.

[0171] S3: Add 1g of polyvinyl pyrrolidone (PVP) to 1L of ethylene glycol and dissolve it completely. Then add 0.25g of graphene and stir and disperse it for 30min. Then add 250g of sintered product PVP. B After that, the stirring and dispersion were continued for 5 minutes, and then vacuum filtered to obtain a filter cake, which was washed with anhydrous ethanol solution for 3 times to obtain a coated product, which was then vacuum dried at 80°C and sieved to obtain the second particle M B .

[0172] (3) The first particles and the second particles are uniformly mixed in a mass ratio of 75:25 to obtain a lithium-rich manganese-based positive electrode material.

[0173] Example 3

[0174] (1) Preparation of first particles:

[0175] S1: 1000g of Mn 0.30 Co 0.70 (OH)2 precursor (specific surface area 36.8m 2 / g, D50=3.2μm), 215.88g of Li2O, 3.90g of Al2O3, 5.10g of Nb2O5, and 8.45g of Ta2O5 were mixed uniformly in a high-speed mixer, and the molar ratio of Li to the total of Ni / Co / Mn metal ions was 1.32:1 to obtain mixture A.

[0176] S2: Mixture A was calcined in air in stages, wherein the first stage was calcined at 600°C for 2 h with a heating rate of 10°C / min; the second stage was calcined at 1000°C for 10 h with a heating rate of 10°C / min to obtain calcined product S A .

[0177] S3: The calcined product S A The first particles M were obtained by mechanical grinding and 325 mesh screening. A , the molecular formula is 0.3Li2MnO3·0.7LiCo 0.98 Al 0.01 Nb 0.005 Ta 0.005 O2, D50 = 3.5 μm, specific surface area is 4.22 m 2 / g.

[0178] (2) Preparation of the second granule:

[0179] S1: 1000g of Ni 0.53 Co 0.02 Mn 0.45(OH)2 precursor (specific surface area 5.2m 2 / g, D50=6.5μm), 687.07g of lithium carbonate, 2.82g of Al2O3, 8.30g of SnO2, and 9.48g of CeO2 were mixed uniformly in a high-speed mixer, and the molar ratio of Li to the total of Ni / Co / Mn metal ions was 1.69:1 to obtain a mixture B.

[0180] S2: Mixture B was calcined in air in stages, wherein the first stage was calcined at 600°C for 2 h with a heating rate of 10°C / min; the second stage was calcined at 900°C for 5 h with a heating rate of 10°C / min; the third stage was calcined at 700°C for 15 h to obtain calcined product S B ; S B The sintered product P was obtained by crushing with air jet mill and sieving with 325 mesh. B , which is the core of the second particle, has a molecular formula of 0.1Li2O·0.4Li2MnO3·0.5LiNi 0.94 Co 0.04 Al 0.01 Sn 0.005 Ce 0.005 O2, D50 = 6.28 μm, specific surface area is 1.35 m 2 / g.

[0181] S3: Add 50g of polyvinyl pyrrolidone (PVP) to 1L of ethylene glycol and dissolve it completely. Then add 45g of single-walled carbon nanotubes and stir and disperse them for 240min. Then add 1500g of the sintered product P B The mixture was stirred and dispersed for 60 min, and then vacuum filtered to obtain a filter cake. The filter cake was washed with anhydrous ethanol solution for 3 times to obtain a coated product, which was then vacuum dried at 300 ° C and sieved to obtain the second particle M. B .

[0182] (3) The first particles and the second particles are mixed evenly at a mass ratio of 65:35 to obtain a lithium-rich manganese-based layered material.

[0183] Example 4

[0184] (1) Preparation of first particles:

[0185] S1: 1000g of Ni 0.18 Co 0.18 Mn 0.64 CO3 precursor (specific surface area 92.5m 2 / g, D50=10.5μm), 391.09g of lithium carbonate, and 5.75g of Nb2O5 were mixed uniformly in a high-speed mixer, and the molar ratio of Li to the total of Ni / Co / Mn metal ions was 1.23:1 to obtain a mixture A.

[0186] S2: Mixture A was calcined in air in stages, wherein the first stage was calcined at 400°C for 4 h with a heating rate of 4°C / min; the second stage was calcined at 865°C for 15 h with a heating rate of 4°C / min to obtain calcined product S. A .

[0187] S3: The calcined product S A The first particles M were obtained by mechanical grinding and 325 mesh screening. A , the molecular formula is -0.1Li2O·0.4Li2MnO3·0.5LiNi 0.33 Co 0.33 Mn 0.33 Nb 0.01 O2, D50 = 10.23 μm, specific surface area is 2.17 m 2 / g.

[0188] (2) Preparation of the second granule:

[0189] S1: 1000g of Co 0.36 Mn 0.64 (OH)2 precursor (specific surface area 15.12m 2 / g, D50=4.2μm), 813.13g of LiOH·H2O, 1.98g of Al2O3, 1.75g ​​of Y2O3, and 3.79g of La2O3 were mixed uniformly in a high-speed mixer, and the molar ratio of Li to the total of Ni / Co / Mn metal ions was 1.75:1 to obtain mixture B.

[0190] S2: Mixture B was calcined in air in stages, wherein the first stage was calcined at 450°C for 5 h with a heating rate of 3°C / min; the second stage was calcined at 900°C for 3 h with a heating rate of 5°C / min; the third stage was calcined at 900°C for 15 h to obtain calcined product S B ; S B The sintered product P was obtained by crushing with air jet mill and sieving with 325 mesh. B , which is the core of the second particle, has a molecular formula of 0.05Li2O·0.6Li2MnO3·0.35LiCo 0.98 Al 0.01 Y 0.004 La 0.006 O2, D50 = 4.07 μm, specific surface area is 0.72 m 2 / g.

[0191] S3: 20g of polyvinyl pyrrolidone (PVP) was added to 1L of ethylene glycol and fully dissolved, followed by the addition of 5g of multi-walled carbon nanotubes, which were stirred and dispersed for 180min, and the addition of 1000g of the sintered product P B The mixture was stirred and dispersed for 30 min, and then vacuum filtered to obtain a filter cake. The filter cake was washed with anhydrous ethanol solution for 3 times to obtain a coated product, which was then vacuum dried at 100 ° C and sieved to obtain the second particle M. B .

[0192] (3) The first particles and the second particles are mixed evenly at a mass ratio of 80:20 to obtain a lithium-rich manganese-based layered material.

[0193] Example 5

[0194] (1) Preparation of first particles:

[0195] S1: 1000g of Ni 0.30 Mn 0.70 CO3 precursor (specific surface area 87.5m 2 / g, D50=9.8μm), 379.32g of lithium carbonate, and 4.85g of Al2O3 were mixed uniformly in a high-speed mixer, and the molar ratio of Li to the total of Ni / Co / Mn metal ions was 1.19:1 to obtain a mixture A.

[0196] S2: Mixture A was calcined in air in stages, wherein the first stage was calcined at 600°C for 2 h with a heating rate of 5°C / min; the second stage was calcined at 900°C for 10 h with a heating rate of 10°C / min to obtain calcined product S A .

[0197] S3: The calcined product S A The first particles M were obtained by mechanical grinding and 325 mesh screening. A , the molecular formula is -0.1Li2O·0.35Li2MnO3·0.55LiNi 0.49 Mn 0.49 Al 0.02 O2, D50 = 9.35 μm, specific surface area is 3.01 m 2 / g.

[0198] (2) Preparation of the second granule:

[0199] S1: 1000g of MnO2 precursor (specific surface area 1.85m 2 / g, D50=2.20μm), 589.95g of Li2O2 were mixed uniformly in a high-speed mixer, and the molar ratio of Li to the total of Ni / Co / Mn metal ions was 2.23:1 to obtain mixture B.

[0200] S2: Mixture B was calcined in air in stages, wherein the first stage was calcined at 400°C for 2 h with a heating rate of 3°C / min; the second stage was calcined at 1000°C for 2 h with a heating rate of 3°C / min; the third stage was calcined at 850°C for 15 h to obtain calcined product S B ; S B The sintered product P was obtained by crushing with air jet mill and sieving with 325 mesh. B , i.e. the core of the second particle, has a molecular formula of 0.05Li2O·0.95Li2MnO3, D50=2.35μm, and a specific surface area of ​​1.42m 2 / g.

[0201] S3: 1000g of sintered product P B Mix with 10g of graphene by high-speed mixer, and then sieve the mixture to obtain the second particle M B .

[0202] (3) The first particles and the second particles are uniformly mixed in a mass ratio of 70:30 to obtain a lithium-rich manganese-based layered material.

[0203] Example 6

[0204] The preparation method is similar to that of Example 1, with the main difference being that step S3 is omitted when preparing the second particles.

[0205] Comparative Example 1

[0206] The preparation method is similar to that of Example 1, with the main difference being that the preparation step of the second particles is omitted, and the lithium-rich manganese-based layered material only includes the first particles.

[0207] Comparative Example 2

[0208] The preparation method is similar to that of Example 1, with the main difference being that the step of preparing the first particles is omitted, and the lithium-rich manganese-based layered material only includes the second particles.

[0209] Comparative Example 3

[0210] The preparation method is similar to that of Example 1, except that the amount of lithium carbonate added during the preparation of the first particle is adjusted to 389.46 g, and the first particle molecular formula is Li 0.92 Ni 0.34 Co 0.01 Mn 0.64 Al 0.005 Ti0.005 O2, D50 = 10.2 μm, specific surface area is 1.14 m 2 / g.

[0211] Comparative Example 4

[0212] The preparation method is similar to that of Example 1, except that the amount of lithium carbonate added during the preparation of the first particle is adjusted to 804.00 g, and the molecular formula of the first particle is 0.24Li2O·0.23Li2MnO3·0.53LiNi 0.49 Co 0.01 Mn 0.49 Al 0.005 Ti 0.005 O2, D50 = 9.8 μm, specific surface area is 2.59 m 2 / g.

[0213] The lithium-rich manganese-based positive electrode materials in the above examples and comparative examples were prepared into button cells or soft-pack cells, and electrochemical performance tests were performed. The preparation method is as follows:

[0214] (1) Preparation of button cells: The prepared positive electrode material powder was mixed with acetylene black, carbon nanotubes, and polyvinylidene fluoride in a mass ratio of 95:2:1:2, and an appropriate amount of N-methylpyrrolidone was added as a dispersant, and the mixture was ground into a slurry. The slurry was then evenly coated on aluminum foil and vacuum dried at 120°C for 12 h. The dried electrode was rolled with a roller mill and cut into circular electrode pieces with a diameter of 10 mm using a slicer. The loading of active material was controlled at 10 mg / cm 2 The half-cell was assembled in an argon atmosphere glove box with a water partial pressure ≤ 0.1 ppm and an oxygen partial pressure ≤ 0.1 ppm. Metallic lithium was used as the counter electrode, and a 1 mol / L LiPF6 (EC / DMC, 1:1 volume ratio) solution was used as the electrolyte. The assembled specifications were CR2032 button cells.

[0215] (2) Preparation of soft-pack batteries: The prepared positive electrode material powder is mixed with acetylene black, carbon nanotubes, and polyvinylidene fluoride in a mass ratio of 95:2:1:2, and an appropriate amount of N-methylpyrrolidone is added as a dispersant, and the mixture is ground into a slurry; the slurry is then coated on both sides of an aluminum foil and vacuum-dried at 120°C for 12 hours. The negative electrode is composed of graphite (MCMB), Super-P, CMC, and styrene-butadiene rubber in a weight ratio of 94:2:2:2. The average load density of the positive and negative electrodes is approximately 20 mg / cm 2 and 13 mg / cm 2 The battery design capacity is about 1Ah, and the positive and negative electrode capacity balance N / P ratio is set at around 1.10.

[0216] The lithium-rich manganese-based positive electrode materials prepared in Examples 1 to 6 and Comparative Examples 1 to 4 or the batteries further prepared therefrom were subjected to relevant performance tests, and the test results are shown in Tables 1 to 3 below.

[0217] Among them, the test conditions or test standards for each performance test item are as follows:

[0218] (1) Morphology characterization: Scanning electron microscopy (SEM) was used to observe the sample morphology and measure and count the primary particle size of the material.

[0219] (2) Particle size test method: The particle size of each sample was tested using a particle size analyzer. Specific test parameters were: the solvent refractive index was 1.33, and the test was repeated 3 times.

[0220] (3) Specific surface area test method: The specific surface area of ​​each sample was measured using a specific surface area tester and a nitrogen low-temperature adsorption method.

[0221] (4) LiOH and Li2CO3 content test: refer to GB / T 41704-2022.

[0222] (5) Trace water test: The water content of the material was measured by Karl-Fischer titration.

[0223] (6) ICP test: The cathode material sample is dissolved in HCl and prepared into a solution of a certain concentration. The content of metal elements in the material is tested by inductively coupled plasma atomic emission spectrometry.

[0224] (7) Test method for first-week charge / discharge specific capacity and rate performance: The button cell was charged and discharged using a constant current charge / discharge mode at 25°C, with a voltage range of 2.3 to 4.55 V and a current density of 50 mA / g, i.e., a 0.2C rate. After charging and discharging the button cell five times at a 0.2C rate, the cell was then tested using current densities of 0.2C, 1C, 2C, and 5C, to obtain the rate performance of the button cell shown in Table 3.

[0225] (8) Energy retention, voltage decay and DC internal resistance (DCR) test: The soft pack battery was charged and discharged in a cycle test at 25°C using a constant current and constant voltage charge and discharge mode with a voltage range of 2.3 to 4.5 V and a constant current charge current density of 125 mA / g. After charging to 4.5 V, constant voltage charging was performed. When the current density dropped to 5 mA / g, charging was terminated and the discharge step began.

[0226] Energy retention rate after 400 cycles = (400-cycle discharge specific energy / first-cycle discharge specific energy) × 100%.

[0227] Voltage decay after 400 cycles = 400-cycle discharge specific energy / 400-cycle discharge specific capacity - first-cycle discharge specific energy / first-cycle discharge specific capacity.

[0228] (9) The DC internal resistance test uses the HPPC method in the FreedomCAR project's "Power Battery Test Manual for Power-Assisted Hybrid Electric Vehicles" to test the DC internal resistance at 50% SOC during discharge.

[0229] DC internal resistance growth rate after 400 cycles = (400-cycle DCR - first-cycle DCR) / first-cycle DCR × 100%.

[0230] Table 1

[0231] Table 2

[0232] Table 3

[0233] It can be seen from Tables 2 to 3 above that compared with Comparative Examples 1 and 2, the overall electrochemical performance of the embodiment after 400 cycles is higher than that of the comparative examples. This shows that the present application can synergistically improve the long-cycle performance of the material by finely controlling the lithium-oxygen ratio, particle size, specific surface area and other properties of the first and second particles in the lithium-rich manganese-based positive electrode material.

[0234] In addition, a PSD (Particle Size Distribution) test was performed on the positive electrode material of Example 1 to obtain a PSD graph of the positive electrode material provided in Example 1 (as shown in FIG2 ). The positive electrode material provided in Example 1 has a continuous bimodal particle size distribution within a particle size range of 1 to 13 μm. In addition, a SEM (Scanning Electron Microscope) test was performed on the positive electrode material of Example 1 to obtain an SEM graph of the positive electrode material provided in Example 1 (as shown in FIG1 ). The particles include first particles and second particles, and the surface of the second particles is slightly coated with a carbon layer. Both types of particles are formed by agglomeration of primary particles, and D A’ About 30nm, D B’ About 300nm.

[0235] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0236] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A lithium-rich manganese-based cathode material, characterized in that, Comprising a first particle and a second particle, the first particle satisfies chemical formula (1), and the second particle satisfies chemical formula (2): aLi2O·bLi2MnO3·cLiX α X’ β O2(1), xLi2O·yLi2MnO3·zLiY γ Y’ δ O2(2), In formula (1), -0.1 ≤ a ≤ 0, 0 < b ≤ 0.4, b + a > 0, and b + c - a = 1; In formula (2), 0 ≤ x ≤ 0.1, 0.4 ≤ y < 1, and x + y + z = 1; In formula (1) and formula (2), X and Y each independently include at least one of Ni and Co, X' and Y' each independently include at least one of Mn, Al, Na, Mg, B, Ti, Y, Zr, Nb, Sn, La, Ce, Ta, and W, and 0 ≤ β ≤ 0.5 ≤ α ≤ 1, 0 ≤ δ ≤ 0.5 ≤ γ ≤ 1, α + β = 1, and γ + δ = 1; The lithium-oxygen ratio R of the first particles A =(2a + 2b + c) / (a + 3b + 2c), and satisfies: 1 / 2 < R A <7 / 12; The lithium-oxygen ratio R of the second particle B =(2x + 2y + z) / (x + 3y + 2z), and satisfies: R A < R B < 5 / 7.

2. The lithium-rich manganese-based cathode material according to claim 1, characterized in that, In the lithium-rich manganese-based cathode material, the mass percentages of the first particles and the second particles are w A and w B , respectively. The molar masses of the first particles and the second particles are M A and M B , respectively. The lithium-oxygen ratio R of the lithium-rich manganese-based cathode material is R = (R A w A M B + R B w B M A ) / (w A M B + w B M A ), and 0.5 < R ≤ 0.

6.

3. The lithium-rich manganese-based cathode material according to claim 1 or 2, characterized in that, The second particle includes a core and a shell covering at least a part of the surface of the core, the core satisfies the chemical formula (2), and the shell contains a conductive carbon material; Optionally, the specific surface area of the core is 0.1 m 2 / g to 3 m 2 / g; Optionally, the mass percentage of the conductive carbon material in the second particle is 0.1% to 5%; Optionally, the conductive carbon material includes one or more of acetylene black, Ketjen black, conductive graphite, carbon fiber, graphene, multi-walled carbon nanotube, and single-walled carbon nanotube; 4. The lithium-rich manganese-based cathode material according to claim 3, wherein The first particle and the second particle each independently contain primary particles; Optionally, the average primary particle size D' of the first particles A and the average primary particle size D' of the second particles B satisfy: D' A < D' B < 2 μm; Optionally, the volume median diameter Dv501 of the first particle is 3 μm to 16 μm, and the volume median diameter Dv502 of the second particle is 2 μm to 7 μm; Optionally, the specific surface area of the first particles is 1 m 2 / g to 5 m 2 / g, and the specific surface area of the second particles The area is 0.1 m 2 / g to 20 m 2 / g.

5. The lithium-rich manganese-based cathode material according to claim 1 or 2, characterized in that, Satisfy at least one of the following conditions: (1) The volume median diameter Dv50 of the lithium-rich manganese-based cathode material is 3 μm to 16 μm; (2) The specific surface area of the lithium-rich manganese-based cathode material is 1 m 2 / g to 5 m 2 / g; (3) The water content in the lithium-rich manganese-based cathode material < 500 ppm; (4) The LiOH content in the lithium-rich manganese-based cathode material < 3000 ppm; (5) The Li2CO3 content in the lithium-rich manganese-based cathode material < 3000 ppm.

6. A method for preparing a lithium-rich manganese-based cathode material, characterized in that, Include: Mix the first particle and the second particle to prepare the lithium-rich manganese-based cathode material, where the first particle satisfies the chemical formula (1) and the second particle satisfies the chemical formula (2): aLi2O·bLi2MnO3·cLiX α X’ β O2(1), xLi2O·yLi2MnO3·zLiY γ Y’ δ O2(2), In formula (1), -0.1 ≤ a ≤ 0, 0 < b ≤ 0.4, b + a > 0, and b + c - a = 1; In formula (2), 0 ≤ x ≤ 0.1, 0.4 < y < 1, and x + y + z = 1; In formula (1) and formula (2), X and Y each independently include at least one of Ni and Co, X' and Y' each independently include at least one of Mn, Al, Na, Mg, B, Ti, Y, Zr, Nb, Sn, La, Ce, Ta, and W, and 0 ≤ β ≤ 0.5 ≤ α ≤ 1, 0 ≤ δ ≤ 0.5 ≤ γ ≤ 1, α + β = 1, and γ + δ = 1; The lithium-oxygen ratio R of the first particles A =(2a + 2b + c) / (a + 3b + 2c), and satisfies: 1 / 2 < R A <7 / 12; The lithium-oxygen ratio R of the second particle B =(2x + 2y + z) / (x + 3y + 2z), and satisfies: R A < R B < 5 / 7.

7. The method according to claim 6, characterized in that, The preparation method of the first particle includes: Perform a first sintering treatment on a first mixture containing a first precursor and a first lithium source to prepare the first particle, where the first precursor contains manganese element, X element, and X' element; Optionally, the first sintering treatment includes: Heat the first mixture at a heating rate of 1 °C / min to 10 °C / min to 300 °C to 600 °C, keep it warm for 2 h to 8 h, then heat it at a heating rate of 1 °C / min to 10 °C / min to 750 °C to 1000 °C, and keep it warm for 8 h to 20 h; Optionally, the first precursor includes at least one of carbonates, hydroxides, and oxides containing manganese element, X element, and X' element; Optionally, the first lithium source includes one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium chloride, lithium oxide, and lithium peroxide; Optionally, the molar ratio of lithium element in the first lithium source to the total molar amount of metal elements in the first precursor is 1.0 - 1.45:1; Optionally, the specific surface area of the first precursor is 10 m 2 / g to 100 m 2 / g; Optionally, the median particle size D501 of the first precursor is 3 μm - 16 μm.

8. The method according to claim 6 or 7, characterized in that, The method for preparing the second particle includes: Performing a second sintering treatment on a second mixture containing a second precursor and a second lithium source to obtain a sintered product, wherein the second precursor contains manganese element, Y element, and Y' element; Performing a coating treatment on the sintered product to prepare the second particle; Optionally, the second sintering treatment includes: Heating the second mixture at a heating rate of 1 °C / min - 10 °C / min to 300 °C - 600 °C, holding for 2 h - 8 h, then heating at a heating rate of 1 °C / min - 10 °C / min to 900 °C - 1200 °C, and holding for 1 h - 5 h, and then cooling to 700 °C - 900 °C and holding for 6 h - 15 h; Optionally, the second precursor includes at least one of carbonates, hydroxides, and oxides containing manganese element, Y element, and Y' element; Optionally, the second lithium source includes one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium chloride, lithium oxide, and lithium peroxide; Optionally, the molar ratio of lithium element in the second lithium source to the total molar amount of metal elements in the second precursor is 1.4 - 2.25:1; Optionally, the specific surface area of the second precursor is 5 m 2 / g to 50 m 2 / g; Optionally, the median particle size D502 of the second precursor is 1.5 μm - 8 μm.

9. The method according to claim 8, characterized in that, The coating treatment includes: Mixing the sintered product with a conductive carbon material; Optionally, the mass ratio of the conductive carbon material to the sintered product is (0.1 - 3):100; Optionally, the conductive carbon material includes one or more of acetylene black, Ketjen black, conductive graphite, carbon fiber, graphene, multi-walled carbon nanotube, and single-walled carbon nanotube.

10. A positive electrode plate, characterized in that, Including the lithium-rich manganese-based cathode material according to any one of claims 1 - 5 or the lithium-rich manganese-based cathode material prepared by the method according to any one of claims 6 - 9.

11. A battery, characterized in that, Including the cathode electrode sheet according to claim 10.

12. An electronic device, characterized in that, Including the battery according to claim 11.

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