A positive electrode material, a preparation method and application thereof

Abstract

The embodiment of the present application provides a kind of positive electrode material and its preparation method and application.Positive electrode material includes as follows positive electrode matrix;Li a Ni b Co c Mn d M e O x D y ;Wherein, M includes Ti, Mo, W, Nb, Ta, V, Sb, Si, Sn, Zr, Cr, Al, La, Y, Sr, Mg, Zn, Na and K at least one;D includes F, Cl, S, P, Se and B at least one;1 less than a=1.55, 0.24=0.5, 0=0.05, 0.5=0.75, 0=0.05, 0 less than y=0.05, 2 less than x=3;0.0012=y / R, R is the proportion of the charge capacity provided by oxygen ion in the total charge capacity of positive electrode material in the first charging process of positive electrode material. When the positive electrode sheet including the positive electrode material is applied to battery, the initial efficiency and cycle performance of the battery can be improved.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to a cathode material, its preparation method, and its application. Background Technology

[0002] With the increasing driving range of electric vehicles and the optimization of energy storage capacity in energy storage systems, batteries need to have higher specific capacity and voltage platforms. Lithium-rich manganese-based cathode materials, due to their low Ni and Co content and synergistic charge compensation mechanism between anions and cations, have a theoretical specific capacity of 250-300 mAh / g, far exceeding that of traditional ternary cathode materials (such as NCM and NCA) and lithium iron phosphate (LFP), making them key candidate materials for next-generation high-energy-density batteries. At the same time, lithium-rich manganese-based cathode materials have a high Mn content and significantly reduced Ni and Co content, reducing dependence on scarce resources (such as cobalt), which aligns with the battery industry's trend towards cost reduction, efficiency improvement, and sustainable development.

[0003] However, lithium-rich manganese-based cathode materials have problems such as high initial irreversible capacity and structural instability caused by oxygen release during cycling. Summary of the Invention

[0004] This application provides a cathode material, and when the cathode sheet containing this cathode material is applied to a battery, it can improve the battery's initial efficiency and cycle performance. The preparation method of this cathode material is simple and suitable for widespread application.

[0005] This application provides a cathode material, wherein the cathode material comprises a compound represented by Formula 1;

[0006] Li a Ni b Co c Mn d M e O x D y Formula 1;

[0007] Wherein, M includes at least one of Ti, Mo, W, Nb, Ta, V, Sb, Si, Sn, Zr, Cr, Al, La, Y, Sr, Mg, Zn, Na, and K; D includes at least one of F, Cl, S, P, Se, and B;

[0008] 1<a≤1.55, 0.24≤b+c≤0.5, 0≤c≤0.05, 0.5≤d≤0.75, 0≤e≤0.05, 0<y≤0.05, 2<x<3;

[0009] 0.0012≤y / R≤0.15, where R is the proportion of the charging capacity provided by oxygen ions during the first charging process of the cathode material in the total charging capacity of the cathode material.

[0010] The cathode material as described above, wherein 0.2 ≤ R ≤ 0.8.

[0011] The cathode material described above, where R = Q2 / Q1;

[0012] Wherein, Q1 is the initial charge capacity of the positive electrode material in the range of 2.5-4.6V;

[0013] Q2 is the initial charge capacity of the cathode material in the 4.4V-4.6V range.

[0014] The cathode material as described above includes a Li2MnO3 phase and a layered transition metal oxide phase.

[0015] The cathode material as described above, wherein the cathode material includes a first portion and a second portion located at least partially on the outer periphery of the first portion;

[0016] The first part includes Li, Ni, Mn, D, optionally Co, and optionally M;

[0017] The second part includes at least one of M and D.

[0018] The cathode material as described above, wherein the second part includes D.

[0019] This application also provides a method for preparing the cathode material as described above, comprising:

[0020] The raw material system, including a manganese-rich precursor, a lithium source, a D source, and optionally an M source, is subjected to a first calcination treatment in an oxygen-containing atmosphere to obtain the cathode material including the cathode matrix.

[0021] The temperature of the first calcination treatment is 400-1000℃, and the first calcination treatment includes at least one stage of heat preservation sintering.

[0022] The temperature of at least one of the heat preservation sintering stages is higher than the melting point temperature of the D source, and the heat preservation sintering time of at least one stage is 2-15 hours; the melting point temperature of the D source is 300-900℃.

[0023] In the raw material system, the molar ratio of the manganese-rich precursor, the lithium source, the D source, and the M source is (0.9-1):(0.5-1.55):(0.0001-0.05):(0-0.1).

[0024] The preparation method described above further includes, after the first calcination treatment, adding an additive and performing a second calcination treatment;

[0025] The additive includes at least one of M source and D source.

[0026] This application also provides a positive electrode sheet, wherein the positive electrode sheet comprises the positive electrode material as described above.

[0027] This application also provides a battery, wherein the battery includes a positive electrode as described above.

[0028] This application establishes a mathematical relationship between the anion doping amount (y) and the oxygen ion participation capacity contribution ratio (R) in the cathode material (0.0012≤y / R≤0.15), thereby achieving synergistic optimization of redox reversibility and energy density in lithium-rich manganese-based cathode materials, which can improve the battery's first efficiency and cycle performance. Attached Figure Description

[0029] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0030] Figure 1 The first charge-discharge curve of the battery in Example 1;

[0031] Figure 2 The cycle capacity retention curve is for the battery in Example 1. Detailed Implementation

[0032] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0033] Existing lithium-rich manganese-based cathode materials suffer from problems such as high initial irreversible capacity and structural instability caused by oxygen release during cycling. This application establishes a mathematical relationship between anion doping amount (y) and the ratio of oxygen participation in capacity contribution (R), thereby achieving synergistic optimization of oxygen redox reversibility and energy density in lithium-rich manganese-based materials, and improving the battery's initial efficiency and cycle performance.

[0034] A first aspect of this application provides a cathode material, the cathode material comprising the compound shown in Formula 1;

[0035] Li a Ni b Co c Mn d M e O x D yFormula 1;

[0036] Wherein, M includes at least one of Ti, Mo, W, Nb, Ta, V, Sb, Si, Sn, Zr, Cr, Al, La, Y, Sr, Mg, Zn, Na, and K; D includes at least one of F, Cl, S, P, Se, and B;

[0037] 1<a≤1.55, 0.24≤b+c≤0.5, 0≤c≤0.05, 0.5≤d≤0.75, 0≤e≤0.05, 0<y≤0.05, 2<x<3;

[0038] 0.0012≤y / R≤0.15, where R is the proportion of the charging capacity provided by oxygen ions in the total charging capacity of the cathode material during the first charging process.

[0039] The cathode material of the present invention is a compound comprising at least Li, Ni, Mn, D, and O elements. In some embodiments, the cathode material further comprises Co and / or M elements.

[0040] The inventors discovered that during the first charge of lithium-rich manganese-based cathode materials, the total capacity of the first charge cycle can be divided into two parts based on the different sources of capacity contribution: the charging capacity below 4.4V is mainly provided by the oxidation of transition metal ions; the charging capacity above 4.4V is mainly provided by the oxidation of oxygen ions. R refers to the proportion of the capacity provided by oxygen ions in the total charging capacity of the cathode material (the proportion of the charging capacity above 4.4V in the total charging capacity during the first charge cycle). R represents the degree to which oxygen participates in the capacity contribution of the cathode material. When R is too high, the degree of oxygen oxidation is too high, causing oxygen to be released in the form of oxygen gas, triggering serious side reactions and structural transformations, and deteriorating electrical performance. When R is too low, the capacity contribution provided by oxygen is too low, resulting in low capacity utilization and insufficient energy density of the cathode material.

[0041] The D element in the cathode material has a higher bond energy with the transition metal Mn, which can suppress the migration of transition metal ions and the irreversible release of oxygen, improve the redox reversibility of oxygen and the structural stability of the cathode material. However, if the doping amount of D element is too high, the redox reversibility of oxygen is improved but the contribution of oxygen to the capacity will be affected, resulting in a decrease in energy density. If the doping amount of D element is too low, it cannot improve the redox reversibility of oxygen, and the electrochemical performance cannot be effectively improved.

[0042] The inventors discovered that when y / R < 0.0012, the impurity content is too low, resulting in poor oxygen redox reversibility and a decreased cycle life of the material. When y / R > 0.15, the impurity content is too high, leading to insufficient oxygen capacity contribution and a decrease in energy density. Only when the cathode material satisfies 0.0012 ≤ y / R ≤ 0.15 can both high capacity and oxygen redox reversibility be guaranteed, achieving a balance between the cathode material's energy density and overall performance.

[0043] Therefore, by designing y / R, this application can effectively suppress structural degradation, transition metal migration, and electrolyte side reactions caused by irreversible anion redox (such as oxygen release) during cycling without sacrificing specific capacity; maximize the reversibility of anion redox, improve the long-term cycle life of the cathode material, and reduce the risk of thermal runaway caused by oxygen release from the source, thereby enhancing the intrinsic safety of the battery and simultaneously achieving high energy density and excellent cycle stability.

[0044] It is worth mentioning that the low or absence of Co content in the cathode material of this application can improve the anion stability of the cathode material; and the low Ni content in the cathode material of this application can further reduce the cost of the cathode material. When the cathode material also includes M element, M element can reduce the possibility of phase transition of the cathode material during battery charging and discharging, improve the cycle performance of the battery, and M element can further synergize with D element to more effectively improve the structural stability and capacity of the cathode material, further improving the cycle performance and energy density of the battery.

[0045] For example, 'a' can be any one of 1.01, 1.05, 1.1, 1.2, 1.4, 1.55, or a range consisting of any two of them;

[0046] b+c can be a range of any one of 0.24, 0.3, 0.35, 0.4, 0.5, or any two of them;

[0047] c can be any one of 0, 0.001, 0.003, 0.01, 0.02, 0.03, 0.05, or a range consisting of any two of them;

[0048] d can be any of 0.51, 0.53, 0.6, 0.7, 0.75 or any combination of two of them;

[0049] e can be any one of 0, 0.0001, 0.001, 0.003, 0.01, 0.02, 0.03, 0.05, or a range consisting of any two of them;

[0050] y can be any one of 0.0001, 0.001, 0.003, 0.01, 0.02, 0.03, 0.05 or a range of any two of them;

[0051] y / R can be any one of 0.0012, 0.002, 0.005, 0.01, 0.05, 0.1, 0.15 or a range of any two of them.

[0052] In some implementations, b+c+d+e=1.

[0053] In this application, R can be selected based on redox kinetics and the structural stability of the cathode material, combined with the selection of D, to ensure the capacity and stability of the cathode material and improve the energy density and cycle performance of the battery. In some embodiments of this application, 0.2≤R≤0.8 indicates a suitable oxygen capacity contribution, the cathode material is not prone to oxygen evolution, has excellent stability, and the cathode material has excellent capacity.

[0054] For example, R can be a range of any one of 0.2, 0.3, 0.4, 0.5, 0.7, 0.8 or any two of them.

[0055] In some embodiments of this application, R = Q2 / Q1;

[0056] Q1 represents the initial charging capacity of the cathode material in the 2.5-4.6V range.

[0057] Q2 represents the initial charging capacity of the cathode material in the 4.4V-4.6V range.

[0058] That is, by distinguishing the capacity contribution of transition metal oxidation (below 4.4V) and oxygen oxidation (above 4.4V), the regulatory effect of anion doping on oxygen redox is quantified.

[0059] In some embodiments of this application, the cathode material comprises a Li₂MnO₃ phase and a layered transition metal oxide phase (the molar ratio of nickel to manganese is typically 1:1). The Li₂MnO₃ phase primarily provides the anion redox capacity, while the layered phase (e.g., LiNi)... 0.5 Mn 0.5 O2 mainly contributes to the redox capacity of cations, thus this cathode material can maximize the battery's cycle performance and energy density.

[0060] In some embodiments of this application, the positive electrode material includes a first portion and a second portion located at least partially on the periphery of the first portion;

[0061] The first part includes Li, Ni, Mn, D, optional Co (which may or may not include Co), and optional M (which may or may not include M).

[0062] The second part includes at least one of M and D.

[0063] It is understood that the cathode material of this application comprises a first part and a second part from the inside out. The second part in this application may be continuous or discontinuous. The first part and the second part in this application may or may not have a clear dividing line (the first part and the second part are an integral structure).

[0064] The M element in the second part can be the same as or different from the M element in the first part; the D element in the second part can be the same as or different from the D element in the first part.

[0065] The second part, located on the outer periphery of the first part, can protect the first part, reduce the risk of dissolution of transition metal elements in the first part upon contact with the electrolyte, and improve the cycle performance of the battery.

[0066] Furthermore, when the second part includes D, the D element (at least one of F, Cl, S, P, Se, and B) has strong covalent bond characteristics, which helps to build a stable interfacial barrier, suppressing side reactions between the cathode material and the electrolyte and reducing the dissolution of transition metal ions. At the same time, the D element in the second part can form a synergistic effect of lattice matching with the D element in the first part, reducing interfacial impedance, enhancing structural stability, widening ion diffusion channels, improving ion conduction efficiency, and buffering volume deformation during charge and discharge processes, ultimately achieving a simultaneous improvement in material cycle life, rate performance, and structural stability.

[0067] The element M in Part II of this application may exist in the form of elemental M or in the form of a compound including M. The compound including M may include at least one of oxides of element M and polyanionic compounds including element M.

[0068] Element D can exist in the form of compounds containing element D. For example, it can include at least one of metal fluorides, metal chlorides, metal sulfates, sulfides, metal phosphates, phosphides, metal selenates, selenides, borates, and borides.

[0069] A second aspect of this application provides a method for preparing a cathode material, comprising:

[0070] The raw material system, including a manganese-rich precursor, a lithium source, a D source, and optionally an M source (optionally meaning that it may or may not include an M source), is subjected to a first calcination treatment in an oxygen-containing atmosphere to obtain the cathode material including the cathode matrix.

[0071] The temperature of the first calcination treatment is 400-1000℃, and the first calcination treatment includes at least one stage of heat preservation sintering;

[0072] The temperature of at least one heat preservation sintering stage is higher than the melting point temperature of the D source, and the heat preservation sintering time of at least one stage is 2-15 hours; the melting point temperature of the D source is 300-900℃.

[0073] In the raw material system, the molar ratio of manganese-rich precursor, lithium source, D source and M source is (0.9-1):(0.5-1.55):(0.0001-0.05):(0-0.1).

[0074] In this application, the temperature of the first calcination treatment is 400-1000℃, which not only ensures the full melting of the D source and improves the doping uniformity of the D element, but also avoids the excessive decomposition of the Li2MnO3 phase. At the same time, the oxygen-containing atmosphere (such as air) can also suppress the excessive decomposition of the Li2MnO3 phase in the first calcination treatment. The temperature of at least one stage of heat preservation sintering is higher than the melting point temperature of the D source, which can further promote the full melting of the D source, thereby obtaining a cathode material with 0.0012≤y / R≤0.15.

[0075] In some embodiments of this application, the preparation method further includes: after the first calcination treatment, adding an additive and performing a second calcination treatment;

[0076] The additives include at least one of the M source and the D source.

[0077] In the second calcination process, the product after the first calcination process forms a first part, and the additive forms a second part located at least part of the outer periphery of the first part.

[0078] In some embodiments, when the additive includes an M source, the formed second portion includes the M element; when the additive includes a D source, the formed second portion includes the D element; when the additive includes both an M source and a D source (the M source and the D source can be the same compound), the formed second portion includes both the M element and the D element.

[0079] The manganese-rich precursor of this application can be a manganese-rich hydroxide precursor and / or a manganese-rich oxide precursor commonly used in the art. The manganese-rich precursor of this application may or may not include cobalt.

[0080] This application does not impose any particular limitation on the lithium source, which can be a lithium-containing compound and / or a lithium-containing element commonly used in the field.

[0081] In this application, the D source can be an elemental substance containing D and / or a compound containing D, which are commonly used in the art.

[0082] This application does not specifically limit the source of M, and it can be any elemental substance containing element M and / or a compound containing element M commonly used in the art. In some embodiments, the source of D and the source of M can be the same compound.

[0083] A third aspect of this application provides a positive electrode sheet, including the positive electrode material of the first aspect, which has both excellent capacity and cycle performance.

[0084] A fourth aspect of this application provides a battery including a positive electrode from the third aspect, wherein the arrangement has excellent energy density and cycle performance.

[0085] A fifth aspect of the invention also provides an electronic device including the battery described above. This battery exhibits excellent energy density and cycle performance under high voltage, making it suitable for various electronic devices (e.g., new energy vehicles and energy storage devices).

[0086] The present invention will be further described below with reference to specific embodiments.

[0087] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; and the reagents and materials are commercially available unless otherwise specified.

[0088] Example 1

[0089] The battery in this embodiment is prepared by a method including the following steps:

[0090] 1) Preparation of cathode materials

[0091] Manganese-rich precursor, lithium carbonate, M source, and D source were mixed uniformly in a molar ratio of 0.996:0.66:0.002:0.01 to obtain a raw material system. The raw material system was subjected to a first calcination treatment in a box furnace, and then naturally cooled to room temperature. After crushing and sieving, the cathode material was obtained.

[0092] The first calcination treatment includes: heating to 500℃ at a heating rate of 2℃ / min and holding for 5 hours, and then heating to 880℃ at a heating rate of 2℃ / min and holding for 12 hours.

[0093] The manganese-rich precursor is Ni 0.35 Mn 0.65 (OH)2, with M source being Nb2O5 and D source being Li2SO4, has a melting point of 848℃.

[0094] 2) Preparation of positive electrode sheet

[0095] A uniform positive electrode slurry is formed by thoroughly mixing the positive electrode material, carbon black conductive agent Super-P, and polyvinylidene fluoride (PVDF) binder P at a mass ratio of 90:5:5 with an appropriate amount of N-methylpyrrolidone. The positive electrode slurry is then coated onto the surface of aluminum foil, dried at 120℃, rolled, and punched to produce a positive electrode sheet with a diameter of 13 mm, including a positive electrode active layer. The loading of the positive electrode active layer is 12 mg / cm². 2 .

[0096] 3) Battery manufacturing

[0097] In an argon-filled glove box, a 2032 coin cell was assembled with a lithium sheet as the negative electrode, a polypropylene microporous membrane (Celgard 2400) as the separator, a 1M LiPF6 electrolyte (the solvent includes EC and DMC, with a volume ratio of EC to DMC of 1:1) and the positive electrode sheet in step 2).

[0098] Other battery parameters are shown in Table 1.

[0099] Example 2

[0100] The battery preparation method in this embodiment is basically the same as that in Embodiment 1, except that:

[0101] 1) Preparation of cathode materials

[0102] The molar ratio of manganese-rich precursor, lithium carbonate, M source, and D source is 0.985:0.76:0.015:0.001; the manganese-rich precursor is Ni. 0.25 Mn 0.75 (OH)2, with MoO3 as the M source and Li3BO3 as the D source, has a melting point of 840℃.

[0103] Example 3

[0104] The battery preparation method in this embodiment is basically the same as that in Embodiment 1, except that:

[0105] 1) Preparation of cathode materials

[0106] The raw material system was obtained by mixing manganese-rich precursor, lithium carbonate, M source and D source in a molar ratio of 0.99:0.61:0.01:0.01. The raw material system was subjected to a first calcination treatment in a box furnace, and then naturally cooled to room temperature. After crushing and sieving, the cathode material was obtained.

[0107] The first calcination treatment includes: heating to 500℃ at a heating rate of 2℃ / min and holding for 5 hours, and then heating to 900℃ at a heating rate of 2℃ / min and holding for 12 hours.

[0108] Among them, the manganese-rich precursor is Ni 0.4 Mn 0.6 (OH)2, M source is WO3, D source is Li2SeO4, and its melting point is 820℃.

[0109] Example 4

[0110] The battery preparation method in this embodiment is basically the same as that in Embodiment 1, except that:

[0111] 1) Preparation of cathode materials

[0112] The raw material system was obtained by uniformly mixing manganese-rich precursor, lithium carbonate, M source and D source in a molar ratio of 0.99:0.59:0.005:0.05. The raw material system was subjected to a first calcination treatment in a box furnace, and then naturally cooled to room temperature. After crushing and sieving, the cathode material was obtained.

[0113] The first calcination treatment includes: heating to 500℃ at a heating rate of 2℃ / min and holding for 5 hours, and then heating to 920℃ at a heating rate of 2℃ / min and holding for 12 hours.

[0114] Among them, the manganese-rich precursor is Ni 0.42 Mn 0.58 (OH)2, with M source being Ta2O5 and D source being Li3PO4, has a melting point of 837℃.

[0115] Example 5

[0116] The battery preparation method in this embodiment is basically the same as that in Example 4, except that:

[0117] 1) Preparation of cathode materials

[0118] The molar ratio of manganese-rich precursor, lithium carbonate, M source, and D source is 0.98:0.56:0.01:0.02; the manganese-rich precursor is Ni. 0.45 Mn 0.55 (OH)2, M source is Cr2O3, D source is LiCl, and its melting point is 605℃.

[0119] Example 6

[0120] The battery preparation method in this embodiment is basically the same as that in Embodiment 1, except that:

[0121] 1) Preparation of cathode materials

[0122] The raw material system was obtained by uniformly mixing manganese-rich precursor, lithium carbonate, M source and D source in a molar ratio of 0.96:0.54:0.01:0.03. The raw material system was subjected to a first calcination treatment in a box furnace, and then naturally cooled to room temperature. After crushing and sieving, the cathode material was obtained.

[0123] The first calcination treatment includes: heating to 500℃ at a heating rate of 2℃ / min and holding for 5 hours, and then heating to 950℃ at a heating rate of 2℃ / min and holding for 12 hours.

[0124] Among them, the manganese-rich precursor is Ni 0.48 Mn 0.52 (OH)2, with M source being ZrO2 and D source being KF, has a melting point of 858℃.

[0125] Example 7

[0126] The battery preparation method in this embodiment is basically the same as that in Example 1, except that:

[0127] 1) Preparation of cathode materials

[0128] The raw material system was obtained by uniformly mixing manganese-rich precursor, lithium carbonate, M source and D source in a molar ratio of 0.95:0.56:0.05:0.02. The raw material system was subjected to a first calcination treatment in a box furnace, and then naturally cooled to room temperature. After crushing and sieving, the cathode material was obtained.

[0129] The first calcination treatment includes: heating to 500℃ at a heating rate of 2℃ / min and holding for 5 hours, and then heating to 900℃ at a heating rate of 2℃ / min and holding for 12 hours.

[0130] Among them, the manganese-rich precursor is Ni 0.39 Co 0.02 Mn 0.59 (OH)2, M source is WO3, D source is Li2SO4.

[0131] Example 8

[0132] The battery preparation method in this embodiment is basically the same as that in Embodiment 1, except that:

[0133] 1) Preparation of cathode materials

[0134] The molar ratio of manganese-rich precursor, lithium carbonate, and D source is 1:0.66:0.01; the manganese-rich precursor is Ni. 0.35 Mn 0.65 (OH)2, D source is Li2SO4.

[0135] Example 9

[0136] The battery preparation method in this embodiment is basically the same as that in Embodiment 1, except that:

[0137] 1) Preparation of cathode materials

[0138] After the first calcination treatment, the product of the first calcination treatment (the cathode material of Example 1) was mixed with Al2O3 at a mass ratio of 100:0.5 and then subjected to a second calcination treatment in a box furnace. After that, it was naturally cooled to room temperature, crushed and sieved to obtain a cathode material including a first part and a second part located at least part of the outer periphery of the first part.

[0139] The second calcination process includes heating to 500℃ at a heating rate of 2℃ / min and holding at that temperature for 8 hours.

[0140] Example 10

[0141] The battery preparation method in this embodiment is basically the same as that in Example 9, except that:

[0142] 1) Preparation of cathode materials

[0143] Replace Al2O3 with Al2(SO4)3.

[0144] Example 11

[0145] The battery preparation method in this embodiment is basically the same as that in Example 6, except that:

[0146] 1) Preparation of cathode materials

[0147] The raw material system was obtained by uniformly mixing manganese-rich precursor, lithium carbonate, M source and D source in a molar ratio of 0.97:0.54:0.01:0.02. The raw material system was subjected to a first calcination treatment in a box furnace, and then naturally cooled to room temperature. After crushing and sieving, the cathode material was obtained.

[0148] The first calcination treatment includes: heating to 500℃ at a heating rate of 2℃ / min and holding for 5 hours, and then heating to 920℃ at a heating rate of 2℃ / min and holding for 12 hours.

[0149] Among them, the manganese-rich precursor is Ni 0.48 Mn 0.52 (OH)2, M source is ZrO2, D source is KF.

[0150] Comparative Example 1

[0151] The preparation method of the battery in this comparative example is basically the same as that in Example 1, except that:

[0152] 1) Preparation of cathode materials

[0153] Manganese-rich precursor, lithium carbonate, M source, and D source were mixed uniformly in a molar ratio of 0.996:0.66:0.002:0.0007 to obtain a raw material system. The raw material system was subjected to a first calcination treatment in a box furnace, and then naturally cooled to room temperature. After crushing and sieving, the cathode material was obtained.

[0154] The first calcination treatment includes: heating to 500℃ at a heating rate of 2℃ / min and holding for 5 hours, then heating to 840℃ at a heating rate of 2℃ / min and holding for 12 hours.

[0155] Among them, the manganese-rich precursor is Ni 0.35 Mn 0.65 (OH)2, M source is Nb2O5, D source is Li2SO4.

[0156] Comparative Example 2

[0157] The preparation method of the battery in this comparative example is basically the same as that in Example 2, except that:

[0158] 1) Preparation of cathode materials

[0159] Manganese-rich precursor, lithium carbonate, M source and D source were mixed evenly in a molar ratio of 0.985:0.76:0.015:0.001 to obtain a raw material system. The raw material system was subjected to a first calcination treatment in a box furnace, and then naturally cooled to room temperature. After crushing and sieving, the cathode material was obtained.

[0160] The first calcination treatment includes: heating to 500℃ at a heating rate of 2℃ / min and holding for 5 hours, then heating to 820℃ at a heating rate of 2℃ / min and holding for 12 hours.

[0161] Among them, the manganese-rich precursor is Ni 0.25 Mn 0.75 (OH)2, with MoO3 as the M source and Li3BO3 as the D source, has a melting point of 840℃.

[0162] Comparative Example 3

[0163] The preparation method of the battery in this comparative example is basically the same as that in Example 3, except that:

[0164] 1) Preparation of cathode materials

[0165] Manganese-rich precursor, lithium carbonate, M source and D source are mixed uniformly in a molar ratio of 0.99:0.61:0.01:0.06 to obtain a raw material system. The raw material system is subjected to a first calcination treatment in a box furnace, and then naturally cooled to room temperature. After crushing and sieving, the cathode material is obtained.

[0166] The first calcination treatment includes: heating to 550℃ at a heating rate of 2℃ / min and holding for 5 hours, then heating to 900℃ at a heating rate of 2℃ / min and holding for 12 hours.

[0167] Among them, the manganese-rich precursor is Ni 0.40 Mn 0.60 (OH)2, M source is WO3, D source is Li2SeO4, and its melting point is 820℃.

[0168] Performance testing

[0169] The following performance tests were performed on the cathode materials and batteries in the examples and comparative examples, and the results are shown in Table 1.

[0170] 1. Content testing of various elements in the cathode material

[0171] ICP testing was performed using an Optima 7000 / Avio500 instrument. 0.4g of the positive electrode material was weighed and digested in 10ml of aqua regia to obtain the test solution. The test solution was then tested using the standard curve method for quantification.

[0172] When testing the main elements Li, Ni, Co, and Mn, the test solution was diluted 100 times with a 2% (w / w) HNO3 aqueous solution before testing.

[0173] When testing other elements, no dilution is required; the solution to be tested can be tested directly.

[0174] 2. Testing of elements in Part Two

[0175] The elements in the second part were identified using SEM-EDS.

[0176] 3. Battery electrochemical performance testing

[0177] The electrochemical performance of the 2032 coin cell was tested at 25°C using the Xinwei Battery Testing System, with a 1C charge / discharge current density of 250 mA / g.

[0178] a. The prepared coin cells were subjected to charge-discharge tests at 2.5-4.6V and 0.1C (cutoff current 0.05C) to evaluate the initial charge-discharge capacity of the cathode material, the percentage of charging capacity above 4.4V, and the initial efficiency.

[0179] b. The prepared coin cells were cycled 100 times at 2.5-4.6V and 1C (cutoff current 0.05C) to evaluate the cycling performance of the cathode material.

[0180] Figure 1 The first charge-discharge curve of the battery in Example 1; Figure 2This is the cycle capacity retention curve of the battery in Example 1. From... Figure 1 It can be seen that the initial charge capacity Q1 of the battery in Example 1 is 277 mAh / g, of which the charge capacity above 4.4V Q2 is 137 mAh / g. Calculating Q2 / Q1, the proportion of the initial charge capacity above 4.4V, R, is 49.5%, which is the oxygen participation capacity contribution rate. The ratio of the anion doping amount y (y=0.01) to the oxygen participation capacity contribution R (R=49.5%) in Example 1 yields y / R=0.02020. Figure 2 As shown, the battery in this embodiment has excellent first-efficiency performance and cycle stability.

[0181] Table 1

[0182]

[0183]

[0184] By comparing the data in Table 1, it can be concluded that the anion doping amount of the cathode materials in the examples all meets the requirement of 0.0012≤y / R≤0.15. The discharge capacity of each material varies due to the different contents of the Li2MnO3 phase, but all of them exhibit a coulombic efficiency of over 90%, indicating that the oxidation-reduction of oxygen has good reversibility during the initial activation process. After 100T of cycles, all of them exhibit a capacity retention rate of over 90%, indicating that during the charge-discharge cycle, the interfacial side reactions are low, the lattice oxygen is stable, and the structure has good stability. This can simultaneously ensure high capacity and reversible oxidation-reduction of oxygen, achieving a balance between energy density and overall performance.

[0185] The lithium-rich manganese-based cathode of Example 8, without the introduction of M element doping, exhibits performance close to that of the lithium-rich manganese-based cathode of Example 2, indicating that the key to performance improvement lies in satisfying the anion doping amount of 0.0012≤y / R≤0.15. Compared with Example 2, Examples 9 and 10 added a second calcination treatment, which further improved stability and first-time efficiency. This is because the second calcination treatment can obtain a cathode material including a first part and a second part located at least partially on the periphery of the first part. The second part can protect the first part and reduce the possibility of dissolution of transition metal elements in the first part. Furthermore, Example 10 uses an additive containing D element in the second calcination treatment. The resulting second part can not only protect the first part, but is also more compatible with the first part, further improving the interfacial stability of the cathode material. At the same time, the D element in the second part can also reduce oxygen release and alleviate the volume strain of the cathode material during charging and discharging. The D element in the first part and the D element in the second part have a synergistic effect, resulting in a more significant improvement in the stability and first-time efficiency of the obtained cathode material. By comparing the differences between Example 6 and Example 11, it can be seen that when the R value is in the preferred range of 20% to 80%, the electrochemical performance is better.

[0186] Comparative analysis of Comparative Example 1 with Example 1 and Comparative Example 2 with Example 2 shows that, although based on the same manganese-rich precursor and maintaining the same cation doping process, y / R < 0.0012, i.e., the sintering temperature is too low, below the melting point of the anion dopant, and the anions cannot be uniformly dispersed in the bulk phase. This leads to uneven oxidation-reduction of oxygen in the bulk phase, increased stress, and decreased reversibility of oxygen oxidation-reduction, further causing the collapse of the cathode material structure and deterioration of stability. In contrast, compared to Example 3, Comparative Example 3 has y / R > 0.15, indicating an excessively high anion doping amount. This suppresses oxygen oxidation-reduction, resulting in insufficient oxygen capacity contribution. At the same time, the excessive accumulation of anions at the grain boundaries further hinders the diffusion of lithium ions, significantly increases polarization, and triggers the decomposition of the electrolyte. The decomposition products accelerate the erosion of the cathode material, leading to a severe deterioration in the capacity and stability of the cathode material.

[0187] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A positive electrode material, characterized in that, The cathode material includes the compound shown in Formula 1; Li a Ni b Co c Mn d M e O x D y Formula 1; Wherein, M includes at least one of Ti, Mo, W, Nb, Ta, V, Sb, Si, Sn, Zr, Cr, Al, La, Y, Sr, Mg, Zn, Na, and K; D includes at least one of F, Cl, S, P, Se, and B; 1<a≤1.55, 0.24≤b+c≤0.5, 0≤c≤0.05, 0.5≤d≤0.75, 0≤e≤0.05, 0<y≤0.05, 2<x<3; 0.0012≤y / R≤0.15, where R is the proportion of the charging capacity provided by oxygen ions during the first charging process of the cathode material in the total charging capacity of the cathode material.

2. The cathode material according to claim 1, characterized in that, 0.2≤R≤0.8。 3. The cathode material according to claim 1 or 2, characterized in that, R = Q2 / Q1; Wherein, Q1 is the initial charging capacity of the positive electrode material in the range of 2.5-4.6V; Q2 is the initial charging capacity of the positive electrode material in the 4.4V-4.6V range.

4. The cathode material according to any one of claims 1-3, characterized in that, The cathode material comprises a Li2MnO3 phase and a layered transition metal oxide phase.

5. The cathode material according to any one of claims 1-4, characterized in that, The positive electrode material includes a first portion and a second portion located at least partially on the outer periphery of the first portion; The first part includes Li, Ni, Mn, D, optionally Co, and optionally M; The second part includes at least one of M and D.

6. The cathode material according to claim 5, characterized in that, The second part includes D.

7. A method for preparing the cathode material according to any one of claims 1-6, characterized in that, include: The raw material system, including a manganese-rich precursor, a lithium source, a D source, and optionally an M source, is subjected to a first calcination treatment in an oxygen-containing atmosphere to obtain the cathode material. The temperature of the first calcination treatment is 400-1000℃, and the first calcination treatment includes at least one stage of heat preservation sintering. The temperature of the at least one heat preservation sintering stage is higher than the melting point temperature of the D source, and the heat preservation sintering time of the at least one stage is 2-15 hours; the melting point temperature of the D source is 300-900℃. In the raw material system, the molar ratio of the manganese-rich precursor, the lithium source, the D source, and the M source is (0.9-1):(0.5-1.55):(0.0001-0.05):(0-0.1).

8. The preparation method according to claim 7, characterized in that, The process includes, after the first calcination treatment, adding an additive and then performing a second calcination treatment. The additive includes at least one of M source and D source.

9. A positive electrode plate, characterized in that, The positive electrode sheet comprises the positive electrode material according to any one of claims 1-6.

10. A battery, characterized in that, The battery includes the positive electrode as described in claim 9.

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