A lithium-poor high-capacity manganese-based positive electrode material and a preparation method and application thereof

Abstract

This invention provides a lithium-poor high-capacity manganese-based cathode material, its preparation method, and its applications, relating to the field of battery cathode material preparation technology. The molecular formula of the lithium-poor high-capacity manganese-based cathode material is Li. x Na y Mn a M 1‑a O2, wherein M is one or more combinations of Mg, Zn, Ni, W, Co, Al, Zr, Cu, Ti, and Fe, 0.3≤x≤0.8, 0.2≤y≤0.5, and 0.5<x+y≤1.2, 0.5<a≤1; the crystal structure is a composite of a lithium-containing ternary layered phase, a sodium-containing P2 phase, and a LiMn6 phase. This invention exhibits ultra-low delithiation capability, strong reversibility, high specific capacity, and high discharge voltage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery cathode material preparation, and particularly relates to a lithium-poor high-capacity manganese-based cathode material and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of new energy technology, the consumption of lithium resources has also increased sharply, resulting in a one-time surge in lithium salt prices to 600,000 yuan / ton in 2023, which has seriously restricted the healthy and sustainable development of the lithium battery industry. Although the price of lithium has recently risen, it is still high, resulting in a high proportion of lithium cost in raw material cost. Therefore, it is particularly important to improve the utilization rate of lithium.

[0003] In commonly used cathode materials, Li accounts for more than 1 in the atomic ratio of the molecular formula, such as LiCoO2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2 and other layered cathode materials. In order to obtain high-capacity cathode materials, researchers continue to increase the content of lithium components in the molecular formula, such as high-capacity lithium-rich cathode material with lithium content as high as 1.2 in the molecular formula, such as Li 1.2 Mn 0.54 Co 0.13 Ni 0.13 O2 and the like. As can be seen, the industry usually increases the lithium content to increase the specific capacity of the cathode material. The least lithium content is spinel LiMn2O4 (which can also be written as Li 0.5 MnO2), which accounts for only 0.5 atoms. However, the specific capacity of the spinel cathode material is only about 145 mAh / g, and the actual reversible specific capacity is only 120-135 mAh / g, and the specific energy density is only about 450 mAh / g. How to use less lithium to obtain a higher specific capacity cathode material is an important development direction.

[0004] From the perspective of the crystal structure of the material, among the many cathode materials, the layered oxide structure is one of the best lithium storage capacity materials, such as high-nickel and lithium-rich materials, which belong to this type of layered oxide. However, in high-manganese compounds, when the lithium content is low and in the low lithium state, x < 1, the crystal structure changes to a spinel structure with less lithium content or even a rock salt structure, reducing the specific capacity of the material. Therefore, if a lithium-poor high-capacity manganese-based cathode material is to be achieved, major improvements and innovations in component design and synthesis methods are needed to achieve cost-effective materials. SUMMARY

[0005] In view of the above problems, the present application develops a high-capacity low-lithium manganese-based lithium ion battery cathode material through component design.

[0006] One of the purposes of the present application is to provide a lithium-poor high-capacity manganese-based cathode material.

[0007] The second purpose of the present application is to provide a preparation method of the lithium-poor high-capacity manganese-based cathode material.

[0008] The third purpose of the present application is to provide an application of the lithium-poor high-capacity manganese-based cathode material.

[0009] In order to achieve the above-mentioned purposes of the present application, the following technical solutions are adopted:

[0010] In a first aspect, the present application provides a lithium-poor high-capacity manganese-based cathode material, the molecular formula of the lithium-poor high-capacity manganese-based cathode material is Li x Na y Mn a M 1-a O2, wherein M is one or a combination of Mg, Zn, Ni, W, Co, Al, Zr, Cu, Ti and Fe, 0.3≤x≤0.8, 0.2≤y≤0.5, and 0.5<x+y≤1.2, 0.5<a≤1.

[0011] The crystal structure of the lithium-poor high-capacity manganese-based cathode material is a composite of a ternary layered phase, a sodium-containing P2 phase and a LiMn6 phase, and the LiMn6 phase is dispersed in the ternary layered phase and the P2 phase.

[0012] Preferably, the middle is a sodium-containing P2 phase, and the two sides are ternary layered phases, forming a sandwich structure.

[0013] Preferably, the ternary layered phase corresponds to a space group R3m, the sodium-containing P2 phase corresponds to a space group P63 / mmc, and the LiMn6 phase corresponds to a space group C / 2m.

[0014] The lithium ion cathode material of the present application has a sodium-rich low-lithium characteristic, has a composite crystal structure of a lithium ternary layered structure phase (R3m), a sodium-containing P2 phase (P63 / mmc), and a LiMn6 (C / 2m) phase dispersed in the two phases, wherein the content of each structure can be adjusted, and a three-layer sandwich ("sandwich") structure is presented in the c-axis direction. The two sides of the primary particle sheet layer in the <003> direction are ternary layered structure phases (R3m), and the interplanar spacing thereof is The crystal structure of the middle region is a sodium-containing P2 phase, and the interplanar spacing thereof is larger

[0015] In a second aspect, the present application provides a preparation method of the above-mentioned lithium-poor high-capacity manganese-based cathode material, comprising the following steps:

[0016] The manganese-based precursor and lithium salt are mixed in stoichiometric ratio, and the sodium salt is mixed in stoichiometric ratio with an excess of 20-50%, and then sintered in air, cooled, and sieved to obtain a lithium-poor high-capacity manganese-based positive electrode material.

[0017] The manganese-based precursor includes a hydroxide precursor Mn a M 1-a (OH)2, a carbonate precursor Mn a M 1-a CO3, an oxalate precursor Mn a M 1-a (COO)2, 0.5

[0018] The lithium salt is one or more selected from lithium carbonate, nitrate, lithium acetate, and lithium hydroxide;

[0019] The sodium salt is one or more selected from sodium carbonate, sodium bicarbonate, sodium acetate, and sodium sulfate.

[0020] In some embodiments, the sintering has a heating rate of 2-10℃ / min, a sintering temperature of 700-950℃, and a holding time of 8-20h.

[0021] In a specific embodiment, the preparation of the lithium-poor high-capacity manganese-based positive electrode material includes the following steps:

[0022] (1) Dissolve nickel sulfate and manganese sulfate in stoichiometric ratio in deionized water to prepare an aqueous solution with a total metal concentration of 2 mol / L, the precipitating agent is sodium hydroxide with a concentration of 2 mol / L, the complexing agent is ammonia water with a concentration of 0.6 mol / L, and the stirring speed is 400-600 r / min. The temperature of the reaction kettle is controlled at 50℃. After a suitable reaction time, age for 24h, filter, wash, and dry to obtain a transition metal hydroxide precursor;

[0023] (2) Weigh the precursor and lithium salt in stoichiometric ratio, and weigh the sodium salt in stoichiometric ratio with an excess of 30%, and then mechanically mix them uniformly;

[0024] (3) Heat treatment under air: heat at a rate of 5℃ / min to 700-950℃, hold for 8-20h, naturally cool, and sieve to obtain the product.

[0025] In a third aspect, the present application provides a use of the above-mentioned lithium-poor high-capacity manganese-based positive electrode material in the preparation of a positive electrode sheet and a lithium ion battery.

[0026] The form of the battery is not limited, and can be a cylindrical, soft package, square, half-knife, and rhombic battery, etc.

[0027] Advantages:

[0028] (1) The present application obtains a low-lithium and sodium-rich positive electrode material by a low-lithium and sodium-rich component design strategy and phase structure optimization, and the sodium-rich design ensures that it is still a layered phase structure under low-lithium conditions, ensuring high lithium storage capacity of the material. It is a crystal structure composed of a ternary layered phase, a LiMn6 phase, and a sodium-containing P2 phase, and stacked in the c-axis direction. The middle layer is a P2 phase, and the upper and lower layers are ternary layered phases, i.e., a "sandwich" structure in the c-axis direction. The component with a specific molecular formula designed by the present application can prepare a positive electrode material with a special crystal structure.

[0029] (2) The present application obtains a low-lithium and manganese-rich positive electrode material with high capacity and high specific energy characteristics under extremely low-lithium and high-manganese conditions.

[0030] (3) The positive electrode material of the present application has a rich redox potential different from traditional positive electrode materials, such as reduction potentials of 4.3V, 3.9V, 3.73V, 3.3V, 2.7V, and 2.5V.

[0031] The present application has been described in detail above, but the above embodiments are merely illustrative in nature and are not intended to limit the present application. In addition, the present application is not limited by any theory described in the foregoing prior art or summary of the invention or in the following examples. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 TEM image of Example 1 and schematic diagram of two-phase sandwich structure;

[0033] Figure 2 XRD image of the positive electrode material of Examples 1-6;

[0034] Figure 3 SEM image of Example 6 and Example 7, left image is Example 6, right image is Example 7;

[0035] Figure 4 First charge-discharge diagram of Examples 1-4;

[0036] Figure 5 First charge-discharge dQ / dV diagram of Examples 1-3;

[0037] Figure 6 First charge-discharge diagram of Examples 5-6;

[0038] Figure 7 First charge-discharge diagram of Examples 7-9;

[0039] Figure 8The first charge-discharge graph of Comparative Example 1-2;

[0040] Figure 9 Cycle performance of Example 6 at 0.5C. DETAILED DESCRIPTION

[0041] The application will be further described in conjunction with the following examples. It should be noted that the following examples are provided for illustration purposes only and do not constitute a limitation on the scope of the present application.

[0042] Unless otherwise specified, the raw materials, reagents, methods, etc. used in the examples are conventional raw materials, reagents, methods in the art.

[0043] Electrochemical performance evaluation: evaluation was performed using 2032 button cells, and the test was performed on a Blue Electric battery test system, with a current setting of 1C = 150 mAh / g for charge and discharge, and a voltage window of 2.0-4.8V.

[0044] Example 1

[0045] High-capacity low-lithium lithium-ion positive electrode material Li 0.3 Na 0.5 Ni 0.2 Mn 0.8 Preparation of Li

[0046] A stoichiometric ratio of Ni 0.2 Mn 0.8 (OH)2was first prepared by a hydroxide coprecipitation method, and then lithium carbonate and sodium carbonate were mixed and sintered. Specifically, it includes:

[0047] A solution with a metal concentration of 2 mol / L was prepared by dissolving nickel sulfate and manganese sulfate in deionized water according to the stoichiometric ratio, the precipitating agent was sodium hydroxide with a concentration of 2 mol / L, the complexing agent was ammonia water with a concentration of 0.6 mol / L, and the stirring speed was 400-600 r / min. The temperature of the reaction kettle was controlled at 50°C, and after a suitable reaction time, the solution was aged for 24h, filtered, washed, and dried to obtain the transition metal hydroxide precursor Ni 0.2 Mn 0.8 (OH)2.

[0048] Then, lithium carbonate and sodium carbonate (sodium carbonate was added in excess of 30% based on the stoichiometric ratio) were added according to the chemical ratio and mechanically mixed, and the sintering schedule was as follows: the temperature was raised to 850°C at a rate of 5 / min, and held for 12h, and then naturally cooled, sieved, and the product was obtained.

[0049] The phase distribution was determined by TEM characterization, such as Figure 1The XRD shows that the material has a three-layer sandwich structure in the c-axis direction, i.e., a "sandwich" structure, and the crystal structure of the middle region is a sodium-containing P2 phase. Figure 2 The XRD shows that the material has a three-layer sandwich structure in the c-axis direction, i.e., a "sandwich" structure, and the crystal structure of the middle region is a sodium-containing P2 phase.

[0050] The XRD shows that the material has a three-layer sandwich structure in the c-axis direction, i.e., a "sandwich" structure, and the crystal structure of the middle region is a sodium-containing P2 phase. Figure 4 As shown in Table 1, the first discharge capacity of the material is 146.8 mAh / g, which is much higher than the capacity of Comparative Example 1, Li 0.3 Ni 0.2 Mn 0.8 The capacity of the O2 component is only 16.4 mAh / g, and the first efficiency is 74.25%, as shown in Table 1. Figure 8 The XRD shows that the material has a three-layer sandwich structure in the c-axis direction, i.e., a "sandwich" structure, and the crystal structure of the middle region is a sodium-containing P2 phase. Figure 5 The XRD shows that the material has a three-layer sandwich structure in the c-axis direction, i.e., a "sandwich" structure, and the crystal structure of the middle region is a sodium-containing P2 phase.

[0051] Example 2

[0052] High-capacity low-lithium lithium ion cathode material Li 0.35 Na 0.4 Ni 0.2 Mn 0.8 O2 was prepared by the same synthesis method as in Example 1, and the lithium and sodium content was adjusted to Li 0.35 Na 0.4 The sodium carbonate was used in an excess of 30% on a stoichiometric basis. Sintering was performed in a programmed temperature mode: the temperature was raised to 850°C at a rate of 5°C / min, and the temperature was maintained for 12 h; the temperature was then naturally lowered, the material was crushed and sieved to obtain the product.

[0053] Figure 2 The XRD shows that the material has a three-layer sandwich structure in the c-axis direction, i.e., a "sandwich" structure, and the crystal structure of the middle region is a sodium-containing P2 phase.

[0054] As shown in Table 1, the first discharge capacity of the material is 146.8 mAh / g, which is much higher than the capacity of Comparative Example 1, Li Figure 4

[0055] Example 3

[0056] High-capacity low-lithium lithium ion cathode material Li 0.4 Na 0.4 Ni 0.2 Mn 0.8 ​O2 preparation: The synthesis method is the same as in Example 1, except that the lithium content is adjusted to Li 0.4 Na 0.4 Sodium carbonate is added in 30% excess on a stoichiometric basis. Sintering is carried out using a programmed temperature rise method: the temperature rises at a rate of 5℃ / min to 850℃, and is held at that temperature for 12 hours; the product is obtained by natural cooling, crushing, and sieving.

[0057] The obtained items are similar Figure 2 As shown, the crystal structure of this cathode material consists of a lithium-containing ternary layered phase, a sodium-containing P2 phase, and LiMn6; the corresponding space groups are R3m, P63 / mmc, and C / 2m. With increasing lithium content, the diffraction peak at 18.6° increases, while the diffraction peak at 16° decreases, indicating that the lithium-containing O3 layered phase increases with increasing lithium content, while the sodium-containing P2 phase decreases.

[0058] like Figure 4 As shown in Table 1, the material's initial discharge was 155.5 mAh / g, with an initial efficiency of 69.91%; the discharge voltage was 3.68 V. Figure 5 As shown, it has a rich redox potential that is different from traditional cathode materials, with reduction potentials of 4.3V, 3.9V, 3.73V, 3.3V, 2.7V and 2.5V.

[0059] Example 4

[0060] High-capacity, low-lithium lithium-ion cathode material Li 0.45 Na 0.4 Ni 0.2 Mn 0.8 O2 preparation: The synthesis method is the same as in Example 1, except that the lithium content is adjusted to Li 0.45 Na 0.4 Sodium carbonate is added in 30% excess on a stoichiometric basis. Sintering is carried out using a programmed temperature rise method: the temperature rises at a rate of 5℃ / min to 850℃, and is held at that temperature for 12 hours; the product is obtained by natural cooling, crushing, and sieving.

[0061] The obtained items are similar Figure 2 As shown, the crystal structure of this cathode material consists of a lithium-containing ternary layered phase, a sodium-containing P2 phase, and LiMn6; the corresponding space groups are R3m, P63 / mmc, and C / 2m.

[0062] like Figure 4 As shown in Table 1, the material's initial discharge was 136.1 mAh / g, with an initial efficiency of 79.26%; the discharge voltage was 3.65 V.

[0063] Example 5

[0064] High-capacity, low-lithium lithium-ion cathode material Li 0.5 Na0.4 Ni 0.2 Mn 0.8 Preparation of O2: The synthesis method is the same as in Example 1. Sintering is carried out by programmed temperature rise: the temperature rises at a rate of 5℃ / min to 850℃, and is held at that temperature for 12h; the product is obtained by natural cooling, crushing and sieving.

[0065] The obtained items are similar Figure 2 As shown, the crystal structure of this cathode material consists of a lithium-containing ternary layered phase, a sodium-containing P2 phase, and LiMn6; the corresponding space groups are R3m, P63 / mmc, and C / 2m.

[0066] like Figure 6 As shown in Table 1, the material's initial discharge was 194.2 mAh / g, with an initial efficiency of 70.25%; the discharge voltage was 3.63 V.

[0067] Example 6

[0068] High-capacity, low-lithium lithium-ion cathode material Li 0.56 Na 0.4 Ni 0.2 Mn 0.8 O2 preparation: The synthesis method is the same as in Example 1, except that the lithium content is adjusted to Li 0.56 Na 0.4 .

[0069] The obtained items are similar Figure 2 As shown, the crystal structure of this cathode material consists of a lithium-containing ternary layered phase, a sodium-containing P2 phase, and LiMn6; the corresponding space groups are R3m, P63 / mmc, and C / 2m. Its morphology was determined using SEM, as shown below. Figure 3 As shown, the particles in Example 6 have a near-spherical morphology and a D50 of 8 μm.

[0070] like Figure 6 As shown in Table 1, the material's initial discharge was 175.4 mAh / g, with an initial efficiency of 90.9%; the discharge voltage was 3.66 V. Figure 9 As shown, under 0.5C cycling, the specific capacity is 142.3 mAh / g in the first cycle, and after 70 cycles, the specific capacity is 172 mAh / g, with an energy density as high as 572 Wh / kg. This achieves the design goals of high capacity and high specific energy under low lithium conditions.

[0071] Example 7

[0072] High-capacity, low-lithium lithium-ion cathode material Li 0.5 Na 0.4 Ni 0.25 Mn 0.75 Preparation of O2: Ni was synthesized according to the synthesis method of Example 1. 0.25Mn 0.75 (OH)2, then mixed with lithium carbonate in stoichiometric ratio, and sodium carbonate in 30% excess of stoichiometric ratio, and sintered. The synthesis method is the same as Example 1. The sintering is performed by temperature programming: the temperature is raised to 850°C at a rate of 5°C / min, and kept for 12 hours; then naturally cooled, crushed and sieved to obtain the product.

[0073] As Figure 7 As shown in Table 1, the first discharge capacity of the material is 134.8 mAh / g, much higher than the capacity of Comparative Example 2, Li 0.5 Ni 0.25 Mn 0.75 The capacity of the O2 component is only 72.2 mAh / g, as shown in Table 1. Figure 8 As shown in Table 1, the first efficiency is 70.93%; the discharge voltage is 3.65 V.

[0074] Example 8

[0075] The precursors and raw materials are weighed according to stoichiometric ratio, and Li 0.6 Na 0.3 Ni 0.25 Mn 0.75 O2 is synthesized. The sintering is performed by temperature programming: the temperature is raised to 800°C at a rate of 5°C / min, and kept for 15 hours; then naturally cooled, crushed and sieved to obtain the product.

[0076] As Figure 7 As shown in Table 1, the first discharge capacity of the material is 160.9 mAh / g, and the first efficiency is 86.68%; the discharge voltage is 3.65 V.

[0077] Example 9

[0078] The precursors and raw materials are weighed according to stoichiometric ratio, and Li 0.7 Na 0.3 Ni 0.25 Mn 0.75 O2 is synthesized. The sintering is performed by temperature programming: the temperature is raised to 900°C at a rate of 5°C / min, and kept for 20 hours; then naturally cooled, crushed and sieved to obtain the product.

[0079] As Figure 7 As shown in Table 1, the first discharge capacity of the material is 180.1 mAh / g, and the first efficiency is 83.97%; the discharge voltage is 3.62 V.

[0080] Example 10

[0081] The precursors and raw materials are weighed according to stoichiometric ratio, and Li 0.8 Na 0.4 Ni 0.25 Mn 0.75O2. The sintering was performed by temperature programming: the temperature was raised to 850°C at a rate of 3°C / min, and the temperature was kept for 15 h; the product was obtained by natural cooling, crushing and sieving.

[0082] As shown in Table 1, the first discharge of the material was 182.1 mAh / g, the first efficiency was 84.53%, and the discharge voltage was 3.69 V.

[0083] Example 11

[0084] High-capacity low-lithium lithium-ion positive electrode material Li 0.5 Na 0.4 Ni 0.1 Mn 0.9 O2. The sintering was performed by temperature programming: the temperature was raised to 850°C at a rate of 3°C / min, and the temperature was kept for 15 h; the product was obtained by natural cooling, crushing and sieving. 0.1 Mn 0.9 (OH)2, and then lithium carbonate was mixed in a stoichiometric ratio, and sodium carbonate was mixed in an excess of 30% based on the stoichiometric ratio. The synthesis method was the same as that of Example 1. The sintering was performed by temperature programming: the temperature was raised to 850°C at a rate of 5°C / min, and the temperature was kept for 12 h; the product was obtained by natural cooling, crushing and sieving.

[0085] As shown in Table 1, the first discharge of the material was 182.1 mAh / g, the first efficiency was 84.53%, and the discharge voltage was 3.69 V.

[0086] Example 12

[0087] The same as Example 11, the precursors and raw materials were weighed in a stoichiometric ratio to prepare Li 0.6 Na 0.4 Ni 0.1 Mn 0.9 O2.

[0088] As shown in Table 1, the first discharge of the material was 182.1 mAh / g, the first efficiency was 84.53%, and the discharge voltage was 3.69 V.

[0089] Example 13

[0090] The same as Example 11, the precursors and raw materials were weighed in a stoichiometric ratio to prepare Li 0.7 Na 0.3 Ni 0.1 Mn 0.9 O2.

[0091] As shown in Table 1, the first discharge of the material was 182.1 mAh / g, the first efficiency was 84.53%, and the discharge voltage was 3.69 V.

[0092] Example 14

[0093] The same as Example 11, the precursors and raw materials were weighed in a stoichiometric ratio to prepare Li0.8 Na 0.2 Ni 0.1 Mn 0.9 O2.

[0094] As shown in Table 1, the first discharge of the material is 161.4 mAh / g, the first efficiency is 76.78%, and the discharge voltage is 3.66 V.

[0095] Example 15

[0096] High-capacity low-lithium lithium-ion positive electrode material Li 0.6 Na 0.3 Ni 0.4 Mn 0.6 O2is prepared according to the synthesis method of Example 1. The synthesis method is the same as Example 1. The sintering is carried out in a programmed temperature mode: the temperature is raised to 850°C at a rate of 5°C / min, and the temperature is maintained for 12 h; the temperature is naturally lowered, the product is crushed and sieved. 0.4 Mn 0.6 (OH)2, and then mixed and sintered with lithium carbonate and sodium carbonate. The synthesis method is the same as Example 1. The sintering is carried out in a programmed temperature mode: the temperature is raised to 850°C at a rate of 5°C / min, and the temperature is maintained for 12 h; the temperature is naturally lowered, the product is crushed and sieved.

[0097] As shown in Table 1, the first discharge of the material is 169 mAh / g, the first efficiency is 74.98%, and the discharge voltage is 3.65 V.

[0098] Comparative Example 1

[0099] The stoichiometric ratio of Li 0.3 Ni 0.2 Mn 0.8 O2, the precursor Ni 0.2 Mn 0.8 (OH)2, and then mixed and sintered with lithium carbonate and sodium carbonate. The synthesis method is the same as Example 1. The sintering is carried out in a programmed temperature mode: the temperature is raised to 850°C at a rate of 5°C / min, and the temperature is maintained for 12 h; the temperature is naturally lowered, the product is crushed and sieved.

[0100] Comparative Example 2

[0101] The stoichiometric ratio of Li 0.5 Ni 0.25 Mn 0.75 O2, the precursor Ni 0.25 Mn 0.75 (OH)2, and then mixed and sintered with lithium carbonate and sodium carbonate. The synthesis method is the same as Example 1. The sintering is carried out in a programmed temperature mode: the temperature is raised to 850°C at a rate of 5°C / min, and the temperature is maintained for 12 h; the temperature is naturally lowered, the product is crushed and sieved.

[0102] Table 1: First charge-discharge capacity, first efficiency and discharge voltage of the examples and comparative examples

[0103]

[0104] The above embodiments are only used to illustrate the technical solutions of the present application, but not limit the present application. Although the present application is described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced equivalently without departing from the spirit and essence of the present application defined in the claims of the present application.

Claims

1. A lithium-poor, high-capacity manganese-based cathode material, characterized in that, The molecular formula of the lithium-poor high-capacity manganese-based cathode material is Li. x Na y Mn a M 1-a O2, where M is one or more combinations of Mg, Zn, Ni, W, Co, Al, Zr, Cu, Ti and Fe, 0.3≤x≤0.8, 0.2≤y≤0.5, and 0.5<x+y≤1.2, 0.5<a≤1; The crystal structure of the lithium-poor high-capacity manganese-based cathode material is a composite of a ternary layered phase, a sodium-containing P2 phase, and a LiMn6 phase, with the LiMn6 phase dispersed in the ternary layered phase and the P2 phase.

2. The lithium-poor, high-capacity manganese-based cathode material according to claim 1, characterized in that, The middle phase is a sodium-containing P2 phase, and the two sides are ternary layered phases, forming a sandwich structure.

3. The lithium-poor, high-capacity manganese-based cathode material according to claim 1, characterized in that, The space group corresponding to the ternary layered structure is R3m, the space group corresponding to the sodium-containing P2 structure is P63 / mmc, and the space group corresponding to LiMn6 is C / 2m.

4. A method for preparing a lithium-poor, high-capacity manganese-based cathode material according to any one of claims 1-3, characterized in that, Includes the following steps: Manganese-based precursors and lithium salts are mixed in stoichiometric ratios, and sodium salts are added in excess of 20-50% in stoichiometric ratios. The mixture is then sintered in air, cooled, and sieved to obtain lithium-poor high-capacity manganese-based cathode materials.

5. The preparation method according to claim 4, characterized in that, The manganese-based precursor includes the hydroxide precursor Mn. a M 1-a (OH)2, carbonate precursor Mn a M 1-a CO3, oxalate precursor Mn a M 1-a One of (COO)2, 0.5 < a ≤ 1.

6. The preparation method according to claim 4, characterized in that, The lithium salt is selected from one or more of lithium carbonate, nitrate, lithium acetate, and lithium hydroxide; The sodium salt is selected from one or more of sodium carbonate, sodium bicarbonate, sodium acetate, and sodium sulfate.

7. The preparation method according to claim 4, characterized in that, The sintering heating rate is 2-10℃ / min, the sintering temperature is 700-950℃, and the holding time is 8-20h.

8. The application of a lithium-poor high-capacity manganese-based cathode material according to any one of claims 1-3 or a lithium-poor high-capacity manganese-based cathode material prepared by the preparation method according to any one of claims 4-7 in the preparation of cathode sheets and lithium-ion batteries.

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