Lithium-poor high-capacity manganese-based positive electrode material as well as preparation method and application thereof

Abstract

The invention provides a lithium-poor high-capacity manganese-based positive electrode material as well as a preparation method and application thereof, and relates to the technical field of preparation of battery positive electrode materials. The molecular formula of the lithium-poor high-capacity manganese-based positive electrode material is LixNayMnaM1-aO2, M is one or a combination of more of Mg, Zn, Ni, W, Co, Al, Zr, Cu, Ti and Fe, x is more than or equal to 0.3 and less than or equal to 0.8, y is more than or equal to 0.2 and less than or equal to 0.5, x + y is more than 0.5 and less than or equal to 1.2, and a is more than 0.5 and less than or equal to 1; the crystal structure is formed by compounding a lithium-containing ternary layered phase, a sodium-containing P2 phase and a LiMn6 phase. The lithium ion battery has the characteristics of ultra-low lithium removal capability, ultra-strong reversibility, high specific capacity and relatively high discharge voltage.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of cathode materials for batteries, and particularly relates to a lithium-deficient high-capacity manganese-based cathode material, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of new energy technologies, the consumption of lithium resources has also increased sharply, resulting in the price of lithium salts soaring to 600,000 yuan / ton in 2023, which has severely restricted the healthy and sustainable development of the lithium battery industry. Although the lithium price has recently rebounded, it is still very high, resulting in a high proportion of lithium costs in the raw material costs. Therefore, it is particularly important to improve the lithium utilization rate.

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

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

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

[0006] One of the objectives of the present invention is to provide a lithium-deficient and high-capacity manganese-based cathode material.

[0007] Another objective of the present invention is to provide a preparation method for the above-mentioned lithium-deficient and high-capacity manganese-based cathode material.

[0008] A further objective of the present invention is to provide an application of the above-mentioned lithium-deficient and high-capacity manganese-based cathode material.

[0009] In order to achieve the above objectives of the present invention, the following technical solutions are specifically adopted:

[0010] In the first aspect, the present invention provides a lithium-deficient and high-capacity manganese-based cathode material, and the molecular formula of the lithium-deficient and high-capacity manganese-based cathode material is Li x Na y Mn a M 1-a O2, where 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-deficient and 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 corresponding space group of the ternary layered phase is R3m, the corresponding space group of the sodium-containing P2 phase is P63 / mmc, and the corresponding space group of the LiMn6 phase is C / 2m.

[0014] The lithium-ion cathode material of the present invention has the characteristics of rich sodium and low lithium, and has a crystal structure of a composite 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, where the content of each structure can be adjusted, and a three-layer sandwich structure is presented in the c-axis direction. On both sides of the primary particle lamella in the <003> direction is the ternary layered structure phase (R3m), and its interplanar spacing is The crystal structure of the middle region is a sodium-containing P2 phase, and its interplanar spacing is relatively large, which is

[0015] In the second aspect, the present invention provides a preparation method for the above-mentioned lithium-deficient and high-capacity manganese-based cathode material, including the following steps:

[0016] Mix a manganese-based precursor and a lithium salt in a stoichiometric ratio, and mix the sodium salt in an amount 20-50% in excess of the stoichiometric ratio, then sinter in air, cool down, and screen to obtain a lithium-poor and high-capacity manganese-based cathode 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, where 0.5 < a ≤ 1, and M is one or a combination of Mg, Zn, Ni, W, Co, Al, Zr, Cu, Ti, and Fe.

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

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

[0020] In some embodiments, the heating rate of sintering is 2-10 °C / min, the sintering temperature is 700-950 °C, and the heat preservation time is 8-20 h.

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

[0022] (1) Dissolve nickel sulfate and manganese sulfate in a 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, and the complexing agent is ammonia water with an ammonia water concentration of 0.6 mol / L; the stirring speed is 400-600 r / min. Control the temperature of the reaction kettle at 50 °C. After reacting for an appropriate time, age for 24 h, filter, wash, and dry to obtain the hydroxide precursor of the transition metal;

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

[0024] (3) Perform heat treatment in air: heat up to 700-950 °C at a heating rate of 5 °C / min, keep warm for 8-20 h, cool down naturally, and screen to obtain.

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

[0026] The form of the battery is not limited and can be cylindrical, soft-pack, square, half-knife, and diamond-shaped batteries, etc.

[0027] Advantageous effects:

[0028] (1) Through the component design strategy of rich sodium and low lithium and the phase structure optimization, the present invention obtains a cathode material with low lithium, rich sodium, and high manganese. The rich sodium design ensures that it is still a layered phase structure under low lithium conditions, guaranteeing the 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, stacked in the c-axis direction. The middle layer is the P2 phase, and the upper and lower layers are the ternary layered phase, presenting a "sandwich" structure in the c-axis direction. The components with a specific molecular formula composition designed by the present invention can prepare a cathode material with a special crystal structure.

[0029] (2) The present invention obtains a lithium-poor and manganese-rich cathode material with high capacity and high specific energy characteristics under extremely lithium-poor and high manganese conditions.

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

[0031] The present invention has been described in detail above, but the above embodiments are essentially illustrative only and are not intended to limit the present invention. In addition, the present invention is not limited by any theory described in the foregoing prior art, invention content, or the following examples. Description of the drawings

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

[0033] Figure 2 XRD patterns of the cathode materials of Examples 1-6;

[0034] Figure 3 SEM images of Examples 6 and 7, the left figure is Example 6, and the right figure is Example 7;

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

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

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

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

[0039] Figure 8First charge-discharge curves of Comparative Examples 1-2;

[0040] Figure 9 Cycling performance of Example 6 at 0.5C. Detailed implementation manners

[0041] The present invention will be further described below in conjunction with embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of protection required by the present invention.

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

[0043] Electrochemical performance evaluation: A 2032 coin cell was used for evaluation. The test was carried out on a Blue Energy battery test system. The charge-discharge current was set to 1C = 150 mAh / g, and the voltage window was 2.0 - 4.8V.

[0044] Example 1

[0045] Preparation of high-capacity low-lithium type lithium-ion cathode material Li 0.3 Na 0.5 Ni 0.2 Mn 0.8 O2:

[0046] In stoichiometric ratio, first use the hydroxide co-precipitation method to prepare Ni 0.2 Mn 0.8 (OH)2, and then mix and sinter with lithium carbonate and sodium carbonate. Specifically, it includes:

[0047] Dissolve nickel sulfate and manganese sulfate in deionized water according to stoichiometric ratio to prepare a solution with a metal concentration of 2 mol / L. The precipitant is sodium hydroxide with a concentration of 2 mol / L, and the complexing agent is ammonia water with a concentration of 0.6 mol / L; the stirring speed is 400 - 600 r / min. Control the temperature of the reaction kettle at 50°C. After the reaction for an appropriate time, age for 24 h, filter, wash, and dry to obtain the transition metal hydroxide precursor Ni 0.2 Mn 0.8 (OH)2.

[0048] Then add lithium carbonate and sodium carbonate according to the chemical ratio (sodium carbonate is added in an amount 30% in excess based on the stoichiometry) and mix mechanically. The sintering regime is as follows: heat up to 850°C at a heating rate of 5 / min, hold for 12 h, cool naturally, and sieve to obtain the product.

[0049] The phase distribution is determined by TEM characterization, as Figure 1As shown, a three-layer sandwich structure is presented in the c-axis direction, i.e., a "sandwich" structure. On both sides of the primary particle lamella in the <003> direction are lamellar phases, and the crystal structure in the middle region is a sodium-containing P2 phase. The phase structure of the material is determined by XRD. As Figure 2 shown, by comparing with the standard spectrum, the crystal structure of this cathode material is composed of a lithium-containing ternary lamellar phase, a sodium-containing P2 phase, and LiMn6, and the corresponding space groups are R3m, P63 / mmc, and C / 2m.

[0050] As Figure 4 and Table 1 show, the first discharge capacity of the material is 146.8 mAh / g, which is much higher than that of Comparative Example 1. The capacity of the Li 0.3 Ni 0.2 Mn 0.8 O2 component is only 16.4 mAh / g. As Figure 8 shown, the first efficiency is 74.25%; the discharge midpoint voltage is 3.71 V. As Figure 5 shown, it has rich redox potentials, with reduction potentials of 4.3 V, 3.9 V, 3.73 V, and 2.6 V.

[0051] Example 2

[0052] Preparation of high-capacity low-lithium type lithium-ion cathode material Li 0.35 Na 0.4 Ni 0.2 Mn 0.8 O2: The synthesis method is the same as that of Example 1. Adjust the lithium and sodium contents to Li 0.35 Na 0.4 , and sodium carbonate is in excess by 30% on a stoichiometric basis. Sintering is carried out by means of programmed temperature rise: the heating rate is 5 °C / min to rise to 850 °C, and keep warm for 12 h; then cool naturally, crush, and sieve to obtain the product.

[0053] Figure 2 As shown by its XRD, the crystal structure of this cathode material is composed of a lithium-containing ternary lamellar phase, a sodium-containing P2 phase, and LiMn6, and the corresponding space groups are R3m, P63 / mmc, and C / 2m.

[0054] As Figure 4 and Table 1 show, the first discharge capacity of the material is 143.4 mAh / g, the first efficiency is 77.31%; the discharge midpoint voltage is 3.64 V.

[0055] Example 3

[0056] High-capacity low-lithium type lithium-ion cathode material Li 0.4 Na 0.4 Ni 0.2 Mn 0.8Preparation of O2: The synthesis method is the same as that of Example 1, and the lithium content is adjusted to Li 0.4 Na 0.4 , and sodium carbonate is in excess by 30% on a stoichiometric basis. Sintering is carried out by a programmed heating method: heating rate is 5 °C / min to 850 °C, and keep warm for 12 h; then cool naturally, crush and screen to obtain the product.

[0057] The obtained product phases are as Figure 2 shown. The crystal structure of this cathode material is composed 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. As the lithium content increases, the diffraction peak at 18.6° becomes stronger, and the diffraction peak at 16° becomes weaker, indicating that the lithium-containing O3 layered phase increases with the increase of lithium content, and the sodium-containing P2 phase decreases.

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

[0059] Example 4

[0060] Preparation of high-capacity low-lithium type lithium-ion cathode material Li 0.45 Na 0.4 Ni 0.2 Mn 0.8 O2: The synthesis method is the same as that of Example 1, and the lithium content is adjusted to Li 0.45 Na 0.4 , and sodium carbonate is in excess by 30% on a stoichiometric basis. Sintering is carried out by a programmed heating method: heating rate is 5 °C / min to 850 °C, and keep warm for 12 h; then cool naturally, crush and screen to obtain the product.

[0061] The obtained product phases are as Figure 2 shown. The crystal structure of this cathode material is composed 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] As Figure 4 and Table 1 show, the first discharge of the material is 136.1 mAh / g, and the first efficiency is 79.26%; the discharge medium voltage is 3.65 V.

[0063] Example 5

[0064] High-capacity low-lithium type 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 that of Example 1. Sintering is carried out by a programmed temperature rise method: the heating rate is 5 °C / min to 850 °C, and it is kept warm for 12 h; then it is cooled naturally, pulverized and sieved to obtain the product.

[0065] The obtained phases are as Figure 2 shown. The crystal structure of this cathode material is composed 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] As Figure 6 and Table 1 show, the first discharge of the material is 194.2 mAh / g, and the first efficiency is 70.25%; the discharge medium voltage is 3.63 V.

[0067] Example 6

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

[0069] The obtained phases are as Figure 2 shown. The crystal structure of this cathode material is composed 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 morphological structure is characterized by SEM. As Figure 3 shown, the particle morphology of Example 6 is nearly spherical, and D50 is 8 μm.

[0070] As Figure 6 and Table 1 show, the first discharge of the material is 175.4 mAh / g, and the first efficiency is 90.9%; the discharge medium voltage is 3.66 V. As Figure 9 shown, under 0.5C cycling, the first week is 142.3 mAh / g, and when the cycle reaches 70 weeks, the specific capacity is 172 mAh / g, and the energy density is as high as 572 wh / kg. The design goal of high capacity and high specific energy is achieved under low-lithium conditions.

[0071] Example 7

[0072] High-capacity low-lithium type lithium-ion cathode material Li 0.5 Na 0.4 Ni 0.25 Mn 0.75 O2 preparation: Synthesize Ni according to the synthesis method of Example 1 0.25Mn 0.75 (OH)2, and then mix and sinter with lithium carbonate in a stoichiometric ratio. Sodium carbonate is mixed and sintered with an excess of 30% on a stoichiometric basis. The synthesis method is the same as that of Example 1. Sintering is carried out by a programmed heating method: the heating rate is 5 °C / min to 850 °C, and the temperature is kept for 12 h; then it is cooled naturally, crushed and sieved to obtain the product.

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

[0074] Example 8

[0075] Same as Example 7, weigh the precursor and raw materials according to the stoichiometric ratio to synthesize Li 0.6 Na 0.3 Ni 0.25 Mn 0.75 O2. Sintering is carried out by a programmed heating method: the heating rate is 5 °C / min to 800 °C, and the temperature is kept for 15 h; then it is cooled naturally, crushed and sieved to obtain the product.

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

[0077] Example 9

[0078] Same as Example 7, weigh the precursor and raw materials according to the stoichiometric ratio to synthesize Li 0.7 Na 0.3 Ni 0.25 Mn 0.75 O2. Sintering is carried out by a programmed heating method: the heating rate is 5 °C / min to 900 °C, and the temperature is kept for 20 h; then it is cooled naturally, crushed and sieved to obtain the product.

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

[0080] Example 10

[0081] Same as Example 7, weigh the precursor and raw materials according to the stoichiometric ratio to synthesize Li 0.8 Na 0.4 Ni 0.25 Mn 0.75O2. Sintering is carried out by means of programmed heating: heating rate is 3 °C / min to 850 °C, holding for 15 h; natural cooling, pulverizing and sieving to obtain the product.

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

[0083] Example 11

[0084] High-capacity low-lithium type lithium-ion cathode material Li 0.5 Na 0.4 Ni 0.1 Mn 0.9 Preparation of O2: Synthesize Ni 0.1 Mn 0.9 (OH)2 according to the synthesis method of Example 1, and then mix and sinter lithium carbonate in stoichiometric ratio, and sodium carbonate is mixed and sintered with an excess of 30% on the stoichiometric basis. The synthesis method is the same as that of Example 1. Sintering is carried out by means of programmed heating: heating rate is 5 °C / min to 850 °C, holding for 12 h; natural cooling, pulverizing and sieving to obtain the product.

[0085] As shown in Table 1, the first discharge of the material is 164.7 mAh / g, the first efficiency is 81.8%; the discharge medium voltage is 3.65 V.

[0086] Example 12

[0087] Same as Example 11, weigh the precursor and raw materials according to the 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 is 175.9 mAh / g, the first efficiency is 97.83%; the discharge medium voltage is 3.56 V.

[0089] Example 13

[0090] Same as Example 11, weigh the precursor and raw materials according to the 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 is 172.2 mAh / g, the first efficiency is 75.29%; the discharge medium voltage is 3.64 V.

[0092] Example 14

[0093] Same as Example 11, weigh the precursor and raw materials according to the 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 capacity of the material is 161.4 mAh / g, the first efficiency is 76.78%; the average discharge voltage is 3.66 V.

[0095] Example 15

[0096] Preparation of high-capacity and low-lithium-type lithium-ion cathode material Li 0.6 Na 0.3 Ni 0.4 Mn 0.6 O2: Synthesize Ni 0.4 Mn 0.6 (OH)2 according to the synthesis method of Example 1, and then mix and sinter with lithium carbonate and sodium carbonate. The synthesis method is the same as that of Example 1. Sintering is carried out by a programmed temperature rise method: the heating rate is 5 °C / min to 850 °C, and keep the temperature for 12 h; cool naturally, pulverize and sieve to obtain the product.

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

[0098] Comparative Example 1

[0099] With 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 mix and sinter with lithium carbonate in a stoichiometric ratio. The sintering process is the same as that of Example 1.

[0100] Comparative Example 2

[0101] With 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 only mix and sinter with lithium carbonate acid. The sintering process is the same as that of Example 7.

[0102] Table 1 First charge and discharge capacities, first efficiencies and average discharge voltages of examples and comparative examples

[0103]

[0104] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the same. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: without departing from the spirit and essence defined by the claims of the present invention, the technical solutions described in the foregoing embodiments may be modified, or some or all of the technical features may be equivalently replaced; and such modifications or replacements are still within the scope defined by the claims of the present invention.

Claims

1. A lithium-poor high-capacity manganese-based positive electrode material, characterized in that: The molecular formula of the lithium-poor high-capacity manganese-based positive electrode material is Li x Na y Mn a M 1-a O2, wherein M is one or more 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 positive electrode material is a composite of a ternary layered phase, a sodium-containing P2 phase and a LiMn6 phase, wherein the LiMn6 phase is dispersed in the ternary layered phase and the P2 phase.

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

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

4. A method for preparing the lithium-deficient high-capacity manganese-based positive electrode material according to any one of claims 1 to 3, characterized in that: The following steps are involved: A manganese-based precursor and a lithium salt are mixed in a stoichiometric ratio, and a sodium salt is mixed in an excess of 20-50% in a stoichiometric ratio, and then sintered in air, cooled, and sieved to obtain a lithium-poor high-capacity manganese-based positive electrode material.

5. The preparation method according to claim 4, characterized in that: The manganese-based precursor includes a 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 one or more selected from lithium carbonate, nitrate, lithium acetate and lithium hydroxide; The sodium salt is one or more selected from 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°C / min, the sintering temperature is 700-950°C, and the holding time is 8-20h.

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

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