A cathode material, its preparation method and application

Abstract

The present invention provides a cathode material, a preparation method thereof and an application. The chemical formula of the cathode material is xLi2MnO3·(1−x−y)LiNi a T M(1‑a) O2·yLiMn b A (1‑b) PO4, wherein 0 < x < 1, 0 < y < 1, 0 ≤ a ≤ 1, 0.5 ≤ b ≤ 1, T M and A each independently include a metal element; the cathode material can form a continuous phase transition, has a supercrystalline domain structure and a stable layered structure, can stabilize lattice oxygen, reduce voltage drop, and thus can significantly improve the cycling performance of the battery at high voltages.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries and relates to a positive electrode material and a preparation method and application thereof. Background Art

[0002] Manganese-based positive electrode materials for lithium batteries include lithium manganate LiMnO2, spinel lithium manganate LiNi 0.5 Mn 1.5 O4 and lithium-rich manganese-based Li[Li 1 / 3 Mn 2 / 3 ]O2, etc. Among them, lithium-rich manganese-based cathode materials have attracted widespread attention due to their high capacity. However, these cathode materials require a voltage above 4.4V to achieve their high capacity, and suffer from problems such as lattice oxygen precipitation and large voltage drop. As a result, the cycling performance is poor, and the cycling performance is further deteriorated at high temperatures. Conventional element doping schemes in existing technologies have made it difficult to effectively modify lithium-rich manganese-based materials, unable to reduce voltage drop and stabilize lattice oxygen.

[0003] For example, CN 112701273A discloses a method for preparing a fluorine-doped lithium-rich manganese-based cathode material, wherein the lithium-rich manganese-based cathode material has the general chemical formula: xLi2MnO3·(1-x)LiMO 2-y F 2y , wherein 0.1≤x≤0.9, 0<y≤0.05, and M is one or more of Ni, Co, Mn, Cr, Fe, Ti, Mo, Ru, V, Nb, Zr and Sn; the preparation method comprises the steps of: using a soluble metal salt, a precipitant, a soluble fluorine-containing compound and water to prepare a fluorine-doped lithium-rich manganese-based precursor by a precipitation reaction; uniformly mixing the fluorine-doped lithium-rich manganese-based precursor with a lithium salt, and obtaining a fluorine-doped lithium-rich manganese-based positive electrode material through pre-sintering and high-temperature sintering; it uses a soluble fluorine-containing compound as a fluorine source to simultaneously achieve fluorine doping during the co-precipitation of the lithium-rich manganese-based precursor, and the cycle performance of the lithium-rich material after doping is improved, but it cannot solve the problems of lattice oxygen precipitation and large voltage drop of the lithium-rich manganese-based material.

[0004] Based on the above research, it is necessary to provide a positive electrode material that can stabilize lattice oxygen, has a stable layered structure, reduces voltage drop, and improves the cycle stability of lithium-rich manganese-based materials at high voltage. Summary of the Invention

[0005] The purpose of the present invention is to provide a positive electrode material and its preparation method and application, in particular to provide a super-lithiated manganese-based positive electrode material and its preparation method and application, wherein the positive electrode material can form a continuous phase transition, has a supercrystalline domain structure and a stable layered structure, can stabilize lattice oxygen, reduce voltage drop, and significantly improve the cycle performance of the positive electrode material under high voltage.

[0006] To achieve the object of the present invention, the following technical solutions are adopted in the present invention:

[0007] In a first aspect, the present invention provides a cathode material, and the chemical formula of the cathode material is xLi2MnO3·(1 - x - y)LiNi a T M(1-a) O2·yLiMn b A (1-b) PO4, wherein, 0 < x < 1, 0 < y < 1, 0 ≤ a ≤ 1, 0.5 ≤ b ≤ 1, and T M and A each independently include a metal element.

[0008] The cathode material of the present invention is a solid solution material. Since the lithium-rich manganese-based material is composed of a Li2MnO3 phase and a LiNi a T M(1-a) O2 phase, the lattice oxygen mainly comes from the Li2MnO3 phase. Among them, the precipitation of lattice oxygen is caused by the instability of lattice oxygen under high voltage and high delithiation state on the one hand, and on the other hand, due to the different phase transition points of the two phases, the lattice distortion is large, which further causes the instability of lattice oxygen, resulting in the precipitation of lattice oxygen during long-term cycling. Therefore, the present invention introduces a third lithium compound LiMn b A (1-b) PO4 into the lithium-rich manganese-based material to form a super-lithiated manganese-based cathode material. This lithium compound and the Li2MnO3 phase as well as the LiNi a T M(1-a) O2 phase can form a supercrystal domain structure. During the charge and discharge process, when the voltage is between 3.8 and 4.4 V, LiMn b A (1-b) PO4 completes the phase transition, enabling the Li2MnO3 phase and the LiNi a T M(1-a) O2 phase to form a continuous phase transition, thereby stabilizing the lattice oxygen, stabilizing the layered structure, reducing the voltage drop, and improving the cycling stability of the manganese-based material at high voltage.

[0009] The 0 < x < 1 can be, for example, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 0.95, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0010] The 0 < y < 1 can be, for example, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 0.95, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable, and preferably 0 < y ≤ 0.3.

[0011] The LiMn of the present invention bA (1-b) The proportion of PO4 not only affects the stability of lattice oxygen and lattice distortion, but also affects the overall capacity of the material.

[0012] The 0≤a≤1 can be, for example, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, and 0.5≤b≤1 can be, for example, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0013] Preferably, the T M The present invention includes any one or a combination of at least two of Mn, Ni, Co, Al, Ti, W, Nb, Zr, Y, Sr or Fe. Typical but non-limiting combinations include a combination of Mn and Ni, or a combination of Co and Al.

[0014] Preferably, A includes any one or a combination of at least two of Ni, V, Mg, Al, Nb, Zr, Cr, Si, Zn, Ti, Co or Fe. Typical but non-limiting combinations include a combination of Ni and V, and a combination of Mg and Al.

[0015] In a second aspect, the present invention provides a method for preparing the positive electrode material according to the first aspect, the preparation method comprising the following steps:

[0016] (1) Lithium source, LiNi a T M(1-a) O2 precursor and LiMn b A (1-b) PO4 is mixed and dried to obtain raw powder of positive electrode material;

[0017] (2) Sintering the raw powder of the positive electrode material in step (1) to obtain the positive electrode material.

[0018] The positive electrode material obtained by the present invention is composed of lithium source, LiNi a T M(1-a) O2 precursor and LiMn b A (1-b) PO4 is used as raw material to form a solid solution material with uniform distribution of different phases and a microscopic super-domain structure.

[0019] Preferably, the LiMn b A (1-b) PO4 in the form of sol-gel solution with lithium source and LiNi a T M(1-a) O2 precursor is mixed.

[0020] When preparing the positive electrode material of the present invention, the lithium source and LiNi a T M(1-a) O2 precursor and LiMn b A (1-b) PO4 sol-gel solution is mixed, and sol-gel state LiMn b A (1-b) On the one hand, PO4 is conducive to the formation of LiMn b Ni (1-b) PO4 nanopowder, on the other hand, can be mixed evenly with the precursor and lithium source, which helps the sintering process of LiMn b Ni (1-b) PO4 forms a microscopic super-domain structure with other phases.

[0021] Preferably, the LiMn b A (1-b) The sol-gel solution of PO4 was prepared by the following method:

[0022] The lithium source, manganese source, phosphorus source, A metal source and solvent are mixed according to the formula, and then acid and chelating agent are added and stirred to obtain the LiMn b A (1-b) Sol-gel solution of PO4.

[0023] Preferably, the concentration of the mixed solution obtained by mixing the lithium source, manganese source, phosphorus source, element A source and solvent according to the formula amount is 0.1-1 mol / L, for example, it can be 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.7 mol / L, 0.9 mol / L or 1 mol / L, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0024] Preferably, the concentration of the acid is 0.1-1 mol / L, for example, 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.7 mol / L, 0.9 mol / L or 1 mol / L, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0025] Preferably, the acid comprises any one of citric acid, salicylic acid, oxalic acid or EDTA (ethylenediaminetetraacetic acid) or a combination of at least two thereof, and a typical but non-limiting combination comprises a combination of citric acid and salicylic acid.

[0026] Preferably, the concentration of the chelating agent is 1-2 mol / L, for example, 1 mol / L, 1.5 mol / L or 2 mol / L, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0027] Preferably, the chelating agent comprises polyethylene glycol.

[0028] Preferably, the stirring temperature is 25-50°C, for example, 25°C, 30°C, 40°C or 50°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0029] Preferably, the drying method in step (1) is spray drying.

[0030] The present invention adopts the spray drying method. On the one hand, it can form a precursor with a higher specific surface area by spray granulation, and on the other hand, it can evenly mix the lithium source and the precursor, thereby synthesizing Li2MnO3 phase and LiT M Superlithiated manganese-based materials with more uniform O2 phase distribution.

[0031] Preferably, the spray drying temperature is 100-300°C, for example, 100°C, 150°C, 200°C, 250°C or 300°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0032] Since the spray drying time is related to the size of the equipment, the present invention does not impose a specific limitation on the spray drying time, but is preferably within 30 seconds to 2 minutes, for example, 30 seconds, 1 minute, or 2 minutes, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0033] Preferably, in the mixture obtained by mixing in step (1), lithium ions and T M The molar ratio of the ions is (1.20-1.36):1, for example, 1.20:1, 1.3:1 or 1.36:1, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0034] Preferably, in the mixture obtained by mixing in step (1), LiMn b A (1-b) The molar percentage of PO4 is 0.01-30%, for example, it can be 0.2%, 1%, 5%, 10%, 15%, 20%, 25% or 30%, but is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0035] Preferably, the particle size D50 of the mixture mixed in step (1) is 0.2-1.5 μm, for example, 0.2 μm, 0.5 μm, 1.0 μm or 1.5 μm, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0036] Preferably, the mixing method includes ball milling.

[0037] Before spray drying in the present invention, the mixture is first ball-milled to a particle size between 0.2 - 1.5 μm, and then spray drying is carried out. The two materials can be evenly mixed, which helps to form a composite phase during the subsequent sintering process. If the particle size is too small, during the spraying process, more particles are lost, the yield of raw powder is reduced, and the production efficiency is affected. If the particle size is further smaller, the obtained particles are difficult to sinter and are prone to abnormal growth, resulting in uneven composition. If the particle size is too large, the two materials are difficult to form a good uniform mixture, which causes segregation of the other material and is not conducive to the formation of the supercrystalline domain structure.

[0038] Preferably, the precursor of LiNi a T M(1-a) O2 includes Ni a Mn (1-a) (OH)2 and is prepared by the following method:

[0039] Mix the precipitant, complexing agent, and Ni and / or T M metal source to obtain a reaction solution. After the reaction solution reacts, the precursor of LiNi a T M(1-a) O2 is obtained.

[0040] Preferably, the pH of the reaction solution is 7 - 12. For example, it can be 7, 8, 9, 10, 11, or 12, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0041] Preferably, in the reaction solution, the concentration of the complex ion is 0.1 - 1 mol / L. For example, it can be 0.1 mol / L, 0.5 mol / L, or 1 mol / L, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0042] Preferably, the temperature of the reaction is 40 - 60 °C. For example, it can be 40 °C, 50 °C, or 60 °C, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0043] Preferably, the reaction continues until the particle size of the precursor is 3 - 10 μm. For example, it can be 3 μm, 5 μm, 7 μm, 9 μm, or 10 μm, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0044] Preferably, the concentration of the complexing agent is 0.1 - 1 mol / L. For example, it can be 0.1 mol / L, 0.5 mol / L, or 1 mol / L, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable, including NH4OH.

[0045] Preferably, the concentration of the precipitant is 0.1-2 mol / L, for example, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L or 2 mol / L, but is not limited to the listed values. Other values not listed within the numerical range are also applicable, including sodium hydroxide.

[0046] Preferably, the precipitant, complexing agent and Ni and / or T M The three raw materials of metal source are in solution form and flow into the reactor to react. The Ni and / or T M In the metal source, the concentration of the metal source is 0.1-2 mol / L, for example, it can be 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L or 2 mol / L, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0047] Preferably, the sintering temperature in step (2) is 800-1000°C, for example, 800°C, 900°C or 1000°C, and the sintering time is 24-48h, for example, 24h, 36h or 48h, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0048] Preferably, the sintering in step (2) is followed by pulverization and demagnetization screening.

[0049] Preferably, the particle size D50 of the positive electrode material in step (2) is 2-5 μm, for example, it can be 2 μm, 3 μm, 4 μm or 5 μm, and the size of the primary particles is between 0.4-2 μm, which means that the minimum size of the primary particles is above 0.4 μm, for example, it can be 0.4 μm, 0.5 μm, 0.4 μm, and the maximum size of the primary particles is below 5 μm, for example, it can be 5 μm, 4.5 μm or 4 μm, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0050] The lithium source of the present invention includes lithium carbonate and / or lithium nitrate, the phosphorus source includes but is not limited to ammonium hydrogen phosphate, and the manganese source includes but is not limited to manganese nitrate.

[0051] As a preferred technical solution of the preparation method of the present invention, the preparation method comprises the following steps:

[0052] (1) LiMn b A (1-b) PO4 sol-gel solution, LiNi a T M(1-a)The precursor of O2 and the lithium source are ball-milled and mixed until the particle size of the mixture is 0.2-1.5 μm, and then spray-dried at 100-300 ° C to obtain the raw powder of the positive electrode material, wherein the lithium ions and T M The molar ratio of ions is (1.20-1.36):1, LiMn b A (1-b) The molar percentage of PO4 is 0.01-30%;

[0053] The LiNi a T M(1-a) The precursor of O2 is Ni a Mn (1-a) (OH)2, the LiMn b A (1-b) The sol-gel solution of PO4 was prepared by the following method:

[0054] The lithium source, manganese source, phosphorus source, A metal source and solvent are mixed according to the formula to obtain a mixed solution with a concentration of 0.1-1 mol / L, and then an acid and a chelating agent are added and stirred to obtain the LiMn b A (1-b) Sol-gel solution of PO4;

[0055] (2) The raw powder of the positive electrode material in step (1) is sintered at 800-1000° C., and then crushed, demagnetized, and sieved to obtain the positive electrode material having a particle size D50 of 2-5 μm and a primary particle size distribution of 0.4-2 μm.

[0056] In a third aspect, the present invention provides a lithium-ion battery, comprising the positive electrode material as described in the first aspect.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] The present invention introduces a third lithium compound into the lithium-rich manganese-based material to form a super-lithiated manganese-based positive electrode material. b A (1-b) PO4 can form a super-domain structure of continuous phase transformation with the two phases in the manganese-based material, thereby stabilizing the Li2MnO3 phase, reducing the precipitation of its lattice O, reducing the voltage drop, and improving the cycle performance under high voltage; at the same time, the present invention adopts a specific preparation method, by adopting a method of combining specific raw materials and spray drying to obtain a solid solution material with three phases evenly distributed, which can not only make the different phases evenly distributed, but also enable the positive electrode material to form a super-domain structure. DETAILED DESCRIPTION

[0059] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0060] Example 1

[0061] This example provides a cathode material, and the chemical formula of the cathode material is 0.2Li2MnO3·0.55LiNi 0.5 Mn 0.5 O2·0.25LiMn 0.7 V 0.3 PO4;

[0062] The preparation method of the cathode material includes the following steps:

[0063] (1) Ball-mill and mix the sol-gel solution of LiMn 0.7 V 0.3 PO4, Li2CO3 and Ni 0.5 Mn 0.5 (OH)2 until the particle size D50 of the mixture is 1.0 μm, and then perform spray drying at 200 °C for 1 min to obtain the raw powder of the cathode material. Among them, in the mixture, the molar ratio of lithium ions to T M ions is 1.3:1, and the molar percentage content of LiMn 0.7 V 0.3 PO4 is 25%;

[0064] The sol-gel solution of LiMn 0.7 V 0.3 PO4 is prepared by the following method:

[0065] Mix LiNO3, vanadium nitrate, Mn(NO3)2, NH4H2PO4 and distilled water according to the formula amount to obtain a mixed solution with a concentration of 0.5 mol / L, and then add citric acid with a concentration of 0.5 mol / L and polyethylene glycol with a concentration of 1.5 mol / L, and stir at 40 °C to obtain the sol-gel solution of LiMn 0.7 V 0.3 PO4;

[0066] The Ni 0.5 Mn 0.5 (OH)2 is prepared by the following method:

[0067] Flow the mixed solution of manganese sulfate and nickel sulfate with a concentration of 1 mol / L, the sodium hydroxide solution with a concentration of 1.2 mol / L and the ammonia water with a concentration of 0.5 mol / L into the reaction kettle, control the pH to 10, and react at 50 °C until Ni with a particle size D50 of 7 μm is obtained0.5 Mn 0.5 (OH)2;

[0068] (2) The raw powder of the positive electrode material in step (1) is sintered at 900° C. for 36 hours, and then crushed, demagnetized, and sieved to obtain the positive electrode material having a particle size D50 of 4 μm and a primary particle size distribution between 0.4 and 2 μm.

[0069] Example 2

[0070] This embodiment provides a positive electrode material having a chemical formula of 0.25Li2MnO3·0.65LiNi 0.5 Mn 0.5 O2·0.1LiMn 0.7 V 0.3 PO4;

[0071] The preparation method of the positive electrode material comprises the following steps:

[0072] (1) LiMn 0.7 V 0.3 Sol-gel solution of PO4, Li2CO3 and Ni 0.5 Mn 0.5 (OH)2 was ball milled and mixed until the particle size D50 of the mixture was 0.2 μm, and then spray dried at 100 ° C for 2 min to obtain the raw powder of the positive electrode material, wherein the lithium ions and T M The molar ratio of ions is 1.36:1, LiMn 0.7 V 0.3 The mole percentage of PO4 is 10%;

[0073] The LiMn 0.7 V 0.3 The sol-gel solution of PO4 was prepared by the following method:

[0074] LiNO3, vanadium nitrate, Mn(NO3)2, NH4H2PO4 and distilled water were mixed according to the formula to obtain a mixed solution with a concentration of 1 mol / L, and then citric acid with a concentration of 1 mol / L and polyethylene glycol with a concentration of 2 mol / L were added, and stirred at 50°C to obtain the LiMn 0.7 V 0.3 Sol-gel solution of PO4;

[0075] The Ni 0.5 Mn 0.5 (OH)2 was prepared by the following method:

[0076] A mixed solution of manganese sulfate and nickel sulfate with a concentration of 0.1 mol / L, a sodium hydroxide solution with a concentration of 2 mol / L, and ammonia water with a concentration of 0.1 mol / L are fed into a reaction kettle, the pH is controlled to be 12, and the reaction is carried out at 40 °C until Ni with a D50 particle size of 10 μm is obtained 0.5 Mn 0.5 (OH)2;

[0077] (2) Sinter the green powder of the positive electrode material described in step (1) at 800 °C for 48 h, then crush, demagnetize and screen it to obtain the positive electrode material with a D50 particle size of 2 μm and the size distribution of primary particles between 0.5 - 1.5 μm

[0078] Example 3

[0079] This example provides a positive electrode material, and the chemical formula of the positive electrode material is 0.25Li2MnO3·0.65LiMn 0.5 Ni 0.5 O2·0.1LiMn 0.7 Ni 0.3 PO4;

[0080] The preparation method of the positive electrode material includes the following steps:

[0081] (1) Ball-mill and mix the sol-gel solution of LiMn 0.7 Ni 0.3 PO4, Li2CO3 and Ni 0.5 Mn 0.5 (OH)2 until the D50 of the mixture is 1.5 μm, and then spray-dry at 300 °C for 30 s to obtain the green powder of the positive electrode material. Among them, in the mixture, the molar ratio of lithium ions to T M ions is 1.20:1, and the molar percentage content of LiMn 0.7 Ni 0.3 PO4 is 10%;

[0082] The sol-gel solution of LiMn 0.7 Ni 0.3 PO4 is prepared by the following method:

[0083] Mix LiNO3, nickel nitrate, Mn(NO3)2, NH4H2PO4 and distilled water according to the formula amount to obtain a mixed solution with a concentration of 0.1 mol / L, then add EDTA with a concentration of 0.1 mol / L and polyethylene glycol with a concentration of 1 mol / L, and stir at 25 °C to obtain the sol-gel solution of LiMn 0.7 Ni 0.3 PO4;

[0084] The Ni 0.5 Mn 0.5 (OH)2 was prepared by the following method:

[0085] A mixed solution of manganese sulfate and cobalt sulfate with a concentration of 2 mol / L, a sodium hydroxide solution with a concentration of 0.1 mol / L, and ammonia water with a concentration of 1 mol / L were flowed into a reactor, the pH was controlled to 7, and the reaction was carried out at 60°C until Ni particles with a particle size D50 of 3 μm were obtained. 0.5 Mn 0.5 (OH)2;

[0086] (2) The raw powder of the positive electrode material in step (1) is sintered at 1000° C. for 24 hours, and then crushed, demagnetized, and sieved to obtain the positive electrode material having a particle size D50 of 5 μm and a primary particle size distribution between 0.4 and 2 μm.

[0087] Example 4

[0088] This embodiment provides a positive electrode material. The positive electrode material has a chemical formula of 0.2Li2MnO3·0.55LiNi 0.5 Mn 0.5 Except for O2·0.25LiMnPO4, the rest are the same as in Example 1;

[0089] The preparation method of the positive electrode material is the same as that of Example 1 except that the raw materials are adaptively changed according to the chemical formula.

[0090] Example 5

[0091] This embodiment provides a positive electrode material. The positive electrode material has a chemical formula of 0.1Li2MnO3·0.45LiNi 0.5 Mn 0.5 O2·0.45LiMn 0.7 V 0.3 Except for PO4, the rest are the same as in Example 1;

[0092] The preparation method of the positive electrode material is the same as that of Example 1 except that the raw materials are adaptively changed according to the chemical formula.

[0093] Example 6

[0094] This embodiment provides a positive electrode material, the chemical formula of which is 0.2Li2MnO3·0.55LiNi 0.5 Mn 0.5 O2·0.25LiMn 0.7 V 0.3 PO4;

[0095] The preparation method of the positive electrode material is as follows:0.7 V 0.3 PO4 is mixed with Li2CO3 and Ni 0.5 Mn 0.5 (OH)2 in powder form, and the rest is the same as in Example 1. Among them, the powder of the said LiMn 0.7 V 0.3 PO4 is obtained by drying and grinding the sol-gel solution described in Example 1.

[0096] Example 7

[0097] This example provides a cathode material, and the chemical formula of the cathode material is 0.2Li2MnO3·0.55LiNi 0.5 Mn 0.5 O2·0.25LiMn 0.7 V 0.3 PO4;

[0098] The preparation method of the said cathode material is the same as in Example 1 except that spray drying is not carried out in step (1), but forced air drying is carried out at 200 °C.

[0099] Example 8

[0100] This example provides a cathode material, and the chemical formula of the cathode material is 0.2Li2MnO3·0.55LiNi 0.5 Mn 0.5 O2·0.25LiMn 0.7 V 0.3 PO4;

[0101] The preparation method of the said cathode material is the same as in Example 1 except that the particle size D50 of the mixture in step (1) is 0.05 μm.

[0102] Example 9

[0103] This example provides a cathode material, and the chemical formula of the cathode material is 0.2Li2MnO3·0.55LiNi 0.5 Mn 0.5 O2·0.25LiMn 0.7 V 0.3 PO4;

[0104] The preparation method of the said cathode material is the same as in Example 1 except that the particle size D50 of the mixture in step (1) is 3 μm.

[0105] Example 10

[0106] This example provides a cathode material, and the chemical formula of the cathode material is 0.2Li2MnO3·0.[[ID=0]] 0.5 Mn 0.5 O2·0.25LiMn 0.7 V 0.3 PO4;

[0107] The preparation method of the positive electrode material comprises the following steps:

[0108] (1) Weigh 0.27Li2MnO3·0.73LiNi 0.5 Mn 0.5 O2 and LiMn 0.7 V 0.3 PO4 according to the formula, ball-mill and mix them until the D50 of the mixture is 1.0 μm, and then dry at 200 °C to obtain the raw powder of the positive electrode material;

[0109] (2) Sinter the raw powder of the positive electrode material obtained in step (1) at 900 °C, then crush, demagnetize and screen it to obtain the positive electrode material with a D50 of 4 μm and the size distribution of primary particles between 0.4 - 2 μm.

[0110] Comparative Example 1

[0111] This comparative example provides a positive electrode material, and the chemical formula of the positive electrode material is 1 / 3Li2MnO3·2 / 3LiMn 0.5 Ni 0.5 O2;

[0112] The preparation method of the positive electrode material is the same as that of Example 1 except that the sol-gel solution of LiMn 0.7 V 0.3 PO4 is not added and the raw material addition amount is changed adaptively.

[0113] Comparative Example 2

[0114] This comparative example provides a positive electrode material, and the chemical formula of the positive electrode material is 0.27Li2MnO3·0.73LiMn 0.5 Ni 0.5 O2;

[0115] The preparation method of the positive electrode material is the same as that of Example 1 except that the sol-gel solution of LiMn 0.7 V 0.3 PO4 is not added.

[0116] The positive electrode materials obtained in the above embodiments and comparative examples were mixed with conductive carbon black, binder PVDF and NMP to form a slurry, which was then coated on aluminum foil, baked at 120°C, and then roll-pressed to form a positive electrode sheet. The positive electrode sheet was then assembled with a lithium sheet, a separator, and a positive and negative electrode shell to form a buckle test performance. The gram capacity at 0.1C, 2.5-4.6V, the capacity retention rate after 100 charge and discharge cycles at 45°C, 2.5V~4.6V and 1C, and the voltage drop after 100 charge and discharge cycles at 45°C, 2.5V~4.6V and 1C are shown in Table 1:

[0117] Table 1

[0118]

[0119] From the above table we can see that:

[0120] The positive electrode material of the present invention can significantly improve the cycle performance of the battery and reduce the voltage drop. Specifically, it can be seen from Examples 1 and 4 that the third lithium compound is preferably doped with metal element A, which can further improve the structural stability of the positive electrode material and improve the performance of the material; it can be seen from Examples 1 and 5 that the proportions of the three phases should be coordinated with each other, and the third lithium compound is not easy to account for too much. When the proportion is within a further preferred range, the comprehensive electrochemical performance of the material can be further guaranteed; it can be seen from Examples 1 and 6-7 that in the preparation process of the present invention, the sol-gel solution of the third lithium compound is used as a raw material, and then spray-dried, which is not only beneficial to the components. The mixing between the phases is more uniform, which is also conducive to the formation of a super-domain structure; it can be seen from Example 1 and Examples 8-9 that controlling the particle size within the preferred range before spray drying can further improve the performance of the material; it can be seen from Example 1 and Example 10 that directly mixing the phases cannot obtain a uniformly distributed solid solution material. The present invention uses specific raw materials for mixing and preparing, which can make the phases evenly distributed, which is conducive to the formation of a super-domain structure of a continuous phase; it can be seen from Example 1 and Comparative Examples 1-2 that the third lithium compound introduced by the present invention can form a super-domain structure of continuous phase transformation between the two phases in the lithium-rich manganese-based material, thereby reducing the precipitation of lattice O and reducing the voltage drop.

[0121] In summary, the present invention provides a positive electrode material and a preparation method and application thereof, and in particular provides a super-lithiated manganese-based positive electrode material and a preparation method and application thereof. The positive electrode material can form a continuous phase transition, has a supercrystalline domain structure and a stable layered structure, can stabilize lattice oxygen, reduce voltage drop, and significantly improve the cycle performance of the positive electrode material under high voltage.

[0122] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing a cathode material, characterized in that The chemical formula of the positive electrode material is xLi2MnO3·(1-x-y)LiNi a T M(1-a) O2·yLiMn b A (1-b) PO4, where 0 < x < 1, 0 < y < 1, 0 ≤ a ≤ 1, 0.5 ≤ b ≤ 1, A includes a metal element, and the T M is Mn, and the positive electrode material has a supercrystal domain structure; The preparation method of the positive electrode material comprises the following steps: (1) Mix a lithium source, a precursor of LiNi a T M(1-a) O2, and LiMn b A (1-b) PO4, and perform spray drying at 100 - 300 °C to obtain a raw powder of the cathode material; (2) Sinter the raw powder of the positive electrode material obtained in step (1) at a temperature of 800 - 1000 °C for 24 - 48 h to obtain the positive electrode material; The LiMn b A (1-b) PO4 is mixed with a lithium source and a precursor of LiNi a T M(1-a) O2 in the form of a sol-gel solution; The LiMn b A (1-b) sol-gel solution of PO4 is prepared by the following method: Mix a lithium source, a manganese source, a phosphorus source, an A metal source and a solvent according to the formulation amounts, then add an acid and a chelating agent and stir to obtain the sol-gel solution of LiMn b A (1-b) PO4; The A includes any one or a combination of at least two of Ni, V, Mg, Al, Nb, Zr, Cr, Si, Zn, Ti, Co, or Fe; the acid includes any one or a combination of at least two of citric acid, salicylic acid, oxalic acid, or EDTA; the chelating agent includes polyethylene glycol.

2. The preparation method according to claim 1, characterized in that, 0<y≤0.3。 3. The preparation method according to claim 1, wherein The concentration of the mixed solution obtained by mixing the lithium source, manganese source, phosphorus source, A element source, and solvent according to the formula amounts is 0.1 - 1 mol / L.

4. The preparation method according to claim 1, characterized in that, The concentration of the acid is 0.1 - 1 mol / L.

5. The preparation method according to claim 1, characterized in that, The concentration of the chelating agent is 1 - 2 mol / L.

6. The preparation method according to claim 1, wherein, The temperature of the stirring is 25 - 50 °C.

7. The preparation method according to claim 1, characterized in that, In the mixture obtained by mixing in step (1), the molar ratio of lithium ions to T M ions is (1.20 - 1.36):

1.

8. The preparation method according to claim 1, characterized in that, In the mixture obtained by mixing in step (1), the molar percentage content of LiMn b A (1-b) PO4 is 0.01 - 30%.

9. The preparation method according to claim 1, wherein In step (1), the mixture is mixed until the particle size D50 of the mixture is 0.2 - 1.5 μm.

10. The preparation method according to claim 1, wherein The mixing method includes ball milling.

11. The preparation method according to claim 1, characterized in that, The precursor of LiNi a T M(1-a) O2 includes Ni a Mn (1-a) (OH)2 and is prepared by the following method: Mix a precipitating agent, a complexing agent, and a Ni and / or T M metal source to obtain a reaction solution. After the reaction solution undergoes a reaction, a precursor of LiNi a T M(1-a) O2 is obtained.

12. The preparation method according to claim 11, characterized in that, The pH of the reaction solution is 7 - 12.

13. The preparation method according to claim 11, wherein, In the reaction solution, the concentration of the complex ion is 0.1 - 1 mol / L.

14. The preparation method according to claim 11, characterized in that, The temperature of the reaction is 40 - 60 °C.

15. The preparation method according to claim 11, wherein The reaction continues until the particle size of the precursor is 3 - 10 μm.

16. The preparation method according to claim 1, wherein, After the sintering in step (2), crushing, demagnetization, and sieving are also carried out.

17. The preparation method according to claim 1, wherein, The particle size D50 of the positive electrode material in step (2) is 2 - 5 μm, and the size of the primary particles is between 0.4 - 2 μm.

18. The preparation method according to claim 1, characterized in that, The preparation method comprises the following steps: (1) Mix the sol-gel solution of LiMn b A (1-b) PO4, the precursor of LiNi a T M(1-a) O2 and a lithium source by ball milling until the particle size D50 of the mixture is 0.2 - 1.5 μm, and then perform spray drying at 100 - 300 °C to obtain the green powder of the cathode material. Among them, in the mixture, the molar ratio of lithium ions to T M ions is (1.20 - 1.36):1, and the molar percentage content of LiMn b A (1-b) PO4 is 0.01 - 30%; The precursor of the LiNi a T M(1-a) O2 is Ni a Mn (1-a) (OH)2, and the sol-gel solution of the LiMn b A (1-b) PO4 is prepared by the following method: Mix a lithium source, a manganese source, a phosphorus source, an A metal source and a solvent according to the formulation amounts to obtain a mixed solution with a concentration of 0.1-1 mol / L, and then add an acid and a chelating agent and stir to obtain the sol-gel solution of b A (1-b) LiMnPO4; (2) Sinter the raw powder of the positive electrode material obtained in step (1) at 800 - 1000 °C for 24 - 48 h, then crush, demagnetize, and sieve to obtain the positive electrode material with a particle size D50 of 2 - 5 μm and the size distribution of the primary particles between 0.4 - 2 μm.

19. A lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode material prepared by the preparation method of the positive electrode material according to any one of claims 1 - 18.

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