Composite material containing lithium-rich lithium ferrite and layered positive electrode material as well as preparation method and application of composite material

Abstract

The invention discloses a composite material containing lithium-rich lithium ferrite and a layered positive electrode material as well as a preparation method and application of the composite material. The composite material contains lithium-rich lithium ferrite and a main active substance layered positive electrode material, can contain or does not contain a carbon coating layer, and can contain or does not contain a coating layer of other elements except carbon. Wherein the lithium-rich lithium ferrite is mainly used for improving the first efficiency and the cycle performance of the battery cell; the carbon layer which can be contained or not contained is mainly used for improving the electronic conductivity and air stability of the material; the coating layer can contain or does not contain other elements and is mainly used for improving the electrical property and improving the air stability to a certain degree; in addition, the air stability of the LFO is further improved due to the layered material, particularly, when the composite material is applied to a high-nickel ternary material system, the compatibility of the composite material and the high-nickel ternary material can be further improved, and the problems of side reaction and gas production are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials containing lithium-rich lithium ferrite and layered positive electrode materials for lithium-ion batteries, and in particular to a composite material of lithium-rich lithium ferrite and layered positive electrode materials, and a preparation method and application thereof. Background Art

[0002] With the widespread application of lithium-ion batteries in various fields, improving their performance has become a hot topic in industry research. Lithium-ion batteries (LIBs) need to provide high energy density and long cycle life to meet the growing demand for electric vehicle batteries. However, significant irreversible capacity loss occurs during the initial cycle, mainly due to the formation of a solid electrolyte interface (SEI) on the negative electrode surface, which greatly reduces the energy density and cycle life of the complete battery. Fortunately, various anode and cathode pre-lithiation technologies have been developed to address this critical issue. Pre-lithiation compensates for the initial active lithium loss (ALL), effectively improving the cycle life and energy density while maintaining compatibility with the current commercial production of LIBs.

[0003] Lithium-rich lithium iron oxide, as a key material, plays a vital role in improving the cycle life performance of energy storage batteries. It can improve the problem of reduced initial coulombic efficiency of the negative electrode, thereby increasing the capacity, cycle life and energy density of lithium batteries. Lithium replenishment technology adds lithium ions to the battery before operation to replenish the lithium consumed by the solid electrolyte interface film (SEI film) formed during the initial charging process, thereby reducing irreversible lithium loss at the positive electrode and improving the battery's initial efficiency and cycle life.

[0004] Lithium-rich iron oxide (LFO, chemical formula Li5FeO4) is currently the mainstream positive electrode lithium supplement material. LFO is a lithium metal oxide with an inverse fluorite structure. Due to its high specific capacity, it has become the mainstream positive electrode lithium-rich iron oxide. On the other hand, the positive electrode materials used in high-energy-density batteries are generally layered positive electrode materials (such as high-nickel NCM\NCA systems). It can be seen that LFO and layered positive electrode materials have certain incompatibilities in the chemical system. Therefore, from the perspective of chemical system compatibility, the use of a uniform layered positive electrode material coating will make LFO more compatible with the layered positive electrode material energy storage system, while suppressing problems such as gas production and achieving optimal performance.

[0005] Chinese Patent Publication No. CN116830306A discloses a ternary cathode material and its preparation method and application. The structural formula of the ternary cathode material is Li(Ni x Co y Mn z)O2@Li5FeO4, where 0.6≤x<1, 0<y≤0.4, 0 <x+y<1,所述三元正极材料的内部为中空结构,所述三元正极材料从内到外镍含量先增多后减少。其核心利用磷酸锂和富锂型普鲁士蓝材料复合物作为模板剂,以共沉淀法合成三元材料前驱体,与锂源混合经过煅烧后,模板剂中的C和N转化为气体去除,构造内部为中空结构的三元材料,能增大比表面积,增大电解液的浸润程度。其核心还是由于高温下普鲁士蓝分解形成的中空结构三元材料,增加电解液浸润程度。而且其采用的锂源Li3PO4以及富锂型普鲁士蓝,在高温下普鲁士蓝中的CN结构碳化后形成中空结构和Fe离子然后与其余的Li3PO4反应,生成以LiFePO4为主的产物、剩余部分如Fe离子过量则会生成Li5FeO4,而不是单纯的Li5FeO4,根据专利强调的是内层中空结构具有增加电解液浸润的能力,从而提高循环,且其专利的实施例中Li3PO4摩尔添加量是0.15mol,而亚铁氰化钠的添加量是0.1mol,也就意味着磷酸根过量后只会生成LiFePO4,而不会有Li5FeO4。

[0006] In this proposal, our company proposes a composite material containing lithium-rich ferrite and layered oxide. In this composite material, there are mainly two core materials (lithium-rich ferrite a, layered positive electrode material b, a+b=100 parts) and a carbon coating layer that may or may not be present and a coating layer d of other elements that may or may not be present. This composite material can be used as a lithium supplement additive when the lithium-rich ferrite content is high, such as (90≤a≤100). Only a small amount of this composite material needs to be added when replenishing lithium; when the lithium-rich ferrite content is in a moderate range (10≤a≤90), the addition amount is even higher. When the lithium-rich ferrite content is low, it means that the layered positive electrode material content is high. This composite material can be used as a positive electrode material containing lithium-rich ferrite (0≤a≤10). It can be used as a layered positive electrode material with its own lithium supplement, which can achieve a long-cycle positive electrode material. The patent of this invention can achieve different application scenarios through different conditions and the proportions of lithium-rich ferrite and layered positive electrode materials. In addition, the inclusion of layered materials further improves the air stability of LFO, especially when the composite material is applied to a high-nickel ternary material system, the composite material can further improve its compatibility with the high-nickel ternary material and inhibit side reactions and gas production problems. Summary of the Invention

[0007] The purpose of the present application is to provide a composite material by adjusting the proportion of lithium-rich lithium iron phosphate and layered positive electrode, so as to achieve high lithium-rich lithium iron phosphate content and high lithium supplement capacity. Only a small amount of the composite material needs to be added to achieve high capacity lithium supplement, but there may be uneven lithium supplement and lithium precipitation risk; if (90≤a≤100), only a small amount of the composite material needs to be added during lithium supplement, and the lithium-rich lithium iron phosphate content in the moderate interval is more convenient for uniform lithium supplement, such as (10≤a≤90), which can be used as an adjustable lithium supplement additive, and is more suitable for uniform lithium supplement. When the lithium-rich lithium iron phosphate content is low, it means that the content of the layered positive electrode material is high, and the composite material can be used as a positive electrode material containing lithium-rich lithium iron phosphate (0≤a≤10), which can be used as a positive electrode material without adding lithium-rich lithium iron phosphate to achieve long cycle.

[0008] A composite material containing lithium-rich lithium iron phosphate and layered positive electrode material, by adjusting the proportion of lithium-rich lithium iron phosphate and layered positive electrode material, the switching of different application scenarios is realized freely. In addition, the good coating of the layered positive electrode material can improve the air stability of the lithium-rich lithium iron phosphate, and at the same time inhibit the production of gas, realize the optimization of performance, and to a certain extent, solve the incompatibility problem of the chemical system.

[0009] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0010] In the first aspect, the present application provides a multi-coated composite material containing lithium-rich lithium iron phosphate and layered positive electrode material, which contains lithium-rich lithium iron phosphate, and the main active substance layered positive electrode material, and can contain or not contain a carbon coating layer, and can contain or not contain an element coating layer other than carbon. The weight of lithium-rich lithium iron phosphate a plus the weight of active substance b is 100 parts. Wherein 0≤a≤100 parts; 0≤b≤100; 0≤c≤10; 0≤d≤1%.

[0011] As a specific technical scheme, when the content of lithium-rich lithium iron phosphate is high, the lithium-rich lithium iron phosphate is high in capacity, and only a small amount of the composite material needs to be added to achieve the effect of lithium supplement. At this time, the content of lithium-rich lithium iron phosphate in the composite material can be 90≤a≤100, specifically 100 parts, 98 parts, 96 parts, 94 parts, 92 parts, 90 parts, or any numerical ratio thereof, and the content of layered positive electrode material can be 0≤b≤10; specifically 0 parts, 2 parts, 4 parts, 6 parts, 8 parts, 10 parts, or any numerical ratio thereof.

[0012] When the content of lithium-rich ferrite is moderate, the composite material can be used as a medium-capacity lithium-rich ferrite and can be suitable as a uniform lithium supplement additive. The ratio of 10≤a≤90 can be 90 parts, 80 parts, 70 parts, 60 parts, 50 parts, 40 parts, 30 parts, 20 parts, 10 parts, or any numerical ratio therein. The content of the layered positive electrode material can be 10≤b≤90; specifically, it can be 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, or any numerical ratio therein.

[0013] When the content of lithium-rich ferrite is low, the composite material can be used as a long-cycle positive electrode material. The content of lithium-rich ferrite in the composite material is in the range of 0≤a≤10, specifically 10 parts, 8 parts, 7 parts, 6 parts, 4 parts, 2 parts, 1 part, or any numerical ratio therein. The content of the layered positive electrode material can be in the range of 90≤b≤100, specifically 90 parts, 92 parts, 94 parts, 96 parts, 98 parts, 100 parts, or any numerical ratio therein.

[0014] Furthermore, the carbon content is 0≤c≤10%; it can be 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any numerical ratio therein. The carbon content is preferably 0≤c≤5%, more preferably 0≤c≤3%. The thickness of the carbon coating is set to ≤100nm, preferably ≤50nm, and even more preferably ≤20nm.

[0015] In a second aspect, the present invention provides a method for preparing the composite material, comprising the following steps:

[0016] S1. Weigh a lithium-rich lithium ferrite precursor and a layered cathode material precursor in proportion, add them to deionized water, prepare an aqueous solution of a lithium source and a carbon source (optional) in proportion, control the solid content to ≤60%, stir, and then grind to control the D50 particle size to ≤0.5 μm to obtain a slurry;

[0017] S2, drying the slurry to obtain a precursor powder;

[0018] S3, placing the precursor powder obtained in step S3 into a furnace with atmosphere for a first sintering at a temperature of 400° C. to 650° C. for a holding time of 4 h to 16 h to obtain a first sintered product;

[0019] S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent is added (optionally), mixed evenly, and then sintered for the second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product may or may not be subjected to CVD deposition treatment. Finally, the desired product is crushed, classified, demagnetized, and packaged.

[0020] As a specific technical solution, in step S1, the precursor of the lithium ferrite-rich product includes iron oxide, iron hydroxide, iron nitrate, iron sulfate, nickel ferrous sulfate, iron chloride, ferrous oxalate, iron acetate, and iron citrate. The molar ratio of the added precursors is the molar ratio of LFO in the final product.

[0021] As a specific technical solution, in step S1, the precursor of the layered oxide can be a layered positive electrode material of the main active material, and the molar ratio of the added layered oxide is the molar ratio of the layered material in the final product; the layered positive electrode material can be a ternary material (single or polycrystalline material of any proportion of NCM or NCA precursor, and multi-material modified with ternary material as the main structure); lithium cobalt oxide precursor material, and cobalt-free layered precursor material; wherein the layered ternary precursor structure formula and the chemical formula of the ternary material precursor are Ni x Co y M (1-x-y) (OH)2, wherein M can be at least one of Mn, Al, W, Zr, Mg, B, Nb, Ta, Mo, La and Ti, wherein x, y, z are the atomic proportions of nickel, cobalt and M, generally in the range of 0≤x≤1, 0≤y≤1, 0≤z≤1 and x+y+z=1. And the structural formula of the multi-component material modified with the ternary material as the main structure is Ni x Co y M z N 1-x-y-z (OH)2, wherein M is at least one of Mn, Al, W, Zr, Mg, B, Nb, Ta, Mo, La and Ti, 0.33≤x≤1, 0≤y≤0.33, 0≤z≤0.33, N is Mn, Al, W, Zr, Mg, B, Nb, Ta, Mo, La and Ti, and M and N are not the same element.

[0022] As a specific technical solution, the lithium source includes one or a combination of two or more of lithium carbonate, lithium oxide, lithium hydroxide, lithium acetate, lithium citrate, lithium oxalate, and lithium adipate.

[0023] As a specific technical solution, in step S1, the molar addition ratio of the lithium source to LFO is 4.9≤Li / Fe≤5.3, and preferably the addition ratio is 4.97≤Li / Fe≤5.15.

[0024] As a specific technical solution, in step S1, the molar addition ratio of the lithium source to the layered oxide precursor is 0.9≤Li / layered oxide precursor≤1.1, more preferably 0.9≤Li / layered oxide precursor≤1.05.

[0025] As a specific technical solution, the carbon source includes an inorganic carbon source and / or an organic carbon source.

[0026] The inorganic carbon source includes at least one of carbon nanotubes, graphene, graphite, fullerene, and amorphous carbon. As an example, fullerene can be C 20 、C 60 、C 70 、C 76 、C 80 wait.

[0027] The organic carbon source includes one or a combination of two or more of glucose, hydroxymethyl cellulose, sucrose, soluble starch, PEG, cellulose, petroleum, and asphalt.

[0028] As a specific technical solution, in step S1, the mol amount of the carbon source added is equivalent to the molar amount of carbon, which is 0≤carbon coating amount≤10% of the weight of (lithium-rich lithium ferrite + layered positive electrode material). As an example, the amount of carbon source added can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., or any value therein. The 0≤coating thickness≤50nm, preferably the coating thickness 0≤coating thickness≤20nm. As an example, the coating thickness can be 1nm, 5nm, 10nm, 15nm, 20nm, 30nm, 40nm, 50nm, etc., or any value therein.

[0029] As a specific technical solution, the solid content of the slurry is ≤60%, preferably ≤40, and more preferably ≤35%.

[0030] As a specific technical solution, the particle size D after grinding 50 ≤0.5μm, preferably D 50 ≤0.4μm, more preferably D 50 ≤0.3μm.

[0031] As a specific technical solution, the drying treatment adopts any one of spray drying, flash evaporation and centrifugal drying.

[0032] As an example, the drying process may be spray drying, where the air inlet temperature of the spray drying is ≥180°C and the air outlet temperature is ≥90°C.

[0033] As a specific technical solution, the atmosphere is one of oxygen, nitrogen, argon, and air, or a combination of two or more.

[0034] As a specific technical solution, the surface coating elements include oxides, hydroxides, sulfates, nitrates and other salts of B, N, Mg, Al, F, Si, P, S, K, Ca, Sc, V, Ti, Cr, Mn, Ni, Ga, Ge, La, Se, Rb, Sr, Y, Nb, Mo, Ru, Eu, Er, Yb, Dy, Cs, Sb, Sn, Se, Te, Bi, Zn, Cu, Ce, Rh, Tb, Lu, Hf, Ta, W, Os, Ir, Pt, Au, Pb, Zr, Cd, Pd, Ag, etc. Specifically, the surface coating elements may be one or a combination of two or more of aluminum oxide, boehmite, zirconium oxide, zinc oxide, titanium oxide, calcium dioxide, silicon oxide, silicon dioxide, magnesium oxide, tin oxide, nickel oxide, cobalt oxide, manganese oxide, phosphorus pentoxide, tantalum oxide, tungsten oxide, niobium oxide, strontium oxide, cerium oxide, lanthanum oxide, etc.

[0035] As a specific technical solution, in step S5, the coating amount of the surface coating agent is ≤1% (10000 ppm).

[0036] Preferably, the coating amount of the surface coating agent is ≤8000 ppm.

[0037] More preferably, the coating amount of the surface coating agent is ≤6000ppm.

[0038] As a specific technical solution, the D50 particle size of the surface coating agent is ≤500nm.

[0039] Preferably, the D50 particle size of the surface coating agent is ≤100 nm.

[0040] Preferably, the D50 particle size of the surface coating agent is ≤50 nm.

[0041] As a specific technical solution, in the physical coating technical solution, the grinding particle size D50 is controlled to be D50≤0.5μm, preferably D50≤0.4μm, and more preferably D50≤0.2μm.

[0042] As a specific technical solution, the covering gas during the CVD deposition process is any one of acetylene, ethylene, methane, ethane, and propane.

[0043] As a specific technical solution, the temperature of the CVD deposition process is 700° C. to 900° C., and the time is 2 hours to 16 hours.

[0044] As a specific technical solution, after CVD deposition treatment, the particles are crushed to a D50 particle size of ≤10 μm, and a more preferred particle size of ≤5 μm.

[0045] In a third aspect, the present invention also provides an application of a composite material containing lithium-rich lithium ferrite and an active substance or a composite material prepared by the above-mentioned composite material or preparation method in a battery, wherein the battery includes any one of a lithium-ion battery, a solid-state battery, and a semi-solid-state battery.

[0046] Compared with the existing technology, by adjusting the proportion of lithium-rich lithium ferrite and iron phosphate composite material, a high lithium replenishment capacity is achieved when the content of lithium-rich lithium ferrite is high. Only a small amount of this composite material needs to be added to achieve high-capacity lithium replenishment, but there may be uneven lithium replenishment and the risk of lithium precipitation; when the content of lithium-rich lithium ferrite is moderate (10≤a≤90), it can be used as a uniform lithium replenishment additive; adding an appropriate amount of composite material can achieve uniform lithium replenishment, thereby avoiding the risk of local lithium precipitation. When the content of lithium-rich lithium ferrite is low (0≤a≤10), especially when the content of lithium-rich lithium ferrite is between about 1-5%, it can be used as a long-cycle positive electrode material, achieving long-cycle without the need for additional addition of lithium-rich lithium ferrite.

[0047] A composite material containing lithium-rich ferrite and a layered cathode material. By adjusting the ratio of lithium-rich ferrite to the layered cathode material, it can be freely switched between different application scenarios. Furthermore, the good coating of the layered cathode material improves the air stability of the LFO and suppresses gas production, achieving optimized performance. This, to a certain extent, resolves chemical system incompatibility issues and effectively improves the cycle life of the energy storage battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0049] Figure 1 Schematic diagram of the preparation of the composite material containing lithium-rich lithium ferrite and layered positive electrode material of the present invention. DETAILED DESCRIPTION

[0050] The technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are also within the scope of protection of the present invention.

[0051] In the Examples and Comparative Examples, the experimental methods used are conventional methods unless otherwise specified, and the materials and reagents used are commercially available unless otherwise specified.

[0052] The present invention will be further described in detail below through detailed embodiments in conjunction with the accompanying drawings.

[0053] Example 1

[0054] This embodiment provides a composite material containing lithium-rich ferrite and layered positive electrode material, wherein the lithium-rich ferrite is 2% and the layered positive electrode material is 98%. Figure 1 As shown, the preparation method of the composite material is as follows:

[0055] S1. Weigh 2% iron oxide and 98% NCM811 precursor in proportion and add them to deionized water. Prepare a lithium source and aqueous solution in proportion. Control the solid content of the total slurry to 35%. After stirring, further grind to control the D50 particle size to ≤ 0.5 μm to obtain a slurry.

[0056] S2, drying the slurry to obtain a precursor powder;

[0057] S3, placing the precursor powder obtained in step S3 into a furnace with atmosphere for a first sintering at a temperature of 400° C. to 650° C. for a holding time of 4 h to 16 h to obtain a first sintered product;

[0058] S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent is added (optionally), mixed evenly, and then sintered for the second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product may or may not be subjected to CVD deposition treatment. Finally, the desired product is crushed, classified, demagnetized, and packaged.

[0059] Example 2

[0060] This embodiment provides a composite material containing lithium-rich ferrite and layered positive electrode material, wherein the lithium-rich ferrite is 4% and the layered positive electrode material is 96%. Figure 1 As shown, the preparation method of the composite material is as follows:

[0061] S1. Weigh 4% iron oxide and 96% NCM811 precursor in proportion and add them to deionized water. Prepare a lithium source and aqueous solution in proportion. Control the solid content of the total slurry to 35%. After stirring, further grind to control the D50 particle size to ≤ 0.5 μm to obtain a slurry.

[0062] S2, drying the slurry to obtain a precursor powder;

[0063] S3, placing the precursor powder obtained in step S3 into a furnace with atmosphere for a first sintering at a temperature of 400° C. to 650° C. for a holding time of 4 h to 16 h to obtain a first sintered product;

[0064] S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent is added (optionally), mixed evenly, and then sintered for the second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product may or may not be subjected to CVD deposition treatment. Finally, the desired product is crushed, classified, demagnetized, and packaged.

[0065] Example 3

[0066] This embodiment provides a composite material containing lithium-rich ferrite and a layered positive electrode material, wherein the lithium-rich ferrite accounts for 6% and the layered positive electrode material accounts for 94% (this solution is an in-situ growth layered oxide technology solution). The preparation method of the composite material is as follows:

[0067] S1. Preparation of lithium-rich ferrite precursor: weigh a nickel source with a molar ratio of 2% of the lithium-rich ferrite content, dissolve it in deionized water to prepare a solution with a certain concentration of 3 mol / L; add a lithium hydroxide solution with a precipitant mass concentration of 30% and an ammonia aqueous solution with a complexing agent concentration of 34.7%, and obtain a hydroxide after 12 hours of reaction time. Wash and dry to obtain a lithium-rich ferrite precursor.

[0068] S2. Preparation of layered positive electrode material precursor: prepare nickel salt, cobalt salt, manganese salt or aluminum salt solution, mix nickel salt, cobalt salt, manganese salt or aluminum salt solution evenly (Ni: Co: Mn / Al according to the molar ratio of 60: 20: 20), prepare a layered precursor solution with a metal salt mol concentration of 2.2 mol / L, and evenly disperse the above-mentioned S1 lithium iron oxide precursor powder in the ternary material precursor solution. A 30% concentration of sodium hydroxide solution precipitant solution and a 34.7% ammonia aqueous solution with a complexing agent concentration are added to the reactor together with the mixed solution to react for 12 hours and precipitate. After sufficient reaction, let it stand and age for 12 hours; the aged solution is subjected to solid-liquid separation and washed.

[0069] Preparation of S3 composite materials containing lithium-rich ferrite and ternary materials: The S2 precursor is mixed with a lithium source, the molar ratio of the lithium source to the nickel element in the lithium-rich ferrite being (2.06:1), and the molar ratio of the lithium source to the layered oxide being (1.03:1). 2% glucose may be added proportionally, mixed thoroughly, and sintered under atmospheric conditions. The sintered material is crushed, classified, and demagnetized to obtain the desired material.

[0070] S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent alumina (4000 ppm) is added, mixed evenly, and then sintered for the second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product can be subjected to CVD deposition treatment or not. Finally, it is crushed, classified, demagnetized, and packaged to obtain the desired product.

[0071] Example 4

[0072] This embodiment provides a composite material containing lithium-rich ferrite and layered positive electrode material, wherein the lithium-rich ferrite is 8% and the layered positive electrode material is 92%. Figure 1 As shown, the preparation method of the composite material is as follows:

[0073] S1. Weigh 8% iron oxide and 92% NCM811 precursor in proportion, add them to deionized water, prepare a lithium source and aqueous solution in proportion, control the solid content of the total slurry to 35%, stir and further grind to control the D50 particle size ≤ 0.5 μm, to obtain a slurry;

[0074] S2, drying the slurry to obtain a precursor powder;

[0075] S3, placing the precursor powder obtained in step S3 into a furnace with atmosphere for a first sintering at a temperature of 400° C. to 650° C. for a holding time of 4 h to 16 h to obtain a first sintered product;

[0076] S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent is added (optionally), mixed evenly, and then sintered for the second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product may or may not be subjected to CVD deposition treatment. Finally, the desired product is crushed, classified, demagnetized, and packaged.

[0077] Example 5

[0078] This embodiment provides a composite material containing lithium-rich ferrite and layered positive electrode material, wherein the lithium-rich ferrite is 10% and the layered positive electrode material is 90%. Figure 1 As shown, the preparation method of the composite material is as follows:

[0079] S1. Weigh 10% iron oxide and 90% NCM811 precursor in proportion and add them to deionized water. Prepare the lithium source and aqueous solution in proportion. Control the solid content of the total slurry to 35%. After stirring, further grind to control the D50 particle size to ≤ 0.5 μm to obtain a slurry.

[0080] S2, drying the slurry to obtain a precursor powder;

[0081] S3, placing the precursor powder obtained in step S3 into a furnace with atmosphere for a first sintering at a temperature of 400° C. to 650° C. for a holding time of 4 h to 16 h to obtain a first sintered product;

[0082] S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent is added (optionally), mixed evenly, and then sintered for the second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product may or may not be subjected to CVD deposition treatment. Finally, the desired product is crushed, classified, demagnetized, and packaged.

[0083] Example 6

[0084] This embodiment provides a composite material containing lithium-rich ferrite and layered positive electrode material, wherein the lithium-rich ferrite is 20% and the layered positive electrode material is 80%. Figure 1 As shown, the preparation method of the composite material is as follows:

[0085] S1. Weigh 20% iron oxide and 80% NCM811 precursor in proportion and add them to deionized water. Prepare a lithium source and aqueous solution in proportion. Control the solid content of the total slurry to 35%. After stirring, further grind to control the D50 particle size to ≤ 0.5 μm to obtain a slurry.

[0086] S2, drying the slurry to obtain a precursor powder;

[0087] S3, placing the precursor powder obtained in step S3 into a furnace with atmosphere for a first sintering at a temperature of 400° C. to 650° C. for a holding time of 4 h to 16 h to obtain a first sintered product;

[0088] S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent is added (optionally), mixed evenly, and then sintered for the second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product may or may not be subjected to CVD deposition treatment. Finally, the desired product is crushed, classified, demagnetized, and packaged.

[0089] Example 7

[0090] This embodiment provides a composite material containing lithium-rich ferrite and layered positive electrode material, wherein the lithium-rich ferrite is 30% and the layered positive electrode material is 70%. Figure 1 As shown, the preparation method of the composite material is as follows:

[0091] S1, take 2% iron oxide and 98% NCM811 precursor by proportion, add lithium source and water solution according to proportion, control solid content of total slurry to 35%, further grind after stirring to control D50 particle size ≤0.5 μm, and obtain slurry;

[0092] S2, dry the above slurry to obtain precursor powder;

[0093] S3, put the precursor powder obtained in step S3 into a furnace with atmosphere to perform first sintering, the sintering temperature is 400-650 DEG C, the holding time is 4-16 h, and a first sintering product is obtained;

[0094] S4, crush the first sintering product obtained in step S3 to D50 particle size ≤40 μm, add a small amount of surface coating agent (which can be added or not added) and mix uniformly, then perform second sintering, the sintering temperature is 650-1300 DEG C, the holding time is 8-24 h, the second sintering product obtained can be selected to perform CVD deposition treatment, or not, finally crush, classify, remove magnetism, package to obtain the required product.

[0095] Example 8

[0096] The embodiment provides a composite material containing lithium-rich lithium iron phosphate and a layered positive electrode material, wherein the lithium-rich lithium iron phosphate is 40%, and the layered positive electrode material is 60%. As shown in the figure, the preparation method of the composite material is as follows: Figure 1

[0097] S1, take 2% iron oxide and 98% NCM811 precursor by proportion, add lithium source and water solution according to proportion, control solid content of total slurry to 35%, further grind after stirring to control D50 particle size ≤0.5 μm, and obtain slurry;

[0098] S2, dry the above slurry to obtain precursor powder;

[0099] S3, put the precursor powder obtained in step S3 into a furnace with atmosphere to perform first sintering, the sintering temperature is 400-650 DEG C, the holding time is 4-16 h, and a first sintering product is obtained;

[0100] S4, crush the first sintering product obtained in step S3 to D50 particle size ≤40 μm, add a small amount of surface coating agent (which can be added or not added) and mix uniformly, then perform second sintering, the sintering temperature is 650-1300 DEG C, the holding time is 8-24 h, the second sintering product obtained can be selected to perform CVD deposition treatment, or not, finally crush, classify, remove magnetism, package to obtain the required product.

[0101] Example 9

[0102] ​This embodiment provides a composite material containing lithium-rich ferrite and layered positive electrode material, wherein the lithium-rich ferrite is 50% and the layered positive electrode material is 50%. Figure 1 As shown, the preparation method of the composite material is as follows:

[0103] S1. Weigh 50% iron oxide and 50% NCM811 precursor in proportion and add them to deionized water. Prepare the lithium source and aqueous solution in proportion. Control the solid content of the total slurry to 35%. After stirring, further grind to control the D50 particle size to ≤ 0.5 μm to obtain a slurry.

[0104] S2, drying the slurry to obtain a precursor powder;

[0105] S3, placing the precursor powder obtained in step S3 into a furnace with atmosphere for a first sintering at a temperature of 400° C. to 650° C. for a holding time of 4 h to 16 h to obtain a first sintered product;

[0106] S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent is added (optionally), mixed evenly, and then sintered for the second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product may or may not be subjected to CVD deposition treatment. Finally, the desired product is crushed, classified, demagnetized, and packaged.

[0107] Example 10

[0108] This embodiment provides a composite material containing lithium-rich ferrite and layered positive electrode material, wherein the lithium-rich ferrite is 60% and the layered positive electrode material is 40%. Figure 1 As shown, the preparation method of the composite material is as follows:

[0109] S1. Weigh 60% iron oxide and 40% NCM811 precursor in proportion and add them to deionized water. Prepare lithium source and aqueous solution in proportion. Control the solid content of the total slurry to 35%. After stirring, further grind to control the D50 particle size to ≤ 0.5 μm to obtain a slurry.

[0110] S2, drying the slurry to obtain a precursor powder;

[0111] S3, placing the precursor powder obtained in step S3 into a furnace with atmosphere for a first sintering at a temperature of 400° C. to 650° C. for a holding time of 4 h to 16 h to obtain a first sintered product;

[0112] S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent is added (optionally), mixed evenly, and then sintered for the second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product may or may not be subjected to CVD deposition treatment. Finally, the desired product is crushed, classified, demagnetized, and packaged.

[0113] Example 11

[0114] This embodiment provides a composite material containing lithium-rich ferrite and layered positive electrode material, wherein the lithium-rich ferrite is 70% and the layered positive electrode material is 30%. Figure 1 As shown, the preparation method of the composite material is as follows:

[0115] S1. Weigh 70% iron oxide and 30% NCM811 precursor in proportion and add them to deionized water. Prepare a lithium source and aqueous solution in proportion. Control the solid content of the total slurry to 35%. After stirring, further grind to control the D50 particle size to ≤ 0.5 μm to obtain a slurry.

[0116] S2, drying the slurry to obtain a precursor powder;

[0117] S3, placing the precursor powder obtained in step S3 into a furnace with atmosphere for a first sintering at a temperature of 400° C. to 650° C. for a holding time of 4 h to 16 h to obtain a first sintered product;

[0118] S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent is added (optionally), mixed evenly, and then sintered for the second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product may or may not be subjected to CVD deposition treatment. Finally, the desired product is crushed, classified, demagnetized, and packaged.

[0119] Example 12

[0120] This embodiment provides a composite material containing lithium-rich ferrite and layered positive electrode material, wherein the lithium-rich ferrite is 80% and the layered positive electrode material is 20%. Figure 1 As shown, the preparation method of the composite material is as follows:

[0121] S1. Weigh 80% iron oxide and 20% NCM811 precursor in proportion and add them to deionized water. Prepare a lithium source and aqueous solution in proportion. Control the solid content of the total slurry to 35%. After stirring, further grind to control the D50 particle size to ≤ 0.5 μm to obtain a slurry.

[0122] S2, drying the slurry to obtain a precursor powder;

[0123] S3, placing the precursor powder obtained in step S3 into a furnace with atmosphere for a first sintering at a temperature of 400° C. to 650° C. for a holding time of 4 h to 16 h to obtain a first sintered product;

[0124] S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent is added (optionally), mixed evenly, and then sintered for the second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product may or may not be subjected to CVD deposition treatment. Finally, the desired product is crushed, classified, demagnetized, and packaged.

[0125] Example 13

[0126] This embodiment provides a composite material containing lithium-rich ferrite and layered positive electrode material, wherein the lithium-rich ferrite is 90% and the layered positive electrode material is 10%. Figure 1 As shown, the preparation method of the composite material is as follows:

[0127] S1. Weigh 90% iron oxide and 10% NCM811 precursor in proportion, add them to deionized water, prepare a lithium source and aqueous solution in proportion, control the solid content of the total slurry to 35%, stir and further grind to control the D50 particle size ≤ 0.5 μm, to obtain a slurry;

[0128] S2, drying the slurry to obtain a precursor powder;

[0129] S3, placing the precursor powder obtained in step S3 into a furnace with atmosphere for a first sintering at a temperature of 400° C. to 650° C. for a holding time of 4 h to 16 h to obtain a first sintered product;

[0130] S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent is added (optionally), mixed evenly, and then sintered for the second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product may or may not be subjected to CVD deposition treatment. Finally, the desired product is crushed, classified, demagnetized, and packaged.

[0131] Example 14

[0132] This embodiment provides a composite material containing lithium-rich ferrite and layered positive electrode material, wherein the lithium-rich ferrite is 98% and the layered positive electrode material is 2%. Figure 1 As shown, the preparation method of the composite material is as follows:

[0133] S1. Weigh 98% iron oxide and 2% NCM811 precursor in proportion and add them to deionized water. Prepare a lithium source and aqueous solution in proportion. Control the solid content of the total slurry to 35%. After stirring, further grind to control the D50 particle size to ≤ 0.5 μm to obtain a slurry.

[0134] S2, drying the slurry to obtain a precursor powder;

[0135] S3, placing the precursor powder obtained in step S3 into a furnace with atmosphere for a first sintering at a temperature of 400° C. to 650° C. for a holding time of 4 h to 16 h to obtain a first sintered product;

[0136] S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent is added (optionally), mixed evenly, and then sintered for the second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product may or may not be subjected to CVD deposition treatment. Finally, the desired product is crushed, classified, demagnetized, and packaged.

[0137] Example 15

[0138] This embodiment provides a composite material containing lithium-rich ferrite and layered positive electrode material, wherein the lithium-rich ferrite is 96% and the layered positive electrode material is 4%. Figure 1 As shown, the preparation method of the composite material is as follows:

[0139] S1. Weigh 96% iron oxide and 4% NCM811 precursor in proportion and add them to deionized water. Prepare a lithium source and aqueous solution in proportion. Control the solid content of the total slurry to 35%. After stirring, further grind to control the D50 particle size to ≤ 0.5 μm to obtain a slurry.

[0140] S2, drying the slurry to obtain a precursor powder;

[0141] S3, placing the precursor powder obtained in step S3 into a furnace with atmosphere for a first sintering at a temperature of 400° C. to 650° C. for a holding time of 4 h to 16 h to obtain a first sintered product;

[0142] S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent is added (optionally), mixed evenly, and then sintered for the second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product may or may not be subjected to CVD deposition treatment. Finally, the desired product is crushed, classified, demagnetized, and packaged.

[0143] Example 16

[0144] The embodiment provides a composite material containing lithium-rich lithium ferrite and a layered positive electrode material, wherein the lithium-rich lithium ferrite is 94%, and the layered positive electrode material is 6%. As shown in the figure, the preparation method of the composite material is as follows: Figure 1

[0145] S1, 96% iron oxide and 4% NCM811 precursor are weighed according to the proportion and added into deionized water, a lithium source and an aqueous solution are prepared according to the proportion, the total slurry is controlled to have a solid content of 35%, and after stirring, further grinding is performed to control the D50 particle size to be less than or equal to 0.5 μm, so that a slurry is obtained;

[0146] S2, the slurry is dried to obtain a precursor powder;

[0147] S3, the precursor powder obtained in step S3 is put into a furnace body with an atmosphere to perform first sintering, the sintering temperature is 400-650 DEG C, the holding time is 4-16 h, and a first sintering product is obtained;

[0148] S4, the first sintering product obtained in step S3 is crushed to have a D50 particle size of less than or equal to 40 μm, a small amount of surface coating agent is added (which can be added or not added) and uniformly mixed, and then second sintering is performed, the sintering temperature is 650-1300 DEG C, the holding time is 8-24 h, the second sintering product obtained can be selected to perform CVD deposition treatment, or can not be subjected to CVD deposition treatment, finally, the product is obtained by crushing, grading, removing magnetism and packaging.

[0149] Embodiment 17

[0150] The embodiment provides a composite material containing lithium-rich lithium ferrite and a layered positive electrode material, wherein the lithium-rich lithium ferrite is 98%, and the layered positive electrode material is 2%. As shown in the figure, the preparation method of the composite material is as follows: Figure 1

[0151] S1, 96% iron oxide and 4% NCM811 precursor are weighed according to the proportion and added into deionized water, a lithium source and an aqueous solution are prepared according to the proportion, the total slurry is controlled to have a solid content of 35%, and after stirring, further grinding is performed to control the D50 particle size to be less than or equal to 0.5 μm, so that a slurry is obtained;

[0152] S2, the slurry is dried to obtain a precursor powder;

[0153] S3, the precursor powder obtained in step S3 is put into a furnace body with an atmosphere to perform first sintering, the sintering temperature is 400-650 DEG C, the holding time is 4-16 h, and a first sintering product is obtained;

[0154] ​​S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent is added (optionally), mixed evenly, and then sintered for the second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product may or may not be subjected to CVD deposition treatment. Finally, the desired product is crushed, classified, demagnetized, and packaged.

[0155] Example 18

[0156] This embodiment provides a composite material containing lithium-rich ferrite and layered positive electrode material, wherein the lithium-rich ferrite is 90% and the layered positive electrode material is 10%. Figure 1 As shown, the preparation method of the composite material is as follows:

[0157] S1. Weigh 90% iron oxide and 10% NCM811 precursor in proportion, add them to deionized water, prepare a lithium source and aqueous solution in proportion, control the solid content of the total slurry to 35%, stir and further grind to control the D50 particle size ≤ 0.5 μm, to obtain a slurry;

[0158] S2, drying the slurry to obtain a precursor powder;

[0159] S3, placing the precursor powder obtained in step S3 into a furnace with atmosphere for a first sintering at a temperature of 400° C. to 650° C. for a holding time of 4 h to 16 h to obtain a first sintered product;

[0160] S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent is added (optionally), mixed evenly, and then sintered for the second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product may or may not be subjected to CVD deposition treatment. Finally, the desired product is crushed, classified, demagnetized, and packaged.

[0161] Example 19

[0162] This embodiment provides a composite material containing lithium-rich ferrite and layered positive electrode material, wherein the lithium-rich ferrite is 2% and the NCA precursor material is 98%. Figure 1 As shown, the preparation method of the composite material is as follows:

[0163] S1. Weigh 2% iron oxide and 98% NCA811 precursor in proportion and add them to deionized water. Prepare a lithium source and aqueous solution in proportion. Control the solid content of the total slurry to 35%. After stirring, further grind to control the D50 particle size to ≤ 0.5 μm to obtain a slurry.

[0164] S2, drying the slurry to obtain a precursor powder;

[0165] S3, placing the precursor powder obtained in step S3 into a furnace with atmosphere for a first sintering at a temperature of 400° C. to 650° C. for a holding time of 4 h to 16 h to obtain a first sintered product;

[0166] S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent is added (optionally), mixed evenly, and then sintered for the second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product may or may not be subjected to CVD deposition treatment. Finally, the desired product is crushed, classified, demagnetized, and packaged.

[0167] Example 20

[0168] This embodiment provides a composite material containing lithium-rich ferrite and layered positive electrode material, wherein the lithium-rich ferrite is 2% and the layered positive electrode material is 98%. Figure 1 As shown, the preparation method of the composite material is as follows:

[0169] S1. Weigh 2% iron oxide and 98% Co3O4 in proportion and add them to deionized water. Prepare a lithium source and aqueous solution in proportion. Control the solid content of the total slurry to 35%. After stirring, further grind to control the D50 particle size to ≤ 0.5 μm to obtain a slurry.

[0170] S2, drying the slurry to obtain a precursor powder;

[0171] S3, placing the precursor powder obtained in step S3 into a furnace with atmosphere for a first sintering at a temperature of 400° C. to 650° C. for a holding time of 4 h to 16 h to obtain a first sintered product;

[0172] S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent is added (optionally), mixed evenly, and then sintered for the second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product may or may not be subjected to CVD deposition treatment. Finally, the desired product is crushed, classified, demagnetized, and packaged.

[0173] Example 21

[0174] This embodiment provides a composite material containing lithium-rich ferrite and layered positive electrode material, wherein the lithium-rich ferrite is 2% and the layered positive electrode material is 98%. Figure 1 As shown, the preparation method of the composite material is as follows:

[0175] S1. Weigh 2% iron oxide and 98% Ni(OH)2 in proportion and add them to deionized water. Prepare a lithium source and aqueous solution in proportion. Control the solid content of the total slurry to 35%. After stirring, further grind to control the D50 particle size to ≤ 0.5 μm to obtain a slurry.

[0176] S2, drying the slurry to obtain a precursor powder;

[0177] S3, placing the precursor powder obtained in step S3 into a furnace with atmosphere for a first sintering at a temperature of 400° C. to 650° C. for a holding time of 4 h to 16 h to obtain a first sintered product;

[0178] S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent is added (optionally), mixed evenly, and then sintered for the second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product may or may not be subjected to CVD deposition treatment. Finally, the desired product is crushed, classified, demagnetized, and packaged.

[0179] Comparative Example 1

[0180] This embodiment provides a lithium-rich lithium ferrite material, and the preparation method of the material is as follows:

[0181] S1. Weigh ferric oxide and lithium source in proportion, grind to control the D50 particle size to ≤1 μm, and further grind to control the D50 particle size to ≤0.5 μm;

[0182] S2. 2% glucose can be added in proportion, mixed evenly, ground, and the D50 particle size is controlled to be ≤0.5 μm, and then dried to obtain a precursor powder;

[0183] S3, placing the precursor powder obtained in step S3 into a furnace with atmosphere for a first sintering at a temperature of 400° C. to 650° C. for a holding time of 4 h to 16 h to obtain a first sintered product;

[0184] S4. The calcined product obtained in step S4 is crushed to a D50 particle size of ≤40 μm, a small amount of alumina as a surface coating agent is added and mixed evenly, and then a second sintering is performed at a sintering temperature of 650° C. to 1300° C. and kept warm for 8 h to 24 h. The obtained second calcined product can be optionally subjected to CVD deposition treatment or not. Finally, the desired product is obtained by crushing, grading, demagnetizing, and packaging.

[0185] Comparative Example 2

[0186] Commercial layered lithium battery positive electrode material NCM811, Ni:Mn:Co=8:1:1.

[0187] Comparative Example 3

[0188] Commercial lithium cobalt oxide positive electrode material LCO.

[0189] The composite materials obtained in Examples 1 to 21 and Comparative Examples 1 and 2 were used as positive electrode lithium supplement materials. Under a dew point environment of -45°, the composite material, a carbon black conductive agent (SP), and a binder polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 8:1:1. Then, 120% by weight of N-methylpyrrolidone (NMP) was added as a solvent, mixed, and a 2024 button battery was prepared. The charging capacity was tested. The charge and discharge range was 2.0 V to 4.4 V, and the charge and discharge rate was 0.01 C. The test data are shown in Table 1 below.

[0190] Table 1 Test data of batteries made of different lithium-rich lithium iron oxides

[0191]

[0192]

[0193] As can be seen from Table 1 above, the charge capacity decreases with the increase of iron phosphate. This is because the charge capacity of the ternary NCM811 itself is about 232 mAh / g and the discharge capacity is about 218 mAh / g, while the theoretical specific capacity of LFO is equivalent to 867 mAh / g, and the actual performance is about 700-740 mAh / g, but its discharge capacity is very low (about 30 mAh / g). Therefore, it can be seen that as the addition amount of ternary material increases, its charge capacity decreases, but its discharge capacity increases. From Comparative Example 1, it can be seen that the uncoated LFO has a charge capacity of only 546.3 Ah / g and a discharge capacity of 29.3 mAh / g due to its poor air stability. In Example 14, the LFO coated with 2% NCM811 has a charge capacity of up to 733 mAh / g and a discharge capacity of 35 mAh / g.

[0194] On the other hand, Examples 1-5 show that a low LFO content and a high NCM ratio can serve as a self-contained lithium supplement cathode material, exhibiting both higher charge capacity and relatively high discharge capacity. The charge capacity increases with increasing LFO content, from 242 mAh / g to 282 mAh / g, while the discharge capacity decreases from 214 mAh / g to 199 mAh / g.

[0195] In Examples 6-13% with moderate lithium supplementation, it can be seen that increasing the amount of ternary material reduces charge capacity, but increases discharge capacity. At low LFO content, charge capacity increases from 334 mAh / g to 692 mAh / g, while discharge capacity decreases from 180 mAh / g to 50 mAh / g. These examples are suitable as additives for uniform lithium supplementation, mitigating the risk of localized lithium deposition caused by uneven lithium supplementation.

[0196] As can be seen in Examples 14-18 with high LFO and low NCM coating, as the LFO content further increases, the charging capacity can reach up to 733 mAh / g and the discharge capacity can reach 35 mAh / g. The composite material in this ratio range is suitable for addition as a small amount of lithium supplement to high nickel positive electrode materials. At the same time, since its coating material is the same positive electrode material, it has better compatibility with the system and can better suppress the side reactions and gas production problems of the system.

[0197] In Example 19, a composite material prepared using high-density NCA and low-LFO exhibited similar trends, with a charge capacity of 250 mAh / g and a discharge capacity of 208 mAh / g. This composite material can also be used as a positive electrode material with a self-contained lithium supplement. It can also be used to prepare composite materials with varying proportions for uniform lithium supplementation or high-capacity lithium supplementation.

[0198] In addition, in Examples 20 and 21, layered materials lithium cobalt oxide and lithium nickel oxide were also used to prepare lithium cobalt oxide and lithium nickel oxide. In Example 21, it can be seen that the composite material of lithium nickel oxide and LFO has a charge capacity of 223 mAh / g and a discharge capacity of 167 mAh / g. As can be seen in Example 20 and Comparative Example 3, pure commercial lithium cobalt oxide has a charge capacity of approximately 213 mAh / g and a discharge capacity of 196 mAh / g at 4.4 V, while the charge capacity of the composite material prepared in Example 20 is approximately 228 mAh / g and the discharge capacity is 194 mAh / g. Similarly, it can also be used to prepare composite materials with different proportions for uniform lithium supplements or high-capacity lithium supplements.

[0199] Furthermore, it can be seen that the composite material containing lithium-rich ferrite and layered positive electrode material obtained by adjusting the ratio of LFO and layered ternary material in the present invention can be used as a high-capacity lithium supplement additive when the content of lithium-rich ferrite is high, and can be used as a lithium supplement additive with a moderate addition amount when the content of lithium-rich ferrite is moderate, which is suitable for uniform lithium supplementation and improving the problem of local lithium precipitation caused by uneven dispersion of high-capacity lithium-rich ferrite. When the content of lithium-rich ferrite is low, it can be used as a positive electrode material containing a small amount of lithium-rich ferrite.

[0200] In addition, lithium-rich lithium iron oxide is mainly used to improve the initial efficiency and cycle performance of the battery cell; the layered positive electrode material as the main active material can improve the air stability after being coated at the same time; the carbon layer that may or may not be contained is mainly used to improve the electronic conductivity and air stability of the material; the coating layer that may or may not contain other elements is mainly used to improve the electrical performance and can also improve the air stability to a certain extent.

[0201] The composite material containing lithium-rich lithium ferrite and ternary materials provided by the present invention is used in electrode plates, batteries, battery packs, and electrical equipment. The battery includes any one of a lithium-ion battery, a solid-state battery, and a semi-solid-state battery.

[0202] The above embodiments are merely illustrative of the concepts and technical solutions of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical concepts disclosed herein are intended to be covered by the claims of the present invention.

[0203] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation method can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. The present invention discloses a composite material containing lithium-rich lithium ferrite and a layered positive electrode material, which comprises lithium-rich lithium ferrite and a layered positive electrode material as a main active material; and a coating layer that may or may not contain a carbon coating layer, and a coating layer that may or may not contain other elements other than carbon, wherein the weight of the lithium-rich lithium ferrite a + the weight of the active material b = 100%; the weight of the carbon coating layer is c, and the weight of the coating layer of other elements other than carbon is d.

2. According to claim 1, it is characterized in that The mass a of the lithium-rich lithium ferrite is: 0≤a≤100%; the structural formula of the lithium-rich lithium ferrite is Li5FeO4.

3. According to claim 1, it is characterized in that The main active material is a layered positive electrode material, 0%≤the percentage of the layered positive electrode material mass in the total material weight≤100%; the layered positive electrode material can be a ternary material (single or polycrystalline material of any proportion of NCM, NCA, and multi-material modified with ternary material as the main structure); lithium cobalt oxide positive electrode material, and cobalt-free layered positive electrode material; the layered ternary positive electrode material structure is LiNi x Co y M 1-x-y O2, wherein M is at least one of Mn, Al, W, Zr, Mg, B, Nb, Ta, Mo, La and Ti, 0.33≤x≤1.0, 0≤y≤0.33, and the structural formula of the multi-element material modified with the ternary material as the main structure is LiNi x Co y M z N 1-x-y-z O2, wherein M is at least one of Mn, Al, W, Zr, Mg, B, Nb, Ta, Mo, La and Ti, 0.33≤x≤1, 0≤y≤0.33, 0≤z≤0.33, N is Mn, Al, W, Zr, Mg, B, Nb, Ta, Mo, La and Ti, and M and N are not the same element.

4. According to claim 1, the carbon coating layer comprises a coating layer formed by an inorganic carbon source and / or an organic carbon source and / or an organic gas, 0%≤the percentage of the mass of carbon in the weight of the whole material≤10%, and the coating thickness of the carbon layer is 0nm≤≤100nm; the inorganic carbon source comprises at least one of carbon nanotubes, graphene, graphite, fullerene, VGCF, amorphous carbon, soft carbon, and hard carbon, or a combination of two or more thereof; the organic carbon source comprises one of glucose, cellulose, sucrose, starch, PEG, PEO, cellulose, petroleum, asphalt, and PVP, or a combination of two or more thereof; the organic gas carbon source comprises chain alkanes (C n H 2n+2 (where n ≥ 1), such as methane (CH4), ethane (C2H6), propane (C3H8), etc.), cyclic alkanes have the general formula C n H 2n (where n ≥ 3), such as cyclopropane (C3H6), cyclohexane (C6H 12 ) etc., olefins with the general formula C n H 2n (where n ≥ 2), such as ethylene (C2H4), propylene (C3H6), butene (C4H8), etc.; olefin molecules contain carbon-carbon double bonds, and the general formula of alkynes is C n H 2n-2 (where n ≥ 2), such as acetylene (C2H2), propyne (C3H4), butyne (C4H6), etc. Alkyne molecules contain carbon-carbon triple bonds, which can be one or more of the above compounds.

5. According to claim 1, it may or may not contain a coating layer of other elements except carbon to improve the performance of the material, and the coating layer thickness can be 0nm≤coating thickness≤50nm; 0≤d coating amount accounts for the mass ratio of the total material≤1%; its coating elements can include: one or more composites of B, N, Mg, Al, F, Si, P, S, K, Ca, Sc, V, Ti, Cr, Mn, Ni, Ga, Ge, La, Se, Rb, Sr, Y, Nb, Mo, Ru, Eu, Er, Yb, Dy, Cs, Sb, Sn, Se, Te, Bi, Zn, Cu, Ce, Rh, Tb, Lu, Hf, Ta, W, Os, Ir, Pt, Au, Pb, Zr, Cd, Pd, Ag, etc.

6. The present invention also discloses a composite material containing lithium-rich lithium ferrite and a layered positive electrode material and a preparation method thereof, characterized in that: The following steps are involved: S1. Weigh a lithium-rich lithium ferrite precursor and a layered cathode material precursor in proportion and add them to deionized water. Prepare an aqueous solution of a lithium source and a carbon source (optional) in proportion, control the solid content to ≤60%, stir, and then grind to control the D50 particle size to ≤0.5 μm to obtain a slurry. S2, drying the slurry to obtain a precursor powder; S3, placing the precursor powder obtained in step S2 into a furnace with atmosphere for a first sintering at a temperature of 400°C to 650°C and a holding time of 4h to 16h to obtain a first sintered product; S4. The calcined product obtained in step S3 is crushed to a D50 particle size of ≤40 μm, a small amount of surface coating agent is added (optionally), mixed evenly, and then sintered for a second time at a sintering temperature of 650° C. to 1300° C. for 8 h to 24 h. The obtained calcined product may or may not be subjected to CVD deposition treatment. Finally, the desired product is crushed, classified, demagnetized, and packaged.

7. The preparation method according to claim 6, characterized in that The lithium iron oxide-rich precursor includes one or a combination of two or more of iron oxide, iron hydroxide, iron nitrate, iron sulfate, ferrous sulfate, and nickel chloride. The ratio of the lithium iron oxide-rich precursor and the ternary precursor is consistent with the addition ratio in the final product.

8. The preparation method according to claim 6, characterized in that The lithium source includes one or a combination of two or more of lithium carbonate, lithium oxide, lithium hydroxide, lithium acetate, lithium citrate, lithium oxalate, and lithium adipate.

9. The preparation method according to claim 6, characterized in that The molar ratio range of the proportionally added ternary precursor and lithium is: 0.9≤Li:(x+y+z)=1.1, and the molar ratio range of Li and Fe in the proportionally added lithium ferrite-rich precursor is: 4.90≤Li / Fe≤5.

3.

10. The preparation method according to claim 6, characterized in that The drying treatment adopts any one of spray drying, flash evaporation and centrifugal drying; the drying temperature is ≥180°C.

11. The preparation method according to claim 6, characterized in that The sintering atmosphere is one of oxygen, nitrogen, argon, and air, or a combination of two or more thereof; the temperature of the CVD deposition process is 600° C. to 900° C., and the time is 2 h to 16 h; and the particle size D50 after the pulverization is ≤10 μm.

12. An application of the composite material containing lithium-rich lithium ferrite and layered positive electrode material according to claim 1 or the composite material containing lithium-rich lithium ferrite and layered positive electrode material obtained by the preparation method according to any one of claims 1 to 11 in electrode sheets, batteries, battery packs, and electrical equipment, wherein the battery includes any one of a lithium-ion battery, a solid-state battery, and a semi-solid-state battery.

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