CN-118970048-B - Lithium-rich lithium ferrite material and preparation method and application thereof

CN118970048BCN 118970048 BCN118970048 BCN 118970048BCN-118970048-B

Abstract

The invention provides a lithium ferrite material rich in lithium, a preparation method and application thereof, and belongs to the technical field of lithium ion batteries. The lithium-rich lithium ferrite material comprises a core and a coating layer coated on the surface of the core, wherein the core is made of lithium-rich lithium ferrite doped with a first doping element, the coating layer is made of carbon doped with a second doping element, the first doping element comprises at least one of Ti, W, ni, ce, co, and the second doping element comprises at least one of B, N, S, O, P. The lithium-rich lithium ferrite material is used as a lithium supplementing agent in a battery, so that the capacity of the battery can be further improved and the gas yield can be reduced.

Inventors

LI MINGMING
LIU XINGLIANG
JIA XUEYING
ZHOU BO
WANG YI

Assignees

合肥国轩高科动力能源有限公司

Dates

Publication Date: 20260508
Application Date: 20240730

Claims (10)

1. The lithium-rich lithium ferrite lithium supplementing agent material is characterized by comprising a core and a coating layer coated on the surface of the core, wherein the material of the core is lithium-rich lithium ferrite doped with a first doping element, the material of the coating layer is carbon material doped with a second doping element, the first doping element comprises at least one of Ti, W, ni, ce, co, the second doping element comprises at least one of B, N, S, P, the chemical formula of the core is Li 5 Fe (1-x) M x O 4 , M is the first doping element, and x is more than or equal to 0.001 and less than or equal to 0.002; The preparation method of the lithium-rich lithium ferrite lithium supplementing agent material comprises the following steps: Step S1, carrying out first mixed grinding on a lithium source, an iron source and a first doping material, and obtaining a core material after first sintering treatment; s2, mixing and dispersing a carbon source and a second doping material in a solvent, and heating and stirring until the solvent volatilizes to obtain a coating layer precursor; And step S3, carrying out second mixing grinding on the core material and the coating layer precursor, and obtaining the lithium-rich lithium ferrite lithium supplementing agent material after second sintering treatment.
2. The lithium-rich lithium ferrite lithium filler material of claim 1, wherein the first doping element comprises at least one of Ti, W, ni, ce and/or the second doping element comprises at least one of N, S.
3. The lithium-rich lithium ferrite lithium-supplementing material according to claim 1 or 2, wherein the D50 particle size of the lithium-rich lithium ferrite lithium-supplementing material is 3-8 μm, and/or the thickness of the coating layer is 1-20 nm, and/or the molar ratio of iron element to the first doping element is 1 (0.001-0.0021) in the material of the core, and/or the molar ratio of carbon element to the second doping element is (4-9): (0.2-0.5) in the material of the coating layer.
4. A method of preparing a lithium-rich lithium ferrite lithium-supplementing material according to any one of claims 1 to 3, comprising the steps of: Step S1, carrying out first mixed grinding on a lithium source, an iron source and a first doping material, and obtaining a core material after first sintering treatment; s2, mixing and dispersing a carbon source and a second doping material in a solvent, and heating and stirring until the solvent volatilizes to obtain a coating layer precursor; Step S3, carrying out second mixed grinding on the core material and the coating layer precursor, and obtaining the lithium-rich lithium ferrite lithium supplementing agent material after second sintering treatment; The first doping material comprises a first doping element, the second doping material comprises a second doping element, the first doping element comprises at least one element of Ti, W, ni, ce, co, the second doping element comprises at least one element of B, N, S, P, and the second doping material comprises at least one of cyanamide, glutathione, sodium borohydride and phytic acid.
5. The method of claim 4, wherein in step S1, the first dopant material comprises at least one of TiO 2 、WO 3 、NiO、CeO 2 、Co 2 O 3 .
6. The method according to claim 4 or 5, wherein in step S1, the lithium source comprises at least one of Li 2 O、LiOH、Li 2 C 2 O 4 、Li 2 CO 3 , and/or the iron source comprises at least one of Fe 2 O 3 、Fe 2 (C 2 O 4 ) 3 、Fe(NO 3 ) 3 , and/or wherein in step S2, the carbon source comprises at least one of conductive carbon black, graphite, and graphene.
7. The method according to claim 4 or 5, wherein in step S1, the molar ratio of the lithium element in the lithium source, the iron element in the iron source, and the first doping element in the first doping material is (5.5-6): 1 (0.001-0.0021), and/or in step S2, the mass ratio of the carbon source to the second doping material is (5-10): 1, and/or in step S3, the mass ratio of the core material to the clad precursor is (20-50): 1.
8. The method according to claim 4 or 5, wherein in step S1, the first sintering treatment is performed under an inert atmosphere, the first sintering treatment comprises a first-stage sintering and a second-stage sintering, the first-stage sintering is performed at a temperature of 400-600 ℃ for 4-6 hours, the second-stage sintering is performed at a temperature of 700-850 ℃ for 3-5 hours, and the second-stage sintering is performed at a temperature of 400-600 ℃ for 4-6 hours, and the heating rate of 5-10 ℃ per min, and/or the solvent comprises at least one of water, ethanol, and acetone in step S2, and the heating temperature of 60-100 ℃.
9. A positive electrode sheet comprising a positive electrode active material and a lithium supplementing agent, wherein the lithium supplementing agent comprises the lithium-rich lithium ferrite lithium supplementing agent material according to any one of claims 1 to 3 or the lithium-rich lithium ferrite lithium supplementing agent material produced by the production method according to any one of claims 4 to 8.
10. A lithium ion battery, comprising a positive plate, an electrolyte, a diaphragm and a negative plate, wherein the positive plate is the positive plate of claim 9.

Description

Lithium-rich lithium ferrite material and preparation method and application thereof Technical Field The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium-rich lithium ferrite material, a preparation method and application thereof. Background In recent years, as demands for portable devices, electric vehicles, etc., continue to increase, higher demands are being placed on the capacity of lithium ion batteries. In the first charge process of a lithium ion battery, a solid electrolyte membrane (SEI film) is formed on the surface of the negative electrode, so that lithium from the positive electrode is permanently consumed, irreversible capacity loss is formed, the coulomb efficiency of the first cycle is low, and the capacity of the battery is reduced. Therefore, how to supplement lithium ions consumed in the SEI film formation process to increase the capacity of a battery is a current research hotspot. At present, the pre-lithiation technology adds lithium into the battery to supplement lithium ions, and mainly comprises negative electrode lithium supplement and positive electrode lithium supplement. Among them, the lithium-rich lithium ferrite positive electrode lithium supplementing agent is receiving attention because of its advantages of high potential and good compatibility with the main materials of the existing battery, but its lithium ion conductivity and electron conductivity are poor and stability is poor, which not only results in difficulty in exerting the whole capacity, but also affects the processability of the slurry. At present, the surface of the positive electrode lithium supplementing agent is mostly coated with a carbon layer to improve the conductivity and stability of lithium ions and electrons, so that the carbon layer is used for isolating the external environment, and the carbon layer is used for forming a conductive network to improve the conductivity of the material. However, the compatibility of the carbon layer and the lithium ferrite is poor, the coating is often uneven and unstable, the stability of the lithium ferrite in the slurry and the capacity of the battery are still affected, in addition, the lithium ferrite positive electrode lithium supplementing agent can generate oxygen molecules or oxygen free radicals in the first charging process, the oxygen molecules or oxygen free radicals diffuse into the electrolyte and undergo oxidative decomposition reaction with partial components in the electrolyte to form a large amount of gases such as carbon dioxide, hydrogen and the like, the gas yield is increased, the phenomena of swelling and the like of the battery still prevent the application of the lithium ferrite serving as the positive electrode lithium supplementing agent. Therefore, how to reduce the gas yield while ensuring the stability and the lithium supplementing capacity is a technical problem to be solved in the field. Disclosure of Invention The invention mainly aims to provide a lithium-rich lithium ferrite material, and a preparation method and application thereof, so as to solve the problems of poor stability, difficult exertion of lithium supplementing capacity and large gas yield when the lithium-rich lithium ferrite is used as a positive electrode lithium supplementing agent in the prior art. In order to achieve the above object, according to a first aspect of the present invention, there is provided a lithium-rich ferrite material, including a core and a coating layer coated on a surface of the core, wherein the core is made of lithium-rich ferrite doped with a first doping element, and the coating layer is made of carbon doped with a second doping element, and the first doping element includes at least one of Ti, W, ni, ce, co and the second doping element includes at least one of B, N, S, O, P. The first doping element and the second doping element are introduced to enable the inner core to have oxygen vacancies, the coating layer is provided with nucleation sites, on one hand, adsorption is formed between the oxygen vacancies of the inner core and the nucleation sites of the coating layer, the bonding strength of the inner core and the coating layer is enhanced, the coating layer is enabled to be coated more uniformly and firmly, so that the coating effect is improved, the problems of poor stability and difficult maximum play of lithium supplementing capacity of the lithium-rich ferrite lithium material caused by uneven and infirm coating layer are avoided, the stability of the lithium-rich ferrite lithium material and the capacity of a battery are facilitated to be further improved, on the other hand, due to the existence of the oxygen vacancies in the inner core and the nucleation sites in the coating layer, oxygen molecules or oxygen free radicals generated by the battery in the first charging process can be bound in the material through typing or adsorption, the escaping is reduced, the problem th