CN-121983504-A - Positive electrode slurry and preparation method thereof

CN121983504ACN 121983504 ACN121983504 ACN 121983504ACN-121983504-A

Abstract

The application belongs to the technical field of battery materials, and particularly relates to positive electrode slurry and a preparation method thereof. According to the application, through accurately introducing the lithium supplementing agent adapting to the lithium iron phosphate system, permanent lithium source loss caused by SEI film formation in the first circulation of the battery can be pertinently supplemented, the first coulomb efficiency of the battery is fundamentally improved, the core short plate with excessively high lithium consumption in the traditional dry process is effectively compensated, meanwhile, the preparation flow of the positive electrode slurry is innovatively optimized, the step-by-step composite strategy of firstly preparing a binder colloidal dispersion, then realizing nanometer deagglomeration dispersion of the conductive agent and finally adding the positive electrode active substance and the lithium supplementing agent for interfacial cladding is adopted, the limitation of relying on mechanical shearing force and lacking solvent auxiliary infiltration in the traditional dry process is broken through the synergistic effect of the colloidal dispersion on the powder, the interfacial tension and agglomeration resistance of the powder are greatly reduced, and the industry pain point of overlong dispersing time consumption of the traditional process is solved.

Inventors

WU HAO
WANG KAIBIN
LI LINHE
WU ZHENXING
WANG CHENXI
WANG HONG

Assignees

天能新能源(湖州)有限公司

Dates

Publication Date: 20260505
Application Date: 20260105

Claims (8)

1. The preparation method of the positive electrode slurry is characterized by comprising the following steps: placing the binder in a solvent, and stirring and dissolving to obtain colloidal dispersion; Introducing a conductive agent into the colloidal dispersion, and forming conductive composite slurry through high-speed shearing and dispersion; Adding an anode active material and a lithium supplementing agent into the conductive composite slurry, and mechanically stirring to realize interface infiltration to obtain a slurry precursor; and carrying out vacuum defoaming treatment on the slurry precursor to obtain the anode slurry.
2. The method for preparing a positive electrode slurry according to claim 1, wherein the lithium supplementing agent comprises at least one of lithium difluorooxalato borate, lithium oxalate, lithium nickelate, lithium silicate, lithium squarate and lithium ferrite.
3. The preparation method of the positive electrode slurry according to claim 1, wherein the conductive agent adopts a composite system of super carbon black and carbon nano tubes, and the mass ratio of the super carbon black to the carbon nano tubes is (2:1) - (4:1).
4. The method for preparing a positive electrode slurry according to claim 1, wherein the addition ratio of the positive electrode active material, the conductive agent, the binder and the lithium supplementing agent is 90.0 to 96.0 parts, 1.5 to 3.5 parts, 1.2 to 2.5 parts and 1.0 to 5.0 parts by mass.
5. The method for preparing the positive electrode slurry according to claim 4, wherein an antifoaming agent is further added in the vacuum defoaming treatment process, and the antifoaming agent is an organosilicon or polyether modified organosilicon compound.
6. The method for producing a positive electrode slurry according to claim 5, wherein the defoaming agent is added in an amount of 0.1 to 0.5 parts by mass.
7. A positive electrode slurry prepared by the preparation method of any one of claims 1 to 6.
8. The positive electrode slurry according to claim 7, wherein the positive electrode slurry has a solid content of greater than 72%.

Description

Positive electrode slurry and preparation method thereof Technical Field The application belongs to the technical field of battery anode materials, and particularly relates to lithium iron phosphate anode slurry added with a lithium supplementing agent. Background The lithium iron phosphate positive electrode slurry is a core functional material for manufacturing a lithium ion battery positive electrode, and is mainly prepared by mixing a lithium iron phosphate (LFP) positive electrode active material, a conductive agent (such as carbon black, carbon nano tubes, graphene and the like), a binder (such as PVDF) and an organic solvent (such as NMP) according to a specific proportion, wherein the component dispersion uniformity and the viscosity stability of the lithium iron phosphate positive electrode slurry directly determine the conductivity and the structural strength of a positive electrode plate, and further influence the energy density, the cycle life and the production consistency of the battery. The existing preparation method of the lithium iron phosphate positive electrode slurry mainly comprises two major types, namely a dry process and a wet process, wherein all raw materials are required to be mixed and dispersed in a solvent in the whole process in the wet process, and the dispersion is realized by the synergistic effect of solvent infiltration and mechanical shearing, but the problems of large solvent consumption, high subsequent recovery cost and long production period exist, the dry process uses the mechanical shearing force as a core, firstly pre-mixes solid powder, and then gradually adds the solvent for kneading and dispersing, so that the method has the characteristics of less solvent consumption, easy improvement of solid content and better environmental protection. Because the traditional wet process has the defects of high environmental protection cost and low production efficiency, and the dry process can reduce the consumption of the binder and improve the solid content of the slurry by optimizing the mixing step, the current mainstream and most common preparation mode is dry double-screw kneading pulping, and the mode efficiently realizes the uniform mixing of solid powder and the sufficient kneading of the subsequent solvent by the strong shearing and conveying action of the screw, so that the slurry performance is ensured to be stable. For example, the patent with the application number 202411972474.2 discloses a method for preparing modified lithium iron phosphate anode slurry by a dry method, which specifically comprises the steps of firstly dry-mixing a lithium iron phosphate anode material, a binder PVDF and a first conductive agent (composed of at least two of carbon black, carbon nano tubes and graphene) to obtain a first premix, adding an organic solvent (preferably NMP) into the first premix, gradually increasing the stirring speed, continuously stirring for at least 55min to obtain a second premix, adding a second conductive agent (the material of which the same as that of the first conductive agent is in an optional range), a binder PVP and a proper amount of organic solvent into the second premix, and continuously stirring at a gradual speed for at least 90min to obtain the lithium iron phosphate anode slurry. The performance test result shows that the solid content of the modified slurry is stabilized at 55% -65%, the viscosity is controlled at 4000-9000 mpa and s, the resistivity of the positive plate prepared from the slurry is as low as 15-17 omega cm, the peeling strength can reach 75-85N/m, and compared with the traditional process product (the resistivity is 19-21 omega cm, the peeling strength is 30-40N/m), the conductivity and the structural bonding stability are greatly improved. However, the lithium iron phosphate active material and the conductive agent are ultrafine powder which is easy to agglomerate, the uniform coating of the adhesive on the surface of the powder is realized only by relying on mechanical shearing force, the interfacial tension and agglomeration resistance of the powder are broken through, the dispersion kneading time is obviously longer, further, the problem that the adhesive is easy to locally coat too thick or lack and the conductive agent is easy to form an isolated conductive area is limited by the uniformity bottleneck of dry mixing, the reaction of the surface of the active material and the electrolyte is aggravated, a thicker irreversible SEI film is formed, the first coulombic efficiency is lower and the permanent lithium source is lost, the theoretical performance gain caused by high solid content is directly counteracted, and the whole energy density of the battery is finally reduced. Disclosure of Invention The application provides a preparation method of positive electrode slurry with simple preparation process and higher overall energy density of a battery, which is realized by the following technical scheme: A preparation m