Composite positive electrode lithium supplement additive and preparation method and application thereof

Abstract

The invention provides a composite positive electrode lithium supplement additive and a preparation method and application thereof. The composite positive electrode lithium supplement additive comprises a positive electrode lithium supplement agent and a conductive carbon layer located on the surface of the positive electrode lithium supplement agent, the median particle size D50 of the positive electrode lithium supplement agent is less than 1 mum. The surface of the small-particle-size positive electrode lithium supplement agent (the median particle size D50 is less than 1 mum) is coated with the conductive carbon layer, so that the rate characteristic of the material can be improved, the lithium supplement agent material can be applied to lithium iron phosphate in a non-voltage matching interval, the charge capacity of the lithium supplement agent is promoted, and efficient lithium supplement is realized.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and relates to a composite positive electrode lithium supplement additive and a preparation method and application thereof. Background technique [0002] Compared with lead-acid batteries, nickel-cadmium batteries and nickel-hydrogen batteries, lithium-ion batteries have the advantages of high energy density, high power density, high operating voltage, good cycle performance, long life, low self-discharge and wide temperature range. The energy density and cycle life of ion batteries are closely related to their first coulombic efficiency and the formation of negative electrode solid electrolyte interface (SEI) film. During the first charge and discharge process of lithium ion batteries, the formation of SEI film leads to battery capacity loss, and the loss ratio reaches 7-10%. , in order to solve the problem of capacity loss, the capacity loss of lithium-ion batteries during the fir...

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Problems solved by technology

However, the existing lithium supplement materials mainly involve metal lithium strips, stabilized metal lithium powder, lithium compounds or organolithium salts, among which the activity of metal lithium and organolithium salts is still too high to be stored stably for a long time, which increases the difficulty of operation and production risks, lithium compounds including Li 2 NiO 2 , Li 5 FeO 4 , Li 2 O. Li 2 S, LiF or Li 3 N, etc. are easy to store, can be used directly as positive electrode additives in the existing lithium-ion battery manufacturing process, and have low process requirements. They are the most suitable lithium supplement materials for industrialization, but lithiated positive electrode lithium supplements have the following disadvantages:

[0004] ②Lithium delithiation (charging) voltage window is 2.8-4.3V higher, which does not match the voltage window (2.5-3.65V) of lithium iron phosphate battery, and cannot be popularized and applied in lithium iron phosphate battery. 3.65-4.3V, there is a lithium supplementary agent for charging alone, which requires a high rate of material, and the required rate is at least 0.6-2.4C. At present, the lithium supplementary material cannot meet the rate requirement

[0007] The above scheme has the problem of poor rate performance or high requirements for the use environment, so it is necessary to develop a positive electrode lithium supplement additive with good rate performance and lower use environment requirements

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