Lithium ion battery cathode additive and preparation method thereof, lithium ion battery cathode piece and lithium ion battery

Abstract

The embodiment of the invention provides a lithium ion battery cathode additive. The lithium ion battery cathode additive is of a nuclear shell wrapping structure formed by simple substance lithium powder and polymer wrapped on the surface of the simple substance lithium powder, wherein the polymer can be dissolved in carbonic ester solvent, the polymer cannot react with N,N-dimethylformamide, N,N-dimethylacetamide, N-2-methyl pyrrolidone, tetrahydrofuran, acetone or methyl alcohol, and the polymer stably exists at the temperature of 0-150 DEG C. The lithium ion battery cathode additive can be taken as a lithium source to be added in lithium ion battery cathode material, and is used for compensating lithium consumption of lithium ion battery cathode during the first charging and discharging process. The embodiment of the invention further provides a preparation method of the lithium ion battery cathode additive, a lithium ion battery cathode piece and a lithium ion battery containing the lithium ion battery cathode additive. The lithium ion battery is high in energy density and long in cycle life.

Description

technical field [0001] The invention relates to the field of lithium ion batteries, in particular to a lithium ion battery negative electrode additive, a preparation method thereof and a lithium ion battery. Background technique [0002] Among many energy storage technologies, lithium-ion batteries are widely used in mobile phones and notebook computers due to their advantages such as light weight, small size, high working voltage, high energy density, high output power, high charging efficiency, no memory effect, and long cycle life. and other fields have been widely used. In recent years, the idea of ​​developing lithium-ion batteries with higher energy density and higher power density has become more urgent as the demand for applications such as small-sized portable devices and high-power electric vehicles has increased. [0003] The current problem is that during the first cycle of the lithium-ion battery system, the electrolyte and the negative electrode material will ...

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Problems solved by technology

[0003] The current problem is that during the first cycle of the lithium-ion battery system, the electrolyte and the negative electrode material will react at the solid-liquid interphase level to form a layer of SEI film. This process will consume lithium in the active material of the negative electrode material, resulting in Reduction of Initial Capacity of Li-ion Batteries

[0004] In this regard, the current solutions include: (1) Prioritize the formation of SEI films before assembling lithium-ion batteries, thereby reducing the consumption of irreversible capacity. Under dry conditions, the negative electrode is soaked in the electrolyte, and the external circuit is connected to form an SEI film on the surface. After cleaning and drying, the negative electrode is assembled with other components into a battery, so as to avoid the formation of SEI during the initial formation and improve the battery life. First-time efficiency; but in the scheme, not only the process conditions are harsh and the process is cumbersome, resulting in a large waste of cost, but also the negative electrode needs to be cleaned and dried many times after film formation, which affects the performance of the electrode, especially the bonding effect of the electrode have a great impact, so the safety of the lithium-ion battery system cannot be guaranteed

(2) Provide a "lithium source" to compensate for the loss of lithium ions during the first charge / discharge of the lithium-ion battery, thereby reducing the irreversible capacity. For example, the US FMC company provides metal lithium powder that can exist stably in the air-stabilized lithium Metal Powder (SLMP), and introduce it into the negative electrode material in the form of slurry mixing or rolling, that is, use the additional lithium source to compensate for the loss of lithium due to the formation of the SEI film during the first charge and discharge of the lithium-ion battery, thereby reducing the The purpose of irreversible capacity and increase energy density; but in this scheme, due to the form of SLMP: the main coating layer outside the lithium metal is lithium carbonate, and a small amount of lithium oxide or lithium hydroxide, hydrocarbons, when the lithium source participates in the reaction Residual lithium carbonate will increase the internal resistance of the system. Although a very small amount of hydrogen fluoride in the electrolyte may dissolve part of it, it may still affect the performance of lithium-ion batteries

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