Quick formation method for lithium ion battery adapting to various cathode material systems

Abstract

The invention provides a quick formation method for a lithium ion battery adapting to various cathode material systems. The formation method is divided into three stages, and in each stage, constant-current charging of the battery is realized through different currents, and the upper-limit cut-off voltage of each stage is controlled as the end condition. Currents selected in each stage gradually increase in a stepped manner, so that an SEI (Solid Electrolyte Interphase) film can be slowly and uniformly produced on the surface of a graphite negative pole; and selected upper-limit cut-off voltages are in different ranges respectively according to different cathode material systems, so that the SEI film can be effectively produced while the excessive lithium ion consumption is avoided. Besides, after each stage finishes, a certain standing time is set, so that the SEI films formed in each stage can be in steady states as far as possible According to the invention, not only is the production efficiency of the formation procedure improved, but also the quality of the SEI films in the formation process is guaranteed, and further, the comprehensive electrochemical performance of the lithium ion battery is improved.

Description

Technical field [0001] The invention relates to a method for forming a lithium ion battery. Background technique [0002] Lithium-ion secondary batteries have become currently widely used power products due to their advantages such as high cell voltage, high energy and power density, long life, light weight, no memory effect, and no pollution. Its application fields mainly include various portable electronic consumer products (such as smart phones, tablet computers, digital cameras, etc.); supporting energy storage for solar / wind power plants; electric vehicles (EV) and hybrid electric vehicles (HEV); military weapons and equipment; aerospace Wait. Especially in recent years, with the application in electric vehicles, people have put forward higher performance requirements for lithium-ion batteries. The improvement of lithium-ion battery performance is not only restricted by the performance improvement of various battery materials (such as cathode materials, anode materials, el...

AI Technical Summary

Problems solved by technology

The formation method using low current and limiting charging time is helpful to the formation of SEI film, thereby improving the performance of lithium-ion batteries, but this traditional formation method has the following disadvantages: (1) Long time small current will lead to excessive Lithium ions participate in the chemical reaction to form the SEI film, resulting in an increase in the growth thickness of the SEI film and an increase in the polarization impedance, which in turn affects the first charge and discharge efficiency, long-term cycle performance and rate performance of the battery; (2) The low-current formation process takes a long time , affecting the production efficiency, but shortening the low current formation time cannot ensure the full formation of the SEI film

Although high-current formation can improve production efficiency, the increase in current density will lead to the formation of an SEI film that is not dense and cannot effectively protect the negative electrode material, which will lead to the gradual deterioration of the performance of the battery during use.

Therefore, the traditional chemical formation process must accurately grasp the charging time of small currents, which is difficult to analyze and control through effective means.

[0005] At present, the published patents for the formation method are either aimed at lithium-ion batteries with a single specific positive and negative electrode system (such as lithium iron phosphate for the positive electrode in CN102324572A, and lithium titanate for the negative electrode), or the formation method used is very complicated. Usually includes multiple links such as constant current charging, constant voltage charging, constant current discharging, pulse charging or intermediate pumping operation, etc., which is time-consuming (such as CN101212066A, CN10728579A, CN102324570A, CN101728579A, CN101777669A, CN101764261A, etc.)

In addition, the chemical synthesis method involved in the published patents simply explains the cycle performance of the battery, but does not test and compare the rate performance of the battery, so the rate performance of the battery produced by this method is unknown

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