Lithium ion battery and formation method thereof

Abstract

The invention discloses a lithium ion battery formation method. A negative electrode active substance of a lithium ion battery comprises a lithium-rich manganese-based positive electrode material. Theformation method includes at least three times of charge-discharge cycles; in the two former charge-discharge cycles, charge cut-off voltage is lower than 4.4V, discharge current is higher than charge current, and the second-time charge current is higher than the first-time charge current; in the last charge-discharge cycle, the charge cut-off voltage is not lower than 4.4V, and the charge current is not lower than the second-time charge current. By the step voltage charge-discharge formation method, a stable SEI film can be formed on the surface of a negative electrode in repeated low-voltage charge-discharge processes while a stable CEI film is formed on the surface of a positive electrode, side reaction between electrolyte and an electrode piece can be inhibited, gas generation is reduced, and accordingly the problem of battery swelling is solved. In addition, by the method, structural stability and capacity exertion of the lithium-rich manganese-based positive electrode material under a high voltage can be improved, and the cycle performance and the energy density of the battery are improved as well.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a lithium ion battery and a formation method thereof. Background technique [0002] As a new type of high-energy green battery, lithium-ion batteries are widely used in portable electronic products such as notebook computers and mobile phones, and are expanding to large and medium-sized energy storage equipment and new energy electric vehicles. This has a great impact on the energy density of lithium-ion batteries. And safety and so on put forward higher requirements. [0003] At present, power batteries at home and abroad mainly use ternary layered positive electrode materials or lithium iron phosphate positive electrode materials and graphite negative electrodes, and their energy density is ≤180Wh / kg. However, according to Japan's "NEDO Next Generation Automotive Battery Technology Development Roadmap 2013", it is proposed that by 2020, the energy den...

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Problems solved by technology

[0006] CN 103647115A proposes that the lithium-rich manganese-based battery is activated at a high voltage (cut-off voltage > 4.4V) and the battery is charged and discharged at a low voltage, although the battery releases a high-capacity lithium-rich manganese-based solid solution material through activation , it has higher capacity and cycle stability at a lower charge cut-off voltage, but due to the high initial activation voltage, the battery will be severely flattened during the first activation process to consume electrolyte and destroy the stability of the electrode structure, which will eventually affect the long-term cycle stability of the battery.

US 2013 / 0043843 A1 proposed a staged low-voltage charging method to improve the cycle stability of lithium-rich manganese-based batteries, but because its formation voltage is <4.4V, the capacity of the battery is low and cannot meet the needs of high specific energy batteries

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