Lithium Ion Battery

Abstract

The present application provides a lithium ion battery. The lithium ion battery includes an electrode assembly and an electrolyte, and the electrode assembly includes a positive pole piece, a negative pole piece, and a separator. The positive electrode active material in the positive electrode sheet includes Li x co y m 1‑y o 2‑z Q z , 0.5≤x≤1.2, 0.8≤y<1.0, 0≤z≤0.1, M is selected from one or more of Al, Ti, Zr, Y, Mg, and Q is selected from one of F, Cl, S species or several. The electrolyte contains additive A, additive B and additive C, the additive A is a polynitrile six-membered nitrogen heterocyclic compound with a low oxidation potential, the additive B is an acid anhydride compound, and the additive C is a halogen-substituted cyclic carbonate compounds. The lithium ion battery of the present application has excellent cycle performance and storage performance, especially under high temperature and high voltage conditions.

Description

technical field [0001] The present application relates to the field of energy storage materials, in particular, to a lithium ion battery. Background technique [0002] Lithium-ion batteries are widely used in electric vehicles and consumer electronics due to their advantages such as high energy density, high output power, long cycle life and low environmental pollution. The current demand for lithium-ion batteries is: high voltage, high power, long cycle life, long storage life and excellent safety performance. [0003] Lithium-ion batteries currently widely use LiCoO 2 As a positive electrode active material, LiCoO in a fully discharged state 2 and half-charged Li 0.5 COO 2 (4.2V vs. Li) The performance is relatively stable when cycling, so the lithium ions that are actually used are only 1 / 2 of the actual lithium ion content. And when the voltage is greater than 4.2V, LiCoO 2 Lithium ions in the remaining 1 / 2 content can continue to be removed, but during the deep de...

AI Technical Summary

Problems solved by technology

And when the voltage is greater than 4.2V, LiCoO 2 Lithium ions in the remaining 1 / 2 content can continue to be removed, but during the deep delithiation process, Co 3+ Will be oxidized to very unstable Co 4+ , together with the surface oxygen that has lost a large number of electrons, oxidizes the electrolyte. At this time, a large amount of gas will be generated inside the battery and cause the battery to bulge.

At the same time, due to the corrosion effect of HF in the electrolyte on the surface of the positive electrode, the Co 4+ After being dissolved in the electrolyte, it deposits on the surface of the negative electrode, catalyzes the reduction of the electrolyte, and also produces a large amount of gas that causes the battery to bulge

In addition, due to the large overlap between the 3d energy level of Co and the 2p energy level of O, deep delithiation will also cause the lattice oxygen to lose a large amount of electrons, making LiCoO 2 The unit cell shrinks violently along the c-axis, which induces instability or even collapse of the local bulk phase structure, and finally causes LiCoO 2 Loss of active sites, rapid loss of lithium-ion battery capacity

Therefore LiCoO 2 Very poor performance when used in high voltage regimes greater than 4.2V

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