Lithium ion secondary battery and anode thereof

Abstract

The invention provides a high-energy-density lithium ion secondary battery. The lithium ion secondary battery mainly comprises an anode, a cathode, an isolating film, electrolyte and a packaging bag, wherein a positive active material is a mixed material of a lithium cobaltate series active substance A and a high-nickel ternary active substance B; the positive active material is subjected to surface coating treatment of a metal fluoride MeFx (Me is one of Al, Mg, Co and Ni) after mixing; and the mass ratio of the active substance B to the active substance A is between 0.25 and 3.0, and the compacted density is more than or equal to 3.8g/cm<3>. The lithium ion secondary battery has the characteristics of high capacity, high compacted density, high working voltage and good cycle performance at a voltage more than or equal to 4.25V, and the problem that the battery generates a gas during high-temperature storage is solved at the same time.

Description

Technical field: [0001] The invention relates to the technical field of lithium ion batteries, in particular to a lithium ion secondary battery with high energy density and its positive electrode material. Background technique: [0002] The lithium-ion secondary battery with aluminum-plastic composite film as the outer packaging has the characteristics of high energy density, excellent safety performance, large-capacity monomer and environmental protection; and because of its advantages of thinness, lightness and arbitrary shape, it can be customized In order to achieve miniaturization, light weight, and maximum utilization of space, there is an increasing demand for it as a power source for portable devices such as mobile phones, notebook computers, wireless headsets, Bluetooth devices, MPx, and watches. In addition, this lithium-ion battery is also attracting attention as a power source for Scooter, xEV, etc. [0003] The cathode material is one of the key materials restr...

AI Technical Summary

Problems solved by technology

Same as LiCoO 2 In comparison, high-nickel ternary materials have the following advantages: at 4.2V, the actual specific capacity can be as high as 170-210mAh / g, which is significantly higher than that of LiCoO 2 ; Nickel resources are relatively abundant, cheap, and non-polluting to the environment. Therefore, high-nickel ternary materials have attracted much attention in recent years, but their actual compacted density is only 3.6g / cm 3 , The discharge voltage platform is low and the material itself has certain defects: it has strong water absorption, and it is easy to gel during the preparation of the slurry, which is difficult to prepare; it is particularly worth noting that: Li in the structure + and Ni 2+ Mixing is easy to occur, leading to the release of active oxygen, and at the same time, high-valent nickel ions are easily dissolved into the electrolyte, which catalyzes the decomposition of the electrolyte, and makes lithium-ion secondary batteries made of high-nickel ternary materials generate a large amount of gas during high-temperature storage. , Deteriorating battery performance, especially for lithium-ion batteries that use aluminum-plastic composite film as the outer packaging, the outer casing is relatively soft, and the generation of gas will cause rapid expansion and deformation of the battery, which will bring serious safety hazards and limit its use.

However, the cleaning process with deionized water in this method easily destroys the surface structure of the high-nickel active material, resulting in the inability to effectively form a LiF protective layer on the surface of the positive electrode material during the subsequent chemical formation and aging process; susceptible to LiPF 6 The attack of the decomposition product HF thus produces H 2 O, H 2 O will further catalyze LiPF 6 Decomposition, resulting in rapid battery capacity decay during subsequent cycles

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