Functional additive for high-voltage lithium ion battery, electrolyte for high-voltage lithium ion battery and high-voltage lithium ion battery

Abstract

The invention relates to the field of lithium ion batteries, and particularly provides a functional additive for a high-voltage lithium ion battery, an electrolyte for the high-voltage lithium ion battery and the high-voltage lithium ion battery. The functional additive comprises metal cation and anion groups; metal includes at least one of sodium, potassium, rubidium, cesium, francium, alkaline earth metal and a first sub-group element in a periodic table of chemical elements or a second sub-group element in the periodic table of the chemical elements; and the anion group includes at least one of a sulfur-containing anion group, a boron-containing anion group and a cyanide-containing anion group. The specific metal cation and anion groups in the functional additive jointly form a main framework of an SEI film; and a layer of the SEI film which is dense and uniform and is low in impedance can be formed on the surface of a positive electrode of the lithium ion battery, so that the decomposition of an electrolyte solvent and a conductive lithium salt is inhibited, a positive electrode material is prevented from being corroded by a decomposition byproduct of the electrolyte solvent orthe conductive lithium salt, the structure of the positive electrode material is stabilized, and the cycling stability of the battery is improved.

Description

technical field [0001] The invention relates to the field of lithium-ion batteries, in particular to a functional additive for high-voltage lithium-ion batteries, an electrolyte solution for high-voltage lithium-ion batteries and a high-voltage lithium-ion battery. Background technique [0002] The theoretical capacity of the existing common commercial lithium-ion cathode materials is relatively large, but since the cut-off voltage is not higher than 4.2V, the energy density of the lithium-ion battery is not high enough. As the market demand for high-energy-density lithium-ion batteries continues to increase, in addition to continuous research and development of new materials, how to improve the energy density of batteries on the basis of existing materials is also one of the research hotspots, and improving the cut-off voltage of cathode materials It is an effective means to increase energy density. [0003] However, increasing the cut-off voltage of the cathode material a...

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Problems solved by technology

[0003] However, increasing the cut-off voltage of the cathode material also faces many problems: First, as the voltage continues to increase, the oxidation activity of the cathode material continues to increase, and the reaction between the cathode material and the electrolyte also accelerates, and the stability of the structure of the cathode material decreases. , resulting in a decrease in the cycle performance of the battery

Secondly, the conventional electrolyte used in conjunction with the positive electrode material has extremely poor compatibility at high voltage, and the commonly used electrolyte is prone to oxidative decomposition at high voltage, and the produced by-products have a negative impact on battery performance. On the one hand, The internal impedance of the battery will increase. On the other hand, the positive electrode material of the battery will also be corroded. Especially for ternary materials, nickel-cobalt-manganese plasma will be dissolved from the positive electrode material under high voltage, causing the structure of the positive electrode material to collapse, resulting in capacity loss. Irreversible attenuation, which in turn leads to a decrease in the cycle performance of the battery

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