Electrolyte additive for improving high-temperature performance of lithium battery, electrolyte and electrochemical device

Abstract

The invention discloses an electrolyte additive for improving the high-temperature performance of a lithium battery, an electrolyte and an electrochemical device. The electrolyte additive comprises at least one selected from a compound I or a compound II with a structure shown in the description, and the electrolyte additive can relatively improve the capacity retention ratio of a lithium battery containing the electrolyte additive at high temperature, and also can improve the capacity retention ratio at relatively high temperature and charge-discharge voltage.

Description

technical field [0001] The present application relates to the field of lithium batteries, more specifically, to an electrolyte additive for improving the high-temperature performance of a lithium battery, an electrolyte containing the electrolyte additive, and an electrochemical device. Background technique [0002] Lithium battery is a secondary battery (rechargeable battery) that mainly relies on lithium ions (Li + ) to work by moving between positive and negative poles. During the charging process of lithium battery, Li + Deintercalation from the positive electrode, intercalation into the negative electrode through the electrolyte, makes the negative electrode in a lithium-rich state, and realizes the conversion of electrical energy into chemical energy, while the discharge process is just the opposite. [0003] Lithium batteries are widely used in 3C consumer batteries, power batteries, and energy storage batteries due to their high operating voltage, high energy densi...

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Problems solved by technology

However, these lithium salts still have other defects. For example, although LiBF4 has excellent high-temperature performance, its SEI film formation is unstable; LiBOB and LiF2PO 2, etc. have low solubility in carbonate solvent systems, and there is a risk of crystallization when the temperature changes; LiFSI is considered to be the most promising to replace LiPF6 as the main lithium salt, and its high temperature performance is excellent , but the price is high, and it has a corrosive effect on metal aluminum, so it will harm the aluminum current collector and aluminum battery case, so it needs to be matched with other suitable additives to prevent corrosion of aluminum, which further increases the cost

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