Lithium supplementing composite diaphragm and preparation method thereof

Abstract

The invention discloses a lithium supplementing composite diaphragm and a preparation method thereof. The lithium supplementing composite diaphragm comprises a base membrane, one side, facing a positive electrode, of the base membrane is coated with a lithium supplementing layer, the material of the lithium supplementing layer comprises a lithium supplementing active substance and a binder, and the lithium supplementing active substance is metal oxide lithium salt. The lithium supplementing active substance adopts the metal oxide lithium salt, so that the gram volume of the positive electrodematerial can be improved, the lithium ion transmission rate is increased, and the rate capability and the cycle performance of the lithium ion battery are improved; on the other hand, the mechanical property of the diaphragm can be effectively enhanced, the temperature resistance of the diaphragm is improved, and the safety performance of the lithium ion battery is enhanced; besides, compared witha traditional method that the surface of the positive electrode material is coated with the metal oxide lithium salt serving as the lithium supplementing active substance, the metal oxide lithium salt is applied to the diaphragm, the mass of the positive electrode material cannot be increased, and therefore reduction of the gram volume of the positive electrode material due to addition of the lithium supplementing active substance can be avoided.

Description

technical field [0001] The invention relates to the technical field of lithium-ion batteries, in particular to a lithium-supplementing composite diaphragm and a preparation method thereof. Background technique [0002] Lithium-ion batteries are widely used in digital, electric vehicles, energy storage and other fields due to their excellent energy density, rate performance and long service life. Lithium-ion batteries are mainly composed of positive electrodes, negative electrodes, electrolytes, diaphragms, and battery casings, and rely on lithium ions to migrate and deintercalate between the positive and negative electrodes to provide energy during operation. The separator should not only block the direct contact between the positive and negative electrodes, but also provide a migration channel for lithium ions. Its design is directly related to the electrochemical performance and safety performance of lithium-ion batteries. But at present, the commonly used polyolefin sepa...

AI Technical Summary

Problems solved by technology

However, at present, the commonly used polyolefin separator exhibits large thermal shrinkage at high temperatures, which causes the deformation of the separator and leads to direct contact between the positive and negative electrodes, causing short-circuit thermal runaway or even explosion.

[0003] In addition, during the initial charging process, the formation of SEI film on the negative electrode will consume part of the lithium ions that migrate from the positive electrode to the negative electrode, resulting in low initial charge and discharge efficiency of lithium-ion batteries.

Moreover, during the subsequent charge-discharge cycle, the damage and repair of the SEI film will continue to consume active lithium ions, resulting in a decrease in the reversible capacity of the lithium-ion battery and accelerated cycle attenuation.

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