Metal lithium composite cathode as well as preparation method and application thereof

Abstract

The invention discloses a metal lithium composite cathode as well as a preparation method and application thereof. The preparation method comprises the following steps: forming a metal lithium layer on the surface of a polymer film in a depositing manner at least by adopting a vacuum physical deposition method, and obtaining a composite band; respectively arranging one composite band at two sidesof a cathode piece, enabling the metal lithium layer in each composite band to contact the cathode piece, applying pressure to a composite structure consisting of the cathode piece and the composite band, obtaining the cathode piece with two side surfaces being respectively combined with the metal lithium layer, thus obtaining the metal lithium composite cathode. The lithium band is prepared through the vacuum physical deposition method, and a pressure-rolling process is combined, so that the metal lithium layer can be uniformly, continuously and thinly covered on the cathode, thereby obtaining a pre-lithiated cathode. The defect that the lithium band is easily broken is avoided, and at the same time the cathode is compacted, and the density of the cathode is increased. The metal lithium composite cathode is utilized to improve the first-time charge / discharge efficiency of a cathode material, can serve as a lithium-containing cathode and be matched with a lithium-free anode, and has abroad application prospect.

Description

Technical field [0001] The invention relates to a method for preparing a lithium-containing negative electrode, in particular to a metal lithium composite negative electrode and a preparation method thereof, and its application in a lithium battery, belonging to the technical field of lithium ion batteries. Background technique [0002] Currently marketed lithium secondary batteries widely use carbon materials such as graphite as a negative electrode. Although graphite has higher safety than metal lithium, its theoretical specific capacity is lower, only 372mAh / g. Therefore, the development of high-capacity anode materials has attracted attention. For example, the theoretical specific capacity of silicon is as high as 4200mAh / g, and metal lithium deposition is not easy to occur during the charging and discharging process, and its capacity and safety are higher than graphite. The theoretical specific capacity of hard carbon is 500-700mAh / g. The common problem with these materia...

AI Technical Summary

Problems solved by technology

Lithium sources for negative electrode pre-lithiation include: lithium powder, lithium strip, etc. Among them, passivated lithium powder is mostly used as lithium source in traditional metal lithium composite negative electrodes, which is coated on the surface of the negative electrode sheet or mixed into the battery slurry. It is easy to implement, but its disadvantage is that lithium powder is easy to fly during use, causing great environmental pollution, low safety performance, and high cost of lithium powder

However, using ultra-thin lithium strips as a lithium source, on the one hand, the lithium strips prepared by mechanical methods are thicker, have excess capacity, uneven surface, and uneven thickness, resulting in poor battery consistency, and ultra-thin lithium strips are prone to adhesion during processing. , broken belt and other phenomena; on the other hand, using vacuum evaporation or magnetron sputtering technology to directly cover lithium on the negative electrode, due to its high temperature will cause the negative electrode to be pulverized and fail, and it is difficult to achieve one-time double-sided lithium coating

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