Multilayer thin film negative electrode for lithium battery, preparation method and application

Abstract

The invention discloses a multilayer film negative electrode for a lithium battery, a preparation method and application and belongs to the technical field of lithium ion batteries. The multilayer film negative electrode formed by a carbon film and a tin film is provided aiming at the problems that due to the fact that the size of a tin-based battery changes during lithium insertion and extraction, a tin substrate cracks, is pulverized and fails, the first-time circulating capacity loss of an electrode formed by nano particles is obvious, and the cycle performance improving magnitude of a non-nanocrystalline film is limited, wherein the carbon film is prepared through a vacuum coating process, and the tin film is prepared through a sputter coating process. The multilayer film structure can provide more lithium embedded channels and lithium embedded positions, lithium ion insertion and extraction are benefited better, meanwhile, the carbon film has the functions of an elastomer and an electronic transmission network, electrode collapses caused by volume expansion in the tin electrode charge and discharge process can be relieved, and the high utilization rate of the tin electrode after deep circulation can be kept when the carbon film serves as the electronic transmission network.

Description

technical field [0001] The invention relates to a multilayer thin film negative electrode for a lithium battery, and also relates to a preparation method and application of the negative electrode, belonging to the technical field of lithium ion batteries. Background technique [0002] With the increasing demand for multi-functional portable and high-energy electronic equipment, and the urgent need for the use of electric vehicles to reduce environmental pollution, the development of high specific capacity, high stability, high security, long life, and low cost New lithium-ion batteries are particularly important. Anode materials are an important part of lithium batteries and play a decisive role in the overall performance of lithium batteries. At present, commercial carbon anode materials mainly have the following problems: 1) the actual specific capacity is low, between 300 and 330mAh / g; 2) the irreversible capacity loss is large for the first time, and lithium is irrevers...

AI Technical Summary

Problems solved by technology

At present, commercial carbon anode materials mainly have the following problems: 1) the actual specific capacity is low, between 300 and 330mAh / g; 2) the irreversible capacity loss is large for the first time, and lithium is irreversibly embedded in the lattice to form a solid electrolyte interface film; 3 ) rate discharge performance is poor, limited by the diffusion coefficient of lithium ions (about 10 -10 cm 2 / s)

Tin and lithium can form high atomic ratio Li 22 sn 5 The alloy phase, with a theoretical specific capacity of up to 990mAh / g, is the basis for the development of high-performance tin-based anode materials, but when pure tin is used as an anode material, the volume changes greatly during the alloying and dealloying processes, and the mechanical properties of tin itself The performance makes it unable to withstand the resulting stress, so the electrode is prone to deformation and cracking

Similarly, the active substance that plays a major role in the tin-based negative electrode material is tin, which can form a lithium-tin alloy with lithium, and with the continuous intercalation and extraction of lithium ions, the tin matrix will produce a huge volume change (up to 259%), leading to electrode deformation and cracking, which gradually collapsed and pulverized, showing poor charge-discharge cycle performance

However, if the tin particles are small enough, the cycle performance can be improved to a certain extent, and the small particles are accompanied by a high specific surface area, which will easily cause a serious attenuation of the specific capacity in the first cycle during the formation of the SEI film.

The invention patent with the publication number CN101414674A discloses a tin / carbon nano-multilayer film negative electrode. By preparing a tin / carbon nano-multi-layer film on a copper foil substrate, the internal stress caused by the volume change during tin intercalation and delithiation can be weakened, and the internal stress can be kept relatively stable. Complete film initial structure, however, the capacity of the tin / carbon nano-multilayer negative electrode is only maintained at 515mAh / g after 20 charge-discharge cycles, and the first Coulombic efficiency is 73%. The electrode performance needs to be further improved

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