Microstructure Design And Self-healing Mechanism Of The Interface Between Three Dimensional Current Collector And Liquid Metal

Lithium-ion batteries（LIBs）with good cyclical stability and high energy density have been widely used in portable electronic products.However,the fast capacity fading or even severe safety hazard of LIBs may happen when cracks,perforations or other damages occurred by external force,high or low temperature impacts.In particular,for current collector functioned as structural support and electron conduction,it is prone to deformation,active material shedding or even breakage under the action of external force,resulting in increased internal resistance of the battery or even short circuit,which increases the safety hazards of LIBs.In this paper,aiming at the damage problems of lithium-ion battery current collectors such as perforation and active material shedding and endrite growth on the electrode surface and internal short circuit,,based on the interface design of liquid metal and three-dimensional current collector,a highly stable,puncture-resistant three-dimensional carbon-based current collector and foamed copper current collector have been prepared to improve cyclical stability of LIBs.The specific research contents are as follows:（1）Based on the principle of the thermal decomposition of AgNO₃,a three-dimensional（3D）porous carbon nanotube film collector（CNTs/Ag）modified with silver nanoparticles was prepared via soaking and heating process;Furthermore,based on the good wettability between molten lithium and Ag particles,the free-standing CNTs/Ag/L anode was obtained through the uniform combination of molten lithium on the surface and internal structure of the silver nanoparticle-modified carbon nanotube film.The highly conductive carbon nanotubes can effectively facilitate electron transfer during the plating/stripping process.Moreover,the decorated Ag nanoparticles can effectively improve the lithiophilicity of Li and regulate the Li plating/stripping process with negligible dendrite growth.In addition,the CNTs/Ag/Li anode has a capacity of 1m Ah cm^-2 after being cycled for 200 cycles at a current density of 10^-3 A/cm²,showing good cyclical stability.Furthermore,using S/C as the cathode and CNTs/Ag/Li electrode as the anode,a lithium-sulfur battery was prepared,and its capacity retention rate reached 82%after 100 cycles at a current of 0.5C,showing a good cyclical stability.Therefore,the CNTs/Ag three-dimensional current collector prepared by a simple three-step manufacturing process can extend the cycle life of the lithium metal positive electrode,effectively and prevent the formation of lithium dendrites in LIBs,and reduce the short-circuit damage of the battery.（2）Based on alloying reaction of liquid metal,a newly composite current collector was obtained through the introducing of eutectic gallium indium alloy（EGa In）to the inner and outer surface of micro-etched foamed copper under an optimized temperature and press.Furthermore,graphite was coated on the composite current collector and used as the anode to measure their electrochemical performance under a thin needle damage.Namely,the microstructure and stability of the composite current collectors is highly associated with the alloying reaction conditions.And a good electric conductivity and good self-healing property of the obtained composite current collector can be obtaind at a heating at 160℃for 4h condition.In addition,the self-healing capacity of the graphite anode is superior with a capacity retention of 94.2%,namely the specific capacity of graphite anode before and after needle damage is about 328 m Ah/g and 309 m Ah/g,respectively,which is better than that of graphite anode coated on the cupper foil.Therefore,the above results verifies that the EGa In-foamed copper composite current collector can realize self-healing function when the electrode is damaged,and can effectively prevent LIBs perforations and scratches damage and enhances the safety of LIBs.