Graphical Design Of Surface Structures And Performance Study For Current Collectors In Lithium Ion Batteries

As an environmentally friendly and high-energy rechargeable power supply,lithium-ion battery(LIB)has a great application prospect in the new-generation portable electronic products,new energy vehicles and industrial energy storage devices.Current collector is considered as a key component in LIBs,its surface structures play an important role in the electrode strength,charge transfer efficiency,and the electrochemical properties of LIBs.The problems of loose adhesion and uneven contact with the active materials are easy to occur,because of the monotonous surface structure of the anode current collector for the commercial LIBs.These problems may cause the pulverization and exfoliation of the active materials from the current collector,thereby leading to the performance failure of LIBs.Aiming at the above problems,an anode current collector with graphical surface structure for LIBs was proposed in this thesis.The design and preparation of the graphical surface structure,the test and evaluation of the surface functional layer,the optimization of material system for the current collector and its influence on the electrochemical performance of LIBs were systematically studied.Specifically,the main contents include the following:(1)Preparation of the graphical surface structure and evaluation of the CuO functional layerWe designed graphical sunk structures on the surface of a copper plate and prepared a CuO functional layer in these structures by combining photolithography and a new-type corrosion process.The surface morphology of the graphical CuO/Cu composite current collector,electrical conductivity of the electrode,accuracy verification of equivalent circuit model for the electrode with double-layer active materials and cycling performance of the battery were studied via SEM test,pressure-resistance test,EIS test and cycling discharge/charge test.The influence mechanism of the graphical surface structure and CuO functional layer on the battery performance was revealed.(2)Optimization strategy and mechanism of the performance for the CuO material systemBinder-free hierarchical core/shell CF/CuO composite electrode was prepared by combining surface metallization of carbon fibers and heat treatment process.Aiming at the poor electrical conductivity of the CuO material system,we used high-conductivity carbon fibers to enhance the electrical conductivity of the CuO electrode material.Characterization methods of XRD,XPS,SEM and TEM and electrochemical test were used to study the optimization mechanism of the conductivity for the CuO material system and dissect the influence of the CF/CuO system on the electrochemical performance of LIBs.(3)Preparation and electrochemical performance test of the checkerboard-like CNF/CuO/Cu composite current collectorCheckerboard-like CNF/CuO/Cu composite current collector was prepared via a new-type nickel plating process,catalyst activation process and chemical vapor deposition process.The mechanical property and electrochemical performance of the composite current collector were systematically studied.The checkerboard-like grooves on the current collector not only improved the strength and conductivity of the electrode,but also coupled with the CNF and CuO functional layer.This effectively enhanced the lithium storage property of the electrode and remitted the severe volume change of the electrode material during repeated discharge/charge processes.As a result,the reversible capacity,rate capability and cycle life of LIBs were simultaneously improved in this project.