Study on Electrochemical Performance of Silicon and Carbon-based Anodes and Ultra-high Pressure Device Trial Manufacture
Supervisor:qian yi tai
With the development of society,commercial graphite anodes with low specific capacity can not meet the increasing energy demand.We tried to prepare high-capacity silicon-based composite electrode materials,hoping to alleviate the volume expansion of silicon and avoid the capacity degradation caused by the poor conductivity of silicon.Three-dimensional porous carbon materials were prepared by molten zinc thermal method for high-rate anode of potassium ion batteries.The main contents are:(1)In order to improve the conductivity of silicon,silicon and metal germanium are also compounded.The conductivity of germanium is much larger than that of silicon,and germanium can form an alloy with metal lithium to storage lithium.When the electrode material loading is about 1 mg cm-2,the initial discharge and charge capacities of pure silicon and SG-4 are 3216.2/2532.7 and 2780.4/1964.6 mA h g-1,respectively,and the coulombic efficiencies are 78.7%and 70.6%,respectively.The silicon/germanium composite exhibits better cycle performance than pure silicon.When the current density is 0.6 A g-1,the pure silicon capacity decreases from 3114 mA h g-1 to 637 mA h g-1 after 150 cycles of charge and discharge,and SG-4 decreases from 2040.3 mA h g-1 to 1761.0 mA h g-1,and the capacity retention rate is good.When the current density is 0.2,0.6,1.2,2.4,5 and 10 A g-1,respectively,the corresponding SG-4 specific capacities are 2207.2,1899.2,1535.9,1103.6,800.6 and 542 mA h g-1,respectively.(2)The carbon as the anode material of potassium ion was studied.The three-dimensional porous carbon material was successfully prepared by using molten salt zinc reduction method and sucrose as precursor,and it was used as the anode material of potassium ion battery.The prepared 3-D porous carbon has a large number of interconnected channels,which can effectively alleviate the volume effect of the electrode during the charge-discharge cycling process,improve the infiltration of electrolyte to the electrode,shorten the diffusion path of K+,therefore,it shows excellent cycle stability and rate performance.3-D porous carbon electrode delivers the specific capacity of 174.6 mAh g-1 after 2500 cycles at current density of 0.5 A g-1 and 170 mAh g-1 at a high rate of 4.4 A g-1.It is a promising anode material for potassium ion batteries.(3)The research of high-pressure experiment is often inseparable from the research of equipment.At present,there are few high-pressure devices which can stabilize pressure under high pressure and adapt to various chemical reaction systems.A two-sided top high pressure experimental device and a stable pressure reactor have been developed,which can be used to study some systems with low pressure and liquid reactants.The purpose of this device is to stabilize pressure in time when pressure fluctuation occurs during chemical reaction.The device design and experiment show that the structure of the high pressure device with stable pressure is feasible and has good application prospects.