Surface Modification Of Ultrasonic Peening And Organic Carbon For Copper Foil Collector In Lithium Ion Batteries

Current collector is an important part of lithium ion battery.It can not only carry the active material,but also collect and output the current generated by the electrode active material,which helps to reduce the internal resistance of lithium ion battery and improve the coulomb efficiency,cycle stability and rate performance.However,the conventionalsmooth copper collector has the problems of weak bond with the active material,easy to be corroded by organic electrolyte and electrochemical impedance etc..As a result,the negative electrode material coated on it mainly has the problems of low practical specific capacity,large first irreversible capacity loss and power discharge performance insertion.Therefore,it is necessary to develop new Current collector and carbon negative materials to meet the application requirements of high-power power batteries.Meanwhile,this paper mainly does the following three works:?1?A novel ultrasonic peening technique was developed to obtain a special copperfoil with microcrystalline morphology surface.The obtained microcrystalline Cu-graphite electrode displays better conductivity,higher bonding strength withgraphite particles,and stronger corrosion resistance to the electrolyte than the pristine copper foil,which lead to its superior lithium storage performance.Show that,the initial charging capacities of Cu-graphite/Li electrodes with ultrasonic peening times of 9 and 15s are as high as 312.4 and359.5mAh?g-1,respectively,which are much higher than those of a pristine Cu-graphite electrode(282.3 mAh?g^-1).After 380 cycles,thedischarging capacities remain at 239.0 and332.8 mAh?g-1with capacity retentions of 76.5%and 92.6%,respectively,which are also much higher than those of the pristine Cu-graphite electrode?187.6 mAh?g^-11 and 66.4%after270 cycles,respectively?.After ultrasonic peening on the copper foil surface,the capacity,cycling and rateperformance of the Cu-graphite electrode are greatly improved in both a Cu-graphite/Li half battery and an LiNi_0.8Co_0.1Mn_0.1/Cu-graphite full battery,which resultwould providing a new idea for the development of large-capacity and long-life electrode collector materials for lithium-ion batteries.?2?In order to improve the surface behavior of Cu foil collector for lithium-ion batteries?LIBs?,a 3,4,9,10-perylenetetracarboxylic dianhydride?3,4,9,10-PTCDA?compound is electrospun as carbon source onto the Cu foil surface,then cracks and carbonizes at high temperature to obtain a organic carbon membrane?2.8?m?covered on copper foil.The obtained organic carbonized Cu foil display a larger electrolyte contact angle,and can effectively block the corrosion of electrolyte and enhance the corrosion resistance of electrolyte.In addition,this organic carbon layer can effectively increase the adhesion between graphite and copper foil,reduce the interface impedance,and significantly improve the conductivity and battery all properties of the graphite electrode.Results show that,the initial charging capacity of organic carbonized Cu-graphite/Li electrode is as high as 355.9mAh?g^-1,which is higher than the pristine Cu-graphite electrode(300.9 mAh?g^-1).After 454cycles,the charging capacity remains at 345.9 mAh?g^-1with capacity retentions of 97.2%,which is also much larger than the capacity and retentions of pristine Cu foil is 236.9 mAh?g^-1with retentions of 78.7%after 300 cycles.After a carbon film is formed on the surface of Cu foil,the conductivity,capacity,cycling and rate performance of both a half battery based on Cu-graphite/Li electrode and an full battery based on the organic carbonized Cu-graphite/LiNi_0.8Co_0.1.1 Mn_0.1.1 electrode are greatly improved,which provides a new insight for the design of high performance collector in LIBs.?3?On the basis of organic carbon modified copper foil,the organic hard carbon negative carbon material with large capacity and small irreversible capacity loss was further explored.PTCDA was used as the carbon source to adjust the microstructure and pore size distribution of hard carbon by changing the carbonization temperature,so as to explore its lithium storage performance.The PTCDA powder was mainly sintered at three carbonation temperatures of1000oC,1100oC and 1200oC to obtain hard carbon materials in turn.Results show that the initial charging capacity of three carbonation temperatures of 1000oC,1100oC and 1200oC is278.20,344.85,326.91 mAh?g^-1,respectively after 159,166,213 times after cycle,specific capacity and capacity retention rate of 267.91 mAh?g^-1and 96.30%,326.23 mAh?g^-1and94.60%,270.84 mAh?g^-11 and 82.85%.The initial charging capacity of graphite/lithium half battery is 338.40 mAh?g^-1,and after 141 cycles,the specific capacity is 298.72 mAh?g^-11 and the capacity retention rate is 88.27%.The results show that the PTCDA organic hard carbon obtained at the carbonization temperature of 1100oC has the best battery performance,which is significantly improved compared with the graphite negative electrode.The results may provide a new idea for the development of hard carbon materials for lithium ion batteries.