Study Of Copper Modification And Alloying On Silicon As Anode Material Of Lithium-Ion Batteries

In recent years,environmental protection has been highly concerned by the whole society,the new energy automobile industry and new energy power plant energy storage embrace rapid development,thereby requirements for capacity density,fast charging and safety of lithium-ion battery are further improved.The actual capacity of the most mature graphite anode material is close to the theoretical limit,while the silicon anode material has attracted widespread attention due to its high theoretical capacity,high embedded lithium-ion potential,high natural abundance,and other significant advantages,is considered the most likely anode material for next-generation lithium-ion batteries.However,the large volume change effect in the electrochemical reaction accompanied by the high embedded lithium capacity of silicon,and the poor electrical conductivity of silicon as a semiconductor,severely limits the electrochemical performance of silicon anode materials and is a major obstacle to the commercialization of silicon anode materials.In this paper,sub-micron silicon particles prepared from photovoltaic broken silicon wafer by ball milling from a low cost point of view more suitable for industrialization,and the process of copper modification without electrochemical deposition is investigated to obtain Si/Cu particles with lower resistance copper modification.The main findings of this paper are summarized as follows.(1)In electrochemical-free deposition,CuSO4+HF deposited liquid systems can achieve better deposition effects.Based on the product electrical properties and deposition uniformity,the CuSO4 concentration in the deposition liquid system and the deposition speed parameters have an equilibrium value to achieve the best deposition effect,when the CuSO4 concentration is 10 mM and the stirring speed of 260 rpm is the appropriate deposition process.(2)The resistivity of Si/Cu powder with copper modification reaches 89 k?,which is 81%lower than that of Si particles and shows an advantage in electrochemical impedance spectrum,In the multiplicity performance versus cycling performance test,Si/Cu pellets achieved a capacity of 711 mAh·g-1 at a current density of 2.0 C,710 mAh·g-1 higher compared to Si,and maintained a specific capacity of 655 mAh·g-1 after 160 cycles at a current density of 0.5 C,a 299 mAh·g-1 increase compared to Si.(3)Cu-Si alloy structure can be formed by rapid heat treatment on Cu modified Si particles to reduce the contact resistance between Cu and Si.By exploring the rapid heat treatment process,annealing temperature of 600? and annealing time of 120 s can successfully obtain Si/Cu3Si/Cu composite structure.(4)The resistivity and electrochemical impedance of the Si/Cu3Si/Cu composite structure particles obtained by rapid heat treatment are significantly better than those of Si/Cu particles and Si particles,and in the multiplicity performance and cycling performance tests,the volume at current density 2.0 C reaches 997 mAh·g-1,which is 291 mAh·g-1 higher than that of Si/Cu particles,and the specific volume at current density 0.5 C is 1126 mAh·g-1 after 160 cycles,which is 471 mAh·g-1 higher than that of Si/Cu particles.