Preparation Of Hard Carbon From Pyrolysis Anthracite And Its Applications For Lithium/Sodium-Ion Batteries

With the booming development of society and the increasing demand for secondary batteries,developing sodiun·ion batteries has become an important research topic in the field of electrochemical energy storage with the lower cost than the lithium-ion batteries.In this article,hard carbon materials were prepared by pyrolysis of low-cost anthracite precursors?it is simplified to WYM hereinafter?,and then their electrochemical performance as anode electrodes of sodium ion batteries and lithium ion batteries were studied.The main results are as follows:?1?The preparation temperature of hard carbon materials were optimized with the comparison of the lithium/sodium storage performance of hard carbon prepared from the anthracite at different temperatures.As a result,the hard carbon material obtained at 1200??WYM1200?shows the best electrochemical performance.On one hand,when it is applied as the anode of the lithium-ion battery with the current density of 50 mA g^-1,the first-cycle eoulombic efficiency could reach 72%with the specific capacity of 245 mA h g^-1 and the capacity retention ratio of 92.7%after 50 cycles and 87.4%after 150 cycles.On the other hand,it also exhibits excellent performances as the anode of sodium-ion battery with the current density of 25 mA g^-1,such as the first-cycle coulombic efficiency of 71%,the specific capacity of 214 mA h g^-1 and the capacity retention ratio of 94%after 50 cycles and also 94%after 80 cycles.?2?Considering the low first-cycle coulombic efficiency and the poor rate performance of WYM1200,pressing calcination and chemical vapor deposition?CVD?were used to enhance its elctrochemical performance with the coated-carbon and the reduced specific surface area.The CVD conditions were optimized with the temperature of 700?,time of 2h and the C₂H₂/Ar gas flow of 20/135ml.The obtained hard carbon materials with the coated-carbon show the improved electrochemical performances,such as the first-cycle coulombic efficiency of 80%and 79%,the specific capacity of 270 mA h g^-1 and 220 mA h g^-1 in the lithium-ion batteries and the sodium-ion batteries,respectively.?3?The influence of the electrolyte on the electrochemical performance of hard carbon also has been studied.The results show that the ether electrolyte is better than carbonate electrolyte no matter in the lithium-ion batteries or the sodium-ion batteries.The lithium-ion battery capacity with the electrolyte of 1M LiClO₄ PC+DME could be increased by about 20 mA h g^-1 with the better cycle stability compared those with the carbonate electrolytes.In addition,the rate performance of the sodium-ion battery would be enhanced with the ether electrolyte,especially in the current density range of 100 to 500 mA g^-1.