Frabrication And Electrochemical Performances Of Hard Carbon Anodes For Lithium (Sodium) Ion Batteries

The development of energy storage technology has put forward higher requirments of lithium ion battery performance and the research for high performance anode materials has been one of the important development direction for lithium ion battery.As lithium ion battery has the shortcomings of limited lithium resources and high cost,the research of sodium ion battery with abundant resources and low cost has also been an important development direction of energy storage technology.Hard carbon is a promising anode material both for lithium and sodium ion batteries due to its stable structure,long cycling life,good safety performance,high capacity and high rate discharge performance.In our work,the research work is carried out around the preparation,the modification of structure and morphology as well as the improvement of the electrochemical performance of newly developed pyrolytic hard carbons as anodes for lithium and sodium ion battery.The specific research contents are as follows:?1?Via carbonization of butterfly wings,carbonaceous photonic crystals?CPCs?were derived as anode materials for lithium and sodium ion batteries.The CPCs inherits the wing's unique photonic structure and the derived CPCs?CPC800?by carbonization at 800 ? delivers the best performances.CPC800 offers high specific capacities of 590mAh/g?LIBs?and 235mAh/g?NIBs?at 0.05A/g.More impressively,CPC800 displays ultralong cycling stability for LIBs and NIBs applications,sustaining more than 10000 cycles with no evident observation of the fading of capacity.?2?The peanut shells derived porous hard carbons?PSDHCs?by pyrolysis have been investigated as anodes of lithium and sodium ion batteries.600? is found to be the favorable pyrolysis temperature for preparation of the PSDHC sample?PSDHC-600?with the best electrochemical performances for LIBs applications.Furthermore,from the activated peanut shells in KOH solution,the produced PSDHC-600 A is observed to offer greatly enhanced Li+/Na+ ion storages.For LIBs applications,PSDHC-600 A delivers a retained capacity of 474mAh/g after 400 cycles at 1A/g.At a high current rate of 5A/g,PSDHC-600 A sustains over 10000 cycles with no obvious sign of fade in capacity.For NIB applications,a capacity of 193mAh/g is retained after 400 cycles at 0.25A/g.Even at 1A/g,PSDHC-600 A can be stably cycled over 3000 cycles.?3?We have prepared orange peel derived hard carbons?OPDHC-A?by activation-pyrolysis process as anodes of lithium/sodium ion batteries.For LIBs applications,OPDHC-A delivers a retained capacity of 301mAh/g after 100 cycles at 1A/g.At a high current rate of 2A/g,OPDHC-A can steadily cycled up to 3000 cycles.For NIBs applications,a capacity of 146mAh/g is retained after 100 cycles at 0.25A/g.For long cycling life test,OPDHC-A delivers reversible capacity of 117mAh/g after 3000 cycles at 1A/g.The OPDHC-A anodes shows excellent capacity performance and cycle stability.?4?Using polystyrene ball?MPS?as carbon source,polystyrene derived porous carbon?PDPC?was prepared by pyrolysis process as anode for lithium ion battery.At the current density of 2A/g,the PDPC anodes can be recycled up to more than 2000 times and with the reversible capacity of 83mAh/g.Further,by using the method of chemical vapor deposition,PDPC/WS₂ composite was prepared as anodes for lithium ion battery.PDPC/WS₂ shows significantly improved capacity performance.At the current density of 1A/g,it delivers reversible capacity of 282mAh/g after 1220 cycles.At the current density of 2A/g,the PDPC/WS₂ anode can maintain the impressive capacity retentions of 70% after 2000 cycles.The PDPC and PDPC/WS₂ anodes show excellent capacity performance and cycle stability.