Synthesis Of Silicon And Antimony Based Anode Materials For Energy Storage

Silicon-based and antimony-based anode materials have high theoretical specific capacity for rechargeable secondary batteries,but the volume expansion would lead to capacity decay during alloy-dealloy process.This thesis aims to construct high performance silicon-based and antimony-based anode materials.A molten-salt chemical exfoliation methodology was developed for producing mesoporous Si nanosheets.Sponge-like amorphous silicon was prepared by magnesiothermic reduction of silicon tetrachloride.Antimony nanocrystals embedded ultrathin carbon nanosheets were prepared by a solvothermal reaction of antimony trichloride.The main research content is as follows:1.Mesoporous silicon nanosheets are prepared by chemical exfoliation process of calcium silicide in low-temperature molten salt,exhibiting high reversible capacity and excellent rate performance for lithium ion batteries.Calcium silicide was used as the silicon source while aluminum trichloride was used as the low-temperature molten salt,and the reaction was carried out at 195 ℃.The mesoporous sheet structure could not only effectively alleviate the volume expansion of silicon,but also provide short channels for fast migration of lithium ions and electrons.With the unique two-dimensional structure,the as-prepared Si nanosheets delivered good cycle performance and appealing rate performance for lithium ion batteries,including high reversible capacity of 2163,1947 and 1527 mAh g^-1 at 2.4,6.0 and 15.0 A g^-1 after 200 cycles,respectively.Even at 90 A g^-1,a capacity retention of 357 mAh g^-1 can be maintained.2.An amorphous Si material with a sponge-like structure is obtained by a magnesiothermic reduction of silicon tetrachloride,which has good cycle stability for lithium ion battery and a certain reversible capacity for sodium ion battery.Sponge-like porous amorphous silicon was prepared by reacting silicon tetrachloride and magnesium powder at 380℃.The amorphous nature of the as-prepared silicon can avoid the crystalline-to-amorphous transformation in the initial cycle,and the sponge-like porous structure can provide space to accommodate the volume expansion of silicon.When the as-prepared sponge-like amorphous silicon was applied as an anode for rechargeable batteries,it exhibited a reversible capacity of 1125 mAh g^-1 after 100 cycles at 1A g^-1 for Li-ion batteries（LIBs）and a reversible capacity of 176 mAh g^-1 at 100 mA g^-1 over 100 cycles for Na-ion batteries（NIBs）.3.The antimony nanocrystals embedded ultrathin carbon nanosheets（Sb/CNS）are prepared through a one-step solvothermal reaction,which has stable potassium storage performance and excellent sodium storage performance.Sb/CNS were prepared through a one-step solvothermal reaction between ferrocene and antimony trichloride in hexane at 330 ℃.The mechanically stable carbon nanosheets could accommodate the volume change of high-capacity Sb,and help to form a stable solid electrolyte interface（SEI）film during discharge/charge process.As an anode for potassium-ion batteries,the Sb/CNS composite delivered a reversible capacity of 288.2 mAh g^-1 at 50 mA g^-1 after 50 cycles,and a capacity of 247 mAh g^-1 can be maintained even at 200 mA g^-1 over 600 cycles.Besides,the Sb/CNS electrode exhibited a high specific capacity of 338 mAh g^-1 at 200 mA g^-1 over 240 cycles for Na-ion batteries.