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.