Research On Modification Of Silicon-based Anode Materials For Lithium-ion Battery

Lithium ion battery is a new type of battery which attracts many interests of majority enterprises and scientific research institutions because of numerous advantages.The applied fields become more and more widely,ranging from portable electronic devices to electric vehicles as well as aerospace.Lithium-ion batteries are becoming more and more popular.In this paper,two main lines are carried out.One is the preparation of P-Si,Si/C,Si/G and Si/C/G composite materials.The electrochemical properties are also concerned.The other starts from SnO₂,which uses the 3D porous structure of foamed nickel to prepare the electrode plate by a very simple way,and then assemble batteries to test electrochemical performance.Firstly,micron Si is selected as raw material.Si powder is etched with HF and AgNO₃,then analyzed by SEM,BET and electrochemical performance.Secondly,glucose and graphene oxide are used as carbon sources.Si/C,Si/G and Si/C/G composite materials synthesize by using pyrolysis and hydrothermal methods,then the electrochemical properties are tested.Si/C composite material is cycled at 1 A g^-11 for 980cycles,and the tested discharge specific capacity is 395 mAh g^-1.When the Si/C/G?mass ratio 5:1:1?composite galvanostaticly charges and discharges with 100 cycles under the current density of 0.2 A g^-1,the tested discharge specific capacity is 858 mAh g^-1.If it is cycled at 2A g^-1 for 200 cycles,the discharge specific capacity is 301 mAh g^-1.The discharge specific capacity is 375 mAh g^-1 for 10 A g^-1 current density after 100 cycles.As for Si/C/G?mass ratio 10:1:1?,when the current density is 0.2 A g^-1,discharge specific capacity is 2488 mAh g^-1 after 200 cycles.Discharge specific capacity is 631 mAh g^-1 for2 A g^-1 current density after 600 cycles.In the multiplying power performance testing,the current density ranges from 0.25 A g^-1 to 32 A g^-1.The charge and discharge specific capacity can reach as high as 500 mAh g^-1 under a large current density of 32 A g^-1.These reaults fully indecates that Si/C/G three-layer material effectively inhibits the expansion of silicon in the process of removing lithium,which greatly improves the electrochemical properties of silicon anode.The second part selects SnO₂,CNTs and GO as raw materials.The raw materials are impacted to the 3D fluffy porous nickel foam to make electrodes directly,then electrochemical performance is tested.If negative electrode material is merely SnO₂,the discharge spacific capacity is 302 mAh g^-1 when under galvanostatic discharge-charge of1 A g^-1 after 40 cycles.When SnO₂/CNTs is used as negative material,discharge specific capacity is 292 mAh g^-1 after 300 cycles in 1 A g^-1 current density.If cycled at 4 A g^-1,the discharge specific capacity will be 337 mAh g^-1 after 100 cycles.If SnO₂/G is chosen as the anode electrode material,discharge specific capacity is maintained at 420 mAh g^-1with 2 A g^-1 current density for 2500 cycles.In addition,when the cathode material is SnO₂/CNTs/G?mass ratio 5:1:1?,the discharge specific capacity is 695 mAh g^-1 under the current density of 0.1 A g^-1 after 175 cycles and 334 mAh g^-1 for 1 A g^-1 current density after 3300 cycles.Besides,when the copper foil is used as current collector,the charging specific capacity is maintained in 392 mAh g^-1 after 560 cycles with the current density of 0.1 A g^-1 and 522 mAh g^-1 after 1000 cycles with 1 A g^-1.These results show that the introduce of carbon nanotubes and graphene greatly limits the volume effect of tin oxide.