Synthesis And Performance Study Of A New Type Of Sodium Ion Battery Anode Material

Due to the increase in energy demand,the depletion of fossil fuels and the serious environmental problems caused by the use of energy,the energy issue has attracted great attention,and various new clean energy sources are rapidly emerging.Lithium-ion batteries?LIBs?are widely used as batteries because of their high energy conversion efficiency,stable recyclability,and power and energy characteristics for different grid functions.However,due to limited lithium resources,the cost increase of LIB will not be able to meet the growing industrial demand.Finding a low-cost,high-security smart grid and improving the life of large-scale energy storage batteries are urgent problems to be solved.Na has the advantages of abundant reserves,low cost and easy availability,exhibit physicochemical properties similar to Li,the potential of sodium is lower and the energy loss is smaller.Therefore,sodium ion batteries are more suitable for large grid fixed applications.In a large power grid,the low cost and long cycle life of the battery are more important for the overall system.In this paper,the effects of micro-structure,particle size and doping type of sodium ion battery anode materials on sodium storage performance were studied.The details are as follows:?1?NaTi₂?PO₄?₃ is synthesized by Na₂CO₃,TiO₂ and NH₄H₂PO₄ as raw materials,an anode electrode material for sodium ion battery,by ball milling,spray drying and calcination.The synthesis temperature of NaTi₂?PO₄?₃ material was studied.The XRD results show that there are obvious Miscellaneous peaks when the calcination temperature is 600-900?.When the calcination temperature reaches 1000?,the pure phase NaTi₂?PO₄?₃ material can be obtained.Using C₈H₂₀O₄Ti as the titanium source,a pure phase NaTi₂?PO₄?₃ material was formed by the same preparation method at a calcination temperature of 750?.The NaTi₂?PO₄?₃ material formed by the two kinds of titanium sources was tested for sodium storage performance,and NaTi₂?PO₄?₃ synthesized by using C₈H₂₀O₄Ti as the titanium source showed good stability and cyclability,at 1 C rate,the discharge capacity of the first circle is 80mAh/g,and there is still 52.3 mAh/g after 200 cycles;while NaTi₂?PO₄?₃ synthesized with TiO₂ as the titanium source,at 1 C rate,only 31.1 mAh/g for 200 cycles.Low Temperature Synthesis of NaTi₂?PO₄?₃ Material Solution Using C₈H₂₀O₄Ti as Titanium Source,carbon doping to improve the electrochemical performance of NaTi₂?PO₄?₃.The results show that the specific capacities of NTP/C are as high as121.4 mAh/g at 1C and 108 mAh/g after 200 cycles.The above data demonstrates that carbon doping increases the conductivity of Na⁺in the insertion/extraction process of NaTi₂?PO₄?₃ material and accelerates charge transfer kinetics,resulting in increased cycle stability.?2?The NaTi₂?PO₄?₃/C material is synthesized by three different carbon-containing sodium sources,Na₃C₆H₅O₇·2H₂O,C₇H₅NaO₂ and C₁₀H₁₄N₂Na₂O₈·2H₂O.The thermogravimetric results showed that the carbon content was 4.11%,1.4%and 4.95%,respectively.Composites with a carbon content of 4.95%have the best electrochemical performance.After circulating 500 cycles at 1 C,there is a charge and discharge capacity of 103.5 m Ah/g,and after 2000 cycles at 5 C,Capacity is 73.47 mAh/g,even at a high rate of 20 C,there is still a charge and discharge capacity of 72.6 mAh/g.This method uses one-step synthesis of NaTi₂?PO₄?₃/C composite without external carbon source is more economical and more suitable for mass production,and has great application prospects for future industrialization.?3?The NaSn_xTi_2-x?PO₄?₃ composite was prepared by using C₄H₁₀O₂Sn as the Sn source.The EDS elemental map showed that Sn was uniformly distributed in the NaSn_xTi_2-x?PO₄?₃ composite.The ICP-AES results showed that the Sn element content was 1.42%.The performance results show that the NaSn_xTi_2-x?PO₄?₃composite has a high discharge specific capacity of 87 mAh/g at the 1C rates,and has a capacity of 55.5 mAh/g after 200 cycles;pure phase NaTi₂?PO₄?₃ materials,at 1C rates,the first circle provides a discharge specific capacity of 58.8mAh/g,38.5 mAh/g after 200 cycles.The NaSn_xTi_2-x?PO₄?₃ composite provides higher capacity and better cycle stability than pure phase NaTi₂?PO₄?₃.?4?Sodium ion battery anode material SnS₂ material is synthesized by hydrothermal method using SnCl₄·5H₂O and C₅H₁₀NS₂Na·3H₂O,the material had a discharge capacity of 257.8 mAh/g after 100 cycles at a current density of 100 mA/g.In order to improve the electrochemical performance of the SnS₂ electrode material,we coated the SnS₂ material with graphene oxide.The FESEM image shows that the material is a two-dimensional sheet structure.The sodium storage performance test shows that the SnS₂/GO composite material is in a current density of 100 mA/g,the initial discharge capacity are as high as 841.4 mAh/g.After 100 cycles,SnS₂/GO still provides a high discharge capacity of 471.1 mAh/g.This excellent performance is attributed to the coating results of graphene oxide,which helps to relieve the volume change stress during the insertion and removal of sodium ions and enhances the conductivity of SnS₂ materials.