Preparation And Electrochemical Performance Of TiO₂/carbo N-coated Graphite Flakes And Nitrogen-Doped Porous Carbon-Supported Sulfur Cathode Materials

Aiming at the shortcomings of dual-ion battery graphite cathode materials such as large volume changes during charge and discharge cycles and serious electrolyte decomposit ion,a simple dissolution-precipitation method combined with high-temperature carbonizat ion was used to prepare Ti O₂ nanoparticles and carbon-coated graphite flakes cathode materials.In addit ion,in view of the low conductivit y of the sulfur posit ive electrode in lit hium-sulfur batteries and the decrease in cycle performance caused by the shuttle of polysulfides,nitrogen-doped porous carbon spheres are prepared through spray cracking and high-temperature carbonization,and then sulfur is loaded as the posit ive electrode material of the lit hium-sulfur battery.Using a variety of structural characterization and electrochemical analysis methods,the microstructure,chemical composit ion and electrochemical performance of the above two cathode materials were compared and studied,and the following conclusions were obtained:（1）In dual-ion battery,Ti O₂/carbon coated graphite flakes（TO/GF）cathode materials,Ti O₂ nanoparticles are evenly distributed on the surface of the graphit e flakes,and the amorphous carbon layer firmly binds the Ti O ₂ nanoparticles on the surface of the graphite flakes,so t hat TO/GF has high structural stabilit y.（2）TO/GF has excellent charge-discharge cycle performance.Under the voltage window of 3.00～4.98 V,TO/GF achieves 10000 stable charge and discharge cycles,and the capacit y decay rate of each cycle is only 0.0021%.After raising the upper limit of the voltage window to 5.2 V,TO/GF achieved 2000 stable charge-discharge cycles.（3）The uniformly distributed Ti O₂ nanoparticles divide the surface of the graphite flakes into nano-domains.These nano-domains greatly reduce the decomposit ion of the electrolyte during the charge-discharge cycle,and quickly form a stable cathode-electrolyte interface CEI interfaces.Through the uniform coating of Ti O₂nanoparticles,the domain boundary of the graphite sheet surface is an effective way to obtain stable cycle performance.（4）The nitrogen-doped porous carbon support has a large specific surface area and a rich mesoporous network,so the sulfur content of the lit hium-sulfur battery cathode material S@N/C obtained after sulfu r loading reaches 86%.And S@N/C exhibits excellent cycle stabilit y and rate performance.After 3000 cycles at a current densit y of 2 A g^─1,the reversible specific capacit y is still 581.1 m Ah g^─1.Nitrogen-doped porous carbon spheres are highly efficient sulfur carriers.