Synthesis And Electrochemical Performance Of Lithium-sulfur (Lithium-Selenium) Battery Cathode Materials

The growing demand for mobile power sources in electric vehicles and portable electronic products has prompted people to conduct extensive research in the development of high-performance electrochemical energy storage devices.At present,the lithium-ion battery（LIB）graphite anode is approaching its theoretical capacity limit and cannot meet the growing demand for energy density in future portable electronic devices and large-scale energy storage systems.Lithium metal batteries are considered to be the most likely energy storage devices to replace lithium ion batteries due to their ultra-high specific capacity and extremely low electrode potential of Li.Therefore,this"beyond LIB"next-generation battery（such as lithium-sulfur（Li-S）and lithium-selenium（Li-Se））has become a very attractive energy storage device.However,the serious shuttle effect,poor conductivity and other issues of Li-S and Li-Se battery cathode electrodes have hindered their further development.Therefore,the development of advanced lithium metal battery cathode materials is of great significance to meet the needs of the booming power supply market.In this thesis,we synthesized novel cathode materials for lithium metal batteries,and conducted a systematic electrochemical study.The main research contents are as follows:（1）In Chapter 2,we synthesized CsPbBr₃ perovskite nanoparticles（Pr NP）as adsorbents to fix lithium polysulfide（Li PSs）.The synthesized Cs Pb Br ₃ perovskite nanoparticles and sulfur-carbon active material were coated on the current collector together as a cathode electrode of Li-S battery.The Li-S battery showed good electrochemical performance.At a current density of 0.2 C,the specific capacity of525.3 m Ah g^-1 was maintained after 200 cycles,and the average attenuation rate was0.23%.When the current density was as high as 1 C,the specific capacity of 334.2m Ah g^-1 was maintained after 400 cycles.Compared with the sulfur electrode without Cr Pb Br₃ perovskite nanoparticle adsorbent,the electrochemical performance was greatly improved.（2）In Chapter 3,we designed a covalent selenium embedded in hierarchical nitrogen-doped carbon nanofibers（CSe@HNCNFs）for ultra-high areal capacities lithium-selenium batteries.When the mass loading was 1.87 mg cm^-2,the obtained lithium-selenium battery maintained a high specific capacity of 762 m Ah g^-1 after2500 cycles,with almost no capacity decay.In addition,when the mass load ing was increased to 37.31 mg cm^-2,an ultra-high areal capacity of 7.30 m Ah cm^-2 could be obtained,which greatly exceeds the previously reported areal capacity of lithium-selenium batteries.