Design And Electrochemical Study Of Cathode Materials For Lithium-sulfur Batteries Modified By Rare Earth Elements

In the past few years,the times have developed rapidly,with rapid progress and development in all aspects.Informatization and industrialization will inevitably increase the demand for and consumption of resources.The widespread use of fossil fuels(such as oil and coal)has caused serious environmental pollution and exacerbated the conflict between the supply and demand of natural resources.The shortage of resources and the deterioration of the environment have put tremendous pressure on sustainable development.Therefore,the exploration of sustainable resources has become an urgent requirement.With the rapidly increasing demand for high-performance portable electronic products and electric vehicles,lithium-sulfur batteries(LSBs)are regarded as the next generation of rechargeable batteries due to their high specific energy,environmental friendliness,and low-cost production.The hopeful candidate represents one of the most mature battery systems and has received widespread attention.However,in the past few decades,the shuttle effect has been considered to be the main reason for the poor performance of LSBs,which ultimately leads to the migration of active materials and the"dead"sulfur/Li₂S supported on the surface of the positive and negative electrodes.Leading to a serious decline in battery performance,because its shuttle effect makes it impossible to fully achieve high discharge capacity and stable long-cycle performance.Especially in practical applications,the inherent shortcomings of these LSBs prevent them from entering the energy storage market in the near future:(1)We rationally developed a mesoporous reduced graphene oxide(r GO)gel scaffold embedded pine-like Sm₂O₃(Sm-MPG)as mediator along the target of synergizing lithium polysulfides trapping and reaction-intensifying.The results demonstrated that the chemical interaction between the reversible redox of Sm³⁺and Sm²⁺and lithium polysulfides conduces a high sulfur loading,high capacity,good rate capability,and good cycling performance of Li-S battery.The Sm-MPG-S composite cathode,with the sulfur areal loading of about 3 mg cm^-2,delivered an initial specific capacity of 989 m Ah g^-1 and retained a good cyclic stability with a low capacity decay ratio of about 0.042%per cycle at 0.5 C for over 1000 cycles.Even at a high current rate of 4 C,the cycling performance was still satisfactory with a capacity decay ratio of 0.053%per cycle and about 47%capacity retention after 1000 cycles.(2)We proposed a sulfur host which is composed of interlacing metal Co and Eu₂O₃particles embedded in hollow conductive carbon scaffold to form double-end binding sites towards efficiently lithium polysulfides constraining and conversion.The composition and structure of the cathode composite were well discussed.Strongly electronegative O^2-in Eu₂O₃ and active Lewis electron acceptor Co accelerated the surface reaction of intermediates thermodynamically.With this rational design,the cathode delivered a reversible capacity over 1000 m Ah g^-1 at 0.5 C,and performed an excellent rate and cycling stability.Moreover,at the high sulfur areal loading of 4.2 mg cm^-2,the cathode delivered an areal capacity of about 2.5 mAh g^-1 at 1 C during 100 cycles.