Preparation Of Anode/Cathode Materials And Structural Design For Alkali Metal Batteries,and The Performance Study

Nowadays,the commercial batteries are limited by the theoretical specific capacity of electrode materials,and it is difficult to further increase capacity.As the rapid increase of battery usage and the increase of penetrating rate,the energy storage batteries with low cost,high energy density and long life must be developed.To satisfy future demand for energy storage devices,there are two main solutions:（i）along with the development direction of current commercial lithium ion battery,developing and exploring novel anode and cathode materials are the focus in the investigation field;（ii）developing a new energy storage system with low cost and high energy density,such as lithium-sulfur batteries and room-temperature sodium-sulfur batteries.The main purpose of this thesis is to develop new lithium ion anode material and new configuration of sulfur-based metal battery.The research contents and results are as follows:（1）The macroporous ZnMn₂O₄/C nanospheres composites were prepared by an improved solvothermal method and then a calcination process.The as-prepared macroporous ZnMn₂O₄/C nanospheres features two main characteristics:（i）macroporous microspheres containing numerous nanoparticles,which help to tolerate the large volume change and shorten the path length of Li⁺transport;and（ii）the introduction of carbon improves overall electronic conductivity of the composite material.The electrochemical performance of macroporous ZnMn₂O₄/C microspheres can be significantly improved by using water-soluble CMC that can be easy to cross-link with each other as binder.The results shows high discharge capacities of1249 mA h g^-1after 100 cycles at a current density of 200 mA g^-1and 820 mA h g^-1after 500 cycles at 500 mA h g^-1were achieved in the macroporous ZMO/C microspheres anode with water-soluble CMC,and were far better than the theoretical capacity of commercial graphite.（2）We firstly prepare poly（L-cysteine）-functionalized rGO by a simple one-step process.Subsequently,a novel linear sulfur covalently attached to thiol-rich reduced graphite oxide（rGO）was applied as a cathode for LOSBs and was prepared by copolymerization of poly（L-cysteine）-functionalized rGO and elemental sulfur.Among them,poly（L-cysteine）provide abundant thiol groups,which are beneficial due to the ability to combine with more linear sulfur,the rGO nanosheets can improve the conductivity of organosulfur composites,and G-PSS effectively curbed the emergence of diffluent long-chain lithium polysulfides.Besides,we prepared nitrogen and sulfur co-doped rGO（N,S-G）by using L-cysteine and and graphene oxide as original materials via simple hydrothermal reaction.N,S-G further coated onto polymer separator to prepare N,S-G-functionalized separator,in which polar N,S-G layer effectively held the lithium polysulfides escaping from organosulfur cathode through synergistic electrostatic interactions and can also be used as an embedded collector to reduce the internal resistance of lithium-organosulfur battery.Finally,the organosulfur cathode and N,S-G-functionalized separator are applied to lithium-organosulfur battery.As a result,this novel configuration provides a high initial discharge capacity of 1364 mAh g^-1at 0.2 C and a high discharge capacity of750 mAh g^-1at 1 C after 700 cycles with a very low capacity decay rate of 0.037%per cycle.In addition,we further used density-functional theory（DFT）calculations to verify the experimental results and analyze the reaction mechanism.（3）The highly uniform Fe³⁺/polyacrylamide nanospheres（FPNs）are fabricated on a large-scale and low-cost for the first time through a novel and facile approach.Subsequently,graphene and FPNs are simultaneously introduced onto a side surface of separator to form FPNs-graphene functionalized separator（FPNs-G/separator）,in which the mesoporous FPNs chelate as typical Lewis base with strong polar effectively anchor and block SPSs,and the large area graphene sheets solve intrinsic mechanical brittleness of FPNs and improve overall conductivity for RT/Na-S batteries.In addition,mesoporous nitrogen-doped carbon nanospheres（PNC-Ns）obtained from carbonizing FPNs are applied as the matrix of sulfur for improving the utilization of sulfur,enhancing overall conductivity of cathode,and inhibiting the shuttle of sodium polysulfides（SPSs）.When S/PNC-Ns as a cathode and FPNs-G/separator as a separator are assembled into a RT/Na-S battery,the battery delivers high discharge capacity（639 mAh g^-11 with a capacity retention of 73.2%at0.1 C after 400 cycles based on the second cycle）,stable cycle life（396 mAh g^-11 with a capacity retention of 68.3%at 0.5 C after 800 cycles based on the second cycle）,and good rate performance（228 mAh g^-11 at 2 C）.