Preparation And Modification Research Of Li₂NaV₂?PO₄?₃ Nanocomposites Cathode Material

Rhombohedral Li₂NaV₂?PO₄?₃?R-LNVP?has become the ideal choice for lithium/sodium ion batteries cathode materials due to its open frame structure has large ion transport channel and high electrochemical stability.It has been confimed there have significant effect when modificated electrode materials by nanosize,coating and doping,this paper is also studied from these three aspects.Li₃V₂?PO₄?₃ as the base material in this paper,in ensuring that the premise of nano materials and carbon coated,regulation the morphology of Li₃V₂?PO₄?₃,using sodium elements replaced of lithium elements in Li₃V₂?PO₄?₃.Even in the end all three lithium elements are replaced by sodium elements.Formed Na₃V₂?PO₄?₃ assembly sodium battery test performance.Besides,also explored the magnesium metal doping in vanadium site and the relaxation phenomena in LIBs.Sodium lignin come from papermaking black liquor is employed as carbon source,sodium source,nucleation agent and structure template,using the method of simple sol-gel.The R-LNVP particles are nucleating and growing attach to lignin molecular chain.So the nanoparticles morphology size can be regulated.And through the carbon thermal reduction process form the biological carbon in the electrode material,finally,successfully fabricating superlattice-bearing Li₂NaV₂?PO₄?₃nano-wafers in carbon nanofibers towards high performance batteries.The nanocoposites cathode exhibits high reversible capacities,i.e.,137.2 mAh/g at 0.1 C in LIBs,but also 91.04 mAh/g at 0.2 C in SIBs.More importantly,it could consume2.36 liters papermaking black liquor when one kg nanocomposite was synthesised.Not only can reduce the papermaking black liquor pollution to the environment,but also can reduce the cost of the synthesis of nanocomposites.The results show that the papermaking black liquor can be converted into high performance electrode materials in the process of nanocomposites synthesis.It also has important theoretical value and practical significance in the research and development of new cathode material and the application of sodium ion batteries.Glass fiber lubricant wastewater as a raw to synthetic Li₃V₂?PO₄?₃ which contains a lot of surfactant,formed the porous Li₃V₂?PO₄?₃/C materials.The materials deliver a good cycle performance.The residual capacity is about 92 mAh/g after 1000cycles at 10 C.In order to give full play to the advantages of porous structure and further improve electrochemical performance.We repeat the above experiment with hydrothermal method.It is interesting to note that porous structure,hydrangea structure and spheroidal structure.These three structure are interlaced with each other.Through the electrochemical test,the material has excellent cycle stability at 10 C,the discharge capacity is 65 mAh/g after 1000 cycles and capacity attenuation rate keep within 10%.It could consume 24.51 liters glass fiber lubricant wastewater when one kg nanocomposite was synthesised.It also can meet the requirements of mass production because production method is simple,low cost and the performance of product is high.We have modified Li₃V₂?PO₄?₃ cathode by Mg²⁺doping in vanadium situ.We explored the quantity of magnesium metal doping in order to acquire the best electrochemical performance,the premise is to ensure that the crystal doesn't change.Glass fiber lubricant wastewater as raw materials synthesis Li₃Mg_xV_2-x?PO₄?₃ using sol-gel auxiliary hydrothermal method.Numerous‘grain'build up‘stack'in morphology under the surfactant and hydrothermal dual function.The advantage on structure can provide larger specific surface area is advantageous to lithium ion embedded in and out in the process of charging and discharging.Electrochemical tests proved doping trace magnesium metal in the material has little influence on charge and discharge performance.The optimal performance is acquired when x=0.2 in Li₃Mg_xV_2-x?PO₄?₃.The discharge capacity is nearly 70 mAh/g at 10 C and the coulombic efficiency is above 95%after 100 cycles.Glass fiber lubricant wastewater as carbon source and soft template synthesis Na₃V₂?PO₄?₃ cathode.Compared with pure Na₃V₂?PO₄?₃ found that the high rate performance has improved dramatically.The rate performance only to 5 C,but for experiment sample discharge capacity is about 30 mAh/g at 10 C.The capacity attenuation rate is less than 5%.This section have explored the relaxation phenomena that exist in the lithium ion battery.The source of the relaxation phenomena was explained through electrochemical charge-discharge test,cyclic voltammograms and electrochemical impedance spectroscopy.Based on the relaxation phenomenon,the modification of the battery electrode was studied.