Study On The Properties Of Thermal Battery Cathode Material CoS₂and CoS₂-LVO Composite Materials

CoS2will produce impurities CoSO4, CoS and S in the synthesis processand storage. Impurities can cause resistivity increase, polarization increase,thermal stability decrease, resulting in voltage spike. Relatively low dischargevoltage CoS2compared to vanadium oxide cathode material, can not meet thehigh power output requirement. For the above two aspects, on the basis of thepre-purification method, the paper have made further improvement on thepurification process, and used the method of vanadium oxide doped to modifyCoS2to improve the discharge voltage. Specific studies and results are asfollows.At70℃, the content of impurities in the purified CoS2changes with dryingtime were further analyzed. The optimal drying time for CoS2is6h, if washedwith ethanol,4h is optimal. Drying time will not have a significant impact on theimpurity content of S. The effect of concentration of sodiumhydroxide on Simpurity content was studied. It is found that the content of S impurity woulddecrease with increasing the concentration of sodium hydroxide and tend toreach aminimum value. The effect of ethanol cleaning process on content of eachimpurity in CoS2was studied. After the ethanol cleaning process, the impurity ofCoSO4content is lower0.05%than that not been cleaned, impurities content ofCoS and S show no significant decrease.The purification process CoS2wasfinally optimized.The structure and electrical properties of CoS2after purification werestudied. The effect of purification technology on the crystal structure and hightemperature thermal stability and its appearance morphology were mainlystudied. Thermal stability of CoS2was significantly improved after purification,CoS2exterior appearance become porous, which will effectively increase thespecific surface area. After different purification steps, the electrical propertieswere improved, the larger discharge current density, the electrical propertiesimprovement is more significant.The effect of different argon flow rate on products change of metavanadatethermal decomposition was studied.Vanadium oxide (VO2,V2O5,V6O13) andLithiationVanadium Oxide (LiV3O8, LiV2O5)were prepared. When the flow rateof argon gas was40,30,20,0mL/min, the main phase thermal decompositionproduct was VO2,V3O7,V6O13,V2O5respectively. The effect of LiBr·H2O contenton species of LVO was determined. When the amount of LiBr·H2O was20%,30%,50%, LVO was LiV3O8, mixture of LiV2O5and LiV3O8, LiV2O5 respectively. Electric properties of LiV3O8were studied and it is found that thedischarge voltage is higher than the discharge voltage of CoS2about0.4V, butthe discharge life is shorter. CoS2-LVO cathode material was prepared, and itselectrical property was tested. When the doping ratio of LVO and VO2was5%and constant discharge current was140mA/cm2, the voltage was increased by0.17V and0.19V respectively than CoS2, the discharge capacity was increased by25.2%,33.8%respectively up to1.5V. The discharge products development ofLiV3O8was tested by XRD characterization, from LiV3O8to LiV2O5and Li3VO4finally, the vanadium valence change is accompanied by+5→+4/+5→+5.