Reasaech On Moification Of Phenazine Andoe And Lithium Manganate Cathode For Aqueous Rachargeable Batteries

Extensive results have been achieved in improving the utilization rate of renewable energy,mobile digital products and green transportation;in order to further increase the utilization rate of clean energy.It is particularly important to manufacture a positive electrode material with high energy density and low cost.In addition,the lack of lithium resources and potential safety hazards make its application bottleneck.As an alternative,aqueous rechargeable batteries(ARB)stand out.However,conventional inorganic electrode materials are often corroded by the electrolyte,which affects the cycle stability and causes serious attenuation.Phenazine(PNZ),an organic material,has good stability under alkaline conditions,but its own conductivity is extremely poor.In the second part of this article,nano-sized phenazine and its composite materials were prepared by the precipitation-dissolution method.The nano phenazine/carbon composite shows good electrochemical reversibility and stability in 6 M NaOH electrolyte,and the maximum capacity at 1 C of nano-PNZ/KCB is 178 mAh g-1.After being modified by nano-TiO2,it can above 200 mAh g-1.In order to prolong the life of the electrode in the ARB,and slow down the irreversible capacity loss caused by the dissolution of the electrolytic material.In the third part of this article,by optimizing the electrolyte type and concentration,the electrochemical stability window is widened and the side reaction of hydrogen and oxygen evolution in water is suppressed.When the concentration of LiTFSI solution reaches 9 m,the electrochemical window is widened to 2 V.Moreover,the 9 m LiTFSI solution greatly increases the cycle life of the LiMn2O4 electrode.The first discharge specific capacity is 106 mAh g-1 at a rate of 1 C.Using P(VDF-HFP)polymer as the substrate,the gel electrolyte coating is prepared.When the concentration of LiTFSI is 10%,the ionic conductivity of the gel electrolyte can reach 7.6×10-3 S cm-1.The life of the LMO coated with the gel electrolyte is significantly improved.After 2500 cycles with a capacity retention of 68.4%at 5 C.The lithium nickel manganese oxide(LiNi0.5Mn1.5O4,LNMO)material is obtained on the basis of LMO,which has more outstanding performance than LMO.However,the low cycle life caused by the instability of the interface of the material during the charge-discharge,which brings the biggest challenge in practical applications.Surface coating and element doping can make the LNMO interface more stable.SiO2 eliminate the HF generated by the side reaction of the electrolyte.Therefore,the cycle life of the LNMO can be prolonged.In the last part of this article,the LNMO was modified by KH570.After calcination at high temperature,the in-situ coating of LNMO by SiO2 and the Si doping are realized.The results show that when the SiO2 amount is 0.8wt%,the composite has the best electrochemical performance.The capacity retention is about 90%after 1000 cycles.