Effect Of Binders On The Electrochemical Properties Of Cathode Materials For Sodium/Zinc-Ion Batteries

Phosphate and manganese-based materials have become the most promising cathode materials in the field of large-scale electrochemical energy storage due to its high discharge capacity and abundant resources.The selection of suitable binder can not only solve the problems of transition metal dissolution and increase of irreversible products in the two types of cathode materials,but also achieve good cycle stability and rate performance.However,the NMP as solvent of the traditional PVDF binder,is expensive and easy to pollute the environment.In addition,PVDF binder is prone to oxidative decomposition at higher voltages,resulting in performance degradation.Therefore,the development and design of novel binder is the key means to achieve low-cost and high-performance sodium/zinc ion battery.In this paper,with the goal of realizing high-performance sodium/zinc ion batteries,the effects of aqueous and non-aqueous binders on the electrochemical performance of cathode materials are investigated,and the mechanism of action of the binders is further understood.The main conclusions are as follows:（1）Sodium lignosulfonate（LS）is used as a multifunctional binder for Na₃V₂（PO₄）₃ cathode materials of sodium-ion batteries.Compared with PVDF binder,LS binder can build a stable solid permeable interface between the cathode and electrolyte,which inhibits the further oxidation and decomposition of electrolyte during charge and discharge.meanwhile,the cathode with LS binder also exhibits faster transfer capability of Na⁺ion and electron,lower interfacial resistance,and achieves excellent electrochemical performance.At a current density of 1 C,after 300 cycles,the reversible specific capacity of the cathode with LS binder is still 85.2m A h g^-1,and the capacity retention rate is 82.6%,which is higher than that of the cathode with PVDF binder,which is 42%.（2）PVDF-HFP is firstly used as a binder to improve the electrochemical performance of aqueous zinc/manganese batteries.The results indicate that the aqueous binders are easily partially dissolved when the electrolyte solvent is water,destroying the integrity of the electrode,resulting in poor electrochemical performance.During the charging and discharging process,the cathode with PVDF-HFP binder not only ensures the integrity of the electrode,reduces the charge transfer resistance and voltage polarization,but also suppresses the cracks on the electrode surface.At a small current density of 100 m A g^-1,the cathode with PVDF-HFP binder exhibits a specific discharge capacity of 264.9m A h g^-1 after 90 cycles,with a capacity retention rate of 92%.Under the same conditions,the capacity retention rate of the cathode with PVDF binder is only 61%.