Research On The Interface Of Magnesium Oxide Fiber Retained Molten Electrolyte And Electrode

The electrolyte of thermal batteries is in molten state at operation temperature,external forces occurred during operation may lead to leakage of the molten electrolyte,resulting in short circuit and collapse of the battery system.In order to improve the stability of thermal batteries,the molten electrolyte is immobilized by a binder.Magnesium Oxide powder has become the main material for the binder because of its good chemical stability and compatibility.Compared to Magnesium Oxide powder,Magnesium Oxide fiber has larger surface area and stronger adsorption capacity than the Magnesium Oxide powder,thus the Magnesium Oxide fiber has attracted wide attention in recent years.In this study,magnesium oxide imporous fiber was prepared by precipitation method,magnesium oxide porous fiber was prepared by hydrothermal method,and different amount of hydrofluoric acid sol ution was used to corrode the magnesium oxide porous fiber,in order to obtain modified magnesium oxide fibers?Mg O-20HF fiber,Mg O-40HF fiber and Mg O-60HF fiber?.As the binders,different fibers are added into binary and ternary electrolyte systems,forming the electrolyte binder,the conductivity and flow behaviour of electrolyte binder were investigated.Then the effects of the binders on battery discharge were also studied.According to the analysis of above investigations,a model cell was built to di scuss the effect of different binders on ionic transportation in interface of thermal batteries.The results showed that,fiber with larger specific surface area can adsorb more electrolyte molten salt,thereby enhancing the flow inhibition abilit y of molten electrolyte.Owing to the corrosion of hydrofluoric acid solution,magnesium fluoride is formed on the surface of modified fibers.Magnesium fluoride has strong activity and adsorption ability,thus it also benefits to inhibiting the flow of molten electrolyte.In the binders,magnesium oxide porous fiber,Mg O-20HF fiber and Mg O-40HF fiber can form a stable three-dimensional network structure,which provides a stable channel for the transportation of Li⁺ions in the electrolyte.This structure can shorten the ion migration distance,so as to reduce the concentration polarization,stable discharge platform.At the interface between anode layer and electrolyte layer,the stable three-dimensional network structure can make the Li⁺ions pass through the interface then enter the electrolyte layer directly.It also can inhibit the dissolution of Li-Si alloy in the electrolyte,thus reduce the self-discharge of model cell at the interface.The stable three-dimensional network structure can also prevent t he powder produced by the Fe S₂ decomposition from entering the electrolyte layer.The fibers at interface can adsorb the powder produced by the Fe S ₂ decomposition,and this provides a channel for Li⁺ions to pass through the interface between cathode layer and electrolyte layer.