Study On Highly Safe Phosphate Es Terelectrolyte And Modification Of Sodium Anodes For Sodium Batteries

Sodium ion battery has a wide range of raw materials and will be widely used in electric vehicles and large-scale energy storage in the future.However,the research on sodium ion battery is still at the initial stage,and there are some problems such as poor cycling performance,incompatible electrolyte,poor safety and sodium negative dendrite,which hinder its further commercialization.In order to improve the safety and recycling performance of sodium batteries,this paper studies the problems of sodium batteries from two aspects: flame retardant electrolyte and negative electrode protection of sodium metal.For the study of high safety electrolyte,the additive with flame retardant effect,toluene diphenyl phosphate(CDP),was introduced to reduce the spontaneous combustion time of the electrolyte,improve the safety of the electrolyte and the cycling stability of the battery.In order to detect the effect of flame retardant,the self-extinguishing experiment and self-spreading experiment were used to obtain the following results.After the addition of CDP,the self-extinguishing time of sodium battery electrolyte was effectively reduced,the flame spreading ability was weakened,and the battery safety performance was greatly improved.The electrochemical properties of flame retardant electrolyte were tested by taking 30%CDP as the optimal ratio based on the test results of solution conductivity and considering the overall performance of the battery.Electrochemical test results show that,In the study of inhibiting dendrite growth by sodium metal negative electrode,the method of three-dimensional fluid skeleton was adopted to inhibit dendrite growth and protect the sodium metal negative electrode.According to the sem observation,no significant dendrite formation was observed after 50 cycles in the sodium negative electrode embedded in the tin-copper mesh,while in the blank control group,obvious dendrites were observed to grow like weeds and fracture to cause dead lithium.Further testing of the electrochemical properties of tin-copper mesh on sodium metal batteries showed that the fluidic concentration of tin-copper mesh doubled the life of the symmetrical battery.In addition to the construction of three-dimensional collector fluid,a protective layer of NaBr that can conduct sodium ions is also built on the surface of sodium metal by spreading NaBr powder on the surface.Through sem observation,it is found that with the continuous battery cycle,the NaBr powder will gradually become uniform and form a dense protective film.Under the action of the protective film,the dendrite of metal sodium cannot grow,thus achieving the effect of protecting the sodium metal.The life of the symmetrical battery is extended 8 times as long as the original life.