Modification of NASICON electrolyte in solid sodium-ion batteries——A short review

In recent years,the development and research of electrochemical energy storage systems that can efficiently transform chemical energy into electrical energy with a long service life have become a key area of study.Sodium-ion batteries,leveraging their chemical similarity to lithium-ion batteries,along with their abundant resources and low cost,are seen as a viable alternative to lithium-ion batteries.Additionally,all-solid-state sodium-ion batteries have drawn significant attention due to safety considerations.Among the solid electrolytes for all-solid-state sodium-ion batteries,the NASICON solid-state electrolyte emerges as one of the most promising choices for sodium battery solid electrolytes.However,to date,there has not been a comprehensive review summarizing the existing problems of NASICON electrolyte materials and the corresponding specific modification methods.This review simply summarizes the present issues of NASICON for all-solid-state sodium-ion batteries,such as,the low ionic conductivity,the poor interface stability and compatibility,and the dendrite formation.Then,the corresponding solutions to address these issues are discussed,including the ion doping,the interface modification,the sintering parameters optimization,and the composite electrolytes regulation.Finally,the perspectives of NASICON solid-state electrolyte are discussed.

Interface issues and challenges for NASICON-based solid-state sodium-metal batteries

All-solid-state sodium(Na)-metal batteries(ASSSMBs)are considered promising candidates for large-scale energy storage systems due to their abundant sodium resources,unparalleled safety performance,and impressive energy density.Na superionic conductors(NASICONs)are among the best enablers of ASSSMBs in view of their high ionic conductivity,ease of synthesis,and excellent thermal stability and good electrochemical/chemical compatibility with common electrodes.However,challenges surrounding the NASICON/electrode interface,such as high interfacial resistance and dendrite formation,have hindered the development of practical ASSSMBs based on NASICONs.This review starts with an explicit summary of the interface problems between the metallic Na anode and NASICON arising from mechanical,chemical,and electrochemical aspects(i.e.,poor interface contact,insulating side-reaction products,and irregular dendrite growth).Subsequently,we systematically analyze and logically categorize modification strategies for addressing anode interface problems and provide a comprehensive discussion on the underlying enhancement mechanisms.As such,we identify underlying and universal interface enhancement mechanisms by comparatively studying various modification strategies.Furthermore,we briefly summarize the challenges in the cathode/electrolyte interface and early-stage research efforts in constructing stable cathode/electrolyte interface and fabricating high-performance composite cathodes.Finally,key suggestions and future prospectives for the advancement of NASICON-based ASSSMBs are outlined.

Na_(3)Zr_(2)Si_(2)PO_(12) solid-state electrolyte with glass-like morphology for enhanced dendrite suppression

Rechargeable batteries based on solid-state electrolytes are of great interest and importance for the next-generation energy storage due to their high energy output and improved safety.For building the solid-state batteries,Na_(3)Zr_(2)Si_(2)PO_(12)(NZSP)represents a promising candidate as it features high chemical stability against air exposure and a high Na^(+)conductivity.NZSP pellets were usually calcined at a high temperature,and the high volatility of Na and P elements easily led to the formation of impurity phase.In this work,the effects of calcination temperature and stoichiometry on the phase purity and ionic conductivity of the NZSP electrolyte were studied.At an elevated sintering temperature,the NZSP electrolyte showed a high ionic conductivity owing to decreased porosity,and the highest ionic conductivity at 30℃was observed to be 2.75×10^(-5)S·cm^(-1)with an activation energy of 0.41 eV.For the stoichiometry,the introduction of 5 mol%excessive P results in formation of more Na_(3)PO_(4) and glass-like phase at the grain boundary,which caused the blurred grain boundary and reduced grain barrier,and effectively suppressed Na dendrite growth,then accounted for improved cycling performance of a Na‖Na symmetric cell.Our work provided insights on reasonable design and preparation of NZSP electrolyte towards practical realization of solid-state Na-metal batteries.