In order to improve the ambient conductivity of all-solid-state electrolytes as well as enhance the diffusion number of lithium ion

all-solid-state polyphosphazene electrolytes containing nanoSiO2 modified with poly(oxyethylene-co-oxypropylene) silane were prepared.The macromonomer of polyphosphazene was prepared through reaction of phosphazene with poly(oxyethylene-co-oxypropylene) monoacrylic ester and poly(ethylene glycol) monomethylether with the yield of 92.6%.Silane coupling agent with polyether was prepared by the hydrosiloxane addition reaction between trimethyloxyl siloxane and allyl poly(ethylene-co-propylene glycol) methyl ether.The silane coupling agent refluxed with SiO2 to form nanoSiO2 modified with poly(oxyethylene-co-oxypropylene) silane.The FT-IR spectrum and XPS together show that SiO2 has been successfully modified by the soft chain.The SEM images of composite electrolytes show that modified nano SiO2 could easily disperse among polymer electrolyte with only a little conglomeration.It is found that the nanoSiO2 content in electrolyte fixed at 10% could reach the best ambient conductivity of 3.14×10-4 S cm-1

which is 2.4 times higher than that of the noncomposite system.Differential scanning calorimetry of nanocomposite solid state electrolytes showed that the glass transition temperature of the electrolyte did not change with the variation of nanoSiO2 content from 2% to 10%

which indicated that nano SiO2 modified with polyether did not change the crosslinking density of nanocomposite system

and the polyether chain could maintain the original flexibility of the solid state electrolytes.The conductivity of electrolyte is increasing with the increase of temperature

which obeys the VTF equation.When the temperature rises up to 50℃

the electrolyte with 10% modified SiO2 shows the best conductivity of 10-3 S cm-1

the corresponding active energy is 4.07 kJ mol-1. The high conductivity can be explained on the one hand

the polyphophazene monomer has the side chain of oxyethylene

which is helpful to solve the lithium salt

the copolymerization of oxyethylene and oxypropylene reduces the glass transition temperature of the polymer and inhibits the crystallization of polyoxyethylene; on the other hand

the nanoparticles modified with soft polyether chains can uniformly disperse in the polymer electrolyte

and the polyether plays the role of plasticizer.The result of DSC also proves such explanation.With increasing the content of lithium salt

the ionic conductivity first increases

then shows a subsequent decline.The highest ambient conductivity of nanocomposite electrolyte is obtained when the concentration of lithium perchlorate is fixed at 8%.The addition of nanoSiO2 reduces the formation of ion cluster.Cyclic voltammogram gives the result of good electrochemical stability of nanocomposite electrolyte and an electrochemical window of more than 4.2 V.Alternating current impedance spectrum accounts for the good interfacial stability between electrolyte and electrode after 7 days of the assembling of the cell

which was explained by the composition of nanoparticles modified with flexible chains which may reduce the interfacial impedance and help the transfusion of ions.The diffusion number of lithium ion in the nanocomposite all-solid-state polymer electrolyte is realized through stable current method

the result indicates that the ion diffusion number increased from 0.25 to 0.34 due to the composite of nanoparticles.