  We present a novel tin based flexible, gel polymer negative electrode for use
in sodium-ion devices. The electrodes have been prepared by trapping tin
micro-particles in a porous electrolyte membrane formed by immersion
precipitation phase-inversion and soaking in a sodium-ion conducting liquid
electrolyte. The tin particles are the active electrode materials as well as
electron conductors, while the gel polymer enable efficient ion-transfer to the
tin particles. The composite gel electrode and its performance in sodium-ion
capacitor has been analyzed using scanning electron microscopy. x-ray
diffraction, cyclic voltammetry and galvanostatic charge-discharge. The
specific capacity of the capacitor shows an initial increase, up to 175
charge-discharge cycles. This increase has been explained by the increase in
surface area of tin due to disintegration of the larger particles upon repeated
insertion/de-insertion of sodium. A high capacitance of 210 mAh g-1 at 1 A g-1
has also been measured.
