Diode-like gel polymer electrolytes for full-cell lithium ion batteries

Abstract

This study designs a positive–intrinsic–negative (PIN)-diode-like gel polymer electrolyte (GPE) for a full-cell graphite|electrolyte|LiFePO₄ lithium ion battery to facilitate interfacial ion transfer at both the anode and cathode. The diode-like GPE comprises an intrinsic poly(acrylonitrile-co-methylacrylate)-hosted electrolyte layer, as well as positive and negative layers that are synthesized by doping the intrinsic layer with TiO₂ and SiO₂ nanoparticles, which respectively exhibits positive and negative zeta potentials. The positive layer that adsorbs PF₆⁻ anions is in contact with the LiFePO₄ cathode of the battery to facilitate the transfer of Li⁺ cations across the interface. The negative layer, which is in contact with the graphite anode, adsorbs Li⁺ cations to suppress accumulation and prevent the intercalation of solvated Li⁺ into the graphitic framework. The intrinsic layer acts as a neutralization zone to lower the current-rectification effect of the p–n junction. This PIN-configuration design for electrolytes enhances the ultimate capacity of the full-cell battery, exhibits high rate capacity retention, and increases the lifespan (87% capacity retained after 500 charge–discharge cycles).