Highly reliable quinone-based cathodes and cellulose nanofiber separators: toward eco-friendly organic lithium batteries

Abstract

Recently, organic compounds are considered as promising candidates for application in next-generation energy storage systems to overcome the disadvantages of conventional inorganic cathode materials, including their low specific capacity and poor disposal systems. In particular, pillar[5]quinone (P5Q) is very effective as it provides active sites that favor Li uptake and promote a high theoretical capacity. Herein, we propose P5Q-derived cathodes, which are enveloped in multi-walled carbon nanotubes and cellulose nanofibers (CNFs), fabricated by a simple vacuum-filtering method. The designed cathode solves the issues associated with organic materials, including their high solubilities in aprotic electrolytes and low conductivities. Furthermore, CNFs are introduced as alternatives to conventional polyolefin separators. CNF separators can effectively suppress the dissolution of active materials in liquid electrolytes. In addition, CNFs improve ionic conductivity (0.88 mS cm−1), electrolyte wettability (electrolyte uptake: 333.41%, porosity: 70 ± 5%), and thermal shrinkage in contrast to conventional polyolefin separators. The Li-ion battery, assembled with the suggested P5Q cathode and CNF separator, exhibits highly stable capacity retention (76.5% after 50 cycles at a 0.2 C rate) and good rate capability, although an organic electrolyte is used.