Dihydrophenazine-derived oligomers from industrial waste as sustainable superior cathode materials for rechargeable lithium-ion batteries

Abstract

Organic materials with the 5,10-dihydrophenazine motif are superior cathode materials for lithium-ion batteries. However, the difficult accessibility and low capacity of such cathodes materials are obstacles to their practical applications. Herein, two novel oligomers, termed poly(5-methyl-10-(2-methacryloxypropyl)-5,10-dihydrophenazine) (PMPPZ) and poly(5-methyl-10-(2-methacryloxyethyl)-5,10-dihydrophenazine) (PMEPZ), were effectively synthesized from an industrial waste phenazine. Both oligomers were exploited successfully as excellent cathode materials for sustainable lithium-ion batteries. PMPPZ and PMEPZ exhibited good electrochemical stability and high initial discharge specific capacities of 88 mA h g⁻¹ and 152 mA h g⁻¹, respectively. Furthermore, upon in situ composition with MWCNTs, a composite material, named PMEPZ–MWCNTs, was achieved with enhanced stability and superior specific discharge capacity with the active-site utilization rate of up to 99%. PMEPZ–MWCNTs delivers high initial discharge capacity of up to 303 mA h g⁻¹ and even 252 mA h g⁻¹ after 300 cycles. Both oligomers exhibit double-electron transfer mechanisms. This work affords an alternative approach to utilizing phenazine as a useful material, circumventing the emission of vast environment harmful gases.