Bio-based poly(benzimidazole-co-amide)-derived N, O co-doped carbons as fast-charging anodes for lithium-ion batteries

Abstract

Lithium-ion batteries (LIBs) that can be charged faster while delivering high capacity are currently in significant demand, especially for electric vehicle applications. In this context, this study introduces a less-explored subject: nitrogen and oxygen dual-doped carbons derived from bio-based copolymers, specifically poly(benzimidazole-co-amide). The synthesis involved varying proportions of benzimidazole to amide, namely, 8.5 : 1.5, 7 : 3, and 5 : 5. The copolymers were pyrolyzed under a nitrogen atmosphere to obtain co-doped carbons, wherein the copolymers acted as single sources of carbon, nitrogen, and oxygen, with the nitrogen content ranging between 12.1 and 8.0 at% and oxygen doping between 11.8 and 25.0 at%, and were named as pyrolyzed polybenzimidazole-co-amide 8.5-1.5, 7-3, and 5-5. Coin cells were fabricated and rate studies were conducted for all three samples, wherein PYPBIPA8.5-1.5 outperformed all others, especially at higher current densities. Intrigued by these interesting results, when long-cycling studies were performed at a high current density of 4.0 A g−1, pyrolysed polybenzimidazole-co-amide 8.5-1.5 showed a delithiation capacity of 135 mA h g−1 compared to pyrolysed polybenzimidazole-co-amide 7-3 and 5-5 with a delithiation capacity of 100 mA h g−1 and 60 mA h g−1, respectively, with a capacity retention of 90% even after 3000 cycles. Furthermore, a full cell (2025-coin cell) was fabricated using the PYPBIPA8.5-1.5 anode and LiNi0.80 Co0.15Al0.05O2 (LiNCAO) cathode.