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 LiNi_0.80 Co_0.15Al_0.05O₂ (LiNCAO) cathode.