K2CO3 activation enhancing the graphitization of porous lignin carbon derived from enzymatic hydrolysis lignin for high performance lithium-ion storage

As an abundant natural aromatic polymer with high carbon content, lignin can be regarded as an abundant carbon matrix precursor to develop cost-effective and environmental friendly porous carbon for energy storage materials. However, the porous lignin-derived carbon remains a great challenge as an anode for Li-ion batteries due to its low degree of graphitization. In this paper, a low-cost, productive and scalable industrial method has been adopted to fabricate highly graphitized lignin-based porous carbon (PLC-EHL-K2CO3) with K2CO3 activation using enzymatic hydrolysis lignin (EHL) as a raw material. PLC-EHL-K2CO3 was composed of multilevel lamellar structure possessing high specific surface area and macro- and mesoporous. Notably, the graphitization of PLC-EHL-K2CO3 was significantly improved compared with the common KOH activation. Meanwhile, the structure of lignin is an important factor affecting the structure of PLC, such as the molecular weight and oxygen functional groups. The high specific surface area, large pore volume and unique multilevel lamellar morphology bestow PLC an excellent lithium storage performance, and PLC-EHL-K2CO3 electrode displays a desirable reversible capacity of 520 mAh·g−1 at a current density of 200 mA g−1 over 200 cycles and increases 47.3% than PLC-EHL-KOH, and even at 1 A g−1 a specific capacity of 260 mAh·g−1 can be retained after 1000 cycles. This higher graphitization porous carbon material from low-cost renewable lignin is a good candidate for lithium storage equipment.