Correlating the mechanism, kinetics, and SEI formation of a boron-doped graphene anode for high-performance alkali ion batteries†

Graphite has been used extensively for Li-ion batteries (LIBs) due to its low cost, abundant resources, and long-term stability. However, graphite exhibits limited capacity in LIBs, significantly poor capacity in Na-ion batteries (SIBs), and inferior cycling stability in K-ion batteries (PIBs), which hinders the development of sustainable next-generation battery technologies. Heteroatom doping and tuning interlayer spacing are known to be effective solutions for carbon-based materials. Such modified anodes can exhibit high capacity and cyclability with numerous active sites. Here, we report boron-doped thermally exfoliated graphene (BTEG), which exhibits a high reversible capacity of 1014 mA h g⁻¹ (LIBs), 295 mA h g⁻¹ (SIBs), and 369 mA h g⁻¹ (PIBs) at a current density of 25 mA g⁻¹. We used operando/in situ measurements such as Raman spectroscopy and electrochemical impedance spectroscopy to investigate the fundamentals involved during the real-time phenomenon of BTEG/alkali-ion batteries. Consequently, it helps assess the reaction mechanism and kinetics to establish a structure–performance relationship for all three batteries with the BTEG anode. Finally, based on solid electrolyte interphase (SEI) understanding and electrolyte tuning, highly reversible batteries were attained for up to 1000 cycles at a high current density of 1 A g⁻¹.