Effect of Nitrogen Dopant Forms of Biochar Cathode on the Discharge Mechanism of Li-O2 Battery

Developing metal-free carbon as a new functional electrocatalyst to improve the performance of Li-O2 batteries has become the holy grail of many researchers. It is remarkable to design specific dopants/defects forms and structural adjustments to improve the electrocatalytic performance of carbon cathode. Here, soybean is chosen as a precursor to prepare two N-self-doped carbon materials (SOH and SHCO) with different allocations of nitrogen functional groups via direct combination of pyrolysis and chemical etching by KOH and KHCO3, respectively. SOH cathode exhibits high specific capacity of 9172 mAh g−1 at current density of 0.02 mA cm−2 and ultra-long cycle life of 784 h at 0.1 mA cm−2. The excellent electrochemical performance of SOH is attributed to its interconnected structure, especially abundant graphite N species, which facilitate the surface adsorption mechanisms of low crystalline Li2O2 growing. The study provides a promising optimized preparation route of N-doped cathode with excellent structure and electrocatalytic performance applied to Li-O2 battery.