Nickel salts-induced microstructure modification of B–N co-doped porous carbons for high-performance supercapacitor electrodes

•High SSA, graphitization degree and heteroatom contents due to nickel chloride.•A Ni-B-N co-doping porous carbon related to nickel acetate.•Higher capacity and rate performance for BNHC-L and BNHC-Y, respectively.•Superior comprehensive property of BNHC-L2Y2 electrode with high mass loading. Herein, we report a facile strategy for microstructure modification of B–N co-doped porous carbons induced by nickel salts. Nickel chloride mainly plays a pore-forming role in the formation of resultant BNHC-L, leading to a high surface area (SSA) of 1000 m2 g−1, and favors high-level heteroatom doping and enhancement of graphitization degree simultaneously. Contrastively, nickel acetate facilitates the generation of Ni–B–N multi-doping porous carbon (BNHC-Y) but seriously hinders the fabrication of nanopores. BNHC-L exhibits superior specific capacitance of 342 F g−1 at 0.5 A g−1 in the three-electrode system due to higher SSA and heteroatom content, and enhanced electrical conductivity than BNHC-Y. BNHC-Y shows better rate performance with a capacitance retention of 60.4% from 0.5 to 100 A g−1 based on its higher mesopore ratio and better wettability than BNHC-L. Notably, as supercapacitor electrode with commercial-level mass loading (~180 µm, ~13 mg cm−2), BNHC-L2Y2 prepared with the dual nickel salts can deliver a high specific capacitance of 245 F g−1 at 0.05 A g−1, superior capacitance retention of 86.1% at 5 A g−1, and excellent cycling stability (94.8% of its initial specific capacitance after 10,000 cycles) because of its considerable SSA, optimal PSD, suitable surface chemistry and enhanced electrical conductivity.