Abstract: In this paper, two-dimensional B/N co-doped porous carbon sheets (BNCSs) were prepared by one-step carbonization using glycine as carbon source and nitrogen source, boric acid as template and boron source. The boric acid template can be removed by water washing, and the synthesis method is green and environmentally friendly. The short pores in BNCSs shorten the transport distance of potassium ions, and the abundant micropores provide a large number of potassium storage active sites. In addition, the higher B/N doping in BNCSs increases the defect degree of carbon matrix, expands the carbon layer spacing, and is conducive to the adsorption, insertion and de-insertion of potassium ions. The measurement results of potassium ion half cell performance indicate that BNCS₈₀₀ electrode shows high specific capacity (310 mA·h/g at 0.05 A/g), excellent rate performance (100 mA·h/g at 2 A/g) and good cycle stability (after 1000 cycles at 1 A/g, the capacity retention is 75.9%). This work provides a simple strategy for preparing cathode materials with high capacity and long life.