NaCl-templated synthesis of hierarchical porous carbon with extremely large specific surface area and improved graphitization degree for high energy density lithium ion capacitors

Abstract

Li ion capacitors (LICs) are emerging as a promising device to integrate the high power density of supercapacitors with the high energy density of Li ion batteries. However, the insufficient specific capacity of the conventional capacitive electrode presents a great challenge in achieving high energy density for LICs. Herein, we demonstrate the synthesis of hierarchical porous carbon with an extremely large specific surface area of 3898 m² g⁻¹ and an improved graphitization degree by using egg white biomass as a precursor and NaCl as a template, in which dual functional NaCl served both as a macropore creating template and a graphitic catalyst to enhance the graphitization degree. With rational design, the developed porous carbon exhibits a noticeably enhanced specific capacity of 118.8 mA h g⁻¹ at 0.1 A g⁻¹ with excellent rate capability and improved cycling stability over 4000 cycles in an organic Li ion conducting electrolyte. Furthermore, the obtained porous carbon was employed as a cathode paired with a Fe₃O₄@C anode for LIC applications, which delivers an integrated high energy density of 124.7 W h kg⁻¹ and a power density of 16 984 W kg⁻¹ as well as a superior capacity retention of 88.3% after 2000 cycles at 5 A g⁻¹, demonstrating the promising application as potential electrode candidates for efficient energy storage systems.