Effective Stabilization of Organic Cathodes Through Formation of a Protective Solid Electrolyte Interface Layer via Reduction

Abstract

2,5‐Dihydroxy‐1,4‐benzoquinone (DHBQ) is a promising cathode material, but its high solubility in electrolytes leads to rapid capacity degradation. This study investigates the dilithium salt of DHBQ, Li2DHBQ, as a cathode material for lithium‐ion batteries (LIBs). Despite minimal solubility, Li2DHBQ cathodes suffer rapid capacity decay due to severe morphological damage within the voltage range of 1.5‐3.0 V. To stabilize morphology, we promoted a protective solid electrolyte interphase (SEI) layer on Li2DHBQ particles by lowering the discharge cutoff voltage. Cycling the battery with a 0.5 V discharge cutoff voltage achieved an optimal SEI layer, significantly improving Li2DHBQ's morphological stability. Consequently, the battery maintained 170 mAh g‐1 with a low decay rate of 0.16% within a voltage range of 0.5‐3.0 V after 200 cycles at 500 mA g‐1. Furthermore, initial cycling at a 0.5 V discharge cutoff for 20 cycles to form an SEI layer, followed by cycling at a normal 1.5 V discharge cutoff, retained a higher capacity of 187 mAh g⁻¹ after 200 cycles. This study demonstrates the effectiveness of forming a cathode SEI layer at low discharge voltages as a new approach to stabilizing organic cathode materials.