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

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.