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

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Organic electrode materials offer sustainable alternatives for lithium-ion batteries (LIBs) due to cost, environmental benefits, and high theoretical capacity.
• 2,5-dihydroxy-1,4-benzoquinone (DHBQ) is a promising organic cathode, but its high electrolyte solubility causes rapid capacity degradation in LIBs.
• The dilithium salt of DHBQ (Li₂DHBQ) exhibits low solubility but still suffers from morphological damage and capacity decay within the 1.5-3.0 V range.

Purpose of the Study:

• To stabilize Li₂DHBQ organic cathode material for improved lithium-ion battery performance.
• To investigate the formation of a protective solid electrolyte interphase (SEI) layer on Li₂DHBQ particles.
• To explore the effect of lowering the discharge cutoff voltage on SEI layer formation and morphological stability.

Main Methods:

• Synthesized and tested the dilithium salt of 2,5-dihydroxy-1,4-benzoquinone (Li₂DHBQ) as a cathode material for LIBs.
• Investigated the impact of varying discharge cutoff voltages, specifically focusing on a 0.5 V cutoff, to promote SEI layer formation.
• Analyzed the morphological stability and electrochemical performance of Li₂DHBQ cathodes under different cycling conditions.

Main Results:

• Cycling Li₂DHBQ with a 0.5 V discharge cutoff voltage optimized the SEI layer's thickness and organic-rich composition, enhancing morphological stability.
• The battery maintained 170 mAh g⁻¹ with a low decay rate (0.16% per cycle) over 200 cycles within the 0.5-3.0 V range at 500 mA g⁻¹.
• An optimized cycling protocol (20 cycles at 0.5 V cutoff, then 1.5 V cutoff) yielded an even higher capacity retention of 187 mAh g⁻¹ after 200 cycles, significantly outperforming the 87 mAh g⁻¹ retention in the standard 1.5-3.0 V range.

Conclusions:

• Forming a cathode SEI layer at low discharge voltages is an effective strategy for stabilizing organic cathode materials like Li₂DHBQ.
• This approach significantly enhances morphological stability and electrochemical performance, addressing capacity degradation issues in organic LIBs.
• The findings present a novel method for improving the durability and lifespan of organic lithium-ion batteries.