Charge-Sharing Based Stabilization of Nano-Porous Organic Electrode for Rechargeable Li-Ion Battery

Abstract

Organic-based lithium-ion batteries have garnered increasing attention due to their potential for cost-effectiveness, sustainability, and high energy density. Despite the promising theoretical prediction, the actual battery performance of organic-based electrodes has frequently fallen below the expected values. This discrepancy is primarily attributed to a low density of active sites, limited ion diffusivity, and high solubility to the electrolyte. This study introduces 5,10-dihydro-5,10-dimethylphenazine (DMPZ) as an organic active material, demonstrating superior electrochemical performance characterized by high capacity and prolonged cycle performance. To achieve a high capacity, a cryogenic milling is employed to create a porous nanostructure, enhancing the surface-to-volume ratio without altering the molecular structure. Consequently, the initial specific capacity of the porous DMPZ electrode reaches 184 mAh g-1 at 0.6 C, representing a remarkable 180% increase compared to non-milled DMPZ. To improve cycle stability, a charge-sharing reaction among organic active materials is facilitated by forming an organic nanocomposite comprising DMPZ and various n-type organic materials. The organic nanocomposite effectively mitigates the elution of organic active materials, ensuring unprecedented cycling stability with a capacity retention exceeding 90% over 500 cycles with initial specific capacity of 248 mAh g-1. C-rate tests at 1.2, 2, 4, and 8 C demonstrate outstanding rate capability, with an average capacity of 105 mAh g-1 at 8 C. The performance enhancement mechanism of the organic nanocomposite cathode is elucidated through experimental analyses, including ex-situ XPS, PiFM, and FTIR. These analyses collectively contribute to a comprehensive understanding of the mechanisms underlying the observed improvements in battery performance.