Effects of alkali additives in saturated LiNO3 aqueous electrolyte for improvement in cycling stability of polyimide anode

Abstract

In this work, the alkali additive is introduced to improve the cycling stability of polyimide anode in saturated LiNO3 aqueous electrolyte. Optimal electrolyte consists of saturated LiNO3 aqueous solution with 0.001 mol L−1 KOH, which improves the capacity retention of polyimide in a three-electrode cell. When assembling with LiCoO2 cathode, the full cells exhibit good cycling stability with high capacity retention even after 1000 cycles. The remarkable improvement in cyclic performance is attributed to the efficient suppression of hydrogen ion accumulation in the electrolyte. Furthermore, theoretical calculation results indicate that the carbonyl interactions with hydrogen ions result in poor structural stability of the polymer. The formation of colloidal LiOH is realized/obtained by introducing an appropriate amount of KOH into the saturated LiNO3 electrolyte. The resulting colloidal LiOH not only reduces the concentration of free hydroxyl ions in the electrolyte, but also continuously releases the hydroxyl ions to react with hydrogen ions. These results suggest that the introduction of alkali in saturated LiNO3 aqueous electrolytes improves the electrochemical stability of polyimide anode, which will push the practical applications of polyimide materials in aqueous Li-ion cells.