Overcrowded Additive in Electrolyte and Crystalline Li2CO3 Artificial Solid Electrolyte Interphase on TiNb2O7 Anode Enable Long Lifespan Aqueous Lithium-Ion Batteries

Abstract

Aqueous lithium-ion batteries (ALIBs) are attracting intense attention because of the intrinsic nonflammable nature of the aqueous electrolytes. However, its own narrow electrochemical window has led to numerous problems such as dissolution of electrode materials, hydrogen evolution at the anode, and poor cycling stability. Here, we report an “overcrowded electrolyte” using 1,4-dioxane as an additive, which has lone pairs of electrons on the oxygen atom to disrupt the original water-hydrogen bonding network by forming intermolecular hydrogen bonds, thereby inhibiting the hydrogen evolution reaction (HER) and decreasing the water activity. Furthermore, a layer of crystalline Li2CO3 is coated onto the surface of the TiNb2O7 anode material by supercritical fluid CO2 technology. The dense hydrophobic Li2CO3 coating layer can serve as a physical protection, which effectively blocks the direct contact between electrolyte and electrode. Under the synergistic effect of those two aspects, HER is greatly suppressed and the interface stability is enhanced. As a result, LiMn2O4/TiNb2O7 full cells exhibit a high initial coulomb efficiency of 95% with a capacity retention rate of 92% over 500 cycles under 1 C rate. This work provides a fundamental understanding of the interfacial chemistry of ALIBs and makes an important step forward in the development of high-performance and low-cost ALIBs for practical applications.