Uniform Surface Modification of Li₂ZnTi₃O₈ by Liquated Na₂MoO₄ To Boost Electrochemical Performance

Poor ionic and electronic conductivities are the key issues to affect the electrochemical performance of Li₂ZnTi₃O₈ (LZTO). In view of the water solubility, low melting point, good electrical conductivity, and wettability to LZTO, Na₂MoO₄ (NMO) was first selected to modify LZTO via simply mixing LZTO in NMO water solution followed by calcining the dried mixture at 750 °C for 5 h. The electrochemical performance of LZTO could be enhanced by adjusting the content of NMO, and the modified LZTO with 2 wt % NMO exhibited the most excellent rate capabilities (achieving lithiation capacities of 225.1, 207.2, 187.1, and 161.3 mAh g^-1 at 200, 400, 800, and 1600 mA g^-1, respectively) as well as outstanding long-term cycling stability (delivering a lithiation capacity of 229.0 mAh g^-1 for 400 cycles at 500 mA g^-1). Structure and composition characterizations together with electrochemical impedance spectra analysis demonstrate that the molten NMO at the sintering temperature of 750 °C is beneficial to diffuse into the LZTO lattices near the surface of LZTO particles to yield uniform modification layer, simultaneously ameliorating the electronic and ionic conductivities of LZTO, and thus is responsible for the enhanced electrochemical performance of LZTO. First-principles calculations further verify the substitution of Mo⁶⁺ for Zn²⁺ to realize doping in LZTO. The work provides a new route for designing uniform surface modification at low temperature, and the modification by NMO could be extended to other electrode materials to enhance the electrochemical performance.