The Structural Distortion Caused by Li-Site Modification Improves the Conductivity of LiZr _<b>2</b> (PO _<b>4</b> ) _<b>3</b> Electrolytes for Potential Applications in Solid-State Batteries

Recent research on Li-ion batteries has promoted the development of solid-state electrolytes (SSEs). The LiZr2(PO4)3 (LZP) ceramic electrolyte exhibits a wide electrochemical stability window and high stability in air, but suffers from poor intrinsically ionic conductivity. This work proves that the modification of Li sites is feasible and effective for improving the electrochemical property. First, combining spectroscopic techniques, including X-ray, neutron diffraction, Raman, and solid-state nuclear magnetic resonance tests, we provide cognitive insights into the relationship between crystal structure changes and conductivity, as follows: (i) The coordinates of Li1-sites are changed slightly. (ii) The Ga atoms are located at six-coordination, promoting the random distribution of lithium over the M1 and M2 sites. (iii) The moderate structural distortion, such as the decrease in bond angle, reduces the barrier for ion transport. The Li0.88Ga0.04Zr2(PO4)3 (LGZP-0.04) exhibits a conductivity of 8.42 × 10–5 S·cm–1 at room temperature, and it reaches 1.67 × 10–4 S·cm–1 at 40 °C. Furthermore, the reason for the enhancement of Li+ conductivity is the lower jump distance and the higher jump frequency calculated based on the conventional hopping theory and the decrease in activation energy (Ea). The Li/LGZP/Li cell could run stably over 1000 h. The maximum specific capacity of Li/LGZP/LFP reaches 152.9 mAh g–1 at 0.5 C, and the capacity retention ratio is 96.5% after 100 cycles.

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