Work

Enhancing the Cycling Stability of Amorphous-Based LiNiO 2 –Li 2 MnO 3 –Li 2 SO 4 Positive Electrodes: Insights from In Situ Transmission Electron Microscopy

Year: 2025

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide Li-rich layered oxides offer high capacities for solid-state batteries. However, they suffer from sluggish ion transport, interfacial side reactions, and structural instability. Herein, we address these limitations using an amorphous-based LiNiO 2 –Li 2 MnO 3 –Li 2 SO 4 positive electrode that couples an S-enriched amorphous matrix with Ni-enriched nanocrystalline domains. A two-step process, in which LiNiO 2 and Li 2 MnO 3 react prior to the addition of Li 2 SO 4, suppresses Ni/Mn segregation and eliminates highly oxidized Li–Ni–O domains formed during charge–discharge reactions. In situ scanning transmission electron microscopy with electron energy-loss spectroscopy directly visualizes the evolution of the Li distribution and electronic states of O and Ni during cycling, confirming that both the nanoparticles and the amorphous matrix are electrochemically active, whereas localized deep charging is absent. The ductile amorphous–crystalline framework accommodates reversible volume changes without cracking and interfacial delamination. Consequently, sulfide-based solid-state cells obtained using the two-step synthesis route delivered 173 mAh/g initially and retained 79% capacity after 300 cycles at an aggressive 4.6 V vs Li cutoff voltage without any positive electrode coating. These findings demonstrate that cation homogeneity, nanoscale particle-size control, and flexibility provided by the amorphous matrix act synergistically to enhance the potential of Li-rich positive electrodes in solid-state batteries. The synthesis strategy and mechanistic insights presented herein provide a clear roadmap for the design of robust, high-capacity amorphous-based positive electrodes with extended lifetimes.

Source: ACS Nano

DOI: 10.1021/acsnano.5c17388