Lithium (Li) metal has been considered as an ideal anode for next-generation Li metal batteries (LMBs). However, Li dendrite formation and low Coulombic efficiency (CE) are major obstacles for the...

Li4Ti5O12 (LTO) has attracted tremendous attention as a stationary Li-ion battery anode material due to its excellent stability. However, the poor rate capability caused by the low electrical conductivity limits its practical use. Previously, Mg-doping in LTO has been used to improve the electrical conductivity and electrochemical properties, but the Mg-doped LTO system generally exhibits large anomalies in the electrical properties and capacities, which limits the reliable mass-production of engineered LTO. In this study, on the basis of first-principles calculations and related experiments, we systematically study the effects of charge-compensating point defects of the Mg-doped LTO on the electrical properties. A combination of first-principles calculations with thermodynamic modeling shows that high-temperature annealing under reducing conditions could effectively alter the Mg-doping site from a Ti4+ to Li+ site and increase the electrical conductivity significantly due to reduced electron effective mass and increased carrier concentration. Mg-doped LTO annealed under reducing condition exhibits a significantly improved rate capability compared with that of LTO annealed under air condition. The theoretical-analysis-associated experimental results provide more general design guidelines for the preparation of doped LTO with the promise of further improvements in performance.

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Separators play an essential role in lithium (Li)-based secondary batteries by preventing direct contact between the two electrodes and providing conduction pathways for Li-ions in the battery cells. However, conventional polyolefin separators exhibit insufficient electrolyte wettability and thermal stability, and in particular, they are vulnerable to Li dendritic growth, which is a significant weakness in Li-metal batteries (LMBs). To improve the safety and electrochemical performance of LMBs, Al2O3 nanoparticles and nanocellulose (NC)-coated non-woven poly(vinylidene fluoride)/polyacrylonitrile separators were fabricated using a simple, water-based blade coating method. The Al2O3/NC-coated separator possessed a reasonably porous structure and a significant number of hydroxyl groups (-OH), which enhanced electrolyte uptake (394.8%) and ionic conductivity (1.493 mS/cm). The coated separator also exhibited reduced thermal shrinkage and alleviated uncontrollable Li dendritic growth compared with a bare separator. Consequently, Li-metal battery cells with a LiNi0.8Co0.1Mn0.1O2 cathode and an Al2O3/NC-coated separator using either liquid or solid polymer electrolytes exhibited improved rate capability, cycle stability, and safety compared with a cell with a bare separator. The present study demonstrates that combining appropriate materials in coatings on separator surfaces can enhance the safety and electrochemical performance of LMBs.