Interface Modifications of Lithium Metal Anode for Lithium Metal Batteries

Lithium metal batteries (LMBs) enable much higher energy density than lithium-ion batteries (LIBs) and thus hold great promise for future transportation electrification. However, the adoption of lithium metal (Li) as an anode poses serious concerns about cell safety and performance, which has been hindering LMBs from commercialization. To this end, extensive effort has been invested in understanding the underlying mechanisms theoretically and experimentally and developing technical solutions. In this review, we devote to providing a comprehensive review of the challenges, characterizations, and interfacial engineering of Li anodes in both liquid and solid LMBs. We expect that this work will stimulate new efforts and help peer researchers find new solutions for the commercialization of LMBs.

Iron-Doped Sodium Vanadium Oxyflurophosphate Cathodes for Sodium-Ion Batteries-Electrochemical Characterization and In Situ Measurements of Heat Generation

Sodium-ion batteries (NaIBs) are increasingly being envisioned for grid-scale energy-storage systems because of cost advantages. However, implementation of this vision has been challenged by the low-energy densities delivered by most NaIB cathodes. Toward addressing this challenge, the authors report the synthesis and characterization of a new iron-doped Na₃Fe_0.3V_1.7O(PO₄)₂F₂ cathode using a novel facile hydrothermal route. The synthesized material was characterized using scanning electron microscopy, X-ray diffraction, and Mössbauer spectroscopy techniques. The obtained discharge capacity in the half-cell configuration lies from 119 to 125 to 130 mA h/g at C/10 while tested using three different electrolyte formulations, dimethyl carbonate-ethylene carbonate (EC)-propylene carbonate (PC), diethyl carbonate-EC, and EC-PC, respectively. The synthesized cathodes were also evaluated in full-cell configurations, which delivered an initial discharge capacity of 80 mA h/g with NaTi₂(PO₄)₃MWCNT as the anode. Ionic diffusivity and interfacial charge transfer kinetics were also evaluated as a function of temperature and sodium concentration, which revealed that electrochemical rate performances in this material were limited by charge-transfer kinetics. To understand the heat generation mechanism of the Na/Na₃Fe_0.3V_1.7O(PO₄)₂F₂ half-cell during charge and discharge processes, an electrochemical isothermal calorimetry measurement was carried out at different current rates for two different temperatures (25 and 45 °C). The results showed that the amount of heat generated was strongly affected by the operating charge/discharge state, C-rate, and temperature. Overall, this work provides a new synthesis route for the development of iron-doped Na₃Fe_0.3V_1.7O(PO₄)₂F₂-based high-performance sodium cathode materials aimed at providing a viable pathway for the development and deployment of large-scale energy-storage based on sodium battery systems.