Insights into Electrochemical Reaction Processes in All-Solid-State Li-Ion Batteries with a MgH ₂ Anode and an NMC 111 Cathode

The urgent global demand for safer, high-energy-density storage solutions has placed all-solid-state lithium-ion batteries at the forefront of next-generation energy technology. Herein, we report the first successful demonstration of a full cell using a hydride-based conversion anode (MgH2-KNbO3) paired with a LiNi0.33Mn0.33Co0.33O2 (NMC 111) cathode for all-solid-state Li-ion batteries, setting a benchmark for hydride-based energy storage. Half-cell evaluations revealed excellent electrochemical behavior across a wide temperature range (30–120 °C). Cyclic voltammetry showed stable redox peaks over the cycles, while galvanostatic charge–discharge profiles displayed distinct plateaus at 0.48 and 0.55 V, confirming strong reversibility and structural stability. Further, rate capability testing over 40 cycles at current rates of 100–500 μA (current density of 82–411 mA g–1) demonstrated stable cycling with sustained capacity retention. To assess real-world potential, the system was advanced to a full-cell configuration (MgH2@KN+LiBH4-LiI+AB||LiBH4-LiI||NMC+LiBH4-LiI+AB). The cell delivered an impressive initial charge/discharge capacity of 1174/915 mAh g–1 at 60 °C, outperforming many commercial anodes, and maintained stable operation for up to 100 cycles across high-temperature to room-temperature conditions. At 90 °C, the full cell preserved 22% (charge) and 20% (discharge) capacities after 100 cycles, while at 30 °C, it still achieved strong initial charge/discharge capacities of 111/109 mAh g–1, proving its capability to function under ambient conditions. A key factor in performance was the catalytic effect of KNbO3 and the utilization of a solid solution of LiBH4-LiI, which enhanced the interfacial conductivity and charge transfer efficiency.