In Situ Cross‐Linked Plastic Crystal Electrolytes for Wide‐Temperature and High‐Energy‐Density Lithium Metal Batteries

Abstract The development of high‐energy‐density lithium metal batteries has been significantly hampered mainly due to the poor electrolyte–electrode compatibility, narrow operating temperature range, and stringent safety concerns of conventional electrolytes. Here, an in situ cross‐linked plastic crystal‐based electrolyte (CPCE) with an optimized composition design is proposed. Based on the interaction of succinonitrile (SN) and ethoxylated trimethylolpropane triacrylate (ETPTA) with polar carbonyl groups, CPCE delivers well‐tuned energy levels and a concentrated coordination structure, leading to an improved electrochemical window and stable electrode–electrolyte interface. In addition, the crystallization of SN molecules is also inhibited, ensuring suitable ion migration in bulky CPCE over a wide temperature range. Moreover, both the nonleakage of cross‐linked ETPTA and the nonflammability of the plastic crystal electrolyte (PCE) further reinforce the safety of CPCE. As a result, the well‐designed CPCE achieves high ion conductivity with a wide electrochemical window (≈5.4 V vs Li + /Li) and a broad operating temperature range (−20 to 100 °C). It also delivers dendrite‐free lithium plating with high Coulombic efficiency of up to ≈99.1%. The Cu|CPCE|LiNi 0.8 Co 0.1 Mn 0.1 O 2 anode‐free pouch cell exhibits high energy density (≈1520 Wh L ‐1 ) and high safety during abuse tests. This study paves a new pathway to realize the practical application of high‐energy‐density lithium metal battery energy storage systems.