Single-Phase Gradient Solvation Electrolyte Boosts Lithium Metal Battery Performance

Lithium metal batteries (LMBs) are heralded as the next generation of energy storage, offering significantly higher energy density compared to conventional lithium-ion counterparts. Ether-based electrolytes, in particular, have shown promise for lithium metal electrodes due to their inherent properties. However, their widespread adoption in high-voltage full cells has been hampered by critical challenges, primarily oxidative decomposition during charging and a substantial decline in redox stability over extended cycling. The root of these issues lies in the complex electrochemical environment within high-voltage cells. During the charging process, the desolvation of solvents and anions is necessary to accommodate lithium ions released from the positive electrode. This process, however, exacerbates the oxidative decomposition of the electrolyte. Furthermore, the continuous consumption of electrolyte components throughout repeated charge-discharge cycles leads to a fundamental alteration of the solvation structure, which in turn diminishes the battery's overall redox stability and shortens its lifespan. In a significant stride forward, researchers have introduced an innovative solution: incorporating a Targeted Ligand Anti-Solvent (TLAS) into an anion-rich, ether-based electrolyte. Crucially, the TLAS exhibits a relatively weaker association ability with Li+ in a static state, meaning it barely participates in the initial solvation process. This subtle characteristic is key to its dynamic function under operational conditions. The true ingenuity of TLAS becomes apparent under the strong electric field present in high-voltage full cells. Here, the orientation and distribution of the TLAS molecules undergo a substantial transformation, activating their coordination ability specifically on the positive electrode surface. This TLAS-mediated dynamic solvation behavior effectively bypasses the inherent decoordination and recoordination of solvents and anions that plague conventional electrolyte systems, thereby minimizing electrolyte reconstruction and mitigating interphase deterioration. Leveraging this novel "gradient solvation electrolyte" strategy, the research team has achieved remarkable performance metrics. They developed a 450 Wh kg−1 lithium metal pouch cell that demonstrated an impressive cycle life exceeding 750 cycles while retaining 80% of its initial capacity. Pushing the boundaries further, they validated another lithium metal pouch cell with an even higher energy density of 605 Wh kg−1, which maintained 96% capacity retention over 150 cycles. This pioneering gradient solvation strategy represents a feasible and highly promising pathway for advanced electrolyte engineering in metal-ion batteries. By dynamically managing the solvation environment, this approach not only addresses long-standing stability issues but also unlocks the full potential of high-energy-density lithium metal batteries, paving the way for more powerful and durable energy storage solutions for various applications.