Designer Lithium Reservoirs for Ultralong Life Lithium Batteries for Grid Storage

Abstract The minimization of irreversible active lithium loss stands as a pivotal concern in rechargeable lithium batteries, particularly in the context of grid‐storage applications, where achieving the utmost energy density over prolonged cycling is imperative to meet stringent demands, notably in terms of life cost. Departing from conventional methodologies advocating electrode prelithiation and/or electrolyte additives, a new paradigm is proposed here: the integration of a designer lithium reservoir (DLR) featuring lithium orthosilicate (Li 4 SiO 4 ) and elemental sulfur. This approach concurrently addresses active lithium consumption through solid electrolyte interphase (SEI) formation and mitigates minor yet continuous parasitic reactions at the electrode/electrolyte interface during extended cycling. The remarkable synergy between the Li‐ion conductive Li 4 SiO 4 and the SEI‐favorable elemental sulfur enables customizable compensation kinetics for active lithium loss throughout continuous cycling. The introduction of a minute quantity of DLR (3 wt% Li 4 SiO 4 @S) yields outstanding cycling stability in a prototype pouch cell (graphite||LiFePO 4 ) with an ampere‐hour‐level capacity (≈2.3 Ah), demonstrating remarkable capacity retention (≈95%) even after 3000 cycles. This utilization of a DLR is poised to expedite the development of enduring lithium batteries for grid‐storage applications and stimulate the design of practical, implantable rechargeable batteries based on related cell chemistries.