Universal strategy of capacity compensation via the electrolyte for Li-ion batteries

Abstract

The initial irreversible capacity loss (ICL) during the first charging process greatly reduces the affordable energy and power densities of commercial Li-ion batteries (LIBs). Though various solid-phase prelithiation additives have been developed, they can hardly be adapted to the existing electrode production lines. Herein, we elucidate that the root cause of ICL is electron loss; therefore, the electron compensation is the most sustainable and economical capacity-compensation method rather than conventional prelithiation. Accordingly, we propose a universal capacity-compensation strategy via the electrolyte and establish general guiding principles for developing soluble capacity-compensation reagents. As a proof of concept, lithium polyphosphides (Li_xPPs) were synthesized and evaluated. Li_xPPs feature desirable solubility in various commercial electrolytes and undergo preferential oxidation at the cathode side, thereby not only compensating for ICL but also contributing to the construction of a stable cathode-electrolyte interphase (CEI). The feasibility of this capacity-compensation electrolyte was validated in multiple mainstream battery systems, including NCM811||graphite, LiFePO₄||graphite, and LiCoO₂||graphite full cells, highlighting both its great adaptability to the existing battery manufacturing processes and its potential to enhance the energy density of LIBs and beyond.