Li 2 CO 3 -rich interphase construction via alternating pulse current-driven CO 2 reduction for high performance LiFePO 4 /graphite full-cell

Featuring of low Li+ diffusion barrier and high Li+ conductivity, a Li2CO3-rich solid electrolyte interphase (SEI) is critical for improving the energy density and cycle life of lithium-ion batteries. As a gaseous additive, CO2 can be added into the electrolyte to in situ generating Li2CO3-contained SEI. However, CO2-derived SEI formation is kinetics limitation. Here, we identify the adsorption of CO intermediate products impeding the full conversion of CO2, and furtherly apply an alternating pulse current (APC) discharge to desorb CO and promote the CO2 decomposition, ultimately in-situ forming a uniform, smooth, and Li2CO3-rich SEI in the first cycle. Owing to the excellent Li+ transport capability and structural stability, this APC-formed SEI enables lithium/graphite (Li/Gr) half-cells achieving a high rate performance (5 C, 180 mAh g-1, and 80.1% after 170 cycles), exceeding currently advanced cells with Li2CO3-contained SEI. Furthermore, we directly employ the Gr anode with the APC pre‑formed Li2CO3-rich SEI to assemble LiFePO4 (LFP)/Gr full-cell. Advantaged by the high Li+ diffusivity and stability, this pre‑formed SEI not only compensates for the active lithium loss, dramatically enhancing the initial coulombic efficiency from 69.2% to 91.7%, but also substantially increases the discharge capacity and long‑term cycling stability (131.8 mAh g-1 after 100 cycles at 0.5 C). This straightforward strategy simultaneously enhances gas additive utilization efficiency and constructs a robust electrolyte/electrode interphase, demonstrating a dual-optimization approach through electrolyte design and interface engineering for high-performance batteries.