Synergistic Ionotronic Strategy for Constructing High-Rate Polyanion-Lattice-Engineered LiFePO ₄

LiFePO4 (LFP)-based lithium (Li)-ion batteries are extensively used in electric vehicles and energy storage systems. However, the one-dimensional Li-ion diffusion channel and poor electronic conductivity limit its fast-charging and low-temperature performance. Herein, we introduce an ionotronic (ion/electron) synergetic strategy to overcome these limitations. Specifically, polyanion lattice engineering is developed by the planar triangle BO33– substitution on tetrahedron PO43–, thereby opening ion-diffusion pathways in the LFP structure. Furthermore, the incorporation of multiwalled carbon nanotubes (MWCNTs) significantly enhances the electronic conductivity of LiFe(PO4)0.98(BO3)0.02 (LFP-BO3). With these synergistic effects, the optimized LFP-BO3/10%MWCNTs exhibits ultrahigh rate capacity (75.3 mAh g–1 at 50 C) and long cycle stability (94.7% capacity retention after 2000 cycles at 10 C) at 25 °C. Moreover, LFP-BO3/10%MWCNTs also delivers excellent low-temperature performance, achieving a discharge capacity of 41.3 mAh g–1 at 40 C and high capacity retention at −20 °C.