Unlocking Ultrafast Charging: Synergizing Embedded Pseudocapacitive Domains and Flexible Lattice Dynamics in Off-Stoichiometric LiTi₂(PO₄)₃ Anodes

Overcoming the intrinsic trade-off between particle size and ionic kinetics of active materials is essential for realizing high volumetric energy density, ultrafast-charging lithium-ion batteries. Here, we report a rational design strategy to unlock ultrafast charging capabilities in off-stoichiometric microscale LiTi₂(PO₄)₃ (LTP) anodes by synergizing embedded pseudocapacitive domains with flexible lattice dynamics. Through precise Ti-deficiency engineering, TiP₂O₇ domains are induced in situ within the LTP subsurface, creating a cohesive hetero-architecture. These domains serve as high-flux kinetic gateways that lower the activation energy for interfacial Li-ion transfer. Concurrently, the induced lattice flexibility, derived from the rotational degrees of freedom in the P─O─P bridges, accommodates rapid ionic flux and mitigates structural strain, while the robust NASICON framework preserves facile bulk diffusion. Consequently, this architecture circumvents typical kinetic limitations, delivering exceptional rate capability at an aggressive 10C rate for over 250 cycles, even with large secondary particles reaching up to 30 µm. This off-stoichiometry-driven approach establishes a versatile paradigm for developing next-generation high-power energy storage materials, extending its potential to all-solid-state battery applications.