Boosting the Reversible, High-Rate Na⁺ Storage Capability of the Hard Carbon Anode Via the Synergistic Structural Tailoring and Controlled Presodiation

Hard carbons (HCs) are extensively investigated as the potential anodes for commercialization of sodium-ion batteries (SIBs). However, the practical deployment of HC anode suffers from the retarded Na⁺ diffusion at the high-rate or low-temperature operation scenarios. Herein, a multiscale modification strategy by tuning HC microstructure on the particle level as well as replenishing extra Na⁺ reservoir for the electrode through a homogeneous presodiation therapy is presented. Consequently, the coulombic efficiency of HC anode can be precisely controlled till the close-to-unit value. Detailed kinetics analysis observes that the Na⁺ diffusivity can be drastically enhanced by two orders of magnitude at the low potential region (< 0.1 V vs. Na⁺/Na), which accelerates the rate-limiting step. As pairing the presodiated HC anode (≈5.0 ± 0.2 mg cm⁻²) with the NaVPO₄F cathode (≈10.3 mg cm⁻²) in the 200 mAh pouch cell, the optimal balance of the cyclability (83% over 1000 cycles), low-temperature behavior till −40 °C as well as the maximized power output of 1500 W kg⁻¹ can be simultaneously achieved. This synergistic modification strategy opens a new avenue to exploit the reversible, ultrafast Na⁺ storage kinetics of HC anodes, which thus constitutes a quantum leap forward toward high-rate SIB prototyping.