P-Block Compounds Incorporated into SEI Enable Ultra-Stable Cell Cycling in Low-Temperature Sodium-Metal Batteries.

Abstract

Sodium metal anodes (SMAs) are pivotal for high-energy-density batteries but suffer from uncontrolled dendrite growth and interfacial instability caused by infinite volume expansion and a fragile solid electrolyte interphase (SEI). Herein, an innovative strategy is proposed, in which a p-block matrix is in-situ formed from NiTe₂ nanocrystals onto N-doped carbon hollow microspheres (NiTe₂@NC) during electrochemical activation to overcome these challenges. The p-block matrix with sodiophilic Na₂Te and conductive metallic nickel effectively reduces the nucleation barrier and establishes bi-continuous ion/electron conduction networks, guiding uniform Na plating. Critically, Na₂Te dominates the formation of a gradient inorganic-rich SEI with high Young's modulus and low Na⁺ diffusion barrier, significantly enhancing mechanical resilience and ion transport kinetics. Consequently, the NiTe₂@NC electrode achieves exceptional cyclability (1,000 cycles at 1.0 mA cm^- ²/1.0 mAh cm^- ² with an average Coulombic efficiency of 99.79%). When configured in full-cells with a Na₄Fe₃(PO₄)₂P₂O₇ cathode, it maintains the capacity retention of over 96.1% (103.9 mAh g^- ¹) after 1,200 cycles at 10.0 C. Critically, the full-cell maintains superior electrochemical resilience with high discharge-capacity and >90% retention at low-temperatures (-20 and -40 °C), demonstrating exceptional practicality for sodium metal batteries. This work establishes a new paradigm for stabilizing reactive metal anodes via in-situ-constructed multifunctional interfaces.