Random‐Matrix Discontinuous Sodiophilic Interfaces Enabling Ultralight Current Collector for Lean‐Electrolyte and Fast‐Charging Anode‐Free Sodium Metal Batteries

ABSTRACT Anode‐free sodium metal batteries, without excess metallic anode, promise high energy density and cost‐effectiveness. However, their practicality is impaired by limited cycling life and poor Na plating/stripping reversibility, especially under lean‐electrolyte and high‐rate conditions. Challenging the prevailing strategy of constructing dense sodiophilic layer, we design a discontinuous array of spatially dispersed sodiophilic sites upon depositing substrate via ultrasonic spray coating to regulate metal nucleation and planar growth. A nano‐layer of alloy‐conversion‐type Bi 0.4 Sb 1.6 Te 3 on Al foil enables ultralight and scalable current collector with minimal loading <0.092 mg cm −2 and low areal density ≈10 4 cm −2 , yet still ensures lateral coalescence of uniform Na nuclei into compact deposits among the discrete Na‐affinitive alloying domains and mitigate volume expansion and coating pulverization during sodiation. Importantly, the random matrix of spray‐coated nanoparticles creates a rough and discontinuous interfacial architecture for improved electrolyte wetting and fast lean‐electrolyte infiltration. As a result, high‐loading NVP||BST@Al anode‐free full cells prove 5C‐fast charging over 400 cycles and a 2.75‐Ah NFPP||BST@Al anode‐free pouch cell demonstrates stable operation exceeding 110 cycles with lean electrolyte of 1.7 g Ah −1 , yielding a high energy density of 205 Wh kg −1 and high‐power density of 226 W kg −1 based on total pouch‐cell weight.