Ahn, Hee-Jae Kim, Young-Hoon Cho, Hye-Young Byeon, Young-Woon Choi, Yong-Seok Kim, Tae-Hong Ahn, Hyo-Jun Lee, Jae-Chul 2026-02-19T04:30:26Z 2026-02-19T04:30:26Z 2026-02-19 2026-02 2405-8297 https://pubs.kist.re.kr/handle/201004/154273 Most alloying-type anodes for Na-ion batteries are fundamentally limited in ultrafast-charging applications due to the formation of Zintl phases: intermetallic compounds with intrinsically high electrical resistivity. This work demonstrates how to overcome this fundamental limitation by employing metal sulfide-based conversion anodes (NiS, CuS, and MnS), which follow a distinct electrochemical pathway that avoids Zintl-phase formation. During cycling in ether-based electrolytes, these sulfides undergo conversion reactions that spontaneously generate highly conductive, in-situ formed metal nanoparticles embedded within a self-assembled three-dimensional nanoporous Na2S matrix. This unique composite structure forms a dual-function architecture that enables both efficient ion diffusion and long-range electron transport, even when using inexpensive microsized sulfide particles. Among the tested materials, NiS exhibits the best performance, delivering a reversible capacity of 600 mAh g–1 at 1C, exceptional cycling stability over 3800 cycles at 10C, and a high-rate capacity of 358 mAh g–1 at 30C. Density functional theory and machine-learning-based molecular dynamics simulations reveal that the strong Ni–S bonding in the intermediate phases suppresses nanoparticle coarsening, resulting in uniformly distributed, nanoscale Ni particles that form an efficient percolation network. These findings establish a new design paradigm for Zintl-free conversion anodes, offering a practical and scalable route toward high-performance, fast-charging Na-ion batteries. English Elsevier BV Ultrafast Na storage enabled by in-situ formed metal nanoparticles in a self-assembled 3D Na2S framework Article 10.1016/j.ensm.2026.104916 1 Energy Storage Materials, v.85 Energy Storage Materials 85 N scie scopus 001676256300001 2-s2.0-105028088135 Chemistry, Physical Nanoscience & Nanotechnology Materials Science, Multidisciplinary Chemistry Science & Technology - Other Topics Materials Science Article HIGH-PERFORMANCE ANODE ION BATTERIES SCALABLE SYNTHESIS CARBON NANOTUBES SODIUM ELECTRODES DISPERSION SODIATION CAPACITY SULFIDES Metal sulfide anode Na-ion battery Fast charging In-situ formed metal nanoparticles Self-assembled 3d structure