SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-025-3824-8
Lithium-ion batteries (LIBs) are pivotal in portable electronics, electrified transportation, and smart grids, where energy conversion and delivery hinge on the coupled transfer of electrons and lithium ions (Li+). Charge transfer at the electrode-electrolyte interface, involving solvated Li+ interacting with the solid electrode, dictates overpotential—the excess energy required to drive reactions—directly impacting energy loss, voltage fade, and power limitations. Despite decades of research, interfacial kinetics remain incompletely understood, hindering advances in energy density, fast charging, and cycling life. Two classical models—electron transfer (ET) and ion transfer (IT)—have been treated as mutually exclusive. The ET model posits quantum tunneling of electrons as rate-determining, with solvated Li+ residing at the outer Helmholtz plane; activation energy is modulated by overpotential, and current-overpotential behavior follows the Butler-Volmer equation. Marcus-Hush-Chidsey theory extends this to high overpotentials, explaining weak temperature dependence in Tafel curvature. Conversely, the IT model identifies physical desolvation of Li+ as the energy-consuming, rate-limiting step, with desolvation barriers (ΔG_desolv) typically tens of kJ/mol, far exceeding electron tunneling activation energies. Strategies to lower IT barriers include electrolyte design, electric field modulation, electrode surface engineering, and alloying. This paper critically examines both models, proposing a coupled ion-electron transfer mechanism to reconcile discrepancies and guide future interfacial engineering.
SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-025-3849-5
Solid-state lithium metal batteries (SLMBs) are a promising alternative to conventional lithium-ion batteries due to their potential for higher energy density and improved safety. However, the solid electrolyte interphase (SEI) formed at the lithium metal anode/electrolyte interface is often brittle, leading to poor interfacial contact, high impedance, and dendrite growth, which limits cycle life and rate capability. Here, we report a functionally gradient ductile SEI design that incorporates AgF and Ag2S into the SEI layer, creating a composition gradient with a lithiophilic Ag/Ag–Li alloy at the anode surface. This ductile SEI exhibits a low generalized stacking fault energy, as confirmed by density functional theory calculations, and maintains structural integrity even at a bending angle of 150°, unlike brittle SEIs that fracture. The ductile SEI enables a high Li-ion diffusion coefficient of 3.8 × 10−8 cm2 s−1 and low activation energy. Consequently, Li|PALA|Li symmetric cells demonstrate exceptional cyclability over 4500 h at an ultrahigh current density of 15 mA cm−2 and areal capacity of 15 mA h cm−2, and stable operation for over 7000 h at −30 °C under practical conditions (5 mA cm−2, 5 mA h cm−2). Full cells with LiNi0.8Co0.1Mn0.1O2 cathodes show superior rate performance and capacity retention at both 25 °C and −30 °C. The cumulative capacity reaches 33750 mA h cm−2, an order of magnitude higher than previously reported SLMBs. This work underscores that the mechanical properties of the SEI are as critical as its ionic conductivity and chemical stability, opening a new frontier in interface design for practical, high-energy-density, and safe solid-state batteries.