Weihua Chen

Magnesium metal batteries represent highly promising candidates for sustainable energy storage owing to their extremely high volumetric capacity (3833 mAh cm–3), abundant raw materials, and intrinsic safety. However, their practical viability is severely impeded by uneven Mg deposition, catastrophic interfacial side reactions, and continuous gassing behavior driven by uncontrolled electrolyte decomposition. Herein, we first report an inorganic inter-reinforced organic composite separator, fabricated by pairing cellulose with a zinc oxide (ZnO)-enhanced layer and designed to regulate the electrolyte solvation architecture by effectively anchoring solvent molecules. Spectroscopic and theoretical analyses reveal that the electron-deficient Zn sites on ZnO enhance the solvent-capture ability of the polar hydroxyl groups on cellulose via bidirectional charge transfer. This interaction reconfigures the Mg2+ solvation sheath into a unique single-cluster structure, steering the formation of a dense, ultrathin, inorganic-rich solid electrolyte interphase (SEI) that facilitates rapid Mg2+ desolvation while suppressing parasitic side reactions. Consequently, the as-assembled Mg||Mg symmetric cells deliver an exceptional cycling lifespan exceeding 2000 h with minimal overpotential and exhibit robust compatibility across diverse electrolyte systems. This inorganic inter-reinforced organic strategy for modulating solvation chemistry offers a generalizable avenue toward long-life and high-safety magnesium metal batteries.

The growing dependence of modern society on batteries places higher demands on safety and energy density. Separators are a key component for electrical insulation and structural stability to ensure battery safety. Their inactive volume, ability to regulate solvated ions and transport efficiency also directly impact the energy density of batteries. This review elucidates the relationship between the thermal stability of linear/cyclic polymers and thermal runaway onset, and discusses how organic/inorganic materials enhance safety and energy density by tuning pore structure, thickness, wettability, and mechanical properties. The differences between monovalent (Li ⁺ /Na ⁺ /K ⁺ ) and multivalent (Mg ²⁺ /Zn ²⁺ /Ca ²⁺ ) ions are compared, and how the polar separator‒electrolyte interaction regulates ion solvation is revealed. Safety‐oriented separator strategies, including thermal runaway mitigation, dendrite suppression, ion flux homogenization, overcharge protection, and aging analysis, are evaluated. Recent advances in separators for high‐energy‐density batteries, such as ultrathin, lightweight, high‐voltage‐stability, electrochemically active, integrated separator‒electrolyte, are summarized. The challenges of balancing safety and energy density are highlighted, specifically porosity and mechanical strength, safety responses compromising energy density, lab‐to‐factory translation gap. Forward‐looking perspectives are outlined through advanced processing, intelligent design, and integration, paving the way for high‐energy‐density intrinsically safe batteries.

Rechargeable Na/Cl ₂ batteries are promising for next‐generation energy storage owing to sodium abundance and high theoretical energy density. However, achieving fast and stable NaCl/Cl ₂ conversion is extremely challenging because of the high lattice energy of NaCl. While amine‐containing organic catalysts can accelerate NaCl/Cl ₂ redox kinetics, a sharp rise in polarization voltage under sustained operation causes severe energy output loss, hindering their practical application. Herein, for the first time, we identify a previously unrecognized poisoning process of nucleophilic amine‐based organocatalysts in the AlCl ₃ /SOCl ₂ electrolyte using in situ Fourier‐transform infrared spectroscopy, producing N‐sulfinylated species. Based on these insights, a resonance‐assisted hydrogen‐bonding strategy is proposed to construct a “resonance quasi‐ring” structure, which simultaneously suppresses SOCl ₂ /AlCl ₃ ‐induced poisoning and further enhances the reaction kinetics. As a result, the anti‐poisoning is improved by an order of magnitude (10‐fold). The assembled Na/Cl ₂ cells delivered a greatly enhanced cycle life (from 200 to 1500 cycles) with only a 90 mV increase in polarization voltage. The effect was further validated in Ah‐level pouch cell models. This work opens a new perspective for constructing efficient and robust organic catalytic systems in harsh electrochemical environments.

Rechargeable Na/Cl ₂ batteries are promising for next‐generation energy storage owing to sodium abundance and high theoretical energy density. However, achieving fast and stable NaCl/Cl ₂ conversion is extremely challenging because of the high lattice energy of NaCl. While amine‐containing organic catalysts can accelerate NaCl/Cl ₂ redox kinetics, a sharp rise in polarization voltage under sustained operation causes severe energy output loss, hindering their practical application. Herein, for the first time, we identify a previously unrecognized poisoning process of nucleophilic amine‐based organocatalysts in the AlCl ₃ /SOCl ₂ electrolyte using in situ Fourier‐transform infrared spectroscopy, producing N‐sulfinylated species. Based on these insights, a resonance‐assisted hydrogen‐bonding strategy is proposed to construct a “resonance quasi‐ring” structure, which simultaneously suppresses SOCl ₂ /AlCl ₃ ‐induced poisoning and further enhances the reaction kinetics. As a result, the anti‐poisoning is improved by an order of magnitude (10‐fold). The assembled Na/Cl ₂ cells delivered a greatly enhanced cycle life (from 200 to 1500 cycles) with only a 90 mV increase in polarization voltage. The effect was further validated in Ah‐level pouch cell models. This work opens a new perspective for constructing efficient and robust organic catalytic systems in harsh electrochemical environments.

Due to the abundant availability and low cost of sodium resources, rechargeable sodium batteries are considered a promising alternative for next‐generation energy storage systems. In this work, we report the resolution of the solvation effect in liquid electrolytes using cryogenic electron microscopy (Cryo‐EM). By employing this technique, we establish a correlation among the lattice parameter of nanocrystals induced by solvation, the coordination number of Na ⁺ , and the salt concentration in the electrolyte. It is demonstrated that electrolytes with weaker solvation effects promote the formation of an anion‐derived solid electrolyte interphase (SEI) with a uniform, dense, and inorganic‐rich structure. Such an SEI provides high mechanical strength for dendrite suppression and favorable ionic conductivity for homogeneous Na ⁺ transport, thereby enhancing cycling stability. Furthermore, combining with density functional theory (DFT) calculations, molecular dynamics (MD) simulations, X‐ray photoelectron spectroscopy (XPS), small/wide angle X‐ray scattering(SAXS/WAXS) and Raman spectroscopy analyses, the critical role of solvation chemistry in stabilizing the electrode–electrolyte interface in sodium metal batteries was clarified. This study advances the understanding of solvation chemistry in sodium‐ion battery electrolytes and establishes Cryo‐EM as a robust analytical technique for directly resolving the microstructure of complex liquid electrolytes, thereby enabling rational electrolyte design.

Sodium-ion batteries hold significant promise for sustainable energy storage by addressing resource scarcity and safety concerns. Elevating the upper-cut-off voltage is crucial for sodium-ion batteries to maximize electrode capacity and narrow their energy-density gap with commercial lithium-ion batteries. However, conventional electrolytes exhibit electrochemical instability on the highly desodiated positive electrode surface, undergoing strongly electrophilic attack and continuous decomposition that results in oligomer-rich interphases and rapid capacity fading. Here, we design a solvent-locked carbonate electrolyte creating electrochemically stable solvent-reinforced solvation structure and anion-rich interfacial shield-derived boride-/fluoride-rich interphase on positive electrode, thereby suppressing current leakage and parasitic reactions. The tailored electrolyte exhibits good compatibility with commercialized oxides and polyanionic positive electrodes. As-assembled Na||Na_2.26Fe_1.87(SO₄)₃ cells deliver extended lifespans operating to 4.5 V, retaining 88.2% capacity after 16,500 cycles at 1000 mA g^–1 (coin cell) and 93.9% after 500 cycles at 100 mA g^–1 (pouch cell). This work will inspire durable electrolyte and interphase design for high-energy batteries and beyond.

Alluaudite‐type Na _2+2x Fe _2−x (SO ₄ ) ₃ demonstrates significant industrial promise as a cathode candidate in sodium‐ion batteries for mitigating the supply risks associated with scarce metals. However, a major challenge stems from intrinsic lattice distortion necessitated by its thermo‐deficient synthesis below 400 °C. This structural heterogeneity became uncontrollable during high‐temperature electrochemical cycling, resulting in severe polyhedral fracture and electrochemical decay. Herein, we achieve highly stable cycling of Na _2.5 Fe _1.75 (SO ₄ ) ₃ cathode through a quasi‐perfect ordered crystal design that exploits dipole interactions between polar bonds with specific low‐frequency microwave (50 Hz). This enhanced ordering strengthens covalent Fe 3 d –O 2 p hybridization, significantly mitigates crystalline defects and stress accumulation, thereby enabling redox reactions and polyhedral evolution to proceed reversibly during deep (de)sodiation. The quasi‐perfect ordering suppresses heterogeneous electrolyte reactions and preserves interfacial integrity throughout extended cycling. Consequently, the developed cathode exhibits remarkable cyclability at 4.5 V, exceeding 4000 cycles at 25 °C and nearly 400 cycles at 60 °C, further validated in pouch cells.

Alluaudite‐type Na _2+2x Fe _2−x (SO ₄ ) ₃ demonstrates significant industrial promise as a cathode candidate in sodium‐ion batteries for mitigating the supply risks associated with scarce metals. However, a major challenge stems from intrinsic lattice distortion necessitated by its thermo‐deficient synthesis below 400 °C. This structural heterogeneity became uncontrollable during high‐temperature electrochemical cycling, resulting in severe polyhedral fracture and electrochemical decay. Herein, we achieve highly stable cycling of Na _2.5 Fe _1.75 (SO ₄ ) ₃ cathode through a quasi‐perfect ordered crystal design that exploits dipole interactions between polar bonds with specific low‐frequency microwave (50 Hz). This enhanced ordering strengthens covalent Fe 3 d –O 2 p hybridization, significantly mitigates crystalline defects and stress accumulation, thereby enabling redox reactions and polyhedral evolution to proceed reversibly during deep (de)sodiation. The quasi‐perfect ordering suppresses heterogeneous electrolyte reactions and preserves interfacial integrity throughout extended cycling. Consequently, the developed cathode exhibits remarkable cyclability at 4.5 V, exceeding 4000 cycles at 25 °C and nearly 400 cycles at 60 °C, further validated in pouch cells.

Fast-charging batteries that can be charged in minutes and store enough energy are highly desired in the electric vehicle and grid storage, but are usually limited to the electrodes with lower carrier diffusion. Herein, self-limited 1, 2, and 3 monolayers SnS2 on the graphene were fabricated as fast-charging anodes for sodium-ion batteries (SIBs). The tunable atomically-thin SnS2 compound was confirmed using synchrotron high-pressure powder X-ray diffraction, atomic force microscopy, and low-dose transmission electron microscopy (TEM). The 1, 2, and 3 atomic-layer SnS2 showed ultra-high phase contact of discharged products; thus, high bulk Na+/electronic conductivity was acquired. Simultaneously, ultra-thin and NaF, Na2CO3-riched solid-electrolyte interphase (6 nm, Cyro-TEM) was oriented construction in ester electrolyte. Benefiting from the synergistic effect of bulk phase and solid-electrolyte interphase, the obtained 3-monolayer SnS2 anode achieved a fast-charging capacity of 300 mAh·g-1 at 30 A·g-1 within 36 s, exhibiting new height of fast-charging ability in SIBs. Meanwhile, it demonstrated long-cycling stability with negligible capacity decay for 600 cycles. The assembled pouch cell with Na3V2(PO4)2F3 cathode showed a high-energy density of about 187.5 Wh·kg-1. The atomic-layer leveled regulation method paves the way for precise synthesis of materials at the atomic level and oriented design of fast-charging rechargeable batteries.

Hydrogel electrolytes (HEs) are promising for zinc batteries owing to their high safety and intrinsic flexibility. However, limited carrier transfer kinetics from bulk phase to the interface of HEs hinder their practical applications at low temperatures. Here, we proposed a sulfonate‐mediated cation‐switching strategy to design antifreezing HEs with rapid ion transport for Zn batteries. The introduced Li ⁺ replaces Zn ²⁺ from oxygen coordination sites via strong sulfonate (−SO ₃ ⁻ ) binding within the polymer matrix. The Li ⁺ ‐O bonds contract the polymer network, which in turn squeezes and rearranges the water molecules and ions in the pores into a highly interconnected state. This shifts the ion transport from a hopping‐dominated transport to a diffusion‐controlled, enhancing both ionic conductivity (7.75 mS cm ⁻¹ ) and Zn ²⁺ transference number (0.32) at −40°C. The liberated Zn ²⁺ further coordinates free water, lowering the glass transition temperature to −53.5°C. Moreover, the sacrificial process of polymer and salts results in the gradient interphase with a ZnS/ZnCO ₃ ‐rich surface and a Li ₂ S/Li ₂ CO ₃ ‐rich bottom, which reduced the Zn ²⁺ ‐diffused activation energy by nearly 50%. The Zn||VO ₂ ‐V ₂ O ₅ /NC full cell with optimized HEs cell exhibits 83.7% capacity retention (5 000 cycles, −40°C) and 92% retention at 180° bending.