Wei Luo

Inorganic ionic crystals, characterized by extended lattices and strong ionic bonding, form the structural foundation of most cathode materials for lithium batteries. Yet, molecular crystals composed of zero‐dimensional building blocks have been largely overlooked. Their inherent structural fragility, dictated by weak van der Waals interactions, is widely presumed to preclude reversible Li ⁺ ion insertion. In this work, we challenge this assumption by providing molybdenum pentachlorides (MoCl ₅ ), coupled with a halide solid electrolyte as a model system. We show that molecular crystal with zero‐dimensional building blocks can support highly reversible electrochemical lithiation. Operando synchrotron x‐ray absorption spectroscopy and x‐ray diffraction reveal that this reversibility is enabled by an electrochemically driven coordination rearrangement, in which discrete Mo ₂ Cl ₁₀ dimers reversibly transform into a framework of corner‐sharing MoCl ₆ octahedra arranged in a zigzag motif. As a result, MoCl ₅ delivers a specific capacity of 172 mAh g ⁻¹ and retains 85.6% of its capacity after 500 cycles in a solid‐state cell. These findings show that the coordination rearrangement enables the MoCl ₅ molecular crystal to undergo reversible lithiation and delithiation, thereby pointing to a broader space for solid‐state intercalation electrochemistry in next‐generation energy storage materials.

LiFe _y Mn _1−y PO ₄ (LFMP) has been regarded as one of the most promising cathode materials for lithium‐ion batteries owing to its higher energy density compared to LiFePO ₄ (LFP). However, induced by the Jahn‐Teller effect of Mn ³⁺ , the interfacial side reactions and unstable cathode‐electrolyte interphase (CEI) of LFMP severely limit the full realization of its high energy density advantage. To address these challenges, we develop a localized weak‐solvation electrolyte consisting of 1.0 M lithium bis(oxalato)borate (LiBOB) in a mixture of tetrahydropyran (THP) and triethyl phosphate (TEP). In this electrolyte, the high HOMO level of LiBOB promotes its preferential interfacial oxidation, while the weak solvation ability of THP weakens the Li ^+– TEP coordination, creating a localized weak‐solvation environment that facilitates the formation of an anion‐derived CEI layer on LFMP. Consequently, a thin boron/phosphorus‐rich CEI effectively suppresses parasitic side reactions and markedly enhances the cycling stability of LFMP. Moreover, even with a high mass loading of 11.8 mg cm ⁻² , this electrolyte enables the LFMP cell to achieve a high‐capacity retention of 95.0% after 300 cycles at 25°C and 85.9% after 150 cycles at 55°C.

The aggressive pursuit of energy-dense lithium-ion batteries has identified nickel-rich cathodes (e.g., LiNi0.9Co0.05Mn0.05O2, NCM90) as indispensable candidates. However, their practical deployment is hindered by severe interfacial degradation driven by Ni4+ and oxygen evolution. While bulk electrolyte engineering is well-explored, deterministic control over the interfacial microenvironment, specifically the electric double layer (EDL), remains a pressing challenge. Herein, we introduce a transformative strategy to reconfigure the EDL via sulfur-fluorine exchange (SuFEx)-driven covalent grafting of 4-nitrobenzenesulfonyl fluoride (NBSF) onto the NCM90 surface. The resulting interfacial dipole field repels detrimental carbonate solvents while inducing anion enrichment at the inner Helmholtz plane. This tailored EDL reshapes interfacial reaction pathways, suppressing solvent dehydrogenation and parasitic oxidation to yield a protective cathode–electrolyte interphase (CEI). Consequently, Ah-level graphite||NCM90 pouch cells achieve 91.5% capacity retention over 300 cycles, outperforming the unmodified system (76.5%). By correlating surface dipole modification, EDL reorganization, and interfacial reactivity, this work provides a mechanistic framework for interface engineering in advanced energy storage systems.

The Li||CuCl ₂ battery was proposed as a prototype for high‐energy‐density lithium batteries in the 1960s. Despite its energy density exceeded that of lithium‐ion batteries at a much lower cost, its development was hindered by the high solubility of CuCl ₂ in conventional carbonate electrolytes. Here, we suppressed the dissolution of CuCl ₂ by rationally fluorinating solvents, thereby maintaining it at solid state during the reversible conversion of CuCl ₂ ↔ CuCl ↔ Cu. As a result, the CuCl ₂ cathode delivered a lithiation capacity of 399 mAh g ⁻¹ and a reversible delithiation capacity of 356 mAh g ⁻¹ . A systematical investigation discovered distinct intermediate phases during conversion: α‐ZnS phase CuCl formed during discharging and β‐ZnS phase CuCl within charging. Besides, the redox chemistry was further extended to Na||CuCl ₂ batteries using an analogous electrolyte, which realized the reversible sodiation/desodiation of CuCl ₂ cathode. The electrolyte design enabled the fundamental understanding of conversion mechanism and the development of soluble chloride cathodes for rechargeable batteries.

The development of low‐cost and sustainable cathode materials is crucial for advancing sodium‐ion battery technology. This work proposes a new rutile‐type NaFe ₂ F ₆ cathode synthesized through an energy‐efficient mechanochemical method without high‐temperature processing. The rutile‐type NaFe ₂ F ₆ possess a unique crystal structure of edge‐sharing MF ₆ octahedra, forming a 1D Na ⁺ diffusion channels with an ultralow migration barrier of 0.299 eV. In situ X‐ray diffraction analysis demonstrates its exceptional structural stability during cycling, with only a 1.94% volume variation and a single‐phase reaction mechanism without phase transitions. The NaFe ₂ F ₆ cathode can deliver a high reversible capacity of 181 mAh g ⁻¹ via a Fe ²⁺ /Fe ³⁺ redox couple. Comprehensive kinetic analyses confirm superior Na ⁺ transport properties compared to conventional FeF ₃ . Given the earth's crust abundance of Na and Fe elements, this work establishes NaFe ₂ F ₆ as an environmentally sustainable and economically viable cathode material, paving the way for large‐scale energy storage applications.

Aqueous zinc metal batteries are ideal candidates for grid storage applications. However, their practical application is hindered by a narrow operating temperature range and a limited electrolyte electrochemical stability window, both of which can be attributed to the water activity. Here, to minimize water activity in the electrolyte solution, we introduce a nanoengineered approach in which the water molecules are confined within a hydrophilic–hydrophobic water solvation sheath. The hydrogen-bond interaction with the hydrophilic groups in the inner solvation layer effectively suppresses water decomposition, and the hydrophobic solvents in the outer solvation layer establish a repulsive effect against water molecules. As a proof of concept, a hydrophobic and non-polar hydrofluoroether cosolvent is introduced into a Zn-ion aqueous electrolyte solution and tested together with various fluorinated hydrotrope molecules to favour the compatibility of the cosolvent with water. By such a water confinement strategy, an average Zn plating/stripping reversibility of 99.92% is achieved for over 4,000 cycles at 2.0 mA cm⁻² and 2.0 mAh cm⁻² in a Zn||Cu coin cell configuration. When tested in a Zn||VOPO₄·2H₂O lab-scale cell configuration, the selected aqueous-hydrotrope hybrid electrolyte solution enables long-lasting and highly reversible battery performance across temperatures from −80 °C to +60 °C.

Grasping the intricacies of the solid electrolyte interphase (SEI) on sodium (Na) metal anodes is critical for developing sodium metal batteries (SMBs). Conventional carbonate electrolytes suffer from poor Na compatibility, forming organic‐rich SEIs that degrade cycling stability. Here, A dual‐sulfite electrolyte (DSE) is presented, where the synergistic effect of sp ³ hybridization in –SO ₃ and p ² –pd hybridization in S═O enables a higher solvent coordination number, promoting the formation of a favored solvent‐derived, inorganic‐dominant SEI. The designed DSE accelerates the passivation process of Na anodes, yielding sulfide complexes in the SEI layer. As a result, paired with a high‐loading layered oxide cathode (NaNi _1/3 Fe _1/3 Mn _1/3 O ₂ , 2.6 mAh cm ⁻² ) and thin Na (100 µm), the DSE enables SMBs to achieve an 85% capacity retention after 450 cycles at an N/P ratio of 4.3. Even with thinner Na (50 µm, N/P = 2.2), the cell retains 86% capacity after 200 cycles.

All‐solid‐state Li batteries that incorporate halide solid‐state electrolytes (SEs) promise the safety, thermal stability, and high energy density needed for electric vehicles and grid‐scale renewable energy storage. However, a substantial fraction of these electrochemical inert SEs is used as catholytes within the composite cathodes to sustain continuous Li‐ion pathways, adding “dead weight” that does not contribute to the overall capacity. This review highlights the emerging redox‐active halide catholytes, specifically Li containing transition metal halide that combine reversible redox chemistry with efficient mixed ionic–electronic conductivity. When integrated into composite cathodes, these materials contribute to an additional 20–50% reversible capacity, and simultaneously lowers the electronic transport tortuosity. Drawing on insights from solid‑state ionics and electronic band structure, the design principles for achieving mixed ionic–electronic conductivity are first outlined, and then summarize recent progress on Fe‐, V‐, and Ti‐based redox‐active halide catholytes, along with their dynamic behavior during cycling. Finally, the conclusion outlined further directions for redox‐active halide catholytes, including the discovery of new materials, anion‑sublattice engineering, and the elucidation of dynamic interface evolution, as well as the exploration of anionic‑redox processes.