Xinhai Yuan

Developing polymer‐based solid electrolytes with efficient Li ⁺ transport, electronic insulation, mechanical robustness, and stable electrode interfaces remains challenging for solid‐state lithium‐metal batteries. Here, a carbon‐free LiFePO ₄ (LFP)/PVDF composite solid electrolyte is designed, where the intrinsically low electronic conductivity of LFP is transformed from a limitation for cathode applications into an electrolyte advantage. Unlike carbon‐coated LFP, carbon‐free LFP acts as an electronically insulating inorganic filler in the PVDF matrix, suppressing electron transport while promoting Li ⁺ migration through abundant LFP/PVDF interfaces. Optimized LFP50 exhibits an ionic conductivity of 4.89 × 10 ⁻⁴ S cm ⁻¹ at 25°C, a Li ⁺ transport activation energy of 0.053 eV, an electronic conductivity on the order of 10 ⁻¹⁰ S cm ⁻¹ , a 5.0 V oxidative stability window, and favorable mechanical properties. These features enable stable Li‐metal interfaces, as demonstrated by a critical current density of 6.2 mA cm ⁻² and uniform Li deposition. Furthermore, LFP50 provides lithium compensation through partial delithiation of cathode‐facing LFP particles, mitigating irreversible lithium loss. Without external pressure, Li|LFP50|LFP and Li|LFP50|NCM811 cells retain 93.8% and 80% capacity after 500 and 165 cycles, respectively. This work demonstrates carbon‐free LFP as a multifunctional filler strategy for regulating Li ⁺ transport, stabilizing electrode interfaces, and advancing solid‐state lithium‐metal batteries.

Advanced solid polymer electrolytes (SPEs) are indispensable for enabling durable, safe, and high‐energy‐density solid‐state lithium metal batteries (SSLMBs). However, the concurrent optimization of lithium‐salt dissociation, Li ⁺ transport, and lithium‐metal interfacial chemistry remains a challenge over decades. In this study, a PPy‐regulated solid polymer electrolyte (PPyPL) featuring chemically differentiated coordination sites is developed to reconstruct ion‐solvation chemistry through site‐selective Li ⁺ /anion coordination. The resulting coordination architecture affords differentiated molecular interactions in which pyrrolic nitrogen sites preferentially coordinate Li ⁺ , whereas hydrogen sites along the PPy backbone interact with bis(trifluoromethanesulfonyl)imide (TFSI ⁻ ) anions, thereby simultaneously promoting lithium‐salt dissociation, accelerating Li ⁺ transport, and directing LiF/Li ₃ N‐rich interphase formation. Benefiting from the synergistic regulation of ion‐solvation chemistry and interfacial evolution, PPyPL achieves an ionic conductivity of 0.76 mS cm ⁻¹ at room temperature (25°C), a Li ⁺ transference number of 0.65, and ultralong Li plating/stripping stability over 8000 h. It further enables outstanding rate capability and durable cycling in both Li||LiFePO ₄ (LFP) and Li||LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811) solid‐state full cells. This work provides a new strategy for regulating Li ⁺ /anion coordination in advanced SPEs toward durable SSLMBs.

Owing to its high energy density, environmental friendliness, and low cost, the high‐voltage Ni–Mn‐based oxides material has emerged as a highly promising cathode candidate. Nevertheless, such kind of material faces significant limitations including hydrofluoric acid (HF) corrosion, transition metal dissolution, and the Jahn–Teller effect, which substantially hinder its large‐scale commercialization. This review comprehensively introduces the fundamental characteristics and limitations of LiNi _0.5 Mn _1.5 O ₄ (LNMO) and LiNi _x Co _y Mn _z O ₂ (NCM), followed by state‐of‐the‐art mitigation approaches of CEI regulation encompassing electrolyte additives, synergistic additive combinations, doping modifications, surface coating engineering, and particle design optimization. Future research could explore the synergistic combination of these modification approaches, potentially sparking novel research avenues.

This review summarizes positive electrode materials and design strategies for aqueous magnesium batteries, including Mn/V-based, PBAs, polyanionic, LDHs, and organic materials, for high voltage and long cycle life.