Zhenzhu Wang

Thermal safety is a key challenge for high‐energy lithium metal batteries. Conventional separators deform under overheating while sustaining ion transport, accelerating thermal runaway. Herein, we report an aramid‐supported shape memory separator that converts temperature rise into reconstruction of ion transport pathways. A covalently crosslinked PETMP‐TMPTA‐IBOA network is photopolymerized within a porous aramid scaffold. At normal operating temperatures, the interconnected pore structure affords an ionic conductivity of 0.29 mS cm ⁻¹ and enables stable Li plating/stripping for over 3000 h. At 140°C, the shape memory network undergoes thermomechanical rearrangement, constricting the percolating pores and increasing the ionic resistance by one order of magnitude. Meanwhile, the aramid scaffold preserves dimensional integrity up to 175°C and maintains electrode isolation after ionic shutdown. The separator is compatible with high‐energy NCM811 and Li‐rich Mn‐based oxide cathodes. In particular, a Li‐rich cathode with high mass loading of 16 mg cm ⁻² cycles stably for 100 cycles at 0.5 C, delivers nearly 250 mAh g ⁻¹ at 60°C, and remains operable up to 125°C. This work establishes thermomechanical reconstruction of ion transport pathways as a general design principle for intrinsically self‐protective lithium metal batteries that reconcile high energy operation with autonomous overheating protection.

Localized Joule heating in high‐rate lithium metal batteries often induces severe thermomechanical failure of polymer separators and accelerates thermal runaway in cells with Ni‐rich NCM cathode. Here we report a multiscale separator design strategy that translates lattice‐level negative thermal expansion into macroscopic thermomechanical self‐compensation. In this design, Cu ₂ P ₂ O ₇ is coupled with the PVDF‐HFP matrix through a PDA mediated interface. Temperature‐dependent structural analysis and thermal‐response tests demonstrate the anisotropic lattice contraction of Cu ₂ P ₂ O ₇ , which relieves the thermally induced deformation of PVDF‐HFP through PDA mediated interfacial interactions. The amine‐rich PDA layer further suppresses corrosive hydrofluoric acid during the cycling, improving interfacial durability. The resulting composite membrane maintains complete dimensional stability up to 200°C while preserving high ionic conductivity and a uniform Li ⁺ flux. As a result, Li||Li symmetric cells with the self‐compensating separator operate for more than 3000 h at 1 mA cm ⁻² . When paired with Ni‐rich NCM811 cathodes, full cells maintain 1000 stable cycles at 5 C and deliver 135 mAh g ⁻¹ at 60°C after 100 cycles. This work demonstrates a solid‐state negative thermal expansion strategy for active separator protection, providing a materials route for mitigating thermomechanical failure in high‐power lithium metal batteries.

Hard carbon (HC) stands out as a competitive anode for sodium-ion batteries, combining abundant, sustainable precursors with desirable electrochemical properties. By employing a simple solution-based approach to control cellulose decomposition, we engineer curved pseudographitic domains with expanded interlayer spacing and rich closed pores from peanut shell precursors. The resulting PSHC-7 delivers 401 mAh g^-1 at 0.06 A g^-1, an initial Coulombic efficiency of 88.6%, 289 mAh g^-1 at 3.0 A g^-1, and 93.1% capacity retention over 4500 cycles. In situ Raman and in situ XRD reveal a multistep "adsorption-intercalation-pore filling" mechanism, while theoretical calculations confirm that hierarchical pores and pseudocapacitive effects enhance Na⁺ transport and storage. The full cells (NVP//PSHC-7) demonstrate practical applicability. This work provides an integrated experimental and theoretical framework linking precursor chemistry, microstructure, and electrochemical performance, offering a facile route to high-efficiency, durable, and cost-effective SIB anodes.