Bo Song

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.

Pressurization is a common method for regulating the crystal structure and physical properties of materials without altering their chemical composition. In this work, the two-dimensional (2D) CuInP ₂ Se ₆ single crystal was prepared using a P ₂ Se ₅ reactive-flux method. The pressure-driven phase transition and evolution of ferroelectric-to-superconductor in CuInP ₂ Se ₆ was demonstrated. A systematic structural transformation from the hexagonal ( P 31c, No. 159) phase to monoclinic ( C c, No. 9) phase and hexagonal ( P 31c, No. 159) phase was observed at 10 GPa and 35 GPa, respectively. Superconductivity emerged in CuInP ₂ Se ₆ at 35 GPa, potentially competing with its intrinsic polarity. These discoveries on pressurized CuInP ₂ Se ₆ offer insight into the interaction of crystalline structure and electrical properties under high-pressure conditions.

Anode‐free sodium metal batteries (AFSMBs) are regarded as promising next‐generation energy storage device because of their exceptionally high energy density and low cost. However, their practical application is still hindered by uncontrolled sodium dendrites growth and unstable solid electrolyte interface (SEI) formation. To address these challenges, a sodiophilic Ag interface was in situ constructed on the copper foil current collector to regulate the uniform Na deposition and promote a stable SEI formation. Combined theoretical calculations and experimental analysis revealed that the Ag interface enables uniform Na deposition by enhancing sodiophilicity and homogenizing the electric field, while also promoting the decomposition of NaPF ₆ to form a robust and thin SEI. Consequently, the Ag─Cu||Na asymmetric cells exhibited stable cycling for over 1100 cycles with a high Coulombic efficiency of 99.87% at 1 mA cm ⁻² . Moreover, AFSMBs paired with Na ₃ V ₂ (PO ₄ ) ₃ cathode delivered a capacity retention of 70% after 500 cycles at 2C. Furthermore, the AFSMBs also maintained stable cycling over 150 cycles at −20°C under 0.05C. These results demonstrate the significant potential of introducing a sodiophilic interfacial layer to regulate uniform sodium deposition and promote stable SEI formation, thereby enabling high‐performance anode‐free sodium metal batteries across ambient and subzero conditions.

The calendar ageing has long plagued practical realization of long‐life lithium‐ion batteries (LIBs), and the interfacial ageing significantly affects electrochemical performances compared with bulk electrolyte hydrolysis, while its mechanism remains insufficiently elucidated. We found electron‐tunneling‐induced interfacial electrochemical degradation of solid electrolyte interphase (SEI) is widespread in most electrode interfacial processes, unlike interfacial chemical etching caused by high‐temperature hydrolysis in LiPF ₆ ‐based electrolytes. During this electrochemical degradation, LiFSI‐based electrolytes will undergo solvent reduction to reconfigure inorganic‐rich SEI (LiF/Li ₃ N/Li ₂ S) to organics (RCO ₃ Li/RCO ₂ Li/RCOLi), leading to active lithium consumption and hindering ion transport. Oppositely, the polymeric SEI (boron‐crosslinked polyether) will evolve from long‐chain ─B─F bonds into ─B─O and LiF in LiDFOB‐based electrolytes via thermally‐induced ageing, effectively suppressing subsequent solvent decomposition. Furthermore, through electrolyte‐exchange experiments, we reveal graphite anode operating via Li ⁺ intercalation/deintercalation, behaves as a “Solvation‐Structure‐Restricted Mechanism” and exhibits low dependence on the pristine SEI and can be rehabilitated by replacing electrolytes after ageing; whereas SiO _x anode governed by Li ⁺ ‐alloying reaction, acts as an “Interface‐Restricted Mechanism” that suffers irreversible capacity decay due to electrochemical degradation, thus being more reliant on the reconstructed polymer‐based SEI enabled by LiDFOB. Our research provides original insights for salt anion selection and interfacial design for high‐energy and long‐cycle‐life LIBs.

Generalized magneto-optical ellipsometry (GME) is designed to suppress second-order magneto-optical contributions in its data analysis, yet previously, this robustness has not been tested under challenging conditions, in which large second-order magneto-optical effects occur. Here, we investigate the reliability of GME using epitaxial bismuth-substituted yttrium iron garnet films that exhibit pronounced second-order magneto-optical effects, which can even become dominant under certain experimental conditions. Despite the presence of these strong effects, the GME data sets and associated fits show excellent agreement for all tested samples, applied field values, and corresponding magnetization states. The extracted magneto-optical parameters are also in excellent agreement with independent magnetometry measurements of the field-dependent magnetization properties of the samples. Further analysis of the intensity modifications caused by second-order magneto-optical effects indicates that they originate from the intrinsic quadratic magneto-optical response of the film materials. These results validate the reliability of GME under challenging conditions and further suggest that combining conventional GME data analysis with polarization-dependent intensity data sets could enable the simultaneous determination of both linear and second-order magneto-optical contributions.

Magneto‐optical functional devices based on iron garnet films are important for optical communication and integrated photonics, where Faraday rotation magnitude, sign, and spectral response can be tuned on demand. However, most reported compensation‐related magneto‐optical responses have been demonstrated in isolated compositions or different formulations, leaving it unclear how a single compositional variable can design compensation temperature, magnetic reversal, and telecommunication‐wavelength Faraday response in a Bi‐rich rare‐earth garnet film. Here, a Bi‐Eu‐Ho‐Ga iron garnet thin‐film platform is established, in which magnetic compensation is systematically tuned through Ga‐mediated Fe‐sublattice dilution. By adjusting Ga content, compensation temperatures of 77, 187 K, 29, and 431 K are achieved in the same materials family. Consequently, distinct Faraday responses are realized at 300 K, including changes in rotation magnitude, sign, and spectra, where large Faraday rotation (−0.081 deg µm ⁻¹ ) is achieved under a low saturation field (≈527 Oe), and a self‐biased state with full zero‐field rotation retention and a large reverse nucleation field (≈350 Oe) is realized. Temperature‐dependent Faraday spectroscopy reveals systematic evolution of the magneto‐optical transition energy associated with the compensation state. This work provides a composition‐guided route to compensation‐regulated Faraday responses in Bi‐rich Eu/Ho co‐substituted iron garnet films for telecommunication‐wavelength components.

Dimeric acceptors have recently emerged as promising giant molecule acceptors (GMAs) for organic solar cells (OSCs), but most systems link two identical monomeric units. Hybrid GMAs combining different acceptor units remain unexplored. Herein, we develop a core‐to‐wing type hybrid strategy coupling BT‐ and BZ‐core acceptor units through flexible ester‐linked alkyl chains, affording three GMAs (BTZ‐2‐2, BTZ‐2‐6, and BTZ‐2‐10). This design enables complementary absorption by combining the spectral features of BT‐ and BZ‐based monomers while preserving favorable crystallization behavior. Among them, BTZ‐2‐6 exhibits the broadest, most red‐shifted absorption, enhanced π‐π stacking, and the highest electron mobility due to the optimal length of its ester‐linked alkyl chain. The PM6:BTZ‐2‐6 binary device delivers 18.53% efficiency and retains nearly 90% of its initial efficiency after 720 h of illumination. Furthermore, the efficiency can be increased to 19.41% by replacing PM6 with D18 as the donor polymer, and further boosted to 20.25% by incorporating BTZ‐2‐6 as a third component into PM6:L8‐BO binary devices. These results demonstrate that core‐to‐wing hybrid GMAs with ester‐linked alkyl chains of different lengths provide an effective strategy for constructing high‐performance GMAs, offering new opportunities for efficient and stable OSCs.

Dimeric acceptors have recently emerged as promising giant molecule acceptors (GMAs) for organic solar cells (OSCs), but most systems link two identical monomeric units. Hybrid GMAs combining different acceptor units remain unexplored. Herein, we develop a core‐to‐wing type hybrid strategy coupling BT‐ and BZ‐core acceptor units through flexible ester‐linked alkyl chains, affording three GMAs (BTZ‐2‐2, BTZ‐2‐6, and BTZ‐2‐10). This design enables complementary absorption by combining the spectral features of BT‐ and BZ‐based monomers while preserving favorable crystallization behavior. Among them, BTZ‐2‐6 exhibits the broadest, most red‐shifted absorption, enhanced π‐π stacking, and the highest electron mobility due to the optimal length of its ester‐linked alkyl chain. The PM6:BTZ‐2‐6 binary device delivers 18.53% efficiency and retains nearly 90% of its initial efficiency after 720 h of illumination. Furthermore, the efficiency can be increased to 19.41% by replacing PM6 with D18 as the donor polymer, and further boosted to 20.25% by incorporating BTZ‐2‐6 as a third component into PM6:L8‐BO binary devices. These results demonstrate that core‐to‐wing hybrid GMAs with ester‐linked alkyl chains of different lengths provide an effective strategy for constructing high‐performance GMAs, offering new opportunities for efficient and stable OSCs.