Jingling Yan

Lithium-rich layered oxides (LROs) are promising cathode materials for high-energy lithium-ion batteries because of their high specific capacity and energy density. However, oxygen release, stress accumulation, and interfacial degradation during high-voltage cycling still hinder their practical application. Here, an aqueous-processed polyimide/carbon hybrid coating is designed to stabilize LROs. The coating is constructed from a polyimide and a conductive carbon network composed of carbon nanotubes and Super P. The hybrid coating layer provides surface protection, while the carbon components form continuous electron-transport pathways. During post-treatment, mild carbothermal reactions further induce surface oxygen vacancies, which help regulate oxygen-related surface reactions. The modified cathode delivers discharge capacities of 246.6 mAh·g−1 at 1 C, with a capacity retention of 94.9% after 200 cycles at 25 °C. This work provides a practical aqueous interfacial coating strategy for improving the durability of high-energy LROs.

Colorless polyimides were prepared from norbornyl bis-benzocyclobutene containing diamines with methyl or fluorine substituents, and the influences of the substituents on the polyimide properties were investigated.

Binders play a critical role in mitigating the severe volume variation of silicon anodes during charge/discharge and maintaining electrode integrity. In this work, a series of polyimide (PI) binders with different functional groups are prepared to systematically investigate the structure-property relationship. The PI-DABA binder containing amide groups can effectively resist electrolyte swelling and possess strong interfacial interactions toward Si materials. In contrast, the PI-APAB binder, which contains ester groups, shows severely degraded mechanical properties upon electrolyte swelling and excessively strong coordination with Li⁺. The PI-PDA binder, which contains no additional polar groups, resists electrolyte swelling but shows weak interfacial interaction with Si particles. As a result, the PI-DABA-based silicon anode exhibits the best performance at 1 A g^-1, retaining over 70% of its initial capacity after 300 cycles with a specific capacity of about 2300 mAh g^-1. It forms a stable solid electrolyte interphase (SEI) featuring an organic-rich outer layer and a LiF-rich inner layer, while PI-APAB or PI-PDA-based SEIs consist of mixed organic and inorganic species. This study uncovers the significant impact of polymer binder structures on their electrolyte swelling behaviors and interfacial interactions and provides practical designing principles toward high-performance polymer binders for silicon anodes in lithium-ion batteries.

Hydrogels exhibit exceptional resistance against bacterial colonization and diatom adhesion, yet suffer from poor mechanical properties, with tensile strengths usually below 1 MPa in marine environments. Despite the significant progress, developing antifouling hydrogels with simultaneous antimicrobial performance, optimal mechanical robustness, and antifouling efficacy suitable for marine applications is still challenging. Herein, a series of polyelectrolyte hydrogels, featuring a fully aromatic backbone, were synthesized by polymerizing 3,3″,4,4″-biphenyltetracarboxylic dianhydride (BPDA) and p-phenylenediamine (PDA), using water as a solvent and different organic bases (namely 1,2-dimethylimidazole (DMZ), 1-(2-hydroxyethyl)imidazole (HIM), imidazole (IM), triethylamine (TEA), and N,N-dimethylethanolamine (DEMA)) to yield poly(amic acid) salt (PAAS) hydrogels with excellent mechanical properties, low swelling ratios in seawater, and favorable antifouling properties. The abundant carboxylate anions in the PAASs facilitated the in situ cross-linking with multivalent cations (e.g., Ca2+, Mg2+) in seawater, improving stability in marine environments. The optimized PAAS hydrogel (DMZ-PAAS-80, with 80 representing the content of PAAS in the hydrogel) achieves high tensile strength (>9.3 MPa), low swelling ratios ( 99.9%), and reduced adhesion of algae and proteins. Overall, the proposed new paradigm paves the way for designing high-performance hydrogels with exceptional mechanical, antiswelling, and antifouling properties, suitable for marine antifouling applications.

Environmentally adaptive hydrogels undergo reconfiguration under external stimuli, suitable for intelligent sensing, bioinspired actuation, and soft robotics. However, achieving programmable three-dimensional (3D) morphing in homogeneous hydrogels under constant stimuli remains quite challenging despite the tremendous research efforts. Herein, inspired by the directional ion-transport actuation of starfish, supramolecular poly(amic acid) salt (PAAS) hydrogels with predictable 3D structure formation were developed through directional metal ion transport imparted by seawater. These hydrogels were prepared through aqueous polymerization of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA) and p-phenylenediamine (PDA) in the presence of organic bases with imidazole moieties (1,2-dimethylimidazole (DMZ), imidazole (IM), and 1-(2-hydroxyethyl)imidazole (HIM)), followed by thermal treatment at 50 °C. The resultant hydrogels, featuring high-density carboxylates, enable programmable 3D shape-morphing under seawater stimulation through spatially asymmetric (Ca²⁺/Mg²⁺)-carboxylate cross-linking and swelling/contraction. The dynamic supramolecular networks provide remarkable reconfigurability, with repeated reconstruction of complex 3D architectures. Specifically, the hydrogels show exceptional stability with low equilibrium swelling ratios (<50%), increased tensile strength (up to 2.1 MPa), and all 180° deformations completed within 70 s. Overall, programming 3D morphologies of homogeneous hydrogels using a single stimulus has potential for advancing shape-morphing engineering.

Piezoelectric elastomers, combining flexibility, resilience, and piezoelectric properties, are promising for wearable devices. Blending ceramic fillers into elastomers is common for fabricating piezoelectric elastomers, but electrical and mechanical mismatches hinder synergistic fusion for a high piezoelectric output. Here, we develop a high-performance piezoelectric elastomer by co-dissolving and evaporating an aqueous solution of a molecular ferroelectric material TMCM-CdCl₃ (TMCM, trimethylchloromethylammonium) and a waterborne polyurethane elastomer. Slightly increasing the TMCM-Cl proportion modulates piezoelectric properties, while adjusting the TMCM-CdCl₃/WPU ratio achieves an optimal balance between piezoelectricity and elasticity. The resulting material exhibits low elastic modulus, large elongation, high elastic recovery, and superior piezoelectric coefficient d₃₃ (42 pC/N) and piezoelectric voltage coefficient (543 × 10^-3 Vm/N) compared to PVDF, enabling a remarkable voltage output up to 7 V. This piezoelectric elastomer not only exhibits outstanding resilience but also excellent electrical output performance, making it a highly suitable energy material for flexible wearable devices.