A biomass-derived aramid-ZrO₂ composite separator for Li-ion batteries has superior electrolyte wettability, thermal stability and ionic conductivity, enabling 128.2 mAh g⁻¹ discharge capacity (10C) and 93.5% energy retention after 1200 cycles.

Positive temperature coefficient (PTC) materials are pivotal for safeguarding lithium iron phosphate batteries, yet their industrial application is hindered by critical drawbacks: excessive film thickness, high internal resistance, and poor solvent sustainability. Addressing these challenges, this study innovatively develops a solvent-free thermal rolling process to fabricate an asymmetric expansion polymer film, specifically thermoplastic polyurethane (TPU) reinforced polyethylene (PE)/carbon composites, which significantly enhances the PTC effect. The core mechanism lies in the asymmetric thermal expansion of TPU and PE: this unique behavior disrupts the conductive carbon network, triggering a sharp PTC transition at around 120 °C. Further validation via an electrochemical-thermal coupling model confirms that the abrupt resistance increase effectively terminates battery discharge, a key safety function. The optimized composite (1% TPU-1% C@PE) exhibits exceptional performance: it features an ultrathin structure (8.5 μm) with low resistance (78 Ω) at room temperature, while reaching a high-resistance state (10 380 Ω) at 120 °C, achieving an impressive resistance ratio of 133.1. Notably, this performance is achieved without compromising the battery's cycling stability. The open circuit voltage of the 1% TPU-1% C@PE battery can quickly drop to 2.5 V within 570 s in an environment of 160 °C, due to the PTC effect. This work not only overcomes long-standing industrial bottlenecks but also provides a practical, scalable strategy, paving the way for advanced safety in lithium battery technology.

Developing cost-effective yet high-performance hard carbon anodes is critical for advancing the commercialization of sodium-ion batteries (SIBs), as they offer a balance of low cost, high capacity, and compatibility with Na⁺ storage mechanisms. Herein, waste towels, an abundant, low-cost precursor with a high carbon yield (>49%), were utilized to synthesize hard carbons via a two-step process: pre-oxidation at 250 °C to stabilize the fibrous structure, followed by carbonization at 1100 °C (THC-1100), 1300 °C (THC-1300), or 1500 °C (THC-1500). Electrochemical evaluations revealed that THC-1300, carbonized at an intermediate temperature, exhibited superior Na⁺ storage performance compared to its counterparts: it delivered a high reversible specific capacity of ~320 mAh/g at 1.0 C (1 C = 320 mA/g), with 78% capacity retention after 200 cycles, demonstrating excellent long-term cyclic stability. Its rate capability was equally impressive, achieving specific capacities of 341.5, 331.2, 302.0 and 234.8 mAh/g at 0.2, 0.5, 2.0 and 5.0 C, respectively, indicating efficient Na⁺ diffusion even at high current densities. Notably, THC-1300 also showed an improved initial Coulombic efficiency (ICE) of 75.4%, reflecting reduced irreversible Na⁺ consumption during the first cycle. These enhancements are attributed to the synergistic effects of THC-1300’s optimized structural and textural properties: a balanced interlayer spacing (d₍₀₀₂₎ = 0.387 nm) that facilitates rapid Na⁺ intercalation, a low BET surface area (1.62 m²/g) helps to minimize electrolyte side reactions. The combined advantages of high specific capacity, improved ICE, and remarkable cycling stability position this waste-towel-derived hard carbon as a highly viable and sustainable candidate for anode materials in next-generation SIBs, addressing both performance and cost requirements for large-scale energy storage applications.

The operational failure of lithium-ion batteries under extreme temperatures (−40~60 °C) stems primarily from electrolyte limitations. While prior efforts improved either low-temperature or high-temperature performance independently, holistic electrolyte design with practical validation remains elusive. Herein, we develop an all-climate electrolyte (ACE) through synergistic coordination of solvent, Li salt, and additive, achieving low viscosity (<10 mPa·s at −40 °C) and high ionic conductivity (7.0 mS cm⁻¹ at −40 °C). Raman and NMR spectra reveal MA and EC co-occupying Li⁺ solvation sheath while EMC acts as a diluent, enabling rapid ion transport. Consequently, LiFePO₄ (LFP)|graphite (Gr) cell delivers unprecedented cyclability: zero capacity decay over 500 cycles at 0 °C, stable operation across −40~60 °C, and 94.1% retention after 100 cycles at 45 °C in Ah-level pouch cells. XPS and SEM analysis demonstrate lithium difluorophosphate (LiDFP) and lithium bis(fluorosulfonyl)imide (LiFSI) collaboratively remodel SEI/CEI interphases, enriching them with LiF, Li₃PO₄, and Li₂SO₄. This inorganic-dominant architecture enhances interfacial Li⁺ kinetics and all-climate stability compared to the baseline electrolyte. Our tripartite electrolyte strategy provides a material-agnostic solution for all-climate energy storage.