Search

Poly(ethylene oxide) (PEO) and its derivatives based gel polymer electrolytes (GPEs) are severely limited in advanced and safe lithium-ion batteries (LIBs) owing to the intrinsically high flammability of liquid electrolytes and PEO. Directly adding flame retardants to the GPEs can suppress their flammability and thus improve the safety of LIBs, but results in deteriorative electrochemical performance. Herein, a novel GPE with chemically bonded flame retardant (i.e. diethyl vinylphosphonate) in cross-linked polyethylene glycol diacrylate matrix, featuring both high-safety and high-performance, is designed. This as-prepared GPE storing the commercial 1 mol L−1 LiPF6 electrolyte resists high temperature of 200 °C and cannot be ignited as well as possesses a high ionic conductivity (0.60 mS cm−1) and good compatibility with lithium. Notably, the LiFePO4/Li battery with this GPE delivers a satisfactory capacity of 142.2 mA h g−1 and a superior cycling performance with a capacity retention of 96.3% and a coulombic efficiency of close to 100% for 350 cycles at 0.2 C under ambient temperature. Furthermore, the battery can achieve steady charge–discharge for 100 cycles with a coulombic efficiency of 99.5% at 1 C under 80 °C and run normally even at a high temperature of 150 °C or under the exposure to butane flame. Differential scanning calorimetry manifests significantly improved battery safety compared to commercial battery systems. This work provides a new pathway for developing next-generation advanced LIBs with enhanced performance and high safety.

In extremely low-temperature environments such as aerospace and polar regions, advanced elastic thermal insulation materials are urgently needed but their development is challenging, as traditional elastic insulators are completely “frozen”, lose elasticity and become brittle. Herein, we proposed a novel structural elastic strategy to create an ultralow-temperature elastic polymer aerogel with highly oriented thin nanosheets and hierarchically honeycomb-like architectures from low-cost raw materials. This approach endowed the polymer aerogel with superelasticity and high strength at liquid nitrogen temperature (−196 °C), where the aerogel can bear more than 10 000 times its weight and repeatedly recover to its original size after force removal. The underlying structural elastic mechanism was revealed by finite element simulation calculation. The resultant robust aerogel also displayed an excellent extreme-condition thermal insulation, which could maintain a pleasant interior environment with small temperature changes under harsh external environments from liquid nitrogen to fire scenarios. It combined the great features of ultralow-temperature superelasticity with high mechanical strength, excellent thermal insulation under extremely harsh conditions, fire retardancy, and performance stability. These results provide new insights and general methods for the development of advanced super-elastic polymeric insulators with high strength at ultralow temperatures.

A novel and green method to prepare porous membrane is reported by simply blending methylcellulose (MC) and lithium polymethacrylic acid (LiPMA) in water. Thanks to the coordination between oxygen atom in MC and Li+ in LiPMA and subsequent micro-phase separation between them, a porous membrane can be obtained after water evaporated. A series of membranes with different pore size and morphology are prepared by controlling the mass ratio of MC/LiPMA. All the membranes exhibit good thermal and electrochemical stability. With the increasing proportion of LiPMA, the obtained membrane has higher electrolyte uptake, resulting in higher ionic conductivity of corresponding gel polymer electrolyte (GPE). When the mass ratio is 5:20, the membrane has the highest the lithium ion transference (0.57), and the GPE reveals the higher ionic conductivity of 0.65 mS cm−1 at room temperature. What's more, the aforementioned GPE exhibits excellent discharge capacity and good cycling performance. Without use of any organic solvents and tedious preparation process, this novel method is environmentally friendly and low-cost, and the obtained GPE exhibits excellent performance, which has a greatly commercial potential.

Solid-state battery (SSB) has a new application prospect in the fields of safe energy storage, but the solid electrolyte usually fails to maintain excellent ionic conductivity, good mechanical properties and close interfacial contact with the electrode materials simultaneously. A newly-designed poly(ionic liquid)-based quasi solid electrolyte (PIL-QSE) is prepared via one-step in-situ cross-linked polymerizing 1-vinyl-3-dodecylimidazolium bis(trifluoromethanesulfonyl) imide (VDIM-TFSI), which is filled in poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) porous membrane prepared via phase inversion. The leakage-free PIL-QSE containing a compact cross-linked network structure exhibits optimal performances with outstanding flexibility, favorable thermal stability and improved electrochemical performances including a high room-temperature ionic conductivity of 0.70 mS cm−1, a superior electrochemical window up to 5.0 V as well as a high lithium ion transference of 0.52. Furthermore, the PIL-QSE can suppress dendrite formation leading to a good battery performance. The LiFePO4|PIL-QSE|Li cells can maintain a discharge capacity 140.7 mAh g−1 at 0.05 C with 99.8% coulomb efficiency after 200 cycles and 125.9 mAh g−1 at 0.1 C with 98.9% capacity contention after 100 cycles at 25 °C. Because of the flexibility of PIL-QSE, the pouch-type battery based on PIL-QSE cannot only light the red LED lamp in a normal state, but also in a bended/cut state. Both of the excellent performance and easy fabrication of PIL-QSE make it potentially as one of the most promising electrolyte materials for SSPB.