Polymer Electrolyte/Sulfur Double-Shelled Anisotropic Reduced Graphene Oxide Lamellar Scaffold Enables Stable and High-Loading Cathode for Quasi-Solid-State Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) can replace lithium-ion batteries by delivering a higher specific capacity. However, the areal capacity of current LSBs is low because the intrinsic limitations of sulfur make achieving a high sulfur loading difficult. Herein, the authors report vertically aligned reduced graphene oxide (rGO) with sulfur and poly(ethylene oxide)-based polymer electrolyte double-shell layers (VRG@S@PPE) as a high-loading sulfur cathode. The addition of vapor-grown carbon fiber (VGCF) into rGO is the key to success, as it allows for gas evacuation from internal nano/micropores without structural collapse, enabling perfect double-shell layer contact. Owing to the anisotropic rGO lamellar structure that enables straightforward ion/electron transport and provides numerous active sites, sulfur-infiltrated rGO reinforced via VGCF (VRG@S) exhibits a high capacity of 998 mAh g^-1 after 100 cycles at 0.1 C under high sulfur loading (6 mg cm^-2 ). Interestingly, an additional polymer electrolyte layer further increases the cycle retention (1005 and 718 mAh g^-1 after 100 cycles at 0.1 and 1 C, respectively), because intimate contact between the solid polymer electrolyte and sulfur could suppress the loss of sulfur due to lithium polysulfide (LPS) shuttling or volume change during lithiation/delithiation. Therefore, it is possible to realize safe and stable quasi-solid-state LSBs with high sulfur loading.

New Diglyme-based Gel Polymer Electrolytes for Na-based Energy Storage Devices

This work presents for the first time a new diglyme-based gel polymer (DOBn-GPE) suitable for Na-based energy storage devices. The DOBn-GPE, which contains a methacrylate-based polymer, exhibited an excellent high ionic conductivity (2.3 mS cm-1 at 20 °C), broad electrochemical stability (>5.0 V), and high mechanical stability. DOBn-GPE could be successfully used for the realization of Na-ion capacitors, sodium-metal batteries, and sodium-ion batteries, displaying performance comparable with those of systems containing liquid electrolytes at room temperature and at 60 °C. The results of these investigation indicated that the development of diglyme-based gel polymer electrolytes represents a promising strategy for the realization of advanced Na-based energy storage devices.

Single-Ion Conducting Double-Network Hydrogel Electrolytes for Long Cycling Zinc-Ion Batteries

As one of the promising alternatives of lithium-ion batteries, zinc-ion batteries (ZIBs) have received growing interest from researchers due to their good safety, eco-friendliness, and low cost. Nevertheless, aqueous ZIBs are still a step away from practical applications due to the nonuniform deposition of Zn and parasitic side reactions, which cause capacity fading and even short circuit. To tackle these problems, here we introduce a single-Zn-ion conducting hydrogel electrolyte (SIHE), P(ICZn-AAm), synthesized with iota carrageenan (IC) and acrylamide (AAm). The SIHE manifests single Zn²⁺ conductivity via the abundant sulfates fixed on the IC polymer backbone, delivering a high Zn²⁺ transference number of 0.93. It also exhibits outstanding ionic conductivity of 2.15 × 10^-3 S cm^-1 at room temperature. The enhanced compatibility at the electrode-electrolyte interface was verified by the stable Zn striping/plating performance along with a homogenous and smooth Zn deposition layer. It is also found that the passivation of the Zn anode can be effectively prohibited due to the lack of free anions in the electrolyte. The practical performance of the SIHE is further investigated with Zn-V₂O₅ batteries, which showed a stable capacity of 271.6 mA h g^-1 over 150 cycles at 2 C and 127.5 mA h g^-1 over 500 cycles at 5 C.

Flexible, Flame-Resistant, and Dendrite-Impermeable Gel-Polymer Electrolyte for Li-O2 /Air Batteries Workable Under Hurdle Conditions

Gel-polymer electrolytes are considered as a promising candidate for replacing the liquid electrolytes to address the safety concerns in Li-O₂ /air batteries. In this work, by taking advantage of the hydrogen bond between thermoplastic polyurethane and aerogel SiO₂ in gel polymer, a highly crosslinked quasi-solid electrolyte (FST-GPE) with multifeatures of high ionic conductivity, high mechanical flexibility, favorable flame resistance, and excellent Li dendrite impermeability is developed. The resulting gel-polymer Li-O₂ /air batteries possess high reaction kinetics and stabilities due to the unique electrode-electrolyte interface and fast O₂ diffusion in cathode, which can achieve up to 250 discharge-charge cycles (over 1000 h) in oxygen gas. Under ambient air atmosphere, excellent performances are observed for coin-type cells over 20 days and for prototype cells working under extreme bending conditions. Moreover, the FST-GPE electrolyte also exhibits durability to protect against fire, dendritic Li, and H₂ O attack, demonstrating great potential for the design of practical Li-O₂ /air batteries.