The operation of aqueous zinc-ion batteries in flexible energy storage field is plagued by the uncontrollable growth of Zn-dendrite and inevitable freeze of water below 0 ℃. Therefore, it is necessary to design a hydrogel electrolyte with good mechanical property and freezing resistance to uniform the Zn-deposition and resist flexibility loss at low temperature. We find that the mechanical property (strength and toughness) of hydrogel electrolyte has a significant impact on the suppression of dendrite growth and the uniform deposition of zinc ions. Herein, a polyacrylate hydrogel is prepared in one step by UV curing method with Zn(CF₃SO₃)₂ salt and PVA addition to increase the antifreezing ability and mechanical properties. The adsorption of water molecules by HEA and PVA reduces the freezing point of the hydrogel, which is beneficial for enhancing the electrochemical stability at low temperature. On this basis, the Zn-symmetrical battery with hydrogel electrolyte has a long lifespan of 4710 h at 0.5 mA cm^-2 and 0.5 mAh cm^-2 at room temperature. Furthermore, the hydrogel electrolyte exhibits an outstanding stability at low temperature of -20 ℃, the lifespan of symmetrical battery reaches to 4000 h at 0.5 mA cm^-2 and 0.5 mAh cm^-2. The assembled full cell with NVO cathode and hydrogel electrolyte possesses a high capacity retention ratio of 77 % after 10000 cycles at -20 ℃. The flexible cell can power LED lamp under bending, warping and cutting without liquid leakage and an electronic watch at the operating temperature of -20 ℃.

Energy-storage technologies based on lithium-ion batteries are advancing rapidly. However, the occurrence of thermal runaway in batteries under extreme operating conditions poses serious safety concerns and potentially leads to severe accidents. To address the detection and early warning of battery thermal runaway faults, this study conducted a comprehensive review of recent advances in lithium battery fault monitoring and early warning in energy-storage systems from various physical perspectives. The focus was electrical, thermal, acoustic, and mechanical aspects, which provide effective insights for energy-storage system safety enhancement.

Lithium-iodine (Li-I₂) battery exhibits high potential to match with high-rate property and large energy density. However, problems of the system, such as evident sublimation of iodine elements, dissolution of iodine species in electrolyte, and lithium anode corrosion, prevent the practical use of rechargeable Li-I₂ batteries. In this work, a molten Li-I₂ typical cell design which has distinct advantages based on the solid-state garnet electrolyte with the eutectic iodate cathode is firstly developed. The U-shaped ceramic electrolyte tube can separate Li anode from the eutectic iodate cathode, so as to better tackle the above-mentioned inherent challenges for the liquid electrolyte systems. Without self-discharging and lithium anode corrosion, this solid-state battery system demonstrates high safety margin and excellent electrochemical performance. Also, the simple battery structure also indicates the easy assembly process and recycling of electrode materials. With the cathode loading of 593 mg in a single cell, an energy density of ~ 506.7 Wh·kg⁻¹ was achieved at 1 C and a long-term cycling life for 2,000 cycles also displays negligible capacity decay.

A stable lithium-metal anode is critical for high performance lithium-metal batteries. However, heterogeneous Li plating/stripping may induce lithium dendrites formation on bare lithium-metal anode, which lowers the cell Coulombic efficiency and weakens battery safety. We found that bare Li metal surface becomes bumpy and cratered with numerous pits formation during Li stripping. These pits enhance electric field distortion and heterogeneous ion distribution during plating. Li plating preferentially happens on the edge of the pits, intensifying the voltage variation and Li dendrites growth, which leads to the cell rapid death or separator piercing. Herein, we propose a facile and mass-producible method to homogenize Li plating/stripping via adding lithiophilic particles into Li metal. Zinc particles were uniformly pressed in Li metal by a facile and scalable physical strategy of "rolling", and transformed into LiZn alloy in situ through Li-Zn alloying at room temperature in a few minutes. The critical role of modified LiZn/Li composite anode in stabilizing electrode surface was revealed by both electrochemical test and simulation. Compared with bare Li anode, the evenly dispersed LiZn alloy particles in Li metal can effectively regulate the Li plating/stripping on electrode surface, reducing deepness of pits during stripping and directionally inducing Li plating to maintain electrode surface stability. On this basis, the pits depth of LiZn/Li composite during Li stripping is reduced to ~ 15 μm, which is much shallower than that of bare Li metal of ~ 40 μm. The LiZn/Li composite electrode can stably cycle for 600 h under Li plating/stripping capacity of 1 mAh·cm^-2 and current density of 1 mA·cm^-2 without any short circuit. Furthermore, assembled LiZn/Li||LiFePO₄ full cell presents better cycling stability and rate performances than that of based on bare Li anode.