A safety-monitoring method based on the overall impedance of a battery pack is investigated to address the inefficiency and invasiveness of traditional disassembly based cell impedance measurements. By measuring the impedance values of individual cells via the AC injection method and conducting a superposition analysis, the relationship between the overall pack impedance and electrochemical states of the individual cells is established. An online measurement method for the overall impedance is developed, incorporating a weighted scoring system for the characteristic frequency points and local overcharge warning method based on the optimal single frequency point. Experimental results using a 280 A·h 1P16S lithium iron phosphate battery showed that the overall impedance effectively reflects individual cell characteristics under normal operating conditions and accurately inherits high-frequency impedance features during overcharge. The weighted scoring system identified 700 Hz as the optimal characteristic frequency, enabling a warning approximately 3 min earlier than those of traditional voltage-based methods. This noninvasive online impedance detection approach provides a new solution for early intervention to prevent the overcharging of battery energy storage systems.

The interface problems in zinc-ion batteries severely limit their electrochemical performance, even in hydrogel (HG) electrolyte (HE). Herein, a strategy of reconfiguring the hydrogen bond networks by thermal gelation is proposed to enhance the battery interface stability. The strategy introduces methyl cellulose into acrylamide, which can effectively stabilize the electrode interface and reconstruct the hydrogen bond networks of the electrolyte through its unique thermos-gelation property. Methylcellulose is dissolved by heating and cooled to form gel. This thermal gelation strategy formed hydrogen bonds with a large amount of free water and methyl cellulose, which not only reduced the water activity but also enhanced the intermolecular polymerization network and also promoted the solvation of Zn²⁺. More importantly, the symmetric batteries with HE-HG hydrogel electrolyte exhibited a long cycling life of 8000 h. The Zn||Zn_0.25V₂O₅ (Zn||ZVO) battery displays the low-capacity decay rate for 800 cycles at 1 C at −20 °C. The pouch battery maintains a capacity of 255 mAh·g⁻¹ after 100 cycles under 2.5 A·g⁻¹ at −20 °C. This study provides a new way to enhance the interfacial stability, which helps to realize the scale application of flexible zinc-ion batteries.

Aqueous zinc-ion batteries are considered an ideal choice for energy storage technology in new power systems due to their high theoretical capacity, high safety, and environmental friendliness. However, in practical applications, Zn anodes face a series of problems and challenges, such as Zn dendrite irregular growth, electrode cross-section corrosion, and hydrogen reduction side reactions. This has importantly impeded the large-scale utilization of zinc-ion batteries. Therefore, it is necessary to characterize the failure mechanism of zinc-metal anodes, but the current failure mechanism of Zn anodes is not well characterized, leading to different mechanism elaborations. Although many studies have been conducted to improve the interfacial stability of Zn-metal anode interfaces, there are few systematic summaries of the key role played by in situ characterization in revealing the interfacial mechanisms of Zn-metal anodes. In this paper, the main problems and failure mechanism of zinc anode interface are discussed. Then, the application of in situ characterization technology in zinc anode interfaces and the latest research progress are summarized from different aspects. The purpose of this review is to better understand the development of zinc-ion batteries and the improvement of the stability of the Zn anode interface, thus accelerating the large-scale production of zinc batteries. Finally, the research direction of the in situ characterization of zinc anodes is summarized and suggested.

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 °C. 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 ultraviolet (UV) curing method with Zn(CF₃SO₃)₂ salt and polyvinyl alcohol (PVA) addition to increase the antifreezing ability and mechanical properties. The adsorption of water molecules by 2-hydroxyethyl acrylate (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 °C, 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 NaV₃O₈·1.5H₂O (NVO) cathode and hydrogel electrolyte possesses a high capacity retention ratio of 77% after 10,000 cycles at −20 °C. The flexible cell can power light-emitting diode (LED) lamp under bending, warping and cutting without liquid leakage and an electronic watch at the operating temperature of −20 °C.

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.