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Lithium metal batteries (LMBs) are considered one of the most promising next-generation rechargeable batteries due to their high specific capacity. However, severe dendrite growth and subsequent formation of dead lithium (Li) during the battery cycling process impede its practical application. Although extensive experimental studies have been conducted to investigate the cycling process, and several theoretical models were developed to simulate the Li dendrite growth, there are limited theoretical studies on the dead Li formation, as well as the entire cycling process. Herein, we developed a phase-field model to simulate both electroplating and stripping process in a bare Li anode and Li anode covered with a protective layer. A step function is introduced in the stripping model to capture the dynamics of dead Li. Our simulation clearly shows the growth of dendrites from a bare Li anode during charging. These dendrites detach from the bulk anode during discharging, forming dead Li. Dendrite growth becomes more severe in subsequent cycles due to enhanced surface roughness of the Li anode, resulting in an increasing amount of dead Li. In addition, it is revealed that dendrites with smaller base diameters detach faster at the base and produce more dead lithium. Meanwhile, the Li anode covered with a protective layer cycles smoothly without forming Li dendrite and dead Li. However, if the protective layer is fractured, Li metal preferentially grows into the crack due to enhanced Li-ion (Li + ) flux and forms a dendrite structure after penetration through the protective layer, which accelerates the dead Li formation in the subsequent stripping process. Our work thus provides a fundamental understanding of the mechanism of dead Li formation during the charging/discharging process and sheds light on the importance of the protective layer in the prevention of dead Li in LMBs.

Aqueous manganese metal batteries have emerged as promising candidates for stationary storage due to their natural abundance, safety, and high energy density. However, the high chemical reactivity and sluggish migration kinetics of the Mn metal anode induce a severe hydrogen evolution reaction (HER) and dendrite formation, respectively. The situation deteriorates in the low-concentration electrolyte especially. Here, we propose a novel approach to construct an Mn-enriched interfacial layer (Mn@MIL) on the Mn metal anode surface to address these challenges simultaneously. The Mn@MIL acts as a physical barrier to not only suppress HER but also accelerate the Mn 2+ diffusion kinetics through the Mn 2+ saturated interfacial layer to inhibit dendrite growth. Therefore, in the low-concentration electrolyte (1 M MnCl 2 ), the Mn||Mn symmetric cells and Mn||V 2 O 5 full cells with high mass loading demonstrate promising cycling stability with minimal polarization and parasitic reactions, making them more suitable for practical applications in a smart grid.

Aqueous zinc-ion batteries (AZIBs) are widely regarded as desirable energy storage devices due to their inherent safety and low cost. Hydrogel polymer electrolytes (HPEs) are cross-linked polymers filled with water and zinc salts. They are not only widely used in flexible batteries but also represent an ideal electrolyte candidate for addressing the issues associated with the Zn anode, including dendrite formation and side reactions. In HPEs, an abundance of hydrophilic groups can form strong hydrogen bonds with water molecules, reducing water activity and inhibiting water decomposition. At the same time, special Zn 2+ transport channels can be constructed in HPEs to homogenize the Zn 2+ flux and promote uniform Zn deposition. However, HPEs still face issues in practical applications, including poor ionic conductivity, low mechanical strength, poor interface stability, and narrow electrochemical stability windows. This Review discusses the issues associated with HPEs for advanced AZIBs, and the recent progresses are summarized. Finally, the Review outlines the opportunities and challenges for achieving high performance HPEs, facilitating the utilization of HPEs in AZIBs.

Aqueous zinc-ion batteries (AZIBs) have gained significant attentions for their inherent safety and cost-effectiveness. However, challenges, such as dendrite growth and anodic corrosion at the Zn anode, hinder their commercial viability. In this paper, an organic-inorganic coating layer (Nafion-TiO 2 ) was introduced to protect the Zn anode and electrolyte interface. Briefly, Nafion effectively shields against the corrosion from water molecules through the hydrophobic wall of -CF 3 and guided zinc deposition from the -SO 3 functional group, while TiO 2 particles with a higher Young's modulus (151 GPa vs 120 GPa from Zn metal) suppress the zinc dendrite formation. As a result, with the protection of Nafion-TiO 2, the symmetrical Zn∥Zn battery shows an improved cycle life of 1,750 h at 0.5 mA cm -2 , and the full cell based on Zn∥MnO 2 shows a long cycle life over 1,500 cycles at 1 A g -1 . Our research offers a novel approach for protecting zinc metal anodes, potentially applicable to other metal anodes such as those in lithium and sodium batteries.

Lithium (Li) metal has garnered significant attention as the preferred anode for high-energy lithium metal batteries. However, safety concerns arising from the growth of Li dendrites have hindered the advancement of Li metal batteries. In this study, we first elucidate the impact of external pressure and internal stress on dendrite growth and dissolution behavior of Li metal batteries during continuous charging-discharging cycles, employing a developed electrochemomechanical phase-field model. A typical parameter is defined to calculate the amount of dead Li that affects the electrochemical performance of Li metal batteries during multiple cycles. The underlying mechanisms of dendrites observed from in situ experiments are explained through the developed phase-field model. After charging/discharging, dendrites with a treelike structure yield a greater amount of dead Li compared to those with a needlelike configuration. Increasing the pressure appropriately can effectively reduce the growth points of dendrites and suppress the Li dendrite growth. Excessive pressure not only induces dendritic fractures that lead to the formation of dead Li but also undermines the battery performance. The accumulated internal stress might threaten the structural stability of the Li metal, thereby influencing the evolution of the Li dendrite morphology. A reasonable strategy is proposed to strike a balance between external pressure and the growth and dissolution of Li dendrites. These findings offer valuable insights into the judicious application of pressure to mitigate the advancement of electroplating reactions.

Difluoroethylene carbonate (DFEC) featuring abundant fluorine atoms has been proposed as a multifunctional electrolyte additive to boost the stability of the electrolyte-electrode interphase of lithium metal batteries. Thus, introducing the DFEC additive enables a high capacity retention rate of the Li||NCM811 full cell (up to 75% after 200 cycles) at 4.5 V high voltage.

Uncontrolled dendrite growth and water-related side reactions in mild electrolytes are the main causes of poor cycling stability of zinc anodes, resulting in the deterioration of aqueous zinc-based batteries. Herein, a multifunctional fluorapatite (Ca 5 (PO 4 ) 3 F) aerogel (FAG) interface layer is proposed to realize highly stable zinc anodes via the integrated regulation of Zn 2+ migration kinetics and Zn (002) orientation deposition. Owing to the well-defined aerogel nanochannels and the rich Zn 2+ adsorption sites resulting from the ion exchange between Ca 2+ and Zn 2+ , the FAG interface layer could significantly accelerate the Zn 2+ migration and effectively homogenize the Zn 2+ flux and nucleation sites, thus promoting rapid and uniform Zn 2+ migration at the electrode/electrolyte interface. Additionally, during the cycling process, the F atoms from FAG promote the in situ generation of ZnF 2 , which facilitates the manipulation of the preferred Zn (002) orientation deposition, thus efficiently suppressing dendrite growth and side reactions by combining with the above synergistic effects. Consequently, the FAG-modified Zn anode displays a stable cycle life of over 4000 h at 1 mA cm -2 and exhibits highly reversible Zn plating/stripping behavior. Meanwhile, the Zn||MnO 2 full cells exhibit improved cycle stability over 2000 cycles compared with that of the bare Zn, highlighting the virtues of the FAG protective layer for highly reversible Zn anodes. Our work brings the insight in to stabilize Zn anodes and power the commercial applications of aqueous zinc-based batteries.

Aqueous zinc-ion batteries are considered as an ideal substitute for lithium-ion batteries due to their abundant resource storage, high safety, and low price. However, zinc anodes exhibit poor reversibility and cyclic stability in most conventional aqueous electrolytes. Herein, an environmentally friendly Zn(CH 3 SO 3 ) 2 electrolyte is proposed to solve the problems of common aqueous electrolytes. The bulky CH 3 SO 3 - anions can regulate the solvation structure of Zn 2+ by replacing some water molecules in the primary solvation sheath of Zn 2+ , thus slowing the hydrogen evolution side reactions and formation of zinc dendrite. Additionally, the changing solvation structure weakens the bonding between Zn 2+ and the surrounding water molecules, which is conducive to the transport and charge transfer of Zn 2+ , thus improving the battery capacity. In the Zn(CH 3 SO 3 ) 2 electrolyte, Zn plating/stripping exhibits a high Coulombic efficiency of >98% and long-term cyclic stability over 800 h. The specific capacity of the assembled Zn//V 2 O 5 cell in 3 mol L -1 Zn(CH 3 SO 3 ) 2 reaches 350 mA h g -1 at 0.1 A g -1 , much higher than that in the ZnSO 4 electrolyte (213 mA h g -1 ). In conclusion, this work offers insights into the exploration of advanced green electrolyte systems for zinc-ion batteries.

Liquid cell transmission electron microscopy has become a powerful and increasingly accessible technique for in situ studies of nanoscale processes in liquid and solution phase. Exploring reaction mechanisms in electrochemical or crystal growth processes requires precise control over experimental conditions, with temperature being one of the most critical factors. Here we carry out a series of crystal growth experiments and simulations at different temperatures in the well-studied system of Ag nanocrystal growth driven by the changes in redox environment caused by the electron beam. Liquid cell experiments show strong changes in both morphology and growth rate with temperature. We develop a kinetic model to predict the temperature-dependent solution composition, and we discuss how the combined effect of temperature-dependent chemistry, diffusion, and the balance between nucleation and growth rates affect the morphology. We discuss how this work may provide guidance in interpreting liquid cell TEM and potentially larger-scale synthesis experiments for systems controlled by temperature.

Lithium-sulfur chemistry has greatly expanded the boundaries of lithium batteries, but the persistent parasitic reaction of soluble sulfur intermediates with lithium anode remains a primary challenge. Understanding and regulating the solvation structures of lithium ions (Li + ) and polysulfides (LiPSs) are critical to addressing the above issues. Herein, inspired by the natural superhydrophilic resistance to contamination, we developed a zwitterionic nanoparticles (ZWP) separator capable of modulating the solvated of Li + and LiPSs. The dense solvated layer induced by ZWP effectively prevents the movement of LiPSs without compromising Li + transport. Moreover, the high electrolyte affinity of the ZWP effectively results in minimizing the deposition of LiPSs on the separator. Furthermore, the structure of the solvated Li + and LiPSs is also unveiled by molecular simulation and nuclear magnetic resonance (NMR). In addition, in situ UV setup proved the ZWP separator can effectively suppress the shuttle of LiPSs. The restricted space formed by the tightly packed ZWP stabilizes the lithium deposition and regulates dendrite growth. Consequently, the performance of lithium-sulfur batteries is significantly improved and good cycle stability is maintained even at high sulfur loadings (5 mg cm -2 ). This contribution provides a new insight into the rational design of lithium-sulfur battery separators.

Aqueous Zn batteries (AZBs) are a promising energy storage technology, due to their high theoretical capacity, low redox potential, and safety. However, dendrite growth and parasitic reactions occurring at the surface of metallic Zn result in severe instability. Here we report a new method to achieve ultrafine Zn nanograin anodes by using ethylene glycol monomethyl ether (EGME) molecules to manipulate zinc nucleation and growth processes. It is demonstrated that EGME complexes with Zn 2+ to moderately increase the driving force for nucleation, as well as adsorbs on the Zn surface to prevent H-corrosion and dendritic protuberances by refining the grains. As a result, the nanoscale anode delivers high Coulombic efficiency (ca. 99.5%), long-term cycle life (over 366 days and 8800 cycles), and outstanding compatibility with state-of-the-art cathodes (ZnVO and AC) in full cells. This work offers a new route for interfacial engineering in aqueous metal-ion batteries, with significant implications for the commercial future of AZBs.

Developing a poly(ethylene oxide) (PEO)-based polymer electrolyte with high ionic conductivity and robust mechanical property is beneficial for real applications of all-solid-state lithium metal batteries (ASSLMBs). Herein, an excellent organic/inorganic interface compatibility of all-solid-state composite polymer electrolytes (CPEs) is achieved using a novel imidazolium-type poly(ionic liquid) with strong electrostatic interactions, providing insights into the achievement of highly stable CPEs. The key properties such as micromorphologies, thermal behavior, crystallinity, t Li + , mechanical property, lithium anode surficial morphology, and electrochemical performance are systematically investigated. The combined experimental and density functional theory (DFT) simulation results exhibit that the strong electrostatic interaction and ion-dipole interaction cooperated to improve the compatibility of the CPE, with a high ionic conductivity of 1.46 × 10 -4 S cm -1 at 40 °C and an incredible mechanical strain of 2000% for dendrite-free and highly stable all-solid-state LMBs. This work affords a promising strategy to accelerate the development of PEO-based polymer electrolytes for real applications in ASSLMBs.

Enabling highly stable alkali metal anodes in gas atmospheres, such as oxygen and carbon dioxide, is critical for the implementation of emerging metal-gas batteries with high energy density and improved safety. Herein, we demonstrate a three-salt electrolyte system to tackle the problems of gas crossover and uncontrolled metallic dendrite growth for all-climate sodium-gas batteries by the formation of an electrochemically/chemically stable solid electrolyte interphase that is rich in fluoride and sulfate compounds. Consequently, the sodium metal anodes present high reversible capacity (10 mAh cm -2 at 1.5 mA cm -2 ) and long cycle life (2000 h) in gas atmospheres across a wide operating temperature range. Using the three-salt electrolyte, all-climate sodium-oxygen and sodium-carbon dioxide batteries are demonstrated with a reversible capacity of 1000 mAh g -1 over 100 cycles at ambient temperature and good adaptability to temperatures from -60 to 60 °C.

Severe challenges are restraining the practical application of solid-state batteries, such as the dendrite growth and unsatisfactory compatibility between solid electrolyte and electrode. Here, we propose an interface dynamic control (IDC) strategy to ensure the stable operation of NASICON-based solid-state sodium batteries. First, we introduce intergranular phase (CuO) to effectively promote the densification of Na 3 Zr 2 Si 2 PO 12 with an optimized ionic conductivity of 1.74 × 10 -3 S cm -1 at 25 °C. Moreover, the kinetically formed Na-Cu-O interlayer reveals outstanding conductive capability. The dramatically reduced interfacial area-specific resistance (70 ohm cm -2 ) boosts the resistance to Na dendrite growth, ensuring the excellent cycling stability of symmetric Na cells at a current density of 0.4 mA cm -2 and room temperature. All-solid-state sodium metal batteries with Na 3 V 1.5 Cr 0.5 (PO 4 ) 3 cathode and modified Na 3 Zr 2 Si 2 PO 12 ceramic electrolyte reveal a high retention of 87.4% at 100 mA g -1 over 300 cycles. This work opens up a new route for the rational interface design of NASICON-structure solid electrolyte toward the application in the high energy-density and high safety electrochemical energy storage devices.

The quiescent electrolyte causes serious concentration polarization and dendrite problems during the charging and discharging of the battery, which restricts the development of metal secondary batteries and flow batteries. Herein, we report a new concept of ion motors, with which the directional driving and uniformity of the electrolyte are realized to eliminate the concentration polarization and dendritic phenomenon for secondary metal batteries and flow batteries without additional external energy. In this study, a dendrite-free secondary metal battery with ion motors is constructed to eliminate a considerable concentration polarization voltage by a tiny induced counter electromotive force generated by Lorentz force, significantly improving the output power and energy efficiency of the battery. An actual pump-free flow battery with an ion motor is also assembled, which overcomes the problems of low energy efficiency and the complex structure caused by the traditional flow battery requiring 1-2 pumps to drive the electrolyte. The efficiency of ion motors to drive the electrolyte is hundreds of times higher than that of the mechanical pump. Therefore, the ion motor provides a universal strategy for designing more pump-free flow batteries and metal secondary batteries without the risk of dendrites in the future.

Rechargeable aqueous zinc-ion batteries (ZIBs) have attracted extensive attention due to their low cost and high safety. However, the critical issues of dendrite growth and side reactions on the Zn metal anode hinder the commercialization of ZIBs. Herein, we demonstrated that the formation of Zn 4 SO 4 (OH) 6 ·5H 2 O byproducts is closely relevant to the direct contact between the Zn electrode and SO 4 2- /H 2 O. On the basis of this finding, we developed a cation-exchange membrane of perfluorosulfonic acid (PFSA) coated on the Zn surface to regulate the Zn plating/stripping behavior. Importantly, the PFSA film with abundant sulfonic acid groups could simultaneously block the access of SO 4 2- and H 2 O, accelerate the Zn 2+ ion transport kinetics, and uniformize the electrical and Zn 2+ ion concentration field on the Zn surface, thus achieving a highly reversible Zn plating/stripping process with corrosion-free and dendrite-free behavior. Consequently, the PFSA-modified Zn anode exhibits high reversibility with 99.5% Coulombic efficiency and excellent plating/stripping stability (over 1500 h), subsequently enabling a highly rechargeable Zn-MnO 2 full cell. The strategy of the cation-exchange membrane proposed in this work provides a simple but efficient method for suppression of side reactions.

Nonlithium (Li) metal-sulfur batteries are a viable technology for large-scale energy storage due to their relative high energy densities and low cost. However, their practical application is still hindered by the insufficient reversibility and/or limited cycling stability. Herein, we report a high-performance calcium/sodium-sulfur (Ca/Na-S) hybrid battery enabled by a multi-ion chemistry. The introduction of Na ions in the electrolyte greatly boosts the conversion of Ca polysulfides, which has been verified by theoretical calculation and experimental investigation. Meanwhile, the presence of Ca ions constructs a protective electrostatic shield around the initial protrusions on the Na metal anode without prereduction, thus efficiently suppressing the Na dendrite growth. The as-developed Ca/Na-S cell exhibited a high reversible capacity of 947 mAh g -1 at 0.1 C with long cycle life, clearly demonstrating the feasibility of this multi-ion strategy for developing low-cost non-Li metal-sulfur batteries.

Potassium-metal batteries are attractive candidates for low-cost and large-scale energy storage systems due to the abundance of potassium. However, K metal dendrite growth as well as volume expansion of K metal anodes on cycling have significantly hindered its practical applications. Although enhanced performance has been reported using carbon hosts with complicated structure engineering, they are not suitable for mass production. Herein, a highly potassiophilic carbon nanofiber paper with abundant oxygen-containing functional groups on the surface and a 3D interconnected network architecture is fabricated through a facile, scalable, and environmental-friendly biosynthesis method. As a host for K metal anode, uniform K nucleation and stable plating/stripping performance are demonstrated, with a stable cycling of 1400 h and a low overpotential of 45 mV, which are much better than all carbon hosts without complicated structure engineering. Moreover, full cells pairing the carbon nanofiber paper/K composite anodes with K 4 Fe(CN) 6 cathodes exhibit excellent cycle stability and rate capability. The results provide a promising way for realizing dendrite-free K metal anodes and high-performance potassium-ion batteries.

The lithium-secondary battery is considered to be the most prospective electrochemical energy storage in the upcoming decades. However, its real application still much depends on the effective strategy toward Li dendrite growth. After years of effort, many successful works have been reported on improving the solid-electrolyte interphase (SEI), either via electrolyte optimization or building artificial SEI while intrinsically adjusting the electrochemical reduction of Li + has been rarely mentioned. Inspired by the successful works in the electroplating industry, in this paper, a Li-chelating agent, benzo-15-crown-5 (B15C5) was used to regulate Li-reduction kinetics from an electrochemical view. Owing to the coordination with Li + , Li + + complex + e - → Li[complex] is generated and proved by a decreased i value. B15C5 confined within the PVC matrix has been coated on a Li anode. With thus-obtained B15C5-PVC-Li, dendrite growth has been significantly reduced and prolonged cycling has been observed in Li|Li symmetric cells. Electrochemically modulated Li deposition has been further accessed by the full cell of LiFePO 0 value. B15C5 confined within the PVC matrix has been coated on a Li anode. With thus-obtained B15C5-PVC-Li, dendrite growth has been significantly reduced and prolonged cycling has been observed in Li|Li symmetric cells. Electrochemically modulated Li deposition has been further accessed by the full cell of LiFePO 4 . This study provides an alternate approach to address the dendrite growth issue and sheds more light on the Li-deposition kinetics.2 . This study provides an alternate approach to address the dendrite growth issue and sheds more light on the Li-deposition kinetics.

High-energy-density Li-metal batteries are of great significance in the energy storage field. However, the safety hazards caused by Li dendrite growth and flammable organic electrolytes significantly hinder the widespread application of Li-metal batteries. In this work, we report a highly safe electrolyte composed of 4 M lithium bis(fluorosulfonyl)imide (LiFSI) dissolved in the single solvent trimethyl phosphate (TMP). By regulating the solvation structure of the electrolyte, a combination of nonflammability and Li dendrite growth suppression was successfully realized. Both Raman spectroscopy and molecular dynamics simulations revealed improved dendrite-free Li anode originating from the unique solvation structure of the electrolyte. Symmetric Li/Li cells fabricated using this nonflammable electrolyte had a long cycle life of up to 1000 h at a current density of 0.5 mA cm -2 . Furthermore, the Li 4 Ti 5 O 12 /TMP-4/Li full cells also exhibited excellent cycling performance with a high initial discharge capacity of 170.5 mAh g -1 and a capacity retention of 92.7% after 200 cycles at 0.2 C. This work provides an effective approach for the design of safe electrolytes with favorable solvation structure toward the large-scale application of Li-metal batteries.

The growth and proliferation of Li dendrites during repeated Li cycling has long been a crucial issue that hinders the development of secondary Li-metal batteries. Building a stable and robust solid state electrolyte interphase (SEI) on the Li-anode surface is regarded as a promising strategy to overcome the dendrite issues. In this work, we report a simple strategy to engineer the interface chemistry of Li-metal anodes by using tiny amounts of dimethyl sulfate (DMS, C 2 H 6 SO 4 ) as the SEI-forming additive. With the preferential reduction of DMS, an SEI layer composed of Li 2 S/Li 2 O forms on the Li surface. This inorganic SEI layer features high structural modulus and low interfacial resistant, enabling a dense and dendrite-free Li deposition as evidenced by scanning electron microscopy, atomic force microscopy, and in situ optical images. In addition, this SEI layer can prevent the deposited Li from direct contact with corrosive electrolytes, thus rendering an improved cycling stability of Li anodes with an average Coulombic efficiency of 97% for up to 150 cycles. When the DMS additive is introduced into a Li/NCM full cell, the cycle life of Li-metal batteries can be also improved significantly. This work demonstrates a feasible route to suppress Li dendrite growth by designing appropriate film-forming additives to regulate the interfacial properties of the SEI layer, and also the sulfonyl-based derivatives revealed in this work represent a large variety of new film-forming molecules, providing a broad selectivity for constructing high efficiency and cycle-stable Li anodes to address the intrinsic problems of rechargeable Li-metal batteries.

The safety issue caused by the dendrite growth is not only a key research problem in lithium-ion batteries but also a critical concern in alkali metal (i.e., Li, Na, and K)-oxygen batteries where a solid metal is usually used as the anode. Herein, we demonstrate the first dendrite-free K-O 2 battery at ambient temperature based on a liquid Na-K alloy anode. The unique liquid-liquid connection between the liquid alloy and the electrolyte in our alloy anode-based battery provides a homogeneous and robust anode-electrolyte interface. Meanwhile, we manage to show that the Na-K alloy is only compatible in K-O 2 batteries but not in Na-O 2 batteries, which is mainly attributed to the stronger reducibility of potassium and relatively more favorable thermodynamic formation of KO 2 over NaO 2 during the discharge process. It is observed that our K-O 2 battery based on a liquid alloy anode shows a long cycle life (over 620 h) and a low discharge-charge overpotential (about 0.05 V at initial cycles). Moreover, the mechanism investigation into the K-O 2 cell degradation shows that the O 2 crossover effect and the ether-electrolyte instability are the critical problems for K-O 2 batteries. In a word, this study provides a new route to solve the problems caused by the dendrite growth in alkali metal-oxygen batteries.