Abstract: Zn metal has been considered as a promising anode material for rechargeable aqueous metal-ion batteries. However, the propensity of dendrite growth during plating restricts its practical applicatio...

Abstract: Developing reversible lithium metal anodes with high rate capability is one of the central aims of current battery research. Lithium metal anodes are not only required for the development of innova...

Abstract: Owing to the high capacity of the metallic Zn anode and intrinsically safe aqueous electrolyte, aqueous Zn-based batteries are advanced energy storage technology alternatives beyond lithium-ion batteries, providing a cost benefit, high safety, and competitive energy density. There has been a new wave of research interest across the family of Zn batteries, but fundamental understanding of the Zn electrode and its performance improvement still remain inconclusive. Based on the pH value of the electrolyte, Zn-based batteries can be divided into two types, with one adopting alkaline electrolyte and the other mild (including slightly acidic) electrolyte. As the behavior of the Zn electrode in these two distinctive systems is different, their requirements to yield excellent performance are different. In this Review, we present a comprehensive overview of the Zn electrode and its fundamentals in both systems. First, the differences and similarities of the Zn electrode in both systems are outlined. Specific attention is paid to the working principles and technical challenges. Then, Zn electrode issues and recently proposed strategies for each system are summarized and compared. Finally, a perspective on future research directions towards practical applications of aqueous Zn batteries is included.

Abstract: Metallic zinc is an attractive anode material for aqueous rechargeable batteries because of its high theoretical capacity and low cost. However, state-of-the-art zinc anodes suffer from low coulombic efficiency and severe dendrite growth during stripping/plating processes, hampering their practical applications. Here we show that eutectic-composition alloying of zinc and aluminum as an effective strategy substantially tackles these irreversibility issues by making use of their lamellar structure, composed of alternating zinc and aluminum nanolamellas. The lamellar nanostructure not only promotes zinc stripping from precursor eutectic Zn88Al12 (at%) alloys, but produces core/shell aluminum/aluminum sesquioxide interlamellar nanopatterns in situ to in turn guide subsequent growth of zinc, enabling dendrite-free zinc stripping/plating for more than 2000 h in oxygen-absent aqueous electrolyte. These outstanding electrochemical properties enlist zinc-ion batteries constructed with Zn88Al12 alloy anode and KxMnO2 cathode to deliver high-density energy at high levels of electrical power and retain 100% capacity after 200 hours. Aqueous rechargeable Zn-ion batteries are attractive energy storage devices, but their wide adoption is impeded by the irreversible metallic Zn anode. Here the authors report lamellar-nanostructured eutectic Zn/Al alloys as reversible and dendrite-free anodes for improved battery performance.

Abstract: Despite the prevalence of lithium ion batteries in modern technology, the search for alternative electrochemical systems to complement the global battery portfolio is an ongoing effort. The search has resulted in numerous candidates, among which mildly acidic aqueous zinc ion batteries have recently garnered significant academic interest, mostly due to their inherent safety. As the anode is often fixed as zinc metal in these systems, most studies address the absence of a suitable cathode for reaction with zinc ions. This has led to aggressive research into viable intercalation cathodes, some of which have shown impressive results. However, many investigations often overlook the implications of the zinc metal anode, when in fact the anode is key to determining the energy density of the entire cell. In this regard, we aim to shed light on the importance of the zinc metal anode. This perspective offers a brief discussion of zinc electrochemistry in mildly acidic aqueous environments, along with an overview of recent efforts to improve the performance of zinc metal to extract key lessons for future research initiatives. Furthermore, we discuss the energy density ramifications of the zinc anode with respect to its weight and reversibility through simple calculations for numerous influential reports in the field. Finally, we offer some perspectives on the importance of optimizing zinc anodes as well as a future direction for developing high-performance aqueous zinc ion batteries.

Abstract: Rechargeable aqueous zinc-ion batteries are a promising candidate for next-generation energy storage devices. However, their practical application is limited by the severe safety issue caused by uncontrollable dendrite growth on zinc anodes. Here we develop faceted titanium dioxide with relatively low zinc affinity, which can restrict dendrite formation and homogenize zinc deposition when served as the protective layer on zinc anodes. The as-prepared zinc anodes can be stripped and plated steadily for more than 460 h with low voltage hysteresis and flat voltage plateau in symmetric cells. This work reveals the key role of crystal orientation in zinc affinity and its internal mechanism is suitable for various crystal materials applied in the surface modification of other metal anodes such as lithium and sodium. Zinc affinity plays a key role in the zinc plating and stripping processes but its internal mechanism is still unclear. Here, the authors report a protective layer with controllable zinc affinity by adjusting the crystal orientation to suppress the dendrite growth on the zinc anode interface.

Abstract: Carbon-based materials have been considered as the most promising anode materials for both sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs), owing to their good chemical stability, high electrical conductivity, and environmental benignity. However, due to the large sizes of sodium and potassium ions, it is a great challenge to realize a carbon anode with high reversible capacity, long cycle life, and high rate capability. Herein, by rational design, N-doped 3D mesoporous carbon nanosheets (N-CNS) are successfully synthesized, which can realize unprecedented electrochemical performance for both SIBs and PIBs. The N-CNS possess an ultrathin nanosheet structure with hierarchical pores, ultrahigh level of pyridinic N/pyrrolic N, and an expanded interlayer distance. The beneficial features that can enhance the Na-/K-ion intercalation/deintercalation kinetic process, shorten the diffusion length for both ions and electrons, and accommodate the volume change are demonstrated. Hence, the N-CNS-based electrode delivers a high capacity of 239 mAh g-1 at 5 A g-1 after 10 000 cycles for SIBs and 321 mAh g-1 at 5 A g-1 after 5000 cycles for PIBs. First-principles calculation shows that the ultrahigh doping level of pyridinic N/pyrrolic N contributes to the enhanced sodium and potassium storage performance by modulating the charge density distribution on the carbon surface.

Abstract: Aqueous Zn-ion batteries (ZIBs) are promising safe energy storage systems that have received considerable attention in recent years. Based on the electrochemical behavior of Zn2+ in the charging and discharging process, herein we review the research progress on anode materials for use in aqueous ZIBs based on two aspects: Zn deposition and Zn2+ intercalation. To date, Zn dendrite, corrosion, and passivation issues have restricted the development of aqueous ZIBs. However, many strategies have been developed, including structural design, interface protection of the Zn anode, Zn alloying, and using polymer electrolytes. The main aim is to stabilize the Zn stripping/plating layer and limit side reactions. Zn2+-intercalated anodes, with a high Zn2+ storage capacity to replace the current metal Zn anode, are also a potential option. Finally, some suggestions have been put forward for the subsequent optimization strategy, which are expected to promote further development of aqueous ZIBs.

Abstract: Summary Li metal has been attracting increasing attention as an anode in all-solid-state batteries because of its lowest electrochemical potential and high capacity, although the problems caused by dendritic growth impedes its further application. For a long time, all-solid-state Li metal batteries (ASLBs) are regarded to revive Li metal due to high mechanical strength. However, numerous works revealed that the dendrite issue widely exists in ASLBs, and the mechanism is complex. This review provides a systematic and in-depth understanding of the thermodynamic, kinetic, electrochemical, chemomechnical, structural stability, and characterizations of Li dendrite in ASLBs. First, the mechanisms for dendrite formation and propagation in polymer, ceramic and glass electrolyte were discussed. Subsequently, based on these mechanisms of dendrite growth, we reviewed various strategies for dendrite suppression. Furthermore, advanced characterization techniques were reviewed for better understanding of dendrite in solid-state batteries.

Abstract: To advance current Li rechargeable batteries further, tremendous emphasis has been made on the development of anode materials with higher capacities than the widely commercialized graphite. Some of these anode materials exhibit capacities above the theoretical value predicted based on conventional mechanisms of Li storage, namely insertion, alloying, and conversion. In addition, in contrast to conventional observations of loss upon cycling, the capacity has been found to increase during repeated cycling in a significant number of cases. As the internal environment in the battery is very complicated and continuously changing, these abnormal charge storage behaviors are caused by diverse reactions. In this review, we will introduce our current understanding of reported reactions accounting for the extra capacity. It includes formation/decomposition of electrolyte-derived surface layer, the possibility of additional charge storage at sharp interfaces between electronic and ionic sinks, redox reactions of Li-containing species, unconventional activity of structural defects, and metallic-cluster like Li storage. We will also discuss how the changes in the anode can induce capacity increase upon cycling. With this knowledge, new insights into possible strategies to effectively and sustainably utilize these abnormal charge storage mechanisms to produce vertical leaps in performance of anode materials will be laid out.

Abstract: High-rate lithium (Li) ion batteries that can be charged in minutes and store enough energy for a 350-mile driving range are highly desired for all-electric vehicles. A high charging rate usually leads to sacrifices in capacity and cycling stability. We report use of black phosphorus (BP) as the active anode for high-rate, high-capacity Li storage. The formation of covalent bonds with graphitic carbon restrains edge reconstruction in layered BP particles to ensure open edges for fast Li+ entry; the coating of the covalently bonded BP-graphite particles with electrolyte-swollen polyaniline yields a stable solid-electrolyte interphase and inhibits the continuous growth of poorly conducting Li fluorides and carbonates to ensure efficient Li+ transport. The resultant composite anode demonstrates an excellent combination of capacity, rate, and cycling endurance.

Abstract: Zinc metal anode has garnered a great deal of scientific and technological interest. Nevertheless, major bottlenecks restricting its large-scale utilization lie in the poor electrochemical stability and unsatisfactory cycling life. Herein, a Janus separator is developed via directly growing vertical graphene (VG) carpet on one side of commercial glass fiber separator throughout chemical vapor deposition. A simple air plasma treatment further renders the successful incorporation of oxygen and nitrogen heteroatoms on bare graphene. Thus-derived 3D VG scaffold affording large surface area and porous structure can be viewed as a continuation of planar zinc anode. In turn, the Janus separator harvests homogenous electric field distribution and lowered local current density at the interface of the anode/electrolyte, as well as harnesses favorable zincophilic feature for building-up uniform Zn ionic flux. Such a separator engineering enables an impressive rate and cycle performance (93% over 5000 cycles at 5 A g-1 ) for Zn-ion hybrid capacitors and outstanding energy density (182 Wh kg-1 ) for V2 O5 //Zn batteries, respectively. This strategy with large scalability and cost-effectiveness represents a universal route to protect prevailing metal anodes (Zn, Na, K) in rechargeable batteries.

Abstract: Solid-state electrolytes (SSEs) are widely considered as an “enabler” to inhibit dendrite growth of lithium-metal anodes for high-energy and highly safe next-generation batteries. However, recent s...

Abstract: Rechargeable lithium-ion batteries with high energy density that can be safely charged and discharged at high rates are desirable for electrified transportation and other applications1-3. However, the sub-optimal intercalation potentials of current anodes result in a trade-off between energy density, power and safety. Here we report that disordered rock salt4,5 Li3+xV2O5 can be used as a fast-charging anode that can reversibly cycle two lithium ions at an average voltage of about 0.6 volts versus a Li/Li+ reference electrode. The increased potential compared to graphite6,7 reduces the likelihood of lithium metal plating if proper charging controls are used, alleviating a major safety concern (short-circuiting related to Li dendrite growth). In addition, a lithium-ion battery with a disordered rock salt Li3V2O5 anode yields a cell voltage much higher than does a battery using a commercial fast-charging lithium titanate anode or other intercalation anode candidates (Li3VO4 and LiV0.5Ti0.5S2)8,9. Further, disordered rock salt Li3V2O5 can perform over 1,000 charge-discharge cycles with negligible capacity decay and exhibits exceptional rate capability, delivering over 40 per cent of its capacity in 20 seconds. We attribute the low voltage and high rate capability of disordered rock salt Li3V2O5 to a redistributive lithium intercalation mechanism with low energy barriers revealed via ab initio calculations. This low-potential, high-rate intercalation reaction can be used to identify other metal oxide anodes for fast-charging, long-life lithium-ion batteries.

Abstract: Rechargeable aqueous zinc-ion batteries (ZIBs) have attracted increasing attention as an energy storage technology for large-scale applications, due to their high capacity (820 mA h g−1 and 5854 A h L−1), inherently high safety, and their low cost. However, the overall performance of ZIBs has been seriously hindered by the poor rechargeability of Zn anodes, because of the dendrite growth, passivation, and hydrogen evolution problems associated with Zn anodes. Herein, Al2O3 coating by an atomic layer deposition (ALD) technique was developed to address the aforementioned problems and improve the rechargeability of Zn anodes for ZIBs. By coating the Zn plate with an ultrathin Al2O3 layer, the wettability of Zn was improved and corrosion was inhibited. As a result, the formation of Zn dendrites was effectively suppressed, with a significantly improved lifetime in the Zn–Zn symmetric cells. With the optimized coating thickness of 100 cycles, 100Al2O3@Zn symmetric cells showed a reduced overpotential (36.5 mV) and a prolonged life span (over 500 h) at 1 mA cm−2. In addition, the 100Al2O3@Zn has been verified in Zn–MnO2 batteries using layered δ-MnO2 as the cathode and consequently exhibits superior electrochemical performance with a high capacity retention of 89.4% after over 1000 cycles at a current density of 1 mA cm−2 (3.33C for MnO2) was demonstrated. It is expected that the novel design of Al2O3 modified Zn anodes may pave the way towards high-performance aqueous ZIBs and shed light on the development of other metal anode-based battery systems.

Abstract: With the rapid expansion in energy demands and depletion of fossil fuel reservoirs, the importance of clean energy production and storage has increased drastically. The renewable energy recourses are cost effective, sustainable and carbon dioxide emission free alternatives. Nevertheless, this energy is not always available and needs to be stored. Lithium ion batteries (LIBs) are rapidly used in various applications such as powering electronics, electric vehicles and grid energy storage. However, the increasing concerns regarding load leveling of renewable energy and rise in cost of LIBs due to limited availability of lithium reserves arises doubts whether LIBs alone can meet the rising demands for mid-to-large-scale energy storage. Therefore, attention has been shifted towards development of sodium ion batteries (SIBs) which have wide reserves and low precursor cost and thus is considered as appropriate choice for solar and wind energy development. The prime problem encountered in development of large-scale SIBs is the low effectiveness of appropriate anode material because of large size and sluggish kinetics of Na ions. A comprehensive study regarding anode materials is reported focusing on storage mechanism and structural changes involved during storage of Na ions in various classes of anode materials including carbon-based materials, conversion, conversion/alloying and organic materials. A brief overview of various components of SIBs such as cathode, electrolyte and separator are also discussed.

Abstract: Sodium-based dual-ion batteries (Na-DIBs) show a promising potential for large-scale energy storage applications due to the merits of environmental friendliness and low cost. However, Na-DIBs are generally subject to poor rate capability and cycling stability for the lack of suitable anodes to accommodate large Na+ ions. Herein, we propose a molecular grafting strategy to in situ synthesize tin pyrophosphate nanodots implanted in N-doped carbon matrix (SnP2O7@N-C), which exhibits a high fraction of active SnP2O7 up to 95.6 wt% and a low content of N-doped carbon (4.4 wt%) as the conductive framework. As a result, this anode delivers a high specific capacity ∼400 mAh g-1 at 0.1 A g-1, excellent rate capability up to 5.0 A g-1 and excellent cycling stability with a capacity retention of 92% after 1200 cycles under a current density of 1.5 A g-1. Further, pairing this anode with an environmentally friendly KS6 graphite cathode yields a SnP2O7@N-C||KS6 Na-DIB, exhibiting an excellent rate capability up to 30 C, good fast-charge/slow-discharge performance and long-term cycling life with a capacity retention of ∼96% after 1000 cycles at 20 C. This study provides a feasible strategy to develop high-performance anodes with high-fraction active materials for Na-based energy storage applications.

Abstract: In this work, the carbon balance during high-rate CO2 reduction in flow electrolyzers was rigorously analyzed. The CO2 consumption at gas-diffusion electrodes due to electrochemical conversion and reaction with OH− at the electrode/electrolyte interface leads to a substantial reduction in the volumetric flowrate of gas flow out of the electrolyzer, especially when highly concentrated alkaline electrolytes and elevated current densities are utilized, which is primarily due to an elevated pH at cathode/electrolyte interface. Without considering the CO2 consumption, the faradaic efficiencies for major gas products could be significantly overestimated during high current density CO2 reduction conditions, particularly in the case of high pH electrolyte. In addition, a detailed carbon balance path is elucidated via a two-step procedure of CO2 reaction with OH− at the cathode/electrolyte interface and subsequent CO2 generation at the anode/electrolyte interface caused by a relatively low pH in the vicinity of the anode. Based on the proposed two-step carbon balance path, a systematic exploration of gases released in the anolyte reveals the transformation of a HCO3− or OH− catholyte to a CO32− catholyte, which was further confirmed by pH measurements.

Abstract: Constructing heterojunction and introducing interfacial interaction by designing ideal structures have the inherent advantages of optimizing electronic structure and macroscopic mechanical property...