Rechargeable Metal Research Articles

Quantifying Capacity Loss Mechanisms of Li Metal Anodes Beyond Inactive Li0

Lithium metal anodes are promising alternatives to graphite for use in next-generation lithium-ion batteries due to their higher capacity (3,860 mAh/g vs. 372 mAh/g). However, Li anodes still display excessive capacity loss over cycling, leading to underwhelming Coulombic efficiency (CE, <99.9%) compared to graphite (>99.95%).1 These losses can derive from: (1) the formation of electronically isolated Li0 (often referred to as ‘dead’ or inactive’); and (2) the parasitic reactions between Li and the electrolyte that form the solid electrolyte interphase (SEI). Characterization of the Li anode has historically relied on surface characterization techniques such as XPS and FTIR, which cannot quantitatively reveal the total amounts of specific SEI phases. More precise quantification has recently become possible due to advances in chemical titration, which notably revealed that inactive Li0 is the dominant loss mechanism at low-to-moderate CE (<90%).2 At high CE (>90%), SEI losses are increasingly dominant and become the loss mode to minimize. Despite its importance, titration of SEI losses have thus far largely focused on LiH,3-5 with precise quantification of other accompanying phases still lacking.To bridge this gap, here we apply quantitative titration based on GC, ICP-AES and NMR to track an extended array of key SEI phases: semicarbonates (ROCO2Li), lithium carbide (Li2C2), olefins (RLi), LiF, P-containing phases, and total Li loss with, which teach new insights beyond inactive Li0. In 1 M LiPF6 EC/DEC, we demonstrate chemical resolution up to 71% of Li loss and 33% of SEI loss inventory. The analysis was also expanded to additional carbonate electrolytes of varying CEs (from <10% to >96%). Soluble SEI phases were particularly important at ultra-low CE (<10%), and their formation was suppressed higher CEs. Among the quantifiable SEI phases, ROCO2Li was consistently the major phase, but its proportions were invariant with CE. Instead, Li2C2, a minor phase, exhibited clear inverse correlation with CE. These results add further nuance beyond inactive Li0 to the current understanding of capacity loss, and demonstrate that, while minor phases often receive less focus and are harder to characterize, they can play governing roles in SEI function, particularly at high CE when formation of inactive Li0 is minimized. Hobold, G. M.; Lopez, J.; Guo, R.; Minafra, N.; Banerjee, A.; Shirley Meng, Y.; Shao-Horn, Y.; Gallant, B. M., Moving Beyond 99.9% Coulombic Efficiency for Lithium Anodes in Liquid Electrolytes. Nat. Energy 2021, 6 (10), 951-960. Fang, C.; Li, J.; Zhang, M.; Zhang, Y.; Yang, F.; Lee, J. Z.; Lee, M. H.; Alvarado, J.; Schroeder, M. A.; Yang, Y.; Lu, B.; Williams, N.; Ceja, M.; Yang, L.; Cai, M.; Gu, J.; Xu, K.; Wang, X.; Meng, Y. S., Quantifying Inactive Lithium in Lithium Metal Batteries. Nature 2019, 572 (7770), 511-515. Tao, M.; Xiang, Y.; Zhao, D.; Shan, P.; Sun, Y.; Yang, Y., Quantifying the Evolution of Inactive Li/Lithium Hydride and Their Correlations in Rechargeable Anode-Free Li Batteries. Nano Lett. 2022. Xu, G.; Li, J.; Wang, C.; Du, X.; Lu, D.; Xie, B.; Wang, X.; Lu, C.; Liu, H.; Dong, S.; Cui, G.; Chen, L., The Formation/Decomposition Equilibrium of LiH and Its Contribution on Anode Failure in Practical Lithium Metal Batteries. Angew. Chem. Int. Ed. Engl. 2021, 60 (14), 7770-7776. Xiang, Y.; Tao, M.; Zhong, G.; Liang, Z.; Zheng, G.; Huang, X.; Liu, X.; Jin, Y.; Xu, N.; Armand, M.; Zhang, J. G.; Xu, K.; Fu, R.; Yang, Y., Quantitatively Analyzing the Failure Processes of Rechargeable Li Metal Batteries. Sci. Adv. 2021, 7 (46), eabj3423.

Nanospinbar-Assisted Convective Ionic Transfer Toward Dendrite-Free Li Metal Batteries

Building high-energy-density batteries with Li-metal anodes (LMAs) featuring ultrahigh specific capacity (3860 mAh g−1) and low working voltage (−3.04 V vs. SHE) have been revisited to surpass the energy density limit of current Li-ion batteries. For instance, a successful transition from conventional graphite (372 mAh g–1) to ultrathin LMAs can deliver higher cell energies (over 500 Wh kg–1). Nonetheless, Li electrodeposition is challenging due to the dendrite formation and random growth. Extensive Li dendrite growth can enlarge the active surface area where side reactions occur, thereby severely deteriorating the Li surface and depleting the electrolyte, leading to poor cycling stability. Eventually, the Li dendrite tips can pierce the separator, causing cell short-circuiting, thereby increasing the safety risk. This is a major hurdle that must be overcome prior to commercialization. Therefore, inhibiting uneven dendritic Li plating is essential for safe and stable cycling of rechargeable lithium metal batteries (LMBs).Inhibiting uneven, dendritic Li electroplating is crucial for the safe and stable cycling of LMBs. Homogeneous, fast Li+ transport toward the Li surface is required for uniform, dendrite-free deposition. Electrodeposition strongly depends on the mass transfer of the ionic species. In a diffusion-limited regime, such as higher currents and lack of convection, inherently limited Li+ diffusion causes a strong concentration gradient or even total Li+ depletion. Moreover, traditional ionic transport of static liquid electrolytes involving electromigration and molecular diffusion can trigger a greater disparity in Li concentration over the Li surface, leading to irregular dendrite growth.This study presents a microturbulence-assisted convective Li+ transfer for suppressing dendrite growth using a magnetic nanospinbar (NSB)-dispersed colloidal electrolyte. We synthesized an ultrahigh-aspect-ratio NSB consisting of a paramagnetic Fe3O4 nanoparticle array and a silica outer coating. Manipulating the external electromagnetic force can remotely control the rotation of individual NSBs without dispersion failure, thereby generating a microturbulence flow inside the cell. Regardless of the electrolyte composition, rotating the NSB can reduce the Li+ diffusion layer thickness from the bulk and evenly redistribute Li+ flux over the Li surface, thereby suppressing Li dendrite growth. The NSB-dispersed electrolyte with advanced salt/solvent compositions demonstrated stable cycling of LMBs over 600 cycles at 70% capacity retention, thereby outperforming the NSB-free cell.Figure. 1. Concept of convective Li+ transfer assisted by remote NSB stirring. Apart from stagnant electrolytes, magnetic-field-responsive NSB dispersed in the liquid electrolyte can redistribute Li+ flux near LMA through remote stirring, enabling facile, homogenous Li+ transfer and thereby leading to uniform, dendrite-free Li electroplating Figure 1

Carbonate-Based Localized High Concentrated Electrolyte for Long-Cycle-Life Lithium Metal Batteries

Rechargeable Lithium Metal Batteries (LMBs) using high-voltage cathodes can deliver the highest possible energy densities among all electro-chemistries. However, the notorious reactivity of metallic lithium as well as the catalytic nature of the cathode materials largely prevent their practical application. Here, we demonstrate a formulated carbonate-based high concentrated electrolyte with LiPF6 that supports the most commercial aggressive and high-voltage cathode to realize a highly stable Li metal full-cell with limited metallic Li. The formation of stable Li2O/LiF-rich solid electrolyte interface (SEI) layers afforded stable operations of resultant LMBs under practical working conditions. Our electrolyte contributes to both high efficiency of 99.5% for Li||Cu half cell and ~100% for lithium full cells based on 4.3 V Ni-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes. Notably, at a loading of 4.0 mAh.cm−2, our full cells showed a capacity retention of ~80% over 280 cycles at lean electrolyte condition of 5 μL.mAh-1. The effective stabilization that inhibited the aggressive chemistries at extreme potentials in LMBs upon practical conditions by our electrolyte was determined to be the formation of the dense, inorganic-rich interphase.

Flash Point of Gel-Polymer Electrolytes: Effect of the Molecular Interaction between Nitrile (HNBR) and Carbonyl (PC)

Gel-polymer electrolytes are receiving increasing attention as they compromise between a good ionic conductivity (10-3S/cm) [1, 2] and good safety features. The solvent trapped into the polymeric matrix increases the ionic conductivity while the polymeric matrix enhances safety due to its mechanical strength repressing dendrite growth [3, 4]. Gel polymer electrolytes are almost universally presumed to be less flammable than current commercialize battery (organic liquid electrolyte) [5, 6]. However, there is no universal test to compare the flammability of a liquid and the flammability of a gel.Our work focuses on the flash point measurement of gel-polymer electrolytes. The flash point temperature is a standardized test and is one of the top experiments to measure flammability [7]. The Flash point temperature is well studied for liquid electrolytes [7, 8] but had never been conducted for gel-polymers. We developed a method to analyze the flash point of gel-polymer electrolytes by pairing the closed-cup flash point tester with a thermal imaging camera. This new apparatus was used it to analyze a promising system: HNBR with different grade of nitrile doped with PC. The goal is to find the relation between the flash point and the nitrile contains in the polymeric matrices.Our research sheds light on the effect of molecular interactions between the nitrile of HNBR and the carbonyl of PC on the flammability of the overall gel-polymer electrolyte with FT-IR. The study has also been conducted adding a lithium salt (LiTFSI) to be representative of real battery application. Agrawal, R.C. and G.P. Pandey, Solid polymer electrolytes: materials designing and all-solid-state battery applications: an overview. J. Phys. D: Appl. Phys., 2008. 41(22): p. 223001-223019.Cheng, X., et al., Gel Polymer Electrolytes for Electrochemical Energy Storage. Advanced Energy Materials, 2018. 8(7).Hassouna, J. and B. Scrosati, Review—Advances in Anode and Electrolyte Materials for the Progress of Lithium-Ion and beyond Lithium-Ion Batteries. Journal of The Electrochemical Society, 2015. 162 p. A2582-A2588.Ren, W., et al., Advanced gel polymer electrolytes for safe and durable lithium metal batteries: Challenges, strategies, and perspectives. Energy Storage Materials, 2021. 34: p. 515-535.Castillo, J., et al., Safe, Flexible, and High-Performing Gel-Polymer Electrolyte for Rechargeable Lithium Metal Batteries. Chemistry of Materials, 2021. 33(22): p. 8812-8821.Li, Q., et al., Progress in electrolytes for rechargeable Li-based batteries and beyond. Green Energy & Environment, 2016. 1(1): p. 18-42.Liu, X.S. and Z.Y. Liu, Research Progress on Flash Point Prediction. Journal of Chemical and Engineering Data, 2010. 55(9): p. 2943-2950.Catoire, L., S. Paulmier, and V. Naudet, Experimental determination and estimation of closed cup flash points of mixtures of flammable solvents. Process Safety Progress, 2006. 25(1): p. 33-39.

(Invited) Mechanistic Understandings of Interfacial Instabilities of Na and Zn Metal Anodes in Liquid Electrolytes

Next-generation high-energy batteries require rechargeable metal anodes, but hazardous dendrites tend to form during recharging, causing short-circuiting risks and capacity loss. In this presentation, we will exploit our understanding of lithium whiskers and dendrites to investigate the interfacial instabilities of Na metal anode and Zn metal anode, through the intimate combination of operando microscopy and novel transport models. Our results demonstrate the necessity to carefully avoid the transport-controlled scenario, in which fast-advancing dendritic growths would become inevitable to short the cell. Within the reaction-controlled regime, however, resolving the interfacial instability and metal whiskers leads to ideally smooth, non-porous, ingot-type Na metal plating, which enabled the anode-free Na metal full cells with a record-high capacity retention rate of 99.93% per cycle at 3C charge and discharge. Chronopotentiometry tests of this ideal metal electrode revealed an inverse correlation between the penetration overpotential and the pore size of the separator, which can be captured by a new model we named as the Young-Laplace critical overpotential. Following a similar principle, we investigated the growth of Zn dendrites in operando in our capillary cells. We discovered for the first time that seemingly negligible pore-wall charges, far away from the bulk electrolyte, can affect the morphology of Zn dendrites, which suggests that by depositing negative and positive charges on the pore walls, a bipolar separator not only can ensure uniform cation flux to improve the interfacial stability but also can stop localized dendrite penetration autonomously toward ideal safety.

Controlling Electrodeposition Via Electrokinetic Phenomena and Phase Separation

This talk will review the basic physics of dendritic instabilities in electrodeposition and how they may be suppressed, in some cases, by controlling electrokinetic phenomena in the electrolyte or phase separation in the electrode: 1) It is shown both theoretically and experimentally that, if electrodeposition occurs in charged porous media above the diffusion-limited current, then dendritic growth can be suppressed by surface conduction and electro-osmotic flows through the phenomenon of “shock electrodeposition”, as in many examples with copper. 2) It is also shown theoretically and experimentally that dendritic electrodeposition on a multiphase electrode can be avoided by avoiding the separation of a resistive phase, as illustrated by lithium plating on graphite. Examples include composite metal materials manufacturing, metal nanotube growth in templates, rechargeable metal batteries, and conductive-bridge random access memory (CB-RAM). These phenomena may also be leveraged to enhance the selectivity of electrodeposition for metal separations.

Nano and phase engineering of Fe-Cu alloy exsolved perovskite oxide-based hetero-catalysts for efficient oxygen evolution reaction

The electrochemical oxygen evolution reaction (OER), a crucial reaction in water electrolyzers and rechargeable metal–air batteries, requires for active electrocatalysts. Perovskite oxides possessing flexible composition and adjustable crystal structure and high intrinsic catalytic activity are potential candidates. However, distinct issues like low electrical conductivity and limited active sites hinder their wide application. To address these issues, we propose an integrated strategy that combines nanoarchitecture synthesis, nanoparticle exsolution design, and hybrid phase assembly with multi-interfacial interaction to create a phase controllable Fe/Cu nanoparticles-Ruddlesden-Popper structural-simple perovskite composites. Our results indicate that the composite catalyst LSFCN-R600 that was finally treated in 10% H2/N2 at 600 °C for 10 h with optimal metal phase exsolution and maximum surface/interfacial oxygen defects displayed the best OER activity: η10 = 381 mV and the Tafel slope 120 mV dec−1 as well as reliable performance in 20 h potentiostat test. The nano and heterostructural phase design increases the charge transfer rate and electrochemically active area. Our approach provides a reliable method for fabricating highly efficient perovskite oxide-based electrocatalysts that can be applied to various reactions and energy technologies.

Manipulating underpotential deposition nucleation of zinc deposition towards high-stable zinc metal battery

The uneven Zn deposition severely hinders the commercial application of zinc anode and rechargeable aqueous zinc metal batteries (AZMBs). In this work, the underpotential deposition (UPD) behavior of zinc is unveiled and a stable zinc anode host with underpotential deposition nucleation site of copper (3DH-Cu) is fabricated to guide homogeneous zinc deposition and enable long cycling stable rechargeable AZMBs. The uniformly distributed Cu UPD nucleation sites can avoid the electron concentration, reduce the nucleation barrier, and accelerate the deposition kinetics, which is attributed to the narrow band gap of Cu UPD nucleation sites, thus achieving a low nucleation overpotential of ~20 mV and a low activation energy (Ea) of 24.3 kJ mol−1. The 3DH-Cu@Zn anode exhibited an extremely stable overpotential (37 mV), and a high average Coulombic Efficiency of 99.4 % in 1000 cycling under 10 mA cm−2/1mAh cm−2 condition. A full cell with 3DH-Cu@Zn anode and NaV3O8-1.5H2O cathode (NVO) provides long cycle life and a low capacity degradation at 1Ag−1(above 150mAh g−1 capacity after 1000 cycles). Hopefully, anode design based on UPD can be considered to improve the electrochemical performance of AZMBs.

Photoelectrochemical Engineering for Light-Assisted Rechargeable Metal Batteries: Mechanism, Development, and Future.

Rechargeable battery devices with high energy density are highly demanded by our modern society. The use of metal anodes is extremely attractive for future rechargeable battery devices. However, the notorious metal dendritic and instability of solid electrolyte interface issues pose a series of challenges for metal anodes. Recently, considering the indigestible dynamical behavior of metal anodes, photoelectrochemical engineering of light-assisted metal anodes have been rapidly developed since they efficiently utilize the integration and synergy of oriented crystal engineering and photocatalysis engineering, which provided a potential way to unlock the interface electrochemical mechanism and deposition reaction kinetics of metal anodes. This review starts with the fundamentals of photoelectrochemical engineering and follows with the state-of-art advance of photoelectrochemical engineering for light-assisted rechargeable metal batteries where photoelectrode materials, working principles, types, and practical applications are explained. The last section summarizes the major challenges and some invigorating perspectives for future research on light-assisted rechargeable metal batteries.

Graphene-like AlP3 monolayer: A high-performance anode material for Li/Na/K-ion batteries

The rational design of anode materials with high capacity, good stability, and fast diffusion rate are crucial demands for rechargeable alkali metal ion batteries (AMIBs). Herein, the density functional theory calculations have been carried out to investigate the feasibility of an AlP3 monolayer with folded graphene-like structure as an anode material for AMIBs. The results indicated that the alkali metal atoms (AM = Li, Na, and K) can be stably adsorbed on the AlP3 monolayer surface and further enhance the conductivity of the system. The average open-circuit voltages are only 0.70 V, 0.28 V, and 0.37 V for Li, Na, and K storages, respectively. The diffusion energy barriers of Li, Na, and K atoms are 0.56 eV, 0.41 eV, and 0.20 eV, respectively. Furthermore, the AlP3 monolayer possesses a high theoretical specific capacity of 447 mAh g−1, 894 mAh g−1, and 1565 mAh g−1 for Li, Na, and K-ion batteries, respectively. Overall, the AlP3 monolayer is an excellent anode material for AMIBs, especially for K-ion batteries.

Highly lithiophilic and structurally stable Cu–Zn alloy skeleton for high-performance Li-rich ternary anodes

Lithium (Li)-rich ternary alloy, comprising a multi-alloy phase as the built-in three-dimensional (3D) framework and a Li metal phase as a reversible Li reservoir, is a promising high-energy–density anode for rechargeable Li metal batteries. The introduction of metal/metalloid components to the alloy can effectively regulate Li deposition and maintain the dimensional integrity of the Li anode. Herein, the lithium–copper–zinc (Li–Cu–Zn) ternary alloy, as a new type of alloy anode, is synthesized via a facile thermal melting method. The fully delithiated 3D scaffold comprised two Cu–Zn alloy phases named CuZn and CuZn5. These alloy phases exhibit higher lithiophilicity and structural stability than Li–Zn and Li–Cu alloys. Moreover, the CuZn phase is electrochemically inert, ensuring the geometric stability of the anode, while the CuZn5 phase can readily undergo alloying reaction with Li to form the LiZn phase, thereby facilitating uniform Li nucleation and deposition. The hybridized multiphase alloy structure and specific energy storage mechanism of the Cu–Zn based alloy scaffold in the ternary alloy anode facilitate dendrite-free Li deposition and prolonged cycle lifetime. The Li metal full battery based on lithium iron phosphate (LiFePO4) cathode exhibits high cycling stability with high-capacity retention of 95.4% after 1000 cycles at 1C.

Fluorinated Nonflammable In Situ Gel Polymer Electrolyte for High-Voltage Lithium Metal Batteries.

Rechargeable lithium metal batteries (LMBs) offer excellent opportunities for applications requiring high-energy-density battery systems. So far, it has received a lot of interest in pairing higher-energy-density high-voltage nickel-rich cathodes. Here, fluorinated solvents were used instead of the usual carbonate solvents to prepare gel polymer electrolytes (FGPE) by in situ polymerization of polymers introducing the fluorine-containing groups. Theoretically and experimentally, FGPE has proven to be ultra-compatible with the lithium metal anode and LiNi0.8Co0.1Mn0.1O2 cathode. A stable plating/stripping process of over 2000 h can be achieved for symmetrical lithium cells using FGPE. The Li||FGPE||NCM811 cell has a longer cycle life at a high voltage (4.5 V). In addition, the zero self-extinguishing time indicates that the FGPE has sufficient safety. In summary, the design of this electrolyte provides ideas to improve the safety and energy density of LMBs.

Morphology evolution of electrodeposited lithium on metal substrates

Lithium (Li) metal is deemed to be the high-energy-density anode material for next generation batteries, but its practical application is impeded by the uneven electrodeposition during charge of battery, which leads to the low Coulombic efficiency and potential safety issue. Here, multiscale modeling is fabricated to understand the morphology evolution of Li during electrodeposition process, from the self-diffusion of Li adatoms on electrode surface, to the nucleation process, and to the formation of Li microstructures, revealing the correlation between final morphology and deposition substrates. Energy batteries and self-diffusion of Li adatom on various substrates (lithium, copper, nickel, magnesium, and silver) result in the different nucleation size, which is calculated by kinetic Monte Carlo simulation based on classical nucleation theory. Formation of Li substructures that are grown from Li nuclei, is revealed by phase field modeling coupled with cellular automaton method. Our results show that larger Li nuclei is obtained under faster self-diffusion of Li adatom, leading to the low aspect ratio of Li substructures and the subsequent morphology evolution of electrodeposited Li. Furthermore, the electrodeposition of Li is strongly regulated by the selection of substrates, giving the practical guideline of anode design in rechargeable Li metal batteries. It is worthy to mention that this method to investigate the electro-crystallization process involving nucleation and growth can be transplanted to the other metallic anode, such as sodium, potassium, zinc, magnesium, calcium and the like.

Towards a high-performance anode for zinc metal batteries: A tri-functional nitrogen-defective graphitic carbon nitride material for anode protection

As an important potential candidate for large-scale energy storage, rechargeable zinc metal batteries have become a research hotspot. Zn metal anodes are an extremely crucial component of rechargeable Zn metal batteries. However, the Zn dendrites, the evolution of hydrogen and side reactions on the surface of the Zn metal anodes severely hinder its commercial use. Here, we report a modified Zn metal anode with a layer of nitrogen-defective graphitic carbon nitride (NDCN) nanosheets coated onto a commercial Zn foil by a simple spraying method. The NDCN coating on the anode’s surface not only provides zincophilic sites, but also drives the deposition of zinc with a particular crystallographic orientation. At the same time, the formation of zinc dendrites and the evolution of hydrogen were suppressed, which enhanced the reversibility of the anode. Thus, the symmetric cells with the NDCN-protected zinc foil (NDCN@Zn) electrodes remained stable for 2000 h at a current density of 5 mA cm−2. More importantly, the long-term cycling performance of the full cell tested at 1 A g−1 retained approximately 88 % of its capacity even after 2300 cycles. This simple but effective method will provide a reference for future studies on protecting the anodes of zinc metal batteries.

Promoting a Stable Interface Using Localized High-Concentration Carbonate-Based Electrolyte for Li Metal Batteries.

Rechargeable lithium metal batteries (LMBs) using high-voltage cathodes have been attractive in delivering high-energy density, but it is still challenging to reach excellent cycling performance for practical applications due to the notorious reactivity of metallic lithium as well as the unstable nature of the cathode. Here, we demonstrate a formulated carbonated-based electrolyte with LiPF6 that supports the most commercial aggressive and high-voltage cathode with the combination of cosolvent, diluent, and additives to address the issue in LMBs by providing a stable interface/interphase on both the anode and cathode. The electrolyte's solvation structure is adjusted to reduce free carbonate solvents in the decomposition and contribution to the solid-electrolyte interphase (SEI) formation. The thin LiF-rich SEI and achieved uniform Li deposition afforded a high Coulombic efficiency of 99.5% for Li|Cu half cells and good cycling stability in Li||NMC811 full cells. The Li||NMC811 full cells showed good cycling life with a capacity retention of ∼80% over 280 cycles at an areal capacity of 4.0 mAh cm-2, the lean electrolyte of 5 μL mAh-1, and a thin 50 μm Li metal, demonstrating its advantage toward practical applications.

Practical level of low-N/P ratio sodium metal batteries: On the basis of deposition/dissolution efficiency in the aspects of electrolytes and temperature

Rechargeable sodium metal batteries have drawn immense interest as next-generation batteries, owing to their high theoretical energy density and the natural abundance of Na resources. However, Na metal batteries with excess amounts of Na metal which typically employ traditional organic electrolytes, are plagued by a myriad of electrochemical deficiencies that cause low Coulombic efficiencies, severe dendrite formation, thermal runaways, and fire hazards during operations. To establish a pathway for high energy density Na metal batteries, this work focuses on the practicability of the Na lean-metal battery and presents an in-depth perspective into the electrochemical mechanisms of utilizing a bis(fluorosulfonyl)amide ionic liquid electrolyte at both room- and intermediate temperatures. Here, the ionic liquid electrolyte is confirmed to yield a higher Na metal deposition/dissolution efficiency than common organic electrolytes. Electrochemical and computational investigations entailing the ionic liquid performance reveal that elevating the operating temperature to 90 °C increases the number of anions coordinated with Na+ and leads to the formation of a robust anion-based interfacial layer that facilitates effective and smooth Na metal deposition/dissolution. Furthermore, full cells comprising a Na metal negative with restricted loading mass and a Na3V2(PO4)3 positive electrode (low negative/positive electrode capacity ratio of 1.97, weight ratio of 0.19) demonstrates outstanding cycleability with high Coulombic efficiency (∼100%) and practical energy density (280 Wh kg–1).

Constructing stable interfaces for wide-temperature and high-rate aqueous zinc metal batteries by dual-salt cosolvent electrolyte

Rechargeable aqueous zinc metal batteries are large-scale new energy storage system due to their low cost and high safety. Nonetheless, a series of problems faced by zinc anode at wide temperatures will also limit its development, such as serious zinc dendrites and parasitic reactions. Herein, we report a dual-salt cosolvent electrolyte in which the addition of zinc perchlorate and 2-methyltetrahydrofuran assists the formation of stable SEI on the Zn anode surface. The ZnF2-rich SEI was constructed in-situ, which effectively inhibited the growth of zinc dendrite and exacerbation of parasitic reaction. Meanwhile, such solvents break the hydrogen bond network between the water molecules and change the solvation structure of Zn2+. Consequently, the Zn||Zn symmetric cells could remain stable during cycling for 9200 min at −20 °C and 6000 min at 60 °C (5 mA cm−2). Significantly, AZMBs exhibited an ultrahigh cumulative cycling capacity of 2250 mAh cm−2 at 20 °C. The PANI@V2O5 full cells maintained a capacity of 78.80 mAh/g after 250 cycles at −20 °C (2 A/g) and exhibited a long cycle life at 60 °C (more than 200 cycles). This study demonstrates a promising pathway for the future exploitation of high-rate AZMBs for operation under wide temperature.

Manipulating Lewis acid–base interactions in metal-organic frameworks for optimizing zinc-ion diffusion, deposition, and reaction behaviors

The dendrite growth and side reactions of Zn anodes severely impair the performance of aqueous rechargeable Zn metal batteries. Although various artificial protective layers (APLs) have been developed to address these issues, the engineering of multifunctional APLs at the molecular level remains a challenge. Herein, a strategy of manipulating the Lewis acid–base interactions at the molecular level within metal-organic frameworks (MOFs) was conducted to optimize the Zn2+ diffusion, deposition, and reaction behaviors for stabilizing Zn anodes. A series of APLs based on isostructural UiO-66 type MOFs with different functional groups (–NH2, –OH, –SO3H, and –COOH) were developed to systematically study the influence of different host-guest interactions for zinc deposition. The results show that the more Lewis base chemical groups result in the improved ability of MOFs in trapping Zn2+, transporting Zn2+, accelerating the desolvation of Zn2+, regulating pH values, and decreasing the side reactions, rendering suppressed dendrite growth. Thus, UiO-66-2COOH shows the best performance in regulating Zn2+ deposition, delivering an excellent Zn plating/stripping cycling of up to 2700 h at 1 mAh/cm2 and 1600 h at 5 mAh/cm2, as well as full cells with remarkably improved C-rate and cycling performance.

Artificial bi-functional layers promoting Zn2+ desolvation and homogeneous deposition for reversible zinc metal anodes

Rechargeable aqueous zinc-ion hybrid supercapacitors (ZHSs) are drawing extensive attention because of their cost-effectiveness and diminished safety hazards. Nevertheless, large-scale application of ZHSs has been hindered by the severe side reactions and rampant dendrites growth on the surface of Zn metal anodes. Herein, we propose a three-dimensional organic–inorganic composite frame material as an artificial bi-functional layer coated on the zinc foil, featuring nitrogenous functional groups with zincophilicity (abbreviated as NCFM@Zn). The nitrogen (N) site's strong adsorption capacity and synergistic effect of the sub-nanopore size promote rapid desolvation of zinc ions and reduce side reactions, while also prolonging galvanized nucleation's Sand's time and allowing for even nucleation. Moreover, the uniform distribution of N on the layer results in homogeneous zinc ions flux and supports consistent zinc plating while inhibiting dendrites generation. As a result of this unique artificial bi-functional layer, symmetric Zn cells can survive 2500 h at 2.5 mA cm−2. High-areal-capacity zinc||activated carbon hybrid supercapacitors also demonstrate 20,000 cycles at high Coulombic efficiency, thus highlighting the utter convenience and potential of this strategy for modifying rechargeable metal hybrid supercapacitor surfaces.

Weakly coordinated Li ion in single-ion-conductor-based composite enabling low electrolyte content Li-metal batteries

The pulverization of lithium metal electrodes during cycling recently has been suppressed through various techniques, but the issue of irreversible consumption of the electrolyte remains a critical challenge, hindering the progress of energy-dense lithium metal batteries. Here, we design a single-ion-conductor-based composite layer on the lithium metal electrode, which significantly reduces the liquid electrolyte loss via adjusting the solvation environment of moving Li+ in the layer. A Li||Ni0.5Mn0.3Co0.2O2 pouch cell with a thin lithium metal (N/P of 2.15), high loading cathode (21.5 mg cm−2), and carbonate electrolyte achieves 400 cycles at the electrolyte to capacity ratio of 2.15 g Ah−1 (2.44 g Ah−1 including mass of composite layer) or 100 cycles at 1.28 g Ah−1 (1.57 g Ah−1 including mass of composite layer) under a stack pressure of 280 kPa (0.2 C charge with a constant voltage charge at 4.3 V to 0.05 C and 1.0 C discharge within a voltage window of 4.3 V to 3.0 V). The rational design of the single-ion-conductor-based composite layer demonstrated in this work provides a way forward for constructing energy-dense rechargeable lithium metal batteries with minimal electrolyte content.