Multidimensional visualization of the dynamic evolution of Li metal via in situ/operando methods.

The growing demands for high-energy density electrical energy storage devices stimulate the coupling of conversion-type cathodes and lithium (Li) metal anodes. While promising, the use of these "Li-free" cathodes brings new challenges to the Li anode interface, as Li needs to be dissolved first during cell operation. In this study, we have achieved a direct visualization and comprehensive analysis of the dynamic evolution of the Li interface. The critical metrics of the interfacial resistance, Li growth, and solid electrolyte interface (SEI) distribution during the initial dissolution/deposition processes were systematically investigated by employing multidimensional analysis methods. They include three-electrode impedance tests, in situ atomic force microscopy, scanning electrochemical microscopy, and cryogenic scanning transmission electron microscopy. The high-resolution imaging and real-time observations show that a loose, diffuse, and unevenly distributed SEI is formed during the initial dissolution process. This leads to the dramatically fast growth of Li during the subsequent deposition, deviating from Fick's law, which exacerbates the interfacial impedance. The compactness of the interfacial structure and enrichment of electrolyte species at the surface during the initial deposition play critical roles in the long-term stability of Li anodes, as revealed by operando confocal Raman spectroscopic mapping. Our observations relate to ion transfer, morphological and structural evolution, and Li (de)solvation at Li interfaces, revealing the underlying pathways influenced by the initial dissolution process, which promotes a reconsideration of anode investigations and effective protection strategies.

Molecular Structure Engineering of Isomeric Additives for Long Lifetime Zn Anodes.

Modulating the solvation structure of hydrated zinc ions using organic additives stands as a pragmatic approach to suppress dendrite formation and corrosion on zinc metal anodes (ZMAs), thereby enhancing the rechargeability of aqueous Zn-ion batteries. However, fundamental screening principles for organic additives with diverse molecular structures remain elusive, especially for isomers with the same molecular formula. This study delves into the impact of three isomeric hexagonal alcohols (mannitol, sorbitol, and galactitol) as additives in adjusting Zn2+ solvation structural behaviors within ZnSO4 baseline electrolytes. Electrical measurements and molecular simulations reveal the specific molecular structure of mannitol, which features interweaving electron clouds between adjacent hydroxyl groups, achieving a high local electron cloud density. This phenomenon significantly enhances desolvation abilities, thus establishing a more stable anode/electrolyte interface chemistry. Even at 5 mA cm-2 for 2.5 mAh cm-2 capacity, Zn||Zn symmetric cells with mannitol-regulated electrolyte display an impressive 1170 h lifespan, far exceeding those with other isomer additives and is nearly tenfold longer than that with a pure ZnSO4 electrolyte (120 h). Rather than strictly adhering to focusing on chemical composition, this study with emphasis on optimizing molecular structure offers a promising untapped dimension to screen more efficient additives to enhance the reversibility of ZMAs.

Rapidly Prepared Lithophilic Frameworks Stabilizes Lithium Anodes via Altered Lithium Deposition Patterns.

Lithium metal batteries are regarded as promising candidates for next-generation energy storage systems. However, their anodes are susceptible to interfacial instability due to significant volume changes, which significantly impacts the cycle life of lithium metal batteries. Here, a rapid method for the fabrication of 3D-hosts with interface modified layers is reported. A simple infiltration and heating process enables the transformation of copper foam into Zn-BDC-modified copper foam within 1 min, rendering it suitable for use as a current collector for lithium metal anodes. The Zn-BDC nanosheets with high lithiophilicity are uniformly distributed on the surface of the current collector, facilitating the uniform deposition of lithium and reducing the volume change. Consequently, the half cell exhibits a remarkably low overpotential (26 mV) at a current-density of 4 mA cm-2 and is cycled stably for 1000 h. Furthermore, it demonstrates a significant enhancement in performance in the LiFePO4 full cell. This study provides a crucial reference on the connection between the interfacial modification of the current collector and the lithium deposition behavior, which promotes the practicalization of lithium metal anodes.

Zincophilic Metal-Organic-Framework Interface Mitigating Dendrite Growth for Highly Reversible Zinc Metal Batteries.

Aqueous Zn-ion batteries are the ideal candidate for large-scale energy storage systems owing to their high safety and low cost. However, the uncontrolled deposition and parasitic reaction of Zn metal anode hinder their commercial application. Here, the 2D metal-organic-framework (MOF) nanoflakes covered on the surface of Zn are proposed to enable dendrite-free for long lifespan Zn metal batteries. The MOF can facilitate the desolvation process to accelerate reaction kinetic due to its special channel structure. The abundant zincopilicity sites of MOF can realize the homogenous Zn2+ deposition. Consequently, their synergetic effect makes the MOF protected Zn anode good electrochemical performance with a long cycle life of 1400 h at 1 mA cm-2 and a high depth of discharge of 30 mAh cm-2 (DOD ≈ 54%) continued for over 700 h. This work provides a novel strategy for high-performance rechargeable Zn-ion batteries.

High-Areal Capacity, High-Rate Lithium Metal Anodes Enabled by Nitrogen-Doped Graphene Mesh.

Hosts hold great prospects for addressing the dendrite growth and volume expansion of the Li metal anode, but Li dendrites are still observable under the conditions of high deposition capacity and/or high current density. Herein, a nitrogen-doped graphene mesh (NGM) is developed, which possesses a conductive and lithiophilic scaffold for efficient Li deposition. The abundant nanopores in NGM can not only provide sufficient room for Li deposition, but also speed up Li ion transport to achieve a high-rate capability. Moreover, the evenly distributed N dopants on the NGM can guide the uniform nucleation of Li so that to inhibit dendrite growth. As a result, the composite NGM@Li anode shows satisfactory electrochemical performances for Li-S batteries, including a high capacity of 600 mAh g-1 after 300 cycles at 1 C and a rate capacity of 438 mAh g-1 at 3 C. This work provides a new avenue for the fabrication of graphene-based hosts with large areal capacity and high-rate capability for Li metal batteries.

Transient Zwitterions Dynamics Empowered Adaptive Interface for Ultra-Stable Zn Plating/Stripping.

A highly reversible zinc anode is crucial for the commercialization of zinc-ion batteries. However, the change in the microstructure of the electric double layer originated from the dynamic change in charge density on the electrode greatly impacts anode reversibility during charge/discharge, which is rarely considered in previous research. Herein, the zwitterion additive is employed to create an adaptive interface by coupling the transient zwitterion dynamics upon the change of interfacial charge density. Ab initio molecular dynamics simulations suggest the molecular orientation and adsorption groups of zwitterions will be determined by the charging state of the electrode. ZnSO4 electrolyte with zwitterion fulfills a highly reversible Zn anode with an average Coulombic efficiency of up to 99.85%. Zn/Zn symmetric cells achieve greatly enhanced cycling stability for 700 h with extremely small voltage hysteresis of 29 mV under 5 mA cm-2 with 5 mAh cm-2 . This study validates the adaptive interface based on transient dynamics of zwitterions, which sheds new light on developing highly reversible metal anodes with a high utilization rate.

Light-Assisted Lithium Metal Anode Enabled by In Situ Photoelectrochemical Engineering.

Rechargeable battery devices with high energy density are highly demanded by the modern society. The use of lithium (Li) anodes is extremely attractive for future rechargeable battery devices. However, the notorious Li dendritic and instability of solid electrolyte interface (SEI) issues pose series of challenge for metal anodes. Here, based on the inspiration of in situ photoelectrochemical engineering, it is showed that a tailor-made composite photoanodes with good photoelectrochemical properties (Li affinity property and photocatalytic property) can significantly improve the electrochemical deposition behavior of Li anodes. The light-assisted Li anode is accommodated in the tailor-made current collector without uncontrollable Li dendrites. The as-prepared light-assisted Li metal anode can achieve the in situ stabilization of SEI layer under illumination. The corresponding in situ formation mechanism and photocatalytic mechanism of composite photoanodes are systematically investigated via DFT theoretical calculation, ex situ UV-vis and ex situ XPS characterization. It is worth mentioning that the as-prepared composite photoanodes can adapt to the ultra-high current density of 15 mA cm-2 and the cycle capacity of 15 mAh cm-2 under light, showing no dendritic morphology and low hysteresis voltage. This work is of great significance for the commercialization of new generation Li metal batteries.

Stabilizing Anode-Electrolyte Interface for Dendrite-Free Zn-Ion Batteries Through Orientational Plating with Zinc Aspartate Additive.

The stability of aqueous Zn-ion batteries (AZIBs) is detrimentally influenced by the formation of Zn dendrites and the occurrence of parasitic side reactions at the Zn metal anode (ZMA)-electrolyte interface. The strategic manipulation of the preferential crystal orientation during Zn2+ plating serves as an essential approach to mitigate this issue. Here, Zn aspartate (Zn-Asp), an electrolyte additive for AZIBs, is introduced not only to optimize the solvation structure of Zn2+ , but also to crucially promote preferential Zn2+ plating on the (002) crystal plane of ZMA. As a result, both side reactions and Zn dendrites are effectively inhibited, ensuring an anode surface free of both dendrites and by-products. The implementation of Zn-Asp leads to significant enhancements in both Zn||Zn symmetric and Zn||Ti batteries, which demonstrate robust cyclability of over 3200 h and high Coulombic efficiency of 99.29%, respectively. Additionally, the Zn||NaV3 O8 ·1.5H2 O full battery exhibits remarkable rate capability, realizing a high capacity of 240.77 mA h g-1 at 5 A g-1 , and retains 92.7% of its initial capacity after 1000 cycles. This research underscores the vital role of electrolyte additives in regulating the preferential crystal orientation of ZMA, thereby contributing to the development of high-performing AZIBs.

Manipulating the Host-Guest Chemistry of Cucurbituril to Propel Highly Reversible Zinc Metal Anodes.

Rechargeable aqueous zinc-ion batteries are practically plagued by the short lifespan and low Coulombic efficiency (CE) of Zn anodes resulting from random dendrite deposition and parasitic reactions. Herein, the host-guest chemistry of cucurbituril additive with Zn2+ to achieve longstanding Zn anodes is manipulated. The macrocyclic molecule of cucurbit[5]uril (CB[5]) is delicately designed to reconstruct both the CB[5]-adsorbed electric-double layer (EDL) structure at the Zn interface and the hydrated sheath of Zn2+ ions. Especially benefiting from the desirable carbonyl rims and suitable hydrophobic cavities, the CB[5] has a strong host-guest interaction with Zn2+ ions, which exclusively permits rapid Zn2+ flux across the EDL interface but retards the H2O radicals and SO4 2-. Accordingly, such a unique particle redistributor warrants long-lasting dendrite-free deposition by homogenizing Zn nucleation/growth and significantly improved CE by inhibiting side reactions. The Zn anode can deliver superior reversibility in CB[5]-containing electrolyte with a ninefold increase of cycle lifetime and an elevated CE of 99.7% under harsh test conditions (10 mA cm-2/10 mA h cm-2). The work opens a new avenue from the perspective of host-guest chemistry to propel the development of rechargeable Zn metal batteries and beyond.

Oriented Metal Stripping for Highly Reversible Zinc Anode.

Aqueous zinc metal batteries are a viable candidate for next-generation energy storage systems, but suffer from poor cycling efficiency of the Zn anode. Emerging approaches aim to regulate zinc plating behavior to suppress uncontrolled dendrites, while the stripping process is seldom considered. Herein, an oriented metal stripping strategy is demonstrated to stabilize the Zn anode by removing high-index facets for exposing the (002) plane through the addition of anionic additive sodium citrate (SC). Consequently, high-index facets that coordinate strongly with SC are preferentially stripped out due to a reduced stripping barrier, rendering stable (002) facet preponderant in epitaxial plating. After repeat stripping/plating, the ultra-high proportion of 93% for (002) and large-size grains of ≈100 µm (six times larger than before) can be obtained. Zn anode shows continuous 25 000 cycles with low overpotential at 100 mA cm-2 in symmetric cells and more than 70 h of stable operation even at an ultra-high depth of discharge of 92.3%. Moreover, an extremely long lifespan of 12 000 cycles at 10 A g-1 with a high capacity retention of 89% is achieved by the assembled Zn//I2 battery. This work provides a distinctive approach to improving the stripping process to design highly efficient zinc anodes for promising aqueous zinc metal batteries.

Bottom Deposition Enables Stable All-Solid-State Batteries with Ultrathin Lithium Metal Anode.

Modern strides in energy storage underscore the significance of all-solid-state batteries (ASSBs) predicated on solid electrolytes and lithium (Li) metal anodes in response to the demand for safer batteries. Nonetheless, ASSBs are often beleaguered by non-uniform Li deposition during cycling, leading to compromised cell performance from internal short circuits and hindered charge transfer. In this study, the concept of "bottom deposition" is introduced to stabilize metal deposition based on the lithiophilic current collector and a protective layer composed of a polymeric binder and carbon black. The bottom deposition, wherein Li plating ensues between the protective layer and the current collector, circumvents internal short circuits and facilitates uniform volumetric changes of Li. The prepared functional binder for the protective layer presents outstanding mechanical robustness and adhesive properties, which can withstand the volume expansion caused by metal growth. Furthermore, its excellent ion transfer properties promote uniform Li bottom deposition even under a current density of 6 mA·cm-2. Also, scanning electron microscopy analysis reveals a consistent plating/stripping morphology of Li after cycling. Consequently, the proposed system exhibits enhanced electrochemical performance when assessed within the ASSB framework, operating under a configuration marked by a high Li utilization rate reliant on an ultrathin Li.

Oxygen Vacancy and Bandgap Simultaneous Modulation to Achieve High Lithiophilicity and Mechanical Strength of Lithium Metal Anodes.

Metal oxides with conversion and alloying mechanisms are more competitive in suppressing lithium dendrites. However, it is difficult to simultaneously regulate the conversion and alloying reactions. Herein, conversion and alloying reactions are regulated by modulation of the zinc oxide bandgap and oxygen vacancies. State-of-the-art advanced characterization techniques from a microcosmic to a macrocosmic viewpoint, including neutron diffraction, synchrotron X-ray absorption spectroscopy, synchrotron X-ray microtomography, nanoindentation, and ultrasonic C-scan demonstrated the electrochemical gain benefit from plentiful oxygen vacancies and low bandgaps due to doping strategies. In addition, high mechanical strength 3D morphology and abundant mesopores assist in the uniform distribution of lithium ions. Consequently, the best-performed ZnO-2 offers impressive electrochemical properties, including symmetric Li cells with 2000 h and full cells with 81% capacity retention after 600 cycles. In addition to providing a promising strategy for improving the lithiophilicity and mechanical strength of metal oxide anodes, this work also sheds light on lithium metal batteries for practical applications.

In Situ Plasma Polymerization of Self-Stabilized Polythiophene Enables Dendrite-Free Lithium Metal Anodes with Ultra-Long Cycle Life.

Constructing a flexible and chemically stable multifunctional layer for the lithium (Li) metal anodes is a highly effective approach to improve the uneven deposition of Li+ and suppress the dendrite growth. Herein, an organic protecting layer of polythiophene is in situ polymerized on the Li metal via plasma polymerization. Compared with the chemically polymerized thiophene (C-PTh), the plasma polymerized thiophene layer (P-PTh), with a higher Young's modulus of 8.1 GPa, shows strong structural stability due to the chemical binding of the polythiophene and Li. Moreover, the nucleophilic C─S bond of polythiophene facilitates the decomposition of Li salts in the electrolytes, promoting the formation of LiF-rich solid electrolyte interface (SEI) layers. The synergetic effect of the rigid LiF as well as the flexible PTh-Li can effectively regulate the uniform Li deposition and suppress the growth of Li dendrites during the repeated stripping-plating, enabling the Li anodes with long-cycling lifespan over 8000 h (1 mA cm-2, 1 mAh cm-2) and 2500 h (10 mA cm-2, 10 mAh cm-2). Since the plasma polymerization is facile (5-20 min) and environmentally friendly (solvent-free), this work offers a novel and promising strategy for the construction of the forthcoming generation of high-energy-density batteries.

Synergistic Gradient Anodes for Long-Term Stability in Aqueous Zinc-Ion Batteries.

The stability of aqueous zinc metal anodes is still constrained by their severe dendrite growth. Optimizing electric field distribution and crystallography to modulate the diffusion and deposition behavior of zinc ions can effectively suppress dendrite growth. However, the fabrication strategy to directly endow specific textured zinc anodes with gradient electric field distribution is still lacking. Herein, a strategy combining crystal reconstruction of commercial zinc foil with graphene oxide (GO) protective layer is proposed to construct an in situ gradient electric field-enhanced strong (002) textured GO@ZnO/Zn(002) anode. Based on the experimental and theoretical results, the GO protective layer can regulate a wide-range homogeneous Zn2+ ions flow, while the dense and uniform ZnO/Zn(002) nanoneedles /nanoparticles can enhance localized polarized electric field to accelerate rapid localized transfer of Zn2+ ions and guide them toward directional deposition along (002) plane. Therefore, the hierarchical GO@ZnO/Zn(002) anode enables the symmetric cell to operate continuously and stably for 5700 and 4200 h at 2 and 4 mA cm-2, respectively, which is comparable to or better than most high-end Zn anodes. This work presents new insights into the zinc foil reconstruction and gradient electric field fabrication strategy, offering a scalable approach for the development of long-term stable metal anodes.

3D Magnetic Metal-Organic Frameworks Current Collectors Accelerate the Lithium-Ion Diffusion Rate for Superlong Cyclic Lithium Metal Anode.

Lithium, is the most ideal anode material for lithium-based batteries. However, the overgrowth of lithium dendrites and the low lithium-ion diffusion rate at low temperatures limit the further application of lithium metal anodes. Here, the applied magnetic field is introduced inside the lithium metal anode by using a novel magnetic metal-organic framework as a current collector. The magnetic field can improve the conductivity of this novel current collector, thus accelerating the diffusion of lithium ions in the battery, an advantage that is particularly prominent at low temperatures. In addition, the current collector can stabilize the solid electrolyte interface and inhibit the growth of lithium dendrites, resulting in excellent electrochemical performance. The symmetrical cell at room temperature can exceed 4600 h with a hysteresis voltage of only 9 mV. After 300 cycles at room temperature, the capacity of full cell is still 142 mA h g-1 , and it remains stable for 380 cycles at 5 °C (capacity above 120 mA h g-1 ). The strategy of constructing novel current collector with magnetic field can promote the further application of lithium batteries in extreme conditions such as low temperatures.

A 3D Lithiophilic Host for Dendrite-Free Lithium Metal Anode via One-Step Carbonization of an Energetic Metal-Organic Framework.

Low Coulombic efficiency (CE) and safety issues are huge problems that hinder the practical application of Li metal anodes. Constructing Li host structures decorated with functional species can restrain the growth of Li dendrites and alleviate the great volume change. Here, a 3D porous carbonaceous skeleton modified with rich lithiophilic groups (Zn, ZnO, and Zn(CN)2 ) is synthesized as a Li host via one-step carbonization of a triazole-containing metal-organic framework. The nano lithiophilic groups serve as preferred sites for Li nucleation and growth, regulating a uniform Li+ flux and uniform current density distribution. In addition, the 3D porous network functions as a Li reservoir that provides rich internal space to store Li, thus alleviating the volumetric expansion during Li plating/stripping process. Thanks to these component and structural merits, an ultra-low overpotential for Li deposition is achieved, together with high CE of over 99.5% for more than 500 cycles at 1 mA cm-2 and 1 mAh cm-2 in half cells. The symmetric cells exhibit a prolonged cycling of 900 h at 1 mA cm-2 . The full cells by coupling Zn/ZnO/Zn(CN)2 @C-Li anode with LiFePO4 cathode deliver a high capacity retention of 94.3% after 200 cycles at 1 C.

An In Situ Generated Organic/Inorganic Hybrid SEI Layer Enables Li Metal Anodes with Dendrite Suppression Ability, High-Rate Capability, and Long-Life Stability.

High-quality solid electrolyte interphase (SEI) layers can effectively suppress the growth of Li dendrites and improve the cycling stability of lithium metal batteries. Herein, 1-(6-bromohexanoyl)-3-butylurea is used to construct an organic/inorganic hybrid (designated as LiBr-HBU) SEI layer that features a uniform and compact structure. The LiBr-HBU SEI layer exhibits superior electrolyte wettability and air stability as well as strong attachment to Li foils. The LiBr-HBU SEI layer achieves a Li+ conductivity of 2.75 × 10-4 S cm-1, which is ≈50-fold higher than the value measured for a native SEI layer. A Li//Li symmetric cell containing the LiBr-HBU SEI layer exhibits markedly improved cyclability when compared with the cell containing a native SEI layer, especially at a high current density (e.g., cycling life up to 1333 h at 15 mA cm-2). The LiBr-HBU SEI layer also improves the performance of lithium-sulfur cells, particularly the rate capability (548 mAh g-1 at 10 C) and cycling stability (513 mAh g-1 at 0.5 C after 500 cycles). The methodology described can be extended to the commercial processing of Li metal anodes as the artificial SEI layer also protects Li metal against corrosion.

Achieving Dendrite-Free Zinc Metal Anodes via Molecule Anchoring and lon-Transport Pumping.

The potential for scale-up application has been acknowledged by researchers for rechargeable aqueous zinc-ion batteries (ZIBs). Nonetheless, the progress of the development is significantly impeded due to the instability of the interface between the zinc anode and electrolyte. Herein, efficient and environmentally benign valine (Val) were introduced as aqueous electrolyte additive to stabilize the electrode/electrolyte interface (EEI) via functional groups in additive molecules, thus achieving reversible dendrite-free zinc anode. The amino groups present in Val molecules have a strong ability to adsorb on the surface of zinc metal, enabling the construction of anchored molecular layer on the surface of zinc anodes. The strongly polar carboxyl groups in Val molecules can act as ion-transport pumps to capture zinc ions in the electric double layer (EDL) through coordination chemistry. Therefore, this reconstructed EEI could modulate the zinc ion flux and simultaneously suppress side reactions and dendritic growth of Zn. Consequently, a long stable cycling up to 1400 h at a high current density of 20 mA cm-2 is achieved. Additionally, Zn//V2O5 full cell with Val additive exhibit enhanced cyclability, retaining 77 % capacity after 3000 cycles, displaying significant potential in promoting the commercialization of ZIBs.

Field-Assisted Regulation Induced by Cobalt-Doped ZnO for Dendrite-Free Lithium Metal Anodes.

Lithium metal batteries are deemed as an optimal candidate for the next generation of durable energy storage devices. However, the growth of lithium dendrite and significant volume expansion pose as obstacles that impede the application of lithium metal batteries. In this work, a functional copper current collector was designed by coating it with Co-doped ZnO (Co/ZnO) to enhance the lithiophilicity through local electric fields and built-in magnetic fields induced by the ferromagnetic material. The incorporation of Co not only induces a local electric field and thus accelerating electron transfer, but also imparts the ferromagnetic behavior to ZnO, resulting in an internal magnetic field to regulate the dynamic trajectory. Profiting from the above advantages, the symmetric cells have excellent cycle stability in 1 mA cm-2 and 1 mAh cm-2 , maintaining ultra-low voltage for over 2000 h. This study provides a realizable pathway for next-generation current collector of copper modification.

Enhanced low-temperature resistance of lithium-ion batteries based on methyl propionate-fluorinated ethylene carbonate electrolyte.

Low temperature has been a major challenge for lithium-ion batteries to maintain satisfied electrochemical performance, as it leads to poor rechargeability and low capacity retention. Traditional carbonate solvents, vinyl carbonate and dimethyl carbonate are indispensable components of commercial electrolytes. However, the higher melting point of these carbonate solvents causes their electrical conductivity to be easily reduced when temperatures drop below zero, limiting their ability to facilitate lithium ion transport. In this work, we demonstrate that the use of methyl propionate (MP) carboxylate and fluorocarbonate vinyl (FEC) electrolytes can overcome the limitations of low temperature cycling. Compared with carbonate electrolyte, MP has the characteristics of low melting point, low viscosity and low binding energy with Li+, which is crucial to improve the low temperature performance of the battery, while FEC is an effective component to inhibit the side reaction between MP and lithium metal. The carefully formulated MP-based electrolyte can generate a solid electrolyte interface with low resistance and rich in inorganic substances, which is conducive to the smooth diffusion of Li+, allowing the battery to successfully cycle at a high rate of 0.5 C at -20 °C, and giving it a reversible capacity retention rate of 65.3% at -40oC. This work designs a promising advanced electrolyte and holds the potential to overcome limitations of lithium-ion batteries in harsh conditions.