Uncontrollable Dendrite Growth Research Articles

A Highly Reversible Zinc Anode for Rechargeable Aqueous Batteries.

Zinc metal holds a great potential as an anode material for next-generation aqueous batteries due to its suitable redox potential, high specific capacity, and low cost. However, the uncontrollable dendrite growth and detrimental side reactions with electrolytes hinder the practical application of this type of electrodes. To tackle the issues, an ultrathin (∼1 μm) sulfonated poly(ether ether ketone) (SPEEK) solid-electrolyte interphase (SEI) is constructed onto the Zn anode surface by a facile spin-coating method. We demonstrate that the polymeric SEI simultaneously blocks the water molecules and anions, uniformizes the ion flux, and facilitates the desolvation process of Zn2+ ions, thus effectively suppressing the side reactions and Zn dendrite formation. As a result, the newly developed Zn@SPEEK anode enables a symmetric cell to stably operate over 1000 cycles at 5 mA cm-2 without degradation. Moreover, with the Zn anode paired with a MnO2 cathode, the full cell exhibits an improved Coulombic efficiency (over 99% at 0.1 A g-1), a superior rate capability (127 mA h g-1 at 2 A g-1), and excellent cycling stability (capacity retention of 70% over 1000 cycles at 1 A g-1). This work provides a facile yet effective strategy to address the critical challenges in Zn anodes, paving the way for the development of high-performance rechargeable aqueous batteries.

Unravel SEI Formation on Li Metal Interfaces By Mechanistic Multi-Scale Modelling

Nowadays, lithium metal anodes are often referred to as the ‘holy grail’ of next-generation battery technology. Compared to graphite anodes used in state-of-the-art lithium-ion batteries they promise several times higher energy densities [1]. However, Li metal shows a high reactivity with liquid electrolytes and uncontrolled dendrite growth which hinders a safe and efficient cyclability and therefore the commercial application in rechargeable batteries. Thus, stabilization of the solid-electrolyte interphase (SEI) between liquid electrolyte and the lithium surface is the key challenge to be solved before bringing this promising battery technology to market. In order to suppress unwanted effects such as dendrite formation, persistent loss of active material and high kinetic losses, this layer of electrolyte decomposition products needs to be electrically insulating and should prevent direct contact of metal with electrolyte while ensuring a good ionic conductivity and mechanical stability.Such a beneficial SEI design requires detailed understanding of the fundamental formation mechanism and the resulting chemical SEI composition and structure depending on electrolyte composition. In literature, a large range of experimental methods are applied to characterize the SEI under various conditions [2]. These approaches are mainly descriptive and struggle to identify and understand the underlying mechanisms. Theoretical approaches like density functional theory (DFT), ab-initio molecular dynamics (MD) or classical MD are well suited to determine reaction mechanisms and to model the very beginning of SEI formation in the ns-range. However, they are too computationally expensive to model technical relevant length- and time scales [3].Therefore, this work focuses on overcoming these restrictions by developing an efficient multiscale-model with input from ab-initio calculations. The acceleration originates from focusing on rare events such as reaction or diffusion processes in a 3-dimensional kinetic Monte Carlo instead of considering the vibrational motions of single atoms like in molecular dynamics. Thereby, every process is represented by a probability derived from ab-initio calculations to ensure physical correctness. An additional coupling with efficient ordinary differential equations as shown in [4] ensures electroneutrality in the simulation box.Implementation of the degradation reactions for a 1.2M LiPF6/EC electrolyte obtained from molecular simulations (see Figure 1, appendix), allows to unravel the initial SEI formation, the emerging structure and its composition within the first µs. The simulation suggests an almost instantaneous formation of SEI species on the pristine Li metal within the first nanoseconds after immersion. Due to this early passivation layer the formation process slows down continuously until electron tunneling is blocked by SEI species and a first passivation of the lithium surface is reached. Interestingly, the formed passivation layer mainly consists of inorganic species such as LiF close to the lithium metal surface and Li2CO3 throughout the whole layer but only of minor organic (CH2OCO2Li)2-molecules, suggesting that organic species are mainly formed at larger time scales which is the reason for the typical layering structure of the SEI.In summary this novel approach allows unprecedented insight of initial SEI-formation and thereby extends the accessible insight, time- and length-scales compared to molecular simulations.

Asymmetric Sodiophilic Host Based on a Ag-Modified Carbon Fiber Framework for Dendrite-Free Sodium Metal Anodes.

Sodium (Na) metal is considered a promising anode material for high-energy Na batteries due to its high theoretical capacity and abundant resources. However, uncontrollable dendrite growth during the repeated Na plating/stripping process leads to the issues of low Coulombic efficiency and short circuits, impeding the practical applications of Na metal anodes. Herein, we propose a silver-modified carbon nanofiber (CNF@Ag) host with asymmetric sodiophilic features to effectively improve the deposition behavior of Na metal. Both density functional theory (DFT) calculations and experiment results demonstrate that Na metal can preferentially nucleate on the sodiophilic surface with Ag nanoparticles and uniformly deposit on the whole CNF@Ag host with a "bottom-up growth" mode, thus preventing unsafe dendrite growth at the anode/separator interface. The optimized CNF@Ag framework exhibits an excellent average Coulombic efficiency of 99.9% for 500 cycles during Na plating/stripping at 1 mA cm-2 for 1 mAh cm-2. Moreover, the CNF@Ag-Na symmetric cell displays stable cycling for 500 h with a low voltage hysteresis at 2 mA cm-2. The CNF@Ag-Na//Na3V2(PO4)3 full cell also presents a high reversible specific capacity of 102.7 mAh g-1 for over 200 cycles at 1 C. Therefore, asymmetric sodiophilic engineering presents a facile and efficient approach for developing high-performance Na batteries with high safety and stable cycling performance.

Highly stable and durable Zn-metal anode coated by bi-functional protective layer suppressing uncontrollable dendrites growth and corrosion

Although rechargeable aqueous zinc batteries (RAZB) have experienced their renaissance recently, Zn-metal anodes still suffer from serious dendrites growth and inevitable Zn corrosion in mild aqueous electrolyte during cycling. It is imperative to provide a simple and effective strategy to address the above problems. Herein, we have developed a one-step strategy to in-situ fabricate a homogeneous and stable protective layer composing of dense ZnF2 and embedded Cu particles on the electrode at room temperature. The ZnF2-Cu protective layer with both high Zn2+ transfer number (0.758) and homogeneous nucleation sites (Cu particles) with excellent zinc affinity exhibits remarkable synergistic effect for dual purpose: 1) to effectively inhibit severe dendrites growth via regulating Zn nucleation and 2) to suppress Zn corrosion and the accompanying hydrogen evolution by preventing Zn metal surface from aqueous electrolyte attacking. As a result, the ZnF2-Cu@Zn anodes can maintain stable cycling for>1600 h with super low over-potential and increased average coulombic efficiency (CE). In addition, the ZnF2-Cu@Zn || V2O5 full cells provide a reversible capacity of 103 mA h g−1 after 2000 cycles at an ultra-high current density of 10 A g−1. This work proposes a promising approach for the practical application of RAZB in the future.

Lithiophilic Cu‐Li2O matrix on a Cu Collector to Stabilize Lithium Deposition for Lithium Metal Batteries

Lithium metal anode is the most ideal candidate for next‐generation energy storage system. However, the uncontrolled dendrite growth, infinite volume expansion, and undesired side reactions lead to serious safety issues and hinder their potential application. Herein, a pre‐lithiation strategy is proposed to construct a high‐lithiophilic Cu‐Li2O matrix on commercial Cu foil. The in situ‐generated Li2O promises adequate nucleation sites and strengthens solid electrolyte interphase and lateral lithium deposition. Meanwhile, the existence of 3D matrix reduces the local current density. The synergy effect of Li2O and Cu suppresses the growth of lithium dendrites. As a result, Cu‐Li2O matrix reveals an enhanced lithium plating/stripping behavior with Coulombic efficiency of 98.46% after 270 cycles. The symmetrical cell assembled by Li‐plated electrodes displays a prolonged lifespan of 1400 h. The work demonstrates a scalable and effective approach for modified current collectors toward stable Li metal anode.

In situ constructing lithiophilic and Ion/Electron Dual-Regulated current collector for highly stable lithium metal batteries

The uncontrollable dendrite growth is the most critical barrier that hinders the practical applications of Li metal anodes. Herein, a novel lithiophilic and mixed ion/electron conductive current collector is constructed via a facile in-situ activation process of nickel sulfide on the Nickel foam (NF). Such current collector exhibits excellent lithiophilicity, high Li+ diffusion coefficient and electron conductivity due to its unique vertical-aligned and interconnected arrays consisting of lithium sulfide and nickel on NF skeleton. Especially, the mixed ion/electron conductive arrays not only effectively regulate the ionic flux and electric field, but also provide continuous pathways for the fast transportation of both the Li+ and electron. As a result, the growth of Li dendrites is suppressed. Moreover, full cells with low Negative/positive (N/P) ratio exhibit superior cycling stability, high-capacity retention and outstanding rate performance. Typically, full cells pairing with LiFePO4 (LFP) cathodes with a N/P ratio of 6.3 show long-term cycling for over 700 and 350 cycles at high rates of 5C and 10C, delivering ultrahigh capacity retentions of over 95.7% and 86.4%, respectively. Even with an ultralow N/P ratio of 1.2 with LFP loading of 2.45 mAh cm−2, the full cell still shows excellent cycling stability for over 130 cycles. This work sheds new light on the development of dendrite-free Li metal anodes for high-performance Li metal batteries with lithiophilic and ion/electron dual-regulated current collector.

Immunizing Aqueous Zn Batteries against Dendrite Formation and Side Reactions at Various Temperatures via Electrolyte Additives.

Aqueous Zn-ion batteries own great potential on next generation wearable batteries due to the high safety and low cost. However, the uncontrollable dendrites growth and the negligible subzero temperature performance impede the batteries practical applications. Herein, it is demonstrated that dimethyl sulfoxide (DMSO) is an effective additive in ZnSO4 electrolyte for side reactions and dendrites suppression by regulating the Zn-ion solvation structure and inducing the Zn2+ to form the more electrochemical stable (002) basal plane, via the higher absorption energy of DMSO with Zn2+ and (002) plane. Moreover, the stable reconstructed hydrogen bonds between DMSO and H2 O dramatically lower the freezing point of the electrolyte, which significantly increases the ionic conductivity and cycling performance of the aqueous batteries at subzero temperatures. As a consequence, the symmetrical Zn/Zn cell can be kept stable for more than 2100 h at 20°C and 1200 h at -20°C without dendrite and by-products formation. The Zn/MnO2 batteries can perform steadily for more than 3000 cycles at 20°C and 300 cycles at -20°C. This work provides a facile and feasible strategy on designing high performance and dendrite free aqueous Zn-ion batteries for various temperatures.

Interphase Building of Organic-Inorganic Hybrid Polymer Solid Electrolyte with Uniform Intermolecular Li+ Path for Stable Lithium Metal Batteries.

Lithium (Li) metal has been generally noticed as the most prospective anode for next-generation batteries attributed to its outstanding theoretical capacity and low electrochemical potential. Nevertheless, the unstable solid-electrolyte interphase (SEI) and uncontrollable dendrite growth cause poor reversibility and fetter the practical application of Li metal anodes. Herein, a new organic-inorganic hybrid polymer artificial SEI (POSS-LiBMAB) layer with uniform lithium-ion paths at a molecular level is designed to stabilize Li metal anodes. The SEI layer is constructed by the thiol-ene "click chemistry" reaction between inorganic polyhedral oligomeric silsesquioxane containing eight-mercaptopropyl (POSS-SH) with lithium bis (allylmalonato) borate (LiBMAB) on Li foil. What is more, the POSS-LiBMAB film can be cross-linked and self-reinforced via intermolecular SC bonds. Benefiting from its flexible polymeric covalent structure and noble inorganic Si8 O16 -type cubes, the organic-inorganic hybrid polymer layer is flexible and effectively tolerates the volume change of Li metal anodes during plating/stripping cycles. In addition, this layer shows loose and uniformly distributed electrostatic interaction between Li+ and charge delocalized sp3 boron-oxygen anions, which aids to form a uniform intermolecular Li+ path regulating the homogeneous distribution of Li+ flux on Li anodes. Finally, the designed POSS-LiBMAB layer has high ionic conductivity and lithium-ion transference number, which can effectively promote Li+ diffusion and guide Li deposition beneath the SEI layer. Therefore, with the protection of the POSS-LiBMAB layer, the Li metal anode exhibits stable cycling at 5mA cm-2 for more than 1000 h, and the LFP//Li full cells also present outstanding cycling stability.

Stable all-solid-state lithium metal batteries with Li3N-LiF-enriched interface induced by lithium nitrate addition

All-solid-state lithium metal batteries (ASSLMBs) show great potential for high energy density as well as enhanced safety. However, the practical application is still hampered by uncontrollable dendrite growth and limited cycling stability. Herein, a stable Li3N-LiF-enriched interface is in-situ induced between poly (ethylene oxide) (PEO)-based solid electrolyte and Li anode by introducing lithium nitrate (LiNO3). Combining surface characterizations and molecular dynamics simulations, firstly, it reveals that the addition of LiNO3 facilitates the decomposition of lithium bis(trifluoromethylsulfonyl) imide (LiTFSI) to preferentially form LiF. The Li3N-LiF-enriched interface greatly improves interface contact between solid electrolyte and Li anode, leading to homogenous Li deposition. With LiNO3 addition, the critical current density of PEO-based electrolyte can be enhanced to high value of > 0.9 mA cm–2. Meanwhile, all-solid-state LMBs coupled with LiFePO4 cathode show superior cycling stability and Coulombic efficiency (CE), especially, the initial CE is up to 94.12 % at 0.5 C. Even paired with high-potential NCM cathode, promoted electrochemical performances can be achieved, with 91.4 % capacity retention after 200 cycles at 0.3 C. What's more, this work illustrates the importance of interface modification in ASSLMBs from the perspective of the relationship between impedances and overpotentials.

Dendrite-free lithium deposition enabled by a vertically aligned graphene pillar architecture

Uncontrollable dendrite growth and poor reversibility of lithium (Li) metal anode hinder the practical implementation of Li metal based batteries. Herein, we report a feasible and scalable electrospraying strategy for fabricating a vertically aligned graphene (VAG) pillar architecture with low tortuosity and high specific surface area as both current collector and host material for Li metal anode. Columnar and dense Li with large granular size plates into the VAG electrode by the aid of the pillar structure, which could ensure continuous ion transfer and lower actual current density for uniform nucleation, as well as provide more accommodation with proper space size. The hollow graphene pillars and the surrounding sufficient space enables smooth Li plating under high capacity depth and abstains volume fluctuation of the whole electrode. The VAG pillar modified Li anode delivers low overpotential of 25 mV over 280 h under a high rate of 3 mA cm−2, and high Coulombic efficiencies for 250 cycles at a capacity of 1 mAh cm−2. More importantly, full cells paired with the high capacity LiFePO4 cathode exhibit excellent cycling stability and rate capability, demonstrating the high Li utilization efficiency and improved ion migration kinetic in the low tortuous VAG architecture.

Interfacially Redistributed charge for robust lithium metal anode

Li metal is the ultimate anode material for Li based battery with high energy density. However, inhomogeneous charge distribution from the unbalanced ion/electron transport is usually generated at the electrode surface, leading to the uncontrollable dendrites with poor reversibility. Herein, interconnected Li 3 P@Cu ion/electron conductive interlayer activated from interfacial reaction between Cu 3 P arrays and metallic Li is efficiently constructed on Li foil surface through room-temperature mechanical rolling process for charge redistribution. Demonstrated by theoretic calculation, the diffusion barrier of Li + is remarkably reduced from Li 3 P interphase with high ionic conductivity, while the electron-conductive Cu domains ensures well-dispersed current density, facilitating the uniform distribution of interfacial Li + flux. Furthermore, the interconnected skeletons with extensive active channels significantly enhances the electrochemical kinetics and promotes the reversibility of Li plating/stripping processes. As expected, a prolonged lifespan of symmetrical cells over 1500 h with lower polarization is successfully achieved at 1 mA cm −2 , further improving the rates and cycling performances of LiFePO 4 based full cells in mass loading of 8.5 mg cm −2 with a capacity retention up to 91.7% after 300 cycles. This work proposed a rational interlayer design for interfacial charge redistribution and presents an efficient strategy to realize dendrite-free Li metal anode. The practical application of Li metal battery is predominately retarded by the uncontrollable dendrite growth from unbalanced ion/electron transport. In this work, a room-temperature interfacial reaction was applied to construct Li 3 P/Cu mixed conductive layer for interfacial charge redistribution via a facial mechanical rolling press method. Interestingly, the derived coating layer with mixed ion/electron conductive feature significantly enhances the electrochemical kinetics and promotes the interfacial charge redistribution with a dendrite-free deposition morphology. Greatly, Li@MCI based symmetric cells achieves a prolonged lifespan over 1500 h at 1 mA cm −2 with lower polarization than that of Li based cells, which further promotes the rate performance and stability of the Li@MCI based full batteries with a high-loading LiFePO 4 cathode (8.5 mg cm −2 ). • Interconnected Li 3 P@Cu MCI was efficiently constructed on Li foil surface for interfacial charge redistribution. • Enhanced electrochemical Kinetics has been demonstrated by DFT calculations and symmetric cell. • Epitaxially growth of lithium was achieved within Li 3 P@Cu interlayer. • Li 3 P@Cu modified Li metal exhibited robust electrochemical performance over 1500 h.

Strongly coupled tungsten oxide/carbide heterogeneous hybrid for ultrastable aqueous rocking‐chair zinc-ion batteries

Aqueous Zinc-ion batteries (ZIBs) are recognized as the most pivotal competitor of lithium-ion batteries due to their abundant reserves, remarkable safety and affordable cost. However, the uncontrollable dendritic growth and extremely low utilization (<5%) of zinc metal anode severely limit the practicality and energy density of ZIBs. Herein, a novel rocking-chair ZIBs with excellent cycling stability and high energy density is developed via employing tungsten oxide/carbide (WO3/WC) layered heterogeneous hybrid with strong-coupling effect as the intercalated anode and MnO2/graphite cathode. Benefiting from the favorable interface energy and electronic coupling with prominent charge-transfer between WO3 and WC, the WO3/WC//Zn batteries deliver admirable capacity of 164 mAh g−1 under 0.1 A g−1 with suitable Zn2+ intercalated potential of 0.43 V (vs. Zn2+/Zn), long-term cyclability with 90.2% after 1000 cycles under 1 A g−1, and reversible Zn2+ intercalation behavior. Consequently, the assembled WO3/WC||MnO2/graphite rocking-chair ZIBs offer excellent capacity of 69 mAh g−1 at 0.1 A g−1, impressive cyclic stability (100% after 10,000 cycles) and exceptional energy density of 85 Wh kg−1, suppressing most of reported rocking‐chair ZIBs. Therefore, this research provides a novel insight for designing safe and high-efficient ZIBs.

Highly lithiophilic ZnO nanosheets decorated Ni foam as a stable host for high-performance lithium metal anodes

Uncontrollable dendrite growth and infinite volume expansion in lithium metal anodes results in the severe safety hazards and poor stability. 3D hosts with lithiophilic property are expected to solve the issues. Herein, we proposed a highly lithiophilic ZnO nanosheets array decorated Ni foam (ZnO-NF) as a stable 3D host to inhibit the dendrite formation fabricated by thermal infusion method. The uniformly distributed ZnO nanosheets can improve the lithiophilicity of Ni foam, and regulate Li nucleation, leading to a uniform Li stripping/plating behavior. Additionally, the large surface area of the ZnO-NF framework can reduce local current density and the 3D porous structure can restrain the volume expansion. Compared with the bare Li foils anode, the as-obtained Li@ZnO-NF composite anode exhibits much stable stripping/plating profiles with an ultra-low overpotential (16 mV) for ultralong lifespan (1000 h) at a current density of 1 mA cm−2 in symmetric cell without significant fluctuations. Moreover, remarkable rate capability and long-term cycling stability (80.3% capacity retention after 450 cycles at 1 C) are obtained in full cells paired with a LiFePO4 cathode. This work will provide a new pathway to design the highly lithiophilic host towards high-performance lithium metal anodes.

Porous Lithiophilic Li–Si Alloy‐Type Interfacial Framework via Self‐Discharge Mechanism for Stable Lithium Metal Anode with Superior Rate

AbstractLithium is regarded as an ideal anode for next‐generation Li metal batteries (LMB) as it exhibits extraordinarily high theoretical capacity and the lowest electrochemical potential among all anode candidates. However, safety concerns and poor cycling stability of Li induced by uncontrollable dendrite growth and severe side reactions impede its practical application for LMB. Although various strategies for fabricating Li anodes have been suggested, developing high‐rate LMB remains a significant challenge. To address this challenge, the use of a 3D porous Li–Si alloy‐type interfacial framework (LSIF) created via a “self‐discharge” mechanism with the aid of an electrolyte is proposed here. Exploiting the in situ spontaneous prelithiation, lithiophilic Li15Si4 particles are homogenously arranged to build porous 3D LSIF. The balanced ionic/electronic conducting LSIF serves as a stable Li host, helping to suppress dendrite growth and volume expansion during cycling. The LSIF@Li anode possesses a strong affinity toward Li, rapid Li diffusion kinetics, and low nucleation/diffusion barriers. Moreover, the LSIF@Li symmetric cells are capable of stable cycling (over 1000 cycles) even at an ultrahigh current density (15 mA cm–2). When paired with LiNi0.5Co0.2Mn0.3O2 or LiFePO4, LSIF@Li full cells show improved rate capability and long‐term cycling stability (≈2000 cycles) at 10 C.

Zincophilic Laser‐Scribed Graphene Interlayer for Homogeneous Zinc Deposition and Stable Zinc‐Ion Batteries

Zinc metal is an important anode material for next‐generation energy storage systems. Unfortunately, uncontrollable dendrite growth caused by nonuniform Zn nucleation during the plating process severely restricts their practical applications. Herein, a nitrogen‐doped 3D laser scribed graphene (NLSG) with a large surface area and uniform distribution of nucleation sites is used as the interlayer to control Zn nucleation behavior and suppress Zn dendrite growth. The N‐containing functional groups in the carbon matrix are highly zincophilic, which induces uniform nucleation of Zn and guides homogenous Zn deposition. Meanwhile, the large specific area can effectively decrease the local current density, which is more favorable for highly reversible Zn plating/stripping. Benefiting from superior properties, the NLSG demonstrates improved electrochemical performance with high Coulombic efficiency (99.4%) and enhanced cycling performance (200 h). Compared with the bare Zn anodes, the NLSG‐coated Zn//MnO2 battery demonstrates higher capacity retention (72.3% vs 59.3%) after 1200 cycles.

Nano-channel-based physical and chemical synergic regulation for dendrite-free lithium plating

Uncontrollable dendrite growth resulting from the non-uniform lithium ion (Li+) flux and volume expansion in lithium metal (Li) negative electrode leads to rapid performance degradation and serious safety problems of lithium metal batteries. Although N-containing functional groups in carbon materials are reported to be effective to homogenize the Li+ flux, the effective interaction distance between lithium ions and N-containing groups should be relatively small (down to nanometer scale) according to the Debye length law. Thus, it is necessary to carefully design the microstructure of N-containing carbon materials to make the most of their roles in regulating the Li+ flux. In this work, porous carbon nitride microspheres (PCNMs) with abundant nanopores have been synthesized and utilized to fabricate a uniform lithiophilic coating layer having hybrid pores of both the nano- and micrometer scales on the Cu/Li foil. Physically, the three-dimensional (3D) porous framework is favorable for absorbing volume changes and guiding Li growth. Chemically, this coating layer can render a suitable interaction distance to effectively homogenize the Li+ flux and contribute to establishing a robust and stable solid electrolyte interphase (SEI) layer with Li-F, Li-N, and Li-O-rich contents based on the Debye length law. Such a physical-chemical synergic regulation strategy using PCNMs can lead to dendrite-free Li plating, resulting in a low nucleation overpotential and stable Li plating/stripping cycling performance in both the Li‖Cu and the Li‖Li symmetric cells. Meanwhile, a full cell using the PCNM coated Li foil negative electrode and a LiFePO4 positive electrode has delivered a high capacity retention of ∼ 80% after more than 200 cycles at 1 C and achieved a remarkable rate capability. The pouch cell fabricated by pairing the PCNM coated Li foil negative electrode with a NCM 811 positive electrode has retained ∼ 73% of the initial capacity after 150 cycles at 0.2 C.

Chlorinated dual-protective layers as interfacial stabilizer for dendrite-free lithium metal anode

Lithium metals offer great promises to achieve higher energy density beyond conventional lithium-ion batteries (LIBs) because of its ultrahigh specific capacity (3860 mAh g−1) and the lowest reduction potentials (-3.04 V vs. standard hydrogen electrode). Unfortunately, the application of lithium metal anode has been long-standingly handicapped by uncontrollable dendrite growth, which induces instable solid electrolyte interface (SEI), performance degradation and thermal runaway. Herein, a compositionally favorable and structurally robust dual-protective layer (DPL) is proposed, where at the bottom, in-situ formed LiCl film provides sufficient rigidity (6.5 GPa) and low Li+ diffusion barriers (0.09 eV) against dendrite growth. The poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) gel-electrolyte as the top layer is rationally selected with high flexibility to accommodate volume variation. Due to the synergy of DPL, the instability of interface is ultimately regulated to favor an extremely stabilized SEI with enhanced Li+ diffusion kinetics. Depth profiling of X-ray photoelectron spectroscopy (XPS) revealed a spontaneously-formed gradient SEI hierarchy, a first-of-this-kind structure that enables long-term cycle stability and high rate capability. Cryo-electron microscopy (cryo-EM) provides direct proof on the formation of halide-rich SEI interlayers that strengthen the interfacial stability during cycles. As a consequence, dendrite-proof lithium deposition, critical Li+ flux and fast ion-diffusion kinetics have been synergistically achieved to greatly improve the high-rate cycle stability (10 mA cm−2), high Coulombic efficiency (99.5%), and prolonged cycle lifespan (1600 h) for lithium metal batteries (LMBs). The design of DPL from this contribution has opened up opportunities of lithium chlorides in purpose of constructing dendrite-free and Li+ permeable interface, and provided insights for the realization of high energy density LMBs.

Saccharin Anion Acts as a "Traffic Assistant" of Zn2+ to Achieve a Long-Life and Dendritic-Free Zinc Plate Anode.

Due to the great advantages of low cost, high capacity, and excellent safety, the Zn metal is a promising candidate material for rechargeable aqueous battery systems. However, its practical applications have been restricted by the uncontrollable dendrite growth and electrode side reactions (such as corrosion, passivation, and hydrogen evolution reactions) during the plating process. Herein, we reveal that the dendrite growth would expose the electrode to more highly active tips, exacerbating the passivation of the electrode and the decomposition of the electrolyte by in situ optical microscopies. We propose a low-cost, nontoxic, low-concentration (less than 1 g/L), and effective electrolyte additive, saccharin sodium, which can guide an even Zn deposition without obvious electrode side reactions in the charge/discharge process. The saccharin anion acts as a "traffic assistant" of Zn2+ and demonstrates its great potential for practical application. The assembled Zn symmetrical battery shows an excellent cycling performance at a high current density and capacity (an extremely long cycle life over 3800 h is obtained at 5 mA/cm2 and 8 mA h/cm2, and 20 mA/cm2 and 5 mA h/cm2 show a lifetime over 800 h), and the full cell (coupled to an AC electrode) presents a stable cycle life with a capacity retention of 86.4% even after 8000 cycles at 5 mA/cm2. The saccharin sodium proposed in this work is promising to solve the anode problems in advanced Zn batteries.

Scalable and Controllable Synthesis of Interface-Engineered Nanoporous Host for Dendrite-Free and High Rate Zinc Metal Batteries.

Rechargeable zinc (Zn)-ion batteries are regarded as highly prospective candidates for next-generation renewable and safe energy storage systems. However, the uncontrolled dendrite growth of the Zn anode impedes their practical application. Here, a scalable and controllable approach is developed for converting commercial titanium (Ti) foil to 3D porous Ti, which retains good resistance to corrosion, high electrical conductivity, and excellent mechanical properties. Benefiting from a spontaneous ultrathin zincophilic titanium dioxide (TiO2) interfacial layer and continuous 3D structure, the 3D porous Ti can act as an effective host to achieve a 3D Ti/Zn metal anode. By ensuring homogeneous nucleation, uniform current distribution, and volume change accommodation, the dendritic growth of 3D Ti/Zn metal anode is effectively inhibited with stable Zn plating/stripping up to 2000 h with low polarization. When conjugated with a 3D sulfur-doped Ti3C2Tx MXene@MnO2 nanotube cathode, a high rate and stable Zn cell is achieved with 95.46% capacity retention after 500 cycles at a high rate of 5 A g-1. This work may also be interesting for researches in porous metals and other battery systems.

3D oxidized polyacrylonitrile/Ag framework guided bottom-up lithium deposition for dendrite-free lithium metal batteries

Lithium (Li) metal anode is considered as the “Holy Grail” for next-generation ultrahigh-energy-density lithium-ion batteries, but its application is tremendously limited by the demerits of uncontrolled dendrite growth, unrestricted volume expansion, and continuous side reactions. Herein, a 3D oxidized polyacrylonitrile (PAN)/Ag framework is designed to realize a bottom-up Li deposition and dendrite-free growth. The electronic insulator nature of the oxidized PAN guides a bottom-up lithium deposition to largely prevent volume expansion. In addition, the Ag nanoparticles on the PAN surface directly form a Li-Ag alloy with as-deposited Li, resulting in a low nucleation barrier. Furthermore, Li-Ag, as a Li+ conductor, induces a uniform and dense Li deposition. As a result, the oxidized PAN/Ag framework offers a long lifespan over 1200 h at a current density of 0.5 mA cm−2 and an areal capacity of 1 mAh cm−2. Moreover, in a full cell coupled with LiNi0.9Co0.1O2 cathode, a capacity retention of 84% after 100 cycles is achieved. This study provides a guideline to fabricate stable Li metal anode and highlights the key role of controlling electronic and ionic transportation separately in the 3D framework.