Suppress Li Dendrite Research Articles

Selective and uniform Li-ion boosting polymer electrolytes for dendrite-less quasi-solid-state batteries

Solid-state Li-metal batteries (LMBs) are attracting extensive attention owing to their exceptionally high energy density. Solid electrolytes play a vital role in the practical application of LMBs due to their nonflammable nature and interfacial stability with Li metal, but they ordinarily have a low ionic conductivity and dimensional stability. Here, a selective Li+ conductive solid-state electrolyte (SLCSE) that comprises a highly conductive yet mechanically robust, anion-immobilized (CMA) polymer matrix synthesized by soft-rigid coupled ether-abundant epoxy monomers and branched polyamine, is reported. Rationally incorporated rigid benzene-ring constituents in the CMA matrix not only enhance mechanical strength but also boost Li+ transportation by suppressing crystallinity. The semi-interpenetrating network of the CMA matrix and polyvinylidene fluoride-co-hexafluoropropylene displays synergistic Li+ acceleration behavior by promoting the dissociation and diffusion of Li+ while immobilizing anions, which is elucidated via molecular dynamics simulations. The SLCSE exhibits a high ionic conductivity (3.4 mS cm−1) with a high Li+ transference number (0.77), and SLCSE-based LMBs (Li/SLCSE/LiCoO2 cell) show a high discharge capacity of 146 mAh g−1 (0.2 C) and 126 mAh g−1 (3 C). Furthermore, they show exceptional long cycle stability (90% capacity retention after 500 cycles at 0.5 C), representing remarkable Li dendrite suppression capability.

Structurally Tailored Hierarchical Cu Current Collector with Selective Inward Growth of Lithium for High‐Performance Lithium Metal Batteries

AbstractLi‐metal is gaining attention as a next generation anode active material, of which the primary attribute is its energy density. However, Li dendrite formation is the primary challenge. Herein, a design strategy with increased structural dimensions and hierarchy for Li‐metal anode is investigated to stabilize the dendrite formation for extending the cycle life with high reversibility. For this, diverse structural current collectors (CCs) are fabricated by manipulating structural design in different length scales and characterized as a Li‐metal anode. The hierarchy (i.e., nanostructures inside the microcavities) can not only reduce the current density on entire anode surface but also concentrate the local electrical field onto inner surfaces of the microstructures, inducing preferential Li nucleation inside microcavities and promoting confined growth of Li. It is confirmed that introduction of structural hierarchy can enhance the cycle life by 364% and the preservation of coulombic efficiency > 90% by 266%. The design strategy is extended by exploring a practical one‐step fabrication of the hierarchical CC with even greater performance via the inward growth mechanism. This work elucidates the mechanism of inward Li growth using tailored surface geometries for Li dendrite suppression, which can be a guideline for designing structured anode CCs for Li‐metal batteries.

Multiscale Structural Gel Polymer Electrolytes with Fast Li+ Transport for Long‐Life Li Metal Batteries

AbstractLi metal batteries (LMBs) are considered as promising candidates for future rechargeable batteries with high energy density. However, Li metal anode (LMA) is extensively sensitive to general liquid electrolytes, leading to unstable interphase and dendrites growth. Herein, a novel gel polymer electrolyte consisting of a micro‐nanostructured poly(vinylidene fluoride‐co‐hexafluoropropylene) matrix and inorganic fillers of Zeolite Socony Mobil‐5 (ZSM‐5) and SiO2 nanoparticles, is fabricated to expedite Li+ ions transport and suppress Li dendrite growth. Due to the Lewis acid interaction, SiO2 can absorb amounts of PF6− and promote the dissociation of LiPF6. The specific sub‐nanometer pore structure of ZSM‐5 greatly enhances the Li+ ion transference number. These structures can restrain the decomposition of electrolytes and build stable interphase on LMA. Therefore, the Li||Ni0.8Co0.1Mn0.1O2 full cell maintains 92% capacity retention after 300 cycles at 1 C (1 C ≈190 mAh g−1) in carbonate electrolyte. This multiscale design provides an effective strategy for electrolyte exploration in high‐performance LMBs.

Stabilization of garnet/Li interphase by diluting the electronic conductor.

The high interfacial resistance and lithium (Li) dendrite growth are two major challenges for solid-state Li batteries (SSLBs). The lack of understanding on the correlations between electronic conductivity and Li dendrite formation limits the success of SSLBs. Here, by diluting the electronic conductor from the interphase to bulk Li during annealing of the aluminium nitride (AlN) interlayer, we changed the interphase from mixed ionic/electronic conductive to solely ionic conductive, and from lithiophilic to lithiophobic to fundamentally understand the correlation among electronic conductivity, Li dendrite, and interfacial resistance. During the conversion-alloy reaction between AlN and Li, the lithiophilic and electronic conductive LixAl diffused into Li, forming a compact lithiophobic and ionic conductive Li3N, which achieved an ultrahigh critical current density of 2.6/14.0 mA/cm2 in the time/capacity-constant mode, respectively. The fundamental understanding on the effect of interphase nature on interfacial resistance and Li dendrite suppression will provide guidelines for designing high-performance SSLBs.

Working Principles of Lithium Metal Anode in Pouch Cells

AbstractLithium metal battery has been considered as one of the potential candidates for next‐generation energy storage systems. However, the dendrite growth issue in Li anodes results in low practical energy density, short lifespan, and poor safety performance. The strategies in suppressing Li dendrite growth are mostly conducted in materials‐level coin cells, while their validity in device‐level pouch cells is still under debate. It is imperative to address dendrite issues in pouch cells to realize the practical application of Li metal batteries. This review presents a comprehensive overview of the failure mechanism and regulation strategies of Li metal anodes in practical pouch cells. First, the gaps between the scientific findings in materials‐level coin cells and device‐level pouch cells are underscored. Specific attention is paid to the mechanistic understanding and quantitative discussion on the failure mechanisms of pouch‐type Li metal batteries. Subsequently, recently proposed strategies are reviewed to suppress dendrite growth in pouch cells. The state‐of‐the‐art electrochemical performance of pouch cells, especially the cell‐level energy density and lifespan, is critically concerned. The review concludes with an attempt to summarize the scientific and engineering understandings of pouch‐type Li metal anodes and propose some novel insights for the practical applications of Li metal batteries.

Electrochemically Dealloyed 3D Porous Copper Nanostructure As High-Performance Anode Current Collector of Li-Metal Batteries

Li metal anode is the ultimate choice for Li batteries owning to its highest theoretical capacity (3806 mAh/g) and lowest redox potential (-3.04 V vs. standard hydrogen electrode) among possible candidates.[1] However, despite the advantages of Li metal anodes, a number of remaining challenges must be addressed before its commercialization: undesired dendrite growth of Li, and irreversible parasitic reactions between Li and electrolyte, etc.Stabilization of Li metal is essential for commercial application of Li metal anodes. In the past few years, several strategies have been developed to suppress Li dendrite growth and stabilize SEI formation during Li plating/stripping processes. Among these strategies, 3D current collectors showed its high potential in Li anode stabilization due to its much larger surface area, which can provide much more Li nucleation sites, alleviate volumetric changes of Li anode, and decrease practical current density. Thus, compared to flat Cu foil used in commercial Li-ion batteries, 3D Cu current collectors can facilitate uniform Li deposition, mitigate Li dendrite growth, and enhance Li cycling stability.[2]Our previous work reported a 3D porous Cu current collector fabricated via a facile one-step electrodeposition method directly on commercial Cu foil. [3] The fabricated 3D porous Cu current collector showed stable long-term cycling with a high areal capacity of 6 mAh/cm2 and no Li dendrite growth was observed during cycling process. However, for the one-step electrodeposition method, the thickness of the porous Cu deposition layer is limited. Thus, preparation of 3D porous Cu layers with both high thickness and high porosity is necessary to further improve the areal capacity of this current collector. Recently, we developed a new two-step electrochemical process to fabricate thick and porous Cu layer: a thick Cu-Zn alloy was first electrodeposited on commercial Cu foil, and Zn was then removed electrochemically, leaving a thick and highly porous 3D Cu layer. Compared to our previous method, this 3D Cu layer has a high thickness of ~14 um and porosity of ~72%. This new 3D Cu current collector can achieve stable Li cycling up to 230 h at high areal capacity of ~10 mAh/cm2 at a high current density of 10 mA/cm2, demonstrated its high commercial application potential in Li-metal batteries. Tarascon, J.M. and M. Armand, Issues and challenges facing rechargeable lithium batteries. Nature, 2001. 414(6861): p. 359-367.Yang, C.P., et al., Accommodating lithium into 3D current collectors with a submicron skeleton towards long-life lithium metal anodes. Nature Communications, 2015. 6.Ma, X., Z. Liu, and H. Chen, Facile and scalable electrodeposition of copper current collectors for high-performance Li-metal batteries. Nano Energy, 2019. 59: p. 500-507.

Development of a Three-Dimensional Porous Scaffold Adopting Lithiophilic Silver for a High-Performance Lithium Metal Anode

Lithium metal is the most promising candidate for a high-capacity anode in Li-ion batteries due to the highest theoretical specific capacity (3,860 mAh g-1) and the lowest redox potential (-3.04 V vs S.H.E.) [1]. However, the Li metal anode (LMA) is still challenging to be used practically due to mossy-like dendrite formation, dead Li growth, and infinite volume expansion resulting in safety hazards. Various approaches have been proposed to suppress Li dendrite growth, such as constructing an artificial solid electrolyte layer (ASEI) [2], modifying organic electrolyte [3], preparing lithiophilic substrates [4], and using a 3D scaffold [5].Among them, introducing a 3D scaffold is one effective method to prevent Li dendrite growth due to its high surface area to greatly reduce low local current density, based on Sand’s formula [6]. Furthermore, the 3D scaffold can accommodate Li metals inside a porous structure, reducing the cell volume expansion. In fact, owing to the advantages of a 3D scaffold, a variety of 3D scaffolds based on Cu [5], Ni [7], and carbon [8] have been reported over the past several years. However, the lithium metal is preferentially deposited on the top of the 3D scaffold since the top of the bare 3D scaffolds has low diffusion resistance than the bottom of the scaffold due to the short diffusion length. As one of the solutions, introducing lithiophilic materials to the bottom of the 3D scaffold can be regarded as an effective way to induce Li nucleation inside the porous scaffold [9]. However, since morphological properties like porosity, pore size, and thickness also affect the Li deposition behaviors inside the 3D scaffold [9, 10], both factors should be considered simultaneously.Here, we propose a rational design of a 3D porous scaffold for dendrite-free LMA, adopting lithiophilic silver on a current collector. Specifically, we suggest optimal structural properties of 3D scaffolds, such as porosity, pore size, and thickness to induce the Li nucleation inside the bottom of the current collector, thereby achieving inner space Li deposition. We deposited Ag nanoparticles with 20 nm evaporation thickness by a thermal evaporation method on the commercial copper foils. (thickness ≈ 25 µm). The 3D scaffold was obtained by simple mixing and casting processes. The Cu nanoparticles (Cu NPs), silica particles, and PVdF binder were added to PP bottles at a weight ratio of 1:1:0.1, and the mixture was mixed by a high-energy ball mill. A mixed sample was cast on the copper foil and Ag coated copper foil. Cu NPs were welded by heating at 350 ℃ in a H2/Ar flow (1:1=v:v) for 2h. Afterward, silica particles were etched with 5% hydrofluoric acid (aq). As a result, porous copper scaffold (pCu) and Ag coated porous copper scaffold (AgpCu) were fabricated for Li metal anodes.The SEM images of pCu are shown in Fig. 1a, b, and c from which we can see the uniformly distributed sphere-like pore generated through the etching of silica particles. The average diameter of the formed pore is around 1 µm, which is the same as the size of silica used in the experiment. Fig. 1c presents a cross-sectional SEM image of a pCu with a thickness of ~80 µm.The deposited Li morphology is investigated by optical and SEM images in Fig. 2. When Li is deposited at 0.5 mA cm-2 for 4 mAh cm-2, shiny Li is observed on the top of the pCu in optical images (Fig. 2a). In contrast with pCu, AgpCu shows a clean brown optical image on the top without Li metals in Fig. 2c. In addition, the SEM images of Fig. 2b and d shows the morphologies of Li deposits Li on the pCu and AgpCu, respectively, indicating that a silver inside layer in AgpCu effectively induces inner deposition of Li.

Agglomeration-Free and Air-Inert Garnet for Upgrading PEO/Garnet Composite Solid State Electrolyte

Due to the intrinsically high ionic conductivity and good interfacial stability towards lithium, garnet-type solid electrolytes are usually introduced into polymer electrolytes as fillers to prepare polymer/garnet composite electrolytes, which can improve the ionic conductivity and enhance the mechanical strength to suppress Li dendrites. However, the surface Li2CO3 and/or LiOH passive layers which form when garnet is exposed to the air greatly reduce the enhancement effect of garnet on the composite electrolyte. Furthermore, compared with micro-size particles, nano-size garnet fillers exhibit a better effect on enhancing the performance of composite solid electrolytes. Nevertheless, inferior organic/inorganic interphase compatibility and high specific surface energy of nanofillers inevitably cause agglomeration, which severely hinders the effect of nanoparticles for promoting composite solid electrolytes. Herein, a cost-effective amphipathic 3-Aminopropyltriethoxysilane coupling agent is introduced to modify garnet fillers, which effectively expands the air stability of garnet and greatly improves the dispersion of garnet fillers in the polymer matrix. The well-dispersed garnet filler/polymer interface is intimate through the bridging effect of the silane coupling agent, resulting in boosted ionic conductivity (0.72 × 10−4 S/cm at room temperature) of the composite electrolyte, enhanced stability against lithium dendrites (critical current density > 0.5 mA/cm2), and prolonged cycling life of LFP/Li full cells.

Artificial SEI Film via Synchronous Reaction‐Diffusion‐Assembly on Li Liquid Metal

AbstractSolid electrolyte interphase (SEI) is considered as an effective way to suppress Li dendrite. However, most of the constructed SEI films are usually nonuniform and incompact due to the uncertain interface between Li and electrolyte, finally resulting in failure to Li anode protection. To overcome such disadvantage, a stable pristine SEI film is formed successfully by self‐diffusion and assembly when the surface reaction occur between the molten Li and the substrate, benefitting from the ultra‐high chemical activity, atomic level smoothness, and flowability of liquid lithium. It is an inside–outside process via the obtained Li composites migrating from reaction interface to the Li liquid metal surface. Then, the obtained SEI can lead to a stable and long‐lifespan Li integrated electrode, showing the self‐diffusion/assembly strategy upon liquid Li‐metal is a promising way for practical dendrite‐free anode.

Lithium‐Metal Batteries via Suppressing Li Dendrite Growth and Improving Coulombic Efficiency

Lithium‐metal batteries (LMB) are recognized as one of the most promising candidates for the next generation of batteries due to their high energy density. Extensive studies have been refocused on the field in the past decade to make the technology commercially viable. Despite exciting progress that has been made, the practical application of LMBs is still hampered by the uncontrollable Li plating morphology and inferior Coulombic efficiency (CE) during cycling. Herein, first, the relevant research that has been carried out in the past decade (2010–2021) is briefly summarized and then the Li plating behaviors, mechanistic understanding of these behaviors, and strategies to suppress Li dendrite growth are discussed. Finally, the methods and techniques to improve Coulombic efficiency (CE) is discussed, especially the design of liquid electrolytes, and possible research directions for the future development of LMBs.

High Formability Bromide Solid Electrolyte with Improved Ionic Conductivity for Bulk-Type All-Solid-State Lithium–Metal Batteries

Solid electrolytes with excellent formability and high room-temperature Li-ion conductivities used in bulk-type all-solid-state lithium-metal batteries (ASSLBs) are expected to suppress the formation of Li dendrites that affects the application of metal Li anodes with high energy density. However, voids and cracks within sintered electrolytes lead to short-circuiting of ASSLBs due to the formation of Li dendrites. This work aimed to develop solid electrolytes with high formability and high room-temperature Li-ion conductivities that can suppress Li dendrites’ formation in ASSLBs. Three indicators of bulk moduli, lithium-ion migration energies, and energies above the hull were investigated: formability, ionic conductivity, and thermodynamic stability. The 109 inorganic materials containing elements of Li and Br listed in the open web-based database of the Materials Project were surveyed due to their weak Coulombic interaction with Li ions and high polarizability. LiGaBr4 with monoclinic symmetry (LGB, S.G.: P121/a1) was focused on due to its lower values for all three analyzed indicators. A ball milling mechanochemical synthesis method was adopted to synthesize LGB. It indicated that the obtained LGB possessed a monoclinic structure with a lithium ionic conduction of 2.0 × 10–5 S cm–1 (cold isostatic pressed powder) at 25 °C. The ionic conductivity was nearly three times higher than that of the conventional sintered LGB and comparable to that of a typical oxide-type electrolyte of LISICON-type Li3.55(Ge0.45Si0.10V0.45)O4 (LGSV) at 25 °C, which is appealing for applying the sintered samples for Li-metal anodes. The SEM and the distribution of relaxation times (DRT) analysis demonstrated that LGB contributed minimal grain-boundary resistance due to tight connections between the particles, while the LGSV oxides contributed an extremely large grain-boundary resistance. An ASSLB using LGB powder as an electrolyte, bare LiCoO2 as a cathode, and lithium metal as the anode exhibited the ability to function smoothly, while short-circuiting occurred at the second cycle with LGSV, demonstrating that LGB is a pure ionic conductor and may be suitable for use in ASSLB that can prevent Li dendrites with electrochemical stability.

Dynamic Ionic Transport Actuated by Nanospinbar‐Dispersed Colloidal Electrolytes Toward Dendrite‐Free Electrodeposition

AbstractInhibiting uneven dendritic Li electroplating is crucial for the safe and stable cycling of Li metal batteries (LMBs). Homogeneous and fast Li+ transport towards the Li surface is required for uniform and dendrite‐free deposition. However, the traditional ionic transport of static liquid electrolytes involving electromigration and molecular diffusion can trigger a greater disparity in the Li concentration over the Li surface, leading to irregular dendrite growth. Here, a convective Li+ transfer for suppressing dendrite growth through magnetic nanospinbar (NSB)‐dispersed colloidal electrolytes is presented. An ultrahigh‐aspect‐ratio NSB consisting of a paramagnetic Fe3O4 nanoparticle array and silica outer coating is synthesized. Manipulating the external electromagnetic force can remotely control the rotation of individual NSBs without dispersion failure, thereby generating mesoscale turbulence inside the cells. Regardless of the electrolyte composition, rotating the NSB can reduce the Li+ diffusion layer thickness from the bulk and evenly redistribute the Li+ flux over the Li surface, thereby suppressing Li dendrite growth. The NSB‐dispersed electrolyte with advanced salt/solvent compositions demonstrates stable cycling of LMBs over 600 cycles with 70% capacity retention, thereby outperforming the NSB‐free cell.

Oxide doping improving interface performance for Li7P3S11 solid electrolytes

Controlling parasitic interface reactions and the Li dendrite growth remains challenging for all-solid-state (ASS) Li batteries, though the progress in Li-ion transport of solid electrolytes (SEs). Herein, ZnO and ZrO2 oxides are used as dopants to synthesize Li7P3S11 (LPS) glass SEs through mechanochemical synthesis. The oxide doping not only improves the ionic conductivity and air stability of LPS SEs, but more importantly also enhances the chemical stability in the interface of Li|SE as well as the Li dendrite suppression capability. Combining FIB milling with SEM-EDS detection, transversal Li dendrite deposition and growth are disclosed to occur inside the interface layer. The ASS battery using the oxide-doped LPS SE and metallic Li anode significantly outperforms that with the O-free LPS, demonstrating the merits of oxide doping toward advancing sulfide SEs.

Controllable lithium deposition with toruloid PCF/Z-67 scaffold for dendrite-free lithium metal anodes

Li metal anode has been considered as the most promising anode due to its high theoretical capacity and low redox potential. However, uncontrollable Li dendrites growth during Li deposition seriously shortens lifetime of Li metal anode. CNTs films have been regarded as the 3D frameworks for suppressing Li dendrites growth, whereas a relatively high density of CNTs film leads to Li depositing on the top of CNTs film, giving rise to lower efficiency of CNTs films. In this regard, PCF/Z-67 film is prepared by vacuum filtration of toruloid [email protected] on the separator. The film is auto-transferred to the surface of Li metal anode during cycling. The ZIF-67 nanoparticles increase the interspace of film, providing more space to accommodate deposited Li. Besides, the lithiophilic functional groups in the ZIF-67 are conducive to lower nucleation barrier of Li. At a current density of 1 mA cm−2, the Li||Li symmetrical cell consist of [email protected]/Z-67 foil can cycle stably for more than 1000 h with a hysteresis voltage of 8 mV, due to the synergistic effect of CNT and ZIF-67. The coulombic efficiency of the cell with PCF/Z-67 can stabilize at 95% under a current density of 1 mA cm−2 after 200 cycles. In addition, [email protected]/Z-67||LiFePO4 full cell delivers outstanding rate capacity and cycling stability compared with Li foil. The results demonstrate that the 3D porous framework assembled with [email protected] is an available strategy to enhance the electrochemical properties of Li metal anodes.

In Situ Construction of a LiF-Enriched Interfacial Modification Layer for Stable All-Solid-State Batteries.

All-solid-state batteries (ASSBs), particularly based on sulfide solid-state electrolytes (SSEs), are expected to meet the requirements of high-energy-density energy storage. However, the unstable interface between the ceramic pellets and lithium (Li) metal can induce unconstrained Li-dendrite growth with safety concerns. Herein, we design a carbon fluoride-silver (CFx-Ag) composite to modify the SSEs. As lithium fluoride (LiF) nanocrystals can be in situ formed through electrochemical reactions, this LiF-enriched modification layer with high surface energy can more effectively suppress Li dendrite penetration and interfacial reactions between the SSEs and anode. Remarkably, the all-solid-state symmetric cells using a lithium-boron alloy (LiB) anode can stably work to above 2,500 h under 0.5 mA cm-2 and 2 mAh cm-2 at 60 °C without shorting. A modified LiB||LiNi0.6Mn0.2Co0.2O2 (NMC622) full cell also demonstrates an improved capacity retention and high Coulombic efficiency (99.9%) over 500 cycles. This work provides an advanced solid-state interface architecture to address Li-dendrite issues of ASSBs.

Cover Feature: Double‐Network Ionogel Electrolyte with Superior Mechanical Performance and High Safety for Flexible Lithium‐Ion Batteries (ChemElectroChem 14/2022)

The Cover Feature shows a double-network ionogel electrolyte (DNIE) through the preparation of interpenetrating polymer networks. This DNIE exhibits good mechanical properties, excellent flexibility, nonflammability, high ionic conductivity, electrochemical stability (>4.8 V), and the ability to suppress Li dendrite formation. More information can be found in the Research Article by Z. Li et al.

Double‐Network Ionogel Electrolyte with Superior Mechanical Performance and High Safety for Flexible Lithium‐Ion Batteries

AbstractThe development of high‐performance solid‐state electrolytes to replace conventional liquid organic electrolytes has received intensive attention because of the improvements in the safety, flexibility, reliability, and cycling stability of lithium‐ion batteries (LIBs). In this work, we present a double‐network ionogel electrolyte (DNIE) through the preparation of interpenetrating polymer networks (IPNs). This DNIE exhibits good mechanical properties, excellent flexibility, nonflammability, high ionic conductivity (4.13×10−4 S cm−1 at room temperature), electrochemical stability (>4.8 V), and the ability to suppress Li dendrite formation. The Li/LiFePO4 cell assembled with the DNIE exhibits superior cycling performance while also delivering a steady high discharge capacity of 133.7 mAh g−1 and a Coulombic efficiency of 99.8 % after 220 cycles at a charge/discharge rate of 0.2 C. Importantly, the DNIE(200 %)‐20 % electrolytes can be prepared on the surface of graphite anodes through in situ gelling, which can improve the stability of the active layer and the adhesion between the active layer and current collector in mechanical bending at different angles. After assembling into soft‐packed batteries in the configuration of LiCoO2|DNIE(200 %)‐20 %|graphite via the in situ gelling of DNIE(200 %)‐20 % on the surface of the graphite electrode, the flexible batteries showed excellent cycling stability (capacity retention >98 %) even when folded more than 100 times.

Critical Role of Pits in Suppressing Li Dendrites Revealed by Continuum Mechanics Simulation and In Situ Experiment

Dendrite growth and surface pitting are critical factors hindering the development of ultra-high energy density rechargeable lithium battery. However, the mechanism of dendrite growth promoted by pits on the surface of lithium metal remains unclear. In this study, we propose a combination of continuum mechanics simulations and develop an in situ experimental observation device to investigate the effects of pit size, curvature of pit edge, overpotential, and lithium-ion concentration gradient on dendrite growth. Results show that a larger size and curvature of pits can reduce the deposition rate of lithium and dendrite morphology significantly. Larger overpotential can aggravate dendritic nucleation and thereby promotes dendrite growth. Uneven lithium-ion concentration gradient distribution significantly influences the direction of the dendrite growth and leads to the formation of branches. The lithium deposition behavior near the ideal pit predicted by continuum mechanics is consistent with that observed in the in situ experiments. These results lay the basis for future studies to determine the effect of the surface morphology of lithium metal electrodes on the electrodeposition stability and performance of lithium metal batteries.

Self-Healable, Highly Stretchable, Ionic Conducting Polymers as Efficient Protecting Layers for Stable Lithium-Metal Electrodes.

Although numerous studies on polymeric protective films to stabilize lithium (Li)-metal electrodes have been reported, the construction of self-healing polymers that enables the long-term operation of Li-metal batteries (LMBs) at relatively low temperatures has rarely been demonstrated. Herein, a highly stretchable, autonomous self-healable, and ionic-conducting polymer network (SHIPN) is synthesized as an efficient protective film for LMBs. The network backbone, synthesized from copolymerization of poly(ethylene glycol)-mono-methacrylate (PEGMMA) and 2-[[(butylamino)carbonyl]oxy]ethyl acrylate (BCOE), is chemically cross-linked via diisocyanate. With SHIPN-modified electrodes, enhanced electrochemical performance can be achieved in Li/Cu, Li/Li, and Li/LiFePO4 (Li/LFP) cells. The SHIPN@Li/LFP cell delivers a capacity retention of 85.6% after 500 cycles at 5 °C, resulting from the low-temperature self-healability of SHIPN. In full cells with a high-mass-loading LFP cathode (∼17 mg cm-2), the capacity retention is at least 300% higher than that with a bare Li electrode. Further physical characterizations of electrodes confirm the effect of SHIPN in enhancing the interfacial stability and suppressing Li dendrite growth. Our results will provide insights into rationally designing soft and hybrid materials toward stable LMBs at different temperatures.

A High-Capacity Polyethylene Oxide-Based All-Solid-State Battery Using a Metal-Organic Framework Hosted Silicon Anode.

Polyethylene oxide (PEO)-based solid electrolytes have been widely studied in all-solid-state lithium (Li) metal batteries due to their favorable interfacial contact with electrodes, facile fabrication, and low cost, but their inferior Li dendrite suppression capability renders low actual areal capacities of Li metal anodes. Here, we develop a high-capacity all-solid-state battery using a metal-organic framework hosted silicon (Si@MOF) anode and a fiber-supported PEO/garnet composite electrolyte. Si nanoparticles are embedded in the micro-sized MOF-derived carbon host, which efficiently accommodates the repeated deformation of Si over cycles while providing sufficient charge transfer pathways. As a result, the Si@MOF anode shows excellent interfacial stability toward the composite polymer electrolyte for over 1000 h and achieves a high reversible areal capacity of 3 mAh cm-2. The full cell using the LiFePO4 (LFP) cathode is able to deliver 135 mAh g-1 initially and maintains 73.1% of the capacity after 500 cycles at 0.5 C and 60 °C. More remarkably, the full cells with high LFP loadings achieve areal capacities of more than 2 mAh cm-2, exceeding most PEO-based ASSBs using metallic Li. Finally, the pouch cell using the proposed design exhibits decent electrochemical performance and high safety.