Low Voltage Polarization Research Articles

Chitosan-based gel polymer electrolytes for high performance Li-ion battery

This study explores the use of glutaraldehyde-crosslinked chitosan-based gel polymer electrolytes (GPEs) in lithium-ion batteries (LIBs). GPEs are prepared by solution casting using two different molecular weights of chitosan including 150 kDa as medium and 400 kDa as high molecular weight (MMWCS and HMWCS, respectively) with varying amounts of crosslinker. Degree of crystallinity was 25.9 and 24.1 % for HMWCS and MMWCS, respectively that was decreased to 18.3 and 22.7 % by using 5 % crosslinker and 17.8 and 21.1 % by using 10 % crosslinker, and 17.2 and 17.6 % by using 20 % crosslinker. The obtained ionic conductivity for HMWCS and MMWCS was 3.1 × 10−3 and 2.9 × 10−3 S.cm−1. After crosslinking by 5, 10, and 20 % crosslinker, the ionic conductivity was obtained to 0.9 × 10−3 and 0.3 × 10−3 S.cm−1, 6.3 × 10−3 and 5 × 10−3 S.cm−1, and 1.1 × 10−3 and 0.5 × 10−3 S.cm−1 for high and medium molecular weight, respectively. Lithium-ion transfer number was obtained between 0.34 and 0.83 and the highest t+ value was obtained for the MMWCS-GA10. Electrochemical stability window of the prepared polymer electrolytes was >5 V and samples showed no remarkable dendrite growth after cycling analyses. The symmetric cells demonstrated reliable performance, operating for over 300 h without any short-circuiting, which indicates excellent reversible cycling stability for chitosan-based lithium-ion batteries. Furthermore, the Gr/GPE cell exhibited very low voltage polarization, with the over-potential decreasing from 10 mV initially to 6 mV after 300 h at the same current density. Discharge capacity was obtained higher than 170 mAh/g at 0.2C with CE = 97 % for both HMWCS-GA20 and HMWCS-GA20.

Turning crisis into opportunity: Intrinsically polarised low concentration eutectic electrolytes enable highly reversible zinc anodes

Low-concentration electrolytes (LCEs) hold great promise for sustainable energy storage due to their low viscosity, excellent wettability, and cost-effectiveness. However, their intrinsic polarization issues often lead to side reactions and dendrite growth, hindering their broader application. Herein, we present an approach to convert the negative effects of intrinsic polarization in LCEs into advantages, overcoming these challenges. The experimental and theoretical analyses demonstrate that acetate-adsorbed zinc anodes can harness the intrinsic polarization of LCEs to direct the electrocrystallization process on their surfaces. This promotes the preferential orientation of Zn(002) plane with high stability, resulting in symmetric batteries loaded with low-concentration eutectic electrolytes (LCEE) that maintain surprisingly low voltage polarization during the dendrite-free growth of up to 3150 h. In addition, by forming an organic-inorganic composite film enriched with N and Cl, LCEE achieves rapid migration of Zn2+. This allows Zn//PANI full batteries with LCEE to demonstrate superior capacity and cycling stability compared to other Zn-based batteries with LCEs. This study not only achieves a divergent design in LCEs but also provides clear guidance for future electrolyte development.

Achieving Long Cycle Life of Zn-Ion Batteries through Three-Dimensional Copper Foam.

Metallic zinc anodes in aqueous zinc-ion batteries (ZIBs) suffer from dendritic growth, low Coulombic efficiency, and high polarization during cycling. To mitigate these challenges, current collectors based on three-dimensional (3D) commercial copper foam (CCuF) are generally preferred. However, their utilization is constrained by their thickness, low electroactive surface area, and increased manufacturing expenses. In this study, the synthesis of cost-effective current collectors with exceptionally large surface areas designed for ZIBs that can be cycled hundreds of times is reported. A zinc-coated CuF anode (Zn/CuF) was prepared with a 3D porous CuF current collector produced by the dynamic hydrogen bubble template (DHBT) method. Electrochemically generated copper foam could be obtained within seconds while offering a thickness as low as 30-40 μm (CuF5 achieved a thickness of ∼38 μm in 5 s) via the DHBT method. The excellent electrical conductivity and open pore structure of the 3D porous copper scaffold ensured the uniform deposition/stripping of Zn during cycling. During the 500 h Zn deposition/stripping process, the as-synthesized CuF5 current collector offered fast electrochemical kinetics and low polarization as well as a relatively high average Coulombic efficiency of 99% (at a current density of 5 mA cm-2 and a capacity of 1 mAh cm-2). Furthermore, the symmetric cell exhibited low voltage polarization and a stable voltage profile for 1000 h at a current density of 0.1 mA cm-2. In addition, full cells containing the Zn/CuF anode coupled with an as-synthesized α-MnO2 nanoneedle cathode in aqueous electrolyte were also prepared. Capacities of 266 mAh g-1 at 0.1 A g-1 and 94 mAh g-1 at 2 A g-1 were achieved after 200 charge/discharge cycles with a stable Coulombic efficiency value close to 99.9%.

Regulating ionic transport and interface chemistry via high-dielectric BaTiO3 porous scaffolds for aqueous Zn-ion batteries

Rechargeable aqueous Zn-ion batteries (AZIBs) are gaining considerable attention as alternatives to Li-ion batteries owing to their excellent safety, high energy density, low cost, and environmental friendliness. However, their Zn anodes suffer from severe dendritic growth, the hydrogen evolution reaction (HER), and corrosion, which limit the commercialization of AZIBs. To address this challenge, we designed a solution involving the development of a high-dielectric hydrophobic BaTiO3 (BTO) porous scaffold layer that is strategically applied to the Zn surface. This BTO layer effectively impedes the dendritic growth of Zn. The distinct polarizability of the BTO layer actively diminishes the electric-field gradient, thereby minimizing the interaction between the H2O molecules and the Zn surface. This phenomenon helps suppress dendritic growth, thus ensuring the uniform deposition of Zn and preventing the HER. The electrochemical performance of a symmetric cell containing the Zn@BTO electrode exhibits low-voltage polarization and stable charge–discharge performance for up to 500 h. In addition, a full-cell AZIB containing a high-capacity α-MnO2 cathode and Zn@BTO anode exhibits good rate capability and a long life of up to 500 cycles. This study demonstrates the development of a cost-effective dendrite-free Zn anode integrated with a highly dielectric hydrophobic BTO porous scaffold layer as a stable Zn–electrolyte interface layer for high-performance AZIBs.

Synergistically regulating Zn-ion flux and accelerating ion transport kinetics via zincophilic covalent organic framework interlayer for stable Zn metal anode

Zn metal is considered as an ideal anode for aqueous zinc-ion batteries (AZIBs) owing to the inherent merits of low cost, high theoretical capacity, and remarkable safety. However, the formation of Zn dendrites and water-induced parasitic reactions hamper the commercialization of AZIBs. Herein, a synergetic strategy to accelerate ion transfer kinetics and regulate Zn-ion flux has been proposed to achieve dendrite-free Zn anodes via a series of zincophilic covalent organic framework (COF) films. The nanoporous and mechanically stable COF films synthesized by the liquid–liquid interfacial polymerization can be straightforward transferred on the Zn foil surface through a dip-coating technique. Benefiting from the affinity between Zn2+ and electron-rich ketone, the zincophilic COF interlayers promote the de-solvation of hydrated Zn2+, simultaneously offer ample Zn2+ transport channels to facilitate rapid diffusion and regulating a homogenous Zn2+ flux, thereby inhibiting the dendritic growth and leading to the uniform Zn deposition. Additionally, the COF films with strong adherence and large surface area effectively separate Zn anodes from bulk aqueous electrolytes, inhibiting the water-induced corrosion reactions. As a result, the symmetric cell with COF-modified Zn anode exhibited a stable cycling lifetime more than 900 h at 1 mA∙cm−2 and 1 mAh∙cm−2, accompanied by a low voltage polarization of merely 74.3 mV. As a simple approach to synergistically restrict Zn-ion flux and enhance ion transport kinetics using zincophilic COF films via interfacial synthesis, this work would provide new insights into developing highly stable Zn anodes.

Achieving highly stable sodium metal batteries with self-adapting and high-ionic-mobility ceramic fiber membranes

Tough issues like sodium (Na) dendrite growth and poor anode reversibility hinder the practical application of sodium metal batteries (SMBs) with moderate liquid electrolytes. To settle these problems, using a smart self-adapting Al2SiO5 ceramic fiber (CF) membrane is demonstrated to enable homogeneous Na depositions and inhibit the dendritic growth. This inorganic membrane itself has superb thermal stability, high ionic mobility (Na+ transference number: 0.65) and electrolyte wettability over traditional glass fiber (GF) or polymeric ones, guaranteeing the low voltage polarization (14 mV) and long-cyclic lifetime (over 600 h) in symmetric cells testing. Notably, aluminous components in CF membranes would interact with F-based molecules in the electrolyte phase, thereby releasing some Al3+ species that can be electrochemically deposited onto the anodic interface. The packed (+)Na3V2(PO4)3|CF|Na(−) full SMBs exhibit far superior cyclic stability (capacity retention over 78.7 % after 600 cycles at 1C) than other counterparts. The in-situ detection/postmortem analysis reveal that Al/F-based inorganics formed in as-built SEI layers play a vital role in Na metal anode protection. This work may provide a viable strategy to overcome the constraints of high-energy SMBs in practical applications.

Constructing a LiPON Layer on a 3D Lithium Metal Anode as an Artificial Solid Electrolyte Interphase with Long-Term Stability

The problem of lithium dendrite growth has persistently hindered the advancement of lithium metal batteries. Lithium phosphorus oxynitride (LiPON), functioning as an amorphous solid electrolyte, is extensively employed as an artificial solid electrolyte interphase (SEI) owing to its remarkable stability and mechanical strength, which is beneficial for effectively mitigating dendrite growth. Nevertheless, the significant challenge arises from the volume changes in the Li metal anode during cycling, leading to the vulnerability of LiPON due to its high rigidity, which impedes the widespread use of LiPON. To address this problem, our study introduces a lithium-boron (Li-B) alloy as the anode, featuring a 3D structure, which can be synergistic with the artificial LiPON layer during cycling, leading to a better performance. The average Coulombic efficiency (CE) of a Li || Cu half-cell reaches 95% over 120 cycles. The symmetric cells exhibit sustained operation for 950 h with a low voltage polarization of less than 20 mV under a current density of 0.5 mA/cm2 and for 410 h under 1 mA/cm2.

Multifunctional single-ion conductor-integrated PEO-based solid polymer electrolytes endow highly stable and dendrite-free lithium metal batteries

Poly(ethylene oxide) (PEO) based solid polymer electrolytes (SPEs) hold great promise for circumventing the safety issues caused by liquid electrolytes, which are widely used as one of the leading technical strategies for constructing solid-state lithium metal batteries (LMBs). Unfortunately, developing PEO-based SPEs applicable to high-performance LMBs remains challenging due to the uncontrolled formation of lithium dendrites and sluggish ion migration. In this study, we present the fabrication of highly conductive and mechanically robust composite SPEs (CSPEs) for use in dendrite-proof LMBs by adding a new bis(sulphonyl)imide-based single-ion conductor (LiPEBI) as functional polymer fillers into PEO SPEs network. As expected, the as-prepared CSPEs can simultaneously achieve an excellent mechanical strength of 2.1 MPa, a considerable elongation at a break of 1491.0%, and an optimized degree of crystallization of 37.1%. In addition, introducing the LiPEBI additive promotes the homogeneous distribution of Li-ions and accelerates the ionic transport, resulting in an enhanced ionic conductivity of 4.17 × 10−4 S cm−1 and lithium ion transference number (tLi+) of 0.45 at 60 °C for CSPEs. Such comprehensive physical and electrochemical performances are favorable to suppressing lithium dendrite growth and prolonging the lifespan of LMBs. As a result, the Li||Li symmetrical cells assembled by the CSPEs display a remarkably stable cyclic performance with an extremely low voltage polarization of 60.3 mV over 500 h under 50 μA cm−2 at 60 °C. Also, the CSPEs-based Li||LiFePO4 batteries illustrate superior rate performance up to 1 C and deliver long-term cycling stability with a high discharge capacity of 128.8 mAh g−1 after 100 cycles under 0.4 C at 60 °C. We believe the novel CSPEs have great potential for actual application in the construction of high-safety and dendrite-free solid-state LMBs.

Three-Dimensional Nitrogen-Doped Carbonaceous Networks Anchored with Cobalt as Separator Modification Layers for Low-Polarization and Long-Lifespan Aluminum-Sulfur Batteries.

Aluminum-sulfur (Al-S) batteries have attracted extensive interest due to their high theoretical energy density, inherent safety, and low cost. However, severe polarization and poor cycling performance significantly limit the development of Al-S batteries. Herein, three-dimensional (3D) nitrogen-doped carbonaceous networks anchored with cobalt (Co@CMel-ZIF) is proposed as a separator modification layer to mitigate these issues, prepared via carbonizations of a mixture of ZIF-7, melamine, and CoCl2. It exhibits a 3D network structure with a moderate surface area and high average pore diameter, which is demonstrated to be effective in adsorbing the aluminum polysulfides and hindering the mobility of polysulfides across the separator for enhanced cyclic stability of Al-S batteries. Meanwhile, Co@CMel-ZIF are characterized by abundant catalytic pyridinic-N and Co-Nx active sites that effectively eliminate the barrier of sulfides' conversion and thereby facilitate the polarization reduction. As a result, Al-S cells based on the separator modified with Co@CMel-ZIF exhibit a low voltage polarization of 0.47 V under the current density of 50 mA g-1 at 20 °C and a high discharge specific capacity of 503 mAh g-1 after 150 cycles. In contrast, the cell employing a bare separator exhibits a polarization of 1.01 V and a discharge capacity of 300 mAh g-1 after 70 cycles under the same conditions. This work demonstrates that modifying the separators is a promising strategy to mitigate the high polarization and poor cyclability of Al-S batteries.

Highly reversible zinc metal anode modified with high-nitrogen containing covalent triazine frameworks

We successfully synthesized high-nitrogen containing covalent triazine frameworks (NCTF) as a coating for zinc anodes. The NCTF organic protective layer not only effectively separates Zn anode from the electrolyte, but also regulates Zn2+ transport path, thus inhibiting the occurrence of side reactions. Thus, Zn@NCTF symmetric cell achieves a long cycle lifespan of more than 720 h at 0.5 mA cm−2 and maintains a stable and low voltage polarization of 49 mV. In addition, the Zn@NCTF//(NH4)2V3O8 full cell displays the reversible capacity of 195.6 mAh/g after 500 cycles at 1 A/g.

The Restrained Li/Gel Polymer Electrolyte Interface Deterioration Enabled by the Synergetic Effect of Ultra‐Lithiophilic Interphase and Interfacial Coupling Skeleton

AbstractQuasi‐solid‐state lithium metal batteries are deemed as one of the most promising next‐generation energy storage devices due to their enhanced safety and high energy density. However, the Li/Gel polymer Electrolyte (GPE) interface deterioration induced by the side reactions, dendrite growth during Li plating, and contact loss during Li stripping will inevitably lead to the failure of the battery. Herein, a Li/Li23Sr6–Li3N/Sr2N anode structure (LSN) prepared by hot‐rolling process is designed, where Sr2N serves as an inert skeleton to retain the interfacial coupling and to avoid contact loss. At the same time, the Li3N–Li23Sr6 interphase with high Li adsorption energy and fast Li+ transfer kinetics regulate the Li plating behavior. Benefitting from the design, when coupled with the carbonate‐based GPE, the lifespan of the symmetric battery with the LSN is extended to 1300 h at 0.2 mA cm−2/0.2 mAh cm−2. Furthermore, the LSN||LiFePO4 (LFP) full cell exhibits a steady cycle with extremely low voltage polarization at 0.5 C after 200 cycles. This study provides a practical strategy to stabilize the Li/GPE interface and deepens the understanding of Li+ plating/stripping behaviors through the interphase.

Combustion Activation Induced Solid-State Synthesis for N, B Co-Doped Carbon/Zinc Borate Anode with a Boosting of Sodium Storage Performance.

Zinc borates have merits of low voltage polarization and suitable redox potential, but usually suffer from low rate capability and poor cycling life, as an emerging anode candidate for Na+ storage. Here, a new intercalator-guided synthesis strategy is reported to simultaneously improve rate capability and stabilize cycling life of N, B co-doped carbon/zinc borates (CBZG). The strategy relies on a uniform dispersion of precursors and simultaneously stimulated combustion activation and solid-state reactions capable of scalable preparation. The Na+ storage mechanism of CBZG is studied: 1) ex situ XRD and XPS demonstrate two-step reaction sequence of Na+ storage: Zn6 O(OH)(BO3 )3 +Na+ +e- ↔3ZnO+Zn3 B2 O6 +NaBO2 +0.5H2 ①, Zn3 B2 O6 +6Na+ +6e- ↔3Zn+3Na2 O+B2 O3 ②; reaction ① is irreversible in ether-based electrolyte while reversible in ester-based electrolyte. 2)Electrochemical kinetics reveal that ether-based electrolyte possesses faster Na+ storage than ester-based electrolyte. The composite demonstrates an excellent capacity of 437.4mAh g-1 in a half-cell, together with application potential in full cells (discharge capacity of 440.1 mAh g-1 and stable cycle performance of 2000 cycles at 5 A g-1 ). These studies will undoubtedly provide an avenue for developing novel synthetic methods of carbon-based borates and give new insights into the mechanism of Na+ storage in ether-based electrolyte for the desirable sodium storage.

A Fluorinated‐Polyimide‐Based Composite Nanofibrous Separator with Homogenized Pore Size for Wide‐Temperature Lithium Metal Batteries

Lithium (Li) is known for excellent theoretical specific capacity and most negative electrochemical potential, while still restricted by the irregular lithium dendrites and safety risks in practical applications of lithium metal batteries (LMBs) due to thermal runaway. Herein, a fluorinated‐polyimide (F‐PI)‐based composite nanofibrous separator containing poly(vinylidene fluoride) (PVDF) component, which is designed as PVDF/F‐PI, is developed via a facile electrospinning strategy for wide‐temperature LMBs. First, abundant polar trifluoromethyl (–CF3) groups in F‐PI create an electronegative environment to facilitate rapid Li‐ions (Li+) transport. Meanwhile, the PVDF component, acting as both the physical linker between F‐PI nanofibers and the regulator of homogenized pore size, simultaneously improves the mechanical properties and homogenizes the Li+ flux on the electrode surface. Therefore, a steady circulation of 2400 h is achieved for the symmetric cell using PVDF/F‐PI separator, which still displays a stable cycle life with a low voltage polarization of 15 mV in 1000 h even under 60 °C. Therefore, the fluorinated‐PI‐based composite nanofibrous separator with high ionic conductivity and uniform pore structure offers a practical method for design of functionalized separators in wide‐temperature LMB applications.

Tuning Li Nucleation by a Hybrid Lithiophilic Protective Layer for High-Performance Lithium Metal Batteries

Lithium (Li) metal has been recognized as the most promising anode material for next-generation rechargeable batteries. However, the practical application of Li anodes is hampered by the growth of Li dendrites. To address this issue, a robust and uniform Sb-based hybrid lithiophilic protective layer is designed and built by a facile in situ surface reaction approach. As evidenced theoretically and experimentally, the as-prepared hybrid protective layer provides outstanding wettability and fast charge-transfer kinetics. Moreover, the lithiophilic Sb embedded in the protective layer provides a rich site for Li nucleation, which effectively reduces the overpotential and induces uniform Li deposition. Consequently, the symmetric cell exhibits a long lifespan of over 1600 h at 1 mA cm-2 and 1 mAh cm-2 with a low voltage polarization. Furthermore, excellent cycling stability is also obtained in Li-S full cells (60% capacity retention in 800 cycles at 1 C) and Li||LFP full cells (74% capacity retention in 500 cycles at 5 C). This work proposed a facile but efficient strategy to stabilize the Li metal anode.

Adsorption-catalysis design with cerium oxide nanorods supported nickel-cobalt-oxide with multifunctional reaction interfaces for anchoring polysulfides and accelerating redox reactions in lithium sulfur battery

The charge and discharge working mechanisms in lithium sulfur batteries contain multi-step complex reactions involving two-electron transfer and multiple phase transformations. The dissolution and diffusion of lithium polysulfides cause a huge loss of active material and fast capacity decay, preventing the practical use of lithium sulfur batteries. Herein, CeO2 nanorods supported bimetallic nickel cobalt oxide (NiCo2Ox) was investigated as a cathode host material for lithium sulfur batteries, which can provide adsorption-catalysis dual synergy to restrain the shuttle of polysulfides and stimulate rapid redox reaction for the conversion of polysulfides. The polar CeO2 nanorods with abundant surface defects exhibit chemisorption towards lithium polysulfides and the excellent electrocatalytic activity of NiCo2Ox nanoclusters can rev up the chain transformation of lithium polysulfides. The electrochemical results show that the battery with NiCo2Ox/CeO2 nanorods can demonstrate high discharge capacity, stable cycling, low voltage polarization and high sulfur utilization. The battery with NiCo2Ox/CeO2 nanorods unveils a high specific capacity of 1236 mAh g−1 with a very low capacity fading of 0.09% per cycle after 100 cycles at a 0.2C current rate. Moreover, the excellent performance with high sulfur loading (>5 mg cm−2) verifies a huge promise for future commercial applications.

An ultrathin Zn-BDC MOF nanosheets functionalized polyacrylonitrile composite separator with anion immobilization and Li+ redistribution for dendrite-free Li metal battery

Uncontrolled lithium dendrite growth and dead Li accumulation will seriously reduce coulombic efficiency, shorten the cycle life and cause great safety hazards, which are the main reason that restricts the further development of lithium metal batteries (LMBs). Herein, an ultrathin Zn-BDC metal-organic framework nanosheets functionalized polyacrylonitrile (Zn-BDC/PAN@PAN) composite separator is prepared via an electrospinning combined with electrospraying technique for inhibiting dendrite growth and achieving high-performance lithium batteries. Introduction of Zn-BDC/PAN skin layer not only immobilizes anions, increases the ionic conductivity and Li+ transfer number (0.68), but also makes pore size distribution uniform and homogenizes Li+ flux. These advantages enable Zn-BDC/PAN@PAN separator to achieve a stable Li plating/stripping behavior over 1000 h at 2 mA cm−2 with a low voltage polarization difference only about 10 mV, and the Li metal after the cycle displays a dense and smooth surface with no obvious dendrite growth, further confirming that the Zn-BDC/PAN@PAN separator can inhibit Li dendrites growth. Furthermore, the assembled Li/LiFePO4 battery also shows stable cycle performance with a discharge capacity of 142.2 mA h g−1 after 300th cycle and high rate capability (121.3 mA h g−1 at 10C), indicating that the promising application of the composite separator in constructing dendrite-free LMBs. This work provides a feasible strategy to enhance the cell performance of LMBs through Li+ flux regulation.

Uniformly MXene‐Grafted Eutectic Aluminum‐Cerium Alloys as Flexible and Reversible Anode Materials for Rechargeable Aluminum‐Ion Battery

AbstractAluminum is an attractive anode material in aqueous multivalent‐metal batteries for large‐scale energy storage because of its high Earth abundance, low cost, high theoretic capacity, and safety. However, state‐of‐the‐art aqueous aluminum‐ion batteries based on aluminum anode persistently suffer from poor rechargeability and low coulombic efficiency due to irreversibility of aluminum stripping/plating and dendrite growth. Here eutectic aluminum‐cerium alloys in situ grafted with uniform ultrathin MXene (MXene/E‐Al97Ce3) as flexible, reversible, and dendrite‐free anode materials for rechargeable aqueous aluminum‐ion batteries is reported. As a result of the MXene serving as stable solid electrolyte interphase to inhibit side reactions and the lamella‐nanostructured E‐Al97Ce3 enabling directional Al stripping and deposition by making use of symbiotic α‐Al metal and intermetallic Al11Ce3 lamellas, the MXene/E‐Al97Ce3 hybrid electrodes exhibit reversible and dendrite‐free Al stripping/plating with low voltage polarization of ± 54 mV for ≥1000 h in a low‐oxygen‐concentration aqueous aluminum trifluoromethanesulfonate (Al(OTF)3) electrolyte. These superior electrochemical properties endow soft‐package aluminum‐ion batteries assembled with MXene/E‐Al97Ce3 anode and AlxMnO2 cathode to have high initial discharge capacity of ≈360 mAh g−1 at 1 A g−1, and retain ≈85% after 500 cycles, along with the coulombic efficiency of as high as 99.5%.

Rational Design of an Artificial SEI: Alloy/Solid Electrolyte Hybrid Layer for a Highly Reversible Na and K Metal Anode.

The practical application of a Na/K-metallic anode is intrinsically hindered by the poor cycle life and safety issues due to the unstable electrode/electrolyte interface and uncontrolled dendrite growth during cycling. Herein, we solve these issues through an in situ reaction of an oxyhalogenide (BiOCl) and Na to construct an artificial solid electrolyte interphase (SEI) layer consisting of an alloy (Na3Bi) and a solid electrolyte (Na3OCl) on the surface of the Na anode. As demonstrated by theoretical and experimental results, such an artificial SEI layer combines the synergistic properties of high ionic conductivity, electronic insulation, and interfacial stability, leading to uniform dendrite-free Na deposition beneath the hybrid SEI layer. The protected Na anode presents a low voltage polarization of 30 mV, achieving an extended cycling life of 700 h at 1 mA cm-2 in the carbonate-based electrolyte. The full cell based on the Na3V2(PO4)3 cathode and hybrid SEI-protected Na anode shows long-term stability. When this strategy is applied to a K metal anode, the protected K anode also reaches a cycling life of over 4000 h at 0.5 mA cm-2 with a low voltage polarization of 100 mV. Our work provides an important insight into the design principles of a stable artificial SEI layer for high-energy-density metal batteries.

Limited Lithium Loading Promises Improved Lithium-Metal Anodes in Interface-Modified 3D Matrixes.

Confining Li metal in a three-dimensional (3D) matrix has been proven effective in improving the Li-metal anodes; however, in most studies, the loading of Li in the 3D matrix is far excessive, resulting in a dense bulk Li-metal anode with a low Li-utilization rate, forfeiting the effect of the 3D matrix. Here, we show that limiting the loading of Li metal within an interface-modified 3D carbon matrix not only increases the Li-utilization rate but also improves the electrochemical performance of the Li-metal anode. We use lithiophilic Fe2O3 granules anchored on a 3D carbon fiber scaffold to guide molten Li dispersion onto the fibers with controlled Li loading. Limiting Li loading maximizes the interface lithiophilic effect of the Fe2O3 granules while preserving sufficient space for electrolyte infusion, collectively ensuring uniform Li deposition and fast Li+ transport kinetics. The Li anode with limited Li dosage achieves remarkably improved Li-anode performances, including long lifespan, low voltage polarization, and low electrochemical resistance in both the symmetric cells and full cells. The improved electrochemical performance of the limited Li anode substantiates the importance to reduce Li loading from a fresh perspective and provides an avenue for building practical Li-metal batteries.

A Multifunctional Artificial Interphase with Fluorine‐Doped Amorphous Carbon layer for Ultra‐Stable Zn Anode

AbstractBuilding an artificial interphase layer for tackling uncontrollable Zn dendrites and serious side reactions is a highly desirable strategy, but it is often hampered by the limited Zn2+ transport. Here, a stable fluorine‐doped amorphous carbon (CF) artificial layer is constructed on a Cu current collector (CF‐Cu) via facile carbonization treatment of a fluoropolymer coating to realize underlying Zn deposition. As evidenced experimentally and theoretically, this inorganic CF layer with ionic conductivity and electronic insulation successfully triggers dendrite‐free Zn deposition at the CF‐Cu interface with preferred Zn(002) crystal plane stacking parallel to the substrate surface, thus greatly promoting the inhibition of Zn‐dendrites and blocking of interfacial side reactions. The introduced fluorine atoms as abundant zincophilic sites play an important role in driving fast zinc‐ion transfer kinetics, which can partly convert into ZnF2 as an artificial solid Zn2+ conductor to further guide uniform Zn deposition. Consequently, the CF‐Cu electrode enables high reversibility with 99% coulombic efficiency and a long cycling stability of 1900 cycles at 2 mA cm–2. The integrated CF‐Cu@Zn anode achieves up to 2200 h cycles with a low voltage polarization. This study provides inspiration for the design of artificial interphase layers for stable nondendritic metal batteries.