Electrolyte Wettability Research Articles

Heteroatom co-doped biomass carbon modified electrodes for all-vanadium redox flow batteries with ultra-low decay rate of energy efficiency

The intermittent nature of renewable energy calls for advanced energy storage systems, of which all-vanadium redox flow batteries (VRFBs) are recognized as the most promising long-duration energy storage devices. The most common electrode for VRFBs is graphite felt (GF), however with poor hydrophilicity and weak electrochemical activity, making it difficult to be a perfect electrode. In this work, we report a nitrogen-phosphorus co-doped biomass carbon modified GF (NP-GF), in which the introduction of cross-linking agents enhances the linkage between the carbon material and the GF. With excellent electrolyte wettability and electrochemical catalytic activity, the NP-GF electrode exhibits enhanced electrochemical activity and reversibility for VO2+/VO2+ and V2+/V3+ in electrochemical tests. The coulombic efficiency (CE), voltage efficiency (VE), and energy efficiency (EE) are all boosted at current densities of 80–280 mA cm−2 in VRFB single cell tests assembled with NP-GF. The power density of the VRFB reaches a peak of 757.0 mW cm−2. Furthermore, the VRFB has an extremely low EE decay rate per cycle (0.0018 %), demonstrating superior electrochemical performance stability.

Scalable fabrication of free-standing and integrated electrodes with commercial level of areal capacity for aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) present a highly promising avenue for the deployment of grid-scale energy storage systems. However, the electrodes fabricated through conventional methodologies not only suffer from insufficient mass loadings, but also are susceptible to exfoliation under deformations. Herein, a scalable and cost-effective freezing-thawing method is developed to construct free-standing and integrated electrode, comprising H11Al2V6O23.2, carboxymethyl cellulose, and carbon nanotubes. Benefiting from the synergistic effect of these components, the resultant electrode exhibits superior flexibility and robustness, large tensile strength, exceptional electrical conductivity, and favorable electrolyte wettability. Under a large mass loading of 8 mg cm−2 (corresponding to a negative/positive electrode capacity ratio of 2.09), the electrode achieves remarkable capacity of 345.2 mAh/g (2.76 mAh cm−2) at 0.2 A/g and maintains 235.2 mAh/g (1.88 mAh cm−2) at 4 A/g, while sustaining an impressive capacity retention of 97.7 % over 5000 cycles. These considerably outperform conventional electrodes employing traditional binders. Even at an elevated mass loading of 14 mg cm−2 or when operated at a low temperature of − 30 °C, the electrode continues to deliver excellent electrochemical performance (e.g., extraordinary areal capacity of 4.32 mAh cm−2). In addition, the electrode owns outstanding tolerance to external forces. This research contributes to our understanding of the pivotal challenges within the realm of AZIB technology.

Layer-Resolved Mechanical Degradation of a Ni-Rich Positive Electrode

The effects of electrochemical aging on the mechanical properties of electrodes in lithium-ion batteries are challenging to measure and are largely unknown. Mechanochemical degradation processes occur at different scales within an electrode and understanding the correlation between the degradation of mechanical properties, electrochemical aging, and morphological changes is crucial for mitigating battery performance degradation. This paper explores the evolution of mechanical and electrochemical properties at the layer level in a Ni-rich positive electrode during the initial stages of electrochemical cycling. The investigation involves complementary cross-section analyses aimed at unraveling the connection between observed changes on both macroscopic and microscopic scales. The macroscopic constitutive properties were assessed using a U-shaped bending test method that had been previously developed. The compressive modulus exhibited substantial dependency on both the porous structure and binder properties. It experienced a notable reduction with electrolyte wetting but demonstrated an increase with cycling and aging. During the initial stages of aging, electrochemical impedance spectra revealed increased local resistance near the particle–electrolyte interface. This is likely attributable to factors such as secondary particle grain separation and the redistribution of carbon black. The swelling of particles, compression of the binder phase, and enhanced particle contact were identified as probable factors adding to the elevation of the elastic modulus within the porous layer as a result of cycling.

Nanosilica-filled flame-retardant copolyester electrospun composite separators for high-performance safe lithium-ion batteries

The essential role of separators in battery safety and electrochemical performance makes it necessary to create advanced separators for next-generation energy storage systems. However, conventionally commercial polyolefin separators often have problems with poor thermal stability and insufficient electrolyte wettability, resulting in restricted battery performance and serious safety issues of lithium-ion batteries. Herein, we report a separator composed of silica (SiO2) nanoparticles and intrinsically flame-retardant copolyester P(ET-co-PN)5 electrospun nanofibers, i.e. SiO2@P(ET-co-PN)5 (SP) separator. The copolyester nanofiber's three-dimensional skeleton filled with close-packed SiO2 nanoparticles endows the separator with good mechanical performance (tensile strength of 9.8 MPa) and electrolyte wettability (electrolyte uptake of 333 %), superior heatproof and fireproof properties (no shrinkage at 250 °C, PHRR of 111.6 W/g, and THR of 9.4 kJ/g). The LiFePO4/SP/Li cells exhibit high capacity of 150.2 mAh/g, high average Coulombic efficiency of nearly 100 %, and impressive capacity retention close to 100 % after 220 cycles at 0.5 C. Notably, the LiFePO4/SP/Li cells can endure 1000 cycles at 5 C with 53 % of capacity retention and approximately 100 % of Coulombic efficiency. Moreover, it delivers an initial capacity of 148 mAh/g and retains 123.2 mAh/g over 45 cycles at 120 °C.

Synergistically Stabilizing Zinc Anodes by Molybdenum Dioxide Coating and Tween 80 Electrolyte Additive for High-Performance Aqueous Zinc-Ion Batteries.

Recently, aqueous zinc-ion batteries (ZIBs) have become increasingly attractive as grid-scale energy storage solutions due to their safety, low cost, and environmental friendliness. However, severe dendrite growth, self-corrosion, hydrogen evolution, and irreversible side reactions occurring at Zn anodes often cause poor cyclability of ZIBs. This work develops a synergistic strategy to stabilize the Zn anode by introducing a molybdenum dioxide coating layer on Zn (MoO2@Zn) and Tween 80 as an electrolyte additive. Due to the redox capability and high electrical conductivity of MoO2, the coating layer can not only homogenize the surface electric field but also accommodate the Zn2+ concentration field in the vicinity of the Zn anode, thereby regulating Zn2+ ion distribution and inhibiting side reactions. MoO2 coating can also significantly enhance surface hydrophilicity to improve the wetting of electrolyte on the Zn electrode. Meanwhile, Tween 80, a surfactant additive, acts as a corrosion inhibitor, preventing Zn corrosion and regulating Zn2+ ion migration. Their combination can synergistically work to reduce the desolvation energy of hydrated Zn ions and stabilize the Zn anodes. Therefore, the symmetric cells of MoO2@Zn∥MoO2@Zn with optimal 1 mM Tween 80 additive in 1 M ZnSO4 achieve exceptional cyclability over 6000 h at 1 mA cm-2 and stability (>700 h) even at a high current density (5 mA cm-2). When coupling with the VO2 cathode, the full cell of MoO2@Zn∥VO2 shows a higher capacity retention (82.4%) compared to Zn∥VO2 (57.3%) after 1000 cycles at 5 A g-1. This study suggests a synergistic strategy of combining surface modification and electrolyte engineering to design high-performance ZIBs.

Crosslinked PVA/Citric Acid Nanofibrous Separators with Enhanced Mechanical and Thermal Properties for Lithium-Ion Batteries

Electrospinning polyvinyl alcohol (PVA) nanofibrous membranes have gained increased attention for their uses as separators for lithium-ion batteries (LIBs) due to their high porosity and excellent electrolyte wettability, but their poor mechanical and thermal properties have limited their further development. In this work, a crosslinked PVA composite separator (PVA/CA-H) was first prepared via the electrospinning of the PVA and citric acid (CA) mixed solution and then the heating of the nanofibrous membrane, and the effects of the amount of CA on the structure and performance of the PVA/CA-H separator were investigated. The hydroxyl group of PVA and the carboxyl group of CA were crosslinked under the heat treatment, resulting in a slight reduction in the porosity and pore size of the composite separator compared to pure PVA, and to compensate for this issue, the mechanical strengths, as well as the thermal dimensional stability of the PVA/CA-H separator, were significantly improved. Meanwhile, the PVA/CA-H separator exhibited good electrolyte uptake (158.1%) and high ionic conductivity (1.63 mS cm−1), and, thus, the battery assembled with the PVA/CA-H separator exhibited a capacity retention of 96.3% after 150 cycles at 1 C. These features mean that the crosslinked PVA composite separator can be considered as a prospective high-safety and high-performance separator for LIBs.

Waterborne spontaneous and robust coating of POSS nanoparticles on hydrophobic surfaces for application as an advanced separator in lithium ion batteries

Waterborne spontaneous and robust coating of the catechol-functionalized polyoctahedral silsesquioxane (CA-POSS) is studied on the surface of hydrophobic substrates as a model organic-inorganic hybrid material. The CA-POSS was synthesized at room temperature, which readily produces an instant thin layer coating on the hydrophobic substrates such as mica film and polyethylene (PE) separator. The CA-POSS instantly forms nano-scale level coating with robust adhesion upon contact with the substrate surfaces in a basic aqueous medium at ambient conditions, unlike common coating methods that use prepared POSS particle dispersion. The surface roughness of the CA-POSS coated PE separator (PE-CAP) and mica was observed in AFM analysis. The PE-CAP separator showed highly enhanced hydrophilicity, electrolyte wettability, mechanical strength, and thermal stability. The PE-CAP separator is studied in lithium ion batteries (LIBs) using LiCoO2 cathode and Lithium metal anode has shown the highest specific capacity of ∼171.3 mAh g−1 with capacity retention of ∼99 % after 100 cycles in comparison to pristine PE separator (∼159.4 mAh g−1, 92 %).

Decorating carbon quantum dots onto VO2 nanorods to boost electron and ion transport kinetics for high–performance zinc–ion batteries

Rechargeable aqueous Zn–ion batteries (RAZIBs) are regarded as attractive alternatives for large–scale energy storage. V–based cathode materials have gained great attention due to the merits of rich valence states, controllable morphology, diverse crystal structures, and controllable chemical compositions. However, the development of high–performance V–based cathode is still impeded by sluggish electron/ion transport kinetics. To address this issue, this work reveals that the electrochemical performance of the VO2 cathode can be significantly boosted by decorating carbon quantum dots (CQDs) onto the VO2 nanorods via a facile hydrothermal reaction. The VO2/CQDs sample is characterized to have strong interface interaction with the presence of CO bond. Compared to the CQD–free counterpart, the obtained VO2/CQDs sample exhibits higher specific surface area (18.7 vs 4.4 m2 g−1), better electrolyte wettability (53° vs 114° for contact angle), reduced charge–transfer resistance (1.8 vs 19.9 Ω), and facilitated ion diffusion coefficient (1.66 × 10−10 vs 4.56 × 10−11 cm2 s−1). Benefiting from these features, a high attainable capacity of 427 mAh g−1 at 0.2 A g−1 can be reached for VO2/CQDs, corresponding to the specific energy of 333 Wh kg−1 (based on the mass of VO2/CQDs). When the current density increases to 8 A g−1, VO2/CQDs can still deliver 309 mAh g−1, showing great promise for high–rate capability. Moreover, the VO2/CQDs cathode renders stable cycle performance with retaining 229 mAh g−1 after 2000 cycles. By contrast, the unmodified sample demonstrates moderate electrochemical performance (373 and 186 mAh g−1 at 0.2 and 8 A g−1, respectively). The results highlight the importance of the CQDs decoration strategy, which can effectively boost electron/ion transport in oxide–based cathodes for high–performance RAZIBs.

A Magnesium Carbonate Hydroxide Nanofiber/Poly(Vinylidene Fluoride) Composite Membrane for High-Rate and High-Safety Lithium-Ion Batteries.

Simultaneously high-rate and high-safety lithium-ion batteries (LIBs) have long been the research focus in both academia and industry. In this study, a multifunctional composite membrane fabricated by incorporating poly(vinylidene fluoride) (PVDF) with magnesium carbonate hydroxide (MCH) nanofibers was reported for the first time. Compared to commercial polypropylene (PP) membranes and neat PVDF membranes, the composite membrane exhibits various excellent properties, including higher porosity (85.9%) and electrolyte wettability (539.8%), better ionic conductivity (1.4 mS·cm-1), and lower interfacial resistance (93.3 Ω). It can remain dimensionally stable up to 180 °C, preventing LIBs from fast internal short-circuiting at the beginning of a thermal runaway situation. When a coin cell assembled with this composite membrane was tested at a high temperature (100 °C), it showed superior charge-discharge performance across 100 cycles. Furthermore, this composite membrane demonstrated greatly improved flame retardancy compared with PP and PVDF membranes. We anticipate that this multifunctional membrane will be a promising separator candidate for next-generation LIBs and other energy storage devices, in order to meet rate and safety requirements.

Towards high performance Li metal batteries: Surface functionalized graphene separator with improved electrochemical kinetics and stability

Lithium (Li) metal is a promising anode for next-generation batteries owing to its ultrahigh theoretical capacity (3,860 mAh g−1) and the lowest reduction potential (−3.04 vs SHE at RT). However, the development of Li-metal batteries (LMBs) is still in the research stage due to the inherent problems related to the growth of Li dendrites and unlimited volume change in Li metal. Among diverse approaches, the introduction of functional separators is regarded as an effective strategy for improving the safety and electrochemical performance of LMBs. Herein, we deposited two different graphene layers onto the separators to explore the influence of surface functionalized graphene layer on the electrochemical performance and cycle stability of LMBs. When a surface functionalized graphene separator (SFGS) was used in the LMBs, it exhibited superior electrolyte wettability than a graphene separator (GS), contributing to the improved ionic conductivity and homogeneous Li-ion flux. Due to the improved electrochemical kinetics and reversible electrochemical reactions, Li/Cu cells with the SFGS exhibited the most stable cycle performance with a high Coulombic efficiency of 98 % over 200 cycles compared with other Li/Cu cells. Our strategy would resolve many issues related to the poor electrochemical reversibility of Li-metal anodes and advance the development of practical surface-modified separators for high-performance LMBs.

Water-based dual polymer ceramic-coated composite separator for high-energy-density lithium secondary batteries

A simple, eco-friendly, and effective additive-free technique for stabilizing a coating slurry, using alumina (Al2O3) inorganic particles and aqueous dual polymers—sodium carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA) is developed. The slurry preparation process is optimized by determining the polymer binders (CMC/PVA) content in the ceramic slurry and studying the interaction between the polymer binders and Al2O3 ceramic particles by changing the mixing order of the slurry components. CMC effectively controls the viscosity of the slurry to maintain a stable slurry dispersion. In contrast, PVA significantly influences the formation of a uniform ceramic coating layer on the polyethylene (PE) separator. This results in a synergistic effect to produce an optimal ceramic-coated composite separator (CCS). Compared to the bare PE separators, the prepared Al2O3 CCSs display improved physical properties, such as high adhesion strength of the ceramic coating layer, thermal stability, electrolyte wettability, and increased ionic conductivity. Moreover, the CCSs exhibit enhanced electrochemical performance. Half cells (LiMn2O4/Li metal) comprising CCSs retained 96.5% (144.8 mAh g−1) of the initial discharge capacity even after 200 cycles, while bare PE separators lose their capacity rapidly after 150 cycles, retaining only 22.62% (33.5 mAh g−1) at the 200th cycle.

Optimizing Na plating/stripping by a liquid sodiophilic Ga-Sn-In alloy towards dendrite-poor sodium metal anodes

Benefited by the abundant Na resources and high theoretical capacity of Na, rechargeable sodium metal batteries exhibit great potentials for next-generation energy storage systems. However, there are several key puzzles of Na anodes restricting the wide application, including high activity of Na metal, uncontrollable dendrite growth and unstable solid-electrolyte interface (SEI). In this work, a liquid alloy comprised of Ga, Sn and In was uniformly coated on commercial Cu foil in order to regulate the Na plating/stripping behaviors and thereupon enable stable sodium metal battery. The liquid sodiophilic Ga-Sn-In alloy on Cu foil (GSIC) can enhance the wettability of electrolyte and melted Na and decrease the Na nucleation overpotential. Based on the results of ex situ SEM and in situ optical microscopy, the Ga-Sn-In alloy coating layer can induce the uniform Na plating and decrease the volume expansion, enabling dendrite-poor capability. By taking NVP as cathode and optimal Na-GSIC as Na anode, the sodium metal full battery manifests a high reversible capacity of 108.7 mAh g−1 at the 1st cycles and offers 87.4 mAh g−1 (80.4% retention) at 5 C after 250 cycles. Such sodiophilic liquid alloy current collector would pave new pathway on designing feasible and highly stable Na metal anodes for sodium metal batteries.

Directional interface electron transfer from Fe2O3 to biomass-derived carbon originated from F-dopant-induced site-specific growth

Site-specific growth of active phase on surface functionalization carbon substrate has drawn attention to improve the catalytic activity and stability of electrocatalyst. Herein, F-dopant-induced Fe2O3 site-specific growth improves the directional interface electron transfer from Fe2O3 to biomass-derived carbon. Electron redistribution between Fe2O3 and F-doped carbon (FC) optimizes the adsorption energy of intermediates to improve electrocatalytic intrinsic activities. The hydrophilic/aerophobic surface of Fe2O3/FC benefits to the fast reaction kinetics for water splitting. FC as hydrophilic end enhances wettability of electrolyte on electrode surface and facilities H2O adsorption. Fe2O3 as aerophobic end is conducive to the formation and overflow of bubbles from catalyst surface. It is a simple way to achieve directional interface electron transfer in heterogenous catalysis that F doping can induce site-specific growth for the improvement of activity and stability.

Uniform lithium deposition regulated by lithiophilic Mo3N2/MoN heterojunction nanobelts interlayer for stable lithium metal batteries

Lithium metal batteries (LMBs) are of significant importance for high-energy rechargeable batteries owing to its ultra-high theoretical specific capacity and lowest reduction potential. However, the lithium dendrite growth during the continuous plating/stripping process results in poor cycle property, serious security issues and low Coulombic efficiency to working LMBs. To effectively inhibit lithium dendrite issues, a multifunctional lithiophilic interlayer constructed by heterostructural Mo3N2/MoN nanobelt (MoNx) is exploited as regulator to adjust lithium deposition. The results reveal that MoNx/PP exhibits high lithium-ion transference number, ion conductivity and excellent electrolyte wettability, which action synergistically to regulate lithium-ion diffusion and flux. DFT calculation further demonstrates that the co-existence of heterostructure and polar bonds can effectively enhance the interaction between MoNx and lithium, which can supply more deposition sites for promoting homogenous and smooth lithium plating. The advantages mentioned above endow symmetric Li//Li cell used MoNx/PP with a super-long-life of 1500 h at 5 mA cm−2. Furthermore, Li//LiFePO4 full cell presents excellent cycling stability and ultra-low-capacity decay rate of 0.033 %/cycle after 500 cycles even at 3C. This work offers a creative strategy and insight to reasonably design lithiophilic interlayer to regulate Li uniform depositions in working LMBs.

3D-printed film architecture via automatic micro 3D-printing system: Micro-intersection engineering of V2O5 thin/thick films for ultrafast electrochromic energy storage devices

Existing approaches to develop electrochromic (EC) energy storage devices typically focus on the modification of active materials toward a porous morphology, crystallinity, heteroatom-doping, and hybridization/composites with functional materials; however, these approaches may be unsuitable for the full commercialization of EC energy storage devices owing to their complex and expensive processes and incompatibility with large-scale and mass production. Herein, we fabricate 3D-printed film architectures for ultrafast EC energy storage devices, including micro-intersections of vanadium oxide (VO) thin/thick films, via an automatic micro 3D-printing system without active material modification. The micro-intersection originates from the one-pot 3D-printing of vertical lines, creating VO grid-micropatterns with nanoscale thin/thick films on fluorine-doped tin oxide (FTO)/glass. The micro-intersection density was engineered by adjusting the number of printed-lines per unit area and optimized micro-intersection density (OD-3DVO) allows enhanced behaviors of electrons and Li-ions as follows: (i) the thin film architecture alleviates rate-limiting processes that produce sluggish electron transfer and ionic diffusion kinetics by shortening transport channels between FTO and the electrolyte, thereby accelerating ultrafast charge transport. (ii) Micro-width/nano-depth 3D-wells induce capillary force pumping and deep electrolyte infiltration at the interface, thereby enhancing electrolyte wettability. (iii) grid-micropatterned film morphology provides extensive redox sites and high visible transmissivity; thus, the OD-3DVO active layers in EC energy storage devices featured simultaneously enhanced optical and energy storage performances, especially ultrafast switching speeds (0.7 and 0.9 s for coloration and bleaching) and record-high areal energy density at high areal power density (14.03 µWh/cm2 at 25 mW/cm2).

Regulating Li ions transportation and deposition with polydopamine/polyethyleneimine functional separator for superior Li metal battery

Multifunctional modified separators have the potential to effectively regulate Li ion deposition, suppress the growth of dendrite and improve the safety of lithium metal batteries (LMBs). Here, we designed a separator, constructed by co-deposition of polydopamine (PDA) and polyethyleneimine (PEI) on PP separator. Due to the introduction of polar functional groups such as amine groups, PDA/PEI-3 modified separator exhibits better electrolyte wettability, higher Li ion migration number (0.9), lower energy barrier and faster ion transfer kinetics. Electrochemical tests prove that PDA/PEI-3 modified separator has achieved better cycling stability at different current density in Li//Li symmetric cells and higher CE in Li//Cu cells. Meanwhile, the Li/LFP full cells show more excellent rate performance and long cycle performance (80%). SEM and XPS also prove that modified separator has achieved homogenized Li ions flux and more uniform LiF-rich SEI layer. This work provides a simple and effective strategy for functional separator to protect Li metal anode and improve safety performance of LMBs.

Thermally stable 3D cross-linked fluorinated polyimide/PVDF-HFP hybrid separator for lithium battery applications

Commercial Celgard 2325 separators suffer from poor flexibility, poor electrolyte wettability, and thermal instability, which can cause internal short circuits and thermal runaway in lithium rechargeable batteries. A novel 3D cross-linked and thermotolerant fluorinated polyimide (PI) / PVDF-HFP (PV) hybrid nanofiber separator rich in polar functional groups was fabricated using an electrospinning technique. PI and PV polymers are joined by a hydrogen bond through their exposed amide (–NH) and fluorinated (-CF) functional groups to build a supramolecular polymer cross-linked system. The separator exhibited high porosity (75 %), outstanding electrolyte uptake ability (775 %), strong mechanical properties (15.7 MPa), excellent thermal stability, and flexibility. As a result, the separator showed excellent Li+-conductivity (3.3 mS cm−1) and high Li+-transference number (tLi+ = 0.7) and maintained a proper-contacted electrolyte/electrode interaction for stable Li plating/stripping. Furthermore, when the PI/PV hybrid separator was applied in anode-free Li-metal batteries (a protocol of Cu/NMC cell), or Li-ion (MCMB /NMC) batteries, the cells achieved a high capacity and long lifetime. Remarkably, the Cu/NMC cell fabricated with a PI/PV hybrid separator is more robust and continues to function even after being heated at a high temperature of 140 °C for 1 h.

Flexible eggshell membrane enabled dendrite-free Zn metal anode for aqueous zinc-ion batteries

Aqueous zinc ion batteries (AZIBs) are ideal choices for large-scale energy storage due to their outstanding merits of high safety and low cost. However, the severe dendritic growth on zinc anodes limits their further application. Artificial interface layer construction is an effective strategy to solve this problem. Here, the low-cost and easilyprepared flexible eggshell membrane (ESM) is chosen as an interface protective layer to achieve a dendrite-free Zn anode. Compared with the bare Zn, the flexible ESM protected Zn anode affords better electrolyte wettability, more homogeneously distributed Zn2+ flux and much lower onset potential of hydrogen evolution, which are favorable for uniform and dense zinc deposition without formation of zinc dendrites. Our symmetric cell based on Zn@ESM electrode presents superior cycling stability of over 2000 h at 0.25 mA⋅cm−2 and over 4000 h at 0.5 mA⋅cm−2, while the symmetric cell with bare Zn only work less than 200 h. Moreover, the cycling stability of Zn@ESM//K1.14(VO)3.33[Fe(CN)6]2·6.8H2O full cell is also enhanced to retain 100% capacity after 600 cycles.

The synergistic effect of C/TiO2-SiO2 Janus film revitalizes the lithium metal anode

Li metal is an ideal anode for rechargeable lithium-based batteries due to its high specific capacity (3860 mAh g−1) and low redox potential (−3.04 V vs. SHE). Nevertheless, the constant growth of lithium dendrites and infinitely large volume change limit its practical application. Here, we designed a Janus film with opposite conductivity on two sides, where the non-conductive SiO2 separates the lithium metal anodes from the electrolyte, allowing the lithium ions to pass through and then deposit on the C/TiO2 scaffold with conductivity on the other side. SiO2 can homogenize the lithium ions flow well owing to its excellent electrolyte wettability, while its high mechanical strength inhibits lithium-dendrite growth. As a bridge between the lithium metal anode and the lithium plating, the C/TiO2 layer acts as an ion redistributor to form a higher lithium-ion concentration region near the electrode interface, thus weakening the dendrite growth caused by concentration polarization. The synergistic effect of SiO2 and C/TiO2 scaffold has achieved dendrite-free metal lithium deposit. Therefore, with the Janus film modified lithium metal electrode, the symmetrical cell can achieve 1500 h cycle at a current density of 3 mA cm−2, accompanied by a low overpotential of 80 mV. Furthermore, an ultrahigh capacity retention of 99% is achieved after long-term cycling of 250 times in LiFePO4||Li full cells at 1 C.

A Keggin Al13 -Montmorillonite Modified Separator Retards the Polysulfide Shuttling and Accelerates Li-Ion Transfer in Li-S Batteries.

The commercialization of Li-S batteries as a promising energy system is terribly impeded by the issues of the shuttle effect and Li dendrite. Keggin Al13 -pillared montmorillonite (AlMMT), used as the modified film of the separator together with super-P and poly (vinylidene fluoride) (PVDF), has a good chemical affinity to lithium polysulfide (LiPS) to retard the polysulfide shuttling, excellent electrolyte wettability, and a stable structure, which can improve the rate capability and cycling stability of Li-S batteries. Density function theory (DFT) calculations reveal the strong adsorption ability of AlMMT for LiPS. Consequently, the modified film allows Li-S batteries to reach 902 mAh g-1 at 0.2C after 200 cycles and 625 mAh g-1 at 1C after 1000 cycles. More importantly, a high reversible areal capacity of 4.04 mAh cm-2 can be realized under a high sulfur loading of 6.10mg cm-2 . Combining the merits of rich resources of montmorillonite, prominent performance, simple operation and cost-effectiveness together, this work exploits a new route for viable Li-S batteries for applications.