Adjusting Ion Diffusion Kinetics of Li Deposition Enabled by an Elastic Porous Melamine Sponge Host for Stable Lithium Metal Anodes.

Lithium (Li) dendritic growth and huge volume expansion seriously hamper Li-metal anode development. Herein, we design a lightweight 3D Li-ion-affinity host enabled by silver (Ag) nanoparticles fully decorating a porous melamine sponge (Ag@PMS) for dendrite-free and high-areal-capacity Li anodes. The compact Ag nanoparticles provide abundant preferred nucleation sites and give the host strong conductivity. Moreover, the high specific surface area and polar groups of the elastic, porous melamine sponge enhance the Li-ion diffusion kinetics, prompting homogeneity of Li deposition and stripping. As expected, the integrated 3D Ag@PMS-Li anode delivered a remarkable electrochemical performance, with a Coulombic efficiency (CE) of 97.14% after 450 cycles at 1 mA cm-2. The symmetric cell showed an ultralong lifespan of 3400 h at 1 mA cm-2 for 1 mAh cm-2. This study provides a facile and cost-effective strategy to design an advanced 3D framework for the preparation of a stable dendrite-free Li metal anode.

Homogeneously Planar-Exposure LiB Fiber Skeleton Toward Long-Lifespan Practical Li Metal Pouch Cells.

LiB alloy is promising lithium (Li) metal anode material because the continuous internal LiB fiber skeleton can effectively suppress Li dendrites and structural pulverization. However, the unvalued surface states limit the practical application of LiB alloy anodes. Herein, the study examined the influence of the different exposure manners of the internal LiB fiber skeleton owing to the various surface states of the LiB alloy anode on electrochemical performance and targetedly proposed a scalable friction coating strategy to construct a lithiated fumed silica (LFS) functional layer with abundant electrochemically active sites on the surface of the LiB alloy anode. The LFS significantly suppresses the inhomogeneous interfacial electrochemical behavior of the LiB alloy anode and enables the exposure of the internal LiB fiber skeleton in a homogeneously planar manner (LFS-LiB). Thus, a 0.5 Ah LFS-LiB||LiCoO2 (LCO) pouch cell exhibits a discharge capacity retention rate of 80% after 388 cycles. Moreover, a 6.15 Ah LFS-LiB||S pouch cell with 409.3 Wh kg-1 exhibits a discharge capacity retention rate of 80% after 30 cycles. In conclusion, the study findings provide a new research perspective for Li alloy anodes.

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

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

Building Sustainable Saturated Fatty Acid-Zinc Interfacial Layer toward Ultra-Stable Zinc Metal Anodes.

The commercialization pace of aqueous zinc batteries (AZBs) is seriously limited due to the uncontrolled dendrite growth and severe corrosion reaction of the zinc anode. Herein, a universal and extendable saturated fatty acid-zinc interfacial layer strategy for modulating the interfacial redox process of zinc toward ultrastable Zn metal anodes is proposed. The in situ complexing of saturated fatty acid-zinc interphases could construct an extremely thin zinc compound layer with continuously constructed zincophilic sites which kinetically regulates Zn nucleation and deposition behaviors. Furthermore, the multifunctional interfacial layer with internal hydrophobic carbon chains as a protective layer is efficient to exclude active water molecules from the surface and efficiently inhibit the surface corrosion of zinc. Consequently, the modified anode shows a long cycle life of over 4000 h at 5 mA cm-2. In addition, the assembled Zn||V2O5 full cells based on modified zinc anodes have excellent rate performance and long cycle stability.

Dual Active Sites of Oversaturated Fe-N5 and Fe2 O3 Nanoparticles for Accelerating Redox Kinetics of Polysulfides.

The shuttling effect and sluggish reaction kinetics are the main bottlenecks for the commercial viability of lithium-sulfur (Li-S) batteries. Metal-nitrogen-carbon single atom catalysts have attracted much attention to overcoming these obstacles due to their novel electrocatalytic activity. Herein, a novel cooperative catalytic interface with dual active sites (oversaturated Fe-N5 and polar Fe2 O3 nanocrystals) are co-embedded in nitrogen-doped hollow carbon spheres (Fe2 O3 /Fe-SA@NC) is designed by fine atomic regulation mechanism. Both experimental verifications and theoretical calculations disclose that the dual active sites (Fe-N5 and Fe2 O3 ) in this catalyst (Fe2 O3 /Fe-SA@NC) tend to form "FeS" and "LiN/O" bond, synchronically enhancing chemical adsorption and interface conversion ability of polysulfides, respectively. Specially, the Fe-N5 coordination with 3D configuration and sulfiphilic superfine Fe2 O3 nanocrystals exhibit the strong adsorption ability to facilitate the subsequent conversion reaction at dual-sites. Meanwhile, the nitrogen-doped hollow carbon spheres can promote Li+ /electron transfer and physically suppress polysulfides shuttling. Consequently, Li-S battery with the Fe2 O3 /Fe-SA@NC-modified separator exhibits a high capacity retention of 78% after 800 cycles at 1 C (pure S cathode, S content: 70 wt.%). Furthermore, the pouch cell with this separator shows good performance at 0.1 C for practical application (S loading: 4 mg cm-2 ).

Reactive Polymer as Artificial Solid Electrolyte Interface for Stable Lithium Metal Batteries.

Lithium (Li) metal anodes have the highest theoretical capacity and lowest electrochemical potential making them ideal for Li metal batteries (LMBs). However, Li dendrite formation on the anode impedes the proper discharge capacity and practical cycle life of LMBs, particularly in carbonate electrolytes. Herein, we developed a reactive alternative polymer named P(St-MaI) containing carboxylic acid and cyclic ether moieties which would in situ form artificial polymeric solid electrolyte interface (SEI) with Li. This SEI can accommodate volume changes and maintain good interfacial contact. The presence of carboxylic acid and cyclic ether pendant groups greatly contribute to the induction of uniform Li ion deposition. In addition, the presence of benzyl rings makes the polymer have a certain mechanical strength and plays a key role in inhibiting the growth of Li dendrites. As a result, the symmetric Li||Li cell with P(St-MaI)@Li layer can stably cycle for over 900 h under 1 mA cm-2 without polarization voltage increasing, while their Li||LiFePO4 full batteries maintain high capacity retention of 96 % after 930 cycles at 1C in carbonate electrolytes. The innovative strategy of artificial SEI is broadly applicable in designing new materials to inhibit Li dendrite growth on Li metal anodes.

3D Patternable Supercapacitors from Hierarchically Architected Porous Fiber Composites for Wearable and Waterproof Energy Storage.

High-performance wearable supercapactors (SCs) are gaining prominence as portable energy storage devices. To further enhance both energy and power density, the significant relationship between structure and performance inspires a delicate design of 3D patternable supercapacitors with a hierarchical architecture of porous conductive fibers composited with pseudocapacitive materials. In this work, the polypyrrole nanowires arrays decorated 3D graphite felt fiber assembly is initially fabricated as the conductive scaffold, followed by the distribution of the highly conductive and pseudocapacitive NiCoSe2 nanoparticles. Moreover, to realize the goal of standardized batch and pattern processing of the wearable SCs, laser engraving and silicone sealing techniques are employed, and SC devices with different patterns are successfully fabricated and encapsulated. Notably, the resulting SCs exhibit both stable electrochemical performance and effective waterproof properties, with the highest specific capacitance of 5.21 F cm-3 (113.36 F g-1 ) at the current density of 0.025 A cm-3 (0.5 F g-1 ), and the highest energy density of 1.09 mWh cm-3 (22.14 Wh kg-1 ) at a power density of 16.5 mW cm-3 (358.7 W kg-1 ).

Design of Novel Wearable, Stretchable, and Waterproof Cable-Type Supercapacitors Based on High-Performance Nickel Cobalt Sulfide-Coated Etching-Annealed Yarn Electrodes.

Rapid advances in functional electronics bring tremendous demands on innovation toward effective designs of device structures. Yarn supercapacitors (SCs) show advantages of flexibility, knittability, and small size, and can be integrated into various electronic devices with low cost and high efficiency for energy storage. In this work, functionalized stainless steel yarns are developed to support active materials of positive and negative electrodes, which not only enhance capacitance of both electrodes but can also be designed into stretchable configurations. The as-made asymmetric yarn SCs show a high energy density of 0.0487 mWh cm-2 (10.19 mWh cm-3 ) at a power density of 0.553 mW cm-2 (129.1 mW cm-3 ) and a specific capacitance of 127.2 mF cm-2 under an operating voltage window of 1.7 V. The fabricated SC is then made into a stretchable configuration by a prestraining-then-releasing approach using polydimethylsiloxane (PDMS) tube, and its electrochemical performance can be well maintained when stretching up to a high strain of 100%. Moreover, the stretchable cable-type SCs are stably workable under water-immersed condition. The method opens up new ways for fabricating flexible, stretchable, and waterproof devices.

Nitroxyl radical triggered the construction of a molecular protective layer for achieving durable Zn metal anodes.

The issues of dendrite growth, hydrogen evolution reaction, and zinc anode corrosion have significantly hindered the widespread implementation of aqueous zinc-ion batteries (AZIBs). Herein, trace amounts of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) additive is introduced into AZIBs to protect the zinc metal anode. Trace amounts of the TEMPO additive with nitroxyl radical can provide fast Zn2+ transport and anode protection ability by forming an adsorbed molecular layer via Zn-O bond. This interface not only provides strong interfacial compatibility and promotes dynamic transport of Zn2+, but also induces deposition of Zn2+ along Zn (002) plane. Additionally, the molecular protective layer significantly inhibits hydrogen evolution reaction (HER) and corrosion. The Zn anodes achieve high Coulombic efficiency of up to 99.75 % and long-term plating/stripping of more than 1400 h at 1 mA cm-2 and 0.5 mAh cm-2. The Zn//Zn symmetric cell can operate continuously for 2500 h at a current density of 1 mA cm-2 and 1 mAh cm-2, and it can still last for nearly 1400 h even when the current density is increased to 5 mA cm-2. Furthermore, the Zn//V2O5 full cell using TEMPO/ZnSO4 electrolyte effectively maintains a maximum capacity retention rate of 53.4 % even after 1500 cycles at 5 A/g. This innovative strategy introduces trace additive with free radicals into the electrolyte, which may help to achieve large-scale, ultra-long-life, and low-cost AZIBs.

Constructing Orbital Coupling-Modulated Homogeneous Dual-Atom Fe-Fe Sites for Boosting Bidirectional Conversion of Polysulfides.

Homogeneous dual-atom catalysts (HDACs) have garnered significant attention for their potential to overcome the shuttling effect and sluggish reaction kinetics in lithium-sulfur (Li-S) batteries. However, modulating the electron structure of metal atomic orbitals for HDACs to dictate the catalytic activity toward polysulfides has remained meaningful but unexplored so far. Herein, an interfacial cladding strategy is developed to obtain a new type of dual-atom iron matrix with a unique FeN2P1-FeN2P1 coordination structure (Fe2@NCP). The 3d orbital electrons of the Fe centers are redistributed by incorporating phosphorus atoms into the first coordination sphere. The theoretical calculations disclose that the strong coupling between the Fe d orbital and the S p orbital exhibits an enhanced Fe-S bond and improved reactivity toward polysulfides. Moreover, the Fe2@NCP catalyst achieves robust adsorption ability toward Li2Sn (1 ≤ n ≤ 8) and significantly boosts bidirectional sulfur redox reaction kinetics by lowering the Li2S deposition/decomposition energy barriers. Consequently, the assembled Li-S batteries present a high retention ratio of 77.3% after 500 cycles at 1C. Furthermore, the Li-S pouch cell also exhibits good performance at 0.1C (80.2% retention over 100 cycles) for practical application with a sulfur loading of 4.0 mg/cm2. The outcome of this study will facilitate the design of homogeneous dual-atom catalysts for Li-S batteries.

Solvothermal synthesis of hollow urchin-like SnO2 nanospheres with superior lithium storage behavior.

Hollow urchin-like SnO2 nanospheres with ultrathin nanorods have been successfully synthesized via a simple complex solvothermal route. The formation mechanism of the as-synthesized SnO2 nanospheres was simply explained. When tested as anode, the as-obtained hollow urchin-like SnO2 nanospheres exhibit excellent rate and cycling performances. It was expected that the as-synthesized SnO2 nanospheres could be applied as anode materials for future lithium-ion batteries.

A separator modified by barium titanate with macroscopic polarization electric field for high-performance lithium-sulfur batteries.

The detrimental "shuttling effect" of lithium polysulfides and the sluggish kinetics of the sulfur redox reaction in lithium-sulfur batteries (LSBs) impede the practical application. Considering the high polar chemistry facilitates the anchoring of polysulfides, ferroelectric materials have gradually been employed as functionalized separators to suppress the "shuttling effect". Herein, a functional separator coated with BaTiO3 with a macroscopic polarization electric field (poled-BaTiO3) is designed for retarding the problematic shuttle effect and accelerating redox kinetics. Theoretical calculations and experiments revealed that resultant positive charged alignments on the poled-BaTiO3 coating can chemically immobilize polysulfides, effectively improving the cyclic stability of LSBs. Moreover, the simultaneous reinforcement of the built-in electric field in the poled-BaTiO3 coating can also improve Li-ion transportation for accelerating redox kinetics. Benefiting from these attributes, the as-developed LSB attains an initial discharge capacity of 1042.6 mA h g-1 and high cyclic stability of over 400 cycles at 1 C rate. The corresponding LSB pouch cell was also assembled to validate the concept. This work is anticipated to provide new insight into the development of high-performing LSBs through engineering ferroelectric-enhanced coatings.

Highly Reversible Lithium Metal Anode Enabled by 3D Lithiophilic-Lithiophobic Dual-Skeletons.

Lithium metal is a promising anode for high-energy-density lithium batteries, but its practical application is still hindered by intrinsic defects such as infinite volume expansion and uncontrollable dendrite growth. Herein, a dendrite-free 3D composite Li anode (Li-B@SSM) is prepared by mechanical rolling of lithiophilic LiB nanofibers supported by Li-B composite and lithiophobic stainless-steel mesh (SSM). Featuring hierarchical lithiophilic-lithiophobic dual-skeletons, the Li-B@SSM anode shows an ultrahigh Coulombic efficiency of 99.95% and a long lifespan of 900 h under 2 mA cm-2 /1 mAh cm-2 . It is demonstrated that the abnormally reversible Li stripping/plating processes should be closely related to the site-selective plating behavior and spatial confinement effect induced by the robust lithiophilic-lithiophobic dual-skeletons, which alleviates the volume changes, suppresses the growth of Li dendrites, and reduces the accumulation of "dead" Li. More importantly, the application feasibility of the Li-B@SSM anode is also confirmed in full batteries, of which the Li-B@SSM|LiFePO4 full cell shows a high capacity retention of 97.5% after 400 cycles while the Li-B@SSM|S pouch battery exhibits good cycle stability even under practically harsh conditions. This work paves the way for the facile and efficient fabrication of high-efficiency Li metal anodes toward practical applications.

In Situ Formed Tribofilms as Efficient Organic/Inorganic Hybrid Interlayers for Stabilizing Lithium Metal Anodes.

The practical application of Li metal anodes (LMAs) is limited by uncontrolled dendrite growth and side reactions. Herein, we propose a new friction-induced strategy to produce high-performance thin Li anode (Li@CFO). By virtue of the in situ friction reaction between fluoropolymer grease and Li strips during rolling, a robust organic/inorganic hybrid interlayer (lithiophilic LiF/LiC6 framework hybridized -CF2-O-CF2- chains) was formed atop Li metal. The derived interface contributes to reversible Li plating/stripping behaviors by mitigating side reactions and decreasing the solvation degree at the interface. The Li@CFO||Li@CFO symmetrical cell exhibits a remarkable lifespan for 5,600 h (1.0 mA cm-2 and 1.0 mAh cm-2) and 1,350 cycles even at a harsh condition (18.0 mA cm-2 and 3.0 mAh cm-2). When paired with high-loading LiFePO4 cathodes, the full cell lasts over 450 cycles at 1C with a high-capacity retention of 99.9%. This work provides a new friction-induced strategy for producing high-performance thin LMAs.

Interfacial friction enabling ≤ 20 µm thin free-standing lithium strips for lithium metal batteries.

A practical high-specific-energy Li metal battery requires thin (≤20 µm) and free-standing Li metal anodes, but the low melting point and strong diffusion creep of lithium metal impede their scalable processing towards thin-thickness and free-standing architecture. In this paper, thin (5 to 50 µm) and free-standing lithium strips were achieved by mechanical rolling, which is determined by the in situ tribochemical reaction between lithium and zinc dialkyldithiophosphate (ZDDP). A friction-induced organic/inorganic hybrid interface (~450 nm) was formed on Li with an ultra-high hardness (0.84 GPa) and Young's modulus (25.90 GPa), which not only enables the scalable process mechanics of thin lithium strips but also facilitates dendrite-free lithium metal anodes by inhibiting dendrite growth. The rolled lithium anode exhibits a prolonged cycle lifespan and high-rate cycle stability (in excess of more than 1700 cycles even at 18.0 mA cm-2 and 1.5 mA cm-2 at 25 °C). Meanwhile, the LiFePO4 (with single-sided load 10 mg/cm2) ||Li@ZDDP full cell can last over 350 cycles with a high-capacity retention of 82% after the formation cycles at 5 C (1 C = 170 mA/g) and 25 °C. This work provides a scalable approach concerning tribology design for producing practical thin free-standing lithium metal anodes.

Stabilizing Lithium Metal Batteries by Synergistic Effect of High Ionic Transfer Separator and Lithium-Boron Composite Material Anode.

The development of lithium (Li) metal batteries (LMBs) has been limited by problems, such as severe dendrite growth, drastic interfacial reactions, and large volume change. Herein, an LMB (8AP@LiB) combining agraphene oxide-poly(ethylene oxide) (PEO) functionalized polypropylene separator (8AP) with a lithium-boron (LiB) anode is designed to overcome these problems. Raman results demonstrate that the PEO chain on 8AP can influence the Li+ solvation structure in the electrolyte, resulting in Li+ homogeneous diffusion and Li+ deposition barrier reduction. 8AP exhibits good ionic conductivity (4.9 × 10-4 S cm-1), a high Li+ migration number (0.88), and a significant electrolyte uptake (293%). The 3D LiB skeleton can significantly reduce the anode volume changes and local current density during the charging/discharging process. Therefore, 8AP@LiB effectively regulates the Li+ flux and promotes the uniform Li deposition without dendrites. The Li||Li symmetrical cells of 8AP@LiB exhibit a high electrochemical stability of up to 1000 h at 1 mA cm-2 and 5 mAh cm-2. Importantly, the Li||LiFePO4 full cells of 8AP@LiB achieve an impressive 2000 cycles at 2C, while maintaining a high-capacity retention of 86%. The synergistic effect of the functionalized separator and LiB anode might provide a direction for the development of high-performance LMBs.

An evolution from 3D face-centered-cubic ZnSnO3 nanocubes to 2D orthorhombic ZnSnO3 nanosheets with excellent gas sensing performance.

We have successfully observed the development of three-dimensional (3D) face-centered-cubic ZnSnO(3) into two-dimensional (2D) orthorhombic ZnSnO(3) nanosheets, which is the first observation of 2D ZnSnO(3) nanostructures to date. The synthesis from 3D to 2D nanostructures is realized by the dual-hydrolysis-assisted liquid precipitation reaction and subsequent hydrothermal treatment. The time-dependent morphology indicates the transformation via a 'dissolution-recrystallization' mechanism, accompanied by a 'further growth' process. Furthermore, the 2D ZnSnO(3) nanosheets consist of smaller sized nanoflakes. This further increases the special specific surface area and facilitates their application in gas sensing. The 2D ZnSnO(3) nanosheets exhibit excellent gas sensing properties, especially through their ultra-fast response and recovery. When exposed to ethanol and acetone, the response rate is as fast as 0.26 s and 0.18 s, respectively, and the concentration limit can reach as low as 50 ppb of ethanol. All these results are much better than those reported so far. Our experimental results indicate an efficient approach to realize high-performance gas sensors.

"Two Birds with One Stone": F Doping Ni-Co Hydroxide as High-Performance Cathode Material for Aqueous Zn Batteries.

Cathode materials have impeded the development of aqueous Zn batteries (AZBs) for a long time due to their low capacity and poor cycling stability. Here, a "two birds with one stone" strategy is devised to optimize the Ni-Co hydroxide cathode material (NCH) for AZBs, which plays an essential role in both composition adjustment and morphology majorization. The F-doped Ni-Co hydroxide (FNCH) exhibits a unique nanoarray structure consisting of the 2D flake-like unit, furnishing abundant active sites for the redox reaction. A series of analyses prove that FNCH delivers improved electrical conductivity and enhanced electrochemical activity. Contributing to the unique morphology and adjusted characteristics, FNCH presents a higher discharge-specific capacity, more advantageous rate capability and competitive cycling stability than NCH. As a result, an aqueous Zn battery assembled with a FNCH cathode and Zn anode exhibits a high capacity of 0.23 mAh cm-2 at 1 mA cm-2, and retains 0.10 mAh cm-2 at 10 mA cm-2. More importantly, the FNCH-Zn battery demonstrates no capacity decay after 3000 cycles with a conspicuous capacity of 0.15 mAh cm-2 at 8 mA cm-2, indicating a superior cycling performance. This work provides a facile approach to develop high-performance cathodes for aqueous Zn batteries.

A Functional Organic Zinc-Chelate Formation with Nanoscaled Granular Structure Enabling Long-Term and Dendrite-Free Zn Anodes.

Aqueous Zn metal batteries suffer from rapid cycling deterioration due to the severe water corrosion and dendrite growth on Zn anodes. Herein, a highly antiwater Znx-diethylenetriaminepenta(methylene-phosphonic acid) interface layer with good zinc affinity and special nanoscaled 3D granular structure is designed on Zn metal to address these problems. Experimental results combined with theoretical analysis and COMSOL simulations reveal that the hydrophobic groups in such Zn-based organic complex are the decisive factor in preventing H2O from damaging Zn anode surface. The massive Zn2+ attractive sites formed by interaction of methylene-phosphonic acid groups and Zn cause ion channel for fast zinc-ion adsorption and migration. And the developed nano granular architecture on the surface induces redistributed Zn2+ ion flux to realize homogenization with smooth and compact surface deposition. Under the synergism, such modified anodes exhibit long cycling lifespan over 1300 h with a relatively low polarization voltage at 5 mA cm-2. Also, the assembled full cells (including Zn//V2O5 and Zn//MnO2 cell) based on this anode are also demonstrated. The work provides a simple, low cost, and efficient pathway by combining the two concepts of structural design and constructing protective layers on the surface to prepare high-performance Zn anodes toward prospering aqueous zinc-metal batteries.