Self-Adaptive Liquid Film: Dynamic Realization of Dendrite-Free Zn Deposition Toward Ultralong-Life Aqueous Zn Battery.

The poor reversibility and stability of Zn metal anode (ZMA) caused by uncontrolled Zn deposition behaviors and serious side reactions severely impeded the practical application of aqueous Zn metal battery. Herein, a liquid-dynamic and self-adaptive protective layer (LSPL) was constructed on the ZMA surface for inhibiting dendrites and by-products formation. Interestingly, the outer LSPL consists of liquid perfluoropolyether (PFPE), which can dynamically adapt volume change during repeat cycling and inhibit side reactions. Moreover, it can also decrease the de-solvation energy barrier of Zn2+ by strong interaction between C-F bond and foreign Zn2+ , improving Zn2+ transport kinetics. For the LSPL inner region, in-situ formed ZnF2 through the spontaneous chemical reaction between metallic Zn and part PFPE can establish an unimpeded Zn2+ migration pathway for accelerating ion transfer, thereby restricting Zn dendrites formation. Consequently, the LSPL-modified ZMA enables reversible Zn deposition/dissolution up to 2000 h at 1 mA cm-2 and high coulombic efficiency of 99.8% at 4 mA cm-2 . Meanwhile, LSPL@Zn||NH4 V4 O10 full cells deliver an ultralong cycling lifespan of 100 00 cycles with 0.0056% per cycle decay rate at 10 A g-1 . This self-adaptive layer provides a new strategy to improve the interface stability for next-generation aqueous Zn battery.

Structural Design of 3D Current Collectors for Lithium Metal Anodes: A Review.

Due to the ultrahigh theoretical specific capacity (3860 mAh g-1) and low redox potential (-3.04 V vs. standard hydrogen electrode), Lithium (Li) metal anode (LMA) received increasing attentions. However, notorious dendrite and volume expansion during the cycling process seriously hinder the development of high energy density Li metal batteries. Constructing three-dimensional (3D) current collectors for Li can fundamentally solve the intrinsic drawback of hostless for Li. Therefore, this review systematically introduces the design and synthesis engineering and the current development status of different 3D collectors in recent years (the current collectors are divided into two major parts: metal-based current collectors and carbon-based current collectors). In the end, some perspectives of the future promotion for LMA application are also presented.

Construction of Bimetallic Heterojunction Based on Porous Engineering for High Performance Flexible Asymmetric Supercapacitors.

It remains a great challenge to design and manufacture battery-type supercapacitors with satisfactory flexibility, appropriate mechanical property, and high energy density under high power density. Herein, a concept of porous engineering is proposed to simply prepare two-layered bimetallic heterojunction with porous structures. This concept is successfully applied in fabrication of flexible electrode based on CuO-Co(OH)2 lamella on Cu-plated carbon cloth (named as CPCC@CuO@Co(OH)2 ). The unique structure brings the electrode a high specific capacity of 3620 mF cm-2 at 2 mA cm-2 and appropriate mechanical properties with Young's modulus of 302.0 MPa. Density functional theory calculations show that porous heterojunction provides a higher intensity of electron state density near the Fermi level (E-Ef  = 0 eV), leading to a highly conductive CPCC@CuO@Co(OH)2 electrode with both efficient charge transport and rapid ion diffusion. Notably, the supercapacitor assembled from CPCC@CuO@Co(OH)2 //CC@AC shows high energy density of 127.7 W h kg-1 at 750.0 W kg-1 , remarkable cycling performance (95.53% capacity maintaining after 10 000 cycles), and desired mechanical flexibility. The methodology and results in this work will accelerate the transformative developments of flexible energy storage devices in practical applications.

Carbonized Polymer Dots for Controlling Construction of MoS2 Flower-Like Nanospheres to Achieve High-Performance Li/Na Storage Devices.

Despite being one of the most promising materials in anode materials, molybdenum sulfide (MoS2 ) encounters certain obstacles, such as inadequate cycle stability, low conductivity, and unsatisfactory charge-discharge (CD) rate performance. In this study, a novel approach is employed to address the drawbacks of MoS2 . Carbon polymer dots (CPDs) are incorporated to prepare three-dimensional (3D) nanoflower-like spheres of MoS2 @CPDs through the self-assembly of MoS2 2D nanosheets, followed by annealing at 700 °C. The CPDs play a main role in the creation of the nanoflower-like spheres and also mitigate the MoS2 nanosheet limitations. The nanoflower-like spheres minimize volume changes during cycling and improve the rate performance, leading to exceptional rate performance and cycling stability in both Lithium-ion and Sodium-ion batteries (LIBs and SIBs). The optimized MoS2 @CPDs-2 electrode achieves a superb capacity of 583.4 mA h g-1 at high current density (5 A g-1 ) after 1000 cycles in LIBs, and the capacity remaining of 302.8 mA h g-1 after 500 cycles at 5 A g-1 in SIBs. Additionally, the full cell of LIBs/SIBs exhibits high capacity and good cycling stability, demonstrating its potential for practical application in fast-charging and high-energy storage.

Carbonized Polymer Dots with Controllable N, O Functional Groups as Electrolyte Additives to Achieve Stable Li Metal Batteries.

Electrolyte additive is an effective strategy to inhibit the uncontrolled growth of Li dendrites for lithium metal batteries (LMBs). However, most of the additives are complex synthesis and prone to decompose in cycling. Herein, in order to guide the homogeneous deposition of Li+ , carbonized polymer dots (CPDs) as electrolyte additives are successfully designed and synthesized by microwave (M-CPDs) and hydrothermal (H-CPDs) approaches. The controllable functional groups containing N or O (especially pyridinic-N, pyrrolic-N, and carboxyl group) enable CPDs to keep stable in electrolytes for at least 3 months. Meanwhile, the clusters formed between CPDs and Li+ through electrostatic interaction effectively guide the uniform Li dispersion and limit the "tip effect" and dendrite formation. Moreover, as lithiophilic groups increase, the strong electrostatic interference for the solvation effect of Li+ in the electrolyte is formed, which induces faster Li+ diffusion/transfer. As expected, H-CPDs achieve the ultra-even Li+ transfer. The corresponding Li//LiFePO4 full cell delivers a high capacity retention rate of 93.8% after 200 cycles, which is much higher than that of the cells without additives (61.2%) and with M-CPDs (83.7%) as additives. The strategy in this work provides a theoretical direction for CPDs as electrolyte additives used in energy storage devices.

Reshaping Inner Helmholtz Layer and Electrolyte Structure via Multifunctional Organic Molecule Enabling Dendrite-Free Zn Metal Anode.

The dendrite growth and parasitic reactions that occur on Zn metal anode (ZMA)/electrolyte interface hinder the development of aqueous zinc ion batteries (AZIBs) in next-generation renewable energy storage systems. Fortunately, reconstructing the inner Helmholtz layer (IHL) by introducing an electrolyte additive, is viewed as one of the most promising strategies to harvest the stable ZMA. Herein, (4-chloro-3-nitrophenyl) (pyridin-4-yl) methanone (CNPM) with quadruple functional groups is introduced into the ZnSO4 electrolyte to reshape the interface between ZMA and electrolyte and change the solvation structure of Zn2+ . Density functional theory (DFT) calculations manifest that the ─C═O, ─Cl, ─C═N─, and ─NO2 functional groups of CNPM interact with metallic Zn simultaneously and adsorb on the ZMA surface in a parallel arrangement manner, thus forming a water-poor IHL and creating well-arranged ion transportation channels. Furthermore, theoretical calculations and experimental results demonstrate that CNPM absorbed on the Zn anode surface can serve as zincophilic sites for inducing uniform Zn deposition along the (002) plane. Benefiting from the synergistic effect of these functions, the dendrite growth and parasitic reactions are suppressed significantly. As a result, ZMA exhibits a long cycle life (2900 h) and high coulombic efficiency (CE) (500 cycles) in the ZnSO4 +CNPM electrolyte.

ZnF2 -Riched Inorganic/Organic Hybrid SEI: in situ-Chemical Construction and Performance-Improving Mechanism for Aqueous Zinc-ion Batteries.

Uncontrolled dendrites growth and serious parasitic reactions in aqueous electrolytes, greatly hinder the practical application of aqueous zinc-ion battery. On the basis of in situ-chemical construction and performance-improving mechanism, multifunctional fluoroethylene carbonate (FEC) is introduced into aqueous electrolyte to construct a high-quality and ZnF2 -riched inorganic/organic hybrid SEI (ZHS) layer on Zn metal anode (ZMA) surface. Notably, FEC additive can regulate the solvated structure of Zn2+ to reduce H2 O molecules reactivity. Additionally, the ZHS layer with strong Zn2+ affinity can avoid dendrites formation and hinder the direct contact between the electrolyte and anode. Therefore, the dendrites growth, Zn corrosion, and H2 evolution reaction on ZMA in FEC-included ZnSO4 electrolyte are highly suppressed. Thus, ZMA in such electrolyte realize a long cycle life over 1000 h and deliver a stable coulombic efficiency of 99.1 % after 500 cycles.

Sustainable and Robust Graphene Cellulose Paper Decorated with Lithiophilic Au Nanoparticles to Enable Dendrite-free and High-Power Lithium Metal Anode.

Lithium metal anodes (LMAs) with high energy density have recently captured increasing attention for development of next-generation batteries. However, practical viability of LMAs is hindered by the uncontrolled Li dendrite growth and infinite dimension change. Even though constructing 3D conductive skeleton has been regarded as a reliable strategy to prepare stable and low volume stress LMAs, engineering the renewable and lithiophilic conductive scaffold is still a challenge. Herein, a robust conductive scaffold derived from renewable cellulose paper, which is coated with reduced graphene oxide and decorated with lithiophilic Au nanoparticles, is engineered for LMAs. The graphene cellulose fibres with high surface area can reduce the local current density, while the well-dispersed Au nanoparticles can serve as lithiophilic nanoseeds to lower the nucleation overpotential of Li plating. The coupled relationship can guarantee uniform Li nucleation and unique spherical Li growth into 3D carbon matrix. Moreover, the natural cellulose paper possesses outstanding mechanical strength to tolerate the volume stress. In virtue of the modulated deposition behaviour and near-zero volume change, the hybrid LMAs can achieve reversible Li plating/stripping even at an ultrahigh current density of 10 mA cm-2 as evidenced by high Coulombic efficiency (97.2 % after 60 cycles) and ultralong lifespan (1000 cycles) together with ultralow overpotential (25 mV). Therefore, this strategy sheds light on a scalable approach to multiscale design versatile Li host, promising highly stable Li metal batteries to be feasible and practical.

Micro/Nanoengineered α-Fe2 O3 Nanoaggregate Conformably Enclosed by Ultrathin N-Doped Carbon Shell for Ultrastable Lithium Storage and Insight into Phase Evolution Mechanism.

The Fe-based transition metal oxides are promising anode candidates for lithium storage considering their high specific capacity, low cost, and environmental compatibility. However, the poor electron/ion conductivity and significant volume stress limit their cycle and rate performances. Furthermore, the phenomena of capacity rise and sudden decay for α-Fe2 O3 have appeared in most reports. Here, a uniform micro/nano α-Fe2 O3 nanoaggregate conformably enclosed in an ultrathin N-doped carbon network (denoted as M/N-α-Fe2 O3 @NC) is designed. The M/N porous balls combine the merits of secondary nanoparticles to shorten the Li+ transportation pathways as well as alleviating volume expansion, and primary microballs to stabilize the electrode/electrolyte interface. Furthermore, the ultrathin carbon shell favors fast electron transfer and protects the electrode from electrolyte corrosion. Therefore, the M/N-α-Fe2 O3 @NC electrode delivers an excellent reversible capacity of 901 mA h g-1 with capacity retention up to 94.0 % after 200 cycles at 0.2 A g-1 . Notably, the capacity rise does not happen during cycling. Moreover, the lithium storage mechanism is elucidated by ex situ XRD and HRTEM experiments. It is verified that the reversible phase transformation of α↔γ occurs during the first cycle, whereas only the α-Fe2 O3 phase is reversibly transformed during subsequent cycles. This study offers a simple and scalable strategy for the practical application of high-performance Fe2 O3 electrodes.

Molecular Engineering of Phenylbenzimidazole-Based Orange Ir(III) Phosphors toward High-Performance White OLEDs.

To develop B-O complementary-color white organic light-emitting diodes (WOLEDs) exhibiting high efficiency and low roll-off as well as color stability simultaneously, we have designed two orange iridium(III) complexes by simply controlling the position of the methoxyl group on the cyclometalated ligand. The obtained emitters mOMe-Ir-BQ and pOMe-Ir-BQ show good photophysical and electrochemical stabilities with a broadened full width at half-maximum close to 100 nm. The corresponding devices realize highly efficient electrophosphorescence with a maximum current efficiency (CE) and power efficiency (PE) of 24.4 cd A-1 and 15.3 lm W-1 at a high doping concentration of 15 wt %. Furthermore, the complementary-color all-phosphor WOLEDs based on these phosphors exhibit good performance with a maximum CE of 31.8 cd A-1, PE of 25.0 lm W-1, and external quantum efficiency of 15.5%. Particularly, the efficiency of this device is still as high as 29.3 cd A-1 and 14.2% at the practical brightness level of 1000 cd m-2, giving a small roll-off. Meanwhile, extremely high color stability is achieved by these devices with insignificant chromaticity variation.

Oxygen-Deficient Titanium Dioxide Nanosheets as More Effective Polysulfide Reservoirs for Lithium-Sulfur Batteries.

In this work, oxygen-deficient anatase TiO2 nanosheets (A-TiO2-x NSs) are proposed as a substrate to improve the electrochemical properties of sulfur electrodes for lithium-sulfur (Li-S) batteries. The A-TiO2-x NSs are prepared by partly reducing pristine TiO2 nanosheets (A-TiO2 NSs) in NaBH4 solution. With some oxygen vacancies on the surface of the TiO2 nanosheets, A-TiO2-x NSs not only promote electronic transfer, but also act as more effective polysulfide reservoirs to minimize the dissolution of lithium polysulfides (LiPSs) than the A-TiO2 NSs control. Hence, upon utilization as modifiers for cathodes of Li-S batteries, the A-TiO2-x NSs-modified sulfur (A-TiO2-x NSs-S) cathode exhibits a higher reversible specific capacity and greater cycling performance and rate capability than the A-TiO2 NSs-modified one (A-TiO2 NSs-S). For example, A-TiO2-x NSs-S delivers an initial specific capacity of 1277.1 mAh g-1 at 0.1 C and maintains a stable Coulombic efficiency of approximately 99.2 % after the first five cycles; these values are higher than those of 997.3 mAh g-1 and around 96.7 %, respectively, for A-TiO2 NSs-S. The enhanced electrochemical properties of the A-TiO2-x NSs-S cathode can be ascribed mainly to the more effective adsorption of dissolvable and diffused LiPSs by the oxygen vacancies. Therefore, utilization of the structure of oxygen vacancies in Li-S batteries demonstrates great prospects for practical application.

Achieving High Performances of Nondoped OLEDs Using Carbazole and Diphenylphosphoryl-Functionalized Ir(III) Complexes as Active Components.

Nondoped electroluminescent devices offer advantages over their doped counterparts such as good reproducibility, reduced phase separation between host and guest materials, and potential of lower-cost devices. However, low luminance efficiencies and significant roll-off values are longstanding issues for nondoped devices, and a rational design strategy for the preparation of efficient phosphors is highly desired. In this work, cyclometalated Ir(III) complexes 3CzIr(mtpy), 4CzIr(mtpy), 3POIr(mtpy), and 4POIr(mtpy) bearing carbazole (Cz) or diphenylphosphoryl (Ph2PO) groups substituted at different positions of 1,2-diphenyl-H-benzimidazole (HPBI) were designed and synthesized. Owing to the steric effects induced by these groups, a significant intermolecular interaction was avoided, thereby reducing self-quenching and triplet-triplet annihilation (TTA) at high brightness. Simultaneously, attached functional moieties manipulate the charge-carrier character and enhance the EL performance of the complexes. Device N3-10, based on 3POIr(mtpy), successfully realized excellent performance and improved efficiency stability, rendering a turn-on voltage of 2.5 V, a maximum current efficiency of 29.7 cd A-1, and a maximum power efficiency of 31.1 lm W-1, which are all almost 3-fold higher than that of the control device N-10 based on parent complex. Inspiringly, all of the devices showed reduced efficiency roll-off as luminance increased. To the best of our knowledge, these are good results for green-emitting PHOLEDs using vacuum evaporation techniques, and they provide fundamental insights into the future realization of efficient phosphorescent Ir(III) complexes and corresponding nondoped devices.

Alkali-Metal-Ion-Functionalized Graphene Oxide as a Superior Anode Material for Sodium-Ion Batteries.

Although graphene oxide (GO) has large interlayer spacing, it is still inappropriate to use it as an anode for sodium-ion batteries (SIBs) because of the existence of H-bonding between the layers and ultralow electrical conductivity which impedes the Na(+) and e(-) transformation. To solve these issues, chemical, thermal, and electrochemical procedures are traditionally employed to reduce GO nanosheets. However, these strategies are still unscalable, consume high amounts of energy, and are expensive for practical application. Here, for the first time, we describe the superior Na storage of unreduced GO by a simple and scalable alkali-metal-ion (Li(+) , Na(+) , K(+) )-functionalized process. The various alkali metals ions, connecting with the oxygen on GO, have played different effects on morphology, porosity, degree of disorder, and electrical conductivity, which are crucial for Na-storage capabilities. Electrochemical tests demonstrated that sodium-ion-functionalized GO (GNa) has shown outstanding Na-storage performance in terms of excellent rate capability and long-term cycle life (110 mAh g(-1) after 600 cycles at 1 A g(-1) ) owing to its high BET area, appropriate mesopore, high degree of disorder, and improved electrical conductivity. Theoretical calculations were performed using the generalized gradient approximation (GGA) to further study the Na-storage capabilities of functionalized GO. These calculations have indicated that the Na-O bond has the lowest binding energy, which is beneficial to insertion/extraction of the sodium ion, hence the GNa has shown the best Na-storage properties among all comparatives functionalized by other alkali metal ions.

The Influence of Surface Modification on the Photoluminescence of CdTe Quantum Dots: Realization of Bio-Imaging via Cost-Effective Polymer.

To impart biocompatibility, stability, and specificity to quantum dots (QDs)-and to reduce their toxicity-it is essential to carry out surface modification. However, most surface-modification processes are costly, complicated, and time-consuming. In addition, the modified QDs often have a large size, which leads to easy aggregation in biological environments, making it difficult to excrete them from in vivo systems. To solve these problems, three kinds of conventional polymers, namely, polyvinyl alcohol (PVA, neutral), sodium polystyrene sulfonate (PSS, negative charged), and poly(diallyl dimethyl ammonium chloride) (PDDA, positive charged) were selected to modify the surface of QDs at low cost via a simple process in which the size of the QDs was kept small after modification. The effect of polymer modification on the photoluminescence (PL) properties of the QDs was systematically investigated. High quantum yields (QYs) of 65 % were reached, which is important for the realization of bio-imaging. Then, the cytotoxicity of CdTe QD-polymer composites was systematically investigated via MTT assay using the Cal27 and HeLa cell lines, especially for high concentrations of QD-polymer composites in vitro. The experimental results showed that the cytotoxicity decreased in the order CdTe-PDDA>CdTe>CdTe-PSS>CdTe-PVA, indicating that PSS and PVA can reduce the toxicity of the QDs. An obvious cytotoxicity of CdTe-PVA and CdTe-PSS was present until 120 h for the Cal27 cell line and until 168 h for the HeLa cell line. At last, the Cal27 cell line was selected to realize bio-imaging using CdTe-PSS and CdTe-PVA composites with different emission colors under one excitation wavelength.

A plum-pudding like mesoporous SiO2/flake graphite nanocomposite with superior rate performance for LIB anode materials.

A novel kind of plum-pudding like mesoporous SiO2 nanospheres (MSNs) and flake graphite (FG) nanocomposite (pp-MSNs/FG) was designed and fabricated via a facile and cost-effective hydrothermal method. Transmission electron microscopy (TEM) analysis showed that most of the MSNs were well anchored on FG. This special architecture has multiple advantages, including FG that offers a conductive framework and hinders the volume expansion effect. Moreover, the porous structure of MSNs could provide more available lithium storage sites and extra free space to accommodate the mechanical strain caused by the volume change during the repeated reversible reaction between Li(+) and active materials. Due to the synergetic effects of its unique plum-pudding structure, the obtained pp-MSNs/FG nanocomposite exhibited a decent reversible capacity of 702 mA h g(-1) (based on the weight of MSNs in the electrode material) after 100 cycles with high Coulombic efficiency above 99% under 100 mA g(-1) and a charge capacity of 239.6 mA h g(-1) could be obtained even under 5000 mA g(-1). Their high rate performance is among the best-reported performances of SiO2-based anode materials.

Fabrication of functionalized polysulfide reservoirs from large graphene sheets to improve the electrochemical performance of lithium-sulfur batteries.

The effect of graphene lateral size on the electrochemical performance of lithium-sulfur (Li-S) batteries is often ignored. In this study, the thermally exfoliated large lateral-sized graphene (denoted LTG) was employed as the conductive matrix to support sulfur, and its performance was then compared with that of a smaller lateral-sized graphene (denoted STG) for Li-S batteries. The results showed that the LTG-S composite exhibited much higher capacity retention (53%) versus the STG-S (29%) and better rate capabilities. Because they were both identical in morphology, in terms of sulfur content and sulfur distribution, the improved properties probably resulted from the potential prevention of polysulfide diffusion upon cycling due to the larger graphene-based network and higher aspect ratio of the LTG matrix, referred as better polysulfide reservoirs. To further improve the cell performance, a reduced graphene oxide-coated carbon fiber paper (RCF) was inserted between the LTG-S cathode and the separator by a simple drop-coat method, which provided an increased conductive surface area for polysulfides to be oxidized/reduced and buffered volume expansion. As expected, the discharge capacities of 1143 and 622 mA h g(-1) at first use and after 100th cycles were obtained with an average Coulombic efficiency of 99.7%, which were higher than 847 and 455 mA h g(-1) for the cathode without the RCF, respectively. This study highlights the significance of large graphene sheets and interlayers on the inhibition of polysulfide diffusion and offers a new way to solve the problems of Li-S batteries.

Manipulation of the LiZn Alloy Process toward High-Efficiency Lithium Metal Anodes.

Synthesis of alloy-type materials (X) is one of the most effective approaches to limit lithium dendrites in Li metal anode (LMA) because of their satisfactory lithiophilicity and easy electrochemical reaction with lithium. However, current investigations have only focused on the influence of the resulting alloyed products (LiX) on the properties of LMA, but the alloying reaction process between Li+ and X has been mostly ignored. Herein, by masterly taking advantage of the alloying reaction process, a novel approach is developed to more effectively inhibit lithium dendrites than the conventional strategy that just considers the utilization of alloyed products LiX. A three-dimensional substrate material loaded with metallic Zn on the surface of Cu foam is synthesized by a simple electrodeposition process. During Li plating/stripping, both alloy reaction processes between Li+ and Zn and LiZn product are involved, which makes the disordered Li+ flux near the substrate first react with Zn metal and then results in an even Li+ concentration for more uniform Li nucleation and growth. The full cell (Li-Cu@Zn-15//LFP) exhibits the reversible capacity of 122.5 mAh g-1, and a high capacity retention of 95% is achieved after 180 cycles. This work proposes a valuable concept for the development of alloy-type materials in energy storage devices.

Ion sieve membrane: Homogenizing Li+ flux and restricting polysulfides migration enables long life and highly stable Li-S battery.

Limited by the notorious Li dendrites growth and serious polysulfide shuttle effect, the development of lithium-sulfur (Li-S) batteries is stagnant. Herein, a multifunctional separator composed of Cu-based metal-organic framework (Cu-MOF) and Li-Nafion was proposed to address the above intractable issues. The Cu-MOF with homogeneous porous structure and abundant Lewis acidic sites not only promotes uniform Li+ flux, but also exhibits a strong chemical interaction with polysulfides to inhibit the shuttle effect. Moreover, the narrow pore size distribution in the Cu-MOF and negatively charged gap endowed by the -SO3- groups both act as ion sieve to facilitate the passage of Li+ and restrict the migration of polysulfide anions, synergistically mitigating the dendritic Li growth and polysulfides shuttling. As a result, the symmetric cell with MOF/Nafion separator achieves ultralong cycling stability (1000 h) and ultralow overpotential of 20 mV at a current density of 1.0 mA cm-2. Importantly, in the assembled Li-S full battery, the modified PP separator presents the superior cycle stability with capacity retention of 90% after 300 cycles at 0.5 C. Current outcomes open up a new route to design functional separators with ion permselective for realizing the dendrite-free and high-performance Li-S battery.

Spatially Confined Li Growth on Honeycomb-like Lithiophilic Layered Double Hydroxide Nanosheet Arrays toward a Stable Li Metal Anode.

A lithium metal anode (LMA) is appealing due to its high theoretical capacity and low electrochemical potential. Unfortunately, the practical application of LMAs is restricted by the uncontrollable Li dendrite growth and tremendous volume change. Herein, lithiophilic honeycomb-like layered double hydroxide (LDH) nanosheet arrays supported on a flexible carbon cloth (NiMn-LDHs NAs@CC) are synthesized as the Li host to spatially confine the Li deposition, guiding Li growth via a conformal and uniform manner. First, the lithiophilic NiMn-LDHs NAs as nucleation seeds render the CC substance outstanding lithiophilicity and reduce the nucleation barrier. The hierarchical honeycomb-like structure then directs the oriented Li deposition and provides an open channel for fast ion transport. Finally, the CC skeleton offers a high specific surface for decreasing the inhomogeneous distribution of the current density and enough space for alleviating the volume variations, synergistically inhibiting the dendritic Li growth. As a consequence, the NiMn-LDHs NAs@CC symmetric cell exhibits a low overpotential of less than 17 mV at 2 mA cm-2 and a long lifespan of 2100 h at 3 mA cm-2. In addition, when paired with the LiNiCoMnO2 (NCM111) cathode, the NiMn-LDHs NAs@CC@Li full cell presents enhanced cycling stability and rate capability in comparison to the CC@Li full cell, implying the great potential of the NiMn-LDHs NAs@CC in stabilizing the LMA.

Regulating Li nucleation/growth via implanting lithiophilic seeds onto flexible scaffolds enables highly stable Li metal anode.

Lithium (Li) metal is deemed as an ideal and promising star anode for high energy storage but its application still is impeded due to uncontrollable Li dendrite growth and tremendous dimension change. Although the flexible and conductive three-dimensional (3D) skeleton can improve the structural and interfacial stability of Li anode, its inherently lithiophobic feature usually brings a high nucleation barrier, uneven Li+ flux, and large concentration polarization, leading to inhomogeneous Li plating/stripping. Here, we develop target material (denoted as Mo2C NPs@CC) consisting of well-distributed molybdenum carbide nanoparticles (Mo2C NPs) with intrinsic lithiophilicity serving as lithiophilic seeds implanted onto the carbon cloth, breaking the dilemma of ordinary 3D conductive skeletons. The Mo2C NPs with large Li absorption energy provide plentiful lithiophilic sites for guiding the uniform and thin Li-nuclei layer formation, thereby realizing flat Li growth and stable electrode/electrolyte interface. Moreover, the high electronic conductivity of Mo2C-modified 3D scaffolds can balance the lithiophilicity, ensuring the fast electron transport in the whole electrode, effectively lowering the local current density, and providing enough space for buffering volume change, and synergistically suppresses the growth of Li dendrites. As a result, a prolonged lifespan of 5000 cycles with low voltage hysteresis of 10 mV at current density of 2 mA cm-2 with area capacity (Ca) of 1 mA h cm-2 has been achieved, giving rational guidance for designing high-performance composite Li anodes.