Facile Synthesis of Ant‐Nest‐Like Porous Duplex Copper as Deeply Cycling Host for Lithium Metal Anodes

Suppressing the dendrite formation and managing the volume change of lithium (Li) metal anode have been global challenges in the lithium batteries community. Herein, a duplex copper (Cu) foil with an ant‐nest‐like network and a dense substrate is reported for an ultrastable Li metal anode. The duplex Cu is fabricated by sulfurization of thick Cu foil with a subsequent skeleton self‐welding procedure. Uniform Li deposition is achieved by the 3D interconnected architecture and lithiophilic surface of self‐welded Cu skeleton. The sufficient space in the porous layer enables a large areal capacity for Li and significantly improves the electrode–electrolyte interface. Simulations reveal that the structure allows proper electric field penetration into the connected tunnels. The assembled Li anodes exhibit high coulombic efficiency (97.3% over 300 cycles) and long lifespan (>880 h) at a current density of 1 mA cm^?2 with a capacity of 1 mAh cm^?2. Stable and deep cycling can be maintained up to 50 times at a high capacity of 10 mAh cm^?2.     

Highly Stable Potassium Metal Anodes with Controllable Thickness and Area Capacity

K metal battery is a kind of high-energy-density storage device with economic advantages. However, due to the dendrite growth and difficult processing characteristics, it is difficult to prepare stable K metal anode with thin thickness and fixed area capacity, which severely limits its development. In this work, a multi-functional 3D skeleton (rGCA) is synthesized by simple vacuum filtration and thermal reduction, and K metal anodes with controllable thickness and area capacity (K content) can be fabricated by changing the raw material mass and graphene layer spacing of rGCA. Moreover, the graphene sheet layer of rGCA can relax stress and relieve volume expansion; carbon nanotubes can serve as the fast transport channel of electrons, reducing internal impedance and local current density; Ag nanoparticles can induce the uniform nucleation and deposition of K⁺. The K metal composite anodes (rGCA-K) based on the conductive skeleton can effectively suppress dendrites and exhibit excellent electrochemical performance in symmetric and full cells. The controllable fabrication process of stable K metal anode is expected to help K metal batteries move toward the stage of commercial production.     

Rational Engineering of p-n Heterogeneous ZnS/SnO2 Quantum Dots with Fast Ion Kinetics for Superior Li/Na-Ion Battery

Constructing heterogeneous nanostructures is an efficient strategy to improve the electrical and ionic conductivity of metal chalcogenide-based anodes. Herein, ZnS/SnO₂ quantum dots (QDs) as p-n heterojunctions that are uniformly anchored to reduced graphene oxides (ZnS-SnO₂@rGO) are designed and engineered. Combining the merits of fast electron transport via the internal electric field and a greatly shortened Li/Na ion diffusion pathway in the ZnS/SnO₂ QDs (3–5 nm), along with the excellent electrical conductivity and good structural stability provided by the rGO matrix, the ZnS-SnO₂@rGO anode exhibits enhanced electronic and ionic conductivity, which can be proved by both experiments and theoretical calculations. Consequently, the ZnS-SnO₂@rGO anode shows a significantly improved rate performance that simple counterpart composite anodes cannot achieve. Specifically, high reversible specific capacities are achieved for both lithium-ion battery (551 mA h g⁻¹ at 5.0 A g⁻¹, 670 mA h g⁻¹ at 3.0 A g⁻¹ after 1400 cycles) and sodium-ion battery (334 mA h g⁻¹ at 5.0 A g⁻¹, 313 mA h g⁻¹ at 1.0 A g⁻¹ after 400 cycles). Thus, this strategy to build semiconductor metal sulfides/metal oxide heterostructures at the atomic scale may inspire the rational design of metal compounds for high-performance battery applications.     

A Lightweight 3D Cu Nanowire Network with Phosphidation Gradient as Current Collector for High‐Density Nucleation and Stable Deposition of Lithium

Lithium metal anodes with high energy density are important for further development of next‐generation batteries. However, inhomogeneous Li deposition and dendrite growth hinder their practical utilization. 3D current collectors are widely investigated to suppress dendrite growth, but they usually occupy a large volume and increase the weight of the system, hence decreasing the energy density. Additionally, the nonuniform distribution of Li ions results in low utilization of the porous structure. A lightweight, 3D Cu nanowire current collector with a phosphidation gradient is reported to balance the lithiophilicity with conductivity of the electrode. The phosphide gradient with good lithiophilicity and high ionic conductivity enables dense nucleation of Li and its steady deposition in the porous structure, realizing a high pore utilization. Specifically, the homogenous deposition of Li leads to the formation of an oriented texture on the electrode surface at high capacities. A high mass loading (≈44 wt%) of Li with a capacity of 3 mAh cm^?2 and a high average Coulombic efficiency of 97.3% are achieved. A lifespan of 300 h in a symmetrical cell is obtained at 2 mA cm^?2, implying great potential to stabilize lithium metal.     

Mixed Ionic and Electronic Conductor for Li‐Metal Anode Protection

Li‐metal is the optimal choice as an anode due to its highest energy density. However, Li‐anodes suffer safety problems from dendritic Li‐growth and continuous corrosion by liquid electrolytes. Here, an effective strategy of using ultrathin and conformal mixed ionic and electronic ceramic conductor (MIEC) is proposed to stabilize Li‐anodes. An ultrathin Li_0.35La_0.52[V]_0.13TiO₃ (LLTO) ceramic film with superior ionic conductivity is first obtained by sintering single‐crystal LLTO nanoparticles, which have controlled surface facets and particle sizes. Then the MIEC property is developed in the LLTO film by introducing toluene as catalyst, which triggers the chemical reactions between LLTO and Li‐metal, leading to high electronic conductivity in the LLTO film. After evaporating toluene, a hybrid LLTO/Li anode with a conformal and stable interface is formed. When applying the hybrid anodes in Li‐metal batteries, the MIEC ceramic film blocks Li‐corrosion from electrolyte and the formation of Li‐dendrites by buffering the Li‐ion concentration gradient and leveling secondary current distribution on Li‐metal surface. At the same time, the Coulombic efficiency of batteries reaches to 98%. This finding will impact the general approach for tailoring the properties of Li‐metal anodes for achieving better Li‐metal battery performance.     

MXene-Based Dendrite-Free Potassium Metal Batteries

Potassium metal batteries are considered as attractive alternatives beyond lithium-ion batteries. However, uncontrollable dendrite growth on the potassium metal anode has restrained their practical applications. A high-performance potassium anode achieved by confining potassium metal into a titanium-deficient nitrogen-containing MXene/carbon nanotube freestanding scaffold is reported. The high electronic transport and fast potassium diffusion in this scaffold enable reduced local current density and homogeneous ionic flux during plating/stripping processes. Furthermore, as verified by theoretical calculations and experimental investigations, such “potassium-philic” MXene sheets can induce the nucleation of potassium, and guide potassium to uniformly distribute in the scaffold upon cycling. Consequently, the as-developed potassium metal anodes exhibit a dendrite-free morphology with high Coulombic efficiency and long cycle life during plating/stripping processes. Such anodes also deliver significantly improved electrochemical performances in potassium–sulfur batteries compared with bare potassium metal anodes. This work can provide a new avenue for developing potassium metal-based batteries.     

三维亲锂Cu@Sn纳米锥集流体用于无枝晶锂金属负极

锂在集流体上的不均匀沉积将导致严重的枝晶生长和体积膨胀等问题,传统的商业化泡沫铜集流体由于具有较大的体积和质量会降低电池的能量密度.本文通过简单的电沉积方法制备了体积小、重量轻,具有亲锂性的3D Cu@Sn纳米锥集流体.从成核与沉积的角度出发,纳米锥结构与亲锂的锡纳米颗粒的协同作用促进了锂的均匀沉积,可有效地抑制锂枝晶的生长.组装的半电池在1 mA cm^-2下经过100次循环后,库仑效率高达97.6%,锂对称电池在1 mA cm^-2下可以稳定循环600 h.将沉积金属锂后的Cu@Sn/Li复合负极与LiFePO₄组装的液态全电池在1 C倍率下, 550个循环之后,容量保持率为95.1%.此外, Cu@Sn纳米锥集流体在固态电池Li/Cu@Sn|PVDF–HFP–5 wt%Si O₂|LFP中也表现出优异的电化学性能,在1 C倍率下, 500个循环之后,放电容量未发生衰减.     

Controlling Nucleation in Lithium Metal Anodes

Rechargeable batteries are regarded as the most promising candidates for practical applications in portable electronic devices and electric vehicles. In recent decades, lithium metal batteries (LMBs) have been extensively studied due to their ultrahigh energy densities. However, short lifespan and poor safety caused by uncontrollable dendrite growth hinder their commercial applications. Besides, a clear understanding of Li nucleation and growth has not yet been obtained. In this Review, the failure mechanisms of Li metal anodes are ascribed to high reactivity of lithium, virtually infinite volume changes, and notorious dendrite growth. The principles of Li deposition nucleation and early dendrite growth are discussed and summarized. Correspondingly, four rational strategies of controlling nucleation are proposed to guide Li nucleation and growth. Finally, perspectives for understanding the Li metal deposition process and realizing safe and high‐energy rechargeable LMBs are given.     

Nanoarray Architecture of Ultra-Lithiophilic Metal Nitrides for Stable Lithium Metal Anodes

Lithium metal anode (LMA) is puzzled by the serious issues corresponding to infinite volume change and notorious lithium dendrite during long-term stripping/plating process. Herein, the transition metal nitrides array with outstanding lithiophilicity, including CoN, VN, and Ni₃N, are decorated onto carbon framework as “nests” to uniform Li nucleation and guide Li metal deposition. These transition metal nitrides with excellent conductivity can guarantee the fast electron transport, therefore maintain a stable interface for Li reduction. In addition, the designed multi-dimensional structure of metal nitride array decorated carbon framework can effectively regulate the growth of Li metal during the stripping/plating process. Of note, attributing to the lattice-matching between CoN and Li metal, the composite Li/CoN@CF anode exhibits ultra-stable cycling performance in symmetrical cells (over 4000 h@1 mA cm⁻² with 1 mAh cm⁻² and 1000h@20 mA cm⁻² with 20 mAh cm⁻²). The assembled full cells based on Li/CoN@CF composite anode, LiFePO₄ or S as cathodes, deliver excellent cycling stability and rate capability. This strategy provides an effective approach to develop a stable lithium metal anode for lithium metal batteries.     

Directly Grown Vertical Graphene Carpets as Janus Separators toward Stabilized Zn Metal Anodes

Zinc metal anode has garnered a great deal of scientific and technological interest. Nevertheless, major bottlenecks restricting its large-scale utilization lie in the poor electrochemical stability and unsatisfactory cycling life. Herein, a Janus separator is developed via directly growing vertical graphene (VG) carpet on one side of commercial glass fiber separator throughout chemical vapor deposition. A simple air plasma treatment further renders the successful incorporation of oxygen and nitrogen heteroatoms on bare graphene. Thus-derived 3D VG scaffold affording large surface area and porous structure can be viewed as a continuation of planar zinc anode. In turn, the Janus separator harvests homogenous electric field distribution and lowered local current density at the interface of the anode/electrolyte, as well as harnesses favorable zincophilic feature for building-up uniform Zn ionic flux. Such a separator engineering enables an impressive rate and cycle performance (93% over 5000 cycles at 5 A g⁻¹) for Zn-ion hybrid capacitors and outstanding energy density (182 Wh kg⁻¹) for V₂O₅//Zn batteries, respectively. This strategy with large scalability and cost-effectiveness represents a universal route to protect prevailing metal anodes (Zn, Na, K) in rechargeable batteries.     

Effect of copper content on the thermal conductivity and thermal expansion of Al–Cu/diamond composites

Al–Cu matrix composites reinforced with diamond particles (Al–Cu/diamond composites) have been produced by a squeeze casting method. Cu content added to Al matrix was varied from 0 to 3.0 wt.% to detect the effect on thermal conductivity and thermal expansion behavior of the resultant Al–Cu/diamond composites. The measured thermal conductivity for the Al–Cu/diamond composites increased from 210 to 330 W/m/K with increasing Cu content from 0 to 3.0 wt.%. Accordingly, the coefficient of thermal expansion (CTE) was tailored from 13 × 10⁻⁶ to 6 × 10⁻⁶/K, which is compatible with the CTE of semiconductors in electronic packaging applications. The enhanced thermal conductivity and reduced coefficient of thermal expansion were ascribed to strong interface bonding in the Al–Cu/diamond composites. Cu addition has lowered the melting point and resulted in the formation of Al₂Cu phase in Al matrix. This is the underlying mechanism responsible for the strengthening of Al–Cu/diamond interface. The results show that Cu alloying is an effective approach to promoting interface bonding between Al and diamond.     

Cu Current Collector with Binder-Free Lithiophilic Nanowire Coating for High Energy Density Lithium Metal Batteries

Despite significant efforts to fabricate high energy density (ED) lithium (Li) metal anodes, problems such as dendrite formation and the need for excess Li (leading to low N/P ratios) have hampered Li metal battery (LMB) development. Here, the use of germanium (Ge) nanowires (NWs) directly grown on copper (Cu) substrates (Cu-Ge) to induce lithiophilicity and subsequently guide Li ions for uniform Li metal deposition/stripping during electrochemical cycling is reported. The NW morphology along with the formation of the Li₁₅Ge₄ phase promotes uniform Li-ion flux and fast charge kinetic, resulting in the Cu-Ge substrate demonstrating low nucleation overpotentials of 10 mV (four times lower than planar Cu) and high Columbic efficiency (CE) efficiency during Li plating/stripping. Within a full-cell configuration, the Cu-Ge@Li – NMC cell delivered a 63.6% weight reduction at the anode level compared to a standard graphite-based anode, with impressive capacity retention and average CE of over 86.5% and 99.2% respectively. The Cu-Ge anodes are also paired with high specific capacity sulfur (S) cathodes, further demonstrating the benefits of developing surface-modified lithiophilic Cu current collectors, which can easily be integrated at the industrial scale.     

Design Strategies to Enable the Efficient Use of Sodium Metal Anodes in High-Energy Batteries

Sodium-based batteries have attracted considerable attention and are recognized as ideal candidates for large-scale and low-cost energy storage. Sodium (Na) metal anodes are considered as one of the most promising anodes for next-generation, high-energy, Na-based batteries owing to their high theoretical specific capacity (1166 mA h g⁻¹) and low standard electrode potential. Herein, an overview of the recent developments in Na metal anodes for high-energy batteries is provided. The high reactivity and large volume expansion of Na metal anodes during charge and discharge make the electrode/electrolyte interphase unstable, leading to the formation of Na dendrites, short cycle life, and safety issues. Design strategies to enable the efficient use of Na metal anodes are elucidated, including liquid electrolyte engineering, electrode/electrolyte interface optimization, sophisticated electrode construction, and solid electrolyte engineering. Finally, the remaining challenges and future research directions are identified. It is hoped that this progress report will shape a consistent view of this field and provide inspiration for future research to improve Na metal anodes and enable the development of high-energy sodium batteries.     

The Interaction in Electrolyte Additives Accelerates Ion Transport to Achieve High-Energy Non-Aqueous Lithium Metal Batteries

Electrolyte engineering is a feasible strategy to realize high energy density lithium metal batteries. However, stabilizing both lithium metal anodes and nickel-rich layered cathodes is extremely challenging. To break through this bottleneck, a dual-additives electrolyte containing fluoroethylene carbonate (10 vol.%) and 1-methoxy-2-propylamine (1 vol.%) in conventional LiPF₆-containing carbonate-based electrolyte is reported. The two additives can polymerize and thus generate dense and uniform LiF and Li₃N-containing interphases on both electrodes’ surfaces. Such robust ionic conductive interphases not only prevent lithium dendrite formation in lithium metal anode but also suppress stress-corrosion cracking and phase transformation in nickel-rich layered cathode. The advanced electrolyte enables Li||LiNi_0.8Co_0.1Mn_0.1O₂ stably cycle for 80 cycles at 60 mA g⁻¹ with a specific discharge capacity retention of 91.2% under harsh conditions.     

Uniform Distribution of Alloying/Dealloying Stress for High Structural Stability of an Al Anode in High‐Areal‐Density Lithium‐Ion Batteries

Aluminum (Al) is one of the most attractive anode materials for lithium‐ion batteries (LIBs) due to its high theoretical specific capacity, excellent conductivity, abundance, and especially low cost. However, the large volume expansion, originating from the uneven alloying/dealloying reactions in the charge/discharge process, causes structural stress and electrode pulverization, which has long hindered its practical application, especially when assembled with a high‐areal‐density cathode. Here, an inactive (Cu) and active (Al) co‐deposition strategy is reported to homogeneously distribute the alloying sites and disperse the stress of volume expansion, which is beneficial to obtain the structural stability of the Al anode. Owing to the homogeneous reaction and uniform distribution of stress during the charge/discharge process, the assembled full battery (LiFePO₄ cathode with a high areal density of ≈7.4 mg cm^?2) with the Cu–Al@Al anode, achieves a high capacity retention of ≈88% over 200 cycles, suggesting the feasibility of the interfacial design to optimize the structural stability of alloying metal anodes for high‐performance LIBs.     

Multicomponent Hybridization Transition Metal Oxide Electrode Enriched with Oxygen Vacancy for Ultralong-Life Supercapacitor

Transition metal oxide electrode materials for supercapacitors suffer from poor electrical conductivity and stability, which are the research focus of the energy storage field. Herein, multicomponent hybridization Ni-Cu oxide (NCO-Ar/H₂-10) electrode enriched with oxygen vacancy and high electrical conductivity including the Cu_0.2Ni_0.8O, Cu₂O and CuO is prepared by introducing Cu element into Ni metal oxide with hydrothermal, annealing, and plasma treatment. The NCO-Ar/H₂-10 electrode exhibits high specific capacity (1524 F g⁻¹ at 3 A g⁻¹), good rate performance (72%) and outstanding cyclic stability (109% after 40,000 cycles). The NCO-Ar/H₂-10//AC asymmetric supercapacitor (ASC) achieves high energy density of 48.6 Wh kg⁻¹ at 799.6 W kg⁻¹ while exhibiting good cycle life (117.5% after 10,000 cycles). The excellent electrochemical performance mainly comes from the round-trip valence change of Cu⁺/Cu²⁺ in the multicomponent hybridization enhance the surface capacitance during the redox process, and the change of electronic microstructure triggered by a large number of oxygen vacancies reduce the adsorption energy of OH⁻ ions of thin nanosheet with crack of surface edge, ensuring electron and ion-transport processes and remitting the structural collapse of material. This work provides a new strategy for improving the cycling stability of transition metal oxide electrode materials.     

Bioderived Ionic Liquids with Alkaline Metal Ions for Transient Ionics

Choline lactate, an ionic liquid composed of bioderived materials, offers an opportunity to develop biodegradable electrochemical devices. Although ionic liquids possess large potential windows, high conductivity, and are nonvolatile, they do not exhibit electrochemical characteristics such as intercalation pseudocapacitance, redox pseudocapacitance, and electrochromism. Herein, bioderived ionic liquids are developed, including metal ions, Li, Na, and Ca, to yield ionic liquid with electrochemical behavior. Differential scanning calorimetry results reveal that the ionic liquids remained in liquid state from 230.42 to 373.15 K. The conductivities of the ionic liquids with metal are lower than those of the pristine ionic liquid, whereas the capacitance change negligibly. A protocol of the Organization for Economic Co-operation and Development 301C modified MITI test (I) confirms that the pristine ionic liquid and ionic liquids with metal are readily biodegradable. Additionally, an ionic gel comprising the ionic liquid and poly(vinyl alcohol) is biodegradable. An electrochromic device is developed using an ionic liquid containing Li ions. The device successfully changes color at −2.5 V, demonstrating the intercalation of Li ions into the WO₃ crystal. The results suggest that the electrochemically active ionic liquids have potential for the development of environmentally benign devices, sustainable electronics, and bioresorbable/implantable devices.     

Achieving Ultra-Stable All-Solid-State Sodium Metal Batteries with Anion-Trapping 3D Fiber Network Enhanced Polymer Electrolyte

All-solid-state sodium metal batteries paired with solid polymer electrolytes (SPEs) are considered a promising candidate for high energy-density, low-cost, and high-safety energy storage systems. However, the low ionic conductivity and inferior interfacial stability with Na metal anode of SPEs severely hinder their practical applications. Herein, an anion-trapping 3D fiber network enhanced polymer electrolyte (ATFPE) is developed by infusing poly(ethylene oxide) matrix into an electrostatic spun fiber framework loading with an orderly arranged metal-organic framework (MOF). The 3D continuous channel provides a fast Na⁺ transport path leading to high ionic conductivity, and simultaneously the rich coordinated unsaturated cation sites exposed on MOF can effectively trap anions, thus regulating Na⁺ concentration distribution for constructing stable electrolyte/Na anode interface. Based on such advantages, the ATFPE exhibits high ionic conductivity and considerable Na⁺ transference number, as well as enhanced interfacial stability. Consequently, Na/Na symmetric cells using this ATFPE possess cyclability over 600 h at 0.1 mA cm⁻² without discernable Na dendrites. Cooperated with Na₃V₂(PO₄)₃ cathode, the all-solid-state sodium metal batteries (ASSMBs) demonstrate significantly improved rate and cycle performances, delivering a high discharge capacity of 117.5 mAh g⁻¹ under 0.1 C and rendering high capacity retention of 78.2% after 1000 cycles even at 1 C.     

Electrical properties of γ-CuCl thin films

The electrical properties of thin film CuCl, a wide band gap material with potential applications in the optoelectronic industry, has been studied using admittance spectroscopy in the frequency range 10 mHz–1 MHz and temperature range 280–400 K. The electrical conductivity of CuCl films was found to be mainly ionic and the temperature dependency follows the Arrhenius relationship. The power-law exponent of the AC dispersive regimes was found to be almost temperature independent. Further to this, DC electronic hole conductivity of the order of 2.3 × 10⁻⁷ S/cm was deduced to be in coexistence with Cu⁺ ionic conductivity using irreversible electrodes (Au), while a total conductivity of the order of 6.5 × 10⁻⁷ S/cm was obtained using reversible electrodes (Cu) at room temperature.     

Large‐Scale Modification of Commercial Copper Foil with Lithiophilic Metal Layer for Li Metal Battery

The application and development of lithium metal battery are severely restricted by the uncontrolled growth of lithium dendrite and poor cycle stability. Uniform lithium deposition is the core to solve these problems, but it is difficult to be achieved on commercial Cu collectors. In this work, a simple and commercially viable strategy is utilized for large‐scale preparation of a modified planar Cu collector with lithiophilic Ag nanoparticles by a simple substitution reaction. As a result, the Li metal shows a cobblestone‐like morphology with similar size and uniform distribution rather than Li dendrites. Interestingly, a high‐quality solid electrolyte interphase layer in egg shell‐like morphology with fast ion diffusion channels is formed on the interface of the collector, exhibiting good stability with long‐term cycles. Moreover, at the current density of 1 mA cm^?2 for 1 mAh cm^?2, the Ag modified planar Cu collector shows an ultralow nucleation overpotential (close to 0 mV) and a stable coulombic efficiency of 98.54% for more than 600 cycles as well as long lifespan beyond 900 h in a Li|Cu‐Ag@Li cell, indicating the ability of this method to realize stable Li metal batteries. Finally, full cells paired with LiNi_0.8Co_0.1Mn_0.1O₂ show superior rate performance and stability compared with those paired with Li foil.