Super-Assembled Hierarchical CoO Nanosheets-Cu Foam Composites as Multi-Level Hosts for High-Performance Lithium Metal Anodes

Revisiting porous foam Cu host based Li metal anode: The roles of lithiophilicity and hierarchical structure of three-dimensional framework

Lithium (Li) metal anode (LMA) is one of the most promising anodes for high energy density batteries. However, its practical application is impeded by notorious dendrite growth and huge volume expansion. Although the three-dimensional (3D) host can enhance the cycling stability of LMA, further improvements are still necessary to address the key factors limiting Li plating/stripping behavior. Herein, porous copper (Cu) foam (CF) is thermally infiltrated with molten Li-rich Li-zinc (Li-Zn) binary alloy (CFLZ) with variable Li/Zn atomic ratio. In this process, the LiZn intermetallic compound phase self-assembles into a network of mixed electron/ion conductors that are distributed within the metallic Li phase matrix and this network acts as a sublevel skeleton architecture in the pores of CF, providing a more efficient and structured framework for the material. The as-prepared CFLZ composite anodes are systematically investigated to emphasize the roles of the tunable lithiophilicity and hierarchical structure of the frameworks. Meanwhile, a thin layer of Cu-Zn alloy with strong lithiophilicity covers the CF scaffold itself. The CFLZ with high Zn content facilitates uniform Li nucleation and deposition, thereby effectively suppressing Li dendrite growth and volume fluctuation. Consequently, the hierarchical and lithiophilic framework shows low Li nucleation overpotential and highly stable Coulombic efficiency (CE) for 200 cycles in conventional carbonate based electrolyte. The full cell coupled with LiFePO4 (LFP) cathode demonstrates high cycle stability and rate performance. This work provides valuable insights into the design of advanced dendrite-free 3D LMA toward practical application.

Constructing Sn-Cu2O Lithiophilicity Nanowires as Stable and High-Performance Lithium Metal Anodes

Lithium (Li) metal batteries (LMBs) have garnered significant research attention due to their high energy density. However, uncontrolled Li dendrite growth and the continuous accumulation of "dead Li" directly lead to poor electrochemical performance in LMBs, along with serious safety hazards. These issues have severely hindered their commercialization. In this study, a lithiophilic layer of Sn-Cu2O is constructed on the surface of copper foam (CF) grown with Cu nanowire arrays (SCCF) through a combination of electrodeposition and plasma reduction. Sn-Cu2O, with excellent lithiophilicity, reduces the Li nucleation barrier and promotes uniform Li deposition. Simultaneously, the high surface area of the nanowires reduces the local current density, further suppressing the Li dendrite growth. Therefore, at 1 mA cm-2, the half cells and symmetric cells achieve high Coulombic efficiency (CE) and stable operation for over 410 cycles and run smoothly for more than 1350 h. The full cells using an LFP cathode demonstrate a capacity retention rate of 90.6% after 1000 cycles at 5 C, with a CE as high as 99.79%, suggesting excellent prospects for rapid charging and discharging and long-term cyclability. This study provides a strategy for modifying three-dimensional current collectors for Li metal anodes, offering insights into the construction of stable, safe, and fast-charging LMBs.

Metal-Organic Framework-Derived Co9S8 Nanowall Array Embellished Polypropylene Separator for Dendrite-Free Lithium Metal Anodes

Developing a reasonable design of a lithiophilic artificial solid electrolyte interphase (SEI) to induce the uniform deposition of Li+ ions and improve the Coulombic efficiency and energy density of batteries is a key task for the development of high-performance lithium metal anodes. Herein, a high-performance separator for lithium metal anodes was designed by the in situ growth of a metal-organic framework (MOF)-derived transition metal sulfide array as an artificial SEI on polypropylene separators (denoted as Co9S8-PP). The high ionic conductivity and excellent morphology provided a convenient transport path and fast charge transfer kinetics for lithium ions. The experimental data illustrate that, compared with commercial polypropylene separators, the Li//Cu half-cell with a Co9S8-PP separator can be cycled stably for 2000 h at 1 mA cm-2 and 1 mAh cm-2. Meanwhile, a Li//LiFePO4 full cell with a Co9S8-PP separator exhibits ultra-long cycle stability at 0.2 C with an initial capacity of 148 mAh g-1 and maintains 74% capacity after 1000 cycles. This work provides some new strategies for using transition metal sulfides to induce the uniform deposition of lithium ions to create high-performance lithium metal batteries.

Enhancing Lithium-Ion Diffusion Kinetics in a 3D Lithium Metal Host through Surface Modification with Hierarchical Multimetal Oxides

Lithium metal is a promising anode candidate to achieve high-energy-density lithium metal batteries (LMBs) due to its ultrahigh theoretical capacity (3860 mA h g-1) and low electrochemical potential (-3.04 V vs S.H.E). Unfortunately, the commercialization of lithium metal anodes is hindered by the growth of Li dendrites and the infinite Li volume changes during the cycling process. Herein, we introduce a 3D hierarchical multimetal oxide nanowire framework as a current collector for Li metal anodes. The hierarchical metal oxide layers of CoO and CuxO provide abundant Li nucleation sites and thus offer uniform Li plating and regulate Li nucleation during the charge/discharge process. As a result, half cells present a prolonging Coulombic efficiency of 97% at 1 mA cm-2 with a capacity of 1 mA h cm-2 for over 300 cycles. A stable cyclability of symmetric cells is demonstrated under 1 mA cm-2 with a capacity of 1 mA h cm-2 for 1500 h. Full cells paired with an LFP cathode show a stable capacity of 131.5 mA h g-1 with a capacity retention of 92% for 200 cycles. These results will shed insights into the design of 3D Cu current collectors for high-performance composite Li metal anodes.

Engineering High-Performance Li Metal Batteries through Dual-Gradient Porous Cu-CuZn Host

Porous copper (Cu) current collectors show promise in stabilizing Li metal anodes (LMAs). However, insufficient lithiophilicity of pure Cu and limited porosity in three-dimensional (3D) porous Cu structures led to an inefficient Li-Cu composite preparation and poor electrochemical performance of Li-Cu composite anodes. Herein, we propose a porous Cu-CuZn (DG-CCZ) host for Li composite anodes to tackle these issues. This architecture features a pore size distribution and lithiophilic-lithiophobic characteristics designed in a gradient distribution from the inside to the outside of the anode structure. This dual-gradient porous Cu-CuZn exhibits exceptional capillary wettability to molten Li and provides a high porosity of up to 66.05%. This design promotes preferential Li deposition in the interior of the porous structure during battery operation, effectively inhibiting Li dendrite formation. Consequently, all cell systems achieve significantly improved cycling stability, including Li half-cells, Li-Li symmetric cells, and Li-LFP full cells. When paired synergistically with the double-coated LiFePO4 cathode, the pouch cell configured with multiple electrodes demonstrates an impressive discharge capacity of 159.3 mAh g-1 at 1C. We believe this study can inspire the design of future 3D Li anodes with enhanced Li utilization efficiency and facilitate the development of future high-energy Li metal batteries.

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.

Highly lithiophilic and structurally stable Cu-Zn alloy skeleton for high-performance Li-rich ternary anodes

Lithium (Li)-rich ternary alloy, comprising a multi-alloy phase as the built-in three-dimensional (3D) framework and a Li metal phase as a reversible Li reservoir, is a promising high-energy-density anode for rechargeable Li metal batteries. The introduction of metal/metalloid components to the alloy can effectively regulate Li deposition and maintain the dimensional integrity of the Li anode. Herein, the lithium-copper-zinc (Li-Cu-Zn) ternary alloy, as a new type of alloy anode, is synthesized via a facile thermal melting method. The fully delithiated 3D scaffold comprised two Cu-Zn alloy phases named CuZn and CuZn5. These alloy phases exhibit higher lithiophilicity and structural stability than Li-Zn and Li-Cu alloys. Moreover, the CuZn phase is electrochemically inert, ensuring the geometric stability of the anode, while the CuZn5 phase can readily undergo alloying reaction with Li to form the LiZn phase, thereby facilitating uniform Li nucleation and deposition. The hybridized multiphase alloy structure and specific energy storage mechanism of the Cu-Zn based alloy scaffold in the ternary alloy anode facilitate dendrite-free Li deposition and prolonged cycle lifetime. The Li metal full battery based on lithium iron phosphate (LiFePO4) cathode exhibits high cycling stability with high-capacity retention of 95.4% after 1000 cycles at 1C.

A Gradient Lithiophilic Structure for Stable Lithium Metal Anodes with Ultrahigh Rate and Ultradeep Capacity

Using three-dimensional current collectors (3DCC) as frameworks for lithium metal anodes (LMAs) is a promising approach to inhibit dendrite growth. However, the intrinsically accumulated current density on the top surface and limited Li-ion transfer in the interior of 3DCC still lead to the formation of lithium dendrites, which can pose safety risks. In this study, it reports that gradient lithiophilic structures can induce uniform lithium deposition within the interior of the 3DCC, greatly suppressing dendrite formation, as confirmed by COMSOL simulations and experimental results. With this concept, a gradient-structured zinc oxide-loaded copper foam (GSZO-CF) is synthesized via an easy solution-combustion method at low cost. The resulting Li@GSZO-CF symmetric cells demonstrate stable cycling performance for over 800 cycles, with an ultra-deep capacity of 10 mAh cm-2 even under an ultra-high current density of 50 mA cm-2 , the top results reported in the literature. Moreover, when combined with a LiFePO4 (LFP) cathode under a low negative/positive (N/P) capacity ratio of 2.9, the Li@GSZO-CF||LFP full cells exhibit stable performance for 200 cycles, with a discharge capacity of 130 mAh g-1 and retention of 85.5% at a charging/discharging rate of 1C. These findings suggest a promising strategy for the development of new-generation LMAs.

High Rate and Low-Temperature Stable Lithium Metal Batteries Enabled by Lithiophilic 3D Cu-CuSn Porous Framework

Lithium (Li) metal is regarded as the "Holy Grail" of anodes for high-energy rechargeable lithium batteries by virtue of its ultrahigh theoretical specific capacity and the lowest redox potential. However, the Li dendrite impedes the practical application of Li metal anodes. Herein, lithiophilic three-dimensional Cu-CuSn porous framework (3D Cu-CuSn) was fabricated by a vapor phase dealloying strategy via the difference in saturated vapor pressure between different metals and the Kirkendall effect. CuSn alloy sites were converted into LiSn alloy sites through the molten Li infusion method, and composite Li metal anodes (3D Cu-LiSn-Li) are achieved. Alloyed tin, as the bridge between the porous copper substrate and metallic Li, plays a critical role in optimizing Li nucleation and enhancing the fast lithium migration kinetics. This work demonstrates that lithiophilic binary copper alloys are an effective way to achieve room-temperature high rate performance and satisfied low-temperature cycling stability for Li metal batteries.

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 Ni₃ N, 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.

Advanced Composite Lithium Metal Anodes with 3D Frameworks: Preloading Strategies, Interfacial Optimization, and Perspectives

Lithium (Li) metal is regarded as the most promising anode candidate for next-generation rechargeable storage systems due to its impeccable capacity and the lowest electrochemical potential. Nevertheless, the irregular dendritic Li, unstable interface, and infinite volume change, which are the intrinsic drawbacks rooted in Li metal, give a seriously negative effect on the practical commercialization for Li metal batteries. Among the numerous optimization strategies, designing a 3D framework with high specific surface area and sufficient space is a convincing way out to ameliorate the above issues. Due to the Li-free property of the 3D framework, a Li preloading process is necessary before the 3D framework that matches with the electrolyte and cathode. How to achieve homogeneous integration with Li and 3D framework is essential to determine the electrochemical performance of Li metal anode. Herein, this review overviews the recent general fabrication methods of 3D framework-based composite Li metal anode, including electrodeposition, molten Li infusion, and pressure-derived fabrication, with the focus on the underlying mechanism, design criteria, and interfacial optimization. These results can give specific perspectives for future Li metal batteries with thin thickness, low N/P ratio, lean electrolyte, and high energy density (>350 Wh Kg^-1 ).

Electrochemistry of P-C Bonds in Phosphorus-Carbon Based Anode Materials

Phosphorus-carbon anode materials for alkali-metal ion storage in rechargeable batteries can simultaneously achieve high-energy density and fast charging. The P-C-bonded structure in the phosphorus-carbon materials has been observed and acknowledged to be a critical structural feature that renders improved cycling stability and rate performance. However, the underlying mechanisms, especially the role played by P-C bonds, remain elusive. By combining computational simulations and spectroscopic characterizations, we reveal that the stability of P-C bonds is critical to the electrochemical performance. In the discharge process, P-P bonds are fragile, while the bonding state of the P-C bonds is almost unchanged since electrons were mainly received by the P atoms to form lone pairs. The preserved P-C clusters can effectively serve as a reunion center for the recovery of P-P bonds in the recharging process, leading to a moderate energy change and improved cycling reversibility and structural stability of the phosphorous for electrochemical energy storage.

Environment-friendly degradable zinc-ion battery based on guar gum-cellulose aerogel electrolyte

With the vigorous development of electronics and the increasingly prominent problem of environmental pollution, it is particularly important to exploit environmentally friendly electronic devices. Transient electronics represent a kind of device that once the specified functions have completed can completely or partially disappear through physical or chemical actions. In this work, we introduce a novel guar gum-cellulose aerogel (GCA) membrane based on natural biomaterials and successfully use it as an electrolyte film to fabricate a degradable zinc-ion battery (DZIB). All components of the prepared DZIBs can be successfully degraded or disintegrate in phosphate-buffered saline (PBS) containing a solution of proteinase K after approximately 40 days. This electrolyte film has a high ionic conductivity of approximately 4.73 × 10^-2 S cm^-1 and a good mechanical stress property. When applied to DZIB, the production of zinc dendrites can be restrained, leading to the battery showing excellent electrochemical performance. The battery exhibits a specific capacity of 309.1 mA h g^-1 at a current density of 308 mA g^-1 after 100 cycles and a steady cycling ability (100% capacity retention after 200 cycles). More importantly, the electrochemical performance of DZIB is better than that of transient batteries reported in the past, taking a solid step in the field of transient electronics in the initial stage.

Uniform Deposition of Li-Metal Anodes Guided by 3D Current Collectors with In Situ Modification of the Lithiophilic Matrix

The lithium (Li)-metal anode is deemed as the "holy gray" of the next-generation Li-metal system because of its high theoretical specific capacity, minimal energy density, and lowest standard electrode potential. Nevertheless, its commercial application has been limited by the large volume variation during charge and discharge, the unstable interface between the Li metal and electrolyte, and uneven deposition of Li. Herein, we present a 3D host (Cu) with lithiophilic matrix (CuO and SnO₂) in situ modification via a facile ammonia oxidation method to serve as a current collector for the Li-metal anode. The 3D Cu host embellished by CuO and SnO₂ is abbreviated as 3D CSCC. By increasing interfacial activity, lowering the nucleation barrier, and accommodating changes in volume of the Li metal, the 3D CSCC electrode effectively demonstrates a homogeneous and dendrite-free deposition morphology with an excellent cycling performance up to 3000 h at a 1.0 mA cm^-2 current density. Additionally, the full cells paired with Li@3D CSCC anodes and LiCoO₂ cathodes show good capacity retention performance at 0.2 C.

Wood-Derived Bimetallic and Heteroatomic Hierarchically Porous Carbon Aerogel for Rechargeable Flow Zn-Air Batteries

It is necessary to correctly research and synthesize efficient and inexpensive catalysts to achieve reversible oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which is also a prerequisite for zinc-air batteries (ZABs). However, it is still a huge challenge to manufacture electrocatalysts with durable and high electrocatalytic performance from biomass. Here, a convenient method of delignification was used to transform natural balsa wood into a layered porous carbon material, FeCo alloy supported on a N, S-doped wood-based carbon aerogel (FeCo@NS-CA) as the cathode in rechargeable flow ZAB. The obtained FeCo@NS-CA with the porous lamellar architecture exhibits superior bifunctional electrocatalysis, including excellent electrochemical activities and superior stabilities. For ORR, relative to the reversible hydrogen electrode, the onset potential of FeCo@NS-CA is 0.97 V, and the half-wave potential is 0.85 V, which is consistent with the potential of commercial Pt/C. For OER, FeCo@NS-CA obtained an overpotential of 450 mV, which is very similar to the overpotential of the benchmark RuO₂. The superior performance could be owing to the alloy carrier interaction between the FeCo alloy and the wood-based carbon aerogel co-doped with N and S. Moreover, the bifunctional air cathode in a flow ZAB assembled with the FeCo@NS-CA catalyst at a current density of 10 mA cm^-2; the power density is 140 mW cm^-2, and the specific capacitance is 760 mA h g_Zn^-1, with a remarkable long-term stability of 400 h better than ZAB of benchmark Pt/C + RuO₂. This research lays the foundation for transforming abundant biomass resources into high environmental protection materials for energy-related applications.