Rechargeable Metal Research Articles

High-performance rechargeable metal–air batteries enabled by efficient charge transport in multielement random alloy electrocatalyst

The integration of bifunctionally active sites of multielement random alloy catalysts with other metal oxide electrocatalysts is a promising strategy for efficient electrochemical reactions. In this study, a novel combination of virtual crystal approximation and hydrothermal synthesis was used to investigate the composition-dependent structure and electrical property in a Ag1−xNix catalyst. The combination showed that a hexagonal closed-packed structure of Ag1−xNix with a compositional ratio of 6:4 (Ag:Ni) had electrical conductivity of ∼2 × 107 S∙cm−1 and an ionization potential of − 5.4 eV. Furthermore, the bifunctional oxygen electrocatalytic efficiencies of Ag0.6Ni0.4 were improved by forming a heterointerface with the CoNb2O6 electrocatalyst, resulting in a discharge-charge voltage gap of 0.81 V over 587 h, peak power density of 178.9 mW∙cm−2, and specific capacity of 806.8 mA∙h∙g−1 in a zinc–air battery. This approach was applied to pouch-type zinc–air batteries, resulting in long-term stability of over 158.6 h at 10 mA∙cm−2.

Ultra-long-life and ultrathin quasi-solid electrolytes fabricated by solvent-free technology for safe lithium metal batteries

The excessive consumption of organic solvent and enhancement of environmental protection protocols necessitate the exploitation of desirable approach to handle our solid-state electrolytes. Herein, we report an all solvent-free method for the preparation of low-cost, recyclability, flexible, ultrathin, and high ionic conductivity quasi-solid polymer electrolytes (QPE) membrane, which is an 5 μm-thick PE separators filled with polyether-block-polyamide (PEO-b-PA6)/LiTFSI/tetraethylene glycol dimethyl ether (TEGDME) (PPLT) that can be used as a safe lithium metal batteries. The self-fusion characteristics of the PEO-b-PA6 with supramolecular hydrogen bonds guarantees the intimate and perfect interfaces even during extreme deformations and crack of the solvent-free machining process. The ultrathin PE separators is mechanically strong, preventing batteries from short-circuiting even after more than 1200 h of cycling, and the ionic conductivity of PPLT reaches up to 1.02 × 10−4 S cm−1 at 30 ℃ by adding only 25 wt% of TEGDME as plasticizer. The LFP//Li cells using PPLT as electrolyte exhibits excellent reversible capacity of 116 mAh g−1 at 1 C after 700 cycles at 28 °C. In addition, the polymer soft-pack batteries using PPLT achieve highly reversible capacity of 124.9 mAh g−1 after 200 cycles at 0.2 C. It is noted that this solvent-free film-making process and outstanding electrochemical performance of this QPE could be further delivered to other room temperature rechargeable solid-state lithium metal batteries and enlighten safe, low-carbon green and high-energy solid-state batteries.

Understanding the solvation structures of glyme-based electrolytes by machine learning molecular dynamics

Glyme-based electrolytes are of great interest for rechargeable lithium metal batteries due to their high stability, low vapor pressure, and non-flammability. Understanding the solvation structures of these electrolytes at the atomic level will facilitate the design of new electrolytes with novel properties. Recently, classical molecular dynamics (CMD) and ab initio molecular dynamics (AIMD) have been applied to investigate electrolytes with complex solvation structures. On one hand, CMD may not provide reliable results as it requires complex parameterization to ensure the accuracy of the classical force field. On the other hand, the time scale of AIMD is limited by the high cost of ab initio calculations, which causes that solvation structures from AIMD simulations depend on the initial configurations. In order to solve the dilemma, machine learning method is applied to accelerate AIMD, and its time scale can be extended dramatically. In this work, we present a computational study on the solvation structures of triglyme (G3) based electrolytes by using machine learning molecular dynamics (MLMD). Firstly, we investigate the effects of density functionals on the accuracy of machine learning potential (MLP), and find that PBE-D3 shows better accuracy compared to BLYP-D3. Then, the densities of electrolytes with different concentration of LiTFSI are computed with MLMD, which shows good agreement with experiments. By analyzing the solvation structures of 1 ns MLMD trajectories, we found that Li+ prefers to coordinate with a G3 and a TFSI− in equimolar electrolytes. Our work demonstrates the significance of long-time scale MLMD simulations for clarifying the chemistry of non-ideal electrolytes.

Complementary combination of lithium protection strategies for robust and longevous lithium metal batteries

A ten-fold higher specific capacity than commercial graphite anodes makes lithium metal anodes extremely attractive for rechargeable battery applications. However, the safety concerns associated with lithium dendrites represent a major barrier to the practical application of lithium metal batteries. Over the past decades, several mechanisms for the growth of lithium dendrites have been proposed from different perspectives. This has led to a variety of strategies to protect the lithium metal anode, such as preparation of artificial solid electrolyte interphase (SEI) and pseudo-liquid anodes. In this review, we present an overview of protection strategies for lithium metal anodes in terms of preventing lithium dendrite growth and regulating lithium deposition behaviours or healing the existing lithium dendrites. Firstly, the mechanisms of dendrite growth and anode corrosion are summarized and compared to better understand the lithium-ion deposition behaviours, which is critical for theoretically guiding the exploration of highly stable lithium anodes. Subsequently, the potential for integrating different strategies is discussed to combine and make full use of the advantages of each strategy, which can facilitate the development of emerging strategies and the improvement of established ones. The availability of the proposed strategies will further narrow the gap between experimental research and the commercial application of rechargeable lithium metal batteries.

Boosting the Bifunctional Oxygen Electrode Activity of Nitrogen-decorated Carbon Networks via Ni/NiO Addition for Li-Air and Zn-Air Batteries

Designing efficient and cost-effective oxygen electrode catalysts for metal-air batteries is the most intrinsic requisite for next-generation energy storage devices. In this work, bifunctional air-breathing electrode catalysts made of nitrogen-doped carbon (NC) and nickel/nickel oxide/nitrogen-doped carbon (NNONC) nanocomposites are explored for rechargeable Li-Air and Zn-Air batteries. The integration of Ni/NiO nanoparticles on the NC enhances the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities of the NC. Ni, nickel oxide, and NC acted synergistically to create additional reaction sites, high conductivity, and rapid diffusion pathways, resulting in increased catalytic activity. The CR-2032 coin-type and split cell Li-Air batteries were made with NNONC composite as cathode and Lithium metal as anode. The split cell had a high discharge capacity of 3330 mA h g−1 at a current density of 100 mA g−1. Moreover, the NNONC used as bifunctional cathode catalyst in the rechargeable Zn-Air battery. Where Anode is made of zinc-can from a used zinc carbon battery. The Zn-Air battery has good electrochemical activity, such as good cycle life and low overpotentials of 0.31 and 0.19 V for charging and discharging, respectively. Thus, NNONC can be a promising bifunctional catalyst for both the non–aqueous and aqueous rechargeable metal–air batteries.

3D Free‐Standing Carbon Nanofibers Modified by Lithiophilic Metals Enabling Dendrite‐Free Anodes for Li Metal Batteries

Li metal with high‐energy density is considered as the most promising anode for the next‐generation rechargeable Li metal batteries; however, the growth of Li dendrites seriously hinders its practical application. Herein, 3D free‐standing carbon nanofibers modified by lithiophilic metal particles (CNF/Me, Me=Sn, Fe, Co) are obtained in situ by the electrospinning method. Benefiting from the lithophilicity, the CNF/Me composite may effectively prevent the formation of Li dendrites in the Li metal batteries. The optimized CNF/Sn–Li composite electrode exhibits a stable cycle life of over 2350 h during Li plating/stripping. When matched with typical commercial LiFePO4 (LFP) cathode, the LFP//CNF/Sn–Li full cell presents a high initial discharge specific capacity of 139 mAh g−1 at 1 C, which remains at 146 mAh g−1 after 400 cycles. When another state‐of‐the‐art commercial LiNi0.8Co0.1Mn0.1O2 (NCM(811)) cathode is used, the assembled NCM//CNF/Sn–Li full cell shows a large initial specific discharge capacity of 206 mAh g−1 at substantially enhanced 10 C, which keeps at the good capacity of 99 mAh g−1 after 300 cycles. These results are greatly superior to the counterparts with Li as the anodes, indicating the great potential for practical utilization of the advanced CNF/Sn–Li electrode.

Metal–Organic Framework-Derived Mn/Ni Dual-Metal Single-Atom Catalyst for Efficient Oxygen Reduction Reaction

Non-precious-metal-based oxygen reduction reaction (ORR) catalysts hold great prospects for rechargeable metal–air batteries and reversible electrolyzer/fuel cell systems. Among the various earth-abundant and noble-metal-free catalysts, Mn- and Ni-based single-atom catalysts (SACs) are attracting attention for ORRs. Herein, we designed a facile and efficient strategy to obtain Mn/Ni dual-metal single-atom catalysts, in which atomic Mn and Ni sites were dispersed on nitrogen-doped porous carbon. The optimized Mn/Ni catalysts showed excellent ORR electrocatalytic performance with a half-wave potential of 0.803 V, comparable to that of commercial Pt/C catalysts. Meanwhile, the electron transfer number was determined to be 3.9, indicating a good four-electron reaction process. The excellent electrocatalytic performance was attributed to the N-doped porous carbon structure with a large specific surface area, which afforded abundant active sites to anchor the single Mn and Ni atoms.

Double-Transition-Metal MXene Films Promoting Deeply Rechargeable Magnesium Metal Batteries.

Magnesium metal batteries are promising candidates for next-generation high-energy-density and low-cost energy storage systems. Their application, however, is precluded by infinite relative volume changes and inevitable side reactions of Mg metal anodes. These issues become more pronounced at large areal capacities that are required for practical batteries. Herein, for the first time, double-transition-metal MXene films are developed to promote deeply rechargeable magnesium metal batteries using Mo2 Ti2 C3 as a representative example. The freestanding Mo2 Ti2 C3 films, which are prepared using a simple vacuum filtration method, possess good electronic conductivity, unique surface chemistry, and high mechanical modulus. These superior electro-chemo-mechanical merits of Mo2 Ti2 C3 films help to accelerate electrons/ions transfer, suppress electrolyte decomposition and dead Mg formation, as well as maintain electrode structural integrity during long-term and large-capacity operation. As a result, the as-developed Mo2 Ti2 C3 films exhibit reversible Mg plating/stripping with high Coulombic efficiency of 99.3% at a record-high capacity of 15 mAh cm-2 . This work not only sheds innovative insights into current collector design for deeply cyclable Mg metal anodes, but also paves the way for the application of double-transition-metal MXene materials in other alkali and alkaline earth metal batteries.

3D porous and Li-rich Sn–Li alloy scaffold with mixed ionic-electronic conductivity for dendrite-free lithium metal anodes

The rechargeable lithium metal batteries (LMBs) have attracted considerable attention as the promising candidates of next-generation energy storage technologies, but they often suffer from the dendrite growth and short lifespan, especially at high current densities and low negative/positive capacity (N/P) ratios. Herein, a facile, low-cost, and scalable route was developed to prepare the 3D porous and Li-rich Sn–Li alloy scaffolds to ensure homogeneous Li plating/stripping under high current density. The Li-rich Sn–Li alloy scaffolds exhibit considerable affinity with Li, which can not only guide the uniform Li deposition without dendrites formation, but also re-store active Li to supplement the irreversible Li loss, thus contributing to the long-term cycling stability. As a result, Li||Cu cell maintains an average Coulombic efficiency of 96.5 % even at a current density of 5 mA cm−2. When coupling this anode with LFP cathode, the thus-assembled full cells achieve a superior capacity retention of 87 % over 400 cycles at 5 C. Stable cycling of LMBs with a low N/P capacity ratio of 1.5 is also demonstrated, showing the prominence of this strategy for developing high-energy-density LMBs.

Emerging Carbon Nanotube‐Based Nanomaterials for Stable and Dendrite‐Free Alkali Metal Anodes: Challenges, Strategies, and Perspectives

Alkali metals (Li, Na, and K) are promising candidates for high‐performance rechargeable alkali metal battery anodes due to their high theoretical specific capacity and low electrochemical potential. However, the actual application of alkali metal anodes is impeded by the challenges of alkali metals, including their high chemical reactivity, uncontrolled dendrite growth, unstable solid electrolyte interphase, and infinite volume expansion during cycling processes. Introducing carbon nanotube‐based nanomaterials in alkali metal anodesis an effective solution to these issues. These nanomaterials have attracted widespread attention owing to their unique properties, such as their high specific surface area, superior electronic conductivity, and excellent mechanical stability. Considering the rapidly growing research enthusiasm for this topic in the last several years, we review recent progress on the application of carbon nanotube‐based nanomaterials in stable and dendrite‐free alkali metal anodes. The merits and issues of alkali metal anodes, as well as their stabilizing strategies are summarized. Furthermore, the relationships among methods of synthesis, nano‐ or microstructures, and electrochemical properties of carbon nanotube‐based alkali metal anodes are systematically discussed. In addition, advanced characterization technologies on the reaction mechanism of carbon nanotube‐based nanomaterials in alkali metal anodes are also reviewed. Finally, the challenges and prospects for future study and applications of carbon nanotube‐based AMAs in high‐performance alkali metal batteries are discussed.

NiFe-based tungstate@layered double hydroxide heterostructure supported on graphene as efficient oxygen evolution reaction catalyst

Oxygen evolution reaction (OER) plays a key role in water splitting and rechargeable metal–air batteries, thus eagerly demanding efficient, robust, and low-cost electrocatalysts. Two-dimension layered double hydroxides (LDHs) have been widely recognized as one of the most promising OER catalysts due to the high activity and large specific surface area. However, the insufficient electrical conductivity and resistance against corrosion seriously restrict their capabilities of charge transport and long-term stability. Herein, a NiFe-based heterostructure catalyst is proposed by the coupling of NiFe-based LDH (termed NiFe-LDH) nanosheets and amorphous NiFe-tungstate (termed NiFeWO4) nanoparticles, both of which possess the same stoichiometric Ni/Fe ratio (3:1), on graphene substrate (termed NiFeWO4@NiFe-LDH/G). Attributed to the synergy of individual components, NiFeWO4@NiFe-LDH/G exhibits superb electrocatalytic activity for OER in an alkaline electrolyte, with extremely low overpotential of 222 mV at a current density of 10 mA cm-2 and Tafel slope of 32.1 mV dec-1, far surpassing the benchmark IrO2 catalyst. Furthermore, NiFeWO4@NiFe-LDH/G exhibits superior stability and durability to IrO2. Comprehensive characterizations and electrochemical measurements together with DFT calculations reveal that the hetero-assembly of NiFe-LDH and NiFeWO4 generates more efficient NiFe active sites than that of the individual components via a strong chemical binding interaction, which can modulate the electronic structures and optimize the energetics of active sites for OER intermediates. As a result, a low cell voltage of 1.48 V is achieved for the water splitting in two-electrode Pt/C‖NiFeWO4@NiFe-LDH/G electrolysis cell at 10 mA cm-2, overwhelmingly prevailing over the 1.69 V for the Pt/C‖IrO2 benchmark cell. This work provides an ingenious heterostructure design for efficient and stable OER electrocatalysts.

Improving Zn ion transport behavior and uniform deposition using artificial ZnOHF coated film for deeply rechargeable Zn metal anodes

Aqueous Zn metal batteries have attracted much attention for their environmental benignity and superb security. However, their reversibility and stability have been largely limited by uncontrollable dendrite growth and interface parasitic reactions on Zn anodes yet, which seriously restricts the commercialization process. Herein, the ZnOHF film has been in-situ grown on the surface of Zn anode to cope with these problems of aqueous Zn metal batteries. The grain-like uniform ZnOHF film can provide adsorption sites with low diffusion barrier to homogenize Zn2+ deposition, also evidently inhibit the side reaction of hydrogen evolution. As a result, the assembled ZnOHF@Zn||ZnOHF@Zn symmetrical cells exhibit a stable cycling performance (1000 and 700 h at the current density of 0.2 and 10 mA cm−2, respectively). In addition, the ZnOHF@Zn||VO2 full cell shows the coulombic efficiency (CE) close to 100% at a current density of 2 A g−1 after 500 cycles, delivering a maintained capacity of 160.2 mAh g−1.

Frontispiece: Recent Progress in Rechargeable Sodium Metal Batteries: A Review

Recent developments in the field of rechargeable sodium metal batteries are summarized in herein. In particular, three main parts of sodium metal batteries are covered: cathode materials, electrolyte systems, and anode design. For more details, see the Review by R. Cao, S. Jiao, et al. (DOI: 10.1002/chem.202202380).

Gas induced formation of inactive Li in rechargeable lithium metal batteries

The formation of inactive lithium by side reactions with liquid electrolyte contributes to cell failure of lithium metal batteries. To inhibit the formation and growth of inactive lithium, further understanding of the formation mechanisms and composition of inactive lithium are needed. Here we study the impact of gas producing reactions on the formation of inactive lithium using ethylene carbonate as a case study. Ethylene carbonate is a common electrolyte component used with graphite-based anodes but is incompatible with Li metal anodes. Using mass spectrometry titrations combined with 13C and 2H isotopic labeling, we reveal that ethylene carbonate decomposition continuously releases ethylene gas, which further reacts with lithium metal to form the electrochemically inactive species LiH and Li2C2. In addition, phase-field simulations suggest the non-ionically conducting gaseous species could result in an uneven distribution of lithium ions, detrimentally enhancing the formation of dendrites and dead Li. By optimizing the electrolyte composition, we selectively suppress the formation of ethylene gas to limit the formation of LiH and Li2C2 for both Li metal and graphite-based anodes.

Platinum nanosheets synthesized via topotactic reduction of single-layer platinum oxide nanosheets for electrocatalysis

Increasing the performance of Pt-based electrocatalysts for the oxygen reduction reaction (ORR) is essential for the widespread commercialization of polymer electrolyte fuel cells. Here we show the synthesis of double-layer Pt nanosheets with a thickness of 0.5 nm via the topotactic reduction of 0.9 nm-thick single-layer PtOx nanosheets, which are exfoliated from a layered platinic acid (HyPtOx). The ORR activity of the Pt nanosheets is two times greater than that of conventionally used state-of-the-art 3 nm-sized Pt nanoparticles, which is attributed to their large electrochemically active surface area (124 m2 g−1). These Pt nanosheets show excellent potential in reducing the amount of Pt used by enhancing its ORR activity. Our results unveil strategies for designing advanced catalysts that are considerably superior to traditional nanoparticle systems, allowing Pt catalysts to operate at their full potential in areas such as fuel cells, rechargeable metal–air batteries, and fine chemical production.

Unveiling the effect and correlative mechanism of series-dilute electrolytes on lithium metal anodes

An emerging development direction for electrolytes is the utilization of low-concentration electrolytes (LCE, generally less than 0.5 M) owing to their promising properties such as better wetting ability, reduced costs, and fast electrochemical kinetics, which have been studied in several battery scenarios. However, the direct assessment of LCEs with Li metal anodes has not yet been done, which would provide new insights to high-energy-density rechargeable lithium metal batteries (LMBs). For this purpose, apparent cycling performances of Li metal anode (LMA) in series-diluted (0.1∼1.0 M) ether-based electrolytes are reported in this study with Li||Li and Li||Cu cells, showing the enhanced performances with the concentration increasing. Moreover, the concentration effect and the underlying mechanism are revealed in detail by using coordinated post-mortem analyses and theoretical simulations, demonstrating that the preferential solvent decomposition in LCEs induces the organic-dominant interfacial layer on LMAs. Such layer demonstrates low interface stability, causing poor cycling performance among various current densities in Li half cells. However, comprehensive results also indicate that LCEs are facing a good opportunity because of the fast interfacial charge transfer kinetics originating from the weak solvation nature. This work elucidates the roles of electrolyte concentration on the LMA and uncovers their correlative mechanism of series-diluted electrolytes. It is a certain breakthrough for this timely research to provide a comprehensive perspective for designing novel low-concentration electrolytes.

Interphases in aqueous rechargeable zinc metal batteries

The review describes the progress of research on the aqueous interphases within rechargeable zinc metal batteries.

Energy-dense anode-free rechargeable lithium metal batteries based on thick cathodes and pulse charging strategies

In combination with a thick cathode and pulse charging strategies, anode-free lithium metal batteries demonstrated reduced polarization at 5 mA cm−2 and a capacity retention of 79.4% after 50 cycles.

S-functionalized 2D V2B as a promising anode material for rechargeable lithium ion batteries.

The development of novel high specific capacity anode materials is urgently needed for rechargeable metal ion batteries. Herein, S-functionalized V2B as the electrode material for Li/Na/K ion batteries are comprehensively investigated using first-principles calculations. Specifically, V2BS2 was verified with good electrical conductivity via band structure and density of states calculations. Phonon dispersion and ab initio molecular dynamic simulations were performed and confirmed the dynamic and thermal stability of V2BS2. The use of V2BS2 with a high theoretical specific capacity of 606 mA h g-1 for lithium ion batteries (LIBs) due to the bilayer adsorption of Li atoms is encouraging, which is attributed to the double empty orbitals of the S atoms and small lattice mismatch (1.5%) between the Li layers and substrate. Furthermore, dendrite formation would be well prohibited and safety issues for battery operation would be ensured for V2BS2 as electrode materials because of the low open circuit voltage with 0.37 V. The high charge/discharge rate for LIBs is also achievable owing to the high mobility of adatoms on the surface of V2BS2. Our work not only finds use as a promising material for the field of energy storage, but also provides constructive design strategies for developing high performance anode materials for rechargeable metal ion batteries.

Cu-CNTs current collector fabricated by deformation-driven metallurgy for anode-free Li metal batteries

Rechargeable anode-free Li metal batteries (AFLMBs) with improved energy density and reduced cost are beneficial for emission peak and carbon neutralization. Herein, multi-walled carbon nanotubes reinforced Cu matrix composite (Cu-CNTs) enabled by deformation-driven metallurgy (DDM) technology is proposed to retrieve the lithiophilicity of current collectors (CCs) in AFLMBs. Fine-grained Cu-CNTs with a large number of grain boundaries and homogenous distribution of broken CNTs are achieved based on the severe plastic deformation principle since the CNTs inhibit slide of dislocations and migration of grain boundaries. Grain boundaries in fine-grained Cu-CNTs with low-size distribution gradients provide desirable nucleation sites due to their higher disorder and active state. Excellent lithiophilicity of the broken CNTs is exhibited where its layered structure for Li ion insertion contributes to uniform Li deposition. Half cells assembled by Cu-CNTs CC with 2 vol% CNTs display advanced cycling stability with an average coulombic efficiency of 97.8% after 500 cycles at 1.0 mA‧cm−2. Full cells with LiFePO4 cathode possess excellent capacity retention of 69.4% after 100 cycles at 0.5 C. This work provides a novel strategy for fabricating CCs to achieve superior electrochemical performances for future applications of AFLMBs.