Rechargeable Metal Research Articles

Towards Rechargeable Aluminum Metal Batteries for Low-Temperature Space & Electromobility Applications

Rechargeable aluminum metal batteries are promising next-generation electrochemical energy storage devices due to the high energy density, inherent safety, low cost, earth abundance, and recyclability of aluminum. Aluminum batteries using graphite cathodes and chloroaluminate-containing electrolytes have recently been the focus of intense research in the energy storage and electroplating community, particularly due to their fast-charging capabilities. Engineered graphite cathodes have been shown to exhibit supercapacitor-like rate performance since chloroaluminate anions intercalate into graphite with significant pseudocapacitive characteristics1,2. Batteries with high considerable pseudocapacitive charge storage3 are especially attractive for energy storage systems that need to function at low temperatures and ideally exhibit high specific power. For example, robotic spacecraft that embark on planetary science missions often have typical mission temperature targets of -40 to -60 °C. However, state-of-the-art lithium-ion batteries with predominant faradaic diffusion-limited charge storage suffer from lithium plating, dendritic growth, and severe capacity loss at low temperatures. While organic electrolyte mixtures have been developed that enable moderate low-temperature performance, new battery concepts, including those using ionic liquid electrolytes, are needed to enable new paradigms for low-temperature space missions and electromobility.Herein we present, for the first time, results towards rechargeable aluminum-graphite batteries designed specifically for low-temperature applications that demonstrate high capacity retention and favorable electrochemical kinetics at temperatures down to -40 °C. We first disentangle quantitatively the faradaic diffusion-limited, pseudocapacitive, and capacitive contributions to the overall charge storage for different graphite materials. Moreover, we shed light on the relationships between graphite structure, ion mass transport, and the overall rates of electrochemical aluminum deposition/dissolution and chloroaluminate anion intercalation. We then develop ionic liquid electrolytes with mixed anion-cation compositions to impart disorder and disrupt crystallization at low temperatures. The resulting aluminum-graphite batteries were characterized by variable-temperature and rate cyclic voltammetry (CV), galvanostatic cycling, electrochemical impedance spectroscopy (EIS), and solid-state nuclear magnetic resonance (NMR) spectroscopy to understand their reaction mechanisms and factors limiting their rate performance. The ionic liquid electrolyte mixtures were also characterized by a combination of differential scanning calorimetry (DSC) and electrochemical methods to understand their freezing points and electrochemical stability. The results provide fundamental insights into the design of aluminum-graphite batteries for low-temperature space and electromobility applications.

(Digital Presentation) Effects of Sulfur Cathode Topography on Cycling of Practical Li–S Batteries

Lithium–sulfur (Li–S) batteries are one of the most promising next-generation energy storage technologies due to their high theoretical energy and low cost.[1-2] However, Li–S cells with practically high energy still suffer from a very limited cycle life with reasons which remain unclear.[3] Here, through cell study under practical conditions, we prove that an internal short circuit is a root cause of early cell failure and was ascribed to the crosstalk between the S cathode and Li anode. The cathode topography dictates S reactions through influencing the local resistance and electrolyte distribution, particularly under lean electrolyte conditions. The inhomogeneous reactions of S cathodes are easily mirrored by the Li anodes, resulting in exaggerated localized Li plating/stripping, Li filament formation and eventually cell internal short circuit. Manipulating cathode topography was proven effective to extend the cell cycle life under practical conditions. The findings of this work shed new light on the electrode design for extending cycle life of high-energy Li–S cells, which are also applicable for other rechargeable Li or metal batteries. Details of the progress will be discussed at the conference.

(Invited) Key Aspects in Enabling Lithium Metal Batteries

Lithium metal batteries hold the promise for next generation rechargeable batteries. The recent breakthroughs in electrolyte formation, pressure control algorithm and quantitative characterization tools have made this promise closer to reality. In this talk, I will provide an overview of those recent breakthroughs and share a few new perspectives on the surprisingly challenging issues in enabling rechargeable lithium metal batteries.

(Digital Presentation) A Polymeric/Inorganic Composite Coatings on the Separator for High-Energy Lithium Metal Battery

Lithium metal (Li) is a highly promising anode for next-generation rechargeable due to its high specific capacity (3,860 mA/g) and low negative electrochemical potential (-3.040 V vs. the standard hydrogen electrode). However, the issues such as high reactivity with electrolyte, infinite volume expansion, and uneven Li plating/stripping, cause low Coulombic efficiency, unstable growth of the solid-electrolyte interphase (SEI), and lithium dendrites. SEI plays an important role in the stabilization of lithium metal anodes in rechargeable batteries. Here we report a polymeric inorganic composite coatings (PICC) on the Celgard separator to regulate the Li-ion transport during charge/discharge of the battery. Such coatings enable uniformly deposition of Li, form a stable SEI film and in turn improve the electrochemical performance of the rechargeable batteries. Firstly, poly(vinylidene fluoride) (PVDF) and Li6.03La3Zr1.75Nb0.25Al0.24O12 (LLZO) were mixed at a mass ratio of 1:2, 1:1 and 1:2 in DMF, respectively. Afterwards the mixtures were coated onto the Celgard separator using doctor blades. In the carbonate-based electrolyte, the cycle life of Li‖Cu batteries with coating (PVDF:LLZO=1:2) increases from 30 cycles for uncoated batteries to 120 cycles of and a high Coulomb Efficiency of 96% is achieved. Moreover, when a high mass loading of 15 mg/cm2 NCM811 is chosen as cathodes, the Li‖NCM811 batteries using the PICC exhibit decent rate and cycling performance. After 100 cycles, the capacity retention at 0.2C of 94% is obtained, and the specific capacity is still 191 mAh/g. These results indicate that PICC can improve the electrochemical performance of Li anodes for high-energy rechargeable lithium metal batteries.

(Digital Presentation) In-Depth Analysis of Interfacial Processes between Lithium Metal and Polymer Electrolyte Using Electrochemical Impedance Spectroscopy and Distribution of Relaxation Times

Rechargeable solid-state lithium metal batteries are highly promising systems beyond lithium-ion technology, potentially affording high gravimetric and volumetric energy densities. Despite substantial progress in this field, significant challenges remain, including interfacial changes upon cell operation and achievement of reversible lithium inventory. Here, polymer electrolytes may offer flexible solutions and operational safety, providing compromises among conflicting demands of mechanical robustness and sufficient ionic conductivity, though advancements and tailored design of future polymer materials of functional layers and cell designs require input from insights into interfacial processes, characteristic charge transfer rates and associated resistances at electrode|electrolyte interfaces, respectively.In this work, electrochemical impedance spectroscopy (EIS) is therefore carefully exploited for the analysis of relevant charge transfer processes in case of introduced polymer electrolytes[1], invoking a distribution of relaxation times (DRT) approach. The obtained complex permittivity and conductivity of the materials upon variation of temperature as well as explicit modification of the thin lithium metal electrodes with artificial polymer layers yield characteristic data of the evolution of interfacial resistances and the corresponding charge transfer reactions, in this way demonstrating the significant diagnostic strength of EIS/DRT analysis for future developments. In addition, operando EIS/DRT analysis is done upon plating of lithium metal, complemented by 7Li solid-state NMR spectra acquired at various states during lithium deposition, thereby revealing occurring species and their microstructures based on the 7Li NMR chemical shifts.In summary, EIS/DRT analysis is utilized as powerful diagnostic technique, highlighting how to exploit observable trends of characteristic parameters at electrode|electrolyte interfaces for future design of polymer-based materials as well as high performance cell concepts. [1]Chiou et al., Journal of Power Sources 538 (2022) 231528 Figure 1

(Invited) Electrolyte Design for Wide-Temperature Li-Ion and Li-Metal Batteries

Improving the wide temperature operation of rechargeable batteries is vital to the operation of electronics in extreme environments, where systems capable of higher energy, high-rate discharge and long cycling are in short supply. In this talk, we will show electrolyte designs to achieve high-energy density and stable cycling performance in wide temperature range for both lithium-ion and lithium metal batteries. We will show how to circumvent the sluggish ion desolvation process found in typical lithium-ion batteries during discharge. These batteries are enabled by a novel ester electrolyte, which simultaneously provided high electrochemical stability and ionic conductivity at low temperature. Then we will extend the fundamental understanding developed from these system to other high-capacity, high-rate electrodes, leading to further improved energy density and stability for both high and extremely low temperatures, demonstrated by rechargeable Li metal batteries using both high-Ni oxide and sulfur cathodes.

Highly Reversible Zn Metal Anode Enabled by Sustainable Hydroxyl Chemistry

Enhancing Zn anode reversibility with sustainable chemistries is urgent for unlocking rechargeable Zn metal battery technology to complement Li-ion batteries and meet the growing demand for sustainable energy storage. However, conventional practices in electrolyte design which address anode irreversibility through altering the Zn2+ solvation shell often rely on costly concentrated chemicals1-2.In this work, we demonstrate a sustainable and cost-effective electrolyte design strategy by using methanol as a solvent exemplar. The designed electrolyte exhibits unprecedented Zn reversibility combined with high depth of discharge (Coulombic efficiency (CE) >99.5% with 50% Zn utilization and a dendrite-free behavior >1800h) at 25°C due to the determinant interphasial chemistries enabled by the hydroxyl group. Moreover, the Zn anode also shows a high CE >99.5% with 20% Zn utilization at -40°C when supported by a desirable electrolyte bulk transport property. Excellent performance is demonstrated in the Zn || metal-free organic cathode full cells in a wide temperature range. The microscopic characterization and modeling identify the mechanism of unique interphase chemistry and its functionalities as the key factors responsible for dictating reversible Zn chemistry.Reference E. Blanc, D. Kundu, L. F. Nazar, Joule 2020, 4, 771–799.Ma, M. A. Schroeder, O. Borodin, T. P. Pollard, M. S. Ding, C. Wang, K. Xu, Nature Energy 2020, 5, 743-749.

CoS2 nanoparticles-embedded N-doped carbon hybrid derived from ZIF-L as bifunctional oxygen electrocatalysts for rechargeable Zn-air batteries

The unique CoS 2 @N-doped carbon hybrids with core-shell structure could effectively improve oxygen bifunctional catalysis for Zn−air batteries. • The ZIF-L (Zn,Co) template-sacrificing and two-steps pyrolysis synthesis method. • Unique CoS 2 @ N -doped carbon hybrids with core–shell structure and small-size pores. • The bifunctional oxygen catalyst with long-term stability for rechargeable Zn-air battery. Zeolitic imidazolate frameworks (ZIFs) with controllable tunability of compositions and morphologies are identified as efficacious self-sacrificial precursors to prepare functionally-oriented nanostructured materials. Pressingly, we urgently need to use highly efficient bifunctional oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) electrocatalysts for the enhancement of rechargeable metal air batteries research. Herein, the unique CoS 2 @ N -doped carbon (CoS 2 @NC-X) hybrids are successfully achieved via direct calcination and sulfurization of 2D leaf-like bimetallic imidazole framework (ZnCo-ZIF-L). Owing to the synergic effect between intrinsic activity of CoS 2 nanoparticles, the unique core–shell structure and small-size pores, the optimal CoS 2 @NC-60 is demonstrated to exhibit excellent ORR- and OER- catalytic activity. In particular, the ORR of CoS 2 @NC-60 not only possesses a half-wave potential of 0.84 V (compared to RHE), but also has a limiting current density of 5.18 mA cm −2 . Furthermore, CoS 2 @NC-60 possesses an overpotential (compared to RHE) of 350 mV required to drive the current density of 10 mA cm −2 . As a validation, the CoS 2 @NC-60 catalyst is intended for use in rechargeable Zn-air batteries, where it has the outstanding long-term stability (550 h) and an exceptional power density (170.6 mW cm −2 ). This facile synthetic strategy renders a feasible way to further probe non-noble metal electrochemical catalysts.

2D metal–organic frameworks and their derivatives for the oxygen evolution reaction

Electrocatalytic oxygen evolution reaction (OER) is a critical half reaction for energy conversion and storage technologies such as water electrolysis, rechargeable metal–air batteries, carbon dioxide reduction reaction, and so on. Unfortunately, large overpotential is needed to overcome the sluggish kinetics of OER. With ultra-thin thickness, large specific surface area, rich and adjustable pore structure, and well-defined metal centers, two dimensional (2D) metal-organic frameworks (MOFs) have been widely investigated for OER. By virtue of the desirable chemical composition and diverse structural type, 2D MOFs are also employed as precursors and sacrificial templates to prepare metal-decorated porous carbon, metal oxides, metal hydroxides, metal sulfides, metal phosphides, and so on. These 2D MOFs derivatives with high surface area and abundant metal sites exhibit excellent OER performance. Herein, the current advances on 2D MOFs and their derivatives as (pre)electrocatalysts are summarized, including the synthetic strategy and OER performance. Moreover, the structure-performance relationships and actual active species or sites of 2D MOFs and their derivatives toward OER are discussed. The current scientific and technological challenges and future perspectives related with 2D MOF and their derivatives in practical applications are also mentioned at last.

Two-dimensional carbon-based heterostructures as bifunctional electrocatalysts for water splitting and metal–air batteries

The continuous depletion of fossil fuels and the effects of climate change have encouraged prompt action to attain carbon neutrality. Technologies that transform and store renewable energy are crucial for creating a sustainable society, which is independent of fossil fuels. In this regard, electrochemical water splitting based on the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is an attractive technique for producing carbon-free hydrogen fuels. Additionally, rechargeable metal–air batteries (MABs) are another intriguing way for renewable energy storage through reversible oxygen reactions (OER and the oxygen reduction reaction, ORR). Herein, we comprehensively review bifunctional electrocatalysts for water splitting (HER and OER) and MABs (OER and ORR), particularly 2D carbon material-derived heterostructures. The synthesis and properties of 2D carbon materials and their energy conversion and storage mechanisms are discussed to highlight the bifunctionality of the heterostructures. Recent studies on bifunctional electrocatalysts based on 2D carbon-derived heterostructures are also reviewed. Finally, perspectives for future studies and multifunctional catalysts are presented.

Halogenated Zn2+ Solvation Structure for Reversible Zn Metal Batteries.

Rechargeable aqueous Zn metal batteries have become promising candidates for large-scale electrochemical energy storage owing to their high safety and affordable low cost. However, Zn metal anode suffers from dendritic growth and hydrogen evolution reaction (HER), deteriorating the electrochemical performance. Here, we demonstrate that these challenges can be conquered by introducing a halogen ion into the Zn2+ solvation structure. By designing an electrolyte composed of zinc acetate and ammonium halide, the electron-donating anion I- can coordinate with Zn2+ and transform the traditional Zn(H2O)62+ to ZnI(H2O)5+, in which I- could transfer electrons into H2O and thus suppress HER. The dynamic electrostatic shielding layer formed by concomitant NH4+ can restrict the dendritic growth. As a result, the halogenated electrolyte achieves a high initial coulombic efficiency (CE) of 99.3% in the Zn plating/stripping process and remains at an average of ∼99.8% with uniform Zn deposition. Moreover, Zn-I batteries are constructed by using dissociative I- as the cathode and carbon felt-polyaniline as the conductive and adsorptive layer, exhibiting an average CE of 98.6% without capacity decay after 300 cycles. This work provides insights into the halogenated Zn2+ solvation structure and offers a general electrolyte design strategy for achieving a highly reversible Zn metal anode and batteries.

Back to the basics: Advanced understanding of the as-defined solid electrolyte interphase on lithium metal electrodes

The design and control of the solid electrolyte interphase (SEI) is essential for the implementation of rechargeable lithium metal based batteries and has been a major research theme of lithium metal electrodes for over 50 years. However, research on an as-defined SEI is challenging due to the inevitable presence of a native passivation layer (NPL), commonly contaminating an in situ formed SEI and its characteristics. Herein we present an original study on an uncontaminated SEI being an exclusive reaction product of lithium and a liquid aprotic electrolyte, highlighting the largely negative influence of the NPL on different SEI characteristics and functional additive evaluation. A preformed as-defined SEI (pSEI) was generated by an in-house designed advanced pre-treatment method, ensuring high reproducibility and exclusion of the NPL by cutting and pressing lithium metal in solution/electrolyte. The implementation of a pSEI allows for a systematic study and an unclouded comparison of the two common functional additives vinylene carbonate (VC) and fluoroethylene carbonate (FEC) in an equal molar setting. The introduction of an as-defined SEI allowed to clearly distinguish between enhancing influence on the SEI characteristics and full cell performance by FEC and the largely negative effect of VC on different SEI characteristics.

Modeling the effects of pulse plating on dendrite growth in lithium metal batteries

The formation of dendrites on lithium electrodes presents safety and cycling challenges for the development of high-performance, rechargeable lithium metal batteries. While a constant current (CC) charging protocol has been standard, recent studies have shown that a pulse plating (PP) charging protocol is effective at reducing dendrite growth and improving cycle life. In this study, dendrite growth at the anode-electrolyte interface was simulated using an Extended Butler-Volmer Smoothed Particle Hydrodynamics (eBV-SPH) model implemented in LAMMPS. Square waveform PP protocols were implemented and compared to CC results to understand the effect of charging protocols on lithium deposition and dendrite morphology. The charging conditions were controlled by the applied potential, as the model does not currently enforce galvanostatic conditions. Past studies compared CC and PP results at a single charging current density. In similar work on lithium-ion batteries, PP and CC results compared at the identical mean current resulted in little to no benefit to cycling performance. In this investigation, lithium anode PP protocols performed worse when compared with CC plating at the identical mean current. The PP and CC simulation results from the eBV-SPH model simulated the expected morphology and behavior found in experimental investigations and provide more detailed morphologies than previous computational simulations.

Building Metal‐Molecule Interface towards Stable and Reversible Zn Metal Anodes for Aqueous Rechargeable Zinc Batteries

AbstractAqueous zinc ion batteries (AZIBs) are receiving increasing attention for large‐scale energy storage systems owing to their appealing features with intrinsic safety, low cost, and scalability. Unfortunately, the water‐induced parasitic reactions and dendrite growth on the Zn anode severely impede the further development of AZIBs. Herein, a thiourea additive is introduced into ZnSO4 electrolyte to construct unique metal‐molecule interface for simultaneously regulating the Zn anode interface chemistry and the bulk electrolyte environment. Experimental results and theoretical calculations reveal that the formed metal‐molecule interface can not only serve as a corrosion inhibitor for alleviating the water‐induced side reactions, but also act as a Zn2+ ion regulator for promoting the homogenous Zn deposition, thus achieving a corrosion‐free and dendrite‐free Zn anode. Consequently, the Zn|Zn symmetric cell exhibits an extended lifespan of 1200 h at 1 mA cm–2, 1mAh cm–2, and a high cumulative capacity of 3000 mAh cm–2 at 10 mA cm–2. When paired with V2O5 cathode, the Zn|V2O5 full cell delivers a high capacity retention of 76.0% after 1000 cycles at 1 A g–1. This study paves a new way to modulate Zn electrode interface chemistry by the novel design of metal‐molecule interface for advanced rechargeable Zn metal batteries and beyond.

Single Iron Atom Anchored on ZIF‐8 Derived Carbon Framework to Directionally Regulate Lithium Deposition with Minimum Nucleation Overpotential

AbstractLithium (Li) metal has earned valuable status among the most auspicious anodes for the assembly of next‐generation rechargeable batteries. However, the dendritic growth and infinite change in volume of metallic Li anode strongly hinder its use for practical applications. Here, the preparation of atomically dispersed iron doped ZIF‐8 through pyrolysis (Fe@NC) to lower the Li nucleation overpotential and control the Li deposition on specific positions is reported. Thermodynamic and kinetic simulations show that the doped single Fe atoms can improve the atomic structure, increase the adsorption energy and enhance the diffusion capacity of Li. Moreover, the specific framework structure of Fe@NC can induce Li metal to nucleate in interior space of the material which can hinder the Li growth along one direction and restrain its volume expansion. As‐fabricated electrode displays nearly no nucleation overpotential at current density of 2 mA cm–2 and offers higher average Coulombic efficiency up to 99.0% for 100 cycles at current density 2 mA cm–2, and higher areal capacity up to 5 mAh cm–2. Also, the fabricated Fe@NC/LiFePO4 based full cells exhibit a longer lifespan of 100 cycles at 0.5 C. The results provide new insights for future rechargeable Li metal batteries.

MnCo2O4/N-doped graphene quantum dot vigorously coupled to MXene nanosheet: A bifunctional Oxygen electrocatalyst outperforms Pt/IrO2 benchmark electrocatalysts in metal-air batteries

The rational design and fabrication of a high performance, durable, and cost effective bifunctional electrocatalyst employed for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of remarkably great importance for the commercialization of rechargeable metal–air batteries. While electrocatalysts designed based on spinel oxides have been deemed as promising catalyst materials for the ORR and OER, their catalytic performance still must be considerably enhanced to satisfy the prerequisites of practical applications. In this work, a heterostructure (MnCo2O4/N-GQD/MXene) of Ti3C2Tx (MXene) nanosheets decorated with spinel manganese-cobalt oxide (MnCo2O4) nanoparticles and N-doped-graphene quantum dots(N-GQD) fabricated via facile hydrothermal method. The presence of plentiful active reaction sites, high surface area and distinctive electronic structure, resulting from robust interfacial interaction, lead to the higher electron conductivity and faster ORR/OER kinetics in Zn-air batteries. Therefore, the obtained MnCo2O4/N-GQD/MXene electrocatalyst presenting an outstanding ORR performance with a low over potential of only 22 mV, half-wave potential (E1/2) of 0.87 V (vs RHE), and remarkable long-term durability, strikingly outperforms commercial Pt/C (20 % w/w). Concerning OER, the MnCo2O4/ N-GQD/MXene exhibiting an onset potential of 1.54 V(vs RHE) and a Tafel slope of 65 mV dec−1 displays better performance than IrO2. The zinc-air battery with MnCo2O4/ N-GQD/MXene cathode shows superior peak power density (152.8 mW cm−2), tremendous capacity efficiency up to 753 mAh g−1 and substantial stability, proving that MnCo2O4/ N-GQD/MXene could feasibly be used in metal–air batteries.

Stabilization of Lithium Metal Interfaces by Constructing Composite Artificial Solid Electrolyte Interface with Mesoporous TiO2 and Perfluoropolymers.

The next generation of high-energy-density storage devices is expected to be rechargeable lithium metal batteries. However, unstable metal-electrolyte interfaces, dendrite growth, and volume expansion will compromise lithium metal batteries (LMB) safety and life. A simple drop-casting method is used to create a double-layer functional interface composed of inorganic mesoporous TiO2 and F-rich organics PFDMA. For high-quality lithium deposition, TiO2 can provide uniform mechanical pressure, abundant mesoporous channels, and increased ionic conductivity, while PFDMA provides enough F to form LiF in the first cycle and improves Li-electrolyte compatibility. Experimentsand simulations are combined toinvestigate the optimized mechanism of the LiF-rich solid electrolyte interface (SEI). The high binding energy of organic matter and Li demonstrates that Li+ preferentially binds with the F atom in organic matter. As a result, the tightly bound double-layer structure can inhibit lithium dendrite growth and slow electrolyte decomposition. Consequently, the symmetric Li||Li cell has a high stability performance of over 800 h. The assembled LiFePO4 ||Li cell can sustain 300 cycles at a 1 C rate and has a reversible capacity of 136.7 mAh g-1 .

Chemo-Mechanical Effects of Stack Pressure and Temperature on Anode-Free Lithium Metal Batteries

Electrochemical cells using rechargeable lithium metal anodes are sensitive to operating temperature and stack pressure. Current understanding generally assumes that temperature drives changes in lithium metal surface chemistry while stack pressure impacts the anode morphology. In this study, we provide quantifiable evidence for these assumptions and propose mechanisms to guide understanding of temperature and pressure effects on lithium metal cell dynamics. Beyond the direct coupling of pressure with mechanics and temperature with kinetics, we also explore possible effects of temperature on cell mechanics and stack pressure on cell chemistry. We investigate an electrolyte composition based on LiDFOB salt, using a range of operando and ex situ techniques. Mechanistic mapping of temperature- and pressure-dependent cell behavior will aid development of improved lithium metal batteries.

Co/N nanoparticles supported on a C3N4/polydopamine framework as a bifunctional electrocatalyst for rechargeable zinc-air batteries

• An electrocatalyst with Co NPs on a graphitized N -doped carbon framework are prepared. • The synthetic strategy avoids the excessive growth and aggregation of metal nanoparticles. • The catalyst has an improved ORR and OER activity compared with Pt/C and Ir/C, respectively. • The synthetic catalyst-containing ZABs present an outstanding discharging performance. Metal N -doped carbons (M N C) and specifically cobalt-based N -doped carbons (Co N C) have attracted extensive attention as suitable multifunctional catalysts. Their high catalytic activity, originating from the strong coupling effect of Co with N, lead to the formation of active sites with suitable binding energies for promoting the discharging and charging reactions. Herein, we propose the synthesis of an efficient bifunctional electrocatalyst (ZIFCNDA) prepared by the introduction of Co ions during the polymerisation of dopamine, which lead to the direct doping of a carbon framework and the localized growth of Co-based MOFs polyhedrons, generating Co-based nanoparticles (Co NPs) upon pyrolysis. The C 3 N 4 -controlled polydopamine growth formed thin graphitized carbon nanosheets which can facilitate the transfer of electrons to the catalytically active sites. The ZIFCNDA catalyst was able to efficiently catalyse both the oxygen reduction (ORR) and oxygen evolution (OER) reactions). The ZAB containing the developed catalyst presented a stable discharge voltage of 1.1 V at a high current density of 10 mA cm −2 with higher stability and longer cycle life compared to their counterparts constructed using Pt/C and Ir/C in air–cathode. This study illustrates a platform to enhance the catalytic activity of the ORR and OER catalyst via promoting the formation of well distributed cobalt active sites, achieved due to the insertion of cobalt ions during the polymerization process of dopamine, instead of on a previously prepared framework and their application for rechargeable metal–air batteries.

Comonomer-Tuned Gel Electrolyte Enables Ultralong Cycle Life of Solid-State Lithium Metal Batteries.

Rechargeable lithium metal batteries (LMBs) are considered the "holy grail" of energy storage systems. Unfortunately, uncontrollable dendritic lithium growth inherent in these batteries has prevented their practical applications. The benefits of solid-state electrolyte for LMBs are limited due to the common compromise between ionic conductivity and mechanical property. This work proposes a mechanism for simultaneous improvement in ionic conductivity and mechanical strength of gel polymer electrolyte (GPE) which is based on tunable cross-linked polymer network through adjusting monomer ratios. With increasing bisphenol A ethoxylate dimethacrylate (E2BADMA) and poly(ethylene glycol) diacrylate (PEGDA) mass ratios in GPE precursors, the formed polymer network experienced a composition evolution from a 3D cross-linked mono PEGDA network to triple PEGDA, E2BADMA, and PEGDA/E2BADMA networks and then to dual E2BADMA and PEGDA/E2BADMA networks, accompanied by the increase in both storage modulus (from 6 to 37 MPa) and ionic conductivity (from 0.06 to 0.44 mS cm-1). As a result, the E2BADMA/PEGDA mass ratio of 2:1 facilitates the successful fabrication of a dual-network-supported GPE (PEEPL-12) with a mechanical strength of 37 MPa and superior electrochemical properties (a high ionic conductivity of 0.44 mS cm-1 and a wide electrochemical stability window of 4.85 V vs Li/Li+). Such polymer electrolyte-based symmetric lithium metal batteries delivered a long cycle life (2000 h at 0.1 mA cm-2 and 0.1 mAh cm-2), and the Li|PEEPL-12|LiFePO4 cell delivered a high capacity of 140 mAh g-1 at the 100th cycle at the current density of 0.1 C (1 C = 170 mAh g-1). A more thorough investigation indicated the formation of a stable solid electrolyte interphase layer on a lithium metal anode. These extraordinary features open up a venue for fabrication of advanced polymer electrolyte for long-cycle-life lithium metal batteries.