Solid-state Zinc-air Batteries Research Articles

Single-Anion Conductive Solid-State Electrolytes with Hierarchical Ionic Highways for Flexible Zinc-Air Battery.

Flexible zinc-air batteries are leading power sources for next-generation smart wearable electronics. However, flexible zinc-air batteries suffer from the highly-corrosive safety risk and limited lifespan due to the absence of reliable solid-state electrolytes (SSEs). Herein, a single-anion conductive SSE with high-safety is constructed by incorporating a highly amorphous dual-cation ionomer into a robust hybrid matrix of functional carbon nanotubes and polyacrylamide polymer. The as-fabricated SSE obtains dual-penetrating ionomer-polymer networks and hierarchical ionic highways, which contribute to mechanical robustness with 1200% stretchability, decent water uptake and retention, and superhigh ion conductivity of 245 mS·cm-1 and good Zn anode reversibility. Remarkably, the flexible solid-state zinc-air batteries delivers a high specific capacity of 764 mAh·g-1 and peak power density of 152 mW·cm-2 as well as sustains excellent cycling stability for 1050 cycles (350 hours. This work offers a new paradigm of OH- conductors and broadens the definition and scope of OH- conductors.

“Seaweed Structure” design for solid gel electrolyte with hydroxide ion conductivity enabling flexible zinc air batteries

The construction of solid-state electrolytes for flexible zinc-air batteries is extremely challenging. A flexible and highly conductive solid electrolyte designed with a “seaweed structure” is reported in this work. Sodium alginate serves as the backbone to form a robust network structure, and the grafted quaternary ammonium groups provide channels for rapid ion transport, achieving excellent flexibility and hydroxide conductivity. The conductivity of the modified electrolyte membrane (QASA) is 5.23 × 10−2 S cm−1 at room temperature and reaches up to 8.51 × 10−2 S cm−1 at 75 °C. In the QASA based battery, bending at any angle is realized, and the power density is up to 57.28 mW cm−2. This work provides a new way to prepare high conductivity, green solid-state zinc-air batteries, and opens up a research line of thought for flexible energy storage materials.

N-P covalent bond regulation of mesoporous carbon-based catalyst for lowered oxygen reduction overpotential and enhanced zinc-air battery performance

Developing sustainable metal-free carbon-based electrocatalysts is essential for the deployment of metal-air batteries such as zinc-air batteries (ZABs), among which doping of heteroatoms has attracted tremendous interest over the past decade. However, the effect of the heteroatom covalent bonds in carbon matrix on catalysis was neglected in most studies. Here, an efficient metal-free oxygen reduction reaction (ORR) catalyst is demonstrated by the N-P bonds anchored carbon (termed N,P-C-1000). The N,P-C-1000 catalyst exhibits superior specific surface area of 1362 m2 g−1 and ORR activity with a half-wave potential of 0.83 V, close to that of 20 wt% Pt/C. Theoretical computations reveal that the p-band center for C-2p orbit in N,P-C-1000 has higher interaction strength with the intermediates, thus reducing the overall reaction energy barrier. The N,P-C-1000 assembled primary ZAB can attain a large peak power density of 121.9 mW cm−2 and a steady discharge platform of ∼1.20 V throughout 120 h. Besides, when served as the cathodic catalyst in a solid-state ZAB, the battery shows flexibility, conspicuous open circuit potential (1.423 V), and high peak power density (85.8 mW cm−2). Our findings offer a strategy to tune the intrinsic structure of carbon-based catalysts for improved electrocatalytic performance and shed light on future catalysts design for energy storage technologies beyond batteries.

Recycling the spent cobalt-based perovskites for the high-active oxygen catalysts in zinc-air batteries

Cobalt (Co) is widely used in energy storage and conversion devices, although its content on our planet is not adequate. Therefore, recycling Co from the spent Co-enriched materials is indispensable. Co-based perovskites, which contain abundant Co, are extensively utilized in solid oxide fuel cells, three-way catalysts, and oxygen-permeable membranes, and the recovery of Co from the spent Co-based perovskites is necessary to meet the long-term requirement of Co. In this work, a facile and universal thermal reduction method (750 °C and N2 atmosphere) is employed to convert the spent cobalt-based perovskites into high-performance bifunctional oxygen catalysts for zinc-air batteries (ZABs), achieving high-efficient Co recovery and re-utilization. At high temperatures, melamine and dopamine hydrochloride are transformed into carbon nanotubes, C3N4 and reducing gases (such as NH3 and H2). Simultaneously, the metal elements in the spent Co-based perovskites (SrNb0.1Co0.7Fe0.2O3,SNCF) are converted into nano-scale alloy particles and metal nitrides. Then, the phase structures, micromorphology, and element valences of the obtained multiphase oxygen catalyst (SNCF–Ni-PM) are characterized by X-ray diffraction, scanning/transmission electron microscopy, and X-ray photoelectron spectroscopy, respectively. The electrochemical properties, including oxygen catalytic activities and stability, of SNCF-Ni-PM are measured by linear sweep voltammetry, chronopotentiometry, chronoamperometry, and cyclic voltammetry methods. Considering the practical applications, the aqueous and solid-state ZABs are assembled and measured. The results demonstrate that the multiphase SNCF-Ni-PM mainly includes carbon nanotubes, C3N4 nanosheets, and FeNiN or CoFe nanoparticles. Moreover, SNCF-Ni-PM exhibits excellent bifunctional oxygen catalytic activity, with an oxygen evolution reaction (OER) potential at 10 mA cm−2 of 1.51 V and an oxygen reduction reaction (ORR) half-wave potential of 0.77 V, outperforming most of the reported oxygen catalysts. Using SNCF-Ni-PM, the aqueous and solid-state ZABs can achieve high power densities of 295.9 and 228.4 mW cm−2, respectively, being superior to most ZABs. In addition, the aqueous ZAB with SNCF-Ni-PM can operate stably for 300 h with a slight degradation. This work provides a feasible method for effectively recycling Co from the spent Co-based perovskites.

Main Group SnN4O Single Sites with Optimized Charge Distribution for Boosting the Oxygen Reduction Reaction.

Transition metal single-atom catalysts (SACs) have been regarded as possible alternatives to platinum-based materials due to their satisfactory performance of the oxygen reduction reaction (ORR). By contrast, main-group metal elements are rarely studied due to their unfavorable surface and electronic states. Herein, a main-group Sn-based SAC with penta-coordinated and asymmetric first-shell ligands is reported as an efficient and robust ORR catalyst. The introduction of the vertical oxygen atom breaks the symmetric charge balance, modulating the binding strength to oxygen intermediates and decreasing the energy barrier for the ORR process. As expected, the prepared Sn SAC exhibits outstanding ORR activity with a high half-wave potential of 0.912 V (vs RHE) and an excellent mass activity of 13.1 A mgSn-1 at 0.850 V (vs RHE), which surpasses that of commercial Pt/C and most reported transition-metal-based SACs. Additionally, the reported Sn SAC shows excellent ORR stability due to the strong interaction between Sn sites and the carbon support with oxygen atom as the bridge. The excellent ORR performance of Sn SAC was also proven by both liquid- and solid-state zinc-air battery (ZAB) measurements, indicating its great potential in practical applications.

Electronic Reservoir Regulation Stabling IrO x as Efficient Cathode for Solid-State Zinc–Air Batteries

Electronic Reservoir Regulation Stabling IrO _x as Efficient Cathode for Solid-State Zinc–Air Batteries

Facile Composition of CoNi and Graphene as a Free-Standing Cathode for a High-Performance Solid-State Zinc–Air Battery

The development of solid-state zinc–air batteries (SZABs) has stimulated significant interest. However, the practical use of SZABs still encounters difficulties due to the complicated preparation process and low-performance air cathode. In this study, we developed a free-standing CoNi/graphene composite cathode without current collectors and binders. The simplified cathode structure decreased the preparation process, and the self-assembled conductive matrix increased charge transfer, which holds promise for facile preparation and high-performance SZABs. Specifically, a free-standing CoNi/graphene film was fabricated by a simple composition method. The CoNi/graphene electrocatalyst exhibited comparable oxygen reduction reaction (ORR) catalytic activity to that of Pt/C. Furthermore, the CoNi/graphene film could be directly used as a cathode, which showed an open-circuit voltage of 1.41 V and a power density of 210 mW cm−2 in alkaline liquid ZABs, as well as an open-circuit voltage of 1.43 V and a power density of 40 mW cm−2 in alkaline SZABs. This facile preparation and excellent performance offer substantial potential for practical SZAB applications.

Extending the Cycle Lifetime of Solid-State Zinc-Air Batteries by Arranging Stable Zinc Species Channels.

The solid-state zinc-air batteries have attracted extensive attention due to their high theoretical energy density, high safety, and the compact structure. In this work, a novel hydrogel solid-state electrolyte was developed that was equipped with an interpenetrating network of zinc polyacrylate (PAZn) and polyacrylamide (PAM). At the same time, a cyclodextrin derivative with sulfonate groups was introduced as an additive. From the design of anionic groups in the network, effective and stable channels for zinc species have been established. The unique structure of the additives regulates the uniform deposition of zinc. After using this solid-state electrolyte, the cycle lifetime of solid-state zinc-air batteries assembled have been significantly extended. The byproducts were greatly suppressed and generated the smooth zinc electrode surface after the charge-discharge cycling.

Preparation of cellulose acetate based flexible separator and its application in zinc–air batteries

Flexible solid-state zinc–air batteries as a wearable energy storage device with great potential, and their separators, which control ion permeability, inhibit zinc dendrite generation, and regulate catalytic active sites, have been developed as gel electrolyte separators with high retention of electrolyte uptake. However, the gel electrolyte separator still has problems such as poor affinity with the electrolyte and poor ionic conductivity, which limits its further application. In order to further improve the electrolyte absorption, ionic conductivity and mechanical strength of cellulose acetate(CA)/polyvinyl alcohol (PVA) nanofibers, TiO2 was added to CA/PVA to increase the porosity, and glutaraldehyde (GA) was used to modify the CA/PVA/TiO2 separator by acetal reaction with CA and PVA to make the molecules closely linked. The results shows that the optimal mass fractions of TiO2 and GA were 2% and 5%, respectively. At this time, the porosity and absorption rate of the separator increased from 48% to 68.2% and 142.4% to 285.3%, respectively. The discharge capacity reached 179 mA cm−3, and the cycle stability rate was 89% after 7 stable constant current charge/discharge cycles.

2D arrays of hollow carbon nanoboxes: outward contraction-induced hollowing mechanism in Fe-N-C catalysts.

Maximizing the utilization efficiency of monatomic Fe sites in Fe-N-C catalysts poses a significant challenge for their commercial applications. Herein, a structural and electronic dual-modulation is achieved on a Fe-N-C catalyst to substantially enhance its catalytic performance. We develop a facile multi-component ice-templating co-assembly (MIC) strategy to construct two-dimensional (2D) arrays of monatomic Fe-anchored hollow carbon nanoboxes (Fe-HCBA) via a novel dual-outward interfacial contraction hollowing mechanism. The pore engineering not only enlarges the physical surface area and pore volume but also doubles the electrochemically active specific surface area. Additionally, the unique 2D carbon array structure reduces interfacial resistance and promotes electron/mass transfer. Consequently, the Fe-HCBA catalysts exhibit superior oxygen reduction performance with a six-fold enhancement in both mass activity (1.84 A cm-2) and turnover frequency (0.048 e- site-1 s-1), compared to microporous Fe-N-C catalysts. Moreover, the incorporation of phosphorus further enhances the total electrocatalytic performance by three times by regulating the electron structure of Fe-N4 sites. Benefitting from these outstanding characteristics, the optimal 2D P/Fe-HCBA catalyst exhibits great applicability in rechargeable liquid- and solid-state zinc-air batteries with peak power densities of 186 and 44.5 mW cm-2, respectively.

Recycling the Spent LiNi1- x - yMnxCoyO2 Cathodes for High-Performance Electrocatalysts toward Both the Oxygen Catalytic and Methanol Oxidation Reactions.

The traditional recycling methods of the spent lithium ion batteries (LIBs) involve the intricate and cumbersome steps. This work proposes a facile method of acid leaching followed by the sulfurization treatment to achieve the high Li leaching efficiency, and obtain high-performance multi-function electrocatalysts for oxygen reduction (ORR), oxygen evolution (OER), and methanol oxidation reactions (MOR) from the spent LIB ternary cathodes. By this method, the Li leaching efficiency from the spent LIB ternary cathode can reach 98.3%, and the transition metal sulfide heterostructures (LNMCO-H-450S) consisting MnS, NiS2, and NiCo2S4 phases can be obtained. LNMCO-H-450S shows the superior bifunctional oxygen catalytic activities with ORR half-wave potential of 0.763V and OER potential at 10mA cm-2 of 1.561V, surpassing most of the state-of-the-art electrocatalysts. LNMCO-H-450S also demonstrates the superior MOR catalytic activity with the potential at 100mA cm-2 being 1.37V. Using LNMCO-H-450S as the oxygen catalyst, this work can construct the aqueous and solid-state zinc-air batteries with high power density of 309 and 257mW cm-2, respectively. This work provides a promising strategy for the efficient recovery of Li, and reutilization of Ni, Co, and Mn from the spent LIB ternary cathodes.

Activity promotion of bifunctional catalysis by Se-doping and the application in rechargeable zinc-air batteries

Efficient bifunctional catalysts capable of catalyzing both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are required for the air electrode. Herein, the Se-doped FeNiP nanoparticles/N, P dual-doped carbon composite catalysts (FeNiP/SeNPC-2) were developed. The Se elements combine with various elements to form a compact heterogeneous material. At the same time, the Se-doping have modulated the crystal and surface structures, which have improved the catalytic activities of ORR and OER. The overpotential of OER was significantly negatively shifted, accompanied by a significant positive shift of the onset potential of ORR. FeNiP/SeNPC-2 has displayed an overpotential of 269 mV at the current density of 10 mA cm−2 for OER, and with a high half-wave potential (0.86 V) of ORR. The liquid zinc-air battery assembled using FeNiP/SeNPC-2 exhibited a power density of 171 mW cm−2 and stably charge-discharge cycled for 150 h. The solid-state zinc-air battery exhibited a power density of 88 mW cm−2 and stably charge-discharge cycled for 42 h. Subsequently, the solid-state zinc-air batteries of cylindrical hollow design are integrated as modules for driving devices.

Long-Range Regulation of Se Doping for Oxygen Reduction of Atomically Dispersed Sb Catalysts for Ultralow-Temperature Solid-State Zn–Air Batteries

Regulating the p-orbital valence electrons of atomically dispersed main-group metals to improve the inherent electrocatalytic activity has attracted extensive concerns. Herein, we designed and synthesized an atomically dispersed Sb–SeNC catalyst containing SbN2C2 and SeC2 structures, which have been identified by X-ray absorption spectroscopy and density functional theory (DFT) calculations. Sb–SeNC exhibits a high activity for the oxygen reduction reaction (ORR), and a Sb–SeNC-based flexible solid-state zinc–air battery (ZAB) can work efficiently at −40 °C, with a peak power density of 54.1 mW cm–2 and a rate discharge operation of about 44 h. DFT calculations further confirm the long-range regulation mechanism of the SeC2 moiety for the ORR of SbN2C2 and obtain the volcano relationship of Uonset vs the Se–N distance. When the Se–N distance is 7.4 Å, the adsorption ability of active site Sb can be regulated to an optimal state related to the RDS: *O → *OH, while the smaller Se–N distance in short-range would lead to the excessive attenuation of adsorption ability of active site and decrease of ORR activity, which therefore yields the long-range regulation effect of Se doping on the ORR activity of SbN2C2. This long-range regulation strategy may provide a promising approach to boost the catalytic activity of main-group metal catalysts to achieve its application in ultralow-temperature solid-state ZABs.

Spinel LiMn2O4 as Electrocatalyst toward Solid-State Zinc–Air Batteries

Efficient oxygen reduction reaction (ORR) electrocatalysts are the key to advancement of solid-state alkaline zinc–air batteries (ZAB). We demonstrate an electrocatalyst, spinel lithium-manganese oxide LiMn2O4 (LMO) by a simple hydrothermal method. Scanning electron microscope (SEM), X-ray diffraction (XRD), and Raman spectra indicate that the as-synthesized LiMn2O4 presents nanoscale irregular-shaped particles with the well-known spinel structure. The polarization curve, chronoamperometery curve, and linear scanning voltammograms of rotating disk electrode (RDE) results reveal that the as-synthesized LiMn2O4 possesses a higher electrocatalytic activity than that of electrolytic manganese dioxide for the ORR. A solid-state zinc–air cell with LiMn2O4 as the air electrode catalyst has a long voltage plateau of discharge and a discharge capacity of 188.4 mAh at a constant discharge current density of 10 mA·cm−2. In summary, spinel LiMn2O4 in which the JT effect enables electron hoping between Mn3+ and Mn4+ can be regarded as an effective robust oxygen reduction catalyst.

Nitrogen-doped NiCo2O4 nanowires on carbon paper as a self-supported air cathode for rechargeable Zn-air batteries

A noble-metal-free bifunctional electrocatalyst with outstanding activity and stability is of great importance for the development of rechargeable zinc-air batteries (ZABs). Herein, we employed a facile strategy to fabricate nitrogen-doped NiCo2O4 nanostructures on carbon paper as a binder-free air cathode for rechargeable ZABs. An optimized process of nitrogen plasma treatment has enhanced the electrical conductivity of the metal oxide and induced abundant active sites into the crystal structures, resulting in enhanced electrocatalytic activities toward oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Notably, mild plasma treatment leads to efficient N doping while the morphology and specific surface area of the catalyst both remain unchanged. The air cathode with NiCo2O4 doped with nitrogen in 2 min plasma treatment and integrated into a zinc-air battery with liquid electrolyte provided a small charge-discharge voltage gap and distinguished cycling stability superior to the air cathode with noble-metal catalyst counterparts. Furthermore, the solid-state zinc-air battery with this material displays excellent stability with just a small increase of the charge-discharge voltage gap over 20 h of operation. This work illustrates the promising potential of plasma treatment in the fabrication of high-performance catalysts.

Gel Polymer-Based Composite Solid-State Electrolyte for Long-Cycle-Life Rechargeable Zinc–Air Batteries

Developing high-performance, safe, and flexible solid-state electrolytes (SSEs) for rechargeable solid-state zinc–air batteries (ZABs) is becoming increasingly crucial but remains fraught with tremendous challenges. Herein, a novel multinetwork cross-linked composite gel electrolyte (PVAA-Cellulose) was constructed by introducing poly(acrylic acid) (PAA) and ultrafine cellulose to the poly(vinyl alcohol) (PVA) gel electrolyte. By virtue of the extensive porous network and hydrogen bonding, the PVAA-Cellulose SSEs achieve optimal water retention, thermal stability, and high ionic conductivity of 123 mS cm–1 compared with PVAA (mixture of PVA and PAA). The investigation of the effects of different SSEs on zinc anodes after ZAB cycling reveals that PVAA-Cellulose SSE can effectively inhibit dendrite growth and oxidation byproduct generation on zinc anodes, which contributes to the long-term cycling stability of ZABs. As a result, solid-state ZABs assembled with PVAA-Cellulose SSEs possess a high power density of 74 mW cm–2, a specific capacity of 724 mAh gZn–1, and a long cycle stability of 54 h as well as the outstanding flexibility exhibited by the flexible ZAB devices.

Mechanically Strong, Freeze-Resistant, and Ionically Conductive Organohydrogels for Flexible Strain Sensors and Batteries.

Conductive hydrogels as promising material candidates for soft electronics have been rapidly developed in recent years. However, the low ionic conductivity, limited mechanical properties, and insufficient freeze-resistance greatly limit their applications for flexible and wearable electronics. Herein, aramid nanofiber (ANF)-reinforced poly(vinyl alcohol) (PVA) organohydrogels containing dimethyl sulfoxide (DMSO)/H2 O mixed solvents with outstanding freeze-resistance are fabricated through solution casting and 3D printing methods. The organohydrogels show both high tensile strength and toughness due to the synergistic effect of ANFs and DMSO in the system, which promotes PVA crystallization and intermolecular hydrogen bonding interactions between PVA molecules as well as ANFs and PVA, confirmed by a suite of characterization and molecular dynamics simulations. The organohydrogels also exhibit ultrahigh ionic conductivity, ranging from 1.1 to 34.3Sm-1 at -50 to 60°C. Building on these excellent material properties, the organohydrogel-based strain sensors and solid-state zinc-air batteries (ZABs) are fabricated, which have a broad working temperature range. Particularly, the ZABs not only exhibit high specific capacity (262mAhg-1 ) with ultra-long cycling life (355cycles, 118h) even at -30°C, but also can work properly under various deformation states, manifesting their great potential applications in soft robotics and wearable electronics.

Advances in polymer electrolytes for solid-state zinc–air batteries

Schematic illustration of the main research characteristics of polymer electrolytes for solid-state zinc–air batteries.

FeCo/N-co-doped 3D carbon nanofibers as efficient bifunctional oxygen electrocatalyst for Zn-air batteries.

Flexible zinc-air batteries (ZABs) are expected to become a promising candidate in energy storage equipment for wearable electronic devices. However, the sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have impeded the development of ZABs. Herein, an FeCo- and N-codoped bifunctional electrocatalyst (FeCoNCF) is fabricated by simple one-pot and pyrolysis strategies. Concretely, the bacterial cellulose (BC) and Prussian blue analogue (PBA) derived transition metal and nitrogen doped carbon (M-N-C) composites provide ORR and OER active sites. FeCoNCF exhibits outstanding ORR and OER activities. It displays a favorable high half-wave potential (0.81 V) and a low overpotential at 10 mA cm-2 (341 mV), which are on a par with commercial Pt/C and RuO2, and shows outstanding stability. The sandwich-type flexible zinc-air battery containing FeCoNCF shows a favorable power density (49.29 mW cm-2) and superior cycling stability.

Hydroxide ion-conducting viologen-bakelite organic frameworks for flexible solid-state zinc-air battery applications.

Adaptable polymer-based solid-state electrolytes can be a game-changer toward safe, lightweight flexible batteries. We present a robust Bakelite-type organic polymer covalently decked with viologen, triazine, and phenolic moieties. Its flexible structure with cationic viologen centers incorporates counter-balancing free hydroxide ions into the polymeric framework. By design, the aromatic groups and heteroatoms in the framework can be activated under an applied potential to prompt a push-pull drive, setting off the towing of hydroxide ions via weak electrostatic, van der Waals, and hydrogen-bond interactions. The frontier orbitals from a DFT-modeled structure certify this. The hydroxyl-polymer requires minimal KOH wetting to maintain a humid environment for Grotthuss-type transport. The hydroxide ion conductivity reaches a value of 1.4 × 10-2 S cm-1 at 80 °C and 95% RH, which is retained for over 15 h. We enhanced its practical utility by coating it as a thin solid-state separator-cum-electrolyte on readily available filter paper. The composite exhibits a conductivity of 4.5 × 10-3 S cm-1 at 80 °C and 95% RH. A zinc-air battery (ZAB) constructed using this polymer-coated paper as electrolyte yields a maximum power density of 115 mW cm-2 and high specific capacitance of 435 mA h g-1. The power density recorded for our ZAB is among the best reported for polymer electrolyte-based batteries. Subsequently, the flexible battery fabricated with IISERP-POF11_OH@FilterPaper exhibits an OCV of 1.44 V, and three batteries in series power a demo traffic signal. To underscore the efficiency of hydroxide ion transport through the complex multifunctional backbone of the polymer, we calculated the diffusion coefficient for OH- (Exp: 2.9 × 10-5 cm2 s-1; Comp. 5.2 × 10-6 cm2 s-1) using electrochemical methods and MD simulations. Climbing-edge NEB calculations reveal a large energy barrier of 2.11 eV for Zn2+ to penetrate the polymer and identify hydroxide ions within the polymer, suggesting no undesirable Zn2+ crossover. Our findings assert the readily accessible C-C-linked cationic polymer's capacity as a solid-state electrolyte for ZABs and any anion-conducting membrane.