Search

Developing low-cost and high-efficiency bifunctional electrocatalysts for both oxygen evolution and reduction reactions is urgent to fulfill the practical application of rechargeable Zn-air batteries (ZABs). However, to explore the high catalytic performance of air electrocatalysts still remains a challenge. In response, a three-dimensionally ordered macroporous (3DOM) Co3O4 electrocatalyst is designed and synthesized through a nanocasting strategy. A well-controlled phosphorization treatment is further conducted to induce defect engineering on the resulting P-doped Co3O4–δ (3DOM P-Co3O4–δ). With the oxygen vacancy (Vo) tailoring, partial reduction from Co3+ to Co2+ is verified as the key to improving the intrinsic electrocatalytic bifunctionality. By incorporating the geometric and electronic merits, 3DOM P-Co3O4–δ possesses an ORR half-wave potential of 0.82 V and an OER overpotential of 366 mV to achieve 10 mA cm–2, which is comparable to noble-metal benchmarks. Particularly, under galvanostatic cycling measurements, ZABs using 3DOM P-Co3O4–δ containing air cathode showcase a potential gap of 0.84 V with negligible voltage fading over 250 h at 10 mA cm–2.

The utilization of mildly acidic electrolyte and corresponding Mn salt pairing unlocked a path toward highly rechargeable Zn-MnO2 batteries, but long-term feasibility of these cathode-preserving strategy under practical conditions is never verified. In this study, in-situ MnO2 electrodeposition occurring in the battery recharging process is discovered to be a side reaction that substantially nullifies the practicality of the strategy. Particularly, it is identified to be responsible for irreversibly converting the electrolyte Mn ions to electrochemically passive species and triggering battery performance deterioration. These newfound recognitions lead to the formulation of a kinetic inhibition strategy, which is executed through an unconventional cathode electrode design. Specifically, graphite nanosheets with limited surface defects are incorporated into MnO2 electrodes to hinder the rate determining Mn adsorption process and thus effectively suppress the electrodeposition reaction. The resulting thin film binder-free MnO2 electrodes achieve near-full one-electron capacity reversibly for over 600 cycles, with an average columbic efficiency of ~99.8%. Overall, this study reveals the importance of suppressing MnO2 electrodeposition in Zn-MnO2 batteries and provides a contrasting view on key factors that dictate the stability of the system.

With the rapid development of flexible and wearable electronics, flexible zinc-air battery technology attracts ever-increasing attention and is considered as one of the most promising energy storage systems. However, its practical application is still at the preliminary stage. In this review, the basic battery configurations and design principles are discussed for flexible zinc-air battery, followed by challenges and recent progresses in developing each battery component, in terms of polymer electrolyte, metal anode and air cathode. An overview of flexible zinc-air battery is provided here with the aim to present a clear picture of current research directions.

The ability to extract/insert more than one Li per formula unit has made Li-rich layered oxides (LLO) one of the most promising cathode materials. However, irreversible transformations triggered by over-delithiation such as phase transitions, oxygen release and Jahn–Teller effects of Mn3+ have limited its practical application. In this work, the irreversible processes during repetitive de/lithiation were found to be diminished by establishing a gradient cationic redox couple of Mn3+/Mn4+ in Li1.2Ni0.2Mn0.6O2. As revealed by STEM, XPS and XAS measurements, the partial substitution of O2− by F− ions promoted nearby Li/transition metal mixing and reduced the valence state of Mn on the surface. Such a configuration shifted the surface redox center towards cationic redox couple (Mn3+/Mn4+), reducing the irreversible oxygen release as well as the ensuing structure and oxidation state changes. As a result of the modification, the product delivered a discharge capacity of 203.4 mA h g−1 after 80 cycles at 0.2C and achieved capacity retention of 89.6% after 100 cycles at 0.5C. The suppressed irreversible processes during repetitive cycling were investigated through ex situ X-ray absorption energy near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy and DFT calculations, which confirmed the well-preserved oxidation states and atomic configurations in modified Li1.2Ni0.2Mn0.6O2. Overall, this research provided a new avenue to control the irreversible processes in LLO without changing the anion redox behavior of lattice O2− in the bulk area by accommodating the cationic redox couple on the surface.

Deploying the application of Au-based catalysts directly on CO2 reduction reactions (CO2 RR) relies on the simultaneous improvement of mass activity (usually lower than 10 mA mg-1Au at -0.6 V) and selectivity. To achieve this target, we herein manipulate the interface of small-size Au (3.5 nm) and CeO2 nanoparticles through adjusting the surface charge of Au and CeO2 . The well-regulated interfacial structure not only guarantees the utmost utilization of Au, but also enhances the CO2 adsorption. Consequently, the mass activity (CO) of the optimal AuCeO2 /C catalyst reaches 139 mA mg-1Au with 97 % CO faradaic efficiency (FECO ) at -0.6 V. Moreover, the strong interaction between Au and CeO2 endows the catalyst with excellent long-term stability. This work affords a charge-guided approach to construct the interfacial structure for CO2 RR and beyond.

Simultaneously improving energy efficiency (EE) and material stability in electrochemical CO2 conversion remains an unsolved challenge. Among a series of ternary Sn-Ti-O electrocatalysts, 3D ordered mesoporous (3DOM) Sn0.3 Ti0.7 O2 achieves a trade-off between active-site exposure and structural stability, demonstrating up to 71.5 % half-cell EE over 200 hours, and a 94.5 % Faradaic efficiency for CO at an overpotential as low as 430 mV. DFT and X-ray absorption fine structure analyses reveal an electron density reconfiguration in the Sn-Ti-O system. A downshift of the orbital band center of Sn and a charge depletion of Ti collectively facilitate the dissociative adsorption of the desired intermediate COOH* for CO formation. It is also beneficial in maintaining a local alkaline environment to suppress H2 and formate formation, and in stabilizing oxygen atoms to prolong durability. These findings provide a new strategy in materials design for efficient CO2 conversion and beyond.

Zn-based electrochemistry has recently been considered as the most promising family to challenge the dominant status of Li-based battery technologies. Besides its more abundant reserves, the modera...

The notorious shuttling behaviors and sluggish conversion kinetics of the intermediate lithium polysulfides (LPS) are hindering the practical application of lithium sulfur (Li-S) batteries. Herein, an ultrafine, amorphous, and oxygen-deficient niobium pentoxide nanocluster embedded in microporous carbon nanospheres (A-Nb2O5-x@MCS) was developed as a multifunctional sulfur immobilizer and promoter toward superior shuttle inhibition and conversion catalyzation of LPS. The A-Nb2O5-x nanocluster implanted framework uniformizes sulfur distribution, exposes vast active interfaces, and offers a reduced ion/electron transportation pathway for expedited redox reaction. Moreover, the low crystallinity feature of A-Nb2O5-x manipulates the LPS chemical affinity, while the defect chemistry enhances the intrinsic conductivity and catalytic activity for rapid electrochemical conversions. Attributed to these superiorities, A-Nb2O5-x@MCS delivers good Li-S battery performances, that is, high areal capacity of 6.62 mAh cm-2 under high sulfur loading and low electrolyte/sulfur ratio, superb rate capability, and cyclability over 1200 cycles with an ultralow capacity fading rate of 0.024% per cycle. This work provides a synergistic regulation on crystallinity and oxygen deficiency toward rapid and durable sulfur electrochemistry, holding a great promise in developing practically viable Li-S batteries and enlightening material engineering in related energy storage and conversion areas.

The first-cycle behavior of layered Li-rich oxides, including Li2MnO3 activation and cathode electrolyte interphase (CEI) formation, significantly influences their electrochemical performance. However, the Li2MnO3 activation pathway and the CEI formation process are still controversial. Here, the first-cycle properties of xLi2MnO3·(1- x) LiNi0.3Co0.3Mn0.4O2 ( x = 0, 0.5, 1) cathode materials were studied with an in situ electrochemical quartz crystal microbalance (EQCM). The results demonstrate that a synergistic effect between the layered Li2MnO3 and LiNi0.3Co0.3Mn0.4O2 structures can significantly affect the activation pathway of Li1.2Ni0.12Co0.12Mn0.56O2, leading to an extra-high capacity. It is demonstrated that Li2MnO3 activation in Li-rich materials is dominated by electrochemical decomposition (oxygen redox), which is different from the activation process of pure Li2MnO3 governed by chemical decomposition (Li2O evolution). CEI evolution is closely related to Li+ extraction/insertion. The valence state variation of the metal ions (Ni, Co, Mn) in Li-rich materials can promote CEI formation. This study is of significance for understanding and designing Li-rich cathode-based batteries.

Ultramicroporous carbon materials play a critical role in CO2 capture and separation, however facile approaches to design ultramicroporous carbon with controllable amount, ratio and size of pores are still challenging. Herein, a novel strategy to design carbon nanospheres with abundant, uniform, and tunable ultramicroporosity was developed based on an in-situ ionic activation methodology. The adjustable ion-exchange capacity derived from oxidative functionalization was found capable of substantially governing the ionic activation and precisely regulating the ultramicroporosity in the resultant product. An ultrahigh ultramicropore content of 95.5% was achieved for the optimally-designed carbon nanospheres, which demonstrated excellent CO2 capture performances with extremely high capacities of 1.58 mmol g−1 at typical flue gas conditions and 4.30 mmol g−1 at 25 °C and ambient pressure. Beyond that, the CO2 adsorption mechanism in ultramicropore was also investigated through molecular dynamics simulation to guide the pore size optimization. This work provides a novel and facile guideline to engineer carbon materials with abundant and tunable ultramicroporosity towards superior CO2 capture performance, which also delivers great potential in extensive applications such as water purification, catalysis, and energy storage.

Here, we report an efficient surface decorated, e.g. oxidation and nitrogen doped, cobalt sulfide (O-N-Co9S8) oxygen electrocatalyst, which shows excellent activity especially for oxygen evolution reaction (OER), and good stability over 900 charge-discharge cycles at 10 mA cm−2 in Zinc-air battery. Moreover, we found that O-N-Co9S8 was completely converted into Co3O4 after OER, showing oxide is actual active phase. Density functional theory calculations reveal the continuous exposure of oxidized surface Co sites during O-N-Co9S8 → Co3O4 is essential for its high OER activity. These Co sites promote the kinetics for OH∗ transformation to O∗ and also ensure fast O2 desorption. Once Co3O4 is generated, the high activity is contributed by its resulting characteristic surfaces. Thus, we propose and demonstrate that oxides in-situ generated during OER are more active than the directly calcined oxides. This work advances fundamental insight of metal chalcogenides “catalysts” and guides the design of active OER catalysts.

Mn and N codoped carbon materials are proposed as one of the most promising catalysts for the oxygen reduction reaction (ORR) but still confront a lot of challenges to replace Pt. Herein, a novel gas-phase migration strategy is developed for the scale synthesis of atomically dispersed Mn and N codoped carbon materials (g-SA-Mn) as highly effective ORR catalysts. Porous zeolitic imidazolate frameworks serve as the appropriate support for the trapping and anchoring of Mn-containing gaseous species and the synchronous high-temperature pyrolysis process results in the generation of atomically dispersed Mn-N

The implementation of pristine metal-organic frameworks as air electrode may spark fresh vitality to rechargeable zinc-air batteries, but successful employment is rare due to the challenges in regulating their electronic states and structural porosity. Here we conquer these issues by incorporating ligand vacancies and hierarchical pores into cobalt-zinc heterometal imidazole frameworks. Systematic characterization and theoretical modeling disclose that the ligand editing eases surmountable energy barrier for *OH deprotonation by its efficacy to steer metal d-orbital electron occupancy. As a stride forward, the selected cobalt-zinc heterometallic alliance lifts the energy level of unsaturated d-orbitals and optimizes their adsorption/desorption process with oxygenated intermediates. With these merits, cobalt-zinc heterometal imidazole frameworks, as a conceptually unique electrode, empowers zinc-air battery with a discharge-charge voltage gap of 0.8 V and a cyclability of 1250 h at 15 mA cm–2, outperforming the noble-metal benchmarks., Low intrinsic activity and accessibility of active sites limit the application of metal-organic framework as catalyst for Zn-air battery. Here, authors present a cation substitution strategy to regulate the electronic state of metal sites and modify its porosity, which enables battery operation.

The rational design of cathode host materials is significant in fulfilling high-efficiency sulfur electrochemistry as well as boosting the energy density of lithium–sulfur (Li–S) batteries. Herein, we develop a stringed “tube on cube” nanohybrid (CPZC) with a ternary hierarchical architecture, which contains a fibrous carbon skeleton, highly porous carbon cube filler, and abundant CNT tentacles as an advanced matrix for sulfur electrodes. The as-developed CPZC delivers excellent conductivity, abundant active interfaces, and strong confinement to polysulfide, and thus is capable of significantly expediting the sulfur redox kinetics and promoting battery durability. The fabricated sulfur electrode achieves a superb rate capability up to 10C, outstanding cyclability over 2000 cycles, and more importantly, excellent performance under high a sulfur loading and sparing electrolyte with a high energy density of 348.8 W h kg−1 and 327.6 W h L−1 at the system level, which reveals its potential in promoting the practical application of Li–S batteries.

Increasing both catalytic site accessibility and intrinsic activity of multishelled materials is critical to boost its efficiency for bifunctional oxygen electrocatalysis and initiate its application in metal–air batteries. Herein, a hierarchical porous double-shelled (Mg,Co)3O4 electrocatalyst with controllable Mg substitution is synthesized via a proposed in situ coordinating process. The hierarchical porosity optimizes the availability of active sites and broadens diffusion channels for oxygen species. Meanwhile, Mg substitution greatly increases electrical conductivity and realizes novel insight of tailoring lattice alkalinity. Specifically, Mg substitution positively influences oxygen electrocatalysis by inducing lattice buffer zones that promote hydroxyl detachment from nearby catalytic sites. As a result, the final hybrid of (Mg,Co)3O4 encapsulated in N-doped graphitized carbon affords superior bifunctional oxygen electrocatalytic activities, outperforming state-of-the-art noble-metal benchmarks. W...

Inspired by the excellent absorption capability of spongelike bacterial cellulose (BC), three-dimensional hierarchical porous carbon fibers doped with an ultrahigh content of N (21.2 atom %) (i.e., nitrogen-doped carbon fibers, NDCFs) were synthesized by an adsorption–swelling strategy using BC as the carbonaceous material. When used as anode materials for sodium-ion batteries, the NDCFs deliver a high reversible capacity of 86.2 mAh g–1 even after 2000 cycles at a high current density of 10.0 A g–1. It is proposed that the excellent Na+ storage performance is mainly due to the defective surface of the NDCFs created by the high content of N dopant. Density functional theory (DFT) calculations show that the defect sites created by N doping can strongly “host” Na+ and therefore contribute to the enhanced storage capacity.

In this work, a composite consisting of layered Li[Li0.2Ni0.12 Mn0.56Co0.12]O2 (LNMC) and spinel Li[Ni0.5Mn1.5]O4 (LNMO) was synthesized by a modified Pechini method. Extensive analysis was carried out to investigate the synergistic effect between the layered oxide and spinels in the composite by comparing its properties with baseline individual compounds, as well as a physical mixture of LMNC and LNMO. Comparing to the LNMC, the compsoite cathode exhibited a similar initial capacity of ∼250 mA·h/g at 0.1 C, but a much higher first-cycle effeciency, better cyclability and rate capability, attributed to the presence of spinel. The synertistic effect of integrated spinel on the microstructure, crystal strucutre, Mn oxidation states, and Li+/Ni2+ disordering of the composite was studied by X-ray absorption near edge structure (XANES), electron microscopy, and X-ray diffraction (XRD). The presence of a spinel component in the composite cathode is the origin for the improvement of cyclability and rate capabili...

In this article, we report improved capacity retention in lithium-sulfur (Li-S) batteries by replacing the conventional Polyvinylidene fluoride (PVDF) binder with inexpensive guar gum (GG). The S/GG cathode exhibits a discharge capacity of 777 mAh g−1 at 0.2 C after 150 cycles, in comparison to 491 mAh g−1 of S/PVDF cathode. FTIR results show that there is interaction between GG and sulfur species. This interaction is potentially capable of maintaining the active sulfur species, which could to a certain extent inhibit shuttling effect. What's more, GG shows limited dissolving and swelling capacity in the electrolyte and higher viscosity and hardness than those of PVDF. Such properties of GG provide the electrode with appropriate extensibility to alleviate the negative impact from the volume variation. Keywords: Lithium-sulfur batteries, Guar gum, Aqueous binder, Cycleability

The poor durability of bifunctional oxygen electrocatalysts is one main bottleneck that suppresses the widespread application of rechargeable metal-air batteries. Herein, a "ship in a bottle" design is achieved by impregnating fine transition metal dichalcogenide nanoparticles into defective carbon pores that act as interconnected nanoreactors. The erected 3D porous conductive architecture provides a "highway" for expediting charge and mass transfer. This design not only delivers a high surface-to-volume ratio to increase numbers of exposed catalytic sites but also precludes nanoparticles from aggregation during cycling owing to the pore spatial confinement effect. Therefore, the long-term plague inherent to nanocatalyst stability can be solved. Moreover, the synergistic coupling effects between defect-rich interfaces and chemical bonding derived from heteroatom-doping boost the catalytic activity and prohibit the detachment of nanoparticles for better stability. Consequently, the developed catalyst presents superior bifunctional oxygen electrocatalytic activities and durability, out-performing the best-known noble-metal benchmarks. In a practical application to rechargeable Zn-air batteries, long-term cyclability for over 340 h is realized at a high current density of 25 mA cm-2 in ambient air while retaining an intact structure. Such a universal "ship in a bottle" design offers an appealing and instructive model of nanomaterial engineering for implementation in various fields.

Dual ion batteries are one of the emerging substitutes for lithium ion batteries with high operating voltages and energy density, but their recent advancements have been limited by unsatisfactory cathode stability in the form of irreversible exfoliation. To address this bottleneck, a strategy to selectively incorporate carboxylic anhydride functionality between graphite layers is developed to enforce a stabilizing effect to the crystal structure, which allows for effective performance optimization through particles downsizing and interlayer distance tuning without the compromises of intercalation site disruption and voltage deduction. The resulting graphite cathode experienced significant capacity, rate capability and stability improvements, achieving a highly reversible capacity of 91.2 mAh g−1 at 2 C, which then cycled consistently for over 1,000 cycles. Overall, this work removes a major handicap that has limited the development of dual ion batteries and demonstrates a design pathway for high performance graphite intercalation cathode suitable for anion intercalation with both enhanced stability and discharge capacity.

Desirable sulfur electrochemistry strongly relies on host-guest interactions, which calls for rational designs on the surface fine structure of sulfur reservoir materials. Herein, we for the first time, explore the coordinative unsaturation in ferric hexacyanoferrate (FeHCF) for sulfur immobilization and catalyzation towards improved lithium-sulfur (Li–S) batteries. A simple ammonia etching treatment is implemented to selectively remove FeIII–H2O moieties, leaving vast coordinatively unsaturated Fe sites with a simultaneous establishment of considerable mesoporosity in the activated matrix (denoted as FeHCF-A). As a sulfur-host, the massive meso-scale channels endow FeHCF-A with abundant active interfaces and ion/mass transfer pathways, while more importantly, the coordinatively unsaturated Fe sites are revealed with higher adsorbability and conversion catalytic activity to polysulfides. Attributed to theses chemical and structural superiorities, the as-developed FeHCF-A enables a fast, stable, and efficient sulfur electrochemistry, e.g., good rate capability up to 5C and excellent cyclability with an ultralow decay rate of 0.024% per cycle over 500 cycles, as well as a commendable areal capacity of 4.5 mAh cm−2 under high sulfur loading. This work affords a new and insightful perspective of coordinative chemistry for material engineering in Li–S batteries as well as other related fields.

Na0.67-xKxMn0.72Ni0.14Co0.14O2 (x = 0, 0.01, 0.03, 0.05) layered cathodes were prepared as the cathode of sodium-ion batteries by a co-precipitation method. The effects of K+ doping were investigated, as the doping amount of K+ could change the structure and finally influence the electrochemical performances. The appropriate content of K+ could expand the Na+ diffusion channel and improve both the cycleability and rate performance. The Na0.66K0.01Mn0.72Ni0.14Co0.14O2 composite showed enhanced cycle performance with an initial capacity of 141 mAh g−1 and 112 mAh g−1 maintained after 100 cycles at 2.0C rate. Meanwhile, the pristine Na0.67Mn0.72Ni0.14Co0.14O2 (without K+ doping) showed a lower initial capacity of 112 mAh g−1 with 67 mAh g−1 retained after 100 cycles at 2.0C. What’s more, the Na0.66K0.01Mn0.72Ni0.14Co0.14O2 sample delivered a high reversible capacity of 88.4 mAh g−1 even at 8.0C, which was much higher than that of Na0.67Mn0.72Ni0.14Co0.14O2 (35 mAh g−1). These results demonstrated that the K+ doping could be a feasible strategy to enhance the performance of layered cathode for sodium ion battery.

Layered Li1.3Mn0.58Ni0.12Co0.11O2+δ, a solid solution of 0.53 Li2MnO3⋅0.47 LiMn0.4Ni0.3Co0.3O2, has been successfully synthesized by using an improved solvothermal strategy and used as the cathode material of a Li-ion battery. The pure phase of the layered structure is characterized by using X-ray diffraction and Raman spectroscopy. Electrochemical tests demonstrate that as-synthesized layered Li1.3Mn0.58Ni0.12Co0.11O2+δ exhibits high discharge capacities of 349.4, 322.4, 304.6, and 291.7 mAh g−1 at 0.1, 0.2, 0.5, and 1 C rates, respectively. Such high reversible capacities could be ascribed to the enrichment of oxygen in the materials, which was evidenced clearly by a potential plateau below 3.0 V in the discharge process and originated form the electrochemical oxygen reduction.

Li-rich materials, Li1.140Mn0.622Ni0.114Co0.124O2, of a layered/spinel heterostructure were synthesized by a one-step solvothermal route with subsequent moderate heat treatment. The as-prepared materials consist of hierarchical microspheres and an integral layered/spinel heterostructure. The effects of calcination time on both the structure and electrochemical performance of materials have been studied systematically. It has been found that the formation of the spinel structure could be controlled by adjusting the calcination time at 650 °C, and the materials calcined at this temperature for 24 hours present the optimal electrochemical performance. High initial efficiencies of 101% at 0.2C and 92% at 2C, as well as high discharge capacities of 280, 256, 234 and 206 mA h g−1 respectively at 1C, 2C, 5C and 10C have been achieved. The empty 16c octahedral site and 3D Li+ diffusion channel provided by the spinel have been regarded as the key to the improvement of electrochemical performances.

Guar gum (GG) has been applied as a binder for layered lithium-rich cathode materials of Li-ion batteries for the first time. Compared with the conventional PVDF binder, electrodes with GG as the binder exhibit significantly suppressed voltage and capacity fading. This study has introduced a multi-functional binder for layered lithium-rich cathode materials.

It’s well known that ion-doping could modify the crystal structure and adjust the corresponding performance of cathode, but how the doped ions affect the structure formations during high-temperature calcination still remains a daunting challenge, which is critical for the ideal controlled synthesis. In our pervious study, we have found that the cationic ion doping can both tune the single phase structure and adjust the phase ratio in layer-tunnel Na0.6MnO2. And in the present study, we furtherly try to track the influence of varied Fe3+ and Ti4+ on the formation process of layer-tunnel hybrid structures and focus on the thermal behavior, structure evolution and morphology change. The kinetics-preferred layered structure can be detected at the initial stage and transfer to the thermodynamic-stable tunnel structure at increased temperature. The Fe3+ can stabilize the formed layer structure while the Ti4+ promote the latter transformation. More interesting, the Ti4+ plays a dominant role when Fe3+/Ti4+ were co-doped. The impressive results can be related with the more orderly structure of layer phase and distorted coordination in tunnel phase. This research correlates the synthesis process and the final structure, as well as the ultimate electrochemical performance, which shed new light on the development of advanced oxides cathode.

Zn-air batteries (ZABs) represent promising candidates for the next generation energy conversion and storage systems based on their superior features to those of lithium-ion batteries, including high theoretical energy density, low cost, and high safety. However, their further development and application is severely lagged due to the lack of high efficient and durable bifunctional oxygen electrocatalysts. The widely applied carbon-based catalysts are thermodynamically instable during battery charging. Herein, TiC supported amorphous MnOx (a-MnOx/TiC) is reported for the first time as electrocatalyst for the corrosion resistant oxygen electrodes of ZABs. A-MnOx/TiC delivers a remarkable activity and stability toward both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with a high half-wave potential (0.8 V) for ORR and a low potential (1.56 V) at 10 mA cm−2 for OER, which far outperforms the state of the art ORR catalyst (Pt/C) and OER catalyst (IrO2), as well as the Pt/C-IrO2 and a-MnOx/C bifunctional catalysts. The excellent bifunctional activity of a-MnOx/TiC can be attributed to the efficient synergistic effect between the active amorphous MnOx catalyst and the highly conductive and stable TiC support. More impressively, a-MnOx/TiC demonstrates an outstanding electrochemical stability in strong alkaline electrolyte under OER condition in contrast to the readily oxidized carbon-based a-MnOx/C catalysts. ZAB with a-MnOx/TiC delivers a greater discharge performance with a peak power density of 217.1 mW cm−2 than that of Pt/C-based ZAB, and a surpassing discharge and charge cycling performance and stability to ZABs with Pt/C-IrO2 and a-MnOx/C. Furthermore, a-MnOx/TiC can be applied for solid-state ZABs which exhibit excellent mechanical flexibility and cycle stability under their flat and bent states. The a-MnOx/TiC bifunctional electrocatalyst with extraordinarily high activity and electrochemical stability provides a promising approach for exploring corrosion resistant electrocatalysts for Zn-air batteries with high efficiency and long-term cycling stability.

Exceptional and durable catalysts for Zinc-air batteries are plagued by nanoparticle agglomeration. As a proof-of-concept, we designed carbon-pore-sheathed cobalt nanoseeds by loading cobalt nanoparticles into N-doped defective carbon pores. Introduced N-doping, Co–N–C bond and graphitic/graphenic carbon defects endow the catalyst with exceptional catalytic activity. Most importantly, the design of Co confined within carbon pores effectively solved the dilemma of nanomaterial stability. By balancing the high catalytic activity and stable cyclability, this unique catalyst is among the outstanding bifunctional catalysts, with a high ORR half-wave potential of 0.847 V and a low OER potential at 10 mA/cm2 of 1.593 V. As demonstrated in the full cell, a peak power density of 135 mW/cm2 at a current density of 200 mA/cm2 and 450 h of stable cycling performance without fading at a current density of 30 mA/cm2 was delivered.

Li metal is considered as an ideal anode for Li-based batteries. Unfortunately, the growth of Li dendrites during cycling leads to an unstable interface, a low coulombic efficiency, and a limited cycling life. Here, a novel approach is proposed to protect the Li-metal anode by using a uniform agarose film. This natural biopolymer film exhibits a high ionic conductivity, high elasticity, and chemical stability. These properties enable a fast Li-ion transfer and feasiblity to accomodate the volume change of Li metal, resulting in a dendrite-free anode and a stable interface. Morphology characterization shows that Li ions migrate through the agarose film and then deposit underneath it. A full cell with the cathode of LiFPO4 and an anode contaning the agarose film exhibits a capacity retention of 87.1% after 500 cycles, much better than that with Li foil anode (70.9%) and Li-deposited Cu anode (5%). This study provides a promising strategy to eliminate dendrites and enhance the cycling ability of lithium-metal batteries through coating a robust artificial film of natural biopolymer on lithium-metal anode.

Multishelled hollow structured transition metal oxides (TMOs) are highly potential materials for high energy density energy storage due to their high volumetric energy density, reduced aggregation of nanosized subunits, and excellent capacity and durability. However, traditional synthetic methods of TMOs generally require complicated steps and lack compositional/morphological adjustability. Herein, a general and straightforward strategy is developed to synthesize multishelled porous hollow microspheres, which is constituted of nanosize primary TMO particles, using metal acetate polysaccharide microspheres as the precursor. This universal method can be applied to design TMOs' hollow spheres with tunable shell numbers and composition. The hierarchical porous quadruple-shelled hollow microspheres with nanosized Ni-Co-Mn oxide demonstrate an increased number of active sites, boosted rate capability, enhanced volumetric energy density, and showed great tolerance toward volume expansion upon cycling, thus exhibiting excellent Li

The highly oxidative operating conditions of rechargeable zinc-air batteries causes significant carbon-support corrosion of bifunctional oxygen electrocatalysts. Here, a new strategy for the catalyst support design focusing on oxygen vacancy (OV)-rich, low-bandgap semiconductor is proposed. The OVs promote the electrical conductivity of the oxide support, and at the same time offer a strong metal-support interaction (SMSI), which enables the catalysts to have small metal size, high catalytic activity, and high stability. The strategy is demonstrated by successfully synthesizing ultrafine Co-metal-decorated 3D ordered macroporous titanium oxynitride (3DOM-Co@TiOx Ny ). The 3DOM-Co@TiOx Ny catalyst exhibits comparable activities for oxygen reduction and evolution reactions, but much higher cycling stability than noble metals in alkaline conditions. The zinc-air battery using this catalyst delivers an excellent stability with less than 1% energy efficiency loss over 900 charge-discharge cycles at 20 mA cm-2 . The high stability is attributed to the strong SMSI between Co and 3DOM-TiOx Ny which is verified by density functional theory calculations. This work sheds light on using OV-rich semiconductors as a promising support to design efficient and durable nonprecious electrocatalysts.