Trimetallic Mn‐Fe‐Ni Oxide Nanoparticles Supported on Multi‐Walled Carbon Nanotubes as High‐Performance Bifunctional ORR/OER Electrocatalyst in Alkaline Media

Discovering precious metal‐free electrocatalysts exhibiting high activity and stability toward both the oxygen reduction (ORR) and the oxygen evolution (OER) reactions remains one of the main challenges for the development of reversible oxygen electrodes in rechargeable metal–air batteries and reversible electrolyzer/fuel cell systems. Herein, a highly active OER catalyst, Fe_0.3Ni_0.7O_X supported on oxygen‐functionalized multi‐walled carbon nanotubes, is substantially activated into a bifunctional ORR/OER catalyst by means of additional incorporation of MnO_X. The carbon nanotube‐supported trimetallic (Mn‐Ni‐Fe) oxide catalyst achieves remarkably low ORR and OER overpotentials with a low reversible ORR/OER overvoltage of only 0.73 V, as well as selective reduction of O₂ predominantly to OH^?. It is shown by means of rotating disk electrode and rotating ring disk electrode voltammetry that the combination of earth‐abundant transition metal oxides leads to strong synergistic interactions modulating catalytic activity. The applicability of the prepared catalyst for reversible ORR/OER electrocatalysis is evaluated by means of a four‐electrode configuration cell assembly comprising an integrated two‐layer bifunctional ORR/OER electrode system with the individual layers dedicated for the ORR and the OER to prevent deactivation of the ORR activity as commonly observed in single‐layer bifunctional ORR/OER electrodes after OER polarization.     

A Composite of Carbon‐Wrapped Mo2C Nanoparticle and Carbon Nanotube Formed Directly on Ni Foam as a High‐Performance Binder‐Free Cathode for Li‐O2 Batteries

Cathode design is indispensable for building Li‐O₂ batteries with long cycle life. A composite of carbon‐wrapped Mo₂C nanoparticles and carbon nanotubes is prepared on Ni foam by direct hydrolysis and carbonization of a gel composed of ammonium heptamolybdate tetrahydrate and hydroquinone resin. The Mo₂C nanoparticles with well‐controlled particle size act as a highly active oxygen reduction reactions/oxygen evolution reactions (ORR/OER) catalyst. The carbon coating can prevent the aggregation of the Mo₂C nanoparticles. The even distribution of Mo₂C nanoparticles results in the homogenous formation of discharge products. The skeleton of porous carbon with carbon nanotubes protrudes from the composite, resulting in extra voids when applied as a cathode for Li‐O₂ batteries. The batteries deliver a high discharge capacity of ≈10 400 mAh g^?1 and a low average charge voltage of ≈4.0 V at 200 mA g^?1. With a cutoff capacity of 1000 mAh g^?1, the Li‐O₂ batteries exhibit excellent charge–discharge cycling stability for over 300 cycles. The average potential polarization of discharge/charge gaps is only ≈0.9 V, demonstrating the high ORR and OER activities of these Mo₂C nanoparticles. The excellent cycling stability and low potential polarization provide new insights into the design of highly reversible and efficient cathode materials for Li‐O₂ batteries.     

A Universal Strategy Toward Low-Cost Aqueous Sulfur–Iodine Batteries

Rechargeable aqueous batteries with non-toxic and non-flammable features are promising candidates for large-scale energy storage. However, their practical applications are impeded by the insufficient electrochemical stability windows of aqueous electrolytes and intrinsic drawbacks of current electrodes. Herein, an aqueous sulfur–iodine chemistry that can be deployed in aqueous battery systems by employing water-in-bisalt (WiBS) electrolyte, sulfur composite anode, and iodine composite cathode is demonstrated. The freestanding iodine/carbon cloth cathode and halide-containing WiBS electrolyte can support the continuous I⁺/I⁰ reaction by forming interhalogen. Meanwhile, the highly-concentrated electrolyte and inorganic-based solid electrolyte interphase can effectively suppress the dissolution/diffusion of polysulfides, thus realizing S/S_x²⁻ conversion reactions on the anode. Therefore, the as-assembled aqueous sulfur–iodine batteries based on S/S_x²⁻ and I⁺/I⁰ redox couples can deliver a high energy density of 158.7 Wh kg⁻¹ with a considerable cycling performance and safety. Furthermore, this chemistry can be further extended to multivalent ion-based battery systems. As demonstration models, Ca-based and Al-based aqueous sulfur–iodine batteries are also fabricated, which provide a new avenue towards the development of aqueous batteries for low-cost and highly safe energy storage.     

High-Density Atomic Fe–N4/C in Tubular,Biomass-Derived,Nitrogen-Rich Porous Carbon as Air-Electrodes for Flexible Zn–Air Batteries

Developing low-cost single-atom catalysts (SACs) with high-density active sites for oxygen reduction/evolution reactions (ORR/OER) are desirable to promote the performance and application of metal–air batteries. Herein, the Fe nanoparticles are precisely regulated to Fe single atoms supported on the waste biomass corn silk (CS) based porous carbon for ORR and OER. The distinct hierarchical porous structure and hollow tube morphology are critical for boosting ORR/OER performance through exposing more accessible active sites, providing facile electron conductivity, and facilitating the mass transfer of reactant. Moreover, the enhanced intrinsic activity is mainly ascribed to the high Fe single-atom (4.3 wt.%) loading content in the as-synthesized catalyst.Moreover, the ultra-high N doping (10 wt.%) can compensate the insufficient OER performance of conventional Fe N C catalysts. When as-prepared catalysts are assembled as air-electrodes in flexible Zn–air batteries, they perform a high peak power density of 101 mW cm⁻², a stable discharge–charge voltage gap of 0.73 V for >44 h, which shows a great potential for Zinc–air battery. This work provides an avenue to transform the renewable low-cost biomass materials into bifunctional electrocatalysts with high-density single-atom active sites and hierarchical porous structure.     

MXene‐Bonded Flexible Hard Carbon Film as Anode for Stable Na/K‐Ion Storage

Hard carbon (HC) is a promising anode material for sodium‐ion batteries (SIBs) and potassium‐ion batteries (PIBs), but the volume change during the insertion/extraction of Na⁺ or K⁺ limits the cycle life, especially for PIBs due to the large ion size of K⁺. Moreover, the conventional anodes fabricated through the coating method cannot satisfy the requirement of flexible devices. Here, it is shown that 2D carbide flakes of Ti₃C₂T_x MXene can be used as multifunctional conductive binders for flexible HC electrodes. The use of MXene nanosheets eliminates the need for all the electrochemically inactive components in the conventional polyvinylidene fluoride–bonded HC electrode, including polymer binders, conductive additives, and current collectors. In MXene‐bonded HC electrodes, conductive and hydrophilic MXene 2D nanosheets construct a 3D network, which can effectively stabilize the electrode structure and accommodate the volume expansion of HC during the charge/discharge process, leading to an enhanced electrode capacity and excellent cycle performance as anodes for both SIBs and PIBs. Benefiting from the 3D conductive network, the MXene‐bonded HC film electrodes also present improved rate capability, indicating MXene is a very promising multifunctional binder for next‐generation flexible secondary rechargeable batteries.     

Regulating Graphitic Microcrystalline and Single-Atom Chemistry in Hard Carbon Enables High-Performance Potassium Storage

Hard carbon (HC) has attracted considerable research interest as the most promising anode for potassium-ion batteries (PIBs) due to its tunable interlayer spacing and abundant voids to accommodate K⁺. However, the practical application of hard carbon is severely hampered by low initial Coulombic efficiency (ICE) and high plateau potential. Herein, a manganese ion-catalyzed pyrolysis strategy is explored to regulate the graphitic microcrystalline structure and localized electron distribution in hard carbon that greatly improve K⁺ plateau storage and ICE. Systematic experimental measurements, in situ/ex situ observations, dynamic analysis, and density functional theory calculations elucidate that the introduction of Mn²⁺ ions could catalyze the formation of short-ordered graphitic nanodomains in hard carbon to provide abundant insertions of K⁺, and meanwhile induce localized electron distribution through the Mn─N₃─C coordination structure to enable dynamic K⁺ diffusion and electron transfer kinetics. Consequently, the modulated hard carbon exhibits a high low-potential–plateau capacity, excellent rate capability, and high initial Coulombic efficiency in potassium half-cell configurations. More importantly, the charge storage mechanism of “adsorption–intercalation” is proposed based on the correlation between carbon structures and discharge/charge plateau. This work provides an in-depth insight into the fundamentals of microstructure regulation of hard carbon anode for high-performance PIBs.     

Dual-Phasic Carbon with Co Single Atoms and Nanoparticles as a Bifunctional Oxygen Electrocatalyst for Rechargeable Zn–Air Batteries

The great interest in rechargeable Zn–air batteries (ZABs) arouses extensive research on low-cost, high-active, and durable bifunctional electrocatalysts to boost the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). It remains a great challenge to simultaneously host high-active and independent ORR and OER sites in a single catalyst. Herein a dual-phasic carbon nanoarchitecture consisting of a single-atom phase for the ORR and nanosized phase for the OER is proposed. Specifically, single Co atoms supported on carbon nanotubes (single-atom phase) and nanosized Co encapsulated in zeolitic-imidazole-framework-derived carbon polyhedron (nanosized phase) are integrated together via carbon nanotube bridges. The obtained dual-phasic carbon catalyst shows a small overpotential difference of 0.74 V between OER potential at 10 mA cm⁻² and ORR half-wave potential. The ZAB based on the bifunctional catalyst demonstrates a large power density of 172 mW cm⁻². Furthermore, it shows a small charge-discharge potential gap of 0.51 V at 5 mA cm⁻² and outstanding discharge-charge cycling durability. This study provides a feasible design concept to achieve multifunctional catalysts and promotes the development of rechargeable ZABs.     

Optimized Cathode for High-Energy Sodium-Ion Based Dual-Ion Full Battery with Fast Kinetics

The most used systems based on the graphite-based cathode show unsatisfactory performance in dual-ion batteries. Developing new type cathode materials with high capacity for new type anions storage is an effective way to improve the total performance of dual-ion batteries. Herein, a protonated polyaniline (P-PANI) cathode is prepared to realize efficient and stable storage of ClO₄^–, and a high reversible capacity of 143 mAh g⁻¹ at 0.2 A g⁻¹ after 200 cycles can be obtained, which is competitive compared with common graphite cathodes. In addition, the highly reversible coordination storage mechanism between ClO₄⁻ and P-PANI cathode is indicated, rather than the labored intercalation reactions between PF₆⁻ and graphite. Subsequently, a full cell (P-PANI//N-PDHC) fabricated with a P-PANI cathode and hard carbon anode (N-PDHC) can deliver a high energy density of 284 Wh kg^–1 for 2000 cycles at 2 A g^–1, and the relevant pouch-type full cell can easily power a smartphone. In general, this work may promote the exploitation of sodium-based dual-ion batteries in practical application.     

Low-Cost Zinc Substitution of Iron-Based Prussian Blue Analogs as Long Lifespan Cathode Materials for Fast Charging Sodium-Ion Batteries

Iron-based Prussian blue analogs (Fe-PBAs) are extensively studied as promising cathode materials for rechargeable sodium-ion batteries owing to their high theoretical capacity, low-cost and facile synthesis method. However, Fe-PBAs suffer poor cycle stability and low specific capacity due to the low crystallinity and irreversible phase transition during excess sodium-ion storage. Herein, a modified co-precipitation method to prepare highly crystallized PBAs is reported. By introducing an electrochemical inert element (Zn) to substitute the high-spin Fe in the Fe-PBAs (ZnFeHCF-2), the depth of charge/discharge is rationally controlled to form a highly reversible phase transition process for sustainable sodium-ion storage. Minor lattice distortion and highly reversible phase transition process of ZnFeHCF-2 during the sodium-ions insertion and extraction are proved by in-situ tests, which have significantly impacted the cycling stability. The ZnFeHCF-2 shows a remarkably enhanced cycling performance with capacity retention of 58.5% over 2000 cycles at 150 mA g⁻¹ as well as superior rate performance up to 6000 mA g⁻¹ (fast kinetics). Furthermore, the successful fabrication of the full cell on the as-prepared cathode and commercial hard carbon anode demonstrates their potential as high-performance electrode materials for large-scale energy storage systems.     

Engineering Crystallinity and Oxygen Vacancies of Co(II) Oxide Nanosheets for High Performance and Robust Rechargeable Zn–Air Batteries

Efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) processes highly rely on the rational design and synthesis of high-performance electrocatalysts. Herein, comprehensive characterizations and density functional theory (DFT) calculations are combined to verify the important roles of the crystallinity and oxygen vacancy levels of Co(II) oxide (CoO) on ORR and OER activities. A facile and controllable vacuum-calcination strategy is utilized to convert Co(OH)₂ into oxygen-defective amorphous-crystalline CoO (namely ODAC-CoO) nanosheets. With the carefully controlled crystallinity and oxygen vacancy levels, the optimal ODAC-CoO sample exhibits dramatically enhanced ORR and OER electrocatalytic activities compared with the pure crystalline CoO counterpart. The assembled liquid and quasi-solid-state Zn–air batteries with ODAC-CoO as cathode material achieve remarkable specific capacity, power density, and excellent cycling stability, outperforming the benchmark Pt/C + IrO₂ catalysts. This study theoretically proposes and experimentally demonstrates that the simultaneous introduction of amorphous structures and oxygen vacancies could be an effective avenue towards high-performance electrocatalytic ORR and OER.     

Bifunctional Covalent Organic Framework-Derived Electrocatalysts with Modulated p-Band Centers for Rechargeable Zn–Air Batteries

Fine control over the physicochemical structures of carbon electrocatalysts is important for improving the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in rechargeable Zn–air batteries. Covalent organic frameworks (COFs) are considered good candidate carbon materials because their structures can be precisely controlled. However, it remains a challenge to impart bifunctional electrocatalytic activities for both the ORR and OER to COFs. Herein, a pyridine-linked triazine covalent organic framework (PTCOF) with well-defined active sites and pores is readily prepared under mild conditions, and its electronic structure is modulated by incorporating Co nanoparticles (CoNP-PTCOF) to induce bifunctional electrocatalytic activities for the ORR and OER. The CoNP-PTCOF exhibits lower overpotentials for both ORR and OER with outstanding stability. Computational simulations find that the p-band center of CoNP-PTCOF down-shifted by charge transfer, compared to pristine PTCOF, facilitate the adsorption and desorption of oxygen intermediates on the pyridinic carbon active sites during the reactions. The Zn–air battery assembled with bifunctional CoNP-PTCOF exhibits a small voltage gap of 0.83 V and superior durability for 720 cycles as compared with a battery containing commercial Pt/C and RuO₂. This strategy for modulating COF electrocatalytic activities can be extended for designing diverse carbon electrocatalysts.     

All-Climate Iron-Based Sodium-Ion Full Cell for Energy Storage

The anode materials for sodium-ion batteries (SIBs) such as soft carbon, hard carbon, or alloys suffer from low specific capacity, poor rate capability, and high cost. Various transition metal oxides materials possess high specific capacity and suitable working potential, however, huge volume change and unstable electrode/electrolyte interfaces limit their practical applications. Herein, an ultrathin carbon-coated iron-based borate, (Fe₃BO₅), as an anode material for SIBs is reported. The carbon coated Fe₃BO₅ composite as an anode material possesses a reversible specific capacity of 548 mAh g⁻¹ with a high initial coulombic efficiency of 72.6% at a current density of 50 mA g⁻¹, and maintains a capacity retention ratio of 99% after 1000 cycles at 2000 mA g⁻¹. Moreover, this anode can work well over a wide temperature range (-40–60 °C). Furthermore, a sodium-ion full cell using this anode coupling with iron-based cathode (Na₃Fe₂(PO₄)₂(P₂O₇)@rGO) cathode is fabricated, which exhibits a wide operating temperature range from −40 to 60 °C with a maximum energy density of 175 Wh Kg⁻¹ and a maximum power density of 1680 W Kg⁻¹. Most importantly, this full-cell configuration is low-cost due to its inexpensive iron based raw material for both anode and cathode.     

MO‐Co@N‐Doped Carbon (M = Zn or Co): Vital Roles of Inactive Zn and Highly Efficient Activity toward Oxygen Reduction/Evolution Reactions for Rechargeable Zn–Air Battery

A highly efficient bifunctional oxygen catalyst is required for practical applications of fuel cells and metal–air batteries, as oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are their core electrode reactions. Here, the MO‐Co@N‐doped carbon (NC, M = Zn or Co) is developed as a highly active ORR/OER bifunctional catalyst via pyrolysis of a bimetal metal–organic framework containing Zn and Co, i.e., precursor (CoZn). The vital roles of inactive Zn in developing highly active bifunctional oxygen catalysts are unraveled. When the precursors include Zn, the surface contents of pyridinic N for ORR and the surface contents of Co–N_x and Co³⁺/Co²⁺ ratios for OER are enhanced, while the high specific surface areas, high porosity, and high electrochemical active surface areas are also achieved. Furthermore, the synergistic effects between Zn‐based and Co‐based species can promote the well growth of multiwalled carbon nanotubes (MWCNTs) at high pyrolysis temperatures (≥700 °C), which is favorable for charge transfer. The optimized CoZn‐NC‐700 shows the highly bifunctional ORR/OER activity and the excellent durability during the ORR/OER processes, even better than 20 wt% Pt/C (for ORR) and IrO₂ (for OER). CoZn‐NC‐700 also exhibits the prominent Zn–air battery performance and even outperforms the mixture of 20 wt% Pt/C and IrO₂.     

MXene-Based Anode-Free Magnesium Metal Battery

Rechargeable magnesium batteries (RMBs) are promising next-generation low-cost and high-energy devices. Among all RMBs, anode-free magnesium metal batteries that use in situ magnesium-plated current collectors as negative electrodes can afford optimal energy densities. However, anode-free magnesium metal batteries have remained elusive so far, as their practical application is plagued by low Mg plating/stripping efficiency due to nonuniform Mg deposition on conventional anode current collectors. Herein, for the first time, an anode-free Mg-metal battery is developed by employing a 3D MXene (Ti₃C₂T_x) film with horizontal Mg electrodeposition. The magnesiophilic oxygen and reactive fluorine terminations in MXene enable an enriched local magnesium-ion concentration and a durable magnesium fluoride-rich solid electrolyte interphase on the Ti₃C₂T_x film surface. Meanwhile, Ti₃C₂T_x MXene exhibits a high lattice geometrical fit with Mg (≈96%) to guide the horizontal electrodeposition of Mg. Consequently, the developed Ti₃C₂T_x film achieves reversible Mg plating/stripping with high Coulombic efficiencies (>99.4%) at high-current-density (5.0 mA cm⁻²) and high-Mg-utilization (50%) conditions. When this Ti₃C₂T_x film is coupled with a pre-magnesized Mo₆S₈ cathode, the anode-free Mg-metal full-cell prototype exhibits a volumetric energy density five times higher than its standard Mg-metal counterpart. This work provides insights into the rational design of anode current collectors to guide horizontal Mg electrodeposition for anode-free Mg metal batteries.     

Uniformly MXene-Grafted Eutectic Aluminum-Cerium Alloys as Flexible and Reversible Anode Materials for Rechargeable Aluminum-Ion Battery

Aluminum is an attractive anode material in aqueous multivalent-metal batteries for large-scale energy storage because of its high Earth abundance, low cost, high theoretic capacity, and safety. However, state-of-the-art aqueous aluminum-ion batteries based on aluminum anode persistently suffer from poor rechargeability and low coulombic efficiency due to irreversibility of aluminum stripping/plating and dendrite growth. Here eutectic aluminum-cerium alloys in situ grafted with uniform ultrathin MXene (MXene/E-Al₉₇Ce₃) as flexible, reversible, and dendrite-free anode materials for rechargeable aqueous aluminum-ion batteries is reported. As a result of the MXene serving as stable solid electrolyte interphase to inhibit side reactions and the lamella-nanostructured E-Al₉₇Ce₃ enabling directional Al stripping and deposition by making use of symbiotic α-Al metal and intermetallic Al₁₁Ce₃ lamellas, the MXene/E-Al₉₇Ce₃ hybrid electrodes exhibit reversible and dendrite-free Al stripping/plating with low voltage polarization of ± 54 mV for ≥1000 h in a low-oxygen-concentration aqueous aluminum trifluoromethanesulfonate (Al(OTF)₃) electrolyte. These superior electrochemical properties endow soft-package aluminum-ion batteries assembled with MXene/E-Al₉₇Ce₃ anode and Al_xMnO₂ cathode to have high initial discharge capacity of ≈360 mAh g⁻¹ at 1 A g⁻¹, and retain ≈85% after 500 cycles, along with the coulombic efficiency of as high as 99.5%.     

Revisiting the Role of the Triple-Phase Boundary in Promoting the Oxygen Reduction Reaction in Aluminum–Air Batteries

The decomposition, electron transfer, and protonation of oxygen molecules are typically assumed to be the rate-limiting steps of the oxygen reduction reactions (ORR), and the activation energy barriers of these reactions can be surmounted using catalysts. In this study, the physical rate-limiting step of the ORR consists of the adsorption of gaseous oxygen molecules at the liquid–solid phase boundary, indicating that the formation of a gas–liquid–solid triple-phase boundary (TPB) is important for accelerating the ORR kinetics. This is experimentally confirmed by analyzing the ORR in aluminum–air batteries. Moreover, the formation of a TPB using the hierarchical pores of sparked reduced graphene oxide is demonstrated, which serve as the cathode, and the remarkable electrochemical performance of the fabricated battery is presented. These findings can be used to accelerate the ORR kinetics by maximizing the TPB, particularly in aluminum–air batteries.     

Optimizing Kinetics for Enhanced Potassium-Ion Storage in Carbon-Based Anodes

The sluggish kinetics in traditional graphite anode greatly limits its fast-charging capability, which is critically important for commercialization of potassium ion batteries (PIBs). Hard carbon possesses randomly oriented pseudo-graphitic crystallites, enabling homogeneous reaction current and superior rate performance. Herein, a series of hybrid anodes with different hard carbon/graphite ratios are prepared by uniformly mixing graphite and hard carbon with ball-milling. Comprehensive experimental results in combination phase-field simulations reveal that the hybrid anode possesses a homogeneous reaction current and an intriguing potential difference between K⁺-adsorbed hard carbon and non-potassiated graphite. The homogeneous reaction current in the hybrid anode promotes sufficient utilization of electrode material, leading to an increase in the reversible capacity. The present potential difference between K⁺-adsorbed hard carbon and non-potassiated graphite provides an additional electric field force that facilitates the diffusion of K⁺ from hard carbon into the nearest neighbor graphite. All these together, emphasize the synergistic effects between hard carbon and graphite in hybrid anodes toward satisfactory rate and cycling performance. The hybrid strategy proposed here is compatible with the commercial battery manufacturing, offering a practical pathway for the development of high-performance PIBs.     

Dual‐Salt Mg‐Based Batteries with Conversion Cathodes

Mg batteries as the most typical multivalent batteries are attracting increasing attention because of resource abundance, high volumetric energy density, and smooth plating/stripping of Mg anodes. However, current limitations for the progress of Mg batteries come from the lack of high voltage electrolytes and fast Mg‐insertable structure prototypes. In order to improve their energy or power density, hybrid systems combining Li‐driven cathode reaction with Mg anode process appear to be a potential solution by bypassing the aforementioned limitations. Here, FeS _x (x = 1 or 2) is employed as conversion cathode with 2–4 electron transfers to achieve a maximum energy density close to 400 Wh kg^?1, which is comparable with that of Li‐ion batteries but without serious dendrite growth and polysulphide dissolution. In situ formation of solid electrolyte interfaces on both sulfide and Mg electrodes is likely responsible for long‐life cycling and suppression of S‐species passivation at Mg anodes. Without any decoration on the cathode, electrolyte additive, or anode protection, a reversible capacity of more than 200 mAh g^?1 is still preserved for Mg/FeS₂ after 200 cycles.     

Rotatable Methylene Ether Bridge Units Enabling High Chain Flexibility and Rapid Ionic Transport in a New Universal Aqueous Conductive Binder

Binders play an essential role in maintaining the mechanical integrity and stability of electrodes. Herein, a novel aqueous and conductive binder (OXP/CNT-1.5) consisting of carbon nanotubes (CNTs) interwoven with a flexible nano-film of oxidized pullulan (OXP) is designed. The rotatable methylene ether bridge units within OXP chain endow the binder with high chain flexibility, facilitate rapid ion transport, and buffer severe volumetric expansion during charge-discharge cycling. Furthermore, its tight intertwining with CNTs forms continuously conductive and flexible skeletons, which can firmly grasp active nanoparticles through a “face-to-point” bonding type, guaranteeing the electrodes high conductivity and outstanding mechanical integrity. More importantly, these conductive binders are applicable to the Si/C anode as well as the LiFePO₄ cathode. The as-fabricated Si/C anode delivers a 88.2% capacity retention after 100 cycles and 80.2% capacity retention at 0.5 A g⁻¹ (vs 0.05 A g⁻¹), far surpassing the electrode fabricated by conventional polyvinylidene fluoride binder and carbon black mixtures. The LiFePO₄/Si/C full cells based on OXP/CNT-1.5 demonstrate excellent electrochemical behavior and stability (97.4% capacity retention after 100 cycles). This work highlights the key role of rotatable methylene ether bridge units to enhance the flexibility, ion conductivity, and stability, which is inspiring in the context of designing novel binders for high-performance batteries.     

Controllable Urchin‐Like NiCo2S4 Microsphere Synergized with Sulfur‐Doped Graphene as Bifunctional Catalyst for Superior Rechargeable Zn–Air Battery

Rechargeable zinc–air batteries (ZnABs) are attracting great interest due to their high theoretical specific energy, safety, and economic viability. However, their performance and large‐scale practical applications are largely limited by poor durability and high overpotential on the air‐cathode due to the slow kinetics of the oxygen reduction and evolution reactions (ORR/OER). Therefore, it is highly desired to exploit an ideal bifunctional catalyst to endow the obtained ZnABs with excellent ORR/OER catalytic performances. Herein, a new nonprecious‐metal bifunctional catalyst of urchin‐like NiCo₂S₄ microsphere synergized with sulfur‐doped graphene nanosheets (S‐GNS/NiCo₂S₄) is controllably designed and synthesized by simply tailoring the structure and electronic arrangement, which endow the as‐prepared catalyst with excellent electroactivity and long‐term durability toward ORR and OER. Importantly, ZnABs constructed by this outstanding catalyst exhibit high power density, small charge/discharge voltage gap, and excellent cycle stability, notably outperforming the more costly commercial Pt/C + Ir/C mixture catalyst. These excellent electrocatalytic performances together with the simplicity of the synthetic method, make the urchin‐like NiCo₂S₄ microsphere/S‐GNS hybrid nanostructure exhibit great promise as a superior air‐cathode catalyst for high‐performance rechargeable ZnABs.