Mg-Doped Na4Fe3(PO4)2(P2O7)/C Composite with Enhanced Intercalation Pseudocapacitance for Ultra-Stable and High-Rate Sodium-Ion Storage

Na₄Fe₃(PO₄)₂(P₂O₇) (NFPP) is considered as a promising cathode material for sodium-ion batteries (SIBs) due to its low cost, non-toxicity, and high structural stability, but its electrochemical performance is limited by the poor electronic conductivity. In this study, Mg-doped NFPP/C composites are presented as cathode materials for SIBs. Benefiting from the enhanced electrochemical kinetics and intercalation pseudocapacitance resulted from the Mg doping, the optimal Mg-doped NFPP/C composite (NFPP-Mg5%) delivers high rate performance (capacity of ≈40 mAh g⁻¹ at 20 A g⁻¹) and ultra-long cycling life (14 000 cycles at 5 A g⁻¹ with capacity retention of 80.8%). Moreover, the in situ X-ray diffraction and other characterizations reveal that the sodium storage process of NFPP-Mg5% is dominated by the intercalation pseudocapacitive mechanism. In addition, the full SIB based on NFPP-Mg5% cathode and hard carbon anode exhibits the discharge capacity of ≈50 mAh g⁻¹ after 200 cycles at 500 mA g⁻¹. This study demonstrates the feasibility of improving the electrochemical performance of NFPP by doping strategy and presents a low-cost, ultra-stable, and high-rate cathode material for SIBs.     

Fe2VO4 Nanoparticles Anchored on Ordered Mesoporous Carbon with Pseudocapacitive Behaviors for Efficient Sodium Storage

Iron vanadates are attractive anode materials for sodium-ion batteries (SIBs) because of their abundant resource reserves and high capacities. However, their practical application is restricted by the aggregation of materials, sluggish reaction kinetics, and inferior reversibility. Herein, Fe₂VO₄ nanoparticles are anchored on the ordered mesoporous carbon (CMK-3) nanorods to assemble 3D Fe₂VO₄@CMK-3 composites, by solvothermal treatment and subsequent calcination. The resulting composites provide abundant active sites, high electrical conductivity, and excellent structural integrity. The pseudocapacitive-controlled behavior is the dominating sodium storage mechanism, which facilitates a fast charge/discharge process. The Fe₂VO₄@CMK-3 composites exhibit stable sodium-ion storage (219 mAh g⁻¹ under 100 mA g⁻¹ after 300 cycles), good rate performance (144 mAh g⁻¹ at 3.2 A g⁻¹), and excellent cycling performance (132 mAh g⁻¹ at 1 A g⁻¹ with capacity retention of 96.4% after 800 cycles). When coupled with a NaNi_1/3Fe_1/3Mn_1/3O₂ cathode, the sodium-ion full cell displays excellent cycling stability (94 mAh g⁻¹ after 500 cycles at 500 mA g⁻¹). These findings point to the potential of Fe₂VO₄@CMK-3 for application as anodes in SIBs.     

Unveiling the Effects of Cr Single Atoms with Controllable Configurations on Solid Electrolyte Interphase and Storage Mechanism of Sodium Ions

Single atomic metal (SAM) doping is reported as an effective strategy to promote the electrochemical property of carbon-based anode materials for high-power sodium-ion batteries (SIBs). However, the effects of SAM with different configurations on solid electrolyte interphase (SEI) and energy storage mechanism of Na⁺ are not revealed. Herein, Cr single atoms (CrSAs) are reported with controllable configurations (Cr–N₄ or Cr–N₂) implanted on the N, P co-doped carbon (NPC) anode materials (denoted as CrN₄SAs/NPC or CrN₂SAs/NPC). The CrN₄SAs/NPC anode displays a high specific capacity (318.2 mAh g⁻¹ at 0.05 A g⁻¹) and outstanding rate performance (145.1 mAh g⁻¹ at 5 A g⁻¹), better than those of CrN₂SAs/NPC and NPC. The superiority is originated from the difference of SEI and the energy storage mechanism of sodium ions during electrochemical process, which are unveiled through ex situ characterization and theoretical calculation. The full cell assembled with CrN₄SAs/NPC anode and Na₃V₂(PO₄)₂F₃@C cathode displays a high energy density at a high power density.     

Universal Source-Template Route to Metal Selenides Implanting on 3D Carbon Nanoarchitecture: Cu2−xSe@3D-CN with Se?C Bonding for Advanced Na Storage

The development of high-performance sodium ion batteries (SIBs) is heavily relied on the exploration of the appropriate electrode material for Na⁺ storage, which ought to feature merits of high capacity, easy-to-handle synthesis, high conductivity, expedite mass transportation, and stable structure upon charging–discharging cycle. Herein, a universal source-template method is reported to synthesize a variety of transition metal (e.g., V, Sb, W, Zn, Fe, Co, Ni, and Cu) selenides implanting on N doped 3D carbon nanoarchitecture hybrids (M_mSe_n@3D-CN) with powerful Se C bonding rivet. Benefiting from the superior architecture and potent Se C bonding between Cu_2−xSe and N-doped 3D carbon (3D-CN), the Cu_2−xSe@3D-CN nanohybrids, as anode of SIBs, show high capacity, high-rate capability, and long-cycle durability, which can deliver a reversible capacity of as high as 386 mAh g⁻¹, retain 219 mAh g⁻¹ even at 10 A g⁻¹, and run durably over thousands of charging–discharging cycles. The Cu_2−xSe@3D-CN as anode is also evaluated by developing a full SIB by coupling with the Na₃V₂(PO₄)₃ cathode, which can deliver high energy density and show excellent stability, shedding light on its potential 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.     

Revealing the Double-Edged Behaviors of Heteroatom Sulfur in Carbonaceous Materials for Balancing K-Storage Capacity and Stability

Heteroatoms in the carbon matrix are generally considered as active sites to enhance potassium storage capacity, while their adverse effects on ion batteries remain unclear. Herein, a series of sulfur doped carbon (SCDPx) with adjustable S content and crystallinity are accurately synthesized in the closed autoclave by controlling the ratios of precursors. Electrochemical measurements exhibit that heteroatom sulfur displays double-edged electrochemical activities with a high initial potassium storage capacity but poor cycling stability for carbon anode. Combined with solid-state nuclear magnetic resonance (NMR), catalytic tests, and various ex-situ characterizations, it is demonstrated that abundant S in the carbon would not only form C S C bonds, acting as active sites to reversibly adsorb/desorb potassium ions for high capacity, but also significantly catalyze the reduction and decomposition of the electrolyte including KPF₆ and ethylene carbonate/diethyl carbonate (EC/DEC) to form thicker solid electrolyte interface (SEI) and degrade electrolyte, resulting in rapid capacity decay. As a result, the optimized sample (SCDP2) with the appropriate sulfur doping content exhibits the best electrochemical performance with high capacity (688.4 mA h g⁻¹ at 100 mA g⁻¹), long-term cycling stability (198.4 mA h g⁻¹ at 2000 mA g⁻¹ after 10 000 cycles), and excellent rate capability (238.8 mA h g⁻¹ at 5000 mA g⁻¹).     

Rational Design of a Trifunctional Binder for Hard Carbon Anodes Showing High Initial Coulombic Efficiency and Superior Rate Capability for Sodium-Ion Batteries

Hard carbon (HC) has emerged as a promising anode material for sodium-ion batteries (SIBs), whereas it suffers from low initial Coulombic efficiency (ICE) and poor rate capability. Binders endowed with high electron/ion transport and strong mechanical integrity are expected to boost the practical application of HC anodes, which cannot be realized via the functional design of commercially available binders. Herein, a trifunctional sodium alginate (SA)/polyethylene oxide (PEO) binder with massive hydrophilic functional groups and abundant Na⁺ is synthesized via a feasible esterification reaction. The binder forms a passivation film on glucose-derived carbon (GC) to suppress the electrolyte decomposition and offer stronger adhesion strength. Furthermore, the sluggish Na⁺ conduction is improved via sufficient ionic transfer channels provided by PEO. Notably, effects of Na⁺ compensation and interfacial ionic transport of Na⁺-containing binder for HC anodes are revealed. Therefore, the SA/PEO binder for the GC anode delivers a high ICE up to 87% and a high capacity of 270 mA h g⁻¹ at 0.1 A g⁻¹, both 10% and 80 mA h g⁻¹ higher than that of poly(vinylidene fluoride) binder, respectively. Significantly, this SA/PEO binder can also be applied to coal-based and polymer-based carbon anodes, exhibiting universal applicability.     

Van der Waals Forces between S and P Ions at the CoP-C@MoS2/C Heterointerface with Enhanced Lithium/Sodium Storage

Metal–organic framework-derived metal phosphides with high capacity, facile synthesis, and morphology-controlled are considered as potential anodes for lithium/sodium-ion batteries. However, the severe volume expansion during cycling can cause the electrode material to collapse and reduce the cycle life. Here, novel CoP-C@MoS₂/C nanocube composites are synthesized by vapor-phase phosphating and hydrothermal process. As the anode of LIBs, CoP-C@MoS₂/C exhibits outstanding long-cycle performance of 369 mAh g⁻¹ at 10 A g⁻¹ after 2000 cycles. In SIBs, the composite also displays excellent rate capability of 234 mAh g⁻¹ at 5 A g⁻¹ and an ultra-high the capacity retention rate of 90.16% at 1 A g⁻¹ after 1000 cycles. Through density functional theory, it is found that the S ions and P ions at the interface formed by CoP and MoS₂ can serve as Na⁺/Li⁺ diffusion channels with an action of van der Waals force, have attractive characteristics such as high ion adsorption energy, low expansion rate and fast diffusion kinetics compared with MoS₂. This study provides enlightenment for the reasonable design and development of lithium/sodium storage anode materials composited with MOF-derived metal phosphides and metal sulfides.     

Electrical Conductivity Adjustment for Interface Capacitive-Like Storage in Sodium-Ion Battery

Sodium-ion battery (SIB) is significant for grid-scale energy storage. However, a large radius of Na ions raises the difficulties of ion intercalation, hindering the electrochemical performance during fast charge/discharge. Conventional strategies to promote rate performance focus on the optimization of ion diffusion. Improving interface capacitive-like storage by tuning the electrical conductivity of electrodes is also expected to combine the features of the high energy density of batteries and the high power density of capacitors. Inspired by this concept, an oxide-metal sandwich 3D-ordered macroporous architecture (3DOM) stands out as a superior anode candidate for high-rate SIBs. Taking Ni-TiO₂ sandwich 3DOM as a proof-of-concept, anatase TiO₂ delivers a reversible capacity of 233.3 mAh g⁻¹ in half-cells and 210.1 mAh g⁻¹ in full-cells after 100 cycles at 50 mA g⁻¹. At the high charge/discharge rate of 5000 mA g⁻¹, 104.4 mAh g⁻¹ in half-cells and 68 mAh g⁻¹ in full-cells can also be obtained with satisfying stability. In-depth analysis of electrochemical kinetics evidence that the dominated interface capacitive-like storage enables ultrafast uptaking and releasing of Na-ions. This understanding between electrical conductivity and rate performance of SIBs is expected to guild future design to realize effective energy storage.     

Ultrafast Synthesis of Large-Sized and Conductive Na3V2(PO4)2F3 Simultaneously Approaches High Tap Density,Rate and Cycling Capability

The Na₃V₂(PO₄)₂F₃ (NVPF) cathode material is usually nano-sized particles exhibiting low tap density, high specific surface area, correspondingly low volume energy density, and cycle stability of the sodium-ion batteries (SIBs). Herein, a high-temperature shock (HTS) strategy is proposed to synthesize NVPF (HTS-NVPF) with uniform conducting network and high tap density. During a typical HTS process (heating rate of 1100 °C s⁻¹ for 10 s), the precursors rapidly crystallize and form large-sized and dense particles. The tight connection between particles not only enhances their contact with carbon layers, but also reduces the specific surface area that inhibits side reactions between the interfaces and the electrolyte. Besides, ultrafast synthesis of NVPF reduces the F loss and amount of Na₃V₂(PO₄)₃ impurities, which improve cycling capability. The HTS-NVPF demonstrates a high energy density of 413.4 Wh kg⁻¹ and an ultra-high specific capacity of 103.4 mAh g⁻¹ at 10 C as well as 84.2% capacity retention after 1000 cycles. In addition, the excellent temperature adaptability of HTS-NVPF (−45–55 °C) and remarkable electrochemical properties of NVPF||HC full cell demonstrate extreme competitiveness in commercial SIBs. Therefore, the HTS technique is considered to be a high-efficiency strategy to synthetize NVPF and is expected to prepare other cathode materials.     

A Simple Electrode‐Level Chemical Presodiation Route by Solution Spraying to Improve the Energy Density of Sodium‐Ion Batteries

The formation of a solid electrolyte interface (SEI) on the surface of a carbon anode consumes the active sodium ions from the cathode and reduces the energy density of sodium‐ion batteries (SIBs). Herein, a simple electrode‐level presodiation strategy by spraying a sodium naphthaline (Naph‐Na) solution onto a carbon electrode is reported, which compensates the initial sodium loss and improves the energy density of SIBs. After presodiation, an SEI layer is preformed on the surface of carbon anode before battery cycling. It is shown that a large irreversible capacity of 60 mAh g^?1 is replenished and 20% increase of the first‐cycle Coulombic efficiency is achieved for a hard carbon anode using this presodiation strategy, and the energy density of a Na_0.9[Cu_0.22Fe_0.30Mn_0.48]O₂||carbon full cell is increased from 141 to 240 Wh kg^?1 by using the presodiated carbon anode. This simple and scalable electrode‐level chemical presodiation route also shows generality and value for the presodiation of other anodes in SIBs.     

Phase Engineering of Nickel Sulfides to Boost Sodium- and Potassium-Ion Storage Performance

Sulfides are promising anode candidates because of their relatively large theoretical discharge/charge specific capacity and pretty small volume changes, but suffers from sluggish kinetics and structural instability upon cycling. Phase engineering can be designed to overcome the weakness of the electrochemical performance of sulfide anodes. By choosing nickel sulfides (α-NiS, β-NiS, and NiS₂) supported by reduced graphene oxide (rGO) as model systems, it is demonstrated that the nickel sulfides with different crystal structures show different performances in both sodium-ion and potassium-ion batteries. In particular, the α-NiS/rGO display superior stable capacity (≈426 mAh g⁻¹ for 500 cycles at 500 mA g⁻¹) and exceptional rate capability (315 mAh g⁻¹ at 2000 mA g⁻¹). The combined density functional theory calculations and experimental studies reveal that the hexagonal structure is more conducive to ion absorption and conduction, a higher pseudocapacitive contribution, and higher mechanical ability to relieve the stress caused by the volume changes. Correspondingly, the phase engineered nickel sulfide coupled with the conducting rGO network synergistically boosts the electrochemical performance of batteries. This work sheds light on the use of phase engineering as an essential strategy for exploring materials with satisfactory electrochemical performance for sodium-ion and potassium-ion batteries.     

Lithium-Substituted Tunnel/Spinel Heterostructured Cathode Material for High-Performance Sodium-Ion Batteries

Sodium manganese oxides as promising cathode materials for sodium-ion batteries (SIBs) have attracted interest owing to their abundant resources and potential low cost. However, their practical application is hindered due to the manganese disproportionation associated with Mn³⁺, resulting in rapid capacity decline and poor rate capability. Herein, a Li-substituted, tunnel/spinel heterostructured cathode is successfully synthesized for addressing these limitations. The Li dopant acts as a pillar inhibiting unfavorable multiphase transformation, improving the structural reversibility, and sodium storage performance of the cathode. Meanwhile, the tunnel/spinel heterostructure provides 3D Na⁺ diffusion channels to effectively enhance the redox reaction kinetics. The optimized [Na_0.396Li_0.044][Mn_0.97Li_0.03]O₂ composite delivers an excellent rate performance with a reversible capacity of 97.0 mA h g^–1 at 15 C, corresponding to 82.5% of the capacity at 0.1 C, and a promising cycling stability over 1200 cycles with remarkable capacity retention of 81.0% at 10 C. Moreover, by combining with hard carbon anodes, the full cell demonstrates a high specific capacity and favorable cyclability. After 200 cycles, the cell provides 105.0 mA h g^–1 at 1 C, demonstrating the potential of the cathode for practical applications. This strategy might apply to other sodium-deficient cathode materials and inform their strategic design.     

Unveiling the Anionic Redox Chemistry in Phosphate Cathodes for Sodium-Ion Batteries

Anionic redox chemistry has aroused increasing attention in sodium-ion batteries (SIBs) by virtue of the appealing additional capacity. However, up to now, anionic redox reaction has not been reported in the mainstream phosphate cathodes for SIBs. Herein, the ultrathin VOPO₄ nanosheets are fabricated as promising cathodes for SIBs, where the oxygen redox reaction is first activated accompanied by reversible ClO₄⁻ (from the electrolyte) insertion/extraction. As a result, the VOPO₄ cathode harvests a record-high capacity (168 mAh g⁻¹ at 0.1 C) among its counterparts ever reported. Moreover, the ClO₄⁻ insertion efficiently expands the interlayer spacing of VOPO₄ and accelerates the ion diffusion, enabling an unprecedentedly high rate performance (69 mAh g⁻¹ at 30 C). Via systematic ex situ characterizations and theoretical computations, the anionic redox chemistry and charge storage mechanism upon cycling are thoroughly elucidated. This study opens up a new avenue toward high-energy phosphate cathodes for SIBs by triggering anionic redox reactions.     

Controlled Nitrogen Doping in Crumpled Graphene for Improved Alkali Metal-Ion Storage under Low-Temperature Conditions

The significant performance decay in conventional graphite anodes under low-temperature conditions is attributed to the slow diffusion of alkali metal ions, requiring new strategies to enhance the charge storage kinetics at low temperatures. Here, nitrogen (N)-doped defective crumpled graphene (NCG) is employed as a promising anode to enable stable low-temperature operation of alkali metal-ion storage by exploiting the surface-controlled charge storage mechanisms. At a low temperature of −40 °C, the NCG anodes maintain high capacities of ≈172 mAh g⁻¹ for lithium (Li)-ion, ≈107 mAh g⁻¹ for sodium (Na)-ion, and ≈118 mAh g⁻¹ for potassium (K)-ion at 0.01 A g⁻¹ with outstanding rate-capability and cycling stability. A combination of density functional theory (DFT) and electrochemical analysis further reveals the role of the N-functional groups and defect sites in improving the utilization of the surface-controlled charge storage mechanisms. In addition, the full cell with the NCG anode and a LiFePO₄ cathode shows a high capacity of ≈73 mAh g⁻¹ at 0.5 °C even at −40 °C. The results highlight the importance of utilizing the surface-controlled charge storage mechanisms with controlled defect structures and functional groups on the carbon surface to improve the charge storage performance of alkali metal-ion under low-temperature conditions.     

Effective Coupling of Amorphous Selenium Phosphide with High-Conductivity Graphene as Resilient High-Capacity Anode for Sodium-Ion Batteries

It is of great importance to develop high-capacity electrodes for sodium-ion batteries (SIBs) using low-cost and abundant materials, so as to deliver a sustainable technology as alternative to the established lithium-ion batteries (LIBs). Here, a facile ball milling process to fabricate high-capacity SIB anode is devised, with large amount of amorphous SeP being loaded in a well-connected framework of high-conductivity crystalline graphene (HCG). The HCG substrate enables fast transportation of Na ions and electrons, while accommodating huge volumetric changes of the active anode matter of SeP. The strong glass forming ability of NaxSeP helps prevent crystallization of all stable compounds but ultrafine nanocrystals of Na2Se and Na3P. Thus, the optimized anode delivers excellent rate performance with high specific capacities being achieved (855 mAh g⁻¹ at 0.2 A g⁻¹ and 345 mAh g⁻¹ at 5 A g⁻¹). More importantly, remarkable cycling stability is realized to maintain a steady capacity of 732 mAh g⁻¹ over 500 cycles, when the SeP in the SeP@HCG still remains 86% of its theoretical capacity. A high areal capacity of 2.77 mAh is achieved at a very high loading of 4.1 mg cm⁻² anode composite.     

High Power and Energy Density Aqueous Proton Battery Operated at −90 °C

Freezing electrolyte and sluggish ionic migration kinetics limited the low-temperature performance of rechargeable batteries. Here, an aqueous proton battery is developed, which achieves both high power density and energy density at the ultralow temperature conditions. Electrolyte including 2 m HBF₄  +  2 m Mn(BF₄)₂ is used for the ultralow freezing point of below − 160  ° C and high ionic conductivity of 0.21 mS cm⁻¹ at − 70  ° C. Spectroscopic and nuclear magnetic resonance analysis demonstrate the introduction of BF₄⁻ anions efficiently break the hydrogen-bond networks of original water molecules, resulting in ultralow freezing point. Based on H⁺ uptake/removal reaction in alloxazine (ALO) anode and MnO₂/Mn²⁺ conversion in carbon felt cathode, the aqueous proton battery can operate regularly even at − 90  ° C and obtain a high specific discharge capacity of 85 mA h g⁻¹. Benefiting from the rapid diffusion of proton and the pseudocapacitive character of ALO electrolyte, this battery shows a high specific energy density of 110 Wh kg⁻¹ at a specific power density of 1650 W kg⁻¹ at − 60  ° C. This work presents a new way of developing low-temperature batteries.     

A Self-Healing Volume Variation Three-Dimensional Continuous Bulk Porous Bismuth for Ultrafast Sodium Storage

Bismuth (Bi) has attracted considerable attention as promising anode material for sodium-ion batteries (NIBs) owing to its suitable reaction potential and high volumetric capacity density (3750 mA h cm⁻³). However, the large volumetric expansion during cycling causes severe structural degradation and fast capacity decay. Herein, by rational design, a self-healing nanostructure 3D continuous bulk porous bismuth (3DPBi) is prepared via facile liquid phase reduction reaction. The 3D interconnected Bi nanoligaments provide unblocked electronic circuits and short ion diffusion path. Meanwhile, the bicontinuous nanoporous network can realize self-healing the huge volume variation as confirmed by in situ and ex situ transmission electron microscopy observations. When used as the anode for NIBs, the 3DPBi delivers unprecedented rate capability (high capacity retention of 95.6% at an ultrahigh current density of 60 A g⁻¹ with respect to 1 A g⁻¹) and long-cycle life (high capacity of 378 mA h g⁻¹ remained after 3000 cycles at 10 A g⁻¹). In addition, the full cell of Na₃V₂(PO₄)₃|3DPBi delivers stable cycling performance and high gravimetric energy density (116 Wh kg⁻¹), demonstrating its potential in practical application.     

Organic Molecular Intercalated V3O7·H2O with High Operating Voltage for Long Cycle Life Aqueous Zn-Ion Batteries

V₃O₇·H₂O (VO) is an attractive cathode material for high-capacity aqueous Zn-ion batteries (AZIBs), but it is limited by slow ion mobility and low working platform voltage. Here, a 1,3-propane diamine (DP)-intercalated VO with nanoribbon-assembled thorn flower-like structure is fabricated by a facile hydrothermal method, noted as VO-DP. The study shows that the zinc ion diffusion coefficient in VO-DP (3.1 × 10⁻⁸ cm⁻² s⁻¹) is five orders of magnitude higher than that of a pure VO counterpart. Auxiliary density functional theory simulation shows that the embedded energy of zinc ions in VO-DP significantly decreases from 0.24 to −2.5 eV, thus leading to excellent diffusion kinetics and superior rate performance. Benefiting from these unique properties, AZIBs composed of VO-DP cathodes exhibit high operating voltage (0.89 V), remarkable capacities of 473 mA h g⁻¹ at 0.05 A g⁻¹, excellent rate capability (144 mA h g⁻¹ at 10 A g⁻¹) and long-term cycling performance (73% capacity retention over 15 000 cycles at 10 A g⁻¹).     

Defect Modulation in Cobalt Manganese Oxide Sheets for Stable and High-Energy Aqueous Aluminum-Ion Batteries

Rechargeable aqueous Al-ion batteries (AIBs) are promising low-cost, safe, and high energy density systems for large-scale energy storage. However, the strong electrostatic interaction between the Al³⁺ and the host material, usually leads to sluggish Al³⁺ diffusion kinetics and severe structure collapse of the cathode material. Consequently, aqueous AIBs currently suffer from low energy density as well as inferior rate capability and cycling stability. Here, defective cobalt manganese oxide nanosheets are reported as cathode material for aqueous AIBs to improve both reaction kinetics and stability, delivering a record high energy density of 685 Wh kg⁻¹ (based on the masses of the cathode and anode) and a reversible capacity of 585 mAh g⁻¹ at 100 mA g⁻¹ with a retention of 78% after 300 cycles. The impressive energy density and cycling stability are due to a synergistic effect between the substituted cobalt atoms and the manganese vacancies, which improve the structural stability and promote both electron conductivity and ion diffusion. When applied in aqueous Zn-ion batteries, a high specific energy of 390 Wh kg⁻¹ at 100 mA g⁻¹ is realized while retaining 84% initial capacity over 1000 cycles. The study offers a new pathway to building next-generation high-energy aqueous rechargeable metal batteries.