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Aqueous Mn-ion batteries (MIBs) exhibit a promising development potential due to their cost-effectiveness, high safety, and potential for high energy density. However, the development of MIBs is hindered by the lack of electrode materials capable of storing Mn2+ ions due to acidic manganese salt electrolytes and large ion radius. Herein, the tunnel-type structure of monoclinic VO2 nanorods to effectively store Mn2+ ions via a reversible (de)insertion chemistry for the first time is reported. Utilizing exhaustive in situ/ex situ multi-scale characterization techniques and theoretical calculations, the co-insertion process of Mn2+/proton is revealed, elucidating the capacity decay mechanism wherein high proton activity leads to irreversible dissolution loss of vanadium species. Further, the Grotthuss transfer mechanism of protons is broken via a hydrogen bond reconstruction strategy while achieving the modulation of the electric double-layer structure, which effectively suppresses the electrode interface proton activity. Consequently, the VO2 demonstrates excellent electrochemical performance at both ambient temperatures and -20 °C, especially maintaining a high capacity of 162 mAh g-1 at 5 A g-1 after a record-breaking 20 000 cycles. Notably, the all-vanadium symmetric pouch cells are successfully assembled for the first time based on the "rocking-chair" Mn2+/proton hybrid mechanism, demonstrating the practical application potential.
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Intensifying the synergy between confined carbon nanopores and ionic liquids (ILs) and a deep comprehension of the ion behavior is required for enhancing the capacitive storage performance. Despite many theoretical insights on the storage mechanism, experimental verification has remained lacking due to the intricate nature of pore texture. Here, a compressed micropore-rich carbon framework (CMCF) with tailored monolayer and bilayer confinement pores is synthesized, which exhibits a compatible ionophilic interface to accommodate the IL [EMIM][BF4]. By deploying in situ Raman spectroscopy, in situ Fourier-transform infrared spectroscopy, and solid-state nuclear magnetic resonance, the effect of the pore textures on ions storage behaviors is elucidated. A voltage-induced ion gradient filling process in these ionophilic pores is proposed, in which ion exchange and co-ion desorption dominate the charge storage process. Moreover, it is established that the monolayer confinement of ions enhances the capacity, and bilayer confinement facilitates the charging dynamics. This work may guide the design of nanoconfinement carbon for high-energy-density supercapacitors and deepen the understanding of the charge storage mechanism in ionophilic pores.
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Vanadium-based compounds have attracted significant attention as cathodes for aqueous zinc metal batteries (AZMBs) because of their remarkable advantages in specific capacities. However, their low diffusion coefficient for zinc ions and structural collapse problems lead to poor rate capability and cycle stability. In this work, bilayered Sr0.25V2O5·0.8H2O (SVOH) nanowires are first reported as a highly stable cathode material for rechargeable AZMBs. The synergistic pillaring effect of strontium ions and water molecules improves the structural stability and ion transport dynamics of vanadium-based compounds. Consequently, the SVOH cathode exhibits a high capacity of 325.6 mAh g-1 at 50 mA g-1, with a capacity retention rate of 72.6% relative to the maximum specific capacity at 3.0 A g-1 after 3000 cycles. Significantly, a unique single-nanowire device is utilized to demonstrate the excellent conductivity of the SVOH cathode directly. Additionally, the energy storage mechanism of zinc insertion and extraction is investigated using a variety of advanced in situ and ex situ analysis techniques. This method of ion intercalation to improve electrochemical performance will further promote the development of AZMBs in large-scale applications.
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Rechargeable magnesium batteries (RMBs) have received increased attention due to their high volumetric capacity and safety. Nevertheless, the sluggish diffusion kinetics of highly polarized Mg2+ in host lattices severely hinders the development of RMBs. Herein, we report an electron injection strategy for modulating the Mo 4d-orbital splitting manner and first fabricate a dual-phase MoO2.8F0.2/MoO2.4F0.6 heterostructure to accelerate Mg2+ diffusion. The electron injection strategy triggers weak Jahn-Teller distortion in MoO6 octahedra and reorganization of the Mo 4d-orbital, leading to a partial phase transition from orthorhombic phase MoO2.8F0.2 to cubic phase MoO2.4F0.6. As a result, the designed heterostructure generates a built-in electric field, simultaneously improving its electronic conductivity and ionic diffusivity by at least one order of magnitude compared to MoO2.8F0.2 and MoO2.4F0.6. Importantly, the assembled MoO2.8F0.2/MoO2.4F0.6//Mg full cell exhibits a remarkable reversible capacity of 172.5 mAh g-1 at 0.1 A g-1, pushing forward the orbital-scale manipulation for high-performance RMBs.
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Lithium-sulfur batteries (LSBs) are considered as promising candidates in the next generation of high energy density devices. However, the serious shuttle effect, irreversible dendrite growth of Li metal anode, and the potential safety hazard impede the practical application of LSBs. Herein, a novel homogeneous Janus membrane based on functionalized MOFs crosslinked by aramid nanofibers is designed and synthesized to simultaneously solve the above challenges in quasi-solid-state LSBs. The aramid nanofibers with good mechanical properties and thermal stability act as a homogeneous scaffold to crosslink the MOF particles with different ligands on both sides and this Janus membrane upgrades the stability and safety on both the cathode and anode. Specifically, the amino ligand-decorated MOFs contribute to homogenize Li-ion flux and stabilize the lithium anode, and the sulfonic ligand-decorated MOFs effectively suppress the shuttle effect by the dual effects of chemical adsorption and electrostatic repulsion. The quasi-solid-state LSBs assembled with this homogeneous Janus membrane deliver excellent rate performance and cycling stability. Moreover, it exhibits a high initial capacity of 923.4 mAh g-1 at 1 C at 70 °C, and 697.3 mAh g-1 is retained after 100 cycles, indicating great potential for its application in high-safety LSBs.
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Single-atom catalysts (SACs) have been increasingly explored in lithium-sulfur (Li-S) batteries to address the issues of severe polysulfide shuttle effects and sluggish redox kinetics. However, the structure-activity relationship between single-atom coordination structures and the performance of Li-S batteries remain unclear. In this study, a P, S co-coordination asymmetric configuration of single atoms is designed to enhance the catalytic activity of Co central atoms and promote d-p orbital hybridization between Co and S atoms, thereby limiting polysulfides and accelerating the bidirectional redox process of sulfur. The well-designed SACs enable Li-S batteries to demonstrate an ultralow capacity fading rate of 0.027% per cycle after 2000 cycles at a high rate of 5 C. Furthermore, they display excellent rate performance with a capacity of 619 mAh g-1 at an ultrahigh rate of 10 C due to the efficient catalysis of CoSA-N3PS. Importantly, the assembled pouch cell still retains a high discharge capacity of 660 mAh g-1 after 100 cycles at 0.2 C and provides a high areal capacity of 4.4 mAh cm-2 even with a high sulfur loading of 6 mg cm-2. This work demonstrates that regulating the coordination environment of SACs is of great significance for achieving state-of-the-art Li-S batteries.
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Potassium ion batteries (PIBs) are a viable alternative to lithium-ion batteries for energy storage. Red phosphorus (RP) has attracted a great deal of interest as an anode for PIBs owing to its cheapness, ideal electrode potential, and high theoretical specific capacity. However, the direct preparation of phosphorus-carbon composites usually results in exposure of the RP to the exterior of the carbon layer, which can lead to the deactivation of the active material and the production of "dead phosphorus". Here, the advantage of the π-π bond conjugated structure and high catalytic activity of metal phthalocyanine (MPc) is used to prepare MPc@RP/C composites as a highly stable anode for PIBs. It is shown that the introduction of MPc greatly improves the uneven distribution of the carbon layer on RP, and thus improves the initial Coulombic efficiency (ICE) of PIBs (the ICE of FePc@RP/C is 75.5% relative to 62.9% of RP/C). The addition of MPc promotes the growth of solid electrolyte interphase with high mechanical strength, improving the cycle stability of PIBs (the discharge-specific capacity of FePc@RP/C is 411.9 mAh g-1 after 100 cycles at 0.05 A g-1). Besides, density functional theory theoretical calculations show that MPc exhibits homogeneous adsorption energies for multiple potassiation products, thereby improving the electrochemical reactivity of RP. The use of organic molecules with high electrocatalytic activity provides a universal approach for designing superior high-capacity, large-volume expansion anodes for PIBs.
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Rechargeable aqueous batteries adopting Fe-based materials are attracting widespread attention by virtue of high-safety and low-cost. However, the present Fe-based anodes suffer from low electronic/ionic conductivity and unsatisfactory comprehensive performance, which greatly restrict their practicability. Concerning the principle of physical chemistry, fabricating electrodes that could simultaneously achieve ideal thermodynamics and fast kinetics is a promising issue. Herein, hierarchical Fe3O4@Fe foam electrode with enhanced interface/grain boundary engineering is fabricated through an in situ self-regulated strategy. The electrode achieves ultrahigh areal capacity of 31.45 mA h cm-2 (50 mA cm-2), good scale application potential (742.54 mA h for 25 cm2 electrode), satisfied antifluctuation capability, and excellent cycling stability. In/ex situ characterizations further validate the desired thermodynamic and kinetic properties of the electrode endowed with accurate interface regulation, which accounts for salient electrochemical reversibility in a two-stage phase transition and slight energy loss. This work offers a suitable strategy in designing high-performance Fe-based electrodes with comprehensive inherent characteristics for high-safety large-scale energy storage.
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Deep eutectic electrolytes (DEEs) are regarded as one of the next-generation electrolytes to promote the development of lithium metal batteries (LMBs) due to their unparalleled advantages compared to both liquid electrolytes and solid electrolytes. However, its application in LMBs is limited by electrode interface compatibility. Here, we introduce a novel solid dimethylmalononitrile (DMMN)-based DEE induced by N coordination to dissociate LiTFSI. We confirmed that the DMMN molecule can promote the dissociation of LiTFSI by the interaction between the N atom and Li+, and form the hydrogen bond with TFSI- anion, which can promote the dissociation of LiTFSI to form DEE. More importantly, due to the absence of active α-hydrogen, DMMN exhibits greatly enhanced reduction stability with Li metal, resulting in favorable electrode/electrolyte interface compatibility. Polymer electrolytes based on this DEE exhibit high ionic conductivity (0.67 mS cm-1 at 25 â), high oxidation voltage (5.0 V vs. Li+/Li), favorable interfacial stability and nonflammability. LiâLFP and LiâNCM811 full batteries utilizing this DEE polymer electrolyte exhibit excellent long-term cycling stability and excellent rate performance at high rates. Therefore, the new DMMN-based DEE overcomes the limitations of traditional electrolytes in electrode interface compatibility and opens new possibilities for improving the performance of LMBs.
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Lean-lithium metal batteries represent an advanced version of the anode-free lithium metal batteries, which can ensure high energy density and cycling stability while addressing the safety concerns and the loss of energy density caused by excessive lithium metal. Herein, a mechanically robust carbon nanotube framework current collector with gradient lithiophilicity is constructed for a lean-lithium metal battery. Using the physical vapor deposition method, precise prelithiation of a carbon nanotube framework is achieved, eliminating its irreversible capacity, retaining the porous structure in the framework, and inducing the gradient lithiophilicity formation due to spontaneous lithium ion diffusion. The lithiophilic gradient and three-dimensional porous structure are characterized by time-of-flight secondary ion mass spectrometry (TOF-SIMS), scanning transmission electron microscopy (STEM), and corresponding electron energy loss spectroscopy (EELS), which enables the preferential deposition of lithium ions at the bottom of the carbon nanotube framework, thereby avoiding lithium losses associated with dead lithium. As a result, in the LiFePO4 full cell with an ultralow N/P ratio of 0.15, the initial Coulombic efficiency increases from 77.75 to 95.07%. Collaborating synergistically with the ultrathin (1.5 µm) lithium metal, serving as a gradual lithium supplement, the full cell with an N/P ratio of 1.43 demonstrates an 86% capacity retention after 500 cycles at 1C, far surpassing the copper-based counterparts (0.9%).
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Reconstruction-engineered electrocatalysts with enriched high active Ni species for urea oxidation reaction (UOR) have recently become promising candidates for energy conversion. However, to inhibit the over-oxidation of urea brought by the high valence state of Ni, tremendous efforts are devoted to obtaining low-value products of nitrogen gas to avoid toxic nitrite formation, undesirably causing inefficient utilization of the nitrogen cycle. Herein, we proposed a mediation engineering strategy to significantly boost high-value nitrite formation to help close a loop for the employment of a nitrogen economy. Specifically, platinum-loaded nickel phosphides (Pt-Ni2P) catalysts exhibit a promising nitrite production rate (0.82â mol kWh-1 cm-2), high stability over 66â h of Zn-urea-air battery operation, and 135â h of co-production of nitrite and hydrogen under 200â mA cm-2 in a zero-gap membrane electrode assembly (MEA) system. The in situ spectroscopic characterizations and computational calculations demonstrated that the urea oxidation kinetics is facilitated by enriched dynamic Ni3+ active sites, thus augmenting the "cyanate" UOR pathway. The C-N cleavage was further verified as the rate-determining step for nitrite generation.
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Recently, aqueous iron ion batteries (AIIBs) using iron metal anodes have gained traction in the battery community as low-cost and sustainable solutions for green energy storage. However, the development of AIIBs is significantly hindered by the limited capacity of existing cathode materials and the poor intercalation kinetic of Fe2+. Herein, we propose a H+ and Fe2+ co-intercalation electrochemistry in AIIBs to boost the capacity and rate capability of cathode materials such as iron hexacyanoferrate (FeHCF) and Na4Fe3(PO4)2(P2O7) (NFPP). This is achieved through an electrochemical activation step during which a FeOOH nanowire layer is formed in situ on the cathode. This layer facilitates H+ co-intercalation in AIIBs, resulting in a high specific capacity of 151 mAh g-1 and 93% capacity retention over 500 cycles for activated FeHCF cathodes. We found that this activation process can also be applied to other cathode chemistries, such as NFPP, where we found that the cathode capacity is doubled as a result of this process. Overall, the proposed H+/Fe2+ co-insertion electrochemistry expands the range of applications for AIBBs, in particular as a sustainable solution for storing renewable energy.
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All-solid-state lithium batteries with polymer electrolytes suffer from electrolyte decomposition and lithium dendrites because of the unstable electrode/electrolyte interfaces. Herein, a molecule crowding strategy is proposed to modulate the Li+ coordinated structure, thus in situ constructing the stable interfaces. Since 15-crown-5 possesses superior compatibility with polymer and electrostatic repulsion for anion of lithium salt, the anions are forced to crowd into a Li+ coordinated structure to weaken the Li+ coordination with polymer and boost the Li+ transport. The coordinated anions prior decompose to form LiF-rich, thin, and tough interfacial passivation layers for stabilizing the electrode/electrolyte interfaces. Thus, the symmetric Li-Li cell can stably operate over 4360 h, the LiFePO4||Li full battery presents 97.18% capacity retention in 700 cycles at 2 C, and the NCM811||Li full battery possesses the capacity retention of 83.17% after 300 cycles. The assembled pouch cell shows excellent flexibility (stand for folding over 2000 times) and stability (89.42% capacity retention after 400 cycles). This work provides a promising strategy to regulate interfacial chemistry by modulating the ion environment to accommodate the interfacial issues and will inspire more effective approaches to general interface issues for polymer electrolytes.
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Aqueous Zn-ion batteries are an attractive electrochemical energy storage solution for their budget and safe properties. However, dendrites and uncontrolled side reactions in anodes detract the cycle life and energy density of the batteries. Grain boundaries in metals are generally considered as the source of the above problems but we present a diverse result. This study introduces an ultra-high proportion of grain boundaries on zinc electrodes through femtosecond laser bombardment to enhance stability of zinc metal/electrolyte interface. The ultra-high proportion of grain boundaries promotes the homogenization of zinc growth potential, to achieve uniform nucleation and growth, thereby suppressing dendrite formation. Additionally, the abundant active sites mitigate the side reactions during the electrochemical process. Consequently, the 15â µm Fs-Zn||MnO2 pouch cell achieves an energy density of 249.4â Wh kg-1 and operates for over 60 cycles at a depth-of-discharge of 23 %. The recognition of the favorable influence exerted by UP-GBs paves a new way for other metal batteries.
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Calcium-ion batteries (CIBs) have emerged as a promising alternative for electrochemical energy storage. The lack of high-performance cathode materials severely limits the development of CIBs. Vanadium oxides are particularly attractive as cathode materials for CIBs, and preinsertion chemistry is often used to improve their calcium storage performance. However, the room temperature cycling lifespan of vanadium oxides in organic electrolytes still falls short of 1000 cycles. Here, based on preinsertion chemistry, the cycling life of vanadium oxides is further improved by integrated electrode and electrolyte engineering. Utilizing a tailored Ca electrolyte, the constructed freestanding (NH4)2V6O16·1.35H2O@graphene oxide@carbon nanotube (NHVO-H@GO@CNT) composite cathode achieves a 305 mAh g-1 high capacity and 10 000 cycles record-long life. Additionally, for the first time, a Ca-ion hybrid capacitor full cell is assembled and delivers a capacity of 62.8 mAh g-1. The calcium storage mechanism of NHVO-H@GO@CNT based on a two-phase reaction and the exchange of NH4 + and Ca2+ during cycling are revealed. The lattice self-regulation of VâO layers is observed and the layered vanadium oxides with Ca2+ pillars formed by ion exchange exhibit higher capacity. This work provides novel strategies to enhance the calcium storage performance of vanadium oxides via integrated structural design of electrodes and electrolyte modification.
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The discovery of Mn-Ca complex in photosystem II stimulates research of manganese-based catalysts for oxygen evolution reaction (OER). However, conventional chemical strategies face challenges in regulating the four electron-proton processes of OER. Herein, we investigate alpha-manganese dioxide (α-MnO2) with typical MnIV-O-MnIII-HxO motifs as a model for adjusting proton coupling. We reveal that pre-equilibrium proton-coupled redox transition provides an adjustable energy profile for OER, paving the way for in-situ enhancing proton coupling through a new "reagent"- external electric field. Based on the α-MnO2 single-nanowire device, gate voltage induces a 4-fold increase in OER current density at 1.7 V versus reversible hydrogen electrode. Moreover, the proof-of-principle external electric field-assisted flow cell for water splitting demonstrates a 34% increase in current density and a 44.7 mW/cm² increase in net output power. These findings indicate an in-depth understanding of the role of proton-incorporated redox transition and develop practical approach for high-efficiency electrocatalysis.
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Gel-state polymer electrolytes with superior mechanical properties, self-healing abilities and high Li+ transference numbers can be obtained by in situ polymerization of monomers with hydrogen-bonding moieties. However, it is overlooked that the active hydrogen atoms in hydrogen-bond donors experience displacement reactions with lithium metal in lithium metal batteries (LMBs), leading to corrosion of the lithium metal. Herein, it is discovered that the addition of hydrogen-bond acceptors to hydrogen-bond-rich gel-state electrolytes modulates the chemical activity of the active hydrogen atoms via the formation of hydrogen-bonded intermolecular interactions. The characterizations reveal that the added hydrogen-bond acceptors encapsulate the active hydrogen atoms to suppress the interfacial chemical corrosions of lithium metals, thereby enhancing the chemical stability of the polymer structure and interphase. With the employment of this strategy, a 1.1â Ah LiNi0.8Co0.1Mn0.1O2/Li metal pouch cell achieves stable cycling with 96.3 % capacity retention at 100 cycles. This new approach indicates a feasible path for achieving in situ polymerization of highly stable gel-state-based LMBs.
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Current reconstruction chemistry studies are mainly operated at the laboratory scale, where the operating parameters are different from those used in industrial water electrolyzers. This gap leads to unclear reconstruction behaviors under industrial conditions and constrains the application of catalysts. Here, this work presents a new reconstruction mechanism and anomalous detachment phenomena observed in leaching-type oxygen-evolving precatalysts under industrial conditions, different from the reported results obtained under laboratory conditions. The identified detachment issues are closely linked to the production of a potassium salt separate phase, which proves sensitive to the local environment, and its instability easily leads to catalyst stripping from the substrate. By establishing detachment critical point and operating parameter-detachment correlation, a targeted reconstruction strategy is proposed to achieve smooth ligand leaching and effectively solve the detachment issue. Theoretical analyses validate the dual-site regulation in directionally reconstructed catalysts with optimized intermediate adsorption. Under industrial conditions, the coupled electrolyzer delivers an industrial-level current density at low cell voltage with prolonged durability, 1 A cm-2 at 2 V for over 340 h. This work bridges the gap of leaching-type precatalysts between laboratory test conditions and industrial operating conditions.
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Engineering carbonaceous cathode materials with adequately accessible active sites is crucial for unleashing their charge storage potential. Herein, activated meso-microporous shell carbon (MMSC-A) nanofibers are constructed to enhance the zinc ion storage density by forming a gradient-pore structure. A dominating pore size of 0.86 nm is tailored to cater for the solvated [Zn(H2O)6]2+. Moreover, these gradient porous nanofibers feature rapid ion/electron dual conduction pathways and offer abundant active surfaces with high affinity to electrolyte. When employed in Zn-ion capacitors (ZICs), the electrode delivers significantly enhanced capacity (257 mAh g-1), energy density (200 Wh kg-1 at 78 W kg-1), and cyclic stability (95% retention after 10 000 cycles) compared to nonactivated carbon nanofibers electrode. A series of in situ characterization techniques unveil that the improved Zn2+ storage capability stems from size compatibility between the pores and [Zn(H2O)6]2+, the co-adsorption of Zn2+, H+, and SO4 2-, as well as reversible surface chemical interaction. This work presents an effective method to engineering meso-microporous carbon materials toward high energy-density storage, and also offers insights into the Zn2+ storage mechanism in such gradient-pore structures.
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Sodium-ion batteries (SIBs) are potential candidates for large energy storage usage because of the natural abundance and cheap sodium. Nevertheless, improving the energy density and cycling steadiness of SIB cathodes remains a challenge. In this work, F-doping Na3Al2/3V4/3(PO4)3(NAVP) microspheres (Na3Al2/3V4/3(PO4)2.9F0.3(NAVPF)) are synthesized via spray drying and investigated as SIB cathodes. XRD and Rietveld refinement reveal expanded lattice parameters for NAVPF compared to the undoped sample, and the successful cation doping into the Na superionic conductor (NASICON) framework improves Na+ diffusion channels. The NAVPF delivers an ultrahigh capacity of 148 mAh g-1 at 100 mA g-1 with 90.8% retention after 200 cycles, enabled by the activation of V2+/V5+ multielectron reaction. Notably, NAVPF delivers an ultrahigh rate performance, with a discharge capacity of 83.6 mAh g-1 at 5000 mA g-1. In situ XRD demonstrates solid-solution reactions occurred during charge-discharge of NAVPF without two-phase reactions, indicating enhanced structural stability after F-doped. The full cell with NAVPF cathode and Na+ preintercalated hard carbon anode shows a large discharge capacity of 100 mAh g-1 at 100 mA g-1 with 80.2% retention after 100 cycles. This anion doping strategy creates a promising SIB cathode candidate for future high-energy-density energy storage applications.