Although ether‐based electrolytes have been extensively applied in anode evaluation of batteries, anodic instability arising from solvent oxidability is always a tremendous obstacle to matching with ...high‐voltage cathodes. Herein, by rational design for solvation configuration, the fully coordinated ether‐based electrolyte with strong resistance against oxidation is reported, which remains anodically stable with high‐voltage Na3V2(PO4)2O2F (NVPF) cathode under 4.5 V (versus Na+/Na) protected by an effective interphase. The assembled graphite//NVPF full cells display superior rate performance and unprecedented cycling stability. Beyond that, the constructed full cells coupling the high‐voltage NVPF cathode with hard carbon anode exhibit outstanding electrochemical performances in terms of high average output voltage up to 3.72 V, long‐term cycle life (such as 95 % capacity retention after 700 cycles) and high energy density (247 Wh kg−1). In short, the optimized ether‐based electrolyte enriches systematic options, the ability to maintain oxidative stability and compatibility with various anodes, exhibiting attractive prospects for application.
By rational design of the solvation configuration, a cation–solvent fully coordinated ether‐based electrolyte with strong oxidation resistance up to 4.5 V (versus Na+/Na) was developed and applied in graphite//NVPF and LHC//NVPF full cells which showed superior rate performance and unprecedented cycling stability.
Covalent organic frameworks (COF) possess a robust and porous crystalline structure, making them an appealing candidate for energy storage. Herein, we report an exfoliated polyimide COF composite ...(P‐COF@SWCNT) prepared by an in situ condensation of anhydride and amine on the single‐walled carbon nanotubes as advanced anode for potassium‐ion batteries (PIBs). Numerous active sites exposed on the exfoliated frameworks and the various open pathways promote the highly efficient ion diffusion in the P‐COF@SWCNT while preventing irreversible dissolution in the electrolyte. During the charging/discharging process, K+ is engaged in the carbonyls of imide group and naphthalene rings through the enolization and π‐K+ effect, which is demonstrated by the DFT calculation and XPS, ex‐situ FTIR, Raman. As a result, the prepared P‐COF@SWCNT anode enables an incredibly high reversible specific capacity of 438 mA h g−1 at 0.05 A g−1 and extended stability. The structural advantage of P‐COF@SWCNT enables more insights into the design and versatility of COF as an electrode.
We prepare a polyimide covalent organic framework composite anode by effective in‐situ condensation of anhydride and amine on the surface of single‐walled carbon nanotubes. The construction of the conductive network accelerates the transport of electron. Dual electroactive sites in the framework, carbonyls and aromatic naphthalene rings, could store more potassium ions by the enolization and π‐K+ effect.
Hard carbon is regarded as a promising anode material for sodium‐ion batteries (SIBs). However, it usually suffers from the issues of low initial Coulombic efficiency (ICE) and poor rate performance, ...severely hindering its practical application. Herein, a flexible, self‐supporting, and scalable hard carbon paper (HCP) derived from scalable and renewable tissue is rationally designed and prepared as practical additive‐free anode for room/low‐temperature SIBs with high ICE. In ether electrolyte, such HCP achieves an ICE of up to 91.2% with superior high‐rate capability, ultralong cycle life (e.g., 93% capacity retention over 1000 cycles at 200 mA g−1) and outstanding low‐temperature performance. Working mechanism analyses reveal that the plateau region is the rate‐determining step for HCP with a lower electrochemical reaction kinetics, which can be significantly improved in ether electrolyte.
A self‐supporting, flexible, additive‐free and scalable hard carbon paper (HCP) derived from tissue is rationally developed, and it achieves outstanding Na‐storage properties in terms of high initial Coulombic efficiency (91.2%), superior high‐rate capability, ultralong cyclic stability, as well as outstanding low‐T performance in ether electrolyte. More significantly, the Na‐storage and capacity attenuation mechanism of the HCP anode is revealed.
Impossible voltage plateau regulation for the cathode materials with fixed active elemental center is a pressing issue hindering the development of Na‐superionic‐conductor (NASICON)‐type ...Na3V2(PO4)2F3 (NVPF) cathodes in sodium‐ion batteries (SIBs). Herein, a high‐entropy substitution strategy, to alter the detailed crystal structure of NVPF without changing the central active V atom, is pioneeringly utilized, achieving simultaneous electronic conductivity enhancement and diffusion barrier reduction for Na+, according to theoretical calculations. The as‐prepared carbon‐free high‐entropy Na3V1.9(Ca,Mg,Al,Cr,Mn)0.1(PO4)2F3 (HE‐NVPF) cathode can deliver higher mean voltage of 3.81 V and more advantageous energy density up to 445.5 Wh kg−1, which is attributed by the diverse transition‐metal elemental substitution in high‐entropy crystalline. More importantly, high‐entropy introduction can help realize disordered rearrangement of Na+ at Na(2) active sites, thereby to refrain from unfavorable discharging behaviors at low‐voltage region, further lifting up the mean working voltage to realize a full Na‐ion storage at the high voltage plateau. Coupling with a hard carbon (HC) anode, HE‐NVPF//HC SIB full cells can deliver high specific energy density of 326.8 Wh kg−1 at 5 C with the power density of 2178.9 W kg−1. This route means the unlikely potential regulation in NASICON‐type crystal with unchangeable active center becomes possible, inspiring new ideas on elevating the mean working voltage for SIB cathodes.
A high‐entropy effect is delicately introduced into fluorophosphate cathode for sodium‐ion batteries by in situ partial substitution of active V central atom, preparing a high‐entropy carbon‐free Na3V1.9(Ca,Mg,Al,Cr,Mn)0.1(PO4)2F3 cathode, suppressing the occurrence of detrimental phase transition process in the low‐voltage region, and further lifting up the mean working voltage of pristine Na3V2(PO4)2F3, enhancing sodium storage behavior, rate capability, and cycle performance.
Dual‐ion batteries (DIBs) are a viable option for large‐scale energy storage owing to their high energy density, low cost, and environmental friendliness. However, interfacial instability at both the ...cathode and anode in Li‐graphite DIBs (LG‐DIBs) contributes to poor cycling performance and failed energy storage, severely limiting their application potentials. Herein, a two‐pronged strategy is used to improve the interfacial stability, synergistically stabilizing the graphite cathode by applying a rigid/inert surface coating while building a 3D framework on the lithium anode. The resultant LG‐DIBs are ultrastable and achieve a long cycle life (capacity retention of 80% after 2700 cycles at 200 mA−1) in the all‐climate temperature range from −25 to 40 °C. Ex situ characterization reveals that the cathode–electrolyte interphase on graphite is stabilized by suppressing the electrolyte decomposition and reducing graphite exfoliation. Simultaneously, the framework constructed on the lithium anode induces uniform and dendrite‐free Li deposition owing to its 3D structure. This study not only contributes to the development of practical LG‐DIBs but also points out a promising research direction for other new types of batteries.
A two‐pronged approach is adopted to modify and strengthen the anode electrolyte interphase and cathode electrolyte interphase synergistically in Li‐graphite dual‐ion batteries. The battery life is significantly enhanced in all climates from −25 to 40 °C by inducing homogeneous Li deposition and suppressing successive decomposition of the electrolyte on the graphite cathode.
As a cathode for sodium‐ion batteries (SIBs), Na3V2(PO4)2F3 (NVPF) with 3D open framework is a promising candidate due to its high working voltage and large theoretical capacity. However, the severe ...capacity degradation and poor rate capability hinder its practical applications. The present study demonstrated the optimization of Na‐storage performance of NVPF via delicate lattice modulation. Aliovalent substitution of V3+ at Na+ in NVPF induces the generation of electronic defects and expansion of Na+‐migration channels, resulting in the enhancement in electronic conductivity and acceleration of Na+‐migration kinetics. It is disclosed that the formed stronger NaO bonds with high ionicity than VO bonds lead to the significant increase in structural stability and ionicity in the Na+‐substituted NVPF (NVPF‐Nax). The aforementioned effects of Na+ substitution achieve the unprecedented electrochemical performance in the optimized Na3.14V1.93Na0.07(PO4)2F3 (NVPF‐Na0.07). As a result, NVPF‐Na0.07 delivers a high‐rate capability (77.5 mAh g−1 at 20 C) and ultralong cycle life (only 0.027% capacity decay per cycle over 1000 cycles at 10 C). Sodium‐ion full cells are designed using NVPF‐Na0.07 as cathode and Se@reduced graphene oxide as anode. The full cells exhibit excellent wide‐temperature electrochemical performance from −25 to 25°C with an outstanding rate capability (96.3 mAh g−1 at 20 C). Furthermore, it delivered an excellent cycling performance over 300 cycles with a capacity retention exceeding 90% at 0.5 C under different temperatures. This study demonstrates a feasible strategy for the development of advanced cathode materials with excellent electrochemical properties to achieve high‐efficiency energy storage.
An advanced Na3.14V1.93Na0.07(PO4)2F3 cathode with high ionicity and excellent energy‐storage performance is prepared via aliovalent substitution of V3+ at Na+ sites. It exhibits the higher structural stability and improved electron/ion‐transport kinetics than the pristine Na3V2(PO4)2F3 owing to the stronger NaO and VO bonds, thereby extending the cycle life of NASICON cathode materials.
There are still many problems that hinder the development of sodium‐ion batteries (SIBs), including poor rate performance, short‐term cycle lifespan, and inferior low‐temperature property. Herein, ...excellent Na‐storage performance in fluorophosphate (Na3V2(PO4)2F3) cathode is achieved by lattice regulation based on charge balance theory. Lattice regulation of aliovalent Mn2+ for V3+ increases both electronic conductivity and Na+‐migration kinetics. Because of the maintaining of electrical neutrality in the material, aliovalent Mn2+‐introduced leads to the coexistence of V3+ and V4+ from charge balance theory. It decreases the particle size and improves the structural stability, suppressing the large lattice distortion during cathode reaction processes. These multiple effects enhance the specific capacity (123.8 mAh g−1), outstanding high‐rate (68% capacity retention at 20 C), ultralong cycle (only 0.018% capacity attenuation per cycle over 1000 cycles at 1 C) and low‐temperature (96.5% capacity retention after 400 cycles at −25 °C) performances of Mn2+‐induced Na3V1.98Mn0.02(PO4)2F3 when used as cathode in SIBs. Importantly, a feasible sodium‐ion full battery is assembled, achieving outstanding rate capability and cycle stability. The strategy of aliovalent ion‐induced lattice regulation constructs cathode materials with superior performances, which is available to improve other electrode materials for energy storage systems.
An advanced Na3V1.98Mn0.02(PO4)2F3 cathode with excellent energy‐storage performance is prepared via aliovalent substitution of V3+ at Mn2+ sites. It exhibits higher structural stability and improved electron/ion‐transport kinetics than pristine Na3V2(PO4)2F3 owing to aliovalent Mn2+ induced lattice regulation based on charge balance theory leads to the coexistence of V3+/4+, thereby extending the cycle life of NASICON cathode materials.
Dual-ion battery (DIB) composed of graphite cathode and lithium anode is regarded as an advanced secondary battery because of the low cost, high working voltage and environmental friendliness. ...However, DIB operated at high potential (usually ≥ 4.5 V versus Li+/Li) is confronted with severe challenges including electrolyte decomposition on cathode interface, and structural deterioration of graphite accompanying with anions de-/intercalation, hinder its cyclic life. To address those drawbacks and preserve the DIB virtues, a feasible and scalable surface modification is achieved for the commercial graphite cathode of mesocarbon microbead. In/ex-situ studies reveal that, such an interfacial engineering facilitates and reconstructs the formation of chemically stable cathode electrolyte interphase with better flexibility alleviating the decomposition of electrolyte, regulating the anions de-/intercalation behavior in graphite with the retainment of structural integrity and without exerting considerable influence on kinetics of anions diffusion. As a result, the modified mesocarbon microbead exhibits a much-extended cycle life with high capacity retention of 82.3% even after 1000 cycles. This study demonstrates that the interface modification of electrode and coating skeleton play important roles on DIB performance improvement, providing the feasible basis for practical application of DIB owing to the green and scalable coating procedures
A feasible surface coating on graphite cathode of dual-ion battery has been constructed to adjust the features of CEI on graphite with better cycling life. More ordered anions de-/intercalation behavior has also been confirmed through in-situ XRD. Display omitted
The development of high-performance cathodes for sodium-ion batteries (SIBs) is one key issue required for the success of large-scale energy storage systems. In addition to performance degradation ...during cycling, electrode materials are usually hampered by instability when stored in various environments severely restricting their practical application. Here, we report a stable cathode material that shows no obvious capacity attenuation in various storage conditions. The cathode is composed of regular and homogeneous Na3V2(PO4)2O2F0.99Cl0.01 (NVPFCl) microcubes, with electrochemical properties, including high specific capacity (128.2 mA h g-1 at 0.1 C), excellent rate capability (79.8 mA h g-1 at 20 C), long-term cycle life, and all-climate performance. Studies using in/ex situ characterization and electrode kinetics are implemented to reveal the possible reasons for the stability and electrochemical activity of NVPFCl. This work may provide a pathway for the development of all-climate and storage-stable SIB cathode materials.
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•Regular microcube-shaped NVPFCl as cathode material for SIBs•NVPFCl can be stored in air and water and at various temperatures•Structure evolution of NVPFCl before and after storage is studied via in situ XRD•NVPFCl exhibits notable rate capability, long cycle life, and all-climate stability
Gu et al. report a stable Na3V2(PO4)2O2F0.99Cl0.01 cathode, which exhibits negligible capacity attenuation under various storage conditions, including 26 months of exposure to air, immersion in water, and storage at high/low temperatures. It also displays competitive electrochemical properties and all-climate performance in both half and full SIBs.
The amount of spent lithium-ion batteries (LIBs) is constantly increasing as their popularity grows. It is important to develop a recycling method that cannot only convert large amounts of waste ...anode graphite into high value-added products but is also simple and environmentally friendly. In this work, spent graphite from an anode was transformed into a cathode for dual-ion batteries (DIBs) through a two-step treatment. This method enables the crystal structure and morphology of spent graphite to recover from the adverse effects of long cycling and be restored to a regular layered structure with appropriate layer spacing for anion intercalation. In addition, pyrolysis of the solid electrolyte interphase into an amorphous carbon layer prevents the electrode from degrading and improves its cycling performance. The recycled negative graphite has a high reversible capacity of 87 mAh g−1 at 200 mA g−1, and its rate performance when used as a cathode in DIBs is comparable to that of commercial graphite. This simple recycling idea turns spent anode graphite into a cathode material with attractive potential and superior electrochemical performance, genuinely achieving sustainable energy use. It also provides a new method for recovering exhausted batteries.
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•This study demonstrates a new reuse strategy for graphite anode in spent lithium-ion batteries.•The recovered graphite anode is reused as advanced cathode for Li-based dual-ion batteries.•It delivers excellent anion-storage properties including a specific capacity of 84 mAh g−1 and good rate performance.•This work broadens the high-value utilization ideas of recycled electrode materials from spent lithium-ion batteries..
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