Sodium‐ion batteries (SIBs) are still confronted with several major challenges, including low energy and power densities, short‐term cycle life, and poor low‐temperature performance, which severely ...hinder their practical applications. Here, a high‐voltage cathode composed of Na3V2(PO4)2O2F nano‐tetraprisms (NVPF‐NTP) is proposed to enhance the energy density of SIBs. The prepared NVPF‐NTP exhibits two high working plateaux at about 4.01 and 3.60 V versus the Na+/Na with a specific capacity of 127.8 mA h g−1. The energy density of NVPF‐NTP reaches up to 486 W h kg−1, which is higher than the majority of other cathode materials previously reported for SIBs. Moreover, due to the low strain (≈2.56% volumetric variation) and superior Na transport kinetics in Na intercalation/extraction processes, as demonstrated by in situ X‐ray diffraction, galvanostatic intermittent titration technique, and cyclic voltammetry at varied scan rates, the NVPF‐NTP shows long‐term cycle life, superior low‐temperature performance, and outstanding high‐rate capabilities. The comparison of Ragone plots further discloses that NVPF‐NTP presents the best power performance among the state‐of‐the‐art cathode materials for SIBs. More importantly, when coupled with an Sb‐based anode, the fabricated sodium‐ion full‐cells also exhibit excellent rate and cycling performances, thus providing a preview of their practical application.
A high‐voltage sodium‐super‐ion‐conductor‐type cathode significantly enhances the energy density of sodium‐ion batteries. Its low‐strain crystal lattice during the successive (de‐)sodiation and superior Na transport kinetics promise high‐rate capabilities, long‐term cycle life, superior low‐temperature performance, and excellent full‐cell performance, providing a preview of their practical applications.
Conventional ion batteries utilizing metallic ions as the single charge carriers are limited by the insufficient abundance of metal resources. Although supercapacitors apply both cations and anions ...to store energy through absorption and/or Faradic reactions occurring at the interfaces of the electrode/electrolyte, the inherent low energy density hinders its application. The graphite‐cathode‐based dual‐ion battery possesses a higher energy density due to its high working potential of nearly 5 V. However, such a battery configuration suffers from severe electrolyte decomposition and exfoliation of the graphite cathode, rendering an inferior cycle life. Herein, a new surface‐modification strategy is developed to protect the graphite cathode from the anion salvation effect and the deposition derived from electrolyte decomposition by generating an artificial solid electrolyte interphase (SEI). Such SEI‐modified graphite exhibits superior cycling stability with 96% capacity retention after 500 cycles under 200 mA g−1 at the upper cutoff voltage of 5.0 V, which is much improved compared with the pristine graphite electrode. Through several ex situ studies, it is revealed that the artificial SEI greatly stabilizes the interfaces of the electrode/electrolyte after reconstruction and gradual establishment of the optimal anion‐transport path. The findings shed light on a new avenue toward promoting the performance of the dual‐ion battery (DIB) and hence to make it practical finally.
An artificial layer of a solid electrolyte interphase is fabricated on a graphite cathode for a dual‐ion battery (DIB). Such surface modification can alleviate the electrolyte decomposition at the high working voltage of the anion de‐/intercalation processes and the solvation effect of anions, much improving the cycling stability of the Li//graphite DIB.
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.
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.
Incorporation of N,S‐codoped nanotube‐like carbon (N,S‐NTC) can endow electrode materials with superior electrochemical properties owing to the unique nanoarchitecture and improved kinetics. Herein, ...α‐MnS nanoparticles (NPs) are in situ encapsulated into N,S‐NTC, preparing an advanced anode material (α‐MnS@N,S‐NTC) for lithium‐ion/sodium‐ion batteries (LIBs/SIBs). It is for the first time revealed that electrochemical α → β phase transition of MnS NPs during the 1st cycle effectively promotes Li‐storage properties, which is deduced by the studies of ex situ X‐ray diffraction/high‐resolution transmission electron microscopy and electrode kinetics. As a result, the optimized α‐MnS@N,S‐NTC electrode delivers a high Li‐storage capacity (1415 mA h g−1 at 50 mA g−1), excellent rate capability (430 mA h g−1 at 10 A g−1), and long‐term cycling stability (no obvious capacity decay over 5000 cycles at 1 A g−1) with retained morphology. In addition, the N,S‐NTC‐based encapsulation plays the key roles on enhancing the electrochemical properties due to its high conductivity and unique 1D nanoarchitecture with excellent protective effects to active MnS NPs. Furthermore, α‐MnS@N,S‐NTC also delivers high Na‐storage capacity (536 mA h g−1 at 50 mA g−1) without the occurrence of such α → β phase transition and excellent full‐cell performances as coupling with commercial LiFePO4 and LiNi0.6Co0.2Mn0.2O2 cathodes in LIBs as well as Na3V2(PO4)2O2F cathode in SIBs.
α‐MnS nanoparticles are in situ encapsulated into N,S‐codoped nanotube‐like carbon (α‐MnS@N,S‐NTC) as an advanced anode for Li/Na‐ion batteries. The α → β phase transition during the 1st cycle in LIBs is for the first time revealed by ex situ X‐ray diffraction and high‐resolution transmission electron microscopy studies, which improves the electrode kinetics and Li‐storage properties. α‐MnS@N,S‐NTC also exhibits superior performance in Li/Na‐ion half/full cells.
As promising cathode for sodium‐ion batteries, Na+ Superionic Conductor (NASICON)‐type materials have attracted attention owing to their excellent structural stability, superior ionic conductivity, ...and small volume expansion. However, the vanadium‐based NASICON‐type cathode with the biotoxicity and exorbitant price of V element and the iron‐based cathode with low mean working voltage as well as the intrinsic poor electronic conductivity of polyanionic compounds hinder their practical applications. Herein, a double‐carbon‐layer decorated heterogeneous composite, Na3V2(PO4)3‐Na3Fe2(PO4)(P2O7) (NVFPP/C/G), is successfully prepared for addressing these limitations. Due to their synergistic effect, NVFPP/C/G exhibits excellent electrochemical performance in half‐cell system and superior full‐cell performance when matched with hard carbon anode. Furthermore, the phase composition, electrode kinetics, and phase transition are confirmed by combined analyses of slow scanning power X‐ray diffraction, high‐resolution transmission electron microscopy, cyclic voltammetry with various scan rates, galvanostatic intermittent titration technique, ex situ X‐ray photoelectron spectra, and in situ X‐ray diffraction. This study portends a promising strategy to utilize composite structure engineering for developing advanced polyanionic cathodes.
A double‐carbon‐layer decorated heterogeneous Na3V2(PO4)3‐Na3Fe2(PO4)(P2O7) composite is proposed as cathode for sodium‐ion batteries. Due to the synergistic effect, it exhibits excellent electrochemical performance in half‐cell system and superior full‐cell performance. The heterogeneous composite structure engineering strategy provides a new approach to design high‐performance polyanionic cathodes for batteries.
Polyanion‐type phosphate materials are highly promising cathode candidates for next‐generation batteries due to their excellent structural stability during cycling; however, their poor conductivity ...has impeded their development. Isostructural and multivalent anion substitution combined with carbon coating is proposed to greatly improve the electrochemical properties of phosphate cathode in sodium‐ion batteries (SIBs). Specifically, multivalent tetrahedral SiO44− substitute for PO43− in Na3V2(PO4)3 (NVP) lattice, preparing the optimal Na3.1V2(PO4)2.9(SiO4)0.1 with high‐rate capability (delivering a high capacity of 82.5 mAh g−1 even at 20 C) and outstanding cyclic stability (≈98% capacity retention after 500 cycles at 1 C). Theoretical calculation and experimental analyses reveal that the anion‐substituted Na3.1V2(PO4)2.9(SiO4)0.1 reduces the bandgap of NVP lattice and enhanced its structural stability, Na+‐diffusion kinetics and electronic conductivity. This strategy of multivalent and isostructural anion substitution chemistry provides a new insight to develop advanced phosphate cathodes.
Na3+xV2(PO4)3−x(SiO4)x (0 ≤ x ≤ 0.15) cathode materials are prepared via substitution of the inactive PO43− sites in Na3V2(PO4)3 with isostructural SiO44− anions. The substitution effects on crystal structure, electrochemical properties, Na+‐diffusion kinetics and electronic conductivity are systematically investigated. Multivalent and isostructural anionic substitution provides a new strategy for designing polyanionic materials of sodium‐ion batteries.
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.
A superior Na3V2(PO4)3‐based nanocomposite (NVP/C/rGO) has been successfully developed by a facile carbothermal reduction method using one most‐common chelator, disodium ethylenediamintetraacetate ...Na2(C10H16N2O8), as both sodium and nitrogen‐doped carbon sources for the first time. 2D‐reduced graphene oxide (rGO) nanosheets are also employed as highly conductive additives to facilitate the electrical conductivity and limit the growth of NVP nanoparticles. When used as the cathode material for sodium‐ion batteries, the NVP/C/rGO nanocomposite exhibits the highest discharge capacity, the best high‐rate capabilities and prolonged cycling life compared to the pristine NVP and single‐carbon‐modified NVP/C. Specifically, the 0.1 C discharge capacity delivered by the NVP/C/rGO is 116.8 mAh g−1, which is obviously higher than 106 and 112.3 mAh g−1 for the NVP/C and pristine NVP respectively; it can still deliver a specific capacity of about 80 mAh g−1 even at a high rate up to 30 C; and its capacity decay is as low as 0.0355 % per cycle when cycled at 0.2 C. Furthermore, the electrochemical impedance spectroscopy was also implemented to compare the electrode kinetics of all three NVP‐based cathodes including the apparent Na diffusion coefficients and charge‐transfer resistances.
Go nano! A Na3V2(PO4)3‐based nanocomposite (NVP/C/rGO) has been prepared by using Na2EDTA (disodium ethylenediamintetraacetate) as both sodium‐ and nitrogen‐doped carbon sources and employing reduced graphene oxide as the conductor. The double‐carbon‐modified NVP/C/rGO exhibits much improved properties compared to the single‐carbon modified NVP/C and pristine NVP when used as a cathode for sodium‐ion batteries (see figure).
Abstract
As a sodium superionic conductor, Mn‐rich phosphate of Na
3.4
Mn
1.2
Ti
0.8
(PO
4
)
3
is considered as one of the promising cathodes for sodium‐ion batteries owing to its good thermodynamic ...stability and high working voltage. However, Na
3.4
Mn
1.2
Ti
0.8
(PO
4
)
3
is faced with low electronic conductivity, poor cycling stability and complex phase transition caused by multi‐electron transfers, which limits its practical application. Herein, an anion‐regulated strategy is proposed to optimize the Mn‐rich Na
3.4
Mn
1.2
Ti
0.8
(PO
4
)
3
phosphate cathode. After introducing F anions into the lattice, the rate performance is improved from 60.5 to 72.8 mAh g
−1
at 20 C. Ascribed to unique structure design, the reaction kinetics of Na
3.4
Mn
1.2
Ti
0.8
(PO
4
)
3
are significantly improved, as demonstrated by cyclic voltammetry at varied scan rates and galvanostatic intermittent titration technique. The generated M‐F bond inhibits Jahn–Teller effect with an improved cycle stability (85.8 mAh g
−1
after 1000 cycles at 5 C with 94.3% capacity retention). Interestingly, reaction mechanism of Na
3.4
Mn
1.2
Ti
0.8
(PO
4
)
3
with the complex two‐phase and solid solution reactions changes to the whole solid solution reaction after fluorine substitution, and leads to a smaller volume change of 5.41% during reaction processes, which is verified by in situ X‐ray diffraction. This anion regulation strategy provides a new method for designing the high‐performance phosphate cathode materials of sodium‐ion batteries.
