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Niobium oxides have fascinated numerous interests for ultrafast sodium‐ion batteries due to their impressive stability, fast pseudocapacitive kinetics, and high safety features. However, the poor intrinsic electronic conductivity and unrevealed mechanisms largely limit their further applications. Here, inspired by density functional theory (DFT) calculations, the introduction of conductor heterostructure (Nb2O5/NbSe2) can largely decrease the bulk phase inserted energy of Na+ from 9.88 to −3.54 eV, as well as promote the delocalization of electron, greatly improving the electrical conductivity of Nb2O5. As expected, the as‐obtained orthorhombic niobium pentoxide (T‐Nb2O5‐x‐NbSe2@C) delivers a high conductivity of 3.69 S cm−1, exhibiting a great improvement of four orders magnitude than that of the parent Nb2O5 (1.87 × 10−4 S cm−1). Impressively, T‐Nb2O5‐x‐NbSe2@C possesses a high reversible capacity of 249 mAh g−1 at 0.1 A g−1, as well as excellent rate performance of 63 mAh g−1 at 5.0 A g−1, nearly twins the capacity of parent porous Nb2O5. Furthermore, the periodic evolutions of the main peaks for targeted electrodes during repeated charging/discharging processes have been further revealed by in situ XRD, demonstrating a highly reversible inserted/extracted storage mechanism of Na+. This work provides a novel method to improve the conductivity of materials by constructing conductor heterojunction. [ABSTRACT FROM AUTHOR]

Antimony（Sb） has high theoretical specific capacity and moderate reaction potential, but poor cycling stability and rate performance caused by large volume expansion and sluggish reaction kinetics limit its development in alkali‐ion batteries. The construction of carbon/Sb composites can solve this problem, but the traditional single carbon composite and poor Sb/carbon interface have limited promotion. Here, under the guidance of theoretical calculations, a strategy of hierarchical double carbon composite is proposed to enhance the performance of Sb anode, and systematically reveal the lithium/sodium ions (Li+/Na+) storage mechanism of Sb in complex composite system. Sb nanoparticles (Sb NPs) are encapsulated in carbon sphere matrix with strong interfacial chemical bond to form the first level composite material, and then the highly conductive and mechanically strong graphene is used as a three‐dimensional skeleton network to connect the first level composite to form the second level composite material. The hierarchical double carbon/Sb composite exhibits excellent rate (228 mAh g−1 @ 20 A g−1) and long cycling performance (373.7 mAh g−1 @ 2 A g−1 after 2200 cycles, capacity retention of 93.1%). This work may expand structural design and interface regulation of Sb/C composites and providing theoretical guidance for metal anodes development. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs) have rapidly risen to the forefront of energy storage systems as a promising supplementary for Lithium‐ion batteries (LIBs). Na3V2(PO4)2F3 (NVPF) as a common cathode of SIBs, features the merits of high operating voltage, small volume change and favorable specific energy density. However, it suffers from poor cycling stability and rate performance induced by its low intrinsic conductivity. Herein, we propose an ingenious strategy targeting superior SIBs through cross‐linked NVPF with multi‐dimensional nanocarbon frameworks composed of amorphous carbon and carbon nanotubes (NVPF@C@CNTs). This rational design ensures favorable particle size for shortened sodium ion transmission pathway as well as improved electronic transfer network, thus leading to enhanced charge transfer kinetics and superior cycling stability. Benefited from this unique structure, significantly improved electrochemical properties are obtained, including high specific capacity (126.9 mAh g−1 at 1 C, 1 C = 128 mA g−1) and remarkably improved long‐term cycling stability with 93.9% capacity retention after 1000 cycles at 20 C. The energy density of 286.8 Wh kg−1 can be reached for full cells with hard carbon as anode (NVPF@C@CNTs//HC). Additionally, the electrochemical performance of the full cell at high temperature is also investigated (95.3 mAh g−1 after 100 cycles at 1 C at 50 °C). Such nanoscale dual‐carbon networks engineering and thorough discussion of ion diffusion kinetics might make contributions to accelerating the process of phosphate cathodes in SIBs for large‐scale energy storages. [ABSTRACT FROM AUTHOR]

Designing Sb/carbon composite is an effective strategy to enhance the cycle stability and rate capability of Sb anodes for sodium ion batteries. However, the introduction of carbon often leads to a loss in specific capacity and initial Coulombic efficiency (ICE). In this work, a new perspective is adopted by focusing on improving the "sloping capacity" contribution of carbon (C) in Sb/C composites, rather than solely increasing the platform capacity of Sb as traditionally done. Theoretical predictions indicate that constructing Sb/C composites with high Sb and carbon interfacial areas can provide more Na adsorption sites, thus enhancing the "sloping capacity" of amorphous carbon. Guided by DFT, a rational Sb/C/NSCDs‐2(N) is successfully developed by self‐embedding Sb nanodots into 2D‐amorphous carbon sheets doped with N/S. Sb/C/NSCDs‐2(N) exhibits abundant Sb/carbon interfacial areas and excellent nanoscale effects, demonstrating ideal electrochemical sodium storage performances. Impressively, the Sb/C/NSCDs‐2(N) provides a "sloping capacity" close to 160 mAh g−1. Significantly, owing to the fact that these interfaces and defects are not in direct contact with the electrolyte, the side reaction of electrolyte is effectively inhibited, leading to no decrease of ICE. [ABSTRACT FROM AUTHOR]

Interfacial coupling strategy has allured extensive attention for the possibility to endow active electrode materials with superior performance. However, the design of strong coupling engineering with interfacial evolution during electrochemical processes is very challenging. Herein, inspired by the powerful robotic arms and density functional theory calculations, multiple functional groups identified with intense affinity to V atom are successfully grafted on carbon nanotubes (CNTs), thereby in situ building robust interfacial bonds (VOC and VC) to tightly anchor VS4 particles. The largely decreased band gaps and energy barriers show the fortified conductivity of VS4‐CNT heterostructure. Besides, the spacial confinement effect induced by interfacial linkages substantively enhances the mechanical properties to inhibit structural collapse, and restrains the dissolution of polysulfides as verified by molecular dynamics simulations, thus prolonging life span. Excellent energy density of 105.5 Wh kg–1 can be delivered after assembling full sodium‐ion capacitors (activated carbon//VS4‐CNT). Significantly, the reversible interfacial bonds confirmed by various ex situ characteristics during discharge/charge processes hold the key to remarkable sodium storage ability and prominent initial coulombic efficiency. More impressively, strong interfacial coupling effect can establish synergistic soft‐rigid integrated solid‐electrolyte interphase film, which is conducive to elevating the electrochemical performance of electrodes, convincingly constructing advanced sodium‐ion capacitors. [ABSTRACT FROM AUTHOR]

The high‐throughput scalable production of inexpensive and efficient electrode materials at high current densities demanded by industry is a huge challenge for large‐scale implementation of energy storage technologies. Here, inspired by theoretical calculations that a FeS2/TiO2 heterostructure with built‐in electric field (BEF) can reduce the reaction energy barrier and enhance charge transport, the scalable production of cheap FeS2/TiO2 heterostructure is fabricated by utilizing natural ilmenite as precursor, exhibiting excellent electrochemical performances for sodium‐ion capacitors (SICs) anode. Assembling it with activated carbon (AC) cathode for SICs delivers high energy density (73.7 Wh kg−1) and high power density (10 kW kg−1) as well as outstanding cycle lifespan. Impressively, the method breaks through the traditional preparation approach by using natural minerals instead of high‐purity chemical raw materials as precursors for constructing heterojunctions, and price of the mineral is nearly five orders of magnitude lower than that of commercial chemical raw materials with high‐purity, which greatly reduces raw materials cost and is available for mass production. Similarly, the method can be extended to utilize other minerals to construct heterostructures, thus achieving expanded electrochemical performance, which exhibits huge potentials in electrochemical energy storage. [ABSTRACT FROM AUTHOR]

Nowadays sodium‐based energy storage systems (Na‐based ESSs) have been widely researched as it possesses the possibility to replace traditional energy storage media to become next generation energy storage system. However, due to the irreversible loss of sodium ions in the first cycle, development of Na‐based ESSs is limited. Presodiation, as a strategy of adding excess sodium ions to the system in advance, accomplishes the enhancement of electrochemical performance. In this minireview, different presodiation strategies applied in sodium‐based energy storage systems will be summarized in detail, their functions and corresponding mechanisms will be discussed as well. Furthermore, the current novel application of presodiation method in other aspects of Na‐based ESSs will be mentioned additionally. At last, in the view of present research status of presodiation, issues that can be mitigated are put forward and guidelines are given on how to deliberate in‐depth presodiation technology in the future, dedicating to promote the further development of Na‐based ESSs. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs) have grasped renewed attentions in recent years owing to the blooming growth of clean energy and corresponding demands of grid‐scale energy storage. Note that, the properties of cathode materials are quite important to the development of SIBs as they largely determine the energy density, cycle life, and cost of a battery. Direct inheriting those Co/Ni based layered cathodes that are successfully utilized in lithium‐ion batteries seems to be impracticable for SIBs in view of the high materials costs. Fortunately, the discovery of the electrochemical activity of Fe3+/Fe4+ redox couple in sodium layered materials has opened a new way to design high capacity/voltage and low‐cost cathodes for SIBs. To date, various Fe‐based layered oxides have been explored, showing encouraging electrochemical performances in SIBs. However, issues and challenges still remain upon the practical utilization of Fe‐based layered cathodes, calling for further targeted and in‐depth investigations. In this review, the developing history, key problems, and current progress of Fe‐based layered cathodes on electrochemical performances and working mechanism are summarized and discussed. In addition, possible research trends and perspectives are proposed. It is believed that Fe‐based layered oxides will be one of the most attractive cathodes for SIBs. [ABSTRACT FROM AUTHOR]

The use of a sacrificial cathode additive as a pre‐metallation method could ensure adequate metal sources for advanced energy storage devices. However, this pre‐metallation technique suffers from the precise regulation of decomposition potential of additive. Herein, a molecularly compensated pre‐metallation (Li/Na/K) strategy has been achieved through Kolbe electrolysis, in which the electrochemical oxidation potential of a metal carboxylate is manipulated by the bonding energy of the oxygen–metal (O–M) moiety. The electron‐donating effect of the substituent and the low charge density of the cation can dramatically weaken the O–M bond strength, further bringing out the reduced potential. Thus, sodium acetate exhibits a superior pre‐sodiation feature for sodium‐ion battery accompanied with a large irreversible specific capacity of 301.8 mAh g−1, remarkably delivering 70.6 % enhanced capacity retention in comparison to the additive‐free system after 100 cycles. This methodology has been extended to construct a high‐performance lithium‐ion battery and a lithium/sodium/potassium‐ion capacitor. [ABSTRACT FROM AUTHOR]

High‐efficiency energy storage technologies and devices have gained numerous attention because of their ever‐increasing requirement. Sodium‐ion capacitors (SICs), as a burgeoning electrochemical energy storage device, combine virtues of rechargeable batteries and electrochemical double layer supercapacitors, delivering both high energy–power density and long cycling life. In the past decades, great efforts have been made to find suitable anode material to conquer the kinetic imbalance between the battery‐type anode with sluggish bulk redox reaction and the capacitor‐type cathode with fast ion absorption/desorption process. By exploring high‐rate performance anode materials, the great reaction kinetic gap between cathodes and anodes can be narrowed down, which directly affects the energy–power densities of SICs. In this article, an overview of advanced battery‐type anode materials is offered for high‐performance SICs with an emphasis on anode structural design and improved energy–power density, including carbonaceous materials, metallic compounds, MXene, organic polymers, and so on. Furthermore, the implementation of presodiation for the sake of optimizing the SICs is also illustrated. Finally, the challenges faced and the perspectives for future developing trends of SICs are discussed. [ABSTRACT FROM AUTHOR]

Sodium‐ion capacitors (SICs) have triggered considerable attention due to potential high energy densities under high power densities. The presodiation process of anodes is very important for the construction of high‐performance SICs; however, in the current presodiation method, metallic sodium is utilized as the presodiation agent through the assembling/disassembling of half‐cells, which is very complicated and dangerous, greatly hindering the development of SICs. Herein, a novel voltage‐induced high‐efficient in situ presodiation approach is successfully realized by introducing organic sodium salts as the sodium sources into the cathode. Moreover, the irreversible electrochemical characteristic of organic sodium salts triggered by high voltage could provide sufficient sodium sources for presodiation without any negative effects for further operation of SICs. Significantly, the diversified anodes like carbon and TiO2 are successfully presodiated and the corresponding SICs manifest excellent electrochemical performances. This rational strategy is anticipated to shed light on a potential avenue for greatly simplifying the assembly process of the SICs, which may largely accelerate the commercialization process of SICs. [ABSTRACT FROM AUTHOR]

Abstract: Designing potential anodes for sodium‐ion battery with both remarkable durability and high‐rate capability has captured enormous attention so far. The engineering of size and morphology is deemed as an effective manner to boost the electrochemical properties. Owing to the anisotropic self‐assembly of iron selenide, rod‐like FeSe2 coates with nitrogen‐doped carbon is prepared through the thermal reaction of Prussian blue with selenium. Notably, the cyano groups are effectively transformed into N‐doped carbon with FeNC bonds, which uniformly coats FeSe2, prompting Na+ transportations. Interestingly, the particle size is tailored by heating rates, along with increased carbon content, leading to broadened energy levels for redox reaction. Bestowed by these advantages, the FeSe2/N‐C as Na‐storage anode delivers impressive electrochemical properties. Even at a rather high rate of 10.0 A g−1, a considerable capacity of 308 mAh g−1 is yielded over 10 000 loops. Supported by the detailed analysis of kinetic features, reduced size of particles could bring about the enhanced contributions of pseudocapacitive and quickening rate of ions transferring. The phase evolutions are further investigated by in situ EIS and ex‐situ technologies. The work is expected to provide a new strategy to prepare metal‐selenide with controllable size and induce the faster kinetic of high‐rate materials. [ABSTRACT FROM AUTHOR]

Antimony sulfide (Sb 2 S 3 ) has been shown as a promising candidate for sodium ions batteries, in considering the gravimetric energy density and high theoretical capacity. Hollow-sphere Sb 2 S 3 coated with carbon are successfully designed through Oswald ripening process. The Sb 2 S 3 /C utilized as SIBs anode displays excellent electrochemical properties, delivering a high charge capacity of 693.4 mAh g −1 at 0.2 A g −1 between 0.01 and 3.0 V (vs. Na + /Na). Its reversible capacity can keep 545.6 mAh g −1 , with a retention of ∼80% after 100 cycles. Even the current densities return from 6.4 to 0.2 A g −1 , the Sb 2 S 3 /C still maintains 550.8 mAh g −1 after 70 cycles. Combining the large void space with carbon layer, the advantages are noticed when the increased electrolyte penetration area, improved electronic conductivity and shortened Na + diffusion length are attained concurrently, resulting in the excellent specific capacity and cycling stability. The study provides an effect strategy in improving the electrochemical performances of metal sulfides as anode for SIBs. [ABSTRACT FROM AUTHOR]

The ever-increasing demand of lithium-ion batteries (LIBs) caused by the rapid development of various electronics and electric vehicles will be hindered by the limited lithium resource. Thus sodium-ion batteries (SIBs) have been considered as a promising potential alternative for LIBs owing to the abundant sodium resource and similar electrochemical performances. In recent years, significant achievements regarding anode materials which restricted the development of SIBs in the past decades have been attained. Significantly, the sodium storage feasibility of carbon materials with abundant resource, low cost, nontoxicity and high safety has been confirmed, and extensive investigation have demonstrated that the carbonaceous materials can become promising electrode candidates for SIBs. In this review, the recent progress of the sodium storage performances of carbonaceous materials, including graphite, amorphous carbon, heteroatom-doped carbon, and biomass derived carbon, are presented and the related sodium storage mechanism is also summarized. Additionally, the critical issues, challenges and perspectives are provided to further understand the carbonaceous anode materials. [ABSTRACT FROM AUTHOR]

As an anode material for sodium-ion batteries (SIBs), antimony (Sb) has attracted significant interest due to its high theoretical specific capacity. However, it suffers from a huge volume change during the sodiation–desodiation process that leads to poor cyclability. Herein, cross-linked carbon nanosheet frameworks (CCNFs) and Sb nanoparticles (NPs) were combined to construct a high-performance anode material for SIBs. In this composite, Sb nanoparticles were tightly anchored on the carbon frameworks; this provided enhanced structural stability to Sb and prevented the agglomeration during the charge–discharge process. Sb provides a high specific capacity, and the carbon frameworks ensure structural integrity and conductive networks. Moreover, due to this synergistic effect, the as-prepared Sb/CCNFs composite exhibits an excellent cycle stability and rate performances. Considering both the capacity and rate property, the overall performances of the obtained Sb/CCNFs reach the highest level in comparison with those of the reported Sb/C composites. The reversible (charge) capacity can remain 549.3 mA h g−1 after 100 cycles at a current density of 100 mA g−1. Moreover, a superior rate performance is observed as the reversible capacity still reaches 318 mA h g−1 at a high current density of 3200 mA g−1. Therefore, this study proposes an effective methodology to improve the key performances of the SIB anode. [ABSTRACT FROM AUTHOR]

The conventional strategies for obtaining S/N-codoped carbon materials suffer from a series of problems caused by their complicated experimental procedures. Here, S,N-codoped carbon nanosheets were firstly prepared by a solvent-free one-pot method, displaying an ultra-thin sheet-like structure, a tunable interlayer distance ranging from 0.37 nm to 0.41 nm, and a large surface area up to 809 m2 g−1. When they were used as an anode for sodium-ion batteries (SIBs), an outstanding sodium-ion storage performance of 380 mA h g−1 was acquired at 100 mA g−1, which can be attributed to the expanded interlayer distance caused by the introduction of the large covalent radius-sulfur. The initial coulombic efficiency improved to 60.9%, which may benefit from N-doping. Most importantly, an excellent rate capability of ∼178 mA h g−1 was observed at a current density of 5 A g−1 after 5000 cycles, which is among best of the state-of-the-art carbon-based SIBs. Interestingly, the morphology of the obtained carbon materials can be tuned from bulk to flake by adjusting the sulfur content or temperature. Given this, this work provides a new method to construct co-doped carbon (especially tri-doped and multi-doped carbon) and shows that the strategy of co-doping of heteroatoms can effectively optimize the nano/microstructure and enhance the rate capability of the carbon materials. [ABSTRACT FROM AUTHOR]

Rod-like α-MoO 3 is successfully designed by alternating voltage induced electrochemical synthesis (AVIES) approach. The morphology and texture of MoO 3 is effectively controlled by applying various calcination temperature of 300–600 °C. Notably, the α-MoO 3 microrods growing along [001] direction have the high aspect ratio, and the randomly stacked structure can facilitate the charge transfer and offer more active sites for sodium storage. When utilized for sodium-ion batteries, it presents the high charge capacities of 305 mAh g −1 at 1C and 143 mAh g −1 at 10C. Even after 3000 cycles at 10C, a significant capacity of 108 mAh g −1 is still delivered, highlighting its marvelous electrochemical properties. This work may be a compelling exploration for developing metal/metal oxides materials for sodium storages by AVIES. [ABSTRACT FROM AUTHOR]

Yolk-like TiO2 are prepared through an asymmetric Ostwald ripening, which is simultaneously doped by nitrogen and wrapped by carbon from core to shell. It presents a high specific surface area (144.9 m2 g−1), well-defined yolk-like structure (600-700 nm), covered with interweaved nanosheets (3-5 nm) and tailored porosity (5-10 nm) configuration. When first utilized as anode material for sodium-ion batteries (SIBs), it delivers a high reversible specific capacity of 242.7 mA h g−1 at 0.5 C and maintains a considerable capacity of 115.9 mA h g−1 especially at rate 20 C. Moreover, the reversible capacity can still reach 200.7 mA h g−1 after 550 cycles with full capacity retention at 1 C. Even cycled at extremely high rate 25 C, the capacity retention of 95.5% after 3000 cycles is acquired. Notably, an ultrahigh initial coulombic efficiency of 59.1% is achieved. The incorporation of nitrogen with narrowing the band gap accompanied with carbon uniformly coating from core to shell make the NC TiO2-Y favor a bulk type conductor, resulting in fast electron transfer, which is beneficial to long-term cycling stability and remarkable rate capability. It is of great significance to improve the energy-storage properties through development of the bulk type conductor as anode materials in SIBs. [ABSTRACT FROM AUTHOR]

Interconnected carbon nanofibers networks (ICNNs) prepared through the carbonization of polypyrrole (PPy) precursor are utilized as conductive pathways and buffer to improve the Na storage performance of antimony (Sb) as anode for sodium-ion batteries (SIBs). The as-obtained Sb/ICNNs composite exhibits excellent cycle stability. The reversible capacity can remain 542.5 mAh g −1 with a high capacity retention of 96.7% after 100 cycles at a current density of 100 mA g −1 . And the superior rate performance is also observed, the reversible capacity can still reach 325 mAh g −1 at a high current density of 3200 mA g −1 . These great electrochemical performances observed above suggest that this type of composite can be a nice option for advanced SIBs anode materials and may be extended to other active materials/ICNNs composite electrode. [ABSTRACT FROM AUTHOR]

Sb/acetylene black (Sb/AB) composite was firstly applied as anode for sodium-ion batteries (SIBs). A great electrochemical performance of the composite was obtained when utilizing this composite for SIBs. It was found that the charge capacity can reach 473 mAh g −1 in the 70th cycle at a current density of 100 mA g −1 , and we also note that the capacity contributed by Sb was about 624 mAh g −1 , which is very close to its theoretical sodium storage capacity (660 mAh g −1 corresponding to a formula of Na 3 Sb), demonstrating the full utilization of Sb. It is interesting to see that even at a high current density of 1600 mA g −1 , the capacity can still reach 281 mAh g −1 . [ABSTRACT FROM AUTHOR]

Na4Mn1.5Fe1.5(PO4)2P2O7 (NMFPP), with its low cost and high energy density, is essential for accelerating the commercialization of sodium‐ion batteries. However, its practical application is limited by serious voltage hysteresis and detrimental Jahn‐Teller distortions. Herein, a high operating voltage and superior stable Nb‐doped NMFPP with fewer intrinsic anti‐site defects are elaborately designed by the reconstruction of the crystal lattice and electronic distribution. By introducing higher charge density Nb─O bonds, the lengths of Mn‐O bonds are shortened, enhancing lattice stability. As a result, the lattice volume contracted during Na+ extraction/insertion is decreased with niobium‐modified Na4(Mn0.5Fe0.5)2.94Nb0.06(PO4)2P2O7, mitigating lattice distortion from the Jahn‐Teller effect and increasing the capacity retention after 1000 cycles from 57.5% to 82.3%. More importantly, the delayed effect of Mn2+ involvement in redox reactions is significantly reduced, raising the average operating voltage from 3.32 to 3.64 V and increasing the overall energy density by 13%. This study opens new avenues to develop advanced sodium‐ion battery cathode materials with high energy density and long calendar life for energy storage. [ABSTRACT FROM AUTHOR]

Heteroatom modification represents one of the major areas of carbon materials' research in electrical energy storage. However, the influence of heteroatomic state evolution on electrochemical properties remains an elusive topic. Herein, thiophene‐2,5‐dicarboxylic acid is chemically activated to prepare O,S‐diatomic hybrid carbon material (OS–C). The heteroatoms and carbon matrix coexist in the form of CO/CO and CS/SS bonds, which introduce porous networks to the partially graphitized carbon skeleton and provide abundant active sites for better ion absorption. Moreover, the heteroatoms and carbon matrix are bridged to establish stable pseudocapacitive functional groups like quinoid unit and disulfide bonds, which can be electrochemically converted into benzenoid units and mercaptan anions through Faradaic reactions to further improve the reversible capacity. Combined with the detailed kinetic exploration and in situ investigation of the electrochemical impedance spectra, the energy storage mechanism for lithium/sodium is proposed in the following steps: Faradaic reactions at a higher potential range, energy storage at active sites, and ions intercalation on the graphitized parts in the low‐voltage states. Greatly, the electrode can store lithium up to the capacity of ≈700 mAh g−1, while also delivering ≈330 mAh g−1 of sodium storage, providing lifetimes in excess of thousands of cycles. [ABSTRACT FROM AUTHOR]

Antimony-based materials represent promising anode materials for sodium ion batteries (SIBs) owing to their high theoretical capacity, however, the large volume expansion and low ionic conductivity during the electrochemical process prohibit them from reaching their theoretical expectations. In this work, Sb 2 S 3 @C and Sb 2 Se 3 @C nanodots with uniform diameters of 19.0 nm and 20.7 nm were synthesized by H 2 /C thermal reduction and co-sulfurization (selenization) of sodium stibogluconate. Each Sb 2 S 3 and Sb 2 Se 3 nanodot was coated by an interconnecting carbon network with weak graphitization, which further crosslinked together to form a high conductive framework. When applied as anode for SIBs, they exhibited desired sodium storage properties, especially the excellent cycling stability of Sb 2 Se 3 @C nanodots with a reversible capacity of 316.1 mA h g−1 after 100 cycles at 100 mA g−1 and 269.1 mA h g−1 after 200 cycles at 1 A g−1, which was consistent with the calculated result of theoretical volume changes (264% and 246%) and density functional theory (DFT) calculation for both materials during the Na+ intercalation processes, as expected. [Display omitted] • Sb 2 S 3 (Sb 2 S 3) nanodots/C composites have been successfully fabricated. • The volume changes of two materials during the Na+ insertion/deintercalation process have been calculated and analyzed in details. • The satisfactory sodium storage properties are achieved, which is consistent with the result of theoretical calculation. [ABSTRACT FROM AUTHOR]

Here we show that P2/O3 biphasic layered structure is originated from internal heterogeneity of "cationic potential" induced by locally compositional non-uniformity, which largely depends on the temperature-driven reaction thermodynamics and kinetics. The clarified material-formation mechanism enables facile design and preparation of P2/O3 biphasic materials with much-improved sodium-storage performances than single-phase one, promoting the exploration of advanced cathodes for sodium-ion batteries. [Display omitted] Sodium layered oxides generally suffer from deep-desodiation instability in P2 structure and sluggish kinetics in O3 structure. It will be great to design P2/O3 biphasic materials that bring the complementary merits of both structures. However, such exploration is hindered by the ambiguous mechanism of material formation. Herein, supported by theoretical simulations and various spectroscopies, we prove that P2/O3 biphasic structures essentially originate from the internal heterogeneity of cationic potential, which can be realized by constraining the temperature-driven ion diffusion during solid-state reactions. Consequently, P2/O3 biphasic Na 0.7 Ni 0.2 Cu 0.1 Fe 0.2 Mn 0.5 O 2– δ with well-designed quaternary composition is successfully obtained, exhibiting much-improved rate capabilities (62 mAh g−1 at 2.4 A g−1) and cycling stabilities (84% capacity retention after 500 cycles) than its single-phase analogues. Furthermore, synchrotron-based diffraction and X-ray absorption spectroscopy are employed to unravel the underlying sodium-storage mechanism of the P2/O3 biphasic structure. This work presents new insights toward the rational design of advanced layered cathodes for sodium-ion batteries. [ABSTRACT FROM AUTHOR]

Titanium dioxide, promising anode materials for sodium ion batteries, nonetheless, suffers from its inferior charge transfer kinetics owing to low diffusion coefficient and poor electronic conductivity, which results in its unsatisfactory high-rate capability. Here, an oxygen vacancy (OV) engineering assisted in high-content anion (S/Se/P) doping strategy to enhance its charge transfer kinetics for ultrafast sodium-storage performance is proposed to address these issues and expectative results have been obtained. [Display omitted] The rate-determining process for sodium storage in TiO 2 is greatly depending on charge transfer happening in the electrode materials owing to its inferior diffusion coefficient and electronic conductivity. Apart from reducing the diffusion distance of ion/electron, the increasement of ionic/electronic mobility in the crystal lattice is also very important for charge transport. Here, an oxygen vacancy (OV) engineering assisted in high-content anion (S/Se/P) doping strategy to enhance charge transfer kinetics for ultrafast sodium-storage performance is proposed. Theoretical calculations indicate that OV-engineering evokes spontaneous S doping into the TiO 2 phase and achieves high dopant concentration to bring about impurity state electron donor and electronic delocalization over S occupied sites, which can largely reduce the migration barrier of Na+. To realize the speculation, high-content anion doped anatase TiO 2 /C composites (9.82 at% for S in A-TiO 2– x -S/C) are elaborately designed. The optimized A-TiO 2– x -S/C anode exhibits extraordinarily high-rate capability with 209.6 mAh g−1 at 5000 mA g−1. The assembled sodium ion capacitors deliver an ultrahigh energy density of 150.1 Wh kg−1 at a power density of 150 W kg−1 when applied as anode materials. This work provides a new strategy to realize high content anion doping concentration, and enhances the charge transfer kinetics for TiO 2 , which delivers an efficient approach for the design of electrode materials with fast kinetic. [ABSTRACT FROM AUTHOR]

The ultrathin TiO 2 nanosheets doped by nitrogen tightly attaching on carbon nanotubes are designed and evaluated as anode for sodium ion batteries. The TiO 2 nanosheets attaching on carbon nanotubes composite shows a high specific capacity of 248.5 mAh g −1 at the rate of 0.5 C, and it can still deliver a specific capacity of 100.9 mAh g −1 at a high rate of 20 C, which verifies an outstanding sodium storage capacity and an excellent rate capability. More encouragingly, at a rate of 10 C, the specific capacity can be still kept at 154.2 mAh g −1 after 3500 cycles, displaying a remarkable long-term cyclic stability. Note that the corresponding kinetics analysis suggests that the pseudocapacitive behaviour is responsible for the updating sodium storage performances of TiO 2 nanosheets composite. Additionally, the cooperation effects of carbon nanotubes preservation and nitrogen modification can provide fast electronic pathways, and the TiO 2 nanosheets can promote sodium ions transport and increase the active sites for sodium storage. The merits of multiple functional and tailor-designed strategies make contributions to develop high-performance TiO 2 anodes in sodium ion batteries. [ABSTRACT FROM AUTHOR]

Na 3 V 2 (PO 4 ) 3 (NVP) is a very promising cathode material in sodium ion battery for rapidly emerging large-scale energy storage with its classical 3D NASCION structure. However, the cycling life and rate performances are restricted its low electronic conductivity. To overcome these, the double carbon-wrapped Na 3 V 2 (PO 4 ) 3 composite is firstly designed through rheological phase approach, delivering enhanced electrochemical properties. The unique double carbon layers are composed of uniform amorphous carbons as protecting framework for stabilizing the structure, as well as the graphitized carbon sheets playing the role of conductive network for better electronic conductivity. This double carbon-wrapped Na 3 V 2 (PO 4 ) 3 composite exhibits a high reversible capacity of 99.8 mAh g −1 over 500 cycles at 1 C (110 mA g −1 ), yielding the coulombic efficiency of ∼99.8%. Meanwhile, it displays an initial capacity of 73 mAh g −1 at 100 C and remains 55 mAh g −1 at an ultra-rate of 200 C. Even after cycling at 200 C over 12 000 cycles, the Na + -storage capacity of 40 mAh g −1 with a retention of 72.7% is still obtained, highlighting its excellent long cycling life and remarkable rate performances. [ABSTRACT FROM AUTHOR]

Carbon materials have been widely applied in the energy storage devices, however, the preparation of suitable carbon materials for sodium-ion batteries (SIBs) is still a challenge. In this paper, N-doped porous carbon material (NDPCs) with rose-like structure has been successfully prapared through pyrolysis of the as-prepared polyimides in-situ. The NDPCs shows rose-like structure derived from 2D nanosheets, an expanded interlayer distance of 0.387 nm, a high specific surface area of 215.7 m 2 g −1 and the electrochemical performances for Na-ion batteries are systematically investigated. A high reversible specific capacity of 240 mAh g −1 at a current density of 100 mA g −1 is attained and a specific capacity of 224 mAh g −1 is remained even after 100 cycles. Remarkably, even at a high current density of 3.2 A g −1 , the reversible specific capacity of 104 mAh g −1 can be observed. This excellent performance of NDPCs electrode may be ascribed to its superior structure, since the micropore/mesopore might efficiently shorten the diffusion distance of Na-ion and the enlarged interlayer spacing of 0.38 nm is significant for Na-ion insertion/extraction. Significantly, the approach to prepare carbon materials from PI may be generalized to other polymers. [ABSTRACT FROM AUTHOR]

Hard Carbons (HCs) are widely investigated as anode materials for Sodium-ion batteries (SIBs), for the abundance of the precursors and their easy synthesis. However, the intercalation of Na+ in the HCs is a big challenge for the design of high-performance SIBs. Heteroatom-doping can effectively facilitate the intercalation of Na+ in the anode material. Herein, a series of double and triple-atom phosphorus-nitrogen, phosphorus-sulfur, nitrogen-sulfur and phosphorus-nitrogen-sulfur in the camphor wood (Cmph) derived-HCs are fabricated, and their electrochemical performances as anodes for SIBs are investigated. The P–N–S-Cmph delivers high initial coulombic efficiency (ICE) of 70.74%%, an outstanding rate performance and good cycling stability, maintaining a specific capacity of 280 mAh g−1 at 2000 mA g−1 after 500 cycles. The excellent performances of the anode materials are assigned to the synergetic effect of the heteroatom-doping of S, N and P enlarging the interlayer spacing of the doped-Cmph-HCs, increasing the intercalation/deintercalation rate of Na+ in the HCs; disposing more active sites for the Na+ storage. In addition, sulfur can reversibly react with Na+, reducing the irreversible consumption of Na+ by the surface functional groups. This work presents a simple and effective method of designing high performance anode materials for SIBs. • P, N and S co-doping in the biomass hard carbon anodes are developed. • P, N and S-doping increased the Na+ intercalation rate in the anode materials. • S-doping provided more active sites for Na+ storage in the hard carbon anodes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mesoporous sponge-like NFPP@C@rGO caged in cross-linked dual-carbon frameworks was fabricated via a feasible one-step solid state method. • Enhanced electrical conductivity and kinetics at high temperature has been achieved through nanoengineering and interface regulation. • 86.7% capacity retention was obtained after 30,000 cycles at 20 C. • Full cells (NFPP@C@rGO//HC) exhibited outstanding electrochemical performances. Iron-based mixed phosphates sodium ion batteries (SIBs) are promising sustainable storage devices due to the low-costing and non-toxicity characters. Whereas, their real application is seriously restricted by the sluggish Na+ diffusion and inferior intrinsic electronic conductivity. Herein, we propose mesoporous sponge-like structural Na 4 Fe 3 (PO 4) 2 (P 2 O 7) (NFPP) in-situ caged in carbon layer and cross-linked graphene nanosheets (NFPP@C@rGO), toward fast charging and highly stable sodium ion half/full cells in a wide temperature range. This rational strategy gives the cathode superior long-lasting cycling stability, specifically, 86.7 % capacity retention is retained at 20 C for over 30,000 cycles, displaying a capacity loss less than 0.00045 % per cycle. Notably, outstanding thermal stability at 60 °C is achieved and no obvious capacity degradation can be observed after cycling for 200 times at 1 C. Furthermore, the impressive electrochemical performances of full cells are determined, ascribed to the improved electronic conductivity and structural stability (e.g. a small volume change of ∼4.1 % during sodium ion insertion/deinsertion), which is confirmed by in-situ X-ray diffraction (XRD) and X-ray absorption near edge structure (XANES) measurements. All the results above prove that the NFPP@C@rGO is of high potential for advanced energy storage system based on its low costs, long-lasting cyclability and excellent thermal stability. [ABSTRACT FROM AUTHOR]

• The S-doped hard carbon delivered an enhanced ICE of 66.61% as well as excellent rate performance. • The as-acquired anode material exhibited good cycling performance with a reversible capacity of 145.6 mAh/g over 500 cycles at 2000 mA g−1. • The S-doping can expand the interlayer spacing of the hard carbon and provide more active sites for the Na+ storage. The intercalation/deintercalation of Na+ in the hard carbon (HC) has been widely investigated for the construction of high performances sodium-ion batteries (SIBs). In this work, a variety of sulfur-doped HCs were obtained by simple pyrolysis of the sublimated sulfur and the camphor tree (S-Cmph) derived material. When used as anode for SIBs, the S-Cmph-700 (pyrolyzed at 700℃) delivered a capacity of 616.7 mAh/g with an ICE of 66.61 %, high than that of the untreated material pyrolyzed at 1500℃ (50.11 %) (Cmph-1500). Furthermore, excellent rate performance with specific capacities of 372.3, 323, 282.6, 252.6, 221, 181.2 mAh/g at 40, 80, 200, 400, 800 and 2000 mA g−1 can be achieved, respectively. When the current density returned at 40 mA g−1, the anode recovered a specific capacity of 356.8 mAh/g. In addition, the as-acquired anode material exhibited good cycling performance with a reversible capacity of 145.6 mAh/g over 500 cycles at 2000 mA g−1. The improved electrochemical performances of Cmph-HC anode can be attributed to the benefit of the S-doping, leading to the increase of the interlayer spacing of the anode material, which facilitates the intercalation/deintercalation of Na+ ions in the interlayer spacing of the HC material, and provided more active sites in the Cmph-HC anode for the Na+ ions storage. In addition, sulfur can reversibly react with Na+, limiting the irreversible consumption of Na+ and increase the intercalation rate of Na+ inside the anode material. This work presents a low cost, simple and effective way to synthesize a high performances anode material for the commercialization of SIBs. [ABSTRACT FROM AUTHOR]

Cathodic corrosion, a green electrochemical method, has been employed to obtain Sb nanomaterials utilized as anode material for lithium-ion batteries and sodium-ion batteries. Interestingly, two different corrosion mechanisms are found, coming from the impact of electrolyte, resulting in the formation of hexagonal and amorphous Sb in aqueous and organic solution, respectively. With the help of water-soluble carboxymethyl cellulose binder and the electrolyte additive fluoroethylene carbonate, both hexagonal and amorphous Sb electrodes exhibit good cycling stability when utilized as anode materials for lithium-ion batteries and sodium-ion batteries. Additionally, both the hexagonal and amorphous Sb electrodes show very good rate capability in lithium-ion batteries. Even at high current density (2000 mA g −1 ), the hexagonal and amorphous Sb give reversible capacities of 422 and 379 mA h g −1 , respectively. Surprisingly, when used as anode materials for sodium-ion batteries, the hexagonal Sb electrode exhibits a good rate performance of 632, 625, 569, 515 and 426 mA h g −1 at a current density of 100, 200, 500, 1000, and 2000 mA g −1 , respectively. However, limited rate performance is observed from the amorphous Sb electrode in case of sodium-ion battery due to the large impedance. [ABSTRACT FROM AUTHOR]

NASICON Na 3 V 2 (PO 4 ) 3 and Na 3 V 2 (PO 4 ) 2 F 3 have restarted to be investigated electrochemically as promising cathode materials for sodium-ion batteries. Fluorine insertion by replacing partial phosphate groups in Na 3 V 2 (PO 4 ) 3 allows for new family of host lattice structure, Na 3 V 2 (PO 4 ) 2 F 3 . Greatly, fluorine is capable to participate in structural construction to change the ions configuration which involves ions occupation, the species and amount of diverse Na sites, leading to distinct modalities for ions extraction. The inductive effects of (PO 4 ) 3− polyanion by changing electronic cloud density upon compositional atoms could be enhanced under the effects of the formed F-V bond due to its strong ionicity, which can moderate the energetics of the transition metal redox couple to generate relatively high operating potentials. The substitution of fluorine for negative-charge polyanion or anion could be effective to improve the electrochemical properties, particularly for the purpose to increase performed voltages by changing atomic environments. [ABSTRACT FROM AUTHOR]

The electrochemical properties ofNa3V2(PO4)2F3cathode utilized in the sodiumion battery are investigated, and the ion migration mechanisms areproposed as combined via the first principles calculations. Two differentNa sites, namely, the Na(1) and Na(2) sites, could cause two sodiumions of Na3V2(PO4)2F3to be extracted or inserted by a two-step electrochemicalprocess accompanied by structural reorganization that could be responsiblefor the redox reaction of V3+/4+. Because the calculatedaverage voltage (Vavg) of the second chargingplateau is 4.04 V for the optimized system but 4.38 V for the unoptimizedone, the reorganization of the cathode system can make a stable configurationand lower the extraction energy. Three designed pathways for sodiumions along the x, y, zdirections in Na3V2(PO4)2F3, known as a 3D ions transport tunnel, have activationenergies (Ea) of 0.449, 0.2, and 0.323eV, respectively, by using DFT calculations, demonstrating the differentfeasibilities of the migration directions. [ABSTRACT FROM AUTHOR]

• Bi/GO composites with different Bi content were synthesized by a novel and efficient electrochemical method. • Bi 2 O 2 2+and reduced graphene oxide, which make Bi/GO composites possess high ionic and electrical conductivity, were generated during the reaction. • The small volume expansion of Bi/GO composite during sodiation is attributed to the existence of GO. • The Bi/GO composite anode displays superior rate performance and excellent cycling stability. Bismuth, a promising attribute for sodium-ion batteries, which have been attracting significant attention owing to their advantages of high volumetric capacity and suitable operating potential. However, most traditional Bi-based materials are suffered from pulverization and fracture of the electrodes caused by dramatic volume variation, consequently diminishing the cycle stability. Herein, in this work, bismuth embedded within graphene oxide matrices have been obtained by utilizing a novel and efficient electrochemical method. Through the strong reducing properties of Zintl clusters Bi 2 2−, GO is partially reduced to generate reduced graphene oxide with better electrical conductivity. Simultaneously, Bi is strongly loaded on the GO through Bi-O-C bonding, which can form Bi 2 O 2 2+ with excellent ionic conductivity. Moreover, the volume expansion of Bi during sodiation can be effectively buffered in the GO matrices. As a result, this Bi/GO composite exhibits excellent electrochemical performances in sodium-ion batteries (SIBs), including a high specific capacity of 258 mAh g−1 at 10 A g−1 and an excellent cycle stability with high retained capacity of 315 mAh g−1 after 500 cycles at 2 A g−1. This work paves the way to prepare designated promising electrode materials for high-performance SIBs, and thoroughly understands mechanism of electrochemical methods for preparing materials. [Display omitted] [ABSTRACT FROM AUTHOR]

P2–Na 2/3 Ni 1/3 Mn 2/3 O 2 as a promising cathode material for sodium ion batteries (SIBs) has attracted much attention owing to high capacity and wide operation voltage. However, it suffers from inferior rate and cycling performances due to P2–O2 phase transition and Na+/vacancy ordering during charge/discharge process. Herein, a Fe/Ti co-substitution strategy is successfully utilized to mitigate these issues. Notably, as probed by In-situ X-ray diffraction, the substitution of Ni with Fe significantly stabilizes the interlayer framework by impeding slab glide during deep Na+ extraction, resulting in reversible P2-OP4 phase transition with smaller volume change of host structure compared to P2–O2 transition. Meanwhile, synchrotron X-ray diffraction shows that, the Na+/vacancy ordering is greatly suppressed by further replacing Mn with Ti, which breaks down the long-range ordering of Ni/Mn distribution, promoting Na ion transport. In addition, the charge compensation mechanism of Fe/Ti co-substituted P2–Na 0.67 Ni 0.23 Fe 0.1 Mn 0.57 Ti 0.1 O 2 (NFMT) revealed by Ex-situ X-ray absorption spectroscopy demonstrates that the incorporation of Fe3+/4+ redox couple largely improve the working voltage. Consequently, the obtained NFMT cathode delivers a high energy density over 420 Wh/kg within 4.3–2.6 V, accompanied with remarkably enhanced kinetics and capacity retention. Such co-substitution strategy provides a promising approach to develop high-voltage and cycle-stable cathode materials for SIBs. [Display omitted] • Fe/Ti co-substitution is proposed to modify the P2–Na 2/3 Ni 1/3 Mn 2/3 O 2 cathode. • Fe substitution can prevent the P2–O2 phase transition. • Ti substitution disrupts cation ordering and Na+/vacancy ordering. • Fe/Ti co-substitution can stabilize the reversible OP4 phase. [ABSTRACT FROM AUTHOR]

• N-rich carbon nanotubes with long aspect ratio are constructed by a simple template method. • The nitrogen content in the carbon nanotubes is up to 15.7%. • Excellent cycle durability and rate capability are obtained in sodium/lithium ion batteries. • Quantitative kinetic analysis reveals the dominated capacitive contribution. An effective design of carbon materials with appropriate nanoarchitecture and optimized physicochemical property is critically demanded for superb lithium/sodium storage capacities. N-rich (up to 15.7%) hollow carbon nanotubes (NCNT) with long aspect ratio are well developed via a template method by exploring polypyrrole as the high nitrogen-containing carbon precursor. Owing to the hollow structure with large cavity and long aspect ratio, the NCNT exhibits Li+/Na+ storage capability with favorable volume buffer and rapid ion and electron transfer at high rate, resulting in long-term cycling and high-rate property. Meanwhile, the high N content creates abundant active sites and extrinsic defects, facilitating the improved specific capacity and rate performance. Impressively, our NCNT-600 electrode displays a favorable reversible capacity of 132 mAh g−1 after 5000 cycles at 4000 mA g−1 for SIBs and 170 mAh g−1 after 2000 cycles at the same current for LIBs. Further quantitative kinetic analysis reveals the dominated capacitive contribution of Li+/Na+ storage in NCNT, which is attributed to the porous hollow nanotubes and N-rich carbon with volume strain mitigation and enhanced electronic/ionic transfer capability. Given the cost-effectiveness and material sustainability, our work will shed light on the further design of other carbon-based materials for advanced energy storage devices. [ABSTRACT FROM AUTHOR]