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Sodium‐ion batteries (SIBs), based on hard carbon anodes and Na+‐intercalation compound cathodes, have gained significant attention. Nonetheless, hard carbon anodes involve the storage of Na+ at a low potential, typically below 0.1 V (vs Na/Na+), which increases the risk of dendritic Na growth on the anode surface during overcharging. Herein, a safe organic/inorganic composite anode containing tetrasodium 3,4,9,10‐perylenetetracarboxylate (Na4PTC) and Metallic bismuth (Bi) with a weight ratio of 7:2, which exhibits an average potential of 0.7 V (vs Na+/Na) and a capacity of 150 mAh g−1 is proposed. The electrode reaction involves a reversible coordination reaction within the organic host and alloying reactions within the metallic Bi component. Importantly, the organic component efficiently buffers the volume changes in Bi during the alloying reaction, while the metallic Bi enhances the electronic conductivity of the organic material. As a result, this composite anode shows high cycle stability and rate performance, even under high mass loadings ranging from 10 to 50 mg cm−2. Furthermore, it is demonstrated that the Na‐ion full cell, consisting of the composite anode and the Na3V2O2(PO4)2F cathode, exhibits minimal capacity degradation over 100 cycles while maintaining a high areal capacity of 1.1 mA cm−2. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs), as one of the potential candidates for grid‐scale energy storage systems, are required to tackle extreme weather conditions. However, the all‐weather SIBs with a wide operation‐temperature range are rarely reported. Herein, we propose a wide‐temperature range SIB, which involves a carbon‐coated Na4Fe3(PO4)2P2O7 (NFPP@C) cathode, a bismuth (Bi) anode, and a diglyme‐based electrolyte. We demonstrate that solvated Na+ can be directly stored by the Bi anode via an alloying reaction without the de‐solvent process. Furthermore, the NFPP@C cathode exhibits a high Na+ diffusion coefficient at low temperature. As a result, the Bi//NFPP@C battery exhibits perfect low‐temperature behavior. Even at −70 °C, this battery still delivers 70.19 % of the room‐temperature capacity. Furthermore, benefitting from the high boiling point of the electrolyte, this battery also works well at a high temperature of up to 100 °C. These results are encouraging for the further exploration of wide‐temperature range SIBs. [ABSTRACT FROM AUTHOR]

A porous Na3V2(PO4)3 cathode material coated uniformly with a layer of approximately 6 nm carbon has been synthesized by the sol-gel method combined with a freeze-drying process. The special porous morphology and structure significantly increases the specific surface area of the material, which greatly enlarges the contact area between the electrode and electrolyte, and consequently supplies more active sites for sodium ions. When employed as a cathode material of sodium-ion batteries, this porous Na3V2(PO4)3/C exhibits excellent rate performance and cycling stability; for instance, it shows quite a flat potential plateau at 3.4 V in the potential window of 2.7-4.0 V versus Na+/Na and delivers an initial capacity as high as 118.9 and 98.0 mA h g−1 at current rates of 0.05 and 0.5 C, respectively, and after 50 cycles, a good capacity retention of 92.7 and 93.6 % are maintained. Moreover, even when the discharge current density is increased to 5 C (590 mA g−1), an initial capacity of 97.6 mA h g−1 can still be achieved, and an exciting capacity retention of 88.6 % is obtained after 100 cycles. The good cycle performance, excellent rate capability, and moreover, the low cost of Na3V2(PO4)3/C suggest that this material is a promising cathode for large-scale sodium-ion rechargeable batteries. [ABSTRACT FROM AUTHOR]

Abstract: A well defined nano-structured material, NaV6O15 nanorods, was synthesized by a facile low temperature hydrothermal method. It can perform well as the cathode material of rechargeable sodium batteries. It was found that the NaV6O15 nanorods exhibited stable sodium-ion insertion/deinsertion reversibility and delivered 142mAhg−1 sodium ions when worked at a current density of 0.02Ag−1. In galvanostatic cycling test, a specific discharge capacity of around 75mAhg−1 could be obtained after 30 cycles under 0.05Ag−1 current density. Concerned to its good electrochemical performance for reversible delivery of sodium ions, it is thus expected that NaV6O15 may be used as cathode material for rechargeable sodium batteries with highly environmental friendship and low cost. [Copyright &y& Elsevier]

Abstract As a safe, low-voltage anode material, in recent years, Na 2 Ti 3 O 7 has become regarded as a highly alternative negative material for high energy room-temperature sodium ion batteries. However, its poor ion and electron conductivity produces very poor electrochemical performance of Na 2 Ti 3 O 7 , therefore greatly limiting its practical application in future scalable utilization. We report here a self-doping of Ti3+ into the Na 2 Ti 3 O 7 electrode material, through a very simple post heat-treatment process, that is, annealing the Na 2 Ti 3 O 7 precursor at an argon atmosphere containing 5% H 2. By XPS characterization, it is confirmed that Ti3+ is successfully doped into Na 2 Ti 3 O 7. Benefiting from this self-doped Ti3+ with larger ionic radius and better electronic conductivity, the obtained Na 2 Ti 3 O 7 demonstrates improved electron conductivity and ion diffusion properties. Combined with a carbon coating, this self-doped Na 2 Ti 3 O 7 electrode material exhibits superior electrochemical performance to that of non-doped electrode, e.g., this Na 2 Ti 3 O 7 sample could delivers a specific capacity of 187.8 and 51.9 mAh g−1 from 0.1C to 10C at various rate of discharge, respectively. When recycled back to 0.1C, it can still reach 153 mAh g−1. Compared with numerous reported nanoscale means, we believe this approach is practical and productive, and may extend to other ti-based electrode materials. Highlights • A self-doped Ti3+ of Na 2 Ti 3 O 7 anode is synthesized by a facile sol-gel process. • The Ti3+ enhances the electronic conductivity of Na 2 Ti 3 O 7. • The Ti3+ in crystal lattice of Na 2 Ti 3 O 7 enhances the Na+ diffusion coefficient. • This self-doped Na 2 Ti 3 O 7 material exhibits improved electrochemical performance. [ABSTRACT FROM AUTHOR]

Abstract Na 2+2x Fe 2-x (SO 4) 3 is considered a promising cathode material for advanced sodium ion batteries with higher energy density due to its advantage of high-voltage, earth-abundant elements material and low-cost. However, strongly impeded by its fatal environmental sensitivity and low electronic conductivity, the NFS usually shows unsatisfactory electrochemical performance. Herein, a facile synthesis of microspherical NFS@reduced graphene oxide composites are synthesized through spray-drying method. The well-designed microspherical NFS@rGO with confined NFS nanocrystal in the three-dimensional graphene framework exhibits superb electronic and ionic conductivity as well as structural stability. The NFS@rGO composites show outstanding electrochemical properties: high sodium storage capacity (99 mAh g−1 at 0.1 C), superior rate performance (78 mAh g−1 at 60 C and even up to 72 mAh g−1 at 80 C), ultralong cycling stability (80.8% capacity retention after 2000 cycles at 30 C). The excellent performance makes the NFS@rGO material a prospective electrode candidate for large-scale SIBs. Graphical abstract Image 1 Highlights • The NFS@rGO was successfully prepared through a facile spray-drying method. • The robust 3D graphene skeleton ensures NFS@rGO structural stability. • The 3D highly conductive graphene network boost the electronic conductivity. • The NFS@rGO demonstrates ultrafast and ultralong-term cycling. [ABSTRACT FROM AUTHOR]

[Display omitted] • Na 4 Fe 3 (PO 4) 2 (P 2 O 7) nano-flakes were synthesized by solid-phase reaction. • Nano-flakes shorten the Na+ migration path and accelerate the diffusion of Na+. • The formation of uniform nano-flakes benefits from the control of heating rate. • Nitrogen-doped carbon coated Na 4 Fe 3 (PO 4) 2 (P 2 O 7) nano-flakes demonstrate excellent electrochemical performance. Na 4 Fe 3 (PO 4) 2 P 2 O 7 (NFPP) is expected to be a promising cathode material for sodium ion batteries (SIBs) applied to large-scale energy storage systems owing to its abundant resource and low cost of the raw materials. However, the currently reported methods for preparing NFPP either cannot be applied to mass-production on a large scale because of their high energy consumption, or result in the production of NFPP materials that have poor electrochemical performance. Herein, we prepared a hierarchical nitrogen-carbon-coated NFPP nanoflake by a facile and easily scalable solid-phase ball milling method, in which oleic acid as the surfactant and carbon source. The formation mechanism of this hierarchical open structure constructed by uniform nano-flakes was investigated by a heating-rate controlled experiment, which indicated that heating rates play an important role in morphology and structure of the final products. When used as a cathode material, the present NFPP nano-flakes composites are able to operate in a wide temperature range (−20 ∼ 50 °C) and, can provide specific capacity of 129 mAh/g at 0.1C, with excellent cycling stability (81 % capacity retention at 10C after 1500 cycles) at 25 °C. Furthermore, the NFPP cathode is coupled with the MoS 2 anode (MoS 2 /rGO) to assemble the sodium ion full battery, it exhibits outstanding rate/cycling performances. The present work provides a method of preparing NFPP electrode materials with good performance for s SIBs, which can be easily amplified production. [ABSTRACT FROM AUTHOR]

[Display omitted] • AlF 3 coated nanoscaled Na 3.12 Fe 2.44 (P 2 O 7) 2 @CNTs is synthesized. • Carbon nanotubes build highly conductive networks. • The AlF 3 layer facilitates the formation of cathode-electrolyte interphase film. • AlF 3 coating improves materials structural stability at high temperatures. Sodium ion batteries (SIBs) are applied to the field of energy storage due to their unique advantages, however, large scale energy storage equipment, also requires low cost, good cycling performance, safety performance and good environmental adaptation performance, in order to cope with various climatic conditions. The polyanionic material Na 3.12 Fe 2.44 (P 2 O 7) 2 (NFPO) is considered to be an excellent cathode material for SIBs due to its unique large frame work structure and good thermal stability, leading to good cycle stability and a wide working temperature. Nevertheless, poor intrinsic conductivity of the material brings about large polarization, resulting in low electrochemical reversibility. Especially in high temperature environment, the electrolyte aggravates the erosion of the material and increases the side reactions, making the cycle stability worse. In this study, nanoscale NFPO composites are synthesized by an optimized sol–gel method, while the interface is modified using AlF 3 , to achieve resistance to surface oxidation and corrosion. Impressively, these modified materials exhibit high-temperature electrochemical properties due to the thermal stability and interfacial protection of AlF 3. At 60 °C, it provides a discharge capacity of 130 mAh g−1 at 0.1C, still has a discharge capacity of 100.4 mAh g−1 at 10C, a capacity retention rate of 96.3% after 400 cycles, and has excellent long-term cycling performance (70% capacity retention rate after 6000 cycles at 50C). This work demonstrates the effectiveness of the interfacial modification and provides an impactful strategy for the design of batteries at high temperatures. [ABSTRACT FROM AUTHOR]

Na 4 Fe 3 (PO 4) 2 P 2 O 7 (NFPP) is known as a cathode material with great potential for sodium ion batteries (SIBs) due to its thermodynamic stability, considerable theoretical capacity and small volume change. However, its inherent poor conductivity leads to low discharge capacity and poor cycle stability, which greatly limits its widespread and practical application. In this work, a Mn2+ doped NFPP together with the graphene modification, is proposed. It is found that the optimal Na 4 Fe 2.7 Mn 0.3 (PO 4) 2 P 2 O 7 /rGO(Mn0.3-NFPP/rGO) can provide an initial discharge capacity of 131.5 mAh g−1 at 0.1C, (1C = 129mAh g−1) also an excellent rate performance (70.2 mAh g−1 at 50C) and good long cycle stability (97.2% capacity retention after 2000 cycles at 10C) can be obtained. Impressively, the as-prepared Mn0.3-NFPP/rGO also shows excellent low-temperature performance, at −20 °C, it demonstrates a discharge capacity of 85.3 mAh g−1 at 0.2C and good rate performance. Density functional theory (DFT) calculation shows that Mn2+ doping reduces the Na + migration energy barrier, and also narrows the bandgap of the NFPP lattice, which is beneficial to improve the Na+ diffusion kinetics and conductivity. In addition, the doping of Mn2+ can further help to improve its structural stability during the long cycling process. [Display omitted] • Mn-doped Na 4 Fe 3 (PO 4) 2 (P 2 O 7) together with graphene modification is proposed. • Mn2+ doping reduces the Na + migration energy barrier. • Mn2+ doping narrows the bandgap of Na 4 Fe 3 (PO 4) 2 (P 2 O 7). • The Na + migration is facilitated by Mn2+ doping, particularly at low temperature. [ABSTRACT FROM AUTHOR]

Symmetric sodium ion full batteries with high energy density are expected to become promising storage devices. Na 7 V 4 (P 2 O 7) 4 (PO 4)/C can be assembled into a high energy density symmetric full battery due to 3.85 V operating voltage as a cathode and 0.94 V operating voltage as an anode. Here, the as-prepared Na 7 V 4 (P 2 O 7) 4 (PO 4)/C-GA (graphene aerogel) displays excellent electrochemical behavior as both cathode and anode. As the cathode, it can deliver a reversible capacity of 91.4 mA h g−1 at 1C (1C = 92.8 mA h g−1) and even shows 74 mA h g−1 capacity at 100C. Meanwhile, an ultra-long cycling property is obtained (77.2% capacity retention after 5000 cycles at 20C). As the anode, it can output 92.4 mA h g−1 at 25 mA g−1 and has a 79.2% capacity retention after 300 cycles at 50 mA g−1. Interestingly, the symmetric full battery assembled with NVPP/C-GA outputs an initial 81.9 mA h g−1 capacity, a high 2.84 V working voltage, and 232.6 Wh kg−1 energy density at 25 mA g−1. Therefore, our work shows potential application prospects of the symmetric full battery with Na 7 V 4 (P 2 O 7) 4 (PO 4)/C-GA in energy storage systems. Image 1 • The Na 7 V 4 (P 2 O 7) 4 (PO 4)/C-GA has high ion diffusion coefficients (D Na +). • The 3D GA framework can improve the electronic conductivity of material. • The Na 7 V 4 (P 2 O 7) 4 (PO 4)/C-GA as cathode and anode shows excellent performance. • The symmetric sodium-ion full battery outputs high energy density. [ABSTRACT FROM AUTHOR]

MoS 2 has attracted remarkable attention, attributed to its high specific capacity and graphite-like structure. However, the low rate capability and poor cycle stability are two major obstacles that hinder the practical application of MoS 2 in sodium-ion batteries (SIBs). Herein, MoS 2 grows vertically on the surface of reduced graphene oxide (rGO) and forms a nanowall structure by electrostatic attraction, whose growth has been induced by cetyltrimethyl ammonium bromide (CTAB). This unique nanowall has a large specific surface area, which not only exposes plenty of active sites and shortens the diffusion distance of Na+, but also improves the electronic conductivity and structural stability. Meanwhile, detailed kinetic analysis is also employed to explain the Na+ storage behavior. The pseudo capacitance-dominated contribution ensures a more stable and much faster Na+ storage. Therefore, the MoS 2 @rGO composite displays excellent electrochemical performance. For example, the capacity of the MoS 2 @rGO composite can still be maintained at 571.5 mA h g−1 with 94.1% retention, after 100 cycles at 0.1 A g−1. Impressively, MoS 2 @rGO still exhibits a considerable capacity of 124 mA h g−1 at an ultra-high current density of 40 A g−1. The excellent performance makes the MoS 2 @rGO material a prospective electrode for use in large-scale SIBs. Image 1 • The MoS 2 nanowalls grow vertically on the rGO surface by electrostatic attraction. • The combination of MoS 2 nanowalls and rGO is strengthened by forming a C–S bond. • The composite with MoS 2 nanowalls structure has a large specific surface area. • The MoS 2 nanowalls allows Na+ to deintercalate rapidly along the horizontal direction. • The MoS 2 @rGO composite shows superior cycle and rate performance in SIBs. [ABSTRACT FROM AUTHOR]