Manipulating Na occupation and constructing protective film of P2-Na_(0.67)Ni_(0.33)Mn_(0.67)O_(2) as long-term cycle stability cathode for sodium-ion batteries

P2-Na_(0.67)Ni_(0.33)Mn_(0.67)O_(2)(NNMO)is promising cathode material for sodium-ion batteries(SIBs)due to its high specific capacity and fast Na+diffusion rate.Nonetheless,the irreversible P2-O_(2)phase transformation,Na+/vacancy ordering,and transition metal(TM)dissolution seriously damage its cycling stability and restrict its commercialization process.Herein,Na occupation manipulation and interface stabilization are proposed to strengthen the phase structure of NNMO by synergistic Zn/Ti co-doping and introducing lithium difluorophosp(LiPO_(2)F_(2))film-forming electrolyte additive.The Zn/Ti co-doping regulates the occupancy ratio of Nae/Nafat Na sites and disorganizes the Na+/vacancy ordering,resulting in a faster Na+diffusion kinetics and reversible P2-Z phase transition for P2-Na_(0.67)Ni_(0.28)Zn_(0.05)Mn_(0.62)Ti_(0.05)O_(2)(NNZMTO).Meanwhile,the LiPO_(2)F_(2)additive can form homogeneous and ultrathin cathode-electrolyte interphase(CEI)on NNZMTO surface,which can stabilize the NNZMTO-electrolyte interface to prevent TM dissolution,surface structure transformation,and micro-crack generation.Combination studies of in situ and ex situ characterizations and theoretical calculations were used to elucidate the storage mechanism of NNZMTO with Li PO_(2)F_(2)additive.As a result,the NNZMTO displays outstanding capacity retention of 94.44%after 500 cycles at 1C with 0.3 wt%Li PO_(2)F_(2),excellent rate performance of 92.5 mA h g^(-1)at 8C with 0.1 wt%Li PO_(2)F_(2),and remarkable full cell capability.This work highlights the important role of manipulating Na occupation and constructing protective film in the design of layered materials,which provides a promising direction for developing high-performance cathodes for SIBs.

Designing ultrastable P2/O3-type layered oxides for sodium ion batteries by regulating Na distribution and oxygen redox chemistry

P2/O3-type Ni/Mn-based layered oxides are promising cathode materials for sodium-ion batteries(SIBs)owing to their high energy density.However,exploring effective ways to enhance the synergy between the P2 and 03 phases remains a necessity.Herein,we design a P2/O3-type Na_(0.76)Ni_(0.31)Zn_(0.07)Mn_(0.50)Ti_(0.12)0_(2)(NNZMT)with high chemical/electrochemical stability by enhancing the coupling between the two phases.For the first time,a unique Na*extraction is observed from a Na-rich O3 phase by a Na-poor P2 phase and systematically investigated.This process is facilitated by Zn^(2+)/Ti^(4+)dual doping and calcination condition regulation,allowing a higher Na*content in the P2 phase with larger Na^(+)transport channels and enhancing Na transport kinetics.Because of reduced Na^(+)in the O3 phase,which increases the difficulty of H^(+)/Na^(+) exchange,the hydrostability of the O3 phase in NNZMT is considerably improved.Furthermore,Zn^(2+)/Ti^(4+)presence in NNZMT synergistically regulates oxygen redox chemistry,which effectively suppresses O_(2)/CO_(2) gas release and electrolyte decomposition,and completely inhibits phase transitions above 4.0 V.As a result,NNZMT achieves a high discharge capacity of 144.8 mA h g^(-1) with a median voltage of 3.42 V at 20 mA g^(-1) and exhibits excellent cycling performance with a capacity retention of 77.3% for 1000 cycles at 2000 mA g^(-1).This study provides an effective strategy and new insights into the design of high-performance layered-oxide cathode materials with enhanced structure/interface stability forSIBs.

基于Na-BP-DME@C阳极的长寿命准固态钠-空气电池

钠-空气电池因其能量密度高、成本低而成为金属-空气电池领域的研究热点。然而,以金属钠为阳极的钠-空气电池存在钠枝晶生长、金属钠界面稳定性差以及金属钠的反应活性高等问题,限制了钠-空气电池的快速发展。为解决上述问题,将联苯钠与导电炭黑复合材料Na-BP-DME@C作为阳极,单壁碳纳米角(SWCHNs)作为催化剂,构建准固态钠-空气电池。基于Na-BP-DME@C阳极的准固态钠-空气电池表现出优异的电化学性能,其电压差为1.5 V,功率密度为3.32 mW/cm^(2),在0.1 mA/cm^(2)电流密度下可稳定循环459 h(约459次)。

Pressureless all-solid-state Na/S batteries with self-supporting Na_(5)YSi_(4)O_(12) scaffolds

The development of reliable and affordable all-solid-state sodium metal batteries(ASS-SMBs)requires suitable solid-state electrolytes with cost-efficient processing and stabilized electrode/electrolyte interfaces.Here,an integrated porous/dense/porous Na_(5)YSi_(4)O_(12)(NYS)trilayered scaffold is designed and fabricated by tape casting using aqueous slurries.In this template-based NYS scaffold,the dense layer in the middle serves as a separator and the porous layers on both sides accommodate the active materials with their volume changes during the charge/discharge processes,increasing the contact area and thus enhancing the utilization rate and homogenizing the current distribution.The Na/NYS/Na symmetric cells with the Pb-coated NYS scaffold exhibit significantly reduced interfacial impedance and superior critical current density of up to 3.0 mA cm^(-2)against Na metal owing to enhanced wettability.Furthermore,the assembled Na/NYS/S full cells operated without external pressure at room temperature showed a high initial discharge capacity of 970 mAh g^(-1)and good cycling stability with a capacity of 600 mAh g^(-1)after 150 cycles(based on the mass of sulfur).This approach paves the way for the realization of economical and practical ASS-SMBs from the perspective of ceramic manufacturing.

Na_(0.44)MnO_(2)颗粒尺寸对其作为水系钠离子电池正极性能的影响

水溶性钠离子电池是一种与锂离子电池相辅相成的技术,因其相对较低的成本、改善的安全性和环境友好的电解液而备受青睐。然而,较低的电极容量限制了这种电池的应用。Na_(0.44)MnO_(2)是一种用于钠离子电池的高容量阴极材料,其理论容量为121 mAh/g。文章研究了Na_(0.44)MnO_(2)的尺寸效应对阴极性能的影响。纳米棒通过热处理MnO_(2)纳米片前驱体制备而成,其尺寸通过CTAB和KMnO_(4)的比例进行调控。然后,Na_(0.44)MnO_(2)纳米棒被用作水溶性钠离子电池的活性材料。纳米棒阴极在1 C的初始循环中提供了60 mAh/g的容量,并在经过200个循环后保持了55 mAh/g,比Na_(0.44)MnO_(2)块状阴极高出37.5%。在高倍率的5 C下,该阴极在经过200个循环后仍能提供47 mAh/g的高容量。容量的增加归因于减小的电荷传递阻抗和纳米棒具有较高比表面积所带来的改善的钠离子扩散性能。

Unraveling the incompatibility mechanism of ethylene carbonate-based electrolytes in sodium metal anodes

Ethylene carbonate(EC)is widely used in lithium-ion batteries due to its optimal overall performance with satisfactory conductivity,relatively stable solid electrolyte interphase(SEI),and wide electrochemical window.EC is also the most widely used electrolyte solvent in sodium ion batteries.However,compared to lithium metal,sodium metal(Na)shows higher activity and reacts violently with EC-based electrolyte(NaPF_(6)as solute),which leads to the failure of sodium metal batteries(SMBs).Herein,we reveal the electrochemical instability mechanism of EC on sodium metal battery,and find that the com-bination of EC and NaPF_(6) is electrically reduced in sodium metal anode during charging,resulting in the reduction of the first coulombic efficiency,and the continuous consumption of electrolyte leads to the cell failure.To address the above issues,an additive modified linear carbonate-based electrolyte is provided as a substitute for EC based electrolytes.Specifically,ethyl methyl carbonate(EMC)and dimethyl carbon-ate(DMC)as solvents and fluoroethylene carbonate(FEC)as SEI-forming additive have been identified as the optimal solvent for NaFP_(6)based electrolyte and used in Na_(4)Fe_(3)(PO_(4))_(2)(P_(2)O_(7))/Na batteries.The batter-ies exhibit excellent capacity retention rate of about 80%over 1000 cycles at a cut-off voltage of 4.3 V.

Na_(3)V_(2)(PO_(4))_(3)/C正极材料制备与储钠性能综合实验教学设计

设计了“常温预还原-热处理法制备钠离子电池正极材料磷酸钒钠”综合性研究实验,探究了原料种类和热处理温度对Na_(3)V_(2)(PO_(4))_(3)/C的物相、晶体结构、晶粒尺寸、微观形貌及电化学性能的影响。研究表明,NH_(4)VO_(3)中的V^(5+)更易被草酸常温还原,机械活化后所得前驱体为无定形结构,由该前驱体热处理制备的Na_(3)V_(2)(PO_(4))_(3)/C结晶度更高,且电化学性能更优。通过优化合成温度,发现在700℃下合成的Na_(3)V_(2)(PO_(4))_(3)/C具有最高的比容量、最优的倍率性能和最佳的循环性能。在实验中,学生通过材料制备、结构及形貌表征、电池制作与电化学性能分析等环节,能够达到强化理论知识、提高实验技能、激发创新性思维的目的。

新型Na/CFx可充电池催化剂的制备与性能

类似于锂/氟化碳(Li/CFx)电池,钠/氟化碳(Na/CFx)电池具有低廉的价格和较高的能量密度,是未来锂离子电池的理想替代选项。但是Na/CFx电池目前还存在着极化大和循环性能差等问题。为解决以上问题,在CFx阴极中加入催化剂成为改善电池电化学性能的一个重要途径。分别采用水热法和溶胶-凝胶法制备了催化剂材料Co3O4-TiO2和ZrO2,并对其进行了表征。分别将TiO2、Co3O4、Co3O4-TiO2以及ZrO24种催化剂材料按10%(质量比,下同)加入CFx正极中并组装成电池,然后对电池进行了恒流充放电、交流阻抗以及循环伏安等电化学性能测试。实验结果表明,加入4种催化剂后,Na/CFx电池的放电比容量得到明显提升。其中,ZrO2催化剂表现出最佳的催化性能。经过100次后循环后,含有ZrO2的Na/CFx电池的放电比容量为167.3 m Ah·g^-1,极大地改善了钠/氟化碳电池的循环性能。

Three-Dimensional Self-assembled Hairball-Like VS4 as High-Capacity Anodes for Sodium-Ion Batteries

Sodium-ion batteries(SIBs)are considered to be attractive candidates for large-scale energy storage systems because of their rich earth abundance and consistent performance.However,there are still challenges in developing desirable anode materials that can accommodate rapid and stable insertion/extraction of Na+and can exhibit excellent electrochemical performance.Herein,the self-assembled hairball-like VS4 as anodes of SIBs exhibits high discharge capacity(660 and 589 mAh g−1 at 1 and 3 A g−1,respectively)and excellent rate property(about 100%retention at 10 and 20 A g−1 after 1000 cycles)at room temperature.Moreover,the VS4 can also exhibit 591 mAh g−1 at 1 A g−1 after 600 cycles at 0°C.An unlike traditional mechanism of VS4 for Na+storage was proposed according to the dates of ex situ characterization,cyclic voltammetry,and electrochemical kinetic analysis.The capacities of the final stabilization stage are provided by the reactions of reversible transformation between Na2S and S,which were considered the reaction mechanisms of Na–S batteries.This work can provide a basis for the synthesis and application of sulfur-rich compounds in fields of batteries,semiconductor devices,and catalysts.

Composite solid electrolyte of Na3PS4-PEO for all-solid-state SnS2/Na batteries with excellent interfacial compatibility between electrolyte and Na metal

High ionic conductivity and superior interfacial stability of solid electrolytes at the electrodes are crucial factors for high-performance all-solid-state sodium batteries. Herein, a composite solid electrolyte Na3PS4-polyethylene oxide is synthesized by the solution-phase reaction method with an improved ionic conductivity up to 9.4 × 10-5 S/cm at room temperature. Moreover, polyethylene oxide polymer layer is wrapped homogeneously on the surface of Na3PS4 particles, which could effectively avoid the direct contact between Na3PS4 electrolyte and sodium metal, thus alleviate their side reactions. We demonstrate that all-solid-state battery SnS2/Na with the composite solid electrolyte Na3PS4-polyethylene oxide delivers an enhanced electrochemical performance with 230 m Ah/g after 40 cycles.

Growth of SnO_2 Nanoflowers on N-doped Carbon Nanofibers as Anode for Li-and Na-ion Batteries

It is urgent to solve the problems of the dramatic volume expansion and pulverization of SnO_2 anodes during cycling process in battery systems. To address this issue, we design a hybrid structure of N-doped carbon fibers@SnO_2 nanoflowers(NC@SnO_2) to overcome it in this work. The hybrid NC@SnO_2 is synthesized through the hydrothermal growth of SnO_2 nanoflowers on the surface of N-doped carbon fibers obtained by electrospinning. The NC is introduced not only to provide a support framework in guiding the growth of the SnO_2 nanoflowers and prevent the flower-like structures from agglomeration, but also serve as a conductive network to accelerate electronic transmission along one-dimensional structure effectively. When the hybrid NC@SnO_2 was served as anode, it exhibits a high discharge capacity of 750 Ah g^(-1) at 1 A g^(-1) after 100 cycles in Li-ion battery and 270 mAh g^(-1) at 100 mA g^(-1) for 100 cycles in Na-ion battery, respectively.

Hard carbon derived from rice husk as low cost negative electrodes in Na-ion batteries

Here,we report the synthesis of hard carbon materials(RH) made from natural rice husk through a single pyrolysis process and their application as an anode in sodium-ion batteries.The studies show that the electrochemical properties of RHs are affected by the treatment temperatures,which determine the materials morphology,in particular,their degree of graphitization and extent of continuous channels(nanovoids).The latter are accessible to sodium ions and significantly contribute to charge storage capacity of the produced anodes.The RHs obtained at 1600 °C deliver the highest reversible capacity of276 mAh g^(-1) mainly due to insertion of sodium ions into the nanovoids.This work deepens the basic understanding of the influence of the carbonization temperature on the sodium storage mechanism.

An insight into failure mechanism of NASICON-structured Na3V2（PO4）3 in hybrid aqueous rechargeable battery

NASICON (Na-super-ionic-conductors)-structured materials have attracted extensive research interest due to their great application potential in secondary batteries. However, the mechanism of capacity fading for NASICON-structured electrode materials has been rarely studied. In this paper, we synthesized the NASICON-structured Na3V2(PO4)3/C composite by simple sol-gel and high-temperature solid-phase method and investigated its electrochemical performance in Na-Zn hybrid aqueous rechargeable batteries. After characterizing the structure, morphology and composition variations as well as the interfacial resistance changes of Na3V2(PO4)3/C cathode during cycling, we propose a mechanical and interfacial degradation mechanism for capacity fading of NASICON-structured Na3V2(PO4)3/C in Na-Zn hybrid aqueous rechargeable batteries. This work will shed light on enhancing the mechanical and in terfacial stability of NASICON-structured Na3V2(PO4)3/C in Na-Zn hybrid aqueous rechargeable batteries.

The application of carbon materials in nonaqueous Na‐O2 batteries

Na‐O2 batteries are advantageous as the candidates of next‐generation electric vehicles due to their ultrahigh theoretical energy density and have attracted enormous attention recently.Tremendous efforts have been devoted to improve the Na‐O2 battery performance by designing advanced electrodes with various carbonbased materials.Carbon materials used in Na‐O2 batteries not only function as the air electrode to provide active sites and accommodate discharge products but also as Na anode protectors against dendrite growth and chemical/electrochemical corrosion.In this review,we mainly focus on the application of various carbonbased materials in Na‐O2 batteries and highlight their advances.The scientific understanding on the fundamental design of the material microstructure and chemistry in relation to the battery performance are summarized.Finally,perspectives on enhancing the overall battery performance based on the optimization and rational design of carbon‐based cell components are also briefly anticipated.

Nano-sized carboxylates as anode materials for rechargeable lithium-ion batteries

Nano-sized caiboxylales Na2C7H3NO4 and Na2C6H2N2O4 were prepared and investigated as anode materials for lithium-ion batteries.Both carboxylates exhibit high reversible capacities around 190 mAh/g above a cut-off voltage of 0.8 V vs.Li＋/Li.potentially improving the safety of the batteries.In addition,good rate performance and long cycle life of these carboxylates make them promising candidates as anode materials for lithium-ion batteries.

Enhanced cyclability of sulfur cathodes in lithium-sulfur batteries with Na-alginate as a binder

Na-alginate as a binder in an aqueous solvent has been applied in the preparation of sulfur cathodes for lithium-sulfur batteries.Their electrochemical performances have been investigated by a charge-discharge cycle test and electrochemical impedance spectroscopy (EIS).The EIS tests indicated that the alginate sulfur cathode had lower resistance and better kinetic characteristics than those of the poly (vinylidene fluoride) (PVDF) sulfur cathode using PVDF as a binder in a N-methy-2-pyrrolidone (NMP) solvent.The charge-discharge tests showed that the discharge capacity and the capacity retention rate of Na-alginate sulfur cathode were 508 mAh·g-1and 65.4% at the 50th cycle with a current density of 335 mA·g-1.Compared with PVDF sulfur cathode,the alginate sulfur cathode showed a remarkably better cycle performance.These results show that the alginate binder has promising potential for lithium-sulfur battery applications.

Recent advances on flexible electrodes for Na-ion batteries and Li–S batteries

Flexible energy storage devices are essential for emerging flexible electronics. The existing state-of-the-art Li-ion batteries are slowly reaching their limitation in terms of cost and energy density. Hence, flexible Na-ion batteries (SIBs) with abundanee Na resources and Li-S batteries with high energy density become the alternative for the Li-ion batteries in future. This review summarizes the recent advances in the development of flexible electrode materials for SIBs with metallic matrix and carb on aceous matrix such as carb on nano-tubes, carbon nano-fiber, graphene, carbon cloth, carbon fiber cloth, and cotton textiles. Then, the potential prototype flexible full SIBs are discussed. Further, the recent progress in the development of flexible electrode materials for Li-S batteries based on carb on nano-fiber, carb on nano-tubes, graphene, and cotton textiles is reviewed. Moreover, the design strategies of suitable interlayer, separator, electrolyte, and electrodes to prevent the dissolution and shuttle effect of polysulfides in flexible Li-S batteries are provided. Finally some prospective investigation trends towards future research of flexible SIBs and Li-S batteries are also proposed and discussed. The scientific and engineering knowledge gained on flexible SIBs and Li-S batteries provides conceivable development for practical application in near future.

Manipulating metal-sulfur interactions for achieving high-performance S cathodes for room temperature Li/Na-sulfur batteries

Rechargeable lithium/sodium-sulfur batteries working at room temperature(RT-Li/S,RT-Na/S)appear to be a promising energy storage system in terms of high theoretical energy density,low cost,and abundant resources in nature.They are,thus,considered as highly attractive candidates for future application in energy storage devices.Nevertheless,the solubility of sulfur species,sluggish kinetics of lithium/sodium sulfide compounds,and high reactivity of metallic anodes render these cells unstable.As a consequence,metal-sulfur batteries present low reversible capacity and quick capacity loss,which hinder their practical application.Investigations to address these issues regarding S cathodes are critical to the increase of their performance and our fundamental understanding of RT-Li/S and RT-Na/S battery systems.Metal-sulfur interactions,recently,have attracted considerable attention,and there have been new insights on pathways to high‐performance RT-Li/Na sulfur batteries,due to the following factors:(1)deliberate construction of metal-sulfur interactions can enable a leap in capacity;(2)metal-sulfur interactions can confine S species,as well as sodium sulfide compounds,to stop shuttle effects;(3)traces of metal species can help to encapsulate a high loading mass of sulfur with high‐cost efficiency;and(4)metal components make electrodes more conductive.In this review,we highlight the latest progress in sulfide immobilization via constructing metal bonding between various metals and S cathodes.Also,we summarize the storage mechanisms of Li/Na as well as the metal-sulfur interaction mechanisms.Furthermore,the current challenges and future remedies in terms of intact confinement and optimization of the electrochemical performance of RT-Li/Na sulfur systems are discussed in this review.

Effect of binary conductive additive mixtures on electrochemical performance of polyoxomolybdate as cathode material of lithium ion battery

Binary carbon mixtures, carbon black ECP 600JD(ECP) combined with vapor grown carbon fiber(VGCF) or carbon nanotube(CNT), or graphene(Gr) in different mass ratios, are investigated as the conductive additives for the cathode material polyoxomolybadate Na_3[AlMo_6O_(24)H_6](NAM). Field emission scanning electron microscopy and energy dispersive X-ray spectroscopy show that the surfaces of NAM particles are covered homogeneously with the binary conductive additive mixtures except the combination of ECP and CNT. The optimum combination is the mixture of ECP and VGCF, which shows higher discharge capacity than the combinations of ECP and CNT or Gr. Initial discharge capacities of 364, 339, and 291 m A·h/g are obtained by the combination of ECP and VGCF in the mass ratios of 2:1, 1:1, and 1:2, respectively. The results of electrochemical impedance spectra and 4-pin probe measurements demonstrate that the combination of ECP and VGCF exhibits the highest electrical conductivity for the electrode.

Metal–organic framework derived hierarchical porous TiO_2 nanopills as a super stable anode for Na-ion batteries

Hierarchical porous TiOnanopills were synthesized using a titanium metal-organic framework MIL-125（Ti） as precursor. The as-synthesized TiOnanopills owned a large specific surface area of 102 m/g and unique porous structure. Furthermore, the obtained TiOnanopills were applied as anode materials for Na-ion batteries for the first time. The as-synthesized TiOnanopills achieved a high discharge capacity of 196.4 m Ah/g at a current density of 0.1 A/g. A discharge capacity of 115.9 m Ah/g was obtained at a high current density of 0.5 A/g and the capacity retention was remained as high as 90% even after 3000 cycles. The excellent electrochemical performance can be attributed to its unique hierarchical porous feature.