首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
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.  相似文献   

2.
Smart hybridization of active materials into tailored electrode structure is highly important for developing advanced electrochemical energy storage devices. With the help of sandwiched design, herein a powerful strategy is developed to fabricate three‐layer sandwiched composite core/shell arrays via combined hydrothermal and polymerization approaches. In such a unique architecture, wrinkled MoSe2 nanosheets are sandwiched by vertical graphene (VG) core and N‐doped carbon (N‐C) shell forming sandwiched core/shell arrays. Interesting advantages including high electrical conductivity, strong mechanical stability, and large porosity are combined in the self‐supported VG/MoSe2/N‐C sandwiched arrays. As a preliminary test, the sodium ion storage properties of VG/MoSe2/N‐C sandwiched arrays are characterized and demonstrated with high capacity (540 mA h g?1), enhanced high rate capability, and long‐term cycling stability (298 mA h g?1 at 2.0 A g?1 after 1000 cycles). The sandwiched core/shell structure plays positive roles in the enhancement of electrochemical performances due to dual conductive carbon networks, good volume accommodation, and highly porous structure with fast ion diffusion. The directional electrode design protocol provides a general method for synthesis of high‐performance ternary core/shell electrodes.  相似文献   

3.
The achievement of the superior rate capability and cycling stability is always the pursuit of sodium‐ion batteries (SIBs). However, it is mainly restricted by the sluggish reaction kinetics and large volume change of SIBs during the discharge/charge process. This study reports a facile and scalable strategy to fabricate hierarchical architectures where TiO2 nanotube clusters are coated with the composites of ultrafine MoO2 nanoparticles embedded in carbon matrix (TiO2@MoO2‐C), and demonstrates the superior electrochemical performance as the anode material for SIBs. The ultrafine MoO2 nanoparticles and the unique nanorod structure of TiO2@MoO2‐C help to decrease the Na+ diffusion length and to accommodate the accompanying volume expansion. The good integration of MoO2 nanoparticles into carbon matrix and the cable core role of TiO2 nanotube clusters enable the rapid electron transfer during discharge/charge process. Benefiting from these structure merits, the as‐made TiO2@MoO2‐C can deliver an excellent cycling stability up to 10 000 cycles even at a high current density of 10 A g?1. Additionally, it exhibits superior rate capacities of 110 and 76 mA h g?1 at high current densities of 10 and 20 A g?1, respectively, which is mainly attributed to the high capacitance contribution.  相似文献   

4.
A simple ball‐milling method is used to synthesize a tin oxide‐silicon carbide/few‐layer graphene core‐shell structure in which nanometer‐sized SnO2 particles are uniformly dispersed on a supporting SiC core and encapsulated with few‐layer graphene coatings by in situ mechanical peeling. The SnO2‐SiC/G nanocomposite material delivers a high reversible capacity of 810 mA h g?1 and 83% capacity retention over 150 charge/discharge cycles between 1.5 and 0.01 V at a rate of 0.1 A g?1. A high reversible capacity of 425 mA h g?1 also can be obtained at a rate of 2 A g?1. When discharged (Li extraction) to a higher potential at 3.0 V (vs. Li/Li+), the SnO2‐SiC/G nanocomposite material delivers a reversible capacity of 1451 mA h g?1 (based on the SnO2 mass), which corresponds to 97% of the expected theoretical capacity (1494 mA h g?1, 8.4 equivalent of lithium per SnO2), and exhibits good cyclability. This result suggests that the core‐shell nanostructure can achieve a completely reversible transformation from Li4.4Sn to SnO2 during discharging (i.e., Li extraction by dealloying and a reversible conversion reaction, generating 8.4 electrons). This suggests that simple mechanical milling can be a powerful approach to improve the stability of high‐performance electrode materials involving structural conversion and transformation.  相似文献   

5.
A three‐dimensional porous core‐shell Sn@carbon anode on nickel foam substrate was fabricated by electrostatic spray deposition (ESD) technique followed by high temperature treatment. The carbon shell with a thickness of about 3.2 nm was formed on porous Sn structure at high temperature. 3D porous structure and carbon shell were designed to buffer volume expansion/shrinkage of Sn lattice upon cycling and increase the electrical conductivity. After 315 charge/discharge cycles Sn@carbon anode exhibited high specific capacity of 638 mAh g?1 with the low capacity fade of average 0.11 mAh g?1 per cycle. Sn@carbon based anodes was demonstrated to have promising potential for high performance lithium ion batteries application.  相似文献   

6.
Resources used in lithium‐ion batteries are becoming more expensive due to their high demand, and the global cobalt market heavily depends on supplies from countries with high geopolitical risks. Alternative battery technologies including magnesium‐ion batteries are therefore desirable. Progress toward practical magnesium‐ion batteries are impeded by an absence of suitable anodes that can operate with conventional electrolyte solvents. Although alloy‐type magnesium‐ion battery anodes are compatible with common electrolyte solvents, they suffer from severe failure associated with huge volume changes during cycling. Consequently, achieving more than 200 cycles in alloy‐type magnesium‐ion battery anodes remains a challenge. Here an unprecedented long‐cycle life of 1000 cycles, achieved at a relatively high (dis)charge rate of 3 C (current density: 922.5 mA g?1) in Mg2Ga5 alloy‐type anode, taking advantage of near‐room‐temperatures solid–liquid phase transformation between Mg2Ga5 (solid) and Ga (liquid), is demonstrated. This concept should open the way to the development of practical anodes for next‐generation magnesium‐ion batteries.  相似文献   

7.
Recently, sodium ion batteries (SIBs) have been widely investigated as one of the most promising candidates for replacing lithium ion batteries (LIBs). For SIBs or LIBs, designing a stable and uniform solid electrolyte interphase (SEI) at the electrode–electrolyte interface is the key factor to provide high capacity, long‐term cycling, and high‐rate performance. In this paper, it is described how a remarkably enhanced SEI layer can be obtained on TiO2 nanotube (TiO2 NTs) arrays that allows for a strongly improved performance of sodium battery systems. Key is that a Li+ pre‐insertion in TiO2 NTs can condition the SEI for Na+ replacement. SIBs constructed with Li‐pre‐inserted NTs deliver an exceptional Na+ cycling stability (e.g., 99.9 ± 0.1% capacity retention during 250 cycles at a current rate of 50 mA g?1) and an excellent rate capability (e.g., 132 mA h g?1 at a current rate of 1 A g?1). The key factor in this outstanding performance is that Li‐pre‐insertion into TiO2 NTs leads not only to an enhanced electronic conductivity in the tubes, but also expands the anatase lattice for facilitated subsequent Na+ cycling.  相似文献   

8.
Sodium‐ion capacitors (SICs) are emerging energy storage devices with high energy, high power, and durable life. Sn is a promising anode material for lithium storage, but the poor conductivity of the a‐NaSn phase upon sodaition hinders its implementation in SICs. Herein, a superior Sn‐based anode material consisting of plum pudding‐like Co2P/Sn yolk encapsulated with nitrogen‐doped carbon nanobox (Co2P/Sn@NC) for high‐performance SICs is reported. The 8–10 nm metallic nanoparticles produced in situ are uniformly dispersed in the amorphous Sn matrix serving as conductive fillers to facilitate electron transfer in spite of the formation of electrically resistive a‐NaSn phase during cycling. Meanwhile, the carbon shell buffers the large expansion of active Sn and provides a stable electrode–electrolyte interface. Owing to these merits, the yolk–shell Co2P/Sn@NC demonstrates a large capacity of 394 mA h g?1 at 100 mA g?1, high rate capability of 168 mA h g?1 at 5000 mA g?1, and excellent cyclability with 87% capacity retention after 10 000 cycles. By integrating the Co2P/Sn@NC anode with a peanut shell‐derived carbon cathode in the SIC, high energy densities of 112.3 and 43.7 Wh kg?1 at power densities of 100 and 10 000 W kg?1 are achieved.  相似文献   

9.
Phosphorus and tin phosphide based materials that are extensively researched as the anode for Na‐ion batteries mostly involve complexly synthesized and sophisticated nanocomposites limiting their commercial viability. This work reports a Sn4P3‐P (Sn:P = 1:3) @graphene nanocomposite synthesized with a novel and facile mechanochemical method, which exhibits unrivalled high‐rate capacity retentions of >550 and 371 mA h g?1 at 1 and 2 A g?1, respectively, over 1000 cycles and achieves excellent rate capability (>815, ≈585 and ≈315 mA h g?1 at 0.1, 2, and 10 A g?1, respectively).  相似文献   

10.
SnS2 nanoplatelet electrodes can offer an exceptionally high pseudocapacitance in an organic Na+ ion electrolyte system, but their underlying mechanisms are still largely unexplored, hindering the practical applications of pseudocapacitive SnS2 anodes in Na‐ion batteries (SIBs) and Na hybrid capacitors (SHCs). Herein, SnS2 nanoplatelets are grown directly on SnO2/C composites to synthesize SnS2/graphene‐carbon nanotube aerogel (SnS2/GCA) by pressurized sulfidation where the original morphology of carbon framework is preserved. The composite electrode possessing a large surface area delivers a remarkable specific capacity of 600.3 mA h g?1 at 0.2 A g?1 and 304.8 mA h g?1 at an ultrahigh current density of 10 A g?1 in SIBs. SHCs comprising a SnS2/GCA composite anode and an activated carbon cathode present exceptional energy densities of 108.3 and 26.9 W h kg?1 at power densities of 130 and 6053 W kg?1, respectively. The in situ transmission electron microscopy and the density functional theory calculations reveal that the excellent pseudocapacitance originates from the combination of Na adsorption on the surface/Sn edge of SnS2 nanoplatelets and ultrafast Na+ ion intercalation into the SnS2 layers.  相似文献   

11.
Sodium (Na) super ion conductor structured Na3V2(PO4)3 (NVP) is extensively explored as cathode material for sodium‐ion batteries (SIBs) due to its large interstitial channels for Na+ migration. The synthesis of 3D graphene‐like structure coated on NVP nanoflakes arrays via a one‐pot, solid‐state reaction in molten hydrocarbon is reported. The NVP nanoflakes are uniformly coated by the in situ generated 3D graphene‐like layers with the thickness of 3 nm. As a cathode material, graphene covered NVP nanoflakes exhibit excellent electrochemical performances, including close to theoretical reversible capacity (115.2 mA h g?1 at 1 C), superior rate capability (75.9 mA h g?1 at 200 C), and excellent cyclic stability (62.5% of capacity retention over 30000 cycles at 50 C). Furthermore, the 3D graphene‐like cages after removing NVP also serve as a good anode material and deliver a specific capacity of 242.5 mA h g?1 at 0.1 A g?1. The full SIB using these two cathode and anode materials delivers a high specific capacity (109.2 mA h g?1 at 0.1 A g?1) and good cycling stability (77.1% capacity retention over 200 cycles at 0.1 A g?1).  相似文献   

12.
Due to an ever‐increasing demand for electronic devices, rechargeable batteries are attractive for energy storage systems. A novel rechargeable aluminum‐ion battery based on Al3+ intercalation and deintercalation is fabricated with Ni3S2/graphene microflakes composite as cathode material and high‐purity Al foil as anode. This kind of aluminum‐ion battery comprises of an electrolyte containing AlCl3 in an ionic liquid of 1‐ethyl‐3‐methylimidazolium chloride ([EMIm]Cl). Galvanostatic charge/discharge measurements have been performed in a voltage range of 0.1–2.0 V versus Al/AlCl4 ?. An initial discharge specific capacity of 350 mA h g?1 at a current density of 100 mA g?1 is achieved, and the discharge capacity remains over 60 mA h g?1 and coulombic efficiency of 99% after 100 cycles. Typically, for the current density at 200 mA g?1, the initial charge and discharge capacities are 300 and 235 mA h g?1, respectively. More importantly, it should be emphasized that the battery has a high discharge voltage plateau (≈1.0 V vs Al/AlCl4 ?). These meaningful results represent a significant step forward in the development of aluminum‐ion batteries.  相似文献   

13.
NaVPO4F has received a great deal of attention as cathode material for Na‐ion batteries due to its high theoretical capacity (143 mA h g?1), high voltage platform, and structural stability. Novel NaVPO4F/C nanofibers are successfully prepared via a feasible electrospinning method and subsequent heat treatment as self‐standing cathode for Na‐ion batteries. Based on the morphological and microstructural characterization, it can be seen that the NaVPO4F/C nanofibers are smooth and continuous with NaVPO4F nanoparticles (≈6 nm) embedded in porous carbon matrix. For Na‐storage, this electrode exhibits extraordinary electrochemical performance: a high capacity (126.3 mA h g?1 at 1 C), a superior rate capability (61.2 mA h g?1 at 50 C), and ultralong cyclability (96.5% capacity retention after 1000 cycles at 2 C). 1D NaVPO4F/C nanofibers that interlink into 3D conductive network improve the conductivity of NaVPO4F, and effectively restrain the aggregation of NaVPO4F particles during charge/discharge process, leading to the high performance.  相似文献   

14.
In spite of the satisfactory advancement in preparing TiO2‐based hybrid structures, most methods rely on additional template‐based multistep reactions for engineering the given structure. Herein, a unique self‐template and in situ recrystallization strategy is explored to synthesize uniform flowerlike multicompositional structures of nitrogen‐doped porous carbon nanosheet networks immobilizing TiO2 nanoparticles (TiO2∩NPCSs) via a self‐prepared single precursor and subsequent thermal treatment. Depending on the unique coordination ability of 2,4‐dihydroxybenzoic acid with metal ions under alkaline conditions to form a flowerlike network, a self‐produced single precursor can be achieved. Careful investigations of the self‐prepared precursor reveal a high practicability of the present synthetic scheme. Because of the novel structural and compositional features, these TiO2∩NCSN flowers indicate superior sodium storage properties when evaluated as anodes for sodium‐ion batteries. Impressively, the TiO2∩NCSN flowers deliver high reversible capacities of 152 mAh g?1 at 2C for 3000 cycles and 114 mAh g?1 at 10C for 10000 cycles, as well as an ultrahigh rate capability up to 50C with a capacity of 101 mAh g?1. The facile method could stimulate further capability in precise construction of complex architectures with complicated compositions for different device applications.  相似文献   

15.
Different from previously reported mechanical alloying route to synthesize Sn x P3, novel Sn4P3/reduced graphene oxide (RGO) hybrids are synthesized for the first time through an in situ low‐temperature solution‐based phosphorization reaction route from Sn/RGO. Sn4P3 nanoparticles combining with advantages of high conductivity of Sn and high capacity of P are homogenously loaded on the RGO nanosheets, interconnecting to form 3D mesoporous architecture nanostructures. The Sn4P3/RGO hybrid architecture materials exhibit significantly improved electrochemical performance of high reversible capacity, high‐rate capability, and excellent cycling performance as sodium ion batteries (SIBs) anode materials, showing an excellent reversible capacity of 656 mA h g?1 at a current density of 100 mA g?1 over 100 cycles, demonstrating a greatly enhanced rate capability of a reversible capacity of 391 mA h g?1 even at a high current density of 2.0 A g?1. Moreover, Sn4P3/RGO SIBs anodes exhibit a superior long cycling life, delivering a high capacity of 362 mA h g?1 after 1500 cycles at a high current density of 1.0 A g?1. The outstanding cycling performance and rate capability of these porous hierarchical Sn4P3/RGO hybrid anodes can be attributed to the advantage of porous structure, and the synergistic effect between Sn4P3 nanoparticles and RGO nanosheets.  相似文献   

16.
Nanostructured V2O5 thin films have been prepared by means of cathodic deposition from an aqueous solution made from V2O5 and H2O2 directly on fluorine‐doped tin oxide coated (FTO) glasses followed by annealing at 500°C in air, and studied as film electrodes for lithium ion batteries. XPS results show that the as‐deposited films contained 15% V4+, however after annealing all the vanadium is oxidized to V5+. The crystallinity, surface morphology, and microstructures of the films have been investigated by means of XRD, SEM, and AFM. The V2O5 thin film electrodes show excellent electrochemical properties as cathodes for lithium ion intercalation: a high initial discharge capacity of 402 mA h g?1 and 240 mA h g?1 is retained after over 200 cycles with a discharging rate of 200 mA g?1 (1.3 C). The specific energy density is calculated as 900 W h kg?1 for the 1st cycle and 723 W h kg?1 for the 180th cycle when the films are tested at 200 mA g?1 (1.3 C). When discharge/charge is carried out at a high current density of 10.5 A g?1 (70 C), the thin film electrodes retain a good discharge capacity of 120 mA h g?1, and the specific power density is over 28 kW kg?1.  相似文献   

17.
Sodium‐ion batteries are considered alternatives to lithium‐ion batteries for energy storage devices due to their competitive cost and source abundance. However, the development of electrode materials with long‐term stability and high capacity remains a great challenge. Here, this paper describes for the first time the synthesis of a new class of core–shell MAX@K2Ti8O17 by alkaline hydrothermal reaction and hydrogenation of MAX, which grants high sodium ion‐intercalation pseudocapacitance. This composite electrode displays extraordinary reversible capacities of 190 mA h g?1 at 200 mA g?1 (0.9 C, theoretical value of ≈219 mA h g?1) and 150 mA h g?1 at 1000 mA g?1 (4.6 C). More importantly, a reversible capacity of 75 mA h g?1 at 10 000 mA g?1 (46 C) is retained without any apparent capacity decay even after more than 10 000 cycles. Experimental tests and first‐principle calculations confirm that the increase in Ti3+ on the surface layers of MAX@K2Ti8O17 by hydrogenation increases its conductivity in addition to enhancing the sodium‐ion intercalation pseudocapacitive process. Furthermore, the distorted dodecahedrons between Ti and O layers not only provide abundant sites for sodium‐ion accommodation but also act as wide tunnels for sodium‐ion transport.  相似文献   

18.
The critical challenges of Li‐O2 batteries lie in sluggish oxygen redox kinetics and undesirable parasitic reactions during the oxygen reduction reaction and oxygen evolution reaction processes, inducing large overpotential and inferior cycle stability. Herein, an elaborately designed 3D hierarchical heterostructure comprising NiCo2S4@NiO core–shell arrays on conductive carbon paper is first reported as a freestanding cathode for Li‐O2 batteries. The unique hierarchical array structures can build up multidimensional channels for oxygen diffusion and electrolyte impregnation. A built‐in interfacial potential between NiCo2S4 and NiO can drastically enhance interfacial charge transfer kinetics. According to density functional theory calculations, intrinsic LiO2‐affinity characteristics of NiCo2S4 and NiO play an importantly synergistic role in promoting the formation of large peasecod‐like Li2O2, conducive to construct a low‐impedance Li2O2/cathode contact interface. As expected, Li‐O2 cells based on NiCo2S4@NiO electrode exhibit an improved overpotential of 0.88 V, a high discharge capacity of 10 050 mAh g?1 at 200 mA g?1, an excellent rate capability of 6150 mAh g?1 at 1.0 A g?1, and a long‐term cycle stability under a restricted capacity of 1000 mAh g?1 at 200 mA g?1. Notably, the reported strategy about heterostructure accouplement may pave a new avenue for the effective electrocatalyst design for Li‐O2 batteries.  相似文献   

19.
A 3D transparent conducting oxide (3D‐TCO) has been fabricated by growing Sn‐doped indium oxide (ITO) nanowire arrays on glass substrates via a vapor transport method. The 3D TCO charge‐collection properties have been compared to those of conventional two‐dimensional TCO (2D‐TCO) thin films. For use as a photoelectrode in dye‐sensitized solar cells, ITO‐TiO2 core‐shell nanowire arrays were prepared by depositing a 45 nm‐thick mesoporous TiO2 shell layer consisting of ~6 nm anatase nanoparticles using TiCl4 treatments. Dye‐sensitized solar cells fabricated using these ITO‐TiO2 core‐shell nanowire arrays show extremely fast charge collection owing to the shorter electron paths across the 45 nm‐thick TiO2 shell compared to the 2D TCO. Interestingly, the charge‐collection time does not increase with the overall electrode thickness, which is counterintuitive to conventional diffusion models. This result implies that, in principle, maximum light harvesting can be achieved without hindering the charge collection. The proposed new 3D TCO should also be attractive for other photovoltaic applications where the active layer thickness is limited by poor charge collection.  相似文献   

20.
Construction of stable dendrite‐free Li metal anode is crucial for the development of advanced Li–S and Li–air batteries. Herein, self‐supported TiC/C core/shell nanowire arrays as skeletons and confined hosts of molten Li forming integrated trilayer TiC/C/Li anode are described. The TiC/C core/shell nanowires with diameters of 400–500 nm exhibit merits of good lithiophilicity, high electrical conductivity, and abundant porosity. The as‐prepared TiC/C/Li anode exhibits prominent electrochemical performance with a small hysteresis of less than 85 mV beyond 200 cycles (3.0 mA cm?2) as well as a very high Coulombic efficiency up to 98.5% for 100 cycles at 1.0 mA cm?2. When the structured anode is coupled with lithium iron phosphate or sulfur cathode, the assembled full cells with trilayer TiC/C/Li anodes display enhanced capability retention and improved Coulombic efficiency. This is ascribed to the unique TiC/C matrix, which can not only provide interspace for accommodating “hostless” Li, but also afford interconnected rapid transfer paths for electrons and ions with low local current densities, leading to effective inhabitation growth of Li dendrites and lower interfacial resistance. A fresh way for construction of advanced stable Li metal anodes is provided in this work.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号