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1.
Dark‐colored rutile TiO2 nanorods doped by electroconducting Ti3+ have been obtained uniformly with an average diameter of ≈7 nm, and have been first utilized as anodes in lithium‐ion batteries. They deliver a high reversible specific capacity of 185.7 mAh g?1 at 0.2 C (33.6 mA g?1) and maintain 92.1 mAh g?1 after 1000 cycles at an extremely high rate 50 C with an outstanding retention of 98.4%. Notably, the coulombic efficiency of Ti3+–TiO2 has been improved by approximately 10% compared with that of pristine rutile TiO2, which can be mainly attributed to its prompt electron transfer because of the introduction of Ti3+. Again the synergetic merits are noticed when the promoted electronic conductivity is combined with a shortened Li+ diffusion length resulting from the ultrafine nanorod structure, giving rise to the remarkable rate capabilities and extraordinary cycling stabilities for applications in fast and durable charge/discharge batteries. It is of great significance to incorporate Ti3+ into rutile TiO2 to exhibit particular electrochemical characteristics triggering an effective way to improve the energy storage properties.  相似文献   

2.
Lithium and sodium thiophosphates (and related compounds) have recently attracted attention because of their potential use as solid electrolytes in solid‐state batteries. These compounds, however, exhibit only limited stability in practice as they react with the electrodes. The decomposition products partially remain redox active hence leading to excess capacity. The redox activity of thiophosphates is explicitly used to act as electrode for sodium‐ion batteries. Copper thiophosphate (Cu3PS4) is used as a model system. The storage behavior between 0.01 and 2.5 V versus Na+/Na is studied in half cells using different electrolytes with 1 m NaPF6 in diglyme showing the best result. Cu3PS4 shows highly reversible charge storage with capacities of about 580 mAh g?1 for more than 200 cycles @120 mA g?1 and about 450 mAh g?1 for 1400 cycles @1 A g?1. The redox behavior is studied by operando X‐ray diffraction and X‐ray photoelectron spectroscopy. During initial sodiation, Cu3PS4 undergoes a conversion reaction including the formation of Cu and Na2S. During cycling, the redox activity seems dominated by sulfur. Interestingly, the capacity of Cu3PS4 for lithium storage is smaller, leading to about 170 mAh g?1 after 200 cycles. The results demonstrate that thiophosphates can lead to reversible charge storage over several hundred cycles without any notable capacity decay.  相似文献   

3.
Herein, Ti4+ in P′2‐Na0.67[(Mn0.78Fe0.22)0.9Ti0.1]O2 is proposed as a new strategy for optimization of Mn‐based cathode materials for sodium‐ion batteries, which enables a single phase reaction during de‐/sodiation. The approach is to utilize the stronger Ti–O bond in the transition metal layers that can suppress the movements of Mn–O and Fe–O by sharing the oxygen with Ti by the sequence of Mn–O–Ti–O–Fe. It delivers a discharge capacity of ≈180 mAh g?1 over 200 cycles (86% retention), with S‐shaped smooth charge–discharge curves associated with a small volume change during cycling. The single phase reaction with a small volume change is further confirmed by operando synchrotron X‐ray diffraction. The low activation barrier energy of ≈541 meV for Na+ diffusion is predicted using first‐principles calculations. As a result, Na0.67[(Mn0.78Fe0.22)0.9Ti0.1]O2 can deliver a high reversible capacity of ≈153 mAh g?1 even at 5C (1.3 A g?1), which corresponds to ≈85% of the capacity at 0.1C (26 mA g?1). The nature of the sodium storage mechanism governing the ultrahigh electrode performance in a full cell with a hard carbon anode is elucidated, revealing the excellent cyclability and good retention (≈80%) for 500 cycles (111 mAh g?1) at 5C (1.3 A g?1).  相似文献   

4.
Cathode design is indispensable for building Li‐O2 batteries with long cycle life. A composite of carbon‐wrapped Mo2C nanoparticles and carbon nanotubes is prepared on Ni foam by direct hydrolysis and carbonization of a gel composed of ammonium heptamolybdate tetrahydrate and hydroquinone resin. The Mo2C nanoparticles with well‐controlled particle size act as a highly active oxygen reduction reactions/oxygen evolution reactions (ORR/OER) catalyst. The carbon coating can prevent the aggregation of the Mo2C nanoparticles. The even distribution of Mo2C nanoparticles results in the homogenous formation of discharge products. The skeleton of porous carbon with carbon nanotubes protrudes from the composite, resulting in extra voids when applied as a cathode for Li‐O2 batteries. The batteries deliver a high discharge capacity of ≈10 400 mAh g?1 and a low average charge voltage of ≈4.0 V at 200 mA g?1. With a cutoff capacity of 1000 mAh g?1, the Li‐O2 batteries exhibit excellent charge–discharge cycling stability for over 300 cycles. The average potential polarization of discharge/charge gaps is only ≈0.9 V, demonstrating the high ORR and OER activities of these Mo2C nanoparticles. The excellent cycling stability and low potential polarization provide new insights into the design of highly reversible and efficient cathode materials for Li‐O2 batteries.  相似文献   

5.
A unique watermelon‐like structured SiOx–TiO2@C nanocomposite is synthesized by a scalable sol–gel method combined with carbon coating process. Ultrafine TiO2 nanocrystals are uniformly embedded inside SiOx particles, forming SiOx–TiO2 dual‐phase cores, which are coated with outer carbon shells. The incorporation of TiO2 component can effectively enhance the electronic and lithium ionic conductivities inside the SiOx particles, release the structure stress caused by alloying/dealloying of Si component and maximize the capacity utilization by modifying the Si–O bond feature and decreasing the O/Si ratio (x‐value). The synergetic combination of these advantages enables the synthesized SiOx–TiO2@C nanocomposite to have excellent electrochemical performances, including high specific capacity, excellent rate capability, and stable long‐term cycleability. A stable specific capacity of ≈910 mAh g?1 is achieved after 200 cycles at the current density of 0.1 A g?1 and ≈700 mAh g?1 at 1 A g?1 for over 600 cycles. These results suggest a great promise of the proposed particle architecture, which may have potential applications in the improvement of various energy storage materials.  相似文献   

6.
The intrinsic properties of nanoscale active materials are always excellent for energy storage devices. However, the accompanying problems of ion/electron transport limitation and active materials shedding of the whole electrodes, especially for high‐loaded electrode composed of nanoparticles with high specific surface area, bring down their comprehensive performance for practical applications. Here, this problem is solved with the as proposed “phase inversion” method, which allows fabrication of tricontinuous structured electrodes via a simple, convenient, low cost, and scalable process. During this process, the binder networks, electron paths, and ion channels can be separately interconnected, which simultaneously achieves excellent binding strength and ion/electron conductivity. This is verified by constructing electrodes with sulfur/carbon (S/C) and Li3V2(PO4)3/C (LVP/C) nanoparticles, separately delivering 869 mA h g?1 at 1 C in Li–S batteries and 100 mA h g?1 at 30 C in Li–LVP batteries, increasing by 26% and 66% compared with the traditional directly drying ones. Electrodes with 7 mg cm?2 sulfur and 11 mg cm?2 LVP can also be easily coated on aluminum foil, with excellent cycling stability. Phase inversion, as a universal method to achieve high‐performance energy storage devices, might open a new area in the development of nanoparticle‐based active materials.  相似文献   

7.
The application of Li‐S batteries is hindered by low sulfur utilization and rapid capacity decay originating from slow electrochemical kinetics of polysulfide transformation to Li2S at the second discharge plateau around 2.1 V and harsh shuttling effects for high‐S‐loading cathodes. Herein, a cobalt‐doped SnS2 anchored on N‐doped carbon nanotube (NCNT@Co‐SnS2) substrate is rationally designed as both a polysulfide shield to mitigate the shuttling effects and an electrocatalyst to improve the interconversion kinetics from polysulfides to Li2S. As a result, high‐S‐loading cathodes are demonstrated to achieve good cycling stability with high sulfur utilization. It is shown that Co‐doping plays an important role in realizing high initial capacity and good capacity retention for Li‐S batteries. The S/NCNT@Co‐SnS2 cell (3 mg cm?2 sulfur loading) delivers a high initial specific capacity of 1337.1 mA h g?1 (excluding the Co‐SnS2 capacity contribution) and 1004.3 mA h g?1 after 100 cycles at a current density of 1.3 mA cm?2, while the counterpart cell (S/NCNT@SnS2) only shows an initial capacity of 1074.7 and 843 mA h g?1 at the 100th cycle. The synergy effect of polysulfide confinement and catalyzed polysulfide conversion provides an effective strategy in improving the electrochemical performance for high‐sulfur‐loading Li‐S batteries.  相似文献   

8.
Transition metal oxides, possessing high theoretical specific capacities, are promising anode materials for sodium‐ion batteries. However, the sluggish sodiation/desodiation kinetics and poor structural stability restrict their electrochemical performance. To achieve high and fast Na storage capability, in this work, rambutan‐like hybrid hollow spheres of carbon confined Co3O4 nanoparticles are synthesized by a facile one‐pot hydrothermal treatment with postannealing. The hierarchy hollow structure with ultrafine Co3O4 nanoparticles embedded in the continuous carbon matrix enables greatly enhanced structural stability and fast electrode kinetics. When tested in sodium‐ion batteries, the hollow structured composite electrode exhibits an outstandingly high reversible specific capacity of 712 mAh g?1 at a current density of 0.1 A g?1, and retains a capacity of 223 mAh g?1 even at a large current density of 5 A g?1. Besides the superior Na storage capability, good cycle performance is demonstrated for the composite electrode with 74.5% capacity retention after 500 cycles, suggesting promising application in advanced sodium‐ion batteries.  相似文献   

9.
Room-temperature sodium–sulfur (RT Na–S) batteries have attracted extensive attention because of their low cost and high specific energy. RT Na–S batteries, however, usually suffer from sluggish reaction kinetics, low reversible capacity, and short lifespans. Herein, it is shown that chain-mail catalysts, consisting of porous nitrogen doped carbon nanofibers (PCNFs) encapsulating Co nanoparticles (Co@PCNFs), can activate sulfur via electron engineering. The chain-mail catalysts Co@PCNFs with a micrograde hierarchical structure as a freestanding sulfur cathode (Co@PCNFs/S) can provide space for high mass loading of sulfur and polysulfides. The electrons can rapidly transfer from chain-mail catalysts to sulfur and polysulfides during discharge–charge processes, therefore boosting its conversion kinetics. As a result, this freestanding Co@PCNFs/S cathode achieves a high sulfur loading of 2.1 ± 0.2 mg cm−2, delivering a high reversible capacity of 398 mA h g−1 at 0.5 C (1 C = 1675 mA g−1) over 600 cycles and superior rate capability of an average capacity of 240 mA h g−1 at 5 C. Experimental results, combined with density functional theory calculations, demonstrate that the Co@PCNFs/S can efficiently improve the conversion kinetics between the polysulfides and Na2S via transferring electrons from Co to them, thereby realizing efficient sulfur redox reactions.  相似文献   

10.
Sodium‐ion batteries (SIBs) are regarded as the best alternative to lithium‐ion batteries due to their low cost and similar Na+ insertion chemistry. It is still challenging but greatly desired to design and develop novel electrode materials with high reversible capacity, long cycling life, and good rate capability toward high‐performance SIBs. This work demonstrates an innovative design strategy and a development of few‐layered molybdenum disulfide/sulfur‐doped graphene nanosheets (MoS2/SG) composites as the SIB anode material providing a high specific capacity of 587 mA h g?1 calculated based on the total composite mass and an extremely long cycling stability over 1000 cycles at a current density of 1.0 A g?1 with a high capacity retention of ≈85%. Systematic characterizations reveal that the outstanding performance is mainly attributed to the unique and robust composite architecture where few‐layered MoS2 and S‐doped graphene are intimately bridged at the hetero‐interface through a synergistic coupling effect via the covalently doped S atoms. The design strategy and mechanism understanding at the molecular level outlined here can be readily applied to other layered transition metal oxides for SIBs anode and play a key role in contributing to the development of high‐performance SIBs.  相似文献   

11.
The rational combination of conductive nanocarbon with sulfur leads to the formation of composite cathodes that can take full advantage of each building block; this is an effective way to construct cathode materials for lithium–sulfur (Li–S) batteries with high energy density. Generally, the areal sulfur‐loading amount is less than 2.0 mg cm?2, resulting in a low areal capacity far below the acceptable value for practical applications. In this contribution, a hierarchical free‐standing carbon nanotube (CNT)‐S paper electrode with an ultrahigh sulfur‐loading of 6.3 mg cm?2 is fabricated using a facile bottom–up strategy. In the CNT–S paper electrode, short multi‐walled CNTs are employed as the short‐range electrical conductive framework for sulfur accommodation, while the super‐long CNTs serve as both the long‐range conductive network and the intercrossed mechanical scaffold. An initial discharge capacity of 6.2 mA·h cm?2 (995 mA·h g?1), a 60% utilization of sulfur, and a slow cyclic fading rate of 0.20%/cycle within the initial 150 cycles at a low current density of 0.05 C are achieved. The areal capacity can be further increased to 15.1 mA·h cm?2 by stacking three CNT–S paper electrodes—resulting in an areal sulfur‐loading of 17.3 mg cm?2—for the cathode of a Li–S cell. The as‐obtained free‐standing paper electrode are of low cost and provide high energy density, making them promising for flexible electronic devices based on Li–S batteries.  相似文献   

12.
Although lithium–sulfur (Li–S) batteries are one of the most promising energy storage devices owing to their high energy densities, the sluggish reaction kinetics and severe shuttle effect of the sulfur cathodes hinder their practical applications. Here, single atom zinc implanted MXene is introduced into a sulfur cathode, which can not only catalyze the conversion reactions of polysulfides by decreasing the energy barriers from Li2S4 to Li2S2/Li2S but also achieve strong interaction with polysulfides due to the high electronegativity of atomic zinc on MXene. Moreover, it is found that the homogenously dispersed zinc atoms can also accelerate the nucleation of Li2S2/Li2S on MXene layers during the redox reactions. As a result, the sulfur cathode with single atom zinc implanted MXene exhibits a high reversible capacity of 1136 mAh g?1. After electrode optimization, a high areal capacity of 5.3 mAh cm?2, high rate capability of 640 mAh g?1 at 6 C, and good cycle stability (80% capacity retention after 200 cycles at 4 C) can be achieved.  相似文献   

13.
One of the critical challenges to develop advanced lithium‐sulfur (Li‐S) batteries lies in exploring a high efficient stable sulfur cathode with robust conductive framework and high sulfur loading. Herein, a 3D flexible multifunctional hybrid is rationally constructed consisting of nitrogen‐doped carbon foam@CNTs decorated with ultrafine MgO nanoparticles for the use as advanced current collector. The dense carbon nanotubes uniformly wrapped on the carbon foam skeletons enhance the flexibility and build an interconnected conductive network for rapid ionic/electronic transport. In particular, a synergistic action of MgO nanoparticles and in situ N‐doping significantly suppresses the shuttling effect via enhanced chemisorption of lithium polysulfides. Owing to these merits, the as‐built electrode with an ultrahigh sulfur loading of 14.4 mg cm?2 manifests a high initial areal capacity of 10.4 mAh cm?2, still retains 8.8 mAh cm?2 (612 mAh g?1 in gravimetric capacity) over 50 cycles. The best cycling performance is achieved upon 800 cycles with an extremely low decay rate of 0.06% at 2 C. Furthermore, a flexible soft‐packaged Li‐S battery is readily assembled, which highlights stable electrochemical characteristics under bending and even folding. This cathode structural design may open up a potential avenue for practical application of high‐sulfur‐loading Li‐S batteries toward flexible energy‐storage devices.  相似文献   

14.
Sodium‐ion batteries are attracting increasing interests as a promising alternative to lithium‐ion batteries due to the abundant resource and low cost of sodium. Despite phosphorus (P) has extremely high theoretical capacity of 2595 mAh g?1, its wide application for sodium‐ion battery is highly hampered by its fast capacity fading and low Coulombic efficiency as a result of large volume change upon cycling. Herein, a robust phosphorus anode with long cycle life for sodium‐ion battery via hybridization with functional conductive polymer is presented. To this end, the polyacrylonitrile is first dehydrogenated by sulfur via a facile thermal treatment, forming a conductive main chain embedded with C–S–S moieties. This functional conductive polymer enables the formation of P? S bonds between phosphorus and functional conductive matrix, leading to a robust electrode that can accommodate the large volume change upon substantial volume change in cycling. Consequently, this hybrid anode delivers a high capacity of ≈1300 mAh g?1 at a current density of 520 mA g?1 with high Coulombic efficiency (>99%) and good cycling performance (91% capacity retention after 100 cycles).  相似文献   

15.
3D metal carbide@mesoporous carbon hybrid architecture (Ti3C2Tx@Meso‐C, TX ≈ FxOy) is synthesised and applied as cathode material hosts for lithium‐sulfur batteries. Exfoliated‐metal carbide (Ti3C2Tx) nanosheets have high electronic conductivity and contain rich functional groups for effective trapping of polysulfides. Mesoporous carbon with a robust porous structure provides sufficient spaces for loading sulfur and effectively cushion the volumetric expansion of sulfur cathodes. Theoretical calculations have confirmed that metal carbide can absorb sulfur and polysulfides, therefore extending the cycling performance. The Ti3C2Tx@Meso‐C/S cathodes have achieved a high capacity of 1225.8 mAh g?1 and more than 300 cycles at the C/2 current rate. The Ti3C2Tx@Meso‐C hybrid architecture is a promising cathode host material for lithium‐sulfur batteries.  相似文献   

16.
Na‐ion Batteries have been considered as promising alternatives to Li‐ion batteries due to the natural abundance of sodium resources. Searching for high‐performance anode materials currently becomes a hot topic and also a great challenge for developing Na‐ion batteries. In this work, a novel hybrid anode is synthesized consisting of ultrafine, few‐layered SnS2 anchored on few‐layered reduced graphene oxide (rGO) by a facile solvothermal route. The SnS2/rGO hybrid exhibits a high capacity, ultralong cycle life, and superior rate capability. The hybrid can deliver a high charge capacity of 649 mAh g?1 at 100 mA g?1. At 800 mA g?1 (1.8 C), it can yield an initial charge capacity of 469 mAh g?1, which can be maintained at 89% and 61%, respectively, after 400 and 1000 cycles. The hybrid can also sustain a current density up to 12.8 A g?1 (≈28 C) where the charge process can be completed in only 1.3 min while still delivering a charge capacity of 337 mAh g?1. The fast and stable Na‐storage ability of SnS2/rGO makes it a promising anode for Na‐ion batteries.  相似文献   

17.
As an anode material for lithium‐ion batteries, titanium dioxide (TiO2) shows good gravimetric performance (336 mAh g?1 for LiTiO2) and excellent cyclability. To address the poor rate behavior, slow lithium‐ion (Li+) diffusion, and high irreversible capacity decay, TiO2 nanomaterials with tuned phase compositions and morphologies are being investigated. Here, a promising material is prepared that comprises a mesoporous “yolk–shell” spherical morphology in which the core is anatase TiO2 and the shell is TiO2(B). The preparation employs a NaCl‐assisted solvothermal process and the electrochemical results indicate that the mesoporous yolk–shell microspheres have high specific reversible capacity at moderate current (330.0 mAh g?1 at C/5), excellent rate performance (181.8 mAh g?1 at 40C), and impressive cyclability (98% capacity retention after 500 cycles). The superior properties are attributed to the TiO2(B) nanosheet shell, which provides additional active area to stabilize the pseudocapacity. In addition, the open mesoporous morphology improves diffusion of electrolyte throughout the electrode, thereby contributing directly to greatly improved rate capacity.  相似文献   

18.
Lithium–sulfur (Li–S) batteries are promising energy storage systems due to their large theoretical energy density of 2600 Wh kg?1 and cost effectiveness. However, the severe shuttle effect of soluble lithium polysulfide intermediates (LiPSs) and sluggish redox kinetics during the cycling process cause low sulfur utilization, rapid capacity fading, and a low coulombic efficiency. Here, a 3D copper, nitrogen co‐doped hierarchically porous graphitic carbon network developed through a freeze‐drying method (denoted as 3D Cu@NC‐F) is prepared, and it possesses strong chemical absorption and electrocatalytic conversion activity for LiPSs as highly efficient sulfur host materials in Li–S batteries. The porous carbon network consisting of 2D cross‐linked ultrathin carbon nanosheets provides void space to accommodate volumetric expansion upon lithiation, while the Cu, N‐doping effect plays a critical role for the confinement of polysulfides through chemical bonding. In addition, after sulfuration of Cu@NC‐F network, the in situ grown copper sulfide (CuxS) embedded within CuxS@NC/S‐F composite catalyzes LiPSs conversion during reversible cycling, resulting in low polarization and fast redox reaction kinetics. At a current density of 0.1 C, the CuxS@NC/S‐F composites' electrode exhibits an initial capacity of 1432 mAh g?1 and maintains 1169 mAh g?1 after 120 cycles, with a coulombic efficiency of nearly 100%.  相似文献   

19.
All‐solid‐state lithium metal batteries (ASSLMBs) have attracted significant attention due to their superior safety and high energy density. However, little success has been made in adopting Li metal anodes in sulfide electrolyte (SE)‐based ASSLMBs. The main challenges are the remarkable interfacial reactions and Li dendrite formation between Li metal and SEs. In this work, a solid‐state plastic crystal electrolyte (PCE) is engineered as an interlayer in SE‐based ASSLMBs. It is demonstrated that the PCE interlayer can prevent the interfacial reactions and lithium dendrite formation between SEs and Li metal. As a result, ASSLMBs with LiFePO4 exhibit a high initial capacity of 148 mAh g?1 at 0.1 C and 131 mAh g?1 at 0.5 C (1 C = 170 mA g?1), which remains at 122 mAh g?1 after 120 cycles at 0.5 C. All‐solid‐state Li‐S batteries based on the polyacrylonitrile‐sulfur composite are also demonstrated, showing an initial capacity of 1682 mAh g?1. The second discharge capacity of 890 mAh g?1 keeps at 775 mAh g?1 after 100 cycles. This work provides a new avenue to address the interfacial challenges between Li metal and SEs, enabling the successful adoption of Li metal in SE‐based ASSLMBs with high energy density.  相似文献   

20.
To eliminate capacity‐fading effects due to the loss of sulfur cathode materials as a result of polysulfide dissolution in lithium–sulfur (Li–S) cells, 3D carbon aerogel (CA) materials with abundant narrow micropores can be utilized as an immobilizer host for sulfur impregnation. The effects of S incorporation on microstructure, surface area, pore size distribution, and pore volume of the S/CA hybrids are studied. The electrochemical performance of the S/CA hybrids is investigated using electrochemical impedance spectroscopy, galvanostatical charge–discharge, and cyclic voltammetry techniques. The 3D porous S/CA hybrids exhibit significantly improved reversible capacity, high‐rate capability, and excellent cycling performance as a cathode electrode for Li–S batteries. The S/CA hybrid with an optimal incorporating content of 27% S shows an excellent reversible capacity of 820 mAhg?1 after 50 cycles at a current density of 100 mAg?1. Even at a current density of 3.2C (5280 mAg?1), the reversible capacity of 27%S/CA hybrid can still maintain at 521 mAhg?1 after 50 cycles. This strategy for the S/CA hybrids as cathode materials to utilize the abundant micropores for sulfur immobilizers for sulfur impregnation for Li–S battery offers a new way to solve the long‐term reversibility obstacle and provides guidelines for designing cathode electrode architectures.  相似文献   

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