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1.
For Li‐Se batteries, ether‐ and carbonate‐based electrolytes are commonly used. However, because of the “shuttle effect” of the highly dissoluble long‐chain lithium polyselenides (LPSes, Li2Sen, 4≤n≤8) in the ether electrolytes and the sluggish one‐step solid‐solid conversion between Se and Li2Se in the carbonate electrolytes, a large amount of porous carbon (>40 wt % in the electrode) is always needed for the Se cathodes, which seriously counteracts the advantage of Se electrodes in terms of volumetric capacity. Herein an acetonitrile‐based electrolyte is introduced for the Li‐Se system, and a two‐plateau conversion mechanism is proposed. This new Li‐Se chemistry not only avoids the shuttle effect but also facilitates the conversion between Se and Li2Se, enabling an efficient Se cathode with high Se utilization (97 %) and enhanced Coulombic efficiency. Moreover, with such a designed electrolyte, a highly compact Se electrode (2.35 gSe cm?3) with a record‐breaking Se content (80 wt %) and high Se loading (8 mg cm?2) is demonstrated to have a superhigh volumetric energy density of up to 2502 Wh L?1, surpassing that of LiCoO2.  相似文献   

2.
For Li-Se batteries, ether- and carbonate-based electrolytes are commonly used. However, because of the “shuttle effect” of the highly dissoluble long-chain lithium polyselenides (LPSes, Li2Sen, 4≤n≤8) in the ether electrolytes and the sluggish one-step solid-solid conversion between Se and Li2Se in the carbonate electrolytes, a large amount of porous carbon (>40 wt % in the electrode) is always needed for the Se cathodes, which seriously counteracts the advantage of Se electrodes in terms of volumetric capacity. Herein an acetonitrile-based electrolyte is introduced for the Li-Se system, and a two-plateau conversion mechanism is proposed. This new Li-Se chemistry not only avoids the shuttle effect but also facilitates the conversion between Se and Li2Se, enabling an efficient Se cathode with high Se utilization (97 %) and enhanced Coulombic efficiency. Moreover, with such a designed electrolyte, a highly compact Se electrode (2.35 gSe cm−3) with a record-breaking Se content (80 wt %) and high Se loading (8 mg cm−2) is demonstrated to have a superhigh volumetric energy density of up to 2502 Wh L−1, surpassing that of LiCoO2.  相似文献   

3.
High power and high energy density electrodes for rechargeable lithium-ion batteries are required for electrical mobility applications. Though nano-structuring of electrode materials generally improves the kinetics of the charge transport, thereby increasing the power density, the drawback is the low density of these electrodes compromising the energy density. Combining high power density with high energy density requires dense electrodes with optimal ionic and electronic wiring throughout the electrode microstructure. Here we present a facile and low cost templating method using carbonate salts creating 3D interconnected ionic pathways that improve the ionic charge transport without compromising the electrode density significantly. The method was demonstrated for C/Li4Ti5O12 electrode material resulting in excellent capacity retention reaching ~ 90% at 5 C and ~ 50% at 200 C rate combined with high active material electrode densities around 1.45 gm/cm3.  相似文献   

4.
The high theoretical specific capacity, strong structural designability and relatively inexpensive manufacturing cost make the exploration of organic electrode materials more attractive in recent years. In this article, owing to the large π-conjugated structure, plenty of nitrogen heteroatoms and multiring aromatic system, polyazaacene analogue poly(1,6-dihydropyrazino[2,3 g]quinoxaline-2,3,8-triyl-7-(2H)-ylidene-7,8-dimethylidene) (PQL) was applied as the anode in sodium-ion batteries (SIBs). PQL was almost insoluble in conventional liquid organic electrolyte (1 M NaClO4 in ethylene carbonate (EC)/dimethyl carbonate (DMC) (v:v=1 : 1) with 5 % fluoroethylene carbonate (FEC)), which strongly improved its cycle stability. The initial discharge capacity was obtained to be 1825 mAh g−1 at the current density of 100 mA g−1 and stabilized at 317 mAh g−1 after 400 cycles with the coulombic efficiency as high as 97 %. It not only showed good rate capability at high current densities (202, 183 mAh g−1 at 1 A g−1 and 1.5 A g−1) but also had a superior energy density around 290 Wh kg−1.  相似文献   

5.
As a high‐capacity anode for lithium‐ion batteries (LIBs), MoS2 suffers from short lifespan that is due in part to its unstable solid electrolyte interphase (SEI). The cycle life of MoS2 can be greatly extended by manipulating the SEI with a fluoroethylene carbonate (FEC) additive. The capacity of MoS2 in the electrolyte with 10 wt % FEC stabilizes at about 770 mAh g?1 for 200 cycles at 1 A g?1, which far surpasses the FEC‐free counterpart (ca. 40 mAh g?1 after 150 cycles). The presence of FEC enables a robust LiF‐rich SEI that can effectively inhibit the continual electrolyte decomposition. A full cell with a LiNi0.5Co0.3Mn0.2O2 cathode also gains improved performance in the FEC‐containing electrolyte. These findings reveal the importance of controlling SEI formation on MoS2 toward promoted lithium storage, opening a new avenue for developing metal sulfides as high‐capacity electrodes for LIBs.  相似文献   

6.
The effect of 15-crown-5, which is applied immediately to pure and modified surface of a lithium electrode, on the charge transfer resistance at the electrode/polymer electrolyte interface is studied. The polymer electrolyte consists of a 1: 1 mixture of oligourethan dimethacrylate and polypropylene glycol monomethacrylate (20 wt %), an initiator (azobisisobutyronitrile) (2 wt %), and a 1 M LiClO4 solution in gamma-butyrolactone (78 wt %). The conductivity of this gel electrolyte is 3 × 10?3 S cm?1. The temperature dependence of the impedance of the Li/gel electrolyte/Li electrochemical cells is measured for electrodes of four types. The activation energies for the charge transfer at the Li/electrolyte interface are calculated. It is found that, after treating the test lithium electrodes with 15-crown-5, the charge transfer resistance decreases, and in the case of the modified lithium surface, the activation energy for the process decreases by 1.8 times.  相似文献   

7.
We investigated the first charge–discharge behavior and cycling property of Li batteries using MoS2 electrodes with multi-wall carbon nanotubes (MWNT) as a conducting agent. The MoS2 electrode was prepared using MWNT as the conducting agent. The battery gave a high first discharge capacity of 440 mAhg?1 with a plateau potential region at 1.1 V. The Li/MoS2 battery using MWNT showed a higher discharge capacity compared to acetylene black. After ten cycles of the battery using MWNT, the discharge capacity decreased to 120 mAhg?1, which corresponded to 30% of the first discharge capacity. Adding a carbon nanotube into the MoS2 electrode improved the first discharge behavior, but did not affect the cycling property of the Li/MoS2 cell.  相似文献   

8.
Measuring the distribution of lithium in high capacity lithium-ion battery (LIB) electrodes is essential to understanding the coulombic losses during the lithiation/delithiation processes that occur while charging and discharging the cell. In this research, two half-cell prototypes were fabricated by electrochemically lithiating Sn foil anodes in 1M LiBF4 in a 1:1 (wt:wt) ethylene carbonate and dimethyl carbonate solutions at a constant potential of 0.50 and 0.67 V (vs. Li/Li+). The neutron depth profiling (NDP) technique was employed to study the Li distributions in the anodes. Li concentration profiles were resolved for the samples lithiated under different conditions for LIB studies. In addition, this paper demonstrated an in situ NDP measurement of an electrochemical cell with a thin window design, which reveals the dynamics of lithium distribution within the Sn anode.  相似文献   

9.
Rechargeable lithium-ion batteries (LIBs) dominate the energy market, from electronic devices to electric vehicles, but pursuing greater energy density remains challenging owing to the limited electrode capacity. Although increasing the cut-off voltage of LIBs (>4.4 V vs. Li/Li+) can enhance the energy density, the aggravated electrolyte decomposition always leads to a severe capacity fading and/or expiry of the battery. Herein, a new durable electrolyte is reported for high-voltage LIBs. The designed electrolyte is composed of mixed linear alkyl carbonate solvent with certain cyclic carbonate additives, in which use of the ethylene carbonate (EC) co-solvent was successfully avoided to suppress the electrolyte decomposition. As a result, an extremely high cycling stability, rate capability, and high-temperature storage performance were demonstrated in the case of a graphite|LiNi0.6Co0.2Mn0.2O2 (NCM622) battery at 4.45 V when this electrolyte was used. The good compatibility of the electrolyte with the graphite anode and the mitigated structural degradation of the NCM622 cathode are responsible for the high performance at high potentials above 4.4 V. This work presents a promising application of high-voltage electrolytes for pursuing high energy LIBs and provides a straightforward guide to study the electrodes/electrolyte interface for higher stability.  相似文献   

10.
The LiFePO4/carbon fiber (LFP/CF) cathodes were prepared by using activated carbon fiber cloth as current collector in place of conventional Al foil. The electrochemical properties of LFP/CF electrodes were analyzed by the cyclic voltammetry and galvanostatic charge/discharge tests. The results indicate that the activated carbon fiber cloth with high specific surface area and high porosity makes the LFP/CF electrode that possesses higher mass loading of 18–21 mg cm–2 and stronger redox reaction ability compared with Al foil-based electrode. The LFP/CF electrode shows excellent rate performance and cycle stability. At 0.1C, the discharge capacity is up to 190.1 mAh g–1 that exceeds the theoretical capacity due to the combination effect of battery and capacitor. Furthermore, the LFP/CF electrode shows an initial capacity of 150.4 mAh g–1 at 1C with a capacity retention of 74.7% after 425 cycles, which is higher than 62.4% for LFP/Al foil electrode, and an initial discharge capacity of 130 mAh g–1 at 5C with a capacity retention of 61.5% after 370 cycles. But this composite electrode is not suitable for charging/discharging at higher rate as 10C due to too much mass loading.  相似文献   

11.
La2NiO4+δ , 60 wt.% La2NiO4+δ –40 wt.% La0.6Sr0.4Co0.2Fe0.8O3-δ , and 60 wt.% La2NiO4+δ –40 wt.% Ce0.8Sm0.2O1.9 electrodes were prepared from fine powders on dense Ce0.8Sm0.2O1.9 electrolyte substrates by screen-printing technique. Electrochemical impedance spectroscopy and chronopotentiometry techniques were employed to evaluate the electrochemical properties of the composite electrodes in comparison with the La2NiO4+δ electrode. For the three electrodes, main electrode processes were resolved to be charge-transfer at the electrode/electrolyte interface and oxygen exchange on the electrode surface. The contribution of the surface oxygen exchange process was detected to be dominant for the overall electrode polarization. The addition of Ce0.8Sm0.2O1.9 into La2NiO4+δ was favorable for the charge transfer process whereas it was undesired for the surface oxygen exchange process. On comparison, adding La0.6Sr0.4Co0.2Fe0.8O3-δ into La2NiO4+δ was found to benefit both the two electrode processes. The La2NiO4+δ -La0.6Sr0.4Co0.2Fe0.8O3-δ composite electrode showed optimum electrochemical properties among the three electrodes. At 800 °C, the composite electrode achieved a polarization resistance of 0.20 Ω cm2, an overpotential of 45 mV at a current density of 200 mA cm?2, together with an exchange current density of ~200 mA cm?2.  相似文献   

12.
Over the past decade, TiO2/graphene composites as electrodes for lithium ion batteries have attracted a great deal of attention for reasons of safety and environmental friendliness. However, most of the TiO2/graphene electrodes have large graphene content (9–40 %), which is bound to increase the cost of the battery. Logically, reducing the amount of graphene is a necessary part to achieve a green battery. The synthesis of TiO2 nanosheets under solvothermal conditions without additives is now demonstrated. Through mechanical mixing TiO2 nanosheets with different amount of reduced graphene (rGO), a series of TiO2@graphene composites was prepared with low graphene content (rGO content 1, 2, 3, and 5 wt %). When these composites were evaluated as anodes for lithium ion batteries, it was found that TiO2+3 wt % rGO manifested excellent cycling stability and a high specific capacity (243.7 mAh g?1 at 1 C; 1 C=167.5 mA g?1), and demonstrated superior high‐rate discharge/charge capability at 20 C.  相似文献   

13.
The cathodic stability of the zwitterionic imidazolium compounds was significantly enhanced by the introduction of an ether group at 1 or 2-position on the imidazolium ring. The cycle performance tests showed that the initial cell capacity was maintained almost unchanged up to 100 cycles at 0.5 and 1 C when 2.5 wt.% of 2-butoxymethyl-1-methylimidazolium-3-propylsulfonate or 2-butoxymethyl-1-butylimidazolium-3-propylsulfonate was added to the model electrolyte (1 M LiPF6 in ethylene carbonate, dimethyl carbonate and ethylmethyl carbonate (1/1/1 v/v/v)).Structures of zwitterionic compounds and their interactions with lithium ions were theoretically investigated.  相似文献   

14.
Copper/copper oxide (Cu/Cu2O) electrodes are known to display interesting electrocatalytic performances for the reduction of CO2, and thus, deserve further investigation for optimization. Here, we show that the addition of nitrogen‐based organic additives greatly improves the activity of these electrodes (higher current densities, greater selectivity, and higher faradaic yields). The best effector is found to be tetramethyl cyclam. For example, electrolysis at ?2.0 V versus Fc+/Fc in CO2‐saturated DMF/H2O (99:1, v/v) in the presence of this effector results in formic acid with almost 90 % faradaic yield. SEM and XPS analysis of the electrode surface reveals that the organic additive promotes the formation of active Cu0 nanoparticles from Cu2O during electrolysis. This simple approach provides a straightforward strategy toward the optimization of Cu/Cu2O electrodes.  相似文献   

15.
A composite of aminosilane-grafted TiO2 (TA) and graphene oxide (GO) was prepared via a hydrothermal process. The TiO2/graphene oxide-based (TA/GO) anode was investigated in an ionic liquid electrolyte (0.7 M lithium bis(trifluoromethanesulfonyl)imide (LiNTf2)) in ionic liquid (N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (MPPyrNTf2)) at room temperature and in sulfolane (1 M lithium hexafluorophosphate (LiPF6) in tetramethylene sulfolane (TMS)). Scanning and transmission electron microscopy (SEM and TEM) observations of the anode materials suggested that the electrochemical intercalation/deintercalation process in the ionic liquid electrolyte with vinylene carbonate (VC) leads to small changes on the surface of TA/GO particles. The addition of VC to the electrolyte (0.7 M LiNTf2 in MPPyrNTf2 + 10 wt.% VC) considerably increases the anode capacity. Electrodes were tested at different current regimes in the range 5–50 mA g?1. The capacity of the anode, working at a low current regime of 5 mA g?1, was ca. 245 mA g?1, while a current of 50 mA g?1 resulted in a capacity of 170 mA g?1. The decrease in anode capacity with increasing current rate was interpreted as the result of kinetic limits of electrode operation. A much lower capacity was observed for the system TA/GO│1 M LiPF6 in TMS + 10 wt.% VC│Li.  相似文献   

16.
Summary.  Ce-V mixed oxide films have been deposited by RF sputtering with the aim of increasing the Li charge capacity of counter electrodes in smart windows. Such mixed oxides have shown high transmittance and optical passivity in the visible region. After electrode pre-conditioning by cyclic voltammetry, a good electrochemical reversibility in LiClO4– propylene carbonate electrolyte was observed, and large Li-charge capacity under galvanostatic charging (up to 50 mCċcm−2) has been measured. The electrode charge capacity decreased after prolonged insertion-deinsertion cycles, whereas the photoptic transmittance remained about constant. After 800 cycles the Li-charge capacity decreased to 40 mCċcm−2. The Li diffusion coefficient inside the films measured by electrochemical impedance and by galvanostatic titration ranged from 10−11 cm2ċs−1 to 10−13cm2ċs−1. We observed that the Li charge capacity of the film electrodes is a function of the film deposition conditions, because it increased with the vanadium oxide concentration in the target and with the oxygen content in the sputtering atmosphere. Received June 23, 2000. Accepted (revised) August 7, 2000  相似文献   

17.
Developing high-efficiency, cost-effective, and durable electrodes is significant for electrochemical capacitors and electrocatalysis. Herein, a 3D bifunctional electrode consisting of nickel hydroxide nanosheets@nickel sulfide nanocubes arrays on Ni foam (Ni(OH)2@Ni3S2/NF) obtained from a Prussian blue analogue-based precursor is reported. The 3D higher-order porous structure and synergistic effect of different compositions endow the electrode with large specific surface area, facile ion/electron transport path, and improved conductivity. As a result, the Ni(OH)2@Ni3S2/NF electrode exhibits a high specific capacity of 211 mA h g−1 at a current density of 1 A g−1 and 73 % capacity retention after 5000 cycles at 5 A g−1. Moreover, the Ni(OH)2@Ni3S2/NF electrode has superior electrocatalytic activity for the hydrogen evolution reaction with low overpotentials of 140 and 210 mV at current densities of 10 and 100 mA cm−2, respectively. The synthetic strategy for the unique higher-order porous structure can be extended to fabricate other composite materials for energy storage and conversion.  相似文献   

18.
Olivine-type LiFePO4 composite materials for cathode material of the lithium-ion batteries were synthesized by using a sol-gel method and were coated by a chemical deposition of silver particles. As-obtained LiFePO4/C-Ag (2.1 wt.%) composites were characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), conductivity measurements, cyclic voltammetry, as well as galvanostatic measurements. The results revealed that the discharge capacity of the LiFePO4/C-Ag electrode is 136.6 mAh/g, which is 7.6% higher than that of uncoated LiFePO4/C electrode (126.9 mAh/g). The LiFePO4/C coated by silver nanoparticles enhances the electrode conductivity and specific capacity at high discharge rates. The improved capacity at high discharge rates may be attributed to increased electrode conductivity and the synergistic effect on electron and Li+ transport after silver incorporation.  相似文献   

19.
Lithium‐ion batteries (LIBs) are primary energy storage devices to power consumer electronics and electric vehicles, but their capacity is dramatically decreased at ultrahigh charging/discharging rates. This mainly originates from a high Li‐ion/electron transport barrier within a traditional electrode, resulting in reaction polarization issues. To address this limitation, a functionally layer‐graded electrode was designed and fabricated to decrease the charge carrier transport barrier within the electrode. As a proof‐of‐concept, functionally layer‐graded electrodes composing of TiO2(B) and reduced graphene oxide (RGO) exhibit a remarkable capacity of 128 mAh g−1 at a high charging/discharging rate of 20 C (6.7 A g−1), which is much higher than that of a traditionally homogeneous electrode (74 mAh g−1) with the same composition. This is evidenced by the improvement of effective Li ion diffusivity as well as electronic conductivity in the functionally layer‐graded electrodes.  相似文献   

20.
The possibility of using the LnO x mischmetal (Ln = Ce, La, Nd, Pr, Sm) for preparation of cathodes for solid-oxide fuel cells with the supported YSZ electrolyte is studied. The electrical and electrochemical characteristics of Ln-Mn-O electrodes with the ratio of all lanthanides contained in the mischmetal except for cerium to manganese Ln: Mn = 1: 1 and also of a material comprised of Ln-Mn-O and La0.8Sr0.2MnO3 are studied. The latter electrode material that contains 35?C40 wt % of Ln-Mn-O and was sintered at 1200°C has the specific ohmic resistance of 0.1 ?? cm at 800°C. The polarization conductivity is compared for electrodes made of 100% Ln-Mn-O, 40 wt % Ln-Mn-O + 60 wt % La0.8Sr0.2MnO3, and 100% La0.8Sr0.2MnO3 in the initial state and after their modification through the introduction of an electrocatalyst (PrO2 ? x ). The highest polarization conductivity is typical of Ln-Mn-O + (La, Sr)MnO3 electrodes containing 40 wt % Ln-Mn-O and PrO2 ? x . The polarization conductivity of these electrodes is found to be 25 S/cm2 at 800°C.  相似文献   

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