Template Free and Binderless NiO Nanowire Foam for Li-ion Battery Anodes with Long Cycle Life and Ultrahigh Rate Capability

Abstract

) is achieved after 1000 cycles. Superior rate capability is exhibited by cycling at extremely high current rates, such as 20C and 50C with capacities ca. 164 and 75 mAh g In recent times, electric vehicles (EVs) 1 are vigorously investigated and developed to diminish the dependence on fossil fuels and alleviate the deterioration of natural environment. Hybrid (HEV) and plug-in (PEV) hybrid EVs 2 utilizing both batteries and internal combustion engines (ICEs) can partially resolve these issues, but the consumption of gasoline and emission of greenhouse gases from ICEs still remain problematic. Pure EVs powered by purely lithium ion batteries (LIBs) can totally eliminate these difficulties. However, the cruise range of pure EVs is still limited, such as ca. 300 miles per charge of Tesla Model S 3 . Accordingly, it is crucial to improve the capacity and energy density of LIBs while maintaining the power density simultaneously. Capacity of traditional graphite anode with potential ca. 0.2 V vs. Li is limited to theoretically 372 mAh g −1 and practically ca. 310 mAh g −1for LiC 6 as a result of intercalation reactions 2 . Higher energy density and capacity can be reached by utilizing conversion reactions of metal oxides, such as FeO, CoO, NiO and CuO 4,5 , in potential range 0.01-3 V vs. Li with ca. 700 mAh g −1 by the equation MO + 2Li. Among these, NiO is appealing owing to its high theoretical capacity (718 mAh g −1 ), environmental benignity and low cost 6 . Nonetheless, it still suffers from low cycling stability and low rate capability resulting from large volume expansion and poor electrical conductivity, respectively 7 . To overcome these barriers, various NiO nanostructures have been developed to accommodate mechanical strain during cycling, to improve electrical contact and shorten ion diffusion length to reduce resistivity 6-9 . Three-dimensional curved NiO nanomembranes synthesized by electron beam evaporation demonstrate high capacity (721 mAh g −1 ) at 1.5C over 1400 cycles and high rate capability at 50C with ca. 60 mAh per gram 8 . However, costly processes relying on high vacuum system prevent it from large scale production. NiO nanorods anchored on Ni foam by anodization in oxalic acid at 50 V followed by annealing in air at 400 °C exhibit 706 mAh g −1 at 1A per gram 7 . Nevertheless, high voltage anodization utilizing electricity renders the process expensive. Relatively thick wall of the nanorods (200-500 nm) result in rapid Coulombic efficiency drop to ca. 98% after only 70 cycles 7 . NiO nanofibers with diameters ca. 100 nm prepared by electrospinning and air annealing at 800 °C show maximum capacity 784 mAh g −1 at 80 mA g −1 with low capacity retention (ca. 75%) after 100 cycles 6 . The addition of carbon additive and binder further decrease the specific capacity of the electrode. Ni/NiO nanofoam

Core/Shell NiFe Nanoalloy with a Discrete N‐doped Graphitic Carbon Cover for Enhanced Water Oxidation

“…The second semicircle of the two carbon‐coated alloys at low frequency represents the different mass‐transfer resistance . The small mass‐transfer resistance of NiFe@CN−G is likely related to its mesoporosity which can facilitate OH − diffusion . Overall, the graphitic carbon, alloy core and mesoporous structure in NiFe@CN−G is able to decrease the charge transfer resistance and promote ionic diffusion, giving rise to the superior OER kinetics.…”

A 3D Porous MgFe2O4 Integrative Electrode as a Binder‐Free Anode with High Rate Capability and Long Cycle Lifetime

“…In the anodic process, the peak at 1.5 V corresponds to the oxidation of metal Fe. In addition, a pair of weak redox peaks at 1.75 V and 2.2 V may be assigned to tiny Ni 2+ coming from the slight surface oxidation of Ni foam,, which can also be inferred from the differential capacity curves (dQ/dV) of MFO and N‐MFO electrode (Figure S3). In the second cycle, the cathodic peak at 0.7 V shifts to 0.8 V and the peak at 1.2 V disappears, implying the irreversible structure transformation ,.…”

Kinetics and electrochemical evolution of binary silicon–polymer systems for lithium ion batteries

“…The depressed semicircle in the mid-frequency region is interpreted as the charge-transfer resistance contributing from the reaction at the interface of electrolyte and active material (R ct ). 37 The linear diffusion dri responsible for circuit element at low-frequency (<200 mHz) is Warburg impedance tail (W o ), which is associated with the diffusion of salt in the electrolyte and the diffusion of Li-ions into active materials on the electrode. All the resistances at different frequencies are useful in understanding the kinetics of various anodes.…”