Nickel oxalate dihydrate nanorods attached to reduced graphene oxide sheets as a high-capacity anode for rechargeable lithium batteries

Abstract

In the search for high-capacity anode materials, a facile hydrothermal route has been developed to synthesize phase-pure NiC 2 O 4 ·2H 2 O nanorods, which were crystallized into the orthorhombic structure without using templates. To ensure the electrical conductivity of the nanorods, the produced NiC 2 O 4 ·2H 2 O nanorods were attached to reduced graphene oxide (rGO) sheets via self-assembly layer-by-layer processes that utilize the electrostatic adsorption that occurs in a poly(diallyldimethylammonium chloride) solution. The high electrical conductivity aided by the presence of rGO significantly improved the electrochemical properties: 933 mAh g − 1 for the charge capacity (oxidation), which showed 87.5% efficiency at the first cycle with a retention of approximately 85% for 100 cycles, and 586 mAh g − 1 at 10 C-rates (10 A g − 1 ) for the NiC 2 O 4 ·2H 2 O/rGO electrode. The lithium storage processes were involved in the conversion reaction, which were fairly reversible via a transformation to Ni metal accompanied by the formation of a lithium oxalate compound upon discharge (reduction) and restoration to the original NiC 2 O 4 ·2H 2 O upon charging (oxidation); this was confirmed via X-ray diffraction, transmission electron microscopy, X-ray photoelectron microscopy and time-of-flight secondary ion mass spectroscopy. We believe that the high rate capacity and rechargeability upon cycling are the result of the unique features of the highly crystalline NiC 2 O 4 ·2H 2 O nanorods assisted by conducting rGOs. INTRODUCTIONThe demand for sustainable and green-energy sources is rising because of increasing concerns regarding fast population growth and industrialization worldwide. Lithium-ion batteries have been developed as power sources over several decades and have achieved great commercial success, ranging from mobile to stationary applications. [1][2][3][4] Rechargeable lithium-ion batteries are suitable for the aforementioned applications because of their high energy density and high power properties. 5,6 In commercial batteries, graphite is commonly adopted as the active material for the negative electrodes. Apart from its ability to accommodate Li + ions in its structure and its reversibility, the theoretical capacity of graphite is limited to 372 mAh g − 1 . 7 The predominant intercalation potential of graphite is approximately 0.1 V vs Li/Li + , which results in risks associated with short circuits derived from dendritic growth of Li. In the past, efforts have been made to find high-capacity alternative electrode materials to replace graphite. These new materials can be classified based on their reaction mechanisms: (i) intercalation: Ti-based oxides that store

Nanostructured Electrode Materials for Rechargeable Lithium-Ion Batteries

“…It is known that a broad range of TM-based compounds, such as TM oxides, chalcogenides, fluorides, phosphides, and nitrides, have been investigated as CTAMs, considerably broadening the choices of materials for high-performance LIBs [122][123][124][125][126][127][128][129][130]. Moreover, in comparison with graphite anodes, CTAMs definitely demonstrate adjustable reaction potentials according to the strength of the ionic bonds formed between the TM cations and anions [131].…”

Direct Realization of Complete Conversion and Agglomeration Dynamics of SnO2 Nanoparticles in Liquid Electrolyte

“…1−3 The conversion process in these electrodes is pivotal as it affects the initial Coulombic efficiencies, cycle retention, and reversibility of batteries. 4,5 Recently, it has been proposed from the literature 6−8 that additional capacity can arise from the electrode materials that undergo the conversion reaction, which brings more potential for utilizing conversion reaction-based electrode materials, giving strong potential for application for practical rechargeable batteries. Along with the conversion reaction, the agglomeration of electrode materials is another important factor because it is a frequent phenomenon among nanoparticles (NPs) when used as electrodes.…”

Template-Free Synthesis of Nanoporous Nickel and Alloys as Binder-Free Current Collectors of Li Ion Batteries

“…It is found that the NiC 2 O 4 ·2H 2 O nanowires had very poor initial capacities and very fast capacity decay as shown in Figure S7c , which reflects the fact that the large size of NiC 2 O 4 ·2H 2 O and poor contacts between NiC 2 O 4 ·2H 2 O and Ni ligaments are severely harmful to the electrochemical performances due to the poor electric conductivity of NiC 2 O 4 ·2H 2 O. 39 …”

“…Galvanostatic charges and discharges were performed within a voltage cutoff window of 3.0–0.005 V. Figure 10 b depicts the cyclic performances of NiC 2 O 4 ·2H 2 O@np-Ni electrodes (with ∼1.2 mg/cm 2 NiC 2 O 4 ·2H 2 O) against Ni commercial foam (Ni-CF) electrode with loading of NiC 2 O 4 ·2H 2 O (NiC 2 O 4 ·2H 2 O@Ni-CF, with ∼0.28 mg/cm 2 NiC 2 O 4 ·2H 2 O) at the current density of 100 mA/g. Amazingly, the NiC 2 O 4 ·2H 2 O@np-Ni exhibits a superb high specific capacity up to 3154 and 1910 mAh/g for the first discharge and charge, respectively, both of which are much higher than the reported values using oxalates anodes and the nanoporous metal-based SnO 2 /nanoporous Cu, MnO 2 /nanoporous Cu systems (see Tables S1 and S2 in the Supporting Information )., 39 − 44 The capacity loss in the first cycle is due to the formation of solid electrolyte interphase (SEI). After 30 cycles, the capacity still remains at 1247 and 1166 mAh/g for the discharge and charge, respectively.…”