Papers by Keyword: Negative Electrode

Abstract: This study investigated the effect of a co-solvent on the lithium metal negative electrode to understand the growth of dendritic lithium and the battery performance. An electrolyte was prepared by adding a dimethyl carbonate (DMC) co-solvent in a propylene carbonate (PC) solvent. Adding DMC, considerably improved the unstable and low cyclic efficiency in the PC only electrolyte was considerably improved. Scanning electron microscopy showed that the growth of dendritic lithium was affected by the quantity of DMC. The more DMC was added, the more the dendritic lithium formation was suppressed. Fourier transform infrared spectroscopy revealed that the surface component of the deposited lithium was different, depending on the quantity of DMC added. This study successfully demonstrated that DMC co-solvent could suppress dendritic lithium.

Abstract: We investigated the electrochemical behavior and properties of lithium titanate oxide as the negative electrode for calcium ion batteries during charge/discharge tests in tetrahydrofuran (THF)-based electrolyte. The reversible charge and discharge capacities of ~150 and ~145 mAh g^–1 were observed, respectively, in THF-based electrolyte. They are larger than those obtained in propylene carbonate-based electrolyte. Moreover, interesting charge/discharge curves were observed, which might be attributed to structural changes during the insertion/extraction of calcium ions. These results were confirmed by the charge/discharge curves and scanning electron microscopy images.

Abstract: We investigated the electrochemical properties of carbon-coated niobium dioxide (NbO₂) as a negative electrode material for lithium-ion batteries. Carbon-coated NbO₂ powders were synthesized by ball-milling using carbon nanotubes as the carbon source. The carbon-coated NbO₂ samples were of smaller particle size compared to the pristine NbO₂ samples. The carbon layers were coated non-uniformly on the NbO₂ surface. The X-ray diffraction patterns confirmed that the inter-layer distances increased after carbon coating by ball-milling. This lead to decreased charge-transfer resistance, confirmed by electrochemical impedance spectroscopy, allowing electrons and lithium-ions to quickly transfer between the active material and electrolyte. Electrochemical performance, including capacity and initial coulombic efficiency, was therefore improved by carbon coating by ball-milling.

Abstract: We investigated the electrochemical behavior and properties of multi-wall carbon nanotubes (MWCNTs) as a novel negative electrode for calcium ion batteries during charging and discharging. The second charge and discharge capacities were ~63 and ~43 mAh g^–1 in propylene carbonate-based electrolyte and ~86 and ~60 mAh g^–1 in ethylene carbonate-based electrolyte, respectively. X-ray diffraction analysis results showed that the inter-layer distance of the MWCNTs was increased after charging, indicating that calcium ions were intercalated into the MWCNT graphitic sheets during the charging. The electrochemical performance of the MWCNT electrode was improved by using ball milling to introduce defects.

Abstract: The electrochemical properties of niobium monoxide, NbO, were investigated as a negative electrode material for lithium-ion batteries. Lithium ions were inserted into and extracted from NbO material at potentials < 1.0 V versus Li/Li⁺, involving formation of a solid electrolyte interface (SEI) on the NbO surface in the first cycle. Its reversible capacity is ~67 mAh g^–1 with the capacity retention of ~109% after 50 cycles. The magnitude of charge transfer resistance was greatly decreased by ball-milling the pristine NbO, whereas the ball-milling had no effect on the SEI resistance.

Abstract: The electrochemical behaviors of a spinel lithium titanate oxide (Li₄Ti₅O₁₂, LTO) electrode during as a novel electrode for calcium ion batteries were investigated during the charging and discharging to understand its electrochemical properties. The electrochemical performance of the LTO electrode was improved by the addition of dimethyl carbonate to the PC-based electrolyte. The initial charge and discharge capacities were ~262 and ~85 mAh g^–1, respectively. The results of the X-ray diffraction analysis showed that the lattice constant of LTO increased after charging, indicating that calcium ions were inserted into Li₄Ti₅O₁₂ during the charging.

Abstract: The electrochemical properties niobium dioxide (NbO₂) was investigated as a negative electrode material for lithium ion batteries. The NbO₂ electrode showed a large irreversible capacity and small discharge capacity. The results of X-ray photoelectron spectroscopy indicate that the poor electrode performance of NbO₂ may be caused by niobium pentoxide (Nb₂O₅) formed on the surface of active material. The Nb₂O₅ could be removed by chemical etching to some extent, thus improving the electrode performance.

Abstract: The perovskite-type oxides have a newly application for alkaline batteries due to the excellent cyclic performance. In this work, La_1-xBa_xCoO₃ (x = 0.2, 0.4, 0.6) powders were prepared by a sol-gel method as negative electrode materials for Ni/MH batteries, and their phase structure and electrochemical properties were investigated in details. The effect of Ba substitution on electrochemical kinetic properties, including the exchange current density I₀ and the hydrogen diffusion coefficient D, of La_1-xBa_xCoO₃ electrodes were also evaluated. X-ray diffraction analysis shows that La_1-xBa_xCoO₃ (x = 0.2, 0.4, 0.6) perovskite-type oxides consist of two phases, La_0.5Ba_0.5CoO₃ and BaCoO_2.70. The discharge capacities of La_1-xBa_xCoO₃ negative electrodes tested at 40 mAg^-1 are 65.6, 76.6 and 88.3 mAhg^-1 when x = 0.2, 0.4 and 0.6, respectively. Among the electrodes, La_0.8Ba_0.2CoO₃ electrode has the highest discharge capacity retention ratio of about 87% after 50 cycles at room temperature.

Abstract: The electrochemical properties of hard carbon (HC) have been investigated for use as negative electrode for lithium ion capacitors. The HC electrode was characterized by scanning electron microscope (SEM) method. The HC negative electrode was galvanostatically prelithiated at 0.1C for three cycles between 0.05-2 V. The LIC with activated carbon and HC electrodes was characterized by cyclic voltammetric analysis at the scan rate of 0.1 mV s^-1 with different voltage ranges. The rate capability of the LIC was tested up to 100C and the retention is 54 %. The cycle performance is retained up to 86% at 50C and 80% at 100C even after 10,000 cycles. The results indicate that hard carbon is suitable as negative electrode materials for high power energy applications.

Abstract: In this paper, the influences of different binders (Hydroxypropyl Methyl Cellulose (HPMC), Carboxymethyl Cellulose Sodium (CMC), Polytetrafluoroethylene (PTFE) and Styrene- butadiene Rubber (SBR)) on high-rate discharge performances at low temperature for the negative electrode of Ni/MH battery have been studied by orthogonal experimental design. Electrochemical measurements have been conducted to investigate the capacity, charge-discharge performance, cyclic voltammetry and electrochemical impedance characteristics. The surface morphology and chemical compositions have been investigated by SEM and EDS. Based on the range analysis, the primary and secondary influence factors as well as the optimization results were obtained. From the CV characteristic curves, the oxidization peaks and reduction peaks are not clearly shown, which indicates that the redox reaction does not occur clearly after binders added. The EIS experiments show that the deterioration of the voltage characteristic of the battery is due to drying out of the separator that increases the ohmic resistance (Rs ), and the decay of the discharge capacity is due to the passivity surface that increases the charge-transfer resistance (Rt) of the battery.