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A new simple storage experiment is introduced to show direct evidence of a cathode-anode interaction. The delithiated positive electrodes and/or the lithiated negative electrodes from Li[Ni 1/3 Mn 1/3 Co 1/3 ]O 2 /graphite and LiCoO 2 /graphite pouch cells are stored in Nalgene bottles (high-density polyethylene) filled with 1.0 M LiPF 6 in an ethylene carbonate: diethyl carbonate (EC:DEC, 1:2 v/v ratio) electrolyte for 2 weeks in an Ar-filled glove box at room temperature. During the storage experiment, the color change of the electrolyte, the formation of alkyl dicarbonates, and the decomposition of LiPF 6 are observed. The most important result of this storage experiment is that these reactions are significantly affected by the cathode-anode interaction. The electrolyte color change comes with slightly larger impedance growth during cycling and the alkyl dicarbonates improve coulombic efficiency. The decomposition of LiPF 6 is suppressed by the negative electrode. The experiment and results shown here will be helpful to those who want to research the cathode-anode interaction and improve the performances of Li-ion batteries.

The adhesion strengths between LiFePO4 cathodes and aluminum (Al) current collectors as well as the corresponding electrochemical properties of electrodes with carboxylated poly(vinyl difluoride) (C-PVdF) were experimentally and theoretically investigated. The adhesion strength of LiFePO4 cathodes with C-PVdF on Al current collectors were increased, compared with that of as-received PVdF, resulting in the reduction of the internal resistance of the electrode. These results were supported by theoretical simulations based on the Metropolis Monte Carlo method. Electrochemical experiments indicated that the cyclability and rate capabilities of the cathode were improved as the weight fraction of C-PVdF in the electrode increased up to 70% of the polymer binders. In addition, 18 650-sized full cells employing the electrodes with C-PVdF showed promising performance in terms of rate capability as well as long-term cyclability, which suggests that this strategy can be beneficial for the realization of high power s...

A mixed cathode material between Li2MnO3 and Li[Mn1/3Ni1/3Co1/3]O2 for high capacity lithium secondary batteries was introduced in this study. It was prepared using the sucrose combustion process because this is a simple process. The oxidation states of Mn, Co and Ni ions in the pristine Li[Li(1−x)/3Mn(2−x)/3Nix/3Cox/3]O2 compounds were confirmed to be tetravalent, trivalent and divalent, respectively, via XANES measurements. Electrochemical charge/discharge studies showed that the highest first discharge capacity of 224 mAh/g was obtained in composition of x = 0.5 at a 0.2 C rate. The oxidation state of the Co and Ni ions in the Li[Li1/6Mn1/2Ni1/6Co1/6]O2 changed to higher oxidation states, but that of the Mn ions did not change.

Recently, there have been many reports on efforts to improve the rate capability and discharge capacity of lithium secondary batteries in order to facilitate their use for hybrid electric vehicles and electric power tools. In the present work, we present a ZrO2-coated Li[Li1/6Mn1/2Co1/6Ni1/6]O2. The bare Li[Li1/6Mn1/2Co1/6Ni1/6]O2 shows a high initial discharge capacity of 224 mAh g−1 at a 0.2 C rate. Owing to the stability of ZrO2, it was possible to enhance the rate capability and cyclability. After 1 wt% ZrO2 coating, the ZrO2-coated Li[Li1/6Mn1/2Co1/6Ni1/6]O2 showed a high discharge capacity of 115 mAh g−1 after 50 cycles under a 6 C rate, whereas the bare Li[Li1/6Mn1/2Co1/6Ni1/6]O2 showed a discharge capacity of only 40 mAh g−1 and very poor cyclability under the same conditions. Based on results of XRD and EIS measurements, it was found that the ZrO2 suppressed impedance growth at the interface between the electrodes and electrolyte and prevented collapse of the layered hexagonal structure.

LiFePO{sub 4} is a potential candidate for the cathode material of the lithium secondary batteries. A co-precipitation method was adopted to prepare LiFePO{sub 4} because it is simple and cheap. Nitrogen gas was needed to prevent oxidation of Fe{sup 2+} in the aqueous solution. The co-precipitated precursor shows the high reactivity with the reductive gas, and the single phase of LiFePO{sub 4} is successfully synthesized with the aid of carbon under less reductive conditions. LiFePO{sub 4} fine powder prepared by co-precipitation method shows high rate capability, impressive specific capacity and cycle property.