Effects of Cobalt Deficiency on Nickel-Rich Layered LiNiCoMnO Positive Electrode Materials for Lithium-Ion Batteries.

The role of cobalt deficiency on the crystal structure, surface chemistry, and electrochemical performance of Ni-rich layered LiNiCoMnO (NCM811) positive electrode materials was experimentally studied possibly for the first time. We synthesized pristine and cobalt-deficient NCM811 samples by solid-state reaction. Using a variety of characterization techniques and electrochemical measurements, we show that cobalt nonstoichiometry can suppress Ni/Li cation mixing, but can simultaneously promote the formation of oxygen vacancies, leading to rapid capacity fade and inferior rate capability compared to pristine NCM811.

Defect chemistry and electrical properties of garnet-type LiLaZrO.

Garnet-type cubic LiLaZrO exhibits one of the highest lithium-ion conductivity values amongst oxides (up to ∼2 mS cm at room temperature). This compound has also emerged as a promising candidate for solid electrolytes in all-solid-state lithium batteries, due to its high ionic conductivity, good chemical stability against lithium metal, and wide electrochemical stability window. Defect chemistry of this class of materials, although less studied, is critical to the understanding of the nature of ionic conductivity and predicting the properties of grain boundaries and heterogeneous solid interfaces.

Charge Transport in Electronic-Ionic Composites.

Composite electrodes consisting of cathode particles and an ion-conducting phase can address the limited ion accessibility of the cathode in high-energy all-solid-state lithium batteries. In this Letter, we discuss the microstructure-conductivity relationship in an electronic-ionic composite with a focus on lithium ion conductivity. This study is the first step toward further understanding of electrochemical reactions in all solid multiphase systems.

Evolution of solid/aqueous interface in aqueous sodium-ion batteries.

The microstructural and compositional evolution at the solid/aqueous solution interfaces are investigated to monitor the electrical properties of superionic conducting phosphates and the electrochemical failure of aqueous sodium-ion batteries.

Characterization of electrode materials for lithium ion and sodium ion batteries using synchrotron radiation techniques.

Intercalation compounds such as transition metal oxides or phosphates are the most commonly used electrode materials in Li-ion and Na-ion batteries. During insertion or removal of alkali metal ions, the redox states of transition metals in the compounds change and structural transformations such as phase transitions and/or lattice parameter increases or decreases occur. These behaviors in turn determine important characteristics of the batteries such as the potential profiles, rate capabilities, and cycle lives.

Nonlinear electrical grain boundary properties in proton conducting Y-BaZrO3 supporting the space charge depletion model.

The overall proton conductivity of polycrystalline acceptor-doped BaZrO(3) is limited by the high resistivity of its grain boundaries. To investigate the nature of the electrical response of the grain boundaries as a function of the DC bias, Y-doped BaZrO(3) ceramics with a very large grain size (up to 200 μm) have been prepared in an infrared image furnace. The grains are so large that even individual grain boundaries can be addressed by microelectrodes.

On the proton conductivity in pure and gadolinium doped nanocrystalline cerium oxide.

Conductivity measurements were performed on microcrystalline and nanocrystalline ceria (undoped and doped) in dry as well as wet atmosphere. Below 200-250 °C, the nanocrystalline samples exhibit an enhanced total conductivity under wet conditions, which increases with decreasing temperature. In addition, thermo-gravimetric analysis revealed a strong water uptake below 200 °C.