Thick Solid Electrolyte Research Articles

Kinetics Study of the 5 V Spinel Cathode LiMn1.5Ni0.5O4 Before and After Surface Modifications

The 5 V spinel has been surface-modified with 2 wt % nanosize and by an electrostatic self-assembly method and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, high resolution transmission electron microscopy, and electrochemical measurements. Although the modifications do not change the crystallographic structure of the spinel sample, the surface-modified samples exhibit better cycling performance (at both room and elevated temperatures) and rate capability compared to the bare . Electrochemical impedance spectroscopy and large potential step chronoamperometry measurements demonstrate that the discharge process is controlled by phase transformation and lithium ion diffusion in the bulk material in addition to charge-transfer reaction. Surface modification is found to affect only the charge-transfer reaction kinetics. The enhanced electrochemical performance of the surface-modified samples is attributed to the suppression of the thick solid electrolyte interfacial layer and the consequent improvement in charge-transfer kinetics.

Electrochemical behavior and microstructure variation of hard carbon nano-spherules as anode material for Li-ion batteries

Well-dispersed nanosized hard carbon spherules (nano-HCS) with different hydrogen contents were prepared by a modified hydrothermal method. Their electrochemical behaviors were investigated. The results from Raman spectra and the HRTEM images at different lithiation states show that the microstructure of the nano-HCS with high hydrogen content becomes slightly ordered after several discharging/charging cycles. This “disorder-to-order” transition phenomenon was not observed in the nano-HCS with low hydrogen content. A mechanism is proposed to interpret this phenomenon. Furthermore, the formation of a thick solid electrolyte interphase (SEI) film on the surface of the nano-HCS is demonstrated and it could be decomposed after charging.

저온 고체산화물연료전지 구현을 위한 다층 나노기공성 금속기판의 제조

Submicron thick solid electrolyte membrane is essential to the implementation of low temperature solid oxide fuel cell, and, therefore, development of new electrode structures is necessary for the submicron thick solid electrolyte deposition while providing functions as current collector and fuel transport channel. In this research, a nickel membrane with multi-stage nano hole array has been produced via modified two step replication process. The obtained membrane has practical size of 12 mm diameter and 50 μm thickness. The multi-stage nature provides 20 nm pores on one side and 200 nm on the other side. The 20 nm side provides catalyst layer and 30~40% planar porosity was measured. The successful deposition of submicron thick yttria stabilized zirconia membrane on the substrate shows the possibility of achieving a low temperature solid oxide fuel cell.

Reaction between ZrO 2 8% Y 2O 3 thick film solid electrolyte and alumina substrate

A thick film solid state electrolyte on an alumina substrate has already been applied for fabrication of oxygen sensors. The results of our investigations indicated that the purity of applied alumina substrate influences the electrical characteristics of the sintered, thick film, cubic ZrO 2 solid electrolyte. After firing of the ZrO 2 layer at 1450°C only the cubic modification was present on the 99% alumina substrate. However, on 96% alumina one third of the ZrO 2 was present in the monoclinic modification. Microstructural analysis of fired samples shown that yttria diffused into the silicate glassy phase which is added as a sintering aid to 96% alumina. Due to partial phase transformation of cubic zirconia to the monoclinic modification, a significantly higher dc resistance of sintered films was measured on 96% alumina substrates.