Ganesan Nagasubramanian

Composite Solid Electrolyte for Li Battery Applications

Abstract The electrochemical, bulk and interfacial properties of the polyethylene oxide (PEO) based composite solid electrolyte (CSE) comprising LiI, PEO, and Al2O3 have been evaluated for Li battery applications. The bulk interfacial and transport properties of the CSEs seem to strongly depend on the alumina particle size. For the CSE films with 0.05 micron alumina while the bulk conductivity is around 10−4 (mho cm−1) at 103°C, the Li ion transport number seems to be close to unity at the same temperature. Compared to the PEO electrolyte this polymer composite electrolyte seems to exhibit robust mechanical and interfacial properties. We have studied three different films with three different alumina sizes in the range 0.01–0.3 micron. Effects of Al2O3 particle size on the electrochemical performance of polymer composite electrolyte will be discussed. With TiS2 as cathode a 10 mAh small capacity cell was charged and discharged at C 40 and C 20 rates respectively.

A polyacrylonitrile-based gelled electrolyte: electrochemical kinetic studies

The bulk and interfacial properties of thin films of a polyacrylonitrile-based (PAN-based) gelled electrolyte, which was tested in conjunction with lithium electrodes, were evaluated at room temperature. The typical composition of the gelled electrolyte (GE) studied was PAN (9.13 wt %); propylene carbonate, or PC (84.87 wt %); and LiBF4 (6 wt %). A.c. and d.c. measurements were used to determine the bulk conductivity and the interfacial apparent charge-transfer resistance (Ract) of the GE. While the bulk conductivity remains stable at around 10−3 S cm−1, the Ract varies initially before reaching a steady value. The steady Ract value obtained from the electrochemical measurements is near 1000 ω cm2. The plating/stripping efficiency of lithium, from potentiostatic and galvanostatic measurements, is 70 to 80%.

Effects of 12‐Crown‐4 Ether on the Electrochemical Performance of CoO2 and TiS2 Cathodes in Li Polymer Electrolyte Cells

The effect of adding 12-crown-4 ether (12Cr4) to the polyethylene oxide (PEO) electrolyte on the electrochemical properties of cells with Li(x)CoO2 or TiS2 as the cathode was investigated. The polymer electrolyte films were: (1) PEO, LiBF4; (2) PEO, LiBF4 with 12Cr4; (3) Li(x)CoO2, PEO, and LiBF4; and (4) Li(x)CoO2, PEO, LiBF4, and 12Cr4. It was found that, although 12Cr4 improved the cell performance over cells without 12Cr4 in the shallow c/d cycles (cyclic voltammetric behavior), it did not seem to prolong the active life of the cell. The cells with CoO2 as the cathode failed after a few c/d cycles, while similar cells with TiS2 did not fail even after 12 c/d cycles. The probable cause of failure in the case of CoO2 is ascribed to the instability of the CoO2 cathode.