LiNixMn2−xO4 has been synthesized using sol‐gel and solid‐state methods for 0 < x < 0.5. The electrochemical behavior of the samples was studied in normalLi/LiNixMn2−xO4 coin‐type cells. When x = 0, the capacity of normalLi/LiMn2O4 cells appears at 4.1 V. As x increases, the capacity of the 4.1 V plateau decreases as 1−2x Li per formula unit, and a new plateau at 4.7 V appears. The capacity of the 4.7 V plateau increases as 2x Li per formula unit, so that the total capacity of the samples (both the 4.1 and 4.7 V plateaus) is constant. This is taken as evidence that the oxidation state of Ni in these samples is +2, and therefore they can be written as Li+1Nix+2Mn1−2x+3Mn1+x+4O4−2 . The 4.1 V plateau is related to the oxidation of Mn3+ to Mn4+ and the 4.7 V plateau to the oxidation of Ni2+ to Ni4+ . The effect of synthesis temperature, atmosphere, and cooling rate on the structure and electrochemical properties of LiNi0.5Mn1.5O4 is also studied on samples made by the sol‐gel method. LiNi0.5Mn1.5O4 samples made by heating gels at temperatures below 600°C in air are generally oxygen deficient, leading to Mn oxidation states significantly less than 4. LiNi0.5Mn1.5O4 samples heated above 650°C suffer due to disproportionation into LiNixMn2−xO4 with x < 0.5 and LizNi1−zO with z ≈ 0.2, which occurs above about 650°C. Pure LiNi0.5Mn1.5O4 materials can be made by extended heatings near 600°C or by slowly cooling materials heated at higher temperatures. LiNi0.5Mn1.5O4 made at 600°C has demonstrated good reversible capacity at 4.7 V in excess of 100 mAh/g for tens of cycles.

No abstract

No abstract

Synthesis and Electrochemistry of LiNixMn2-xO4.-Samples of LiNixMn2-xO4 with 0 ¡ x ¡ 0.5 are prepared by solid state reaction of LiOH, Ni(NO3)2·6 H2O, and MnO2 at 750 • C as well as by a sol-gel method using Mn(OAc)2, Ni(NO3)2, and LiOH as precursors and carbon black as stabilizer (250-800 • C), The electrochemical behavior of the samples is studied in Li/LiNixMn2-xO4 coin-type cells. The potential vs. capacity curves show a plateau at 4. 1 V for the Li/LiMn2O4 cells. With increasing x, the length of this plateau decreases and a new plateau at 4.7 V appears. The shift of the plateau potential is caused by the higher binding energy (by 0.6 eV) of the Ni eg electrons compared to the Mn eg electrons. LiNi0.5Mn1.5O4 prepared by the sol-gel technique at a firing temp. of ≈600 . degree.C exhibits a capacity of ¿ 100 mAh/g at 4.7 V which is maintained over tens of cycles. -(ZHONG, Q.; BONAKDARPOUR, A.; ZHANG, M.; GAO, Y.; DAHN, J. R.; J. Electrochem.

Gate oxide damage resulting from PECVD and HDP CVD oxide deposition was investigated using damage sensitive antenna structures with area ratios up to 200,000:1. The effects of various parameters on the charge-induced gate oxide degradation in the HDP CVD tool were studied using an experimental design. The two parameters expected to have the most effect on plasma density and plasma uniformity, microwave power, and magnetic field shape, were also found to correlate with gate oxide charging damage. Detailed experiments varying only microwave power did not reveal damage at lower power, presumably because the induced gate oxide voltage is not large enough to cause F-N tunneling currents under these conditions. Increasing damage occurred with increasing microwave power and the extent and distribution of damage depended on the magnetic field shape as the magnetic field constrains the electron current path to the wafer surface.