A fluoride electrode material for lithium-ion batteries, FeF 3 , was synthesized by a novel solid-state reaction method using polytetrafluoroethylene (PTFE) as a fluoride source instead of HF. FeF 3 was obtained as the main phase according to the XRD patterns of the samples prepared in the present study. Furthermore, the synthesized FeF 3 particles were nanosize. The initial discharge and charge capacities of the FeF 3 sample were 387 and 293 mAh/g, respectively, in the 4.51.0 V region.

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SUMMARY Online partial discharge (PD) measurement is very important for insulation monitoring of high‐voltage equipment. One of the biggest challenges performing online monitoring is discrimination between PD detect signals and external noises. Experimental results using high‐frequency current transformer (CT) sensor show that the current waveforms associated with various PD signals are all damped cosine waveforms, and have unique frequency and decay times of damped oscillation. Therefore, we focused attention on the damped oscillation waveform of the PD current, especially damped cosine waveform having a different number of oscillations. In addition to this, the noise discrimination method using wavelet transform or short‐time Fourier transform is effective. Those noise discriminating processes are applicable to online PD current measurement system.

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