Nonwoven fabric for separator of non-aqueous electrolyte battery and non-aqueous electrolyte battery using the same

A nonwoven fabric for separators of non-aqueous electrolyte batteries which is produced by a wet paper making process, comprising:

• a nonwoven fabric constituted of organic fibers wherein the length of the fibers is 1-30 mm, the nonwoven fabric has a thickness of 10-100 μm and the nonwoven fabric has a thickness non-uniformity index (Rpy) in machine direction of 1000 mV or less as determined below:
• thickness non-uniformity index (Rpy):
• a sample is allowed to run between two spherical tracers;
• variation of thickness of the sample in machine direction is measured using a film thickness measuring equipment which measures the variation of sample thickness as an electric signal through an electric micrometer by scanning the sample at a constant rate of 1.5 m/min in machine direction after zero point adjustment under the condition of ±15 μm/±3 V in sensitivity range of the electric micrometer;
• the resulting signal value is subjected to fast Fourier transform by a FFT analyzer using hanning window as a time window;
• a power spectrum (unit:
• mV2) is obtained by addition averaging of addition of 128 times;
• the power values in the frequency band of 2-25 Hz are totaled;
• the total is multiplied by ⅔;
• and the resulting value is raised to one-second power to obtain the thickness non-uniformity index (Rpy) (unit:
• mV).