Sulfur-based active material, electrode, non-aqueous electrolyte secondary battery and producing methods thereof

A method of producing a non-aqueous electrolyte secondary battery that comprises positive and negative electrodes, wherein at least one of the electrodes is formed from a sulfur-based active material that is obtained by calcination at 250 to 550° C. of (1) heat-expandable particles and (2) sulfur,

• wherein the obtained sulfur-based active material has peaks of 1530 cm−1±8 cm−1, 1320 cm−1±8 cm−1, 940 cm−1±8 cm−1, 470 cm−1±8 cm−1, 370 cm−1±8 cm−1 and 310 cm−1±8 cm−1 within a range of 200 cm−1 to 1800 cm−1 in a Raman spectrum, and wherein the peak 1320 cm−1±8 cm−1 is the main peak,
• wherein the method comprises:
• calcinating at 250 to 550° C. components (1) and (2):
• (1) the heat-expandable particles which comprise an outer shell comprising an acryl-based copolymer and a hydrocarbon included inside the outer shell, wherein the heat-expandable particles have an expansion starting temperature of 150° C. or lower, and
• (2) the sulfur in an amount of 250 to 1500 parts by mass based on 100 parts by mass of the heat-expandable particles to form the sulfur-based active material;
• and
• incorporating the sulfur-based active material into the at least one electrode which is in turn incorporated into the non-aqueous electrolyte secondary battery.