NONAQUEOUS ELECTROLYTE SECONDARY BATTERY AND BATTERY SYSTEM INCLUDING THE SAME

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery simultaneously achieving high energy density and high battery capacity density, and a battery system including the nonaqueous electrolyte secondary battery.SOLUTION: A nonaqueous electrolyte secondary battery simultaneously achieving high energy density and high battery capacity density and a battery system including the nonaqueous electrolyte secondary battery can be provided by forming a positive electrode such that a positive electrode active material and conductive fibers are contained therein. R1 and σ1 of the positive electrode active material and R' and σ' of the conductive fibers satisfy the following formulas (1) and (2): R1-n×σ1=R'-n×σ'...formula (1); and 2(R1+n'×σ1)=R'+n'×σ'...formula (2) (where, n and n' independently represent a positive constant of 3 or less).