Nonaqueous electrolyte secondary battery, and method for fabricating nonaqueous electrolyte secondary battery

A method for fabricating a nonaqueous electrolyte secondary battery comprising a flat wound electrode body comprising

• a positive electrode plate, a negative electrode plate, and a separator, the positive electrode plate and the negative electrode plate being wound with the separator interposed therebetween,
• a nonaqueous electrolyte containing a supporting electrolyte comprising lithium and fluorine, and
• a battery case housing the wound electrode body and the nonaqueous electrolyte, the method comprising:
• an assembly step of housing the wound electrode body and the nonaqueous electrolyte in the battery case to construct a secondary battery assembly;
• and
• an initial charging step of performing initial charging on the secondary battery assembly,
• wherein
• in the initial charging step,
• the secondary battery assembly is charged at a first charging rate until a negative electrode potential with respect to a lithium metal reference (vs. Li/Li+) of the secondary battery assembly reaches a predetermined value ranging from 0.16 V to 0.5 V,
• an amount of a gas remaining in the wound electrode body at end of the initial charging step is 58 cc or less,
• the negative electrode plate comprises a negative electrode core material and a negative electrode active material layer disposed on the negative electrode core material,
• the negative electrode active material layer of the wound electrode body in a winding axis direction has a length L of at least 20 cm,
• a state of charge of the secondary battery assembly after initial charging is 15% or more and 30% or less,
• the battery case has an injection hole for the nonaqueous electrolyte,
• in the assembly step, the nonaqueous electrolyte is injected into the battery case through the injection hole, and
• the initial charging step is performed with the injection hole being open,
• wherein after the initial charging step, the injection hole is sealed with a sealing member, and
• after the negative electrode potential reaches the predetermined value, the secondary battery assembly is charged at a second charging rate which is larger than the first charging rate.