Non-aqueous electrolyte type lithium ion secondary cell

A method for manufacturing a lithium ion secondary cell, wherein the lithium ion secondary cell comprises:

• an electrode body including a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a separator, as constituent members;
• and a non-aqueous electrolyte containing a lithium salt as a supporting salt in an organic solvent, the electrode body and the non-aqueous electrolyte being accommodated in a case, the method comprising:
• (a) preparing the positive electrode, the negative electrode, the separator, and an initial electrolyte serving as constituent members of the cell, the positive electrode active material including, as a main component, a layered oxide containing lithium and a transition metal as constituent metal elements, the initial electrolyte including, as a supporting salt, a lithium salt containing fluorine as a constituent atom, and the supporting salt being dissolved in an organic solvent in a prescribed concentration;
• (b) ascertaining, based on the content of moisture contained in the positive electrode, the negative electrode, the separator, and the initial electrolyte prepared in the step (a), a molar equivalent value α of the total content of moisture to be mixed in the case due to the constituent members;
• (c) substituting a value of the α into the following mathematical expression (A), and calculating a numerical value range of β satisfying the mathematical expression (A)
• −1.3≦log(β/α)≦1 (A)
• wherein α represents the total number of moles of moisture to be mixed in the case when the cell is assembled;
• (d) adding as an additive, a compound represented by the following chemical formula (I):
• in a number of moles within the numerical value range of the β calculated in the step (c) to the initial electrolyte, and preparing a final electrolyte;
• and
• (e) assembling a lithium ion secondary cell under an environment with a dew point of −10° C. or less using the positive electrode, the negative electrode, the separator, and the final electrolyte.