Non-aqueous electrolyte secondary battery

1. A non-aqueous electrolyte secondary battery, comprising:

a positive electrode;

a negative electrode;

a separator interposed between the positive electrode and the negative electrode; and

a non-aqueous electrolyte dissolving a solute in a non-aqueous solvent;

wherein the negative electrode comprises a negative electrode active material containing particulate silicon and/or silicon alloy and a binding agent,

wherein the non-aqueous electrolyte contains fluorinated cyclic carbonate and diisocyanate compound of the general formula (1) below, and

when Li storage volume per unit area of the negative electrode of the non-aqueous electrolyte secondary battery under charging condition is determined as A and the theoretical maximum Li storage volume per unit area of the negative electrode is determined as B, a utilizing rate (%) of negative electrode which is expressed by (A/B)×100 is 45% or less:

OCN—CH 2 -A-CH 2 —NCO  (1)

wherein A represents at least one selected from a chain saturated hydrocarbon group and an aromatic hydrocarbon group expressed by the general formula (b) below, and

wherein R 3 to R 6 represent a hydrogen group or an alkyl group:

2. The non-aqueous electrolyte secondary battery as claimed in claim 1 ,

wherein the diisocyanate compound is a straight chain diisocyanate compound expressed by the general formula (2) below:

wherein x is an integral number of 3 or more.

3. The non-aqueous electrolyte secondary battery as claimed in claim 2 ,

wherein x in the general formula (2) is within a range of 4 to 12.

4. The non-aqueous electrolyte secondary battery as claimed in claim 2 ,

wherein x in the general formula (2) is within a range of 6 to 12.

5. The non-aqueous electrolyte secondary battery as claimed in claim 1 ,

wherein the diisocyanate compound is at least one of diisocyanate compounds expressed by chemical formulas (3) to (5) below:

OCN—CH 2 —CH(CH 3 )—CH 2 —C(CH 3 ) 2 —(CH 2 ) 2 —NCO  (3)

OCN—CH 2 —C(CH 3 ) 2 —CH 2 —CH(CH 3 )—(CH 2 ) 2 —NCO  (4)

6. The non-aqueous electrolyte secondary battery as claimed in claim 1 ,

wherein the diisocyanate compound is added in a range of 0.1 to 5 mass % with regard to the non-aqueous electrolyte excluding the diisocyanate compound.

7. The non-aqueous electrolyte secondary battery as claimed in claim 1 ,

wherein the negative electrode is fabricated by applying a negative electrode composite containing the negative electrode active material of particulate silicon and/or silicon alloy and the binding agent on the surface of a negative electrode current collector and

sintering under a non-oxidizing atmosphere at a temperature which is not lower than a glass transition temperature of the binding agent.

8. The non-aqueous electrolyte secondary battery as claimed in claim 1 ,

wherein the binding agent is polyimide.

9. The non-aqueous electrolyte secondary battery as claimed in claim 1 ,

wherein the fluorinated cyclic carbonate is cyclic carbonate having a fluorine group expressed by the general formula (6) below:

wherein R 9 to R 12 represent a group selected from a hydrogen group and a fluorine group and at least one is the fluorine group.

10. The non-aqueous electrolyte secondary battery as claimed in claim 9 ,

wherein the fluorinated cyclic carbonate is 4-fluoro-1,3-dioxolan-2-one.

11. The non-aqueous electrolyte secondary battery as claimed in claim 1 ,

wherein A in the diisocyanate compound expressed by the general formula (1) is a straight chain diisocyanate compound expressed by the general formula (a) below:

wherein R 1 to R 2 represent the hydrogen group or the alkyl group and n is a natural number.