Nonaqueous electrolyte secondary batteries
A nonaqueous electrolyte secondary battery according to one aspect of the present invention includes an electrode assembly including a negative electrode plate and a positive electrode plate wound together via a separator; a nonaqueous electrolyte; a bottomed cylindrical exterior case accommodating the electrode assembly and the nonaqueous electrolyte; and a sealing member sealing an open end of the exterior case.
1. A nonaqueous electrolyte secondary battery comprising:
an electrode assembly including a negative electrode plate and a positive electrode plate wound together via a separator, the negative electrode plate including a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, the positive electrode plate including a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector;
a nonaqueous electrolyte;
a bottomed cylindrical exterior case accommodating the electrode assembly and the nonaqueous electrolyte; and
a sealing member sealing an open end of the exterior case, wherein
the negative electrode plate has a first exposed portion of the negative electrode current collector and a second exposed portion of the negative electrode current collector which are exposed from the negative electrode active material layer on a coiling start end and on a coiling finish end, respectively,
at least part of the second exposed portion of the negative electrode current collector is in contact with an inner face of a sidewall of the exterior case,
a first negative electrode lead and a second negative electrode lead are joined to the first exposed portion of the negative electrode current collector and to the second exposed portion of the negative electrode current collector, respectively,
the first negative electrode lead and the second negative electrode lead each lead out from one end face of the electrode assembly toward a bottom of the exterior case, and
the first negative electrode lead is joined to the bottom of, the exterior case, the second negative electrode lead is joined to the first negative electrode lead.
2. The nonaqueous electrolyte secondary battery according to claim 1 , wherein the negative electrode active material layer comprises a graphite and a silicon material.
3. The nonaqueous electrolyte secondary battery according to claim 2 , wherein the silicon, material is at least one selected from the group consisting of silicon, silicon oxides, silicon alloys, lithium silicon oxides and silicon composites.
4. The nonaqueous electrolyte secondary battery according to claim 3 , wherein the silicon oxide is represented by the general formula SiO x (0.5≤x<1.6).
5. The nonaqueous electrolyte secondary battery according to claim 3 , wherein the silicon alloy is an alloy of silicon with at least one metal element selected from the group consisting of nickel, iron, copper, titanium, tungsten and molybdenum.
6. The nonaqueous electrolyte secondary battery according to claim 3 , wherein the silicon composite comprises silicon and at least one of a carbon material and a lithium silicon oxide.
7. The nonaqueous electrolyte secondary battery according to claim 2 , wherein the negative electrode active material layer includes the silicon material in an amount of not less than 4 mass % and not more than 20 mass % of the total mass of the graphite and the silicon material.
8. The nonaqueous electrolyte secondary battery according to claim 1 , wherein the surface roughness Ra of the inner face of the sidewall of the exterior case is 0 μm to 1.4 μm inclusive.