Secondary battery and method of producing the secondary battery

1. A method of producing a secondary battery, the method comprising the following sequential operations:

dipping a separator in a polymer electrolytic precursor solution to prepare an impregnated separator;

adhering the impregnated separator to each of a positive electrode layer and a negative electrode layer by sandwiching the impregnated separator between the positive and negative electrode layers and polymerizing an electrolyte of the impregnated separator while applying a pressure to the positive electrode layer, the impregnated separator and the negative electrode layer in a direction of thickness of the positive electrode layer, the impregnated separator and the negative electrode layer, to thereby form a stack structure of the positive electrode layer, a separator layer and the negative electrode layer; and

injecting a liquid electrolyte to the stack structure,

wherein a conductivity of an electrolyte of the negative electrode layer in the secondary battery is higher than a conductivity of an electrolyte of at least one of the separator layer and the positive electrode layer.

2. The method of producing the secondary battery according to claim 1 , wherein

in the injection operation, a pressure is applied to a face of the stack structure from a direction substantially perpendicular to the face of the stack structure such that a thickness of the stack structure has a variation in a range within 5% of a certain thickness.

3. The method of producing the secondary battery according to claim 1 , further comprising:

at least one of the following first and second operations:

a first operation of forming the positive electrode layer, including:

forming a positive electrode current collector having a groove defining a width and a depth, and

forming a positive electrode active material layer on the positive electrode current collector,

wherein each of the width and the depth of the groove of the positive electrode current collector is less than or equal to 10% of an average particle diameter of the positive electrode active material layer, and

a second operation of forming the negative electrode layer, including:

forming a negative electrode current collector having a groove defining a width and a depth, and

forming a negative electrode active material layer on the negative electrode current collector,

wherein each of the width and the depth of the groove of the negative electrode current collector is less than or equal to 10% of an average particle diameter of the negative electrode active material layer.

4. A method of producing a secondary battery, the method comprising the following sequential operations:

dipping a separator in a polymer electrolytic precursor solution to prepare an impregnated separator;

adhering the impregnated separator to each of a positive electrode layer and a negative electrode layer by sandwiching the impregnated separator between the positive and negative electrode layers and polymerizing an electrolyte of the impregnated separator while applying a pressure to the positive electrode layer, the impregnated separator and the negative electrode layer in a direction of thickness of the positive electrode layer, the impregnated separator and the negative electrode layer, to thereby form a stack structure of the positive electrode layer, a separator layer and the negative electrode layer;

injecting a liquid electrolyte to the stack structure; and

vacuum-impregnating the stack structure,

wherein a conductivity of an electrolyte of the negative electrode layer in the secondary battery is higher than a conductivity of an electrolyte of at least one of the separator layer and the positive electrode layer.

5. The method of producing the secondary battery according to claim 4 , wherein

in the injecting operation, a pressure is applied to a face of the stack structure from a direction substantially perpendicular to the face of the stack structure, such that a thickness of the stack structure has a variation in a range within 5% of a certain thickness.

6. The method of producing the secondary battery according to claim 4 , further comprising:

at least one of the following first and second operations:

a first operation of forming the positive electrode layer, including:

forming a positive electrode current collector having a groove defining a width and a depth, and

forming a positive electrode active material layer on the positive electrode current collector,

wherein each of the width and the depth of the groove of the positive electrode current collector, is less than or equal to 10% of an average particle diameter of the positive electrode active material layer, and

a second operation of forming the negative electrode layer, including:

forming a negative electrode current collector, having a groove defining a width and a depth, and

forming a negative electrode active material layer on the negative electrode current collector,

wherein each of the width and the depth of the groove of the negative electrode current collector is less than or equal to 10% of an average particle diameter of the negative electrode active material layer.