Secondary battery

1. A secondary battery comprising:

a plurality of battery modules, each battery module including an electrolyte layer in a form of a plate, a positive electrode disposed on a first main surface of said electrolyte layer and containing a positive electrode active material and a first additive, and a negative electrode disposed on a second main surface of said electrolyte layer and containing a negative electrode active material and a second additive; and

a conductive layer disposed between battery modules, the secondary battery having more than one said battery module and more than one said conductive layer stacked in layers,

wherein each positive electrode has the same total mass of the positive electrode active material and the first additive;

wherein each negative electrode has the same total mass of the negative electrode active material and the second additive; and

wherein said positive electrode active material and said negative electrode active material are varied in content to be set in concentration in accordance with a temperature distribution in the secondary battery.

2. The secondary battery according to claim 1 , wherein:

said battery modules include a first battery module and a second battery module becoming higher in temperature than said first battery module; and

said positive electrode active material and said negative electrode active material contained in said second battery module are lower in concentration than said positive electrode active material and said negative electrode active material contained in said first battery module.

3. The secondary battery according to claim 1 , wherein:

said first additive and said second additive are added in an amount set in accordance with said temperature distribution in the secondary battery.

4. A secondary battery comprising:

a plurality of battery modules, each battery module including an electrolyte layer in a form of a plate, a positive electrode disposed on a first main surface of said electrolyte layer and containing a positive electrode active material and a first additive, and a negative electrode disposed on a second main surface of said electrolyte layer and containing a negative electrode active material and a second additive, and

a conductive layer disposed between battery modules, the secondary battery having more than one said battery module and more than one said conductive layer stacked in layers,

wherein each positive electrode has the same total mass of the positive electrode active material and the first additive;

wherein each negative electrode has the same total mass of the negative electrode active material and the second additive;

wherein said more than one said battery module has higher temperatures at inner portions of the secondary battery than at an end face of the secondary battery in a direction in which said battery modules are stacked in layers; and

wherein said positive electrode and said negative electrode contain said positive electrode active material and said negative electrode active material, respectively, tapered in concentration from said end face of the secondary battery toward said inner portions of the secondary battery in said direction in which said battery modules are stacked in layers.

5. The secondary battery according to claim 4 , wherein said battery module located at said inner portion as seen in said direction in which said battery modules are stacked in layers provides an output serving as a reference output, and each said battery module has said positive electrode and said negative electrode containing said positive electrode active material and said negative electrode active material, respectively, set in concentration to allow each said battery module to provide said reference output.

6. The secondary battery according to claim 4 , wherein said battery module located at said end face provides an output serving as a reference output, and each said battery module has said positive electrode and said negative electrode containing said positive electrode active material and said negative electrode active material, respectively, set in concentration to allow each said battery module to provide said reference output.