There is provided a battery including a positive electrode that includes an active material layer formed on a positive electrode current collector; a negative electrode that includes active material layers formed on first and second principal planes of a negative electrode current collector and the active material layer on the second principal plane has an alloyed region smaller than an alloyed region the active material layer has on the first principal plane between the second principal plane and the current collector; and an electrolyte.
1. A battery comprising:
a positive electrode that includes an active material layer formed on a positive electrode current collector;
a negative electrode that includes a negative electrode current collector having two surfaces defining first and second parallel planes and active material layers formed on the first and second planes of the negative electrode current collector, the active material layer on the second plane having an alloyed region between the active material layer and the negative electrode current collector smaller than an alloyed region of the active material layer on the first plane of the negative electrode current collector; and
an electrolyte.
2. A battery according to claim 1 , wherein the active material layer on the first plane of the negative electrode current collector has a columnar or block shape and the active material layer on the second plane of the negative electrode current collector is a powdery active material.
3. A battery according to claim 1 , wherein the active material layer on the first plane of the negative electrode current collector being of a first material which contains silicon (Si) and the active material layer on the second plane of the negative electrode current collector being of a second material different than the first material but which also contains silicon (Si) or which contains tin (Sn).
4. A battery according to claim 1 , wherein the positive electrode and the negative electrode are wound together.
5. A battery according to claim 1 , wherein the first plane of the negative electrode current collector has an arithmetic mean roughness Ra equal to or greater than 0.2 μm.
6. A battery according to claim 1 , wherein the active material layer on the first plane of the negative electrode current collector is formed by a chemical vapor deposition.
7. A battery according to claim 1 , wherein the active material layer on the first plane of the negative electrode current collector contains silicon (Si) and oxygen (O) with the oxygen (O) being present in the amount of 3 atomic % or more to 45 atomic % or less.
8. A battery according to claim 1 , wherein the active material layer on the first plane of the negative electrode current collector has a multilayer structure including high and low oxygen concentration regions repeatedly formed in the direction approximately perpendicular to the first plane.
9. A battery according to claim 1 , wherein the electrolyte contains a sultone compound.
10. A battery according to claim 1 , wherein the electrolyte contains a cyclic carbonate compound having an unsaturated bond.
11. A battery according to claim 1 , wherein the electrolyte contains a compound having a structure in which hydrogen (H) of cyclic carbonate or chain carbonate is partly substituted with fluorine (F).
12. A battery according to claim 1 , wherein the active material layer of the positive electrode includes:
an inner portion formed of a lithium transition metal composite oxide, and
a surface layer containing at least one compound selected from a lithium transition metal composite oxide different from the lithium transition metal composite oxide forming the inner portion, a metal oxide, a metal halide, a metal phosphate, and a metal sulfate.
13. A battery according to claim 1 , wherein
the alloyed region of the active material on the second plane is not provided between the active material layer of the second plane and the current collector, and
the alloyed region of the active material on the first plane is provided between the active material layer of the first plane and the current collector.