Secondary battery

Abstract

A secondary battery having an excellent capacity maintenance factor or charging/discharging efficiency is provided. A lithium-ion battery comprises an electrode group that a positive electrode and a negative electrode which respective of active materials for the positive and negative electrodes is coated on both surfaces of a collecting member. An area S1 of a portion of then egative electrode 7 not facing the positive electrode 6 is set to be not more than 10% of an area S2 of a portion of the negative electrode 7 facing the positive electrode 6. An influence that the portion not facing the positive electrode affects a battery reaction is controlled, and the decrease in the capacity maintenance factor or the charging/discharging efficiency according to cycling use can be depressed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a lithium-ionbattery of an embodiment to which the present invention is applicable;

FIG. 2 is a schematic perspective view of an electrode group of the lithium-ion battery of the embodiment;

FIG. 3 is a sectional view of the electrode group schematically showing a layered state of a positive electrode, a negative electrode and a separator; and

FIG. 4 is a graph showing test results of a charging/discharging cycling test on batteries of examples and a control.

Claims

1. A secondary battery comprising an electrode group that a positive electrode and a negative electrode which respective of active materials for the positive and negative electrodes is coated on both surfaces of a collecting member or is filled into the collecting member are placed via a separator, wherein, with respect to an electrode having a polarity placed at an outside of the electrode group, an area S1 or a capacity C1 of a portion not facing an electrode having an opposite polarity is set to be not more than 10% of an area S2 or a capacity C2 of a portion facing the electrode having the opposite polarity (S1/S2<=10% or C1/C2<=10%).

2. A secondary battery according to claim 1, wherein the area S1 or the capacity C1 of the portion not facing the opposite electrode is set to be not more than 5% of the area S2 or the capacity C2 of the portion facing the opposite electrode (S1/S2<=5% or C1/C2<=5%).

3. A secondary battery according to claim 1, wherein a ratio of electric capacities per unit area of the positive electrode and the negative electrode is 1:1.

4. A secondary battery according to claim 1, wherein the electrode group is constituted that the positive electrode and the negative electrode are layered via the separator alternately.

5. A secondary battery according to claim 4, wherein the electrode group is infiltrated into an electrolyte and is sealed within a container.

6. A secondary battery according to claim 4, wherein the positive electrode active material is a lithium manganese complex oxide and the negative electrode active material is a carbon material.

7. A secondary battery according to claim 6, wherein the positive electrode is formed that a mixture including the lithium manganese complex oxide is coated on both surfaces of an aluminum foil and the negative electrode is formed that a mixture including the carbon material is coated on both surfaces of a rolled copper foil.

8. A secondary battery according to claim 5, wherein the electrode group is infiltrated into a non-aqueous electrolyte and is sealed by a container made of laminated film.

9. A secondary battery according to claim 8, wherein a positive electrode terminal and a negative electrode terminal are led out of one side among peripheral sides of the container.

10. A secondary battery according to claim 9, wherein the container has an electrolyte pouring opening which is sealedby thermal melting.