Lithium ion secondary battery, electric tool, electric vehicle, and power storage system

摘要

A lithium ion secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode contains a lithium composite oxide. The negative electrode contains a material including at least one of silicon Si and tin Sn as a constituent element. The lithium composite oxide includes lithium Li having a composition ratio a, a first element having a composition ratio b, and a second element having a composition ratio c as a constituent element. The first element including two kinds or more selected from among manganese Mn, nickel Ni, and cobalt Co, and including at least manganese. The second element including at least one kind selected from among aluminum Al, titanium Ti, magnesium Mg, and boron B. The composition ratios a to c satisfy the relationships of 1.1b+c.

主权项

1. A lithium ion secondary battery comprising:
a positive electrode; a negative electrode; and an electrolytic solution, wherein the positive electrode contains a lithium composite oxide, the negative electrode contains an oxide including at least one of silicon Si and tin Sn, the lithium composite oxide includes lithium Li having composition ratio a, a first element having composition ratio b, and a second element having composition ratio c, said first element being two kinds or more selected from the group consisting of manganese Mn, nickel Ni, and cobalt Co, and including at least manganese, said second element being at least one kind selected from the group consisting of aluminum Al, titanium Ti, magnesium Mg, and boron B, and the composition ratios a to c satisfy 1.1b+c, wherein a covering layer is provided on a surface of the lithium composite oxide to cover at least a part of the surface, said covering layer includes a third element, and wherein at least a part of the third element is crystalline in structure, and the third element is in a surface region of the lithium composite oxide ranging from an outermost surface of the lithium composite oxide to a thickness corresponding to 0.1% of a particle size.