Lithium ion battery

A lithium ion battery comprising:

• a positive electrode active material layer;
• a negative electrode active material layer;
• and
• an electrolytic solution, wherein
• the negative electrode active material layer includes a first region and a second region,
• the first region and the second region are arranged alternately in a direction orthogonal to a thickness direction of the negative electrode active material layer,
• the negative electrode active material layer contains a first active material and a second active material,
• the second active material has a larger specific capacity than the first active material,
• the first active material contains graphite,
• the second active material contains at least one kind selected from the group consisting of silicon, silicon oxide, and a silicon-carbon composite material,
• relationships of following formula (1) and formula (2) are met:
• T
• ⁢
• 2
• <
• T
• ⁢
• 1
• (
• 1
• )
• R
• ⁢
• 1
• <
• R
• ⁢
• 2
• (
• 2
• )
• in the formula (1),
• T1 indicates a thickness of the first region during discharging, and
• T2 indicates a thickness of the second region during discharging, and
• in the formula (2),
• R1 indicates a ratio of a mass of the second active material to a total mass of the first active material and the second active material in the first region, and
• R2 indicates a ratio of a mass of the second active material to a total mass of the first active material and the second active material in the second region, and
• at least one of relationships of following formula (3) and formula (4) is met, and at least one of relationships of following formula (5) and formula (6) is met:
• T
• ⁢
• 2
• /
• T
• ⁢
• 1
• ≤
• 0.4
• (
• 3
• )
• T
• 0
• ⁢
• 2
• /
• T
• 0
• ⁢
• 1
• ≤
• 0.3
• (
• 4
• )
• 130
• ⁢
• μm
• ≤
• T
• ⁢
• 1
• (
• 5
• )
• 100
• ⁢
• μm
• ≤
• T
• 0
• ⁢
• 1
• (
• 6
• )
• in the formula (4) and the formula (6),
• T01 indicates a thickness of the first region before initial charging, and
• T02 indicates a thickness of the second region before initial charging.