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

An electric tool, comprising:

• a lithium ion secondary battery including a positive electrode, a negative electrode, and an electrolytic solution,
• wherein the electric tool operates with the lithium ion secondary battery as a power source,
• wherein the positive electrode contains a lithium composite oxide,
• wherein the negative electrode contains a material including at least tin (Sn),
• wherein the lithium composite oxide includes Lithium (Li) with a composition ratio a1, a first element with a composition ratio b, and a second element with a composition ratio c,
• wherein the first element including manganese (Mn) and nickel (Ni),
• wherein the second element including at least one kind selected from a group consisting of aluminum (Al), titanium (Ti), and boron (B), and
• wherein the composition ratios a1, b, and c satisfy 1.1<a1<1.3, 0.7<b+c<0.9, 0.001<c<0.1, and a1>b+c.

An electric vehicle, comprising:

• a lithium ion secondary battery including a positive electrode, a negative electrode, and an electrolytic solution, wherein the electric vehicle operates with the lithium ion secondary battery as a power source,
• wherein the positive electrode contains a lithium composite oxide,
• wherein the negative electrode contains a material including at least tin (Sn),
• wherein the lithium composite oxide includes lithium (Li) with a composition ratio a1, a first element with a composition ratio b, and a second element with a composition ratio c,
• wherein the first element including manganese (Mn) and nickel (Ni),
• wherein the second element including at least one kind selected from a group consisting of aluminum (Al), titanium (Ti), and boron (B), and
• wherein the composition ratios a1, b, and c satisfy 1.1<a1<1.3, 0.7<b+c<0.9, 0.001<c<0.1, and a1>b+c.

A power storage system, comprising:

• a lithium ion secondary battery including a positive electrode, a negative electrode, and an electrolytic solution, wherein the power storage system uses the lithium ion secondary battery as a power storage source,
• wherein the positive electrode contains a lithium composite oxide,
• wherein the negative electrode contains a material including at least tin (Sn),
• wherein the lithium composite oxide includes lithium (Li) with a composition ratio a1, a first element with a composition ratio b, and a second element with a composition ratio c,
• wherein the first element including manganese (Mn) and nickel (Ni),
• wherein the second element including at least one kind selected from a group consisting of aluminum (Al), titanium (Ti), and boron (B), and
• wherein the composition ratios a1, b, and c satisfy 1.1<a1<1.3, 0.7<b+c<0.9, 0.001<c<0.1, and a1>b+c.