Han Tao is not a battalion chief

Wang Ping and the mid-team leader have different grades; therefore

Wang Ping is not a squadron leader.

The performance of the squadron leader is worse than that of Song Dan, so

Song Dan is not a mid-team leader.

Because Wang Ping and Song Dan are not mid-team leaders, Han Tao is.

The squadron leader's performance is worse than Song Dan's, so Song Dan's performance is better than Han Tao's, and Han Tao's performance is better than the captain's.

So Song Dan is not the battalion chief, so Wang Ping is the battalion chief.