A pacemaker is a small electronic medical device implanted in the body, primarily used to treat a slow heartbeat (bradycardia). Its core function is to monitor the heart's own electrical activity and, if the heart beats too slowly or stops, send weak electrical pulses to stimulate the heart muscle, causing it to contract at a normal rate and thus ensuring adequate blood supply to the body. The design of these batteries must meet the stringent requirements of implantable medical devices for long life, high safety, and stable voltage.