So, I'm going to state this for the record here because one of the densest, most arrogant mother fuckers I have met in my time being here just spent an ungodly long time trying to tell me elsewise.
Chi is the life energy that is used in energy bending.
The Wiki said
Energybending is the ability to bend another person's life energy. It predates the four main bending arts, the formation of the four nations, as well as the creation of the Avatar Spirit.
TheWiki said
Enlightened individuals, such as Guru Pathik and Huu, further explained the concept of chi as the life energy that dwells inside every living being connecting them to each other, their surroundings, and the universe as a whole. Different parts of the human body contain concentrated clusters of chi, better known as chakras, or "pools of energy" as Pathik called them. When unlocked, these chakras are crucial for the Avatar to achieve his or her full potential, channeling his or her own energy as well as the energy from the universe
See those two canonical quotes? They're why. The concept of chi is the life energy that dwells within every living being, which is what is being bent and manipulated in energybending. Thus, chi itself is synonymous and interchangeable with life energy. For most people, this fact won't mean anything. However, granted that this is my roleplay and a petulant, arrogant and ultimately wrong kid from the interest check just spent an unjustifiable amount of time telling me energy is no chi, I'm throwing this out to each and everyone of you that intend on roleplaying here.