What is Lithium Iron Phosphate? is an inorganic compound with the formula LiFePO 4. It is a gray, red-grey, brown or black solid that is insoluble in water. Because of its lower cost, high safety, low toxicity, long cycle life and other factors, LFP batteries are finding a number of roles in vehicle use, utility scale stationary applications, and backup power. LFP batteries are cobalt-free.