The cobalt based lithium ion battery was first commercialised by Sony Corporation over 30 years ago. The lithium ion battery represents a significant improvement in battery technology. These batteries possess high specific energy (energy/weight), low rates of self discharge (the ability to hold charge/energy over time) and are generally maintenance free. Lithium ion batteries may be classified as cobalt versus non cobalt based, with major commercial types shown below.
Cobalt forms part of the battery’s cathode (the positive electrode). There are three dominant cobalt-based cathode materials; namely:
- Lithium Cobalt Oxide – (LiCoO2) ~60% Co, commonly called LCO. LCO batteries were developed as an early generation lithium ion battery and have subsequently taken mass market share, particularly for small portable devices. Uses include mobile phones, tablets, laptops and cameras.
- Lithium Nickel Manganese Cobalt Oxide: (LiNiMnCoO2) ~10-15% Co, commonly called NMC. NMC batteries have improved lifespan and specific energy relative to LCO batteries. Uses include EVs, energy storage devices and medical devices.
- Lithium Nickel Cobalt Aluminium Oxide (LiNiCoAlO2) ~9% Co, commonly called NCA. NCA batteries are a more recent development, possess higher energy densities, however, have lower life spans. Uses include medical devices, industrial and electric powertrains, and used specifically for Tesla EVs.
- Lithium Manganese Oxide (LiMn2O4), commonly called LMO. LMO batteries possess specific energies that are typically lower than LCO. Uses include power tools, medical devices and electric powertrains.
- Lithium Iron Phosphate (LiFePO4), commonly called LFP. LFP batteries possess good power characteristics and a long life span, but have lower energy densities than cobalt based batteries.
Key Battery Components
Every battery has two electrodes – the cathode and the anode – sandwiching an electrolyte, usually a liquid. In a rechargeable lithium ion battery, lithium ions shuttle back and forth between the electrodes during charging and discharging. An electric car may run on hundreds or thousands of these small battery cells, assembled into a big battery pack that typically accounts for about 30-40 percent of the total vehicle cost.
Lithium ion batteries are manufactured in a variety of forms that suit their end uses. These forms include cylindrical, pouch and prismatic cells as shown in the figure below.