Spherical Graphite (SPG)
As the world transforms to a clean energy base across the electric vehicles (motor vehicles, passenger and heavy transport) and home energy storage, the global demand for cost effective energy storage solutions continues to drive the growth of the graphite flake market.
Spherical graphite is a crucial ingredient to the efficient operation of lithium ion batteries (LiB). Spherical graphite is the key component of the anode of a LiB which without, the LiB would not function.
Historically SPG has been derived from synthetic graphite, a significantly more costly option when compared against natural flake graphite (NFG).
NFG can disrupt synthetic graphite as the primary source of material used to make SPG as synthetic graphite. There is a significant cost advantage in favour of NFG which is defining, as battery manufacturers seek to reduce the overall cost of LiB’s.
BAT is seeking to provide low cost high quality natural flake graphite (NFG).
Typically, flake graphite is shaped into a rounded, spherical shape by a mechanical attrition processes. The rounded shape of SPG, allows for more efficient packaging of particles in a LiB anode, which increases the energy and recharge capacity of the LiB.
LiB’s require different SPG sizes as the SPG particle size impacts the performance targets of the LiB. i.e. a small SPG particle, d50 of 10 micron, would be used in a LiB that has faster charging requirements, while a LiB battery that had large power requirements would use a larger SPG particle with d50 of 20 micron.
Purification and Coating
The spheronized graphite is then purified to remove deleterious elements including SiO2, Fe, S and other metal elements. Various purification techniques are used. These include aggressive acid purification with hydrofluoric acid and thermal purification, using high temperature furnaces. Both these methods have their advantages and disadvantages.
Aggressive acid purification is a low cost, effective method of purification, but due to the nature of the acids used, including hydrofluoric acid, present a toxic and a dangerous working environment and an environmental management challenge. Thermal purification is an electrical thermal process which is fairly expensive compared to acid purification, but is significantly safer and does not impact the environment.
After purification the Purified SPG is coated to assist with improving the surface and area of the particles. Many LiB manufacturers used their own proprietary technology for coating.
The coated, purified SPG is then packed into the shape of the anode required for the LiB batteries.
Testwork to date has confirmed that BAT’s natural flake graphite from both the Montepuez and Balama Central Projects is ideally suitable for Lithium Ion Battery (LiB) applications.
The global production of graphite and spherical graphite is currently dominated by China. China uses the mechanical shaping and hydrofluoric acid purification techniques to produce purified spherical graphite. With the transition of the world to a clean, green energy platform many LiB’s manufacturers are actively seeking alternative supply options.
BAT has the quality of natural graphite flake products and capacity to be a major supplier to this market. BAT has undertaken several successful spherical and battery anode tests on the Montepuez and Balama Central graphite flake and is in discussions with technology and offtake vendors.
LIB Production Cycle
The LiB production cycle from Pit to Lib is summarised in the diagram below:-