Altech Chemicals Ltd (ASX:ATC) (FRA:A3Y) is considering the possible use of high purity alumina (HPA) in the manufacture of a likely next generation of lithium-ion battery (LiB) – the solid-state LiB.
The company has reviewed and investigated more than one hundred separate research journal articles citing the use of HPA in the development of solid-state LiBs.
Based on this extensive research, Altech believes that 4N (99.99%) HPA will continue to be a potential key ingredient in future commercialised solid-state LiBs.
Similarly, the amount of 4N HPA used is also likely to be higher than the amount used in the current ceramic coated separators.
Conventional lithium-ion battery
A conventional LiB cell consists of two solid electrodes (anode and cathode) that are separated by a pool of liquid electrolyte and a polymer separator sheet.
The electrolyte provides the pathway via which lithium ions travel from anode to cathode (and visa-versa) during battery discharge and recharge.
However, the liquid electrolyte is the LiB’s ‘Achilles’ heel’, as this organic substance is highly corrosive, highly combustible and has a finite operating temperature.
Although low-risk, LiB’s are susceptible to intense flammability (fire and/or explosion) and corrosion should battery integrity be compromised by for example, overcharging, short-circuit, overheating or mechanical abuse.
Also, an inherent challenge of using lithium within a battery is the propensity for dendrites, or branch-like growths of lithium metal, to occur when lithium ions collect in localised areas on the electrode surface, usually the anode.
Solid-state lithium-ion battery
A solid-state LiB has a non-liquid ‘solid-state’ electrolyte which appreciably improves battery safety and allows for significantly higher battery operating temperatures, plus the propensity for dendrite grown across the electrolyte is reduced.
However, solid-state LIB’s have their own challenges, most prominent is slower ion diffusion during battery discharge and re-charge, as the lithium ions must travel through the solid-state electrolyte, as compared to a liquid.
The challenge of reduced ion conductivity in a solid-state LiB is addressed by using a different material for the battery anode.
The graphite anode that is used in a conventional LiB can be replaced by a lithium metal anode in a solid-state LiB, as lithium metal can store 10 times more energy than graphite.
Conventional lithium-ion battery (left) compared to a solid-state lithium-ion battery (right)
Among the different types of solid-state electrolytes, polyethylene oxide (PEO) solid electrolytes have been the most extensively studied.
A recognised limitation of PEO solid electrolytes is the low ion conductivity at lower temperatures due to the crystallisation of the polymer.
However, it has been demonstrated that by adding 4N HPA to the polymer as a filler or active material, the crystallisation temperature is lowered and the polymer remains amorphous, enabling it to maintain its ion conductivities at lower temperatures.
Typical PEO-based, HPA-added, nanocomposite membrane
Based on extensive research in the field, Altech believes that 4N HPA will be a key ingredient of future commercialised solid-state LiBs.
The demand for 4N HPA will likely increase further with the future development of solid-state LiB technology.