Lithium mines: the battle for future energy

The use of lithium-ion batteries in electric and hybrid vehicles promises to minimize the potential impact of conventional vehicles on the environment. In addition, lithium-ion batteries are expected to provide power storage media for renewable energy sources such as solar and wind power. Battery and glass and ceramic manufacturing accounts for the majority of global lithium end-uses.

There are two economically viable sources of lithium: brines and hard rock-type ores. The majority (over 60%) of global lithium production comes from brine, with the remainder from lithium ore. To meet the growing demand for lithium, the beneficiation and metallurgical extraction processes of lithium need to be optimized and improved. Like most minerals, the processing of lithium ore first requires beneficiation, followed by extraction of its compounds in a downstream process.

Flotation is mainly used to extract minerals from lithium ore. During this process, lithium ore is concentrated from 1-3% Li2O to 4-6% Li2O relative to lithium oxide by using dense non-aqueous liquid for dense medium separation during froth flotation. Silicate ores are most widely processed by flotation, and these products are then chemically cleaned by acid or alkali processes. 

During the pickling process, concentrated spodumene ore is placed in a kiln and heated to high temperatures between 1075 °C and 1100 °C. This process converts naturally occurring alpha-spodumene into beta-spodumene, which is more vulnerable to acid attack. The beta-spodumene was further cooled and ball milled. This powder is then calcined in a second kiln with excess sulfuric acid at a temperature of 200-250 °C. During alkaline cleaning, spodumene or lepidolite concentrate is ground and calcined with a mixture of 3.5 parts limestone and 1 part lithium. This is done at temperatures between 900 °C and 1000 °C. During this process, the kiln is then hot-dipped with water, and the product is lithium hydroxide, which can be converted to lithium chloride using hydrochloric acid. Therefore, lithium chloride is a source of electrolytic extraction of lithium. Lithium metal can be obtained by electrolysis of melts consisting of equal mixtures of lithium chloride and potassium chloride. A schematic diagram of the battery is shown in Figure 1 (Freitas, 2000). Lithium chloride is fed into the battery, which operates at temperatures ranging from 400°C to 420°C. Molten LiCl and KCl batteries typically have voltages between 8 V and 9 V and consume 40 kWh of current per kilogram of lithium produced. Steel cathodes and graphite anodes are used with cast iron current collectors. Tables 1 and 2 show that lithium is less dense than electrolytes. Therefore, the metal floats on top. Collectors aid in the recovery of metals. Electrical and ionic conductivities in batteries and fluidity of electrolytes are key parameters controlling process materials and energy balance.