Lithium Australia NL reported that its wholly owned subsidiary VSPC Ltd has successfully produced Li-ion battery cathode material, and Li-ion batteries (LIBs), from tri-lithium phosphate produced directly from mine waste using the SiLeach process.

SiLeach background. During conventional processing, lithium is recovered only from spodumene concentrates, not lithium micas, which until now have been something of a forgotten resource.

Conventional processing to extract lithium also incorporates an energy-intensive roasting phase, occurring at temperatures of more than 1,000 ˚C, followed by sulfation bake, undertaken at about 250 ˚C. Once the residue produced is cooled and leached with water, only lithium (as a sulfate) is recovered, and it is then further processed to produce lithium carbonate.

Unlike conventional processing, SiLeach is a hydrometallurgical process, so no roasting phase is required, which reduces energy consumption. Moreover, there is potential for SiLeach to derive all its energy requirements from waste heat generated during the production of sulfuric acid, which would further reduce operating inputs.

With SiLeach, a combination of sulfuric acid and halides is used to dissociate the strong bonds in silicate lattices at atmospheric pressure, meaning that only simple mechanical components are necessary to conduct the process. Reactions occur rapidly at about 90 ˚C, which is also a distinct advantage in terms of constraining plant footprint and reducing capital costs.

Also unlike conventional processing, all metals within the target minerals are soluble in SiLeach, creating the opportunity to generate significant by-product credits. Finally, SiLeach produces very clean lithium solutions, an advantage in terms of the subsequent production of battery-grade lithium carbonate.

LFP and batteries from waste. This process removes the requirement for generation of high-purity lithium hydroxide or carbonate which has long been one of the most cost-intensive, and challenging steps in the manufacture of LIBs.

The tri-lithium phosphate was converted to lithium-iron-phosphate (LFP) cathode material at the advanced electrochemical laboratory and pilot plant facility in Brisbane, Queensland operated by VSPC. The proprietary processes used to generate the LFP nanoparticles is covered by patents granted to VSPC.

The cathode material was characterized by XRD and SEM, and determined to be of similar quality to VSPC standard LFP material.

VSPC LFP SEM image

LIBs (2032 coin cells) were subsequently produced and tested under a range of charge and discharge conditions and the cells achieved equivalent performance to VSPC’s advanced cathode powders which use lithium carbonate as the manufacturing feed. Battery performance compares very favorably against cells using standard VSPC cathode material produced with industry standard lithium carbonate.

The demonstrated ability to bypass lithium carbonate and lithium hydroxide as battery precursors offers the potential to reduce the cost battery manufacture significantly. Not only that, the use of mine waste in the battery production cycle can provide greater sustainability to global lithium resources.

Lithium Australia is also developing the process for direct production of cathode powders from lithium brines, to not only eliminate the requirement to produce high-purity lithium hydroxide or carbonate but to reduce the requirement for evaporation ponds.

Mine waste to LIB without the requirement to produce a lithium hydroxide or lithium carbonate precursor is a world first. This has the potential to provide a commercial outcome to many stranded resources creating ethical and sustainable supply in the process.