On July 8, Tesla submitted a patent application for processes to extract lithium from a clay mineral and its composite elements. Lithium has been at the forefront of many technological changes since the 1990s thanks to the commercialization of lithium-ion batteries — it is the reason for the revolution in electric vehicles (EVs) and personal technology devices.
Lithium is vital to the clean energy transition for the batteries that provide power and store energy. It is the gateway that allows renewable power to be released steadily and reliably. Demand for lithium has soared in recent years as automakers have moved much more toward EVs, notably since many countries including the UK, Sweden, the Netherlands, France, Norway, and Canada have announced a phaseout of combustion-engine cars.
According to the World Bank, 5× more lithium than is mined currently is going to be necessary to meet global climate targets by 2050.
The new Tesla patent application includes providing a clay mineral comprising lithium, mixing a cation source with the clay mineral, performing a high-energy mill of the clay mineral, and performing a liquid leach to obtain a lithium-rich leach solution.
The Pervasive Need for Lithium
An EV can have 5,000 battery cells and could need 10 kg of lithium. One ton of lithium can help meet the demand of 90 electric cars. About 60,000 tons of lithium carbonate equivalent are required to produce one million electric cars. Tesla CEO Elon Musk has noted that 30 million electric cars need to be produced by 2027, and that would require 1.8 million tons of lithium carbonate equivalent.
Consider the battery pack of a Tesla Model S. Thousands of cylindrical cells — a bit like nested dolls — with components sourced from around the world transform lithium and electrons into enough energy to propel the car hundreds of kilometers, again and again, without tailpipe emissions.
Typically, a main pack holds several modules, each of which is constructed from numerous smaller cells. Inside each cell, lithium atoms move through an electrolyte between a graphite anode and a cathode sheet composed of a metal oxide.
Obtaining lithium by conventional means takes its own environmental toll, due to carbon emissions and water and land degradation. The demand for lithium with a lower environmental footprint appears to be gaining ground.
The Tesla Patent Application Particulars
The patent, titled “Selective Extraction of Lithium from Clay Minerals,” argues that extracting lithium from ore using sodium chloride is an environmentally friendlier way to obtain the metal compared to currently used techniques such as acid leaching. According to Tesla, it also allows for higher recoveries.
Clay minerals consist of microscopic framework layers composed of Li, Na, K, Al, Si, Mg, Ca, Fe, O, and/or OH, and inter-layer spaces through which cations like Li, Na, K, and Mg may be conducted in water or other electrolytes. The position of the lithium atom in this mineral structure makes all the difference for how it can be extracted — if the lithium is found within the framework layer or floating in the interlayer.
Lithium, in small amounts, is widespread in clay minerals. It many be present in clays as impurities, as inclusions, in lattice cavities, absorbed on the surface, or by isomorphous substitution — the latter of which is the most common.
The introduction to the Tesla patent application offers a primer about lithium, explaining that it is a strategic metal for the lithium-ion battery (LIB) and the electric vehicle (EV) industry. The importance of economically extracting lithium from various lithium sources was identified as necessary to reduce the cost of batteries and electric cars.
The document states that, while the dominant lithium sources commonly used for mining are lithium brines — due to the low cost associated with Li extraction from these sources — the ever-increasing demand for LIBs makes it necessary to explore other lithium sources. The new Tesla patent application looks at another method for Li extraction: extracting the Li from clay minerals.
Here’s what the proposed Tesla process for extracting lithium from a clay mineral would comprise:
- providing a clay mineral comprising lithium;
- performing a high-energy mill of the clay mineral;
- mixing a cation source with the clay mineral concurrently with, before or after performing the high-energy mill to form a mixture, wherein the cation source comprises a cation and an anion; and,
- contacting the milled clay material and cation source mixture with a solvent to extract lithium from the milled clay material and form a lithium rich leach solution.
In this process, the lithium is obtained by acid leaching, where clay minerals are mixed with an aqueous solution of common mineral acids, such as H.sub.2SO.sub.4 or HCl, and then heated under atmospheric pressure to leach out the lithium contained in the clay minerals. Tesla claims that this acid leach method not only leaches out lithium, but it also leaches out high concentrations of impurities, including Na, K, Fe, Al, Ca, and Mg.
Lithium is generally extracted from minerals found in igneous rocks composed of large rocks (spodumene) or in water with high concentration of lithium carbonate. In the Tesla patent application, the clay material was described as comprising one or more additional minerals selected from the group consisting of spodumene, lepidolite, zinnwaldite, smectite, hectorite, muscovite, and combinations. The clay mineral comprises one or more additional elements selected from the group consisting of sodium, potassium, iron, aluminum, calcium, magnesium, silicon, chromium, and combinations.
The Tesla patent application notes that high lithium loss from the subsequent removal of the impurity elements, especially Al removal, may significantly lower overall lithium extraction efficiency.
Many different approaches are underway to increase the amount of lithium available for the technology industry.
Vulcan Energy Resources has announced that its main site has significant reserves, with lithium concentrations of 181 milligrams per litre. It is currently carrying out a full feasibility study, with the aim of scaling up to full commercial production of lithium in 2023-24. “We have a resource which is large enough to satisfy a very substantial amounts of the demand in the European markets here for many, many years to come,” Vulcan’s chief executive Francis Wedin told an industry conference last October.
Standard Lithium’s approach has been focused on using a modern technology-based approach to extract lithium not just faster but producing a higher-purity product and reducing the environmental footprint associated with that. Using the Steve Jobs approach of working backwards toward technology development, the project drives the process. That principal has been fundamental to their team in developing its proprietary LiSTR DLE process (LiSTR is an acronym for “lithium stirred tank reactor”).
The Tesla patent application comes at a time of hesitancy that battery-ready lithium might run out by 2025. And as electric cars begin to take over the roads, lithium resources are crucial for the transition to a zero emissions world.