Electric vehicles are growing in popularity as consumers look for greener alternatives to gas guzzling cars. With this rise in EVs comes the growing demand for batteries to power them. Lithium-ion batteries are currently the standard, but their raw materials have sustainability issues. Cobalt mining, for example, has been linked to human rights abuses in some regions. As automakers scramble to source billions of batteries, sustainable alternatives are increasingly important.
New Anode Materials Look to Replace Graphite
The most common anode material in current lithium-ion batteries is graphite. However, graphite has a relatively low capacity. Researchers are exploring alternative anode materials that can store more lithium ions and increase battery capacities. Silicon has emerged as a promising graphite replacement, capable of holding roughly 10 times more lithium than graphite. But silicon also swells dramatically when lithium ions insert into its structure. This swelling causes batteries to quickly degrade. Scientists are developing silicon anodes with conductive additives, porous structures and synthetic binders to counter the swelling issue and unlock silicon's high capacity. Other candidates like tin, germanium and lithium metal offer even higher capacities than silicon and are also being researched.
Cathode Innovations to Reduce Cobalt Dependency
On the cathode side, the most widely used Sustainable Battery Materials is lithium cobalt oxide, or LCO. However, cobalt mining raises ethical and geopolitical concerns. It also only provides around half the capacity of anodes. This imbalance of cathode to anode capacities is another limitation of current batteries. To reduce cobalt usage, researchers are developing lithium nickel manganese cobalt oxide chemistries and high-nickel NMC variants. Manganese-rich and cobalt-free NMCs are another route. Lithium iron phosphates offer even lower cobalt contents and improved safety compared to NMCs and LCO. Other cathode materials in the lab include lithium-rich layered oxides and lithium sulfides for their unusually high capacities. Developing sustainable, high-capacity cathodes is a major priority for battery experts.
Evaluating Alternative Electrolyte Solutions
The electrolyte is what allows lithium ions to shuttle between the cathode and anode during charging and discharging. Conventional lithium-ion batteries use liquid organic electrolytes that pose flammability hazards. This makes them less than ideal for electric vehicles. Solid-state electrolytes could provide improved safety over liquids but achieving high ion conductivity at room temperature has proved difficult. Researchers are working on polymer, inorganic and composite electrolytes that maintain good conductivity while improving safety. Lithium salts beyond the commonly used lithium hexafluorophosphate are also being studied to enhance properties or reduce cost. Developing truly non-flammable, high performing electrolytes is another challenge battery companies aim to overcome.
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