One of the biggest concerns people have about electric vehicles is battery life.
Many drivers worry that the battery may wear out too quickly or that the car might run out of power far from a charging station.
Because of these concerns, scientists around the world are working to make lithium-ion batteries last longer and operate more safely.
A new study offers a promising step forward. Researchers have discovered that adding an extremely thin protective coating to a key battery material can greatly extend the battery’s lifespan.
The research was recently published in the journal Small.
Lithium-ion batteries power many of the devices we use every day, including smartphones, laptops, and electric vehicles.
Inside these batteries are materials called cathodes, which play a major role in storing and releasing energy.
One widely studied cathode material is called lithium nickel manganese cobalt oxide, often shortened to NMC811. Scientists like NMC811 because it can store a large amount of energy and is relatively affordable compared with some other materials.
However, NMC811 has an important weakness. Over time, the material slowly breaks down as the battery charges and discharges repeatedly. Each full charge and discharge is called a cycle. During these cycles, the cathode can release small amounts of oxygen.
That oxygen can react with the liquid electrolyte inside the battery, creating gases and unwanted chemical byproducts. These reactions reduce battery performance and can sometimes even create safety risks.
To solve this problem, researchers led by Xiangbo “Henry” Meng at the University of Arkansas tried adding a protective layer to the NMC811 cathode. They used a special technique called atomic layer deposition to apply a coating made from zirconium sulfide. The coating is extremely thin—only about two billionths of a meter thick.
Even though the coating is tiny, it plays an important role. When oxygen is released from the cathode during battery cycling, the sulfide coating captures it. The oxygen changes the coating’s chemical structure, turning zirconium sulfide into zirconium sulfate. This reaction helps prevent the oxygen from damaging the battery’s electrolyte.
The new sulfate layer also helps stabilize the surface between the cathode and the electrolyte. By doing this, it reduces harmful reactions, prevents tiny cracks from forming inside the cathode, and keeps the material structurally stable during long-term use.
The improvement in performance is impressive. Batteries using the uncoated NMC811 cathode typically last about 200 cycles before their performance drops significantly. With the new coating, the cathode survived more than 1,000 cycles. In tests, the battery was still able to hold about 60 percent of its original charge even after 1,300 cycles.
The experiments were carried out using small coin-cell batteries, which are often used in devices like watches, calculators, and key fobs. However, the technology could eventually be used in much larger batteries, including those in electric vehicles and consumer electronics.
Meng and his team are continuing their research and have already tested several different sulfide coatings. If further testing goes well, this simple nanoscale coating could help future batteries last much longer while also improving safety.
