It was long believed that single-crystal cathodes would solve battery durability problems because they lack the internal junctions (grain boundaries) where cracks typically start. But a new study, published in the journal Nature Nanotechnology, reveals that some single-crystals can start to crack from within after only about 100 charge-discharge cycles.
Why isn't nickel enough? Most electric vehicle manufacturers are betting on cathodes with a high nickel content, as this allows for higher energy density and longer range. The problem arises at high voltages, when the removal of lithium weakens the oxygen bonds in the structure. When cracks form, the liquid electrolyte penetrates them, triggering unwanted chemical reactions. These reactions not only reduce capacity, but also increase heating and thus the risk of fire.
The research team led by Dr. Jing Wang even found that the problem isn't the seams, but the uneven movement of lithium ions. Within a single crystal particle, some regions absorb lithium faster than others. This creates inconsistencies in the crystal lattice:
\u2013 The surface of the particle changes rapidly, while the core lags behind.
\u2013 When the expansion or contraction exceeds the elastic limit of the material, the crystal cracks.
\u2013 Rapid charging increases these risks by forcing the lithium to move even faster and less evenly.
Although the industry is trying to reduce the use of expensive cobalt, tests have shown that a small amount of this element in single crystals actually helps. Cobalt \u201csmoothes\u201d the flow of lithium and reduces the formation of high-voltage zones. On the other hand, manganese in these samples slowed reactions and increased the likelihood of cracking, despite being a cheaper and less ethically controversial alternative.
Scientists now point out that the future of batteries may not lie in maximizing energy, but in ensuring uniform reactions throughout the material. The next step will be to transfer these insights from laboratory particles to full battery cells that will have to withstand real-world driving conditions. The goal is to find accessible elements that will stabilize nickel without causing new forms of internal damage.<\/p>\n