Uncovered the reason that makes fast charging lithium batteries difficult and causes them to take so long to charge
A new research The US Department of Energy (DOE) of the Argonne National Laboratory has revealed a chemical behavior of the graphite terminals of lithium batteries when they are charged and discharged, which explains the reasons that decrease the performance of the batteries. fast-charging batteries in electric vehicles.
Lithium ion batteries contain a positively charged cathode and a negatively charged anode, which are separated by a material called electrolyte that moves the lithium ions between them and thus generates an electrical current. The anode in these batteries is usually made of graphite, the same material found in many pencils.
However, in lithium-ion batteries, graphite is made up of tiny particles. Inside these particles, lithium ions can be inserted in a process called intercalation. When collation is successful, the battery can be successfully charged and discharged. But when a battery charges too fast, the interleaving is poor. Rather than work their way into graphite, lithium ions tend to accumulate on the anode surface, causing a “plating” effect that can cause battery damage.
The coating, cause of deterioration by fast charging
One of the study’s authors, Daniel Abraham, explained that coating is one of the main causes of battery performance deterioration during fast charging. By rapidly charging the battery, they discovered that in addition to the plating on the anode surface, there was a build-up of reaction products within the pores of the electrode. As a result, the anode itself undergoes some degree of irreversible expansion, impairing battery performance.
Using a microscopy technique called scanning electron nanodifraction, Abraham and his colleagues at the University of Illinois Urbana-Champaign observed another notable change in the graphite particles. At the atomic level, the network of graphite atoms at the edges of the particles is distorted due to repeated fast charging, making the intercalation process difficult.
‘Basically what you see is that the graphite’s atomic lattice is deformed, and this prevents the lithium ions from entering the interior of the particles. Instead, they wedge themselves between the particles, ”Abraham said.
The report also indicated that the faster the battery is charged, the more disordered the anode will be from an atomic point of view, which will prevent the lithium ions from being able to move from one side to the other. The solution is to find a way to avoid this loss of organization or to modify the graphite particles in some way so that the lithium ions can intercalate more efficiently.
REFERENCE