Pulsed charging enhances the service life of lithium-ion batteries.
"Lithium-ion batteries are powerful, and they are used everywhere, from electric vehicles to electronic devices. However, their capacity gradually decreases over the course of hundreds of charging cycles. The best commercial lithium-ion batteries with electrodes made of so-called NMC532 and graphite have a service life of up to eight years. Batteries are usually charged with a constant current flow. But is this really the most favourable method? A new study by Prof Philipp Adelhelm's group at Helmholtz-Zentrum Berlin and Humboldt-University Berlin answers this question clearly with no."
I skipped the chemical formula for NMC532 but it's in the article. Basically a lithium, nickel, manganese, cobalt compound.
"Part of the battery tests were carried out at Aalborg University. The batteries were either charged conventionally with constant current or with a new charging protocol with pulsed current. Post-mortem analyses revealed clear differences after several charging cycles: In the constant current samples, the solid electrolyte interface at the anode was significantly thicker, which impaired the capacity. The team also found more cracks in the structure of the NMC532 and graphite electrodes, which also contributed to the loss of capacity. In contrast, pulsed current-charging led to a thinner solid electrolyte interface and fewer structural changes in the electrode materials."
"Helmholtz-Zentrum Berlin researcher Dr Yaolin Xu then led the investigation into the lithium-ion cells at Humboldt University and BESSY II with operando Raman spectroscopy and dilatometry as well as X-ray absorption spectroscopy to analyse what happens during charging with different protocols. Supplementary experiments were carried out at the PETRA III synchrotron. 'The pulsed current charging promotes the homogeneous distribution of the lithium ions in the graphite and thus reduces the mechanical stress and cracking of the graphite particles. This improves the structural stability of the graphite anode,' he concludes. The pulsed charging also suppresses the structural changes of NMC532 cathode materials with less Ni-O bond length variation."
BESSY stands for "Berliner Elektronenspeicherring-Gesellschaft für Synchrotronstrahlung". In English, "Berlin Electron Storage Ring Society for Synchrotron Radiation". Which would be BESRSSR. Never mind. Yes, "Electron Storage Ring" got all smashed together into "Elektronenspeicherring" in the German. "Society" seems like an odd part of the name in English. "Gesellschaft" can be translated "society" but could also be "company". Maybe "organization" would be a better word. Synchrotron radiation is a type of radiation emitted in particle accelerators when charged particles are pushed into going in circles or curved trajectories instead of being allowed to go in straight lines like they want to, and apparently requires "relativistic" speeds, which I take to mean, charged particles near the speed of light.
Raman spectroscopy is a type of spectroscopy where, I'm not sure exactly how it works. You transmit a fixed wavelength of light but the vibrations of the molecules nudge the energy levels up or down such that the molecules will or won't absorb and re-emit ("scatter") the photons. Not sure how the word "dilatometry" fits into all this. "Dilatometry" just means the measurement of the amount of volume a material takes up.
PETRA III is a particle accelerator in Hamburg run by DESY, the German government's national organization for fundamental physics research. DESY stands for "Deutsches Elektronen-Synchrotron" and PETRA stands for "Positron-Electron Tandem Ring Accelerator" (apparently doesn't have both German and English versions?).
All in all, a pretty sophisticated amount of analysis of battery recharging.
Still, the optimal frequency is not known.
BESSY II: How pulsed charging enhances the service time of batteries
#batteries
