NiMH No.7 batteries

NiMH No.7 batteries structural changes revealed

Charging lithium batteries too quickly can damage their internal structure and permanently reduce the battery capacity. We may use LNMO spinel to improve this problem.

Fluorescence analysis results show that the internal structure of the battery is significantly damaged after only a few charges.

Dr. Ulrike Bösenberg, a researcher at the German Electron Synchrotron (DESY) Institute, and his team at the DESY X-ray Synchrotron Radiation Source have directly observed structural changes in lithium batteries for the first time. The researchers' fluorescence analysis shows that the internal structure of the battery is significantly damaged after only a few charges.

Rapid charging of lithium batteries can cause a permanent reduction in their capacity and then deactivate part of the energy storage structure. However, when charging more slowly, such damage does not occur immediately.

In general, lithium batteries have a high charge density, but after several charge and discharge cycles, their storage capacity is greatly reduced. Lithium nickel manganese oxide spinel materials, also known as LNMO spinel, provide a potential solution to this problem. With its high voltage of 4.7V, LNMO spinel has become a strong candidate for next-generation energy storage systems. The electrodes of these spinels are made up of small crystals, or crystallites. These crystals in turn are connected to a thin layer of conductive carbon and a binder material.

During the study, the researchers subjected different electrodes to 25 charge and discharge cycles at three rates and then measured the distribution of the elements that make up the electrodes. It was observed that manganese and nickel leach out of the crystals during fast charging. In addition, pore defects with a diameter of up to 0.1 mm were observed in the electrodes. The damaged areas were then unusable for lithium storage.

To accurately determine the distribution of the various elements in the electrode material, an innovative fluorescence detector called the Maya detector was used. The instrument, developed by Brookhaven National Laboratory and CSIRO, consists of nearly 400 individual components that collect fluorescence emitted by the sample. Due to its high sensitivity and high resolution, the detector can locate multiple chemical elements at the same time.

However, the researchers have not yet figured out where the dissolved manganese and nickel atoms go, and hope to solve this problem in future studies.

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