In Situ Lithium Dendrite Deposition
A key challenge in the development of lithium-ion battery materials is combating the formation of lithium dendrites on the electrode surface after repeated charge/discharge cycles. As dendrites form over repeated cycles, so-called “dead” lithium no longer participates in ion transport. This leads to a reduction in battery capacity, while increasing the potential for the formation of a short circuit between the anode and the cathode.
Researchers used Protochips’ Poseidon Select system to observe the charge/discharge process of lithium-ion batteries in solution using scanning TEM (STEM). A series of real-time STEM images of the working electrode was acquired as the electrochemical potential of the cell was simultaneously cycled from 0 to -4 volts.
At the start of the first cycle, the surface of the platinum working electrode was pristine, and all the lithium was dissolved in the electrolyte solution. As the battery was charged, lithium was deposited on the surface of the working electrode; surface roughening was observed, as the lithium was not deposited in an even layer. Discharging of the battery during the first cycle led to a reduction in lithium on the electrode surface, but lithium dendrites remained on the surface of the electrode and did not redissolve in the electrolyte.
As the number of charge cycles increased, an increase in irreversibility of the electrochemical cell was observed, corresponding to the formation of lithium dendrites and “dead” lithium regions visible in the STEM images. Also visible in the CV curves were characteristic peaks at -2 and -2.5 volts, indicating alloying between the platinum electrode and the lithium in the electrolyte.
Using the Poseidon Select system, researchers successfully imaged the formation of lithium dendrites during battery charge/discharge cycles, while simultaneously collecting electrochemical data using STEM.