Electrochemical Deposition in Energy Storage Devices

Student: Witness Martin

Degree: Ph.D, December 2020

Major Professor: Dr. Jie Xiao

Research Area(s):

Conventional Materials and Processes

View Research Quadslide

Background/Relevance

    • Conventional energy storage devices utilize either aqueous or non-aqueous electrolytes to facilitate the electrochemical deposition of metals within the liquid electrolyte.
    • In the presence of organic solvents, a passivating solid electrolyte interface (SEI) develops on the surface of metals such as lithium during the electrochemical deposition process. While in aqueous systems this passivation layer does not exist.
    • By studying the deposition processes of metal ions in the presence and absence of the SEI a deeper understanding of the factors influencing the cycling of Li metal can be garnered to develop next generation Li metal batteries.

Approach

  • Investigate the diffusion, nucleation and growth of silver under varying currents, various anions, and cation concentrations in an aqueous system.
  • Develop novel electrolytes for use in Li-S battery systems through carefully selected solvents, co-solvents and additives.
  • Investigate the diffusion, nucleation and growth of Li under varying deposition currents, various anions, Li solvation structures and cation concentrations in the non-aqueous system using a microelectrode tool.
  • Investigate novel electrolytes in a Li-S coin cell setup.

Key Results

  • An increase of the Ag cation concentration resulted in a reduced nucleation density as shown in the SEM imaging below.
  • Deposition current density also has an affect on the nucleation rate and crystal size of the deposited Ag material.
  • The novel non-aqueous electrolytes resulted in an improvement of the Coulombic Efficiency of the Li-S coin cell.

Conclusions

  • Cation concentration adjustment has a significant affect on concentration gradient of the system which has a resultant affect on the nucleation and morphology of the deposited material.

  • Increased current density results in faster system kinetics and a propensity towards dendritic growth of the metal.

  • Key performance indicators have shown that the novel non-aqueous electrolytes offer a potential avenue to improve the Li-S system.

Future Work

  • Expand the study of the novel non-aqueous electrolytes to observe their performance in a Li-S system.