On Graded Electrode Porosity as a Design Tool for Improving the Energy Density of Batteries

(Top) Optimization performance for specific energy (Wh/kg) based on two designs: constant and varying-porosity.
(Bottom) The effect of various Bruggeman exponent on cell performances by two designs: constant-porosity and varying-porosity

Scientific Achievement

A clear and unambiguous quantification of the improvements of a varying porosity design is provided using a mathematical approach.

Significance and Impact

This work shows that varying the porosity can only lead to marginal improvements in energy density compared to well-designed constant-porosity electrodes, and suggests that focusing on decreasing the tortuosity would be a better approach.

Research Details

  • An optimization algorithm is developed that allows identification of the optimal design (porosity and thickness) to maximize the energy density for a given time of discharge.
  • The optimal constant-porosity and varying-porosity designs are compared in energy density at different time of discharge requirements, showing little improvement when using a varying porosity design compared to a constant porosity design
  • The effect of tortuosity variation, represented as a decreasing Bruggeman exponent, on energy density is explored, which shows that decreasing the tortuosity leads to a significant increase in energy density.

Work performed at Lawrence Berkeley National Laboratory (JCESR partner) by Yiling Dai and Venkat Srinivasan; J Electrochem Soc, 2016, 163(3), A406-A416. DOI:10.1149/2.0301603jes

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