Simulation of bi-layer cathode materials with experimentally validated parameters to improve ion diffusion and discharge capacity

Abstract

Simulation shows that higher electrode utilization (next to current collector) and first discharge capacity can be achieved at high C-rates with bi-layer design compare to conventional electrodes, alongside an increase in energy-power density.

Revisiting the promise of Bi-layer graded cathodes for improved Li-ion battery performance

“…The average particle diameter for big and small particles are ~ 10µm and ~1µm respectively, confirmed by statistical image analysis. A similar PSD was observed in our previous work on NMC811 [27]. The BET surface area of the milled powder sample is .…”

“…The electrode slurries with small and big particles were dried in an oven at 70° C and 80° C respectively for 10 hours. The further description of the slurry mixing process, single layer electrode fabrication process, and the justification of choosing certain slurry compositions can be found in our previous work on LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) [27]. A recent study has revealed that Ni-rich NMC811 is prone to surface contamination during electrode processing because of its high surface reactivity under ambient air exposure, leading to rapid capacity fade [31].…”

“…Our previous modelling work on graded cathodes predicted that higher electrode utilization (next to the CC) and discharge capacity at higher C-rates (1-4C) can be achieved by positioning large particles with higher porosity in a layer next to the separator and small particles with lower porosity in a layer next to the CC [27]. Such a bi-layer design exhibited an increase of 47.7% in energy density without compromising power density compared to a conventional single layer electrode consisting of big particles at 4C.…”

Biopolimer Peptide Batteries—A New Concept for Environmentally Friendly and Safer Energy Storage

“…These mechanisms lead to an increase in the reaction rate-the number of reactions per unit time-which causes an increase in the potential on the galvanostatic curve. Similar processes occur in [18], where for an inorganic material with smaller particles, the discharge curve is formed at relatively higher potentials and the efficiency of reactions increases. On the other hand, there is an additional increase in surface energy due to the addition of lithium ions to the structure, which in turn leads to a decrease in the energy difference before and after the introduction of lithium [21].…”

“…As a result of the discharge at the cathode/electrolyte interface, the concentration of lithium cations whose penetration into the cathode volume is limited by the mass transfer of the interface and the diffusion coefficient increases. The interaction of lithium ions with the interface and the presence of electrolyte anions can cause a number of undesirable surface reactions that will cause the formation of a passivating film on the cathode surface [17][18][19], which will complicate the further transport of lithium ions. The contribution of such a layer will be reflected in the impedance in the form of an increase in the semicircle responsible for the boundary resistance.…”