Electrochemical Kinetics of SEI Growth on Carbon Black: Part II. Modeling

Abstract

Mathematical models of capacity fade can reduce the time and cost of lithium-ion battery development and deployment, and growth of the solid-electrolyte interphase (SEI) is a major source of capacity fade. Experiments in Part I reveal nonlinear voltage dependence and strong charge-discharge asymmetry in SEI growth on carbon black negative electrodes, which is not captured by previous models. Here, we present a theoretical model for the electrochemical kinetics of SEI growth coupled to lithium intercalation, which accurately predicts experimental results with few adjustable parameters. The key hypothesis is that the initial SEI is a mixed ionelectron conductor, and its electronic conductivity varies approximately with the square of the local lithium concentration, consistent with hopping conduction of electrons along percolating networks. By including a lithium-ion concentration dependence for the electronic conductivity in the SEI, the bulk SEI thus modulates the overpotential and exchange current of the electrolyte reduction reaction. As a result, SEI growth is promoted during lithiation but suppressed during delithiation. This new insight establishes the fundamental electrochemistry of SEI growth kinetics. Our model improves upon existing models by introducing the effects of electrochemical

Review on multi-scale models of solid-electrolyte interphase formation

“…SEI profiles simulated with this mechanism share the same features as those described above for electron conduction. Recent continuum models highlight the unique exponential dependence of SEI growth rate on electrode potential for this mechanism [38,43]. The first such model by Single et al points out that the concentration of radicals at the electrode is determined by its electric potential [38].…”

Revealing electrolyte oxidation via carbonate dehydrogenation on Ni-based oxides in Li-ion batteries by in situ Fourier transform infrared spectroscopy

“…Understanding the (electro-)chemical reactions at the electrified interface between positive electrodes and electrolyte is crucial to develop Li-ion batteries with long cycle life and safety. [1][2][3][4] Layered lithium metal oxides are the most common positive electrode materials, among which LiNi x Mn y Co 1ÀxÀy O 2 (NMC) provides high capacities and potentially lower costs for use in electric vehicles. [5][6][7][8][9] While increasing Ni content in NMC from LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NMC111), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NMC622) to LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NMC811) can greatly increase initial discharge capacities, 5,6,10 the capacity retention decreases during cycling, 10,11 which is accompanied by earlier onset for gas (O 2 and CO 2 ) evolution.…”

Solid–Electrolyte Interphase During Battery Cycling: Theory of Growth Regimes

“…[7,[27][28][29] On the mesoscale, detailed continuum modelss hed light on the processes at the electrochemical interfaces. [30][31][32] In these mesoscale models, it is well-established that transport processes limit SEI growth during long-term battery storage.T ransport limitations lead to ac apacity fade proportionalt ot he square root of elapsed time, that is, p t. Different mechanismsw ere proposed to explain this behavior, [6,33] including solvent diffusion, [2,[30][31][32][34][35][36][37][38][39][40] electronc onduction, [4,30,32,37,[41][42][43][44] electron tunneling, [31,36,45] and the diffusion of neutral lithium atoms. [18,31,46] In ac omparative study of these mechanisms, Single et al [31] identifiedn eutral lithiumd iffusion as likely transport mechanism because it explains the state of…”