The Role of Carbonate and Sulfite Additives in Propylene Carbonate-Based Electrolytes on the Formation of SEI Layers at Graphitic Li-Ion Battery Anodes

Abstract

Density functional theory (DFT) was used to investigate the effect of electrolyte additives such as vinylene carbonate (VC), vinyl ethylene carbonate (VEC), vinyl ethylene sulfite (VES), and ethylene sulfite (ES) in propylene carbonate (PC)-based Li-ion battery electrolytes on SEI formation at graphitic anodes. The higher desolvation energy of PC limits Li + intercalation into graphite compared to solvated Li + in EC. Li + (PC) 3 clusters are found to be unstable with graphite intercalation compounds and become structurally deformed, preventing decomposition mechanisms and associated SEI formation in favor of co-intercalation that leads to exfoliation. DFT calculations demonstrate that the reduction decomposition of PC and electrolyte additives is such that the first electron reduction energies scale as ES > VES > VEC >PC. The second electron reduction follows ES > VES > VEC > VC > PC. The reactivity of the additives under consideration follows ES > VES > VEC > VC. The data demonstrate the supportive role of certain additives, particularly sulfites, in PC-based electrolytes for SEI film formation and stable cycling at graphitic carbon-based Li-ion battery anodes without exfoliation or degradation of the anode structure. The lithium ion battery has been one of the primary power sources driving the digital age, and witnessed a resurgence in interest with the advent of nanoscale materials and advances in cell performance. [1][2][3][4][5][6] Much of the processes and mechanisms underpinning carbonate-based electrolytes in Li-ion batteries, particularly at the anode, still need to be resolved. 7,8 Some commonly used organic solvents are ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) etc. These organic electrolytes are decomposed during intercalation of lithium ions into graphite anode, resulting in the formation of the crucial solid electrolyte interphase (SEI) film. [9][10][11] This film plays an important role in determining capacity retention, cycle life and safety concerns in lithium ion batteries.12,13 SEI films typically comprise Li 2 O, Li 2 CO 3 and related carbonates, LiF (depending on salt used), and polymer phases together with olefins.14 Effective SEI films provide stable surface passivation without significant reduction in electron conduction (higher transfer resistance). On carbon (graphite) anodes, stable SEI films are crucial for stable cycling and are formed below ∼0.8 V vs. Li + /Li. In practical applications of lithium-ion batteries, the selection of the electrode material is critical, particularly when using high surface area nanomaterials. 15 Enhanced chemical stability against electrolyte oxidation and reduction, high ionic conductivity, high boiling points, and low melting points are required, as well as the ability to solvate a wide range of lithium salts such as LiPF 6 , LiBF 4 or LiClO 4 , 16-21 in aprotic and organic solvents such as ethylene carbonate (EC), propylene carbonate (PC), their mixtures, and ...

Review on modeling of the anode solid electrolyte interphase (SEI) for lithium-ion batteries

“…7 Ushirogata et al 107 proposed that the SEI film formation process follows b a near-shore aggregation mechanism instead of a a surface growth mechanism, meaning the reduced electrolyte compounds with limited solubility in the electrolyte can desorb into the electrolyte near the electrode surface, form aggregates, then deposit on the electrode surface to complete the SEI formation (Copyright: The Electrochemical Society) In terms of reduction potential, PC is more difficult to be reduced than EC and VC, 15,111 and more specifically, follows the order of VC > EC > PC for the second electron reduction. 74,118 The ring-opening reaction of VC occurs via a homolytic C (carbonyl carbon)-O rupture first in the solvated complex 111 and is more likely to undergo the second electron reduction than EC or PC. 74 Ushirogata et al 119 considered the effect of VC from both thermodynamic and kinetic point of view via AIMD simulations.…”

“…126 The reduction 127 The sulfite additives were demonstrated to be more efficient than carbonate additives in PC-based electrolytes. 118 Similarly, other sulfites 118 including vinyl ethylene sulfite (VES), butylene sulfite (BS), [128][129][130] sulfuric esters (SE), sultone (PS and PES), fluorinated sultone (FPS), and 1, 3-benzodioxol-2-one (BO) were reported to show higher reduction voltages in calculations and improved capacity retention in experiments (suggesting better SEI) for PCbased electrolytes. [124][125][126][127][128][129][130][131][132][133][134][135] However, none of these studies went on to further comment if the additives lead to any changes in the chemistry, morphology, and properties of the SEI, such as the density, cohesive energy, solubility, and porosity, which were associated with SEI performance as argued by Tasaki 74 and Takenaka et al 108 More additive examples with relatively larger molecular formula were also investigated and are summarized in Table 2.…”

Properties of Ion Complexes and Their Impact on Charge Transport in Organic Solvent-Based Electrolyte Solutions for Lithium Batteries: Insights from a Theoretical Perspective

“…Most often, the ion-solvent cluster is also embedded into a local continuum background with global dielectric constant to increase the accuracy of the calculations. With regard to this attempt, the lithium ion solvation energy can be computed by [56,134]…”

Conductivity and Dielectric Studies of Lithium Trifluoromethanesulfonate Doped Polyethylene Oxide-Graphene Oxide Blend Based Electrolytes

“…The peak shape also has become broad and less intense compared to the peak without addition of ES. Bhatt and O'Dwyer [35] used computational studies to predict theoretical FTIR spectra on ES as additives in propylene carbonate-based Li-ion battery electrolyte in which wavenumber of C=O of propylene carbonate increases as a result of a significant change in the bond length due to the interaction of ES on C=O frequency. This demonstrates that changes in wavenumber could be possibly due to interaction between ES and PEO-GO-LiCF 3 SO 3 system that alter the bond length of C=O of the polymer host.…”