Recent progress in theoretical and computational investigations of Li-ion battery materials and electrolytes

There is an increasing worldwide demand for high energy density batteries. In recent years, rechargeable Li-ion batteries have become important power sources, and their performance gains are driving the adoption of electrical vehicles (EV) as viable alternatives to combustion engines. The exploration of new Li-ion battery materials is an important focus of materials scientists and computational physicists and chemists throughout the world. The practical applications of Li-ion batteries and emerging alternatives may not be limited to portable electronic devices and circumventing hurdles that include range anxiety and safety among others, to their widespread adoption in EV applications in the future requires new electrode materials and a fuller understanding of how the materials and the electrolyte chemistries behave. Since this field is advancing rapidly and attracting an increasing number of researchers, it is crucial to summarise the current progress and the key scientific challenges related to Li-ion batteries from theoretical point of view. Computational prediction of ideal compounds is the focus of several large consortia, and a leading methodology in designing materials and electrolytes optimized for function, including those for Li-ion batteries. In this Perspective, we review the key aspects of Li-ion batteries from theoretical perspectives: the working principles of Li-ion batteries, the cathodes, anodes, and electrolyte solutions that are the current state of the art, and future research directions for advanced Li-ion batteries based on computational materials and electrolyte design

Solid electrolyte interphases at Li-ion battery graphitic anodes in propylene carbonate (PC)-based electrolytes containing FEC, LiBOB, and LiDFOB as additives

Density functional theory is used to investigate the reactivity, reduction and effect of electrolyte additives such as fluoroethylene carbonate (FEC), lithium bis(oxalate) borate (LiBOB) and lithium difluoro(oxalato) borate (LiDFOB) in propylene carbonate (PC)-based Li-ion battery electrolytes. The structural, thermodynamical and calculated infra-red vibrational analyses indicate that FEC additives reduce prior to PC, providing stable SEI film formation near the graphite anode. The reduction and reaction mechanisms of LiBOB and LiDFOB influence the SEI film composition at the graphite surface. These additives contribute to stable SEI film formation without degradation of the anode structure by PC co-intercalation

Key scientific challenges in current rechargeable non-aqueous Li-O2 batteries: experiment and theory

Rechargeable Li–air (henceforth referred to as Li–O2) batteries provide theoretical capacities that are ten times higher than that of current Li-ion batteries, which could enable the driving range of an electric vehicle to be comparable to that of gasoline vehicles. These high energy densities in Li–O2 batteries result from the atypical battery architecture which consists of an air (O2) cathode and a pure lithium metal anode. However, hurdles to their widespread use abound with issues at the cathode (relating to electrocatalysis and cathode decomposition), lithium metal anode (high reactivity towards moisture) and due to electrolyte decomposition. This review focuses on the key scientific challenges in the development of rechargeable non-aqueous Li–O2 batteries from both experimental and theoretical findings. This dual approach allows insight into future research directions to be provided and highlights the importance of combining theoretical and experimental approaches in the optimization of Li–O2 battery systems

The role of carbonate and sulfite additives in propylene carbonate-based electrolytes on the formation of SEI layers at graphitic Li-ion battery anodes

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

Density functional theory calculations for ethylene carbonate-based binary electrolyte mixtures in lithium ion batteries

The density functional theory (DFT) calculations have been performed to investigate the interaction of Li+ with various organic solvents widely used as Li ion rechargeable battery electrolytes such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC); and their EC-based binary mixtures at the level of B3LYP/6-31G (d). The interaction of Li+ with these solvents has been calculated in terms of electronic structures of clusters of the mixtures of organic solvents including a lithium ion. The main objective of our investigation is to help in understanding a stable and enhancing ionic transfer at graphite/electrolyte interface assisted by the mixtures of the solvents. The calculated results favor the stability of EC-based binary mixtures and high EC-content binary mixture systems. In infrared (IR) vibrational spectra, the IR active modes of the solvent show significant changes due to the cation-solvent interaction

Solid electrolyte interphases at Li-ion battery graphitic anodes in propylene carbonate (PC)-based electrolytes containing FEC, LiBOB, and LiDFOB as additives

Density functional theory is used to investigate the reactivity, reduction and effect of electrolyte additives such as fluoroethylene carbonate (FEC), lithium bis(oxalate) borate (LiBOB) and lithium difluoro(oxalato) borate (LiDFOB) in propylene carbonate (PC)-based Li-ion battery electrolytes. The structural, thermodynamical and calculated infra-red vibrational analyses indicate that FEC additives reduce prior to PC, providing stable SEI film formation near the graphite anode. The reduction and reaction mechanisms of LiBOB and LiDFOB influence the SEI film composition at the graphite surface. These additives contribute to stable SEI film formation without degradation of the anode structure by PC co-intercalation

Current progress and scientific challenges in the advancement of organic-inorganic lead halide perovskite solar cells

The solution-processed organic-inorganic lead halide perovskite solar cells have recently emerged as promising candidates for the conversion of solar power into electricity. The certified power conversion efficiencies of these solar cells have rapidly increased from 3.8% in 2009 to 22.1% in 2016. Although the certified experimentally observed value of efficiency of perovskite solar cells to date is up to 22.1%, some main issues such as stability, lead toxicity, and hysteretic behavior in I-V characteristics in addition to high efficiencies have been creating problems regarding their industrial applications. Theoretical results to date have demonstrated that the organic-inorganic lead halide perovskites exhibit a series of superior electronic and optical properties for solar cell applications, such as proper electronic band alignment, controlled doping ability, lattice point defects, ferroelectric properties, dynamic disorder, domain walls, and local structural properties. In this review, the important properties required to produce highly efficient perovskite solar cells are discussed based on experimental and theoretical studies. We also present the key scientific challenges and future research directions for the development of this field regarding their commercialization

Density functional theory calculations for ethylene carbonate-based binary electrolyte mixtures in lithium ion batteries

The density functional theory (DFT) calculations have been performed to investigate the interaction of Li+ with various organic solvents widely used as Li ion rechargeable battery electrolytes such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC); and their EC-based binary mixtures at the level of B3LYP/6-31G (d). The interaction of Li+ with these solvents has been calculated in terms of electronic structures of clusters of the mixtures of organic solvents including a lithium ion. The main objective of our investigation is to help in understanding a stable and enhancing ionic transfer at graphite/electrolyte interface assisted by the mixtures of the solvents. The calculated results favor the stability of EC-based binary mixtures and high EC-content binary mixture systems. In infrared (IR) vibrational spectra, the IR active modes of the solvent show significant changes due to the cation-solvent interaction