Using Atomic Layer Deposition to Hinder Solvent Decomposition in Lithium Ion Batteries: First-Principles Modeling and Experimental Studies (original) (raw)
Related papers
Interfaces and Materials in Lithium Ion Batteries: Challenges for Theoretical Electrochemistry
Topics in current chemistry (Cham), 2018
Energy storage is considered a key technology for successful realization of renewable energies and electrification of the powertrain. This review discusses the lithium ion battery as the leading electrochemical storage technology, focusing on its main components, namely electrode(s) as active and electrolyte as inactive materials. State-of-the-art (SOTA) cathode and anode materials are reviewed, emphasizing viable approaches towards advancement of the overall performance and reliability of lithium ion batteries; however, existing challenges are not neglected. Liquid aprotic electrolytes for lithium ion batteries comprise a lithium ion conducting salt, a mixture of solvents and various additives. Due to its complexity and its role in a given cell chemistry, electrolyte, besides the cathode materials, is identified as most susceptible, as well as the most promising, component for further improvement of lithium ion batteries. The working principle of the most important commercial elect...
ACS Applied Energy Materials, 2019
One of the major bottlenecks to the development of alternatives to existing Li ion battery technology, such as Li metal or multivalent ion (Mg, Ca, Zn, or Al) batteries, has to do with the layer of inorganic and organic compounds that forms at the interface between the metallic anode and electrolyte via solvent and salt decomposition (the solid− electrolyte interphase or SEI). In Li metal batteries the growth of dendrites causes continual formation of new SEI, while in multivalent ion batteries the SEI does not allow for the diffusion of the ions. Finding appropriate electrolytes for such systems and gaining an understanding of SEI formation is therefore critical to the development of secondary Li metal and multivalent ion cells. In this work, we use ab initio molecular dynamics simulations to investigate the initial stages of decomposition of organic electrolytes based on ethylene carbonate (EC) and formation of the SEI on Li, Ca, and Al metal surfaces. We first find that pure EC only decomposes to CO and C 2 H 4 O 2 2− species on each type of surface. However, when a salt molecule is introduced to form an electrolyte, a second EC decomposition route resulting in the formation of CO 3 2− and C 2 H 4 begins to occur; furthermore, a variety of different inorganic compounds, depending on the chemical composition of the salt, form on the surfaces. Finally, we find that EC breaks down more quickly on Li and Ca surfaces than on Al and show that this is because the rate of charge transfer is much faster owing to their lower electronegativity and ionization energies. The molecular level understanding of decomposition and SEI formation generated by this computational modeling can lead to the design of new electrolytes for beyond-Li ion batteries.
Journal of the American Chemical Society, 2001
Reductive decomposition mechanisms for ethylene carbonate (EC) molecule in electrolyte solutions for lithium-ion batteries are comprehensively investigated using density functional theory. In gas phase the reduction of EC is thermodynamically forbidden, whereas in bulk solvent it is likely to undergo one-as well as two-electron reduction processes. The presence of Li cation considerably stabilizes the EC reduction intermediates. The adiabatic electron affinities of the supermolecule Li + (EC) n (n ) 1-4) successively decrease with the number of EC molecules, independently of EC or Li + being reduced. Regarding the reductive decomposition mechanism, Li + (EC) n is initially reduced to an ion-pair intermediate that will undergo homolytic C-O bond cleavage via an approximately 11.0 kcal/mol barrier, bringing up a radical anion coordinated with Li + . Among the possible termination pathways of the radical anion, thermodynamically the most favorable is the formation of lithium butylene dicarbonate, (CH 2 CH 2 OCO 2 Li) 2 , followed by the formation of one O-Li bond compound containing an ester group, LiO(CH 2 ) 2 CO 2 (CH 2 ) 2 OCO 2 Li, then two very competitive reactions of the further reduction of the radical anion and the formation of lithium ethylene dicarbonate, (CH 2 OCO 2 -Li) 2 , and the least favorable is the formation of a C-Li bond compound (Li carbides), Li(CH 2 ) 2 OCO 2 Li. The products show a weak EC concentration dependence as has also been revealed for the reactions of LiCO 3with Li + (EC) n ; that is, the formation of Li 2 CO 3 is slightly more favorable at low EC concentrations, whereas (CH 2 OCO 2 Li) 2 is favored at high EC concentrations. On the basis of the results presented here, in line with some experimental findings, we find that a two-electron reduction process indeed takes place by a stepwise path. Regarding the composition of the surface films resulting from solvent reduction, for which experiments usually indicate that (CH 2 OCO 2 Li) 2 is a dominant component, we conclude that they comprise two leading lithium alkyl bicarbonates,
Physical chemistry chemical physics : PCCP, 2010
The decomposition of ethylene carbonate (EC) during the initial growth of solid-electrolyte interphase (SEI) films at the solvent-graphitic anode interface is critical to lithium ion battery operations. Ab initio molecular dynamics simulations of explicit liquid EC/graphite interfaces are conducted to study these electrochemical reactions. We show that carbon edge terminations are crucial at this stage, and that achievable experimental conditions can lead to surprisingly fast EC breakdown mechanisms, yielding decomposition products seen in experiments but not previously predicted.
The Journal of Physical Chemistry C, 2019
Understanding the solvent decomposition mechanisms at the electrode-electrolyte interface is of great importance to mitigate capacity fading and improve cycling performance of batteries. Firstprinciples calculations were conducted to study the oxidative decomposition reactions of ethylene carbonate (EC) on the (110) surfaces of LiCoO 2 (LCO) and LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM) in lithium ion batteries (LIBs). All the possible oxidative decomposition reaction steps of EC on cathode surfaces, including the H-abstraction reaction and ring-opening reactions caused by C cO e and/or C e-O e bond cleavage, were analyzed from both thermodynamic and kinetic aspects. Our calculation results indicated that EC decompositions were initiated by the ring-opening reaction as the first step reaction on both LCO and NCM surfaces, which was caused by C cO e bond cleavage
The Journal of Physical Chemistry B, 2005
The density functional theory (DFT) calculations have been performed for the reduction decompositions of solvents widely used in Li-ion secondary battery electrolytes, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonates (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), including a typical electrolyte additive, vinylene carbonate (VC), at the level of B3LYP/6-311+G(2d,p), both in the gas phase and solution using the polarizable conductor calculation model. In the gas phase, the first electron reduction for the cyclic carbonates and for the linear carbonates is found to be exothermic and endothermic, respectively, while the second electron reduction is endothermic for all the compounds examined. On the contrary, in solution both first and second electron reductions are exothermic for all the compounds. Among the solvents and the additive examined, the likelihood of undergoing the first electron reduction in solution was found in the order of EC > PC > VC > DMC > EMC > DEC with EC being the most likely reduced. VC, on the other hand, is most likely to undergo the second electron reduction among the compounds, in the order of VC > EC > PC. Based on the results, the experimentally demonstrated effectiveness of VC as an excellent electrolyte additive was discussed. The bulk thermodynamic properties of two dilithium alkylene glycol dicarbonates, dilithium ethylene glycol dicarbonate (Li-EDC) and dilithium 1,2-propylene glycol dicarbonate (Li-PDC), as the major component of solid-electrolyte interface (SEI) films were also examined through molecular dynamics (MD) simulations in order to understand the stability of the SEI film. It was found that film produced from a decomposition of EC, modeled by Li-EDC, has a higher density, more cohesive energy, and less solubility to the solvent than the film produced from decomposition of PC, Li-PDC. Further, MD simulations of the interface between the decomposition compound and graphite suggested that Li-EDC has more favorable interactions with the graphite surface than Li-PDC. The difference in the SEI film stability and the behavior of Li-ion battery cycling among the solvents were discussed in terms of the molecular structures.
Reactive molecular dynamics simulations of Lithium-ion battery electrolyte degradation
2024
The development of reliable computational methods for novel battery materials has become essential due to the recently intensified research efforts on more sustainable energy storage materials. Here, we use a recently developed framework allowing to consistently incorporate quantum-mechanical activation barriers to classical molecular dynamics simulations to study the reductive solvent decomposition and formation of the solid electrolyte interphase for a graphite/carbonate electrolyte interface. We focus on deriving condensed-phase effective rates based on the elementary gas-phase reduction and decomposition energy barriers. After a short initial transient limited by the elementary barriers, we observe that the effective rate shows a transition to a kinetically slow regime influenced by the changing coordination environment and the 1
Volume 6A: Energy, 2014
Lithium-air batteries are very promising energy storage systems for meeting current demands in electric vehicles. However, the performance of these batteries is highly dependent on the electrochemical stability and physicochemical properties of the electrolyte such as ionic conductivity, vapor pressure, static and optical dielectric constant, and ability to dissolve oxygen and lithium peroxide. Room temperature ionic liquids, which have high electrical conductivity, wide electrochemical stability window and also low vapor pressure, are considered potential electrolytes for these batteries. Moreover, since the physicochemical and electrochemical properties of ionic liquids are dependent on the structure of their constitutive cations and anions, it is possible to tune these properties by choosing from various combinations of cations and anions. One of the important factors on the performance of lithium-air batteries is the local current density. The current density on each electrode can be obtained by calculating the rate constant of the electron transfer reactions at the surface of the electrode. In lithium-air batteries, the oxidation of pure lithium metal into lithium ions happens at the anode. In this study, Marcus theory formulation was used to calculate the rate constant of the electron transfer reaction in the anode side using the respective thermodynamics data. The Nelsen's four-point method of separating oxidants and reductants was used to evaluate the inner-sphere reorganization energy. In addition, the Conductor-like Screening Model (COSMO) which is an approach to dielectric screening in solvents has been implemented to investigate the effect of solvent on these reaction rates. All calculations were done using Density Functional Theory (DFT) at B3LYP level of theory with a high level 6-311++G** basis set which is a Valence Triple Zeta basis set with polarization and diffuse on all atoms (VTZPD) that gives excellent reproducibility of energies. Using this methodology, the electron transfer rate constant for the oxidation of lithium in the anode side was calculated in an ionic liquids electrolyte. Our results present a novel approach for choosing the most appropriate electrolyte(s) that results in enhanced current densities in these batteries.
Journal of Power Sources, 2011
We have studied the formation and growth of solid-electrolyte interphase (SEI) for the case of ethylene carbonate (EC), dimethyl carbonate (DMC) and mixtures of these electrolytes using molecular dynamics simulations. We have considered SEI growth on both Li metal surfaces and using a simulation framework that allows us to vary the Li surface density on the anode surface. Using our simulations we have obtained the detailed structure and distribution of different constituents in the SEI as a function of the distance from the anode surfaces. We find that SEI films formed in the presence of EC are rich in Li 2 CO 3 and Li 2 O, while LiOCH 3 is the primary constituent of DMC films. We find that dilithium ethylene dicarbonate, LiEDC, is formed in the presence of EC at low Li surface densities, but it quickly decomposes to inorganic salts during subsequent growth in Li rich environments. The surface films formed in our simulations have a multilayer structure with regions rich in inorganic and organic salts located near the anode surface and the electrolyte interface, respectively, in agreement with depth profiling experiments. Our computed formation potentials 1.0 V vs. Li/Li + is also in excellent accord with experimental measurements. We have also calculated the elastic stiffness of the SEI films; we find that they are significantly stiffer than Li metal, but are somewhat more compliant compared to the graphite anode.