© Yanxin Chen
Quantum mechanics replaces laboratory experiment
To get a better understanding of Li-Ion batteries, junior researchers are using
quantum mechanical methods. The multiscale modelling of batteries,
which is based on quantum mechanical principles, is an option to
develop electrodes and electrolytes using computer-based simulations.
The virtual development of batteries is not only accurate and fast, but
also offers other benefits, since the costs are lower than those of
laboratory experiments. In this way one single experiment can be
sufficient to confirm the computer-based results.
| Project status | Near completion |
|---|---|
| Project duration | January 2012 until December 2016 |
Recent trends in device miniaturization and portability, especially in the development of hybrid and electrical cars, have favored the use of energy storage devices with a high energy density. Li-based batteries are promising candidates as they provide a high storage capacity, long lifetime, and flexible design. By combining various theoretical methods and the development of new methods, we aim to enhance our understanding of the structures, materials properties, and processes relevant for all-solid-state and lithium-sulphur batteries.
The realistic modelling of batteries is very complex and requires different theoretical and numerical approaches since the relevant processes occur on the large range of time and length scales. We plan to develop a multiscale modeling approach to bridge the gap between the different time and length scales and apply these methods to study the structure and stability of the different battery materials (i.e. electrodes, solid or liquid electrolytes, and their interfaces) and their influences on the electronic and macroscopic properties.
Method provides data for battery system
Although many fundamental studies and method developments have been performed to study the crucial processes of energy storages on the various time and length scales, there is still need for careful ab inito studies and the development of multiscale methods such as QM/MM and MD for studying next-generation all-solid-state and Li-S batteries. Making these methods accessible to theoretical studies on energy storage problems and process is the main goal of this junior research group supported by BMBF at Ulm University.
In this project the researchers aim to enhance their understanding of the structure and stability of materials and processes relevant for all-solid-state and Li-S batteries by a bottom-up approach ranging from first-principles to continuum modelling. This work will provide the necessary data and parameters for all-ab initio modelling of battery systems, which cover the various length and time scales.
Multiscale modelling of batteries can be viewed as a tool to virtually design electrodes and electrolytes based on quantum mechanical principles. This virtual battery design is not only accurate and fast, but also beneficial since it is expected to be less expensive than costs of test labours. In this way, a single experiment is sufficient to confirm the computational results.
Sub-projects
- Microscopic modelling based on density functional theory (DFT):
a: Intercalation of Li+: Using DFT calculations we will investigate in details of Li+ intercalation into the cathode and anode materials. Here we aim to calculate the electronic and geometric structure as well as diffusion mechanism and barriers involved in the intercalation process.
b: Ion diffusion in electrolyte: Using DFT calculations we study diffusion of Li+ ions in solid-state electrolytes. This study will help to elucidate the Li+ conduction in all-solid-state-batteries. Using the energy profile for different possible paths the activation energy will be evaluated. Our goal is to determine the transport kinetics and improve our understanding of this process and to study factors that limit the rate of the ion transport. - QM/MM simulations:
The goal is to develop a QM/MM simulation technique, which can describe the important phenomena at electrolyte/electrode interfaces such as (de-)intercalation processes. This allows avoiding the necessity of explicitly tracking very large number of atoms by QM approaches and therefore treating extremely large systems which are out of the reach of pure QM calculations. - Molecular-dynamics simulations:
Molecular dynamics simulations provide reliable accuracy relevant to extended time and length scales. Ab initio molecular dynamics (based on QM) simulations will be used to study Li ion transport in electrode and electrolyte. The effect of temperature on the diffusion barriers will be determined. - Continuum modelling and comparison to experiment:
The junior researchers plan to incorporate the previously described ab initio calculations to this developed continuum model to simulate time-dependent Li+ diffusion within the electrodes and electrolytes as well as the electrochemical intercalation of Li+ into the electrodes. They believe that this first-principles-based continuum approach can be a promising tool to deepen their understanding of crucial processes in energy storages. The validity of their methods will be examined through comparison of the calculated results with the experimental measurements. The next logical step will be to extend this study to other cell systems and predict their practical properties
Working packages
WP1:
- M1.1 03.2012
Perform convergence tests to find the optimal computational and modelling parameters for the microscopic simulations (QM calculations) - M1.2 03.2013
Obtain the mechanism and energy barrier of Li intercalation+ (de-intercalation) into (from) LiCoO2, graphite, Si and Sn (all-solid-state-battery electrodes) - M1.3 10.2013
Determine the most favourable structure of Li-polysulfides and carbon-based electrodes (single graphene layers, graphite surfaces, and different carbon nanotubes) in Li-S batteries - M1.4 04.2014
Determine the structure and stability of the Li-polysulfide/carbon-based electrode interfaces in Li-S batteries - M1.5 12.2014
Find the mechanism and energy barrier for Li ion diffusion in LiI/Al2O3, Garnet-type Li5La3M2O12, and Li7La3Zr2O12 (all-solid-state-battery electrolytes)
WP2:
- M2.1 06.2012
Develop mathematical formulation for QM/MM method - M2.2 12.2013
Implement QM/MM method as a computer program - M2.3 06.2014
Test validity of QM/MM method by comparing calculated results with experimental measurements - M2.4 12.2015
Apply QM/MM method to study the interface of the electrodes and electrolytes mentioned in WP1
WP3:
- M3.1 12.2014
Simulate Li+ ion transport in the LiCoO2 electrode as well as LiI/Al2O3 and Li5La3M2O12 electrolytes (all-solid-state-battery materials) at the atomic scale using ab initio molecular dynamics (MD) - M3.2 08.2015
Construct reactive force fields describing the electrode and electrolytes mentioned in M3.1 - 3.3) 12.2015
Simulation von strukturellen, dynamischen, und mechanischen Eigenschaften der Elektrode/Elektrolyt Grenzschichten über längere Zeit- und Raumskalen mit Hilfe des reaktiven Kraftfelds aus 3.2
WP4:
- M4.1 12.2015
Incorporate the ab initio-based results (QM, QM/MM, and MD) into the continuum model for first-principles-based continuum modelling of a Li-ion battery - M4.1 12.2015
Incorporate the ab initio-based results (QM, QM/MM, and MD) into the continuum model for first-principles-based continuum modelling of a Li-ion battery - M4.3 12.2016
Create a tool package to combine the atomistic and continuum approaches in the multi-scale simulation framework
