Ionic transport properties in amorphous Li-containing Si electrodes

Silicon is a promising anode material of Li-ion batteries, since it has high Li storage capacity, low discharge voltage, and low cost. However, the slow ionic transport associated with large stress generation, large volume change during charge/discharge, and crack formation limit the durability of Si-based negative electrodes. In order to design the Si electrodes with required performance, Cheng’s group is working on understanding the fundamental mechanisms of Li-ion transport in Si electrodes through atomic scale calculations. A number of complications are coupled in this problem, such as: 1) Si electrodes are always operated in amorphous states; 2) Li diffusion is coupled with mechanical effects, concentration effects. The outcome of this study will help guide the design of Si electrodes based on improved basic understanding of the transport problems in amorphous alloys.

Students:

Jie Pan, Qinglin Zhang, Dingying Dang

Funding:

NSF GOALI, DOE BATT, General Motors

Collaborators:

Matthew Beck (UK CME), Juchuan Li (ORNL), Xingcheng Xiao (GM), Mark W. Verbrugge (GM), Yue Qi (MSU)

Understanding the properties of Solid Electrolyte Interphase (SEI)

The properties of SEI formed on electrodes have been recognized as critically important for the durability of lithium ion battery electrodes, such as Si. An ideal SEI should be an electronic insulator, ionic conductor, and an effective passivation which prevents exposure of Si to the electrolyte. However, the naturally formed SEI on the surface of Si electrodes does not satisfy these requirements and thus can lead to severe degradation and capacity loss during cycling. Cheng’s group is working on engineered SEIs with desired mechanical, transport, and electrochemical properties, to improve the performance and durability of lithium ion batteries, using a combination of experimental and computational methods. Ab initio molecular mechanics, molecular dynamics simulations, computational spectroscopy, and finite element modeling are important for the modeling aspects of the projects. This study will provide essential knowledge to guide the design of electrodes and the new generation of electrolytes.

Students:

Qinglin Zhang, Jie Pan, Dingying Dang

Jacob Bonta, Added 12/11/2020

Funding:

NSF GOALI, DOE BATT, General Motors

Collaborators:

Yue Qi (MSU), Xingcheng Xiao (GM), Mark W. Verbrugge (GM), Matthew Beck (UK CME)

Ionic transport properties in self-healing composite electrodes

Cheng’s group demonstrated that room temperature liquid metals, such as Ga, can be integrated in battery electrodes to achieve self-healing of cracks, thus improving the durability of lithium ion batteries. Presently, Cheng’s group is incorporating liquid metals in high capacity electrode materials, such as Si, that are prone to cracking upon charge-discharge cycling. Computational modeling is used to help design and optimize liquid metal based composite electrodes to achieve high electric conductivity and high ionic conductivity. As a result, the kinetics, e.g., diffusion coefficients, is an important factor in liquid based composites electrodes. Cheng’s group is engaged in studying the mechanisms of Li ion transport and lithiation-induced phase transformation in Ga and other liquid metals using quantum mechanics and molecular dynamics calculations. The modeling results will guide the development of liquid metal based electrodes with high energy and power density, as well as long durability.

Students:

Jie Pan, Jiagang Xu, Dingying Dang

Jacob Bonta, Added 12/11/2020

Funding:

NSF GOALI and General Motors

Collaborators:

Matthew Beck (UK CME)

Software:

Research Tools
Quantum Mechanical Calculations
• VASP (commercial code)
• Gaussian09 (commercial code)
• Abinit (open-source software)
• MedeA

Molecular Dynamics / Molecular Mechanics
• LAMMPS (open-source software)
• GROMACS (open-source software)
• ESPResSo (open-source software)

Finite Element Analysis
• COMSOL (commercial software)
• ABAQUS (commercial software)

Data Analysis
• Matlab / Octave
• Origin / MS Excel
• FORTRAN / C / C++ / Bash / Python / etc.

Publications:

Qignlin Zhang, Jie Pan, Xingcheng Xiao, Y.T. Cheng, “Relationships between Synthesis Condition, Structure, Elastic Properties, and the Cycling Performance of Solid Electrolyte Interphase, ” in preparation, to be submitted to Nature Communications
Jie Pan, Qinglin Zhang, Y.T. Cheng, M. Beck, “Coupling Effect of Li Diffusion and Stress in Amorphous Si Electrodes for Li-ion Batteries, ” in preparation, to be submitted to Nano Letters

Grants

Cheng Yang-Tse TCS68344 PR3731RY 001 A combined experimental and modeling approach for the design of high current efficiency Si electrodes General Motors Research 6/1/2013 - 8/31/2017 $205,393
Cheng Yang-Tse NO ID Scope KY EPSCoR: Powering the Kentucky Bioeconomy for a Sustainable Future (Cheng Scope) KY Council on Postsecondary Education 6/1/2014 - 5/31/2015
Cheng Yang-Tse TCS39242 Lithium Ion Battery Anodes General Motors Research 9/1/2010 - 8/31/2016 $94,225
Cheng Yang-Tse TCS56605 Develop surface coatings to improve the cyclic efficiency of lithium ion batteries General Motors Research 5/7/2012 - 5/30/2014 $199,147
Cheng Yang-Tse IIA-1355438 Scope NSF EPSCoR: Powering the Kentucky Bioeconomy for a Sustainable Future (Battery Scope) National Science Foundation 6/1/2014 - 7/31/2019
Cheng Yang-Tse CMMI-1000726 "GOALI: Understanding and Controlling Coupled Mechanical and Chemical
Degradation Phenomena within Insertion Electrodes" National Science Foundation 6/1/2010 - 11/30/2014 $325,000
Cheng, Y T TCS68344 PR3731RY 001 A combined experimental and modeling approach for the design of high current efficiency Si electrodes $57,572 General Motors Research 6/1/2013 5/31/2014