Nano-Materials Design for Enhanced Thermal and Mechanical Properties

Principal Investigator: Levi T. Thompson, University of Michigan, ltt@umich.edu
Student: Siu on Tung, University of Michigan
Government: Yi Ding, Ground Vehicle Power & Mobility, U.S. Army TARDEC
Industry: Hans Herferth, Fraunhofer USA

Li pillar nano structuresLayered oxides such as LiCoO2 are widely used in the cathodes of commercial lithium ion batteries due to their high capacities and energy densities but their mechanical and thermal properties can lead to safety and reliability (e.g. cycle life) challenges in particular for military vehicle applications that are characterized by wide operating temperature ranges, high power outputs, and harsh vibration and shock environments. Stresses induced in oxide particles on repeated lithium insertion and extraction, for example, can cause mechanical fracture, a suspected contributor to capacity fade and resistance increases (ref. 1, 2, 3, 4, 5). We will address shortcomings associated with the layered oxides by modifying their nanoarchitecture (ref. 6).

The premise of this project is that the mechanical and thermal challenges associated with the layered oxide materials can be addressed by incorporating pillaring agents between their layers. This modification is expected to reduce stresses caused by lithium insertion and enhance lithium diffusion thereby improving cycle-life, capacities at high power and resistance to thermal runaway.

The objectives of research are to prepare intercalated two-dimensional lithium ion battery cathode materials, and characterize their structural, compositional, electrochemical, thermal and mechanical characteristics in order to establish a scientific basis for their performance. Nano sized aluminum oxide, titanium oxide or silicon oxide domains are attractive pillaring agents to support the layers and minimize structural expansion and contraction. While considerable research has been conducted to pillar layered aluminosilicates as well as other layered compounds, we are not aware of any efforts to achieve this architecture with the high energy layered oxides used in lithium ion batteries. We will investigate the pillaring of a number of lithium metal oxides including lithium cobalt and lithium nickel-obalt-aluminum oxides.

References:

  1. Y.-T. Cheng and M. W. Verbrugge,“ The influence of surface mechanics on diffusion induced stresses within spherical nanoparticles,” J. Appl. Phys. 104, 083521 (2008).
  2. M. W. Verbrugge and Y.-T. Cheng, “Stress Distribution within Spherical Particles Undergoing Electrochemical Insertion and Extraction,” The Electrochemical Society (ECS) Transactions 16, 127 (2008).
  3. Y.-T. Cheng and M. W. Verbrugge, “Evolution of stress within a spherical insertion electrode particle under potentiostatic and galvanostatic operation,” J. Power Sources 190, 453 (2009).
  4. W.H. Woodford, Y-M Chiang and W.C. Carter, “’Electrochemical Shock’ of Intercalation Electrodes: A Fracture Mechanics Analysis, J. Electrochem. Soc. 157(10) A1052 (2010).
  5. Y.R Wan and H-Y S. Huang, “Lithium-Ion Battery Materials and Mechanical Stress Fields, Transaction on Control and Mechanical Systems 1(5), 192 (2012).
  6. Kang, K., Meng, Y., Bréger, J., Grey, C. and Ceder, G. “Electrodes With High Power And High Capacity For Rechargeable Lithium Batteries, “Science 311, 977 (2006).