Material Design Strategies to Achieve Simultaneous High Power and High Energy Density
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.325
Material Design Strategies to Achieve Simultaneous High Power and High Energy Density Qiyuan Wu1,ŧ, Calvin D. Quilty2,ŧ, Kenneth J. Takeuchi2,3, Esther S. Takeuchi1,2,3, Amy C. Marschilok1,2,3,* 1Energy
and Photon Sciences Directorate, Brookhaven National Laboratory, Upton, NY 11973
2Department
of Chemistry, Stony Brook University, Stony Brook, NY 11794
3Department of Materials Science and Chemical Engineering, Stony Brook University, Stony Brook, NY 11794
ŧ
Equivalent contributions. * corresponding author: [email protected].
ABSTRACT
Emerging applications require batteries to have both high energy and high power which are not necessarily compatible. The typical inverse relationship between power and energy in batteries is often due to the slow ion diffusion in electrode materials. While the optimization of current battery technology may be sufficient to fully address this issue, we present here that novel chemistry-focused strategies based on new fundamental understanding of materials may be applied to lead to the development of a new generation of batteries that store energy sufficiently and deliver it rapidly.
INTRODUCTION Fundamental electrochemistry and related ionic/electronic conduction theories indicate that battery rate capability is often kinetically limited by sluggish solid-state ion diffusion.[1] In many case, ion transfer rates are limiting relative to ion transfer rates; as such this work will focus on strategies for improving ionic diffusion. In fact, one of the key factors in achieving batteries that deliver high capacity over short (dis)charge times is the rate of ion diffusion through the lattice of host materials. Ion diffusion time, t, is controlled by three variables as described in equation 1. (1) In equation 1, x is the distance of ion diffusion, q is the dimensionality constant, and DLi is the lithium ion diffusion coefficient which is correlated to the activation energy of lithium ion diffusion (ΔG) by equation 2, where kB is the Boltzmann constant, D0 is the experimentally determined prefactor, and T is the operating temperature.
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(2) Consideration of these equations suggests three chemistry-focused strategies that can be employed to maximize ionic diffusion and (dis)charge rates in potential electrode materials through control of material properties.[2] First, diffusion distance can be reduced; which can be accomplished by synthesizing materials with smaller crystallite size and higher surface area accessed by lithium ions. Second, the dimensionality constant can be increased by fabricating structures that allow ion diffusion to occur in multiple dimensions. Third, the material can be chemically altered to reduce the activation energy required for lithium ions to di
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