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Research Papers: Computational Modeling of Polymer-Matrix Composites at Different Length Scales

Numerical Study of Composite Electrode's Particle Size Effect on the Electrochemical and Heat Generation of a Li-Ion Battery

[+] Author and Article Information
A. H. N. Shirazi

Institute of Structural Mechanics,
Bauhaus-Universität Weimar,
Marienstr. 15,
Weimar 99423, Germany
e-mail: ali.hn.s@outlook.com

M. R. Azadi Kakavand

Institute of Structural Mechanics,
Bauhaus-Universität Weimar,
Marienstr. 15,
Weimar 99423, Germany
e-mail: mohammadreza.azadi86@gmail.com

T. Rabczuk

Institute of Structural Mechanics,
Bauhaus-Universität Weimar,
Marienstr. 15,
Weimar 99423, Germany
e-mail: timon.rabczuk@uni-weimar.de

1Corresponding author.

Manuscript received October 1, 2015; final manuscript received October 30, 2015; published online April 13, 2016. Assoc. Editor: Abraham Quan Wang.

J. Nanotechnol. Eng. Med 6(4), 041003 (Apr 13, 2016) (8 pages) Paper No: NANO-15-1084; doi: 10.1115/1.4032012 History: Received October 01, 2015; Revised October 30, 2015

Rechargeable lithium-ion batteries (LIBs) are now playing crucial roles in power supply and energy storage systems. Among all types of rechargeable batteries available nowadays, LIBs are one of the most important ways to store energy because of their high energy density, high operating voltage, and low rate of self-discharge. Nonetheless, the performance of LIBs could be improved by different design parameters, such as the size of solid particles in the battery composite electrodes. Therefore, this study aims to investigate the effect of the composite electrode particles size on the electrochemical and heat generation of an LIB. A Newman's electrochemical pseudo two-dimenisonal model was used to model the LIB cell. Reversible heat produced through electrochemical reactions was calculated as well as irreversible heat originating from internal resistances in the battery cell. Our results show that smaller sizes of electrode solid particles improve the thermal characteristics of the battery, especially in higher charge and discharge currents (C-rate). Furthermore, as the solid particle sizes decrease, the battery capacity increases for various C-rates in charge and discharge cycles.

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Figures

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Fig. 1

Schematic of the one-dimensional (1D) electrochemical model in the x-direction of the battery based on the Newman's model. Intercalation of lithium ions is illustrated by small beads. Solid particle's sizes in the electrodes can be same or different. Electrolyte exists in all battery domains while solid particles exist only in electrodes.

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Fig. 2

(a) Equilibrium potential of the LixC6 and (b) LiyCoO2 versus the state of the charge of electrode. Curves of ∂U/∂T for the negative electrode (c) and the positive electrode (d). Dots are the start points of charge and discharge which are summarized with C and D [9]. All data extracted from Ref. [9] are to be used in the simulation of the current paper.

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Fig. 3

Bulk ionic conductivity (a) and bulk salt-diffusion coefficient (b) as a function of concentration [9]

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Fig. 4

Comparison between the model proposed in Ref. [9], which is shown with continuous lines, and the model constructed in the current paper according to the parameters used in Ref. [9], which are shown with circle and rectangle markers. Simulations were done for applied discharge currents of 0.5 and 1 C-rates. A cutoff voltage of 3.3 V was considered in the simulations. In a wide range of the battery discharge, the maximum difference between results of Ref. [9] and our simulation was about 1.5%. The maximum difference occurs in the voltages below 3.5 V, which has an amount of 3%.

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Fig. 5

Charge curves for the size 1(a) and size 5(c) in Table 3 at different C-rates. Discharge curves of size 1(b) and size 5(d) in Table 3 at different C-rates. At a specified C-rate, the cell voltage is plotted versus the charge and discharge capacity of the battery. For the charge process, a cutoff voltage of 4.5 V is considered and for the discharge process the cutoff voltage of 3.3 is considered for the end of the process in simulations.

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Fig. 6

Reversible heat (a) and irreversible heat (b) versus discharge capacity of the battery at different C-rates for size 5 in Table 3. Two heating and cooling zones exist for reversible heat while irreversible heat is positive in the whole range of the battery discharge. At high C-rates, irreversible heat drastically increases because it is a function of applied current with a power of two.

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Fig. 7

Maximum reversible heat in charge (MRH-C) (a) and discharge (MRH-D) (b) for different sizes and C-rates. The maximum amounts were extracted from the curves similar in Fig. 6. At low C-rates, size changes have no noticeable change in MRH. At 5 C-rate in the charge process, there is no heating and therefore there is no maximum heating value. Too fast charging leads to have only the zone of cooling in 5 C-rate.

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Fig. 8

MRC in charge (a) and discharge (b) for the sizes in Table 3. There is no noticeable change in MRC for both charge and discharge cycles with the increase of the solid particles size while increases with the increase of C-rate.

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Fig. 9

Maximum irreversible heat (MIrH-C) (a) in charge and discharge (b) for the sizes in Table 3. There are ascending curves for both charge and discharge cases. Irreversible heat drastically increases with the increase of C-rate since it originates from internal resistances in a battery. These resistances are a function of applied current with a power of two.

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Fig. 10

Overpotential curves in charge (a) and discharge (b) for the sizes in Table 3. Voltage cell initially increases in charging while decreases in discharging.

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Fig. 11

Maximum capacity of the battery during charging (a) and discharging (b) at different C-rates for the sizes in Table 3. Maximum capacity decreases with the increase of solid particle's sizes. As the size increases, although the surface area of the solid particles increases, the active surface area for electrochemical decreases, hence, the maximum capacity decreases with increasing the sizes.

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