Lithium Dendrite Inhibition on Post-Charge Anode Surface: The Kinetics Role
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Lithium Dendrite Inhibition on Post-Charge Anode Surface: The Kinetics Role Asghar Aryanfar1 *,Tao Cheng2, Boris V. Merinov2, William A. Goddard III2, Agustin J Colussi1 and Michael R. Hoffmann1 1 Linde Center for Global Environmental Science, 2Materials and Process Simulation Center California Institute of Technology, 1200 E California Blvd, Pasadena, CA, 91125.
ABSTRACT We report experiments and molecular dynamics calculations on the kinetics of electrodeposited lithium dendrites relaxation as a function of temperature and time. We found that the experimental average length of dendrite population decays via stretched exponential functions of time toward limiting values that depend inversely on temperature. The experimental activation energy derived from initial rates as Ea~ 6-7 kcal/mole, which is closely matched by MD calculations, based on the ReaxFF force field for metallic lithium. Simulations reveal that relaxation proceeds in several steps via increasingly larger activation barriers. Incomplete relaxation at lower temperatures is therefore interpreted a manifestation of cooperative atomic motions into discrete topologies that frustrate monotonic progress by ‘caging’. Keywords: Lithium Dendrites, Kinetics, Activation Energy, Annealing. INTRODUCTION Wireless revolution and need for harnessing intermittent renewable energy sources, has created an exponential demand for energy storage devices such as batteries that require longlasting storage capacity and high-power delivery during last decade [1]. Lithium (Li0), particularly, anode candidate material with an ideal energy density of 3862 mAh/g, could drastically satisfy this demand. However, due to it relatively low surface energy, it has very high propensity to grow dendrites during consecutive recharging. This phenomenon eventually leads to short-circuiting, overheating the cell and possible ignition of the organic electrolyte as well as creating isolated ‘dead lithium’ crystals. [2] The current reports have investigated the effect of charging method, [3, 4] current density [5-7], electrode surface morphology [8-10], solvent and electrolyte chemical composition [1113],electrolyte concentration [5, 14] on dendrite growth. Other methods include the use of powder electrodes [15] and adhesive polymers[16]. Recent studies have tried to explain the dendrite evolution mechanism [17] and have offered impurities as dendrite initiation drive [18, 19]. Current modeling frameworks involve simplifying assumptions that may have fallen short of capturing the comprehensive essentials of dendrite growth. [7, 20, 21] *
Corresponding Author: [email protected], Tel: +1 (626) 395-8736, Fax: +1 (626) 395-8535
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Although the ongoing research tends to extend the battery energy density by developing Lithium-Air and lithium-Sulfur batteries, the dendrite problem remains as a challenging issue in all kinds of rechargeable batteries. [22, 23] Temperature is a highly accessible parameter with foremost important effect in kinetics. It has been found that cycling at higher temperat
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