4.8 Article

Asymmetric Rate Behavior of Si Anodes for Lithium-Ion Batteries: Ultrafast De-Lithiation versus Sluggish Lithiation at High Current Densities

Journal

ADVANCED ENERGY MATERIALS
Volume 5, Issue 6, Pages -

Publisher

WILEY-V C H VERLAG GMBH
DOI: 10.1002/aenm.201401627

Keywords

lithium-ion batteries; silicon; electrodes; rate performance; kinetics; diffusion

Funding

  1. Vehicle Technologies Office of the U.S. Department of Energy under the Batteries for Advanced Transportation Technologies (BATT) Program [DE-AC02-05CH11231, 7056410]
  2. Directorate For Engineering
  3. Div Of Civil, Mechanical, & Manufact Inn [1000726] Funding Source: National Science Foundation

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The combined effect of lithium-ion diffusion, potential-concentration gradient, and stress plays a critical role in the rate capability and cycle life of Si-based anodes of lithium-ion batteries. In this work, Si nanofilm anodes are shown to exhibit an asymmetric rate performance: around 72% of the total available capacity can be delivered during de-lithiation under a high current density of 420 A g(-1) (100C where C is the charge-rate) in 22 s; in striking contrast, only 1% capacity can be delivered during lithiation. A mathematical model of single-ion diffusion is established to elucidate the asymmetric rate performance, which can be mainly attributed to the potential-concentration profile associated with the active material and the ohmic voltage shift under high currents; the difference in chemical diffusion coefficients during lithiation and de-lithiation also plays a role. This clarifies that the charge and discharge rates of lithium-ion-battery electrodes should be evaluated separately due to the asymmetric effect in the electrochemical system.

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