Thick Electrodes for High Energy Lithium Ion Batteries

By Madhav Singh, J. Kaiser, H. Hahn. 2015

392 citations recorded by the source corpus.

Lithium ion cells have undergone a remarkable development regarding energy density, power density, lifetime, safety and costs since their market introduction in the early 1990s. While the early applications focused mainly on consumer electronics, in the second half of the last decade electromobile and stationary energy storage applications moved into scope. Today the industry focuses strongly on cost targets in terms of dollars per Watthour, by lowering both material and production costs and increasing the energy density of the cells while maintaining other factors such as safety and lifetime constant on a high level. Three different cell designs are usually considered for electromobile or stationary energy applications: (i) cylindrical cells, (ii) prismatic shaped cells in hard cases made from metal or plastics, and (iii) pouch bag or coffee bag cells. The latter are widely used and are typically 7 to 13 mm thick which correlates with a few dozen layers of anode and cathode sheets, depending whether they are designed to serve energy or power optimized purposes. To produce such a stack, electrodes need to be cut from an electrode roll for example via laser cutting or punching, cleaned from loose particles, picked up automatically and then placed alternately with high accuracy on top of the growing stack. Compared to other steps in cell production like tab welding, pouch foil packaging and sealing or electrolyte filling, this stapling process takes up a considerable amount of the total cell assembly time. With the goal of reducing the stack assembly time and increasing the throughput of the cutting and stacking machine we have considered to investigate the preparation and characterization of electrodes that are substantially thicker than conventional ones and which would decrease the number of sheets for an electrode stack of given capacity. However, with increasing electrode thickness the mass transport limitations of lithium ions in the electrolyte phase as well as the impedance for electrons in the solid phase of the electrode become dominating. This will reduce the capacity of the cell due to higher overpotentials upon charging and discharging within fixed voltage limits. At the same time, the geometric current density in the separator is higher at a given C-rate for thick electrodes compared to thin ones which causes additional overpotential and, in case of charging, could lead tolithiumplating ongraphite particles invicinitytotheseparator. The concept of thick electrodes has been employed previously 1, 2, 3

Subfields: Automotive Engineering, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/081314b6c65c6724a59f2e374ccf13d53c68adee

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  1. Timo Danner
  2. Simon Hein
  3. F. Font
  4. Jo¨rg Kaiser
  5. B. Protas
  6. A. Latz
  7. J. Foster
  8. H. Hahn

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