Thicker electrode layers for lithium ion cells have a favorable electrode to current collector ratio per stack volume and provide reduced cell manufacturing costs due to fewer cutting and stapling steps. The aim of this work is to investigate the delivery of energy in such cells compared to cells with thinner electrodes. In this regard, lithium ion cells with single sided 70 μm and 320 μm NMC based cathodes and graphite based anodes with low binder and carbon black contents were prepared and tested in half cell and full cell configurations. Thick and thin electrodes showed capacity losses of only 6% upon cycling at C-rates of C/10 and C/5 while cycling at C/2 resulted in significant losses of 37% for the thick electrodes and only 8% for the thin electrodes. Pouch cells with thick electrodes showed 19% higher volumetric energy density at C/5 in comparison to thinner electrodes. This can be an innovative approach to reduce cell costs and to achieve more competitive prices per energy for applications where only medium to small C-rates are required. 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 im...

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Die Elektromobilität und die Speicherung regenerativ erzeugter elektrischer Energie stellen hohe Anforderungen an die Leistung und Kosten von Li‐Ionen‐Zellen. Sie erfordern ein tiefgreifendes Verständnis über die Materialeigenschaften der Rohstoffe und die verfahrenstechnischen Prozesse zur Herstellung der Elektroden. Zahlreiche Parameter müssen in der Produktentwicklung und späteren Produktion gemessen und gesteuert werden, um gezielt spezifische Zelleigenschaften einzustellen und gleichzeitig das Verständnis für einen stabilen Fertigungsprozess zu etablieren.

A series of 250-350 µm-thick single-sided lithium ion cell graphite anodes and lithium nickel manganese cobalt oxide (NMC) cathodes with constant area weight, but varying porosity were prepared. Over this wide thickness range, micron-sized carbon fibers were used to stabilize the electrode structure and to improve electrode kinetics. By choosing the proper porosities for the anode and cathode, kinetic limitations and aging losses during cell cycling could be minimized and energy density improved. The cell (C38%-A48%) exhibits the highest energy density, 441 Wh/L at the C/10 rate, upon cycling at elevated temperature and different Crates. The cell (C38%-A48%) showed 9% higher gravimetric energy density at C/10 in comparison to the cell with as-coated electrodes.