From coin cells to 400 mAh pouch cells: Enhancing performance of high-capacity lithium-ion cells via modifications in electrode constitution and fabrication

• Better component distribution and porosity control enhances electrode performance.
• Carbons and binder in positive electrode are electrochemically active at high voltages.
• Limit graphite content of high-voltage positive electrodes to improve performance.
• Limit cycling window of high-capacity lithium-ion cells to improve calendar life.
• Details of electrode fabrication and pouch cell assembly are provided.

In this article we describe efforts to improve performance and cycle life of cells containing Li1.2Ni0.15Mn0.55Co0.1O2-based positive and graphite-based negative electrodes. Initial work to identify high-performing materials, compositions, fabrication variables, and cycling conditions is conducted in coin cells. The resulting information is then used for the preparation of double-sided electrodes, assembly of pouch cells, and electrochemical testing. We report the cycling performance of cells with electrodes prepared under various conditions. Our data indicate that cells with positive electrodes containing 92 wt.% Li1.2Ni0.15Mn0.55Co0.1O2, 4 wt.% carbons (no graphite), and 4 wt.% PVdF (92–4–4) show ∼20% capacity fade after 1000 cycles in the 2.5–4.4 V range, significantly better than our baseline cells that show the same fade after only 450 cycles. Our analyses indicate that the major contributors to cell energy fade are capacity loss and impedance rise. Therefore incorporating approaches that minimize capacity fade and impedance rise, such as electrode coatings and electrolyte additives, can significantly enhance calendar and cycle life of this promising cell chemistry.