Synergistic Enhancement of Mechanical and Electrochemical Properties in Grafted Polymer/Oxide Hybrid Electrolytes
Felix Scharf, Annalena Krude, Peter Lennartz, Moritz Clausnitzer, Gourav Shukla, Annika Buchheit, Fabian Kempe, Diddo Diddens, Pascal Glomb, Melanie M. Mitchell, Timo Danner, Andreas Heuer, Arnulf Latz, Martin Winter, Gunther Brunklaus
Abstract
Abstract Lithium metal batteries operated with high voltage cathodes are predestined for the realization of high energy storage systems, where solid polymer electrolytes offer a possibility to improve battery safety. Al 2 O 3 _PCL is introduced as promising hybrid electrolyte made from polycaprolactone (PCL) and Al 2 O 3 nanoparticles that can be prepared in a one‐pot synthesis as a random mixture of linear PCL and PCL‐grafted Al 2 O 3 . Upon grafting, synergistic effects of mechanical stability and ionic conductivity are achieved. Due to the mechanical stability, manufacture of PCL‐based membranes with a thickness of 50 µm is feasible, yielding an ionic conductivity of 5·10 −5 S cm −1 at 60 °C. The membrane exhibits an impressive performance of Li deposition in symmetric Li||Li cells, operating for 1200 h at a constant and low overvoltage of 54 mV and a current density of 0.2 mA cm −2 . NMC 622 | Al 2 O 3 _PCL | Li cells are cycled at rates of up to 1 C, achieving 140 cycles at >80% state of health. The straightforward synthesis and opportunity of upscaling as well as solvent‐free polymerization render the Al 2 O 3 _PCL hybrid material as rather safe, potentially sustainable and affordable alternative to conventional polymer‐based electrolytes.