Complex sentence: The chemistry is able to provide 1340 Wh/kg energy density in theory.They have made a prototype cell which demonstrated an energy density of 800 Wh/kg for over 20 cycles.
Split into simpler sentences: The chemistry is able to provide a 1340 Wh/kg energy density in theory. The team made a prototype cell which demonstrated an energy density of 800 Wh/kg for over 20 cycles.