Abstract: A composition-of-matter is described herein, comprising a first layer and third layer separated by a second layer. The first and third layers each comprise a thermoplastic polymer and a substance capable of reversibly releasing lithium or a delithiated form of the substance. The second layer comprises a thermoplastic polymer and is capable of conducting lithium ions. Further described herein is an electrochemical system comprising the composition-of-matter, wherein the first and third layers are each a lithium-based electrode, and batteries and supercapacitors comprising such an electrochemical system, as well as methods for preparing the composition-of-matter or the electrochemical system.