New Class of High-Energy, High-Power Capacitive Devices Enabled by Stabilized Lithium Metal Anodes

Lithium-ion capacitors (LIC) combine the energy storagemechanismsof lithium-ion batteries and electric double layer capacitors (EDLC)and are supposed to promise the best of both worlds: high energy andpower density combined with a long life. However, the lack of lithiumcation sources in the carbon cathode demands the cumbersome step ofprelithiation of the graphite anode, mainly by using sacrificial lithiummetal, hindering the mass adoption of LICs. Here, in a conceptuallynew class of devices termed lithium metal capacitors (LMC), we replacethe graphite anode with a lithium metal anode stabilized by a complexyet stable solid-electrolyte interface (SEI). Via a specialized formationprocess, the well-explored synergetic reaction between the LiNO3 additive and controlled amounts of polysulfides in an ether-basedelectrolyte stabilizes the SEI on the lithium metal electrode. Optimizeddevices at the coin cell level deliver 55 mAh g(-1) at a fast 30C discharge rate and maintain 95% capacity after 8000cycles. At the pouch-cell level, energy densities of 13 Wh kg(-1) are readily achieved, indicating the transferabilityof the technology to practical scales. The LMC, a new class of capacitivedevice, eliminates the prelithiation process of the conventional LIC,allowing practical production at scale and offering exciting avenuesfor exploring versatile cathode chemistries on account of using alithium metal anode.