High-Capacity Rechargeable Li/Cl 2 Batteries with Graphite Positive Electrodes.

Developing new types of high-capacity and high-energy density rechargeable batteries is important to future generations of consumer electronics, electric vehicles, and mass energy storage applications. Recently, we reported ∼3.5 V sodium/chlorine (Na/Cl 2 ) and lithium/chlorine (Li/Cl 2 ) batteries with up to 1200 mAh g -1 reversible capacity, using either a Na or a Li metal as the negative electrode, an amorphous carbon nanosphere (aCNS) as the positive electrode, and aluminum chloride (AlCl 3 ) dissolved in thionyl chloride (SOCl 2 ) with fluoride-based additives as the electrolyte [Zhu et al., Nature , 2021 , 596 (7873), 525-530]. The high surface area and large pore volume of aCNS in the positive electrode facilitated NaCl or LiCl deposition and trapping of Cl 2 for reversible NaCl/Cl 2 or LiCl/Cl 2 redox reactions and battery discharge/charge cycling. Here, we report an initially low surface area/porosity graphite (DGr) material as the positive electrode in a Li/Cl 2 battery, attaining high battery performance after activation in carbon dioxide (CO 2 ) at 1000 °C (DGr_ac) with the first discharge capacity ∼1910 mAh g -1 and a cycling capacity up to 1200 mAh g -1 . Ex situ Raman spectroscopy and X-ray diffraction (XRD) revealed the evolution of graphite over battery cycling, including intercalation/deintercalation and exfoliation that generated sufficient pores for hosting LiCl/Cl 2 redox. This work opens up widely available, low-cost graphitic materials for high-capacity alkali metal/Cl 2 batteries. Lastly, we employed mass spectrometry to probe the Cl 2 trapped in the graphitic positive electrode, shedding light into the Li/Cl 2 battery operation.