High-Capacity Rechargeable Li/Cl 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) and lithium/chlorine (Li/Cl) batteries with up to 1200 mAh g 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) dissolved in thionyl chloride (SOCl) with fluoride-based additives as the electrolyte [Zhu et al., , , (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 for reversible NaCl/Cl or LiCl/Cl 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 battery, attaining high battery performance after activation in carbon dioxide (CO) at 1000 °C (DGr_ac) with the first discharge capacity ∼1910 mAh g and a cycling capacity up to 1200 mAh g. 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 redox. This work opens up widely available, low-cost graphitic materials for high-capacity alkali metal/Cl batteries. Lastly, we employed mass spectrometry to probe the Cl trapped in the graphitic positive electrode, shedding light into the Li/Cl battery operation.