Ultrahigh-energy-density fluorinated calcinated macadamia nut shell cathodes for lithium/fluorinated carbon batteries

Lithium/fluorinated carbon (Li/CFx) batteries are widely applied in various industries because of the high energy densities of CFx compounds. However, incompatibility between high degrees of fluorination and the electrochemical activity of C–F bonds limits further improvements of the energy densities of CFx cathodes. Here, calcined macadamia nut shell is fluorinated with F2 gas below 300 °C. The products deliver specific capacities exceeding 900 mAh g−1, associated with discharge potentials exceeding 3.0 V (vs. Li/Li+). The product fluorinated at 280 °C achieves an unprecedented maximum energy density of 2585 W h kg−1, surpassing the present maximum theoretical energy density of commercial (CF)n (2185 W h kg−1). Its electrochemical properties presumably originate from the complete destruction of the periodic crystalline lattice in the basal plane, which substantially alters the electron distribution within the C–F bonds. This study presents a new approach for designing exceptionally high-energy-density CFx compounds for lithium primary batteries using an accessible and inexpensive raw material.