Porous Hollow Carbon Alkali-Activated Nanoonions As a Conductive Additive for High-Rate Lithium Primary Batteries

Abstract

The high content of the covalent C–F bond of CF_x materials makes the conductivity of the materials worse and the battery polarization serious, which greatly reduces power density and leads to heat generation. Therefore, adding a conductive agent is particularly important, as it improves the electron migration speed in the electrode, suppresses the polarization phenomenon, and promotes the effective use of active substances. In this paper, a carbon nanoonion (CNO) with a hollow porous structure is prepared by a room-temperature alkaline activation method as a conductive agent for the Li/CF_x battery. The porous structures reduce the diffusion resistance of lithium ions, which is beneficial for Li/CF_x batteries to achieve a better rate performance. The electrochemical results show that alkali-activated CNO as a part of the cathode material effectively improves the rate performance of the Li/CF_x batteries. At the 2 C discharge rate, the specific capacity and energy density of CNO-NaOH-5M increased by 83.59% and 144.63%, respectively, compared with the commercial conductive additive SP. The power density and energy density of CNO-NaOH-3M samples at 8 C are 6907.36 and 863.42 Wh/kg, respectively, which was significantly better than the original CNO and SP. As a conductive agent, the increase of the oxygen-containing functional group of alkali-activated CNO improves the infiltrability of the cathode to the electrolyte, and the increase of pore-hollow structure improves the interface contact area, which is conducive to the transmission speed of electrons and lithium ions during discharge so that the Li/CF_x battery has high rate performance.