Ultralong storage life of Li/MnO2 primary batteries using MnO2-(CFx)n with C–F semi-ionic bond as cathode materials

The theoretical self-discharge rate of Li/MnO₂ primary batteries is less than 1% per year, but the actual self-discharge rate is ∼8% per year, and the shelf life of the coin batteries (such as CR2016) is only 5 years. In this paper, MnO₂ mixed some (CF_x)_n as cathode material in Li/MnO₂ primary batteries, not only can effectively reduce self-discharge rate, but also improve capacity density and heighten discharge plateau voltageafter storage. After storage at 25 °C for 60 days, the specific charge capacity of MnO₂ decreases from 293 mAh g⁻¹ to 283 mAh g⁻¹, while MnO₂-(CF_x)_n increases from 312 mAh g⁻¹ to 326 mAh g⁻¹. After storage for 30 days at 45 °C, the self-discharge rates of MnO₂ and MnO₂-(CF_x)_n are 9.21% and 1.92% (0.5 mA cm⁻²), respectively. During storage and the initial stage of discharge, F in MnO₂-(CF_x)_n can act on Mn–O bond and some C–F semi-ionic bonds form when Li⁺ insert into (CF_x)_n layers, these change the unit cell parameters of MnO₂ and the utilization of MnO₂ increases.