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

Abstract

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 (CFx)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-(CFx)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-(CFx)n are 9.21% and 1.92% (0.5 mA cm−2), respectively. During storage and the initial stage of discharge, F in MnO2-(CFx)n can act on Mn–O bond and some C–F semi-ionic bonds form when Li+ insert into (CFx)n layers, these change the unit cell parameters of MnO2 and the utilization of MnO2 increases.