Impact of high-amplitude alternating current on LiFePO4 battery life performance: Investigation of AC-preheating and microcycling effects

•Studying the ageing effects of AC preheating methods on LiFePO4 (LFP) cells.•The ageing impact of shallow charge-discharge cycles, microcycles, on LFP cells.•High-frequency microcycling has a minor degradation impact on LFP cells.•Low-frequency microcycling causes accelerated degradation.•Voltage polarization induced by AC is the key indicator of any likely ageing effect.