Aging Behavior and Mechanisms of Electric Bicycle Batteries under Typically Accelerated Abuse-Testing Conditions

An electric bicycle is an excellent transportation device for short-distance travel. The use of lithium-ion batteries in electric bicycles has increased in recent years. However, cycle life and safety are important issues to be solved owing to the accelerated abuse-testing conditions of electric bicycles. This work studies capacity fading and material changes of electric bicycle batteries under three classically accelerated abuse-testing conditions, including overcharging cycling, high-temperature cycling, and overcharging cycling after high-temperature cycling. The results indicate that the capacity fading rate is ranked as overcharging cycling > overcharging after high-temperature cycling > high-temperature cycling. Overcharging cycling induces serious electrode degradation, including lithium plating, depositions covering the surface of the negative electrode, exfoliation of graphite, transition metal dissolution, and structure disordering of the cathode crystal, especially after 81% SOH. High-temperature cycling induces depositions covering the surface of negative and transition metal dissolution. Lithium plating only occurs near 70% SOH. The primary components of depositions on the surface of the negative electrode in a battery cycled under overcharging and high temperatures are organic and inorganic. Compared to the overcharging condition, electrode degradation under overcharging after high-temperature cycling is suppressed. The results are important to prolong the cycle life and control the safety of the electric bicycle battery.