A safer, symmetric all-organic battery based on temperature-responsive polymers as both cathode and anode

• An all-organic battery with P3OT as both cathode and anode materials was designed. • Introducing of CNTs improves the redox activity of P3OT. • The proposed all-organic battery possesses overheating self-protection ability. • The proposed all-organic battery after thermal shutdown is able to resume its normal function. All-organic batteries that employ organic compounds as the cathode- and anode-active materials have emerged as a promising rechargeable battery chemistry system due to their environmental friendliness, sustainability, flexibility and wide raw materials availability. Just like current lithium-ion batteries, if operated improperly, there are also safe concerns mainly caused by thermal runaway in all-organic batteries. However, the safety protection for all-organic batteries has not been explored by far. In this work, a novel type of temperature-responsive symmetric all-organic battery with overheating self-protection function is proposed based on poly(3-octylthiophene) (P3OT) as both cathode- and anode-active materials. P3OT is anchored on carbon nanotube (CNT) surface to boost its p- and n-type redox activity. Rewarded by this, the resulting all-organic battery delivers a reversible capacity of 97.2 mAh g −1 at 50 mA g −1 between 0.01 and 2 V and exhibits an outstanding cycling stability. More importantly, when being charged under overheating conditions, the designed all-organic battery can always maintain the low state-of-charge. It can provide an early warning of battery overheating, and mitigate the release of chemical energy if the battery finally goes to fire. During the discharge process, the all-organic battery will be rapidly switched off, thus avoiding continuous battery damage. The thermal protection is proved to be derived from the thermal dedoping of PF 6 - from cathode-active P3OT. In addition, the all-organic battery is able to resume its normal function when battery temperature is dropped to room temperature.