High-power graphene supercapacitors for the effective storage of regenerative energy during the braking and deceleration process in electric vehicles

Abstract

Supercapacitors (SCs), with maximal power densities, low self-discharge and wide temperature tolerance, are expected to be ideal electrochemical energy storage (EES) systems for electric vehicles (EVs). Herein, we demonstrated the superior performance metrics of a graphene based SC and its applicability as an advanced EES system for EVs. The 3.0 V graphene SC developed herein possesses a device capacitance of 35.96 F g⁻¹, energy density of 44.95 W h kg⁻¹, power density of 18 750 W kg⁻¹, long cycle life and wide temperature operation (−15 to 80 °C). The role of ohmic leakage, diffusion-mediated charge-redistribution and over-charging issues on the self-discharge mechanism of the graphene SC are studied. The effects of temperature on the capacitive properties of the graphene SC are studied using complex capacitance models. Additionally, the use of a graphene SC as the primary EES system to store regenerative energy during braking/deceleration modes and as an auxiliary power source (in combination with a battery) to drive EVs is also demonstrated. These studies highlight the potential applicability of a graphene SC as an ideal EES system for next-generation EVs.