China turns waste oil into 86% efficient supercapacitor for EVs, energy storage

Scientists in China have claimed a breakthrough that might completely change how we store energy by turning waste oil into a formidable substance for energy storage.

As the world grapples with increasing power demand, supercapacitors are becoming more popular because of their quick charging and discharging times, which makes them perfect for high-performance applications.

The researcher’s novel method provides a sustainable way to make these supercapacitors while addressing waste management and energy storage challenges, according to a press release by the Chinese Academy of Sciences (CAS).

“By using waste oil as a precursor, we’re not only recycling waste into a valuable resource but also creating a supercapacitor material with exceptional electrochemical properties,” Dr. Suyun Xu, a leading researcher on the project, said in the press release.

“Our approach optimizes the pore structure and uses nitrogen doping to elevate the performance of supercapacitors, opening up new possibilities for sustainable, high-efficiency energy storage.”

Turning waste into treasure

The research team from the University of Shanghai for Science and Technology and Tongji University presented their novel approach to turning waste oil into high-performance carbon materials in an October publication.

The team produced nitrogen-doped hierarchical porous carbons (HPCs) using melamine and linoleic acid, which are waste oils.

These materials are especially valuable as supercapacitor electrodes because of their large surface area and superconductivity.

After the materials are heated to high temperatures, potassium hydroxide (KOH) activates them. This treatment results in the creation of HPCs with a surface area of up to 3474.1 m²/g, a critical feature for enhancing storage capacity and performance.

Additionally, mesopores, which make up more than 70% of the pore space in these HPCs, greatly increase the efficiency of ion transport, which is crucial for energy storage.

“These HPCs featured mesopores, accounting for 72.9% to 77.3% of the total pore volume—essential for enhancing the material’s storage capacity and ion transport efficiency,” noted the press release.

Sustainable energy storage for EVs

This innovative discovery not only tackles the issue of energy storage but also promotes a circular economy by repurposing waste oil.

The team contributes to reducing environmental waste while also developing a resource-efficient technology by turning waste oil into useful material.

The enhanced HPCs demonstrate impressive supercapacitor performance, “paving the way for greener, more efficient energy systems worldwide” and boosting renewable energy storage.

“Nitrogen doping, facilitated by melamine, improved conductivity and introduced active sites within the carbon framework, boosting electrochemical reactivity,” noted the press release.

“As a result, the HPCs achieved a specific capacitance of 430.2 F g−1, with a retention rate of 86.5% after 2000 charge/discharge cycles.”

The discovery could lead to a cleaner, more efficient energy future where waste materials are transformed into potent sources for sustainable energy systems, with applications in electric vehicles (EVs), renewable energy storage, and other cutting-edge technologies.

Study abstract

The rational pore structure and abundant surface functional groups of hierarchical porous carbons (HPCs) are important for their practical application in supercapacitors. The liquid linoleic acid and solid melamine were thoroughly mixed and subjected to carbonization under autogenic pressure at elevated temperatures (CAPET), followed by KOH activation, to produce uniformly N-doped HPCs. The structure and surface chemical properties are controlled by adjusting the N-doped ratio. This adjustment results in high conductivity, abundant ion-accessible surfaces, hierarchical porosity with appropriate micro-mesoporous channels, and N and O heteroatoms. The addition of melamine markedly increased the surface area to 3474.1 m2 g−1 and the mesopore volume proportion to 72.9%‒77.3% in the HPCs. The crystal structure and functional groups of the HPCs were revealed by X-ray diffractometer, Raman spectrometry, and X-ray photoelectron spectrometry, indicating that LA-HPCs-N0.5 is a promising electrode material for supercapacitors. This material presented excellent capacitance storage performance and cycling stability, with a specific capacitance of 430.2 F g−1 at 1 A g−1 in a 6 mol L−1 KOH electrolyte system. The capacitance retention rate was 86.5% after 2000 cycles of charging and discharging at 10 A g−1. This study has successfully demonstrated that the template-free preparation of N-doped HPCs from waste oil is feasible, economical, and sustainable.