Revolutionising Electric Vehicle (EV) lubrication with a single lubricating and cooling fluid (C4-MAC-Khan) University of Sheffield in United Kingdom

The UK is committed to a target of net zero emissions by 2050 and with passenger cars accounting for 109M tonnes of carbon emissions a year, there is a proposed a ban on the sale of all polluting vehicles by 2035. With over 14 million electric cars on the road globally in 2020, the majority of the lubricants utilised for these vehicle transmissions were developed for non-electric vehicles.

It is predicted 40 million litres of e-fluids will be sold globally by 2025. EV lubricants are faced with a tougher environment in-comparison to traditional Internal Combustion Engines as they are exposed to high temperatures, particle abrasion and higher levels of oxidation. However, the move away from hot piston engines also opens the possibility of utilising water-based lubricants. It provides the opportunity to use a single fluid for lubricating and cooling EV transmission and battery systems.

The rapid adaptation of these new electrified systems depends on addressing multiple challenges, including the development of new lubricants that can meet the more stringent requirements of lubricating and cooling at the same time. The presence of stray charges combined with extreme operating conditions has led to the failure of crucial components such as gears. There is a growing need for advanced lubricants to not only reduce friction and wear behaviour but to protect the components from the extreme operating conditions and stray electric currents present in an EV.

Biodegradability and sustainability are very important characteristics for dedicated lubricants. This study will novelly explore the use of base-oils synthesised from renewable resources or esters, proteins and PAGs, combined with functionalised nanoparticles such as Al2O3, ZnO or carbon-nanotubes which have shown to improve tribological behaviour. Other than lubrication and wear reduction, another primary challenge of e-fluids is the thermal management of motor and invertor EV components and for the vehicle’s lithium batteries. The development of a single thermal management lubricant suitable for batteries and transmissions is being actively pursued but these efforts are still in the early stages. This study would ambitiously investigate the challenges of using of water-based lubricants as a lubricant and coolant in a challenging environment.

The tribological performance of novel EV-lubricants will be assessed using an electrified Bruker UMT tribometer, which can simplistically replicate the sliding environment and contact conditions observed by gear components within an enclosed EV drivetrain system. This study would further modify the experimental set-up through the addition of ultrasound sensors allowing in-situ measurement of tribofilms formation within the contact. This set-up would allow for real-time assessment of the effect of electrification on protective layers formation and friction and wear behaviour. Combined with advanced tribochemical and lubricant property analysis would allow the development of an in-depth fundamental understanding of tribochemical formation mechanics with water-based fluids and variant lubricant additives under electrified conditions and their role on friction and wear trends. This testing will be validated at a higher TRL level using a gearbox simulator at the partner company site.

This study will furthermore use a novel experimental setup utilising ultrasound sensors techniques developed at the University of Sheffield to evaluate the cooling performance of various transmission lubricants through monitoring lithium battery health. The internal structure and any defects developed in the battery due to cooling or by battery material interactions with the novel e-fluids would be detected using ultra-sound.

Interested candidates are strongly encouraged to contact the project supervisors to discuss your interest in and suitability for the project prior to submitting your application.

Please refer to the EPSRC DLA webpage for detailed information about the EPSRC DLA and how to apply.