Graphene-based Hall-effect sensor maps battery cells
The graphene GHS01AT Hall-effect sensor is optimised for use in relatively low field environments and normal ambient temperatures. Developed by Paragraf, the sensor is suitable for battery applications, such as electric vehicles (EVs).
The sensor brings magnetic field measurement resolution closer to that of more complex magnetic sensors, yet with the small size and ease of use of a Hall sensor, says Paragraf.
The GHS01AT Hall-effect sensors will be of great value in battery cell analysis when investigating the validity of different battery cell chemistry derivatives and form factors under development, Paragraf believes. By using these magnetic sensors, it will be possible to get a more detailed and localised (point-to-point) understanding of battery cell behaviour.
The GHS01AT delivers detailed real-time current density, allowing local cell internal resistance mapping to be carried out. Any variations at different locations in the cell are detected during repeated charge/discharge cycles. If hotspots arise, the local mapping of internal cell resistance in these areas could provide insights into the physical processes occurring in the lead up to their formation.
Such detection might highlight early warning signs which could be monitored in service or scanned for during quality control. It may even provide the information required to help develop battery chemistries and design concepts that safeguard against the risk of potential failure or thermal runaway.
The sensors can be used to measure the current flow into and out of cells measuring real-time magnetic field (current) data. This also means the battery cell itself and the tabs/busbars feeding into the cells are not disrupted during testing.
By utilising a graphene monolayer (just 0.34nm thick), the GHS01AT is not affected by the presence of in-plane stray electromagnetic fields that would severely impact the accuracy of alternative sensing mechanisms, explains Paragraf. The small footprint allows good spatial resolution.
Paragraf also offers the GHS Array starter kit. This compact board enables simultaneous measurements to be taken from up to eight GHS01AT sensors. Each sensor is attached to a probe with a 1.5m serial interface cable and is accompanied by its own temperature sensor for simultaneous temperature monitoring and temperature correction of the magnetic measurement data. The hardware can easily be integrated into existing data acquisition systems. It will help manufacturers through the initial stages before they look to implement larger-scale test rigs with greater numbers of GHS01AT devices.
Battery manufacturers are under intense pressure to develop higher performance products to safely extend EV range and to accelerate charging times, explained Dr Simon Thomas, CEO of Paragraf. Batteries need to be smaller and lighter, with heightened power densities and quicker charge responsiveness. “To do this, they must have access to superior test data that they can analyse. Thanks to our GHS01AT, they now have the technology necessary for such an analysis,” he said.
“This new device easily outperforms what is currently available in terms of both magnetic field and spatial resolution. It means that, for the first time, battery manufacturers can compile comprehensive datasets relating to the internal structure of their products from a current density perspective,” Dr Thomas continued. “By implementing test rigs incorporating GHS01AT sensors, they will be able to ensure the long-term operation and safety of the battery packs they produce.”
