By integrating a pressure sensor foil into a battery pack, the "breathing" during the charging and discharging cycle can be tracked in real-time, enabling an extension the life cycle by up to 30%.
Optimizing EV batteries with printed electronics
For electric vehicles (EVs), the battery is arguably the most important component – and certainly the most expensive. Consumers care strongly about an EV’s range, which of course directly depends on the battery.
How can EV makers ensure that the battery works efficiently, and offers the best possible performance, and what is the role of printed electronics?
Firstly, printed pressure sensors can help improve battery capacity and lifetime. During the charge and discharge cycle, a battery cell constantly changes its volume. If it is clamped and fixed in place in rigid packaging, with no change in volume possible, it will instead change its pressure.
By measuring this, with printed pressure sensors placed around and between the battery cells, the vehicle can gain an insight into the state of charge of the cells. This can help to prevent overcharging, and to perform cell balancing – which maximises battery capacity and lifetime, by correcting any variations in the state of charge between cells in a battery pack. The printed sensors are thin enough that they can be placed to get data from each individual cell, instead of just for the entire battery pack.
In fact, there is an optimal pressure at which the battery has the longest lifetime. By keeping the battery at this pressure, the cycle lifetime (the number of charge/discharge cycles a battery can complete in its life) can be improved by 30 to 40 per cent.
Secondly, temperature sensing is required in EVs. The capacity of the lithium-ion batteries used in EVs varies with temperature, and drops in cold conditions. This is a significant issue for drivers in cold climates, and typically can reduce the vehicle’s range by around 20 per cent1. If the battery is at a higher temperature than normal, we also need to know – it probably shows a fault, which may have safety implications.
The temperature can be measured with printed sensors, enabling any potential issues to be spotted. When a low temperature is detected, printed heating elements can be switched on to warm the battery, thus increasing its energy output. Data on temperature also helps improve cell balancing.
With these two key variables, temperature and pressure, being monitored accurately by printed sensors, the car’s battery management systems can respond to changing conditions, and can maximise battery capacity and lifetime.