Application Note: Solid State Batteries for Automotive Applications

Autonomous or smart transportation has gone from being a concept to a fast-evolving reality in the space of just a few years. Studies predict a very high growth rate in the deployment of technologies in automotive applications, examples being: 

All aspects of the transportation system will be touched by these dramatic developments, not just cars, but also buses, parking systems, planes, trains, traffic management, trucks and, of course, all important safety systems. New devices are therefore now universally seen as key to enabling Smart Transportation. 

Modern cars already have up to 100 sensors and, with increased use of wireless systems such as Bluetooth LE, Wi-Fi & Cellular, more and more devices with added functionality are being developed.   But such devices will often need new power sources in order to operate autonomously for long periods of time (circa 10 years).   This is all the more important as cabling is now the third heaviest component (behind chassis and engine), averaging 100kg (Automotive Sensors, 2017).

The enabling technology for deploying increased sensor numbers is distributed energy storage using Solid State Batteries (SSB) such as Ilika’s Stereax®.

Automotive Devices enhanced by Solid State Batteries

  • Rain sensor: Stereax SSB are moisture resistant and their small size enables ultra-thin sensors with solar energy harvesting, without cabling or bulky coin cells.
  • Key fobs: Ultra-thin fobs may not allow space for coin cells. Can use mechanical impulse from pressing button to charge solid state battery.
  • Battery pack temperature control: Stereax SSB can be used at temperatures up to 100°C.
  • Exhaust sensors: Stereax SSB resistant to high temperatures; no cabling.
  • Pre-collision: Ultra-thin sensors outside cars would not need cabling.

Use case: tyre pressure monitoring system

  • Need for small energy source for Intelligent TPMS to replace coin cells which have insufficient low and high temperature performance.
  • Current devices installed in the valve; new generation powered by Stereax could be placed inside tyre for greater accuracy.
  • These intelligent products could have added functionalities, such as temperature, radial acceleration, tangential acceleration, tread wear out and tyre traceability.

Typical system specifications:

Transmission rate

10 Hz

 

Battery dimensions

14x14x1mm

Average consumption

130 μA

 

Operation when car is not on

2 h

UHF transmission

250 μW

 

Operating temperature

-40° to 100°C

Stereax SSB capacity

250 μAh

 

Energy source

Vibration

Battery expected life

10 years

 

 

 

Autonomous Vehicles / Smart Mobility

It is predicted that there will be 10 Million Autonomous cars on the road by 2020 (BI Intelligence 2016).   This will result in a dramatic increase in the number of sensors per vehicle in order to ensure the vehicle:

  • Knows where it is and where it’s going (GPS, gyros, accelerometers).
  • Can see where it is going (LIDAR: Light Detection and Ranging, 360°).
  • Can get there safely (navigation, guidance, image-capture).

Battery Requirements for Smart Vehicles

  • Safe, with no thermal runaway and no flame.
  • Industrial temperature range, e.g. - 45°C to +85°C, with +100°C very desirable
  • Small footprint and thin profile for integration.
  • Life of product performance – never change the battery.
  • Extremely low self-discharge.
  • No chemical leakage.
  • Impervious to vibration and magnetic fields.
  • Rechargeable thousands of times.

Stereax Advantages for Automotive Devices

  • Ultra-thin profile.
  • Various footprint shapes including custom sizes.
  • High energy density.
  • Low self-discharge.
  • Stereax patent-pending SSB Stacking adds capacity.
  • No battery transportation issues.
  • No product end-of-life disposal issues.
  • Ability to withstand high temperatures.
  • May be combined with supercapacitors for very low temperatures.

Figure 1: Graphic representation of 250 μAh Stereax M250 solid state battery. 

Figure 2: Photographic picture of 250 μAh Stereax M250 solid state battery. 

Stereax® M250

Stereax® P180