Lithium battery breakthrough

In this day and age, if you start reading about current battery technologies it won’t be long before you see lithium mentioned. That’s because in recent years lithium-ion (Li-ion) batteries have come to be recognised as an important breakthrough in the field of portable energy sources.

Compared with other types of primary and secondary cell, Li-ion batteries have very high energy density (the amount of energy stored per unit volume) and specific energy (the amount of energy stored per unit mass).  Also, their cell voltage is high. Just as important in many applications, however, are their long shelf life before they start to deteriorate, and their ability to retain charge for long periods.

These characteristics make Li-ion batteries ideal for use in emergency equipment, such as a flashlight, that is often left untouched for long periods and then expected to work instantly on demand. In fact, the same expectations often apply to test instruments, which sit on the shelf for months but are then required to be ready for immediate use to solve a problem or to help in locating a fault. Li-ion batteries are therefore an excellent option for powering portable test equipment. In some other common applications the most important advantage of Li-ion batteries is their low weight. It is for just this reason that they are almost invariably the battery of choice for electric and hybrid vehicles. The more an electric vehicle weighs, the more energy it takes to move it and the less efficient it becomes. In addition, the extra weight increases wear and tear on the tyres and on the vehicle’s mechanical components in general. It’s easy, therefore, to see the attraction of Li-ion batteries for use in vehicles.

Electric and hybrid vehicles – and the batteries they use – have attracted a lot of attention in recent times, but the number of electric vehicles currently in use worldwide is still very small compared with the number of conventionally fuelled vehicles. This will almost certainly change in the near future. In the UK, for example, it has been suggested that somewhere between 8% and 30% of cars sold in 2020 will incorporate either hybrid or pure battery drive systems.

The main reason that this estimate is so wide is that much depends on future progress in battery technology. The high price of today’s electric vehicles is mainly due to the relatively high cost of the Li-ion batteries used in them. Much research is, however, being done into ways of reducing this cost, and it is reasonable to expect that this will start to bear fruit in the not-too-distant future.

Until then, we have to accept that currently available Li-ion batteries, despite their many advantages over batteries based on older technologies, are still only just adequate in vehicle applications. They are costly and need to deliver even higher energy density and efficiency so that the vehicles can achieve adequate range between charging stations.

Li-ion batteries are, however, still the most promising option for use in electric vehicles and are currently the prime focus of most battery research. This will, however, need to cover not only efficiency and cost concerns but also safety.

The unavoidable downside to cramming so much energy into a small package is the potential for that energy to cause problems if it is incorrectly released. There have already been reported instances of this occurring with Li-ion mobile phone and laptop batteries leading, in the worst cases, to fires. Vehicle batteries will be much larger and will store much more energy, so safety is clearly an area that will need to be given very careful attention. Li-ion batteries are undeniably a breakthrough. They make possible our tiny yet versatile mobile phones, our compact laptops with long run times and test instruments that are ready to use straight off the shelf whenever we need them. And it’s a racing certainty that they’ll be playing an even more significant role in our lives in the very near future.