Key to maximising the use of our renewal energy sources are batteries. There are many different types of battery available, and it is an area of intense research and development. This a simple over view of the types of battery out there and things to consider when deciding which type is most appropriate for the use case.

Classic batteries store energy as chemical energy which is then converted to electricity to power a device.

When thinking about batteries are there are several properties which need to be considered which will have different answers depending on the use case

-          Density of the storage: which indicates how big a battery needs to be

-          Shelf life of the battery: how long before the battery discharges itself

-          Life cycle of the battery: how many cycles of charge / discharge will the battery last

-          Charge speed: speed at which the battery recharges

-          Temperature stability: the range it will function in

-          Safety of the battery: some set ups are more liable to catching on fire (thermal runway) or leakage of the components

-          Source of raw materials to make the components: how abundant will impact cost, how they are extracted will inform the environmental impact

-          Recyclability of the battery: can the components be recovered to be used in new batteries

A battery essentially has four key components which can be made of different materials, these then determine answers to the points above

• Anode

• Cathode

• Electrolyte

• Separator

The battery types are then named according to the components used.

1. Lead Acid

2. Nickel Cadmium / Nickel metal hybrids

3. Alkaline

4. Lithium Ion, including LFP

5. Sodium Ion (salt water)

Lead Acid Batteries

These are the original battery, invented in 1859. They are much cheaper than many other types on the market, however they do not have a long shelf life, discharging when not used and their components are toxic. They are used for the starter motor in petrol/diesel cars, but are not used to power EVs or as energy storage for solar / wind any more.

Nickel Cadmium / Nickel Metal Hybrid Batteries

These are also an established technology and were the original battery re-chargeable battery used in mobile phones and electric cars (EV). They are predominantly cadmium, but other metal hybrids are also available. They were chosen for their long lifespan, but also run the risk of suddenly discharging, known as the memory effect. The nickel and cadmium are both difficult to mine sustainable and highly toxic so disposal is challenging.

Alkaline Batteries

Called so because their electrolyte is alkaline, they have a powdered anode (zinc) with manganese oxide cathode. They are known for their very long shelf life and are the batteries which are used in households to power those small gadgets like clocks, toys, remotes etc. Currently they are the most widely produced type of battery, but although theoretically can be re-charged they are generally designed as single use and not often recycled.

Lithium Ion Batteries

These are the most modern batteries, definitely the current favourite and gaining fast on the more established batteries to become the most produced batteries. They are used in all our phones, laptops and also a favourite for solar storage.

These batteries are widely used in energy storage due to their high energy density. One key advantage of lithium ion batteries is their long cycle life, which refers to the number of charge/discharge cycles they can undergo before their capacity degrades significantly. This makes them a cost-effective option for grid storage applications as they can be used for many years without needing to be replaced

There are several different types of lithium ion combinations but all based around lithium as from an electrochemical perspective is really efficient. The main types are

• Lithium Iron Phosphate (LFP): newer variants with advantages over chemistries

• Lithium Cobalt Oxide (LCO): short life and risk of overheating

• Lithium Manganese Oxide (LMO): Very fast charging but lower capacity

• Lithium Nickel Manganese Cobalt Oxide (NMC): Compact but with thermal issues

• Lithium Nickel Cobalt Aluminium Oxide (NCA): fast charging but prone to thermal runway

• Lithium Titanate Oxide (LTO): lightening fast charging but bulky and contains main rare elements

LFP (LiFePO4) a later variant, becoming the preferred option for EVs and solar storage. It offers similar energy density but with even longer life cycles and with no cobalt or nickel. It also has allows 100% discharge, a wider operating temperature and virtually no risk of thermal runway which the other variants have.

Overall lithium ion based batteries are taking over the market due to their efficiencies and the price of lithium dropping.

Sodium Ion Batteries

Sodium the latest ion being looked at, sometime known as salt water batteries. Using sodium which is not toxic and obviously in abundance offers the potential to be cheaper and with less environmental impact than lithium. These have less energy density and take longer to charge but given the price implications could still become really useful. There are some example of where sodium ion batteries are coming into production, eg in some Chinese EV models along side LFP batteries.

Battery development is progressing rapidly and the mix is expected to change over the next decade

For a more detailed view of the chemistries take a look at the Australian Academy of Science https://www.science.org.au/curious/technology-future/battery-types

New Battery Technologies in Development

Traditionally all the components were in one unit with solid electrodes and the electrolyte being a liquid or gel however there are now newer technologies are looking at alternatives

1.      Flow Batteries

2.      Solid State Batteries

3.      Sand Batteries

Furthermore, there improvements being developed for the electrodes to improve efficiency. One thing to mention here is the addition of powder coating to the electrodes which is just coming into commercial batteries, with Tesla factories being built as we write.

Flow Batteries

This is where the solid electrodes and electrolyte is replaced with two external liquid tanks used as electrodes. This allows there to be easy scaling of size but you do need the space. An additional positive is that they have an incredibly long span life as there is very little degradation giving significant more productive recharge cycles and do not discharge when not being used. On the downside they are slow to charge but you could just replace a tank. They are very safe in terms of leakage and no thermal runway risk.

Solid State Batteries

These batteries have the electrolyte replaced with a solid, and the electrodes are integrated within this. They have a lower risk of flammability, a higher energy density and a faster charging cycle.  However, solid-state batteries may be harder to scale quickly so may be some time before they are commercially available.

Sand Batteries

These are not official batteries in the chemical sense, rather a thermal energy store. They are very cheap and sustainable, however they not very efficient and require a lot of space. Currently usage is only seen where large levels of heat are required eg communal heating projects.

Batteries are a global focus of research and development and we can expect to see improvements coming out in the years to come. China as leaders in EVs are investing substantially in battery efficiency and bringing new technologies to market, like some sodium cells in cars. Here in the UK there are lots of projects led by both academia and industry, looking at improving battery efficiency and sustainability and the government has identified batteries as one of the core focus areas for UK technology. The projects are supported by the UK Battery Industrialisation Centre (UK BIC) in Coventry bringing together expertise and support by government funding, it will be exciting to see what is next brought to market.

The use case, including budget and space, will decide which type of battery is most suitable and it can be expected that all the batteries out there will become more refined year by year.