Lithium-ion batteries power much of our technology; from the mobile phones in our pockets to large battery-powered trucks. But solid-state batteries may be a more powerful, compact, safe, and sustainable option, especially for electric vehicles.
Road travel accounts for approximately 15% of all global CO2 emissions. It’s why many governments around the world have recently set ambitious targets to ensure that all new car sales will be zero emission by 2035.
Countries that have made this pledge include the UK, Singapore, Canada, Chile and all countries that are within the European Economic Area (EEA). Add to this some of the US’s wealthiest and most populous states, such as New York and California, and there is a global appetite for change.
This is one of the factors boosting the demand for electric vehicles (EVs), sales of which have been growing exponentially in the UK and around the world. Now, the race is on to ensure that battery technology and production can keep pace.
The limitations of current EV batteries
EVs are powered by lithium-ion batteries, a technology that’s in huge demand but which faces some serious challenges on the road ahead. Their current iterations are expensive and heavy, whilst there are also doubts over their longevity and safety – particularly in the event of accidents.
The growth in EV manufacturing and the role of battery storage for electricity in the power grid, also means there’s concern about the growing need for critical minerals like cobalt, copper, nickel and lithium. This is prompting battery and EV manufacturers to explore alternatives, such as solid-state batteries.
What are the differences between lithium-ion and solid-state batteries?
Lithium-ion batteries consist of electrical contacts alongside four other main components:
The cathode (positive electrode), which contains the source of lithium ions.
The anode (negative electrode), which is made of an ion acceptor material such as carbon or graphite.
The separator, a plastic-polymer insulating material that keeps the cathode and anode apart.
The electrolyte, a liquid medium that contains lithium salt through which the ions flow.
When you turn on a car that uses a lithium-ion battery, it closes and connects the circuit the battery is part of. This causes the positively charged lithium ions to move through the liquid electrolyte, and the separator, from anode to the cathode. This causes chemical reactions that generate electrons, which move in the opposite direction in the external circuit and generate the electrical current powering the car. When charging, the ions and current move in reverse.
In contrast, solid-state batteries contain a solid lithium metal anode and a solid ceramic electrolyte – which also acts as the separator. Here, the separator becomes part of the solid medium through which the lithium ions move. When charging, the lithium ions form a solid layer of lithium on the anode. This has a smaller volume than the anode in a lithium-ion battery – meaning more energy can be generated by a smaller battery.
The advantages of solid-state batteries
Solid-state batteries make a good alternative to conventional lithium-ion batteries for several reasons:
- Size. The solid electrolyte potentially replaces the need for a separator, which could take up less space than a liquid electrolyte, so solid-state batteries can be made smaller than conventional lithium-ion batteries. Recent scientific advances mean this could eventually be applied to short-haul aircraft and heavy trucks.
- Weight. Lithium is the lightest metal element, so the lithium metal anode in solid-state batteries – and the ability to carry higher energy density in a smaller package – make them a lighter option for EVs. As EVs slowly get bigger, so must the batteries that power them. This increase in weight means the focus is moving from exhausts to other sources of pollution, such as tyre particulates. That creates a compelling case to reduce the weight of EVs (and their batteries), to reduce tyre wear and the number of particles released from them.
- Safety. Lithium-ion batteries contain a volatile, flammable liquid electrolyte, which can cause fires. In contrast, solid-state batteries can tolerate higher temperatures and have a higher thermal stability, which makes them a safer alternative.
- Greater capacity and range. Smaller size and increased energy density means more can be packed into less. This potentially increases mileage, with at least one manufacturer claiming that they will be able to drive 745 miles on one charge.
- Faster recharging. Lithium-ion batteries in EVs typically take somewhere between 20 minutes to twelve hours to recharge. Solid-state batteries could take as little as 10 or 15 minutes to obtain at least 80% charge. Moreover, solid-state batteries can be charged 5 times more than lithium-ion batteries over their lifecycle, increasing longevity.
- Lower carbon footprint. Fewer materials are used in making solid-state batteries, which could reduce their climate impact by 39% compared to lithium-ion batteries.
How CPI is helping to drive advances in battery technology
Solid-state batteries are not without their own challenges. The scarcity of raw materials, particularly lithium, and lack of recycling options make them costly to manufacture and expensive to commercialise.
It’s why we are applying our battery storage expertise and capabilities to try and find solutions to these problems. Using our £27.6 million share from UK Research and Innovation’s Faraday Battery Challenge we are working with Ilika Technologies Ltd, BMW Motorsport Ltd and other partners to develop high silicon content electrodes for integration into EV batteries. We are also working on projects at the forefront of printable electronics, lifecycle analysis and EV battery recycling.
From the research lab to the road, we’re helping to fuel the next generation of efficient and environmentally-friendly electric vehicles.
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