Chemistry Week 2021: How chemistry is driving sustainability through electric vehicle battery technology

The Royal Society of Chemistry (RSC) has opted to hold its annual Chemistry Week this year on 1-12 November 2021, to coincide with the 26th UN Climate Change Conference of the Parties (COP26).  To reflect and celebrate themes that span both COP26 and the RSC’s Chemistry, Sustainability and Circular Economy (CSCE) campaign, the society has chosen ‘sustainability’ as the focus of Chemistry Week 2021. With this in mind, we are marking the event with an article celebrating how chemists are driving forward sustainability in the automotive sector. 

As announced by the government in November 2020, the UK will phase out the sale of new petrol and diesel-powered cars by 2030, with many other countries following similar roadmaps. Such efforts will put huge pressure on the electric vehicle (EV) market to provide alternative vehicles that are convenient, reliable and cost-effective. The engines leading these efforts are the chemists, harnessing all the expertise of their field to revolutionise the automotive industry.

As the world faces the climate change crisis, its historic reliance on fossil fuels in powering the approximately 1.4 billion vehicles in use globally (as of 2021) is becoming increasingly unsustainable. Alternate means of fuelling our vehicles must be found, and, having gained considerable momentum over the past few years, EVs are at the forefront of these efforts.

The classification of EVs encompasses a broad field, including vehicles powered by fuel cells, solar cells and batteries, but they are all united by the fundamental importance of chemistry in governing their efficacy. The most popular type of electric vehicle relies on its onboard battery to store chemical energy that can be transformed into electrical power. This battery is a crucial element in the operation of such EVs, and extensive research is being conducted globally to find compounds – and their combinations – with the most advantageous chemical properties that can bring about the next revolution in battery technology. According to a joint European Patent Office (EPO) and International Energy Agency (IEA) study, patenting activity of battery technologies grew at an average annual rate of 14% between 2005 and 2018. Currently, the most abundant type of battery is the one that helped kick-start fully electric vehicles: the lithium-ion (Li-ion) battery. 

The first patent for a Li-ion battery in its modern form was filed in 1983, by Professor Akira Yoshino while working for the company Asahi Kasei. This helped them to control 17% of the global market share for Li-ion battery separators until 2016. Sony, alongside Asahi Kasei, later went on to commercialise the first Li-ion battery product in 1991, protected by the security afforded by their patents. By 2015, they had shipped over five billion cells and pioneered a revolution in modern battery technology.

While the Li-ion battery was a huge step forward in battery technology – providing much higher charge density and effective rechargeability – within the context of EVs, there are still many limitations to overcome, with capacity being a prominent example. The average range of a fully charged EV (across the spectrum of manufacturers) is around 300km, with many being significantly lower. However, an understanding of the chemical properties that give rise to this limitation – namely the storage density of lithium atoms within the electrode materials – has allowed researchers to develop promising alternatives.

One such example is a prototype lithium-sulfur battery with the potential to more than double the specific energy (energy per unit mass) of Li-ion batteries. This innovation is based on replacing the cobalt-based cathode material with one comprised of S8 sulfur. As Li-ions and electrons converge at this cathode during discharge, a series of sequential reactions eventually reduce the octatomic S8 to eight individual sulfur atoms each bonded to two lithium atoms. In this way, each sulfur atom within the cathode can accommodate two Li-ions, in comparison with the roughly 0.6 Li per host atoms that conventional Li-ion batteries achieve. However, many other alternative solutions are being explored, such as the use of nickel, phosphates, and manganese, hinting that there is still space for innovation in this field.

The speed at which an EV can be charged is also a crucial limitation, with serious consequences for public adoption of fully electric vehicles if not suitably resolved; who wants to spend seven+ hours recharging their car when they forgot to charge it overnight, or take half an hour for a ‘quick’ top up just to get them home? While there are certainly vast infrastructure improvements to be made to alleviate some of this concern, chemistry still has plenty to offer on this front too. This research is primarily focused on the anode and electrolyte, as these are where the rate-limiting steps in the charging process occur. Regarding the anode, the theoretically superior properties of silicon (such as its 10-fold higher specific capacity) have made it a widely studied material. For example, it is the basis of an upcoming EV battery that claims to achieve five-minute charging times. 

The chemistry of electrolytes is also making significant contributions towards resolving these issues.  While conventional Li-ion batteries make use of liquid electrolytes, consisting of lithium salts in various organic solvents, many are turning their attention to the benefits solid-state electrolytes could provide (such as greater energy density and improved safety). Examples such as certain lithium metal oxides exist as a crystalline lattice that can possess extremely high ionic conductivity, permitting the rapid movement of lithium ions between the electrodes. Efforts being made towards the successful development of these solid-state batteries can be demonstrated by the fact that automotive manufacturer Toyota reportedly holds over 1,000 patents in the field. Nonetheless, there undoubtedly remains a wealth of opportunity across the entire field of battery development for the discovery of the next transformative breakthrough.

New technologies, even those as groundbreaking as the Li-ion battery, can take upwards of 20 years to successfully commercialise, so ensuring that you are able to exploit your invention to fully reap the rewards of your work and investment is important. Patents are an invaluable tool in protecting your intellectual property, giving you control over how your ideas are used.