92.Batteries and fuel cells are the subject of research and development across all ‘technology readiness levels’ (TRLs). Battery development is occurring across a wider range of technology readiness levels, with technologies such as lithium-ion being mature but several others at earlier stages of research. Fuel cells are generally considered to be a more mature technology and efforts are focused on higher technology readiness levels, seeking innovations to improve performance and reduce costs. This chapter outlines avenues of research and innovation that may enable the technologies to meet the needs of users more effectively in the applications discussed in chapter 2. (More detail is provided in appendix 1.)
93.In the UK, battery research and development since 2017 has primarily been supported by the Faraday Battery Challenge, which is administered by UK Research and Innovation. The Challenge has invested £318 million since 2017, primarily to set up two new organisations and to fund operations until 2022. The Faraday Institution funds public sector research projects, and acts as a central coordinating body for much of the UK’s activity. The UK Battery Industrialisation Centre provides facilities for product developers to trial the manufacture of new batteries. However, we heard that funding is short-term, for example the Faraday Institution was initially funded for four years up to March 2022, and is currently bidding for renewal of funding primarily for electrochemical research.
94.All batteries operate in the same basic manner, storing chemical energy that can be converted into electrical energy. Once discharged, rechargeable batteries can have their store of energy replenished by the application of electricity; non-rechargeable (or ‘primary’) batteries are not relevant to this report. The simplest form of battery technology is called a ‘cell’, and a battery or ‘battery pack’ is a collection of cells (there around 10,000 cells in an EV battery) although in common parlance this distinction is often not made. The structure and operation of a cell is illustrated in figure 3 and explained in box 2.
A cell consists of two electrodes (an anode and a cathode), an electrolyte surrounding the electrodes, and a semi-permeable membrane separating the electrodes. A casing encloses the components of the cell, and multiple identical cells can be combined to form a battery.
The electrolyte is a material containing chemicals that perform the electrochemical reactions (called ‘redox’ reactions), and that conducts charged particles between the electrodes. When the electrodes of a charged battery are connected to an external electrical circuit, negatively-charged electrons flow from the anode, through the circuit (where their energy performs work, such as driving an electrical motor), and into the cathode. Positively-charged ions (formed when an electron is removed from an atom) travel through the electrolyte to the cathode and recombine with electrons. Some cells can be recharged by reversing the voltage that is applied via the external circuit, such that electrons and ions return to the anode, via the external circuit and the electrolyte, respectively.
95.Battery performance is measured by several metrics. Dr Jerry Barker, Founder and Chief Technology Officer at Faradion Ltd, explained that developers focus on performance, but also on cost and safety. The most significant measures are set out in table 2 along with examples of data for typical electric vehicle batteries.
Description and examples
The amount of energy a battery contains in proportion to its mass, typically measured in watt-hours per gram (Wh/g). A typical lithium-ion battery has an energy density of 250Wh/kg (and 250Wh happens to be enough energy to drive an EV for one mile).
Total energy stored
This is the product of the battery’s energy density and mass. A typical EV battery can store 50kWh of energy (where k stands for kilo, which means 1,000). With an energy density of 250Wh/kg, the battery would weigh around 200kg. With an energy consumption of around 250Wh per mile, its range would be around 200miles.
How long it takes to recharge the battery after its charge has been depleted. This depends on the battery’s total capacity and the current that it can tolerate without overheating.
The number of times the battery can be charged and discharged before its performance falls below an acceptable level. Cycle life is not to be confused with ‘life cycle’, which refers to the sequence of manufacture, use and disposal or recycling of a product.
Cost is measured in dollars per kilowatt-hour (kWh). For example, the cheapest lithium-ion cell produced in 2021 cost $100 per kWh. If the industry could achieve that cost for a battery pack, then a 50kWh EV battery would cost around $5,000.
96.A similar technology is the ‘supercapacitor’. It too stores energy for release in electrical form, but it stores less energy and releases it more rapidly compared to a battery. Supercapacitors were used by some vehicle manufacturers to provide extra power, but present two problems: supercapacitors can suffer from rapid self-discharging; and must be coupled with a higher energy density battery in a BEV adding complexity and cost. Now the favoured approach for vehicles is to develop more powerful batteries or combined ‘battery supercapacitor’. Supercapacitors may still play a role in some applications requiring short bursts of energy, such as power grids, trams, construction vehicles, and so on.
97.Lithium-ion batteries are the most common type of rechargeable battery. The technology is named after the lithium ions that serve as the charged particles that move within the electrolyte. Lithium is attractive for two main reasons: it can lose an electron to become an ion more easily than other metals, and it has a low mass such that its ions move more rapidly in response to an applied voltage. A non-rechargeable lithium battery chemistry was first developed in the early 1970s. After various iterations, the current design was commercialised in 1991. The Nobel Prize for Chemistry was awarded in 2019 to three of the researchers involved in developing these batteries, reflecting the impact of this technology.
98.We heard that lithium-ion batteries have been optimised over several decades to reach the performance level that has enabled them to dominate most battery markets. Improvements have involved new materials and more exacting manufacturing processes, but the resultant extra costs have been offset by the efficiencies of mass-production. The average cost globally of lithium-ion cells fell by 89% in 10 years, from $1,200 per kWh in 2010 to $137 per kWh in 2020, and has reached $100 per kWh in 2021. The costs of battery packs per kWh are higher.
99.A mature technology such as the lithium-ion battery naturally has less scope for further improvements. However, an analogy can be drawn with the semiconductor industry, where the performance of microprocessors was long predicted to be reaching a limit, but advanced engineering pushed the boundaries such that the sector has only recently had to change tack. Strategies include: optimising electrode materials to improve batteries’ lifetimes, energy densities and costs; optimising electrolyte additives (for improved energy density, lifetime and cost); and reducing the volume of inactive components (to improve energy density and cost).
100.A key performance objective is higher energy density for transport applications, in order to reduce the battery’s weight and/or increase the vehicle’s range. Professor Paul Shearing from University College London told us about the likely trajectory of energy density of lithium-ion batteries in coming years. He said that currently a good quality, off-the-shelf lithium-ion battery provides energy density of around 250 watt-hours per kilogram; that “more specialist manufacturing” might get to 300 watt-hours per kilogram; and that “tweaks to the materials and the design of the materials” could reach 350 or 400 watt-hours per kilogram. The Aerospace Technology Institute estimated that “With the introduction of new materials, and new types of electrochemical cell, the market should expect an increase in energy density in the region of 30%, a peak power increase in the range of 300%, and costs decreasing by 60–80% over the next 10 years.”
101.The Faraday Institution is funding a number of projects aiming to improve current lithium-ion battery technology, including improved electrode manufacture to increase performance, and reduced degradation to increase the lifetime. Professor Pam Thomas, CEO of the Faraday Institution, told us that “The incremental changes are worthwhile, and that is what we will have in the short term”, but for the “step changes that we require for net zero at 2050, just pushing the incremental envelope will not be sufficient.”
102.There is merit in the automotive sector continuing to adopt incremental improvements in lithium-ion technology, to make the best use of existing investments in manufacturing. However, it is important that manufacturing processes are adaptable so that non-lithium-ion chemistries can be adopted in future without incurring the full costs of establishing new manufacturing facilities.
103.Several avenues are being explored to take battery technology beyond the limits of lithium-ion chemistry. Witnesses told us about the approaches set out below; these are discussed in more detail in the Nature Communications article from 2020. Each approach would take the technology in a different direction, offering different advantages. They all can be developed in parallel but some could be implemented in combination to give a range of benefits. The Faraday Institution Beyond Lithium Ion portfolio is funding three next-generation batteries “that are looking beyond the fundamental limits of lithium ion technology to the development and commercialisation of new battery chemistries”.
104.Lithium could be replaced with sodium and other metals that have similar chemistries, including, magnesium, calcium and aluminium. Sodium is abundant and easily accessible, and hence has the potential for cheap batteries. Dr Barker told us that sodium-ion technology is more sustainable than lithium-ion owing to its lack of “lithium, … copper or cobalt”, and it is safer than lithium-ion (in terms of ease of shipping). He added that the sodium battery being designed by Faradion “could be built on existing lithium-ion lines, so you do not have to go off and develop a new manufacturing process.” The Faraday Institution is providing £11.5 million over 4 years for the Nexgenna sodium-ion research project., This project aims to develop the technology (from research through to manufacturing) for applications in stationary storage and low-cost vehicles.
105.However, the energy density of sodium-ion technology is lower that of lithium-ion (essentially because sodium ions are larger and hence fewer fit into the same volume). Dr Barker told us that the sodium-ion battery being developed by Faradion has an energy density of around 160 watt hours per kilogram, and that this is expected to rise to “well over 200 watt hours per kilogram”. He said that sodium-ion will not displace the “top-end of the lithium-ion market”, and explained a strategy of “looking to replace lead-acid technology in mobility applications, forklifts, telecoms, and lots of other different application.” He added that “When you have no constraint on weight or volume, you can have large-format applications for renewable storage and grid storage”.
106.Some of the challenges in battery performance can be addressed by moving away from liquid electrolytes, to a solid-state battery with metal electrodes (including lithium, as discussed below) and a ‘solid-state electrolyte’. There are four potential advantages of solid-state batteries compared with liquid electrode batteries: improved fire safety; higher energy density; faster charging times; and longer life. Due to these advantages, Professor Pasta from the University of Oxford said “every automotive company is looking quite heavily into solid state” but timescales for development are uncertain, ranging from the 2030s to the 2040s, whilst some believe it will be “difficult to get solid state produced at cost.” The Faraday Institution is providing £15.3 million over 5 years for the SOBALT project that is researching solid-state batteries. This project aims to remove barriers to manufacturing, for example through new materials or processes, in order to enable commercialisation of solid-state batteries.
107.One strategy for next-generation batteries is to replace the standard anode with one made of pure lithium, to reduce the mass of the anode (by removing the need for graphite) and to be the source of lithium ions in the cell. Two options are being considered: lithium-sulfur batteries and lithium-air batteries. Johnson Matthey anticipates that these technologies can increase energy density by up to ten times with respect to current lithium-ion batteries. They would be cheaper and more sustainable than lithium-ion because they do not use some of the more expensive materials and sulfur is abundant, and lithium air would avoid even the cost of sulfur. Another advantage of lithium-air batteries is better recyclability. The Faraday Institution is providing £7.5 million over 4 years for the LISTAR lithium-sulfur research project. This project aims to advance the technology through fundamental materials research, but also to develop the systems engineering needed to create a commercial product.
108.A redox flow battery (or simply a ‘flow battery’) uses the same basic electrochemical processes as other rechargeable batteries with liquid electrolytes. The difference is that its electrolytes are pumped through the cell from external tanks, allowing larger volumes of electrolyte to interact with the electrodes. The technology decouples the power (determined by the size of the battery) and energy (determined by the size of the tanks), so that it can be deployed at larger scales simply by increasing the amount of electrolyte available in tanks. Flow batteries can offer a number of other advantages: less material-intensive manufacture; less degradation over time; and better fire safety.
109.The large size of flow batteries (including the tanks and pumps for the electrolytes) make them less suited to transport applications, and they are seen as an option for large-scale stationary energy storage. The Faraday Institution has two projects under its Batteries for Emerging Economies portfolio. However, the current lower cost of lithium-ion batteries (including putting used batteries from cars onto power grids) has meant that flow batteries have not yet become established in the UK.
110.We heard that the UK’s current investment in batteries research and development is lower and of shorter duration compared to initiatives in competitor countries. The Faraday Battery Challenge has received £318 million over four years, primarily for the Faraday Institution and the UK Battery Industrialisation Centre. The Faraday Institution’s current funding is £30 million per year out to March 2022, and it is applying for continuation of this core funding. It is also bidding for an additional £20 million per year to expand its work to include engineering aspects. By comparison, in 2019 the European Commission approved €3.2 billion of investments by seven Members States out to 2031, to support “research and innovation projects in all segments of the battery value chain”. This equates to an average of around £270 million per year over ten years. It includes €960 million of investments by France and €1.25 billion by Germany.
111.We heard that the UK lacks sufficient funding across the technology readiness levels. Dr Barker said of battery research and development in the UK that there are funds for lower technology readiness levels, but less for demonstration projects. This echoed concerns from other witnesses about challenges with scaling up, such as lack of availability of materials. For automotive applications, the UK Battery Industrialisation Centre can help to move work through the scale-up stage, but its focus is not on stationary batteries.
112.The number of patents filed is one measure of research and innovation. A joint study by the European Patent Office and the International Energy Agency found that Japanese companies including Panasonic and Toyota Motors hold more than a third of the world’s patents for vehicle batteries. From 2000 to 2018, Asian companies account for nine of the top ten global applicants, and for two-thirds of the top 25.
113.We heard about the need for long-term strategy in research funding. Dr Chamberlain explained that the US battery industry was currently benefitting from research funded in the 1990s. He said that “The United Kingdom has just lagged a bit in overall funding into research”, but that “it is not too late to ramp up your research dollars, so that five to 10 years from now those research projects are turning into companies.” Professor Pam Thomas said: “From a UK perspective, we will not overtake existing manufacturers of the current lithium battery technology. It would serve us better to leapfrog the current technology and look at where we might be able to have a world lead in establishing next-generation technologies.”
114.The UK’s current investments in battery research and development are welcome, but need to be increased and put on a longer-term footing if the UK is to compete internationally. Proposals for additional funding for research and development in the UK should be seen in the context of the Government’s ambition for the UK to be a ‘science superpower’. The Government has made clear spending commitments for research and development: public funding is to reach £22 billion per year by 2024–25 (up from around £15 billion in 2021–22); and total annual UK spending on research and development is to reach 2.4% of GDP by 2027.
115.UK Research and Innovation should prioritise initiatives for batteries and fuel cells in its bid for the 2021 Spending Review. It should seek to support technologies all the way through the technology readiness levels to manufacture.
116.The Government should provide additional funds for the development of batteries and fuel cells, which are essential for achieving the net-zero target and for achieving the UK’s industrial ambitions. This funding can be provided within the budget increases for research and development out to 2024–25. Funding should be comparable to international competitors, and should have long-term certainty in order to build the UK’s research base, develop momentum and ensure that advances are fully exploited.
117.UK Research and Innovation should expand the remit of the Faraday Institution and the UK Battery Industrialisation Centre to include stationary batteries, with commensurate additional funding from Government.
118.UK Research and Innovation should expand its portfolio for developing next generation batteries, with commensurate additional funding from Government. This will help to establish a long-term advantage for the UK, for example in solid-state batteries for vehicles and sodium-ion batteries for stationary storage.
119.Fuel cells are an energy conversion technology, transforming chemical energy from hydrogen-rich fuel (by combining it with oxygen) into electricity and heat (and producing water, along with other by-products when using fuels other than hydrogen). Fuel cells can be complementary to electrolysers, a technology that essentially operates in reverse to fuel cells, in that an electrolyser uses electricity to break down a chemical, for example to break down water to produce hydrogen and oxygen.
120.There are several different types of fuel cell, but they all share a common structure and means of operation, which is illustrated in figure 4 and described in box 3. Fuel cells can be designed to operate with different fuels that contain hydrogen. For the purposes of decarbonisation, most of the interest is in hydrogen. Ammonia is also being considered for applications such as shipping, but poses challenges such as the production of nitrous oxide pollution.
Fuel cells contain an anode and a cathode, with an electrolyte in between, and. a structure called a ‘flow field’ that sits on the outside of each electrode. The flow field allows fuel and air to flow continuously to the anode and cathode, respectively. Common fuels are pure hydrogen (H2), methanol (CH3OH), ammonia (NH3), and methane or biomethane (CH4). The anode is coated with a catalyst (such as platinum), which is a material that assists a chemical reaction but is not itself changed by the reaction, and hence remains in place to assist the reaction again. The catalyst at the anode helps to separate each atom of hydrogen into its constituent protons (H+) and electrons (e-). The electrons flow into an external circuit as an electrical current that can perform work (for example, turn an electric motor) and into the cathode. The protons move through the electrolyte into the cathode. When the protons and electrons meet in the cathode, they combine with the oxygen (O2) atoms from the air that is being pumped across the cathode, generating water (H2O) and heat (again assisted by a catalyst, usually a platinum alloy). Carbon-based materials called ‘ionomers’ are used to bind the catalyst particles in position and to form membranes.
121.There are several different types of fuel cell, broadly distinguished by the type of electrolyte they use and/or by their operating temperature. They can be grouped into three broad types based on their operating temperature, as summarised in table 3. Within each group there are many variations.
Description of technology
Also known as ‘polymer electrolyte membrane’ or ‘proton-exchange membrane’ (PEM) fuel cells. They are well-suited to low-carbon transport applications: they can be designed to run on hydrogen, can start in sub-zero temperatures, and they can be tailored to either light- or heavy-duty vehicles. They use platinum group metals as catalysts, which are expensive.
These are a newer version of fuel cell. The temperature of the heat produced can be useful for other processes (e.g. in industry). They do not use platinum group metals as catalysts.
(up to 1,000°C)
Also called solid oxide fuel cells (SOFC). These can be used for power generation, heating and industrial processes. Their high temperature necessitates thermal shielding, and makes them less suited to portable and transport applications.
122.The main type of electrolyser technology is polymer electrolyte membrane. This technology is very similar to low-temperature proton-exchange membrane fuel cells. Currently, most hydrogen is manufactured from methane using a process called ‘steam methane reforming’ (SMR), which emits CO2 and is associated with upstream methane leakage. As noted earlier, another option being explored is the use of advanced nuclear reactors (also called ‘Generation IV’ technology), for which small-scale demonstration projects are underway.
123.Recent advances and ongoing research are mainly aimed at improving fuel cells’ lifespans and reducing their costs. These advances have primarily been achieved through modifying the materials that are used in fuel cells to be more efficient, longer lasting, and cheaper to acquire and produce. Areas of ongoing research include: alternative catalysts; reduction of degradation; efficiency of manufacturing processes; and provision of ancillary equipment.
124.Cost reduction is a key objective that runs through several of the topics discussed below. Intelligent Energy told us that fuel cell costs have fallen by 50% over the past five years, due to improvements in materials, components, manufacturing and supply chains. For transport applications, the Automotive Council’s 2020 Fuel Cell Roadmap notes that “Light duty vehicles prioritise cost reductions, which will largely be achieved through economies of scale of key components” whereas “Heavy duty vehicles … prioritise durability and can be slightly more tolerant to higher costs if the total cost of ownership for fleet operators is kept low.”
125.UK H2Mobility provided forecasts of performance and cost to 2030. The expectation is that the cost of fuel cells for light-duty vehicles will fall by 42% per kW of power output and the cost of fuel cells for heavy-duty vehicles by a third. In addition, the data suggest that the hydrogen consumption of both types of fuel cell will fall by over 10%. Johnson Matthey told us that the total cost of ownership for fuel cell HGVs is expected to “drop below that of diesel trucks in the second half of the 2020s”.
126.Platinum alloys are the most common catalysts in low-temperature polymer electrolyte membrane fuel cells. Platinum is expensive, and researchers are exploring various avenues to reduce costs whilst maintaining efficiency. The efficiency of platinum-based catalysts can be improved, allowing the amount of platinum to be reduced. The industry aims to cut the content by two-thirds by 2030. An added benefit of reducing the amount of platinum in the catalyst is reduced susceptibility to contaminants in the fuel.
127.Fuel cells can suffer from issues such as ‘side reactions’ at the electrodes and contamination of the catalysts, which degrade their performance over time and hence their reduce lifespan. Degradation is more of an issue for high temperature (solid oxide) fuel cells, in which reactions (including damaging processes) proceed more rapidly. Improvements have been made, with Johnson Matthey noting that “performance and durability have increased significantly over the past 10 years”. However, some of the processes are poorly understood, and further research is required.
128.We heard that fuel cells convert chemical energy into electricity with an efficiency of around 60%, with the rest emitted as heat. If that heat is utilised (as in a CHP unit) then the overall efficiency is well over 90%. However, for applications such as transport in which there is no use for the heat, the aim is to improve the efficiency of electrical generation. Professor Kucernak told us that the long-term goal is efficiency “of over 70%, which seems reasonably achievable”. He said that low-temperature fuel cells are currently optimised for transport, with the aim being to “achieve the largest power density possible” and so the fuel cells are “not necessarily optimised for efficiency”. He advised that for “fuel cells for energy production, for instance in power plants, we can quite easily improve the efficiency by decreasing the power density”.
129.Fuel cells can be manufactured at different scales. Further reductions in size would open up more opportunities in transport and portable systems. For the development of smaller, portable high-temperature fuel cells, one challenge is ensuring the safety of the thermal shielding. There are also drivers for developing larger fuel cells, which are more efficient. Professor Russell said that “the better utilisation of fuel cells is with the larger ones, in integrating that into the whole system [and] making localised use of hydrogen that is produced.”
130.Fuel cells are supported by other equipment, in which improvements are being made, such as compressors, sensors and storage tanks. Professor Brandon told us that “The most expensive part of a hydrogen fuel cell car today is the hydrogen tank, so there is room for innovation in how you carry the fuel. Professor Kucernak said that research into hydrogen storage is needed “to reduce the cost of the storage and improve the efficiency and density”, noting that the current carbon fibre tanks are “quite an expensive technology at the moment” but “mass scale-up will reduce the cost of those materials significantly.” Ammonia can be stored more easily than hydrogen, such that it is being considered for fuel cells applications such as shipping that require higher energy density. However, as noted earlier combustion of ammonia presents a hazard in the event of a spillage, and its combustion produces air pollution, both of which would have to be addressed were ammonia to be used as a fuel.
131.Several witnesses supported deploying fuel cells as part of a wider hydrogen strategy, in which hydrogen would be produced by electrolysers. There is scope to improve performance of electrolysers in terms of energy efficiency, and the separation of the gases that are produced. There is merit in ensuring that the fuel cells and electrolysers can be deployed together and integrated efficiently. Professor Kucernak said it was important to “increase the round-trip efficiency of the conversion of renewable electricity to hydrogen and then convert that hydrogen back into electricity”.
132.Fuel cells will benefit from ongoing innovation to improve performance and durability and to reduce costs. They are well-suited to a range of applications, but the sector may require support to tailor the technology to each application.
133.We heard that public sector funding of fuel cell research and development in the UK is very low compared to its international competitors. UK funding for fuel cell research has fallen in recent years, and it received only £8 million in 2021–22, which equates to 0.14% of the portfolio of the Engineering and Physical Sciences Research Council (EPSRC). The EPSRC website states: “Fuel Cell Technology is not currently a high priority for government or industry and has a comparatively lower impact than other technologies on the UK’s ability to reach its ambitious 2050 greenhouse gas reduction targets.” In 2012, UK Research and Innovation established the H2FC Supergen Hub, which seeks to coordinate activities by convening researchers from universities and industry, and has directed some public sector grant funding. However, some fuel cell development may be able to draw on battery research, for example in electrochemistry and in developing electrodes. By comparison we were told that, Japan provided around £220 million in 2019 for research and development in hydrogen and fuel cells.
134.We heard that some types of fuel cells are a mature technology. ITM Power said that “Low TRL research is not a prerequisite to commercial deployment, but ongoing R&D is important to help improve the economics of [fuel cells] and electrolysers across the 2020s.”Professor Irvine told us that funding for hydrogen in the UK focuses on demonstration projects rather than lower technology readiness levels. One approach that was discussed was to establish organisations similar to those in the battery sector to support research and scale-up.
135.The current funding for fuel cell research and development is inadequate, and the sector needs to be supported through the establishment of initiatives and organisations akin to the Faraday Institution and the UK Battery Industrialisation Centre. These proposals should be seen in the context of the Government’s commitments to significantly increase public funding for research and development.
136.The Government should establish organisations to support research and scale-up for the fuel cell and hydrogen sector, equivalent to the Faraday Institution and the UK Battery Industrialisation Centre, guided by a clear analysis of where research and demonstrations are needed.
156 Technology Readiness Levels (TRLs) were originally developed by NASA as a method of measuring the maturity of space exploration technology, and are now used widely in technology sectors. They range from TRL1 (basic principles), TRL2 (invention and research), and so on though piloting and up to TRL9 (operations).
157 UK Research and Innovation, ‘Faraday Battery Challenge’ (May 2021): [accessed 25 June 2021]
158 The Faraday Institution, ‘About the Faraday Institution’ (2017): [accessed 25 June 2021]
159 UK Battery Industrialisation Centre, ‘Who we are’ (2020): [accessed 25 June 2021]
160 Supplementary written evidence from The Faraday Institution ()
161 (Professor Mauro Pasta)
162 (Dr Jerry Barker)
163 See for example, Electric Vehicle Database, ‘Energy consumption of electric vehicles’ (2021): [accessed 23 June 2021]
164 Technically, this is ‘specific energy’ or ‘gravimetric energy density’, but the terms are used somewhat loosely. A related metric is ‘volumetric energy’, defined as the battery’s energy content in relation to its volume, usually measured in Watt-hours per litre (Wh/l).
165 All capacitors perform the function of storing electrical energy for rapid release. Standard capacitors are made of ceramics. Supercapacitors have larger capacity, and tend to include more advanced materials.
166 The atomic mass of an element is a measure of the mass of an atom of that element, with the unit atomic mass unit (amu). The atomic mass corresponds approximately to the number of protons and neutrons in the atom’s nucleus. The number for any element is not an exact integer due to the existence of isotopes of elements (atoms with the same number of protons and hence the same chemistry, but different numbers of neutrons).
167 As per Newton’s first law of motion, acceleration is inversely proportional to mass, so a lighter ion will accelerate faster in response the force caused by a given electrical potential, reducing its travel time.
168 United States Patent Office, Electrochemical Cell (25 November 1975): [accessed 14 July 2021]
169 Sony Energy Devices Corporation, ‘Keywords to understanding Sony Energy Devices’ (2016): [accessed 14 July 2021]
170 The Royal Swedish Academy of Sciences, ‘Press release: The Nobel Prize in Chemistry 2019’ (2019): [accessed 14 July 2021]
171 (Professor Mauro Pasta)
172 (Professor Mauro Pasta)
173 BloomberNEF, ‘Battery Pack Prices Cited Below $100/kWh for the First Time in 2020, While Market Average Sits at $137/kWh’ (16 December 2020): [accessed 2 July 2021]
174 Encyclopaedia Britannica, ‘Moore’s Law’: [accessed 14 July 2021]
175 Clare Grey and David Hall, ‘Prospects for lithium-ion batteries and beyond—a 2030 vision’, Nature Communications, vol. 11, article 6279 (8 December 2020): [accessed 2 July 2021]
176 (Professor Paul Shearing)
177 Written evidence from the Aerospace Technology Institute ()
178 The Faraday Institution, ‘Lithium-ion’: [accessed 2 July 2021]
179 (Professor Pam Thomas)
180 Clare Grey and David Hall, ‘Prospects for lithium-ion batteries and beyond—a 2030 vision’, Nature Communications, vol. 11, article 6279 (8 December 2020): [accessed 2 July 2021]
181 The Faraday Institution, ‘Beyond lithium-ion’: [accessed 2 July 2021]
182 (Professor Mauro Pasta)
183 (Dr Jerry Barker)
184 (Dr Jerry Barker)
185 The Faraday Institution, ‘Nexgenna—Sodium-ion batteries’: [accessed 2 July 2021]
186 (Dr Jerry Barker)
187 (Professor Serena Corr)
188 The Faraday Institution, Solid-State Batteries: The Technology of the 2030s but the Research Challenge of the 2020s (February 2020): [accessed 2 July 2021]
189 (Professor Mauro Pasta)
190 The Faraday Institution, ‘Solbat—Solid-state metal anode batteries’: [accessed 2 July 2021]
191 (Dr Melanie Loveridge)
192 Written evidence from Johnson Matthey ()
193 The Faraday Institution, ‘LiSTAR—The Lithium-sulfur technology accelerator’: [accessed 2 July 2021]
194 See, for example, discussion here: DNV, ‘Can Flow Batteries compete with Li-ion?’: [accessed 2 July 2021]
195 Weber et al., ‘Redox flow batteries: a review’, Journal of Applied Electrochemistry, vol. 41, article 1137 (21 September 2011): [accessed 2 July 2021]
196 The Faraday Institution, ‘Batteries for emerging economies’: [accessed 7 July 2021]
197 See, for example, discussion in: GTM, ‘Flow Batteries Struggle in 2019 as Lithium-Ion Marches On’ (4 November 2019): [accessed 2 July 2021]
198 Supplementary written evidence from The Faraday Institution ()
199 European Commission, ‘State aid: Commission approves €3.2 billion public support by seven Member States for a pan-European research and innovation project in all segments of the battery value chain’ (9 December 2019): [accessed 2 July 2021]
200 (Dr Jerry Barker)
201 European Patent Office (EPO) and the International Energy Agency (IEA), Innovation in batteries and electricity storage—a global analysis based on patent data (September 2020): [accessed 2 July 2021] The data used is ‘International patent families’ (IPFs), defined as “a high-value invention for which patent applications have been filed at two or more patent offices worldwide”.
202 (Dr Jeffrey Chamberlain)
203 (Professor Pam Thomas)
204 Encyclopaedia Britannica, ‘Types of fuel cells’: [accessed 22 June 2021]. See also Sergio Yesid Gómez and Dachamir Hotza, ‘Current developments in reversible oxide fuel cells’, Renewable and Sustainable Energy Reviews, Volume 61 (August 2016) pp 155–174: [accessed 22 June 2021]
205 (Jo Godden)
206 (Professor Anthony Kucernak)
207 (Professor Andrea Russell) and (Professor Anthony Kucernak)
208 Written evidence from ITM Power plc ()
209 Nuclear Engineering International, ‘UK’s ten point plan supports small and advanced reactors’ (20 November 2020): [accessed 7 July 2021]
210 G.J.K. Acres, ‘Recent advances in fuel cell technology and its applications’, Journal of Power Sources, vol. 100 (30 November 2001) pp 60–66: [accessed 25 June 2021]
211 Written evidence from Intelligent Energy ()
212 Written evidence from the Advanced Propulsion Centre UK Ltd—Fuel Cells ()
213 Written evidence from UK H2Mobility ()
214 Written evidence from Johnson Matthey ()
215 (Professor Andrea Russell)
216 (Professor Nigel Brandon OBE) and Written evidence from ITM Power plc ()
217 H2FC Supergen, ‘Polymer Electrolyte Fuel cells’ (2021): [accessed 25 June 2021]
218 See, for example, Graves et al., ‘Eliminating degradation in solid oxide electrochemical cells by reversible operation’, Nature Materials, vol. 14 (December 2014) pp 239–244: [accessed 25 June 2021]
219 Written evidence from Johnson Matthey ()
220 The European Materials Research Society, the Materials Science and Engineering Expert Committee and the European Science Foundation, Materials for Key Enabling Technologies (21 June 2011): [accessed 25 June 2021]
221 (Professor Anthony Kucernak)
222 (Professor Anthony Kucernak)
223 The European Materials Research Society, the Materials Science and Engineering Expert Committee and the European Science Foundation, Materials for Key Enabling Technologies (21 June 2011): [accessed 25 June 2021]
224 The European Materials Research Society, the Materials Science and Engineering Expert Committee and the European Science Foundation, Materials for Key Enabling Technologies (21 June 2011): [accessed 25 June 2021]
225 (Professor Anthony Kucernak)
226 (Professor Andrea Russell)
227 (Professor Nigel Brandon OBE)
228 and (Professor Anthony Kucernak)
229 (Professor John Irvine)
230 (Professor Anthony Kucernak)
231 Engineering Physical Sciences Research Council (EPSRC), ‘Fuel cell technology’ (2021): [accessed 28 June 2021]
232 Engineering Physical Sciences Research Council (EPSRC), ‘Fuel cell technology’ (2021): [accessed 28 June 2021]
233 H2FC Supergen, ‘About H2FC Supergen’ (2021): [accessed 25 June 2021]. See also H2FC Supergen, H2FC Supergen: Five Years of Impact (April 2017): [accessed 25 June 2021]
234 Written evidence from Ceres Power (). See also (Professor Paul Dodds)
235 Written evidence from ITM Power ()
236 (Professor John Irvine)
237 (Professor Philip Taylor) and (Professor David Greenwood)