Lithium battery replacement technology
In 2019, the Royal Swedish Academy of Sciences awarded the Nobel Prize in Chemistry to three scientists for the development of lithium-ion (Li-ion) batteries that, according to the Academy, have laid the foundation for a fossil fuel-free economy. Li-ion batteries can safely store large amounts of energy, ensuring stable and predictable flows of electricity even in decentralized immobile (i.e., stationary) or mobile modes in remote areas. The increasing popularity of passenger electric vehicles and electric buses is largely a result of the capacity improvement of Li-ion batteries and significant price declines due to investment in productive capacity.
It is the urgent and inescapable mandate for the entire humanity to reduce greenhouse gas (GHG) emissions to mitigate climate change and build a fossil fuel-free economy. As examined below, the utility and transport sectors have been the two major emitters of GHGs and, without reducing GHGs from these two sectors, the Paris Agreement of limiting global warming to 1.5 C cannot be achieved. Li-ion batteries have been a promising clean technology because the battery stores energy in its cells, as opposed to generating energy by combusting fossil fuels in a gasoline and diesel engine, to power a vehicle or provide electricity to a building (see box 1 for the capability of Li-ion batteries). When batteries are recharged with fossil fuel-free electricity, Li-ion batteries fully contribute to a fossil fuel-free economy.
This Frontier Technology Issues examines the recent trends in production and use of Li-ion batteries, in which the two major emitters, utility and transport sectors, have been the two largest users of Li-ion batteries. It considers how the applications of the batteries in the two sectors are expected to reduce GHG emissions. The last section examines the role of governments in removing technological and economic obstacles and encouraging the wider application of Li-ion batteries.
Lithium-ion batteries are helping reduce greenhouse gas emissions
To mitigate climate change and create a fossil fuel-free economy, the global community has agreed that GHG emissions must be reduced rapidly and significantly.1 Human activities have emitted about 50 billion tons of GHGs (CO2 equivalent) at the global level every year from the mid-2010s, in which the electricity and heat sector is the dominant emitter, followed by transport, manufacturing and agricultural sectors (figure 1).
Li-ion batteries are a promising clean technology to replace the conventional fossil-fuel powered device. Batteries have been particularly important in the two sectors most responsible for GHG emissions: electricity generation and transport. Even more importantly, the gains of one sector are leading to further gains in the other, creating a virtuous cycle of lower cost, greater production, and greater demand.
In electricity generation, inexpensive Li-ion batteries are enabling grids to install more renewable energy capacity using solar and wind sources.2 One of the well-known shortcomings of solar and wind-power energy sources is their large variability in power generation. The sun does not always shine, and the wind does not always blow. Batteries are used to store up surplus power when generation is abundant for use or to distribute power when there is a deficit. In addition, the large capacity of batteries to store energy can reduce the maximum capacity needed by power plants (and associated construction costs), which are designed to meet the estimated peak demand during, say, a hot summer day when the use of air conditioners are above normal.
In the transport sector, batteries are enabling a revolution in electric vehicles of all types. Li-ion batteries can help manufacturers replace conventional automobiles with combustion engines powered by fossil fuels. In the United States market alone, global manufacturers have announced plans to introduce nearly 100 purely electric vehicle models by the end of 2024 (Preston, 2021). Demand for Li-ion batteries has grown from mere 19 gigawatt hours (GWh) in 2010 to 285 GWh in 2019. It is forecast to reach 2,000 GWh in 2030—about 8 per cent of world energy supply (figure 2). Passenger and commercial electric vehicles continue to be the dominant uses of Li-ion batteries in terms of capacities installed, followed by stationary (energy) storage.
The increasing popularity of Li-ion batteries owes to its much-improved portability and significant price declines over a quarter-century since the introduction of the battery at the household level. At the beginning of the 1990s, the storage capacity that is required to power a regular-sized house in the United States for a day would have cost about 75,000 and the battery package would have weighed 111kg (equivalent to a size of a beer keg) (Economist, 2021). The same level of capacity can now be obtained at a cost of around 5000,000 from a 40kg, small backpack-sized cell. Figure 3 shows a time series of Li-ion battery at 2018 constant US dollars per kilowatt hour (KWh). Since 2010, the cost per KWh of Li-ion batteries has dropped by 87 per cent.
Progress continues to accelerate. According to the International Energy Agency (IEA, 2020a), batteries in general account for nearly 90 per cent of all patenting activity in electricity storage, and that the rise in innovation has been largely driven by advances in rechargeable Li-ion batteries used in consumer electronic devices and electric cars. Solid-state Li-ion batteries are considered to be the next generation of Li-ion batteries for their higher energy density, safety and faster recharging times. At the same time, more affordable Li-ion batteries have been developed by replacing expensive cobalt—a critical substance—with more commonly available materials at the expense of energy density.
The importance of batteries in the transportation sector
As the battery energy density has soared and have dropped, the Li-ion battery has become the major source for the electrification of various sizes of vehicles such as bicycles, scooters, cars, buses, trucks, and even ferries.4 Shipping and aviation are also making electrification progress, though at the very infant stage. Battery technology has the potential for further becoming a great enabler for sustainable transport.
Electrification of the transportation sector
Sales of new passenger electric vehicles have significantly increased leading to the year 2019, when sales temporarily slowed down to 2.1 million globally (figure 4) (IEA, 2020c). Despite the COVID-19- pandemic, however, the combined effects of existing policies and targeted stimulus responses are estimated to have increased the global sales of new passenger electric vehicles by 40 per cent, reaching over 3 million in 2020, with a market share of new car sales of over 4 per cent (IEA, 2021). Some countries in Europe provided an additional boost to compensate for the impacts of the COVID-19 crisis and re-asserted their targeted support to electric vehicles as part of their economic stimulus programs. At the end of 2020, more than 10 million passenger electric vehicles are estimated to be on the road, making 2020 a record-breaking year for electric mobility.
Electric vehicles have so far served the richer segment of global consumers—the ones who could afford to buy this relatively expensive mode of transformation and find electric vehicles an ideal choice for curbing climate change. The IEA predicts that the number of passenger electric vehicles on the road around the world could hit 125 million by 2030, but as high as 220 million could be on the road by 2030 if governments would undertake more aggressive policies and regulations to fight climate change and cut GHG emissions.
Larger vehicles are electrifying, as well. There are about half a million electric buses (E-buses) on the road, most of which are in China. The E-buses have been used as inner-city transport, and not for long distances, as their shorter ranges are more suitable for electrification. Similarly, the electrification of larger trucks is mostly in urban environments. Electrification of long-distance buses and heavy freight trucks have been dismissed as too costly, as the energy density of Li-ion batteries is too low to compete with the range that conventional buses and trucks cover with a single refueling. Global sales of electric trucks remained low but, as battery technology is improving rapidly, long-distance buses and heavy trucks are forecast to become more competitive (Nykvist and Olsson, 2021).
Electric vehicles and CO2 emissions
Currently, private vehicles—both electric vehicles and conventional cars—emit around 5 billion tons of CO2 annually, with a total annual CO2 emission at around 36 billion tons in 2018. Electric vehicles can reduce CO2 emissions in the transportation sector, with benefits including zero tailpipe emissions. But the electricity is still produced from fossil fuels in many countries, and there are emissions stemming from the manufacturing of the vehicle and the battery. The manufacturing of electric vehicles generally produces more emissions than a conventional car because of the batteries, but on average, electric vehicles account for fewer emissions through the fuel production and vehicle use phases. The life cycle emissions of electric vehicles depend on the CO2 intensity of power generation and in high-carbon intensity electricity systems, electric vehicles might save little CO2 compared to conventional vehicles. Maximizing the use of renewable energy to power electric vehicles is therefore particularly important for sustainable transportation.
According to Hall and Lutsey (2018), overall, electric vehicles typically have lower life-cycle GHG emissions than a typical car in Europe, but the emissions reduction depends on the country and the carbon intensity of local electricity production. When comparing with the most efficient internal combustion engine vehicle, a typical electric car in Europe produces 29 per cent less GHG emissions throughout its life cycle (figure 5).
However, the overall impact of transport electrification on emissions is complicated and different studies take different approaches to quantify the impact. According to estimates from IEA (2020d), based on the current electricity mix, replacing a ten-year-old conventional vehicle with a battery-electric vehicle would generate lifetime emissions savings of 80 per cent in the European Union, 60 per cent lower in the United States and around 40 percent lower in China.
The importance of batteries for the energy sector
As examined in UN DESA (2020), energy storage can help bring modern energy for all, particularly in the sub-Saharan region, where the share of the population with access to modern energy is low. The use of stationary energy storage must grow faster in the coming decades if we are to meet the climate change and sustainable energy Goals. Utility-scale stationary energy storage is in high demand thanks to the growing share of renewable sources of energy—solar and wind—whose power generating capacities vary depending on sun coverage and wind speeds. The large declines in the cost of Li-ion batteries also make it the favored battery technology for stationary storage projects.
Lithium-ion batteries as storage for electrical utilities
Battery storage helps renewable generators reliably integrate with existing grids by storing the excess generation and by smoothing the energy distribution. Batteries can store surplus solar and wind power and distribute it when needed. As more installations are built, electrical grids can accommodate a growing share of variable renewal energy generators such as solar and wind power plants. Batteries also help traditional suppliers manage the stability of energy distribution thanks to their unique ability to quickly absorb, store, and deliver electricity as needed. Among its many uses, batteries help operators regulate the frequency of the electrical current—an important aspect of electricity transmission— help store electricity until transmission capacity is available, and help maintain capacity reserves. Batteries also make isolated and off-grid installations viable and less dependent on diesel generators (figure 7).
While there are many technologies used for utility-scale energy storage, rechargeable Li-ion batteries have become favored in new installations due to their flexibility and scalability, and their declining costs.6 Cost improvements continue as electric vehicle manufacturers invest heavily in improving the design and manufacturing of rechargeable batteries. The low and declining cost of Li-ion batteries has made the technology the preferred choice for new utility-scale battery storage additions (IEA, 2020f). In the United States, average project costs decreased from 5000,152 per KWh of installed storage in 2015 to 625 in 2018 (U.S. Energy Information Administration, 2020). As a result, Li-ion batteries account for over half of all new stationary battery installations since 2013, and nearly 90 per cent in 2016 (figure 8). In recent years, a number of large-scale installations have been completed. In 2017, Tesla installed the (then) world’s largest Li-ion battery system at the Hornsdale Wind Farm in South Australia to help the region solve its recurring power outages. In 2020, the capacity was expanded by 50 per cent owing to its success. Also, in 2020, the world’s largest Li-ion battery was installed in California.
Batteries enable a faster transition to renewable energy
Energy storage plays a key role in the transition to renewable sources of electricity, though the importance depends on the appropriate mix of renewable and clean energy sources (Ratz et al., 2020). As the combined cost of renewable energy generation and battery storage becomes competitive with conventional energy sources, electrical utilities will be able to replace larger portions of current electricity sources with carbon-free alternatives. This is an important point as replacing traditional vehicles with electric vehicles for environmental sustainability also requires a clean source of electricity with which to charge the batteries.
Studies show that carbon emission reductions of 50–80 per cent are possible using mostly solar and wind sources (coupled with storage) and with smaller contributions from other low-carbon sources (nuclear, bioenergy, and carbon-capture natural gas plants). Greater reductions are possible using a higher proportion of non-variable clean sources (nuclear, hydro plants, coal and natural gas with carbon capture and storage, geothermal, and bioenergy) (ibid.).
In all scenarios, significant energy storage and transmission investments are required to provide grid stability, reliability, and economic feasibility. For instance, by reducing the revenue losses from curtailment—when renewable generation exceeds the demand from the grid—storage can make renewable energy investments more profitable and more likely to displace coal and gas generators. For small grids in remote locations, battery storage makes solar and wind installations a more attractive option. In a local community in Hawaii, a 1 megawatt/hour battery system connected to an off-grid solar plant is expected to reduce their use of fossil fuels by 97 per cent. In Martinique, energy storage connected to a solar plant will remove the need of additional back-up generators using fossil-fuels (IRENA, 2019).
Silicon-based batteries
Li-ion batteries have traditionally used graphite anodes, but researchers and companies are now focusing on silicon anodes. The Si-dominant anodes can bind Li-ion 25-times more than the graphite ions. However, these batteries suffer from low electrical conductivity, a slow-diffusion rate and large volumetric fluctuations during lithiation. These limitations result in Si pulverization and instability of the solid electrolyte interphase (SEI).
Two primary strategies have been used to circumvent these challenges: nanotechnology and carbon coating. In the former method, various nano-sized Si anodes are used, which have a high surface area, improved cycle life and rate stability compared to bulk Si anodes. They can also withstand lithiation and delithiation without cracking. Carbon coating uses a combination of nanosized Si with different forms of carbon materials for generation of high-performance Si/C nanocomposite anodes. Recently, doped carbon with heteroatoms as coating agents have attracted a lot of interest. The heteroatom-doped Si-C electrodes bind Li ions more strongly than carbon atoms, leading to an excellent electrochemical performance with stable electrical conductivity.
Si-based batteries have generated a lot of commercial interest due to their potential for low costs and enhanced capabilities for cars and smartphones. The competition is fierce, with many startup companies, including Sila Nanotechnologies, Enovix, Angstron Materials and Enevate, to commercialize Si-dominant Li-Ion batteries.
Room-temperature sodium sulfur (RT-NaS) batteries
One of the most promising alternatives to lithium-sulfur batteries are sodium-sulfur batteries, due to similar physical and chemical properties of Na and Li ions. However, a high temperature (300°C) is needed for battery operation. As a promising alternative, the low-cost RT-NaS battery system has generated extensive research interest for use in large-scale grid applications with enhanced safety. However, due to complex reactions within the battery, the RT-NaS batteries suffer from a lower theoretical capacity.
Various approaches have been used in 2018 to solve the problems of RT-NaS batteries.
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A team of researchers at MIT led by Dr. Sadoway focused on the membrane to solve the problem of the brittle and fragile nature of the beta alumina ceramic electrolyte membrane between the anode and cathode components of the RT-NaS. They demonstrated that a steel mesh coated with a solution of titanium nitride functions as stronger and more flexible material for industrial-scale storage systems. The approach opens up new avenues for battery design, as it can be applied to other molten-electrode battery chemistries as well.
A new approach to rechargeable batteries. RT-NaS battery with a metal mesh membrane. MIT
Schematic illustration of the synthesis of the hollow carbon decorated with cobalt nanoparticles. Nature
- In recent research published in “Nature,” scientists used a multifunctional carbonate electrolyte with high electrochemical performance and increased safety. This approach could be applied to a wide range of Na-based rechargeable battery systems for the advancement of low-cost and high-performance energy storage devices.
Schematic illustration of the electrolytes with conventional 1M NaTFSI in PC electrolyte and (right) 2MNaTFSI in PC:FEC with 10mM InI3 additive electrolyte. Nature
Though RT-NaS batteries are still in the early phase of development, companies like Ambri, a spin-out company from MIT led by Dr. Sadoway, is working to improve the battery design. The next generation of NaS-based energy storage technologies could soon become a reality with the ongoing research efforts and approaches discussed above.
Proton batteries
Many research efforts have been devoted to the generation of high-performance proton exchange membrane (PEM) fuel cells. However, the viability of PEM fuel cells has been a challenge due to their high cost, transportation and storage of hydrogen gas.
A team of researchers at RMIT University recently reported the technical feasibility of a proton battery for the first time. It consists of two parts: a carbon electrode to store hydrogen or protons from water and a reversible PEM fuel cell to generate electricity from the hydrogen. The battery design is innovative, as it uses activated carbon for the electrode, which is cheap, abundant and structurally stable for hydrogen storage and a small volume of liquid acid inside the porous material that conducts protons to and from the membrane of the reversible cell. With this battery, a voltage of 1.8 V is achievable.
The novel battery concept as proposed in 2014 by Professor Andrews from RMIT. Graphical abstract from Professor Andrews research paper
Though a tremendous step for efficient hydrogen-powered energy production, the commercialization of this technology is still a long way off. The team estimates the availability of the battery to be within five to 10 years. ABB Marine and Sintef Ocean are also testing a megawatt-scale propulsion plant to power commercial and passenger ships using hydrogen fuel cells. As these batteries do not require Li-ion at all, aside from using platinum as a catalyst, the remaining materials are inexpensive and abundant and therefore could be a leading contender to the current Li-ion batteries.
SOLID STATE BATTERY ADVANTAGES
The energy density of a battery is how much actual electricity it can output for a given weight or volume. This is key because a battery with higher density means less weight, which could actually increase the range of an EV even if the battery’s electrical output stays the same.
See all 5 photos 5 photos Solid-state battery pack design for electric vehicle (EV) concept illustration, 3D rendering new research and development batteries with solid electrolyte high energy storage for future car industry
As you move toward solid-state batteries, the reason that they’re so useful, and the reason you get this over-performance benefit from them is that they allow the use of higher-energy-density anodes, said Rory McNulty, co-author of Benchmark Mineral Intelligence’s Solid-State and Lithium Metal Batteries Report. McNulty says this increase could mean batteries that are three times more energy-dense than today’s lithium-ion cells.
To put that into perspective, on average, an 80-kilowatt-hour battery pack in an EV today weighs about 1,000 pounds. At three times the density, an 80-kWh solid-state pack would weigh just 333 pounds. Less weight in an EV means more range.
Rapid Charging
Solid state batteries, generally speaking, depending on how thin you can get the electrolyte, should be able to charge much faster than [today’s liquid-electrolyte] lithium-ion batteries. Without the safety concerns, McNulty said.
Specific projections for solid-state battery packs are all over the place, but many solid-state startups estimate a full charge in approximately 10 to 15 minutes. A full charge in today’s typical lithium-ion batteries easily takes an hour or more at a fast charger.
High Stability
Under normal conditions, an EV equipped with lithium-ion batteries is perfectly safe. However, if a battery starts to get too hot due to damage or improper charging, it can start a chain reaction. Those liquid electrolytes that fill the batteries? Well, they’re very flammable.
When a battery goes into what’s called thermal runaway, you get reactions with that liquid, McNulty said. Those chain reactions generate a lot of heat, which then speeds up the reactions further and causes a fire.
With solid-state batteries, there are no liquid electrolytes, so even when you’re charging at incredible rates the risk of fire stays low.
Better and Cheaper EV Batteries: The New Gold Rush
According to numerous statistics, electric vehicle sales will jump in America in the next five years, climbing from 3 percent of car sales today to about 10 percent in 2025 and almost 30 percent by 2030. Demand for better and cheaper EV batteries is creating a new gold rush as university research teams, start-up companies and automakers delve into exciting new technologies and hurry to meet demand.
The goal is to develop improved EV batteries that charge faster and last longer while switching to less expensive and more environmentally friendly materials. With our fingers on the pulse of all things in the zero-emission vehicle universe, check in with GreenCars often for information on the latest technologies that are driving the EV transportation revolution.