There is a buzz around Tesla’s ‘Battery Day’, slated for September 22 this year, when it is expected to announce ground-breaking improvement in its lithium-ion battery technology. Also in the running are Hyundai and Lucid Motors — both of which would love to beat Tesla to the (uniquely psychological) milestone of the 1,000-mile battery.
However, despite its popularity, there is a certain dichotomy brewing around li-ion’s role in energy storage. There seems to be almost an equal push towards and away from the technology as the best minds across the world race towards dirt cheap, safe and universally applicable energy storage.
Having hit global commercial success since the 1990s, lithium-ion batteries have been applied to almost everything: from wristwatches and calculators to grid-scale energy storage and even space missions. Their energy storage capacity keeps getting better every year, they are now much less prone to fire hazards, and of course, they are getting lighter and more affordable, too.
However, their first iterations were developed in the ’70s and ’80s by John Goodenough, M Stanley Whittingham, Rachid Yazami and Koichi Mizushima. Whether it takes the same time for li-ion’s competitors to gain commercial recognition is uncertain, but the developers were awarded the Nobel Prize in Chemistry in 2019 — such has been the technology’s impact on modern life.
The dichotomy stems from the challenges with the chemistry of lithium-ion, and the availability of lithium itself. Any storage technology must satisfy three non-negotiable parameters to be a worthy contender:
- Have high energy density, which is the quantum of energy stored per unit weight of the medium used
- Have a long life cycle, preferably in the tens of thousands before repetitive charging and discharging degrade performance
- Be low cost, which is the most important factor that makes or breaks the chances of commercial success
The price of energy storage has dropped from ~$1,100/kWh in 2010 to ~$150/kWh today. Elon Musk’s Tesla is vying hard to go well below $100/kWh for li-ion powered EVs to be as affordable, or even cheaper, than ICE vehicles. But their driving range is still at roughly 400km to a charge. While nothing to be dismissed, so far the figure hasn’t quite allayed fears of range anxiety.
Research efforts that could help li-ion continue to lead in storage technology are:
1. Amorphous Lithium: which aims to improve li-ion’s cycle performance by sidestepping the problematic formation of dendrites with crystalline lithium.
2. Lithium-metal: With anode-free cells that use metallic lithium. Preliminary research suggests the technology could store 60% more energy pound-for-pound than the li-ion cells used in EVs and laptops. Tesla is also studying lithium-metal batteries with Dalhousie University in Nova Scotia, Canada.
3. Cobalt-free li-ion batteries: The industry consensus is that cobalt, which is a rare-earth metal, stabilises li-ion cell chemistry and boosts its energy density. But it’s also toxic and 50% of the world’s cobalt deposits are in the Democratic Republic of Congo (DRC), where reports suggest artisanal mines employ poor adults and up to 40,000 children under dangerous conditions. There has been mounting international coverage of the mines’ human rights abuses, and the World Bank estimates that at current rates of demand for li-ion, global Cobalt production will have to jump 500% in the next few decades to keep up.
But Tesla is not waiting around. In June, Musk announced that all Tesla Model 3s built in China would use cobalt-free cells, and in July he urged mining firms to focus on nickel. This is because the most common li-ion cell chemistries are NMC (nickel-magnesium-cobalt) and NCA (nickel-cobalt-aluminium). Research is on to put the two together, eliminate cobalt altogether and simply develop NMA batteries at lower costs.
Canada Nickel Company Inc. has jumped at the opportunity. With access to Ontario’s mostly hydroelectric power—coupled with the unique benefit that the serpentine rock that houses the nickel absorbs CO2 when exposed to the air—it is laying claim to be the first miner that ships out carbon-free nickel.
4. Phosphorus-based anodes: Modern-day li-ion cells have anodes made mostly of graphite, but efforts are on to replace them with phosphorus, as it has very high energy density and high coulombic efficiency (the ease at which charge can be transferred in a system) of around 91%.
5. Deep sea deposits of poly metallic nodules: An exciting new prospect as the poly-metallic nodules are said to be 99% pure minerals. Scraping the seafloor to collect them all, though, would raise its own bucket load of violations.
The downside
One would assume that given all the research to better li-ion batteries every which way, investors would be racing each other to grab the largest share of the profits. The unmistakable switch by almost all automakers towards manufacturing BEVs (battery electric vehicles) would augur belief that there is no beating lithium-ion. At least not for e-mobility.
Yet, IHS Markit says that if BEVs were to snare 50% of auto sales by 2030, the demand for lithium would have to grow from 300,000 tonnes in 2019 to around 2 million tonnes. Meanwhile, the Special Issue on Strategic Battery Raw Materials by the United Nations Conference on Trade and Development (UNCTAD), released in February this year, reports that mining lithium causes a great deal of air, soil and water pollution. Therefore, if the practice and the energy behind it is dirty, it would not only threaten local ecologies but also tarnish the “clean” image of BEVs.
The rising demand for li-ion batteries is also likely to swing the price curve around and raise their prices, since lithium, too, is a rare earth metal. China dominates global supplies at the moment and Europe is working hard to expand its market share, but the heavy concentration of lithium deposits in a few countries — Chile (58%), Australia (19%), Argentina (14%) and China (7%) — doesn’t bode well when deposits start to deplete. Any upswing in li-ion battery prices would be bad news for e-mobility.
The dichotomy
Of course, BEVs are not the only application for energy storage. Consumer electronics, utility-scale storage that balance out the intermittency of renewables and residential energy storage are going to be equally important. The current li-ion chemistry is not the silver bullet its backers would like it to be, so research in alternatives is gathering momentum.
In fact, that’s a key reason why some investors are reportedly skittish about pumping in millions more into lithium. While annual battery sales are expected to be worth $116 billion by 2030, data suggests that a new lithium mine takes about 4-6 years to come into full operational capacity. What if the alternatives surge past in the meantime? The technologies listed below have added some fuel to the uneasiness.
The competitors
Fluoride-ion batteries: Also known as FIBs, they are compact, lightweight and apparently hold up to seven times more energy than li-ion per unit weight. Fluoride is obtained from fluorine, which is much more plentiful than lithium and is therefore cheaper. Also, because FIBs are solid-state batteries (they have solid electrolytes), they minimise the risk of catching fire.
Yet, the catch is that so far they only operate successfully at temperatures of around 150 degree Celsius. A cell that was developed by Honda Research Institute, NASA and CalTech did work at room temperature, but it only lasted for seven cycles.
Liquid metal batteries: An area of considerable new interest, these work with metal electrodes and electrolyte solutions. The metal is kept in a molten state by heating the battery up to above 240 degrees Celsius—which limits its everyday practicality. The chemistry offers stable performance and negligible self-discharge—unlike li-ion batteries that tend to lose 5% of their charge in the first 24 hours if left on stand-by.
Also, this chemistry works much better when it comes to guarding against dendrite formation, which is a well-known issue with li-ion chemistry, as well as against the decomposition of the electrolyte.
Current research is being led by the University of Texas, which is studying a sodium-potassium alloy anode and gallium-based alloy cathode that works at 20 degrees Celsius, stores more energy than a comparable li-ion cell and charges and delivers energy several times faster. The cost of gallium is a deterrent, but the team is looking at alternatives, and sodium and potassium are both plentiful in supply and non-toxic.
Sodium-ion batteries: These use sodium instead of lithium to achieve similar energy storage capacity and charging-discharging rates, but at much lower costs due to the abundance of sodium. New research by the Washington State University (WSU) and the Department of Energy’s Pacific Northwest National Laboratory (PNNL) has indicated a major breakthrough in overcoming the drawback of crystalline sodium deposition on the batteries’ electrodes.
Sodium-sulphur batteries: These use abundantly available sodium and sulphur and are thus touted to lower the cost of energy storage considerably. Manufacturers claim they will also withstand cycles for as long as 15 years vs. about 1.5 years for li-ion batteries. Therefore, even though they currently do not offer the same energy density, Abu Dhabi inaugurated the world’s largest energy storage plant in 2019 using sodium-sulphur batteries.
Their downside, however, is that both the metals are highly reactive and have been known to cause explosions if not handled correctly.
Zinc-air batteries: Again, the low cost of zinc makes it an attractive option, especially for microgrids. These batteries are non-toxic, non-reactive and are not prone to fire hazards. However, reports suggest that at current production levels, the global stockpile of zinc could run out in 25 years.
Redox flow batteries: One of the main contenders when it comes to stationary energy storage. These batteries are fundamentally different in construction as they decouple the medium for storing energy from generating power. In essence, flow batteries house the anode and cathode separate from the electrolyte, and the three can be brought together as and when needed. This enables them to be scaled up to any capacity.
Their advantages include little to no degradation in performance over multiple cycles, and the fact that most commercial variants use vanadium, which is again much more easily available than lithium, and are safe for residential needs as well. For example, VoltStorage from Germany, an energy storage start-up, has launched the first vanadium redox flow battery-powered power storage system similar to Tesla’s PowerWall.
They are, however, considerably heavier than li-ion batteries, and are thus primarily regarded as lower-cost options for stationary and/or grid-scale energy storage. That VoltStorage has also secured funding from SoftBank shows there is merit to the technology.
Hydrogen fuel cells: The biggest challenger of them all, and rightly so. Hydrogen is the most abundant element in the universe, and its fuel cells offer 10X the energy to weight ratio of li-ion cells and therefore significantly greater range for EVs. Toyota has been doggedly researching the technology in its dream of a hydrogen economy despite most of the other large automakers having committed to li-ion. Fuel cells are also considered to be the ideal solution for heavy-duty, long-distance vehicles, such as trucks and buses.
However, hydrogen is extremely reactive, flammable and poses extreme risk of explosion if not handled carefully. Till the time it can be produced by clean energy alone, relying on methane (CH4) only adds to fossil fuel emissions. Hydrogen fuel cells have also been panned by both Tesla and Volkswagen for the high costs of producing, transporting and storing the fuel, and their poor overall efficiency in powering EVs.
Outside of the auto sector, though, with the highest energy density of all elements, hydrogen is very attractive to industries as it can be compressed and/or liquefied and stored in large underground tanks. Compressed hydrogen’s energy density is around 40,000 Wh/kg, which is a whopping 140 times the 280 Wh/kg available from the best li-ion batteries. This makes it very useful to be used with renewable energy farms. When the fuel is reacted with oxygen to produce electricity, the only by-product is water.
There are other novel experiments currently underway with Energy Vault, liquid air and even regular bricks, but for the foreseeable future they are likely to be niche applications only.
Still not serious enough
All of the above technologies are in various stages of development, but most of them are still in their early stages and nowhere close to commercial viability. With persistent research in the past five years, the fire risk of li-ion batteries has also been considerably reduced. China’s BYD—arguably the world’s largest battery manufacturer—even debuted its fire-proof batteries in May, which are ready to be used in EVs.
Lithium-ion is, therefore, still head and shoulders above its competitors in cost competitiveness and the promise it holds for much greater energy density. Hydrogen fuel cells, redox flow and sodium batteries may progress rapidly in the next decade, but at least for BEVs, lithium-ion is likely to continue as the preferred solution.
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