Solid-state batteries can use a wide range of chemistries, but a leading candidate for commercialization uses lithium metal. Quantumscape, for one, is focused on that technology and raised hundreds of millions in funding before going public in 2020. The company has a deal with Volkswagen that could put its batteries in cars by 2025.
But completely reinventing batteries has proved difficult, and lithium-metal batteries have seen concerns about degradation over time, as well as manufacturing challenges. Quantumscape announced in late December it had delivered samples to automotive partners for testing, a significant milestone on the road to getting solid-state batteries into cars. Other solid-state-battery players, like Solid Power, are also working to build and test their batteries. But while they could reach major milestones this year as well, their batteries won’t make it into vehicles on the road in 2023.
Solid-state batteries aren’t the only new technology to watch out for. Sodium-ion batteries also swerve sharply from lithium-ion chemistries common today. These batteries have a design similar to that of lithium-ion batteries, including a liquid electrolyte, but instead of relying on lithium, they use sodium as the main chemical ingredient. Chinese battery giant CATL reportedly plans to begin mass-producing them in 2023.
Sodium-ion batteries may not improve performance, but they could cut costs because they rely on cheaper, more widely available materials than lithium-ion chemistries do. But it’s not clear whether these batteries will be able to meet needs for EV range and charging time, which is why several companies going after the technology, like US-based Natron, are targeting less demanding applications to start, like stationary storage or micromobility devices such as e-bikes and scooters.
Today, the market for batteries aimed at stationary grid storage is small—about one-tenth the size of the market for EV batteries, according to Yayoi Sekine, head of energy storage at energy research firm BloombergNEF. But demand for electricity storage is growing as more renewable power is installed, since major renewable power sources like wind and solar are variable, and batteries can help store energy for when it’s needed.
Lithium-ion batteries aren’t ideal for stationary storage, even though they’re commonly used for it today. While batteries for EVs are getting smaller, lighter, and faster, the primary goal for stationary storage is to cut costs. Size and weight don’t matter as much for grid storage, which means different chemistries will likely win out.
One rising star in stationary storage is iron, and two players could see progress in the coming year. Form Energy is developing an iron-air battery that uses a water-based electrolyte and basically stores energy using reversible rusting. The company recently announced a $760 million manufacturing facility in Weirton, West Virginia, scheduled to begin construction in 2023. Another company, ESS, is building a different type of iron battery that employs similar chemistry; it has begun manufacturing at its headquarters in Wilsonville, Oregon.
Lithium-ion batteries keep getting better and cheaper, but researchers are tweaking the technology further to eke out greater performance and lower costs.
For many years, nickel-cadmium had been the only suitable battery for portable equipment from wireless communications to mobile computing. Nickel-metal-hydride and lithium-ion emerged In the early 1990s, fighting nose-to-nose to gain customer's acceptance. Today, lithium-ion is the fastest growing and most promising battery chemistry.
Pioneer work with the lithium battery began in 1912 under G.N. Lewis but it was not until the early 1970s when the first non-rechargeable lithium batteries became commercially available. lithium is the lightest of all metals, has the greatest electrochemical potential and provides the largest energy density for weight.
Attempts to develop rechargeable lithium batteries failed due to safety problems. Because of the inherent instability of lithium metal, especially during charging, research shifted to a non-metallic lithium battery using lithium ions. Although slightly lower in energy density than lithium metal, lithium-ion is safe, provided certain precautions are met when charging and discharging. In 1991, the Sony Corporation commercialized the first lithium-ion battery. Other manufacturers followed suit.
The energy density of lithium-ion is typically twice that of the standard nickel-cadmium. There is potential for higher energy densities. The load characteristics are reasonably good and behave similarly to nickel-cadmium in terms of discharge. The high cell voltage of 3.6 volts allows battery pack designs with only one cell. Most of today's mobile phones run on a single cell. A nickel-based pack would require three 1.2-volt cells connected in series.
Lithium-ion is a low maintenance battery, an advantage that most other chemistries cannot claim. There is no memory and no scheduled cycling is required to prolong the battery's life. In addition, the self-discharge is less than half compared to nickel-cadmium, making lithium-ion well suited for modern fuel gauge applications. lithium-ion cells cause little harm when disposed.
Despite its overall advantages, lithium-ion has its drawbacks. It is fragile and requires a protection circuit to maintain safe operation. Built into each pack, the protection circuit limits the peak voltage of each cell during charge and prevents the cell voltage from dropping too low on discharge. In addition, the cell temperature is monitored to prevent temperature extremes. The maximum charge and discharge current on most packs are is limited to between 1C and 2C. With these precautions in place, the possibility of metallic lithium plating occurring due to overcharge is virtually eliminated.
Aging is a concern with most lithium-ion batteries and many manufacturers remain silent about this issue. Some capacity deterioration is noticeable after one year, whether the battery is in use or not. The battery frequently fails after two or three years. It should be noted that other chemistries also have age-related degenerative effects. This is especially true for nickel-metal-hydride if exposed to high ambient temperatures. At the same time, lithium-ion packs are known to have served for five years in some applications.
Manufacturers are constantly improving lithium-ion. New and enhanced chemical combinations are introduced every six months or so. With such rapid progress, it is difficult to assess how well the revised battery will age.
Storage in a cool place slows the aging process of lithium-ion (and other chemistries). Manufacturers recommend storage temperatures of 15°C (59°F). In addition, the battery should be partially charged during storage. The manufacturer recommends a 40% charge.
The most economical lithium-ion battery in terms of cost-to-energy ratio is the cylindrical 18650 (size is 18mm x 65.2mm). This cell is used for mobile computing and other applications that do not demand ultra-thin geometry. If a slim pack is required, the prismatic lithium-ion cell is the best choice. These cells come at a higher cost in terms of stored energy.
The lithium-polymer differentiates itself from conventional battery systems in the type of electrolyte used. The original design, dating back to the 1970s, uses a dry solid polymer electrolyte. This electrolyte resembles a plastic-like film that does not conduct electricity but allows ions exchange (electrically charged atoms or groups of atoms). The polymer electrolyte replaces the traditional porous separator, which is soaked with electrolyte.
The dry polymer design offers simplifications with respect to fabrication, ruggedness, safety and thin-profile geometry. With a cell thickness measuring as little as one millimeter (0.039 inches), equipment designers are left to their own imagination in terms of form, shape and size.
Unfortunately, the dry lithium-polymer suffers from poor conductivity. The internal resistance is too high and cannot deliver the current bursts needed to power modern communication devices and spin up the hard drives of mobile computing equipment. Heating the cell to 60°C (140°F) and higher increases the conductivity, a requirement that is unsuitable for portable applications.
To compromise, some gelled electrolyte has been added. The commercial cells use a separator/ electrolyte membrane prepared from the same traditional porous polyethylene or polypropylene separator filled with a polymer, which gels upon filling with the liquid electrolyte. Thus the commercial lithium-ion polymer cells are very similar in chemistry and materials to their liquid electrolyte counter parts.
Lithium-ion-polymer has not caught on as quickly as some analysts had expected. Its superiority to other systems and low manufacturing costs has not been realized. No improvements in capacity gains are achieved - in fact, the capacity is slightly less than that of the standard lithium-ion battery. Lithium-ion-polymer finds its market niche in wafer-thin geometries, such as batteries for credit cards and other such applications.
Air travelers ask the question, "How much lithium in a battery am I allowed to bring on board?" We differentiate between two battery types: Lithium metal and lithium-ion.
Most lithium metal batteries are non-rechargeable and are used in film cameras. Lithium-ion packs are rechargeable and power laptops, cellular phones and camcorders. Both battery types, including spare packs, are allowed as carry-on but cannot exceed the following lithium content:
Lithium-ion batteries exceeding 8 grams but no more than 25 grams may be carried in carry-on baggage if individually protected to prevent short circuits and are limited to two spare batteries per person.
How do I know the lithium content of a lithium-ion battery? From a theoretical perspective, there is no metallic lithium in a typical lithium-ion battery. There is, however, equivalent lithium content that must be considered. For a lithium-ion cell, this is calculated at 0.3 times the rated capacity (in ampere-hours).
Example: A 2Ah 18650 Li-ion cell has 0.6 grams of lithium content. On a typical 60 Wh laptop battery with 8 cells (4 in series and 2 in parallel), this adds up to 4.8g. To stay under the 8-gram UN limit, the largest battery you can bring is 96 Wh. This pack could include 2.2Ah cells in a 12 cells arrangement (4s3p). If the 2.4Ah cell were used instead, the pack would need to be limited to 9 cells (3s3p).