Since Tesla became a hot topic, news about high-tech battery electric vehicles has emerged almost every now and then. Toyota's hydrogen fuel cell electric car, an aluminum battery electric car that can travel 1600 kilometers, a flow battery car that can travel 600 kilometers on a single charge, graphene batteries, aluminum-ion batteries… It seems that using lithium batteries now is incredibly foolish, and a new energy revolution should have arrived long ago. But is the reality really as rosy as the news portrays? Let's look at the truth.
The truth about electric vehicle batteries
The core technologies of electric vehicles are batteries, motors, and electronic controls, followed by chassis technology and other components found in traditional automobiles. Among these, motor technology is now relatively mature, electronic controls are constantly improving with Moore's Law, and chassis technology has been developing for so many years that it is no longer a bottleneck.
The core issue for electric vehicles lies in the battery. For electric vehicles, an ideal battery should possess the following characteristics.
First, it must have sufficient energy density; there must be enough capacity per unit volume and weight to travel a longer distance.
Second, sufficient power density is required, meaning that a unit volume and unit weight can generate enough power, enabling the vehicle to accelerate quickly and climb hills.
Third, the energy replenishment speed must be fast, whether it is charging or swapping batteries, otherwise it will be limited to urban commuting, with a mode of driving during the day and charging at night.
Fourth, the average cost of use should be low, and the lifespan and price should be competitive in combination.
Currently, electric vehicles on the market mainly use two types of batteries: lithium-ion batteries for high-speed electric vehicles, including lithium iron phosphate, lithium manganese oxide, and ternary lithium batteries; and lead-acid batteries for low-speed electric vehicles.
Regarding the requirements for electric vehicles, lithium batteries have good power density and energy density, but they don't charge quickly and are expensive. Without subsidies, they can only be used in high-end models like Tesla.
Lead-acid batteries have low power density and energy density, and charge slowly, but they are relatively inexpensive, making them suitable for short-distance, low-speed electric vehicles. However, they cause pollution, and China currently discourages their development.
Other rumored high-performance batteries, unfortunately, haven't reached mass production and are not yet on the road. A few experimental bus routes are using them. Only these two have truly passed practical testing and are ready for large-scale use in reality. The rumored advanced batteries are either completely unreliable or still in the laboratory stage.
(I) Hydrogen fuel cells
We first looked at the hydrogen fuel cells developed in Japan. A fuel cell can be understood as a battery that generates electricity by adding fuel, and generally doesn't require recharging. In other words, charging a hydrogen fuel cell is simply refueling it with hydrogen, just like refueling a traditional car.
The advantage of hydrogen fuel cell electric vehicles is that they emit no pollutants, generate electricity with hydrogen, and drive the vehicle with an electric motor. All we need to do is replace gas stations with hydrogen refueling stations.
The process seems simple, but the problems lie in the production, transportation, and storage of hydrogen. Gaseous hydrogen requires high-pressure tanks for storage, while liquid hydrogen requires a large amount of electricity to maintain at very low temperatures. Using it is far more complicated than using fuel oil.
While hydrogen production itself isn't particularly difficult, transporting the produced hydrogen to hydrogen refueling stations requires laying specialized pipelines. Furthermore, these stations need specialized equipment to refuel hydrogen fuel cell electric vehicles. (Hydrogen is embrittlement-prone, placing high demands on the materials used for its transport and storage; hydrogen is also highly susceptible to leakage, explosion, and combustion, requiring extremely high safety standards for the equipment.)
Oil and natural gas have existing infrastructure that can be utilized, and lithium batteries have existing power grids. However, hydrogen fuel cell electric vehicles require building a complete system from scratch, encompassing manufacturing, transportation, and storage—a whole new set of infrastructure. This is far too difficult.
Therefore, unless the government provides subsidies regardless of cost to build the entire infrastructure, hydrogen fuel cell electric vehicles will remain merely decorative. Japan is pursuing this because it holds a dominant position in the entire hydrogen fuel industry chain. Other countries are not foolish enough to invest heavily in rebuilding their own systems and then allow the Japanese to control their lifeline, making it difficult to promote hydrogen fuel cells.
(II) Aluminum-air batteries
Although aluminum-air batteries are metal batteries, they should actually be considered fuel cells. Typically, aluminum-air batteries are not rechargeable; only the aluminum material needs to be replaced.
In fact, the principle of aluminum-air batteries is similar to that of zinc-air batteries commonly found in hearing aids.
The advantage of this type of metal fuel cell is its high energy density, while its disadvantage is its low power density. It works fine for low-power hearing aids, but its power may be insufficient for use in automobiles, often requiring the use of a high-power lithium battery.
Zinc-air batteries are relatively mature, with mass-produced products already available and being tested in automobiles.
Aluminum-air batteries have higher energy density than zinc-air batteries and have a brighter future, but due to the chemical properties of aluminum, it is difficult to guarantee safety and stability. Currently, there are no mass-produced finished products, and practical application is still a long way off.
Moreover, metal fuel cells, because they don't require charging, also face supply chain issues. Both zinc-air and aluminum-air batteries follow this cycle.
1. Metal manufacturing plants electrolyze metal oxides to produce metals;
2. Metal transported to the battery swapping station
3. The battery swapping station replaces the metal oxides in the user's electric vehicle with metal (metal batteries generate oxides after discharging).
4. The factory recycles the oxides and electrolyzes them back into metal.
This process requires establishing a complete industrial chain from manufacturing to transportation, replacement, and recycling. It also involves infrastructure construction. Building a nationwide network of battery swapping stations is virtually an impossible task.
Therefore, even if aluminum-air batteries are successful, they can only be used in places like city buses and taxis where battery swapping can be done at fixed locations (taxi companies swap batteries with taxi companies, and bus companies swap batteries with bus companies). Widespread adoption will be just as difficult as with hydrogen fuel cells.
(III) Flow Battery
Flow batteries are ordinary chemical batteries, but their key feature is that the positive and negative electrolytes are stored separately, solving the problem of high utilization rate of active materials in ordinary chemical batteries. Theoretically, they can achieve higher energy density and more charge-discharge cycles, exhibiting very desirable performance.
However, due to limitations in materials and electrolyte concentration, flow batteries have maintained a low energy density despite years of development. They can be used in energy storage power stations but not in automobiles.
Dr. Yeming Jiang, a scientist at MIT, invented a semi-solid lithium-ion flow battery. He made innovations in materials, which greatly increased the electrolyte concentration, thus enabling the energy density and power density to reach a practical level.
However, Dr. Jiang's battery is still in the laboratory stage, and it will take some time before it becomes a mature finished product, let alone mass production.
NanoFlowcell AG has unveiled a flow battery car, and based on its technical specifications, it appears to have achieved a very high energy density, making it ready for practical use. The vehicle is currently undergoing testing. However, the veracity of these claims remains to be verified.
However, flow batteries are one of the more reliable advanced batteries we've seen recently. Once the laboratory technology is transformed into mass-produced products, it could truly revolutionize the electric vehicle industry. This would allow electric vehicles to travel further, become cheaper (the principle of flow batteries means they use fewer expensive materials), and charge faster (flow batteries can be charged via the grid or by directly replacing the electrolyte for fast charging; however, replacing the electrolyte also requires a supporting supply chain).
(iv) Graphene batteries look beautiful
Graphene has a large specific surface area, which can carry more lithium ions. It can gain and lose lithium ions very quickly. This characteristic provides a physical basis for increasing the capacity of lithium batteries and accelerating the charging and discharging speed.
However, in the experiment, the lithium battery with graphene as the negative electrode had a very poor cycle life. It charged and discharged quickly, but failed after only two charges, so it was obviously unusable.
Therefore, people began to develop various composite materials to serve as negative electrodes, trying to find a material that could combine fast charging and discharging speed, long cycle life, high energy density, and low cost.
Numerous papers have been published in various laboratories, but none have yet yielded practical applications. Recently, the Spanish newspaper El Mundo reported that a Spanish university has developed a graphene battery that boasts high charge/discharge speeds, longer cycle life, higher energy density, and slightly lower cost than current lithium-ion batteries. German automakers will begin testing it.
If the reports are true, then this type of battery is very promising and may change the fate of electric vehicles. If refueling time and charging time are the same, then charging stations can replace gas stations, and electric vehicles can truly replace gasoline vehicles.
The electric vehicles currently on the market use lead-acid batteries and lithium batteries. It's not that electric vehicle companies are stupid and don't know how to adopt new technologies, but rather that among the batteries currently available in terms of energy production capacity, only these two types are usable and reliable. Others are either technologically immature, lack a complete industrial chain, or are too expensive to be commercially viable.
Besides the types of batteries we mentioned earlier, there are also flywheel batteries, nuclear batteries, supercapacitors... These often look beautiful in the laboratory, but there's been no news of them being put into practical use for a long time. So, if you see these kinds of fantasies in the future, you can just laugh it off and not take them seriously.
If something exists, it must have a reason. If a battery is truly practical, it will be widely used within three to five years. The fact that it's not used now means there must be a problem. Breakthroughs in batteries will change the future, but we need to be patient.
