CATL announced the "first-generation sodium-ion battery" at the CATL conference before, and then there are endless discussions about sodium-ion batteries. Some people say that it can replace the lithium-ion power battery in the existing pure electric vehicle. Some people say that we have made a milestone breakthrough in battery technology. This article will bring a detailed interpretation of sodium-ion batteries.

Research of sodium-ion battery

The first thing to say is that, in fact, the research on sodium-ion battery technology has not only begun to emerge in the past few years. In fact, as early as the 1970s and 1980s, when lithium-ion battery technology was just emerging, sodium-ion batteries were naturally placed high expectations by the battery industry. Even the technical principles of sodium-ion batteries had formed a complete system at that time, and this system is still in use today.

Therefore, CATL’s launch of sodium-ion batteries is not a “new species”, but an upgraded version based on the original technology.

Why can sodium-ion batteries be studied together with lithium-ion batteries in the last century?

The reason why sodium-ion batteries and lithium-ion batteries were studied at the same time in the last century is that sodium and lithium are the closest metal elements of the same group on the chemical periodic table. It is well known that "the number of electrons in the outermost layer of the same group of elements is exactly the same." That means that their chemical properties are very similar, so the battery industry put sodium and lithium together for research.

Because whether it is a sodium-ion battery or a lithium-ion battery, they are actually the same in terms of battery technology. All are through the oxidation-reduction chemical reaction between the electrolyte and the metal to change the metal into an ionic state. At this time, the electron as a charge carrier moves between the positive and negative electrodes of the battery to realize the charging and discharging process of the battery.

During the charging process, sodium ions or lithium ions will carry positive charges from the positive electrode to the negative electrode, while the negatively charged electrons move together through the external circuit, and finally, realize the transmission of current. The discharge process is the opposite. Metal ions and charges will migrate from the negative electrode to the positive electrode, thus realizing the reverse direction of current transmission.

Schematic diagram of a battery charging and discharging

However, sodium-ion batteries have fallen behind in the competition with lithium-ion batteries due to their own "shortcomings". So what is the difference between sodium-ion battery and lithium-ion battery?

The defects of sodium-ion batteries compared to lithium-ion batteries

The biggest problem is that the mass of sodium ions is larger than that of lithium ions. As can be seen in the periodic table, lithium ranks 3rd, while sodium ranks 11th, so the difference in energy density under the same mass will be reflected in the battery power.

Take the sodium-ion battery launched by the CATL, the energy density of the sodium-ion battery is 160Wh/kg, while the existing NCM811 ternary lithium battery energy density of the CATL is 200Wh/kg. This means that under the same mass of 1kg, the sodium-ion battery is only 80% of the energy density of the ternary lithium battery. This is equivalent to the fact that most electric vehicles equipped with lithium batteries can basically run about 500 kilometers with a full charge, so only a sodium-ion power battery of the same quality can run 400 kilometers.

From this, we can also see that the power of sodium-ion batteries is lower than that of lithium-ion batteries. In fact, the power of lithium-ion batteries is crushing the power of sodium-ion batteries.

The new nano-silicon lithium battery researched by Chen Liquan, academician of the Chinese Academy of Engineering, is 5 times the capacity of general graphite lithium batteries. In 2018, the solid-state lithium battery developed by Professor Li Hong has completed the design and development of a 300Wh/kg solid-state power battery system. After the laboratory test vehicle is equipped with a solid-state lithium battery, the cruising range has doubled. The 350Wh/kg nano-silicon lithium battery currently under development can allow electric vehicles to travel 1,000 kilometers on a single charge.

Another important point is that sodium-ion batteries are also inferior to lithium-ion batteries in terms of battery charge and discharge "cycle life". According to statistics, the current cycle life of sodium-ion batteries is about 2000 times, while the cycle life of ternary lithium batteries can reach more than 3000 times, and the cycle life of lithium iron phosphate batteries is about 6000 times.

Therefore, in the new energy electric vehicle market, the bulky and short-lived sodium-ion battery is defeated by lithium-ion batteries, directly losing the trillion-dollar new energy market. Sodium-ion batteries can only compete with lead-acid batteries in low-speed electric vehicles, energy storage systems, and other fields.

The advantage of sodium-ion batteries over lithium-ion batteries

The market is demand-oriented. Although the advantages of lithium-ion batteries are obvious, it has a fatal shortcoming, which is low reserves.

Data show that the content of lithium in the earth's crust is about 0.0065%, and raw materials are scarce and expensive. According to the statistics of the United States Geological Survey (USGS), as of 2020, the world's proven recoverable lithium resource reserves are about 8,600 tons.

The shortage of lithium resources means that its price will continue to rise. In the past few years, less than 40 thousand tons of lithium carbonate has now reached 100,000 yuan a ton. The price has been directly increased by 2.5 times, which will greatly affect the material cost of lithium-ion batteries.

Moreover, the “ternary” in the aforementioned ternary lithium battery refers to a polymer containing three metal elements of nickel, cobalt, manganese, and aluminum. It is used as a positive electrode in a ternary lithium electronic battery. But the scarcity of metals such as nickel and cobalt far exceeds that of lithium resources, and their prices are more expensive.

Therefore, the current scarcity of lithium-ion battery materials and rising costs have put the development of lithium batteries into trouble.

In contrast, the reserves of sodium on our planet are extremely rich. After all, there are too many sodium salts in the seawater, which accounts for 70% of the area on our planet, and it is also very convenient to extract industrially. In addition, the reserves of sodium resources in the earth's crust also rank sixth.

The content of the main elements in the crust (mass fraction)

From the perspective of cost, Abundant sodium resources, and easy development and production in the industry means that the price is low. As mentioned above, the price of battery-grade lithium carbonate is 15,000$ per ton, while the price of sodium-ion compounds is only 40$ per ton. 

In addition to the easy availability and low cost of sodium materials, sodium-ion batteries also have advantages that lithium-ion batteries do not have:

For example, in terms of fast charging, the charging time of all sodium-ion batteries can be reduced to 10-20 minutes. Sodium-ion batteries can obviously alleviate the anxiety of electric vehicle owners and meet the demand for reducing charging time.

In terms of discharge retention rate, sodium-ion batteries can work in the operating temperature range of -40°C to 80°C. The lithium-ion battery generally can discharge 90% of the rated capacity at 0°C, and 70% of the rated capacity at -20°C. Looking at it this way, sodium-ion batteries obviously have a better battery life guarantee for winter driving. This must be the gospel of electric car owners in cold regions.

In terms of safety, sodium-ion batteries are much safer than lithium batteries, and will not easily catch fire in scenarios such as overcharge, over-discharge, short circuit, acupuncture, and squeezing. This is particularly important for new energy electric vehicles.

comparison of sodium-ion battery and LFP battery

Therefore, comparing sodium-ion batteries and lithium-ion batteries, each has its own advantages, but each has its own fatal "shortcomings." The new battery released by the CATL is actually a sodium-ion battery and a lithium-ion battery. CATL uses the AB battery system solution to maximize its strengths and avoid weaknesses, give full play to its advantages, and effectively solve the problem of the low energy density of sodium-ion batteries.

AB battery system solution

Behind the competition between sodium and lithium

Although the current reserves of lithium are still abundant. Under the background of the current global "dual carbon goal", the trend of electrification will further increase the consumption of lithium. Experts analyze that lithium will be exhausted in 50 years.

Therefore, in terms of new material batteries, many countries and related companies are deploying new batteries, such as Tesla's cobalt-free batteries, Japan and Canada’s vanadium batteries. India and Europe's cooperation of new aluminum batteries, etc. are also researching and actively promoting to the market.