With the entry of sodium-ion batteries, is the “Three Kingdoms War” of power batteries coming?

CATL launches the first generation of sodium-ion batteries. Can sodium-ion batteries stand out from the competition of ternary lithium batteries and lithium iron phosphate batteries? Will the power battery market stage a "Three Kingdoms War"?

Written by reporter Zhao Tianyu Edited by Chen Yongjie

New Media Editor/Nie Shufang

Interview experts

Zhang Qiang (Professor of Chemical Engineering, Tsinghua University)

Yu Zhenhua (Chairman of Zhongguancun Energy Storage Industry Technology Alliance)

Yang Jun (Professor, School of Chemical Engineering, Shanghai Jiao Tong University)

"80% charge in 15 minutes, no battery degradation at -20 degrees Celsius". Not long ago, CATL, the leader in power batteries, held a press conference to launch its first generation of sodium-ion batteries. Many people exclaimed: CATL is going to reshape electric vehicles!

▲ CATL launches sodium-ion battery (Photo source: Visual China)

Can sodium-ion batteries stand out from their competitors such as ternary lithium batteries and lithium iron phosphate batteries, lead the trend, and become the next generation of battery technology?

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Why is it so difficult for science fiction to become reality?

What is a little surprising is that the concept of sodium battery was first proposed by French science fiction writer Jules Verne in 1870 in his famous science fiction novel "Twenty Thousand Leagues Under the Sea".

In the novel, the Nautilus obtains sodium electrolyte from seawater and makes sodium batteries as energy to propel it forward, because sodium comes from seawater and is a local resource.

The electric shock guns, diving suits, and underwater tunnels predicted in the book were all realized one by one, but there was little progress in sodium battery submarines. It was not until the 1970s, with the advent of the third industrial revolution, that sodium-ion batteries were truly developed. At the same time as the sodium battery, the lithium battery that people are very familiar with today was also born.

Now, more than 40 years have passed, and lithium batteries have long been widely used in production and life, especially becoming the core product of new energy vehicles; but the development of sodium batteries has not been very smooth. For a long time, they have only been used in a small range in energy storage power stations and low-speed vehicles. It was not until 2011 that a company tried to commercialize the product.

Sodium battery, as the name implies, is a battery driven by sodium ions. It is a power battery that realizes the movement of charge by sodium ions "running back and forth" between the positive and negative electrodes of the battery. Because of its poor "quality", it has been forgotten in the corner.

Why have sodium-ion batteries been neglected? This is actually directly related to its chemical properties. In fact, whether it is a sodium battery or a lithium battery, their working principles are similar: at the cathode of the battery, the element loses electrons and turns into a higher-valent ion, which then enters the electrolyte, passes through the diaphragm, and transfers to the anode: although ions can pass through the electrolyte and the diaphragm, electrons cannot, and can only run from the external circuit to the anode and do work outside. This is the discharge process of the battery.

The atomic weight of lithium is 6.94, the lightest among metals; the standard electrode potential of lithium is -3.045V, the lowest among metals; in addition, the specific capacity of lithium is also the highest among metals, while its electrochemical equivalent is the smallest.

This means that lithium batteries can theoretically achieve the highest energy density. In the battery field, if safety and cost factors are not taken into consideration, energy density has an absolute say - lithium batteries are the first choice in the eyes of researchers.

However, if you open the periodic table in a chemistry textbook, the metal element closest to lithium is sodium. They are both located in the first column of the periodic table, have the same number of electrons in their outermost layers, and have similar chemical properties, so they can both act as charge carriers to drive the charging and discharging of batteries.

However, sodium-ion batteries also have obvious flaws, the first of which is insufficient energy density. The atomic weight of lithium is 7, and the atomic weight of sodium is 23. The smaller the atomic weight, the greater the energy density.

▲Sodium-ion batteries were once forgotten (Photo source: Visual China)

This results in that while the energy density of ternary lithium batteries is already above 200Wh/kg (watt-hours per kilogram, a unit of specific energy), the energy density of sodium-ion batteries is only 100-150Wh/kg. Even though the energy density of the sodium-ion batteries currently released by CATL can reach 160Wh/kg, the gap with lithium-ion batteries is also obvious, resulting in significantly low battery utilization efficiency.

Secondly, the radius of sodium ions is 70% larger than that of lithium ions, which makes their movement extremely slow and unable to pass through the negative electrode graphite material. This has also become a bottleneck that has prevented sodium ion batteries from being commercialized.

As a result, in the 1980s when science and technology were not yet developed, lithium-ion batteries and sodium-ion batteries took completely different paths: the former were quickly commercialized and became an indispensable item in the consumer market, while the latter completely stagnated.

Today, the sodium-ion battery released by CATL has allowed more people to see this "ill-fated" technology, and has also added a strong "potential competitor" to the future development of power batteries.

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The love-hate relationship between lithium and sodium

But realistically speaking, sodium batteries are not completely useless. They have two advantages that lithium batteries cannot match.

First of all, in terms of reserves, lithium resources are limited. Data shows that 70% of lithium resources are currently distributed in South America, while 80% of my country's lithium resources are currently imported. With the increase in demand, the price of lithium has also soared, from the initial 38,000 yuan per ton to 160,000 yuan per ton.

Previously, Chen Liquan, an academician of the Chinese Academy of Engineering, had clearly stated that if all cars in the world use lithium-ion batteries and all electricity in the world is stored in lithium-ion batteries, there will not be enough lithium and new batteries must be considered.

▲Global power battery installed capacity list in the first half of 2021 (Photo source/Visual China)

The reserves of sodium resources are very high. In China's Qarhan Salt Lake alone, the sodium chloride reserves are as high as 42.62 billion tons, which is about one hundred times the global lithium reserves. It can be said that sodium resources are very "excellent" "non-renewable energy."

Secondly, in terms of usage properties, although the energy density of sodium ions is not good, its chemical properties are relatively stable, so it is not sensitive to temperature and is not easy to form hard dendrites like lithium dendrites. It also has obvious advantages over similar lithium-ion batteries in terms of low temperature resistance and safety.

Therefore, in theory, as long as sodium ions can move freely in the battery, there is hope to solve the problem of low energy density of sodium batteries, and sodium batteries will have the hope of "reversing" lithium batteries. Against the backdrop of intensified international competition, global energy transformation, carbon reduction and carbon neutrality, developing a new product route such as sodium batteries has very rich political and economic benefits.

This may be the original intention of CATL to "revive" sodium batteries.

The reporter learned that the existing sodium-ion battery positive electrode is generally made of two types of materials: Prussian white and layered oxide. Although sodium ions can pass through, the battery capacity will decay rapidly during the cycle, resulting in a significant decay in the battery energy density, which is very not durable.

So the sodium battery developed by CATL with a new idea was born - the charge rearrangement of the material phase structure solved the problem of rapid capacity decay of Prussian white during the cycle. In terms of negative electrode materials, hard carbon materials with unique pore structures were developed, which have the characteristics of high specific capacity, easy deintercalation, and excellent cycle, and the electrolytes suitable for positive and negative electrode materials were optimized.

▲ Diagram of the working principle of sodium ion battery (Photo source/Visual China)

In this way, sodium ions can move freely between the positive and negative electrodes without excessively attenuating energy. In addition, the production line of lithium-ion batteries can also be used to produce sodium batteries, which effectively controls costs.

According to data released by CATL, the energy density of the "newly born" sodium-ion battery has reached 160Wh/kg after technical optimization, almost reaching the standard of lithium iron phosphate battery (150-210Wh/kg). After charging for 15 minutes at room temperature, the power can reach 80%; and at a low temperature of -20°C, the discharge retention rate is still over 90%. At the same time, the system integration efficiency can also reach over 80%.

The key words "fast charging", "low temperature resistance" and "high integration efficiency" directly hit the current pain points of lithium batteries, and also allow people to see the hope of solving the endurance problem of new energy vehicles, as well as new development ideas for the future of power batteries.

▲Power battery competition (Image by Chai Qingyan, click on the image to enlarge)

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Low energy density remains to be solved

Let’s go back to a year and a half ago. In April 2020, BYD launched its blade battery product in a high-profile manner, hoping to reshape lithium iron phosphate batteries in terms of "endurance" and "safety" and change the entire power battery industry.

But the reality is that blade batteries improve battery life, but cannot avoid the impact of low temperatures. Some consumers even report that their low-temperature resistance is not as good as that of ternary lithium batteries. Many industry insiders also pointed out that blade batteries have only optimized their volume utilization to the extreme, and have not really innovated materials.

This is quite similar to the sodium battery that CATL has recently launched in a high-profile manner.

In the opinion of Zhang Qiang, professor of chemical engineering at Tsinghua University, the biggest problem with sodium-ion batteries is that they still have not solved the problem of low energy density.

Zhang Qiang explained that in the field of passenger cars, the energy density of ternary lithium batteries has been moving towards the goal of 300Wh/kg or even higher. In comparison, the energy density of sodium batteries is only half, and the gap with lithium batteries is still quite obvious. Compared with itself, there is progress, but the energy density is still low in the overall environment. "Although the energy density target of the next generation of sodium batteries is 200Wh/kg, it is difficult to estimate the time required for this research and development process."

Therefore, for the sodium-ion battery released this time, CATL has provided an AB battery solution, that is, encapsulating the sodium-ion module and the lithium-ion module in the same battery pack in a specific ratio, achieving the purpose of "one machine, two uses", creating a new lithium-sodium battery, and creating more scenarios for application.

▲Application scenarios of sodium ion batteries (Photo source/Visual China)

However, this dual-purpose technology solution is more like a self-justification by the company: this solution has never been applied to any mainstream new energy vehicle model before, and even the method of mixing ternary lithium and lithium iron phosphate lithium batteries has never appeared. For mid-to-high-end passenger vehicles that pursue ultra-long battery life and require ultra-high energy density, lithium iron phosphate, ternary lithium batteries and even future solid-state batteries may be their mainstream choices.

"Before the energy density of sodium-ion batteries can be significantly improved, sodium batteries will have few opportunities in the passenger car field, and the first application scenario may be in the energy storage field," said Yu Zhenhua, chairman of the Zhongguancun Energy Storage Industry Technology Alliance.

But even in the field of energy storage, there are many problems that need to be solved on the road to industrialization of sodium batteries: although there is abundant sodium in seawater and salt lakes, my country's related extraction technology is not mature, and it takes a certain amount of time to cultivate upstream and downstream industries; although the price of sodium is lower than that of lithium, the lower energy density means more auxiliary materials and manufacturing costs. According to relevant experimental calculations, the auxiliary materials and manufacturing costs of sodium-ion batteries account for nearly 75%.

"Without the establishment of a connected upstream and downstream industrial chain, it is not easy to control the cost of sodium batteries." Yang Jun, professor at the School of Chemical Engineering of Shanghai Jiao Tong University and deputy director of the Institute of Energy and Technology, believes that based on the current scale, it may take another 2-3 years, or even longer, to form truly market-oriented and industrialized sodium battery products.

Although it will take some time to realize the scale of sodium-ion batteries, it is certain that the entry of sodium-ion batteries into the field of passenger cars is an exploration of power batteries to extend upstream and reduce the impact of raw material price fluctuations. Regardless of whether the road to industrialization is successful, it has sounded the alarm for the high prices of upstream lithium batteries, and also provided more ideas and methods for the development of energy transformation and multi-technical routes.

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Lithium iron phosphate battery has a "turnaround"

As sodium batteries are making a high-profile foray into the field of power batteries, another phenomenon has also attracted widespread attention from industry insiders—the market share balance of ternary lithium batteries and lithium iron phosphate batteries has quietly tilted, which is very intriguing.

Lithium iron phosphate batteries and ternary lithium batteries are the two mainstream batteries in the current market. Some people believe that they are essentially lithium batteries, but there are differences in material structure: lithium iron phosphate batteries use lithium iron phosphate as the positive electrode; ternary lithium batteries are also called ternary polymer lithium batteries, which are mainly made of nickel cobalt aluminum or nickel cobalt manganese as the positive electrode.

However, there are also views that lithium iron phosphate batteries are essentially iron batteries, not true lithium batteries. Therefore, there is a big gap between the two in terms of energy density and safety.

The PO bond in lithium iron phosphate crystals is stable and difficult to decompose. Its ignition point is above 500°C. Even at high temperatures or when overcharged, it will not collapse and generate heat like lithium cobalt oxide, or form strong oxidizing substances. Therefore, lithium iron phosphate batteries have better stability, but they also have obvious shortcomings, namely slow heat release, low heat generation, and low energy density. They have to increase the volume ratio in exchange for a longer battery life.

In traditional perception, although lithium iron phosphate batteries have better safety performance and more cost advantages, from the perspective of energy density and driving range, ternary lithium batteries are superior. Therefore, for a long time, despite the frequent spontaneous combustion of electric vehicles caused by lithium batteries, ternary lithium batteries have still become the favorite of the market.

Data shows that the market share of lithium iron phosphate batteries was 49.6% in 2017, but it fell to 37.8% in 2018 and further to 32% in 2019. In addition to commercial vehicles, almost all passenger cars have begun to use ternary lithium battery products.

Just when people thought that lithium iron phosphate batteries were about to "elegantly exit", the situation took a dramatic turn: first, the market share of lithium iron phosphate batteries stopped falling and rebounded, from Tesla Model 3, Model Y to BYD Han, Xiaopeng P5, etc., more and more car companies began to launch models equipped with lithium iron phosphate batteries.

▲The difference between ternary lithium batteries and lithium iron phosphate batteries in terms of materials used (Photo source/Visual China)

In 2021, the market share of lithium iron phosphate batteries has further expanded. From January to May this year, the domestic output of lithium iron phosphate batteries reached 29.9GWh, surpassing ternary lithium batteries for the first time in nearly three years. This disruptive change has attracted widespread attention in the industry.

Wang Jingzhong, vice chairman of the China Battery Industry Association, analyzed that lithium iron phosphate batteries have always performed better than ternary lithium batteries in terms of safety and other aspects. With the advancement of technology in recent years, not only have their energy density and driving range been enhanced, but their costs have also been greatly reduced, providing a more reliable foundation for the "turnaround" of lithium iron phosphate batteries.

Therefore, with the entry of sodium batteries, people's attention has shifted to a new direction - is it possible for this type of power battery, which is subject to technical factors, to "turn around" like lithium iron phosphate batteries in the future, turning the "fight between dragons and tigers" in the power battery field into "Three Kingdoms"?

Sodium Batteries in the Eyes of Experts>>>

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Sodium-ion batteries have many opportunities in the future

Gan Zizhao, academician of the Chinese Academy of Sciences and professor of the School of Physics at Peking University (Photo by Zhang Xinghai)

As for new energy vehicle batteries, lithium batteries are widely used in the industry, and sodium batteries are less used. However, sodium batteries still have certain advantages over lithium batteries. The negative electrode of lithium batteries is made of copper, while that of sodium batteries is made of aluminum. The price of aluminum is much cheaper than that of copper, so there are many opportunities for sodium batteries in the future.

If we delve deeper into the question of batteries, it will involve our understanding of contemporary condensed matter physics. In batteries, the conductor is ions. With the development of condensed matter physics, the understanding of ionic conductivity will become clearer, which will eventually lead to progress in the battery industry, which is precisely a major progress in the new energy vehicle industry.

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There is no substitution relationship between sodium battery and lithium battery

Zhang Qiang, Professor of Chemical Engineering at Tsinghua University

In the context of advocating energy conservation and emission reduction and reaching the peak of carbon emissions, combined with the country's demand for energy storage, whether it is lithium iron phosphate, ternary lithium or sodium batteries, their existence is meaningful. However, sodium batteries and lithium batteries have different market segments, each with its own jobs and application space, and there is currently no question of who will replace whom.

Specifically, lithium-ion batteries have a high energy density, so they have more advantages in mobile scenarios, such as passenger cars; sodium-ion batteries have a lower energy density and may be more suitable for fixed energy storage, such as energy storage stations. We also need to pay attention to the specific model type, regional differences, etc. For example, the batteries used in Harbin are definitely different from those used in Hainan Island.

In the future, with the transformation of the energy sector, the demand for power batteries will only increase, and there will be a state of supply exceeding demand. So from this perspective, whether it is sodium batteries or lithium batteries, the market will definitely follow the principle of "use whichever is better to make and whichever is better to use". It doesn't matter if the cat is black or white, as long as it catches the mouse, it is a good cat.

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Sodium batteries must improve their "technical content"

Yu Zhenhua, Chairman of Zhongguancun Energy Storage Industry Technology Alliance

Sodium batteries are currently in their infancy. Academically, sodium-ion batteries have not formed a unified technical route, and companies entering the market are also in a state of "crossing the river by feeling the stones"; in the industry, CATL's batteries have not been mass-produced, and even the supply system of key materials is not sound.

Sodium batteries still have a long way to go in the future. In the field of passenger cars, sodium batteries cannot compete with lithium batteries in the short term due to the problem of energy density, and their own "technical content" must be improved.

In the field of energy storage batteries, lithium iron phosphate batteries are currently the main technology route for energy storage batteries. The energy density gap between sodium ion batteries and lithium iron phosphate batteries has narrowed a lot, so when the technology matures in the future, the market may have some differentiated choices, which is also an opportunity for sodium ion batteries.

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Sodium batteries cannot be mass-produced yet and need market testing

Yang Jun, Professor of School of Chemical Engineering and Deputy Director of Institute of Energy and Technology, Shanghai Jiao Tong University

The energy density of the sodium battery released now has reached more than 160Wh/kg, which is quite high and the progress is very obvious, but it should be noted that this does not mean that this battery can be mass-produced now. On the contrary, it may take two or three years to be truly launched on the market. Whether it is in the energy storage field or the passenger car field after it is launched, it needs to be tested by the market to see whether it is a product that meets the demand.

As for the proportion of ternary lithium and lithium iron phosphate batteries, specific analysis is needed. Their usage scenarios are different. There are cost factors and safety factors. For example, the battery for drones must have a very high energy density, and lithium iron phosphate batteries are not suitable. So this aspect is actually difficult to predict.

▲Cover of Beijing Science and Technology News on August 23, 2021

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Produced by: Beijing Science and Technology News | Science Plus Client

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