The proposal of carbon neutrality, the occurrence of extreme weather events, and the ongoing COVID-19 pandemic all serve as reminders of the importance of resources.
Non-renewable energy sources like oil and coal are becoming increasingly scarce, while renewable energy sources like solar, wind, and hydrogen are inexhaustible and highly desirable.
In recent years, large-scale renewable energy power generation facilities such as photovoltaic power generation, wind power generation, and hydropower storage have sprung up all over the world. The problem of original voltage instability that restricts their connection to the power grid has also been solved by the emergence of large-scale energy storage systems.
The only drawback is that existing large-scale energy storage facilities, such as pumped storage power stations, have site selection requirements, and independent lithium-ion battery energy storage power stations are not very safe, all of which have some problems.
Sodium-based energy storage is timely.
At a time when the whole world is in a state of confusion, unsure of where large-scale energy storage should go from here.
Sodium-ion batteries, which have long been sidelined, are now smiling, radiating brilliance, and standing tall, eager to announce to the world: "I, the sodium-ion battery, with abundant raw materials, high safety, flexible site selection, excellent low-temperature performance, and long cycle life, am the best choice for large-scale energy storage!"
Sodium-ion batteries have a similar structure and working principle to lithium-ion batteries. The charging and discharging functions are mainly achieved by sodium ions moving back and forth between the positive and negative electrodes with the help of the electrolyte.
Since September, Chinese companies investing in sodium-ion batteries have been reporting frequent successes. Huayang Technology's sodium-ion battery cell production line officially went into operation, Chuanyi Technology's pilot line officially started production, and Duofuduo's sodium-ion batteries rolled off the production line and are undergoing testing…
Some predict that 2023 is very likely to be the year sodium-ion batteries will experience a breakthrough.
So, what are the different technological approaches to sodium-ion batteries? What materials are involved in each approach? What are their advantages and disadvantages? Which companies are involved in their research and development?
Classification by cathode material
Based on the cathode material, there are currently four mainstream sodium-ion battery technologies: transition metal oxides, polyanionic compounds, Prussian blue (white) compounds, and molten sulfur.
transition metal oxides
Currently, transition metal oxides are the most popular choice, mainly including sodium iron phosphate, sodium iron manganate, and sodium titanomanganate. The variable-valence transition metals involved include vanadium, chromium, manganese, iron, cobalt, nickel, and copper, with manganese and iron being the most prominent.
Sodium-ion batteries that follow the transition metal oxide technology route have the advantage of high specific capacity, but the disadvantage of poor cycle performance, which needs to be improved by doping with active or inert elements.
Zhongke Haina's copper-based oxide and FARADION's nickel-layered oxide have achieved battery energy densities of 145 Wh/kg and 150 Wh/kg~160 Wh/kg, respectively, which are outstanding performances and far exceed those of other technology systems.
According to incomplete statistics from Vico.com, companies that use transition metal oxide technology for sodium-ion battery cathodes mainly include Huayang Technology, CATL, Zhongke Haina, Chuanyi Technology, Rongbai Technology, Dangsheng Technology, GEM, Sodium Innovation Energy, Cubic New Energy, and FARADION.
Polyanionic compounds
Polyanionic compounds involve transition metals such as iron, vanadium, and cobalt, while the anions mainly include phosphate, pyrophosphate, fluorophosphate, and sulfate, primarily sodium vanadium phosphate and sodium fluorophosphate.
Sodium-ion batteries that follow the polyanionic compound technology route have the advantages of high thermal stability, high safety and long cycle life; however, they also have obvious disadvantages, such as low theoretical specific capacity and poor conductivity.
According to incomplete statistics from Vico.com, the companies that use polyanionic compound technology for sodium-ion battery cathodes mainly include Penghui Energy, Zhongna Energy, Jiana Energy, Shandong Zhanggu, and the French organization NAIADES.
Prussian blue (white) compound
Prussian blue (white) is a compound composed of sodium, transition metals, and cyanide ions, and has a face-centered cubic crystal structure.
Sodium-ion batteries that follow the Prussian blue compound technology route have the disadvantage that the cathode material is prone to structural problems during battery cycling, leading to reduced stability and cycle performance. The main solutions are to modify the surface by doping with metal elements, using nanostructures, and surface coating.
Sodium-ion batteries that follow the Prussian blue compound technology route after the defects are resolved have advantages such as low cost, good stability, and excellent chemical performance.
According to incomplete statistics from Vico.com, companies using Prussian blue (white) compound technology for sodium-ion battery cathodes include Ben'an Energy, Xingkong Sodium Battery, GEM Co., Ltd., Hanxing Technology, Penghui Energy, Zhongna Energy, and Shandong Zhanggu.
Molten sulfur
Molten sulfur is the positive electrode material in sodium-sulfur batteries. A sodium-sulfur battery is a molten salt battery consisting of molten electrodes and a solid electrolyte. The negative electrode active material is molten metallic sodium, and the electrolyte is a solid electrolyte.
Sodium-sulfur batteries have advantages such as low cost, high energy density, fast charging and discharging speed, and long cycle life; however, sodium is unstable and easily reacts chemically with water in the air, resulting in poor safety.
According to incomplete statistics from Vico.com, companies that use molten sulfur in their sodium-ion battery cathodes include Mitsubishi and NGK Insulators.
Based on negative electrode materials
Based on the anode material, there are currently three mainstream sodium-ion battery technologies: carbon-based materials, alloy materials, and molten sodium.
carbon-based materials
Carbon-based materials are mainly divided into two types of amorphous carbon: hard carbon and soft carbon. These include activated carbon and high-temperature pyrolysis anthracite, which are the mainstream anode materials for sodium-ion batteries.
Sodium-ion batteries with carbon-based negative electrodes have advantages such as low cost, high capacity, simple preparation, and long cycle life. However, they have disadvantages such as the difficulty in graphitizing hard carbon materials and the low sodium storage capacity of soft carbon materials.
According to incomplete statistics from Vico.com, companies that use carbon-based materials for both the positive and negative electrodes of sodium-ion batteries mainly include BTR, Zhongke Haina, and Huayang Shares.
Alloy materials
Currently, metals such as Sb, Sn, P, Pb, Si, Bi, and Ge undergo alloying reactions with sodium to produce sodium-ion battery alloy anode materials.
Sodium-ion batteries with alloy-based negative electrodes have the advantage of high theoretical specific capacity, but the disadvantages are high cost, scarcity of materials, large volume changes during operation, and lower cost-effectiveness compared to carbon-based materials.
Molten Sodium
Molten sodium is the negative electrode material for sodium-sulfur batteries, with an operating temperature range of 300~350℃.
Sodium-sulfur batteries have advantages such as low cost, high energy density, fast charging and discharging speed, and long cycle life; however, sodium is unstable and easily reacts chemically with water in the air, resulting in poor safety.
According to incomplete statistics from Vico.com, companies that use molten sulfur in their sodium-ion battery cathodes include Mitsubishi and NGK Insulators.
Electrolyte materials as a reference
In terms of electrolyte materials, there are currently three main sodium-ion battery technologies: liquid electrolyte, solid-liquid composite electrolyte, and solid electrolyte.
Liquid electrolytes are mainly divided into esters and ethers, which are composed of sodium salts dissolved in organic solvents; solid-liquid composite electrolytes, also called gel polymer electrolytes, are composed of sodium salts, polymers and plasticizers; solid electrolytes are composed of sodium salts and polymer matrices.
Ionic conductivity, from high to low, is generally classified as liquid electrolyte, solid-liquid composite electrolyte, and solid electrolyte.
Current Development Status
Currently, the sodium-ion battery industry is still immature, characterized by diversified technical routes, lack of cost advantages, imperfect processes, an immature industrial chain, difficulty in large-scale supply of core positive and negative electrode and electrolyte materials, and a lack of relevant standards.
However, the energy storage industry attaches great importance to sodium-ion batteries. There are now more than 20 sodium-ion battery research companies, and Chinese sodium battery companies such as Zhongke Haina and Sodium Innovation Energy have obvious technological advantages.
Future Outlook
It is expected that in the next 3 to 5 years, as established lithium battery companies such as CATL and PENGHUI Energy accelerate their sodium battery layout, and companies such as CAS HAINA and Sodium Innovation Energy leverage their technological advantages, the sodium battery industry chain will be initially formed, and related processes, management and technologies will also mature.
The penetration rate of sodium-ion batteries will increase significantly in low-speed vehicles and energy storage industries.
