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The proposal of the goal of carbon neutrality, the emergence of extreme weather and the continuation of the COVID-19 epidemic all remind people of the importance of resources.
Non renewable energy sources such as oil and coal are used sparingly, while renewable energy sources such as solar, wind, and hydrogen are inexhaustible and tempting.
In recent years, large-scale renewable energy generation facilities such as photovoltaic power generation, wind power generation, and hydropower storage have emerged like mushrooms after rain around the world.
The problem of original voltage instability that restricts their integration into the power grid has also been solved by the emergence of large-scale energy storage systems.
The only drawback is that there are site selection requirements for existing large-scale energy storage facilities and pumped storage power stations, and the safety of lithium-ion battery independent energy storage power stations is not high, all of which have problems to some extent.
Sodium electric energy storage is timely
At a time when the whole world is lost and unsure of the direction of large-scale energy storage.
The sodium ion battery, which had been sitting on the bench for a long time, had a smile on its lips and shone brightly all over its body. It straightened up and eagerly announced to the world, "I, the sodium ion battery, have abundant raw materials, high safety, flexible site selection, excellent low-temperature performance, and long cycle life. It is the best choice for large-scale energy storage
The structure and working principle of sodium ion batteries are similar to lithium-ion batteries, and the charging and discharging functions are mainly achieved by sodium ions traveling back and forth between the positive and negative electrodes through the electrolyte.
Since September, Chinese companies that have laid out sodium ion batteries have received frequent good news. Huayang Corporation's sodium ion battery production line has been officially put into operation, Chuanyi Technology's pilot line has been put into operation, and the finished products of multi fluoride and multi sodium ion batteries have been taken offline for testing
Some predict that 2023 is highly likely to be the year of the sodium ion battery explosion.
So, what are the technical routes for sodium ion batteries? What materials are involved in different technological routes? What are the advantages and disadvantages? What are the research and development companies?
Classified by positive electrode material
According to the positive electrode material, there are currently four mainstream sodium ion battery technology routes, namely transition metal oxides, polyanionic compounds, Prussian blue (white) compounds, and molten sulfur.
Transition metal oxides
At present, transition metal oxides are the most popular, mainly including sodium iron phosphate, sodium iron manganese oxide, and sodium titanium manganese oxide. The variable valence transition metals involved include vanadium, chromium, manganese, iron, cobalt, nickel, and copper, with manganese and iron being the most common.
The sodium ion battery that has gone through the transition metal oxide technology route has the advantage of high specific capacity, but the disadvantage is poor cycling performance, which needs to be improved by doping active or inert elements.
The copper based oxide of Zhongke Hai Sodium and the nickel layered oxide of FARADION in the UK can achieve battery energy densities of 145 Wh/kg and 150Wh/kg~160Wh/kg, respectively, showing impressive performance and far exceeding other technological systems.
According to incomplete statistics from Weikewang Energy Storage, companies that have crossed the metal oxide technology route for sodium ion battery cathodes mainly include Huayang Co., Ltd., CATL, Zhongke Haina, Chuanyi Technology, Rongbai Technology, Dangsheng Technology, Greenmei, Sodium Innovation Energy, Cube New Energy, and FARADION.
Polyanionic compounds
Polyanionic compounds involve transition metals such as iron, vanadium, and cobalt, while anions mainly include phosphate, pyrophosphate, fluorophosphate, and sulfate, including sodium vanadium phosphate and sodium vanadium fluorophosphate.
The advantages of sodium ion batteries using polyanionic compound technology are high thermal stability, high safety, and long cycle life; The disadvantages are also obvious, such as low theoretical specific capacity and poor conductivity.
According to incomplete statistics from Weikewang Energy Storage, the companies that adopt the polyanion compound technology route for the positive electrode of sodium ion batteries mainly include Penghui Energy, Zhongna Energy, Jia Na Energy, Shandong Zhanggu, and the NAIADES organization in France.
Prussian blue (white) compound
Prussian blue (white) compound, composed of sodium, transition metals, and cyanide ions, has a face centered cubic crystal structure.
The disadvantage of sodium ion batteries that follow the Prussian blue compound technology route is that during battery cycling, the positive electrode material is prone to structural problems, resulting in reduced stability and cycling performance of the positive electrode material. The main solution is to doping metal elements, using nanostructures, surface coating, etc. for surface modification.
The sodium ion battery that adopts the Prussian blue compound technology route after defect resolution has the advantages of low cost, good stability, and excellent chemical performance.
According to incomplete statistics from Weikewang Energy Storage, companies that use Prussian blue (white) compound technology for the positive electrode of sodium ion batteries include Ben An Energy, Starry Sky Sodium Battery, Greenmei, Hanxing Technology, Penghui Energy, Zhongna Energy, and Shandong Zhanggu.
Molten sulfur
Molten sulfur is the positive electrode material for sodium sulfur batteries. Sodium sulfur battery is a type of molten salt battery consisting of a molten electrode and a solid electrolyte. The negative electrode active material is molten metal sodium, and the electrolyte is a solid electrolyte.
The advantages of sodium sulfur batteries are low cost, high energy density, fast charging and discharging speed, and long cycle life; The disadvantage is that sodium is unstable and prone to chemical reactions with water in the air, resulting in poor safety.
According to incomplete energy storage statistics from Weike.com, companies that use molten sulfur for the positive electrode of sodium ion batteries mainly include Mitsubishi and NGK Insulators.
Using negative electrode material as the standard
Based on the negative electrode material, there are currently three mainstream sodium ion battery technology routes, namely 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, including activated carbon, high-temperature cracked anthracite, etc. They are the mainstream negative electrode for sodium ion batteries.
Sodium ion batteries with carbon based negative electrodes have the advantages of low cost, high capacity, simple preparation, and long cycle life. The disadvantage is that hard carbon materials are difficult to graphitize, and soft carbon materials have low sodium storage capacity.
According to incomplete energy storage statistics from Weike.com, companies that use carbon based materials for the negative and positive electrodes of sodium ion batteries mainly include Betray, Zhongke HaiNa, and Huayang Co., Ltd.
Alloy materials
At present, metals such as Sb, Sn, P, Pb, Si, Bi, Ge react with sodium to form negative electrode materials for sodium ion batteries.
Sodium ion batteries with alloy materials as the negative electrode have the advantages of high theoretical specific capacity, but the disadvantages are high cost, scarce materials, large volume changes during operation, and lower cost-effectiveness compared to carbon based materials.
Molten sodium
Molten sodium is the negative electrode material of sodium sulfur batteries, with an operating temperature range of 300-350 ℃.
The advantages of sodium sulfur batteries are low cost, high energy density, fast charging and discharging speed, and long cycle life; The disadvantage is that sodium is unstable and prone to chemical reactions with water in the air, resulting in poor safety.
According to incomplete energy storage statistics from Weike.com, companies that use molten sulfur for the positive electrode of sodium ion batteries mainly include Mitsubishi and NGK Insulators.
Electrolyte material as a reference
If electrolyte materials are used as a reference, there are currently three mainstream sodium ion battery technology routes, namely liquid electrolyte, solid-liquid composite electrolyte, and solid electrolyte.
Liquid electrolytes are mainly divided into esters and ethers, consisting of sodium salts dissolved in organic solvents; Solid liquid composite electrolyte, also called gel polymer electrolyte, is composed of sodium salt, polymer and plasticizer; Solid electrolytes are composed of sodium salts and a polymer matrix.
Ionic conductivity, from high to low, generally includes liquid electrolytes, solid-liquid composite electrolytes, and solid electrolytes.
Development Status
At present, the sodium ion battery industry is not yet mature, characterized by diversified technological routes, lack of prominent cost advantages, incomplete processes, immature industrial chains, difficulty in supplying large quantities of core positive and negative electrodes and electrolyte materials, and a lack of relevant standard systems.
However, the energy storage industry attaches great importance to sodium ion batteries. There are now more than 20 sodium ion battery research companies, and China's sodium battery enterprises such as Zhongke Hai Sodium and Sodium Innovation Energy have obvious technological advantages.
Future prospects
It is expected that in the next 3-5 years, with the acceleration of sodium battery layout by established lithium battery companies such as CATL and Penghui Energy, and the leveraging of technological advantages by Zhongke Hai Sodium and Sodium Innovation Energy, the sodium battery industry chain will initially take shape, and related processes, management, and technologies will also mature.
The penetration rate of sodium ion batteries in low-speed transportation and energy storage industries will significantly increase.
