Recently, the production line ceremony for the world's first GWh-level sodium-ion battery production line of Zhongke Haina (Fuyang) was officially held. Related sources also revealed that in 2023, the Fuyang production line is planned to be expanded to 3-5GWh, realizing the promotion and application of 100MW-level sodium-ion battery energy storage system.
The commissioning of this production line signifies that layered transition metal oxide sodium batteries are officially leading the industrialization of sodium batteries! Although the energy storage revolution has a long way to go, it has already shown a glimmer of hope.
The progress of industrialization has been differentiated.
Sodium-ion batteries are mainly composed of positive and negative electrodes, electrolytes, and separators. They are the best alternative to lithium-ion batteries. Depending on the positive electrode material, there are three main technical routes: layered transition metal oxides, Prussian blue compounds, and polyanionic compounds.
The advantages of layered transition metal oxides are that they are simple to prepare, have high specific capacity and high energy density, and can share production lines with ternary materials for lithium batteries. The disadvantages are that layered materials are mostly prone to absorbing water or reacting with air, and have poor structural stability and electrochemical performance.
The advantages of Prussian blue compounds are low cost and high energy density. The disadvantages are that cyanide has potential toxicity, poor conductivity, short cycle life, and the crystal water of the material is not easy to remove, resulting in low compaction density and difficulty in industrialization.
The advantages of polyanionic compounds are that most of them have an open three-dimensional framework, stable material structure, good rate performance, cycle performance and long cycle life. The disadvantages are high cost, poor conductivity and energy density.
In summary, among the three technical routes, layered transition metal oxide sodium-ion batteries have the best electrochemical performance, with a theoretical specific capacity of about 240 mAh/g, which is about 1.4 times that of lithium iron phosphate batteries. Moreover, the raw materials are abundant, the synthesis is simple, and the industrial path is smooth. It is the key technical route that many sodium battery companies, such as Zhongke Haina and Sodium Innovation Energy, are focusing on.
In terms of sodium-ion battery industrialization, with the commissioning of the Zhongke Haina Fuyang production line, the layered transition metal oxide technology route has taken a half-step lead and has begun to widen the gap with the other two technology routes.
Focused layered transition metal oxides
Layered transition metal oxides are composed of overlapping transition metal layers and alkali metal layers. Based on the coordination environment and the way oxygen is stacked, they are classified into O3, P3, P2, O2, etc. Among them, the O3 type (octahedral type) and P2 type (triangular prism type) are the mainstream structures, and their properties are complementary.
O3-type compounds, such as NaNiO2, NaFeO2, and NaCrO2, have the advantages of high sodium ion content and high energy density, but the disadvantage of short cycle life.
P2 type, such as Na2/3Ni1/3Mn2/3O2 and Na2/3Fe1/2Mn1/2O2, has the advantages of long cycle life and high air stability, but the disadvantage of low specific capacity.
In a comprehensive comparison, the triangular prism structure exhibits superior stability, and related products demonstrate high safety and good rate performance. It is expected to combine high specific capacity with high safety, making it a promising route for future layered transition metal oxide sodium batteries.
In terms of industrial-scale preparation, there are two main preparation processes for layered metal oxide sodium batteries: liquid phase method and solid phase method.
The liquid phase method can use most of the preparation processes for ternary cathode materials of lithium batteries, and the production line equipment has a high reuse rate, making it easy to quickly industrialize. In contrast, the solid phase method requires a higher sintering temperature, but its advantage is that the preparation of precursors does not need to be considered during the production process.
In terms of companies investing in sodium batteries, CATL uses a nickel-based morphological oxide solution; Zhongke Haina uses a copper-iron-manganese oxide solution; and Sodium Innovative Energy uses a sodium ferrite-based oxide solution. Among foreign companies, Faradian uses a nickel-based morphological oxide solution.
Electrolytic manganese dioxide VS High-purity manganese sulfate
During the operation of sodium batteries, sodium ions, due to their large size, can cause approximately 23% irreversible changes to the material structure when they are extracted from the layered structure, and may even lead to material fracture. This seriously affects the power performance, cycle life, and electrode integrity of sodium batteries, and this problem needs to be solved by doping with transition metal elements.
Currently, the transition metal elements doped in layered transition metal oxide sodium batteries mainly include manganese, iron, magnesium, titanium, nickel, and copper. The types and proportions of transition metal elements selected vary depending on the commercial system. However, manganese exists in different systems to varying degrees and is one of the most certain elements in the layered system route of sodium batteries.
Sodium batteries use two main types of manganese raw materials for layered transition metal oxides: electrolytic manganese dioxide and battery-grade manganese sulfate. The preparation methods differ depending on the raw materials.
When electrolytic manganese dioxide is selected as the raw material, the preparation method is the solid-state method, which prepares layered transition metal oxides by directly sintering the raw materials. Zhongke Haina is a representative company that uses this preparation method.
When battery-grade manganese sulfate is used as the raw material, the preparation method is a liquid-phase method, which is slightly complicated. Battery-grade manganese sulfate is used to prepare a multi-component precursor, which is then sintered to prepare layered transition metal oxides. A representative company that uses this preparation method is Sodium Innovation Energy.
Comparing the two methods, the solid-state method is superior in terms of cost and process flow, but the consistency and uniformity of the materials need to be considered.
In conclusion
In today's turbulent world, international energy supply relations are constantly changing. Ensuring my country's energy supply security and reducing dependence on international energy is of paramount importance.
Energy storage plays a crucial role in new power systems, and new types of energy storage are attracting much attention.
Currently, lithium batteries, represented by lithium iron phosphate batteries, have the highest penetration rate in the energy storage field. However, lithium resources have an abundance of only 0.006% in the Earth's crust, and are mostly distributed in Australia and South America. my country's lithium reserves account for only 6% of the global total, and are mostly located in areas with difficult mining conditions, such as the Qinghai-Tibet Plateau. China relies on imports for 80% of its lithium resources, making it highly vulnerable to trade disputes.
Therefore, it is of great importance to be prepared and develop new electrochemical energy storage technologies. Sodium-ion batteries are the preferred alternative to lithium-ion batteries, with significant advantages in terms of external dependence, resource abundance, cost, low-temperature performance, and technological maturity.
With the continued efforts of companies such as CATL, Sinohydro, Sodium Innovative Energy, SVOLT Energy, and TransEnergy, as well as related research institutions, to overcome the current bottleneck technologies, sodium-ion batteries will surely bring about a revolution in energy storage.
