Sodium-ion batteries have multiple advantages in terms of performance
In comparison to lithium iron phosphate (LFP) batteries and ternary lithium batteries, sodium-ion batteries have their own strengths and weaknesses. After mass production, sodium-ion batteries exhibit advantages in terms of raw material cost, better capacity retention in high and low-temperature environments, excellent rate performance, and outstanding safety characteristics. However, they have lower energy density and need improvement in cycle life. Sodium-ion batteries are expected to partially substitute in specific scenarios. In terms of performance, sodium-ion batteries have comprehensively surpassed lead-acid batteries and have the potential for substitution after achieving cost reduction through large-scale production.
High cost-effectiveness aligns with multiple application scenarios, offering vast market potential
Sodium-ion batteries boast multiple advantages in several aspects, contributing to their high cost-effectiveness and ideal applications across various scenarios. Their overall performance surpasses that of lead-acid batteries, positioning them to potentially replace lead-acid batteries in specific markets such as two-wheeled electric vehicles, automotive start-stop systems, and communication base stations. Furthermore, with further improvements in cycle performance and cost reduction through large-scale production, sodium-ion batteries are expected to gradually substitute for lithium iron phosphate batteries in A00-grade pure electric vehicle applications and certain energy storage scenarios.
Application Scenario 1：A00 Class Electric Vehicles - Addressing the current pain point of fluctuating prices of lithium iron batteries due to raw material costs
A00 Class electric vehicles, also known as micro-cars, are characterized by their core selling point of high cost-effectiveness. With a wheelbase between 2 meters and 2.3 meters and a body length within 3.65 meters, these compact vehicles provide a solution to issues such as road congestion and a lack of parking spaces. Priced between 30,000 to 80,000 RMB, they are economically affordable, offering excellent value for money. Popular models in the current market for A00 Class pure electric vehicles include the Changan Oushang MINI EV, Chery QQ Ice Cream, and Changan Benben.
Application Scenario 2：Lead-Acid Battery Market - Sodium-ion battery performance surpasses comprehensively, promising potential for substitution in the lead-acid market
Lead-acid batteries are primarily utilized in three main applications: two-wheeled electric vehicle batteries, automotive start-stop batteries, and backup batteries for communication base stations. According to calculations, the total market demand in 2022 is approximately 560 GWh, with the largest proportion used for automotive start-stop, accounting for approximately 57% (320 GWh). Two-wheeled electric vehicles and base station backup batteries constitute around 24% (128 GWh) and 6% (35 GWh) of the market, respectively.
Two-Wheeled Electric Vehicle Batteries: Mainly referring to the power batteries used in electric two-wheelers, electric three-wheelers, and overseas oil-to-electric converted motorcycles. These batteries exhibit high sensitivity to costs, and the trend towards lightweight design requires a certain emphasis on battery energy density.
Application Scenario 3：Energy Storage - High safety, excellent high and low-temperature performance, and long cycle life, coupled with high adaptability to energy storage needs
High safety, excellent high and low-temperature performance, and long cycle life are performance requirements for energy storage batteries in diverse application scenarios, with low cost being a core competitive advantage. The current application areas for energy storage batteries mainly include electric power storage, communication storage, residential storage, and portable storage.
The pursuit of safety is particularly evident in residential energy storage：In recent years, the frequent occurrence of accidents involving lithium batteries in home energy storage has raised widespread concerns. Therefore, the absolute safety and stability of batteries are crucial guarantees for the long-term development of home energy storage.
The pursuit of high and low-temperature performance is particularly evident in electric power storage and communication storage. Many northern regions experience large temperature variations, requiring batteries to exhibit excellent high and low-temperature performance to resist the aging of their lifespan.
The pursuit of long cycle life is particularly evident in electric power storage：Frequent replacement or disassembly of batteries requires a significant investment in manpower and cost, leading to high upfront costs for the power station. This, in turn, results in low operational returns throughout the entire lifecycle, making the investment return rate insufficient and unfavorable for widespread adoption. Therefore, a long-life battery is crucial for the promotion of large-scale energy storage stations.
Material System Selection: Seeking common ground while acknowledging differences with lithium-ion systems
Currently, sodium-ion battery cathode materials are divided into three main routes: layered transition metal oxides, Prussian blue (white) compounds, and poly-anionic compounds. They are characterized by high energy density, low cost, and long cycle life, respectively.
Layered transition metal oxides are currently the mainstream in industrial production, offering the best overall performance and the highest energy density. They also exhibit excellent rate performance, although their stability is slightly lower. However, they do not have significant shortcomings, making them suitable for applications in high-demand power battery fields. Additionally, their manufacturing process is similar to that of lithium-ion ternary batteries, allowing for the reuse of production equipment. The technology is straightforward, and there is potential for large-scale production to be initiated.
Prussian blue (white) compounds demonstrate a clear cost advantage and excellent theoretical performance, holding promising development potential. They offer high energy density, excellent rate performance, structural stability, and low cost. However, their energy density is relatively low. The synthesis process faces challenges related to crystal water and vacancy defects, leading to degraded actual electrochemical performance and structural deterioration, becoming a bottleneck for this route.
Poly-anionic compounds exhibit outstanding cycle performance. Their stable structure imparts high safety and long cycle life, coupled with relatively low cost. However, their drawback lies in the lower energy density.
Currently, the conventional graphite widely used as the anode in commercial lithium-ion batteries cannot be used as the anode for sodium-ion batteries. The interlayer spacing of graphite is too small, and the larger radius of sodium ions requires more energy for insertion between the graphite layers. This makes it difficult for reversible deintercalation to occur within an effective potential window, resulting in a less practical discharge capacity.
Amorphous carbon has emerged as the leading industrial mainstream route among various sodium-ion anode materials. Currently, representative anode materials include carbon-based materials, metal compounds, and alloy materials. Metal compounds and alloy materials have high theoretical capacities, but they undergo significant volume changes during sodium storage, exhibit poor conductivity, and suffer from severe pulverization, necessitating the development of composite materials to improve performance. Among carbon-based materials, amorphous carbon, including hard carbon and soft carbon, stands out. Due to its non-graphitic structure with freely oriented graphite microcrystals, it contains numerous defects and larger interlayer spacing compared to graphite. This results in better sodium storage performance compared to graphite, and superior cycling performance compared to metal compounds and alloy materials. Amorphous carbon is currently the most likely sodium-ion anode material to achieve industrialization.
The anode has become the bottleneck for the industrialization of sodium-ion batteries. The ability of sodium-ion batteries to achieve large-scale production depends on their successful cost reduction. Currently, the mainstream anode material is hard carbon. In contrast to lithium-ion batteries, where the cathode cost dominates (43%), the cost distribution for sodium-ion batteries sees a significant reduction in the cathode cost share (26%) and an increase in the anode cost share (16%). This shift in cost structure has increased the importance of the anode in overall costs. The immaturity of the domestic hard carbon industry in China has led to a reliance on imported products from Japanese companies, contributing to the high cost of the anode.
3. Current Collectors：Aluminum foil can be used for both cathode and anode, with significant cost advantages.
Both the cathode and anode current collectors in sodium-ion batteries can be made of aluminum foil, providing a cost advantage compared to lithium-ion batteries. This is because lithium undergoes alloying reactions with aluminum at low potentials, requiring the use of copper foil for the anode current collector in lithium-ion batteries. In contrast, sodium does not undergo alloying reactions with aluminum at low potentials, allowing both the cathode and anode in sodium-ion batteries to utilize lower-cost aluminum foil as the current collector.
4.Separator：Lithium-ion separators can be reused, but dedicated separators matching the battery system still need to be developed.
The separator is a crucial component in sodium-ion batteries, primarily serving as an insulating layer and a semi-permeable layer. The separator needs to provide electronic insulation to separate the cathode and anode of the sodium-ion battery, preventing short circuits. Simultaneously, the separator must have ionic conductivity to ensure that sodium ions can pass through the micropores in the separator during charging and discharging. While lithium-ion separators can be reused, the development of dedicated separators tailored to the sodium-ion battery system is still necessary.
Sodium-ion batteries can reuse current lithium-ion battery separators. Commercially available battery separators currently include polyethylene (PE) and polypropylene (PP) separators, which exhibit excellent mechanical properties, chemical stability, and low cost. However, their compatibility with sodium-ion batteries is generally mediocre. Therefore, there is still a need to explore new separators that can be well-matched with sodium-ion battery systems.
The composition of the electrolyte in sodium-ion batteries shares similarities with that of lithium-ion batteries, consisting of solute, solvent, and additives. The electrolyte is an essential component in the battery, playing a critical role in balancing and transferring charges.
Solute： Commonly used sodium salts in the electrolyte include NaClO4, NaPF6, NaBF4, etc. Among them, NaPF6 exhibits the best overall performance and is the current industrial mainstream. Its ionic conductivity and interface migration rate with Na+ are much better than with Li+, resulting in better electrolyte conductivity. This allows for the use of lower concentration electrolytes to achieve cost reduction. Moreover, the production process of NaPF6 is similar to that of LiPF6, and existing LiPF6 production lines can be compatible with the production of NaPF6, reducing the difficulty of large-scale production.
Solvent：Organic electrolytes commonly used in lithium-ion batteries are currently the most promising choice for practical applications in sodium-ion batteries. Mainstream ester and ether solvents each have their advantages and disadvantages, and they are often mixed to meet performance requirements. Ester electrolytes are commonly used in both lithium-ion and sodium-ion batteries. They have advantages such as low viscosity, good volatility, excellent electrochemical stability, and a relatively high dielectric constant. Ether electrolytes exhibit good rate performance and can form a thinner solid electrolyte interface (SEI) film compared to ester electrolytes, reducing the irreversible capacity of the battery. However, an excessively thin SEI film can also lead to poor cyclic performance. Therefore, it is necessary to mix various solvents with different characteristics to meet performance requirements.
Additives：Sodium-ion battery electrolyte additives have good compatibility with those used in lithium-ion batteries. These include film-forming additives, overcharge protection additives, flame retardant additives, and others.
Sodium and lithium share certain similarities in their properties, making the principles of sodium-ion batteries similar to those of lithium-ion batteries. However, differences in ion radius and other factors result in significant differences in their material systems.
Positive：Layered transition metal oxides, Prussian blue (white) compounds, and poly-anionic compounds each have their own characteristics.Layered transition metal oxides are the current industrial mainstream, offering the best overall performance and highest energy density.Prussian blue (white) compounds have a clear cost advantage and excellent theoretical performance, showing great potential.Poly-anionic compounds exhibit outstanding cycling performance.
Negative：Amorphous carbon, particularly hard carbon, stands out as a suitable material for sodium-ion batteries.Hard carbon is the current mainstream due to its excellent performance.The bottleneck for large-scale production of hard carbon lies in finding cost-effective precursor materials with excellent performance and high consistency.
Separator：Lithium-ion battery separators can be reused, but dedicated separators matching the sodium-ion battery system still need development.
Electrolyte：The composition of sodium-ion battery electrolytes shares similarities with lithium-ion battery electrolytes.Sodium salts like NaPF6 exhibit the best overall performance and are the current industrial mainstream.Ester and ether solvents are commonly used in both lithium-ion and sodium-ion batteries. They are often mixed to achieve the required performance.Additives in sodium-ion battery electrolytes are compatible with those used in lithium-ion batteries.
Electrolyte：The composition of electrolyte with lithium-ion battery has similarities, are composed of solute, solvent, additives, three parts. The electrolyte sodium salt NaPF6 has the best comprehensive performance, and is the mainstream of current industrialization. Lithium commonly used organic electrolyte is currently the most promising choice for the practical application of sodium ion, the mainstream ester solvents and ether solvents have their own advantages and disadvantages, and are often mixed to achieve the performance requirements. Additives and lithium-ion battery electrolyte additives compatibility is relatively good.
Current Collectors：Both the cathode and anode current collectors in sodium-ion batteries can be made of aluminum foil, providing a cost advantage.
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