Sodium-Ion Battery Energy Storage: Cost Benefits Not Yet Apparent, but Future Potential in Specific Applications
Sodium-ion battery is a secondary battery that relies on the movement of sodium ions between the positive and negative electrodes to complete charging and discharging. The working principle of sodium-ion battery energy storage is similar to that of lithium-ion battery, and the structure is also composed of positive electrode, negative electrode, separator and electrolyte. The difference lies mainly in the positive electrode material, sodium salt replaces lithium salt, and aluminum foil replaces copper foil.
The advantages of sodium batteries lie in operating temperature, safety, cycle life and charging speed.
1) Safety. Sodium batteries have higher stability and lower risk of thermal runaway, which is crucial for energy storage systems, especially large-scale energy storage facilities. It can effectively reduce the probability of safety accidents and ensure the safety of personnel and equipment.
2) Low temperature performance. Sodium-ion batteries can usually operate stably in an environment of -40℃ to 80℃, while the operating temperature range of ternary lithium-ion batteries is generally between -20℃ and 60℃. When the ambient temperature is below 0℃, the performance of lithium batteries will drop significantly, while sodium-ion batteries can still maintain a capacity retention rate of more than 80% in a low temperature environment of -20℃.
3) Cycle life. Sodium-ion batteries can withstand more charge and discharge cycles, reducing the cost and resource consumption caused by frequent battery replacement, and improving the overall service life and economic benefits of energy storage systems.
4) Charging speed. Sodium-ion batteries can complete the charging process in 10 minutes, while ternary lithium batteries take at least 40 minutes and lithium iron phosphate batteries take 45 minutes.
Cost advantage is an important driving factor for sodium-ion battery energy storage. Looking back at 2022, the price of upstream lithium carbonate rose sharply, and the cost of lithium batteries soared, which made the industry pay more attention to sodium-ion batteries. Sodium-ion batteries, with their advantages such as low raw material costs, are seen as promising to achieve breakthroughs in cost, alleviate the pressure on energy storage costs caused by the high price of lithium resources, and thus gain broader application prospects.
However, the price of lithium carbonate has returned in the past two years, and as a result, the price of lithium batteries has also fallen rapidly. Against this background, the cost advantage of sodium-ion batteries, which was originally expected to be high, is no longer so prominent, and further in-depth exploration is still needed to highlight its competitiveness. After all, when the price of lithium carbonate falls below 100,000 yuan, the cost of lithium batteries will gradually approach the theoretical cost of sodium-ion batteries. In this way, the cost of sodium-ion batteries will be greatly reduced compared to lithium batteries. Substitutability, and its subsequent promotion in the market is likely to face many obstacles.
Although sodium-ion batteries have the potential to have cost advantages, this advantage has not yet been effectively transformed into real market competitiveness and remains at the theoretical level. In the subsequent development process, the sodium-ion battery industry still needs to focus on the key link of reducing costs.
Previously, the industry generally expected that 2023 would be the “first year of sodium electricity”, but the commercialization process has been postponed again and again. We believe that in 2025, sodium electricity will usher in a turning point for accelerated industrial development.
Sodium-ion batteries have unique strategic significance for my country. Although the current market share is still small, sodium power is a key backup option when the international situation is complex and the supply of lithium resources is unstable, and its importance cannot be underestimated. In the future, the market share of sodium power may be difficult to surpass that of lithium power, but it will gradually expand in the market segments and build its own advantages. From the timeline, sodium power is expected to gain a foothold in the market before solid-state batteries and play a key role in a specific period. It is estimated that by 2030, the demand for sodium-ion batteries in the energy storage field will exceed 300GWh.
Solid-State Battery Energy Storage: Higher Energy Density Ceiling, but Interface Issues Need to Be Addressed
Solid-state batteries are mainly composed of positive electrodes, negative electrodes, solid electrolytes and other main materials. The essential difference is that solid-state batteries use non-flammable solid electrolytes instead of the flammable liquid electrolytes of liquid batteries.
According to the liquid content inside the solid-state battery, solid-state batteries can be divided into semi-solid-state batteries and solid-state batteries. According to the definition of the academic community, a battery with a liquid content of more than 10% is a liquid battery; a battery with a liquid content of 5%-10% is defined as a semi-solid-state battery. The liquid in the semi-solid-state battery (Qingtao Energy defines it as a wetting agent) is different from the electrolyte in the liquid battery. The wetting agent has a single component, which improves the wettability of the internal interface of the battery and reduces the battery resistance; the all-solid-state battery does not contain any liquid components.
Schematic Diagram of Traditional Lithium-Ion Battery and All-Solid-State Lithium Battery
Solid-state batteries have three major advantages: 1) Higher safety: solid electrolytes are non-flammable and have better stability and mechanical properties at high temperatures. 2) Higher energy density ceiling: solid electrolytes have a wider electrochemical window, reduce side reactions with electrode materials, and broaden the range of available electrode materials. 3) Longer cycle life: solid electrolytes are not easy to volatilize and there is no leakage problem. Solid-state batteries are also lighter in weight due to the elimination of liquid electrolytes and separators.
Solid-state batteries have significant performance advantages, but there is still a long way to go in terms of practicality and industrialization, and they still face some technical challenges.
1) Ion transport problem: The ion conductivity of solid electrolytes is low, which limits the charge and discharge rate.
2) Lithium dendrite problem: They may grow inside and between crystals, causing battery short circuit and failure.
3) Interface problem: The contact area between the electrode and the electrolyte is small, resulting in increased interface impedance, which is not conducive to the direct conduction of lithium ions between the positive and negative electrodes.
4) Cost problem: At the end of July 2024, the price of NCM prismatic power battery cell was 0.46RMB/Wh, and the price of lithium iron phosphate square power battery cell was 0.37RMB/Wh; according to Xinwangda, the cost of all-solid-state batteries with polymer systems will be reduced to 2.00RMB/Wh in 2026. At present, the cost of solid-state batteries is relatively high, and the room for decline in the next 3-5 years is still unpredictable.
In terms of technology, the sulfide route has great development potential in the field of all-solid-state batteries, and leading battery manufacturers have focused on it. Among them, the precursor lithium sulfide has become a key link in controlling costs. As a core element of all-solid-state battery performance, sulfides in solid electrolytes have emerged with high conductivity and excellent processing performance. In particular, lithium phosphorus sulfur chlorine has stood out with its cost advantage and has become the mainstream choice for mass production. The current market price is in the range of 20,000-40,000 RMB/kg.
However, the current price of lithium sulfide precursors remains high, with a price quote of more than 5 million yuan per ton, which greatly hinders the reduction of costs. We believe that with the continuous innovation of subsequent processes and equipment, its cost is expected to drop significantly. At the same time, the road to commercialization of all-solid-state batteries also faces manufacturing process challenges, especially in the front-end film formation link. The control requirements for the thickness of the solid electrolyte membrane, the uniformity of material dispersion, and the flatness of the negative electrode are strict and need to be accurate to the micron or even nanometer level. At present, the production equipment is not yet mature and it is difficult to support mass production needs.
In 2025, the global market for various types of solid-state batteries will be worth hundreds of billions of yuan. If solid-state batteries can fully leverage their safety advantages and further enhance energy density, while optimizing rate performance, cycle life, and manufacturing processes, they will have a huge potential customer base in specific advantageous scenarios. In addition, if a breakthrough is made in the cost of solid-state batteries, the market space is expected to expand further.
Flow Battery Energy Storage: Distinct Advantages for Long-Term Energy Storage in the Future
Liquid flow batteries can be divided into zinc-iron liquid flow batteries, zinc-bromine liquid flow batteries, all-iron liquid flow batteries, iron-chromium liquid flow batteries, and all-vanadium liquid flow batteries, depending on the positive and negative electrodes and the types of active electricity in the electrolyte solution. Among them, vanadium batteries have taken the lead in entering the early stage of commercialization along with the development of upstream and downstream industries.
All-vanadium liquid flow battery is a battery with vanadium as the active material in a circulating liquid state. The electrolyte is pumped into the battery stack through an external pump. Under the action of mechanical power, the electrolyte circulates between the storage tank and the half-cell, flows through the electrode surface to produce an electrochemical reaction, and then the double electrode plates collect and conduct current, thereby realizing the conversion of chemical energy into electrical energy. This unique circulating flow working mode allows vanadium batteries to have flexibility in energy storage capacity, and different needs can be met by adjusting the electrolyte volume.
Schematic Diagram of All-Flow Battery Energy Storage
Vanadium batteries have unique advantages in the context of long-term energy storage. The power of vanadium batteries is determined by the battery stack, and the energy storage capacity depends on the electrolyte, and the two are independent of each other. In terms of cost, vanadium batteries can effectively amortize the cost of power units along with the energy storage time, thereby reducing the cost per Wh, which is highly consistent with long-term energy storage. In practical applications, if the power needs to be increased, the number of battery stacks can be increased; if the capacity needs to be expanded, the electrolyte concentration and volume can be changed to flexibly meet diverse energy storage needs, providing a highly promising technical solution for the energy storage field.
All-Flow Battery Energy Storage: Output Power and Storage Capacity Can Be Independently Designed
Vanadium batteries also show excellent characteristics in terms of safety and cycle life.
1)Vanadium batteries use inorganic water-based electrolytes, which have no risk of combustion and explosion, and can operate stably under normal temperature and pressure, completely eliminating the risk of thermal runaway. The battery system shows good consistency, and with the efficient battery management mechanism, it ensures high reliability of operation.
2)In terms of cycle life, the calendar life can reach 25 years, the number of charge and discharge cycles can reach 16,000 times, and the electrodes do not participate in the reaction during the reaction process, and deep charge and discharge does not affect the battery life. The capacity can maintain a zero decay state. Vanadium batteries can achieve a 100% capacity retention rate throughout the entire life cycle, and no efficiency decay occurs, providing a solid guarantee for long-term stable energy storage and supply.
In 2024, China’s installed capacity of liquid flow battery energy storage exceeded GWh for the first time, reaching 1.81GWh. According to GGII, liquid flow batteries are rapidly penetrating with hybrid energy storage applications. From January to November 2024, hybrid energy storage projects of all-vanadium liquid flow batteries + lithium iron phosphate batteries (LFP) accounted for nearly 60% of China’s liquid flow battery bidding projects. As the price of liquid flow battery systems continues to decline, it is expected to drop to less than 2MB/Wh in 2026.
Hydrogen Energy Storage: Stored Hydrogen Can Be Converted to Electricity and Used in Various Sectors such as Metallurgy and Transportation
Hydrogen energy is clearly divided according to different categories. In a narrow sense, hydrogen energy storage revolves around the conversion process of “electricity-hydrogen-electricity”. When there is a surplus of electricity supply, especially during non-peak hours, this electricity can be fully utilized to vigorously carry out large-scale hydrogen production activities, successfully and skillfully convert electricity into hydrogen energy for proper storage. This type of hydrogen energy can be used as a reserve energy and supplied to downstream related industries on demand; it can also be used when the peak electricity demand comes and the electricity demand rises sharply. The key technology of fuel cells can be used to quickly convert the stored hydrogen into electricity and transmit it to the grid in time, effectively playing a key role in regulating the balance of electricity supply and demand.
Hydrogen energy storage in a broad sense emphasizes the one-way conversion characteristics of “electricity-hydrogen”. The stored hydrogen is widely used in many fields such as transportation and steel. For example, it can be used to power hydrogen fuel cell vehicles to drive travel and help the green and low-carbon transformation of the steel industry; or through a series of complex chemical reactions, hydrogen can be converted into valuable chemical derivatives such as methanol and ammonia for use in other industries such as chemical production. After the conversion and application, the hydrogen will no longer flow back into the power grid for power generation.
Hydrogen energy storage has the following significant advantages:
1)Long-term: The key elements of long-term energy storage are the mobility of energy carriers and the decoupling of capacity and power. Although pumped storage and compressed air energy storage have the mobility of energy carriers, their application is limited by geographical location. In contrast, hydrogen energy storage is more suitable for long-term charging and discharging needs of more than 4 hours, and can achieve seasonal energy transfer. Its average continuous discharge time can reach 500-1000 hours. The self-discharge rate of hydrogen energy storage is extremely low, almost zero, which enables it to adapt to energy storage cycles of more than one year without geographical restrictions.
2)Large capacity: The energy density of hydrogen energy storage in liquid hydrogen can reach 143 MJ/kg (about 40kWh/kg), which is more than 100 times that of electrochemical energy storage such as lithium batteries; in terms of calorific value, the calorific value of hydrogen can reach 120MJ/kg, which is 3-4 times that of traditional fossil energy such as coal, natural gas, and oil. Energy storage is one of the few energy storage methods that can store more than 100 GWh of energy.
Comparison of Discharge Time and Capacity Performance Across Different Energy Storage Technologies
3) Cross-regional: Hydrogen can be transported in various ways, including gaseous, liquid and solid forms. Hydrogen energy storage is not restricted by the power transmission and distribution network and can achieve cross-regional peak load regulation. However, electrochemical energy storage power stations are limited by power grid and transportation conditions and are difficult to achieve cross-regional peak load regulation. Especially in offshore wind energy development, with the large-scale development of offshore wind power, the transmission and consumption of offshore power has become a challenge. Using offshore wind power to produce hydrogen can effectively solve the problems of large-scale grid connection and consumption of offshore wind power and high cost of deep-sea power transmission.
Hydrogen can be said to be the ultimate form of energy. Hydrogen can be produced by electrolysis of water, which is almost inexhaustible; it can generate electricity by reacting with oxygen, and only water is generated, which is truly zero carbon emission. However, the challenges faced by hydrogen storage and transportation are also severe. The special physical and chemical properties of hydrogen are accompanied by safety risks during transportation, whether in high-pressure gas or low-temperature liquid. In addition, the low density of hydrogen leads to its low transportation efficiency. Even under high pressure conditions, a 49-ton heavy truck can only transport about 300 kilograms of hydrogen. The extremely low boiling point of liquid hydrogen requires us to invest huge technology and energy costs in maintaining its liquid state.
As for when hydrogen energy storage will become a pillar industry, we believe there are two key stages worth paying attention to:
The first turning point: Globally, policies have been set to support the development of hydrogen energy storage. In November 2024, the Ministry of Industry and Information Technology publicly solicited opinions on the “Action Plan for the High-Quality Development of New Energy Storage Manufacturing Industry” (Draft for Comments). The opinions pointed out the development of long-term energy storage technologies such as compressed air, and the appropriate advance layout of long-term energy storage technologies such as hydrogen energy storage. Actively encourage thermal power to reasonably configure new energy storage and expand new energy application scenarios such as wind and solar hydrogen storage. Explore the use of renewable energy to produce hydrogen in areas where new energy is rich and local absorption capacity is low, such as deserts, Gobi, and wastelands.
The second turning point: When offshore wind power hydrogen production and solid-state hydrogen storage technology are commercialized, hydrogen energy is expected to play a key role in the production of industrial fields such as steel and cement, as well as green methanol and other products. It is expected that by 2035, hydrogen energy production capacity will reach 5 trillion yuan, becoming an important force in the energy industry. On the cost side, the current cost of building hydrogen stations is high. The construction cost of a standard hydrogen station is at least 2 million US dollars, about 15 million yuan, and the cost of a high-pressure hydrogenation system is as high as 20 million yuan. Among them, hydrogen compressors account for 30% of the cost of hydrogen stations. Faced with the challenge of limited cost reduction space, domestic hydrogen compressor companies urgently need to increase technological innovation to achieve cost-effectiveness and market competitiveness.
Hybrid Energy Storage: Integrating Multiple Storage Technologies to Achieve a ‘1+1>2’ Effect
The hybrid energy storage system cleverly integrates two or more different energy storage technologies into one. It aims to learn from the strengths of many and give full play to the unique advantages of various energy storage technologies, thereby achieving more efficient and flexible energy storage and fine management goals.
Hybrid energy storage has attracted much attention in the industry because it can achieve the effect of “1+1>2” through its advantages of strong complementary performance, multiple functions, risk dispersion and high comprehensive efficiency. In 2022, the “14th Five-Year Plan for New Energy Storage Development” issued by the National Development and Reform Commission and the National Energy Administration mentioned that it would promote the joint application of multiple energy storage technologies in combination with system needs and carry out pilot demonstrations of composite energy storage.
From a classification perspective, hybrid energy storage covers the integration of batteries and batteries, such as the combination of batteries of different chemical systems, which utilizes the differences in their respective charging and discharging characteristics to achieve stable energy supply at all times; batteries and supercapacitors are combined, the former ensures long-term energy reserves, and the latter relies on ultra-high power density to respond quickly in instantaneous high-power demand scenarios to fill the energy gap; thirdly, batteries and flywheels work together, and flywheels rely on high-speed rotation to store energy, which can cope with short-term and high-frequency power fluctuations with ease, complementing batteries to ensure stable power output; there is also a combination of batteries and hydrogen storage, which uses hydrogen’s high energy density and flexible conversion characteristics to expand the boundaries of energy storage time.
At present, lithium iron phosphate batteries dominate the field of electrochemical energy storage in my country. However, the single lithium iron phosphate technology route has inherent shortcomings, and hybrid energy storage can effectively make up for it. When a certain energy storage technology suddenly breaks down or fails, other supporting technologies can take over in time to continuously ensure the storage and release of energy and maintain stable operation of the system.
At present, the application of projects that combine lithium batteries with other technical routes has gradually been implemented, and a variety of new energy storage technologies cooperate with each other to meet the needs of multiple scenarios. According to GGII, among the Chinese flow battery bidding projects from January to November 2024, all-vanadium flow battery + lithium iron phosphate battery (LFP) hybrid energy storage projects accounted for nearly 60%. According to CESA, from January to October 2024, a total of 10 hybrid energy storage projects in my country have newly installed capacity, with a total scale of 1.4GW/4.6GWh, accounting for 7.92% of the capacity, an average duration of 3.28 hours, and a total investment of more than 6.7 billion RMB.
Other Emerging Energy Storage: Many Boats Competing, All Have Opportunities
1)Compressed air energy storage: Compress the air and store it in a gas tank, and then use an energy conversion device to convert the air in the gas tank into mechanical energy or electrical energy, thereby realizing energy storage and release. Compressed air energy storage technology has the advantages of large capacity, long energy storage cycle, short construction cycle, and relatively flexible site layout. The storage medium is only air and there is no risk of explosion. Compared with pumped storage, it is not restricted by geographical conditions. It is expected to become an important supplement in the field of large-scale energy storage power stations (>100MW) when combined with other energy storage technologies. Its discharge time can reach more than 4 hours.
2)Flywheel energy storage: Energy is stored through high-speed rotation of the flywheel, and then converted into electrical energy or thermal energy through an energy recovery device. Flywheel energy storage mainly focuses on its role in grid frequency regulation. The flywheel can play a smoothing and slowing role for the grid in a timely manner as the grid changes, becoming an alternative to thermal power frequency regulation.
3)Gravity energy storage: By converting gravitational potential energy into electrical energy, energy storage and release are achieved. Its advantage is that it does not need to transmit electrical energy to distant users through high-voltage transmission lines, has high energy conversion efficiency, and does not generate a lot of environmental pollution. The system conversion efficiency is 80%-90%, and the service life is 25-40 years.
