Sodium battery industry research report
- How do sodium battery work?
- Manufacturing process and route of sodium battery
- Horizontal comparison: sodium battery vs liquid flow, lead acid
The cost and rate capability of sodium battery have advantages over li-ion batteries. The sodium secondary battery that first appeared at that time was a sodium-sulfur battery, with elemental sulfur and metallic sodium as the positive and negative electrodes, β-alumina fast ion conductor as the solid electrolyte, and the working temperature was 300~350℃.
This high-temperature sodium-sulfur battery has a high energy density (150~240Wh/kg) and a cycle life of 2500 times, while the similar lithium-sulfur battery has a cycle life of less than 10 times.
How do sodium battery work?
The working principle of sodium battery is exactly the same as that of lithium-ion batteries, that is, under a certain potential condition, the reversible extraction and insertion of guest alkali metal ions in the host material, in which the higher intercalation potential acts as the positive electrode, and the lower intercalation potential acts as the positive electrode. negative electrode.
The composition and structure of sodium ion batteries are exactly the same as those of lithium ions, mainly including positive electrodes, negative electrodes, electrolytes, battery separator and current collectors. According to whether the main material directly participates in the electrochemical reaction process, they can be divided into active materials and inactive materials.
Sodium battery active material
- Cathode material: oxide, prussian blue, polyanion three main lines
The positive electrode material undergoes an oxidation reaction during charging and a reduction reaction during discharge, and generally has a high reduction potential.
The ideal cathode material should meet the requirements of high reduction potential (but must be lower than the oxidation potential of the electrolyte), large reversible capacity, stable cycle performance, high electronic and ionic conductivity, stable structure and not afraid of air, high safety, and low price.
For sodium battery, the theoretical specific capacity of existing cathode materials is relatively low, thus becoming one of the main determinants of the overall capacity of the battery.
At present, the cathode materials of sodium battery are mainly divided into five types: oxides, polyanions, Prussian blue, fluorides, and organic compounds. The first three types have the highest maturity and have entered the early stage of industrialization. .
- Anode material: carbon-based materials are the most mature
The negative electrode material undergoes a reduction reaction during charging and an oxidation reaction during discharge, and generally has a lower reduction potential.
The ideal cathode material should meet the requirements of low reduction potential (but must be higher than the deposition potential of metallic sodium), large reversible capacity, stable cycling performance, high electronic and ionic conductivity, stable structure and not afraid of air, high safety, and low price.
For sodium battery, the anode material plays an important role in loading and releasing sodium ions, which directly affects the overall kinetic performance of the battery, such as rate performance, power density, etc.
At present, the anode materials of sodium battery are mainly divided into five types: carbon-based materials, titanium-based materials, alloy materials, organic compounds, and other systems. Among them, carbon-based materials have the highest technological maturity and rich resources, and are expected to take the lead in realizing industrialization.
- Electrolyte material: mainly liquid electrolyte
Electrolyte is a bridge for material transfer between positive and negative electrodes. It is used to transport ions to form a closed loop. It is an important guarantee for maintaining electrochemical reactions.
It not only directly affects the rate, cycle life, self-discharge and other properties of the battery, but also determines the stability and safety of the battery. According to the physical form, the electrolyte of sodium-ion battery can be divided into liquid electrolyte and solid electrolyte.
Inactive materials for sodium battery
The inactive materials in sodium battery mainly include separators, current collectors, conductive agents, binders, etc. They do not directly participate in electrochemical reactions, but are essential auxiliary materials, and their compatibility with active materials and other factors will have a significant impact on battery performance.
Manufacturing process and route of sodium battery
Electrode material synthesis
The synthesis method of cathode materials for sodium ion batteries should be determined according to the specific material category, which is mainly divided into solid-phase reaction method and liquid-phase synthesis method. Oxide and polyanion materials can be synthesized by either solid-phase reaction method or liquid-phase synthesis method.
The synthesis process is basically the same as that of the corresponding materials for lithium-ion batteries, so the production line can be compatible to a certain extent.
At present, the solid-phase reaction method is the most widely used in the industry. The uniformity of the product prepared by this method has certain limitations, but the operation is simple and the process flow is short, which is suitable for large-scale production.
The liquid phase synthesis method has high product uniformity, but is relatively expensive, requires high equipment, and has a lot of waste water. In addition, there are technologies such as sol-gel method, microwave synthesis method, spray drying method, ion exchange method, etc., which generally have high cost and are not suitable for industrial production for the time being.
Batteries are assembled into groups
Similar to lithium-ion batteries, the production of sodium battery also undergoes processes such as pulping, coating, assembly, liquid injection, and chemical formation. Among them, the assembly process is mainly to combine the finished positive and negative plates through the diaphragm interlayer to establish the sodium ion path inside the battery, and isolate the positive and negative electrodes to prevent internal short circuits.
The assembly process follows the lithium-ion battery technology and is divided into winding and lamination processes. The former is further divided into cylindrical winding and square winding.
In addition, the structural design and packaging process of sodium-ion battery products basically follow the lithium-ion battery, and the appearance is roughly divided into three categories: cylindrical, soft pack and square hard shell, each with its own advantages and disadvantages.
Horizontal comparison: sodium battery vs liquid flow, lead acid
With the advancement of the industrialization of sodium battery, it is bound to have varying degrees of impact on other secondary battery technologies. Next, a side-by-side comparison of sodium battery with the above three battery technologies is made.
Sodium vs liquid flow: advantages and disadvantages are highly complementary
sodium battery and flow batteries are highly complementary. The former is suitable for small and flexible energy storage, while the latter is suitable for large and medium-scale energy storage. A flow battery is a liquid-phase electrochemical energy storage device.
It is characterized in that the active working substance is dissolved in the electrolyte, and energy storage and release are realized by changing the oxidation valence state of the active substance. Typical representatives include vanadium battery, iron-chromium batteries, and zinc-bromine batteries.
The biggest advantage of flow batteries is their intrinsic safety and long cycle life, especially suitable for medium and large electrochemical energy storage facilities, but the disadvantages are low energy density and narrow operating temperature range, so it is difficult to miniaturize or used in alpine regions.
In contrast, the energy density of sodium battery is about three times that of flow batteries, and it can withstand low temperatures of -40 °C, but the intrinsic safety and cycle life are not as good as flow batteries. In the future, sodium battery and flow batteries are expected to complement each other in the field of energy storage.
For example, household and mobile small-scale energy storage devices have high energy density requirements and are suitable for the use of sodium battery. Large and medium-sized electrochemical energy storage power stations have higher requirements for safety and are suitable for the use of flow batteries.
Sodium vs lead acid: gradually replacing traditional lead acid
sodium battery are expected to gradually replace traditional lead-acid batteries, forcing the development of new technologies such as lead-carbon batteries. The industrial application of lead-acid batteries has been more than a century and a half, and its industrial closed loop of “production-consumption-recycling” has been highly complete. The advantages are low cost, easy recycling, and good safety. The disadvantages are low energy density, short cycle life, long charging time.
At present, lead-acid batteries are still being continuously developed and upgraded. The most representative one is the “lead-carbon battery” that integrates supercapacitor technology.
Its cycle life is as high as 3,000 times, it has fast charging capability, and retains the characteristics of the original lead-acid battery. Safety and other advantages, but the energy density is further reduced, and the manufacturing cost is also increased accordingly.
In contrast, most of the performance of sodium battery is better than that of traditional lead-acid batteries. In the future, as the cost is further reduced, it is expected to gradually replace traditional lead-acid batteries.
At the same time, the rise of sodium battery may indirectly speed up the process of upgrading traditional lead-acid batteries to lead-carbon batteries, and lead-acid batteries may be reborn in the form of lead-carbon batteries in the future.