SES Power explains the principles, materials and prospects of sodium-ion  batteries for you

　　Na-ion batteries first appeared in the early 1980s, and then due to the  better performance of lithium-ion batteries, the research on sodium-ion  batteries was stagnant. After 2010, with the increasing demand for lithium  batteries in various industries around the world, the materials for lithium-ion  batteries are in short supply, and people's research on sodium-ion batteries has  re-emerged.

　　SES Power often uses lithium batteries to customize products, such as  12V100Ah, 24V100Ah, 36V100Ah, 48V100Ah using EVE, CATL, BYD square aluminum  lithium iron phosphate batteries, home energy storage 3KW, 5KW systems,  rack-mounted energy storage systems and other products. But we are quite  concerned about the development of sodium-ion batteries because it means endless  possibilities. Let the senior engineers of SES Power analyze the principle,  composition and prospects of sodium-ion batteries for you.

　　The working principle of sodium ion batteries mainly relies on the movement  of sodium ions between the positive electrode and the negative electrode to  work: during charging, sodium ions are deintercalated from the positive  electrode, and swim through the diaphragm in the electrolyte to embed the  negative electrode, and the negative electrode is in a sodium-rich state; On the  contrary.

　　(Schematic diagram and internal structure of sodium-ion battery)

　　The advantages of sodium-ion batteries are relatively high energy density,  high safety in use (can be discharged to 0V), environmental protection (without  lead, cadmium, mercury and other elements that pollute the environment), wide  resource sources, and low cost.

　　Due to the working principle of sodium-ion batteries and the high  similarity of battery materials to lithium-ion batteries, the process and  equipment for battery production can be reused. This also means that the  investment in battery factories will be greatly reduced.

　　According to different application scenarios, sodium-ion batteries can be  mainly divided into power and energy storage. Compared with the mature  commercialization level of lithium-ion batteries, the commercialization of  sodium-ion batteries is only in its infancy. Only a few companies have carried  out preliminary commercialization of sodium-ion batteries, and a complete and  mature industrial chain has not yet formed.

　　Because sodium-ion batteries work similarly to lithium-ion batteries, many  materials and processes can be reused, even from a raw material perspective. In  terms of raw materials, the first and most obvious difference between sodium-ion  batteries and lithium-ion batteries is the difference in working ions.

　　A: Positive electrode material

　　At present, the cathode materials for sodium-ion batteries are synthesized  in the laboratory, and the sources of sodium are very wide, but large-scale  industrial production has certain requirements for cost, process safety, acidity  and alkalinity, and carbonic acid is most likely to become the raw material for  industrial production. Sodium (i.e. soda ash).

　　Contrary to the uneven and scarce global distribution of lithium resources,  sodium resources are widely distributed around the world, and its abundance in  the earth's crust ranks sixth. The salt we eat daily is the most common sodium  salt - sodium chloride. The most common sources of sodium chloride are sea salt,  lake salt, and rock salt (mineral salt).

　　The structure of sodium ion battery mainly includes five parts: positive  electrode material, negative electrode material, electrolyte, current collector  and separator. Cathode Materials Cathode and anode materials affect key  performance indicators such as energy density, power density, cycle life, and  safety of Na-ion batteries, and are critical to battery performance.

　　Different from the situation in which the cathode technology route of  lithium-ion batteries is basically determined, there are currently more than 100  cathode materials related to sodium-ion batteries, and the technological route  is still in the process of evolution. According to the composition, mainstream  sodium-ion battery cathode materials can be divided into layered metal oxides,  polyanionic compounds and Prussian blue compound systems.

　　B: negative electrode material

　　The negative electrode material is different from the graphite material  negative electrode used in lithium ion batteries. Because the graphite layer  spacing is too small, the intercalation of sodium ions with a larger radius  between the graphite layers requires more energy, and reversible deintercalation  cannot be performed within the effective potential window. Therefore, it is  considered that Conventional graphite cannot be used as a negative electrode for  sodium-ion batteries.

　　The research directions of anode materials for sodium ion batteries include  hard carbon, soft carbon, titanium-based oxides and alloys, etc. The research on  hard carbon is the most, and the current commercial sodium ion batteries also  use hard carbon materials as negative electrodes.

　　C: Diaphragm

　　The separator is used to isolate the positive and negative electrodes of  sodium-ion batteries, preventing short-circuit phenomena, and at the same time  acting as an ion channel.

　　At present, the electrolyte of the most common organic electrolyte-based  sodium-ion battery is very similar to that of the lithium-ion battery, and the  solvent remains unchanged, except that the solute salt is changed from lithium  hexafluorophosphate to sodium hexafluorophosphate, so it can be used with  lithium ion Battery-like separator.

　　D: Electrolyte

　　The electrolyte is the ionic charge carrier necessary for the  electrochemical reaction and is the key to improving the power characteristics  of Na-ion batteries. Electrolytes are mainly composed of solvents, solutions,  additives and the like.

　　The most common electrolyte for sodium-ion batteries is an organic liquid  electrolyte. The organic solvent portion of the organic electrolyte is similar  to the corresponding composition of lithium-ion batteries.

　　E: positive and negative carriers

　　Unlike lithium, since aluminum and sodium do not undergo alloying reactions  at low potentials, the carriers of the positive and negative electrodes of  sodium-ion batteries, that is, current collectors, can use inexpensive aluminum  foils instead of higher-cost copper foils. The current collector aluminum foil  of sodium ion battery is basically the same as that of lithium battery, and the  performance requirements are basically similar.

　　Since the commercialization level of sodium-ion batteries is only in its  infancy, there are relatively few studies on battery systems. CATL has developed  the AB battery system solution in terms of battery system integration, that is,  the sodium-ion battery and lithium-ion battery are mixed and matched in a  certain proportion, integrated into the same battery system, and the balance  control of different battery systems is carried out through the BMS accurate  algorithm.

　　Application market in the current secondary battery market, lithium-ion  batteries are the absolute main force and core. Although lithium-ion batteries  are relatively free of obvious performance limitations, sourcing raw materials  such as lithium carbonate and lithium cobaltate is becoming increasingly  difficult.

　　SES Power believes that although the original intention of sodium-ion  battery research and development is to supplement and replace the application of  lithium-ion batteries in the field of power batteries, because the current  energy density of sodium-ion batteries is not as good as that of lithium-ion  batteries, it is temporarily unable to shake the lithium-ion battery-led  electric power automotive field. In terms of stationary energy storage,  sodium-ion batteries have broad prospects due to their low requirements for  volume and quality. However, from the public information, the cycle life of  sodium-ion batteries is much lower than that of lithium iron phosphate  batteries, and there is no great advantage in cost, especially when lithium iron  phosphate batteries replace lead-acid batteries, even if sodium-ion batteries  can officially mass production can not replace lithium iron phosphate batteries  for a long time.

　　As for our lithium iron phosphate battery that can be used in an  environment of -40 ℃, it has been stabilized after years of research and  development and experiments. We believe that sodium-ion batteries are even more  irreplaceable.