Lithium batteries are subject to the impact of global lithium resource exploitation and production costs, and face many challenges in the commercial process, and sodium-ion batteries are popular for their safety, cost and low temperature advantages, and sodium-ion batteries can be compatible with existing lithium battery production lines, so people have high hopes for sodium-ion batteries, and technical research on sodium-ion batteries is in the ascendant.
However, sodium-ion batteries are prone to oxidative decomposition of electrolyte during long cycling, which leads to the problem of cell gas production. It is of great significance to explore the gas production mechanism of sodium-ion batteries and the determination of in-situ gas production for large-scale commercial use of sodium-ion batteries.
1. Research on sodium-ion battery technology
Sodium-ion batteries work similarly to lithium batteries, in that they are charged and discharged by migrating ions between the positive and negative electrodes. The research on gas production of sodium-ion batteries in the industry mainly focuses on cathode materials, anode materials and electrolytes.
At present, there are three technical routes for the cathode materials of sodium-ion batteries: "transition metal oxide", "polyanion" and "Prussian blue and white", among which the advantages of layered oxide (a kind of transition metal oxide) are simple process, high specific capacity, high voltage platform and good sodium storage effect.
The difficulty lies in the poor cycling stability of layered oxide materials, the large volume change during charging and discharging, and the easy gas production of battery cells.
Due to the high layered oxide residue and lack of stability of sodium-ion batteries, the application of pouch sodium-ion batteries is limited[1]. In other words, if the "layered oxide" technology route achieves a technological breakthrough in the gas production of battery cells, it will be of great help to the large-scale commercial application of sodium-ion batteries.
2. Monitoring means of cell gas production
Most of the existing cell gas production monitoring methods adopt the "Archimedes method", which belongs to the "indirect method" measurement method.
Taking the in-situ volume measurement system developed by a manufacturer in Suzhou as an example, the technical scheme immerses the sample into silicone oil (density 095g cm), then the test temperature is controlled, and the buoyancy data is converted into the mass of the cell according to the Archimedes principle, and then the gas production volume is obtained. This monitoring scheme has problems such as human intervention, complex operation, data distortion, and manual recording, and it is difficult for researchers to obtain authoritative and credible battery gas production data.
In addition, there is also a method in the industry that applies the principle of "ideal gas equation (PV=NRT)" to monitor the gas production of battery cells, which is more complex than the "Archimedes method". According to the difference of the amount of reactive gas substances in the closed container, the test device is particularly complex, and the experimental process has a certain danger.
3. GPT ultra-trace gas measurement
The GPT-1000M in-situ gas production tester developed by Wuhan Electric Relaxation New Energy Co., Ltd. has the advantage of "simplicity", abandons the existing "indirect method" idea, and uses the "direct method" to monitor battery gas production. The gas to be measured is directly introduced into the test cell, and the flow rate change resolution of the ultra-trace gas measurement technology applied to it is accurate by 1 l, helping researchers to directly obtain real and reliable data results.
Compared with the traditional Argied float method, ideal volume calculation method and other instruments, GPT-1000M can directly monitor the trace volume changes of the body, the results are accurate and reliable, repeatable, and the tail can be directly collected, and the equipment can be connected in series with GC-MS, DEMS and other bulk composition detection segments, which provides real and reliable data for material research and development and the analysis and research of the production mechanism of lithium battery cells.
GPT-1000M has passed the national metrology certification).
Compatibility is a major feature of GPT-1000M in-situ gas production tester, compared with the general lithium battery gas production measurement device soft pack or hard shell battery (prismatic cylindrical battery), GPT-1000M can be compatible with monitoring soft pack battery, prismatic battery, hard pack battery, "one thing for multiple purposes" advantage, saving the user's detection cost.
4. Conclusion. From the perspective of commercialization, sodium-ion batteries can also achieve a fast charging capacity of 5-10 minutes. Whether it is energy density or cycle life, sodium-ion batteries are significantly better than lead-acid batteries, and are not inferior to lithium batteries in terms of energy density and cycle life, and the material cost is much lower than that of lithium batteries. Through the GPT-1000M in-situ gas production tester, the gas production mechanism of sodium-ion battery cells was explored, and the material process and electrolyte structure of sodium-ion batteries were optimized, which played an important role in promoting the development of a new generation of sodium-ion battery products.
Citations. 1. Research on Gel Electrolyte Soft-pack Sodium-ion Battery Engineering Science and Technology Edition;Engineering Science and Technology Edition, Huang Huawen, Fan Shanshan, Zhao Wei, Tang Weichao, Guo Panlong, Qiu Yaming.