Canada synthesizes water-based lithium ion battery electrodes that do not require binders
The main components of lithium-ion battery electrodes are active materials, conductive agents and binders, as well as conductive copper foil and aluminum foil. Among them, only active materials can really play a role in capacity.
Among them, the conductive agent mainly conducts electrons between the active material particles, the binder is mainly used to bond the various parts of the electrode, and the copper foil and aluminum foil mainly play the role of The role of deriving electrons to the electrode, so the proportion of active material in the electrode is naturally the higher the better.
The proportion of the binder in the electrode is generally between 3% and 5%. If the electrode preparation process does not require a binder, it can significantly improve the electrode’s performance. Capacity, improve the energy density of the battery.
In recent years, with the development of wearable device technology, flexible battery technology has also attracted more and more attention. The key to flexible battery technology lies in the preparation of flexible electrodes. The traditional electrode preparation process makes the electrode difficult to bend. A viable option is to use carbon nanotubes and graphene to form a conductive network frame for the preparation of binder-free electrodes.
Compared with traditional organic electrolyte system lithium-ion batteries, water-based batteries are lower in cost, safer, and have higher ionic conductivity. Therefore, water-based lithium-ion batteries are compared It is suitable for application in the field of wearable devices. Of course, this is based on further improving the energy density of water-based lithium-ion batteries, and the binder-free electrode is just suitable for this application.
Xiao Zhu of the University of Waterloo in Canada, etc., used carbon nanotubes and LiMn2O4 to synthesize a water-based lithium ion battery electrode that not only does not require the use of a binder, but also has very good elasticity. . They first dispersed the carbon nanotubes CNT in the aqueous solution by high-speed shearing method. Because the CNTs they used have a large aspect ratio, the dispersed solution has very good stability, and they form a relationship between each other. Stable networks, these networks can be used for LiMn2O4 to store nanoparticles, and finally through filtration, a binder-free electrode is obtained.
The electrode has the following advantages:
1) First of all, the overall weight of the electrode is greatly reduced. In this electrode, carbon nanotubes play multiple roles, as both a binder, a conductive agent, and a current collector.
2) Compared with the traditional electrode structure, this electrode has a good connection between the carbon nanotubes, which greatly reduces the pole piece resistance.
3) Due to the porous structure of the electrode, the active material LiMn2O4 exchanges faster with lithium ions, which is beneficial to improve the rate performance of the battery.
4) Because the CNT of the frame structure has good elasticity, it can alleviate the volume expansion and contraction of the active material caused by the insertion and extraction of lithium ions during the charging and discharging process. , Thereby improving the cycle life of the battery.
As can be seen from the above introduction, this process does not require expensive equipment and additional chemicals, which helps to reduce the cost of electrode preparation and simplify the electrode preparation process. At the same time, the conductive network structure formed by CNT can not only ensure good conductivity, but also enhance the structural stability of the electrode and increase the cycle life of the battery.
The electrochemical test shows that the elastic electrode sheet prepared by this method has very excellent rate characteristics, and the specific capacity of the electrode prepared by this method can still reach 72mAh under the super-high rate of 20C. /g, while the CNT+LiMn2O4 prepared by the common process is only 45mAh/g at this rate. At the same time, the electrode also showed good cycle stability. After 300 cycles at a rate of 4C, the capacity only dropped from 116mAh/g to 92mAh/g, and the capacity retention rate was 79.3%.
Binders, conductive agents, and current collectors, the development trend of auxiliary materials that do not provide capacity for the system, is that their proportion in the battery system is getting smaller and smaller. With the continuous advancement of technology, it is believed that one day, these materials will eventually disappear during the preparation of lithium-ion battery electrodes.