From PVDF to PTFE: Tesla ushers in a new era of dry electrodes?
Dry electrode technology welcomes major breakthroughs, and the cost of lithium batteries is expected to be significantly reduced
Recently, Tesla announced during its Q2 earnings conference that its 4680 battery, which uses dry cathode technology, has started assembling its first prototype Cybertruck and entered the vehicle testing and verification phase. The company plans to mass produce and install the 4680 battery, which fully uses dry electrodes, by the end of the year.
This means that Tesla's dry electrode has completed the design freeze and entered the mass production verification stage, and its large cylindrical battery is finally one step closer to low-cost, low-energy large-scale manufacturing.
In the second quarter, Tesla's 4680 production capacity increased by 51% compared to the first quarter, with significant cost reductions. 1400 Cybertrucks per week can carry 4680 batteries, and production capacity continues to climb. By the end of the year, Tesla will achieve a 50% cost reduction compared to existing lithium batteries.
In addition, LG New Energy announced earlier this month that it plans to commercialize dry coating technology by 2028, which aims to replace the high-energy wet process used to manufacture cathode and anode electrodes.
If this method is feasible, the production cost of batteries can be reduced by 30%, which is expected to lower the cost of each electric vehicle by thousands of yuan.
In addition to Tesla and LG, Samsung SDI, Volkswagen, SK On, BMW, Panasonic, as well as domestic companies such as CATL, EVE Energy, and Honeycomb are also developing dry coating technology.
The advantages of dry electrode technology are obvious, and the demand for PTFE is expected to explode
The dry electrode process is a comprehensive upgrade compared to the traditional wet process. In the manufacturing process, the dry electrode has fewer steps, lower manufacturing costs and energy consumption, environmentally friendly raw materials, and is more suitable for large-scale production; In terms of battery performance, dry process batteries can achieve higher energy density, with better electrical and mechanical properties; On the application side, dry electrode technology is more suitable for the manufacturing needs of new generation batteries such as solid-state batteries and 4680.
The dry electrode process can be divided into powder pressing method, powder spraying method, adhesive fibrosis method, etc. After Tesla's acquisition of Maxwell, the adhesive fibrosis method for preparing electrodes has attracted widespread attention.
The commonly used fibrillated adhesives include PTFE, ETEF, and FEP. PVDF cannot be fibrillated, but can be sprayed onto the current collector with an electrostatic spray gun along with other active particles. After heat treatment of the mixture, it can be rolled into a film. However, the adhesion effect is poor, and the adhesion strength of PVDF is less than 1/4 of FEP.
Among them, PTFE is the optimal adhesive choice, mainly because PTFE has a larger polymer molecular weight, which can form longer raw fibers and has good mechanical properties.
In the future, the large-scale penetration of dry electrode technology in the field of lithium batteries will lead to a significant increase in demand for PTFE.
Based on the measurement of 3000 tons of positive and negative electrode materials required at 1GWh and the addition of 5% -10% PTFE, approximately 200 tons of PTFE are needed. EVTank predicts that global shipments of lithium-ion batteries will reach 1926.0 GWh and 5004.3 GWh in 2025 and 2030, respectively. If the dry electrode permeability reaches 3% and 15% respectively in 2025 and 2030, the corresponding PTFE demand will be about 11000 tons and 150000 tons, respectively.
Low end PTFE production capacity overcapacity, high-end production capacity heavily relies on imports
Although PTFE has good prospects in dry electrode technology, it cannot be directly applied to dry electrodes and must be modified.
PTFE is unstable at low potentials and undergoes irreversible reactions with lithium. Therefore, when applied to the negative electrode, it lithiated and consumed active lithium, reducing adhesion and capacity. The higher the PTFE content in the battery, the more lithium is consumed. In the experiment, after excluding the influence of SEI film formation during the first week of charge and discharge, in the second discharge curve, the higher the PTFE content, the smaller the discharge current. Therefore, it is confirmed that polytetrafluoroethylene will react with lithium ions and affect the performance of the battery.
At present, the downstream applications of PTFE produced by domestic enterprises are mainly focused on low-end plastic products, while high-end PTFE used in 5G communication and dry electrodes mainly relies on imports.
High end PTFE varieties include ultrafine powder PTFE, high compression ratio PTFE dispersed resin, and ultra-high molecular weight PTFE. Most of the domestic leading varieties have already entered the market. According to ACMI, Haohua Technology has successfully developed high compression ratio PTFE dispersed resin and applied it to 5G cable production. Meilan Group has a production capacity of 1500 tons/year of ultra-high molecular weight PTFE resin. However, the batch stability of domestically produced high-end materials still lags behind mature products from Kemu and Daikin, and continuous technical optimization is needed.
