Editor's Note
In the coming years, as the demand for power batteries increases in terms of range, safety, longevity, and cost-effectiveness, there will be significant transformations in the production processes of both positive and negative electrode materials, along with a surge in adhesive research and development. Innovation in adhesives will continue to drive progress in battery technology.
"Adhesive is easy to make, but hard to perfect," said Li Rengui, General Manager of Chengdu Zhongkelaifang Energy Technology Co., Ltd., at the 2017 Senior Industrial Lithium Conference. Using a humorous tone, he described how his company has been deeply focused on adhesive technology for 17 years.
In reality, since both the positive and negative electrode materials are inorganic powders, they must be firmly bonded to the metal current collector during the electrode sheet formation process. This makes adhesives essential, like glue. However, due to the complex chemical reactions that occur inside lithium batteries, achieving a stable and reliable bonding effect is not an easy task.
From the perspective of the electrode sheet manufacturing process, lithium battery adhesives need to meet four key requirements: first, they should maintain slurry viscosity over time without sedimentation or failure; second, they should dissolve easily into high-concentration solutions with low heat of vaporization; third, they should be easy to form and not rebound when rolled; fourth, they should be flexible to prevent fragmentation when the electrode breaks.
In addition, the binder used in lithium batteries accounts for about 1-2% of the total weight. Despite its small proportion, it plays a critical role. Due to the specific properties of the polymer binders, they can have unexpected effects on battery performance.
According to long-term research by Japan’s JSR Corporation, adhesives not only meet basic application requirements but also significantly influence various aspects of battery performance, such as bond strength, migration inhibition, internal resistance, expansion control, and cycle life.
Li Rengui noted that after three years of rapid development in lithium batteries, adhesive applications have become relatively mature. Commercially, they are mainly divided into water-based and oil-based adhesives. The positive electrode material typically uses an oily binder called PVDF, which requires NMP solvent. However, this solvent can be harmful to both human health and the environment. For the negative electrode, water-based binders like polypropylene and SBR emulsions are commonly used.
As lithium batteries evolve toward higher energy density, greater safety, and lower costs, the demands on adhesives are increasing. Key challenges include reducing adhesive content, improving high-temperature storage performance, enhancing electrode flexibility, and ensuring excellent roll peeling force.
For instance, Solvay Specialty Polymers introduced a new PVDF adhesive that boosts battery energy density by reducing binder usage. This product uses 30% less binder than previous versions and is expected to improve battery reliability by 15%, effectively extending battery life by one year or more.
As a leader in the domestic battery adhesive industry, Zhongkelaifang's team comes from the Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences. Over 17 years, they have focused on adhesive research and development, producing results that are valuable for others in the industry to learn from.
Take LA136D, a new adhesive for the negative electrode, as an example. First, the team designed the molecular structure from the ground up, considering flexibility and electrochemical resistance. Then, they controlled the secondary structure by adjusting the molecular weight to fine-tune adhesion. Finally, they optimized the tertiary structure to achieve superior battery performance.
In terms of basic performance, LA136D has a decomposition temperature of 280°C and an electrochemical window exceeding 6V. Its most notable feature is its strong bonding capability—significantly improved compared to conventional SBR water-based adhesives, even when used in smaller quantities.
Comparison of Adhesion Between LA136D and SBR
LA136D also shows a clear advantage in electrolyte swelling. In tests using EC:DEC (3:7) electrolyte under an aluminum-plastic film sealed environment at 70°C for 24 hours, LA136D absorbed 10.60% of the electrolyte, while SBR absorbed 34.95%.
When applied to the same battery system, LA136D outperforms SBR in conductive agent dispersion and high-speed coating processes. From a performance standpoint, batteries using LA136D exhibit excellent power characteristics, particularly in low-temperature charge and discharge performance and reduced internal resistance at high temperatures.
It’s worth noting that LA136D is just one example of Zhongkelaifang’s ongoing innovation in adhesives. Looking ahead, as the requirements for power batteries continue to rise in terms of endurance, safety, lifespan, and cost, the production of positive and negative electrode materials will undergo major changes. A lot of research and development will focus on adhesives, leading to the continuous emergence of newer and better adhesive technologies.
2U 4U Atx Power Supply,Atx 1800W Server Power Supply,Atx 1800W Power Supply,Active Pfc Power Supply For Computer
Boluo Xurong Electronics Co., Ltd. , https://www.greenleaf-pc.com