Against the backdrop of the accelerated transformation of new energy vehicles towards "high safety, long range, and green development", battery thermal safety has become a core issue for the high - quality development of the industry. As a dual - core component serving as both the "ion channel" and "safety barrier" of lithium - ion batteries, lithium - ion battery separators directly determine the battery's lifespan, energy density, and safety boundaries. However, traditional polyolefin separators (such as polyethylene PE and polypropylene PP) have a shortcoming of insufficient thermal stability, making them unable to meet the heat generation requirements of 800V high - voltage fast - charging and high - energy - density batteries. The breakthrough in modified nanocellulose technology not only provides a green solution for upgrading the performance of lithium - ion battery separators but also serves as a key support for strengthening the thermal safety line of new energy vehicle batteries.
The core function of lithium - ion battery separators is to achieve physical isolation between the positive and negative electrodes of lithium - ion batteries while accurately regulating the transmission of electrolyte. The performance of separators directly affects the battery's cycle life and thermal safety. Once a separator experiences micropore collapse or melting and closure at high temperatures, it is highly likely to trigger thermal runaway of the battery, endangering the safety of drivers and passengers.
Currently, most traditional lithium - ion battery separators are made of polyolefin materials like PE and PP through a multi - layer composite process. They have a porosity of approximately 45.0% and a pore size ranging from 0.03 to 1.00 μm. Although they can meet the basic ion transmission needs, their thermal stability is significantly insufficient. Most traditional polyolefin separators start to show micropore melting and closure at around 130°C, which makes them unable to cope with the heat generation during the operation of high - energy - density batteries (with a range of over 1,000 kilometers) and 800V high - voltage fast - charging systems (with charging time shortened to less than 30 minutes).
At the same time, traditional coating materials for lithium - ion battery separators also have obvious drawbacks. They mostly rely on inorganic powders (such as aluminum oxide and silicon dioxide) or traditional polymer materials. On one hand, some of these materials are non - degradable, which is contrary to the "dual carbon" goals of the new energy industry. On the other hand, the temperature resistance limit of separators after coating still hardly exceeds 150°C, making them unable to adapt to the local high - temperature peaks during battery operation. This further increases the risk of thermal runaway and fails to meet the safety requirements of modern new energy vehicles for "stable operation under extreme working conditions".
The research team has introduced modified nanocellulose into the field of lithium - ion battery separators, mainly due to its natural green properties and excellent performance advantages. Derived from renewable biomass such as cotton, wood pulp, and straw, modified nanocellulose has a full - life - cycle carbon emission that is only 1/3 of that of traditional petroleum - based materials, perfectly aligning with the concept of green manufacturing. Moreover, after surface modification, the structural stability of its molecular chains is greatly enhanced, with a decomposition temperature exceeding 250°C. It can form a "rigid support network" for separators, breaking through the traditional shortcomings in both structure and performance.
Through the coating process, modified nanocellulose is evenly attached to the surface of substrates like PP and penetrates into the micropores, forming a three - dimensional interwoven support framework. This structure can effectively resist the thermal shrinkage tendency of the substrate's molecular chains at high temperatures. Data shows that the shrinkage rate of uncoated PP separators can reach more than 30% at 180°C, while after being coated with modified nanocellulose, the shrinkage rate can be controlled within 5%. Even when exposed to a high temperature of 200°C for 60 minutes, there is no obvious shrinkage, completely avoiding the short circuit between the positive and negative electrodes caused by separator deformation.
The modification process significantly improves the interface bonding force between nanocellulose and polyolefin substrates, solving the problem of "easy peeling at high temperatures" of traditional coating materials. At the same time, the hydrophilic property of nanocellulose can reduce the contact angle between the separator and the electrolyte, shortening the electrolyte wetting time. This not only improves the ion conduction efficiency and reduces energy loss during charging and discharging but also avoids local overheating caused by uneven electrolyte distribution. It achieves a dual improvement in "thermal stability + energy efficiency", helping to break through the battery's energy density and extend its cycle life.
The industrial value of modified nanocellulose technology has been verified through the practice of Qihong Technology. The cellulose nanocrystal (CNC) coating material developed by the company, as a representative achievement of modified nanocellulose technology, has successfully entered the supply chain of leading lithium - ion battery enterprises, promoting the transformation of lithium - ion battery separators from the "traditional inorganic coating type" to the "green high - performance type".
Qihong Technology's CNC coating material has achieved a leapfrog breakthrough in thermal safety performance. The heat - resistant temperature of lithium - ion battery separators after coating steadily exceeds 180°C, and the membrane - breaking temperature is as high as 200°C. Compared with the temperature resistance limit of 130°C of traditional separators, the thermal stability performance has been improved by more than 40%. In practical applications, even if there is local overheating in the battery, the modified separator can still maintain structural stability, greatly reducing the risk of thermal runaway. In addition, it has outstanding green advantages: the separator can be naturally degraded within 3 - 6 months after being discarded, reducing pollution in the battery recycling process. Currently, the annual coating volume exceeds 100 million square meters, and the large - scale application has further verified the reliability and economy of the technology.
Driven by both the "dual carbon" goals and safety demands of new energy vehicles, modified nanocellulose technology will make breakthroughs in more diverse directions to further strengthen the battery safety protection system:
Multi - function Integration: By introducing flame - retardant groups and conductive particles through composite modification, the "heat resistance, flame retardancy, and conductivity" integration of lithium - ion battery separators will be realized, actively inhibiting combustion and reducing the risk of thermal runaway.
Cost Optimization: The coating process will be optimized, the production process will be simplified, and agricultural wastes such as corn stover will be used as raw materials to reduce costs and promote the popularization of the technology in mid - to low - end vehicle models.
Scenario Expansion: The technology will be extended from the separators of automotive power batteries to the fields of energy storage batteries and consumer electronics batteries, building a multi - scenario safety protection network and improving the battery safety level of the entire industry.
Modified nanocellulose technology provides an innovative path for upgrading the performance of lithium - ion battery separators. It not only breaks through the thermal stability bottleneck of traditional polyolefin separators but also conforms to the "dual carbon" demands of the industry with its green biomass properties, achieving a triple balance of "safety, performance, and environmental protection". With the iteration of technology and the deepening of industrialization, lithium - ion battery separators upgraded with modified nanocellulose are expected to become the mainstream choice in the industry. They will build a stronger barrier for the safety of new energy vehicle batteries and promote the industry towards higher safety standards and better green performance.
![Wechat Wechat Scan](javascript:Site.hoverQrCode("//9752854.s21i.faiusr.com/2/ABUIABACGAAgwrzFxQYogJ3v3wEwwAc4ygc.jpg",this,{"tips":"Scan QRcode"});){kind=link}