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At the 14th Energy Storage International Summit and Exhibition held in early April, a new material brought by Professor Shen Xiaodong's team from Nanjing University of Technology became the focus of the audience - this is the world's first hot topic aerogel insulation sheet for new energy lithium-ion batteries that can withstand high temperatures of 1300 ° C. This 2.3 mm thick and light film not only refreshes the temperature resistance limit of global lithium battery insulation materials, but also breaks the long-term problem of battery thermal runaway safety faced by the new energy industry. It has built a nano-level safety line for the rapidly developing lithium battery industry.
Lithium-ion batteries are the core "heart" of new energy vehicles and energy storage systems, and thermal runaway has always been the "sword of Damocles" hanging over the industry. Once the battery has an internal short circuit, overcharge and other abnormalities, the temperature of a single cell can rise sharply to more than 1,000 degrees Celsius in five or six seconds, and the heat quickly spreads to adjacent cells, which can easily cause chain explosions and fire accidents. Whether it can quickly block heat transfer at extreme temperatures directly determines the safety bottom line of the battery system, and has also become the core technology highland of the global competition in the field of new materials.
From the microscopic perspective of scanning electron microscopy, this ground-breaking aerogel thermal insulation sheet presents a three-dimensional network structure woven by countless nanoparticles, and more than 90% of the space is filled with air. It is this unique nano-porous structure that gives the material ultra-low thermal conductivity far beyond traditional thermal insulation materials. After thousands of debugging and verification, the team's 2.3-mm ultra-thin thermal insulation sheet has achieved amazing thermal barrier ability: after one side continues to withstand 1000 ° C high temperature for 5 minutes, the temperature on the back of the material never exceeds 100 ° C, truly realizing the protective effect of "one side of fire and one side of room temperature".
Behind the eye-catching performance is the team's systematic attack on the core technology of aerogel preparation. For a long time, high-efficiency supercritical drying technology has been an extremely difficult "stuck neck" link in the process of aerogel industrialization. During the drying process of wet gel, the liquid tension in the pores can easily lead to the collapse of the nano network structure. At the same time, the high energy consumption and high cost preparation process also makes it difficult for high-end aerogel materials to be widely popularized. In order to solve this problem, the team step by step broke through the wet gel drying, drying kettle pressure precision control, production cost control and other multiple checkpoints, developed a new preparation process, realized solvent ethanol collection rate of over 99.5%, directly reduced the cost of raw materials by more than half, cleared the core obstacle for the large-scale commercial use of materials.
Traditional silica aerogels are a typical brittle material, while new energy batteries will continuously and repeatedly squeeze the thermal insulation material between the cells during the charge and discharge cycle, which can easily lead to the fragmentation of traditional aerogels and the significant decline of thermal insulation performance. This is also the core pain point that aerogels have been difficult to popularize on a large scale in the field of power batteries before. In response to this industry problem, the team took inspiration from the high elastic properties of silicone rubber materials and innovatively proposed the technical idea of selectively "knocking out" the connection nodes of the nanopore mesh, in order to release the deformation space of the nano network and improve the overall elasticity of the material.
By repeatedly adjusting the amount and type of catalyst and precisely adjusting the pH of the reaction solution, the team established a mild and controllable reaction environment for the hydrolysis-polymerization reaction during the growth of aerogel nanopores, and finally formed a long chain-like, relatively loose and free microscopic morphology of the aerogel skeleton. The modified aerogel material, under extreme conditions with an elastic compression rate of more than 90%, still maintains intact internal nanostructures and core properties, completely solving the industry's stubborn problems of traditional aerogels with high brittleness and poor compression resistance, and perfectly adapts to the complex working conditions of the whole life cycle of power batteries.
After more than 20 years of technological development and iteration, Shen Xiaodong's team has not only achieved a leap-forward improvement in the temperature resistance of aerogel materials from the original 650 ° C to the current 1300 ° C, but also extended the thermal insulation time of the material to 2 hours. They have also built a complete high-temperature resistant aerogel material system, successfully developed silicon carbide, silicon nitride, aluminum nitride, boron nitride and other high-performance aerogel insulation materials suitable for different extreme scenarios, breaking the foreign technology monopoly in the high-end aerogel field.
At present, this series of high-temperature resistant aerogel insulation materials with completely independent intellectual property rights has long since left the laboratory and achieved large-scale industrial landing. In addition to being widely used in high-end fields such as industrial high-temperature kilns and aerospace, it has also been used in batches to support the power battery products of leading domestic enterprises such as Ningde Times, BYD, Sungrow, and Xiaomi Automobile, becoming the core components of the safety protection of new energy vehicles and energy storage systems.
With the outline of the national "Tenth Five-Year Plan" clearly proposing to accelerate the development of strategic emerging industries such as new energy and new materials, Shen Xiaodong's team also has a clear plan for the future development of technology. "We will continue to strengthen the process of basic research and industrialization, and promote aerogel insulation materials from'high-end selection 'of new energy batteries to'mainstream must match'." Shen Xiaodong said that the team will continue to explore the application scenarios of materials in more cutting-edge fields such as fire emergency, commercial aerospace, and space computing power, and make every effort to promote the establishment of China's independent and controllable aerogel nanomaterials industry system, so that China's new material technology can continue to occupy a leading position in the global competition.
