Application of aerogel in the battery industry
At present, the most widely used battery industry is lithium-ion batteries. From the mobile phone, computer, ipad in the home appliance market, to new energy vehicles in the power field, cruise ships, to thermal batteries used in weapons and equipment, lithium-ion batteries are not available. Not at all. However, lithium-ion batteries have their inevitable safety problems due to their structural characteristics and the nature of the materials used. For example, the strength and thermal stability of the separator between the positive and negative electrodes of a lithium ion battery are not ideal, which may easily lead to internal short circuit of the battery; at higher temperatures, a strong exothermic reaction inside the battery may cause an increase in the temperature and internal pressure of the lithium ion battery. The electrolyte and anode materials of lithium ion batteries are all flammable materials.
Especially in the power lithium-ion battery scene, due to the special high voltage and high working current required in the power field, thousands of single cells are often used in groups. At this time, the safety of the battery is more prominent. . For example, Tesla's car battery pack uses thousands of lithium-ion battery cells. A large number of batteries are compactly arranged in a confined space. If some of the monomers enter the thermal runaway state due to mechanical damage, thermal shock, internal short circuit, overcharge, etc., the temperature of the surrounding cells will also rise, and then the heat will be out of control. Spread to the entire battery pack, ultimately causing disastrous consequences of overall combustion and explosion. As far as the current battery material technology level is concerned, this safety issue has not been completely solved. Therefore, the current insulation, flame retardant and fire protection of lithium ion batteries is an effective means to reduce the risk of thermal runaway of lithium ion batteries.
Aerogel is the lowest solid material with the lowest thermal conductivity. The thermal insulation properties of aerogel insulation blankets, heat insulation boards, thermal insulation papers, etc. can be up to 5 to 10 times that of ordinary products, combined with excellent fire retardant. Soft, impact resistant, noise-reducing and other functions, in addition to good promotion in the field of industrial energy conservation, civil insulation, etc. With the development of aerogel industry, the application of aerogel in the battery field is more and more extensive.
01 single cell aerogel insulation protection
The thermal runaway of the single cell is the source of the thermal runaway of the entire battery pack. This is because when a single cell triggers thermal runaway, the heat is suddenly increased, and the heat dissipation is much less than the heat generated, causing heat to pass to the surrounding cells. Then, it will quickly trigger large-scale thermal runaway of peripheral batteries, creating a safety hazard. Therefore, thermal protection between the cells is an effective means to eliminate the safety hazard of the entire battery pack. The thermal protection between the cells is to add an insulation layer between the cells to block the thermal runaway from the uncontrolled monomer cells to the surrounding cells, reducing the damage of the battery pack and the accompanying damage.
The thermal insulation material between the individual cells, as a kind of thermal protection material that can effectively delay or block the thermal runaway of the single cell to the whole battery system, must have the following conditions:
a. Flame retardant (up to V0 level)
b. aging resistance, chemical stability;
c. does not produce toxic gases;
d. good elasticity, low thermal conductivity, waterproof, moisture-proof and vibration-proof;
e. Light weight, low thickness and thin
Aerogels have extremely low thermal conductivity, and researchers have verified the thermal insulation protection of aerogel insulation panels between individual cells. The aerogel separator was verified by wrapping four 200mm insulation materials with a 6Ah capacity 20mm separation distance module and adding a 1cm thickness aerogel insulation board between the two monomers (Fig. 1) for thermal runaway propagation experiments. Blocking of thermal runaway in single cell thermal protection.
The experimental results show that after the thermal runaway of monomer A, the monomer B in the blank without heat protection is quickly heated, and the thermal runaway occurs. The maximum temperature of the experimental monomer B with aerogel insulation plate between the monomers is only 110. °C, successfully blocked the thermal runaway propagation of 6Ah monomer at 20mm spacing, and the voltage of the uncontrolled monomer is basically unchanged, which plays a good role in protecting the safety hazard of battery pack thermal runaway caused by single cell explosion.
In addition, aerogels can further reduce the safety distance between monomers due to their excellent thermal insulation properties. In order to save more space and increase the total power of the battery pack, the aerogel company has developed a series of high-performance ultra-thin aerogel insulation boards, insulation paper and other products to meet the needs of the battery industry safety and high energy density.
Figure 1: Experimental installation diagram of 1cm aerogel insulation board between cells
Figure 2: Thermal runaway propagation blocking test for insulation panels between cells B Single cell temperature and blank group B Single cell temperature curve comparison
02 battery pack / box overall protection
Lithium-ion power battery packs have a thermal runaway accident. The protection against thermal runaway of lithium-ion battery systems requires thermal protection between the battery cells, between the battery modules, and between the battery box and the passenger compartment. Increasing the thermal resistance of the heat-uncontrolled cells to the other systems of the battery, thereby achieving the purpose of hindering the spread of thermal runaway. In addition to excellent heat insulation, fire resistance and flame retardant properties, aerogel felts are also soft, arbitrarily tailorable and processable. It can be used for thermal protection between battery modules of different shapes, battery boxes and passenger compartments.
03 Aerogel protection for thermal batteries
Thermal batteries are widely used in the field of weapons due to their high discharge current density, long storage life, and low environmental temperature. The EAP-12188 battery from the JAS-39 light fighter emergency rescue power supply, the GPS-9 battery on the global positioning remote gun, the AN/SSQ-62 C battery on the sonar buoy, can be seen on all kinds of missiles and shells. To the shadow of the hot battery. The typical operating temperature of a thermal battery is between 450"C and 600"C. The entire discharge process relies on the initial thermal "input", which depends on the battery cooling rate and the freezing temperature of the battery.
For long-life thermal batteries, the key issue is to have good insulation. The aerogel insulation blanket has an ultra-low thermal conductivity, and the maximum operating temperature can reach 900-1100 °C. The thermal battery insulation tube made of aerogel material can be used as the thermal insulation layer of the thermal battery to perfectly solve the aerospace and weapon fields. High performance and long life requirements of thermal batteries.
With the development of China's aerogel industry, the application form of aerogel in the battery field will be more diversified, and the application range will also spread from the earliest military thermal battery to more civilian battery fields, such as new energy power batteries, Thermal insulation and flame retardant protection for lithium-ion batteries and batteries for electronic equipment.