The use of a new polymer based on boron nitride can expand the scope of capacitors as batteries

While oil and gas companies spend a huge amount of effort and resources on the exploration and development of new deposits of fossil fuels, scientists are working on the other side of the "energy issue" : the storage and delivery of electricity in extreme conditions. Today, the market of power supplies is dominated by rechargeable batteries, but they have an alternative - capacitors, which have several advantages over batteries: lightweight, fast charge-discharge cycle, do not lose capacity over time.

To ensure proper functioning, when creating a capacitor, it is necessary to use dielectric materials, which behave, in fact, as insulators, and provide charge storage. Polymer dielectrics have greater efficiency compared to classical materials and can work in conditions of more intense electric fields without breakdowns, which ensures greater reliability of the product.

Now the main disadvantage of modern capacitors is their inability to operate at high temperatures, which does not meet the requirements of the scope of their possible application (extreme conditions). However, the developed composite polymer is devoid of these disadvantages and has a wider spectrum of use than previously used materials. The material was obtained by scientists by combining particles of a traditional polymer with hexagonal boron nitride nanosheets.

The new material (called BCB / BNNS) can be successfully used as a dielectric, capable of more effectively preventing current leakage and having a stable dielectric constant. The material consists of benzene-cyclobutane combined with boron nitride nanosheets. In its structure, boron nitride used by scientists is similar to graphene sheets with a thickness of one atom. The resulting material has superior properties compared to previously available.

However, researchers are not pioneers. The properties of hexagonal boron nitride as a dielectric were previously known. For example, in 2010, according to a joint study of scientists from universities in Houston, Tokyo and Krasnoyarsk, a work was published in which boron nitride was considered in combination with graphene as an alternative to silicon in microelectronics.

To test the dielectric properties, a team of scientists compared the polymer they obtained with other, the best dielectrics on the market today. The first test for BCB / BNNS was the dielectric constant test at an AC frequency of 10 ⁴ Hz and temperatures up to 300 ° C.


The dependence of the dielectric constant (for vacuum = 1) of materials at different temperatures.

As the graph shows, unlike other materials, the dielectric properties of BCB / BNNS remain virtually unchanged (changing ε _r- the relative dielectric constant at a temperature of 300 ° C is only 1.7% versus 8% for the best dielectric currently in use). The tests were carried out using direct current, during which scientists obtained the same results.

When using a dielectric as an insulating material, it is important to eliminate energy loss. For BCB / BNNS, the scattering coefficient does not change with increasing ambient temperature. But the new polymer is not ideal: the loss from dispersion increases from 0.09% to 0.13% with increasing temperature from 25 to 300 ° C. Only one material has similar characteristics, when all the others lose much more charge with increasing temperature.


Schedule of variation of the scattering coefficient with increasing temperature.

Researchers also tested new material in a capacitor charge-discharge cycle and measured the current density during discharge.


The current density during discharge at a temperature of 200 ° C.


The efficiency of the charge-discharge cycle at a temperature of 200 ° C.

The results can be considered excellent, since it is extremely important for polymer dielectrics to hold a charge at high temperatures. With increasing current leakage with increasing temperature, the efficiency of the charge-discharge cycle decreases and heat is released inside the capacitor itself, which reduces its parameters and service life.

Most capacitor failures occur due to its overheating and failure of the entire structure (explosion and many familiar "bloating" of the capacitor). In some cases, an increase in the temperature of the structure leads to the so-called thermal breakdown. Despite the presence of effective dielectrics, many of them have poor thermal conductivity, which leads to the accumulation of heat inside the capacitor, which, in turn, increases the risk of thermal breakdown. The new material has a thermal conductivity in the range from 300 to 2000 W / (m · K).


Thermal drawing of various materials during operation compared to BCB / BNNS

The BCB / BNNS polymer has a thermal conductivity of 300 to 2000 W / (m · K). Such a wide range of values ​​of the coefficient of thermal conductivity tells us that this polymer can be used, inter alia, as a radiator material as passive cooling of elements in electronics.

Potentially BCB / BNNS can be used in flexible electronics of the future, since it does not lose or change its properties under mechanical stress (bending, twisting, etc.), including mechanical stress at high temperatures (up to 250 ° C)

Earlier, another group of scientists from Rice University examined boron nitride.and as an anti-corrosion material, which was proposed to be sprayed by chemical vapor deposition by a layer with a thickness of several atoms, which protected materials from oxidation at temperatures up to 1100 ° C.

via ArsTechnica