Image source: website of International Electric and Hybrid Vehicle Technology magazine

With the increasing attention to environmental protection and climate change, more and more people are choosing electric vehicles as their means of transportation. However, range anxiety remains a "heart disease" for car owners. However, breakthroughs in quantum technology have brought more possibilities for solving the range problem of electric vehicles.

The diamond quantum sensor developed by scientists at Tokyo University of Technology in Japan can increase the range of electric vehicles by about 10%, according to the Nihon Keizai Shimbun recently. This technology can accurately measure the stored power, thereby maximizing the performance of car batteries. Their goal is to put this technology into practical application as early as 2030.

There is an error in the measurement of electric vehicle batteries

Normally, the current of an electric vehicle battery can reach several hundred amperes, but due to the difficulty in accurately measuring the charging capacity, the set capacity of the battery is about 10% less than the actual amount of stored power.

Professor Liu Xiaobing from the School of Physical Engineering at Qufu Normal University stated in an interview with Science and Technology Daily that there are multiple reasons why the battery level of electric vehicles is difficult to measure.

For example, small changes in battery voltage and current can significantly affect the detection of power, especially for lithium iron phosphate LiFePO4 batteries, whose discharge curve is gentle and the accuracy of cell voltage measurement is difficult to accurately control. Any small error in the sensor may lead to significant power measurement errors.

Secondly, battery packs typically consist of dozens of battery cells, with overall performance determined by the weakest cell. Accurately evaluating battery capacity requires real-time monitoring of each battery cell, which poses significant challenges for space layout and cost control.

In addition, during the operation of electric vehicles, the battery is in a continuously changing state of charge and discharge, which requires sensors to accurately monitor these changes in real time. However, rapid charge discharge cycles and dynamic load changes may exceed the sensor's ability to respond quickly.

Therefore, if there is a sensor that can measure the charging amount with high accuracy, it will be able to fully utilize the performance of car batteries, "said Liu Xiaobing.

Diamonds are highly favored in the field of quantum sensing

For a long time, diamonds have been favored in the field of quantum sensing due to their coherent nitrogen vacancy (NV) centers, adjustable spin, magnetic field sensitivity, and ability to operate at room temperature. Liu Xiaobing introduced that diamonds themselves have extremely high chemical stability and physical durability, making them the hardest and most thermally conductive material in the world. This also makes diamond quantum sensors very suitable for long-term applications in harsh environments.

Tokyo Institute of Technology and automobile parts manufacturing company Yazaki Corporation have set their sights on diamond quantum sensors. They designed special structures in the partial crystallization of diamonds to give them the property of emitting red fluorescence under green laser irradiation. According to the quantum state of internal electrons, the intensity of fluorescence will change. Due to the influence of surrounding current, magnetic force, and temperature, the quantum state of electrons can also change, so the magnetic force can be calculated based on the fluorescence intensity.

According to reports, the sensor can be installed on a metal component called a "busbar". Busbar "is the channel through which batteries transmit electricity. Traditional sensors measure current in units of 1 ampere, while newly developed sensors measure current in units of 10 milliamps, increasing accuracy by 100 times. Therefore, the charging capacity can be made close to the actual storage capacity of the battery without leaving 10% space, thereby extending the battery's range.

Liu Xiaobing further explained the scientific principles of diamond quantum sensors. He stated that the NV center is a composite defect formed by replacing a carbon atom with a nitrogen atom in the diamond lattice, accompanied by a vacancy at an adjacent position, with controllable and readable electron spin states. By optical excitation, its spin state can be read out, thereby obtaining external environmental information. The NV center is extremely sensitive to the external environment and has nanometer level spatial resolution. It has significant advantages in detecting weak electric and magnetic field changes in the environment, which makes diamond quantum sensors have great potential in measuring charge levels.

Countries compete for the quantum diamond highland

Compared to superconducting quantum interferometers that have already been put into use, diamond quantum sensors have higher detection sensitivity and spatial resolution, as well as multiple advantages such as simple operation, strong environmental adaptability, and wider application range.

At present, diamond quantum sensors have also become one of the forefront fields of international quantum competition. Western countries such as the United States, the United Kingdom, and the European Union have identified NV center quantum control and quantum sensor applications as key areas of support.

Yazaki Corporation's goal is to achieve the practical use of diamond quantum sensors as early as 2030 and supply them to automobile manufacturers and component manufacturers. Although the peripheral equipment is relatively large now, by using small semiconductor lasers, the size of quantum sensors can be reduced to 10 cubic centimeters, and the cost is also comparable to previous current sensors.

However, Professor Muko Hatano from Tokyo Institute of Technology stated that the biggest cost factor is diamonds. The diamonds used to manufacture quantum sensors are artificially synthesized, which is different from natural diamonds extracted from mines and used in jewelry. The use of inexpensive circuit boards and the mass production method of extracting diamonds from biogas can significantly reduce manufacturing costs.

Liu Xiaobing stated that as a major producer and consumer of electric vehicles, China still heavily relies on foreign imports for quantum grade diamonds, which has become an important issue facing the development of new energy vehicles. At present, his team has collaborated with other universities and research institutions to successfully prepare artificial quantum diamonds.

Shandong Chaojing New Materials Company in China has achieved large-scale production of centimeter level quantum diamonds.
Liu Xiaobing believes that although diamond quantum sensors currently face cost challenges, considering their unique performance and potential applications, as well as the cost reduction brought about by later technological advances, the future market prospects are very promising.

Source: Science and Technology Daily
Date: November 27th