Blockbuster! Lithium cobalt oxide battery, this time really go up!
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2020/12/11 09:23:46
Power supply is an important support for the continuous operation of spacecraft in the vast space.During the Chang 'e-5 mission, Institute 811 of the 8th Institute of China Aerospace Science and Technology Corporation undertook the research and development of the power products of the orbiter, lander and lifter on four platforms: lander, lifter, orbiter and returner.Power system by the power source controller, lithium ion battery and solar cell array, in order to ensure the best performance guarantee of the mission, China aerospace science and technology corporation, which is eight yuan 811 developed by researchers gather enough horsepower, "power controller than the highest power of domestic and international leading, lithium ion battery application space than the highest energy, the solar cell array area than the highest power of domestic", are they to hand over a satisfactory answer.
Adapt to multiple states in multiple flight stages
Chang e five tasks include vehicle emission, transfer to the moon, the brake in recent months, ring on operation and the decrease of the surface, working surface, surface rise, rendezvous and docking, ring months waiting, transfer and then into the recovery phase 11, lander, rise, the orbiter, return have a variety of combination and separation in the flight status, how the power supply with the best state to adapt to the much more flight phase of the multiple state and development personnel to carry out the change.
The power controller, the "brain" of the probe's power system, underwent an upgrade from THE PCU to the PCDU in order to solve the problem of energy shortage and limited weight resources during the chang 'e-5 flight.
"Going from PCU to PCDU is about upgrading from a single function to a multi-function.In chang 3 and chang 4 tasks, power controller only include power control module, the goddess of the moon 5 focuses on the regulation of power modules, power distribution module, control module, intelligent interface unit several functions such as sensitivity, this is the first lunar exploration project application, "chang e v power source product designer, director of the Zheng Lei said.
And in the single machine, also experienced a complete transformation, the development personnel in reference to foreign relevant technical data, weighing the pros and cons, bold challenge, domestic initiative of a number of highly integrated technology, so that the specific power of the power controller to reach the highest level, the international leading level, to achieve the performance of the leap to improve.
Chang e v power supply products technical director Xu Zefeng said, "for the original circuit board integration density is not high question, after many experiments, we abandoned the domestic satellite model direct plug-in technology, widely used for the first time the large table type process, the first time in application of this technology in the subsequent other models has led to a new situation;At the same time, innovative use of signal motherboard, printed board current-carrying technology and bus bar optimization measures between modules, to achieve a high degree of module cable integration, significantly reduce the volume and weight.By comparing with the products of Chang 'e-3, it can be seen that the original direct-insert technology has been replaced by double-sided patch, which greatly improves the circuit board integration density.The circuit boards, which used to be densely packed with wires, now have a few clear lines, and the product density has increased.The number of modules has been reduced from five to two, a third of the size of the Chang 'e-3 controller.These technologies, in the subsequent realization of more than 20 patents licensed.
According to the working mode of Chang 'e-5, after reaching the lunar orbit, the combination of the lander and ascender separates from the combination of the orbiter and the reentry vehicle, and the lander and ascender fall to the lunar surface to collect samples.
After fully considering the time of the lunar mission and the working mode of the power supply products, according to the overall plan, the researchers have optimized the energy design of the combination of lander and riser."The lander's power products include solar arrays and power controllers, and the riser's power products include solar arrays, power controllers and lithium-ion batteries.Before separation, the solar battery circuit of the lander was responsible for supplying power to the assembly during the flight phase and the illumination phase of the lunar surface phase.When the assembly is separated at the lunar surface stage, the riser quickly switches roles and is powered by a solar cell circuit during the illumination period.And in the off-light period, the lander and the riser share a set of lithium-ion batteries, which power the assembly."
Power four combination of "around, down, back" the ultimate goal
In lunar missions, the probes require much more energy than traditional satellites.Chang 'e-5 is designed to be a four-vessel mission, and it needs to accomplish three goals of "orbiting, landing and returning" at one time. It requires more energy than any other lunar or deep-space exploration mission in China.Therefore, it is an important problem for researchers to improve the energy supply capacity of solar arrays and lithium ion batteries.
"In order to improve the solar array's power generation, we have set ourselves a goal to maximize the patch area on the front of the solar array," said Chen Cheng, chang 'e-5 solar cell circuit technology chief.
However, during the lunar exploration mission, the solar cell panel area is severely limited. At the same time, different from ordinary satellites, the configuration of the probe itself determines the irregular shape of the panel. The Chang 'e-5 solar cell panel has various shapes such as triangles and polygons.Baseplate area is small, and strange shape, how to do?
"For normal satellite models, we only design solar cell circuits with a single size solar cell.For Chang 'e-5, we broke the conventional thinking and used batteries of various sizes to mix cloth pieces, so that the efficiency of cloth pieces reached more than 91%, which was 5%-10% higher than conventional products.At the same time, the solar cell with the highest efficiency should be selected. The photoelectric conversion efficiency of the Chang 'e-3 and Chang 'e-4 solar cells is 28.6 percent and 30.84 percent respectively, and the Chang 'e-5 solar cell is more than 31 percent.After unremitting efforts, chang 'e-5 solar panel output power per unit area not only in the product development, even now, are the highest level in China.
Specific energy is a major performance index of lithium-ion batteries. The higher the value, the more energy can be stored per unit volume or weight.At the beginning of the research, the highest specific energy of domestic lithium-ion battery cell is 155Wh/kg, and the highest energy is 165Wh/kg in the world.Aiming at the characteristics of Chang 'e-5 lithium ion battery products, such as short service life and high discharge depth, the researchers made a solution after carefully analyzing the feasibility of the technical indicators, referring to a large number of literatures and investigating the technical data of lithium battery enterprises."We chose lithium cobalt oxide positive and graphite negative materials with higher energy than others, selected high molecular weight binder materials to reduce the amount of binder, and optimized the electrode formula to increase the content of active substances," said Wang Xiaorui, chief designer of Chang 'e-5 lithium-ion battery.Behind the light introduction are a large number of process tests, new electrode materials, new material ratio, and completely different physical and chemical parameters in the past, leading to great changes in the process of powder mixing and pulping, etc., but the researchers have verified each process step by step.After 8 months of effort, they increased the weight to energy ratio of the battery to 195Wh/kg.This value, for the current space lithium ion battery specific energy maximum value.
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