This year’s two sessions, as the backbone of the national economy, the automotive industry has become a hot topic at the meeting. With the transformation of China’s social and economic development to high quality and the intensification of world market competition, it is imperative to reform traditional automobiles with new energy as the entry point. During the two sessions, representatives of the automotive industry expressed their views on the whole vehicle manufacturing, battery system and after-sales operation and maintenance in the new energy automotive industry chain. Yin Tongyue, Secretary of the Party Committee and chairman of the board of directors of Chery Automobile Co., Ltd. also put forward their own views.
He suggested accelerating the process of commercial vehicle electrification, breaking through the points of passenger vehicles and commercial vehicles, and promoting the coordinated development of the entire automotive industry. And hope to adjust the peak and valley electricity policy, reduce the electricity price at night, guide new energy vehicles to reserve electricity at night, reduce carbon emissions. This coincides with the expectations of the new energy vehicle in the government’s work report.
In view of this transformation goal, Chery began to layout as early as 1999. In technology research and development, through independent innovation, open cooperation and other ways, it has established a vehicle integration, key parts development capability system, and formed a strong accumulation of technology in the field of new energy. Up to now, Chery has declared more than 770 patents in the field of new energy, ranking the forefront of domestic automobile enterprises.
In response to the call of national carbon emission reduction and sustainable development, Chery combines the characteristics of fuel stack with the actual situation of fuel cell system development in China. An electric-electric hybrid drive system for fuel cell vehicles using fuel cell engines and power storage batteries is proposed. The Son of Orient (2010) is successfully developed. Ruichi G5 (2013) and Arizer 3 (2016) three generation fuel cell vehicles, participating in the 2008 Olympic Games, the 2010 World Expo demonstration operation, become China’s first batch of new energy vehicle license enterprises.
In 2016, Chery New Energy Vehicle Technology Co., Ltd. and Wuhu Construction Investment Co., Ltd., Japan’s Anchuan Electric Co., Ltd. jointly established Chery Anchuan Electric Drive System Co., Ltd., in the new energy drive motor and controller research and development and production painstaking. In 2017, Chery’s first self-developed 95 kW motor and controller went off the production line in Wuhu, Anhui Province, creating a more competitive market for the Chery series of new energy vehicles, making Chery in this field to reach the world’s advanced level.
Standing in the automotive industry reform outlet: new energy becomes the next WEATHERVANE
December 28, 2017 Chery electric drive system off
In addition to the establishment of a sound R&D system, Chery also undertook a number of “provincial and municipal” and “national” new energy technology research and development of key special tasks, to help the overall industry to electric transformation. Chery undertakes more than 20 key scientific and technological projects at provincial and municipal levels, and more than 30 major special projects for energy saving and new energy vehicles under the National 863 Program. Since the Ministry of Science and Technology launched the National Key R&D Program for New Energy Vehicles in 2016, Chery has led and participated in six projects. Among them, in 2017 led the implementation of 2, ranking first in the industry.
Standing in the automotive industry reform outlet: new energy becomes the next WEATHERVANE
Chery undertakes the launching ceremony of the national key new energy vehicle project
The automotive industry is undergoing an endogenous power transformation and the electrification of commercial vehicles is on the fast track. Chery timely adjusts its driving direction, formulates a “full-range + 457” new energy technology plan, covering the full-scale and full-range passenger vehicles of pure electric and plug-in hybrid technology platform, which not only accelerates the development of the company’s new energy vehicles, but also promotes China. The development of the new energy automobile industry has stepped up to a higher level, while assuming social responsibility and contributing to energy conservation and emission reduction. It is estimated that by 2020, Chery will realize the electrification of all models.
Lithium ion battery characteristics
Lithium is the smallest and most active metal on the chemical periodic table. Small volume, high volume density, widely welcomed by consumers and engineers. However, the chemical characteristics are too active, which brings great danger. When exposed to air, lithium metal will explode with intense oxidation of oxygen. To improve safety and voltage, scientists have invented materials such as graphite and lithium cobalt to store lithium atoms. The molecular structure of these materials forms tiny nanoscale storage lattices that can be used to store lithium atoms. In this way, even if the battery shell ruptures, oxygen enters, because the oxygen molecule is too big to enter these small storage cells, so that lithium atoms will not contact with oxygen and avoid explosion. This principle of lithium-ion batteries enables people to obtain high capacity density, but also to achieve safety purposes.
Electrical explosion protection test
When lithium ion batteries are charged, the lithium atoms of positive electrodes will lose electrons and become lithium ions. Lithium ions swim through the electrolyte to the anode, enter the anode cell, and obtain an electron, which is reduced to lithium atoms. When discharging, the whole procedure is reversed. In order to prevent the battery’s positive and negative electrodes from directly touching and short-circuiting, the battery will be coupled with a diaphragm paper with many holes to prevent short-circuiting. Good diaphragm paper can also be in the battery temperature is too high, automatically close the pores, so that lithium ions can not penetrate, to self-waste martial arts, to prevent danger.
The lithium battery core will start to produce side effects when the charge exceeds 4.2V. The higher the overcharging voltage, the higher the risk. When the lithium cell voltage is higher than 4.2V, the number of lithium atoms left in the cathode material is less than half, and the cell often collapses, causing a permanent decline in battery capacity. If the charge continues, subsequent lithium metal will accumulate on the surface of the anode material because the cell of the anode is already filled with lithium atoms. These lithium atoms will grow dendrites from the surface of the negative electrode to lithium ions. These lithium metal crystals will pass through the separator paper to make the positive and negative poles short circuited. Sometimes the battery explodes before the short circuit occurs, because during the overcharge process, materials such as electrolyte will crack to produce gas, causing the battery shell or pressure valve to swell and rupture, allowing oxygen to react with lithium atoms deposited on the negative surface, and then explode. Therefore, when charging lithium batteries, it is necessary to set the voltage limit, so as to take into account the battery life, capacity, and safety. The ideal charge voltage limit is 4.2V. The discharge voltage of the lithium core should also have a lower voltage limit. When the core voltage is lower than 2.4V, some materials will start to be destroyed. And because the battery will self-discharge, the longer the discharge voltage will be lower, therefore, it is better not to discharge 2.4 V before stopping. The lithium battery releases only about 3% of the battery capacity during the period from 3.0V to 2.4V. Therefore, 3.0V is an ideal discharge cut-off voltage.
In addition to voltage limitation, current limitation is also necessary. When the current is too large, the lithium ion will not enter the storage cell and will aggregate on the surface of the material. When these ions get electrons, they produce lithium atom crystals on the surface of the material, which, like overcharging, can be dangerous. If the battery shell breaks, it will explode.
Therefore, the protection of lithium-ion batteries should include at least three items: charge voltage upper limit, discharge voltage lower limit, and current upper limit. In general, in addition to lithium battery batteries, there will be a protective plate, this plate is mainly to provide these three protections. However, the protection of these three protection is obviously not enough, and the global lithium battery explosion is still frequent. To ensure the safety of the battery system, we must make a more careful analysis of the cause of the battery explosion.
Explosion type analysis
The type of battery core explosion can be classified into three types: external short circuit, internal short circuit and overcharge. The exterior here refers to the exterior of the battery, including the short circuit caused by poor insulation design inside the battery pack.
When a short circuit occurs outside the battery and the electronic components fail to cut off the circuit, high heat will occur inside the battery, resulting in partial vaporization of electrolyte, which will expand the battery shell. When the temperature inside the battery reaches 135 degrees Celsius, good quality diaphragm paper closes the pores, the electrochemical reaction terminates or nearly terminates, the current suddenly drops, and the temperature slowly drops, thus avoiding explosion. However, poor pore closure, or diaphragm paper with no pore closure, will keep the battery temperature rising, more electrolyte vaporization, and eventually burst the battery shell, or even raise the battery temperature to make the material burn and explode the internal short circuit mainly because the burr between copper and aluminum foil breaks through the diaphragm, or lithium. The dendrites of atoms break through the diaphragm. These tiny needled metals can cause short circuit. Because the needle is very thin and has a certain resistance value, the current will not be very large.
Copper and aluminum foil burrs are caused by the production process, and the observed phenomenon is that the battery leakage is too fast, most of which can be detected by the battery factory or assembly plant screen. Moreover, because the burr is fine, sometimes it will be burned, so that the battery will return to normal. Therefore, the probability of burglings caused by short circuit burr is not high. Such a view can be obtained from the battery factory often charged within a short time, the voltage on the low side of the bad battery, but few explosions, statistical support. Therefore, the explosion caused by internal short circuit is still mainly caused by explosion.
Lithium ion battery has high energy density and high average output voltage. Small self discharge, good battery, less than 2% per month (recoverable). No memory effect. The working temperature range is -20 ~ 60 C. It has excellent cycling performance, fast charge and discharge, high charging efficiency of 100%, and high output power. Long service life. No toxic or harmful substances are called green batteries.
Charging is an important step in battery reuse. The charging process of lithium ion batteries is divided into two stages: constant current fast charging stage and constant voltage current decreasing stage. In the constant current fast charging stage, the voltage of the battery gradually rises to the standard voltage of the battery, and then goes to the constant voltage stage under the control chip. The voltage no longer rises to ensure no overcharge. The current gradually decreases to the set value with the increase of the battery capacity, and finally the battery is charged. The power statistics chip can calculate the battery power by recording the discharge curve. The discharge curves of lithium-ion batteries will change after repeated use. Although there is no memory effect in lithium-ion batteries, improper charge and discharge will seriously affect the battery performance.
The first charge and discharge, if the time is long enough (usually 3-4 hours), can make the electrode as much as possible to reach the highest oxidation state (sufficient electricity), discharge (or use) is forced to put the specified voltage, or until the automatic shutdown, so as to activate the battery capacity.
But in the ordinary use of lithium-ion batteries, do not need this operation, can be charged at any time according to needs, charging is neither necessary to be charged until, nor need to discharge first. Like the first charge and discharge operation, it only takes 1–2 consecutive intervals every 3–4 months.
The more the 3.7V lithium battery is discharged, the greater the battery loss will be, the more fully charged the battery will be, and the greater the battery loss will be. 3.7V lithium battery is preferably in the middle state of electricity, so the battery life is the longest.
3.7V lithium battery
First of all, too high and too low power status has the most adverse impact on the life of 3.7V lithium battery, while the number of charge-discharge cycles is secondary. In fact, the number of rechargeable times marked on most sales of electrical appliances or batteries is based on a benchmark of 80 percent discharge. Experiments show that for some notebook 3.7V lithium batteries, the battery voltage often exceeds the standard voltage of 0.1 volt, that is, from 4.1 volt to 4.2 volt, the battery life will be halved, and then increased by 0.1 volt, the battery life will be reduced to one-third of the original; long-term low or no power status will make the battery internal electricity. The resistance of sub mobility is getting larger and larger, resulting in smaller battery capacity. NASA has set its Hubble Space Telescope battery consumption at 10 percent of its total capacity to ensure it can be recharged and discharged 100,000 times without having to be updated.
Secondly, temperature also has a significant impact on the life of 3.7V lithium batteries (which cell phones and other small electronic devices can ignore). The environment below freezing point may cause 3.7V lithium batteries to burn down as soon as the electronics are turned on, while the overheated environment may reduce the capacity of the batteries. Therefore, if a laptop runs on an external power supply for a long time and does not take the battery off, the battery will remain in the heat of the laptop discharge for a long time, and more importantly, the battery will be in a state of 100% power for a long time, and will soon be discarded (including my own laptop battery is finished).