IT168 evaluation time back two months ago, August 2, when Samsung's Mobile Division President Gao Dongzhen proudly to introduce the world's flagship mobile phone Galaxy Note7 to the world in New York, not only Samsung, almost no one It was thought that in just over a month later, this Android flagship, which was used by Samsung to fight against Apple's new products this year, was fermented and spread on the Internet because of successive incidents of combustion, and even the airline announced "with unprecedented precedence" It is not recommended to carry Note7 aircraft." In the face of this situation, ATL, one of Samsung and battery makers, did not give the cause of the accident in its official statement. Our today's machine observation room came to talk about the burning of Samsung Note7.
At the beginning of the article, we need to explain one thing: According to the information that is currently being exposed to Note7, the results of most mobile phones are fierce and not explosions, and burning does not mean explosion. In fact, mobile phone battery burning/explosion is not new. Searching old news in the past, almost all mobile phone brands have very similar products, so here we need to explain why the mobile phone battery will burn / explosion.
Why does the battery burn / explode?
Cell phone batteries have experienced nickel-cadmium batteries, nickel-metal hydride batteries, and are now in the era of lithium-ion batteries. Compared to previous products, lithium-ion batteries have the characteristics of higher energy density and lighter weight, so most mobile phones today use lithium-ion batteries. Lithium-ion batteries are generally classified into liquid lithium-ion batteries and polymer lithium batteries, but they are composed of a positive electrode, a negative electrode, an electrolyte, and a separator that prevents short-circuiting. The electrolyte infiltrates the positive and negative electrodes while the lithium ions are in the electrolyte. The movement between the positive and negative poles enables the battery to work. The separator is used to prevent the positive and negative electrodes from separating due to the short circuit between the positive and negative electrodes. In addition, the biggest difference between lithium-ion polymer batteries and liquid lithium-ion batteries is that they use solid or gel-like objects as electrolytes. In the event of an accident, solid or gel-like objects will appear to be vaporized. It will burn, but it will not explode. This also explains what we mentioned in the previous section that the vast majority of Note7 is a combustion rather than an explosion.
Lithium-ion battery structure (images from the network)
The above explanation only describes the principle of the battery from the most basic structure. In actual life, the mobile phone battery is not only a single diaphragm, but is composed of multi-layer diaphragms. The interior of the battery punctures the diaphragm due to possible impurities inside the product. Causes the positive and negative electrodes to contact to cause a short circuit, and what happens afterwards is naturally self-evident. It seems that the essential reason for the battery burning is still on the "that film." According to speculation, in addition to its own quality problems (battery impurities inside the battery puncture the diaphragm) and external factors artificially causing the battery to burn, the Note7 battery problem may appear in the following two aspects, we have also conducted analysis.
1, because of fast charge and cause battery problems?
Samsung Note7 fast charge measurement (continuously adjust the current according to temperature)
Fast charging has become the standard for almost all smart phones currently. No matter which flagship is used, down to thousands of machines, no matter what kind of fast charging protocol is adopted, almost all mobile phones on the market today use various fast charging technologies. The Samsung Note7 supports its own AFC and Qualcomm QC 2.0 fast charging protocol, while the Note7 battery capacity is 3500mAh, the standard charger charging power is 5V2A, 9V1.67A, the actual charging power (standard charger) is about 14W, The battery is about 1.2C charge rate, compared with the current Meizu Pro6, Le Pro3 such domestic flagship dynamic standard 24W charging power, 1.5C charge rate there is some distance, and throughout the Note7 battery burning incident, there are some The user is burning when the phone is not charging. Therefore, it cannot simply be said that fast charging will cause problems with the Note7 battery.
2. There is a problem with the design of the battery itself:
Note7 internal dismantling diagram
On this issue, we need to understand one word first: the energy density of the battery. The energy density of the battery is the data derived from the battery capacity/volume, and the amount of electricity stored in the battery per unit volume of the battery. Undoubtedly, a larger battery energy density can bring about better battery life (under the same conditions). We know that smart phones are highly integrated products, and the internal space is called “expensiveâ€. Therefore, for mobile phones whose volume is hardly changed, there is not much room for the battery. The change.
Here is a data: the previous generation of Note5, the battery capacity of 3000mAh, and the Note7 battery capacity is almost unchanged in volume is 3500mAh, according to calculations, Note5 battery energy density is 580Wh/L, and Note7 is 691Wh/L. In order to get a higher energy density, perhaps Samsung has chosen to make the layer of "separator" mentioned above as thin as possible, so as to free up more space to increase the energy density of the battery capacity . The space between the negative electrode and the separator has almost reached the limit . Perhaps the new technology in the battery is not perfect enough, making the Note7 battery itself has some hidden dangers.
Looking back, at the technology electronics seminar held by Samsung in mid-15th, Samsung said that it will achieve an energy density of 700wh/L by the end of 15th, and will launch a 750wh/L, 4.40V energy density battery sample in the third quarter; By raising the voltage to 4.5V in 2017, the battery energy density will reach 780wh/L. According to the time difference between R&D and commercial use, we did not rule out that the 691Wh/L battery on the Note7 may be a high-energy-density battery that Samsung had successfully developed last year. It was only in the final commercial stage that there was a problem with the design. The situation now occurs.
Network transmission SDI battery design problems
As for other reasons, such as cell phone burning due to high temperature, overcharging, and other factors, this is just a different cause of the different types of mobile phones that cause the burning of mobile phones, and has been mentioned in some other previous reports or speculations, such as SDI. The reason for the difference in quality with ATL batteries and the dismantling of Note7 by iFix found that the international version used lithium batteries instead of lithium polymer batteries, but these reasons were also due to several incidents of damages of the Bank of China's Note7. And it becomes less convincing.
The future development of mobile phone batteries
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　 In recent years, the rapid development of smart phones in processors, screens, and other areas has made the functions of smart phones more and more important in our normal lives, making mobile phones increasingly dependent on battery life. Although people are constantly looking for other materials such as hydrogen fuel cells, graphene batteries, etc., to try to change the status quo, unfortunately, according to the current level of science and technology, the battery industry seems to be difficult to achieve a greater degree of breakthrough in the next few years. Therefore, at present, both terminal and chip manufacturers are actively increasing the charging speed to "curve the country."
　　 Conclusion: When Samsung Note7 was just released, almost all media believed that this was Samsung's best chance against Apple for many years. However, Note7 caught in the “explosion gate†was like a martial arts master who was suffering from chronic illness. It is hard to play well. Let us imagine that in recent years, Samsung has been able to claim the top level in the field of smart phones in mobile screens, processors, cameras, and other aspects, but it is difficult to make breakthroughs in terms of batteries because of the current technology, so Note7 is It is not difficult to understand the technical changes in the battery. Unlike Apple, Samsung has always applied new technologies directly to its products, but it may be a little faster this time.
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