Finally, it’s clear! Why is it so difficult to improve mobile phone batteries?

From a mini black and white screen with a few pixels to a stunning full screen with millions of pixels, the progress of technology is so astonishing. However, there is an important component of the mobile phone that has not been greatly improved for decades, and it is the battery that people complain about the most.

In the era of feature phones, it was not uncommon for a fully charged mobile phone to last 2-3 days or even longer. But in the era of large-screen smartphones, the battery life of mobile phones has suddenly dropped to one day, or even less.

Why doesn't Moore's Law apply to the development of batteries? Why is it so difficult to reduce the size and increase the capacity of batteries? What kind of development process has the battery gone through? Today, let's talk about the past and present of mobile phone batteries.

In the early days, the problem of whether or not to use cylindrical nickel-cadmium batteries was solved with mature technology.

In the 1980s, the world's first real mobile phone, the Motorola DynaTAC 8000X, was launched. This square brick-like thing weighed 2 pounds (907 grams) and was priced at $3,995, or about RMB 25,261. So what does its battery look like?

The internal design of the battery compartment is ugly. Six cylindrical batteries are tied together with tape to form a battery pack with an output voltage of 7.5V. Compared with the common 3.8V battery voltage today, the power consumption is much higher. The battery it uses is the Nickel-Cadmlum Battery (Nickel-Cadmlum Battery) that was widely used at that time.

A device that needs 7.5V high voltage power supply naturally consumes a lot of power. Despite being equipped with such a huge battery pack, the talk time of Motorola DynaTAC 8000X is only a little over 20 minutes. What's more terrible is that it takes up to 10 hours to fully charge it.

In addition to short battery life and long charging time, nickel-chromium batteries also have a serious memory effect, which prevents users from charging them as they use them.

But in that era, lithium batteries and nickel-metal hydride batteries with higher capacity were still in the laboratory stage. Scientists could only continue to use nickel-chromium materials, but they tried their best to improve the internal space to make the battery occupy a smaller volume. They also optimized the circuits and reduced power consumption by adopting new technologies, thereby reducing the size of mobile phones through continuous innovation.

In the early 1990s, the miniaturization of batteries was achieved through customization.

By the early 1990s, with the establishment of the 2G standard, mobile communication technology had become increasingly mature and ushered in explosive growth. However, the size of traditional "big brothers" had become the most complained about issue by users. It could be said that whoever designed a smaller phone would own the market.

Therefore, in order to miniaturize, mobile phone manufacturers began to abandon the traditional battery compartment containing cylindrical nickel-chromium batteries and instead use customized miniaturized nickel-chromium battery packs.

In October 1992, Nokia launched its first GSM network mobile phone 1011, which adopted this design. Its weight was controlled at 476g, almost half the weight of the early "big brother".

Although the system design voltage is still 7.2V, thanks to the improved power consumption control, the standby time of the machine can reach 12 hours, and the 3-hour talk time is 6 times that of the first generation "big brother" mobile phones.

But this kind of performance still requires charging once a day, and the charging time of nickel-chromium batteries is about 10 hours, which is quite inconvenient when you think about it.

What is the memory effect?

If you have come into contact with old-fashioned mobile phones from the 1990s, you must remember that these phones must be charged for a long time when used for the first time, and they must be deeply charged and discharged regularly every month or so.

Otherwise, the battery capacity of the mobile phone will be significantly reduced. This is the memory effect. This phenomenon is most common in the early nickel-cadmium batteries, and there is a slight effect in the middle-stage nickel-metal hydride batteries. In the later lithium battery era, this problem no longer exists. Therefore, in the lithium battery era, we can charge and use the mobile phone at any time.

By the 1990s, with the advancement of semiconductor circuit technology, the size of mobile phones became smaller and smaller on engineers' drawings. However, the size of the battery could not be reduced in proportion to the size of the entire device.

The reason is clear to everyone. The power that nickel-cadmium batteries can provide is limited. If you want your phone to have a good battery life, you can only maintain a larger battery space ratio.

In 1990, nickel-metal hydride batteries began to be commercialized

The advent of nickel-metal hydride batteries has given the industry new hope for mobile phone batteries, because the cost of this battery technology is not much higher than that of nickel-chromium batteries, but the battery capacity has been significantly improved.

What also makes the designers very happy is that compared with nickel-chromium batteries, nickel-metal hydride batteries are not only more environmentally friendly, but also have a less obvious memory effect, making them an ideal alternative product.

For mobile phone users in the early 1990s, the mobile phone was shaped like a brick. However, there was a mobile phone that overturned everyone's perception, that is the Motorola StarTAC, which has a shell-like flip cover design and can be easily held in one hand. Of course, the miniature size is inseparable from the miniaturized battery design.

The Motorola StarTAC uses a small nickel-metal hydride battery, and the battery voltage is reduced from the traditional 7.5V to 3.6V.

The lithium battery era: from faltering to dominating the world

In 1992, the lithium-ion battery that Sony had been developing for many years was finally put into commercial use. However, due to its high price and not-so-significant power advantage, it could only try it out on its own products.

However, all this was broken with an advertising slogan in 1994. That year, Dell's notebook products first adopted lithium-ion batteries.

The slogan was: "Dell laptops allow you to use them on a plane from New York to Los Angeles!" This slogan is as fresh in people's memory as "Charge for five minutes and talk for two hours."

Since then, many mobile phone manufacturers have used lithium-ion batteries in their products as a major selling point. This also laid the foundation for lithium-ion batteries to surpass nickel-metal hydride batteries and become the standard configuration of mobile phones.

Remember the Motorola StarTAC we talked about earlier? The machine also launched lithium-ion batteries as accessories, but they were only optional and required a higher price than the original NiMH batteries. Because lithium batteries can bring higher battery capacity, this accessory was very popular at the time.

By the end of the 1990s, with the innovation of lithium battery material technology and the advancement of manufacturing technology, both capacity and cost were reduced. In addition, lithium batteries have the advantage of no memory effect, so they have won the favor of more and more mobile phone manufacturers. The era of lithium batteries has arrived!

At the beginning of the 21st century, mobile phones were reborn

Now we are at the first decade of the 20th century. I believe this was the happiest time for mobile phone enthusiasts born in the 1980s and 1990s. Because in this decade, there were many products with imaginative appearances, such as the following models:

The shape of mobile phone batteries has been evolving, and has subtly influenced the appearance of mobile phones. At first, because it took up a huge volume, the size of the mobile phone was also huge; later, the battery was reduced a lot, and mobile phones began to appear in subversive designs such as flip phones.

Later, when the battery could be easily hidden inside the phone, the design of the phone began to be more imaginative. It can be seen that the size of the phone battery has a huge impact on the appearance of the phone!

Why are nickel-chromium and nickel-metal hydride batteries eliminated?

Nickel-chromium batteries contain metallic chromium, which can pollute the environment. In addition, this type of battery has an obvious memory effect and its battery capacity is not advantageous. It is not suitable for mobile phones that need to be charged at any time, so it will be eliminated.

Although nickel-metal hydride batteries are very environmentally friendly, they have a mild memory effect, but this problem has been alleviated as the technology matures. Compared with lithium-ion batteries, they have a disadvantage in capacity, and as the cost of the latter decreases, the cost advantage of nickel-metal hydride batteries is no longer there, so lithium-ion batteries will eventually replace the two.

Why are all the No. 5 and No. 7 NiMH rechargeable batteries on the market instead of lithium batteries?

Because in the early days, the voltage of No. 5 batteries was specified as 1.2V, and many products were born under this standard, such as clocks, recorders, remote controls and other products, and the platform voltage of nickel-hydrogen batteries is exactly 1.2V, and they are superior to lithium batteries in terms of number of cycles and cost, so lithium batteries with a platform voltage of 3.7V have little meaning to exist.

Big screen era - batteries once again become a bottleneck for development

In 2007, Apple released the iPhone, with a large screen on the front, a button, and an earpiece. This minimalist design caused quite a stir at the time, but later this large-screen design seemed to have become the industry standard and has continued to this day.

However, under this design, batteries once again become a bottleneck restricting the development of mobile phones, as the battery life of mobile phones returns to the level of one charge a day.

If we take apart any mobile phone today, we will find that the battery occupies most of the space inside. And today's lithium batteries have a higher energy density than ever before.

However, this cannot stop our increasing dependence on mobile phones, which causes screens, processors, memory and other electronic components to consume large amounts of electrons released from batteries. Mobile phone designers are also constantly looking for solutions. For example, the following examples:

In the ZTE Axon MAX phone I disassembled, the designers took advantage of the fact that lithium-ion polymer batteries can be freely shaped and created stacked batteries to squeeze the little space left inside the phone. However, this method is costly and has little effect, so it has not become mainstream.

Apple used the iPhone X to tell us that if one lithium-ion battery can't solve a problem, then we can use two to solve it. But the fundamental problem is that the battery still occupies most of the space, and the battery life of the phone is not outstanding.

Another method to save the country has become the mainstream in the industry, that is, the introduction of fast charging technology. However, charging too fast will affect the safety and life of the battery.

To this end, some manufacturers have begun to tinker with the battery materials themselves. In the battery of Honor Magic, Huawei introduced a new lithium-ion polymer battery technology, which introduced heteroatoms and changed the molecular structure of the graphite negative electrode, thereby achieving fast charging without affecting the battery life.

The maximum charging power is up to 40W, which allows the device to be fully charged in less than an hour.

However, no matter how advanced the fast charging technology is, it must have a suitable charging environment and equipment constraints, which means that it cannot fundamentally solve the problem of insufficient battery life of mobile phones today.

So the question is, why is it so difficult to improve batteries?

In the past 20 years, lithium-ion batteries have dominated the power supply materials of mobile phones. However, compared with screens, processors and other components, the technological progress of batteries has not been obvious.

But when we are anxious about this, in fact, the scientists who develop batteries may be more anxious than us, because they have deduced almost all the substances that can be composed of all the elements on the periodic table, striving to find new positive and negative electrode materials.

But it is much more difficult to make it safe enough, have enough energy and a high number of charge and discharge cycles, and meet the requirements of industrial low-cost production than simply improving transistor technology and increasing screen size.