Development History of Lithium-ion Battery

Lithium batteries have not only been adopted by portable terminals for more than 20 years, but also expanded into many fields such as electric vehicles and domestic batteries. In the future, as the application scope becomes more and more extensive, it is estimated that mastering the knowledge of lithium batteries will become an essential condition for technicians. This series will introduce you to the history and development of lithium battery development by publishing the article published by the father of lithium battery, Xi Meixu, in the "Nikkei Electronics".

With all due respect to an old story, the Asahi Shimbun (Tokyo version), dated 11 January 2004, published such a story. The Osakaspecial reported a company employee and a college student in mifang city, Osaka prefecture, on suspicion of theft. Thespecial accused them of "stealing electrical products". The author thought that they had taken goods such as electrical appliances from the electrical store. However, this was not the case. So, what did they steal?

A cell phone without a battery is just a brick.

In fact, they "stole electricity" from an outdoor socket. Although the total amount involved in the case was only about 1 yen, thespecial still arrested the two in accordance with the law.

According to the investigation, the company's employees allegedly used a signboard socket in a restaurant in Menzhen City to charge the mobile phone for about 5 minutes. The college students performed a dance in front of the Mefang City station of the Gyeonggi Electric Railway. They removed the plug of the supermarket vending machine from the socket and inserted it into the dual-purpose recording machine with their own music, thus constituting a theft of electricity. Both incidents were caused by the depletion of batteries.

This report tells people that in the modern era when portable products are popular, batteries as power sources, especially secondary batteries, have become indispensable. In other words, "If the cell phone loses its battery, it is only a brick."

I hope that through this article, we will introduce lithium batteries that now occupy the leading position in secondary batteries and are expected to become power sources for electric vehicles in the near future (hereinafter referred to as LIB).

From dry batteries to secondary batteries

Secondary batteries have not been widely used for a long time. Tokyo Communications Industry(now Sony) launched Japan's first transistor radio "TR-55" in 1955, when it used a battery, a dry battery(Figure 1). Later, in 1957, the company developed a dry battery "006P" with a voltage of 9V for small radios(Figure 2). This battery consists of a dry battery the size of a small thumb tip that is superimposed in a square cylinder. The 006P battery is still a common power source such as a radio remote control vehicle. It started late in the battery business, but half a century ago it unexpectedly developed an important product.

After the transistor radio, the portable product that is widely popular should be a dual-purpose machine. In 1963, Hitachi produced a two-in-one radio and open reel recorder. This is said to be Japan's first dual-use machine. The original "cassette recorder + radio" was manufactured by AIWA in 1968. As an opportunity, everyone's electric manufacturing companies successively put goods on the market in the 1970s. The dual-purpose machine was also powered by a dry battery at the time, because it was equipped with a large number of dry batteries No. 1 and No. 2, so the weight was quite heavy.

When it comes to weight, one can not fail to mention the batteries of the early home camera. Since the mid-1970s, cameras have entered the family. At the time, although it was home, the camera was large enough to drive the big guy's secondary battery, only the big lead battery. Costs may also limit the range of options. At the time, nickel-cadmium(hereinafter: Ni-Cd) batteries were also very expensive.

The size of the lead battery used in the camera is similar to that of a chestnut lamb soup. It was once dubbed the "chestnut lamb soup battery." The camera, which was very bulky, was loaded with heavy chestnut lamb soup batteries. It was so heavy that people would inevitably flash to their waist. At that time, the secondary battery was burdened with "triple bitterness", that is, "heavy", "not durable(battery power consumption as soon as possible)", and "long charging time". It was not moving forward at the entrance of the mobile product era.

Since the second half of the 1960s, portable electronic products such as cassette tape recorders, FM radios, and micro-TVs have emerged. The vast majority of products use a battery and rarely see secondary batteries.

However, as the frequency of use of these products increases, primary batteries impose a heavy cost burden on users. This led people to hope for secondary batteries and began to focus on "getting rid of the triple suffering."

The increasing demand for miniaturization and high performance of secondary batteries was when portable music players became popular(`` Walkman "debuted in 1979) and 8mm video tapes appeared(1985). At that time, AV products developed into miniaturization, and outdoor use has become commonplace.

Universal availability of Ni-Cd batteries

At that time, the Ni-Cd battery replaced the lead battery as the protagonist of the battery. Portable music players began using ultra-thin batteries, commonly known as chewing gum cells, and the small Ni-Cd batteries used by cameras also made their way onto the stage of history.

This is due to the significant increase in the capacity of the Ni-Cd battery. For example, the first battery pack model used by Sony's first 8mm camera is the "NP-55", which uses five Ni-Cd batteries that are slightly shorter than the No. 5 dry battery. When it was launched in 1985, the capacity was about 700 mAh. In response to the call for high capacity, Sony improved the battery. By 1989, the battery capacity increased to 1300 mAh.

The NP-55 consists of five Ni-Cd batteries and is used by Sony's first 8mm camera. At the time of its launch in 1985, the capacity was about 700 mAh, and in 1989 it reached 1300 mAh.

The increase in capacity density is due to numerous technological innovations, one of which is the foamed nickel substrate described below. The electrode substrate of the Ni-Cd battery was initially a sintered body of nickel (sintered nickel), and then a foamed nickel substrate was used. The latter is based on polyurethane foam and polymer fiber nonwovens.

The nonwoven fabric is first subjected to electroless plating to obtain electrical conductivity, and then, after usual electroplating, nickel is attached to the surface and then calcined at a high temperature. After the calcination is completed, the substrate such as the urethane resin will disappear, leaving only the nickel skeleton. The voids originally provided in the polymer substrate are intact, and the prepared electrode substrate has a very high porosity. The void ratio has increased from 80% of the past sintered form to a maximum of 98%, revolutionizing the filling rate of the active material*. By using such an electrode, the capacity can be increased by about 30%.

* Active material = substance that participates in the positive and negative electrodes of the power generation reaction. A battery is a device that converts energy generated by a chemical reaction between a positive electrode and a negative electrode into an electric energy output, and a substance that participates in a chemical reaction is called a positive electrode active material and a negative electrode active material. For example, the positive electrode active material of the Ni-Cd battery is NiOOH (nickel hydroxide), and the negative electrode active material is Cd (cadmium).

The foamed nickel substrate debuted in the second half of the 1980s, and Sony was already developing similar technologies in the first half of the 1970s. At the time, Sony also commercialized a desktop calculator (a large device that is different from the current calculator) and built a Ni-Cd battery as a power source. In order to achieve weight reduction of the battery, the battery also uses a non-electrical plating and a usual electroplating nonwoven fabric as a substrate. Unfortunately, we did not expect to remove the nonwoven substrate by calcination.

However, Sayong lost his horse and knew it was a blessing. If our electrodes develop to the extent of foamed nickel substrates, Ni-Cd batteries (and later Ni-MH batteries) may become the main products of Sony batteries, which will greatly delay the development of LIB in the future. After all, Sony did not have a strong secondary battery product at that time, and invested in the development of a new secondary battery LIB.

Now, when the camera is powered, the camera has more and more requirements for increasing the capacity of the battery.

During the five years from 1985 to 1989, the energy density increase rate of Ni-Cd batteries reached 15-20% per year. However, the capacity is still insufficient. After entering 1990, battery performance needs to continue to increase at the same speed.

However, according to past experience, the secondary battery technology “achievable capacity is only about 1/5 of the theoretical capacity”. According to this rule, in 1990, Ni-Cd battery technology has basically reached the limit. After that, if you do not develop a new battery, you will not be able to meet the needs of the product.

Moreover, Ni-Cd batteries are facing another major obstacle - the environmental hazard of cadmium. Readers should have heard of the "pain" caused by cadmium. This disease is caused by residents of the Shentongchuan River basin that flows through Toyama Prefecture. It is also famous internationally. English is even called Japanese, which is itai-itaidisease. Cadmium has become a well-known harmful substance Note 1). Therefore, battery companies are forced to get rid of Ni-Cd batteries as soon as possible.

Note 1) Because there are no patients in other cadmium-contaminated areas, there are also opinions that cadmium is not the only cause of illness.

High Performance Secondary Battery Expectation Theory

Since the Ni-Cd battery does not work, a new type of secondary battery must be developed. The demand for high-energy density batteries has long been there.

For example, in the last years of the Taisho period, Fengtianzuoji offered a reward to the Imperial Invention Association. "The Japanese who have developed a battery with an output power of 100 horsepower and can run continuously for 36 hours, weighing less than 60 and weighing less than 10 square feet, are rewarded with 1 million yen."-According to the gold price at that time, this bonus is approximately equivalent to about 2 billion yen today. It's an astronomical number.

1 horsepower of the old measure = 761.2 W. If the performance of the above mentioned battery is converted to ISO units, the energy density per unit weight and unit volume is 9850 Wh/L or more, and 12180 Wh/kg or more. The power density is 2820 W/L or more, And 340W/kg or more.

In terms of power density, LIB meets the requirements. The problem is energy density. The energy density of the current LIB is only about 600Wh/L and 210Wh/kg, which shows how ridiculous Zuoji's request is. One can not help but speculate that it is not because it can not be realized, so it is only a heavy prize of 2 billion yen Haikou.

Regardless of whether or not the request can be achieved, the call for high-energy density batteries has become louder since the second half of the 1980s. As mentioned above, because it is predicted that the Ni-Cd battery will eventually fail to meet the requirements of the camera, battery companies have been preparing early to start developing new secondary batteries. In response to this trend, the Ni-MH battery(nickel-metal hydride battery) was created in 1990 and the LIB was created in 1991.

Ni-MH Battery Debut

The attention of the Ni-MH battery is locked in the theoretical capacity density of hydrogen *. When hydrogen is a negative electrode of the battery, the theoretical capacity density is 26316 mAh/g, which is an excellent electrode material. In contrast, Lithium(Li) is 3861 mAh/g and cadmium is 477 mAh/g, which shows that the potential of hydrogen is huge.

The problem eventually boils down to the form in which hydrogen is used. For example, by canning 10L hydrogen(equivalent to about 2170Ah) into a high-pressure cylinder(200kg/cm2), the volume will be reduced to 50mL. Although the volume is small, it is best to avoid handling 200 atmosphere-pressure high-pressure containers. There is also a way to compress 10L hydrogen to 13mL. That is liquid hydrogen at -250 °C, but it is not practical to apply this form to batteries.

* Theoretical capacity density = capacity to generate electricity for each substance. The amount of electricity that can be produced by an active substance per unit weight(volume) depends on the atomic weight of the substance(the compound is the molecular weight) and the chemical price when it is converted into ions. Therefore, after the material is determined, the amount of electricity that can be achieved will also be determined. It's called theoretical capacity.

Compared with the above two forms, there is also a more convenient form-hydrogen storage alloy. For example, the LaNi5 alloy can form a compound LaNi5H5N1 .7 with hydrogen and absorb 10L of hydrogen in an alloy with a volume of 7.5 ml. The compression rate can reach about 1/1300. However, in this form, the theoretical capacity density per unit weight is 366 mAh/g, which is sharply reduced to less than 1/70 compared to the 26316 mAh/g of hydrogen itself. This is due to the very large molecular weight of LaNi5H5 .7, which is approximately 438. However, hydrogen storage alloys also paved the way for hydrogen to serve as an electrode active substance, making the Ni-MH battery commercialized in 1990.

Hope to achieve a large capacity of lithium negative electrode

Although the strength can not catch up with hydrogen, lithium is used as a negative pole, and the theoretical capacity density per unit weight and unit volume has also reached 3861 mAh/g and 2062 mAh/m2. Moreover, the standard unipolar potential(based on the standard hydrogen electrode) is as high as -3.04 V, achieving a very high absolute value. That is, a lithium negative battery can increase the terminal voltage. If the charge(Wh) is used to represent the energy density, the value will increase. In fact, as a battery using metallic lithium as a negative electrode, button lithium batteries have long been put into practice. This is a battery with a positive electrode using manganese dioxide(MnO2) and a negative electrode using lithium. It has been widely used in memory backup power supplies and other applications.

The characteristics of lithium batteries are as follows:

1 The voltage is up to 3.0 V.

2 Large energy density

3 Low self-discharge

4.There is a wide range of operating temperatures

Not only battery technicians, but everyone should hope to directly play these characteristics and realize the secondary battery of lithium batteries.

But good things, in front of the second battery, stands a huge difficulty. Among them, safety and the lack of the required cycle life of charge and discharge are the two most difficult to solve. No answer has yet been found.

In the process of repeated charging and discharging, needle-shaped metallic lithium continues to grow.

The reason is lithium dendritic crystals(dendritic crystals) that grow when charged. Figure 4 shows the shape of the lithium precipitated when charging. It is not difficult to see from the figure to call it dendritic or needle-like crystallization. The crystal needle penetrates the diaphragm, causes an internal short circuit, poses a threat to safety, or falls off the electrode, resulting in reduced capacity, that is, cyclic deterioration.

So, is it not possible that Ni-Cd batteries that also use metal negative poles do not have this problem? The discharge product of cadmium-CdO(cadmium oxide) or Cd(OH) 2(cadmium hydroxide) is insoluble in the electrolyte and will stay in situ and be generated on the electrode. Therefore, after charging, it will be converted back to cadmium in situ.

As far as negative metal materials are concerned, zinc(Zn) is far better than cadmium. The capacity per unit weight of zinc is about 1.7 times that of Cd, and the capacity per unit volume is about 1.4 times. Moreover, in the same case of positive polar active substances, the battery voltage of zinc can be about 0.4 V. This is why dry batteries, silver oxide batteries and other primary batteries use zinc as a negative electrode.

However, when the zinc negative electrode is applied to the secondary battery, dendritic problems will occur like lithium. When zinc is used as a negative electrode, the discharge product ZnO(zinc oxide) is dissolved in the electrolyte in the form of zinc acid ion Zn O22-to produce dendrites. Although zinc will be precipitated when charged, zinc at this time can not be returned to its original position and will be electrically resolved at an easily precipitated position. After the precipitation begins, the tip part is used as the active point, and the precipitation will continue, and the dendritic electroanalytic product-dendritic crystal continues to grow. Without this phenomenon, Ni-Cd is estimated to have been replaced by Ni-Zn even if there is no public hazard problem.

The discharge product of cadmium is insoluble in the electrolyte, accumulates on the electrode, and reconverts to cadmium after charging. The discharge product of zinc is dissolved in the electrolyte and precipitated in the form of dendritic crystals when charging.

When lithium is used as a negative electrode, the discharge product will also dissolve in the electrolyte, so as with zinc, there will be dendritic problems caused by the precipitation mechanism. Neither lithium nor zinc is currently an effective means of preventing dendritic crystals. Therefore, secondary batteries using lithium negative poles must also wait until the LIB is completed before they can appear.

The page contains the contents of the machine translation.