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The Development History of Lithium Batteries


Whether you live in the city or the countryside, have you ever noticed one thing that is ubiquitous these days, revolutionizing the way people work and live? This is a lithium battery. Without it, there would be no laptops, smartphones, and tablets; without it, there would be no rebirth of Apple, no Xiaomi; without it, there would be no rise of WeChat, Zhang Xiaolong, Zhishe Academic Circle, and of course there would be no Zhishe Academic Circle. of you.

1. The lightest

metallic lithium element was discovered in 1817 by Alfredson, a student of the Swedish chemist Berzilius, who named it Lithium. In 1855, Bunsen and Machison used the method of electrolytically melting lithium chloride to obtain metal lithium. The industrial production of lithium was proposed by Gensha in 1893. It took 76 years for lithium to be recognized as an element to be produced industrially. At present, the production of lithium by electrolysis of LiCl still consumes a large amount of electric energy, and the power consumption for refining one ton of lithium is as high as 60,000 to 70,000 kWh.

Lithium served the medical profession mainly as an anti-gout drug for more than 100 years after his birth. The National Aeronautics and Space Administration (NASA) was the first to engage in research on lithium primary batteries, because their analysis showed that lithium batteries can provide the highest voltage with the smallest volume. According to P=UI, lithium has a high energy density, so lithium batteries are a kind of high-efficiency batteries.

The battery voltage is closely related to the activity of the negative electrode metal. As a very active alkali metal, lithium batteries can provide higher voltage. For example, lithium batteries can provide a voltage of 3V, ② lead batteries only have 2.1V, and carbon-zinc batteries only have 1.5V. Another characteristic of lithium is "light". The density of lithium is 0.53g/cm3, which is the lightest of all metals, so light that it can float in kerosene. As the No. 3 element, lithium that exists in nature is composed of two stable isotopes 6Li and 7Li, so the relative atomic mass of lithium is only 6.9. This means that metallic lithium can provide more electrons than other active metals at the same mass. In addition, lithium has another advantage. Lithium ions have a small ion radius, so lithium ions move more easily in the electrolyte than other larger ions.

Although metallic lithium has many advantages, there are still many difficulties to be overcome in the manufacture of lithium batteries. First of all, lithium is a very active alkali metal element that can react with water and oxygen, and it can react with nitrogen at room temperature. For such a naughty creature, it is very difficult to preserve it, whether it is in water or in kerosene, it will float and burn. Chemists finally had to force it into petroleum jelly or liquid paraffin. As a result, the storage, use or processing of metal lithium is much more complicated than other metals, and has very high environmental requirements. Therefore, lithium batteries have not been used for a long time. With the development of science and technology, the technical barriers of lithium batteries have been broken one by one, and lithium batteries have gradually entered the stage, and lithium batteries have entered a large-scale practical stage.

2. Lithium metal battery

In 1958, Harris considered that lithium, as an alkali metal, would react with water and air, and proposed the use of an organic electrolyte as the electrolyte for lithium metal batteries. According to the relevant work requirements of the battery, the organic electrolyte solvent needs to have three properties. ①The solvent is a polar solvent, and the solubility of lithium salt in the polar solvent is relatively high, so the conductivity of the electrolyte is relatively high; ②The solvent must be aprotic Polar solvents, because proton-containing solvents are easy to react with lithium; ③The solvent should have a lower melting point and a higher boiling point, so that the electrolyte has as wide a temperature range as possible. The proposal of this concept was immediately widely recognized by the scientific community, and triggered quite a boom in research and development.

In the development of metal lithium primary batteries, the electrochemical properties of the traditional cathode materials such as Ag, Cu, and Ni compounds have not met the requirements at the initial stage, and people have to look for new cathode materials. In 1970, Japan's Sanyo company used manganese dioxide as the positive electrode material to create the first commercial lithium battery. In 1973, Panasonic began to mass-produce lithium primary batteries in which the positive electrode active material is fluorinated carbon material as the positive electrode. In 1976, the lithium-iodine primary battery with iodine as the positive electrode came out. Then some batteries for specific fields such as lithium silver vanadium oxide (Li/Ag2V4O11) batteries also appeared one after another, which are mainly used in implantable cardiac devices. After the 1980s, the cost of lithium mining was greatly reduced, and lithium batteries began to be commercialized.

Early metal lithium batteries belonged to primary batteries, which could only be used once and could not be recharged. The success of lithium batteries has greatly stimulated people's enthusiasm for continuing to develop rechargeable batteries, and the prelude to the development of lithium secondary batteries has begun. In 1972, Exxon Corporation of the United States developed the world's first metal lithium secondary battery by using titanium disulfide as the positive electrode material and metallic lithium as the negative electrode material. This rechargeable lithium battery has the excellent performance of deep charge and discharge 1000 times and the loss of each cycle does not exceed 0.05%.

Lithium secondary battery research has been very in-depth, but so far the secondary battery with metal lithium as the negative electrode has not been put into commercial production, because the lithium secondary battery has not solved the safety problem of charging. When a lithium battery is charged, lithium ions obtain electrons at the negative electrode and precipitate in the form of metal, but the deposition rate of lithium on the electrode is different, so metallic lithium will not cover the electrode surface uniformly, but will form during the deposition process. Dendritic crystals. These dendritic crystals go through charge and discharge cycles, and when the branches are long enough, they can be connected from the positive electrode to the negative electrode, causing an internal short circuit in the battery. This situation may cause the battery to emit a lot of heat, which may cause the battery to catch fire or explode. After 1989, most enterprises stopped the development of lithium secondary batteries.

3. Liquid Lithium-ion Batteries

In order to solve the dendrites produced during the precipitation of metal lithium, Armand first proposed the concept of RCB in 1980. The two poles of the battery no longer use metallic lithium, but lithium inlays. In the chimera, metal lithium does not exist in crystal form, but exists in the gap between the chimeras in the form of ions and electrons. When charging, the current drives out the lithium ions in the positive electrode chimera, and these lithium ions "swim" into the negative electrode chimera through the electrolyte between the positive electrode and the negative electrode; while discharging, the lithium ions are inserted from the negative electrode The compound "swims" back to the positive electrode chimera through the electrolyte. Therefore, the process of charging and discharging is the intercalation and deintercalation process of lithium ions. Lithium ions can swing at the two poles of the battery, so it is also called "Rocking Chair Battery" (abbreviated as RCB).

The first negative electrode intercalation material is graphite, which we are not familiar with. Everyone knows that graphite has a layered structure with a layer spacing of 0.355nm, while lithium ions are only 0.07nm, so it is easy to insert into graphite to form a graphite interlayer compound composed of C6Li. In 1982, RRAgarwal and JRSelman of the Illinois Institute of Technology discovered that lithium ions have the characteristics of intercalating graphite. They found that the process of intercalation of lithium ions into graphite is not only fast, but also reversible.

The search for positive electrode intercalation materials began as early as the lithium secondary battery period. In 1970, MSWhittingham found that lithium ions could be reversibly intercalated and precipitated in the layered material TiS2, which was suitable for lithium battery cathodes. In 1980, John Goodenough, a professor of physics in the United States, found LiCoO2, a new substance, which also has a layered structure similar to graphite. In 1982, Goodenough discovered LiMn2O4 with a spinel structure. This spinel structure can provide a three-dimensional lithium ion intercalation channel, while ordinary positive electrode materials only have a two-dimensional diffusion space. In addition, the decomposition temperature of LiMn2O4 is high, and the oxidation property is much lower than that of lithium cobaltate (LiCoO2), so it is safer. In 1996, Goodenough discovered LiFePO4 with an olive tree structure. This material has higher safety, especially high temperature resistance, and its overcharge resistance far exceeds that of traditional lithium-ion battery materials.

In 1990, Japan's Sony (Sony) took the lead in developing lithium-ion batteries. In 1992, the commercialized rechargeable lithium cobalt oxide battery was launched by Sony, who renamed the technology "Li-ion". This logo can be found on many cell phone batteries or laptop batteries. The "lithium battery" mentioned in many electronic products actually refers to lithium-ion batteries. Its practical application greatly reduces the weight and volume of portable electronic devices such as mobile phones and notebook computers. The use time is greatly extended. Since lithium-ion batteries do not contain heavy metal chromium, compared with nickel-chromium batteries, the pollution to the environment is greatly reduced.

The negative electrode of the most widely used lithium-ion battery at present uses graphite, the positive electrode uses lithium cobaltate, and the electrolyte uses an organic solvent containing lithium salt (such as lithium hexafluorophosphate). When discharging, the lithium embedded in the graphite negative electrode is oxidized and enters the electrolyte, and goes to the positive electrode to be embedded in the lattice gap of cobalt oxide to form lithium cobalt oxide; when charging, lithium is deintercalated from lithium cobalt oxide and slips back into graphite , and so on. The working voltage of such a battery can reach more than 3.7 volts, and the energy density is greatly improved.

4. Polymer lithium-ion battery

The main structure of a general battery includes three elements: positive electrode, negative electrode and electrolyte. The so-called polymer lithium-ion battery means that at least one or more of the three main structures use polymer materials as the main battery system. In the currently developed polymer lithium-ion battery system, polymer materials are mainly used to replace the electrolyte solution. Lithium batteries that we widely use today are exactly divided into two types: lithium ion batteries (Li-ion) and lithium polymer batteries (Li-Po).

In 1973, Wright et al. found that polyoxyethylene-alkali metal salt complexes had high ion conductivity. Since then, ion-conductive polymers have attracted people's attention. In 1975, Feullade and Perche discovered that the alkali metal salt complexes of polymers such as PEO, PAN, and PVDF had ion conductivity, and made ion-conducting membranes based on PAN and PMMA. In 1978, Dr. Armadnd of France predicted that such materials could be used as electrolytes for energy storage batteries, and proposed the idea of ​​solid electrolytes for batteries. Therefore, the development and research of polymer electrolytes has been launched worldwide. The earliest polymer electrolyte used in lithium secondary batteries is a complex system of PEO and lithium salt, but due to the poor conductivity of this system at room temperature, it has not been applied industrially. It was later found that the conductivity of the polymer electrolyte can be significantly improved by blending and adding a plasticizer to the polymer electrolyte.

In lithium-ion batteries, the positive and negative electrodes must not be in direct contact, otherwise a short circuit will occur, causing a series of safety problems. The electrolyte of polymer lithium-ion batteries exists in the form of solid or colloidal state, which can avoid the problems of electrolyte leakage and large leakage current in liquid electrolytes. Moreover, the polymer material has strong plasticity and can be made into a large-area ultra-thin film to ensure sufficient contact with the electrodes. Because the electrolyte is captured by the network in the polymer and dispersed evenly in the molecular structure, the safety of the battery is also greatly improved. In 1995, Sony Corporation of Japan invented the polymer lithium battery, and the electrolyte is a gel polymer. In 1999, polymer lithium-ion batteries were commercialized.

The future trend of lithium-ion enables lithium-ion batteries to have higher energy density, power density, better cycle performance and reliable safety performance. At present, lithium batteries still have some safety problems. For example, some mobile phone manufacturers do not strictly control the quality of separator materials or process defects, resulting in local thinning of the separator and the inability to effectively isolate the positive and negative electrodes, resulting in battery safety issues. Secondly, lithium batteries are prone to short circuits during charging. Although most lithium-ion batteries now have short-circuit protection circuits and explosion-proof wires, in many cases, this protection circuit may not work in various situations, and the explosion-proof wires can only play a limited role. .

 

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