The history of lithium batteries

The lightest metal

Lithium was discovered in 1817 by alfredson, a student of the Swedish chemist berzelius, who named it lithium. It was not until 1855 that Benson and marchison obtained metallic lithium by electrolytic melting of lithium chloride, and the industrial production of lithium was proposed by gensa in 1893. It took 76 years for lithium to be considered an element before it was made commercially. Now electrolysis LiCl lithium, still need to consume a lot of electricity, every ton of lithium refining up to 60, 70 thousand degrees.

For more than 100 years after its birth, lithium served the medical community primarily as an antigout. NASA was the first to study lithium batteries because their analysis showed that they could provide the highest voltage at the smallest volume. According to P=UI, lithium has a high energy density, so lithium battery is an efficient battery.

Battery voltage is closely related to the cathode metal activity, as a very active alkali metal, lithium battery can provide a higher voltage. For example, lithium battery can provide 3V voltage, the lead battery is only 2.1V, and carbon zinc battery is only 1.5V. Another characteristic of lithium is its lightness. At 0.53g/cm3, lithium is the lightest of all metals, so light that it floats in kerosene. As element 3, naturally occurring lithium is composed of two stable isotopes, 6Li and 7Li, so its atomic mass is only 6.9. This means that lithium metal can provide more electrons than other reactive metals at the same mass. Lithium also has another advantage. Lithium ions have a small radius, so they move through the electrolyte more easily than other large ions.

Although metallic lithium has many advantages, there are still many difficulties to overcome in manufacturing lithium batteries. First of all, lithium is a very reactive alkali metal that can react with water and oxygen, and it can react with nitrogen at room temperature. It was so difficult for such a naughty fellow to keep it that it would come up and burn, whether in water or kerosene, that the chemists had to force it into petroleum jelly or liquid paraffin. As a result, lithium metal is much more complicated to preserve, use or process than other metals, and is very demanding to the environment. So lithium batteries have not been used for a long time. With the development of science and technology, the technical barriers of lithium battery break through one by one, lithium battery has gradually stepped on the stage, lithium battery has entered the large-scale practical stage.

Lithium metal battery

In 1958, Harris considered that lithium as an alkali metal would react with water and air, and proposed to use organic electrolyte as the electrolyte of lithium metal battery. According to the relevant work requirements of the battery, the organic electrolyte solvent needs to have three properties, (1) the solvent is a polar solvent, the solubility of lithium salt in the polar solvent is large, so that the conductivity of the electrolyte is large; Solvent must be aprotic polar solvent, because the solvent containing protons and lithium easy to react; (3) the solvent to have a lower melting point and a higher boiling point, so that the electrolyte has the widest possible temperature range. The idea was immediately recognized by the scientific community and sparked a boom in research and development.

In the initial development of lithium metal primary battery, the electrochemical properties of traditional anode materials, such as Ag, Cu and Ni compounds, have been unable to meet the requirements, so people have to look for new anode materials. In 1970, Japanese company Sanyo used manganese dioxide as the positive electrode material to make the first commercial lithium battery. In 1973, panasonic began mass production of cathode active material for carbon fluoride materials for cathode lithium battery. In 1976, the lithium iodine galvanic battery with iodine as the positive electrode was invented. Then came specialized batteries such as the lithium silver vanadium oxide (Li/Ag2V4O11) batteries used in implanted heart devices. After the 1980s, the cost of lithium mining was greatly reduced, and lithium batteries began to be commercialized.

Early lithium metal batteries were disposable and could not be recharged. The success of lithium battery has greatly stimulated people's enthusiasm to continue to develop rechargeable batteries. In 1972, Exxon used titanium disulfide as the positive electrode material and lithium metal as the negative electrode material to develop the world's first lithium metal secondary battery. This rechargeable lithium battery can be deeply charged and discharged 1000 times and the loss of each cycle is not more than 0.05% of the excellent performance.

The research on lithium secondary battery has been very deep, but so far none of the secondary battery with lithium metal as the negative electrode has been put into commercial production, because lithium secondary battery has not solved the safety problem of charging. When a lithium battery is charged, electrons from the lithium ions in the negative electrode are separated out as metals, but the lithium deposits at a different rate on the electrode, so the lithium metal does not evenly cover the surface of the electrode, but forms dendritic crystals in the process of deposition. After charging and discharging cycles, these dendritic crystals can be connected from the positive pole to the negative pole when the dendrite is long enough, resulting in a short circuit inside the battery. In this case, a large amount of heat may be released from the battery, which may cause the battery to catch fire or explode. After 1989, most enterprises stopped the development of lithium secondary batteries.

Liquid lithium ion battery

Armand first proposed the concept of RCB in 1980 in order to solve the dendritic crystallization caused by lithium metal precipitation. Instead of metallic lithium at the poles of the battery, they use chimeras of lithium. In the chimera, lithium metal does not exist in crystal form, but in the form of ions and electrons in the gap between the chimera. During charging, the current drives the lithium ions out of the positive electrode chimera. These lithium ions "swim" into the negative electrode chimera through the electrolyte between the positive electrode and the negative electrode. When discharging, the lithium ions "swim" back to the positive electrode chimera through the electrolyte from the negative electrode chimera. Because of that, in the process of charge and discharge is the insertion and release of lithium ions, which can swing at the Battery poles and is known as' rockin 'Chair Battery' (RCB).

So the first negative imbedded material that we're familiar with is graphite. As we all know, graphite has a lamellar structure with a spacing of 0.355nm, while lithium ion is only 0.07nm, so it is easy to insert into graphite and form interlamellar compounds composed of C6Li. In 1982 r.r. garwal and j.r. elman of the Illinois institute of technology found that lithium ions had the property of being embedded in graphite. They found that the process by which lithium ions are embedded in graphite is not only fast but also reversible.

The search for anode - embedded materials began as early as the days of lithium secondary batteries. In 1970, m.s. whittingham discovered that lithium ions could be reversibly embedded and precipitated in TiS2, a laminar material, making it suitable for the positive electrode of lithium battery. In 1980, John Goodenough, an American physics professor, discovered LiCoO2, a graphite-like layered structure. In 1982, Goodenough discovered the spinel structure LiMn2O4, which can provide three-dimensional lithium ion delamination channel, while ordinary anode materials only have two-dimensional diffusion space. In addition, the decomposition temperature of LiMn2O4 is high, and its oxidability is much lower than that of lithium cobalt oxide (LiCoO2), so it is more secure. In 1996, Goodenough also found that LiFePO4 with olive tree structure has higher safety, especially high temperature resistance and overcharge resistance, which is much better than traditional lithium ion battery materials.

In 1990 Japan's Sony pioneered the development of lithium-ion batteries. In 1992, a commercial rechargeable lithium cobalt oxide battery was launched by SONY and the technology was renamed "li-ion". This logo can be found on many cell phone batteries or laptop batteries. In many electronic products, "lithium battery" actually refers to lithium ion battery. Its practicality makes people's mobile phones, laptops and other portable electronic devices greatly reduce in weight and volume. Use time is greatly extended. Because lithium ion batteries do not contain heavy metal chromium, compared with nickel-chromium batteries, greatly reducing the environmental pollution.

The most widely used lithium-ion batteries use graphite for the negative electrode, lithium cobalt oxide for the positive electrode, and organic solvents containing lithium salts, such as lithium hexafluorophosphate, for the electrolyte. When discharging, the lithium embedded in the graphite negative electrode is oxidized into the electrolyte, and runs to the positive electrode embedded in the lattice gap of cobalt oxide to form lithium cobalt oxide. On charge, the lithium slips out of the lithium cobalt oxide and back into the graphite, and so on. Such a battery, the working voltage can reach more than 3.7 volts, greatly improving the energy density.

Polymer lithium ion batteries

The main components of a typical battery include a positive electrode, a negative electrode and an 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 developed polymer lithium ion battery system, polymer materials are mainly used to replace electrolyte solution. Lithium batteries, which are widely used today, can be classified into li-ion batteries and li-po batteries.

In 1973, Wright et al. found that polyoxyethylene-alkali metal salt complex had high ionic conductivity. Since then, people have paid more attention to ionic conductivity polymers. In 1975, Feullade and Perche found that the alkali metal complexes of PEO, PAN,PVDF and other polymers had ionic conductivity, and made ionic conductive films based on PAN and PMMA. In 1978, Dr. Armadnd of France predicted that such materials could be used as electrolytes for energy-storing batteries, and came up with the idea of a solid electrolyte for batteries. Therefore, the development of polymer electrolytes has been carried out worldwide. The polymer electrolyte first used in lithium secondary battery has the complex system formed by PEO and lithium salt, but due to the poor conductivity of this system at room temperature, it cannot be used in industry. It was found that the conductivity of the polymer electrolyte could be significantly improved by using co-mixing and adding plasticizer to the polymer electrolyte.

In lithium ion battery, positive pole and negative pole cannot contact directly certainly, can produce short circuit otherwise, cause a series of safety problems. The electrolyte of polymer lithium ion battery is in solid or colloidal state, which can avoid the problem of electrolyte leakage and leakage current. Moreover, the plasticity of the polymer material is strong, which can be made into a large area of ultra-thin film to ensure sufficient contact with the electrode. 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 of Japan invented the polymer lithium battery, the electrolyte is a polymer gel. Polymer lithium-ion batteries were commercialized in 1999.

The future trend of lithium ion makes lithium ion battery have higher energy density, power density, better cycle performance and reliable safety performance. At present, there are still some safety problems in lithium battery. For example, some mobile phone manufacturers do not strictly control the quality of diaphragm material or process defects, resulting in local thinning of diaphragm and inability to effectively isolate the positive and negative poles, thus causing battery safety problems. Secondly, short circuit is easy to occur in the charging process of lithium battery. Although most lithium-ion batteries are now equipped with short-circuit protection circuits and explosion-proof wires, in many cases, this protection circuit may not work in various situations, and the role of explosion-proof wires is limited.

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