In 800, the Italian physicist Alessandro Volt invented the first battery in human history-the Volt pile. This initial battery made of zinc sheets (anode) and copper sheets (cathode) and paper sheets (electrolyte) soaked in salt water proves the possibility of artificial manufacture of electricity.
Since then, the battery has experienced more than 200 years of development as a device that can provide continuous and stable current, and continues to meet people's needs for flexible use of electricity.
In recent years, with the huge demand for the use of renewable energy and the increasing attention to environmental pollution, secondary batteries (rechargeable batteries or accumulators) represented by lithium batteries-this type of energy that can convert other forms of energy Electric energy, and energy storage technology, which is stored in the form of chemical energy in advance, continues to innovate the energy system.
The growth of lithium batteries shows the progress of society from another side. In fact, whether it is mobile phones, computers, cameras, or electric vehicles, the rapid development is based on the maturity of lithium battery technology.
The birth of lithium batteries
The battery has positive and negative poles. The positive electrode is also the cathode, which is usually made of more stable materials, while the negative electrode is the anode, which is usually made of "higher activity" metal materials. The positive and negative electrodes are separated by an electrolyte, and electrical energy is stored in the two electrodes in the form of chemical energy.
The chemical reaction between the two poles produces ions and electrons. The ions are transferred inside the battery and force the electrons to pass outside the battery to form a loop, thereby generating electricity.
In the 1970s, the oil crisis broke out in the United States, coupled with new requirements for power supplies in the military, aviation, and medicine fields, which promoted the exploration of rechargeable batteries to store renewable clean energy.
Among all metals, the specific gravity of lithium is extremely small and the electrode potential is extremely low. In other words, in theory, the lithium battery system can obtain the maximum energy density. Therefore, lithium has naturally entered the vision of battery designers.
However, due to the high activity of lithium, it may react violently when encountering water or air to burn and explode. Therefore, how to "tame" lithium has become the key to battery development. In addition, lithium easily reacts with water at room temperature. If lithium metal is to be used in the battery system, the introduction of non-aqueous electrolyte is very critical.
In 1958, Harris proposed the use of organic electrolytes as the electrolyte for metal galvanic batteries. In 1962, Chilton Jr. and Cook from Lockheed Missile and SpaceCo. of the US military put forward the idea of a "lithium non-aqueous electrolyte system".
Chilton and Cook designed a new type of battery using lithium metal as the negative electrode, Ag, Cu, Ni and other halides as the positive electrode, and low melting point metal salt LiC1-AlCl3 dissolved in propylene carbonate as the electrolyte. Although many problems of the battery make it remain conceptual and fail to be commercialized, the work of Chilton and Cook opened the prelude to the research of lithium batteries.
In 1970, Japan's Matsushita Electric Company and the US military independently synthesized a new type of cathode material-carbon fluoride almost simultaneously. Matsushita Electric successfully prepared a crystalline carbon fluoride with the molecular expression (CFx)n (0.5≤x≤1) and used it as the positive electrode of a lithium primary battery. The invention of lithium fluoride primary battery is an important step in the history of lithium battery development. For the first time, "intercalation compound" was introduced into the design of lithium battery.
However, in order to achieve reversible charging and discharging of lithium batteries, the key lies in the reversibility of chemical reactions. At that time, most non-rechargeable batteries used lithium negative electrodes and organic electrolytes. Therefore, in order to realize rechargeable batteries, scientists began to work on reversible intercalation of lithium ions into layered transition metal sulfide positive electrodes.
Stanley Whittingham of ExxonMobil found that using layered TiS2 as the cathode material to measure the intercalation chemistry can achieve reversible charge and discharge, and the discharge product is LiTiS2.
In 1976, the battery developed by Whittingham achieved good primary efficiency. However, after repeated charging and discharging several times, because lithium dendrites are formed inside the battery, the dendrites grow from the negative electrode to the positive electrode, forming a short circuit, causing the risk of igniting the electrolyte and ultimately failing.
In addition, in 1989, due to a fire accident in the Li/Mo2 secondary battery, with the exception of a few companies, most companies withdrew from the development of lithium metal secondary batteries. Because of unsolvable safety issues, the development of lithium metal secondary batteries has basically stopped.
In view of the ineffectiveness of various improvements, research on lithium metal secondary batteries has stalled. In the end, the researchers chose a subversive solution, that is, a rocking chair battery, where the positive and negative electrodes of the lithium secondary battery are all served by intercalation compounds.
In the 1980s, Goodenough was studying the structure of layered LiCoO2 and LiNiO2 cathode materials at Oxford University in the United Kingdom. In the end, the researchers achieved reversible deintercalation of more than half of the lithium from the cathode material. This achievement finally gave birth to the birth of lithium-ion batteries.
In 1991, Sony introduced the first commercial lithium-ion battery (graphite anode, lithium compound cathode, and lithium salt dissolved in organic solvent as the electrode solution). Due to the characteristics of high energy density and different formulations of lithium batteries that can adapt to different use environments, lithium batteries are finally commercialized and widely used in the market.
Power battery for the future
Relying on the advantages of high energy density and high safety, lithium-ion batteries began to run wildly, quickly leaving other secondary batteries behind. In just over ten years, lithium-ion batteries have completely occupied the consumer electronics market and expanded to the field of electric vehicles, achieving remarkable achievements.
At this stage, lithium-ion batteries have become the most important power source for electric vehicles, and their development has undergone three generations of technology. Among them, the lithium cobalt oxide cathode is the first generation, lithium manganate and lithium iron phosphate are the second generation, and the ternary technology is the third generation. With the development of positive and negative materials in the direction of higher gram capacity and the gradual maturity and improvement of safety technologies, higher energy density cell technology is moving from the laboratory to industrialization and applied to more scenarios.
At present, from mobile phones and digital products to electric vehicles and ships, lithium-ion batteries have played an increasingly important role in our lives.
