The birth process of lithium-ion batteries

The birth process of lithium-ion batteries

The birth of everything has a certain background. The production of lithium-ion batteries is also inseparable from this. The oil crisis in the 1960s and 1970s forced people to look for new alternative energy sources. As metal lithium is the lightest of all metals, has the lowest redox potential, and has the highest mass energy density, lithium batteries have become one of the alternative energy sources. The commercialization of primary lithium batteries was achieved in the early 1970s. There are many types of lithium primary batteries, among which the common ones are Li//Mn, Li//C (x<1), and CuLi//SO. The first two are mainly for civilian use, while the latter are mainly for military use. Compared with the general primary battery, it has obvious advantages:

① High voltage, traditional dry batteries are generally 1.5V, while lithium primary batteries can be as high as 3.9V;

② High specific energy, 2 to 5 times that of traditional zinc anode batteries;

③ Wide operating temperature range, lithium primary battery can generally work at -40~70℃;

④Large specific power, can discharge large current;

⑤Stable discharge, most lithium primary batteries have a stable discharge curve;

⑥ long storage time, is expected to be up to 10 years.

Therefore, under the promotion of lithium primary batteries, research on rechargeable and dischargeable lithium secondary batteries has been started almost at the same time as the research on lithium primary batteries.

Read more: Advantages and disadvantages of lithium ion batteries

With the increasing population and limited earth resources, people are forced to improve the utilization rate of resources, and the use of rechargeable batteries is one of the effective ways, thus promoting the research and development of lithium secondary batteries. Check out environmentally friendly rechargeable lead-acid replacement lithium battery products – go now.

With the increasing awareness of environmental protection, the use of toxic metals such as lead and cadmium is increasingly restricted, so it is necessary to find new rechargeable batteries that can replace traditional lead-acid batteries and nickel-cadmium batteries. Lithium secondary batteries are naturally one of the strong candidates.

The continuous development of electronic technology promotes the development of various electronic products towards miniaturization, such as the popularization of portable phones, miniature cameras, notebook computers, etc., and the development of miniaturization must be accompanied by the miniaturization of power supplies. The capacity of traditional lead-acid batteries, etc. is not high, so new battery systems must also be found. The advantages of lithium primary batteries make lithium secondary batteries a strong candidate.

Before the end of the 1980s, people mainly focused on the lithium secondary battery system with metal lithium and its alloys as the negative electrode. However, when lithium is charged, the uneven surface potential (unevenness) of the metal lithium electrode causes uneven surface potential, resulting in uneven deposition of lithium. This non-uniform deposition process causes lithium to deposit too quickly in some locations, resulting in dendrite-like crystals (dendrites). When the dendrite develops to a certain extent, on the one hand, it will break, resulting in “dead lithium”, which will cause the irreversibility of lithium; on the other hand, what is more serious is that the dendrites pass through the separator and connect the positive and negative electrodes, resulting in a short circuit, generating a large amount of heat, causing the battery to catch fire or even explode, which brings serious safety hazards. One of the representative ones is the Li//TiS2 system studied by Exxon in the late 1970s. The charging and discharging process is shown as follows:

The birth process of lithium-ion batteries

Although Exxon has not been able to commercialize the lithium secondary battery system, its role in promoting lithium secondary battery research cannot be underestimated. The main reason why the lithium secondary battery with metal lithium or its alloy as the negative electrode can not be commercialized is that the problem of cycle life has not been fundamentally solved, because:

① As mentioned above, during the charging process, the surface of lithium cannot be very uniform, so it is impossible to fundamentally solve the problem of dendrite growth, and thus can not fundamentally solve the safety hazard;

② Lithium metal is relatively active, and it is easy to react with non-aqueous liquid electrolytes, resulting in high pressure and danger.

Then in 1980, Goodenough et al. proposed lithium cobalt oxide (LiCo) as a positive electrode material for lithium rechargeable batteries, which opened the prototype of lithium ion batteries. In 1985, it was found that carbon materials can be used as negative electrode materials for lithium rechargeable batteries, and lithium ion batteries were invented. In 1986, the prototype design of lithium ion batteries was completed, and the commercialization of Li//Mo rechargeable batteries was realized. However, the fire accident of Li//Mo rechargeable battery in 1989 completely led to the end of the rechargeable battery, and the main reason was that the safety problem was not really solved. “It came out after a long call”, people finally found in the late 1980s and early 1990s that carbon materials with a graphite structure were used to replace the metal lithium negative electrode, and the positive electrode used composite oxides of lithium and transition metals such as lithium cobalt oxide. The rechargeable battery system constituted in this way can successfully solve the safety hazard existing in the lithium secondary battery with metal lithium or its alloy as the negative electrode, and the energy density is higher than that of the previous charge-discharge battery. At the same time, since the potential of the intercalation compound Li formed by the metal lithium and the graphitized carbon material is less than 0.5V different from the potential of the metal lithium, the voltage loss is not large. During the charging process, lithium intercalates into the layered structure of graphite and escapes from the layered structure during discharge. This process is reversible and the cycle performance of the formed lithium secondary battery system is very good. In addition, carbon materials are cheap and non-toxic, and it is relatively stable in the air when it is in the discharge state, which avoids the use of active metal lithium on the one hand, and avoids the generation of dendrites on the other hand, which significantly improves the cycle life and fundamentally solves the safety problem. Therefore, the secondary battery was commercialized in 1991.

According to the classic electrochemical naming rules, the name of the rechargeable battery should be the positive electrode in the front and the negative electrode in the back, so the battery system should be named “cobalt oxide lithium-graphite rechargeable battery”. But this is not easy for ordinary people to remember, so it should have a simple name. Since the charging and discharging process is realized by the movement of lithium ions, people call it “lithium ion battery”. As for the naming of this battery system, there should be no full blame, because it is impossible to understand its nature from the name alone. In my country, in order to facilitate communication, the business community refers to “lithium-ion batteries” as “lithium batteries” for short.