Li-ion batteries Advantages and disadvantages!

The first work with lithium-based batteries began as early as 1912, but it was not until the early 1970s that the first non-rechargeable commercial lithium batteries appeared. Lithium is the lightest of metals and has a large negative electrochemical potential, so batteries based on it theoretically provide the highest specific energy capacity. Attempts to develop rechargeable lithium batteries continued in the 1980s, but invariably ended in failure due to safety concerns. Due to the high aggressiveness of lithium and the instability of the connections based on it, the batteries behaved inappropriately, especially during charging. Then the researchers switched to non-metallic lithium batteries that use lithium ions. Such technologies made it possible to achieve, of course, a lower energy density, but Li-Ion, subject to certain precautions, became completely safe both during charging and discharging. In 1991, Sony Corporation created the first commercially successful lithium-ion battery, and since then, the company's lithium-based batteries have been very popular, actively developing and improving. Other manufacturers have also mastered similar technologies and produce Li-Ion batteries for various devices. Today, lithium-based batteries are considered the most efficient and convenient in many respects: they have a large specific energy capacity (2-3 times higher than that of NiCd batteries), show good load characteristics both at low and high temperatures, have a small internal resistance and very long self-discharge (2-5% per month). At the same time, the Li-Ion battery does not have the disadvantages of NiMH and behaves similarly to NiCd (the form of their discharge characteristics is similar and differs only in voltage). A flat discharge curve ensures efficient use of stored energy in the required voltage spectrum. Now it is the most advanced and rapidly developing technology. Manufacturers are constantly improving batteries based on lithium ions. There is a constant search and improvement of electrode materials and electrolyte composition. In parallel, efforts are being made to improve the safety of lithium-ion batteries both at the level of current sources and only at the level of control electrical circuits. Li-Ion batteries are used mainly where high energy capacity is required with small size and weight. However, the lithium-based cells themselves are quite capricious, and to ensure the safety and durability of their operation, special control integrated circuits and control switches are required, which limit the peak voltage on each cell during charging and prevent too sharp a drop in the voltage at the cell terminals during discharge. In addition, they have temperature sensors and thermal fuses that monitor cell temperature to avoid dangerous overheating during charging/discharging (however, nickel-based batteries may also contain an internal thermal fuse and temperature sensor). The maximum charge/discharge current drops are limited and cannot exceed the rated current by more than two times. All this together is designed to protect the consumer from physical damage in the event of a violation of the battery's electrical operating modes. Observance of all precautions allows to avoid dangerous metallization of lithium, which occurred during overloads of early batteries of this type. Another problem is the degradation (aging) of Li-Ion batteries, which is why most manufacturers keep silent about their service life. Often times, battery damage caused by misuse, use of a faulty charger, overcooling or overheating, and sometimes manufacturer or supplier failure is attributed to memory effect, but lithium-based batteries are affected by it. Some inevitable reduction in capacity occurs already a year after release, regardless of whether the battery is in active use or not. After two or three years, many Li-Ion batteries irreversibly lose their capacity and, unlike NiCd batteries, cannot be regenerated. However, other chemical batteries (including disposable ones) are also prone to age-related degenerative effects. Degradation is especially noticeable in the same NiMH batteries if they have been exposed to high temperatures (including during storage). For Li-Ion batteries, manufacturers recommend a storage temperature of no higher than 15 °C. In addition, the battery must be charged during storage. Fields of application of Li-Ion batteries are portable computers, cellular phones and communicators. Moreover, manufacturers constantly improve the chemical properties of batteries and expand the range of applications (various improvements are issued every six months or even more often). Advantages of lithium-ion batteries: high specific energy capacity with great potential for further improvement; relatively low self-discharge - about 3-5% in the first month, then a decrease to 1-3% per month, but additionally about 3% per month is consumed by the control circuit (this is 2-3 times lower than NiCd and NiMH); high voltage of a single cell (3.6 vs. 1.2 V in NiCd and NiMH), which simplifies the design and reduces dimensions - one cell can be used where three were previously needed; low operating costs - no need for periodic discharge/charge; almost complete absence of "memory" - they can be put on charge whenever you want and kept in the charger for as long as you want (chargers for Li-Ion batteries automatically turn off after the end of the charge). Disadvantages of lithium-ion batteries: the need for protection circuits that limit the voltage and current during charging/discharging and monitor the temperature of the cell, which, in turn, practically eliminates the possibility of lithium metallization. However, this leads to an additional increase in cost and a decrease in battery reliability; the battery is safe only as long as it is not damaged; batteries of this type are prone to aging, and even when they are not used, and high temperature contributes to accelerated degradation. To reduce the aging process, it is necessary to store them at a low temperature and charged at 60-90%; moderate discharge current; high cost (2-3 times higher than NiCd and NiMH).