Lithium-ion batteries are a type of rechargeable battery that primarily functions by the movement of lithium ions between the positive and negative electrodes. During charging and discharging, Li+ ions repeatedly insert and extract between the two electrodes: during charging, Li+ ions extract from the positive electrode, pass through the electrolyte, and insert into the negative electrode, leaving the negative electrode in a lithium-rich state; the reverse occurs during discharging.
Lithium-based batteries are divided into lithium batteries and lithium-ion batteries. Mobile phones and laptops use lithium-ion batteries, which are commonly referred to as lithium batteries. These batteries generally use materials containing lithium as electrodes and are representative of modern high-performance batteries. However, true lithium batteries are rarely used in everyday electronic products due to their inherent dangers.
The lithium-ion battery was first successfully developed by Sony Corporation of Japan in 1990. It involves embedding lithium ions into carbon (petroleum coke and graphite) to form the negative electrode (traditional lithium batteries use lithium or lithium alloys as the negative electrode). Common positive electrode materials include LixCoO2, LixNiO2, and LixMnO4. The electrolyte is typically LiPF6 + diethylene carbonate (EC) + dimethyl carbonate (DMC).
Petroleum coke and graphite, used as negative electrode materials, are non-toxic and abundant. Lithium ions are intercalated into carbon, overcoming the high reactivity of lithium and solving the safety issues inherent in traditional lithium batteries. The positive electrode, LixCoO2, achieves high levels of charge/discharge performance and lifespan, reducing costs. In short, the overall performance of lithium-ion batteries has improved. It is expected that lithium-ion batteries will occupy a large market share in the 21st century.
In 1970, Exxon's M.Whittingham used titanium sulfide as the positive electrode material and lithium metal as the negative electrode material to make the first lithium battery. The positive electrode material of the lithium battery is manganese dioxide or thionyl chloride, and the negative electrode is lithium. The battery has voltage after assembly and does not need to be charged. Lithium-ion batteries (Li-ion Batteries) are developed from lithium batteries. For example, the button batteries used in cameras in the past are lithium batteries. This type of battery can also be charged, but its cycle performance is not good. Lithium crystals are easily formed during charge and discharge cycles, causing internal short circuits in the battery. Therefore, this type of battery is generally prohibited from being charged. [2]
In 1982, R.R. Garwal and J.R. Selman of the Illinois Institute of Technology discovered that lithium ions have the property of intercalating into graphite; this process is rapid and reversible. At the same time, the safety concerns surrounding lithium-ion batteries made with metallic lithium were a major concern, so researchers attempted to utilize this property of lithium ions intercalating into graphite to create rechargeable batteries. The first usable lithium-ion graphite electrode was successfully fabricated by Bell Labs.
In 1983, M. Thackeray, J. Goodenough, and others discovered that manganese spinel is an excellent cathode material, possessing low cost, stability, and excellent electrical and lithium conductivity. Its decomposition temperature is high, and its oxidizing power is far lower than that of lithium cobalt oxide, thus avoiding the dangers of combustion and explosion even in the event of short circuits or overcharging.
In 1989, A. Manthiram and J. Goodenough discovered that using a polymeric anion cathode would produce a higher voltage.
In 1992, Sony Corporation of Japan invented the lithium-ion battery, which uses carbon material as the negative electrode and a lithium-containing compound as the positive electrode. During charging and discharging, no metallic lithium is present; only lithium ions are present. Subsequently, lithium-ion batteries revolutionized consumer electronics. Batteries using lithium cobalt oxide as the positive electrode material remain the primary power source for portable electronic devices to this day.
In 1996, Padhi and Goodenough discovered that phosphates with an olivine structure, such as lithium iron phosphate (LiFePO4), are safer than traditional cathode materials, especially in terms of high temperature resistance and overcharge resistance, which far exceeds that of traditional lithium-ion battery materials.
Looking back at the history of battery development, three characteristics emerge in the current global battery industry: first, the rapid development of green and environmentally friendly batteries, including lithium-ion batteries and nickel-metal hydride batteries; second, the shift from primary batteries to rechargeable batteries, which aligns with sustainable development strategies; and third, the further development of batteries towards smaller, lighter, and thinner designs. Among commercially available rechargeable batteries, lithium-ion batteries have the highest specific energy, especially polymer lithium-ion batteries, which enable the thinning of rechargeable batteries. Because of their high volumetric and gravimetric energy density, rechargeability, and lack of pollution, lithium-ion batteries possess the three major characteristics of current battery industry development, leading to rapid growth in developed countries. The development of the telecommunications and information markets, particularly the widespread use of mobile phones and laptops, has created market opportunities for lithium-ion batteries. Polymer lithium-ion batteries, with their unique safety advantages, will gradually replace liquid electrolyte lithium-ion batteries and become the mainstream lithium-ion battery. Polymer lithium-ion batteries are hailed as the "battery of the 21st century," ushering in a new era for rechargeable batteries, and their development prospects are very optimistic.
In March 2015, Sharp Corporation of Japan, in collaboration with Professor Isao Tanaka of Kyoto University, successfully developed a lithium-ion battery with a lifespan of up to 70 years. This prototype long-life lithium-ion battery has a volume of 8 cubic centimeters and can withstand 25,000 charge-discharge cycles. Sharp also stated that the battery's performance remained stable even after 10,000 actual charge-discharge cycles.
Steel shell/aluminum shell/cylindrical/flexible packaging series:
(1) Positive electrode - The active material is generally lithium manganese oxide or lithium cobalt oxide, or lithium nickel cobalt manganese oxide. Electric bicycles generally use lithium nickel cobalt manganese oxide (commonly known as ternary) or ternary + a small amount of lithium manganese oxide. Pure lithium manganese oxide and lithium iron phosphate have gradually faded out due to their large size, poor performance or high cost. Electrolytic aluminum foil with a thickness of 10-20 micrometers is used as the conductive electrode fluid.
(2) Separator - a specially shaped polymer film with a microporous structure that allows lithium ions to pass through freely, while electrons cannot pass through.
(3) Negative electrode - The active material is graphite or carbon with a similar graphite structure, and the conductive current collector uses electrolytic copper foil with a thickness of 7-15 micrometers.
(4) Organic electrolytes are carbonate solvents containing lithium hexafluorophosphate, while gel electrolytes are used for polymers.
(5) Battery casing - divided into steel casing (square type is rarely used), aluminum casing, nickel-plated iron casing (used for cylindrical batteries), aluminum-plastic film (soft packaging), etc., as well as the battery cap, which is also the positive and negative terminals of the battery.
Based on the different electrolyte materials used in lithium-ion batteries, lithium-ion batteries are divided into liquid lithium-ion batteries (LIB) and polymer lithium-ion batteries (PLB).
Lithium-ion batteries (Li-ion)
Rechargeable lithium-ion batteries are currently the most widely used batteries in modern digital products such as mobile phones and laptops. However, they are relatively delicate and should not be overcharged or over-discharged (as this will damage or render the battery unusable). Therefore, protective components or circuits are incorporated into the batteries to prevent damage to these expensive devices. Lithium-ion battery charging requires high precision, ensuring a termination voltage accuracy within ±1%. Major semiconductor manufacturers have developed various lithium-ion battery charging ICs to guarantee safe, reliable, and fast charging.
Mobile phones primarily use lithium-ion batteries. Proper use of lithium-ion batteries is crucial for extending battery life. Depending on the requirements of different electronic products, they can be made into flat rectangular, cylindrical, rectangular, and button-type batteries, and are also available in battery packs composed of several batteries connected in series and parallel. The rated voltage of lithium-ion batteries varies depending on the materials used, but is generally 3.7V, while lithium iron phosphate (LiFePO4) batteries are rated at 3.2V. The termination voltage for a fully charged battery is generally 4.2V, and for LiFePO4 it is 3.65V. The termination discharge voltage for lithium-ion batteries is 2.75V to 3.0V (battery manufacturers provide the operating voltage range or termination discharge voltage; these parameters may vary slightly, but are generally 3.0V for LiFePO4 and 2.5V for LiFePO4). Continuing to discharge below 2.5V (2.0V for LiFePO4) is called over-discharge, which can damage the battery.
Lithium-ion batteries with lithium cobalt oxide as the cathode are not suitable for high-current discharge. Excessive current discharge reduces discharge time (due to higher internal temperatures and energy loss) and may pose a danger. However, lithium iron phosphate batteries with a cathode can be charged and discharged at 20C or even higher currents (C is the battery capacity; for example, C=800mAh, a 1C charging rate means a charging current of 800mA), making them particularly suitable for electric vehicles. Therefore, the maximum discharge current specified by the battery manufacturer should be used in practice, and should be kept below this maximum. Lithium-ion batteries have specific temperature requirements; manufacturers provide charging, discharging, and storage temperature ranges. Overcharging can cause permanent damage to lithium-ion batteries. The charging current should be based on the battery manufacturer's recommendations, and a current-limiting circuit is required to prevent overcurrent (overheating). Commonly used charging rates are 0.25C to 1C. During high-current charging, battery temperature should be monitored to prevent overheating damage or explosion.
Lithium-ion battery charging is divided into two stages: first, constant current charging, and then constant voltage charging when the battery approaches the termination voltage. For example, an 800mAh battery has a termination charging voltage of 4.2V. The battery is charged at a constant current of 800mA (1C charging rate). Initially, the battery voltage rises at a large slope. When the battery voltage approaches 4.2V, it switches to constant voltage charging at 4.2V. The current gradually decreases, and the voltage change is minimal. When the charging current drops to 1/10-50C (the setting varies between manufacturers and does not affect usage), it is considered nearly fully charged, and charging can be terminated (some chargers start a timer after reaching 1/10C and end charging after a certain time).
