Six common lithium battery characteristics and parameters

We often talk about ternary lithium batteries or iron lithium batteries, which are all named after the positive active material. This article summarizes six common lithium battery types and their main performance parameters. As we all know, the same technical route of the cell, the specific parameters are not exactly the same, this paper shows the current general level of parameters. Three types of lithium batteries include lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4) and lithium nickel cobalt manganese oxide (LiNiMnCoO2 or NMC).

Lithium cobalt oxide (LiCoO2)

Its high specific energy makes it a popular choice for mobile phones, laptops and digital cameras. The battery consists of cobalt oxide cathode and graphite carbon anode. The cathode has a layered structure. During the discharge, lithium ions move from the anode to the cathode, while the charging process flows in the opposite direction.

The cathode has a layered structure. During discharge, lithium ions move from the anode to the cathode. Flow from cathode to anode during charging.

The disadvantages of lithium cobalt oxide are relatively short life, low thermal stability and limited load capacity (specific power). Like other cobalt-mixed lithium ion batteries, lithium cobalt oxide has a graphite anode, and its cycle life is mainly limited by the solid electrolyte interface (SEI), mainly manifested in the gradual thickening of SEI films and anodic lithium plating during rapid or low-temperature charging. Newer material systems add nickel, manganese and/or aluminum to improve life, load capacity and reduce costs. Lithium cobalt oxide shall not be charged or discharged at a current higher than the capacity. This means that 18650 batteries with 2,400mAh can only be charged and discharged at a rate of 2,400mA or less. Forcing a quick charge or applying a load higher than 2400mA can lead to overheating and overload stress. For optimal fast charging, the manufacturer recommends a charging ratio of 0.8C or about 2,000mA. The battery protection circuit limits the charging and discharging rate of the energy unit to a safe level of about 1C. The hexagon spider diagram summarizes lithium cobalt oxide performance in terms of specific energy or capacity associated with operation; Specific power or the ability to provide a large current; Safety; Performance under high and low temperature environment; Life includes calendar life and cycle life; Cost characteristics. Other important features not shown in the spider diagram include toxicity, rapid charge capacity, self-discharge, and shelf life. Due to the high cost of cobalt and the significant performance improvements achieved by mixing it with other active cathode materials, lithium cobalt oxide is gradually being replaced by lithium manganate, particularly NMC and NCA.

Lithium manganate (LiMn2O4)

Spinel lithium manganate battery was first published in 1983 in the materials research report. In 1996, Moli energy commercialized lithium-ion batteries using lithium manganate as a cathode material. The structure forms a three-dimensional spinel structure, which can improve the ion flow on the electrode, thus reducing the internal resistance and improving the current carrying capacity. Another advantage of spinel is high thermal stability, improved safety, but the cycle and calendar life is limited. Low internal resistance allows fast charging and large current discharge. The 18650 cell, lithium manganate battery can discharge at a current of 20-30a and has moderate heat accumulation. It can also apply a load pulse of up to 50A1 seconds. In the electricity flow continuous high load can lead to heat accumulation, battery temperature should not exceed 80 ° C (176 ° F). Lithium manganate is used in power tools, medical devices, as well as hybrid and pure electric vehicles. Figure 4 illustrates the formation of a three-dimensional crystal skeleton on the cathode of a lithium manganate battery. The spinel structure usually consists of a diamond shape connected into a crystal lattice, which usually appears after battery formation.

Lithium manganate cathode crystallization has a three-dimensional skeleton structure formed after the formation. Spinel provides low resistance but lower specific energy than lithium cobalt oxide.

Lithium nickel cobalt manganate (LiNiMnCoO2 or NMC)

One of the most successful lithium ion systems is the cathode combination of nickel manganese cobalt (NMC). Similar to lithium manganate, this system can be customized for use as an energy battery or a power battery. For example, an NMC in an 18650 battery under medium load conditions has a capacity of approximately 2,800mAh and can provide a 4A to 5A discharge current; the same type of NMC is optimized for a specific power with a capacity of only 2,000mAh, but can provide 20A Continuous discharge current. The silicon-based anode will reach 4000mAh or more, but the load capacity is reduced and the cycle life is shortened. The silicon added to the graphite has a defect that the anode expands and contracts with charging and discharging, so that the mechanical stress of the battery is largely unstable. The secret of NMC lies in the combination of nickel and manganese. Similar to this is the salt, in which the main components sodium and chloride are themselves toxic, but they are mixed as a seasoning salt and a food preservative. Nickel is known for its high specific energy, but its stability is poor; the manganese spinel structure can achieve low internal resistance but low specific energy. The two active metals have complementary advantages. The NMC is the battery of choice for power tools, electric bikes and other electric power systems. The cathode combination is typically one-third nickel, one-third manganese and one-third cobalt, also known as 1-1-1. This provides a unique blend that also reduces raw material costs due to reduced cobalt content. Another successful combination is NCM, which contains 5 parts nickel, 3 parts cobalt and 2 parts manganese (5-3-2). Other different amounts of cathode material combinations can also be used. Due to the high cost of cobalt, battery manufacturers have switched from cobalt to nickel cathodes. Nickel-based systems have higher energy density, lower cost, and longer cycle life than cobalt-based batteries, but their voltages are slightly lower. New electrolytes and additives can charge a single battery to more than 4.4V, increasing power.

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