We often talk about ternary lithium batteries or iron-lithium batteries, which are named after lithium batteries according to positive active materials. In this paper, six common types of lithium batteries and their main performance parameters are summarized. As we all know, the specific parameters of the same technology line are not exactly the same. This paper shows the general level of the current parameters. Six kinds of lithium batteries include: lithium cobalt oxide (LiCoO 2), lithium manganate (LiMnO 4), lithium nickel cobalt manganate (LiNiMnCoO 2 or NMC), lithium nickel cobalt aluminate (LiNiCoAlO 2 or NCA), lithium iron phosphate (LiFePO4), lithium titanate (Li4Ti5O12
Lithium cobalt oxide
Its high specific energy makes lithium cobalt oxide 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 structure is shown in Figure 1.
Figure 1: Lithium cobalt oxide structure
The cathode has a layered structure. During discharge, lithium ions move from the anode to the cathode, and flow from the cathode to the anode during charging. The disadvantages of lithium cobalt are relatively short life, low thermal stability and limited load capacity (specific power). Like other cobalt-mixed lithium-ion batteries, lithium cobalt oxide uses graphite anode. Its cycle life is mainly limited by the solid electrolyte interface (SEI), which is mainly manifested in the gradual thickening of SEI film and the lithium plating problem during rapid charging or low-temperature charging. The newer material system adds nickel, manganese and/or aluminium to improve service life, load capacity and reduce costs.
Lithium cobalt oxide should not be charged and discharged at currents above capacity. This means that 18650 batteries with 2,400 mAh can only be charged and discharged at less than or equal to 2,400 mA. Forced rapid charging or application of loads higher than 2400mA will lead to overheating and overload stress. In order to obtain the best fast charging rate, the manufacturer recommends a charging rate of 0.8C or about 2,000 mA. The battery protection circuit limits the charging and discharging rate of the energy unit to a safe level of about 1C.
Hexagonal spider chart (Figure 2) summarizes the performance of lithium cobalt in specific energy or capacity related to operation; specific power or ability to provide large current; safety; performance in high and low temperature environments; life including calendar and cycle life; cost characteristics. Other important features not shown in the spider chart include toxicity, rapid charging capacity, self-discharge and shelf life.
Figure 2: Spider chart of average lithium cobalt batteries.
Lithium cobalt has excellent performance in high specific energy, but it can only provide general performance in power characteristics, safety and cycle life.
|voltage||Nominal value is 3.60V; typical operating range is 3.0-4.2V/battery|
|Specific energy (capacity)||150-200 Wh/kg. Special batteries provide up to 240Wh/kg.|
Charging (C Rate)
|0.7-1C, charging to 4.20V (most batteries); typical charging time is 3 hours; more than 1C charging current will shorten the battery life.|
1C; discharge cut-off voltage 2.50V. The discharge current above 1C will shorten the battery life.
|Circle life||500-1000, depending on discharge depth, load and temperature|
|Thermal runaway||150 degrees C (302 degrees F). Full-filled state easily leads to thermal runaway|
|application||Very high specific energy, limited specific power. Cobalt is expensive. It is used as an energy battery. Market share is stable.|
Very high specific energy, limited specific power. Cobalt is expensive. It is used as an energy battery. Market share is stable.