Characteristics and parameters of lithium cobaltate (LiCoO 2) battery
We often talk about ternary lithium batteries or iron-lithium batteries, which are named after the positive active material. Six common lithium battery types and their main performance parameters, the same technical route of the battery, the specific parameters are not exactly the same, this article shows the general level of the current parameters. The six lithium batteries specifically include: lithium cobalt oxide (LiCoO2), lithium manganate (LiMn2O4), lithium nickel cobalt manganese oxide (LiNiMnCoO2 or NMC), lithium cobalt aluminum aluminate (LiNiCoAlO2 or NCA), lithium iron phosphate (LiFePO4) , lithium titanate (Li4Ti5O12). Let us first look at the performance and parameters of lithium cobalt oxide (LiCoO2) batteries.
Lithium cobaltate (LiCoO 2) battery
Its high specific energy makes lithium cobalt oxide a popular choice for mobile phones, notebooks and digital cameras. The battery consists of a cobalt oxide cathode and a graphite carbon anode. The cathode has a layered structure in which lithium ions move from the anode to the cathode during discharge, and the charging process flows in the opposite direction. The structure is shown in the figure below.
Lithium cobaltate structure
The cathode has a layered structure. During discharge, lithium ions move from the anode to the cathode; during charging, the flow flows from the cathode to the anode.
Lithium cobalt oxide has the disadvantage of relatively short life, low thermal stability and limited load capacity (specific power). Like other cobalt-mixed lithium-ion batteries, lithium cobalt oxide uses a graphite anode, and its cycle life is mainly limited by the solid electrolyte interface (SEI), which is mainly manifested by the gradual thickening of the SEI film, and the anodic plating of the fast charging or low-temperature charging process. Lithium problem. Newer material systems add nickel, manganese and/or aluminum to increase life, load capacity and reduce costs.
Lithium cobaltate should not be charged and discharged at a current higher than the capacity. This means that an 18650 battery with 2,400 mAh can only be charged and discharged at 2,400 mA or less. Forcing rapid charging or applying a load higher than 2400 mA can cause overheating and overload stress. For the best fast charging, the manufacturer recommends a charge rate 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 hexagonal spider map (Figure 2) summarizes the performance of lithium cobalt oxide in terms of specific energy or capacity associated with operation; specific power or ability to provide large currents; safety; performance in high and low temperature environments; lifetime including calendar life and cycle Life; cost characteristics. Other important features not shown in the spider map include toxicity, fast charging capability, self-discharge, and shelf life.
Due to the high cost of cobalt and the significant performance improvements brought about by mixing materials with other active cathode materials, lithium cobalt oxide is being gradually replaced by lithium manganate, especially NMC and NCA.
Spider map of the average lithium cobalt oxide battery
Lithium cobaltate excels in high specific energy, but only provides general performance in terms of power characteristics, safety and cycle life.
|Lithium cobalt oxide: LiCoO2 cathode (about 60% Co), graphite anode|
Short type: LCO or Li-cobalt. Since 1991
|Voltage||The nominal value is 3.6V; the typical working range is 3.0-4.2V/battery|
|Energy ratio||150-200Wh/kg, special battery provides up to 240Wh/kg|
|Charging (C rate)||0.7-1C, charging to 4.20V (most batteries); typical charging time is 3 hours; charging current above 1C will shorten battery life|
|Discharge (C rate)||1C; discharge cut-off voltage 2.50V, discharge current above 1C will shorten battery life|
|Cycle life||500-1000, related to depth of discharge, load, temperature|
|Thermal runaway||150 ° C, full charge state is easy to bring thermal runaway|
|application||Cell phone, tablet, laptop, camera|
|Comment||Very high energy ratio, limited power ratio, cobalt is very expensive, used as an energy battery, and the market share is stable.|