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A Comprehensive Guide to Common Lithium Battery Parameters and Calculation Formulas
1. The theoretical capacity of electrode materials refers to the capacity that can be provided by assuming that all lithium ions in the material participate in electrochemical reactions. Its value is calculated by the following formula: where Faraday constant (F) represents the charge carried by each mole of electron, in C/mol. It is the product of Avogadro number NA=6.02214 × 1023mol-1 and elementary charge e=1.602176 × 10-19 C, and its value is 96485.3383 ± 0.0083 C/mol
Therefore, the mainstream formula for calculating the theoretical capacity of materials is as follows:
The molar mass of LiFePO4 is 157.756 g/mol, and its theoretical capacity is as follows: Similarly, the molar mass of the ternary material NCM (1:1:1) (LiNi1/3Co1/3Mn1/3O2) is 96.461 g/mol, and its theoretical capacity is 278 mAh/g. The molar mass of LiCoO2 is 97.8698 g/mol. If all lithium ions are removed, its theoretical gram capacity is 274 mAh/g
In graphite negative electrode, when the amount of lithium insertion is maximum, a lithium carbon interlayer compound is formed, with the chemical formula LiC6, which means that 6 carbon atoms are combined with one Li. The molar mass of 6 carbons is 72.066 g/mol. The maximum theoretical capacity of graphite is: for silicon negative electrode, it is composed of 5Si+22Li++22e- ↔ Li22Si5 shows that the molar mass of 5 silicon atoms is 140.430 g/mol, and 5 silicon atoms combine with 22 Li atoms. Therefore, the theoretical capacity of the silicon negative electrode is: These calculated values are the theoretical gram capacity. To ensure the reversibility of the material structure, the actual lithium-ion deintercalation coefficient is less than 1. The actual gram capacity of the material is: the actual gram capacity of the material=the lithium-ion deintercalation coefficient x the theoretical capacity
