How to calculate the lithium battery parameters?

How to calculate the lithium battery parameters? (1) The theoretical capacity of the electrode material The theoretical capacity of the electrode material, that is, the capacity supplied by assuming that all lithium ions in the material participate in the electrochemical reaction, is calculated by the following formula: Among them, the Faraday constant (F) represents every The amount of charge carried by a mole of electrons, in C/mol, is the product of the Avogadro constant NAu003d6.02214×1023mol-1 and the element charge eu003d1.602176×10-19C, and its value is 96485.3383±0.0083C/mol. The formula for calculating the theoretical bearing capacity of mainstream materials is as follows: The molar mass of LiFePO4 is 157.756g/mol, and its theoretical capacity is: Similarly, the molar mass of the ternary material NCM(1:1) (lini1/3co1/3mn1/3O2) is 96.461 g/mol, its theoretical capacity is 278mAh/g, and the molar mass of LiCoO2 is 97.8698g/mol. If all lithium ions are released, its theoretical capacity is 274mah/g. In the graphite negative electrode, when the lithium embedding amount is the largest, a lithium-carbon intercalation compound is formed, the chemical formula is LiC6, that is, 6 carbon atoms are combined with 1 lithium atom. The mass of 6cmol is 72.066g/mol, and the maximum theoretical capacity of graphite is: silicon anode, Li4+22+5+e-22↔Li22Si5 shows that the molar mass of pentasilicon is 140.430 g/mol, five silicon atoms and Li 22 , Is the theory of silicon anode capacity: these calculated values u200bu200bare the theoretical capacity. In order to ensure the reversibility of the material structure, the actual de-intercalation coefficient of lithium ions is less than one. The actual material gram capacity is: actual material gram capacity u003d lithium ion embedding coefficient × theoretical capacity (2) battery design capacity battery design capacity u003d coating layer density × active material ratio × active material grams × electrode coating area where the surface density is A key design parameter is important in the coating and rolling process control. When the compaction density is constant, the increase of the coating density means that the thickness of the electrode increases, the electron transfer distance increases, and the electron resistance increases, but the degree of addition is limited. In the thick electrode film, the increase of the lithium ion migration resistance in the electrolyte is an important reason that affects the characteristics of the multiplier. Considering the interlacing of porosity and pores, the migration distance of ions in the pores is several times the thickness of the electrode film. (3) N/P ratio G negative electrode active material capacity × negative electrode active material density × content ratio of negative electrode active material u0026pide; (G positive electrode active material capacity × positive electrode active material density × content ratio in the positive electrode active material) The N/P of the graphite negative electrode battery is greater than 1.0, generally 1.04~1.20. This is important for safety design and to prevent the evolution of negative electrode lithium. The design should consider the process capacity, such as coating deviation. However, when the N/P is too large, the irreversible capacity loss of the battery will cause the battery capacity to be too low and the battery energy density to decrease. The lithium titanate negative electrode adopts the design of excess positive electrode, and the battery capacity is determined by the capacity of the lithium titanate negative electrode. Over-design of the positive electrode is conducive to improving the high-temperature performance of the battery: high-temperature gas mainly comes from the negative electrode. When the positive electrode is designed excessively, the negative electrode potential is low, and SEI is easily formed on the surface of lithium titanate. (4) The compaction density and porosity of the coating During the processing, the calculation formula for the compaction density of the battery electrode coating is as follows: Considering that the metal foil is stretched when the electrode plate is rolled, the surface of the coating after rolling The density calculation formula is as follows: The coating is composed of active material phase, carbon rubber phase and pores. The porosity calculation formula is as follows: In the formula, the average density of the coating is: (5) Main effect initial effect u003d first discharge capacity/first charge capacity In daily processing, it is usually converted into volume first, and then The volume is divided into several parts, and a part of it is charged, and then the electricity is added to the volume, and then discharged, so: initial effect u003d (formation of charge capacity + new capacitance)/capacitor first discharge capacity (6) energy density volume Energy density (Wh/L) u003d battery capacity (mAh) × 3.6 (V) / (thickness (cm) × width (cm) × length (cm)) mass energy density (Wh/KG) u003d battery capacity (mAh) × 3.6(V)/Battery statement: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete the previous one: Six advantages of lithium batteries