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Analyze the calculation formula of common lithium battery parameters

by:Vglory      2021-04-11
The calculation formula of lithium battery parameters is commonly used (1) Theoretical capacity of the electrode material The theoretical capacity of the electrode material, that is, the capacity supplied by the assumption that all lithium ions in the material participate in the electrochemical reaction, calculated as follows: Among them, the Faraday constant ( F) represents the amount of charge per mole of electrons, the unit is C/mol, which is the product of Avogadro's constant NAu003d6.02214×1023mol-1 and the basic charge eu003d1.602176×10-19C, and its value is 96485.3383±0.0083C /mol Therefore, the calculation formula for 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 NCM(1:1) (lini1/3co1/3mn1/3o2) can be obtained It is 96.461g/mol, its theoretical capacity is 278mAh/g, and the mass of LiCoO2mol is 97.8698g/mol. If all lithium ions come out, 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 6c mole is 72.066g/mol, 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 desorption coefficient of lithium ion is less than 1, and the actual grams of material is: actual grams of material u003d actual grams of lithium ion × theoretical capacity (2) battery design capacity battery design capacity u003d Coating density × active material ratio × active material grams × electrode coating area Among them, the surface density is a key design parameter, which is important in the control of the coating and rolling process. When the compaction density is pressed, 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 this increase is limited. The increase in the migration resistance of lithium ions in the electrolyte is an important factor that affects the characteristics of the multiplier in the thick film. Taking into account the porosity and curvature of the pores, the migration distance of ions in the pores is many times larger than the thickness of the sheet. (3) N/P ratio: grams of negative active material × density of negative active material × ratio of negative active material content u0026pide; (gram of positive active material × density of positive active material × ratio of positive active material content) N/ of graphite cathode battery P should be greater than 1.0, generally 1.04~1.20. This is important for safe design and to prevent the evolution of lithium anodes. Process performance, such as coating deviation, should be considered during design. But when the N/P is too large, the irreversible capacity loss of the battery leads to low battery capacity and lower battery energy density. Regarding the lithium titanate negative electrode, the excess design of the positive electrode is adopted, and the battery capacity is determined by the capacity of the lithium titanate negative electrode. Too much positive electrode design is conducive to improving the high-temperature performance of the battery: high-temperature gas mainly comes from the negative electrode. In the over-positive electrode design, the negative electrode potential is low, and it is easy to form an SEI film 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 pole piece coating is as follows: Taking into account the extension of the metal sheet during rolling, the calculation formula for the surface density of the coating after rolling is as follows : The coating is composed of active material phase, carbonaceous cement phase and pores. The porosity calculation formula is as follows: In the formula, the average density of the coating is: (5) The first effect, the first effect u003d the first discharge capacity/the first charging capacity. In daily processing, it is generally converted into a part of Expenses, then part of the expenses will be supplemented before being discharged. Therefore: the first effect u003d (converted to charge capacity + divide the capacity to supplement the capacity) / remove the capacity 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 Weight Statement: Some pictures and content of articles published on this site are from In the Internet, if there is any infringement, please contact to delete the previous article: Requirements for the vehicle lithium-ion battery supervision system
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