An Exact Closed-Form Impedance Model for Porous-Electrode Lithium-Ion Cells

Abstract

Building a complete cell impedance model and quickly calculating its frequency response are essential for battery design, optimization, and online management. Based on the widely accepted pseudo-two-dimensional (P2D) model, we build a complete full-order partial-dierential-equation (PDE) model for porous-electrode lithium-ion cells that includes a configurable electrical double-layer model at the solid-electrolyte interface (SEI). With the help of a numeric method, cell impedance and frequency responses of the cell’s electrochemical variables at different locations inside the cell are obtained and analyzed. Moreover, in order to achieve the fast calculation of impedance and frequency responses, we derive transfer functions of the internal electrochemical variables, which give a set of exact closed-form equations for cell impedance and internal-variable frequency responses. The Nyquist plot results calculated by the closed-form equations are exactly consistent with the results of numeric simulations using the full-order model, which verifies the accuracy of the transfer functions and the effectiveness of the simplified method.

A study on half‐cell equivalent circuit model of lithium‐ion battery based on reference electrode

“…Based on the external characteristics of the battery, the ECM of the battery can be established, and the actual internal state of the battery can be estimated by combining the electrochemical theory of the battery. At present, the parameters of the ECM are mainly obtained through optimization parameter identification, 5,6 EIS fitting, and other methods 7‐9 . The electrochemical model (the P2D model is widely studied) is more complex, and the parameters have increased significantly compared with the ECM.…”

“…At present, the parameters of the ECM are mainly obtained through optimization parameter identification, 5,6 EIS fitting, and other methods. [7][8][9] The electrochemical model (the P2D model is widely studied) is more complex, and the parameters have increased significantly compared with the ECM. The model calculation is more complicated, requires more time, but has higher accuracy.…”

Experimental investigation of state‐of‐power measurement for lithium‐ion batteries

“…5 Besides, to ensure the safety and reliability of EVs, a well-designed battery management system (BMS) should be equipped. [6][7][8][9][10] The main functions of a BMS for an EV are to monitor, 11 diagnose, and manage the battery system and to ensure it in a stable state. [12][13][14][15] Accurate peak power estimation is one of the core functions.…”

“…After determining the battery model, another key issue is parameter identification. Some studies 8,10,25 used offline identification to obtain model parameters. Other studies 23,26,32 adopted online identification methods.…”

“…The critical problems restricting the development of LIBs are primarily their specific energy, 3 safety, 4 and durability 5 . Besides, to ensure the safety and reliability of EVs, a well‐designed battery management system (BMS) should be equipped 6‐10 . The main functions of a BMS for an EV are to monitor, 11 diagnose, and manage the battery system and to ensure it in a stable state 12‐15 .…”