Mathematical modelling, simulation, optimization, and model-based diagnostics of lithium-ion batteries (LIBs) are broad and growing scientific disciplines. Among many different modelling techniques, equivalent circuit models (ECM) are widely used in practical applications because of their relative simplicity (hence, low computational cost and therefore embeddable), ease of parameterization (because a battery is an electrical system, it can be well-described by electrical circuit elements), and nevertheless a high fidelity of the simulation output. ECMs can be simulated either in the frequency domain or in the time domain. In the frequency domain, they are used to simulate or analyze electrochemical impedance spectroscopy (EIS). In the time domain, they are used to simulate typical battery operation scenarios such as constant-current discharge or pulse tests.

Despite their broad usage, there are surprisingly few open-source codes for simulating battery ECMs in the time domain. Two prominent examples are BatPar, specialized on parameter identification; and PyECN, specialized on 3D electro-thermal behavior of cells. To the best of our knowledge, there are no other scientifically-published open-source time-domain ECM codes. Here we close this gap for the community. This poster presentation introduces LIBquiv, a MATLAB class for time-domain simulation of battery ECMs. LIBquiv has two key features, (1) flexibility and (2) ease of use:
(1) Flexibility: LIBquiv is able to simulate ECMs of various complexity. Depending on the parameterization, LIBquiv can represent simple, empirical ECMs or more complex, physics-informed ECMs including aging-sensitive and thermal ECMs.
(2) Ease of use: LIBquiv is object-oriented. This allows a quite intuitive use by handling the battery object just like a real battery would be operated experimentally. Simple, one-line commands allow constant-current (CC), constant-voltage (CV) or constant-power (CP) simulations including cut-off criteria.

LIBquiv has been used in several previous publications, the investigated models including large-format lithium iron phosphate (LFP) cells and cylindrical Panasonic cells with aging. Full parameter sets of these and other examples are provided with the code. The code is available on GitHub at https://github.com/ines-energy/LIBquiv .