*2.4. Experiments*

We applied the proposed GB modelling approach to a single lithium-ion battery cell. All experiments were carried out using a commercial single cell of the Chinese manufacturer CALB, model CA180FI. The large-format prismatic cell has a nominal capacity of 180 Ah and a nominal voltage of 3.2 V. It uses LFP at the positive electrode and graphite at the negative electrode. The cell was investigated experimentally under a controlled laboratory environment (climate chamber CTS 40/200 Li) using a battery cycler with fourwire measurement (Biologic VMP3). Details on the cell and characterisation methods can be found in our previous publication [18]. Here we carried out additional measurements for GB model parameterisation and testing.

We measured experimental data sets representing several different operation scenarios. Constant current constant voltage (CCCV) charge and discharge curves were measured with different C-rates of 0.1 C, 0.28 C and 1 C (corresponding to 18 A, 50 A and 180 A, respectively) during the CC phase. The upper and lower cut-off voltages were 3.65 V and 2.5 V, respectively, and a cut-off current of the CV phase of C/20 was used. Additionally, one charge and one discharge curve were acquired with included current pulses: During 50 A CC operation, every two SOC-percent the current was reduced to 25 A for 30 s. This gives rise to two dynamic voltage answers, one at beginning and one at end of pulse.

Furthermore, two independent measurements for model testing were carried out. Firstly, the cell was cycled with 50 A between 25% and 75% SOC for around 44 h after fully charging, in the following referred to as half cycles. We started from a fully-charged cell and a first discharge to 25% SOC. The SOC cycling range was controlled by Coulomb counting. After 40 half cycles it was fully charged again. Secondly, the cell was fully charged and afterwards subjected to a dynamic load profile over 48 h representing a home storage battery in a single-family house. The synthetic load profile was taken from Ref. [41] (obtained with a load profile generator [42]), where a battery system of 5 kWh was investigated, and downscaled to the energy of the present cell (576 Wh). All measurements were carried out at an ambient temperature of *T* = 25 °C.

The number of data points per measurement series was large. Therefore, beginning from the first value, we decided to only keep measurement values if the current varied by |Δ*i*bat| ≥ 0.5 A or the measured voltage varied by |Δ*v*bat| ≥ 0.5 mV between two subsequent values. Table 1 summarises the characteristics of the used measurement data. The

number of used measurement values and the total duration are given for the different series. It is worth mentioning that these values vary widely. The shortest data set for training only spans *t* = 3932 s. The longest training data set takes *t* = 41,846 s. The test data sets cover much longer durations.

**Table 1.** Measurement data for training and testing the model.


The measurement data were made available and used as voltage versus time and current versus time series. The measured battery current served as the external input of the model. As proposed in [17], we interpolated the measured current values linearly for providing values at arbitrary times as required by the numerical solver (cf. below).
