Aging dataset LCO battery with mechanical measurements

Aging dataset of a commercial 22Ah LCO-graphite pouch Li-Po battery.

The cycling procedure involves aging steps consisting of 22 aging cycles at 1C CC discharge and C/2 CC-CV charge, with no pauses in between. Periodic RPTs are carried out after each aging step. In particular, two series of RPTs are alternated, referred to as RPT-A and RPT-B, with this pattern: 22 aging cycles -> RPT-A -> 22 aging cycles -> RPT-A + RPT-B -> repeat.

The RPT-A consists of three high rate cycles (1C CC discharge and C/2 CC-CV charge) with 1 hour rest.
The RPT-B consists of three high rate cycles (1C CC discharge and C/2 CC-CV charge) with 1 hour rest, one low rate cycle (C/20) and the HPPC test. In this way, high rate test cycles are carried out periodically every 25 cycles (22 aging + 3 test), whereas low rate test cycles and HPPC are carried out every 50 cycles. The exact number at which each reference performance test was carried out is reported in the sixth column of the data structure.

In total, 1125 cycles were achieved untill SOH 70%.

The cycling reference performance tests (high rate cycling 1C-C/2, and low rate cycling C/20-C/20) are reported in the MATLAB structure called Aging_Dataset_Cycling. On the other, the data of the HPPC tests are reported in the MATLAB structure called Aging_Dataset_HPPC.

The data structure of cycling reference performance tests is a MATLAB cell organized so that in the first row there are data of RPT-A (high rate cycles), and in the second row the data of RPT-B (low rate cycles). In the first column there are discharge data, in the second column the charge data, in the third column the data recorded in the one hour rest after discharge and in the fourth column the data recorded in the one hour rest after charge. In each element of this 2x4 matrix there is a cell containing the structures referring to each reference performance tests. The different reference performance tests are organized so that in the row there are the reference performance tests carried out at different aging cycles (detailed in the vector in the sixth column of the main data structure) and in the column there are the tests repeated at the same aging cycles for statistical studies. Generally RPT-A tests are repeated three times and RPT-B tests are repeated one times. Then, each cell, e.g. D{1,1}{1,1} contains a structure with the data of that test coded as explained in the bullet list below.

The data recorded during the reference performance test, reported in the data structure, were:

• Time test [s]. Variable name: Time.
• Battery temperature [°C]. Variable name: T_batt.
• Ambient temperature [°C]. Variable name: T_amb.
• Battery voltage [V]. Variable name: V_batt.
• Charging current [A]. Variable name: I_PS
• Discharging current [A]. Variable name: I_EL
• Laser sensor 1 reading [V]. Variable name: Las1
• Laser sensor 2 reading [V]. Variable name: Las2
• Battery deformation [mm], meant as the thickness change of the battery. Variable name: Dthk

Deformation measurements were carried out measuring the out-of-plane displacement of the two largest surfaces of the battery with a couple of laser sensors, as explained in these Figures. The two sensor readings are expressed in Volt, ranging from 0V (start measuring distance) to 10V (end measuring distance), and are proportional to the distance between the laser (fixed) and the battery surface (moving because of the thickness change). The reversible deformation within a single cycle is already computed in the variable Battery deformation and it is expressed in millimeter. The reversible deformation is computed as the sum of the two laser readings (1V = 1mm), net of the sum of the two initial laser readings. The single laser readings are useful to compute the irreversible deformation, namely how the thickness of the battery changes during aging. This is possible because the laser remained fixed during the whole aging test, and the reference was not lost. Therefore, to calculate the deformation of the battery at any given moment during the aging test, it is necessary to sum the two laser readings at the given moment and subtract the sum of the two initial laser readings.

Example of the data structure: D{1,1} contains all the discharge data of all the RPT-A tests. In total, there are 47 lines and 4 columns, because RPT-A tests were conducted at 47 different aging levels (the respective number of cycles is reported in the vector stored in the sixth column first row of the main data structure), and the tests are repeated up to 4 times at the same aging level, even if most of the time were repeated just three times. Then, D{1,1}{1,1} contains the discharge data of the first reference performance(RPT-A) test carried out at the first aging level (10 cycles), D{1,1}{1,2} contains the discharge data of the second reference performance(RPT-A) test carried out at the first aging level, D{1,1}{2,1} contains the discharge data of the first reference performance (RPT-A) test carried out at the second aging level (20 cycles), and so on. D{1,2} contains all the charge data of all the RPT-A tests and D{2,1} and D{2,2} contain all the discharge and charge data of the RPT-B (low rate-C/20) test. The substructures work similarly as described for D{1,1}.

The data structure of the HPPC reference performance tests is a MATLAB cell organized so that in the rows there are the data referring to different aging cycles, and the first ten columns correspond to the SOC at which the HPPC test is carried out, going from 100% to 10%. The 11th contains the number of aging cycles at which the test in that column was carried out. Each structure in this matrix refers to a single HPPC test and contains the following data:

• Time test [s]. Variable name: Time.
• Battery voltage [V]. Variable name: V_batt.
• Charging current [A]. Variable name: I_PS
• Discharging current [A]. Variable name: I_EL

Ambient temperature was controlled with a climatic chamber and it was kept constant at 20°C during all the tests.