Lithium ion and advanced sensing techniques are improving continuously, to respond current demands and to evaluate different states of a battery which can not be evaluated using conventional measurements. In this sense, in this abstract advanced LiNiMnA/GrSi cell instrumented with strain and impedance spectroscopy is evaluated.
The cell is built with a high voltage (22 Ah), cobalt-free and lithium-rich LNMA (Li1.1Ni0.35Mn0.54Al0.01O2) cathode. The anode is graphite with 10% silicon (Si metal, not silicon oxide SiOx). Due to cell technology specification, the cell pressure has been preloaded to 200Kpa, to keep manufacturer specifications.
The cell has been instrumented with 3 strain gauges and an impedance spectroscopy, to track the evolution of these parameters during the tests. Two types of tests were designed, thermal cycle test (between 15ºC and 35ºC) and conventional cycle test (from C/10 to C/2) in full DoD spectrum.
The evolution of the impedance spectroscopy in conventional cycle aging test has been tested. The challenge is to correlate these results with battery temperature, current rate and SoC level. It has been found that both the magnitude and phase of the impedance follow the expected behavior described by the Arrhenius law. Both are dependent on the temperature. At higher temperatures the phase is shifting to more resistive behavior while at colder temperatures shifts to more capacitive behavior.
Similarly, the same challenges arise for the evolution of the strain gauges during conventional cycle and thermal cycle respectively. As it is shown in the poster, there is a straightforward relation between strain levels and battery voltage or SoC. This can be very useful for redundancy in voltage measurements of the cell or for overcharge protection of the cells. Further investigation is needed during the data processing to analyze this promising sensing techniques to detect Lithium-ion internal states such as SoC and other inner states.
All in all, advanced instrumentation have been installed into a cobalt free, high volage battery. It has been demonstrated that the information given by the advanced sensing could be useful for advanced SoX and further diagnosis, such as overcharge protection or redundancy measurements.