Due to its improved capacity compared to graphite, silicon is a promising candidate to handle the demands of high-energy batteries. With the introduction of new materials, further aspects of the battery system must be reconsidered. One of those aspects is the heat generation during the charging and discharging of a cell, which delivers important information for the development of cooling systems, the battery management system and the overall performance of the cell. Since the reversible heat presents an important contribution to the overall heat generation during cycling, the entropy coefficient is the main value that needs to be determined. This study evaluates the entropy coefficient of custom-produced 2032 coin half-cells with lithium counter electrodes, containing 45 wt% nanosilicon and 45 wt% carbon black. The potentiometric method, utilizing VR and self-discharge curves, produced reliable results, yielding entropy coefficient values between 95% SoC and 10% SoC during delithiation. These values of the entropy coefficient are consistently negative. Furthermore, ICA measurements identified two phase transitions during delithiation, with these transitions shifting to lower SoC as SoH decreases, impacting the slope of the entropy coefficient.

The demand for high-energy cells in electric vehicles is driving the need for new battery materials, such as high-capacity silicon anodes. To fully integrate and utilize the potential of these materials, optimization of battery management systems and cooling solutions is essential. Calorimetry provides necessary data for such optimization through in-operando heat flux measurements. In this study, we evaluated the impact of temperature on the capacity and heat generation of custom-produced coin half-cells, each containing 45 wt% nano-silicon as the sole active material. Twelve half-cells were divided into four groups, with each group tested at a different temperature (15 °C, 25 °C, 40 °C, and 60 °C). To determine the material-specific heat flux signature of silicon and capacity changes, each group underwent calorimetry and incremental capacity analysis, repeated after 25 cycles. Our results indicate a beneficial effect of elevated temperatures on the capacity of silicon anodes and a reduction in dissipated heat. Additionally, for the first time, we observed a deviation from the characteristic heat flux signature of silicon anodes at sub-room temperatures, appearing as an additional exothermic peak during delithiation.

The heat generation of lithium-ion batteries is a critical parameter, as it significantly affects cell temperature. Poor thermal management can lead to elevated cell temperatures, accelerating side reactions, reducing cell lifetime, and, in extreme cases, causing thermal runaway. Therefore, understanding heat generation is crucial for the commercialization of emerging battery materials. Due to its high energy density, lithium–nickel–manganese–oxide (LNMO) is an attractive candidate for next-generation cathode materials; however, the composition of its heat generation is not yet fully understood. To address this, the state-of-charge (SoC)-dependent entropy coefficient and resistance of disordered LNMO cathodes are determined using the potentiometric method. The results show that both values are strongly influenced by the redox reactions of Ni and Mn. The entropy coefficient varies between 5.2 and −32.4 J ${\mathrm{mol}}^{-1}{\mathrm{K}}^{-1}$, depending on the SoC. Furthermore, the resistance exhibits a switching dependence on kinetics and mass transfer. The resulting heat flux calculations indicate that, at SoC < 20%, heat generation is dominated by the kinetic behavior of LNMO, leading to two exothermal peaks during discharge and one exothermal peak during charge. This behavior is validated through a comparison with a low-current calorimetric measurement.

Quantifying heat generation across current, temperature, and material variations advances understanding of thermal behavior in high-voltage LNMO cathodes.