Understanding Low Temperature Limitations of LiNi_0.5Co_0.2Mn_0.3O₂ Cathodes for Li-Ion Batteries

Abstract

A major drawback of today's Li-ion batteries is inadequate performance at low temperatures, which slows down user-friendliness and market expansion of electromobility. Due to the systems complexity, many possible low-temperature limitations and various dependencies on the operating conditions exist. The origin of the performance limitations at low temperatures is still controversial and not completely clarified. We herein demonstrate a comprehensive analysis of the performance limitations at low temperatures using a LiNi0.5Co0.2Mn0.3O2-based cathode. To separate the overvoltage phenomena, the complex system is decomposed as much as possible and individual aspects are investigated separately. Complementary electrochemical methods are employed to quantify the C-rate and SOC dependence of the individual overvoltage phenomena. Based on comprehensive analysis of the intercalation kinetics, mass and charge transport, we obtain a coherent picture of the performance limitations as a function of operating conditions. This can serve for targeted optimization or parameterizing models to simulate battery behavior. However, the present work is not only concerned with identifying the low-temperature limits of the system studied but also shows how the rate-determining step of the electrode reaction can be efficiently identified as a function of temperature, SOC, and C-rate, which can serve as guideline for future work.

Boosting the Low-Temperature Performance of Graphite Anodes by Creating an Electrochemically Active Interface

“…21 To elucidate the rate-limiting steps of the graphite anode operation under low-temperatures, electrochemical impedance spectroscopy (EIS) measurements were conducted using a fitting method based on a previous report. 31 The total impedance was divided into four components: the electrolyte and electrode resistance (R ee ), contact resistance (R con ), charge transfer resistance (R ct ), and diffusion resistance (R diff ). The resistance between the electrolyte and electrode reflects the degree of wetting between the electrolyte and electrode, which can be determined by the high-frequency resistance of the cell.…”

“…To elucidate the rate-limiting steps of the graphite anode operation under low-temperatures, electrochemical impedance spectroscopy (EIS) measurements were conducted using a fitting method based on a previous report . The total impedance was divided into four components: the electrolyte and electrode resistance ( R ee ), contact resistance ( R con ), charge transfer resistance ( R ct ), and diffusion resistance ( R diff ).…”

“…The cycling performance and capacity retention at a low-temperature (−20 °C) were further examined and compared with those of the pristine graphite anodes. To gain a deeper understanding of the intercalation kinetics and charge transfer limitations during low-temperature operation, electrochemical impedance spectroscopy (EIS) was employed to analyze performance limitations . It was observed that the lithium benzenesulfonate layer on the graphite surface greatly reduced charge transfer resistance, resulting in an improved low-temperature capacity retention (0.1C, ∼150 mAh g –1 ) of 44.8% compared with that of pristine graphite (∼122 mAh g –1 , 37.0%).…”

Advantages of a Solid Solution over Biphasic Intercalation for Vanadium-Based Polyanion Cathodes in Na-Ion Batteries

“…As an example, temperaturedependent conductivity measurements for 1 M LiPF 6 in the EC/DMC/DEC 1:1:1 electrolyte demonstrated that the Arrhenius plot shows two regions with different slopes at temperatures higher than the freezing point of the electrolyte, which can be attributed to partial solidifying and precipitation of the EC component at −21 °C. 24 For the electrolyte used in this study, 1 M NaPF 6 in a 1:1 v/v mixture of ethylene carbonate and propylene carbonate (EC-PC) with 5% of fluoroethylene carbonate (FEC), no change of the slope of the Arrhenius plot for the conductivity of the electrolyte was observed upon approaching −30 °C, and the calculated apparent activation energy of 28 ± 2 kJ mol −1 is close to the value reported for the Li-ion electrolyte 24 (Figure S1). Therefore, we conclude that the state of the electrolyte does not change appreciably throughout the range of operating temperatures (+20 ÷ −30 °C).…”

“…The choice of MIB chemistry for operation under extreme conditions is quite challenging, as the performance metrics are dependent on a large number of particle-level, electrode-level, and cell-level parameters . Detailed electroanalytical studies of performance limitations can shed light onto the limiting factors for particular materials, , yet these are strictly valid for a specific particle morphology and size, electrode architecture, type of carbon coating and carbon additive, and electrolyte composition and purity, as well as on the type of the anode used in the cell and the geometry of the cell itself. This makes comparison of low-temperature and high-power performance of different electrode materials quite uncertain and inconclusive, with the questions regarding the relative importance of particle-level kinetic factors still being open.…”