5 Search Results

Tracking the active lithium (Li) inventory in an electrode shows the true state of a Li battery, akin to a fuel gauge for an engine. However, non-destructive Li inventory tracking is currently unavailable. Here, in this work, we used the theoretical capacity of a transition metal oxide to convert capacity into a Li inventory analysis. The Li inventory in electrodes was tracked reliably to show how battery formulations and test methods affect performance. Contrary to capacity, Li inventory tracking reveals stoichiometric variations near the electrode–electrolyte interface. Verifiable results rationalized differences in measurements, clarifying and reducing interferences from cell formulations andmore » experimental manipulations. By tracing four variables from formation to end-of-life, we characterize electrode and cell performance with a thermodynamic framework. Accurate rationalization of subtle differences in Li inventory utilization promises precise battery engineering, evaluation, failure analysis and risk mitigation. The method could be applicable from cell design optimization and fabrication to battery management, improving battery performance and reliability.« less

While it is expected that inhomogeneity negatively affects battery performance, a quantitative understanding of the influence of inhomogeneity has remained elusive due to the difficulty of measuring it in a precise and rapid manner. Here, the ability of high-energy synchrotron x-rays to effectively probe the inhomogeneity in battery cathode films is demonstrated both for fundamental studies of single-layer cathode films and for improving manufacturing processes for industrially relevant multi-layer stacks. High-energy lateral mapping studies were carried out for very high energy density batteries (~300 Wh/kg) made from NMC622 cathodes and Li metal anodes, where NMC622 denotes Li(Ni_0.6Mn_0.2Co_0.2)O₂. It was firstmore » demonstrated for a multi-layer pouch cell (7 layers, ~ 3mm thick) that both local and long-range variations in the NMC loading can be precisely quantified, allowing the quality of the coating process to be assessed. Next, it was shown that for a single cathode layer extracted from a pouch cell battery cycled to failure that local variations in the cathode state-of-charge (SOC) can be mapped with a sensitivity of about 0.1%. Finally, in this manner it was possible to identify three hot spots in which the local performance was much worse than for the rest of the cell as well as to gain insights into the specific failure mechanisms affecting both these local regions and the cell as a whole.« less

A safe and reliable battery operation needs effective diagnostic tools. A quantitative failure analysis (FA) to enable cell qualification and quantify its effectiveness for reliable and safe operation of rechargeable Li batteries (RLB) is shown here. The method can identify and quantify potential failure based on the state of charge (SOC) under any operating conditions. A precise and accurate electrochemical analytic diagnosis (eCAD) of 14 rechargeable Li || NMC622 cells of the same build are used as an example. The FA by eCAD can quantitatively decipher good, bad and ugly cells in cycle aging. The cell qualification is based onmore » thermodynamic SOC, not experimental conditions. The method provides a quantitative failure mode and effect analysis (FMEA) to reveal diverse “dead Li” formation that affects the reversibility of the Li anode and charge retention in the cell. This cell qualification method highlights the potential to improve cell quality for safe operation, with strong implications for early fault detection, FA, risk mitigation, state estimation and life prediction for reliable and safe RLB operations« less

Rechargeable lithium battery (RLB) technology is transforming portable devices, vehicle electrification, and grid modernization. To make RLB durable, reliable and safe, conducting failure mode and effect analysis (FMEA) to identify failure mechanism under the operating conditions is very desirable. However, this ability is often overlooked or even lacking. The failure analysis (FA) is often conducted by laboratory testing and postmortem analysis, and the knowledge typically empirical. Here we present a quantitative approach for FMEA that can reveal how failure modes and effects reduce the capacity of a RLB. This approach is based on the state of the battery for FMEA,more » contrary to the conventional approach based on operating or testing conditions. The key aspect of this FMEA method is to convert the experimental results to a state-of-charge (SOC)-based analytic methodology. Such a conversion can separate the thermodynamic and kinetic attributes of capacity fade based on compositional correspondence in the electrode, so the loss and the decreased utilization of the active materials can be determined respectively.« less

Lithium-sulfur batteries are very promising for next-generation energy storage. However, most studies use flooded electrolyte to achieve high specific capacity at the expense of lowering specific energy. Understanding lithium-sulfur battery performance with lean electrolytes is highly desirable. In this paper, a modified Pechini method is developed to synthesize nanoporous carbon host decorated with Ni₃S₂@Ni particles. Such cathode delivers enhanced specific capacities with extended cycling life in lean electrolytes, due to the dual functions of Ni₃S₂ shell, which can both facilitate reaction kinetics and promote electrolyte wetting. This work highlights a strategy to rationally design cathodes for high-energy lithium-sulfur batteries.