• Energy Research

Abstract Thermal stability of charged LiCoO 2 cathodes with various surface areas of active material is investigated in order to quantify the effect of LiCoO 2 surface area on thermal stability of cathode. Thermogravimetric analyses and calorimetry have been conducted on charged cathodes with different active material surface areas. Besides reduced thermal stability, high surface area also changes the active material decomposition reaction and induces side reactions with additives. Thermal analyses of LiCoO 2 delithiated chemically without any additives or with a single additive have been conducted to elaborate the effect of particle size on side reactions. Stability of cathode–electrolyte system has been investigated by accelerating rate calorimetry (ARC). Arrhenius activation energy of cathode decomposition has been calculated as function of conversion at different surface area of active material.

We report on an effective approach to speed up the measurement of thermodynamic characterization curves (entropy of reaction ΔrS(x)) of rechargeable batteries, in particular commercial 18,650 lithium ion cells. We propose and demonstrate a measurement and data processing protocol that reduces the time required to record entropy profiles from time scales of weeks to time scales of hours - without loss in accuracy. For time consuming studies such as investigations on ageing of battery cells, entropy profile measurements thus become as feasible as conventional electrochemical characterisation techniques like dV/dQ or cyclic voltammetry. We demonstrate this at the examples of two ageing protocols applied to a commercial high power and a commercial high energy cell, respectively: (i) accelerated calendric aging by storing cells at 100% state of charge at 60 °C and (ii) continuous cycling with a 1 C current at 25 °C.

Heating districts have become one of the key infrastructures to efficiently and sustainably supply heat to consumers. With the current climate change crisis, not only are heating districts of the essence but their efficient and optimized operation as well. To analyze and achieve such an optimization, transient simulations of heating districts are needed. These simulations are a means of upgrading older town networks to smarter energy grids as well as an effective tool for the planning and building of newer heating networks. Therefore, this work presents an easy simulation method for the transient simulation of heating districts based on a control theory approach. The simulation method can calculate multiple-loop networks as well as non-looped networks and correctly predict how a heating network can behave over time. Additionally, this approach allows for the inclusion of new renewable energy sources into existing heating networks and to simulate the resulting network behavior. The method was tested on five different testcases involving a single-loop network, a multiple-loop network, and a real-life non-looped network. In each case, the calculated massflows were validated with the software Epanet (Version 2.2), while the simulated temperatures were compared to the theoretical steady-state values as well as the theoretical times of arrival of each heating network. The simulation results present a good approximation in each testcase. Finally, the limitations of the method are discussed, and a recommendation for the usage of the approach is given.

Hollow hierarchical spheres self-organized from the ultrathin nanosheets of α-Fe2O3 were prepared by a simple process. These ultrathin nanosheet subunits possess an average thickness of around 3.5 nm and show preferential exposure of (110) facets. Their Li ion storage and visible-light photocatalytic water oxidation performance are tested. Such hierarchical nanostructures show high Li storage properties with good cycling stability and excellent rate capabilities. The water oxidation catalytic activity is 70 μmol h−1 g−1 for O2 evolution under visible light irradiation and can be maintained for 15 hours. The structural features of these α-Fe2O3 nanocrystals are considered to be important to lead to the attractive properties in both Li storage and photocatalytic water oxidation, e.g. hollow interior, ultrathin thickness and largely exposed active facets.

In this work, we have successfully grown single-crystalline nanoneedle arrays of NiCo2O4 on conductive substrates such as Ni foam and Ti foil through a simple solution method together with a post-annealing treatment. Remarkably, the NiCo2O4–Ni foam binder-free electrode exhibits greatly improved electrochemical performance with very high capacitance and excellent cycling stability.

AbstractWe present a detailed analysis of the behavior of a new zinc‐air flow cell. This system offers several unique insights into the zinc electrochemistry. Due to the constant slurry flow, concentration gradients are completely destroyed every few seconds and therefore negligible and it is possible to take samples from the anode without interrupting the discharge process. To clarify the underlying processes, the potential of the zinc electrode, the zincate concentration (by titration) and the zinc‐particles (by SEM) were analyzed. These measurements offer the unique opportunity to distinguish between thermodynamic and kinetic contributions to the cell voltage. We found, that in this system zinc passivation, is caused by a critical zincate concentration and the steep increase of the cell potential is a kinetic effect, caused by partial passivation. The key factor for passivation, which limits the capacity to 82 mAh gzinc−1 or 41 mAh gslurry−1, is the nucleation of ZnO before the critical zincate concentration is reached. This allows capacities of up to 420 mAh gzinc−1 or 210 mAh gslurry−1. These results are therefore not only essential for a further increase of the practical capacity of the system but also offer unique insights in the zinc electrochemistry.

A facile two-step strategy involving a polyol method and subsequent thermal annealing treatment is successfully developed for the general synthesis of metal oxide/carbon coaxial nanocables. Benefitting from the strong coupling effect, these hybrid nanocables exhibit remarkable lithium storage properties with high capacity, long cycle life and excellent rate capability.

Abstract Accurate health estimation and lifetime prediction of lithium-ion batteries are crucial for durable electric vehicles. Early detection of inadequate performance facilitates timely maintenance of battery systems. This reduces operational costs and prevents accidents and malfunctions. Recent advancements in “Big Data” analytics and related statistical/computational tools raised interest in data-driven battery health estimation. Here, we will review these in view of their feasibility and cost-effectiveness in dealing with battery health in real-world applications. We categorise these methods according to their underlying models/algorithms and discuss their advantages and limitations. In the final section we focus on challenges of real-time battery health management and discuss potential next-generation techniques. We are confident that this review will inform commercial technology choices and academic research agendas alike, thus boosting progress in data-driven battery health estimation and prediction on all technology readiness levels.