• Energy Research

AbstractGraphitized carbon materials from biomass resources were successfully synthesized with an iron catalyst, and their electrochemical performance as anode materials for lithium‐ion batteries (LIBs) was investigated. Peak pyrolysis temperatures between 850 and 2000 °C were covered to study the effect of crystallinity and microstructural parameters on the anodic behavior, with a focus on the first‐cycle Coulombic efficiency, reversible specific capacity, and rate performance. In terms of capacity, results at the highest temperatures are comparable to those of commercially used synthetic graphite derived from a petroleum coke precursor at higher temperatures, and up to twice as much as that of uncatalyzed biomass‐derived carbons. The opportunity to graphitize low‐cost biomass resources at moderate temperatures through this one‐step environmentally friendly process, and the positive effects on the specific capacity, make it interesting to develop more sustainable graphite‐based anodes for LIBs.

To achieve a broader public acceptance for electric vehicles based on lithium-ion battery (LIB) technology, long driving ranges, low cost, and high safety are needed. A promising pathway to address these key parameters lies in the further improvement of Ni-rich cathode materials for LIB cells. Despite the higher achieved capacities and thus energy densities, there are major drawbacks in terms of capacity retention and thermal stability (of the charged cathode) which are crucial for customer acceptance and can be mitigated by protecting cathode particles. We studied the impact of surface modifications on cycle life and thermal stability of LiNi0.90Co0.05Mn0.05O2 layered oxide cathodes with WO3 by a simple sol–gel coating process. Several advanced analytical techniques such as low-energy ion scattering, differential scanning calorimetry, and high-temperature synchrotron X-ray powder diffraction of delithiated cathode materials, as well as charge/discharge cycling give significant insights into the impact of surface coverage of the coatings on mitigating degradation mechanisms. The results show that successful surface modifications of WO3 with a surface coverage of only 20% can prolong the cycle life of an LIB cell and play a crucial role in improving the thermal stability and, hence, the safety of LIBs.

In almost all state‐of‐the‐art lithium‐ion batteries, the negative electrode is made from graphite. For dual‐ion batteries (DIBs), graphite electrodes can even be used as negative and positive electrodes as the electrolyte provides both cations and anions for energy storage. As the amount of active material is very high in graphite electrodes, one of the main structure‐controlling parameters is its particle size distribution (PSD). Based on changes in the active material particle size and resulting changes in electrode structure, the corresponding cell characteristics like coulombic efficiency or power density are strongly affected. Herein, results for graphite positive electrodes manufactured with different PSDs of one typical commercial synthetic graphite are displayed. A high‐performance single‐wheel air classifier is used to create the differently distributed graphite particle fractions that do not vary in particle shapes for all fractions created. To gain a better understanding of the particle size impact on electrode properties, the electronic and mechanical properties, as well as the electrode structure, are investigated. The electrochemical performance of the Li metal/graphite system is correlated with structure properties influenced by PSD.

We present highly promising results for the use of graphite as both electrodes in a “dual-carbon” cell. An ionic liquid-based electrolyte mixture allows stable and highly reversible ion intercalation/de-intercalation into/from the electrodes.

AbstractCarbons are considered as anode active materials in potassium‐ion batteries (PIBs). Here, the correlation between material properties of disordered (non‐graphitic) and ordered graphitic carbons and their electrochemical performance in carbon||K metal cells is evaluated. First, carbons obtained from heat treatment of petroleum coke at temperatures from 800 to 2800 °C are analyzed regarding their microstructure and surface properties. Electrochemical performance metrics for K+ ion storage like specific capacity and Coulombic efficiency (CEff) are correlated with surface area, non‐basal planes and microstructure properties, and compared to Li+ ion storage. For disordered carbons, the specific capacity can be clearly correlated with the defect surface area. For highly ordered graphitic carbons, the degree of graphitization strongly determines the specific capacity. The initial CEff of graphitic carbons shows a strong correlation with basal and non‐basal planes. Second, kinetic limitations of ordered graphitic carbons are re‐evaluated by analyzing commercial graphites regarding particle size and surface properties. A clear correlation between particle size, surface area and well‐known challenges of graphitic carbons in terms of low‐rate capability and voltage hysteresis is observed. This work emphasizes the importance of bulk and surface material properties for K+ ion storage and gives important insights for future particle design of promising carbon anodes for PIB cells.

In order to meet the sophisticated demands for large-scale applications such as electro-mobility, next generation energy storage technologies require advanced electrode active materials with enhanced gravimetric and volumetric capacities to achieve increased gravimetric energy and volumetric energy densities. However, most of these materials suffer from high 1st cycle active lithium losses, e.g., caused by solid electrolyte interphase (SEI) formation, which in turn hinder their broad commercial use so far. In general, the loss of active lithium permanently decreases the available energy by the consumption of lithium from the positive electrode material. Pre-lithiation is considered as a highly appealing technique to compensate for active lithium losses and, therefore, to increase the practical energy density. Various pre-lithiation techniques have been evaluated so far, including electrochemical and chemical pre-lithiation, pre-lithiation with the help of additives or the pre-lithiation by direct contact to lithium metal. In this review article, we will give a comprehensive overview about the various concepts for pre lithiation and controversially discuss their advantages and challenges. Furthermore, we will critically discuss possible effects on the cell performance and stability and assess the techniques with regard to their possible commercial exploration.

Popularization of electric vehicles (EVs) is an effective solution to promote carbon neutrality, thus combating the climate crisis. Advances in EV batteries and battery management interrelate with government policies and user experiences closely. This article reviews the evolutions and challenges of (i) state-of-the-art battery technologies and (ii) state-of-the-art battery management technologies for hybrid and pure EVs. The key is to reveal the major features, pros and cons, new technological breakthroughs, future challenges, and opportunities for advancing electric mobility. This critical review envisions the development trends of battery chemistry technologies, technologies regarding batteries, and technologies replacing batteries. Wherein, lithium-ion batteries, lithium-metal batteries (such as solid state batteries), and technologies beyond lithium (‘post-lithium’) will be actively explored in the next decades. Meanwhile, the data-driven electrothermal model is promising and identified with an impressive performance. Technologies of move-and-charge and wireless power drive will help alleviate the overdependence of batteries. Finally, future high-energy batteries and their management technologies will actively embrace the information and energy internet for data and energy sharing.