Recent Research and Progress in Batteries for Electric Vehicles

The actual batteries in use: The current progress in the performance and sustainability of traction batteries is due to a combination of engineering and chemistry progress. More space for material in the battery pack allows more creativity in the choice of materials leading to batteries with longer range, faster charging, and more sustainable composition. The developments in the field of e-mobility currently exceed all previous goals and expectations, and the speed of development is rapid. The battery costs dropped by 98 % in the last three decades and the storage capacity increased by a factor of three to four in the same period. The recent strong progress in the development of lithium-ion batteries (LIB) can be associated to both the progress in the engineering of the battery pack, and the progress of active materials for the cathode. From the system perspective, only a fraction of the overall improvement is due to better chemistries. Even larger contributions are expected from new cell-to-pack and the cell-to-chassis designs. The new designs provide more space for the active material so that also less energetic, but more sustainable, safer and cheaper materials can be (re)considered, such as LiFePO4 which encounters a renaissance at the moment. The sodium ion battery is currently emerging as a potential alternative to the LIB. Li-air and Li−S batteries are not ready for application in cars, yet. A potential future candidate is the solid-state battery, which shall benefit from the use of a safe Li metal anode, delivering higher capacities and rate capabilities

Beyond Intercalation Chemistry for Rechargeable Mg Batteries: A Short Review and Perspective

Rechargeable magnesium (Mg) batteries are an attractive candidate for next-generation battery technology because of their potential to offer high energy density, low cost, and safe use. Despite recent substantial progress achieved in the development of efficient electrolytes, identifying high-performance cathode materials remains a bottleneck for the realization of practical Mg batteries. Due to the strong interaction between the doubly charged Mg2+ ions and the host matrix, most of the conventional intercalation cathodes suffer from low capacity, high voltage hysteresis, and low energy density in Mg based battery systems. Alternatively, the thermodynamically favorable conversion reaction may circumvent the sluggish Mg2+ diffusion kinetics. In this review, the focus will be laid on promising cathodes beyond the typical intercalation-type materials. We will give an overview of the recent emerging Mg systems with conversion-type and organic cathodes

Electrochemical synthesis of carbon-metal fluoride nanocomposites as cathode materials for lithium batteries

Herein we have demonstrated an electrochemical method for the synthesis of carbon-metal fluoride nanocomposites (CMFNCs). Electrochemical intercalation of transition metal ions into graphite fluoride (CF$_{x}$) resulted in the formation of CMFNCs. As a proof-of-concept, we have synthesized C-FeF$_{2}$ and C-NiF$_{2}$ nanocomposites by the electrochemical intercalation of Fe$^{2+}$ and Ni$^{2+}$ into CF$_{x}$ from corresponding non-aqueous electrolytes. The C-FeF$_{2}$ and C-NiF$_{2}$ nanocomposites synthesized by this method showed high reversible capacity and cycling stability compared to chemically synthesized analogs as cathode materials for lithium batteries. The reversible capacity of chemically synthesized C-FeF$_{2}$ is 181 mAh g$^{-1}$, whereas electrochemically synthesized material is 349 mAh g$^{-1}$ after 20 cycles. The better cycling performance of electrochemically synthesized C-FeF$_{2}$ was attributed to the homogeneous distribution of FeF$_{2}$ nanoparticles within the carbon matrix enabled by the electrochemical intercalation of Fe$^{2+}$. The electrochemical method described here is emission-free, cost-effective, occurs at room temperature, and extendable to the synthesis of several other CMFNCs. Moreover, it might provide new avenues for the synthesis of advanced functional materials

Time Resolved Measurements of pH in Aqueous Magnesium‐Air Batteries during Discharge and Its Impact for Future Applications

In aqueous magnesium air batteries, the influence of the electrochemical behavior on pH of the electrolyte has not been investigated yet, which has a critical effect on the cell performance. We have monitored the evolution of the pH at various discharge current densities in situ in the Mg-air primary cells, which produce sparingly soluble magnesium hydroxide (Mg(OH)$_{2}$). These experiments show the temporal evolution of the pH of the electrolyte in the cell discharge, depending on the current density. The pH first increases rapidly to a maximum of pH 11 and then drops down slowly to the equilibrium at pH 10.7. At the peak pH oversaturation of Mg(OH)$_{2}$ is paramount, leading to the precipitation which balances the Mg(OH)$_{2}$ concentration in the electrolyte. This precipitation process coats both cathode and anode which leads to a decrease in cell efficiency and voltage. The results show that the cell design of Mg-air batteries is important for their lifetime and cell performance. The performance of the aqueous magnesium cell is increased several folds when the design is changed to a simple electrolyte flow cell

Towards stable and efficient electrolytes for room-temperature rechargeable calcium batteries

Rechargeable calcium (Ca) batteries have the prospect of highenergy and low-cost. However, the development of Ca batteries is hindered due to the lack of efficient electrolytes. Herein, we report novel calcium tetrakis(hexafluoroisopropyloxy)borate Ca[B(hfip)₄]₂ based electrolytes exhibiting reversible Ca deposition at room temperature, a high oxidative stability up to 4.5 V and high ionic conductivity >8 mS cm¯¹. This finding opens a new approach towards room-temperature rechargeable calcium batteries

Ionically conducting inorganic binders: a paradigm shift in electrochemical energy storage

Among the key components in batteries, binders play a vital role by interconnecting active materials and conductive additives and facilitating the coating of electrode materials on the desired substrates thus enabling the flexible fabrication of batteries. Further, they aid in buffering volume changes that arise in electrode materials and enhance their cycling stability. Presently, polyvinylidene fluoride-based binders are employed widely, despite their high cost, non-eco-friendliness, and energy inefficiency. Several water processable binders have been investigated as alternatives, but they suffer from various intrinsic issues. Here, we reveal the potential of several ionically conducting inorganic binders (ICIBs). These ICIBs are not only ionically conducting, but also water processable, chemically compatible, eco-friendly, low-cost, thermally stable (>1000 °C), emission-free, and importantly, safe to use. These inorganic binders outperformed standard polyvinylidene fluoride-based binders in several aspects. Surprisingly, ICIBs are absorbing the exothermic heat evolved by charged cathode materials at high temperatures, which will significantly enhance the safety of the batteries. The unique intrinsic ionic conductive properties combined with binding abilities enabled the flexible processing and functioning of solid-state batteries, otherwise challenging due to the mechanical rigidity, chemical incompatibility, and interfacial issues posed by solid electrolytes. The inorganic binders introduced here will make battery manufacturing and recycling more energy-efficient, eco-friendly, flexible, safe, and above all, cost-effective

Cathode Materials and Chemistries for Magnesium Batteries: Challenges and Opportunities

Rechargeable magnesium batteries hold promise for providing high energy density, material sustainability, and safety features, attracting increasing research interest as post-lithium batteries. With the progressive development of Mg electrolytes with enhanced (electro-)chemical stability, tremendous efforts have been devoted to the exploration of high-energy cathode materials. In this review, recent findings related to Mg cathode chemistry are summarized, focusing on the strategies that promote Mg2+ diffusion by targeting its interaction with the cathode hosts. The critical role of the cathode–electrolyte interfaces is elaborated, which remains largely unexplored in Mg systems. The approaches to optimization of cathode–electrolyte combinations to unlock the kinetic limitations of Mg2+ diffusion, enabling fast electrochemical processes of the cathodes, are highlighted. Furthermore, representative conversion chemistries and coordination chemistries that bypass bulk Mg2+ diffusion are discussed, with particular attention given to their key challenges and prospects. Finally, the hybrid systems that combine the fast kinetics of the monovalent cathode chemistries and high-capacity Mg anodes are revisited, calling for further practical evaluation of this promising strategy. All in all, the aim is to provide fundamental insights into the cathode chemistry, which promotes the material development and interfacial regulations toward practical high-performance Mg batteries