Lithium‐ion batteries (LIBs) are promising candidates within the context of the development of novel battery concepts with high energy densities. Batteries with high operating potentials or high ...voltage (HV) LIBs (>4.2 V vs Li+/Li) can provide high energy densities and are therefore attractive in high‐performance LIBs. However, a variety of challenges (including solid electrolyte interface (SEI), lithium plating, etc.) and related safety issues (such as gas formation or thermal runaway effects) must be solved for the practical, widespread application of HV‐LIBs. Most of these challenges arise in the region between the electrodes: the electrolyte region. This review provides an overview of recent development and progress on the electrolyte region, including liquid electrolytes, ionic liquids, gel polymer electrolytes, separators, and solid electrolytes for HV‐LIBs applications. A focus on improving the safety of these systems, with some perspectives on their relative cost and environmental impact, is given. Overall, the new information is encouraging for the development of HV‐LIBs, and this review serves as a guide for potential strategies to improve their safety, allowing the development of HV‐LIBs, including solid‐state batteries, to be accelerated to practical relevance.
With the need for high energy density battery storage growing, the interest in high‐voltage lithium‐ion batteries (HV‐LIBs) is subsequently increasing. The inherent safety limitations resulting from high‐voltage operation require attention before widespread commercial use of these devices. This review outlines the way forward to improve the safety and sustainability of HV‐LIBs by modifying the electrolyte region.
Current lithium (Li)‐metal anodes are not sustainable for the mass production of future energy storage devices because they are inherently unsafe, expensive, and environmentally unfriendly. The ...anode‐free concept, in which a current collector (CC) is directly used as the host to plate Li‐metal, by using only the Li content coming from the positive electrode, could unlock the development of highly energy‐dense and low‐cost rechargeable batteries. Unfortunately, dead Li‐metal forms during cycling, leading to a progressive and fast capacity loss. Therefore, the optimization of the CC/electrolyte interface and modifications of CC designs are key to producing highly efficient anode‐free batteries with liquid and solid‐state electrolytes. Lithiophilicity and electronic conductivity must be tuned to optimize the plating process of Li‐metal. This review summarizes the recent progress and key findings in the CC design (e.g. 3D structures) and its interaction with electrolytes.
Anode‐free Li‐metal batteries (AFLMBs) are a promising candidate for future high‐energy density batteries, however, besides many advantages (safety and low cost), they still face challenges in terms of poor cycling life. This work discusses the challenges, current status, and important discoveries in optimizing the current collector as the host for Li‐metal plating, since its critical role for achieving superior electrochemical performance.
Due to the ever-growing importance of rechargeable lithium-ion batteries, the development of electrode materials and their processing techniques remains a hot topic in academia and industry. Even the ...well-developed and widely utilized active materials present issues, such as surface reactivity, irreversible capacity in the first cycle, and ageing. Thus, there have been many efforts to modify the surface of active materials to enhance the electrochemical performance of the resulting electrodes and cells. Herein, we review the attempts to use polymer coatings on the anode active materials. This type of coating stands out because of the possibility of acting as an artificial solid electrolyte interphase (SEI), serving as an anode protective layer. We discuss the prominent examples of anodes with different mechanisms: intercalation (graphite and titanium oxides), alloy (silicon, tin, and germanium), and conversion (transition metal oxides) anodes. Finally, we give our perspective on the future developments in this field.
The steadily growing electric vehicle market is a driving force in low‐cost, high‐energy‐density lithium‐ion battery development. To meet this demand, LiNi0.975Al0.025O2 (LNA), a high‐energy‐density ...and cobalt‐free cathode material, has been developed using a low‐cost and efficient co‐precipitation and lithiation process. This article explores how further processing (i.e., washing residual lithium from the secondary particle surface and applying a secondary heat treatment at 650 °C) changes the chemical environment of the surface and the electrochemical performance of the LNA cathode material. After washing, a nonconductive nickel oxide (NiO) phase is formed on the surface, decreasing the initial capacity in electrochemical tests, and suppressing high‐voltage (H2) to (H3) phase transition results in enhanced cycle properties. Furthermore, the secondary heat treatment re‐lithiates surface NiO back to LNAand increases the initial capacity with enhanced cycle properties. Electrochemical tests are performed with the cells without tap charge to suppress the H2 to H3 phase transition. Results reveal that avoiding charging cells at a high voltage for a long time dramatically improves LNA's cycle life. In addition, the gas analysis tests performed during charge and discharge to reveal how the amount of residual lithium compounds on the surface affects gas formation are studied.
Cobalt‐free aluminium‐modified LiNiO2 cathode materials are washed and secondary heat‐treated to investigate the effect of surface composition on the electrochemical performance in Li‐ion full cells. Results show that for prolonged cycle life high voltage H2 to H3 phase transition should be avoided and how residual lithium compound affects to the gas formation during charge.
Calcium fluoride is widely investigate known to be a promising solid material for optics, electronics, and electrochemistry. In this work, we report the successful preparation of calcium fluoride ...with enhanced defect structure obtained by the application of vapor pressure followed by high‐energy ball milling, creating CaF2 nano‐powder, achieving increased ionic conductivities in the order of 1.9 · 10−5 S·cm−1 at room temperature relying on fluoride surface interstitial defect with an activation energy of 0.35 eV. The materials were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), X‐ray photoelectron spectroscopy (XPS), nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR). It is revealed that the calcium fluoride electrolyte keeps in its basic cubic structure, becomes nano‐powdered material with crystallite/particle size of 12/30 nm. Surface defect structures are enhanced, which is visible with XPS, NMR, and EPR spectroscopy. The synthesized material provided considerable ionic conductivity enhancement introducing attraction for electrochemical testing for fluoride‐ion batteries (FIB).
Calcium fluoride solid electrolytes have been identified as a candidate for solid‐state fluoride‐ion batteries (FIBs). Here, we investigate the doping of CaF2 with samarium — Ca1−xSmxF2+x (0 ≤ x ≤ ...0.15) — obtained by solid synthesis via high‐energy ball milling. Structural, morphological, and ionic conductivity studies of the as‐prepared materials were examined. It reveals that the fluorite‐type structure is dominating with a crystallite size of 12–14 nm. The highest ionic conductivity at room temperature had been obtained for Ca0.95Sm0.05F2.95 with a value of 2.8 × 10−6 S·cm−1. It proves that a small content of Sm doping can considerably improve the ionic conductivity of CaF2.
Abstract
The transition from conventional liquid electrolyte Li-ion batteries towards solid-state systems requires a paradigm shift on how these batteries are fabricated and how the R&D process can ...be augmented in order to fulfil the ever-increasing demand for reliable and high-performance energy storage systems. This work briefly looks over the main aspects of printed electronics and its potential to accelerate the development of solid-state batteries. It emphasizes the main challenges related to the fabrication of solid-state batteries and how printed electronics can address them in a timely and affordable manner. Importantly, the proposed printed electronics methods and solutions highlight the ability for immediate upscaling to mass production as well as downscaling for rapid prototyping and custom designing.
Nowadays, solid electrolytes are considered the main alternative to conventional liquid electrolytes in lithium batteries. The fabrication of these materials is however limited by the strict ...synthesis conditions, requiring high temperatures which can negatively impact the final performances. Here, it is shown that a modification of garnet‐based Li7La3Zr2O12 (LLZO) and the incorporation of tellurium can accelerate the synthesis process by lowering the formation temperature of cubic LLZO at temperatures below 700 °C. Optimized synthesis at 750 °C showed a decrease in particle size and cell parameter for samples with higher amounts of Te and the evaluation of electrochemical performances reported for LLZO Te0.25 a value of ionic conductivity of 5,15×10−5 S cm−1 after hot‐pressing at 700 °C, two orders of magnitude higher than commercial Al‐LLZO undergoing the same working conditions, and the highest value at this densification temperature. Partial segregation of Te‐rich phases occurs for high‐temperature densification. Our study shows the advantages of Te insertion on the sintering process of LLZO garnet and demonstrates the achievement of highly conductive LLZO with a low‐temperature treatment.
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