Lithium ion batteries have become an integral part of our daily lives. Among a number of different cathode materials nickel-rich LiNi x Co y Mn z O 2 is particularly interesting. The material can deliver high capacities of ∼195 mAh g −1 putting it on the map for electric vehicles. With an increasing nickel content, a number of issues arise in the material limiting its performance. The Li/Ni mixing, highly reactive surface and formation of micro cracks are the most pressing ones. An overview of recent literature exploring these phenomena is herein summarized and were applicable solutions will be highlighted. With the advent of lithium ion batteries (LIB) in 1991 came a rapidly increasing development of consumer electronics.1,2 Soon LIB were the power source of choice for manufacturer of laptop computers and cell phones. While smart phones are getting smaller and have to operate more energy demanding applications LIB have to keep up with the pace. Cell manufactures have developed more refined ways to assemble cells leading to high energy densities of modern LIB for consumer applications. 3,4 In the meantime, scientists have developed better active materials and are constantly improving over existing ones. 5 The early LIB used lithium cobalt oxide (LCO) as cathode and graphite as anode material. LCO has a high tap density making it an ideal choice for small devices. The battery market has grown tremendously over the last 35 years and is expected to increase even more rapidly within the next years. 6 With the new market segment of electrical vehicles (EV) becoming more important every year LIB have found an additional application with a huge potential. Even though fuel cells are a natural competitor for LIB the large commitment necessary to build a hydrogen infrastructure plays into the hands of eager battery suppliers.Electrical propulsion needs battery materials with high capacities to satisfy consumer demands of a ∼500 km driving range long cycle life.4,7 Several materials have been identified as viable candidates for EVs ranging from layered mixed transition metal oxides, layered lithium rich materials and lithium sulfur batteries. [8][9][10][11] The technologically most advanced material option is layered nickel rich LiNi x Co y Mn z O 2 (NCM, x > 0.6) cathodes. The current generation of some EVs is already employing NCM523. Unfortunately, the implementation of higher nickel contents still needs to overcome a number of challenges to be viable. The review at hand will outline the development of the NCM material family with the first emphasis being on the individual endmembers LiCoO 2 , LiNiO 2 and LiMnO 2 . Problems and recent advances of these materials will be outlined. The second emphasis will be on the layered material LiNi x Co y Mn z O 2 with a focus on nickel rich materials. Problems and attempted solutions to mitigate them will be presented.= These authors contributed equally to this work.* Electrochemical Society Fellow. z E-mail: schippf@biu.ac.il Lithium Cobalt Oxide; LiCoO 2The first lithium intercal...

One of the major hurdles of Ni‐rich cathode materials Li1+x(NixCozMnz)wO2, y > 0.5 for lithium‐ion batteries is their low cycling stability especially for compositions with Ni ≥ 60%, which suffer from severe capacity fading and impedance increase during cycling at elevated temperatures (e.g., 45 °C). Two promising surface and structural modifications of these materials to alleviate the above drawback are (1) coatings by electrochemically inert inorganic compounds (e.g., ZrO2) or (2) lattice doping by cations like Zr4+, Al3+, Mg2+, etc. This paper demonstrates the enhanced electrochemical behavior of Ni‐rich material LiNi0.8Co0.1Mn0.1O2 (NCM811) coated with a thin ZrO2 layer. The coating is produced by an easy and scalable wet chemical approach followed by annealing the material at ≥700 °C under oxygen that results in Zr doping. It is established that some ZrO2 remains even after annealing at ≥800 °C as a surface layer on NCM811. The main finding of this work is the enhanced cycling stability and lower impedance of the coated/doped NCM811 that can be attributed to a synergetic effect of the ZrO2 coating in combination with a zirconium doping.

Silicon is widely regarded as one of the most promising anode materials for lithium ion and next-generation lithium batteries because of its high theoretical specific capacity. However, major issues arise from the large volume changes during alloying with lithium. In recent years, much effort has been spent on preparing nanostructured silicon and optimizing various aspects of material processing with the goal of preserving the electrode integrity upon lithiation/delithiation. The performance of silicon anodes is known to depend on a large number of parameters and, thus, the general definition of a "standard" is virtually impossible. In this work, we conduct a comparative performance study of silicon anode tapes prepared from commercially available materials while using both a well-defined electrode configuration and cycling method. Our results demonstrate that the polymer binder has a profound effect on the cell performance. Furthermore, we show that key parameters such as specific capacity, capacity retention, rate capability, and so forth can be strongly affected by the choice of silicon material, polymer binder and electrolyte system - even the formation of metastable crystalline Li15Si4 is found to depend on the electrode composition and low potential exposure time. Overall, the use of either poly(acrylic acid) with a viscosity-average molecular weight of 450.000 or poly(vinyl alcohol) Selvol 425 in combination with both silicon nanopowder containing a native oxide surface layer of ∼1 nm in diameter and with a monofluoroethylene carbonate-based electrolyte led to improved cycling stability at high loadings.

Nickel-rich layered lithiated Ni−Co−Mn oxides (NCMs) are emerging as the most promising candidates for next-generation Li-ion battery cathodes. Progress, however, is hindered by an incomplete understanding of processes that lead to performance-limiting impedance growth and reduced cycling stability. These processes typically involve surface reconstruction and O 2 release at the cathode surface, both of which are difficult to monitor in the working cell. We demonstrate that online electrochemical mass spectrometry can be used to measure the gas release from NCMs of varying Ni content at practically relevant potentials and under operando electrochemical conditions. We find that for cathode potentials up to 4.3 V (vs Li + /Li) there is virtually no trade-off between Ni-mediated specific-charge enhancement and parasitic surface reactions. However, at potentials greater than 4.3 V, surface-reconstruction processes giving rise to substantial CO 2 and O 2 release occur, implying that surfacereconstructed layers a few nanometers thick may form already after the first charge. Ni content and the Ni/Co ratio are found to govern the onset, rate, and extent of these surface-reconstruction processes. These results provide novel insights into the role of Ni in governing the surface stability and performance of Li-ion layered oxides.

Ni-rich layered oxides, like NCM-811, are promising lithium-ion battery cathode materials for applications such as electric vehicles. However, pronounced capacity fading, especially at high voltages, still lead to a limited cycle life, whereby the underlying degradation mechanisms, e.g. whether they are detrimental reactions in the bulk or at the surface, are still controversially discussed. Here, we investigate the capacity fading of NCM-811/graphite full-cells over 1000 cycles by a combination of in situ synchrotron X-ray powder diffraction, impedance spectroscopy, and X-ray photoelectron spectroscopy. In order to focus on the NCM-811 material, we excluded Li loss at the anode by pre-lithiating the graphite. We were able to find a quantitative correlation between NCM-811 lattice parameters and capacity fading. Our results prove that there are no considerable changes in the bulk structure, which could be responsible for the observed ≈20% capacity loss over the 1000 cycles. However, we identified the formation of a resistive surface layer, which is responsible for (i) an irreversible loss of capacity due to the material lost for its formation, and (ii) for a considerable impedance growth. Further evidence is provided that the surface layer is gradually formed around the primary NCM-811 particles.