Hadar Sclar

On the Performance of LiNi1 / 3Mn1 / 3Co1 / 3O2 Nanoparticles as a Cathode Material for Lithium-Ion Batteries

We report on the behavior of nanometric LiMn 1/3 Ni 1/3 CO 1/3 O 2 (LiMNC) as a cathode material for Li-ion batteries in comparison with the same material with submicrometric particles. The LiMNC material was produced by a self-combustion reaction, and the particle size was controlled by the temperature and duration of the follow-up calcination step. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared, Raman spectroscopy, electron paramagnetic resonance, inductively coupled plasma, and atomic force microscopy were used in conjunction with standard electrochemical techniques (cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy) for characterizing the electrode materials. The effect of cycling and aging at 60°C was also explored. Nanomaterials are much more reactive in standard electrolyte solutions than LiMNC with a submicrometric particle. They develop surface films that impede their electrochemical response, while their bulk structure remains stable during aging and cycling at elevated temperatures. The use of nanomaterials in Li-ion batteries is discussed.

On the Surface Chemistry of Cathode Materials in Li-Ion Batteries

The main cathode materials for Li batteries include the following systems: transition metal oxides and sulfides (MO x , MS x ), lithiated transition metal oxides and sulfides (Li x MO y , Li x MS y ), and LiMPO4 olivine compounds. There are also oxygen- and sulfur-based cathodes whose main solid components are carbonaceous materials. Most of these cathodes develop very rich surface chemistry that affects very strongly their electrochemical performance. The main reactions are acid–base reactions (with acidic solution species, HF, PF5, PF3O, etc.); nucleophilic reactions between the basic compounds and the electrophilic alkyl carbonate solvents; polymerization; possible oxidation of solution species; and dissolution of transition metal ions. The behavior of many cathodes in Li-ion batteries is controlled by surface-film formation, passivation phenomena, and Li-ion migration through solid electrolyte interphases formed on the active mass by spontaneous reactions. We describe herein major surface processes, techniques that can address and analyze them, as well as means to improve the performance of cathodes in Li-ion batteries by controlling their surface phenomena.

Horizons for Li-Ion Batteries Relevant to Electro-Mobility: High-Specific-Energy Cathodes and Chemically Active Separators

Li-ion batteries (LIBs) today face the challenge of application in electrified vehicles (xEVs) which require increased energy density, improved abuse tolerance, prolonged life, and low cost. LIB technology can significantly advance through more realistic approaches such as: i) stable high-specific-energy cathodes based on Li1+ x Niy Coz Mnw O2 (NCM) compounds with either Ni-rich (x = 0, y → 1), or Li- and Mn-rich (0.1 < x < 0.2, w > 0.5) compositions, and ii) chemically active separators and binders that mitigate battery performance degradation. While the stability of such cathode materials during cell operation tends to decrease with increasing specific capacity, active material doping and coatings, together with carefully designed cell-formation protocols, can enable both high specific capacities and good long-term stability. It has also been shown that major LIB capacity fading mechanisms can be reduced by multifunctional separators and binders that trap transition metal ions and/or scavenge acid species. Here, recent progress on improving Ni-rich and Mn-rich NCM cathode materials is reviewed, as well as in the search for inexpensive, multifunctional, chemically active separators. A realistic overview regarding some of the most promising approaches to improving the performance of rechargeable batteries for xEV applications is also presented.