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The development of cathode materials represents the key bottleneck to further push the performance of current Li-ion batteries (LIB) beyond the commercial benchmark. Li-rich transition-metal-layered oxides (LRLOs) are a promising class of materials to use as high-capacity/high-potential positive electrodes in LIBs thanks to the large lithium content (e.g., ∼1.2 Li equiv per formula unit) and the exploitation of multiple redox couples (e.g., Mn4+/3+, Co4+/3+, Ni4+/3+/2+). In this work, we propose and demonstrate experimentally a Co-free overlithiated LRLO material with a limited nickel content, i.e., Li1.25Mn0.625Ni0.125O2. This LRLO is able to exchange reversibly an outstanding practical specific capacity at room temperature, i.e., 230 mAh g-1 at C/10 for almost 200 cycles, and can sustain high current rates, i.e., 118 mAh g-1 at 2C. This material has been successfully prepared by a facile solution combustion synthesis and characterized by scanning electron microscopy (SEM), X-ray photoemission spectroscopy (XPS), X-ray absorption near-edge spectroscopy (XANES), X-ray diffraction (XRD), and Raman techniques. Overall, our positive electrodes based on Li1.25Mn0.625Ni0.125O2 overlithiated Co-free LRLO is a step forward in the development of the materials for batteries with improved performance and better environmental fingerprint.

Transition-metal (TM) layered oxides have been attracting enormous interests in recent decades because of their excellent functional properties as positive electrode materials in lithium-ion batteries. In particular LiCoO2 (LCO), LiNiO2 (LNO) and LiMnO2 (LMO) are the structural prototypes of a large family of complex compounds with similar layered structures incorporating mixtures of transition metals. Here, we present a comparative study on the phase stability of LCO, LMO and LNO by means of first-principles calculations, considering three different lattices for all oxides, i.e., rhombohedral (hR12), monoclinic (mC8) and orthorhombic (oP8). We provide a detailed analysis&mdash, at the same level of theory&mdash, on geometry, electronic and magnetic structures for all the three systems in their competitive structural arrangements. In particular, we report the thermodynamics of formation for all ground state and metastable phases of the three compounds for the first time. The final Gibbs Energy of Formation values at 298 K from elements are: LCO(hR12) &minus, 672 &plusmn, 8 kJ mol&minus, 1, LCO(mC8) &minus, 655 &plusmn, LCO(oP8) &minus, 607 &plusmn, LNO(hR12) &minus, 548 &plusmn, LNO(mC8) &minus, 557 &plusmn, LNO(oP8) &minus, LMO(hR12) &minus, 765 &plusmn, 10 kJ mol&minus, LMO(mC8) &minus, 779 &plusmn, LMO(oP8) &minus, 780 &plusmn, 1. These values are of fundamental importance for the implementation of reliable multi-phase thermodynamic modelling of complex multi-TM layered oxide systems and for the understanding of thermodynamically driven structural phase degradations in real applications such as lithium-ion batteries.

The current state-of-the-art quantum mechanics methodologies were applied to derive information on the bulk and surface properties of the P2-type layered oxide Na0.85Li0.17Ni0.21Mn0.64O2 (NLNMO), a cathode material. The special quasi-random structure (SQS) approach was employed to identify the arrangement of Li, Ni, and Mn ions in a supercell containing 115 atoms. Both the cell parameters and atomic positions were determined from DFT-PBE+U calculations to highlight specific distortions induced by the dopants (Ni and Li). The analysis of atomic partial charges and atomic magnetic moments revealed that Li has a purely structural role, while Ni and Mn actively participate in both redox processes and electronic conduction. Using a new surface slab model, the interaction between the layered Na0.85Li0.17Ni0.21Mn0.64O2 (001) surface and the Na ions was examined to identify the most favorable adsorption sites and the possible paths for the migration of the Na ions on the electrode surface.

Proton-conducting solid-oxide electrolyzer and fuel cells (PC-SOECs/FCs) represent viable, intermediate-temperature green technologies for H2 production and conversion. While PC ceramics have been extensively investigated as electrolytes for PC-SOECs/FCs, the development of corresponding single-phase electrode components has been hindered by difficulties in finding efficient mixed proton–electron conductors (MPECs), with also effective catalytic activity toward oxygen reduction and evolution reactions (ORR/OER). To address this challenge, we applied first-principles methods (PBE+U) to design new perovskite-oxide MPEC electrodes based on the known BaZrO3 PC ceramic. Our strategy has been to modify the parent material by substituting Zr with earth abundant transition metals, namely Mn and Fe. We found Zr : Mn and Zr : Fe ratios of 0.75 : 0.25 to be sufficient to obtain electronic structural features that can enable electric conductivity. We also investigated other relevant processes for MPEC-based electrodes: hydration, proton migration, and ORR/OER electrocatalysis. From calculations of key descriptors associated with these processes, we found that Zr substitution with Mn or Fe delivers in both cases promising PC-SOEC/FC electrodes. Moreover, our first-principles results highlight the specific qualities of Mn and Fe: the first provides better electronic features and electrocatalytic activities, whereas the latter allows for better hydration and proton migration. In perspective, our findings present clear indications for the experimental implementation and test of new low-cost materials for solid-oxide electrochemical cells.