Tuning Li-excess to optimize Ni/Li exchange and improve stability of structure in LiNi0.8Co0.1Mn0.1O2 cathode material for lithium-ion batteries

Elucidating the charge-transfer and Li-ion-migration mechanisms in commercial lithium-ion batteries with advanced electron microscopy

“…These technologies have significantly enriched our understanding of LIBs. For example, the charge-transfer mechanisms and phase-transformation processes in commercial LIB cathode materials, such as LFP and LiNixCoyMnzO2 (NCM) [97][98][99][100][101][102][103][104][105][106][107][108][109][110][111][112][113], can be investigated by HAADF, ABF, and EELS with scanning TEM (STEM), in addition to their effects on the thermal stability of LIBs. Moreover, the process of transition metal (TM) dissolution, locations of TM deposits, and effects of TM dissolution on battery performance can be clarified by HAADF, energy-dispersive spectroscopy (EDS)-STEM, and EDS-scanning electron microscopy (SEM) [97,98,114].…”

Boosting the Electrochemical Performance of Lithium‐Rich Cathodes by Oxygen Vacancy Engineering

“…For the Ni 2p spectrum, the peak corresponding to the Ni 2p 3/2 state can be deconvoluted into two peaks, located at 856.88 eV and 854.58 eV, ascribed to Ni 3 + and Ni 2 + states, respectively. [51,52] The small peak area of Ni 3 + corresponding to LLO (12.7 %) is larger than that of LLO-500 (10.4 %), which may be due to the enhanced oxygen vacancies of LLO-500 resulting in the compensation of Ni 2 + ions from Ni 3 + ions, trapping the Ni ions to avoid transform to Li layer, [38,39,53] increasing the transport of Li ions to the Li layer, and then enhance the electron transport and electrochemical performance. [38,39] Figure S15 shows the oxygen vacancy dependence of the samples in different temperatures.…”

“…[51,52] The small peak area of Ni 3 + corresponding to LLO (12.7 %) is larger than that of LLO-500 (10.4 %), which may be due to the enhanced oxygen vacancies of LLO-500 resulting in the compensation of Ni 2 + ions from Ni 3 + ions, trapping the Ni ions to avoid transform to Li layer, [38,39,53] increasing the transport of Li ions to the Li layer, and then enhance the electron transport and electrochemical performance. [38,39] Figure S15 shows the oxygen vacancy dependence of the samples in different temperatures. It can be seen that the concentration of the oxygen vacancy increases as the annealing temperature rises from 200 to 500 °C and then decreases as the temperature rises to 600 °C.…”

“…In Figure 2(g), the distinct lattice fringes of ~0.47 nm can be observed in the HRTEM micrograph of the LLO-500 sample. [37][38][39] Furthermore, the high-angle annular dark-field (HAADF) imaging in scanning transmission electron microscopy (STEM) of the LLO-500 clearly shows that no rocksalt phase exists (Figure 2h). The STEM and the corresponding elemental mapping images of the LLO-500 sample confirm the uniform distribution of Mn, Ni, Co, and O elements (Supporting Information, Figure S5).…”

Regulation of surface oxygen activity in Li-rich layered cathodes using band alignment of vanadium phosphate surface coatings

“…Due to similar ionic radii for Li + (0.76 Å) and Ni 2+ (0.69 Å), Li/Ni anti-site mixing can readily occur if provided with sufficient free energy in the presence of excess Li or Ni. 76 LLOs natively possess Li-excess at TM layer sites (and further excess Li with LVP coatings); therefore, increased Li/Ni site mixing is expected during the secondary calcination process to produce the NVP/ LVP coating layers on the LLO material. For NMC metal oxide materials, increased Li/Ni disorder implies a decrease in Li storage sites and in-plane 'trapping' of TM ions which are rendered redox inactive by reduced Li + proximity.…”