Rational Design of Coating Ions via Advantageous Surface Reconstruction in High‐Nickel Layered Oxide Cathodes for Lithium‐Ion Batteries

Abstract

The implementation of high‐nickel layered oxide cathodes in lithium‐ion batteries is hampered by the inherent issues of formation of NiO‐like rock‐salt phase as well as residual lithium (e.g., LiOH, LiHCO3, and Li2CO3) on the surface. To overcome the challenges, here a rational strategy is presented of interdiffusion‐based surface reconstruction via dry coating and the design principles for identifying the optimum coating ions on a LiNi0.91Mn0.03Co0.06O2 (NMC91) cathode. Notably, the combined approach of theoretical screening, which involves the consideration of superexchange interactions among different oxidation states and density functional theory calculations, along with experimental analyses, which involve the characterization of the decrease in Ni content and residual lithium on the surface of NMC91, demonstrate the effective reduction in rock‐salt phase and residual lithium. Among the four ions investigated (Al, Co, Fe, and Ti), cobalt‐coated NMC91 is the most effective at reducing the rock‐salt phase and residual lithium by successfully reconstructing the surface of NMC91 and exhibits an excellent capacity retention of 85% in a full cell after 300 cycles at 30 °C.

Addressing Mn Dissolution in High‐Voltage LiNi0.5Mn1.5O4 Cathodes via Interface Phase Modulation

“…[ 1–7 ] LIBs have been extensively applied in the field of electric vehicles. [ 8–11 ] LiNi 0.5 Mn 1.5 O 4 (LNMO) is an excellent and promising cathode material because of its high‐power density and high‐voltage platform. [ 12,13 ] However, the spinel‐structured LNMO is not like layered LiNi 1‐y‐z Mn y Co z O 2 .…”

Hierarchical Doping Engineering with Active/Inert Dual Elements Stabilizes LiCoO2 to 4.6 V

“…[ 26 ] Thereby, during the charging process, the Ni 2+ Li layer −O 2− −Ni 3+ /Co 4+ TM layer would present stronger superexchange interaction than Ni 2+ Li layer −O 2− −Co 3+ /Ni 4+ TM layer ( Figure 3 a). [ 27 ] The inset figure on top of Figure 3b shows the EPR signal for the pristine LCONP sample. The g value at 2.14 belonging to Ni 3+ suggested a certain amount of Ni 3+ ions were actually occupying at the TM layer within LCONP.…”

“…[26] Thereby, during the charging process, the Ni (Figure 3a). [27] The inset figure on top of Figure 3b shows the EPR signal for the pristine LCONP sample. The g value at 2.14 belonging to Ni 3+ suggested a certain amount of Ni 3+ ions were actually occupying at the TM layer within LCONP.…”

Synchrotron radiation based X-ray techniques for analysis of cathodes in Li rechargeable batteries

“…155 This is associated with fatigue phase formation induced by surface reconstructions. 156 In situ heating XRD, which is also termed as time-resolved (TR) XRD is a unique technique for investigation of real-time structural changes in the material during heating. 157,158 Thus, it helps to understand the degradation and stability of cathode materials.…”