Riveting Dislocation Motion: The Inspiring Role of Oxygen Vacancies in the Structural Stability of Ni-Rich Cathode Materials

Abstract

In Ni-rich cathode materials, dislocation can be generated at the surface of primary grains because of the accumulation of stress fields. The migration of dislocation into grains, accelerating the annihilation of reverse dislocation as well as oxygen loss, is considered as the principal origin of crack nucleation, phase transformation, and consequent fast capacity decay. Thus, reducing the dislocation would be effective for improving cathode stability. Here, we report the inspiring role of oxygen vacancies in blocking and anchoring the dislocation. Specifically, a large number of oxygen vacancies can assemble to form dense dislocation layers at the surface of grains. Thanks to the dislocation interaction mechanism, preformed dense dislocation at the surface can effectively rivet the newly developed dislocation during cycling. Ex situ transmission electron microscopy analysis indicates that the intragranular cracks and phase transformation were hindered by the riveted effect, which in turn improved the structural and cycling stability of the Ni-rich cathode. Overall, this work provides novel crystallographic design and understanding of the enhanced mechanical strength of Ni-rich cathode materials.

Revealing the Role of W-Doping in Enhancing the Electrochemical Performance of the LiNi0.6Co0.2Mn0.2O2 Cathode at 4.5 V

“…For accurately revealing the structural evolution after W-doping, HRTEM was performed, with the results shown in Figure j,k. The surface and bulk of the pristine and W-0.5% samples both present a fine layered structure with characteristic spacings of 0.478 and 0.483 nm, respectively, which correspond to the (003) plane. , After W-doping, the lattice fringe spacing increases obviously, in accordance with the above XRD refinement results.…”

Construction and Operating Mechanism of High‐Rate Mo‐Doped Na3V2(PO4)3@C Nanowires toward Practicable Wide‐Temperature‐Tolerance Na‐Ion and Hybrid Li/Na‐Ion Batteries

“…The high‐/medium‐frequency semicircle matches with charge transfer resistance ( R ct ) at the electrode‐electrolyte sur‐/interfaces, and the straight lines in low frequency range refers to the Warburg resistance ( W ) of the Li + /Na + diffusion in the MNVP host. [ 49 ] According to the equivalent circuit (Figure S10a, Supporting Information), the R ct values for the MNVP@C NWs after the 100th, 300th, and 500th cycles are quantitatively fitted as ≈101.8, ≈219.6, and ≈345.6 Ω, respectively, which are significantly lower than those of the NVP@C NWs and BNVP@C (Figure S10b, Supporting Information). Additionally, the D H, app also can be estimated from the low‐frequency plots based on the equation: [ 50 ] D H, app = R 2 T 2 /(2 A 2 n 4 F 4 C 2 σ 2 ) and Z ′ = R ct + σω −1/2 , where R , T , A , n , F , and C correspond to the gas constant, temperature, efficient work area, the number of electrons at charged state, the Faraday constant and the concentration of ions, respectively.…”

A Review of Degradation Mechanisms and Recent Achievements for Ni‐Rich Cathode‐Based Li‐Ion Batteries

“…Wu and co‐workers created oxygen vacancies by treating samples in an N 2 atmosphere. [ 115 ] The obtained high‐density dislocation layers originate from oxygen vacancies, preventing continuous propagation of intergranular cracks inside the particles during cycling. Figure 21c shows TEM analyses and crystal structures of untreated and treated cathodes after cycles.…”