Review—Revealing the Intercrystalline Cracking Mechanism of NCM and Some Regulating Strategies

Abstract

Nickel-rich cathode has received much attention due to its high energy density, high capacity, low cost, and environmental friendliness. The existence of intercrystalline microcracks in NCM seriously affects the structural stability and integrity of the battery crystal surface. Irreversible phase transitions result in changes in lattice parameters, the interface side reactions severely corrode the crystal surface, and secondary particle heterogeneity leads to uneven reactions. Common amorphous microcracks include single crystal, gradient doping, etc. This review first introduces the microcrack mechanism of NCM, and then summarizes two solutions: single crystal and gradient doping. Finally, we present new views and insights, and hope to give enlightenment on the subsequent inhibition of intercrystal microcrack, and construct the reasonable structure of NCM cathode.

Interface and Electrode Microstructure Engineering for Optimizing Performance of the LiNiO2 Cathode in All-Solid-State Batteries

“…After 400 cycles, the secondary particle structure is mostly lost, and only the primary particles (grains) remain. In general, intergranular cracking results from the anisotropic volume changes (“breathing”), interfacial side reactions, and/or heterogeneous SOC distribution during cycling. − Since the pelletized and slurry-cast cathodes use the same (active) materials, namely, LiNbO 3 -coated LiNiO 2 and Li 6 PS 5 Cl, we believe that the latter is primarily causing the particle fracture. As discussed above, the pelletized cathode shows inferior ionic/electronic partial conductivities (tortuous transport pathways), which may lead to nonuniform de/lithiation of the CAM and accumulation of mechanical stress .…”

Review on Oxygen Release Mechanism and Modification Strategy of Nickel-Rich NCM Cathode Materials for Lithium-Ion Batteries: Recent Advances and Future Directions

“…However, during cycling, the nickle-rich material also generates more heat and the structure is more likely to collapse, resulting in reduced capacity retention. − Especially, low capacity retention and poor structural stability under long cycles become more serious. The main reasons for the deterioration of battery performance are as follows: (1) residual lithium compounds on the surface, − (2) Li/Ni mixing phenomenon, − (3) intergranular cracking and mechanical strain, − (4) oxygen evolution, , etc. The main advantages and disadvantages of nickel-rich NCM are summarized in Figure .…”

In situ characterization of crystal phase evolution of the LiNi0.6Co0.2Mn0.2O2 cathode at different current densities

“…21,22 The accumulation of these factors not only eventually leads to the degradation of electrochemical performance, but also to gas production and battery bulging, a severe safety hazard for practical applications. [23][24][25] On the other hand, some researchers argue that intergranular cracking and kinetic limitations are not the main causes of structural fatigue. [26][27][28][29] They propose that the main reason is the mismatch between the laminar structure and the lattice of the rock salt phase epitaxially grown on the primary particles when charged deeply (SOC $ 75%).…”

“…21,22 The accumulation of these factors not only eventually leads to the degradation of electrochemical performance, but also to gas production and battery bulging, a severe safety hazard for practical applications. 23–25…”