Deciphering the degradation discrepancy in Ni‐rich cathodes with a diverse proportion of [003] crystallographic textures

Abstract

The crystal plane plays a very important role in the properties of Ni‐rich cathodes. [003] crystallographic texture regulation has been proven to improve structural stability, and yet, the discrepancy of particles with different exposed ratios of [003] in structural attenuation has not been clarified. Herein, we have unraveled comprehensively the structural decay difference for Ni‐rich cathodes’ primary particles with the different percentages of exposed [003] by regulating the precursor coprecipitation process. The findings based on structural characterization, first‐principles calculations, finite element analysis, and electrochemical test reveal that the length and width of particles represent false[11¯0false] $[1\bar{1}0]$ and [003] directions, respectively, and show that cathode particles with a higher false[11¯0false] $[1\bar{1}0]$/[003] ratio can effectively inhibit structure degradation and intergranular/intragranular crack formation owing to the low oxygen vacancy formation energy on (003) planes and the small local stress on secondary/primary particles. This study may provide guidance for the structural design of layered cathodes.

Enhancing the Integral Structural and Thermal Stability of Ultrahigh-Ni Cathodes via Morphology Refinement and In Situ Interfacial Engineering

“…The primary particles’ aspect ratios of bare samples are entirely distributed in 1.0–2.5, and those of the double-modified materials concentrate in 2.0–4.5. The introduction of tungsten and follow-up calcination make materials prefer to grow an incoherent twin boundary and a small-angle grain boundary with low configuration energy rather than a large-angle grain boundary with high configuration energy. ,− Hence, the modified primary particles with a smaller orientation angle difference have a high aspect ratio. Qiu et al proposed that the length and width of the particles represent the [11̅0] and [003] directions. , Many primary particles with a high aspect ratio expose the (003) crystal planes, which is manifested as more slender primary particles and a radially ordered texture.…”

“…In contrast, the H2 → H3 phase transition peaks of NCM-WF2 are approximately overlapped before and after 100 cycles, which means that the irreversibility and polarization of the H2 → H3 phase transition reduce during the deep (de)­lithiation process. Even if the c -axis of the primary particles arranged closely in the radial direction expands and shrinks, the local stress is so difficult to accumulate in the process of deep (de)­lithiation that weakening the impulse of microcracks ensures the stability of the bulk structure. , It can be seen from the d Q /d V curves of NCM-WF2 that the irreversible phase transition degree is weakened followed by the improvement of material cyclic stability.…”

“…Qiu et al proposed that the length and width of the particles represent the [11̅ 0] and [003] directions. 30,31 Many primary particles with a high aspect ratio expose the (003) crystal planes, which is manifested as more slender primary particles and a radially ordered texture. To further visualize the internal configuration, SEM-FIB images of NCM and NCM-WF2 are displayed in Figure 2g,h and Figure S4a,b.…”

Understanding the Synthesis Kinetics of Single‐Crystal Co‐Free Ni‐Rich Cathodes

“…In situ XRD was carried out to explore the influence of molten-salt synthesis on the phase evolution and structural changes during the charge-discharge process in Fig- ure 4. [30][31][32][33][34][35][36][37][38][39] The 3D contour plots of (003), ( 101), ( 104) and (018)/(110) diffraction peaks of the two materials exhibit an obvious charge-dependent displacement state. The results demonstrate that the two materials undergo a similar structural evolution process, but the changes of c-axis parameters are obviously different.…”

Accumulated Lattice Strain as an Intrinsic Trigger for the First-Cycle Voltage Decay in Li-Rich 3d Layered Oxides

“…Lithium-ion batteries (LIBs) have received considerable attention in the past decades because of their excellent rechargeability and high energy density. − Li- and Mn-rich layered oxide (LMLO) cathode materials are particularly attractive because they can deliver much higher specific capacities (exceeding 250 mA h g –1 ) than the most commonly used layered Li­(Ni, Co, Mn)­O 2 (NCM, R 3̅ m ) cathode materials (around 180 mA h g –1 ). − Such high specific capacity is attributable to the cationic and anionic redox processes in LMLOs, which are different from the transition-metal (TM) redox alone in NCM cathodes on cycling. − There is a high voltage plateau associated with the lattice oxygen oxidation in the first de-lithiation process, but it vanishes upon the lithiation process. − Furthermore, a continuous reduction of the average discharge voltage occurs during the subsequent cycles, which seriously restricts the commercial application of LMLOs. , These inspire tremendous research efforts to decipher the origin of the voltage decay in LMLOs.…”