Comparative Studies of Polycrystal and Single-Crystal LiNi_0.6Co_0.2Mn_0.2O₂ in Terms of Physical and Electrochemical Performance

Abstract

Herein, the physical properties (structure, morphology, lattice strain, specific surface area, particle size, and compaction density) of polycrystal LiNi 0.6 Co 0.2 Mn 0.2 O 2 (PC622) and single-crystal LiNi 0.6 Co 0.2 Mn 0.2 O 2 (SC622) materials have been comparatively investigated. We have also investigated the electrochemical performance of PC622 and SC622 electrodes with different compaction densities. The results show that secondary particle collapse is widely observed in highly compacted PC622 electrodes. Moreover, the improvement in compaction density is beneficial for specific capacity and initial Coulombic efficiency. SC622 exhibits good cycling performance at room temperature (25 °C) and an elevated temperature (55 °C) even when the density increases to 3.52 g cm −3 . The capacity retention values of SC622 are 86.0% (150 cycles, 1C, 25 °C) and 94.1% (100 cycles, 1C, 55 °C), which are significantly higher than PC622 (78.7 and 75.7%, respectively). Further studies via TEM on these electrodes with high compaction densities show that a thinner rock-salt phase region is found on the surface of the SC622 particles. Hence, SC622 maintains crystallite integration, excellent cycling performance, and thermal stability and can easily be manufactured into high compaction density electrodes. KEYWORDS: polycrystal LiNi 0.6 Co 0.2 Mn 0.2 O 2 , single-crystal LiNi 0.6 Co 0.2 Mn 0.2 O 2 , micro/lattice strains, high compacted density, structural stability, particle crack/cleave

Stacking Fault Formation in LiNi0.6Co0.2Mn0.2O2 during Cycling: Fundamental Insights into the Direct Recycling of Spent Lithium-Ion Batteries

“…The NCM622 powder consists of large (10–20 μm) spherical primary particles with diameters of ∼1 μm (Figure f). This particle shape is common among NCM- and NCA-based materials, although NCM622 compounds consisting of large, isolated primary particles with diameters of 2–5 μm were recently proposed to improve the cyclability. , …”

“…This particle shape is common among NCM-and NCA-based materials, although NCM622 compounds consisting of large, isolated primary particles with diameters of 2−5 μm were recently proposed to improve the cyclability. 27,28 Ex Situ XRD Measurements. As described in the Introduction, changes in the crystal structure of NCM622…”

“…Based on the average E during the discharge reaction, energy densities (Ws) of NCM111, NCM523, NCM622, NCM811, and NCA were calculated to be 553, 608, 662, 665, and 713 mW h g −1 , respectively (Figure1e).The NCM622 powder consists of large (10−20 μm) spherical primary particles with diameters of ∼1 μm (Figure1f). This particle shape is common among NCM-and NCA-based materials, although NCM622 compounds consisting of large, isolated primary particles with diameters of 2−5 μm were recently proposed to improve the cyclability 27,28. Ex Situ XRD Measurements.…”

Single‐Crystalline Cathodes for Advanced Li‐Ion Batteries: Progress and Challenges

“…The phenomenon became more and more severe with increasing compacted density while the structure of single‐crystalline particles was well preserved. [ 48 ] Therefore, single‐crystalline cathode materials with high mechanical strength and grain boundary free structure can prevent morphological collapse during cathode manufacturing and electrochemical process. In addition, intergranular and intragranular cracking are critical issues for layered cathodes due to the coupling effect of electrochemistry and mechanics when LIBs are required to work at high voltage.…”

“…Reproduced with permission. [ 48 ] Copyright 2021, American Chemical Society. Reproduced with permission.…”