Exposing the {010} Planes by Oriented Self-Assembly with Nanosheets To Improve the Electrochemical Performances of Ni-Rich Li[Ni_0.8Co_0.1Mn_0.1]O₂ Microspheres

Abstract

A modified Ni-rich Li[NiCoMn]O cathode material with exposed {010} planes is successfully synthesized for lithium-ion batteries. The scanning electron microscopy images have demonstrated that by tuning the ammonia concentration during the synthesis of precursors, the primary nanosheets could be successfully stacked along the [001] crystal axis predominantly, self-assembling like multilayers. According to the high-resolution transmission electron microscopy results, such a morphology benefits the growth of the {010} active planes of final layered cathodes during calcination treatment, resulting in the increased area of the exposed {010} active planes, a well-ordered layer structure, and a lower cation mixing disorder. The Li-ion diffusion coefficient has also been improved after the modification based on the results of potentiostatic intermittent titration technique. As a consequence, the modified Li[NiCoMn]O material exhibits superior initial discharges of 201.6 mA h g at 0.2 C and 185.7 mA h g at 1 C within 2.8-4.3 V (vs Li/Li), and their capacity retentions after 100 cycles reach 90 and 90.6%, respectively. The capacity at 10 C also increases from 98.3 to 146.5 mA h g after the modification. Our work proposes a novel approach for exposing high-energy {010} active planes of the layered cathode material and again confirms its validity in improving electrochemical properties.

Radially Oriented Single‐Crystal Primary Nanosheets Enable Ultrahigh Rate and Cycling Properties of LiNi0.8Co0.1Mn0.1O2 Cathode Material for Lithium‐Ion Batteries

“…[4,21] The optimized high NH 3 ·H 2 O concentration (0.8 mol L −1 ) in the reactor can tune the growth direction and promote the growth of primary particles. To tune the morphology of the precursor, an optimized higher concentration of NH 3 ·H 2 O and stirring speed were used, which were also proved to have significant impact on the coprecipitation process.…”

“…Consequently, cracks may develop and propagate along the grain boundaries until entire pulverization of secondary particles and even spalling off of primary particles, which has been identified as one of the main reasons for the rapid degradation of Ni-rich NCM materials upon long-term cycling. [4] However, structurally and morphologically controlled synthesis of NCM materials with superior rate and cycling properties remains a great challenge, in particular in a mass production manner. [13,16] In view of the high anisotropy in Li + diffusion [17,18] and lattice expansion/contraction [19,20] of hexagonal-layered NCM materials, morphological modulation will be an efficient way to enhance their rate capability and cycling stability.…”

“…[2,4] These drawbacks are largely attributed to their spherical micrometer-sized secondary particles aggregated densely by many randomly oriented primary nanoparticles, [4][5][6] as shown in Figure 1a. Nevertheless, the inferior cycling stability and poor rate capability of Ni-rich oxide cathode materials have to be overcome before they can compete in practical implementation.…”

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3.8 V (vs Li + /Li), making them a class of promising cathode material and attracting considerable attention. As Li + can only diffuse along the 2D {010} plane in the hexagonal-layer structure of NCM materials, [4,7] the randomly exposed crystal planes (not solely the active {010} plane) may substantially hinder the Li + exchange at the electrode/electrolyte interface. [2,4] These drawbacks are largely attributed to their spherical micrometer-sized secondary particles aggregated densely by many randomly oriented primary nanoparticles, [4][5][6] as shown in Figure 1a.

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A General One‐Pot Synthesis Strategy of 3D Porous Hierarchical Networks Crosslinked by Monolayered Nanoparticles Interconnected Nanoplates for Lithium Ion Batteries

“…For layered oxides, the intensity ratio of I (003) / I (104) can usually reflect the degree of cation mixing. For the ratios higher than 1.2, cation mixing is normally negligible, favoring the performance. The ratio values of I (003) / I (104) for 3D‐NCA, 3D‐NCM811, and 3D‐NCM111 are 2.3, 1.6, and 3.8, respectively, suggesting only a slight cation mixing, consistent with the low Ni/Mn occupancies refined.…”