12/30/2023 0 Comments Lithium nmc cathode![]() ![]() As a result of the anisotropic lattice volume change, the microcrack propagation is more serious in those Ni-rich NMC cathodes (Liu et al., 2018 Fan et al., 2020). Although more Li + ions can be extracted from Ni-rich cathodes, the electrostatic repulsion between oxygen slabs increases, too, which leads to a more drastic c/a ratio variation during electrochemical cycling. The mandatory increase of the tap density to over 3.3 g cm −3 generally leads to rapid capacity fading since the polycrystalline secondary particles would crack and collapse during high-pressure electrode pressing (Kim et al., 2018). In the recent decade, the chasing of larger gravimetric capacity has pushed the nickel content of the NMC to over 60% as a tradeoff larger gravimetric capacity, these nickel-rich NMC cathodes are suffering more serious issues caused by the polycrystalline secondary particles (Dixit et al., 2017 Kim et al., 2018 Lee et al., 2018 Liang et al., 2018 Ryu et al., 2018 Fan et al., 2020 Wang et al., 2020b). The polycrystalline nature of the secondary particles presents many issues, including (1) low tap density (<3.3 g cm −3) compared with the single-crystalline LiCoO 2 cathode (3.9 g cm −3), which leads to an inadequate volumetric energy density (Kim et al., 2018), (2) the formation of microcracks inside the secondary particle incurred by the anisotropic lattice expansion and shrink during charging/discharging, which gradually deteriorates the cycling stability (Kim et al., 2018 Liu et al., 2018), and (3) the porous structure of the secondary particle prevents homogeneous carbon coating on each primary particle, which results in unsatisfactory electrical contact between the active material and the current collector (Kimijima et al., 2016b). Most commercially available NMC are polycrystalline secondary particles aggregated by numerous nanosized primary particles, which usually maintain the spherical shape from the precursors. The particle's crystallinity and morphology can put significant influences on the energy density, cycling stability, and rate capability of the NMC cathodes in practical applications (Liu et al., 2018 Fan et al., 2020). Lithium nickel manganese cobalt oxide (NMC) cathodes have been critical pillars of advanced lithium ion batteries at current state (Chen et al., 2019 Xu et al., 2019 Zhou et al., 2019 Kim et al., 2020 Li et al., 2020 Wang et al., 2020b Wu et al., 2020 Zhang, 2020 Zheng et al., 2020). We expect that the more generalized growth mechanism drawn from invaluable previous works could enhance the rational design and the synthesis of cathode materials with superior energy density. In this manuscript, we start a journey from the fundamental crystal growth theory, compare the crystal growth of NMC among different techniques, and disclose the key factors governing the growth of single-crystalline NMC. Various techniques have been explored to synthesize the single-crystalline NMC product, but the fundamental mechanisms behind these techniques are still fragmented and incoherent. Well-dispersed single-crystalline NMC is therefore proposed to be an alternative solution for further development of high-energy-density batteries. ![]() Although the polycrystalline NMC particles have demonstrated large gravimetric capacity and good rate capabilities, the volumetric energy density, cycling stability as well as production adaptability are not satisfactory. Currently, most commercially available NMC products are polycrystalline secondary particles, which are aggregated by anisotropic primary particles. Lithium nickel manganese cobalt oxide (NMC) cathodes are of great importance for the development of lithium ion batteries with high energy density.
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