3.8 V (vs Li + /Li), making them a class of promising cathode material and attracting considerable attention. 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. [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. On the one hand, concomitant with this structure, the surface of secondary particles is terminated with random crystal planes. 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. Meanwhile, the randomly oriented primary nanoparticles induce a prolonged and mazy Li + diffusion pathway inside the secondary particles, because Li + ions have to migrate across the grain boundaries, especially between the grains with inconsistent crystal planes. On the other hand, the successive phase transition accompanied by repeated Li + insertion/extraction would result in anisotropic variation of the lattice parameters, and such variation is severely aggravated with the increase of Ni content. [8] Accordingly, in the Ni-rich oxide cathode materials, the substantial anisotropic lattice expansion/contraction would result in drastic microstrains at the boundaries of randomly oriented primary particles due to the asynchronous volume Ni-rich Li[Ni x Co y Mn 1−x−y ]O 2 (x ≥ 0.8) layered oxides are the most promising cathode materials for lithium-ion batteries due to their high reversible capacity of over 200 mAh g −1 . Unfortunately, the anisotropic properties associated with the α-NaFeO 2 structured crystal grains result in poor rate capability and insufficient cycle life. To address these issues, a micrometersized Ni-rich LiNi 0.8 Co 0.1 Mn 0.1 O 2 secondary cathode material consisting of radially aligned single-crystal primary particles is proposed and synthesized. Concomitant with this unique crystallographic texture, all the exposed surfaces are active {010} facets, and 3D Li + ion diffusion channels penetrate straightforwardly from surface to center, remarkably improving the Li + diffusion coefficient. Moreover, coordinated charge-discharge volume change upon cycling is achieved by the consistent crystal orientation, significantly alleviating the volume-change-induced intergrain stress. Accordingly, this material delivers superior reversible capacity (203.4 mAh g −1 at 3.0-4.3 V) and rate capability (152.7 mAh g −1 at a current density of 1000 mA g −1 ). Further, this structure demonstrates excellent cycling stability without any degradation after 300 cycles. The anisotropic morphology modulation provides a simple, efficient, and scalable way to boost the performance and applicability of Ni-rich layered oxide cathode materials.

A novel progressive concentration gradient cathode material, LiNi0.7Co0.13Mn0.17O2, with superior capacity and cycling stability is reported for the first time.

In article number https://doi.org/10.1002/aenm.201803963, Chunyu Du, Xueliang Sun and co‐workers synthesize a spherical LiNi0.8Co0.1Mn0.1O2 cathode material with radially aligned single‐crystal primary nanosheets. This structure maximizes the exposed active surface, minimizes the transfer length of Li+ and electrons, and significantly alleviates the intergrain stress, thus delivering a superior electrochemical performance in lithium ion batteries.

No abstract

High-capacity Li-rich layered oxides (LLOs) hold giant promise as cathodes for Li-ion batteries but still suffer from cycling instability and voltage decay. The oxygen redox reaction and phase transformation to spinel are major incentives for performance deterioration. Hence, we propose a La-doping strategy to stabilize surface oxygen and reduce spinel phase components. The special La–O bond could exhibit not only an electrovalent characteristic bond but also a relative covalent property, which enhances the stability of lattice oxygen and the reversibility of oxygen redox. The spinel phase composition of surface area could be reduced through La doping, which suppresses capacity fade and voltage decay. Accordingly, the La-doping LLOs with Li and O vacancy defects forming at the surface area exhibit excellent reversible capacity (225 mA h/g at 1 C and 145 mA h/g at 5 C) and rate performance (80.68 and 81.76% capacity retention over 300 cycles at 1 and 5 C). This study could be extended to synthesize other advanced cathode materials for next-generation Li-ion batteries and even be helpful to the R&D of rare-earth utilization.