Perspective on the Preparation Methods of Single Crystalline High Nickel Oxide Cathode Materials

Abstract

Li(NixCoyMnz)O2 (x + y + z = 1, NCM), as one of the most dominant cathode materials in electric vehicle (EV) batteries, faces the challenges of poor cycling stability and safety concerns with the increase of Ni content and charge/discharge capacity. Single crystalline NCM (SC‐NCM) materials have been developed to mitigate these challenges, owing to their lower surface areas, fewer grain boundaries, and better morphological stability. Here, the preparation strategies of SC‐NCM are summarized, including continuous high‐temperature sintering (CHTS), molten salt method, pulse high‐temperature sintering (PHTS), and controllable growth with special orientations or sizes. CHTS produces irregular SC‐NCM particles, but is accompanied by Li‐volatilization and agglomeration during long‐term sintering. The molten salt helps to lower calcination temperature and generate well‐defined crystalline material, but generally causes large capacity loss due to the Li/H exchange in the following water rinsing procedure. To address the above challenges, the PHTS strategy has recently been recently proposed, which mitigates Li‐loss through shortened high‐temperature stage and avoids further water rinsing steps. For improving the C‐rate performance, controllable crystal growth with specific sizes and crystal orientations is highly desired, which calls for further investigation and upgrading of current large‐scale preparation technology.

Enhanced Li-ion intercalation kinetics and lattice oxygen stability in single-crystalline Ni-rich Co-poor layered cathodes

“…In contrast, the introduction of Al increases the surface energy of the main crystal surface (003), which slightly inhibits the growth of the particles and leads to a slightly smaller distribution of particles. The co-introduction of Ba and Al-ions synergistically promotes a more homogeneous crystal growth to obtain similar particle size compared with pristine NCM85, the crystal growth mechanism is similar to that reported by Guo et al 18,27 Fig. S5b† depicts a high-resolution transmission electron microscopy (HRTEM) image of BA-NCM85 with an interplanar spacing of 0.476 nm pointing to the (003) plane.…”

Fluorinated Thiophene-Based Electrolyte Additives Enable a Robust Cathode Electrolyte Interphase with Conformal Homogeneity for a High-Voltage LiNi0.8Co0.15Al0.05O2 Cathode

“…13,14 More importantly, the overhigh cutoff voltage (>4.3 V) of NCA cathode inevitably poses an overwhelming challenge to the electrochemical stability of carbonate-based electrolytes. 15 The decomposition of electrolyte becomes more severe when applying such high working voltages, which consumes more Li + /electrolyte to construct a stable cathode electrolyte interphase (CEI) and induces more side reaction on the electrode/electrolyte interface, thus deteriorating the cycle life of the battery. 16 Therefore, the application of high-voltage NCA cathodes is beneficial to the exploration of high energy density LIBs on the condition that the stability of the CEI layer can be greatly improved and the decomposition of electrolyte can be highly suppressed.…”

“…High nickel LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) is considered one of the promising cathode candidates in recent years due to its outstanding properties, such as superior specific capacity and high operation voltage. − However, although the high nickel content of NCA can greatly improve the specific capacity under high voltages, its cycle life and structural durability suffer from more challenges during the long-term cycling. − Moreover, inevitable phase transformation, severe cation mixing and even particle microcrack are prone to be generated upon cycling on the condition that the content of Ni is higher than 90% in NCA, which will largely deteriorate the electrode/electrolyte interface and worsen the battery performance. , More importantly, the overhigh cutoff voltage (>4.3 V) of NCA cathode inevitably poses an overwhelming challenge to the electrochemical stability of carbonate-based electrolytes . The decomposition of electrolyte becomes more severe when applying such high working voltages, which consumes more Li + /electrolyte to construct a stable cathode electrolyte interphase (CEI) and induces more side reaction on the electrode/electrolyte interface, thus deteriorating the cycle life of the battery .…”

Bismuth-doping boosting Na+ diffusion kinetics of layered oxide cathode with radially oriented {010} active lattice facet for sodium-ion batteries

“…To alleviate the problems, exposing sufficient {010} facets of primary particles is one effective way to provide additional ion transport channels for enhancing Na + diffusion kinetics. , A surfactant-assisted synthesis method was used to effectively promote inducing the growth of the exposed {010} active planes, by lowering the high surface energy of the {010} facets with the addition of surfactants of sodium dodecyl sulfate and polyvinylpyrrolidone. , A surfactant-free coprecipitation method was able to construct a porous and hollow architecture with exposed {010} facets. − Furthermore, rationally designing secondary microparticles assembled with primary nanoparticles is effective at improving diffusion kinetics by shorting the ion diffusion pathway. , However, the diffusion of Na + into the electrolyte is difficult as it entails crossing through multiple grain boundaries due to the random agglomeration of primary particles . In addition, the nanoparticles with large specific surface areas in secondary microparticles easily initiate surface parasitic reactions with electrolyte, accelerate the degradation of the cathode material, and thus result in capacity decay after long cycling. − Therefore, simultaneous combination of the oriented crystal facets and the nanoplatelet-containing microspheres could greatly enhance both the structural stability and Na + diffusion kinetics.…”