Promoting Surface Electric Conductivity for High‐Rate LiCoO₂

Abstract

The cathode materials work as the host framework for both Li + diffusion and electron transport in Liion batteries. The Li + diffusion property is always the research focus, while the electron transport property is less studied. Herein, we propose a unique strategy to elevate the rate performance through promoting the surface electric conductivity. Specifically, a disordered rock-salt phase was coherently constructed at the surface of LiCoO 2 , promoting the surface electric conductivity by over one magnitude. It increased the effective voltage (V eff ) imposed in the bulk, thus driving more Li + extraction/insertion and making LiCoO 2 exhibit superior rate capability (154 mAh g À 1 at 10 C), and excellent cycling performance (93 % after 1000 cycles at 10 C). The universality of this strategy was confirmed by another surface design and a simulation. Our findings provide a new angle for developing high-rate cathode materials by tuning the surface electron transport property.

Dual Modification of P3-Type Layered Cathodes to Achieve High Capacity and Long Cyclability for Sodium-Ion Batteries

“…44 It is wellestablished that the polarization of the cathode and the effective voltage applied to the layered lattice can significantly affect the surface conductivity of the cathode, thereby consequently dominating the rate performance of the electrode. 45 In this work, the lowest surface resistivity was observed for NNCMO-PR, which confirms that the dual modification strategy is effective in improving the fast sodiation/desodiation process. Figure 3f and Table S2 illustrate that the NNCMO-PR cathode exhibits superior rate performance compared to previously reported cathodes with a P3 structure.…”

“…Apart from the difference in ionic conductivity, the electronic conductivity was also compared by measuring their DC resistivities of the electrode surface using the Physics Property Measurement System (PPMS) . It is well-established that the polarization of the cathode and the effective voltage applied to the layered lattice can significantly affect the surface conductivity of the cathode, thereby consequently dominating the rate performance of the electrode . In this work, the lowest surface resistivity was observed for NNCMO-PR, which confirms that the dual modification strategy is effective in improving the fast sodiation/desodiation process.…”

One‐Step Sintering Synthesis Achieving Multiple Structure Modulations for High‐Voltage LiCoO2

“…[ 6f ] Besides, this S/R phases can alleviate the lattice mismatch between the bulk phase and the coating layer, thus facilitating Li + ion transport at the interface. [ 6b,c,11 ] Our previous work has revealed the formation of surface spinel buffering region due to the surface gradient anion‐ and cation‐doping, and similar results have also been demonstrated in other studies, showing that surface spinel can prevent oxygen migration out of the LCO particle at high voltages. [ 8a,12 ] Moreover, the coating layer can mitigate the direct contact between the active cathode material and the electrolyte, which could eliminate the issue of side reactions.…”

Revealing the Grain-Boundary-Cracking Induced Capacity Decay of a High-Voltage LiCoO2 at 4.6 V

“…In recent years, lots of the researchers have paid much attention to develop the high-voltage LCO cycling at 4.6 V. The previous reports of our team show that, the curvature of the cobalt oxide layers nearby the surface region dominates the structural stability of LCO at high potentials, and in turn, the electrode performances. Based on this basis, we have developed some facile methods to reinforce the surface structure of LCO, including reconstructing an Al/F enriched and spinel reinforced surface to reduce the side reaction, and promoting the surface electric conductivity of LCO by over one magnitude via constructing a disordered rock-salt phase in the surface region . Besides, we also have developed a one-step sintering synthesis to achieve a combination of bulk Li/Co antisites, Mg-pillar enriched surface, and thin Mg–O coating layer for enhanced structure stability in both the bulk and surface region …”

“…Based on this basis, we have developed some facile methods to reinforce the surface structure of LCO, including reconstructing an Al/F enriched and spinel reinforced surface to reduce the side reaction, 8 and promoting the surface electric conductivity of LCO by over one magnitude via constructing a disordered rock-salt phase in the surface region. 9 Besides, we also have developed a one-step sintering synthesis to achieve a combination of bulk Li/Co antisites, Mg-pillar enriched surface, and thin Mg−O coating layer for enhanced structure stability in both the bulk and surface region. 10 Meanwhile, similar surface modulation strategies have also been reported by other groups.…”