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The structure instability issues of the highly delithiated LiCoO2 have significantly hindered its high‐voltage applications (≥4.55 V vs Li/Li+). Herein, for the first time, multiple modifications of Li0.9Mg0.05CoO2 (L0.9M0.05CO) via a simple one‐step sintering synthesis are reported. A combination of the bulk Li/Co antisites, a Mg‐pillar enriched surface, and a thin MgO coating layer is achieved to maintain both the bulk and surface structural stability of L0.9M0.05CO upon cycling at an upper cut‐off voltage of 4.6 V. The bulk Li/Co antisites are discovered to enhance the H1‐3 phase evolution reversibility, the Mg pillars that substitute the Li sites effectively reinforces the surface structure, and the thin MgO coating layer can effectively prevent the cathode from severe side reactions. Benefiting from the reduced but reversible H1‐3 phase transition and the reinforced surface structure, L0.9M0.05CO shows an excellent cycle stability. This work provides a new structure modulation route for developing high‐voltage LiCoO2 cathodes. [ABSTRACT FROM AUTHOR]

The cathode materials work as the host framework for both Li+ diffusion and electron transport in Li‐ion 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 LiCoO2, promoting the surface electric conductivity by over one magnitude. It increased the effective voltage (Veff) imposed in the bulk, thus driving more Li+ extraction/insertion and making LiCoO2 exhibit superior rate capability (154 mAh g−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. [ABSTRACT FROM AUTHOR]

The cathode materials work as the host framework for both Li+ diffusion and electron transport in Li‐ion 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 LiCoO2, promoting the surface electric conductivity by over one magnitude. It increased the effective voltage (Veff) imposed in the bulk, thus driving more Li+ extraction/insertion and making LiCoO2 exhibit superior rate capability (154 mAh g−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. [ABSTRACT FROM AUTHOR]

Elevating the cut-off voltage is an effective route to increase the energy density of LiCoO 2 (LCO). However, the highly delithiated LCO faces the issues of poor structural reversibility, O loss, and Co dissolution, etc., especially in the surface region. Herein, the step-like surface degradation (SSD) of pristine LCO (P-LCO) is firstly revealed to be responsible for the rapid capacity decay. To reduce the adverse impact of SSD, a solid electrolyte is coated and annealed to achieve the optimized surface structure chemistry of LCO (SE-LCO), featuring the outermost surface Li 3 PO 4 , surface rock-salt layer, and subsurface spinel-like layer. Benefiting from this surface optimization, the SE-LCO not only shows an enhanced but more reversible phase transition to enhance the structure stability, but also promotes the formation of tough cathode electrolyte interface (CEI) to reduce the O loss and Co dissolution issues. As a result, SE-LCO/graphite cell achieves excellent cycle stability with a remarkable capacity retention of 81.2% after 800 cycles in a potential range of 3–4.55 V, which is among the best reported cell performances. This work broadens the cognition for developing more advanced LCO cathodes. [Display omitted] • The step-like surface degradation (SSD) of P-LCO at 4.6 V is firstly revealed. • The enhanced but more reversible O3/H1–3 phase transition is achieved via tuning surface chemistry. • A tough CEI layer is formed to reduce the O loss and Co dissolution issues upon cycles. [ABSTRACT FROM AUTHOR]

The structure instability issues of the highly delithiated LiCoO2 have significantly hindered its high‐voltage applications (≥4.55 V vs Li/Li+). Herein, for the first time, multiple modifications of Li0.9Mg0.05CoO2 (L0.9M0.05CO) via a simple one‐step sintering synthesis are reported. A combination of the bulk Li/Co antisites, a Mg‐pillar enriched surface, and a thin MgO coating layer is achieved to maintain both the bulk and surface structural stability of L0.9M0.05CO upon cycling at an upper cut‐off voltage of 4.6 V. The bulk Li/Co antisites are discovered to enhance the H1‐3 phase evolution reversibility, the Mg pillars that substitute the Li sites effectively reinforces the surface structure, and the thin MgO coating layer can effectively prevent the cathode from severe side reactions. Benefiting from the reduced but reversible H1‐3 phase transition and the reinforced surface structure, L0.9M0.05CO shows an excellent cycle stability. This work provides a new structure modulation route for developing high‐voltage LiCoO2 cathodes. [ABSTRACT FROM AUTHOR]

The cathode materials work as the host framework for both Li+ diffusion and electron transport in Li‐ion 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 LiCoO2, promoting the surface electric conductivity by over one magnitude. It increased the effective voltage (Veff) imposed in the bulk, thus driving more Li+ extraction/insertion and making LiCoO2 exhibit superior rate capability (154 mAh g−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. [ABSTRACT FROM AUTHOR]

The cathode materials work as the host framework for both Li+ diffusion and electron transport in Li‐ion 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 LiCoO2, promoting the surface electric conductivity by over one magnitude. It increased the effective voltage (Veff) imposed in the bulk, thus driving more Li+ extraction/insertion and making LiCoO2 exhibit superior rate capability (154 mAh g−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. [ABSTRACT FROM AUTHOR]