Abstract
To meet the growing demand for global electrical energy storage, high‐energy‐density electrode materials are required for Li‐ion batteries. To overcome the limit of the theoretical energy density in conventional electrode materials based solely on the transition metal redox reaction, the oxygen redox reaction in electrode materials has become an essential component because it can further increase the energy density by providing additional available electrons. However, the increase in the contribution of the oxygen redox reaction in a material is still limited due to the lack of understanding its controlled parameters. Here, it is first proposed that Li‐transition metals (TMs) inter‐diffusion between the phases in Li‐rich materials can be a key parameter for controlling the oxygen redox reaction in Li‐rich materials. The resulting Li‐rich materials can achieve fully exploited oxygen redox reaction and thereby can deliver the highest reversible capacity leading to the highest energy density, ≈1100 Wh kg−1 among Co‐free Li‐rich materials. The strategy of controlling Li/transition metals (TMs) inter‐diffusion between the phases in Li‐rich materials will provide feasible way for further achieving high‐energy‐density electrode materials via enhancing the oxygen redox reaction for high‐performance Li‐ion batteries.
Highlights
Rechargeable Li-ion batteries have become a key enabler for transformational changes in our society by powering advanced portable electronics and deploying electric vehicles and grid-scale applications.[1]
Synchrotron X-ray diffraction (SXRD) (Figure 1a; Figure S2c,d, Supporting Information) and neutron powder diffraction (NPD) (Figure S2a,b, Supporting Information) clearly show that the samples are composed of the two phases, a rhombohedral phase (R-3m symmetry, “R phase”) such as LiNi0.5Mn0.5O2 (LNMO) and a monoclinic phase (C2/m symmetry, “M phase”) such as Li2MnO3, which is indicated by the broad superstructure peaks at 20–23° in the 2θ range[10] (Figure 1a), which is consistent result with STEM image in Figure S3, Supporting Information
Given the Li-rich layered materials that are composed of the two layered phases,[3b,10a,14b,21] the Li-transition metals (TMs) inter-diffusion between both phases can lead to different composite structure such as the excess Li and Ni incorporation in both layered phases that can remarkably improve reversible oxygen redox activity and layered structure stability
Summary
Rechargeable Li-ion batteries have become a key enabler for transformational changes in our society by powering advanced portable electronics and deploying electric vehicles and grid-scale applications.[1] To meet the soaring demand in high-energydensity Li-ion batteries, an oxygen redox reaction in electrode material has been considered as an essential component because it can provide additional available electrons to overcome the limit of theoretical energy density in conventional electrode materials based only on cationic redox reactions To realize this transformation, Li-rich layered materials (Li1+xTM1−xO2) have recently become one of the most attractive electrode materials because they can exploit the oxygen redox reaction in addition to the transition metal (TM) redox reaction and thereby can deliver much higher capacities (>250 mAh g−1) than conventional layered materials (e.g., LiCoO2).[2]. L. Gu Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190, China. L. Gu School of Physical Sciences University of Chinese Academy of Sciences Beijing 100190, China. Controlling the oxygen redox reaction via the Li/TMs distribution between the phases in Li-rich materials can provide a promising opportunity to design high-energy-density Li-ion electrode materials that can achieve highly exploited oxygen redox reaction
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