Electrode stabilization by surface passivation has been explored as the most crucial step to develop long‐cycle lithium‐ion batteries (LIBs). In this work, functionally graded materials consisting of “conversion‐type” iron‐doped nickel oxyfluoride (NiFeOF) cathode covered with a homologous passivation layer (HPL) are rationally designed for long‐cycle LIBs. The compact and fluorine‐rich HPL plays dual roles in suppressing the volume change of NiFeOF porous cathode and minimizing the dissolution of transition metals during LIBs cycling by forming a structure/composition gradient. The structure and composition of HPL reconstructs during lithiation/delithiation, buffering the volume change and trapping the dissolved transition metals. As a result, a high capacity of 175 mAh g−1(equal to an outstanding volumetric capacity of 936 Ah L−1) with a greatly reduced capacity decay rate of 0.012% per cycle for 1000 cycles is achieved, which is superior to the NiFeOF porous film without HPL and commercially available NiF2‐FeF3powders. The proposed chemical and structure reconstruction mechanism of HPL opens a new avenue for the novel materials development for long‐cycle LIBs.
The metallic tin (Sn) anode is a promising candidate for next‐generation lithium‐ion batteries (LIBs) due to its high theoretical capacity and electrical conductivity. However, Sn suffers from severe mechanical degradation caused by large volume changes during lithiation/delithiation, which leads to a rapid capacity decay for LIBs application. Herein, a Cu–Sn (e.g., Cu3Sn) intermetallic coating layer (ICL) is rationally designed to stabilize Sn through a structural reconstruction mechanism. The low activity of the Cu–Sn ICL against lithiation/delithiation enables the gradual separation of the metallic Cu phase from the Cu–Sn ICL, which provides a regulatable and appropriate distribution of Cu to buffer volume change of Sn anode. Concurrently, the homogeneous distribution of the separated Sn together with Cu promotes uniform lithiation/delithiation, mitigating the internal stress. In addition, the residual rigid Cu–Sn intermetallic shows terrific mechanical integrity that resists the plastic deformation during the lithiation/delithiation. As a result, the Sn anode enhanced by the Cu–Sn ICL shows a significant improvement in cycling stability with a dramatically reduced capacity decay rate of 0.03% per cycle for 1000 cycles. The structural reconstruction mechanism in this work shines a light on new materials and structural design that can stabilize high‐performance and high‐volume‐change electrodes for rechargeable batteries and beyond.
more » « less- Award ID(s):
- 1949840
- NSF-PAR ID:
- 10455255
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials
- Volume:
- 32
- Issue:
- 42
- ISSN:
- 0935-9648
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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