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1. Novel Cu(Zn)–Ge–P compounds as advanced anode materials for Li-ion batteries

   https://doi.org/10.1039/d0ee03553j  

   Li, Wenwu ; Shen, Pengfei ; Yang, Lufeng ; Chen, Anjie ; Wang, Jeng-Han ; Li, Yunyong ; Chen, Hailong ; Liu, Meilin ( April 2021 , Energy & Environmental Science)

   null (Ed.)

   Both electronic and ionic conductivities are of high importance to the performance of anode materials for Li-ion batteries. Many large capacity anode materials (such as Ge) do not have sufficiently high electronic and ionic conductivities required for high-rate cycling. Here, we report a novel ternary compound, copper germanium phosphide (CuGe 2 P 3 ), as a high-rate anode. Being synthesized via a facile and scalable mechanochemistry method, CuGe 2 P 3 has a cation-disordered sphalerite structure and offers higher ionic and electronic conductivities and better tolerance to volume change during cycling than Ge, as confirmed by first principles calculations and experimental characterization, including high-resolution synchrotron X-ray diffraction, HRTEM, SAED, XPS and Raman spectroscopy. Furthermore, the results suggest that CuGe 2 P 3 has a reversible Li-storage mechanism of conversion reaction. When composited with graphite by virtue of a two-stage ball-milling process, the yolk–shell structure of the amorphous carbon-coated CuGe 2 P 3 nanocomposite (CuGe 2 P 3 /C@Graphene) delivers a high initial coulombic efficiency (91%), a superior cycling stability (1312 mA h g −1 capacity after 600 cycles at 0.2 A g −1 and 876 mA h g −1 capacity after 1600 cycles at 2 A g −1 ), and an excellent rate capability (386 mA h g −1 capacity at 30 A g −1 ), surpassing most Ge-based anodes reported to date. Moreover, a series of cation-disordered new phases in the Cu(Zn)–Ge–P family with various cation ratios offer similar Li-storage properties, achieving high reversible capacities with high initial coulombic efficiencies and desirable redox chemistry with improved safety. 

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2. A New Type of Li‐Rich Rock‐Salt Oxide Li 2 Ni 1/3 Ru 2/3 O 3 with Reversible Anionic Redox Chemistry

   https://doi.org/10.1002/adma.201807825  

   Li, Xiang ; Qiao, Yu ; Guo, Shaohua ; Jiang, Kezhu ; Ishida, Masayoshi ; Zhou, Haoshen ( January 2019 , Advanced Materials)

   Li‐rich oxide cathodes are of prime importance for the development of high‐energy lithium‐ion batteries (LIBs). Li‐rich layered oxides, however, always undergo irreversible structural evolution, leading to inevitable capacity and voltage decay during cycling. Meanwhile, Li‐rich cation‐disordered rock‐salt oxides usually exhibit sluggish kinetics and inferior cycling stability, despite their firm structure and stable voltage output. Herein, a new Li‐rich rock‐salt oxide Li₂Ni_1/3Ru_2/3O₃withFd‐3mspace group, where partial cation‐ordering arrangement exists in cationic sites, is reported. Results demonstrate that a cathode fabricated from Li₂Ni_1/3Ru_2/3O₃delivers a large capacity, outstanding rate capability as well as good cycling performance with negligible voltage decay, in contrast to the common cations disordered oxides with space groupFm‐3m. First principle calculations also indicate that rock‐salt oxide with space groupFd‐3mpossesses oxygen activity potential at the state of delithiation, and good kinetics with more 0‐TM (TM = transition metals) percolation networks. In situ Raman results confirm the reversible anionic redox chemistry, confirming O²⁻/O⁻evolution during cycles in Li‐rich rock‐salt cathode for the first time. These findings open up the opportunity to design high‐performance oxide cathodes and promote the development of high‐energy LIBs.

    

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3. Boosting Superior Lithium Storage Performance of Alloy‐Based Anode Materials via Ultraconformal Sb Coating–Derived Favorable Solid‐Electrolyte Interphase

   https://doi.org/10.1002/aenm.201903186  

   Xiong, Bing‐Qing ; Zhou, Xinwei ; Xu, Gui‐Liang ; Liu, Yuzi ; Zhu, Likun ; Hu, Youcheng ; Shen, Shou‐Yu ; Hong, Yu‐Hao ; Wan, Si‐Cheng ; Liu, Xiao‐Chen ; et al ( December 2019 , Advanced Energy Materials)

   Alloy materials such as Si and Ge are attractive as high‐capacity anodes for rechargeable batteries, but such anodes undergo severe capacity degradation during discharge–charge processes. Compared to the over‐emphasized efforts on the electrode structure design to mitigate the volume changes, understanding and engineering of the solid‐electrolyte interphase (SEI) are significantly lacking. This work demonstrates that modifying the surface of alloy‐based anode materials by building an ultraconformal layer of Sb can significantly enhance their structural and interfacial stability during cycling. Combined experimental and theoretical studies consistently reveal that the ultraconformal Sb layer is dynamically converted to Li₃Sb during cycling, which can selectively adsorb and catalytically decompose electrolyte additives to form a robust, thin, and dense LiF‐dominated SEI, and simultaneously restrain the decomposition of electrolyte solvents. Hence, the Sb‐coated porous Ge electrode delivers much higher initial Coulombic efficiency of 85% and higher reversible capacity of 1046 mAh g⁻¹after 200 cycles at 500 mA g⁻¹, compared to only 72% and 170 mAh g⁻¹for bare porous Ge. The present finding has indicated that tailoring surface structures of electrode materials is an appealing approach to construct a robust SEI and achieve long‐term cycling stability for alloy‐based anode materials.

    

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4. Ultrahigh‐Capacity Rocksalt Cathodes Enabled by Cycling‐Activated Structural Changes

   https://doi.org/10.1002/aenm.202300221  

   Ahn, Juhyeon ; Giovine, Raynald ; Wu, Vincent C. ; Koirala, Krishna Prasad ; Wang, Chongmin ; Clément, Raphaële J. ; Chen, Guoying ( May 2023 , Advanced Energy Materials)

   Mn‐redox‐based oxides and oxyfluorides are considered the most promising earth‐abundant high‐energy cathode materials for next‐generation lithium‐ion batteries. While high capacities are obtained in high‐Mn content cathodes such as Li‐ and Mn‐rich layered and spinel‐type materials, local structure changes and structural distortions ( often lead to voltage fade, capacity decay, and impedance rise, resulting in unacceptable electrochemical performance upon cycling. In the present study, structural transformations that exploit the high capacity of Mn‐rich oxyfluorides while enabling stable cycling, in stark contrast to commonly observed structural changes that result in rapid performance degradation, are reported. It is shown that upon cycling of a cation‐disordered rocksalt (DRX) cathode (Li_1.1Mn_0.8Ti_0.1O_1.9F_0.1, an ultrahigh capacity of ≈320 mAh g⁻¹(energy density of ≈900 Wh kg⁻¹) can be obtained through dynamic structural rearrangements upon cycling , along with a unique voltage profile evolution and capacity rise. At high voltage, the presence of Mn⁴⁺and Li⁺vacancies promotes local cation ordering, leading to the formation of domains of a “δphase” within the disordered framework. On deep discharge, Mn⁴⁺reduction, along with Li⁺insertion transform the structure to a partially ordered DRX phase with aβ′‐LiFeO₂‐type arrangement. At the nanoscale, domains of the in situ formed phases are randomly oriented, allowing highly reversible structural changes and stable electrochemical cycling. These new insights not only help explain the superior electrochemical performance of high‐Mn DRXbut also provide guidance for the future development of Mn‐based, high‐energy density oxide, and oxyfluoride cathode materials.

    

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5. A Self‐Healing Room‐Temperature Liquid‐Metal Anode for Alkali‐Ion Batteries

   https://doi.org/10.1002/adfm.201804649  

   Guo, Xuelin ; Ding, Yu ; Xue, Leigang ; Zhang, Leyuan ; Zhang, Changkun ; Goodenough, John B. ; Yu, Guihua ( September 2018 , Advanced Functional Materials)

   Given the high energy density, alkali metals are preferred in rechargeable batteries as anodes, however, with significant limitations such as dendrite growth and volume expansion, leading to poor cycle life and safety concerns. Herein a room‐temperature liquid alloy system is proposed as a possible solution for its self‐recovery property. Full extraction of alkali metal ions from the ternary alloy brings it back to the binary liquid eutectic, and thus enables a self‐healing process of the cracked or pulverized structure during cycling. A half‐cell discharge specific capacity of up to 706.0 mAh g⁻¹in lithium‐ion battery and 222.3 mAh g⁻¹for sodium‐ion battery can be delivered at 0.1C; at a high rate of 5C, a sizable capacity of over 400 mAh g⁻¹for Li and 60 mAh g⁻¹for Na could be retained. Li and Na ion full cells with considerable stability are demonstrated when pairing liquid metal with typical cathode materials, LiFePO₄, and P2‐Na_2/3[Ni_1/3Mn_2/3]O₂. Remarkable cyclic durability, considerable theoretical capacity utilization, and reasonable rate stability present in this work allow this novel anode system to be a potential candidate for rechargeable alkali‐ion batteries.

    

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