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1. Concentrated ternary ether electrolyte allows for stable cycling of a lithium metal battery with commercial mass loading high‐nickel NMC and thin anodes

   https://doi.org/10.1002/cey2.275  

   Yang, Jun ; Li, Xing ; Qu, Ke ; Wang, Yixian ; Shen, Kangqi ; Jiang, Changhuan ; Yu, Bo ; Luo, Pan ; Li, Zhuangzhi ; Chen, Mingyang ; et al ( March 2023 , Carbon Energy)

   A new concentrated ternary salt ether‐based electrolyte enables stable cycling of lithium metal battery (LMB) cells with high‐mass‐loading (13.8 mg cm⁻², 2.5 mAh cm⁻²) NMC622 (LiNi_0.6Co_0.2Mn_0.2O₂) cathodes and 50 μm Li anodes. Termed “CETHER‐3,” this electrolyte is based on LiTFSI, LiDFOB, and LiBF₄with 5 vol% fluorinated ethylene carbonate in 1,2‐dimethoxyethane. Commercial carbonate and state‐of‐the‐art binary salt ether electrolytes were also tested as baselines. With CETHER‐3, the electrochemical performance of the full‐cell battery is among the most favorably reported in terms of high‐voltage cycling stability. For example, LiNi_xMn_yCo_1–x–yO₂(NMC)‐Li metal cells retain 80% capacity at 430 cycles with a 4.4 V cut‐off and 83% capacity at 100 cycles with a 4.5 V cut‐off (charge at C/5, discharge at C/2). According to simulation by density functional theory and molecular dynamics, this favorable performance is an outcome of enhanced coordination between Li⁺and the solvent/salt molecules. Combining advanced microscopy (high‐resolution transmission electron microscopy, scanning electron microscopy) and surface science (X‐ray photoelectron spectroscopy, time‐of‐fight secondary ion mass spectroscopy, Fourier‐transform infrared spectroscopy, Raman spectroscopy), it is demonstrated that a thinner and more stable cathode electrolyte interphase (CEI) and solid electrolyte interphase (SEI) are formed. The CEI is rich in lithium sulfide (Li₂SO₃), while the SEI is rich in Li₃N and LiF. During cycling, the CEI/SEI suppresses both the deleterious transformation of the cathode R‐3m layered near‐surface structure into disordered rock salt and the growth of lithium metal dendrites.

    

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2. WS2 Nanosheet Loaded Silicon-Oxycarbide Electrode for Sodium and Potassium Batteries

   https://doi.org/10.3390/nano12234185  

   Dey, Sonjoy ; Singh, Gurpreet ( December 2022 , Nanomaterials)

   Transition metal dichalcogenides (TMDs) such as the WS2 have been widely studied as potential electrode materials for lithium-ion batteries (LIB) owing to TMDs’ layered morphology and reversible conversion reaction with the alkali metals between 0 to 2 V (v/s Li/Li+) potentials. However, works involving TMD materials as electrodes for sodium- (NIBs) and potassium-ion batteries (KIBs) are relatively few, mainly due to poor electrode performance arising from significant volume changes and pulverization by the larger size alkali-metal ions. Here, we show that Na+ and K+ cyclability in WS2 TMD is improved by introducing WS2 nanosheets in a chemically and mechanically robust matrix comprising precursor-derived ceramic (PDC) silicon oxycarbide (SiOC) material. The WS2/SiOC composite in fibermat morphology was achieved via electrospinning followed by thermolysis of a polymer solution consisting of a polysiloxane (precursor to SiOC) dispersed with exfoliated WS2 nanosheets. The composite electrode was successfully tested in Na-ion and K-ion half-cells as a working electrode, which rendered the first cycle charge capacity of 474.88 mAh g−1 and 218.91 mAh g−1, respectively. The synergistic effect of the composite electrode leads to higher capacity and improved coulombic efficiency compared to the neat WS2 and neat SiOC materials in these cells. 

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3. Phase engineering of layered anode materials during ion-intercalation in Van der Waal heterostructures

   https://doi.org/10.1038/s41598-023-31342-z  

   Parida, Shayani ; Dobley, Arthur ; Carter, C. Barry ; Dongare, Avinash M. ( April 2023 , Scientific Reports)

   Transition metal dichalcogenides (TMDs) are a class of 2D materials demonstrating promising properties, such as high capacities and cycling stabilities, making them strong candidates to replace graphitic anodes in lithium-ion batteries. However, certain TMDs, for instance, MoS₂, undergo a phase transformation from 2H to 1T during intercalation that can affect the mobility of the intercalating ions, the anode voltage, and the reversible capacity. In contrast, select TMDs, for instance, NbS₂and VS₂, resist this type of phase transformation during Li-ion intercalation. This manuscript uses density functional theory simulations to investigate the phase transformation of TMD heterostructures during Li-, Na-, and K-ion intercalation. The simulations suggest that while stacking MoS₂layers with NbS₂layers is unable to limit this 2H → 1T transformation in MoS₂during Li-ion intercalation, the interfaces effectively stabilize the 2H phase of MoS₂during Na- and K-ion intercalation. However, stacking MoS₂layers with VS₂is able to suppress the 2H → 1T transformation of MoS₂during the intercalation of Li, Na, and K-ions. The creation of TMD heterostructures by stacking MoS₂with layers of non-transforming TMDs also renders theoretical capacities and electrical conductivities that are higher than that of bulk MoS₂.

    

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4. 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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5. Multifunctional Separator Allows Stable Cycling of Potassium Metal Anodes and of Potassium Metal Batteries

   https://doi.org/10.1002/adma.202105855  

   Liu, Pengcheng ; Hao, Hongchang ; Celio, Hugo ; Cui, Jinlei ; Ren, Muqing ; Wang, Yixian ; Dong, Hui ; Chowdhury, Aminur Rashid ; Hutter, Tanya ; Perras, Frédéric A. ; et al ( December 2021 , Advanced Materials)

   This is the first report of a multifunctional separator for potassium‐metal batteries (KMBs). Double‐coated tape‐cast microscale AlF₃on polypropylene (AlF₃@PP) yields state‐of‐the‐art electrochemical performance: symmetric cells are stable after 1000 cycles (2000 h) at 0.5 mA cm⁻²and 0.5 mAh cm⁻², with 0.042 V overpotential. Stability is maintained at 5.0 mA cm⁻²for 600 cycles (240 h), with 0.138 V overpotential. Postcycled plated surface is dendrite‐free, while stripped surface contains smooth solid electrolyte interphase (SEI). Conventional PP cells fail rapidly, with dendrites at plating, and “dead metal” and SEI clumps at stripping. Potassium hexacyanoferrate(III) cathode KMBs with AlF₃@PP display enhanced capacity retention (91% at 100 cycles vs 58%). AlF₃partially reacts with K to form an artificial SEI containing KF, AlF₃, and Al₂O₃phases. The AlF₃@PP promotes complete electrolyte wetting and enhances uptake, improves ion conductivity, and increases ion transference number. The higher of K⁺transference number is ascribed to the strong interaction between AlF₃and FSI⁻anions, as revealed through¹⁹F NMR. The enhancement in wetting and performance is general, being demonstrated with ester‐ and ether‐based solvents, with K‐, Na‐, or Li‐ salts, and with different commercial separators. In full batteries, AlF₃prevents Fe crossover and cycling‐induced cathode pulverization.

    

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