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1. A simple and scalable pre-lithiation approach for high energy and low cost lithium ion sulfur batteries

   Chao Shen, Donghao Ye (January 2020, Journal of the Electrochemical Society)

   Sulfur-polyacrylonitrile (S-PAN) composite has been developed as a novel composite cathode material to address many issues with conventional Li-S batteries (LSBs). In this study, a freestanding S-PAN-CNT composite is first developed as the cathode material for LSBs, which is capable to deliver a high specific capacity of 1458 mAh g-1 at 0.2C and a desirable high-rate performance of 1097 mAh g-1 at 2.0 C. Furthermore, a Li2S-PAN-CNT cathode is obtained via in-situ direct pre-lithiation of S-PAN-CNT composite, which exhibits an even improved discharge capacity, cycling performance, and rate capability. Lastly, we develop Li-ion sulfur full batteries based on both S-PAN-CNT and Li2S-PAN-CNT cathode. The excellent electrochemical performance and corresponding theoretical estimation both demonstrate that the proposed system as a promising metal-free Li-ion battery with a high specific capacity, good cycle life, and low cost. 

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2. A Comparative Study on Electrochemical Performance of Single versus Dual Networks in Lithium Metal/Polysulfide-Polyoxide Co-Network/Lithium Titanium Oxide Cathode

   https://doi.org/10.3390/batteries10050163  

   Lee, Hyunsang; Choi, Jae-Won; Kyu, Thein (May 2024, Batteries)

   The present article introduces a strategy for controlling oxidation and reduction reactions within polymer electrolyte membrane (PEM) networks as a means of enhancing storage capacity through the complexation of dissociated lithium cations with multifunctional groups of the polymer network. Specifically, co-polymer networks based on polysulfide (PS) and polyoxide (PO) precursors, photo-cured in the presence of succinonitrile (SCN) and lithium bis(trifluoro methane sulfonyl imide) (LiTFSI) salt, exhibited ionic conductivity on the order of mid 10−4 S/cm at ambient temperature in the 30/35/35 (weight %) composition. Lithium titanate (LTO, Li4Ti5O12) electrode was chosen as an anode (i.e., a potential source of Li ions) against lithium iron phosphate (LFP, LiFePO4) cathode in conjunction with polysulfide-co-polyoxide dual polyelectrolyte networks to control viscosity for 3D printability on conformal surfaces of drone and aeronautic vehicles. It was found that the PS-co-PO dual network-based polymer electrolyte containing SCN plasticizer and LiTFSI salt exhibited extra storage capacity (i.e., specific capacity of 44 mAh/g) with the overall specific capacity of 170 mAh/g (i.e., for the combined LTO electrode and PEM) initially that stabilized at 153 mAh/g after 50th cycles with a reasonable capacity retention of over 90% and Coulombic efficiency of over 99%. Of particular interest is the observation of the improved electrochemical performance of the polysulfide-co-polyoxide electrolyte dual-network relative to that of the polyoxide electrolyte single-network. 

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3. Molybdenum Carbide Electrocatalyst In Situ Embedded in Porous Nitrogen‐Rich Carbon Nanotubes Promotes Rapid Kinetics in Sodium‐Metal–Sulfur Batteries

   https://doi.org/10.1002/adma.202106572  

   Hao, Hongchang; Wang, Yixian; Katyal, Naman; Yang, Guang; Dong, Hui; Liu, Pengcheng; Hwang, Sooyeon; Mantha, Jagannath; Henkelman, Graeme; Xu, Yixin; et al (May 2022, Advanced Materials)

   Abstract This is the first report of molybdenum carbide‐based electrocatalyst for sulfur‐based sodium‐metal batteries. MoC/Mo₂C is in situ grown on nitrogen‐doped carbon nanotubes in parallel with formation of extensive nanoporosity. Sulfur impregnation (50 wt% S) results in unique triphasic architecture termed molybdenum carbide–porous carbon nanotubes host (MoC/Mo₂C@PCNT–S). Quasi‐solid‐state phase transformation to Na₂S is promoted in carbonate electrolyte, with in situ time‐resolved Raman, X‐ray photoelectron spectroscopy, and optical analyses demonstrating minimal soluble polysulfides. MoC/Mo₂C@PCNT–S cathodes deliver among the most promising rate performance characteristics in the literature, achieving 987 mAh g⁻¹at 1 A g⁻¹, 818 mAh g⁻¹at 3 A g⁻¹, and 621 mAh g⁻¹at 5 A g⁻¹. The cells deliver superior cycling stability, retaining 650 mAh g⁻¹after 1000 cycles at 1.5 A g⁻¹, corresponding to 0.028% capacity decay per cycle. High mass loading cathodes (64 wt% S, 12.7 mg cm⁻²) also show cycling stability. Density functional theory demonstrates that formation energy of Na₂S_x(1 ≤x ≤ 4) on surface of MoC/Mo₂C is significantly lowered compared to analogous redox in liquid. Strong binding of Na₂S_x(1 ≤x ≤ 4) on MoC/Mo₂C surfaces results from charge transfer between the sulfur and Mo sites on carbides’ surface. 

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4. Silicon Microreactor as a Fast Charge, Long Cycle Life Anode with High Initial Coulombic Efficiency Synthesized via a Scalable Method

   https://doi.org/https://doi.org/10.1021/acsaem.1c00351  

   He, Qianran; Ashuri, Maziar; Liu, Yuzi; Liu, Bingyu; Shaw, Leon (April 2021, ACS applied energy materials)

   Applications of silicon as a high-performance anode material has been impeded by its low intrinsic conductivity and huge volume expansion (> 300%) during lithiation. To address these problems, nano-Si particles along with conductive coatings and engineered voids are often employed, but this results in high cost anodes. Here, we report a scalable synthesis method that can realize high specific capacity (~800 mAh g-1), ultrafast charge/discharge (at 8 A g-1 Si) and high initial Coulombic efficiency (~90%) with long cycle life (1000 cycles) at the same time. To achieve 1000 cycle stability, micron-sized Si particles are subjected to high-energy ball milling to create nanostructured Si building blocks with nano-channel shaped voids encapsulated inside a nitrogen (N)-doped carbon shell (termed as Si micro-reactor). The nano-channel voids inside a Si micro-reactor not only offer the space to accommodate the volume expansion of Si, but also provide fast pathways for Li ion diffusion into the center of the nanostructured Si core and thus ultrafast charge/discharge capability. The porous N-doped carbon shell helps to improve the conductivity while allowing fast Li ion transport and confining the volume expansion within the Si micro-reactor. Submicron-sized Si micro-reactors with limited specific surface area (35 m2 g-1) afford sufficient electrode/electrolyte interfacial area for fast lithiation/delithiation, leading to the specific capacity ranging from ~800 to 420 mAh g-1 under ultrafast charging conditions (8 A g-1), but not too much interfacial area for surface side reactions and thus high initial coulombic efficiency (~90%). Since Si micro-reactors with superior electrochemical properties are synthesized via an industrially scalable and eco-friendly method, they have the potential for practical applications in the future. 

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5. Task-Specific Phosphonium Iongels by Fast UV-Photopolymerization for Solid-State Sodium Metal Batteries

   https://doi.org/10.3390/gels8110725  

   Porcarelli, Luca; Olmedo-Martínez, Jorge L.; Sutton, Preston; Bocharova, Vera; Fdz De Anastro, Asier; Galceran, Montserrat; Sokolov, Alexei P.; Howlett, Patrick C.; Forsyth, Maria; Mecerreyes, David (November 2022, Gels)

   Sodium metal batteries are an emerging technology that shows promise in terms of materials availability with respect to lithium batteries. Solid electrolytes are needed to tackle the safety issues related to sodium metal. In this work, a simple method to prepare a mechanically robust and efficient soft solid electrolyte for sodium batteries is demonstrated. A task-specific iongel electrolyte was prepared by combining in a simple process the excellent performance of sodium metal electrodes of an ionic liquid electrolyte and the mechanical properties of polymers. The iongel was synthesized by fast (<1 min) UV photopolymerization of poly(ethylene glycol) diacrylate (PEGDA) in the presence of a saturated 42%mol solution of sodium bis(fluorosulfonyl)imide (NaFSI) in trimethyl iso-butyl phosphonium bis(fluorosulfonyl)imide (P111i4FSI). The resulting soft solid electrolytes showed high ionic conductivity at room temperature (≥10−3 S cm−1) and tunable storage modulus (104–107 Pa). Iongel with the best ionic conductivity and good mechanical properties (Iongel10) showed excellent battery performance: Na/iongel/NaFePO4 full cells delivered a high specific capacity of 140 mAh g−1 at 0.1 C and 120 mAh g−1 at 1 C with good capacity retention after 30 cycles. 

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