Highly Stable Porous Polyimide Sponge as a Separator for Lithium-Metal Secondary Batteries

To inhibit Li‐dendrite growth on lithium (Li)‐metal electrodes, which causes capacity deterioration and safety issues in Li‐ion batteries, we prepared a porous polyimide (PI) sponge using a solution‐processable high internal‐phase emulsion technique with a water‐soluble PI precursor solution; the process is not only simple but also environmentally friendly. The prepared PI sponge was processed into porous PI separators and used for Li‐metal electrodes. The physical properties (e.g., thermal stability, liquid electrolyte uptake, and ionic conductivity) of the porous PI separators and their effect on the Li‐metal anodes (e.g., self‐discharge and open‐circuit voltage properties after storage, cycle performance, rate capability, and morphological changes) were investigated. Owing to the thermally stable properties of the PI polymer, the porous PI separators demonstrated no dimensional changes up to 180 °C. In comparison with commercialized polyethylene (PE) separators, the porous PI separators exhibited improved wetting ability for liquid electrolytes; thus, the latter improved not only the physical properties (e.g., improved the electrolyte uptake and ionic conductivity) but also the electrochemical properties of Li‐metal electrodes (e.g., maintained stable self‐discharge capacity and open‐circuit voltage features after storage and improved the cycle performance and rate capability) in comparison with PE separators. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.1

Magnetic nanopore composite beads for simultaneous removal of organic and inorganic pollutants in highly acidic water

A novel magnetic nanocomposite bead was synthesised for the simultaneous removal of cationic, anionic and organic pollutants removal in highly acidic water. Copper, chromium (III), phosphate and toluene were used as representative cationic, anionic and organic pollutants respectively. A 3:4:1 aspect ratio (alginate: nanocomposite: xanthan gum) was used for the beads. The magnetic nanocomposite was characterised using, FT-IR, SEM – EDX and XRD. The beads showed greater removal percentage for phosphate at (97.8 %), followed by copper and chromium at 81.8 % and 81.1 % respectively and toluene also at 81.8 %. Isothermal study showed that both the Freundlich and Langmuir isotherm models were the governing equations for sorption with a more perfect fit for the Freundlich isotherm. Pseudo-second-order model was the governing equation for sorption. This sorbent showed great potential to be used for simultaneous removal of cationic, anionic and organic pollutants removal in water

Synergistically Stabilizing Thin Li Metal through the Formation of a Stable and Highly Conductive Solid Electrolyte Interface and Silver–Lithium Alloy

In this study, a stable solid electrolyte interface (SEI) and a Ag–Li alloy were formed through a simple slurry coating of silver (Ag) nanoparticles and Li nitrate (LiNO3) on a Li metal surface (AgLN-coated Li). The Ag–Li alloy has a high Li diffusion coefficient, which allowed the inward transfer of Li atoms, thus allowing Li to be deposited below the alloy. Moreover, the highly conductive SEI enabled the fast diffusion of Li ions corresponding to the alloy. This inward transfer resulted in dendrite suppression and improved the Coulombic efficiency (CE). The AgLN-coated Li exhibited an initial capacity retention >81% and CE > 99.7 ± 0.2% over 500 cycles at a discharge capacity of 2.3 mA h cm–2

Large-area surface-patterned Li metal anodes fabricated using large, flexible patterning stamps for Li metal secondary batteries

The use of surface-patterned lithium (Li) metal has been proposed as a promising strategy for inhibiting the formation of Li dendrites during repeated Li plating/stripping processes. Nevertheless, the conventional Li metal patterning process is complex, expensive, incompatible with mass production, and incapable of producing finely controlled patterns on the Li metal surface. A large, flexible patterning stamp capable of large-area patterns is developed using a silicon (Si) wafer-based chemical etching process, and its effect on the electrochemical performance of a Li metal anode is investigated. The newly developed stamps have 5,000% larger patterning area compared to the conventional stainless-steel stamps. Furthermore, when compared to conventional surface-patterned Li metal fabricated with conventional stainless-steel stamps (SP-LM), the surface-patterned Li metal fabricated with large and flexible patterning stamps (LAP-LM) demonstrates improved electrochemical performance and stable morphological properties. As a result, the LAP-LM is able to retain up to 85.2% of its initial discharge capacity (85.9 mAh g−1) after 200 cycles at 3C (3.96 mA cm−2), while the SP-LM shows a severe capacity decay after 150 cycles (94.0 mAh g−1 and 13.0 mAh g−1 at the 150th cycle and 200th cycle, respectively). © 2021 Elsevier B.V.1

Upgrading the Properties of Ceramic-Coated Separators for Lithium Secondary Batteries by Changing the Mixing Order of the Water-Based Ceramic Slurry Components

Developing uniform ceramic-coated separators in high-energy Li secondary batteries has been a challenging task because aqueous ceramic coating slurries have poor dispersion stability and coating quality on the hydrophobic surfaces of polyolefin separators. In this study, we develop a simple but effective strategy for improving the dispersion stability of aqueous ceramic coating slurries by changing the mixing order of the ceramic slurry components. The aqueous ceramic coating slurry comprises ceramics (Al2O3), polymeric binders (sodium carboxymethyl cellulose, CMC), surfactants (disodium laureth sulfosuccinate, DLSS), and water. The interaction between the ceramic slurry components is studied by changing the mixing order of the ceramic slurry components and quantitatively evaluating the dispersion stability of the ceramic coating slurry using a Lumisizer. In the optimized mixing sequence, Al2O3 and DLSS premixed in aqueous Al2O3-DLSS micelles through strong surface interactions, and they repel each other due to steric repulsion. The addition of CMC in this state does not compromise the dispersion stability of aqueous ceramic coating slurries and enables uniform ceramic coating on polyethylene (PE) separators. The prepared Al2O3 ceramiccoated separators (Al2O3–CCSs) exhibit improved physical properties, such as high wettability electrolyte uptake and ionic conductivity, compared to the bare PE separators. Furthermore, Al2O3– CCSs exhibit improved electrochemical performance, such as rate capability and cycling performance. The half cells (LiMn2O4/Li metal) comprising Al2O3–CCSs retain 90.4% (88.4 mAh g−1) of initial discharge capacity after 150 cycles, while 27.6% (26.4 mAh g−1) for bare PE. Furthermore, the full cells (LiMn2O4/graphite) consisting of Al2O3–CCSs exhibit 69.8% (72.2 mAh g−1) of the initial discharge capacity and 24.9% (25.0 mAh g−1) for bare PE after 1150 cycles. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.TRU

Preparation and Electrical Properties of Silicone Composite Films Based on Silver Nanoparticle Decorated Multi-Walled Carbon Nanotubes

The electrical properties of silicone composite films filled with silver (Ag) nanoparticle-decorated multi-walled carbon nanotubes (MWNT) prepared by solution processing are investigated. Pristine MWNT is oxidized and converted to the acyl chloride-functionalized MWNT using thionyl chloride, which is subsequently reacted with amine-terminated poly(dimethylsiloxane) (APDMS). Thereafter, APDMS-modified MWNT are decorated with Ag nanoparticles and then reacted with a poly(dimethylsiloxane) solution to form Ag-decorated MWNT silicone (Ag-decorated MWNT-APDMS/Silicone) composite. The morphological differences of the silicone composites containing Ag-decorated MWNT and APDMS-modified MWNT are observed by transmission electron microscopy (TEM) and the surface conductivities are measured by the four-probe method. Ag-decorated MWNT-APDMS/Silicone composite films show higher surface electrical conductivity than MWNT/silicone composite films. This shows that the electrical properties of Ag-decorated MWNT-APDMS/silicone composite films can be improved by the surface modification of MWNT with APDMS and Ag nanoparticles, thereby expanding their applications

Improvement of Electrochemical Performance of Lithium-ion Secondary Batteries using Double-Layered Thick Cathode Electrodes

Various steps in the electrode production process, such as slurry mixing, slurry coating, drying, and calendaring, directly affect the quality and, consequently, mechanical properties and electrochemical performance of electrodes. Herein, a new method of slurry coating is developed: Double-coated electrode. Contrary to single-coated electrode, the cathode is prepared by double coating, wherein each coat is of half the total loading mass of the single-coated electrode. Each coat is dried and calendared. It is found that the double-coated electrode possesses more uniform pore distribution and higher electrode density and allows lesser extent of particle segregation than the singlecoated electrode. Consequently, the double-coated electrode exhibits higher adhesion strength (74.7 N m−1) than the single-coated electrode (57.8 N m−1). Moreover, the double-coated electrode exhibits lower electric resistance (0.152 Ω cm−2) than the single-coated electrode (0.177 Ω cm−2). Compared to the single-coated electrode, the double-coated electrode displays higher electrochemical performance by exhibiting better rate capability, especially at higher C rates, and higher long-term cycling performance. Despite its simplicity, the proposed method allows effective electrode preparation by facilitating high electrochemical performance and is applicable for the large-scale production of high-energy-density electrodes.FALS

Synergistic Effect of Dual-Ceramics for Improving the Dispersion Stability and Coating Quality of Aqueous Ceramic Coating Slurries for Polyethylene Separators in Li Secondary Batteries

We demonstrate that dispersion stability and excellent coating quality are achieved in polyethylene (PE) separators by premixing heterogeneous ceramics such as silica (SiO2) and alumina (Al2O3) in an aqueous solution, without the need for functional additives such as dispersing agents and surfactants. Due to the opposite polarities of the zeta potentials of SiO2 and Al2O3, SiO2 forms a sheath around the Al2O3 surface. Electrostatic repulsion occurs between the Al2O3 particles encapsulated in SiO2 to improve the dispersion stability of the slurry. The CCSs fabricated using a dual ceramic (SiO2 and Al2O3)-containing aqueous coating slurry, denoted as DC-CCSs, exhibit improved physical properties, such as a wetting property, electrolyte uptake, and ionic conductivity, compared to bare PE separators and CCSs coated with a single ceramic of Al2O3 (SC-CCSs). Consequently, DC-CCSs exhibit an improved electrochemical performance, in terms of rate capability and cycle performance. The half cells consisting of DC-CCSs retain 93.8% (97.12 mAh g(-1)) of the initial discharge capacity after 80 cycles, while the bare PE and SC-CCSs exhibit 22.5% and 26.6% capacity retention, respectively. The full cells consisting of DC-CCSs retain 90.9% (102.9 mAh g(-1)) of the initial discharge capacity after 400 cycles, while the bare PE and SC-CCS exhibit 64.7% and 73.4% capacity retention, respectively.TRU

Synergistic effects between dual salts and Li nitrate additive in ether electrolytes for Li-metal anode protection in Li secondary batteries

The practical applications of Li-metal batteries (LMBs) are limited by dendrite formation. Thus, a synergistic approach for enhancing the cycling performance of LMBs by combining dual salts with lithium nitrate as an additive in an ether-based electrolyte system is presented. The dual salts, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium bis(oxalate)borate (LiBOB), and lithium nitrate (LiNO3), are dissolved in a dual ether-based solvent composed of 1,2-dimethoxyethane and 1,3-dioxane. The electrolyte shows high electrochemical stability of up to ∼ 4.6 V, circumventing the drawback of ether-based solvents, which are known to exhibit an oxidation potential of <4 V. Moreover, dendrite inhibition is enhanced by the formation of a robust and passivating solid-electrolyte interface (SEI). Additionally, the rate capability and cycling performance are enhanced up to 1000 cycles, with a 90.0% discharge capacity retention at 1C for the lithium iron phosphate (LFP)/Li battery. Furthermore, Li/Li symmetric cells exhibit a high stability with >2300 h of repeated stripping and plating at 0.5 mA cm−2, which is an enhancement of approximately 300% compared with the reference electrolyte. This study provides a promising strategy for the practical application of ether-based electrolytes for Li-metal anodes in rechargeable batteries at low salt concentrations. © 2022 Elsevier B.V.FALS

Dendrite Suppression by Lithium-Ion Redistribution and Lithium Wetting of Lithium Zeolite Li2(Al2Si4O12) in Liquid Electrolytes

Lithium metal is considered a next-generation anode material for high-voltage, high-energy-density batteries; however, its commercialization is limited because of dendrite formation during charging, which leads to short-circuiting and fire. Li metal is coated with a lithium zeolite Li2(Al2Si4O12) (bikitaite - BKT) for dendrite suppression. The BKT-coated Li metal anode exhibits enhanced cycle performance for both Li/LMO (over 982 cycles) and Li/Li cells (over 2000 h at 0.52.0 mAh cm-2 and 693 h at 2.0 mAh cm-2). Moreover, the voltage profile of the Li/Li cells deviates from the conventional Li plating behavior. We hypothesize that this is due to the Li wetting of the BKT particles during plating, which leads to the formation of an interconnected three-dimensional (3D) Li network. Furthermore, BKT, a Li conductor, promotes even Li+-ion distribution during plating, resulting in the uniform deposition of Li and, consequently, suppressed dendrite formation. This work provides evidence that BKT can be potentially used in Li metal batteries. © American Chemical SocietyFALS