In Situ Formation of Heterojunction in Composite Lithium Anode Facilitates Fast and Uniform Interfacial Ion Transport.

Lithium metal is a highly promising anode for next-generation high-energy-density rechargeable batteries. Nevertheless, its practical application faces challenges due to the uncontrolled lithium dendrites growth and infinite volumetric expansion during repetitive cycling. Herein, a composite lithium anode is designed by mechanically rolling and pressing a cerium oxide-coated carbon textile with lithium foil (Li@CeO2/CT). The in situ generated cerium dioxide (CeO2) and cerium trioxide (Ce2O3) form a heterojunction with a reduced lithium-ion migration barrier, facilitating the rapid lithium ions migration. Additionally, both CeO2 and Ce2O3 exhibit higher adsorbed energy with lithium, enabling faster and more distributed interfacial transport of lithium ions. Furthermore, the high specific surface area of 3D skeleton can effectively reduce local current density, and alleviate the lithium volumetric changes upon plating/stripping. Benefiting from this unique structure, the highly compact and uniform lithium deposition is constructed, allowing the Li@CeO2/CT symmetric cells to maintain a stable cycling for over 500 cycles at an exceptional high current density of 100 mA cm-2. When paired with LiNi0.91Co0.06Mn0.03O2 (NCM91) cathode, the cell achieves 74.3% capacity retention after 800 cycles at 1 C, and a remarkable capacity retention of 81.1% after 500 cycles even at a high rate of 4  C.

Enabling High-Stability of Aqueous-Processed Nickel-Rich Positive Electrodes in Lithium Metal Batteries.

Lithium batteries occupy the large-scale electric mobility market raising concerns about the environmental impact of cell production, especially regarding the use of poly(vinylidene difluoride) (teratogenic) and N-methyl-2-pyrrolidone (NMP, harmful). To avoid their use, an aqueous electrode processing route is utilized in which a water-soluble hybrid acrylic-fluoropolymer together with sodium carboxymethyl cellulose is used as binder, and a thin phosphate coating layer is in situ formed on the surface of the nickel-rich cathode during electrode processing. The resulting electrodes achieve a comparable performance to that of NMP-based electrodes in conventional organic carbonate-based electrolyte (LP30). Subsequently, an ionic liquid electrolyte (ILE) is employed to replace the organic electrolyte, building stable electrode/electrolyte interphases on the surface of the nickel-rich positive electrode (cathode) and metallic lithium negative electrode (anode). In such ILE, the aqueously processed electrodes achieve high cycling stability with a capacity retention of 91% after 1000 cycles (20 °C). In addition, a high capacity of more than 2.5 mAh cm-2 is achieved for high loading electrodes (≈15 mg cm-2 ) by using a modified ILE with 5% vinylene carbonate additive. A path to achieve environmentally friendly electrode manufacturing while maintaining their outstanding performance and structural integrity is demonstrated.

Stabilizing the Li1.3 Al0.3 Ti1.7 (PO4 )3 |Li Interface for High Efficiency and Long Lifespan Quasi-Solid-State Lithium Metal Batteries.

To tackle the poor chemical/electrochemical stability of Li1+x Alx Ti2-x (PO4 )3 (LATP) against Li and poor electrode|electrolyte interfacial contact, a thin poly[2,3-bis(2,2,6,6-tetramethylpiperidine-N-oxycarbonyl)norbornene] (PTNB) protection layer is applied with a small amount of ionic liquid electrolyte (ILE). This enables study of the impact of ILEs with modulated composition, such as 0.3 lithium bis(fluoromethanesulfonyl)imide (LiFSI)-0.7 N-butyl-N-methylpyrrolidinium bis(fluoromethanesulfonyl)imide (Pyr14 FSI) and 0.3 LiFSI-0.35 Pyr14 FSI-0.35 N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14 TFSI), on the interfacial stability of PTNB@Li||PTNB@Li and PTNB@Li||LiNi0.8 Co0.1 Mn0.1 O2 cells. The addition of Pyr14 TFSI leads to better thermal and electrochemical stability. Furthermore, Pyr14 TFSI facilitates the formation of a more stable Li|hybrid electrolyte interface, as verified by the absence of lithium "pitting corrosion islands" and fibrous dendrites, leading to a substantially extended lithium stripping-plating cycling lifetime (>900 h). Even after 500 cycles (0.5C), PTNB@Li||LiNi0.8 Co0.1 Mn0.1 O2 cells achieve an impressive capacity retention of 89.1 % and an average Coulombic efficiency of 98.6 %. These findings reveal a feasible strategy to enhance the interfacial stability between Li and LATP by selectively mixing different ionic liquids.

Co-Crosslinked Water-Soluble Biopolymers as a Binder for High-Voltage LiNi0.5 Mn1.5 O4 |Graphite Lithium-Ion Full Cells.

The use of water-soluble, abundant biopolymers as binders for lithium-ion positive electrodes is explored because it represents a great step forward towards environmentally benign battery processing. However, to date, most studies that employ, for instance, carboxymethyl cellulose (CMC) as a binder have focused on rather low electrode areal loadings with limited relevance for industrial needs. This study concerns the use of natural guar gum (GG) as a binding agent for cobalt-free, high-voltage LiNi0.5 Mn1.5 O4 (LNMO), which realizes electrodes with substantially increased areal loadings, low binder content, and greatly enhanced cycling stability. Co-crosslinking GG through citric acid with CMC allows for an enhanced rate capability and essentially maintains the beneficial impact of using GG as a binder rather than CMC only. Lithium-ion full cells based on water-processed LNMO and graphite electrodes provide a remarkably high cycling stability with 80 % capacity retention after 1000 cycles at 1 C.

A More Sustainable and Cheaper One-Pot Route for the Synthesis of Hydrophobic Ionic Liquids for Electrolyte Applications.

An innovative one-pot synthetic process that uses water as the only processing solvent was used to obtain ionic liquids (ILs) in a yield of approximately 95 mol % and purity greater than 99.3 wt % (<2 ppm each of lithium, bromide and moisture) in a processing time of 1 h. Since no heating is needed for carrying out the reaction and no purification through sorbents is required, energy, time and chemicals can be saved to minimize waste production. The physicochemical and electrochemical validation, including tests in batteries, reported herein shows that the above-mentioned ILs have properties analogous to those of ILs prepared by standard reported procedures and show high performance without any further purification step through sorbents. These characteristics, in combination with low cost, easy execution and scale-up, sustainability and versatility, make the one-pot process even more appealing, especially for industrial-scale applications.

Concentrated Ionic-Liquid-Based Electrolytes for High-Voltage Lithium Batteries with Improved Performance at Room Temperature.

Ionic liquids (ILs) have been widely explored as alternative electrolytes to combat the safety issues associated with conventional organic electrolytes. However, hindered by their relatively high viscosity, the electrochemical performances of IL-based cells are generally assessed at medium-to-high temperature and limited cycling rate. A suitable combination of alkoxy-functionalized cations with asymmetric imide anions can effectively lower the lattice energy and improve the fluidity of the IL material. The Li/Li1.2 Ni0.2 Mn0.6 O2 cell employing N-N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium (fluorosulfonyl)(trifluoromethanesulfonyl)imide (DEMEFTFSI)-based electrolyte delivered an initial capacity of 153 mAh g-1 within the voltage range of 2.5-4.6 V, with a capacity retention of 65.5 % after 500 cycles and stable coulombic efficiencies exceeding 99.5 %. Moreover, preliminary battery tests demonstrated that the drawbacks in terms of rate capability could be improved by using Li-concentrated IL-based electrolytes. The improved room-temperature rate performance of these electrolytes was likely owing to the formation of Li+ -containing aggregate species, changing the concentration-dependent Li-ion transport mechanism.