Dual Immobilization of SnOx Nanoparticles by N-Doped Carbon and TiO2 for High-Performance Lithium-Ion Battery Anodes.

The grain aggregation engendered kinetics failure is regarded as the main reason for the electrochemical decay of nanosized anode materials. Herein, we proposed a dual immobilization strategy to suppress the migration and aggregation of SnOx nanoparticles and corresponding lithiation products through constructing SnOx/TiO2@PC composites. The N-doped carbon could anchor the tin oxide particles and inhibit their aggregation during the preparation process, leading to a uniform distribution of ultrafine SnOx nanoparticles in the matrix. Meanwhile, the incorporated TiO2 component works as parclose to suppress the migration and coarsening of SnOx and corresponding lithiation products. In addition, the N-doped carbon and TiO2/LixTiO2 can significantly improve the electrical and ionic conductivities of the composites, enabling a good diffusion and charge-transfer dynamics. Owing to the dual immobilization from the "synergistic effect" of N-doped carbon and the "parclose effect" of TiO2, the conversion reaction of SnOx remains fully reversible throughout the cycling. Thereby, the composites exhibit excellent cycling performance in half cells and can be fully utilized in full cells. This work may provide an inspiration for the rational design of tin-based anodes for high-performance lithium-ion batteries.

Rational Design of an Electron/Ion Dual-Conductive Cathode Framework for High-Performance All-Solid-State Lithium Batteries.

All-solid-state lithium batteries (ASSLBs) have been paid increasing attention because of the better security compared with conventional lithium-ion batteries with flammable organic electrolytes. However, the poor ion transport between the cathode materials greatly hinders the capacity performance of ASSLBs. Herein, an electron/ion dual-conductive electrode framework is proposed for superior performance ASSLBs. Highly electronic conductive reduced graphene oxide and carbon nanotubes interconnect with active materials in the cathodes, constructing a three-dimensional continuous electron transport network. The composite electrolyte penetrates into the porous structure of the electrode, forming a consecutive ionic conductive framework. Furthermore, the thin electrolyte film formed on the surface of the cathode effectively lowers the interfacial resistance with the electrolyte membrane. Highly electron/ion conductive electrodes, combined with the polyethylene oxide-Li6.4La3Zr1.4Ta0.6O12 (PEO-LLZTO) composite electrolyte, show excellent capacity performance for both LiFePO4 and sulfur (lithium-sulfur battery) active materials. In addition, the LiFePO4 cathode demonstrates superior capacity performance and rate capability at room temperature. Furthermore, the relationship between the low Coulombic efficiency and Li dendrite growth has been revealed in this work. An effective layer is formed on the surface of Li metal by the simple modification of cupric fluoride (CuF2), which can stabilize the electrolyte/anode interface. Finally, high-performance ASSLBs with high Coulombic efficiency can be achieved.

One-Pot Synthesis of a Copolymer Micelle Crosslinked Binder with Multiple Lithium-Ion Diffusion Pathways for Lithium-Sulfur Batteries.

Fast lithium-ion diffusion is very important to obtain high capacity and excellent cycling stability of lithium-sulfur batteries. In this study, a copolymer micelle crosslinked binder (FNA) for lithium-sulfur batteries was successfully synthesized through a one-pot environmentally friendly approach. The micelles were used as crosslinkers and carriers for the electrolyte. The FNA binder provided multiple lithium-ion diffusion pathways to increase the lithium-ion diffusion, which reduced the polarization of the sulfur cathode during the cycling process. The lithium-ion diffusion pathways of the FNA were provided by the electrolyte hosted in the micelles, the polyethylene oxide and polypropylene oxide segments, and the carboxylate and sulfonate groups in the FNA. In addition, FNA possesses strong lithium polysulfides adsorption and high adhesion properties. Therefore, the electrode with the FNA binder presented a reversible capacity of 571 mAh g-1 with a capacity fade of 0.032 % after 1000 cycles at a cycling rate of 0.5 C, which is much higher than those of the polyvinylidene fluoride (PVDF) sulfur cathode.

Vapor Deposition Red Phosphorus to Prepare Nitrogen-Doped Ti3C2Tx MXenes Composites for Lithium-Ion Batteries.

MXenes have great application prospect in energy storage fields due to a series of special physicochemical properties. However, the application of MXenes is greatly limited due to low intrinsic capacity. Here, through spray drying and vapor deposition methods, N-doped Ti3C2Tx and phosphorus composites (N-Ti3C2Tx/P) were prepared for the first time. The red phosphorus particles were absorbed to a walnut-like N-Ti3C2Tx matrix, facilitating the transport of Li+ and electrons. When used as anodes for lithium-ion batteries, the battery can cycle up to 1040 cycles with a high stable capacity of 801 mAh/g at 500 mA/g. Impressively, there is an obvious increase of capacity in the subsequent cycles at higher current density due to the increment of interlayer spacing of Ti3C2Tx nanosheets. XPS measurements confirm that the Ti-O-P bond was formed in the composites, granting the robust structure of the composites and leading to superior performances during cycling. The facile synthesis method of red phosphorus by vapor deposition will facilitate the development of other 2D materials combined with high-capacity red phosphorus for energy storage.

Preparation of an Amorphous Cross-Linked Binder for Silicon Anodes.

An amorphous cross-linked binder is prepared from abundant and low-cost sodium alginate and carboxymethyl cellulose by protonation and mixing and is used to improve the electrochemical performance of silicon anodes in lithium-ion batteries. The amorphous cross-linked structure, formed by intermolecular hydrogen bonding between the functional groups in the two polymers, effectively enhances the flexibility and strength of the binder, resulting in strong adhesion between the binder and other components in the silicon anodes. Furthermore, the binder tolerates large volume changes and reduces the pulverization of silicon during the charge-discharge process. The hydrogen bonding in the binder helps to maintain the anode integrity during the volume change, leading to an excellent cycling stability and superior rate capability with a capacity of 1863 mAh g-1 at 500 mA g-1 after 150 cycles.

New, Effective, and Low-Cost Dual-Functional Binder for Porous Silicon Anodes in Lithium-Ion Batteries.

In this work, a new effective and low-cost binder applied in porous silicon anode is designed through blending of low-cost poly(acrylic acid) (PAA) and poly(ethylene- co-vinyl acetate) (EVA) latex (PAA/EVA) to avoid pulverization of electrodes and loss of electronic contact because of huge volume changes during repeated charge/discharge cycles. PAA with a large number of carboxyl groups offers strong binding strength among porous silicon particles. EVA with high elastic property enhances the ductility of the PAA/EVA binder. The high-ductility PAA/EVA binder tolerates the huge silicon volume variations and keeps the electrode integrity during the charge/discharge cycle process. EVA colloids acting as host materials for electrolytes increase the electrolyte uptake of electrodes. The porous silicon electrode with the PAA/EVA binder exhibits a reversible capacity of 2120 mA h g-1 at 500 mA g-1 after 140 cycles because of the excellent ductility and lithium-ion transport properties of the PAA/EVA binder.

Facile Synthesis of rGO/g-C3N4/CNT Microspheres via an Ethanol-Assisted Spray-Drying Method for High-Performance Lithium-Sulfur Batteries.

rGO/g-C3N4 and rGO/g-C3N4/CNT microspheres are synthesized through the simple ethanol-assisted spray-drying method. The ethanol, as the additive, changes the structure of the rGO/g-C3N4 or rGO/g-C3N4/CNT composite from sheet clusters to regular microspheres. In the microspheres, the pores formed by reduced graphene oxide (rGO), g-C3N4, and carbon nanotube (CNT) stacking provide physical confinement for lithium polysulfides (LiPSs). In addition, enriched nitrogen (N) atoms of g-C3N4 offer strong chemical adhesion to anchor LiPSs. The dual immobilization mechanism can effectively alleviate the notorious "shuttle effect" of the lithium-sulfur battery. Meanwhile, the cathode with high cyclic stability can be achieved. The rGO/g-C3N4/CNT/S cathode delivers a discharge capacity of 620 mA h g-1 after 500 cycles with a low capacity fading rate of only 0.03% per cycle at 1 C. Even, the cathode shows a retained capacity of 712 mA h g-1 over 300 cycles with a high sulfur loading (4.2 mg cm-2) at 0.2 C.