Lithium sodium vanadium phosphate and its phase transition as cathode material for lithium ion batteries

Lithium/Boron Co-doped Micrometer SiOx as Promising Anode Materials for High-Energy-Density Li-Ion Batteries

The carbon-coated silicon monoxide (SiO_x@C) has been considered as one of the most promising high-capacity anodes for the next-generation high-energy-density lithium-ion batteries (LIBs). However, the relatively low initial Coulombic efficiency (ICE) and the still existing huge volume expansion during repeated lithiation/delithiation cycling remain the greatest challenges to its practical application. Here, we developed a lithium and boron (Li/B) co-doping strategy to efficiently enhance the ICE and alleviate the volume expansion or pulverization of SiO_x@C anodes. The in situ generated Li silicates (Li_xSiO_y) by Li doping will reduce the active Li loss during the initial cycling and enhance the ICE of SiO_x@C anodes. Meanwhile, B doping works to promote the Li⁺ diffusion and strengthen the internal bonding networks within SiO_x@C, enhancing its resistance to cracking and pulverization during cycling. As a result, the enhanced ICE (83.28%), suppressed volume expansion, and greatly improved cycling (85.4% capacity retention after 200 cycles) and rate performance could be achieved for the Li/B co-doped SiO_x@C (Li/B-SiO_x@C) anodes. Especially, the Li/B-SiO_x@C and graphite composite anodes with a capacity of 531.5 mA h g^-1 were demonstrated to show an ICE of 90.1% and superior cycling stability (90.1% capacity retention after 250 cycles), which is significant for the practical application of high-energy-density LIBs.

Nitrogen-doped multi-channel carbon nanofibers incorporated with nickel nanoparticles as a multifunctional modification layer of the separator for ultra stable Li–S batteries

This work provided insight into the mechanism of the reversible conversion of LiPSs and the construction of ultra-stable Li–S batteries.

Incorporating the Nanoscale Encapsulation Concept from Liquid Electrolytes into Solid-State Lithium-Sulfur Batteries

Solid-state Li-S batteries are attractive due to their high energy density and safety. However, it is unclear whether the concepts from liquid electrolytes are applicable in the solid state to improve battery performance. Here, we demonstrate that the nanoscale encapsulation concept based on Li₂S@TiS₂ core-shell particles, originally developed in liquid electrolytes, is effective in solid polymer electrolytes. Using in situ optical cell and sulfur K-edge X-ray absorption, we find that polysulfides form and are well-trapped inside individual particles by the nanoscale TiS₂ encapsulation. This TiS₂ encapsulation layer also functions to catalyze the oxidation reaction of Li₂S to sulfur, even in solid-state electrolytes, proven by both experiments and density functional theory calculations. A high cell-level specific energy of 427 W·h·kg^-1 is achieved by integrating the Li₂S@TiS₂ cathode with a poly(ethylene oxide)-based electrolyte and a lithium metal anode. This study points to the fruitful direction of borrowing concepts from liquid electrolytes into solid-state batteries.

Spherical Metal Oxides with High Tap Density as Sulfur Host to Enhance Cathode Volumetric Capacity for Lithium-Sulfur Battery

Effective hosts of sulfur are essential for the application of lithium-sulfur batteries. However, various refined nanomaterials or carbon-based hosts possess low density, high surface area, and large porosity, leading to undesirable reduction on both gravimetric and volumetric energy densities. Herein, spherical metal oxides with high tap density are introduced as carbon-free hosts of sulfur for the first time. The ternary oxides show a superior synergistic effect of adsorption and electrocatalytic conversion of soluble intermediate polysulfides. Besides, oxide microspheres can build stable conductive frameworks and open channels in porous electrodes for fast transport of electrons and active diffusion of electrolyte. Such a synergistic effect and unique structural feature of porous electrodes are favorable for achieving good utilization and stable cycle performance of the sulfur cathode. Typically, the S/LiNi_0.8Co_0.1Mn_0.1O₂ composite exhibits good cycle stability with a low capacity decay rate (0.057% per cycle) during 500 cycles at 0.1 C. Importantly, due to the high tap density (1.81 g cm^-3), the S/LiNi_0.8Co_0.1Mn_0.1O₂ composite delivers a larger volumetric capacity (1601.9 mAh cm^-3_-composite), almost 2.3 times of S/carbon composite (689.4 mAh cm^-3_-composite). Therefore, this work provides a feasible strategy to reach long life and high volumetric capacity of cathode based on metal oxides as sulfur hosts.

Prelithiated Surface Oxide Layer Enabled High-Performance Si Anode for Lithium Storage

SiO _x coating is an effective strategy to prolong the cycling stability of Si-based anodes due to the robust interaction between Si and the SiO _x layer. However, the SiO _x layer-protected Si anode is limited by the relatively low initial Coulombic efficiency and sluggish Li⁺ diffusion ability induced by the SiO _x layer. Herein, we present the preparation of selectively prelithiated Si@SiO _x (Si@Li₂SiO₃) anode by using a facile strategy to resolve the above issues. As the anode for lithium ion batteries, Si@Li₂SiO₃ exhibits a high initial Coulombic efficiency (ICE) of 89.1%, an excellent rate performance (959 mA h g^-1 at 30 A g^-1), and a superior capacity retention (3215 mA h g^-1). The full cell with LiFePO₄ cathode and Si@Li₂SiO₃ anodes is successfully assembled, disclosing a high ICE of 91.1% and excellent long cycling stability. The superior electrochemical performance of Si@Li₂SiO₃ can be attributed to the coating layer, which can strengthen the integrity of the electrode, decrease irreversible reactions, and provide efficient Li⁺ diffusion channels.

Layered hybrid phase Li2NaV2(PO4)3/carbon dot nanocomposite cathodes for Li+/Na+ mixed-ion batteries

Hybrid phase Li₂NaV₂(PO₄)₃ (H-LNVP) is one of the most promising cathode materials for Li⁺/Na⁺ mixed-ion batteries.

Large-scale synthesis of Li3V2(PO4)3@C composites by a modified carbothermal reduction method as cathode material for lithium-ion batteries

Carbon coated Li₃V₂(PO₄)₃composites were prepared by a modified carbothermal reduction method.

Balancing surface adsorption and diffusion of lithium-polysulfides on nonconductive oxides for lithium-sulfur battery design

Lithium-sulfur batteries have attracted attention due to their six-fold specific energy compared with conventional lithium-ion batteries. Dissolution of lithium polysulfides, volume expansion of sulfur and uncontrollable deposition of lithium sulfide are three of the main challenges for this technology. State-of-the-art sulfur cathodes based on metal-oxide nanostructures can suppress the shuttle-effect and enable controlled lithium sulfide deposition. However, a clear mechanistic understanding and corresponding selection criteria for the oxides are still lacking. Herein, various nonconductive metal-oxide nanoparticle-decorated carbon flakes are synthesized via a facile biotemplating method. The cathodes based on magnesium oxide, cerium oxide and lanthanum oxide show enhanced cycling performance. Adsorption experiments and theoretical calculations reveal that polysulfide capture by the oxides is via monolayered chemisorption. Moreover, we show that better surface diffusion leads to higher deposition efficiency of sulfide species on electrodes. Hence, oxide selection is proposed to balance optimization between sulfide-adsorption and diffusion on the oxides.