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Si/carbon and SiOx/carbon composites have been widely studied to meet the increasing demand for high-energy-density lithium-ion batteries. However, it is challenging to seek a balance between high specific capacity and good-mechanical-structure stability. Herein, a micro-level SiOx–TiO2/Si/CNTs composite sphere is prepared as a novel anode material. First, the liquid-phase co-deposition method is used to synthesize SiO2–TiO2 composite uniformly distributed at the primary particle level. Then, carbon nanotubes (CNTs) and a certain amount of Si nanoparticles are added to conduct high-energy ball milling, during which lithium-inactive SiO2 phase converts into active SiOx with partial reduction and oxygen loss. Benefiting from the multi-dimensional electronic and ionic conductive networks provided by cross-linked CNTs and evenly mixed nano-sized TiO2, as well as an optimized balance between high-specific-capacity nano-Si and good-mechanical-structure-stability SiOx, the obtained SiOx–TiO2/Si/CNTs composite microspheres demonstrate a promising cycle stability when used as a negative material (~ 800 mAh g−1 after 100 cycles at 100 mA g−1). This work offers a facile strategy for large-scale production of novel SiOx-based composite anode in high-performance lithium-ion batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Polyurethane elastomer (TPU) is prepared firstly as an artificial SEI of Li metal anode. • IPDI hard chain segment and soft link forging PEO jointly improve elasticity and ion conducting channel of the TPU. • TPU coated Li foil can be stable in air for 45 min without obvious deterioration. • The elastic modulus of TPU is up to 105 Pa and the elongation at break is up to 2854%. • TPU-Li||LFP cell delivers a long cyclelife with 90% retention after 1500 cycles at 5 C. Compared with other anode materials, Li metal anode has higher capacity density and lower electrode potential, which has been considered as one of the most promising anode materials. However, the unstable solid electrolyte interface (SEI) leads to Li dendrite growth and the infinite volumetric expansion of Li metal, which seriously hinders the stability and cycle life of Li metal batteries (LMBs). Here, a polyurethane elastomer (TPU) material with high elasticity and air stability is used as the artificial SEI of Li metal anode. Its designed synergistic effect of soft chain forging and hard chain segments not only gives TPU artificial SEI layer good electronic insulation, Li ion conductivity, Li dendrite growth inhibition, high elastic modulus and flexibility to adapt to Li volume expansion, but also has a significant air protection effect on the Li metal surface, so that the TPU coated Li foil will not occur obvious oxidation phenomenon after being placed in air for 45 min. The Li symmetric battery modified by TPU achieved a stable and long-term cycle performance of 1300 h at 1 mA/cm2, it can also cycle stably at a high current density of 10 mA/cm2. The Coulomb efficiency of the modified Li/Cu half-cell maintains at above 97% after 400 cycles. In addition, the full cell with LiFePO 4 cathode also delivers a very excellent long cycle stability with 90% capacity retention after 1500 cycles at 5 C. This surface modification strategy of SEI on lithium anode has has great research value and will help to improve the widely application of LMBs. [ABSTRACT FROM AUTHOR]

In this work, the effectiveness of dual-additives electrolyte consisting of iodine and caffeic acid (noted as CA@I) in improving electrochemical performance has been demonstrated both experimentally and theoretically. The full cell with a high LiFePO 4 loading (17.4 mg cm−2, 3.0 mAh cm−2) has successfully demonstrated a stable lifetime of more than 370 cycles with a capacity retention of 95.0%. [Display omitted] • A novel iodine and caffeic acid dual-additive electrolyte was proposed for Li metal batteries. • I 3 −/I− redox couple can rejuvenate inactive lithium and be revived itself at the cathode side. • The anionic polymerised caffeic acid modulates composition and improve stability of SEI. • The modified Li|Li battery achieves an ultra-long cyclelife over 7000 h at 1 mA cm−2. Inactive ('dead') lithium and conventional fragile solid-electrolyte interphase (SEI) usually cause performance degradation and safety hazards in Li-metal batteries. Recovering inactive lithium and constructing stable SEI are urgently required to enhance the capacity and lifespan of lithium metal batteries. Herein, we have designed a novel dual-additives electrolyte containing an I 3 −/I− redox couple for reviving the inactive lithium, and caffeic acid (CA) that can be anion-polymerised to modulate the composition and improve stability of the SEI. It's found that the generated I 3 −/I− redox couple can turn the inactive Li 2 O into soluble Li+, and prompt the formation of SEI composed of inorganic LiI, Li 3 N and organic RCOOLi with high stability. Density functional theory (DFT) calculations indicate that the diffusion potential barrier of Li+ is significantly lower on the LiI-rich SEI interface, which can not only accelerate the transport of Li+ at the interface, but also effectively prevent I 3 − from attacking Li metal. Benefiting from this elaborate dual-additives electrolyte design, the symmetrical-cells present a superior electrochemical performance, i.e., high critical current density up to 10 mA cm−2, ultra-long lifespan over 7000 h at 1 mA cm−2, and over 2500 cycles under harsh conditions of high temperature (50 °C) and high current density (5 mA cm−2). In addition, as a proof of concept for practical applications of Li-metal batteries, Li|LiFePO 4 full cell delivers excellent cycle stability and rate performance with low hysteresis voltage at a high cathode loading of 17.4 mg cm−2. [ABSTRACT FROM AUTHOR]

Abstract Tin dioxide (SnO 2) has attracted extensive research attention as promising anode materials for lithium ion batteries due to high theoretical capacity. However, its application is largely hindered by poor electronic conductivity and drastic volume change during the conversion reaction and alloying processes. Herein, we report a three-dimensional nitrogen-doped graphene aerogel decorating ultra-small SnO 2 nanoparticles (3–6 nm) by a facile one-step hydrothermal process. Nanoscaled SnO 2 nanoparticles facilitate limited volume expansion and shortened lithium diffusion pathways, nitrogen-doping increases the positive charge density of carbon atoms adjacent to the nitrogen atom, while the three-dimensional porous graphene aerogel has excellent electronic conductivity and facile electrolyte infiltration, thus prompting the composite electrode excellent electrochemical performance. When used as bind-free anode electrode, the graphene aerogel/SnO 2 composite delivers a high discharge capacity of 1812.0 mAh g−1 in the initial cycle, and the capacity can retain at 778 mAh g−1 after 100 cycles, demonstrating its promising candidate as anode material for energy storage. Graphical abstract Unlabelled Image Highlights • 3D N-doped GA decorating ultra-small SnO 2 is prepared by hydrothermal reaction. • Ultra-small SnO 2 nanocrystals exhibit high activity and limited volume expansion. • N-doping increases positive charge density of C atoms and electronic conductivity. • 3D porous GA has facile electrolyte infiltration and excellent structure stability. • The composite can be used as electrode directly and shows excellent cyclability. [ABSTRACT FROM AUTHOR]

• Graphene bubble film encapsulated Si@C hollow spheres is designed as LIB anodes. • Si hollow spheres are wrapped by interior CVD carbon shell and external GNS layers. • Carbon shell inhibits si particles agglomeration and detrimental interface reactions. • Graphene bubble film enhances structural stability and electronic conductivity. • Enhanced electrochemical performances are presented compared to H-Si@C and G/H-Si. Silicon-based composites have been proposed as the promising anode materials for Li-ion batteries. In order to avoid the operational problems of silicon-based anodes such as the low electric conductivity and huge volume expansion, we succeed in encapsulating Si@C hollow spheres into flexible graphene bubble film as a durable anode with enhanced lithium storage properties. In this design, sub-micrometer-sized Si hollow spheres are wrapped into accessible mesoporous carbon shells. Then, the Si@C hollow spheres are tightly wrapped with amino-functionalized graphene oxide nanosheets and followed by chemical reduction to form a bubble film composite structure. Such closely packed graphene bubble films encapsulating hollow Si@C macrostructure ensures uniform and aggregation-free distribution of silicon spheres in the dual conductive carbon network. This kind of graceful composite structure can not only suppress volume expansion and improve structural stability of the electrode material, but also facilitate the electron transfer and lithium ion migration by shortening the transportation channels. The as-prepared composite exhibits impressive Li storage performance with a high reversible capacity of 813.2 mAh g −1 after 100 cycles at 0.1C. This work offers an appealing strategy for high-performance Si-based anode materials in practical application. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Size-tunable SnS 2 /RGO make facile study the effect of particle size on Li/Na storage. • Ions diffusion coefficient, surface and diffusion capacitive contribution are studied. • Small-sized particle promotes charge/ion transfer and pseudocapacitor contribution. • Controllable dimension promotes fast kinetics for high rate materials. Controlling the particle sizes of electrode materials has long been recognized as an effective way to improve the cycle stability and rate property of both lithium-ion battery (LIB) and sodium-ion battery (SIB). In this paper, a simple one-step hydrothermal process for the preparation of composites with size-tunable tin disulfide on reduced graphene oxide (SnS 2 /RGO) is reported. These novel material allow to comprehensively study the effect of particle sizes on electrochemical properties for LIB and SIB anodes. The structure, morphology, phase compositions, and Li+/Na+ storage behaviors of three different SnS 2 /RGO composites obtained at heat-treatment times of 12, 24 and 48 h are characterized systematically. The electrochemical reaction kinetics is demonstrated by differential charge capacity plots and apparent ion diffusion coefficients. Surface capacitive and diffusion-controlled capacitive contributions to lithium/sodium ions storage are also compared. The results show that the small-sized nanoarchitecture can promote both the charge and ions transfer and thus improve the pseudocapacitor contribution. The reversible capacity maintains at 1211 mAh g−1 for LIB after 200 cycles and 841 mAh g−1 for SIB after 100 cycles, respectively, which is superior to most of the previous reports. This work is expected to provide a profound understanding of composite anodes with controllable dimensions and fast kinetics. The effect of SnS 2 nanoparticle size on the Li and Na storage characteristics of SnS 2 /RGO composite anodes are compared, it show that the decreased particle size promotes the pseudocapacitor contribution, as well as the reversed conversion reaction and structural stability. Image, graphical abstract [ABSTRACT FROM AUTHOR]

A two-phase mixture of SiO x -TiO 2 encapsulated by reduced graphene oxide (SiO x -TiO 2 @RGO, 0 < x < 2) is fabricated for novel composite anode of lithium ion batteries. The dual-phase SiO x -TiO 2 distributes uniformly at primary particle level is synthesized by liquid phase co-deposition before high energy ball milling. The liquid phase co-deposition method ensures dual-phase mixture of SiO x -TiO 2 with uniform distribution at the particle level, while the high energy ball milling prompts conversion of the SiO 2 component without lithium intercalation activity into SiO x anode with partial reduction and oxygen loss. The incorporation of TiO 2 nanocrystal plays the roles of lithium ions and electron conduction (Li x TiO 2) promoter during the electrochemical reaction and prevents the agglomeration of active material particles. The graphene bubble film can decrease irreversible Li+ consumption and film resistance after lithiation, as well as enhance the electronic conductivity. As a consequence, the SiO x -TiO 2 @RGO composite exhibits excellent rate property (420 mAh g−1 at 5 A g−1) and exceptional long-term cycling performance (730 mAh g−1 after 200 cycles at 100 mA g−1). The extraordinary electrochemical property combined with the facile synthesis process shows attractive prospect of the modification strategy at the primary particle level. Image 1 • Two-phase mixture of SiO 2 –TiO 2 encapsulated by RGO is prepared as anode for LIBs. • Liquid phase codeposition ensures SiO x -TiO 2 distribute uniformly at particle level. • High-energy ball milling converts SiO 2 component into active SiO x anode material. • TiO 2 promotes Li+ transport and lithiated Li x TiO 2 improves electronic conductivity. • Graphene bubble film decreases SEI thickening and film resistance after lithiation. [ABSTRACT FROM AUTHOR]