In Situ Surface Reaction for the Preparation of High-Performance Li-Rich Mn-Based Cathode Materials with Integrated Surface Functionalization.

Li-rich Mn-based cathode materials (LLOs) are often faced with problems such as low initial Coulombic efficiency (ICE), limited rate performance, voltage decay, and structural instability. Addressing these problems with a single approach is challenging. To overcome these limitations, we developed an LLO with surface functionalization using a simple fabrication method. This two-step process involved a liquid-stage NaBF4 treatment followed by an in situ chemical reaction during sintering. This reaction led to the creation of oxygen vacancies (OV), spinel structures, and doping with Na at the Li site, B at the tetrahedral interstitial spaces of O in both the transition-metal (TM) layer and Li layers as well as the octahedral interstices in the TM layer, and F at the O site. We have carried out a thorough study and employed density functional theory calculations to reveal the hidden mechanisms. The treatment not only increases the electrical conductivity but also changes the oxygen charge environment and inhibits lattice oxygen activity. Surprisingly, the B-O bond is so strong that it prevents the migration of TM within the tetrahedral interstitial spaces of O in both the TM and Li layers, hence stabilizing its structure. This bonding interaction strengthens the transition of the TM 3d and O 2p states to lower energy levels, thus causing an increase in the redox potentials. Hence, a rise in the operating voltage occurs. Of special importance, this therapy dramatically increases the ICE to 90.29% and keeps a specified capacity of 203.3 mAh/g after 100 cycles at 1C, which is an excellent capacity retention of 89.94%. This study introduces ideas and methods to tackle the challenges associated with LLOs in batteries. It also provides compelling evidence for the development of high-energy-density Li-ion batteries.

Constructing a Stable Conductive Network for High-Performance Silicon-Based Anode in Lithium-Ion Batteries.

The application of carbon nanotubes to silicon nanoparticles has been used to improve the electrical conductivity of silicon-carbon anodes and prevent agglomeration of silicon nanoparticles during cycling. In this study, the composites are synthesized through an uncomplicated technique that involves the ultrasonication mixing of pyrene derivatives and carbon nanotubes and the formation of complexes with silicon nanoparticles in ultrasonic dispersion and magnetic stirring and then treated under vacuum. When the prepared composites are applied as lithium-ion battery anodes, the Si@(POH-AOCNTs) electrode displays a high reversible capacity of 3254.7 mAh g-1 at a current density of 0.1 A g-1. Furthermore, it exhibits excellent cycling stability with a specific capacity of 1195.8 mAh g-1 after 500 cycles at 1.0 A g-1. The superior electrochemical performance may be attributed to a large π-conjugated electron system of pyrene derivatives, which prompts the formation of a homogeneous CNTs conductive network and ensures the effective electron transfer, while the interaction between hydroxyl functional groups of hydroxypyrene and binder synergizes with CNTs network to further enhance the cycling stability of the composite.

A Freestanding 3D Skeleton with Gradationally Distributed Lithiophilic Sites for Realizing Stable Lithium Anodes.

Lithium (Li) metal anodes are drawing considerable attention owing to their ultrahigh theoretical capacities and low electrochemical reduction potentials. However, their commercialization has been hampered by safety hazards induced by continuous dendrite growth. These issues can be alleviated using the ZnO-modified 3D carbon-based host containing carbon nanotubes (CNTs) and carbon felt (CF) fabricated by electroplating in the present study (denoted as ZnO/CNT@CF). The constructed skeleton has lithiophilic ZnO that is gradationally distributed along its thickness. The utilization of an inverted ZnO/CNT@CF-Li anode obtained by flipping over the carbon skeleton after Li electrodeposition is also reported herein. The synergistic effect of the Li metal and lithiophilic sites reduces the nucleation overpotential, thus inducing Li+ to preferentially deposit inside the porous carbon-based scaffold. The composite electrode compels Li to grow away from the separator, thereby significantly improving battery safety. A symmetric cell with the inverted ZnO/CNT@CF-Li electrode operates steadily for 700 cycles at 1 mA cm-2 and 1 mAh cm-2 . Moreover, the ZnO/CNT@CF-Li|S cell exhibits an initial areal capacity of 10.9 mAh cm-2 at a S loading of 10.4 mg cm-2 and maintains a capacity of 3.0 mAh cm-2 after 320 cycles.

A Bifunctional Fluorine-Free Electrolyte Additive for Realizing Dendrite-Free Lithium Anodes.

Owing to the strong energy advantage of lithium anodes, the development of lithium-metal batteries has become an inevitable trend. However, plagued by the instability of solid-electrolyte interphase (SEI) films, lithium metal anodes face challenges such as lithium dendrite formation and volume expansion. Studies have proven that modulating the composition and structure of SEI films by using electrolyte additives is a convenient and valid method. Currently, it is widely accepted that fluoride is an effective additive but, based on the high cost of fluoride production and environmental concerns, the development of fluoride-free additives is of great significance. In this work, the bifunctional additive N,O-bis(trimethylsilyl)acetamide (BSA) is proposed, which can build up a SEI layer that is rich in SiOx and Li3 N on the surface of the lithium anode to control the deposition behavior of lithium and clean the electrolyte of HF to protect the electrode. The experimental results indicate that BSA suppresses the generation of lithium dendrites and controls the volume expansion of lithium anodes. Moreover, compared with the commonly used carbonate electrolytes, the battery containing BSA has the best overall performance. Methodologically, the results can be extended to other additives containing Si-O functional groups to replace the same type of fluorine-containing additives.

Co-Precipitation Synthesis of Co3[Fe(CN)6]2·10H2O@rGO Anode Electrode for Lithium-Ion Batteries.

Rechargeable lithium-ion batteries (LIBs) are known to be practical and cost-effective devices for storing electric energy. LIBs have a low energy density, which calls for the development of new anode materials. The Prussian blue analog (PBA) is identified as being a candidate electrode material due to its facile synthesis, open framework structures, high specific surface areas, tunable composition, designable topologies and rich redox couples. However, its poor electrical conductivity and mechanical properties are the main factors limiting its use. The present study loaded PBA (Co3[Fe(CN)6]·10H2O) on graphene oxide (Co-Fe-PBA@rGO) and then conducted calcination at 300 °C under the protection of nitrogen, which reduced the crystal water and provided more ion diffusion pathways. As a result, Co-Fe-PBA@rGO showed excellent performance when utilized as an anode in LIBs, and its specific capacities were 546.3 and 333.2 mAh g-1 at 0.1 and 1.0 A g-1, respectively. In addition, the electrode also showed excellent performance in the long-term cycle, and its capacity reached up to 909.7 mAh g-1 at 0.1 A g-1 following 100 cycles.

N,O-Bis(trimethylsilyl)trifluoroacetamide as an Effective Interface Film Additive on Lithium Anodes.

Lithium anodes have attracted much attention because of their high energy density, but the existence of lithium dendrites tremendously limits their practical application. Herein, it is creatively proposed to employ N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) as an electrolyte additive to stabilize the solid electrolyte interface. BSTFA is reduced on the lithium anode surface prior to other components to form a passivation layer composed of LiF, Li3N, and SiOx, which not only significantly prevents the continuous consumption of the electrolyte and reduces side reactions but also effectively promotes the uniform deposition of lithium ions with fast Li+ transmission, thereby solving the problem of lithium dendrites. Electrochemical results indicate that BSTFA can obviously reduce polarization in a Li||Li battery at a current density of 1 mA cm-2. Besides, an excellent cycling performance (107 mA h g-1) and Coulombic efficiency (99%) can be obtained for a Li||LiNi0.6Co0.2Mn0.2O2 (NCM622) battery with 0.5 wt % BSTFA at 2 C after 200 cycles, even at a high NCM622 loading of 6 mg cm-2.

Pomegranate-Like Structured Si@SiOx Composites With High-Capacity for Lithium-Ion Batteries.

Silicon anodes with an extremely high theoretical specific capacity of 4,200 mAh g-1 have been considered as one of the most promising anode materials for next-generation lithium-ion batteries. However, the large volume expansion during lithiation hinders its practical application. In this work, pomegranate-like Si@SiOx composites were prepared using a simple spray drying process, during which silicon nanoparticles reacted with oxygen and generated SiOx on the surface. The thickness of the SiOx layer was tuned by adjusting the drying temperature. In the unique architecture, the SiOx which serves as the protection layer and the void space in pomegranate-like structure could alleviate the volume expansion during repeated lithium insertion/extraction. As a lithium-ion battery anode, pomegranate-like Si@SiOx composites dried at 180°C delivered a high specific capacity of 1746.5 mAh g-1 after 300 cycles at 500 mA g-1.

Self-Formed Protection Layer on a 3D Lithium Metal Anode for Ultrastable Lithium-Sulfur Batteries.

Lithium metal anodes are a key component of high-energy-density lithium-sulfur (Li-S) batteries. However, the issues associated with lithium anodes remain unsolved owing to the immature lithium anode construction and protection technology, which leads to internal short circuits, poor capacity retention, and low coulombic efficiency for high-sulfur-loading Li-S batteries. Herein, a highly stable 3D lithium carbon fiber composite (3D LiCF) anode for high-sulfur-loading Li-S batteries was demonstrated, in which a self-formed hybrid solid-electrolyte protection layer was constructed on a lithium metal surface through codeposition of thiophenolate ions and inorganic lithium salts by using diphenyl disulfide as a co-additive in the electrolyte. The aromatic components from thiophenolate could improve the stability of the protection layer, and the 3D structure of the carbon fiber could effectively buffer the volume effect during lithium cycling. A Li-S battery based on a 3D LiCF anode exhibited excellent cycling stability with an energy efficiency of 89.2 % for 100 cycles in terms of a high energy density of 22.3 mWh cm-2 (10 mAh cm-2 area capacity of lithium cycling). This contribution demonstrates versatile and ingenious strategies for the construction of a 3D lithium anode structure and protection layer, providing an effective solution for practical stable Li-S batteries.

Facile Fabrication of Ethoxy-Functional Polysiloxane Wrapped LiNi0.6Co0.2Mn0.2O2 Cathode with Improved Cycling Performance for Rechargeable Li-Ion Battery.

Dealing with the water molecule on the surface of LiNi0.6Co0.2Mn0.2O2 (NCM) cathode and hydrogen fluoride in the electrolyte is one of the most difficult challenges in Li-ion battery research. In this paper, the surface polymerization of tetraethyl orthosilicate (TEOS) on NCM to generate ethoxy-functional polysiloxane (EPS) wrapped NCM (E-NCM) cathode under mild conditions and without any additions is utilized to solve this intractable problem. The differential scanning calorimetry, transmission electron microscopy, and X-ray photoelectron spectroscopy results show that the formed amorphous coating can provide a protective shell to improve the NCM thermal stability, suppress the thickening of the solid electrolyte interphase (SEI) layer, and scavenge HF in the electrolyte. The E-NCM composite with 2 mol % EPS delivers a high discharge capacity retention of 84.9% after 100 cycles at a 1 C discharge rate in the 2.8-4.3 V potential range at 55 °C. Moreover, electrochemical impedance spectroscopy measurements reveal that the EPS coating could alleviate the impedance rise during cycling especially at an elevated temperature. Therefore, the fabricated E-NCM cathode with long-term cycling and thermal stability is a promising candidate for use in a high-energy Li-ion battery.

CO(2) -responsive "smart" single-walled carbon nanotubes.

A new type of "smart" single-walled carbon nanotubes is created by wrapping a pyrene-labeled CO(2) -responsive polymer via π-π stacking. The polymer/SWNT hybrids not only undergo a hydrophobic-hydrophilic transition upon CO(2) stimulus of CO(2) in a mixed solvent, but also exhibit switchable dispersion/aggregation states upon the alternate bubbling of CO(2) and N(2) in pure water.

Enhanced anode performances of polyaniline-TiO2-reduced graphene oxide nanocomposites for lithium ion batteries.

Here, we report a three-layer-structured hybrid nanostructure consisting of transition metal oxide TiO(2) nanoparticles sandwiched between carbonaceous polymer polyaniline (PANI) and graphene nanosheets (termed as PTG), which, by simultaneously hindering the agglomeration of TiO(2) nanoparticles and enhancing the conductivity of PTG electrode, enables fast discharge and charge. It was demonstrated that the PTG exhibited improved electrochemical performance compared to pure TiO(2). As a result, PTG nanocomposite is a promising anode material for highly efficient lithium ion batteries (LIBs) with fast charge/discharge rate and high enhanced cycling performance [discharge capacity of 149.8 mAh/g accompanying Coulombic efficiency of 99.19% at a current density of 5C (1000 mA/g) after 100 cycles] compared to pure TiO(2). We can conclude that the concept of applying three-layer-structured graphene-based nanocomposite to electrode in LIBs may open a new area of research for the development of practical transition-metal oxide graphene-based electrodes which will be important to the progress of the LIBs science and technology.

Enhanced anode performances of the Fe3O4-carbon-rGO three dimensional composite in lithium ion batteries.

A three dimensional composite was constructed by anchoring Fe(3)O(4) nanoparticles encapsulated within carbon shells onto reduced graphene oxide sheets, which exhibited enhanced anode performances in lithium ion batteries with a specific capacity of 842.7 mAh g(-1) and superior recycle stability after 100 cycles.

Improved performances of ß-Ni(OH)2@reduced-graphene-oxide in Ni-MH and Li-ion batteries.

Incorporation of reduced graphene oxide into ß-Ni(OH)(2) presents high performances with specific discharge capacity of 283 mA hg(-1) after 50 cycles in Ni-MH batteries, and 507 mA hg(-1) after 30 cycles in Li ion batteries.

Co3O4@graphene composites as anode materials for high-performance lithium ion batteries.

This paper reports on the synthesis of Co(3)O(4)@graphene composites (CGC) and their applications as anode materials in lithium ion batteries (LIBs). Through a chemical deposition method, Co(3)O(4) nanoparticles (NPs) with sizes in the range of 10-30 nm were homogeneously dispersed onto graphene sheets. Due to their high electrical conductivity, the graphene sheets in the CGC improved the electrical conductivity and the structure stability of CGC. CGC displayed a superior performance in LIBs with a large reversible capacity value of 941 mA hg(-1) in the initial cycle with a large current density and an excellent cyclic performance of 740 mA hg(-1) after 60 cycles, corresponding to 88.3% of the theoretical value of CGC, owing to the interactions between graphene sheets and Co(3)O(4) NPs anchored on the graphene sheets. This synthesis approach may find its application in the design and synthesis of novel electrode materials used in LIBs.

Fabrication of high optical transparent and conductive SWNT based transparent conducting film on flexible plastic substrate using ozone as a redox dopant.

In the present work, single-wall carbon nanotubes-transparent conducting films (SWNTs-TCFs) were fabricated at room temperature on a flexible polycarbonate substrate using the ultrosonication-dip-coating technique. Ozone was employed to reduce the sheet resistance of conductive film. As a result, the sheet resistance of film was decreased drastically after 1.5 hr ozone (O3) treatment and could reach up to 170 omega/square at 80% T at 550 nm wavelength. In addition, aminopropyltriethoxysilane (APTS) was further applied as an adhesion promoter in order to enhance the adhesion between the SWNTs films and the substrate. Experimental results show that ATPS can greatly improve the adhesion of SWNTs coating to the substrate without the loss of conductivity.