Binder-free SnO2–TiO2 composite anode with high durability for lithium-ion batteries

Pseudo-capacitive and kinetic enhancement of metal oxides and pillared graphite composite for stabilizing battery anodes

Nanostructured TiO₂ and SnO₂ possess reciprocal energy storage properties, but challenges remain in fully exploiting their complementary merits. Here, this study reports a strategy of chemically suturing metal oxides in a cushioning graphite network (SnO₂[O]rTiO₂-PGN) in order to construct an advanced and reliable energy storage material with a unique configuration for energy storage processes. The suggested SnO₂[O]rTiO₂-PGN configuration provides sturdy interconnections between phases and chemically wraps the SnO₂ nanoparticles around disordered TiO₂ (SnO₂[O]rTiO₂) into a cushioning plier-linked graphite network (PGN) system with nanometer interlayer distance (~ 1.2 nm). Subsequently, the SnO₂[O]rTiO₂-PGN reveals superior lithium-ion storage performance compared to all 16 of the control group samples and commercial graphite anode (keeps around 600 mAh g^-1 at 100 mA g^-1 after 250 cycles). This work clarifies the enhanced pseudo-capacitive contribution and the major diffusion-controlled energy storage kinetics. The validity of preventing volume expansion is demonstrated through the visualized image evidence of electrode integrity.

The Use of Anodic Oxides in Practical and Sustainable Devices for Energy Conversion and Storage

This review addresses the main contributions of anodic oxide films synthesized and designed to overcome the current limitations of practical applications in energy conversion and storage devices. We present some strategies adopted to improve the efficiency, stability, and overall performance of these sustainable technologies operating via photo, photoelectrochemical, and electrochemical processes. The facile and scalable synthesis with strict control of the properties combined with the low-cost, high surface area, chemical stability, and unidirectional orientation of these nanostructures make the anodized oxides attractive for these applications. Assuming different functionalities, TiO2-NT is the widely explored anodic oxide in dye-sensitized solar cells, PEC water-splitting systems, fuel cells, supercapacitors, and batteries. However, other nanostructured anodic films based on WO3, CuxO, ZnO, NiO, SnO, Fe2O3, ZrO2, Nb2O5, and Ta2O5 are also explored and act as the respective active layers in several devices. The use of AAO as a structural material to guide the synthesis is also reported. Although in the development stage, the proof-of-concept of these devices demonstrates the feasibility of using the anodic oxide as a component and opens up new perspectives for the industrial and commercial utilization of these technologies.

Tin dioxide-based nanomaterials as anodes for lithium-ion batteries

The development of new electrode materials for lithium-ion batteries (LIBs) has attracted significant attention because commercial anode materials in LIBs, like graphite, may not be able to meet the increasing energy demand of new electronic devices. Tin dioxide (SnO2) is considered as a promising alternative to graphite due to its high specific capacity. However, the large volume changes of SnO2 during the lithiation/delithiation process lead to capacity fading and poor cycling performance. In this review, we have summarized the synthesis of SnO2-based nanomaterials with various structures and chemical compositions, and their electrochemical performance as LIB anodes. This review addresses pure SnO2 nanomaterials, the composites of SnO2 and carbonaceous materials, the composites of SnO2 and transition metal oxides, and other hybrid SnO2-based materials. By providing a discussion on the synthesis methods and electrochemistry of some representative SnO2-based nanomaterials, we aim to demonstrate that electrochemical properties can be significantly improved by modifying chemical composition and morphology. By analyzing and summarizing the recent progress in SnO2 anode materials, we hope to show that there is still a long way to go for SnO2 to become a commercial LIB electrode and more research has to be focused on how to enhance the cycling stability.

Nitrogen-doped TiO2(B) nanobelts enabling enhancement of electronic conductivity and efficiency of lithium-ion storage

To enhance the intrinsic electrical conductivities of TiO₂(B) nanobelts, nitrogen(N)-doped TiO₂(B) nanobelts (N-TNB) were prepared in this study by a facile and cost-effective hydrothermal method using urea as the nitrogen source with TiO₂ (P25) nanoparticles. x-ray photoelectron spectroscopy confirmed that the N-atoms preferentially occupied up to ∼0.516 atom% in the interstitial sites of the N-TNB and the maximum concentration of substituted-N bonds in the N-TNB was ∼0.154 atom%, thereby the total concentration of doped nitrogen elements of ∼0.67 atom% improved the high intrinsic electrical conductivity and ionic diffusivity of the TiO₂(B) nanobelts. The as-prepared N-TNB electrode delivered the highest specific capacity of 133.9 mAh g^-1 in the first cycle, with an exceptional cyclic capacity retention at an ultrafast current rate of 1000 mA g^-1; this is not less than 51% after 500 cycles and represents an excellent rate capability of ∼37 mAh g^-1 at an ultra-high rate of 40 C. These values are among the best ever reported on comparison of the delivered highest discharge capacity of N-TNB at 1000 mA g^-1 and high-rate capabilities of its Li⁺ ion storage with the literature data for N-TNB (∼231.5 mAh g^-1 at a very low current density of 16.75 mA g^-1, ∼0.1 C) of similar materials used in sodium-ion batteries. This implies the potential feasibility of these N-TNB as high-capacity anode materials for next-generation, high-energy-density, electrochemical energy-storage devices.

One-step fabrication of nanosized LiFePO4/expanded graphite composites with a particle growth inhibitor and enhanced electrochemical performance of aqueous Li-ion capacitors

It is reported that olivine-type lithium iron phosphate (LFP) for Li-ion batteries is one of the most widely utilized cathode materials, but its high-power applications are limited due to its intrinsically poor ion transfer rate and conductivity. Therefore, it is highly desired to fabricate LFP Li-ion capacitors (LICs) with high power performance and excellent cyclic reversibility, especially in safe, low cost and environmentally friendly aqueous electrolytes. Here, we fabricate LFP/expanded graphite (EG) nanocomposites by a one-step process, in which polyethylene glycol (PEG) is used as the particle growth inhibitor combined with vacuum infiltration of the LFP precursor into EG as a conductive sub-phase, and further investigate their high-power performance in aqueous LICs. Embedding spherical LFP nanoparticles with well-controlled size and agglomeration into the pores of EG and wrapping LFP nanoparticles by EG films contribute to the rapid electron and ion diffusion in LFP/EG composites, resulting in excellent cyclic reversibility and rate performance of LFP/EG composites. The aqueous LFP/EG//active carbon (AC) LICs were assembled in LiNO₃ electrolytes with LFP/EG composites and AC as the positive and negative electrodes, respectively. The optimal LIC shows a power density of 2367.9 W kg⁻¹ at an energy density of 6.5 W h kg⁻¹, dramatically favorable rate characteristics and excellent cycle life with 82.1% capacitance retention of its primary capacitance at 2 A g⁻¹ after 6000 cycles, markedly higher than those of the commercial LFP LIC. The presented aqueous LFP/EG//AC LICs with excellent electrochemical performance are expected to have broad high-power appliances that are cost-sensitive and highly secure.

It is reported that olivine-type lithium iron phosphate (LFP) for Li-ion batteries is one of the most widely utilized cathode materials, but its high-power applications are limited due to its intrinsically poor ion transfer rate and conductivity.