Unusual Improvement of Pseudocapacitance of Nanocomposite Electrodes: Three-Dimensional Amorphous Carbon Frameworks Triggered by TiO2 Nanocrystals

Formicarium-Like Micron Porous Si Synergistically Adjusted by Surface Hard-Soft Nanoencapsulation as Long-Life Lithium-Ion Battery Anode

Micron porous silicon (MPSi) is a promising lithium-ion battery (LIB) anode that can provide enough space to effectively alleviate the volume expansion and large number of transmission channels to rapidly transport the Li-ions. However, a long-term stable MPSi anode at high current density is still a great challenge. Herein, a double-regulated formicarium like-MPSi composite using the surface hard-soft titanium dioxide-few layered MXene nanotemplate (FMPSi@TiO2@FMXene) was designed and synthesized via an in situ assembly strategy as long-life LIB anode. Such hard-soft TiO2-FMXene nanoencapsulation can collaboratively tune the internal/external stress, inhibit the volume expansion, reduce the interfacial reactions, and improve the electrical conductivity of MPSi, resulting in the great enhancement of structural stability and electrochemical performance in cycling even at high current density. Especially, this FMPSi@TiO2@FMXene anode exhibits a high reversible capacity of 1254.9 and 970.4 mAh/g after 500 cycles at 0.5 and 1 A/g, respectively. Moreover, a full cell is assembled with the FMPSi@TiO2@FMXene anode and commercial LiFePO4 (LFP) cathode, exhibiting a high capacity retention rate of 91.6% in 100 cycles. This work provides an effective surface nanoengineering tactic to obtain the structurally stable MPSi anodes by hard-soft nanotemplate for large-scale and long-term LIB application.

Amorphous Anode Materials for Fast-charging Lithium-ion Batteries

Fast-charging technology is set to revolutionize the field of lithium-ion batteries (LIBs), driving the creation of next-generation devices with the ability to get charged within a short span of time. From the anode perspective, it is of paramount importance to design materials that can withstand continuous Li+ insertion/deinsertion at high charging rates and still remain unaffected by factors such as mechanical fractures, electrolyte side reactions, polarisation, lithium plating and heat generation. Herein, the recent advancements in the design of amorphous materials as anodes for fast-charging LIBs have been discussed. While the development of this particular class of materials for application in high-rate anodes has been paid limited attention in recent literature, it holds immense promise for improving the fast-charging capabilities. This concept summarizes the recent strides made in this emerging field, outlining the strategies employed in the design of amorphous anodes and emphasizing the crucial role played by the amorphous nature in achieving fast-charging performance. Further, the successive initiatives that can be undertaken to drive the progress of amorphous materials for fast charging LIBs have also been detailed, which could potentially improve their commercial viability.

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.

Resistive Switching Phenomenon Observed in Self-Assembled Films of Flame-Formed Carbon-TiO2 Nanoparticles

Nanostructured films of carbon and TiO₂ nanoparticles have been produced by means of a simple two-step procedure based on flame synthesis and thermophoretic deposition. At first, a granular carbon film is produced on silicon substrates by the self-assembling of thermophoretically sampled carbon nanoparticles (CNPs) with diameters of the order of 15 nm. Then, the composite film is obtained by the subsequent thermophoretic deposition of smaller TiO₂ nanoparticles (diameters of the order of 2.5 nm), which deposit on the surface and intercalate between the carbon grains by diffusion within the pores. A bipolar resistive switching behavior is observed in the composite film of CNP-TiO₂. A pinched hysteresis loop is measured with SET and RESET between low resistance and high resistance states occurring for the electric field of 1.35 × 10⁴ V/cm and 1.5 × 10⁴ V/cm, respectively. CNP-TiO₂ film produced by flame synthesis is initially in the low resistive state and it does not require an electroforming step. The resistance switching phenomenon is attributed to the formation/rupture of conductive filaments through space charge mechanism in the TiO₂ nanoparticles, which facilitate/hinder the electrical conduction between carbon grains. Our findings demonstrate that films made of flame-formed CNP-TiO₂ nanoparticles are promising candidates for resistive switching components.

Boosting Lithium-Ion Transport Kinetics by Increasing the Local Lithium-Ion Concentration Gradient in Composite Anodes of Lithium-Ion Batteries

Constructing composite electrodes is considered to be a feasible way to realize high-specific-capacity Li-ion batteries. The core-double-shell-structured Si@C@TiO₂ would be an ideal design for such batteries, considering that carbon (C) can buffer the volume change and TiO₂ can constrain the structural deformation of Si. Although the electrochemical performance of the shells themselves is relatively clear, the complexity of the multishell heterointerface always results in an ambiguous understanding about the influence of the heterointerface on the electrochemical properties of the core material. In this work, a multilayer film model that can simplify and simultaneously expand the area of the heterointerface is used to study the heterointerfacial behavior. First, a multilayer film TiO₂/C with different numbers of TiO₂/C heterointerfaces is studied. It shows that the electrochemical performance is enhanced apparently by increasing the number of TiO₂/C heterointerfaces. On the one hand, the TiO₂/C heterointerface exhibits a strong lithium-ion storage capacity. On the other hand, the TiO₂/C heterointerface appears to effectively promote the local Li-ion concentration gradient and thus boost the Li-ion transport kinetics. Then, TiO₂/C is combined with Si to construct a composite anode Si/C/TiO₂. An obvious advantage of TiO₂/C over single TiO₂ and C is observed. The utilization rate of Si is greatly improved in the first cycle and reaches up to 98% in Si/C/TiO₂. The results suggest that the electrochemical performance of Si can be greatly manipulated by the heterointerface between the multishells.