Amorphous SnO2 nanoparticles embedded into a three-dimensional porous carbon matrix as high-performance anodes for lithium-ion batteries

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.

Engineering amorphous SnO2 nanoparticles integrated into porous N-doped carbon matrix as high-performance anode for lithium-ion batteries

A facile in-situ preparation strategy is proposed to anchor amorphous SnO₂ nanoparticles into the porous N-doped carbon (NC) matrix to fabricate amorphous composite powders (am-SnO₂@p-NC), which feature the hierarchically interconnected and well interlaced porous configurations by employing polyvinylpyrrolidone as the soft template. The morphology regulation of the porous structure is precisely realized by adjusting the content of the template and the relationship between structural evolution and electrochemical performance of composite powders is accurately described to explore the optimal template dosage. The results indicate that the am-SnO₂@p-NC-50 % composite electrode can deliver the improved lithium storage capacity and cycling performance when the content of the template is controlled at 0.500 g, in which the initial discharge specific capacity is about 1557.6 mAh/g and the reversible value retains at 841.5 mAh/g after 100 cycles at 100 mA/g. Meanwhile, the discharge specific capacity of 869.8 mAh/g is exhibited for the am-SnO₂@p-NC-50 % composite electrode after 60 cycles when the current density is recovered from 2000 to 100 mA/g. Moreover, the Li⁺ ions diffusion coefficient up to about 5.5 × 10^-12 cm²/s is calculated from galvanostatic intermittent titration technique tests, which can be partly ascribed to the conductive NC substrate that provides the high electronic conductivity, and partly to the highly porous structure that shortens Li⁺ ions transfer pathways and guarantees the fast reaction kinetics. Therefore, the hierarchically porous engineering of carbon networks to confine amorphous transition metal oxide nanoparticles is of great significance in the development of high-performance anode materials for lithium-ion batteries.

Three-Dimensional SnO2 Nanoparticles Synthesized by Joule Heating as Anode Materials for Lithium Ion Batteries

Tin dioxide (SnO2) is a promising material for use as anodes because of its high theoretical capacity (1,494 mAh g−1). However, a critical limitation is the large change in volume during repeated cycling by pulverization of SnO2, which results in capacity fading. In this study, we enhanced cycle life and reduced capacity fading by introducing the use of three-dimensional SnO2 nanoparticles on carbon nanofibers (CNFs) as an anode material, which is fabricated by simple carbothermal shock through the Joule heating method. Our observations show that the SnO2 nanoparticles are about 50 nm in diameter and are uniformly distributed on CNF, and that the strong connections between SnO2 nanoparticles and CNF are sustained even after repeated cycling. This structural advantage provides high reversible capacity and enhanced cycle performance for over 100 cycles. This study provides insight into the fabrication of anode materials that have strong electric connections between active materials and conductive materials due to the Joule heating method for high-performance lithium ion batteries.

Insight on the effect of Ni and Ni-N co-doping on SnO2 anode materials for lithium-ion batteries

With the increased demand for high-rate performance Li-ion batteries, it is necessary to find available methods to improve the rate properties of SnO₂ electrodes. It is noteworthy that doping was considered to be a feasible means. The electronic structures and diffusion energy barriers of Ni-doped and Ni–N co-doped SnO₂ were calculated based on density functional theory. The results estimated that the energy gaps of Ni-doped and Ni–N co-doped SnO₂ are 1.07 eV and 0.94 eV, which both are smaller than the value of 2.08 eV of SnO₂. These exhibit that the conduction properties of SnO₂ can be enhanced by doping with the Ni or Ni–N atoms. Moreover, the diffusion properties of Li can also be improved by doping with Ni–N atoms due to the diffusion energy barrier of Li from the B to C point for Ni–N co-doped SnO₂ being 0.12 eV smaller than the value of 0.24 eV for the pristine SnO₂. Meanwhile, the diffusion energy barriers of Li along other pathways for Ni–N co-doped SnO₂ are almost the same as 0.24 eV for SnO₂. These results show that both the electronic and ionic conductivity of SnO₂ can be enhanced by Ni–N co-doping, which provides a theoretical explanation to promote the rate properties of SnO₂ by Ni–N co-doping as anode materials for Li-ion batteries.

Energy barriers of Li, where red, green and yellow curves represent diffusion energy barriers of Li in the pure, Ni-doped, and Ni–N co-doped SnO₂, respectively.