A Hybrid Structure to Improve Electrochemical Performance of SiO Anode Materials in Lithium-Ion Battery

The wide utilization of lithium-ion batteries (LIBs) prompts extensive research on the anode materials with large capacity and excellent stability. Despite the attractive electrochemical properties of pure Si anodes outperforming other Si-based materials, its unsafety caused by huge volumetric expansion is commonly admitted. Silicon monoxide (SiO) anode is advantageous in mild volume fluctuation, and would be a proper alternative if the low initial columbic efficiency and conductivity can be ameliorated. Herein, a hybrid structure composed of active material SiO particles and carbon nanofibers (SiO/CNFs) is proposed as a solution. CNFs, through electrospun processes, serve as a conductive skeleton for SiO nanoparticles and enable SiO nanoparticles to be uniformly embedded in. As a result, the SiO/CNF electrochemical performance reaches a peak at 20% the mass ratio of SiO, where the retention rate reaches 73.9% after 400 cycles at a current density of 100 mA g-1, and the discharge capacity after stabilization and 100 cycles are 1.47 and 1.84 times higher than that of pure SiO, respectively. A fast lithium-ion transport rate during cycling is also demonstrated as the corresponding diffusion coefficient of the SiO/CNF reaches ~8 × 10-15 cm2 s-1. This SiO/CNF hybrid structure provides a flexible and cost-effective solution for LIBs and sheds light on alternative anode choices for industrial battery assembly.

Effective disproportionation of SiO induced by Na2CO3 and improved cycling stability via PDA-based carbon coating as anode materials for Li-ion batteries

In order to improve the initial coulombic efficiency (ICE) and cycle performance of SiO, in this study, the disproportionation reaction of commercial SiO is performed with the assistance of Na2CO3 under high temperatures. A polydopamine-based carbon is then in situ formed on the surface of the mixture (d-SiO-G) of disproportionated-SiO and graphite. It is found that an appropriate amount of Na2CO3 can effectively enhance the ICE of the commercial SiO due to the formation of Si, SiO2, and silicate; the mass ratio of d-SiO-G to the dopamine monomer is the important factor in influencing the cycling stability of the d-SiO-G@C composite. Due to the synergistic effect of graphite and the polydopamine-based carbon layer, the ICE for the d-SiO-G@C composite is 72.6%, and its capacity retention reaches 86.2% after 300 cycles, which is 11% higher than that of d-SiO-G. The modification method is an effective strategy for SiO materials in commercial applications.

A ternary oxygen-vacancy abundant ZnMn2O4/MnCO3/nitrogen-doped reduced graphene oxide hybrid towards superior-performance lithium storage

Transition metal oxides (TMOs) and metal carbonates exhibit high specific capacity, abundant reserves on Earth, and environmental friendliness as anode materials for lithium-ion batteries (LIBs). However, their poor electrical conductivity and serious volume expansion lead to rapid capacity decay. Herein, a stable and highly conductive composite of an oxygen-vacancy abundant nitrogen-doped reduced graphene oxide (NG) encapsulated ZnMn2O4/MnCO3 (ZnMn2O4/MnCO3/NG) hybrid is successfully fabricated, which can provide more spaces for rapid ion diffusion and corroborate fast electron transport. The ZnMn2O4/MnCO3/NG hybrid exhibits an incredible reversible capacity (916 mA h g-1 at 0.1 A g-1), preeminent cycling stability (800 mA h g-1 at 1 A g-1 after 300 cycles) and outstanding rate capability (459 mA h g-1 at 2 A g-1). The excellent lithium storage performance of ZnMn2O4/MnCO3/NG is attributed to the synergistic effect between ZnMn2O4 and MnCO3, the addition of nitrogen and oxygen defects, and the stable structures of NG, which relieve the volume expansion of the electrode material, improve the electronic conductivity and enhance structural stability and surface capacitive response. This work provides a new idea for constructing oxygen-vacancy abundant NG encapsulated bimetal oxides for energy storage of LIBs.

Effect of Porosity in Activated Carbon Supports for Silicon-Based Lithium-Ion Batteries (LIBs)

Activated carbon supports for Si deposition with different porosities were prepared, and the effect of porosity on the electrochemical characteristics was investigated. The porosity of the support is a key parameter affecting the Si deposition mechanism and the stability of the electrode. In the Si deposition mechanism, as the porosity of activated carbon increases, the effect of particle size reduction due to the uniform dispersion of Si was confirmed. This implies that the porosity of activated carbon can affect the rate performance. However, excessively high porosity reduced the contact area between Si and activated carbon, resulting in poor electrode stability. Therefore, controlling the porosity of activated carbon is essential to improving the electrochemical characteristics.

One-step synthesis of uniformly distributed SiOx-C composites as stable anodes for lithium-ion batteries

SiO_x is one of the most promising anode materials for lithium-ion batteries (LIBs), due to its high theoretical capacity and low cost. However, the huge volume expansion and low electron/ion diffusion rate hinder its further commercial applications. Herein, a simple molecular polymerization method is developed to synthesize N,P co-doped SiO_x-C composites (denoted as SiO_x-C@CNT), in which SiO_x and carbon are uniformly dispersed at the atomic level, and the embedded carbon nanotubes improve the lithium ion diffusion kinetics. Benefiting from the unique structure, the SiO_x-C@CNT composites exhibit a high reversible capacity of 848 mA h g^-1 at 0.1 A g^-1 and long cycling stability (84.0% capacity retention after 1500 cycles). More impressively, the LiCoO₂∥SiO_x-C@CNT full battery also exhibits stable cycle life (only 4.7% capacity loss after 300 cycles at 1 C). These results show the application potential of the SiO_x-C@CNT anode in LIBs.