Search

In the process of ion insertion/deinsertion, VS2 is prone to volume expansion or even structural collapse leading to capacity decrease and low coulomb efficiency (CE), which hinders its practical application. In this paper, VS2/rGO composites were prepared by solvent method. The rGO firmly locks VS2 in its honeycomb structure, effectively preventing the volume expansion or even structural collapse of the electrode during charging and discharging. The layered structure of VS2 and the high conductivity of rGO speed up the lithium ion transport and achieve the cycling stability of the battery. The results show that the starting capacity of the VS2/rGO anode material is 1190/959 mAh g−1, and the starting CE is 80.57 %. It is worth noting that after 150 cycles, the specific discharge/charge capacity of the material can be maintained at 764/736 mAh g−1. The improved electrochemical properties of the VS2 anode are due to the presence of rGO in the material, thus optimizing the structural stability and electrical properties of the composite. [ABSTRACT FROM AUTHOR]

In this paper, a series of iron oxide/reduced graphene oxide/carbon nanotube composites (K3‐Fe2O3‐rGO/CNT) with well‐dispersedFe2O3 particles are prepared by in situ reaction and then heat‐treatment, and its electrochemical and battery performancesare studied as the anode material of lithium‐ion batteries. The results show that the introduction of reduced graphene oxide/carbon nanotube (rGO/CNT) improves the electrochemical and battery performances of the prepared electrode material. In particular, the K3‐Fe2O3‐rGO/CNT (30 %) composite material has a reversible capacity of 1559 mAh g−1 after 100 charge/discharge cycles at 100 mA g−1. And its specific discharge capacityis 641.1, 639.7, 609.5, 578.6 and 543 mAh g−1at the current density of 100, 200, 500, 1000 and 2000 mA g−1, respectively,with 84.7 % of capacity retention even with a 10 times increase in current density. The research of charge storage indicates that the electrochemical process is a mixed control process of diffusion and capacitance. The improved electrochemical and battery performancesfor the composite electrode material can be attributed to the enhanced dispersion of the Fe2O3 and the enhanced conductive network provided by rGO/CNT composite carbon. It makes a promising way to prepare high performance of anode material for lithium‐ion battery. [ABSTRACT FROM AUTHOR]

A potential anode material for lithium‐ion batteries (LIBs), Co3O4 has been widely considered by many scholars because of its excellent properties in terms of electrochemical characteristics and theoretical specific capacity. However, according to the existing research results, we found that the improvement of the electrochemical performance of Co3O4 has encountered a bottleneck because its intrinsic conductivity is not high enough, and more importantly, the volume expansion is too significant during the charge and discharge process, which leads to the material structure breaking. Therefore, this paper proposes a simple and scalable solvothermal and subsequent calcination method to prepare Co3O4 and reduced graphene oxide (RGO) composite nanoparticles with superior microstructures, and their morphological and electrochemical properties were investigated at different calcination temperatures. As a high‐performance anode material for lithium‐ion batteries, the Co3O4/RGO nanoparticles obtained at 550 °C exhibited terrific initial discharge capacity of 1714.2 mAh g−1, the reversible specific capacity of 1191.9 mAh g−1 with quality coulombic efficiency 98.17 % at 0.5 A g−1 after 100 cycles and extraordinary rate performance (907.6 mAh g−1 with a coulombic efficiency of 99.2 % at 2 A g−1). The facile synthesis method and excellent findings have led to better application prospects for Co3O4/RGO nanoparticles. [ABSTRACT FROM AUTHOR]

This paper shows that the number of cycles and the crystal structure play an important role in the capacity and cycling ability of lithium‐ion batteries. However, the detailed dynamics and continuity of the capacity decay mechanism caused by the number of cycles and crystal structure need to be further understood at the nanoscale. Molecular dynamics simulation was used to examine the microstructure development and deformation behavior of the Si anode in an electric field. The results show that the increase of the number of cycles leads to a large expansion of the volume of the Si electrode, which further leads to the loss of capacity and the decrease of cycle capacity, as well as the decrease of structural stability. The formation of Si crystal structure from diamond structure to amorphous depends on the depth of lithiation and desulfurization. Due to the presence of a large number of nanoscale voids, the Si anode has undergone volume expansion. The transformation associated with nanogap nucleation caused by the involuntary diffusion process is driven by more cycles, resulting in irreversible capacity loss of lithium‐ion batteries. The analysis model shows that the stress caused by diffusion is not only related to the position of the Si anode, but also to the cycle time. [ABSTRACT FROM AUTHOR]

Polyvinylidene fluoride‐hexafluoropropylene (PVDF‐HFP) is a standard electrolyte membrane and binder material for lithium‐ion batteries (LIBs) because of the benefits of membrane formation and strong mechanical properties. Still, its use is limited due to unavoidable defects such as high crystallinity and poor electrochemical performance. In this paper, a larger specific surface area and three‐dimensional (3D) permeable lamellae carboxylated g‐C3N4 (HCN) were successfully prepared by HNO3 and introduced into the PVDF‐HFP to obtain a high‐performance composite separator. The wettability and electrolyte absorption of PVDF‐HFP separator can be improved through the carboxylated HCN. More crucially, because PVDF‐HFP has several active sites and low crystallinity, adding HCN can greatly increase the ionic conductivity of separators. The ionic conductivity of PH‐HCN at 25 °C is 0.52 S cm−1, 4.7 times higher than the initial PVDF‐HFP membrane, and the oxidation potential can reach 4.8 V. The assembled lithium‐ion batteries half‐cell has a capacity of 71 % at a 5 C rate and 94 % after 400 cycles at a 2 C rate. Therefore, the improved separator has the potential to be applied to high‐performance LIBs. [ABSTRACT FROM AUTHOR]

The cycling and rate capabilities of LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode material under high cut‐off voltage (≥4.5 V) and high current density have attracted much attention. However, the material's insufficient intrinsic electronic/ion conductivity and interface instability are still key issues restricting its electrochemical performance.In this paper, a graphene/Ta2O5 co‐coating layer is successfully fabricated on the surface of NCM523 to form a cathode material of GTa‐NCM523 to enhance both the electron and lithium‐ion transport during cathode operation. The GTa‐NCM523 cathode material achieves a discharge specific capacity of 147.4 mAh g−1 after 600 cycles at a voltage of 3.0–4.5 V and a rate of 1 C (180 mA g−1) with a capacity retention rate of 81.4 %. In contrast, the uncoated NCM523 only retains 63.2 % of its capability. At an elevated rate of 10 C (1800 mA g−1), the GTa‐NCM523 can achieve a discharge‐specific capacity of up to 113.5 mAh g−1, which is 43.7 % higher than the uncoated NCM523. The co‐coating layer can inhibit HF erosion and accelerate the movement of lithium‐ions and electrons, which account for the superior electrochemical characteristics of the co‐coating layer comprised of graphene and Ta2O5. [ABSTRACT FROM AUTHOR]