Harbin Engineering University

About: Harbin Engineering University is a education organization based out in Harbin, Heilongjiang, China. It is known for research contribution in the topics: Control theory & Microstructure. The organization has 31149 authors who have published 27940 publications receiving 276787 citations. The organization is also known as: HEU.

Bicontinuous hierarchical Na7V4(P2O7)4(PO4)/C nanorod–graphene composite with enhanced fast sodium and lithium ions intercalation chemistry

Abstract: Mixed polyanion materials with a 3D framework for battery electrodes have been attracting significant attention recently in view of the requirements to further improve energy storage and power densities. Herein, we present a design of a hierarchical Na7V4(P2O7)4(PO4)/C nanorod–graphene composite as sodium- and lithium-storage cathode materials. The hierarchical structure is composed of a 1D rectangular Na7V4(P2O7)4(PO4)/C nanorod, which is coated by in situ residual carbon and wrapped by a reduced graphene-oxide sheet. The open network of graphene and the surface carbon coating of the Na7V4(P2O7)4(PO4)/C nanorod provide bicontinuous electron and ion pathways, providing a three-dimensional conductive network for efficient electron and ion transfer. The flexible electrode built from the hierarchical composite free of binder or conductive additive exhibits improved electron conductivity and higher sodium/lithium ion migration coefficients than the pristine Na7V4(P2O7)4(PO4)/C nanorod. It approaches the initial reversible electrochemical capacities of 91.4 and 91.8 mA h g−1 with high discharge potentials over 3.8 V (vs. Na/Na+ or Li/Li+) and good cycling properties with capacity retentions of 95% and 83% after 200 cycles at a 1 C rate in sodium and lithium intercalation systems, respectively. Even at 10 C, it still delivers 87.4% (for sodium) and 78.2% (for lithium) of the capacity and high cycling stability. Taking into consideration the compatibilities of both sodium/lithium ions and their superior electrochemical characteristics, the bicontinuous hierarchical composite is considered to be a promising high-rate capability electrode material for advanced energy storage applications.

Chemical vapor deposition derived flexible graphene paper and its application as high performance anodes for lithium rechargeable batteries

Abstract: We present a novel approach to fabricate flexible graphene papers using chemical vapor deposition (CVD) derived graphene. Expanded vermiculite was used as a layered template in the CVD process to produce bulk materials containing graphene sheets of the order of hundreds of microns at a gram scale. Meshes or carbon nanotubes can be introduced into the graphene sheets by template pretreating. Owing to the large sheet size, the as-obtained graphene sheets were easily fabricated into flexible graphene papers with low surface density and good conductivity, which exhibited greatly enhanced reversible capacity (1350 mA h g−1 at 50 mA g−1) and cycling performance as anodes for lithium rechargeable batteries as compared to the graphene papers fabricated using reduced graphene oxide.