High-performance Li-ion batteries are urgently demanded for portable electronics and new energy electric vehicles. As the key part of these batteries, active materials are commonly required to possess high capacity, large energy density, long cycling stability and good safety.

In order to achieve such high capacity and energy density, the portion of active materials within the electrode should be maximal, while as for long cycling stability and good safety, excellent electron transfer and ion diffusion performances are essential.

Generally, 3D nanostructured materials are expected to meet those requirements. However, conventional 3D battery materials take metal or some other high-density materials as scaffold to support the whole structure, which not only reduces the percentage of active materials but decreases the capacity of full cell as well, and this exactly is the restrict factor of long-term cycling stability.

As to this problem, LIU Jinyun, from a study team led by Prof. LIU Jinhuai and Prof. HUANG Xingjiu, from Institute of Intelligent Machines, Hefei Institutes of Physical Science, Chinese Academy of Sciences, conducted a study on high-performance graphene-based Li-ion batteries, in which three-dimensional (3D) graphene-based Li-ion battery nanocomposites with high capacity and long cycling life were developed.

Joining hands with University of Illinois at Urbana-Champaign, LIU and his co-workers developed a 3D graphene-based battery composite, which showed high loading of active materials and short pathway for ion and electron transfer.

Besides, there was no need of additives such as binders and conductive additives to assemble the presented materials into batteries. Those features made the battery possess a high capacity and good cycling stability. And the prepared 3D graphene/V₂O₅ cathode exhibited a capacity higher than 200 mAh/g after 2000 cycles at 5C (about 12 min for one charge or discharge).

Most of the previous reports showed that a cycling time was less than 1000 cycles, while the capacity  less than 150 mAh/g. To achieve a capacity of the graphene/V₂O₅ cathode charged for one minute, the commercial electrodes and previous reports require longer than five minutes.

In addition, the presented 3D graphene-based nanocomposites design is also applicable in battery anode preparation, such as graphene/Si anodes, showing a good general applicability.

The study was published in Advanced Materials with title Graphene Sandwiched Mesostructured Li-Ion Battery Electrodes, which was selected as a frontispiece article of the journal.

Cross-sectional SEM image of the 3D graphene/V₂O₅ cathode (Frontispiece of Advanced Materials); (b) SEM image of 3D graphene; (c) Charge-discharge curves (5C for 2000 cycles). (Image by LIU Jinyun)