Defects boost graphitization for highly conductive graphene films

Qing Zhang; Qinwei Wei; Kun Huang; Zhibo Liu; Wei Ma; Zehui Zhang; Yanfeng Zhang; Hui-Ming Cheng; Wencai Ren

doi:10.1093/nsr/nwad147

Defects boost graphitization for highly conductive graphene films

Natl Sci Rev. 2023 May 19;10(7):nwad147. doi: 10.1093/nsr/nwad147. eCollection 2023 Jul.

Authors

Qing Zhang^{1

2}, Qinwei Wei^{1

2}, Kun Huang^{1

2}, Zhibo Liu^{1

2}, Wei Ma^{1

2}, Zehui Zhang³, Yanfeng Zhang³, Hui-Ming Cheng^{1

2

4}, Wencai Ren^{1

2}

Affiliations

¹ Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China.
² School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, China.
³ School of Materials Science and Engineering, Peking University, Beijing 100871, China.
⁴ Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China.

Abstract

Fabricating highly crystalline macroscopic films with extraordinary electrical and thermal conductivities from graphene sheets is essential for applications in electronics, telecommunications and thermal management. High-temperature graphitization is the only method known to date for the crystallization of all types of carbon materials, where defects are gradually removed with increasing temperature. However, when using graphene materials as precursors, including graphene oxide, reduced graphene oxide and pristine graphene, even lengthy graphitization at 3000°C can only produce graphene films with small grain sizes and abundant structural disorders, which limit their conductivities. Here, we show that high-temperature defects substantially accelerate the grain growth and ordering of graphene films during graphitization, enabling ideal AB stacking as well as a 100-fold, 64-fold and 28-fold improvement in grain size, electrical conductivity and thermal conductivity, respectively, between 2000°C and 3000°C. This process is realized by nitrogen doping, which retards the lattice restoration of defective graphene, retaining abundant defects such as vacancies, dislocations and grain boundaries in graphene films at a high temperature. With this approach, a highly ordered crystalline graphene film similar to highly oriented pyrolytic graphite is fabricated, with electrical and thermal conductivities (∼2.0 × 10⁴ S cm^-1; ∼1.7 × 10³ W m^-1 K^-1) that are improved by about 6- and 2-fold, respectively, compared to those of the graphene films fabricated by graphene oxide. Such graphene film also exhibits a superhigh electromagnetic interference shielding effectiveness of ∼90 dB at a thickness of 10 μm, outperforming all the synthetic materials of comparable thickness including MXene films. This work not only paves the way for the technological application of highly conductive graphene films but also provides a general strategy to efficiently improve the synthesis and properties of other carbon materials such as graphene fibers, carbon nanotube fibers, carbon fibers, polymer-derived graphite and highly oriented pyrolytic graphite.

Keywords: defects; electrical and thermal conductivity; graphene film; graphitization; thermal management and EMI shielding.