Research ArticleSi/C particles on graphene sheet as stable anode for lithium-ion batteries
Graphical abstract
Introduction
Since the commercialization by Sony in 1991, Li-ion batteries have always been the most widespread rechargeable batteries owing to their high energy density, low self-discharging capacity, long cycle life and sustainability. The electrode materials are the most critical content for LIBs to meet the increasing energy demands for portable electronics, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and microelectronic devices [[1], [2], [3]]. Among the various anode materials, silicon is an excellent candidate due to its high theoretical capacity (Li3.75Si, 3579 mA h g−1 at room temperature), about 10 times than graphite (372 mA h g−1), and low operating voltage (about 0.4 V vs. Li/Li+) [4,5]. Silicon is the second largest reserve element in the earth. Therefore, it can yield mass production of silicon material at low cost. However, the extremely large volume change (>300 %) during lithium insertion/extraction process is limited for commercial applications [6,7]. Severe pulverization and loss of electrical contact with the conductive additive result in the exfoliation of silicon particles from the current collector. The as-formed solid-electrolyte interphase (SEI) film is broken when it is charging in the LIB. The new SEI layer is reformed during discharging in the LIB which consume lithium ions and electrolyte continuously. The excessive growth of SEI causes low electronic conductivity, higher resistance to ionic transport, and eventually result in the capacity loss [8].
Several strategies have been devoted to tackling the above issues, which include: (i) nanostructured materials which keep the size of silicon nanoparticles below the threshold value of about 150 nm, such as, nanoparticles, nanowires, and nanotubes [[9], [10], [11]]; (ii) composites of silicon particles which were coated into active or inactive matrix materials to provide free space to alleviate the mechanical stress induced by large volume change, and prevent the aggregation of the silicon nanoparticles [[12], [13], [14], [15], [16], [17], [18]], (iii) chemical bonding of silicon particles with binder or conductive additive [[19], [20], [21], [22]]. During the coating process with matrix materials, the introduction of chemical bonding can strengthen the contact between the Si particles and matrix materials. The chemical bonding can keep the stability of the structure during the synthetic process.
In this study, the structure of Si/C particles on graphene sheet was obtained by cost-effective and environment friendly process. First, commercial silicon nanoparticles were coated with polydopamine (Si/PDA) through the self-polymerization of dopamine. Second, the Si/PDA particles reacted with graphene oxide (GO) in aqueous solution, due to the hydrogen bonds between the functional groups in polydopamine and carbonyl groups on GO. Last, the Si/C–G was obtained by carbonization process of Si/PDA-GO. The flexibility of carbon layer can be buffer the volume change of Si during the Li alloying reaction. The graphene as barrier can effectively avoid the aggregation of Si/C particles. The Si/C particles can anchor on the surface of graphene and prevent graphene from stacking. The flexibility of graphene as secondary buffer structure can ensure the effective accommodation of huge volume expansion. And the graphene can protect the Si/C particles from contacting with electrolyte directly. This strategy can maintain the stable interface at electrode/electrolyte, preventing the continuous formation of SEI, which can promote the reaction kinetics.
Section snippets
Synthesis of Si/C–G
The fabrication process of Si/C–G was three steps (as shown in Scheme 1). First, 500 mg commercial silicon nanoparticles (<50 nm) were mixed Tris-buffer solution (200 mL, 10 mM; pH 8.5) and ultrasonically dispersed for 30 min. 500 mg of dopamine was added into the solution and ultrasonically dispersed for 30 min. The mixture solution was self-polymerized in atmospheric condition for 2 h with stirring. The suspension was filtered and washed with deionized water for several times, and freezing
Results and discussion
As shown in Fig. 1a, the Fourier transform-infrared (FT-IR) spectra can show the functional groups in Si/PDA-GO materials. The broad band of 3700−3300 cm−1 assigned to the (-O-H) and (-N-H) stretching modes [26], the existence of intermolecular hydrogen bonding in Si/PDA-GO [27], which can ensure Si/PDA particles anchored on the surface of GO. The peak at 1630 cm−1 in Si/PDA-GO can be assigned to the stretching of the ringed CO bonds, and the peak at 1400 cm−1 is attributed to the CN bonding
Conclusions
We have fabricated the structure of Si/C particles on graphene sheets as Si-based anode material to address the key issue of practical application of silicon anode through a facile and scalable method. After self-polymerized of dopamine, the polydopamine layer can provide amount of secondary amine groups to form strong hydrogen bonding with carboxyl groups on the surface of graphene oxide through chemical cross-linking, silicon particles were firmly anchored on graphene sheets. Dopamine was
Declaration of Competing Interest
The authors report no declarations of interest.
Acknowledgements
The authors acknowledge financial support from National Natural Science Foundation of China (Nos. 51525206, 51927803, 51902316), National Key R&D Program of China (2016YFA0200102 and 2016YFB0100100), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA22010602), Liaoning Revitalization Talents Program (No. XLYC1908015).
References (48)
- et al.
Nano Energy
(2020) - et al.
Energy Storage Mater.
(2020) - et al.
Electrochim. Acta
(2016) - et al.
Batteries
(2019) - et al.
Eur. Polym. J.
(2019) - et al.
Solid State Ion.
(2011) - et al.
Carbon
(2013) - et al.
Carbon
(2017) - et al.
Nano Energy
(2020) - et al.
Electrochim. Acta
(2016)