Improving silicon anode durability through uniform dispersion and binding enhancement with polyacrylamide-grafted carbon nanotubes

Abstract

Silicon (Si) anodes offer a high specific capacity (> 3,500 mA h g^-1), but severe volume changes during cycling and poor intrinsic conductivity hinder commercialization. Carbon nanotubes (CNTs) are commonly incorporated to improve the electronic conductivity of Si electrodes, but their tendency to aggregate in polar solvent-based slurries leads to non-uniform electrodes. To address this, we synthesize polyacrylamide-grafted CNTs (PAM-g-CNTs) by covalently attaching hydrophilic acrylamide monomers to CNT surfaces. The PAM chains provide steric hindrance that minimizes van der Waals interactions between PAM-g-CNTs and interacts effectively with polar solvents, thus promoting uniform dispersion and forming a stable electron-conductive network within the electrode. Furthermore, PAM-g-CNTs establish hydrogen bonds with Si particles and binder matrices, enhancing the structural integrity of the electrode. The cycling performance of Si half cells incorporating PAM-g-CNTs shows substantial durability after 200 cycles. Moreover, in high-energy-density Si electrode configurations with reduced binder and conductive agent ratios (active material > 70%), PAM-g-CNT-based cells preserved 70% of their initial capacity after 100 cycles, compared to only 20% retention in Super P-based cells. The functionalization of CNTs with hydrophilic PAM thus proves effective in improving dispersion stability and conductivity while reinforcing electrode cohesion. This strategy presents a promising path for developing durable Si anodes for high-energy-density lithium-ion batteries.

Keywords

Silicon anode / carbon nanotubes / polymer grafting / uniform dispersion / polymeric binder

References

[1] Feng K,Liu W.Silicon-based anodes for lithium-ion batteries: from fundamentals to practical applications.Small2018;14:1702737

[2] Li P,Zheng X.Recent progress on silicon-based anode materials for practical lithium-ion battery applications.Energy Storage Mater2018;15:422-46

[3] Guo J,Wang J.Silicon-based lithium ion battery systems: state-of-the-art from half and full cell viewpoint.Adv Funct Mater2021;31:2102546

[4] Ko M,Cho J.Challenges in accommodating volume change of Si anodes for Li-ion batteries.ChemElectroChem2015;2:1645-51 PMCID:PMC4964884

[5] McDowell MT,Nix WD.25th anniversary article: understanding the lithiation of silicon and other alloying anodes for lithium-ion batteries.Adv Mater2013;25:4966-85

[6] Yang Y,Kang W.Silicon-nanoparticle-based composites for advanced lithium-ion battery anodes.Nanoscale2020;12:7461-84

[7] Yang Y,Zhang Y.Towards efficient binders for silicon based lithium-ion battery anodes.Chem Eng J2021;406:126807

[8] Deng L,Zheng X.Design criteria for silicon-based anode binders in half and full cells.Adv Energy Mater2022;12:2200850

[9] Tang J,Duan X,Dai X.Constructing the bonding between conductive agents and active materials/binders stabilizes silicon anode in lithium-ion batteries.J Energy Chem2023;80:23-31

[10] Huang L,Liu M.Nanoscale precision welding-enabled quasi-3D conductive carbon blacks for fast-charging and long-lasting secondary batteries.Carbon2024;230:119688

[11] Kim DS,Kim SH.Electrochemically exfoliated graphite as a highly efficient conductive additive for an anode in lithium‐ion batteries.Battery Energy2023;2:20230012

[12] Weng W,Zhang Y.Winding aligned carbon nanotube composite yarns into coaxial fiber full batteries with high performances.Nano Lett2014;14:3432-8

[13] Ren J,Chen C.Twisting carbon nanotube fibers for both wire-shaped micro-supercapacitor and micro-battery.Adv Mater2013;25:1155-9, 1224

[14] Liu X,Oh SW.Carbon nanotube (CNT)-based composites as electrode material for rechargeable Li-ion batteries: a review.Compos Sci Technol2012;72:121-44

[15] Lee H,Cho MS,Lee Y.Fabrication of polypyrrole (PPy)/carbon nanotube (CNT) composite electrode on ceramic fabric for supercapacitor applications.Electrochim Acta2011;56:7460-6

[16] Kang HE,Song SG.Recent progress in utilizing carbon nanotubes and graphene to relieve volume expansion and increase electrical conductivity of Si-based composite anodes for lithium-ion batteries.Carbon2024;219:118800

[17] Gao C,Liu Y.Surface modification methods and mechanisms in carbon nanotubes dispersion.Carbon2023;212:118133

[18] Avilés F,Moo-tah L,Vargas-coronado R.Evaluation of mild acid oxidation treatments for MWCNT functionalization.Carbon2009;47:2970-5

[19] Choi JH,Park S.Improved electrochemical performance using well-dispersed carbon nanotubes as conductive additive in the Ni-rich positive electrode of lithium-ion batteries.Electrochem Commun2023;146:107419

[20] Kim H,Lee T.Ozone-treated carbon nanotube as a conductive agent for dry-processed lithium-ion battery cathode.ACS Energy Lett2023;8:3460-6

[21] Zhou J,Zhang K.In situ growth of carbon nanotube wrapped Si composites as anodes for high performance lithium ion batteries.Nanoscale2016;8:4903-7

[22] Feng X,Bie Y,Nuli Y.Nano/micro-structured Si/CNT/C composite from nano-SiO₂ for high power lithium ion batteries.Nanoscale2014;6:12532-9

[23] Forney MW,Raisanen A.High performance silicon free-standing anodes fabricated by low-pressure and plasma-enhanced chemical vapor deposition onto carbon nanotube electrodes.J Power Sources2013;228:270-80

[24] Ding X,Liu X.Advanced anodes composed of graphene encapsulated nano-silicon in a carbon nanotube network.RSC Adv2017;7:15694-701

[25] He Z,Zhu Z,Zheng C.Advances in carbon nanotubes and carbon coatings as conductive networks in silicon‐based anodes.Adv Funct Mater2024;34:2408285

[26] Joo Y,Shea MJ.Isolation of pristine electronics grade semiconducting carbon nanotubes by switching the rigidity of the wrapping polymer backbone on demand.ACS Nano2015;9:10203-13

[27] Abousalman-Rezvani Z,Roghani-Mamaqani H.Functionalization of carbon nanotubes by combination of controlled radical polymerization and “grafting to” method.Adv Colloid Interface Sci2020;278:102126

[28] Deng L,Pan SY.Multivalent amide-hydrogen-bond supramolecular binder enhances the cyclic stability of silicon-based anodes for lithium-ion batteries.ACS Appl Mater Interfaces2021;13:22567-76

[29] Zhang M,Xiao Z.Binder-assisted dispersion of agglomerated carbon nanotubes for efficiently establishing conductive networks in cathodes of Li-ion batteries.Energy Technol2020;8:2000589

[30] Gunavadhi M,Chamundeswari VN.Nanotube-grafted polyacrylamide hydrogels for electrophoretic protein separation.Electrophoresis2012;33:1271-5

[31] Ma H,Xu Z.Functionalizing carbon nanotubes by grafting on intumescent flame retardant: nanocomposite synthesis, morphology, rheology, and flammability.Adv Funct Mater2008;18:414-21

[32] Wang X,Dou S,Wang S.Oxidized carbon nanotubes as an efficient metal-free electrocatalyst for the oxygen reduction reaction.RSC Adv2015;5:41901-4

[33] Li Z,Dai J,Bai R.Effect of multiwalled carbon nanotube-grafted polymer brushes on the mechanical and swelling properties of polyacrylamide composite hydrogels.Polymer2016;85:67-76

[34] Xiong H,Moyo M,Coville NJ.Fischer-tropsch synthesis: iron-based catalysts supported on nitrogen-doped carbon nanotubes synthesized by post-doping.Appl Catal A Gen2014;482:377-86

[35] Abo-hamad A,Alsaadi MA,Hashim MA.Functionalization of carbon nanotubes using eutectic mixtures: a promising route for enhanced aqueous dispersibility and electrochemical activity.Chem Eng J2017;311:326-39

[36] Huang YY.Dispersion of carbon nanotubes: mixing, sonication, stabilization, and composite properties.Polymers2012;4:275-95

[37] Han JT,Woo JS,Oh W.Hydrogen-bond-driven assembly of thin multiwalled carbon nanotubes.J Phys Chem C2008;112:15961-5

[38] Zeng W,Peng X.Enhanced ion conductivity in conducting polymer binder for high-performance silicon anodes in advanced lithium-ion batteries.Adv Energy Mater2018;8:1702314

[39] Weppner W.Determination of the kinetic parameters of mixed-conducting electrodes and application to the system Li₃Sb.J Electrochem Soc1977;124:1569-78

[40] Son B,Choi J.Measurement and analysis of adhesion property of lithium-ion battery electrodes with SAICAS.ACS Appl Mater Interfaces2014;6:526-31

[41] Zhang F,Wei T,Yang M.A new universal aqueous conductive binder via esterification reinforced electrostatic/H-bonded self-assembly for high areal capacity and stable lithium-ion batteries.Energy Environ Sci2024;17:238-48