Mussel‐Inspired Polydopamine‐Functionalized Super‐P as a Conductive Additive for High‐Performance Silicon Anodes

Abstract

Zn, Cd, Hg, etc.), the so-called "lithium alloys." Li alloys, which have a larger number of Li ions per formula unit than graphite, consequently provide higher specifi c capacities than graphite. [ 11 ] For instance, fully lithiated Si (Li 22 Si 5 or Li 4.4 Si) has a theoretical specifi c capacity of 4200 mAh g -1 , the highest among the abovementioned alloying elements. [ 12,13 ] Consequently, Si is considered a promising anode material and, for decades, it has attracted intense research attention. However, the huge volume changes that occur during lithiation and delithiation result in cracking and crumbling ("pulverization") of the active material. [ 5,11 ] This consumes a large amount of available Li ions and electrolytes and forms a passivation fi lm, the so-called solid electrolyte interphase (SEI), [ 14,15 ] on the Si surface exposed to the electrolyte. In addition, loss of electronic interparticle contact occurs. [ 4,16 ] Consequently, these factors eventually lead to capacity fading, and, as a result, the implementation of Sibased anodes in LIBs has not been realized.Generally, the electrodes for LIBs consist of three major constituents: (1) the active materials, (2) polymeric binders, and (3) conductive additives. First, the development and modification of Si active materials have been intensively studied. To release dimensional stress in Si-based active materials during lithiation and delithiation, many nanostructures, including 0D nanoparticles, 1D nanowires and nanotubes, 2D nanosheets and nanofl akes, and core-shell structured nanomaterials, have been explored. [ 17,18 ] These materials reduce mechanical stress because fracture does not occur in Si nanostructures below a critical size. [ 19 ] However, nanostructured materials still suffer from several severe shortcomings; for example, an increased surface area, leading to a larger SEI and consumption of lithium ions, low tap densities, aggregation, and safety problems associated with the fl ammable and explosive tendencies of metallic nanopowders. [ 20,21 ] Therefore, as the next step, nano/microhierarchical structures, in which nanosized Si particles are embedded in a microscale framework, e.g., conductive carbon-based materials, have attracted much interest. [ 17,22,23 ] However, owing to the complex structure of these materials, these approaches generally have high production costs and are not appropriate for mass production. For the successful implementation of Si-based anodes in LIBs, low cost, and scalability are prerequisites.Second, it has been recently verifi ed that the appropriate choice of polymeric binders for Si-based anodes can improveThe study has developed a facile polydopamine (PD) surface coating method for a typical conductive additive, Super-P. This method is effi cient, economical, and environmentally friendly, and it can be used for the mass production of Super-P. PD treatment converts the hydrophobic surfaces of Super-P into hydrophilic surfaces, facilitating slurry preparation, and slurry coating for the fabrication of Si-ba...

Understanding the Effect of Polydopamine Interlayer on the Long‐Term Cycling Performance of Silicon Anodes: A Multiphysics‐Based Model Study

“…The shape of the capacity fade pattern predicted in Figure 5b is similar to that observed experimentally by Song et al. [34] Figure 6 shows the simulated silicon electrode SOC at the EOC for cells with bare and PD-treated Cu current collectors using the extrapolated model parameters in Figure 4. The SOC at EOC decrease steadily for both cell configurations.…”

“…690 cycles for the cells with the bare Cu current collector (Figure 5a). [34] Figure 6 shows the simulated silicon electrode SOC at the EOC for cells with bare and PD-treated Cu current collectors using the extrapolated model parameters in Figure 4. A continuous accelerated capacity decay is predicted for the cells with PD-treated Cu current collector.…”

“…[20,[35][36][37] These side reactions are known to consume Li ions resulting in the formation of the SEI on the surface of the silicon electrode. [20,[35][36][37] These side reactions are known to consume Li ions resulting in the formation of the SEI on the surface of the silicon electrode.…”

“…This assumption was made based on the fact that, the amount of Li ions trapped in the film formation cannot account for the cumulative capacity retention of the cells due to the unlimited supply of Li ions from the Li metal as demonstrated experimentally by Delpuech et al [36] by using quantitative Li NMR [21] spectroscopy. There was a 0.74 increase in the stoichiometric content of Li ions in the charged state relative to when the effect of Li metal was not considered.…”

“…In addition, many previous reports have been made on the occurrence of side reactions on silicon electrodes during (de) lithiation processes. [20,[35][36][37] These side reactions are known to consume Li ions resulting in the formation of the SEI on the surface of the silicon electrode. Two types of SEI have been reported to form during the (de) lithiation processes.…”