Water-Soluble Polymer Assists Multisize Three-Dimensional Microspheres as a High-Performance Si Anode for Lithium-Ion Batteries

Abstract

We report a clean and easy way to tackle the challenges of large-scale applications of silicon (Si) anodes for lithium-ion batteries. Using an aqueous solution of water-soluble polymer carboxymethyl chitosan and nanosilicon as a precursor, multisize three-dimensional (3D) microspheres as a silicon anode material is fabricated by one-step spray-drying. The effective functional groups, viscoelasticity, and hydrophilicity of polymers are retained, which can prevent the agglomeration of nanoparticles, enhance the internal binding force of the secondary particles, buffer volume expansion, promote the formation of a stable solid electrolyte interface (SEI) film, and maintain electrode integrity. Accordingly, when the mass ratio of Si/polymer reaches 4:1, the compound exhibits a reversible capacity of 1484 mAh g–1 and 75% capacity retention after 100 cycles. Silicon and polymer can be combined effectively via spray-drying, so that the electrode has good cycle stability (930 mAh g–1 after 300 cycles at 1 A g–1), excellent rate performance (871 mAh g–1 at 4 A g–1), and high initial Coulombic efficiency (80%).

Scalable Synthesis of Pore-Rich Si/C@C Core–Shell-Structured Microspheres for Practical Long-Life Lithium-Ion Battery Anodes

“…At the same areal capacity (3.8 mAh cm −2 ), the thickness of a Si/C@C electrode film is 31.4 μm before the cycle and 42.2 μm after five cycles (Figure c,d), corresponding to an electrode film expansion of 34.4%. The P-Si/C@C electrode therefore exhibits significantly reduced electrode film swelling compared to reported Si-based anodes. ,− To further evaluate the electrode film thickness change of the P-Si/C@C anode in a full cell, in situ ETC tests were applied for real-time monitoring of electrode thickness changes of the P-Si/C@C anode in a two-electrode cell (Figure S8). Figure e shows the electrode film thickness change of the two anodes during the first 20 cycles (the cycling processes took approximately five days).…”

“…The first discharging and charging capacities are 1413.7 and 1269.6 mAh g −1 , respectively, corresponding to an ICE of 89.8%, which is higher than those Si anodes reported in the literature studies. 14,25,38,39 The improved ICE could be attributed to the low specific surface area and the compact C shell of P-Si/C@C microspheres, which reduces side reactions on the Si surface and prevents the electrolyte from permeating through the entire P-Si/C@C. From the 2 nd to the 5 th cycles, the shape of the charge/discharge profiles shows a trend to overlap, indicating good cycling stability. The cycling performance of the P-Si/C@C microspheres was investigated at 100 mA g −1 .…”

Spatially Confined Silicon Nanoparticles Anchored in Porous Carbon as Lithium-Ion-Battery Anode Materials

“…Meanwhile, the much lower concentration of organic CO in Si@C-PAM indicates that well C coating inhibits the formation of electrolyte reduction products . The formation of more LiF in the SEI layer and fewer Li 2 CO 3 , which originates from the reduction of organic Li salts, is beneficial to the formation of a thin and robust SEI layer of Si@C-PAM so that the sample can promote Li + transport, suppress further electrolyte decomposition, and lessen side reactions to boost the Coulombic efficiency …”

“…58 The formation of more LiF in the SEI layer and fewer Li 2 CO 3 , which originates from the reduction of organic Li salts, is beneficial to the formation of a thin and robust SEI layer of Si@C-PAM so that the sample can promote Li + transport, suppress further electrolyte decomposition, and lessen side reactions to boost the Coulombic efficiency. 59 To intuitively display the effect of Si@C-PAM, with the hierarchically and orderly porous structure in inhibiting the volume variation of Si, the morphology of the electrode sheet before and after cycling was further characterized. The topview and cross-sectional SEM images of uncycled Si@C-PAM and Si@C-Gel anodes were acquired before lithiation (Figure 7a,d,g,j), after the first discharge (Figure 7b,e,h,k), and after the first charge (Figure 7c,f,i,l) under the same mass loading (1.7 mg cm −2 ).…”

High‐Performance Microsized Si Anodes for Lithium‐Ion Batteries: Insights into the Polymer Configuration Conversion Mechanism

“…[ 11 ] The suitable polymers often are electrically and ionically conductive, self‐healing, and elastic. [ 12,13 ] In particular, the conductive self‐healing binders have a large number of hydrogen bonds between polymers, capable of improving the internal mechanical strength of the electrode and endowing silicon anodes strong self‐healing effect, which effectively prevents the electrode degradation caused by the expansion of Si particles. [ 14 ]…”