One-Pot Synthesis of High-Capacity Silicon-Lithium Anodes via On-Copper Growth of a Semi-Conducting, Porous Polymer

20 May 2021, Version 2
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Silicon-based anodes with lithium ions as charge carriers have the highest predicted charge density of 3579 mA h g-1 (for Li15Si4) while being comparatively safe. Contemporary electrodes do not achieve these theoretical values largely because production paradigms remained unchanged since their inception and rely on the mixing of weakly coordinated, multiple components. In this paper, we present the one-pot synthesis of high-performance anodes that reach the theoretical capacity of the fully lithiated state of silicon. Here, a semi-conductive triazine-based graphdiyne polymer network is grown around silicon nanoparticles directly on the current collector, a copper sheet. The current collector (Cu) acts as the catalyst for the formation of a semi-conductive triazine-based graphdiyne polymer network that grows around the inorganic, active material (Si). In comparison to established electrode assemblies, this process (i) omits any steps related to curing, drying, and annealing, (ii) does away with binders and conductivity-enhancing additives that decrease volumetric and gravimetric capacity, and (iii) cancels out the detrimental effects on performance, chemical and physical stability of conventional, three-component anodes (Si, binder, carbon black). This is because, the porous, semi-conducting organic framework (i) adheres to the current collector on which it grows via cooperative van der Waals interactions, (ii) acts effectively as conductor for electrical charges and binder of silicon nanoparticles via conjugated, covalent bonds, and (iii) enables selective transport of mass and charge-carriers (electrolyte and Li-ions) through pores of defined size. As a result, the anode shows extraordinarily high capacity at the theoretical limit of fully lithiated silicon, excellent performances in terms of cycling (exceeding 70% capacity retention after 100 cycles), and high mechanical and thermal stability. These high-performance anodes pave the way for use in flexible, wearable electronics and in environmentally demanding applications.

Keywords

Graphdiyne
Glaser-coupling
Li-ion battery
Silicon anode
One-pot

Supplementary materials

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Appendix 1 Density calculation
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20210513 LiAnMat SI woEN
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20210513 Answers to the editor
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