Synthesis of layered silicon-graphene hetero-structures by wet jet milling for high capacity anodes in Li-ion batteries

Abstract

While silicon-based negative electrode materials have been extensively studied, to develop high capacity lithium-ion batteries, implementing a large-scale production method that can be easily transferred to industy, has been a crucial challenge. Here, a scalable wet-jet milling method was developed to prepare a silicon-graphene hybrid material to be used as negative electrode in lithium-ion batteries. This synthesized composite, when used as an anode in lithium cells, demonstrated high Li ion storage capacity, long cycling stability and high-rate capability. In particular, the electrode exhibited a reversible discharge capacity exceeding 1763 mAh g-1 after 450 cycles with a capacity retention of 98% and a coulombic efficiency of 99.85% (with a current density of 358 mA g-1). This significantly supersedes the performance of a Si-dominant electrode structures. The capacity fade rate after 450 cycles was only 0.005% per cycle in the 0.05-1 V range. This superior electrochemical performance is ascribed to the highly layered, silicon-graphene porous structure, as investigated via focused ion beam in conjunction with scanning electron microscopy (FIB-SEM) tomography. The hybrid electrode could retain 89% of its porosity (under a current density of 358 mA g-1) after 200 cycles compared with only 35% in a Si-dominant electrode. Moreover, this morphology can not only accommodate the large volume strains from active silicon particles, but also maintains robust electrical connectivity. This confers faster transportation of electrons and ions with significant permeation of electrolyte within the electrode. Physicochemical characterisations were performed to further correlate the electrochemical performance with the microstructural dynamics. The excellent performance of the hybrid material along with the scalability of the synthesizing process is a step forward to realize high capacity/energy density lithium-ion batteries for multiple device applications.

3D printed silicon-few layer graphene anode for advanced Li-ion batteries

“…Once the current density is decreased again to the 20 mA g À1 , the electrode recovers more than 95% of its initial capacity. 1 The optimal rate performance of the 3D printed F5 anode is attributed to the conductive network created by the carbon blackdoped PPy and WJM-FLG akes, as well as the buffering of the voids in the 3D electrode structure that improve the Li + accessibility to the active surface area 19,71,72 while containing the volumetric changes during charge/discharge cycles. 19,21,68 Fig.…”

“…1 The optimal rate performance of the 3D printed F5 anode is attributed to the conductive network created by the carbon blackdoped PPy and WJM-FLG akes, as well as the buffering of the voids in the 3D electrode structure that improve the Li + accessibility to the active surface area 19,71,72 while containing the volumetric changes during charge/discharge cycles. 19,21,68 Fig. 3c shows the charge/discharge curves of the F5 electrode for representative cycles at the current density of 20 mA g À1 .…”

“…10 Therefore, several alternatives to graphite have been widely investigated, [11][12][13][14][15] among which silicon (Si) has been demonstrated to be an excellent candidate thanks to its extraordinary theoretical capacity of 4200 mA h g À1 (close to that of metallic Li) and low de-lithiation voltage (i.e., $0.4 V vs. Li/Li + ). 14,[16][17][18][19] In this context, numerous attempts exploited the combination of Si and carbon materials in hybrid electrodes, 14,18,20,21 aiming to overcome the low electrical conductivity of Si, 22 low initial coulombic efficiency, 23 and the electrode instability caused by the Si swelling and contraction upon lithiation and de-lithiation, respectively. [23][24][25] Besides exploring different candidate materials, the electrodes architecture design has become a research hot topic.…”

“…56 Moreover, both WJM-FLG and doped PPy uniformly coat the surface of the Si nanoparticles, limiting the volumetric expansion of electrodes during Si lithiation. 19,57 Meanwhile, the conductive WJM-FLG/ doped PPy network effectively surrounds the Si nanoparticles to prevent the volume change upon the de-lithiation, avoiding aggregation effects that degrade the anode performances. The optimized 3D printed electrode shows a specic capacity up to 345 mA h g À1 at the current density of 20 mA g À1 with a capacity retention of 96% aer 350 cycles.…”

Synthesis of Si /rgo Nano-composites as Anode Electrode for Lithium-ion Battery by Ctab and Citrate Methods: Physical Properties and Voltage-capacity Cyclic Characterizations.

“…Si has a high theoretical gravimetric capacity of 4200mAhg -1 . Volumetric expansion of Si (> 300%) during lithiation/de-lithiation process causes cracking and breakage [8][9][10][11]. On the other hand, Si has poor electrical conductivity and low lithium-ion diffusion capacity due to its semiconductor nature [12].…”