Mechanics of high-capacity electrodes in lithium-ion batteries

Rechargeable batteries, such as lithium-ion batteries, play an important role in the emerging sustainable energy land- scape. Mechanical degradation and resulting capacity fade in high-capacity electrode materials critically hinder their use in high-performance lithium-ion batteries. This paper presents an overview of recent advances in understanding the electrochemically-induced mechanical behavior of the electrode materials in lithium-ion batteries. Particular emphasis is placed on stress generation and facture in high-capacity anode materials such as silicon. Finally, we identify several important unresolved issues for future research.

High mechanical strength Si anode synthesis with interlayer bonded expanded graphite structure for lithium-ion batteries

Despite advancements in silicon-based anodes for high-capacity lithium-ion batteries,their widespread commercial adoption is still hindered by significant volume expansion during cycling,especially at high active mass loadings crucial for practical use.The root of these challenges lies in the mechanical instability of the material,which subsequently leads to the structural failure of the electrode.Here,we present a novel synthesis of a composite combining expanded graphite and silicon nanoparticles.This composite features a unique interlayer-bonded graphite structure,achieved through the application of a modified spark plasma sintering method.Notably,this innovative structure not only facilitates efficient ion and electron transport but also provides exceptional mechanical strength(Vickers hardness:up to658 MPa,Young's modulus:11.6 GPa).This strength effectively accommodates silicon expansion,resulting in an impressive areal capacity of 2.9 mA h cm^(-2)(736 mA h g^(-1)) and a steady cycle life(93% after 100cycles).Such outsta nding performance is paired with features appropriate for large-scale industrial production of silicon batteries,such as active mass loading of at least 3.9 mg cm^(-2),a high-tap density electrode material of 1.68 g cm^(-3)(secondary clusters:1.12 g cm^(-3)),and a production yield of up to 1 kg per day.

Stress-dissipated conductive polymer binders for high-stability silicon anode in lithium-ion batteries

Silicon-based anodes with high theoretical capacity have intriguing potential applications for high energy density lithium-ion batteries(LIBs),while suffer from immense volumetric change and brittle solidstate electrolyte interface that causes collapse of electrodes.Here,a stress-dissipated conductive polymer binder(polyaniline with citric acid,PC)is developed to enhance the mechanical electrochemical performance between Si nanoparticles(SiNPs)and binders.Benefiting from the stable triangle network node of citric acid and a considerable distributed of hydroxyl groups,the PC binder can effectively dissipate the stress from SiNPs,thus providing an excellent cyclic stability of Si anodes.Both experimental results and theoretical calculation demonstrate the enhanced adhesion between binders and SiNPs could bond the particles tightly to form a robust electrode.The as-fabricated Si anode exhibits outstanding structural stability upon long-term cycles that exhibit a highly reversible capability of 1021 mA·h·g^(-1)over 500 cycles at a current density of 0.5 C(1 C¼4200mA·g^(-1)).Evidently,this stressdissipated binder design will provide a promising route to achieve long-life Si-based LIBs.

Coordination bonds reinforcing mechanical strength of silicon anode to improve the electrochemical stability

The severe volumetric expansion and poor conductivity of silicon when used as anode in lithium-ion batteries present challenges in maintaining the stability of electrochemical performance.Herein,the binding between silicon nanoparticles and carbon nanotubes(CNTs)is achieved by the utilization of sodium alginate(S A),which is then strengthened by the coordination between Ca^(2+)and the carboxyl group(-COO^(-))of SA,resulting in a stable conductive network with ionic transport pathway.The consolidated binding relationship enables silicon-based anode material to possess high mechanical strength and strong deformation resistance,preventing the separation of silicon from CNTs network.Consequently,this silicon-based anode material demonstrates a discharge specific capacity of811 mAh·g^(-1)after 100 cycles at a current density of 1 A·g^(-1),and exhibits high rate performance,with a discharge specific capacity of 1612 mAh·g^(-1)at 2 A·g^(-1).