5-methyl-1H-benzotriazole as potential corrosion inhibitor for electrochemical-mechanical planarization of copper

According to the electrochemical analysis, the corrosion inhibition efficiency of 5-methyl-lH-benzotriazole （m-BTA） is higher than that of benzotrizaole （BTA）. The inhibition capability of the m-BTA passive film formed in hydroxyethylidenediphosphonic acid （HEDP） electrolyte containing both m-BTA and chloride ions is superior to that formed in m-BTA-alone electrolyte, even at a high anodic potential. The results of electrical impedance spectroscopy, nano-scratch experiments and energy dispersive analysis of X-ray （EDAX） indicate that the enhancement of m-BTA inhibition capability may be due to the increasing thickness of passive film. Furthermore, X-ray photoelectron spectrometry （XPS） analysis indicates that the increase in passive film thickness can be attributed to the incorporation of C1 into the m-BTA passive film and the formation of [Cu（I）CI（rn-BTA）], polymer film on Cu surface. Therefore, the introduction of C1- into m-BTA-containing HEDP electrolyte is effective to enhance the passivation capability of m-BTA passive film, thus extending the operating potential window.

Scratching by pad asperities in copper electrochemical-mechanical polishing

Low dielectric constant materials/Cu interconnects integration technology provides the direction as well as the challenges in the fabrication of integrated circuits(IC) wafers during copper electrochemical-mechanical polishing(ECMP). These challenges arise primarily from the mechanical fragility of such dielectrics, in which the undesirable scratches are prone to produce. To mitigate this problem, a new model is proposed to predict the initiation of scratching based on the mechanical properties of passive layer and copper substrate. In order to deduce the ratio of the passive layer yield strength to the substrate yield strength and the layer thickness, the limit analysis solution of surface scratch under Berkovich indenter is used to analyze the nano-scratch experimental measurements. The modulus of the passive layer can be calculated by the nano-indentation test combined with the FEM simulation. It is found that the film modulus is about 30% of the substrate modulus. Various regimes of scratching are delineated by FEM modeling and the results are verified by experimental data.

Unraveling the heterogeneity of solid electrolyte interphase kinetically affecting lithium electrodeposition on lithium metal anode

The stability and uniformity of solid electrolyte interphase(SEI)are critical for clarifying the origin of capacity fade and safety issues for lithium metal anodes(LMA).However,understanding the interplay of SEI heterogeneity and Li electrodeposition is limited by the coupling of complex electrochemistry and mechanics processes.Herein,the correlation between the SEI failure behavior and Li deposition morphology is investigated through a quantitative electrochemical-mechanical model.The local deformation and stress of SEI during Li electrodeposition identify that the heterogeneous interface between different components first fails.Compared with the well-known mechanical strength,component uniformity plays the most important role in the initial SEI failure and uneven Li deposition,and a relative component uniformity(p>0.01)represents a proper balance to ensure the stability of the naturally heterogeneous SEI.Furthermore,the component regulation of SEI via the designed electrolyte experimentally demonstrates that improving component uniformity benefits SEI stability and the uniform Li electrodeposition for LMA,thereby increasing the capacity by~20%after 300 cycles.These fundamental understandings and proposed strategy can be not only used to guide the SEI optimization via the electrolyte regulation,but also extended to the rational designs of artificial SEI for high-performance LMA.

Monophase-homointerface electrodes intrinsically stabilize high-voltage all-solid-state batteries

The electrochemical stability and contact reliability of heterointerfaces between the solid electrolyte(SE) and electrode are critical for all-solid-state batteries(ASSBs), particularly much more challenging for high-voltage ASSBs, owing to the limited thermodynamically electrochemical window and mechanical inflexibility of SE, aggravating interfacial side reactions and contact failure. Considering all those issues originating from intrinsic heterogeneity in physicochemical features between the cathode material and SE, we are thinking about simplifying the heterointerfaces into a homointerface as a permanent cure to solve all electrochemical-mechanical interfacial failure. Herein, we propose monophase cathodes to construct thermodynamically stable all-in-one homointerfaces in ASS electrodes, removing unstable heterointerfaces by excluding SEs and intrinsically eliminating the Li chemical potential gap to avoid the formation of lithium-depleted space-charge layer and highly resistive mixed ion–electron conductor interphase. Our conception is successfully validated in the layered transition-metal oxide cathodes, which display outstanding stability no matter the MH-LiCoO_(2) cathode charging to 4.7 V or MH-Li_(1.2)Mn_(0.54)Ni_(0.13)-Co_(0.13)O_(2) cathode charging to 5.3 V. It is undeniable that our current version of above-illustrated MH-cathodes would bring out some new challenges for the practical application due to abandoning the SE. However, we believe our work also offers a brandnew direction to ultimately address the electrochemical–mechanical interfacial issues that would be promising for high-energy ASSBs with more discoveries of advanced monophase cathodes in the future.

Evolution of electrochemically induced stress and its effect on the lithium-storage performance of graphite electrode

The electrochemically induced stress is a key factor that affects the lithium-storage performance of electrode materials.In this study,the origin and evolution of the electrochemically induced stress of the graphite electrode were investigated by in situ experiments and simulations.An in situ optical experiment was performed to observe the electrode color to analyze the concentration and diffusion process of lithium ions inside the graphite electrode.An electrochemical-mechanical coupling model under the same experimental conditions was developed and verified by the experimental lithium concentration,and characterization of the spatiotemporal evolution of the potential,lithium concentration,and stress during the diffusion process was realized.The results showed that lithium intercalation leads to compressive stress,which presents a gradient distribution along the Li+diffusion path,and it exhibits a“piecewise”nonlinear growth trend with increasing lithiation time.In addition,as the potential decreases,the stress increases from slow to fast relative to the lithium-concentration increase,showing the characteristic of stages.The influence of stress on the lithium-storage performance is discussed using the local lithium-intercalation rate and phase-interface migration speed as the key parameters.The lithiation mechanism was analyzed from the perspective of the energy,and it was found that the two factors cause the slow diffusion in the late stage of lithiation,thus affecting the actual lithium-storage performance.This study will enhance the understanding of the electro-chemo-mechanical coupling mechanism and provide guidance for enhancing stress-regulated battery performance.