Stress Mitigation of Nanosilicon Anode to Achieve Energy-Dense and Highly-Stable Full Cell.

Nanosilicon (nano-Si) anode is subjected to significant stress concentration, which is caused by extrusion deformation of expanded Si nanoparticles with uneven distribution. The low-strength binder and adhesive interface are unable to withstand the stress, resulting in exfoliation and impeding the use of nano-Si anodes. This work aims to mitigate stress in a Si anode with flexible copper (Cu) skeletons that are metallurgically bonded to uniformly distributed Si nanoparticles. It is worth noting that the proposed porous Si-Cu anode exhibits improved high-load cycling performance and promising potential in the full cell, with an energy density of 463 Wh kg-1 at 0.5 C and retention of 81% after 500 cycles at 2 C. Chemo-mechanical simulation and in (ex) situ observation demonstrate that expansion stress is reduced and more evenly distributed in the anode due to uniform distribution of Si nanoparticles, flexible Cu skeletons, and adequate pores. More importantly, the stress is primarily distributed in the flexible Cu skeletons and bonding interface, preventing anode exfoliation, and ensuring efficient lithium ion/electron transference. This work sheds light on the structure construction of an alloy-type anode.

Contrasting mineralized and barren porphyries in the Zhongdian Arc, insights from biotite and apatite compositions and halogen fugacity.

Copper mineralization in the Pulang (PL) porphyry deposit, Langdu (LD) porphyry-skarn deposit and Songnuo (SN) porphyry prospect in northwestern Yunnan, China, is closely related to the emplacement of quartz monzonite porphyries. The chemical compositions of biotite and apatite from those porphyries were analyzed to calculate the halogen fugacity and to constrain mineralized and barren porphyries. Our data show that biotites from the PL deposit have higher MgO, SiO2, TiO2 and F contents than those from the LD deposit or SN prospect. Compared to those in the LD deposit and SN prospect, the Mg (atoms per formula unit (apfu)) and AlVI (apfu) value in biotite is greater, and the F content is greater and the SO3 and Ce2O3/Y2O3 ratio in apatite are lower in the PL deposit. Ti-biotite thermometry and apatite-biotite geothermometry show that the crystallization temperature of biotite from the PL deposit is higher than that from the SN prospect or LD deposit. The results suggest that oxygen fugacity, magmatic sulfur, and H2O contents cannot be used to efficiently distinguish the PL deposit from the LD deposit and SN prospect. However, the halogen chemistry of biotite from the PL deposit is distinctly different from that of the LD deposit or SN prospect according to the lower IV (F), indicating that mineralized quartz monzonite porphyries in the PL deposit formed during the late magmatic stage, which is in contrast to those in the LD deposit and SN prospect. The mineralized porphyries display a remarkable negative linear relationship (r = - 0.96) with the log (f HF/f HCl) and log (f H2O/f HF) ratio, which can be used to distinguish the mineralized and barren porphyries. Compared with other typical porphyry Cu systems, there is a remarkable positive linear relationship between IV (Cl) and log (f H2O/f HCl). In addition, the linear slope and intercept for log (f H2O/f HCl) ratios and the IV (Cl) of biotite from the potassic and phyllic alteration zones are significantly greater than those from other porphyries.