Robustness of Multi-Project Knowledge Collaboration Network in Open Source Community.

Multi-project parallelism is an important feature of open source communities (OSCs), and multi-project collaboration among users is a favorable condition for an OSC's development. This paper studies the robustness of this type of community. Based on the characteristics of knowledge collaboration behavior and the large amount of semantic content generated from user collaboration in open source projects, we construct a directed, weighted, semantic-based multi-project knowledge collaboration network. Using analysis of the KCN's structure and user attributes, nodes are divided into knowledge collaboration nodes and knowledge dissemination nodes that participate in either multi- or single-project collaboration. From the perspectives of user churn and behavior degradation, two types of failure modes are constructed: node failure and edge failure. Based on empirical data from the Local Motors open source vehicle design community, we then carry out a dynamic robustness analysis experiment. Our results show that the robustness of our constructed network varies for different failure modes and different node types: the network has (1) a high robustness to random failure and a low robustness to deliberate failure, (2) a high robustness to edge failure and a low robustness to node failure, and (3) a high robustness to the failure of single-project nodes (or their edges) and a low robustness to the failure of multi-project nodes (or their edges). These findings can be used to provide a more comprehensive and targeted management reference, promoting the efficient development of OSCs.

Preparing Two-Dimensional Ordered Li0.33 La0.557 TiO3 Crystal in Interlayer Channel of Thin Laminar Inorganic Solid-State Electrolyte towards Ultrafast Li+ Transfer.

Inorganic superionic conductor holds great promise for high-performance all-solid-state lithium batteries. However, the ionic conductivity of traditional inorganic solid electrolytes (ISEs) is always unsatisfactory owing to the grain boundary resistance and large thickness. Here, a 13 µm-thick laminar framework with ≈1.3 nm interlayer channels is fabricated by self-assembling rigid, hydrophilic vermiculite (Vr) nanosheets. Then, Li0.33 La0.557 TiO3 (LLTO) precursors are impregnated in interlayer channels and afterwards in situ sintered to large-size, oriented, and defect-free LLTO crystal. We demonstrate that the confinement effect permits ordered arrangement of LLTO crystal along the c-axis (the fastest Li+ transfer direction), permitting the resultant 15 µm-thick Vr-LLTO electrolyte an ionic conductivity of 8.22×10-5  S cm-1 and conductance of 87.2 mS at 30 °C. These values are several times' higher than that of traditional LLTO-based electrolytes. Moreover, Vr-LLTO electrolyte has a compressive modulus of 1.24 GPa. Excellent cycling performance is demonstrated with all-solid-state Li/LiFePO4 battery.

Oriented Crystal Growth of Li0.33La0.557TiO3 Nanowire Induced by One-Dimensional Polymer Sheath toward Rapid Lithium-Ion Transfer.

Superionic conductor-based solid-state electrolytes with preferred crystal structures hold great promise for realizing ultrafast lithium-ion (Li+) transfer, which is urgently desired for all-solid-state lithium batteries. However, the precise control of crystal growth of superionic conductors is still challenging since the crystals always spontaneously grow to disordered structures with the lowest internal energy to ensure thermodynamic stability. Herein, a coaxial nanowire with a polyvinylpyrrolidone (PVP) sheath and a Li0.33La0.557TiO3 (LLTO) precursor core (PVP/LLTO-caNW) is prepared through coaxial electrospinning, followed by sintering into LLTO nanowire with an oriented crystal structure (LLTO-caNW). We demonstrate that the one-dimensional PVP sheath as a sacrificial layer generates uniform and the strongest adsorption ability on the (110) phase among different LLTO crystal planes, which induces the crystal to preferentially grow along the c-axis (the fastest Li+ transfer direction) during the nucleation and growth processes. As a result, the prepared LLTO-caNW displays an ultrahigh bulk ionic conductivity of 3.13 × 10-3 S cm-1, exceeding most LLTO crystals and approaching the theoretical conductivity. Meanwhile, the oriented crystal growth imparts to LLTO-caNW significantly reduced grain boundary resistance, and the grain-boundary conductivity reaches up to 1.09 × 10-3 S cm-1. This endows the composite solid electrolyte with high ionic conduction performance and superior cycle stability in the assembled all-solid-state lithium battery.