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Lithium-ion batteries (LIBs) are being used in locations and applications never imagined when they were first conceived. To enable this broad range of applications, it has become necessary for LIBs to be stable to an ever broader range of conditions, including temperature and energy. Unfortunately, while negative electrodes have received a great deal of focus in electrolyte development, stabilization of positive electrodes remains an elusive target. Here, we report a novel additive that shows the ability to protect positive electrodes against elevated temperatures and voltages. This additive can be used in small quantities, and its targeted behavior allows it to remain functional in complex electrolyte packages. This can prove an effective approach to targeting specific aspects of cell performance.

The thermal degradation of electrolytes containing lithium hexafluorophosphate (LiPF6) is a well-studied subject. However, practical application of the knowledge is difficult since the effects of t...

We investigated the static reactions of highly delithiated Li(Ni1/3Mn1/3Co1/3)O2, Li(Ni0.5Mn0.3Co0.2)O2, Li(Ni0.6Mn0.2Co0.2)O2, and Li(Ni0.8Mn0.1Co0.1)O2 positive electrodes with 2,3-butanedione an...

A convenient, two-step synthesis of the 5,8-dimethyl-dibenzo[b,j][1,10]phenanthrolines is presented. The first step is a Buchwald-Hartwig amination of 1,2-dibromobenzene and 2’-Aminoacetophenone to produce 1,1’-((1,2-phenylenebis(azanediyl))bis(2,1-phenylene))bis(ethan-1- one), which is converted to the final product via a ring-closing reaction. The overall reaction yield is 63%. The complexation of 5,8-dimethyldibenzo[b,j][1,10]phenanthrolines with 2,2’-bipyridine-4,4’-dicarboxylic acid (dcbpy) and Ru Ru(DMSO)4Cl2 is also reported and the Ru complex might be used to prepare a nanoscale thin film for dye-sensitives solar cell and other optoelectronic devices.

Silicon is considered as one of the most promising anodes for next generation lithium-ion batteries, due to its high theoretical capacity and energy density. However, many technical barriers remain to its implementation, due to its high chemical/electrochemical reactivities with standard electrolytes and incomplete passivation. Here we take the most effective passivating additive of fluoroethylene carbonate (FEC) and study its impact on non-carbonate electrolytes. Our results indicate that esters and ureas-based electrolytes are similarly stabilized by FEC, and have very similar capacity retentions and Coulombic efficiencies to the state-of-the-art carbonate electrolyte. This study indicates the discovery of more efficient additives other than FEC is vital in developing an electrolyte that can successfully enable a silicon-anode battery.

Differential privacy is fast becoming the gold standard in enabling statistical analysis of data while protecting the privacy of individuals. However, practical use of differential privacy still lags behind research progress because research prototypes cannot satisfy the scalability requirements of production deployments. To address this challenge, we present Chorus, a framework for building scalable differential privacy mechanisms which is based on cooperation between the mechanism itself and a high-performance production database management system (DBMS). We demonstrate the use of Chorus to build the first highly scalable implementations of complex mechanisms like Weighted PINQ, MWEM, and the matrix mechanism. We report on our experience deploying Chorus at Uber, and evaluate its scalability on real-world queries.

This work deals with the fabrication and evaluation of color-changing dye-sensitized solar cells (DSSCs) that include N-propanoic acid-functionalized spiropyrans and spirooxazines as sensitizing dyes. We investigated the photophysical properties of these compounds in various solvents and pH conditions using UV-Vis spectroscopy, and their behavior on TiO2 photoanode surfaces using a combination of UV-Vis and FT-IR. Their performance as sensitizing dyes for DSSCs was also analyzed. This study revealed a number of unique properties for this class of compounds that affect their performance as both photochromic compounds and DSSC sensitizers, which allow for future creation of efficient photochromic DSSCs.

Self-Assembling 1,4,5,8-Naphthalentetracarboxylic Diimide- Microwires for Optoelectronic Devices The widespread use of organic electronic devices requires simple yet effective synthesis techniques to create materials with low-cost and high performance. We report the solution phase crystallization of 1,4,5,8-naphthalenetetracarboxylic diimide (NDI) microwires from dimethylsulfoxide. These microwires were characterized by means of scanning electron microscopy, thermal analysis, and infrared and fluorescence spectroscopies. The microwires were also characterized for their electrical properties and were shown to exhibit an n-type semi-conductive property as well as photoresponsive changes in conductivity. The electron mobility within the NDI microwires was determined to be lower than previous literature reports, yet the combination of photo-responsive changes in electrical conductivity may hold promise of photo-sensors, organic light-emitting diodes, and other optoelectronic devices.

A proton-conductive material based on a crystalline assembly of trimesic acid and melamine (TMA⋅M, see picture) is reported. Because of the ordered structure of the assembly, the water-saturated proton conductivity for the TMA⋅M assembly is 5.5 S cm(-1) , which is the highest proton conductivity measured to date. This exceptionally high conductivity and low-cost fabrication of the material make applications feasible for fuel-cell devices.

A security analyst often needs to understand two runs of the same program that exhibit a difference in program state or output. This is important, for example, for vulnerability analysis, as well as for analyzing a malware program that features different behaviors when run in different environments. In this paper we propose a differential slicing approach that automates the analysis of such execution differences. Differential slicing outputs a causal difference graph that captures the input differences that triggered the observed difference and the causal path of differences that led from those input differences to the observed difference. The analyst uses the graph to quickly understand the observed difference. We implement differential slicing and evaluate it on the analysis of 11 real-world vulnerabilities and 2 malware samples with environment-dependent behaviors. We also evaluate it in an informal user study with two vulnerability analysts. Our results show that differential slicing successfully identifies the input differences that caused the observed difference and that the causal difference graph significantly reduces the amount of time and effort required for an analyst to understand the observed difference.

Binary code reutilization is the process of automatically identifying the interface and extracting the instructions and data dependencies of a code fragment from an executable program, so that it is self-contained and can be reused by external code. Binary code reutilization is useful for a number of security applications, including reusing the proprietary cryptographic or unpacking functions from a malware sample and for rewriting a network dialog. In this paper we conduct the first systematic study of automated binary code reutilization and its security applications. The main challenge in binary code reutilization is understanding the code fragment's interface. We propose a novel technique to identify the prototype of an undocumented code fragment directly from the program's binary, without access to source code or symbol information. Further, we must also extract the code itself from the binary so that it is self-contained and can be easily reused in another program. We design and implement a tool that uses a combination of dynamic and static analysis to automatically identify the prototype and extract the instructions of an assembly function into a form that can be reused by other C code. The extracted function can be run independently of the rest of the program's functionality and shared with other users. We apply our approach to scenarios that include extracting the encryption and decryption routines from malware samples, and show that these routines can be reused by a network proxy to decrypt encrypted traffic on the network. This allows the network proxy to rewrite the malware's encrypted traffic by combining the extracted encryption and decryption functions with the session keys and the protocol grammar.