Novel Design and Synthesis of Nanostructured Electrode Materials for Advanced Lithium Ion Batteries

Nowadays, rechargeable lithium-ion batteries (LIBs) have been widely used as energy storage devices for portable electronic devices. The increasing demand for their emerging applications in hybrid electric vehicles (HEVs) and electric vehicles (EVs) requires us to develop LIBs with higher energy density and power density. However, both the commercial cathode material (LiCoO2) and anode material (graphite) exhibit low specific capacity and poor rate capability, which severely hinder the practical application of lithium-ion batteries for transportation. This thesis mainly includes four research works on novel design and synthesis of nanostructured electrode materials for advanced lithium-ion batteries. To improve the electrochemical performances of cathode materials Li4Mn5O12, dual doping of Ni and Fe has been applied. It is found that the facile doping strategy can effectively improve both the operating voltage and reversible specific capacity of Li4Mn5O12, demonstrating as a promising high-voltage cathode material for high-energy high-power LIBs. Li-rich transition metal oxides display very high theoretical capacity but suffer from poor cycling stability and rate capability due to its large initial capacity loss and inferior structural stability upon cycling. To solve these problems, we have designed and synthesized a L@S core–shell structure (Li-rich layered-spinel core–shell heterostructure) via evaporation-induced self-assembly (EISA) of ultrafine Li4Mn4.5Ni0.5O12 nanoparticles onto the surface of Li-rich layered Li[Li0.2Mn0.54Ni0.13Co0.13]O2 (LMNCO), which demonstrates significantly improved specific capacity, cycling performance and rate capability for application as a cathode in new-generation LIBs compared to pristine LMNCO. In addition to cathode materials, we have synthesized two types of high-performance anode materials for LIBs. A novel structure with Sn nanoparticles well-dispersed in the microspheres of manganese-nickel-cobalt carbonate MNCCO3 (Sn@MNCCO3) has been prepared by using a facile one-step solvothermal process. We also synthesized sandwich-like, porous nitrogen-doped carbons by using zeolitic imidazolate framework (ZIF-8) as a template and carbon precursor

Nanostructured Materials Derived from Metal-Organic Frameworks for Energy and Environmental Applications

Nowadays, energy and environmental issues have become the top priority among a series of global issues. Fossil fuels as the dominant source are depleted fast and usually lead to some environmental problems. Heavy metal pollution has posed a severe threat to environment and public health. Metal-organic frameworks (MOFs), as a very promising category of porous materials, have attracted more and more interest in research communities due to their extremely high surface areas, diverse nanostructures and unique properties. To meet the ever-increasing energy demand and tackle the heavy metal pollution in water, MOFs can function as ideal templates to prepare various nanostructured materials for energy and environmental cleaning applications. The aim of this dissertation is to design and synthesize metal-organic frameworks (MOFs) derived nanomaterials with desirable structures, morphologies and compositions for energy applications in Li-ion batteries (LIBs), dye-sensitized solar cells (DSSCs) and electrocatalytic water splitting and environmental application in removal of heavy metal from aqueous systems. Their performances are mainly dependent on the characteristics of nanostructured materials. Briefly, the first two projects are focused on synthesis of ZIF-8 derived N-doped porous carbon and ZIF-67 derived ultrafine Co3O4 nanoparticles/carbon nanotube composites as high-performance anode materials for Li-ion batteries. The third project concentrates on synthesis of CoNi alloy embedded carbon nanocages derived from bimetallic organic frameworks for DSSCs. In addition, MOFs-derived CoNi and CoNx@Co/N-doped carbon tubes are synthesized and evaluated as low-cost electrocatalysts for efficient oxygen evolution reaction (OER). The last project is focused on study of ZIF-8 as an efficient absorbent for removal of copper ions from wastewater

From Government to Market?:A Discrete Choice Analysis of Policy Instruments for Electric Vehicle Adoption (CEIBS Working Paper, No. 039/2020/POM, 2020)

With the calls for policy instruments to shift from “government” to “market”, surging interest leads to a broad debate on the role of market-oriented policy instruments in promoting the adoption of electric vehicles (EVs). As the two prime examples of market-oriented policy instruments, personal carbon trading (PCT) and tradable driving credit (TDC) schemes are theoretically regarded to alter consumers’ EV preferences by both economic and psychological motivations. However, limited studies validate such effects. To fill the gaps, we conduct a discrete choice experimental survey by integrating vehicle, psychological, and policy attributes together. The empirical results from China reveal how consumers make trade-offs between economic and psychological motivations. In particular, although PCT and TDC can stimulate consumers’ EV adoption behaviors through monetary revenues, the positive effect of more revenues from PCT and TDC in promoting EV adoption is not always supported because EV adoption is subject to some psychological attributes, especially perceived norm pressures. It implies that consumers with stricter norms will be driven more by social and moral pressures than by monetary revenues. Even so, PCT and TDC are considered to be more powerful and sustainable than existing financial incentives. These findings not only contribute to the understanding of the interaction between psychological and policy attributes, but also provide insights for policymakers to design novel policy instruments to promote EV adoption

Research on Low Frequency Noise Caused by Beat Vibration of Rotary Compressor

The discontinuity of low frequency noise caused by beat frequency vibration of rotary compressor is studied in this paper. Based on beat frequency theoretical analysis, a finite element model is established to simulate the electromagnetic harmonics. And the contributions of various compressor motor designs to beat frequency vibration are investigated, so the motor optimization design schemes are obtained. The tests show that the method proposed in the paper is effective to improve low frequency noise of the compressor

Numerical and Experimental Research of Noise Reduction due to Low Frequency Pressure Fluctuation of Rotary Compressor

In order to reduce the noise level due to the low frequency pressure fluctuation associated with a rotary compressor, the noise mechanism and noise reduction solutions were conducted by using numerical and experimental methods. A 1D simulation model was established and a sensitivity analysis was conducted for the parameters associated with the low frequency pressure fluctuation of the rotary compressor. Then, a 3D CFD simulation model corresponding to the operation procedure of the rotary compressor was established and the working process of the rotary compressor was simulated. At the same time, the low frequency pressure fluctuation and the noise spectral characteristic were measured by using a refrigerant test fixture established in this work. Based on numerical and experimental research results, several noise reduction solutions and basic methods to restrain the low frequency pressure fluctuation were proposed and verified by using experimental method. A good improvement for the noise performance due to the low frequency pressure fluctuation was obtained. The work in this paper provides a reference and a foundation for the improvement of the noise due to the low frequency pressure fluctuation associated with rotary compressors