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高性能Si系リチウムイオン電池負極用多機能ポリマーバインダーの開発
Get PDF九州工業大学九州工業大学博士学位論文（要旨）学位記番号: 生工博甲第494号 学位授与年月日:令和6年9月25日thesi
高性能Si系リチウムイオン電池負極用多機能ポリマーバインダーの開発
Get PDF九州工業大学博士（工学）1 Introduction| 2 Experimental section| 3 Prelithiated rigid polymer with high ionic conductivity as silicon-based anode binder for lithium-ion batteries| 4 A multifunctional supramolecular polymer binder with hard/soft phase interaction for Si-based lithium-ion batteriesLithium-ion batteries (LIBs) drive the operation of society as the most widely used energy storage device, especially in the fields of mobile devices and electric vehicles (EVs). The demand for the high energy density of the LIBs forces us to develop anode and cathode materials with high specific capacities. The silicon (Si) attracts great attention for its high theoretical specific capacity of 4200 mAh g-1, low lithiation voltage, and plenty of natural resources. However, Si-based electrodes suffer from severe volume expansion and electrode pulverization during cycling, finally causing rapid battery degradation. Many strategies such as Si dimension reduction, morphology control, surface coating, and interface engineering have been proposed to improve the performance of Si anode. Among these, using elaborately designed polymer binders is deemed an efficient tactic to tackle thorny issues. Although binders take a small mass ratio in the electrode preparation (<15%), they can greatly limit the volume expansion and maintain structural instability of the Si electrodes with their specific designed functions, thus improving the electrochemical performance of Si-based LIBs.
In Chapter 1, the overview of LIBs, the development of the Si-based anode materials, the research progress of the polymer binders, and the research purpose of this thesis are introduced. The structure of LIBs and anode/cathode materials are enumerated to give a basic understanding of this research. Then the working mechanism, advantages, and challenges of the Si-based anodes are discussed. Although Si has a high specific capacity, volume expansion (>300%) is the main factor limiting its industrial application. Various methods have been used to improve the electrochemical performance of Si-based anodes, but binder strategies are still one of the favored methods due to their unique role and economically feasible cost. The characteristics of commercially available binders are listed and discussed here, and the design ideas for polymer binders for silicon-based negative electrodes are summarized. Finally, we discuss the research progress of the reported polymer binders and their contributions to the electrochemical performance of Si-based anodes for LIBs.
In Chapter 2, the details of experimental reagents, characterization measurements, the preparation process of Si-based electrodes and cell assembly process, and electrochemical performance measurements are introduced. The purity and manufacturers of chemical reagents are listed, and the models of equipment are indicated. The Si anodes, Si/C anodes, and NCM523 cathodes are prepared according to the detailed description, then they are assembled in the glove box to acquire the half-cells or the full-cells. The essential electrochemical performance, including long-term cycling performance, rate performance, electrochemical impedance spectroscopy, and cyclic voltammetry curves are measured through LAND CT2001A or CHI760 electrochemical workstation.
In Chapter 3, a water-soluble rigid-rod poly(2,2′-disulfonyl-4,4′-benzidine terephthalamide) (PBDT) polymer is described and employed as the binder for Si-based electrodes for the first time. The nematic rigid PBDT bundles wrapped around the Si nanoparticles by hydrogen bonding effectively inhibit the volume expansion of the Si and promote the formation of stable solid electrolyte interfaces (SEI). Moreover, the prelithiated PBDT binder with high ionic conductivity (3.2 × 10−4 S cm−1) not only improves the Li-ions transportation behaviors in the electrode but can also partially compensate for the irreversible Li source consumption during SEI formation. Consequently, the cycling stability and initial coulombic efficiency of the Si-based electrodes with the PBDT binder are remarkably enhanced compared to that with the PVDF binder. This work demonstrates the molecular structure and prelithiation strategy of the polymer binder that plays a crucial role in improving the performance of Si-based electrodes with high-volume expansion.
In Chapter 4, a novel multifunctional polymer binder BDSA–DPA–PEGCE (BDP) incorporated by hard/soft interacting phases was designed. Although the binder design strategy is a key factor for improving the performance of Si anodes of Li-ion batteries, single–function binders may not fulfill their diverse application requirements. The hard domain of the BDP polymer binder is achieved through reversible covalent disulfide exchange, supramolecular noncovalent cooperative H-bonding, and π-π interactions, endowing self-healing ability and enhanced mechanical properties to maintain Si anodes integrity. And the soft phase is dominated by the polyether segment, establishing efficient ion-hopping transportation pathways. Meanwhile, the pre-lithiation strategy is employed for compensating the consumption of Li resources. Volume expansion of Si-based electrodes coordinated by the BDP binder is effectively limited, realizing improved cycling stability, high initial coulombic efficiency of 85.2%, and superior rate performance for Si-based half–cells and NCM523//Si/C full–cell. The BDP binder also promotes the formation of dense, stable, and homogeneous SEI layer.
In general, the cycling stability, initial coulombic efficiency, and rate performance of the Si and Si/C anodes can be improved by the polymer binder’s design. Through polymerization, grafting, cross-linking, pre-lithiation, and other methods, the mechanical properties and ionic conductivity of the polymer binder are effectively improved, thereby optimizing the performance of the Si-based anodes and making it closer to practical applications.This work offers valuable insights for developing advanced polymer binders to satisfy the specific demands of Si-based electrodes for rechargeable batteries, and exploring the field of binders and further improving the performance of Si-based anodes are our goals in the next stage.九州工業大学博士学位論文 学位記番号:生工博甲第494号 学位授与年月日:令和6年9月25日令和6年度doctoral thesi
An Utterance is Enough to the gaze? Gaze Detection from Utterance Information in Multiparty Discussion
Get PDFGaze information has an important role in conversation understanding. Generally, gaze detection is performed using a camera. However, such systems often require expensive equipment. To solve this problem, we propose a method of eye detection using an utterance during conversations. We first annotate an existing discussion corpus with gaze information and then analyze the annotated data. We apply machine learning to construct a gaze detection model. We utilize BERT, a large-scale pre-trained language model, and CART, a traditional machine-learning approach based on a decision tree. Experimental results show that the CART-based model was more accurate than the BERT-based model and show the potential possibilities of gaze detection from utterances.journal articl
Dependence of sensitivity loss on organic film thickness and influence of cantilever warpage in a piezoelectric wideband acoustic sensor coated with an organic film
Get PDFA wideband acoustic sensor is reported, comprising a piezoelectric MEMS acoustic transducer with organic film-coated cantilevers. Considering the sensitivity reduction associated with the application of an organic film, it is necessary to optimize the material selection and thickness of the organic film. Therefore, the relationship between the thickness of the polyurethane film and the consequent loss in sensitivity is elucidated. Our findings demonstrate that the polyurethane film thickness should be approximately 0.5 μm (or less) to limit sensitivity loss to 6 dB. Additionally, both simulations and experimental results reveal that the resonant frequency of the system is significantly influenced by the warpage of the cantilever. This study provides essential insights into optimizing the performance of MEMS acoustic transducers with organic film-coated cantilevers.journal articl
Optical neural network hardware using self-referential holography
Get PDFArtificial intelligence (AI) hardware has attracted much attention in recent years to address future concerns about implementing AI with Neumann-type computers, namely, increasing computational cost and power consumption. We introduce self-referential holographic deep neural network (SR-HDNN): an optoelectronic deep neural network hardware which enables a highly parallel calculation by optical processing unit and a flexible calculation including a nonlinear processing by electronic processing unit are combined to realize several kinds of neural networks. In the presentation, first, we discuss recent trends on AI hardware based on the spatial modulation of light which have been expected to be a hardware implementation method of high-dimension neural network and/or to reduce dimensions of input data to effectively connect electronically-performed neural network or neural network chip. Next, self-referential holography (SRH) which is the base technology of SR-HDNN and how SR-HDNN works will be explained. Then, the advantages will be discussed. Also, we will show the demonstration results of 4-class MNIST handwritten digit image recognition by SR-HDNN using the numerical simulation method with a transmission matrix which describes relationship of the complex amplitude distributions between arbitrary input and output planes.conference pape
Numerical Simulations on Image Recognition by Self-Referential Holographic Deep Neural Network with Electronic Output Layer
Get PDFWe numerically demonstrate a 4-class image recognition task using a self-referential holographic deep neural network (SR-HDNN) and verify the effectiveness of the use of electronic processing as the final layer.conference pape
Internet of Things Implemented with Mruby
Get PDFThe objective of this paper is to develop an Internet of Things (IoT) system that utilizes fusion sensors implemented with Mruby, a lightweight implementation of the Ruby programming language specifically designed for microcontrollers. The Mruby has been adapted to function on compact devices such as the Internet of Things (IoT) and other embedded systems. In addition, to improve communication efficiency in the IoT system. Thus, LoRa is well-suited for integration with the IoT system. The LoRa module, a low-power transmission technology, facilitates communication between embedded systems and other systems. LoRa is a technology that allows communication over long distances while consuming little energy, which is suitable for integration with IoT systems. As a result, this research has focused on embedded system development, which involves creating software and hardware components for IoT and embedded systems through design, coding, and testing processes. This involves a combination of software and hardware engineering, with an emphasis on creating systems that are efficient and reliable and able to satisfy specific performance standards. The microcontroller has successfully created a functional environment for running Mruby. This involves running the Mruby code in the microcontroller environment. The experiment demonstrates the procedure for setting up a Mruby environment and directory structure, along with the creation of a test program that can access real-time data.journal articl
Leveraging the Large Language Model for Activity Recognition: A Comprehensive Review
Get PDFIn this paper, we are using comprehensively review the ways in which Large Language Models (LLMs) advance activity recognition systems, discuss the challenges of implementing LLMs, and compare results between LLM-based methods and traditional approaches. We study the basic concepts of LLMs, subsequently, we systematically analyze the researches that have used LLMs for activity recognition, along with the areas related to these tasks, including object detection and speech recognition, since activity recognition can incorporate object detection and speech recognition techniques in its process to improve accuracy and provide a more comprehensive contextual understanding of human activities. We analyze the insights from 26 related research works using the Systematic Literature Review (SLR) approach. By synthesizing recent research, this review shows that LLMs can be applied in various stages of the activity recognition process, where 10% of surveyed paper are implemented at the data collection stage, 10% at the data preprocessing stage, 50% at the feature extraction stage, and 30% papers at the model training stage. Therefore, the data collection and data preprocessing stages allow for more in-depth exploration of opportunities to integrate LLMs at both stages. Moreover, LLMs offer several advantages over traditional methods, including efficient feature extraction, superior performance compared to widely used techniques, robustness across a wide range of data sets, and important enhancements that lead to state-of-the-art performance.journal articl