Sodium-ion batteries (SIBs) have shown promising prospects for complementarity to lithium-ion batteries (LIBs) in the field of grid-scale energy storage. After a decade of continuous fundamental ...research on SIBs, it's becoming increasingly urgent to advance the commercialization. For SIB anode materials, hard carbon is the most mature and currently the only material likely to be commercialized, but it is still far away from large-scale industrialization. Herein, we carry out a comprehensive overview of the current state of the art in terms of three main aspects. Firstly, a fundamental understanding of the microstructure and sodium storage mechanism of hard carbon is introduced, which can be categorized into three different processes: capacitive adsorption, nanopore filling, and intercalation in carbon interlayers. Then, based on an in-depth understanding of the sodium storage mechanism, optimization methods in terms of increasing the specific capacity, rate performance, initial coulombic efficiency (ICE), and long-cycling stability are comprehensively summarized and analyzed. Finally, potential methods and associated benefits for the design of carbon structures and the solid electrolyte interface (SEI) are discussed, hoping to provide useful guidelines for future research and commercialization.
The sodium storage mechanism of hard carbon, optimization strategies of electrochemical performance, and the scientific challenges towards the commercialization of sodium-ion batteries were systematically summarized and analyzed.
Na2Ti3O7 (NTO) anodes with an ultra-low voltage plateau of 0.3 V have broad application prospects. However, the critical issues of low initial coulombic efficiency (ICE) and cycling instability ...severely hamper their practical applications, and it was difficult to simultaneously improve both in previous studies by doping or carbon coating, especially for an ideal ICE. Unexpectedly, we reported that this can be fulfilled simply by optimizing the binder carboxymethyl cellulose and styrene butadiene rubber (CMC and SBR, CR). The ICE can be significantly improved from 58.6% with common polyvinylidene fluoride (PVDF), to 78.1% with CMC and to the final 82.8% with CMC and SBR. Moreover, the superior coulombic efficiency of each subsequent cycle endows NTO with impressive cycle stability (100th capacity retention of 82.6%) and rate capability (84 mA h g−1 at 10C). The superior performance can be ascribed to both strong mechanical strengths (firm inter-particle cohesion and adhesion between the electrode-film and current collector) to maintain electrode integrity and high-quality solid electrolyte interphase (SEI) film that prevents continuous electrolyte decomposition. Emphatically, more details about the effects of these three binders on the electrode structure, interface properties, and ion storage characteristics were investigated in depth.
Na
2
Ti
3
O
7
(NTO) anodes with an ultra-low voltage plateau of 0.3 V have broad application prospects. However, the critical issues of low initial coulombic efficiency (ICE) and cycling instability ...severely hamper their practical applications, and it was difficult to simultaneously improve both in previous studies by doping or carbon coating, especially for an ideal ICE. Unexpectedly, we reported that this can be fulfilled simply by optimizing the binder carboxymethyl cellulose and styrene butadiene rubber (CMC and SBR, CR). The ICE can be significantly improved from 58.6% with common polyvinylidene fluoride (PVDF), to 78.1% with CMC and to the final 82.8% with CMC and SBR. Moreover, the superior coulombic efficiency of each subsequent cycle endows NTO with impressive cycle stability (100
th
capacity retention of 82.6%) and rate capability (84 mA h g
−1
at 10C). The superior performance can be ascribed to both strong mechanical strengths (firm inter-particle cohesion and adhesion between the electrode-film and current collector) to maintain electrode integrity and high-quality solid electrolyte interphase (SEI) film that prevents continuous electrolyte decomposition. Emphatically, more details about the effects of these three binders on the electrode structure, interface properties, and ion storage characteristics were investigated in depth.
Ultra-stable NTO electrodes with high ICE require suitable binders to provide both good electrode integrity and derived high-quality SEI.
Na 2 Ti 3 O 7 (NTO) anodes with an ultra-low voltage plateau of 0.3 V have broad application prospects. However, the critical issues of low initial coulombic efficiency (ICE) and cycling instability ...severely hamper their practical applications, and it was difficult to simultaneously improve both in previous studies by doping or carbon coating, especially for an ideal ICE. Unexpectedly, we reported that this can be fulfilled simply by optimizing the binder carboxymethyl cellulose and styrene butadiene rubber (CMC and SBR, CR). The ICE can be significantly improved from 58.6% with common polyvinylidene fluoride (PVDF), to 78.1% with CMC and to the final 82.8% with CMC and SBR. Moreover, the superior coulombic efficiency of each subsequent cycle endows NTO with impressive cycle stability (100 th capacity retention of 82.6%) and rate capability (84 mA h g −1 at 10C). The superior performance can be ascribed to both strong mechanical strengths (firm inter-particle cohesion and adhesion between the electrode-film and current collector) to maintain electrode integrity and high-quality solid electrolyte interphase (SEI) film that prevents continuous electrolyte decomposition. Emphatically, more details about the effects of these three binders on the electrode structure, interface properties, and ion storage characteristics were investigated in depth.
Hard carbon (HC) is considered to be an anode material with great promise for sodium-ion batteries (SIBs), on account of the advantages of high reversible specific capacity and abundant source. ...Nevertheless, its poor high-rate and long-term cycle performance, which were caused by the unrestricted decomposition of the electrolyte and sustained formation of the solid–electrolyte interface (SEI) film, limit the practical use. Herein, the balance between high mechanical strength and good flexibility of the SEI layer formed in the discharge/charge process was achieved by modifying the surface of the HC anode with a proper amount of AlF3 coating. In this way, the reversible specific capacity increased from 322 to 346 mA h g–1 at 20 mA g–1. Furthermore, the capacity retention at 100 mA g–1 for 100 cycles of the modified sample considerably increased from 47.4 to 76.5%, as well as rate performance was significantly improved from 69 to 135 mA h g–1 at 200 mA g–1. The improvement of performance is mainly attributed to the rational distribution of organic–inorganic phase components in the SEI film (about 43% inorganic phase and 57% organic phase), which ensures the stability of the SEI layer in the continuous discharge/charge process, resulting in a superior performance. Therefore, this work not only provides an effective method to synthesize HC anode with high electrochemical performance in SIBs but also clearly illustrates the mechanism of how the coating affects the composition of the SEI film to improve the performance of materials.
Pattern-based 3D model compression Kangying, Cai; Wenfei, Jiang; Tao, Luo ...
2016 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP),
03/2016
Conference Proceeding, Journal Article
This paper presents an efficient method to 3D model compression based on repetition detection. The proposed Pattern-Based 3D Mesh Codec (PB3DMC) can achieve good rate-distortion performance on 3D ...models comprising multiple components. The repetition among constituent components is first exploited to generate a compact representation. An optimal bit allocation scheme is then proposed in order to compress the resultant "pattern-instances" representation. Experimental results show that PB3DMC yields a significant gain compared to the algorithms in MPEG's Scalable Complexity 3D Mesh Coding (SC3DMC) toolset, particularly for those models containing repetitive components. Furthermore, a benchmark for PB3DMC is built using 444 models. And PB3DMC is going to be published as an amendment of, MPEG-4 standard.
In this paper, we present an adaptive-coding method for generic triangular meshes including both regular and irregular meshes. Though it is also based on iterative octree decomposition of the object ...space for the original mesh, as some prior arts, it has novelties in the following two aspects. First, it mathematically models the occupancy codes containing only a single–“1” bit for accurate initialization of the arithmetic coder at each octree level. Second, it adaptively prioritizes the bits in an occupancy code using a local surface smoothness measure that is based on triangle areas and therefore mitigates the effect of non-uniform vertex sampling over the surface. As a result, the proposed 3D mesh coder yields outstanding coding performance for both regular and irregular meshes and especially for the latter, as demonstrated by the experiments.
Generic 2D/3D smoothing via regional variation Wenfei Jiang; Tao Luo; Fan Zhang ...
2014 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)
Conference Proceeding
In this paper, we propose a method to measure the relationship between data samples, which is dependent on the possibility whether they are within a homogeneous region or not. By considering the ...regional variation, this possibility is formulated in terms of the maximum local variation along the shortest path connecting the samples. The metric is concretized in both 2D images and 3D meshes, and then integrated into smoothing filters. Benefited from our method, the improved filters tend to effectively preserve the structural component of data. Moreover, our method is implemented in various applications such as image denoising, image decomposition and mesh smoothing, which demonstrates better performance in comparison to the previous work.
Octree decomposition has been proven to be one of the most successful approaches for progressive geometry compression of 3D models. To exploit the spatial correlation among the points, people strive ...to improve the estimation of the non-emptiness of the child-cells during space subdivision. We observe an intrinsic property of 3D models that their tangent planes tend to be continuous at high fidelity layers. Thus, we take the tangent-plane-continuity as a criterion for the non-emptiness estimation, and design a 3D model compression scheme based on this idea. The experimental results show that the proposed codec improves the quality by up to 6dB at equivalent bit-rates.