Li-ion battery materials: present and future

The lithium metal battery is strongly considered to be one of the most promising candidates for high-energy-density energy storage devices in our modern and technology-based society. However, uncontrollable lithium dendrite growth induces poor cycling efficiency and severe safety concerns, dragging lithium metal batteries out of practical applications. This review presents a comprehensive overview of the lithium metal anode and its dendritic lithium growth. First, the working principles and technical challenges of a lithium metal anode are underscored. Specific attention is paid to the mechanistic understandings and quantitative models for solid electrolyte interphase (SEI) formation, lithium dendrite nucleation, and growth. On the basis of previous theoretical understanding and analysis, recently proposed strategies to suppress dendrite growth of lithium metal anode and some other metal anodes are reviewed. A section dedicated to the potential of full-cell lithium metal batteries for practical applicatio...

Toward Safe Lithium Metal Anode in Rechargeable Batteries: A Review.

Materials with good flexibility and high conductivity that can provide electromagnetic interference (EMI) shielding with minimal thickness are highly desirable, especially if they can be easily processed into films. Two-dimensional metal carbides and nitrides, known as MXenes, combine metallic conductivity and hydrophilic surfaces. Here, we demonstrate the potential of several MXenes and their polymer composites for EMI shielding. A 45-micrometer-thick Ti3C2Tx film exhibited EMI shielding effectiveness of 92 decibels (>50 decibels for a 2.5-micrometer film), which is the highest among synthetic materials of comparable thickness produced to date. This performance originates from the excellent electrical conductivity of Ti3C2Tx films (4600 Siemens per centimeter) and multiple internal reflections from Ti3C2Tx flakes in free-standing films. The mechanical flexibility and easy coating capability offered by MXenes and their composites enable them to shield surfaces of any shape while providing high EMI shielding efficiency.

Electromagnetic interference shielding with 2D transition metal carbides (MXenes)

Electrolytes have been identified as some of the most influential components in the performance of electrochemical supercapacitors (ESs), which include: electrical double-layer capacitors, pseudocapacitors and hybrid supercapacitors. This paper reviews recent progress in the research and development of ES electrolytes. The electrolytes are classified into several categories, including: aqueous, organic, ionic liquids, solid-state or quasi-solid-state, as well as redox-active electrolytes. Effects of electrolyte properties on ES performance are discussed in detail. The principles and methods of designing and optimizing electrolytes for ES performance and application are highlighted through a comprehensive analysis of the literature. Interaction among the electrolytes, electro-active materials and inactive components (current collectors, binders, and separators) is discussed. The challenges in producing high-performing electrolytes are analyzed. Several possible research directions to overcome these challenges are proposed for future efforts, with the main aim of improving ESs' energy density without sacrificing existing advantages (e.g., a high power density and a long cycle-life) (507 references).

A review of electrolyte materials and compositions for electrochemical supercapacitors

The effects of temperature and frequency on the dielectric properties, electromagnetic interference shielding and microwave-absorption of short carbon fiber/silica composites

Accumulibacter is the major polyphosphate-accumulating organism (PAO) in global wastewater treatment systems. Its phylogenetic and functional diversity has been continuously updated in recent years. In addition to its widely recognized two sublineages, Types I and II, here we discovered a novel type enriched in laboratory bioreactors. Core gene- and machine learning-based gene feature profiling supported that Type III Accumulibacter was potential PAO with the unique function of using dimethyl sulfoxide as electron acceptor. On the basis of the correlation between the similarity of ppk1 and genome, the number of ppk1-represented Accumulibacter species was estimated to be over one hundred, suggesting that the currently recognized species are only the tip of the iceberg. Meanwhile, multiple Accumulibacter strains co-occurring in a bioreactor were investigated for their inter-strain transcriptional and morphological features. Metatranscriptomics of seven co-occurring strains indicated that the expression level and interphasic dynamics of PAO phenotype-related genes had minimal correlation with their phylogeny. In particular, expression of denitrifying and poly-P metabolism genes had higher inter-strain and interphasic divergence compared with glycogen and polyhydroxyalkanoates metabolic genes. A strategy of cloning rRNA genes from different strains based on similar genomic synteny was successfully applied to differentiate their morphology via fluorescence in situ hybridization. Our study further expanded the phylogenetic and functional diversity of Accumulibacter. We also proposed that deciphering the function and capability of certain Accumulibacter should be environment- and population-specific. Importance Accumulibacter, as the core functional but uncultured taxa for enhanced biological phosphorus removal, has attracted much attentions on its phylogenetic and functional diversity and intra-genus niche differentiation in the last two decades. It was well-known that this genus had two sub-lineages (Type I and II) since 2002. In this study, a novel type (Type III) with proposed novel functional feature was discovered by the metagenomic approach. By linking average nucleotide identity of Accumulibacter genomes and the similarity of the ppk1 sequences, a phylogenetic biomarker that has been largely deposited in database, we estimated that its global species-level diversity was higher than 100. Moreover, as we found the co-occurrence of multiple Accumulibacter strains in one bioreactor, the simultaneous transcriptional divergence of the co-occurring strains was interesting for understanding their niche differentiation in a single community. The results suggested the decoupling feature between transcriptional pattern with phylogeny for co-occurring strains.

Expanding the diversity of Accumulibacter with a novel type and deciphering the transcriptional and morphological features among co-occurring strains

Owing to high-efficiency and scalable advantages of electrolysis in molten salts, electrochemical conversion of carbonaceous resources into graphitic products is a sustainable route for achieving high value-added carbon. To understand the complicated kinetics of converting amorphous carbon (e.g. carbonized lignin-biochar) into highly graphitic carbon, herein this study reports the key processing parameters (addition of Ni, temperature and time) and multi-scale approach of nickel-boosted electrochemical graphitization-catalysis processes in molten calcium chloride. Upon both experiments and modellings, multi-scale analysis that ranges from nanoscale atomic reaction to macroscale cell reveal the multi-field evolution in the electrolysis cell, mechanism of electrochemical reaction kinetics as well as pathway of nickel-boosted graphitization and tubulization. The results of as-achieved controllable processing regions and multi-scale approaches provide a rational strategy of manipulating electrochemical graphitization processes and utilizing the converted biomass resources for high value-added use.

Nickel-promoted Electrocatalytic Graphitization of Biochars for Energy Storage: Mechanistic Understanding using Multi-scale Approaches.

Accurate estimating the state of charge(SOC) of lithium-ion batteries is important for battery management systems. The SOC estimation generally considers ambient temperature instead of internal temperature parameter due to the difficulty of capturing internal temperature. Thanks to a recent work capturing internal temperature, this work proposes a method of SOC estimation for lithium-ion batteries based on internal temperature which has not been investigated in the existing studies. Three kinds of tests are carried out at 0°C, 15°C, 25 °C, 35°C and 45 °C, including maximum capacity test, open circuit voltage test, and dynamic stress test (DST). Subsequently, the second-order RC equivalent circuit model of the battery is established. And the parameters of the battery model are identified by the forgetting factor recursive least squares (FFRLS) algorithm considering the ambient temperature and the internal temperature. Finally, the SOC of the lithium-ion battery is estimated using the DST test data at 0 °C, 25 °C and 45 °C, the model parameter identification results at the two temperatures, and the EKF algorithm. The experimental results show that the SOC estimation accuracy involving the internal temperature of the battery is higher than the SOC estimation accuracy considering the ambient temperature.

Wei-Li Song

Papers

Expanding the diversity of Accumulibacter with a novel type and deciphering the transcriptional and morphological features among co-occurring strains

Nickel-promoted Electrocatalytic Graphitization of Biochars for Energy Storage: Mechanistic Understanding using Multi-scale Approaches.

A Lithium-ion Battery SOC Estimation Method Involving Battery Internal Temperature