Rechargeable lithium‐ion batteries (LIBs) offer the advantages of having great electrical energy storage and increased continuous and pulsed power output capabilities, which enable their applications ...in grid energy storage and electric vehicles (EVs). For safety, high power and durability considerations, spinel Li4Ti5O12 is one of the most appealing potential candidate as an anode material for power LIBs due to its excellent cycling stability and thermal stability. However, there are still a number of challenges remaining for Li4Ti5O12 battery applications. Herein, an updated overview of the latest advances in Li4Ti5O12 research is provided and key challenges for its future development (i.e., fast‐charging, specific capacity, swelling, interface chemistry, matching cathode and electrolyte as well as batteries design and manufacturing) are highlighted.
Spinel Li4Ti5O12 is one of the most appealing potential candidate anode materials for power lithium‐ion batteries due to its excellent cycling and thermal stability. An updated overview of three key industrial application challenges of Li4Ti5O12 (fast‐charging, swelling issues and relatively low energy density) and the latest advances in Li4Ti5O12 research for its future development is provided.
Considering the natural abundance and low cost of sodium resources, sodium‐ion batteries (SIBs) have received much attention for large‐scale electrochemical energy storage. However, smart structure ...design strategies and good mechanistic understanding are required to enable advanced SIBs with high energy density. In recent years, the exploration of advanced cathode, anode, and electrolyte materials, as well as advanced diagnostics have been extensively carried out. This review mainly focuses on the challenging problems for the attractive battery materials (i.e., cathode, anode, and electrolytes) and summarizes the latest strategies to improve their electrochemical performance as well as presenting recent progress in operando diagnostics to disclose the physics behind the electrochemical performance and to provide guidance and approaches to design and synthesize advanced battery materials. Outlook and perspectives on the future research to build better SIBs are also provided.
Room temperature sodium‐ion batteries show great promise for large scale electrochemical energy storage application because of the low cost and large abundance of sodium resource. The progress and main challenges regarding the development of electrode, electrolytes, and advanced diagnostics are summarized with the aim of achieving a high energy density of over 400 Wh kg−1 on the cell level.
Realization of the hydrogen economy relies on effective hydrogen production, storage, and utilization. The slow kinetics of hydrogen evolution and oxidation reaction (HER/HOR) in alkaline media ...limits many practical applications involving hydrogen generation and utilization, and how to overcome this fundamental limitation remains debatable. Here we present a kinetic study of the HOR on representative catalytic systems in alkaline media. Electrochemical measurements show that the HOR rate of Pt‐Ru/C and Ru/C systems is decoupled to their hydrogen binding energy (HBE), challenging the current prevailing HBE mechanism. The alternative bifunctional mechanism is verified by combined electrochemical and in situ spectroscopic data, which provide convincing evidence for the presence of hydroxy groups on surface Ru sites in the HOR potential region and its key role in promoting the rate‐determining Volmer step. The conclusion presents important references for design and selection of HOR catalysts.
Bifunctional mechanism: Experimental evidence for hydroxy groups adsorbed onto Ru surface sites at the hydrogen oxidation reaction (HOR) potential region supports the bifunctional mechanism for the HOR kinetics of Pt‐Ru/C and Ru/C catalysts in alkaline media. The result presents important references for the design and selection of HOR catalysts.
Battery materials research is of crucial importance to the development of next‐generation batteries. However, the transition from lab‐scale studies, typically in gram quantities, to industrially ...relevant ones (i.e., kilogram scale) has been holding back by challenges in scale‐up synthesis and a lack of reliable approaches to verify the electrochemical performance of the lab‐made materials. Here the design and assembly procedures of sub‐Ah‐scale pouch cells that provide validations of several lab‐made Li‐ion and Na‐ion cathode materials available in a limited quantity (<5 g) are reported. These lab‐made pouch cells show superior cycle stability and consistency over the widely used coin cells, exemplified by multiple Ni‐rich layered oxide‐graphite full batteries retaining 84.29 ± 0.16% of the initial capacities over 1000 cycles. A four‐electrode pouch cell with a reparable reference electrode is further designed to monitor impedance growth and Li plating during long‐term electrochemical tests. It can be further integrated with in situ ultrasonic imaging to enable multi‐modal studies. This work provides a powerful platform to evaluate and boost the technology readiness levels of laboratory‐discovered battery materials.
The design, fabrication, and electrochemical testing of lab‐made pouch cells are elucidated, enabling practically relevant evaluation of gram‐scale laboratory‐discovered battery materials. Four‐electrode pouch cells with a reparable reference electrode are further developed to monitor impedance growth and Li plating during long‐term electrochemical tests. The methodology is applicable to a wide range of Li‐ or Na‐ion battery materials and shall accelerate the identification of the promising ones.
O3‐type NaNi1/3Fe1/3Mn1/3O2 (NaNFM) is well investigated as a promising cathode material for sodium‐ion batteries (SIBs), but the cycling stability of NaNFM still needs to be improved by using novel ...electrolytes or optimizing their structure with the substitution of different elements sites. To enlarge the alkali‐layer distance inside the layer structure of NaNFM may benefit Na+ diffusion. Herein, the effect of Ca‐substitution is reported in Na sites on the structural and electrochemical properties of Na1−xCax/2NFM (x = 0, 0.05, 0.1). X‐ray diffraction (XRD) patterns of the prepared Na1−xCax/2NFM samples show single α‐NaFeO2 type phase with slightly increased alkali‐layer distance as Ca content increases. The cycling stabilities of Ca‐substituted samples are remarkably improved. The Na0.9Ca0.05Ni1/3Fe1/3Mn1/3O2 (Na0.9Ca0.05NFM) cathode delivers a capacity of 116.3 mAh g−1 with capacity retention of 92% after 200 cycles at 1C rate. In operando XRD indicates a reversible structural evolution through an O3‐P3‐P3‐O3 sequence of Na0.9Ca0.05NFM cathode during cycling. Compared to NaNMF, the Na0.9Ca0.05NFM cathode shows a wider voltage range in pure P3 phase state during the charge/discharge process and exhibits better structure recoverability after cycling. The superior cycling stability of Na0.9Ca0.05NFM makes it a promising material for practical applications in sodium‐ion batteries.
The effects of Ca‐substitution in Na sites on the structural and electrochemical properties of Na1−xCax/2Ni1/3Fe1/3Mn1/3 O2 (x = 0, 0.05, 0.1) are investigated. All the samples show a single O3 type α‐NaFeO2 structure with slightly increased alkali‐layer distance as Ca content increased. The cycling stabilities of Ca‐substituted samples are remarkably improved due to excellent structure recoverability after cycling.
Modified graphene can self‐gel at the liquid–solid interface in a face‐to‐face manner to form an oriented conductive hydrogel film. This unusual gelation behavior enables a new generation of ...electroconductive hydrogels combining exceptional mechanical strength, high electrical conductivity, mechanical flexibility, and anisotropic responsive properties. Scale bar: 1 μm.
Aqueous Zn‐ion battery is a promising technology for electrochemical energy storage. The formation of Zn dendrites, however, can jeopardize the cell cycle life and thus, hinders the industrial ...adoption of this technology. A fundamental understanding of the kinetic mechanisms is crucial for improving the Zn‐ion battery. Here, in situ and operando X‐ray microscopy methods are utilized to visualize the Zn plating and stripping behaviors under different electrochemical conditions. It is demonstrated that the substrate curvature, local morphology, electrochemical protocols, and the surface chemistry can collectively affect the Zn plating behavior. These results provide new insights for developing the next‐generation dendrite‐free and long‐span aqueous Zn‐ion battery.
Zn plating/stripping process is investigated using in situ X‐ray imaging techniques. The results suggest that initial Zn nucleation has a strong dependence on the substrate‐local‐curvature. The reaction heterogeneities under different current densities are quantified by analyzing the three‐dimensional tomography. The surface properties of the Cu substrate can be affected by ZnSO4 electrolyte, leading to distinguish Zn plating behaviors.
In operando XRD and TXM‐XANES approaches demonstrate that structure evolution in NaNi1/3Fe1/3Mn1/3O2 during cycling follows a continuous change, and the formation of a nonequilibrium solid solution ...phase in the existence of two phases. An O3′ and P3′ monoclinic phase occur, and redox couples of Ni3+/Ni4+ and Fe3+/Fe4+ are mainly responsible in the charge voltage range from 4.0 to 4.3 V.
Synergistic graphenes: The chemical and electrical synergies between graphene derivatives enable a simple, cost‐effective and environmentally friendly strategy for solution‐phase processing of ...graphene oxide (GO) and carbon nanotubes (CNTs). The new nanohybrid exhibits high performance when used as electrodes for supercapacitors (see figure; ER=electrochemically reduced, CCG=chemically converted graphene).
Abstract
Sodium metal batteries (SMBs) using gel polymer electrolytes (GPEs) with high theoretical capacity and low production cost are regarded as a promising candidate for high energy‐density ...batteries. However, the inherent flammability of GPEs and uncontrolled Na dendrite caused by inferior mechanical properties and interfacial stability hinder their practical applications. Herein, an anion‐trapping fireproof composite gel electrolyte (AT‐FCGE) is designed through a chemical grafting–coupling strategy, where functionalized boron nitride nanosheets (M‐BNNs) used as both nanosized crosslinker and anion capturer are coupled with poly(ethylene glycol)diacrylate in poly(vinylidene fluoride‐co‐hexafluoropropylene) matrix, to expedite Na
+
transport and suppress dendrite growth. Experimental and calculation studies suggest that the anion‐trapping effect of M‐BNNs with abundant Lewis‐acid sites can promote the dissociation of salts, thus remarkably improving the ionic conductivity and Na
+
transference number. Meanwhile, the formation of highly crosslinked semi‐interpenetrating network can effectively in situ encapsulate non‐flammable phosphate without sacrificing the mechanical properties. Consequently, the resulting AT‐FCGE shows significantly enhanced Na
+
conductivity, mechanical properties, and excellent interfacial stability. The AT‐FCGE enables a long‐cycle stability dendrite‐free Na/Na symmetric cell, and prominent electrochemical performance is demonstrated in solid‐state SMBs. The approach provides a broader promise for the great potential of fire‐retardant gel electrolytes in high‐performance SMBs and the beyond.
PDF
