Material innovation on high‐performance Na‐ion cathodes and the corresponding understanding of structural chemistry still remain a challenge. Herein, we report a new concept of high‐entropy strategy ...to design layered oxide cathodes for Na‐ion batteries. An example of layered O3‐type NaNi0.12Cu0.12Mg0.12Fe0.15Co0.15Mn0.1Ti0.1Sn0.1Sb0.04O2 has been demonstrated, which exhibits the longer cycling stability (ca. 83 % of capacity retention after 500 cycles) and the outstanding rate capability (ca. 80 % of capacity retention at the rate of 5.0 C). A highly reversible phase‐transition behavior between O3 and P3 structures occurs during the charge‐discharge process, and importantly, this behavior is delayed with more than 60 % of the total capacity being stored in O3‐type region. Possible mechanism can be attributed to the multiple transition‐metal components in this high‐entropy material which can accommodate the changes of local interactions during Na+ (de)intercalation. This strategy opens new insights into the development of advanced cathode materials.
My brave phase: A high entropy oxide (HEO) cathode, containing nine additional components, the layered O3‐phase NaNi0.12Cu0.12Mg0.12Fe0.15Co0.15Mn0.1Ti0.1Sn0.1Sb0.04O2, delivers long cycling stabilities and high rate capability. As more than 60 % of the capacity is stored in the O3‐type region, the entropy stabilization of the O3‐phase gives the cycling stability and better rate performance.
In order to address power and energy demands of mobile electronics and electric cars, Li‐ion technology is urgently being optimized by using alternative materials. This article presents a review of ...our recent progress dedicated to the anode and cathode materials that have the potential to fulfil the crucial factors of cost, safety, lifetime, durability, power density, and energy density. Nanostructured inorganic compounds have been extensively investigated. Size effects revealed in the storage of lithium through micropores (hard carbon spheres), alloys (Si, SnSb), and conversion reactions (Cr2O3, MnO) are studied. The formation of nano/micro core–shell, dispersed composite, and surface pinning structures can improve their cycling performance. Surface coating on LiCoO2 and LiMn2O4 was found to be an effective way to enhance their thermal and chemical stability and the mechanisms are discussed. Theoretical simulations and experiments on LiFePO4 reveal that alkali metal ions and nitrogen doping into the LiFePO4 lattice are possible approaches to increase its electronic conductivity and does not block transport of lithium ion along the 1D channel.
Recent progress in anode and cathode materials for Li‐ion batteries is reviewed. Nanostructured materials, size effects, and efforts on improving cyclic performance, thermal and chemical stability, and theoretical simulations are discussed.
Liquid electrolyte plays a key role in commercial lithium-ion batteries to allow conduction of lithium-ion between cathode and anode. Traditionally, taking into account the ionic conductivity, ...viscosity and dissolubility of lithium salt, the salt concentration in liquid electrolytes is typically less than 1.2 mol l(-1). Here we show a new class of 'Solvent-in-Salt' electrolyte with ultrahigh salt concentration and high lithium-ion transference number (0.73), in which salt holds a dominant position in the lithium-ion transport system. It remarkably enhances cyclic and safety performance of next-generation high-energy rechargeable lithium batteries via an effective suppression of lithium dendrite growth and shape change in the metallic lithium anode. Moreover, when used in lithium-sulphur battery, the advantage of this electrolyte is further demonstrated that lithium polysulphide dissolution is inhibited, thus overcoming one of today's most challenging technological hurdles, the 'polysulphide shuttle phenomenon'. Consequently, a coulombic efficiency nearing 100% and long cycling stability are achieved.
Most P2-type layered oxides exhibit Na(+)/vacancy-ordered superstructures because of strong Na(+)-Na(+) interaction in the alkali metal layer and charge ordering in the transition metal layer. These ...superstructures evidenced by voltage plateaus in the electrochemical curves limit the Na(+) ion transport kinetics and cycle performance in rechargeable batteries. Here we show that such Na(+)/vacancy ordering can be avoided by choosing the transition metal ions with similar ionic radii and different redox potentials, for example, Cr(3+) and Ti(4+). The designed P2-Na(0.6)Cr(0.6)Ti(0.4)O2 is completely Na(+)/vacancy-disordered at any sodium content and displays excellent rate capability and long cycle life. A symmetric sodium-ion battery using the same P2-Na(0.6)Cr(0.6)Ti(0.4)O2 electrode delivers 75% of the initial capacity at 12C rate. Our contribution demonstrates that the approach of preventing Na(+)/vacancy ordering by breaking charge ordering in the transition metal layer opens a simple way to design disordered electrode materials with high power density and long cycle life.
A reduced graphene oxide (rGO) based film is sandwiched between a sulfur cathode and the separator, acting as a shuttle inhibitor to the sulfur and polysulfides. The lithium–sulfur cell with such a ...configuration shows an initial discharge capacity of 1260 mAh g−1 and the capacity remains at 895 mAh g−1 after 100 cycles. The excellent electrochemical performance of the cell is attributed to both the functional groups on the rGO sheets that anchor the sulfur and polysulfides and the carbon additive that helps to produce channels for the electrolyte and polysulfide to enter.
Display omitted
•A reduced graphene oxide (rGO) based interlayer is used as a shuttle inhibitor.•The rGO interlayer improves the cycling performance of the Li–S cell significantly.•Functional groups on the rGO help to anchor the sulfur and polysulfides.•Compromise is required between anchoring sulfides and building electrolyte channels.
Sodium‐ion batteries (SIBs) have attracted more and more attention for scalable electrical energy storage due to the abundance and wide distribution of Na resources. However, the anode still remains ...a great challenge for the application of SIBs. Here the production of uniform hard carbon microtubes (HCTs) made from natural cotton through one simple carbonization process and their application as an anode are reported. The study shows that the electrochemical performance of the HCTs is seriously affected by the carbonization temperature due to the difference in their microstructure and heteroatomic content. The HCTs carbonized at 1300 °C deliver the highest reversible capacity of 315 mAh g−1 and good rate capability due to their unique tubular structure. This contribution not only provides a new approach for the preparation of hard carbon materials with unique tubular microstructure using natural inspiration, but it also deepens the fundamental understanding of the sodium storage mechanism.
A novel hard carbon material with microtube structure constructed from hollow fiber structure of cotton fiber by simple one‐step carbonization approach is presented. The electrochemical sodium storage difference of hard carbon microtubes with different carbonization temperature and the sodium storage mechanism are systematically investigated in this work.
Prussian blues (or iron cyanides) and their analogues are attractive in both fundamental studies and industrial applications owing to their chemical and structural diversity. The large open space in ...their framework provides tunnels and space for the transport and storage of lithium ions. Two Prussian blues were synthesized by a co‐precipitation method. The nanosized Fe4Fe(CN)63 and cubic FeFe(CN)6 deliver reversible capacities of 95 mAh g−1 and 138 mAh g−1, respectively. In comparison, FeFe(CN)6 shows cycling and rate performances superior to Fe4Fe(CN)63.
Plenty of room: Two Prussian blues were synthesized by a co‐precipitation method for the transport and storage of lithium ions through the large open space in their framework. Nanosized particles of Fe4Fe(CN)63 and cubes of FeFe(CN)6 deliver reversible capacities of 95 mAh g−1 and 138 mAh g−1, respectively. In contrast, FeFe(CN)6 shows cycling and rate performances superior to Fe4Fe(CN)63.
Thermal safety is one of the major issues for lithium‐ion batteries (LIBs) used in electric vehicles. The thermal runaway mechanism and process of LIBs have been extensively studied, but the thermal ...problems of LIBs remain intractable due to the flammability, volatility and corrosiveness of organic liquid electrolytes. To ultimately solve the thermal problem, all‐solid‐state LIBs (ASSLIBs) are considered to be the most promising technology. However, research on the thermal stability of solid‐state electrolytes (SEs) is still in its initial stage, and the thermal safety of ASSLIBs still needs further validation. Moreover, the specified reviews summarizing the thermal stability of ASSLIBs and all types of SEs are still missing. To fill this gap, this review systematically discussed recent progress in the field of thermal properties investigation for ASSLIBs, form levels of materials and interface to the whole battery. The thermal properties of three major types of SEs, including polymer, oxide, and sulfide SEs are systematically reviewed here. This review aims to provide a comprehensive understanding of the thermal stability of SEs for the benign development of ASSLIBs and their promising application under practical operating conditions.
Thermal failure is a serious issue for liquid‐electrolyte‐based lithium‐ion batteries, and substituting liquid electrolytes with solid‐state electrolytes is expected to solve this problem. This review summarizes the thermal stability of polymers, oxides, sulfides, and other solid‐state electrolytes from the level of material, interface, and battery, and points out the limitations and future of thermal stability studies in solid‐state batteries.
PDF
