The peak-loading shift function of sodium-ion batteries in large-grid energy store station poses a giant challenge on the account of poor rate performance of cathodes. NASICON type Na3V2(PO4)3 with a stable three-dimensional framework and fast ion diffusion channels has been regarded as one of the potential candidates and extensively studied. Nevertheless, a multilevel integrated tactic to boost the performance of Na3V2(PO4)3 in terms of crystal structure modulation, coated carbon graphitization regulation, and particle morphology design is rarely reported and deserves much attention. In this study, organic ferric was used to prepare Fe-doped Na3V2(PO4)3@C cathode on the account of low cost, environmental friendliness, and catalytic function of Fe on carbon graphitization. The density functional theory calculation depicts that the most stable site for Fe atom is the V site and moderate replacement of Fe at V position would reduce the band gap energy from 2.19 by 0.43 eV and improve the electron transfer, which is crucial for the intrinsic poor conductivity of Na3V2(PO4)3. The experimental results show that Fe element can be introduced into the bulk structure successfully, modulating relevant structural parameters. In addition, the coated carbon layer graphitization degree is also regulated due to the catalysis function of Fe. And, the decomposition of organic ferric would infuse the formation of porous structure, which can promote electrolyte permeation and shorten the electron/ion diffusion. Finally, the optimized Na3V1.85Fe0.15(PO4)3@C could possess a high capacity of 103.69 mA h g–1 and retain 91.45% after 1200 cycles at 1.0C as well as 94.45 mA h g–1 at 20C. In addition, the excellent performance is comprehensively elucidated via ex situ X-ray diffraction and pseudocapacitance characterization. The multifunction contribution of Fe-doping may provide new clue for designing porous electrode materials and a new sight into Fe-doped carbon-coated material.

No abstract

p-Type and n-type thermoelectric semiconductor materials with compatible performance are key components for thermoelectric devices. Great improvement in thermoelectric performance has been achieved in p-type PbTe, whereas the n-type counterpart still shows much inferior thermoelectric performance compared to that of the p-type PbTe. This inspires many strategies focused on advancing n-type PbTe thermoelectrics. Herein, not only effective mass engineering, resonance states, point defects, and nanostructures but also newly developed concepts including dynamic doping for stabilizing the optimal carrier concentration and introducing dislocations for reducing lattice thermal conductivity are summarized. In addition, the synergistic effects for further enhancing the thermoelectric performance are outlined, together with a discussion and outlook for boosting the advancement in n-type PbTe thermoelectric materials. Strategies discussed here are expected to be applicable to other thermoelectric materials.

No abstract

The development of prospective cathode candidates is one of the key issues for the practical application of sodium ion batteries. Although alluaudite Na 2−2x Fe 2−x (SO 4 ) 3 (NFS) cathode combines natural abundance, environmental benign and higher theoretical energy density than conventional polyanionic cathodes, the present available performance is unsatisfying because of limited electronic conductivity. The traditional in situ carbon coating via wet chemistry and thermolysis is infeasible due to the moisture sensitivity and poor thermal stability. In this study, the above issues are simultaneously tackled via a simple but effective method assisted by graphene addition with the merits of high conductivity, hydrophobicity, and stretchable nature. Since the added graphene could affect the growth of NFS particle, the nanoparticle could be wrapped well and form NFS@graphene composite, which could keep from moisture attack. Moreover, the functional groups of the graphene precursor could boost the crystallization. The NFS@graphene could deliver an initial reversible capacity of ∼106 mAh g −1 at 25 °C, and a capacity retention of >98% at 0 °C is retained over 700 cycles. The inspiring results would cast insight on the graphene-assisted synthesis and were meaningful for scaling up the Na 2−2x Fe 2−x (SO 4 ) 3 cathodes. KEYWORDS: Sodium-ion battery, Alluaudite Na 2−2x Fe 2−x (SO 4 ) 3 , Graphene, Multirole, Sustainability

The composite structure materials in sodium-ion batteries (SIBs) have received increasing attentions due to the synergistic effect. P2/P3 composite cathode with the advantages of high reversible capacity and superior reaction kinetics was regarded as one of the promising cathodes for SIBs. Crystal phase component ratio and particle morphology of hybrid structures are closely related with the electrochemical performance, especially the energy density. Herein, P2/P3 hybrid structure materials Na 0.6 Mn 1-x Ni x O 2 were synthesized by co-precipitation method. Furthermore, the component ratio and particle size are tuned and realized via simple Ni 2 + content optimization. The targeted sample Na 0.6 Mn 0.75 Ni 0.25 O 2 shows high tap density over 1.2 g cm À 3 and excellent electrical properties with an initial capacity of 101.36 mA h g À 1 at 0.2 C, corresponding to a high volumetric energy density of 512 Wh L À 1 based on the cathode active material. Moreover, the long-term cycling capacity retention can reach 68 % at 1 C after 500 cycles. The present study develops a promising cathode of SIBs that maybe applied in low-speed electric vehicles. And the simultaneous optimization design represents a potential route for the regulation of composite structures to obtain high performance SIBs.

. Host structural stabilization of Li1.232Mn0.615Ni0.154O2 through K-doping attempt: toward superior electrochemical performances. Electrochimica Acta, 188 336-343.Host structural stabilization of Li1.232Mn0.615Ni0.154O2 through Kdoping attempt: toward superior electrochemical performances Abstract Lithium-rich layered cathodes are known famously for its superior capacity over traditional layered oxides but trapped for lower initial coulombic efficiency, poorer rate capability and worse cyclic stability in spite of diverse attempts. Herein, a new K-stabilized Li-rich layered cathode synthesized through a simple oxalate coprecipitation is reported for its super electrochemical performances. Compared with pristine Li-rich layered cathode, K-stabilized one reaches a higher initial coulombic efficiency of 87% from 76% and outruns for 94% of capacity retention and 244 mAh g-1 of discharge capacity at 0.5C after 100 cycles. Moreover, 133 mAh g-1 of discharge capacity can be delivered even charged at 10C showing a highly-improved rate capability. X-ray diffraction and electrochemical impedance spectroscopy tests show that enlarged Li slab layer caused by K+ accommodation can provide facile Li+ diffusion paths and facilitate Li+ migration from the crystal lattice. As a consequence, the introduction of K+ in the host layered structure can inhibit the detrimental spinel structure growth during cycling. Therefore, the K-stabilized Li-rich layered materials can be considered to be an attractive alternative to meet with the higher power and energy density demands of advanced lithium-ion battery.Keywords structural, stabilization, li1, 232mn0, 615ni0, k, host, doping, performances, attempt, toward, superior, electrochemical, 154o2 Disciplines Engineering | Physical Sciences and Mathematics Publication DetailsZheng, Z., Guo, X., Zhong, Y., Hua, W., Shen, C., Chou, S. & Yang, X. (2016 As a consequence, the introduction of K + in the host layered structure can inhibit the detrimental spinel structure growth during cycling. Therefore, the K-stabilized Li-rich layered materials can be considered to be an attractive alternative to meet with the higher power and energy density demands of advanced lithium-ion battery.

Bi2Te3 is a well-recognized material for its unique properties in diverse thermoelectric applications near room temperature. The considerable efforts on Bi2Te3-based alloys have been extremely extensive in recent years, and thus the latest breakthroughs in high-performance p-type (Bi, Sb)2Te3 alloys are comprehensively reviewed to further implement applications. Effective strategies to further improve the thermoelectric performance are summarized from the perspective of enhancing the power factor and minimizing the lattice thermal conductivity. Furthermore, the surface states of topological insulators are investigated to provide a possibility of advancing (Bi, Sb)2Te3 thermoelectrics. Finally, future challenges and outlooks are overviewed. This review will provide potential guidance toward designing and developing high-efficient Bi2Te3-based and other thermoelectrics.