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A novel complementary approach for promising anode materials is proposed. Sodium titanates with layered Na2Ti3O7 and tunnel Na2Ti6O13 hybrid structure are presented, fabricated, and characterized. The hybrid sample exhibits excellent cycling stability and superior rate performance by the inhibition of layered phase transformation and synergetic effect. The structural evolution, reaction mechanism, and reaction dynamics of hybrid electrodes during the sodium insertion/desertion process are carefully investigated. In situ synchrotron X‐ray powder diffraction (SXRD) characterization is performed and the result indicates that Na+ inserts into tunnel structure with occurring solid solution reaction and intercalates into Na2Ti3O7 structure with appearing a phase transition in a low voltage. The reaction dynamics reveals that sodium ion diffusion of tunnel Na2Ti6O13 is faster than that of layered Na2Ti3O7. The synergetic complementary properties are significantly conductive to enhance electrochemical behavior of hybrid structure. This study provides a promising candidate anode for advanced sodium ion batteries (SIBs).

Sodium-ion batteries (SIBs) have been regarded as a promising candidate for large-scale renewable energy storage system. Layered manganese oxide cathode possesses the advantages of high energy density, low cost and natural abundance while suffering from limited cycling life and poor rate capacity. To overcome these weaknesses, layer-tunnel hybrid material was developed and served as the cathode of SIB, which integrated high capacity, superior cycle ability, and rate performance. In the current work, the doping of copper was adopted to suppress the Jahn-Teller effect of Mn and to affect relevant structural parameters. Multifunctions of the Cu doping were carefully investigated. It was found that the structure component ratio is varied with the Cu doping amount. Results demonstrated that Na/vacancy rearrangement and phase transitions were suppressed during cycling without sacrificing the reversible capacity and enhanced electrochemical performances evidenced with 96 mA h g retained after 250 cycles at 4 C and 85 mA h g at 8 C. Furthermore, ex situ X-ray diffraction has demonstrated high reversibility of the NaMnCuO cathode during Na extraction/insertion processes and superior air stability that results in better storage properties. This study reveals that the Cu doping could be an effective strategy to tune the properties and related performances of Mn-based layer-tunnel hybrid cathode.

It is highly attractive to design FeP-based high-performance anode materials for sodium-ion batteries (SIBs). In this work, we report the development of FeP nanorod arrays on carbon cloth (FeP NAs/CC) as a flexible anode for SIBs. Such FeP NAs/CC delivers a high capacity of 829 mA h g-1 at 0.1 A g-1. At 0.2 A g-1, it still delivers 548 mA h g-1 with an excellent capacity retention of 99.8% even after 100 cycles.

The capacity fluctuation phenomenon during cycling, which is closely related with solid electrolyte interphase and plays a key role for the design for advanced electrode, could be frequently observed in the titanium-based anode. However, the underlying reason for capacity fluctuation still remains unclear with rare related reports. Here, the origin of capacity fluctuation is verified with a long-life NaTiO anode. The reaction mechanism, structural evolution and reaction kinetics during the reported sodiation/desodiation processes were carefully investigated. The gradually enhanced diffusion controlled contribution resulted in the capacity increasing. And the capacity decay could be ascribed to the irreversible reaction of metallic titanium formation and the increasing potential polarization. It is worth noting that sodium ions seem to partially reduce NTO to metallic state, which is irreversible. The present study can provide more information for the design of advanced NaTiO anode.

Intergrown multi-phase composite oxides are critical for LiPS adsorption.

Metal sulfides have been intensively investigated for efficient sodium‐ion storage due to their high capacity. However, the mechanisms behind the reaction pathways and phase transformation are still unclear. Moreover, the effects of designed nanostructure on the electrochemical behaviors are rarely reported. Herein, a hydrangea‐like CuS microsphere is prepared via a facile synthetic method and displays significantly enhanced rate and cycle performance. Unlike the traditional intercalation and conversion reactions, an irreversible amorphization process is evidenced and elucidated with the help of in situ high‐resolution synchrotron radiation diffraction analyses, and transmission electron microscopy. The oriented (006) crystal plane growth of the primary CuS nanosheets provide more channels and adsorption sites for Na ions intercalation and the resultant low overpotential is beneficial for the amorphous Cu‐S cluster, which is consistent with the density functional theory calculation. This study can offer new insights into the correlation between the atomic‐scale phase transformation and macro‐scale nanostructure design and open a new principle for the electrode materials' design.

Voltage polarization during cycling, the charge potential increase of anode or discharge plateau decrease of cathode, is widely observed and would lower the output voltage. Conversely, an anomalous potential plateau negative migration phenomenon was observed in Cu x S anode of sodium-ion battery. In this study, the background mechanism was clarified from the switch of intercalation−conversion reactions and structure evolution. The dynamic cooperation between intercalation and conversion reactions may root the potential plateau negative migration during cycling. In the initial stage, the intercalation-type reaction with Na 3 Cu 4 S 4 and Na 4 Cu 2 S 3 products at 2.13 and 1.92 V would dominate the early migration process of potential plateaus. In the second stage, the conversion-type reaction dominated by Na 2 S and metallic copper formed at 1.85 and 1.53 V in the later period. The aforementioned results would provide new perspective on the electrochemical behavior of transition-metal sulfide anode and provide a clue for reducing voltage polarization.