Rich-Carbonyl Carbon Catalysis Facilitating the Li2CO3 Decomposition for Cathode Lithium Compensation Agent.

The active lithium loss of lithium-ion batteries can be well addressed by adding a cathode lithium compensation agent. Due to the poor conductivity and electrochemical activity, lithium carbonate (Li2CO3) is not considered as a candidate. Herein, an effective cathode lithium compensation agent, the recrystallized Li2CO3 combined with large specific surface area disordered porous carbon (R-LCO@SPC) is prepared. The screened SPC makes it easier for nano-sized Li2CO3 to adsorb and decompose on carbon substrate, meantime, exposing plenty of catalytic active sites of C═O, which can significantly improve the electrochemical activity and conductivity of Li2CO3, thus greatly reducing the decomposition potential of Li2CO3 (4.0 V) and releasing high irreversible capacity (580 mAh g-1) compared to the unmodified Li2CO3 (nearly no capacity above 4.6 V). Meantime, the Li2CO3 can disappear completely without any by-product after the initial cycle accompanied by partially dissolved in electrolyte, optimizing the composition of SEI. The resultant lithium compensation agent applied to LMFP//graphite full cell exhibits a 19.1% increase in energy density, enhancing the rate and cycling performance, demonstrating great practical applications potential in high energy density lithium-ion batteries.

Electrospun graphene-wrapped Na6.24Fe4.88(P2O7)4 nanofibers as a high-performance cathode for sodium-ion batteries.

Na6.24Fe4.88(P2O7)4 is one of the intensively investigated polyanionic compounds and has shown high rate discharge capacity, but its relatively low electronic conductivity hampers the high performance of the batteries. Herein for the first time we report new graphene wrapped Na6.24Fe4.88(P2O7)4 composite nanofibers (NFPO@C@rGO) made from electrospinning for cathodes of SIBs to achieve an even higher performance with a highly stable discharge capacity of ∼99 mA h g-1 at a current density of 40 mA g-1 after 320 cycles, which is 1.6 times higher than that of the pristine Na6.24Fe4.88(P2O7)4 (NFPO@C) composite. In particular, the NFPO@C@rGO composite cathode exhibits an even higher discharge rate capacity of ∼53.9 mA h g-1 at a current density of 1280 mA g-1 (11C) than that of ∼40 mA h g-1 at a current density of 1100 mA g-1 (9.4C) for the reported best high discharge rate performance of NFPO. The superior cycling and high rate capability are attributed to the unique spinning vein fiber based porous structure offering a good intimate contact between NFPO@C and graphene for great electronic conductivity, fast ionic transport, a large reaction surface and a strong solid structure preventing collapse during cycling, thus achieving a high rate discharge performance and high cycling stability.

Highly efficient Au/Fe2O3 for CO oxidation: The vital role of spongy Fe2O3 toward high catalytic activity and stability.

Supported gold catalysts have drawn great attention for many decades due to their outstanding performance in remedying the environment from carbon monoxide (CO) pollution. In this study, due to the large surface area of spongy Fe2O3, fabricated by salt-assisted ultrasonic spray pyrolysis, a considerable amount of Au was loaded on spongy Fe2O3 compared to low-surface-area non-spongy Fe2O3. It is seen that the spongy Fe2O3 catalyst loaded with Au has an interface that can be extremely active for CO desorption and O2 activation. That means it has high catalytic activity in CO oxidation than non-spongy and low surface area Fe2O3 loaded with Au. Also, the incorporation of Au in low alkaline condition further enhances the interaction between Au and Fe2O3, providing more active sites. This made the catalyst to have better activity, good stability over 60 hrs, and there was no carbonate on its surface. It had full conversion at 30 °C on 120 L g-1h-1 with high TOF (2.2 s-1).

Manipulating irreversible phase transition of NaCrO2 towards an effective sodium compensation additive for superior sodium-ion full cells.

During the first charge process of full cells, a solid electrolyte interphase (SEI) film is formed when the active ion from the cathode is consumed, resulting in irreversible capacity loss. This phenomenon has shown to be more serious in sodium-ion full cells than in lithium-ion full cells. Although many strategies have been employed to alleviate the loss of sodium ions, such as presodiation and construction of an artificial solid electrolyte interface, they are both cumbersome and time-consuming. For the first time, NaCrO2 was used as an effective self-sacrificing sodium compensation additive in sodium-ion full cells due to the irreversible phase transition of NaCrO2 in a high voltage region can deliver an irreversible capacity of up to 230 mAh g-1. Based on this design, sodium-ion full cells coupled with hard carbon as the anode exhibited higher capacity, less polarization, greater energy density, and superior cycle stability than those of a pristine electrode. This is mainly attributed to the removal of sodium ions from NaCrO2, which compensates for the loss of sodium ions consumed during the formation of the SEI film on the anode surface during the first charge process. Overall, this work opens up a new avenue for exploring sodium compensation strategy and contributing to practical application of sodium-ion full cells.

Nitrogen-Doped Carbon as a Host for Tellurium for High-Rate Li-Te and Na-Te Batteries.

A nitrogen-doped hierarchical porous carbon sponge, used as a matrix for tellurium accommodation, was designed and prepared in this work. The porosity of the matrix played an important role in enhancing the electrochemical performance of Li/Na-Te batteries. Specifically, the mesopores could accommodate active materials whereas the macropores provided sufficient space for partial Te accommodation and volume expansion in discharge. In addition, N heteroatoms in carbon species could enhance the electrical conductivity and widen its application in lithium/sodium storage. The monolithic and flaky architecture of the nitrogen-doped hierarchical porous carbon sponge/tellurium composite offered a highly conductive network for fast electron transportation. As a result, the nitrogen-doped hierarchical porous carbon sponge/tellurium composite achieved a superior rate performance for Li-Te and Na-Te batteries.

Improving the Performance of Hard Carbon//Na3V2O2(PO4)2F Sodium-Ion Full Cells by Utilizing the Adsorption Process of Hard Carbon.

Hard carbon has been regarded as a promising anode material for Na-ion batteries. Here, we show, for the first time, the effects of two Na+ uptake/release routes, i.e., adsorption and intercalation processes, on the electrochemical performance of half and full sodium batteries. Various Na+-storage processes are isolated in full cells by controlling the capacity ratio of anode/cathode and the sodiation state of hard carbon anode. Full cells utilizing adsorption region of hard carbon anode show better cycling stability and high rate capability compared to those utilizing intercalation region of hard carbon anode. On the other hand, the intercalation region promises a high working voltage full cell because of the low Na+ intercalation potential. We believe this work is enlightening for the further practical application of hard carbon anode.

Sodium-Rich Ferric Pyrophosphate Cathode for Stationary Room-Temperature Sodium-Ion Batteries.

In this article, carbon-coated Na3.64Fe2.18(P2O7)2 nanoparticles (∼10 nm) were successfully synthesized via a facile sol-gel method and employed as cathode materials for sodium-ion batteries. The results show that the carbon-coated Na3.64Fe2.18(P2O7)2 cathode delivers a high reversible capacity of 99 mAh g-1 at 0.2 C, outstanding cycling life retention of 96%, and high Coulomb efficiency of almost 100% even after 1000 cycles at 10 C. Furthermore, the electrochemical performances of full batteries consisting of carbon-coated Na3.64Fe2.18(P2O7)2 nanoparticles as the cathode and commercialized hard carbon as the anode are tested. The full batteries exhibit a reversible capacity of 86 mAh g-1 at 0.5 C and capacity retention of 80% after 100 cycles. Therefore, the above-mentioned cathode is a potential candidate for developing inexpensive sodium-ion batteries in large-scale energy storage with long life.

Fabrication of WS2-nanoflowers@rGO composite as an anode material for enhanced electrode performance in lithium-ion batteries.

In this paper, we descried a simple method to fabricate three-dimensional (3D) composite materials, WS2-nanoflowers @ reduced graphene oxide (WS2-NF@rGO), in which rGO crossed-link the isolated WS2-NF to construct a 3D conductive network and provided protection against the volume changes of WS2 during electrochemical processes simultaneously. This unique structure of the WS2-NF@rGO composite could not only promote both ion and electron diffusion, but also enhance the electrode stability, thus obtaining a high-capacity and long-cycle anode material for lithium-ion batteries. As a result, the WS2-NF@rGO exhibited a reversible capacity of 730mAhg-1 after 150 cycles at 100mAg-1 and maintained a capacity of higher than 260mAhg-1 at 2Ag-1, thus exhibiting great potential as an anode material for lithium storage.