Self-Supporting, Flexible, Additive-Free, and Scalable Hard Carbon Paper Self-Interwoven by 1D Microbelts: Superb Room/Low-Temperature Sodium Storage and Working Mechanism.

Hard carbon is regarded as a promising anode material for sodium-ion batteries (SIBs). However, it usually suffers from the issues of low initial Coulombic efficiency (ICE) and poor rate performance, severely hindering its practical application. Herein, a flexible, self-supporting, and scalable hard carbon paper (HCP) derived from scalable and renewable tissue is rationally designed and prepared as practical additive-free anode for room/low-temperature SIBs with high ICE. In ether electrolyte, such HCP achieves an ICE of up to 91.2% with superior high-rate capability, ultralong cycle life (e.g., 93% capacity retention over 1000 cycles at 200 mA g-1 ) and outstanding low-temperature performance. Working mechanism analyses reveal that the plateau region is the rate-determining step for HCP with a lower electrochemical reaction kinetics, which can be significantly improved in ether electrolyte.

Dendrite-free deposition on lithium anode toward long-life and high-stable Li//graphite dual-ion battery.

Metallic lithium protection plays a crucial role on improving the electrochemical properties of Li-anode-based batteries. Herein, for an advanced Li//graphite dual-ion battery, constructing a robust and conductive film of carbon nanofibers on a Li anode effectively achieves dendrite-free Li growth and hence significantly enhances the long-life cyclic stability.

An FeP@C nanoarray vertically grown on graphene nanosheets: an ultrastable Li-ion battery anode with pseudocapacitance-boosted electrochemical kinetics.

In order to develop promising anode materials for lithium-ion batteries (LIBs), a unique nanocomposite abbreviated as G⊥FP@C-NA, in which a carbon-coated FeP nanorod array (FP@C-NA) is vertically grown on a conductive reduced graphene oxide (G) network, has been successfully prepared via a scalable strategy. Benefiting from the distinctive structure, G⊥FP@C-NA exhibits much improved conductivity, structural stability and pseudocapacitance-boosted ultrafast electrochemical kinetics for Li storage. As a result, the G⊥FP@C-NA delivers a high Li-storage capacity (1106 mA h g-1 at 50 mA g-1), outstanding rate capability (565 mA h g-1 at 5000 mA g-1) and long-term cycling stability (1009 mA h g-1 at 500 mA g-1 after 500 cycles and 310 mA h g-1 at 2000 mA g-1 after 2000 cycles) when used as an anode material for LIBs. As expected, this kind of nanoarray structure is attractive and can also be extended to other electrode materials for various energy storage systems.

Highly Improved Cycling Stability of Anion De-/Intercalation in the Graphite Cathode for Dual-Ion Batteries.

Conventional ion batteries utilizing metallic ions as the single charge carriers are limited by the insufficient abundance of metal resources. Although supercapacitors apply both cations and anions to store energy through absorption and/or Faradic reactions occurring at the interfaces of the electrode/electrolyte, the inherent low energy density hinders its application. The graphite-cathode-based dual-ion battery possesses a higher energy density due to its high working potential of nearly 5 V. However, such a battery configuration suffers from severe electrolyte decomposition and exfoliation of the graphite cathode, rendering an inferior cycle life. Herein, a new surface-modification strategy is developed to protect the graphite cathode from the anion salvation effect and the deposition derived from electrolyte decomposition by generating an artificial solid electrolyte interphase (SEI). Such SEI-modified graphite exhibits superior cycling stability with 96% capacity retention after 500 cycles under 200 mA g-1 at the upper cutoff voltage of 5.0 V, which is much improved compared with the pristine graphite electrode. Through several ex situ studies, it is revealed that the artificial SEI greatly stabilizes the interfaces of the electrode/electrolyte after reconstruction and gradual establishment of the optimal anion-transport path. The findings shed light on a new avenue toward promoting the performance of the dual-ion battery (DIB) and hence to make it practical finally.

Pseudocapacitance-boosted ultrafast Na storage in a pie-like FeS@C nanohybrid as an advanced anode material for sodium-ion full batteries.

In order to develop promising anode materials for sodium-ion batteries (SIBs), a novel pie-like FeS@C (P-FeS@C) nanohybrid, in which all ultrasmall FeS nanocrystals (NCs) are completely embedded into the carbon network and sealed by a protective carbon shell, has been prepared. The unique pie-like structure can effectively speed up the kinetics of electrode reactions, while the carbon shell stabilizes the FeS NCs inside. Studies show that the electrochemical reaction processes of P-FeS@C electrodes are dominated by the pseudocapacitive behavior, leading to an ultrafast Na+-insertion/extraction reaction. Hence, the prepared P-FeS@C nanohybrid exhibits superior Na-storage properties especially high rate capability in half cells. For example, it can deliver reversible capacities of 555.1 mA h g-1 at 0.2 A g-1 over 150 cycles and about 60.4 mA h g-1 at 80 A g-1 (an ultrahigh current density even higher than that of the capacitor test). Furthermore, an advanced P-FeS@C//Na3V2(PO4)2O2F full cell has been assembled out, which delivers a stable specific capacity of 441.2 mA h g-1 after 80 cycles at 0.5 A g-1 with a capacity retention of 91.8%.