Electrolyte anions are critical for achieving high-voltage stable potassium metal batteries (PMBs). However, the common anions cannot simultaneously prevent the formation of ‘dead K’ and the corrosion of Al current collector, resulting in poor cycling stability. Here, we demonstrate cyclic-anion of hexafluoropropane-1,3-disulfonimide (HFDF−) based electrolytes that can mitigate the ‘dead K’ and remarkably enhance the high voltage stability of PMBs. Particularly, even using low salt concentration (0.8 M) and additive-free carbonate-based electrolytes, the PMBs with a high voltage polyanion cathode (4.4 V) also exhibit excellent cycling stability of 200 cycles with a good capacity retention of 83%. This noticeable electrochemical performance is due to the highly-efficient passivation ability of the cyclic anions on both anode and cathode surfaces. This cyclic anion-based electrolyte design strategy is also suitable for lithium and sodium metal battery technologies.
Large‐scale and low‐cost preparation of carbon‐based potassium anode with long life and high capacity is one of the footstones for the development of potassium ion batteries (PIBs). Herein, a low‐cost carbon‐based material, cross‐linked hollow graphitic carbon (HGC), is large scale synthesized to apply for PIBs anode. Its hollow structure can afford sufficient space to overcome the damage caused by the volume expansion of graphitic carbon (GC). While the cross‐linked structure forms a compact interconnection network that allows electrons to rapid transfer between different GC frameworks. Electrochemical measurements demonstrated that the HGC anode exhibited low charge/discharge plateau (about 0.25 V and 0.1 V) and excellent specific capacity as high as 298 mA h g−1 at the current density of 50 mA g−1. And more important, after 200 cycles the capacity of HGC anode still shows 269 mA h g−1 (the decay rate of per cycle is only 0.048%). Meanwhile, the use of commercial traditional electrolyte (KPF6) and cheap raw materials that provide new hope for trying and realizing the large‐scale production of PIBs based on carbon anode materials.
A novel hierarchical architecture-N-doped hollow carbon fibers decorated with N-doped carbon clusters (NHCF@NCC)-was synthesized for high-performance anode material of potassium ion batteries (PIBs). The material is formulated with porous N-doped hollow carbon fibers as the backbone, which effectively shortens the diffusion length of potassium ion and increases the interface between the electrode and electrolyte. In addition, the N-doped carbon clusters attached on the hollow carbon fibers can provide abundant reactive sites. Specially, NHCF@NCC could form a freestanding electrode with a three dimensional interconnected conductive network owing to the ultrahigh aspect ratio. In this way, NHCF@NCC delivers an excellent electrochemical performance as free-standing anode materials of PIBs, exhibiting a high reversible capacity of 310 mA h g −1 at a current density of 100 mA g −1 , a long cycling stability of 1000 cycles with negligible degradation, and a superior rate performance of 153 mA h g −1 at a large current density of 2000 mA g −1 .
Potassium‐based energy storage devices (PEDS) are considered as hopeful candidates for energy storage applications because of the abundant potassium resources in nature and high mobility in the electrolyte. although carbon materials show great potential for potassium‐ion storage, poor rate performance, and unsatisfactory cycle lifespan in existing carbon‐based PIBs anode, it also cannot match the dynamics and stability of the capacitor cathode. Nitrogen doping has been proven to be a effective modification strategy to improve the electrochemical performance of carbon materials. Hence, we prepare carbon nanofibers and g‐C3N4 composites with high nitrogen contents (19.78 at%); moreover, the sum of pyrrolic N and pyridinic N is up to 59.51%. It achieves high discharge capacity (391 mAh g−1 at 0.05 A g−1), rate capacity (141 mAh g−1 at 2 A g−1), and long cycling performance (201 mAh g−1 at 1 A g−1 over 3000 cycles) when as an anode for PIBs. Furthermore, it can deliver promising discharge capacity of 132 mAh g−1 at 0 °C. Moreover, as battery anode for potassium‐ion hybrid capacitors (PIHC) device with an active carbon cathode, it delivers energy/power density (62 and 2102 W kg−1) as well as high reversible capacity (106 mAh g−1 at 1 A g−1).
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