An Ion-Pumping Interphase on Graphdiyne/Graphite Heterojunction for Fast-Charging Lithium-Ion Batteries

The sluggish lithium-ion(Li-ion)transport kinetics in graphite anode hinders its application in fast-charging Li-ion batteries(LIBs).Here,we develop an ionpumping interphase(IPI)on graphdiyne(GDY)/graphite heterojunction anodes to boost the ionic transport kinetics and enable high-performance,fast-charging LIBs.The IPI changed the ion solvation/desolvation environment by covalent/non-covalent interactions with Li ions or solvents to optimize solid-electrolyte interphase(SEI)and regulate Li-ion transport behavior.We studied the in situ growth of few-layer GDY on graphite surface(GDY/graphite)as the IPI and found that the strong interaction between GDY and Li ions enabled surface-induced modification of the ion solvation behavior and surface-assisted desolvation effect to accelerate the Li-ion desolvation process.A functional anion-derived SEI layer with improved Li-ion conductivity was created.Together with the generated built-in electric field at GDY/graphite hetero-interface self-pumping Li ions to intercalate into the graphite,the Li-ion transport kinetics was significantly enhanced to effectively eliminate Li plating and large voltage polarization of the graphite anodes.A fast Li intercalation in GDY/graphite without Li oversaturation at the edge of the graphite was directly observed.The superior performance with high capacity(139.2 mA h g^(-1))and long lifespan(1650 cycles)under extremely fast-charging conditions(20 C,1 C=372 mA g^(-1))was achieved on GDY/graphite anodes.Even at low temperatures(-20℃),a specific capacity of 128.4 mA h g^(-1) was achieved with a capacity retention of 80%after 500 cycles at a 2 C rate.

A potential-responsive ion-pump system based on nickel hexacyanoferrate film for selective extraction of cesium ions

A nickel hexacyanoferrate(NiHCF)film electrode was prepared with NiHCF,conductive carbon black,and polyvinylidene difluoride,which was coated on graphite plate substrate for selective extraction of Cs^(+)ions by using electrochemically switched ion exchange(ESIX)technology.A potential-responsive ionpump system for efficient extraction of Cs+ions was designed,and the effect of wet film thicknesses,charging modes,flow rates,and chamber widths on Cs+ions extraction performance was investigated.In the system,the adsorption capacity and removal percentage of Cs^(+)ions on the NiHCF film electrode reached as high as 147.69 mg·g^(-1)and 92.47%,respectively.Furthermore,the NiHCF film electrode showed high selectivity for Cs^(+)ions and stability.After seven cycles of adsorption/desorption,the desorption percentage could reach about 100%.The excellent Cs^(+)extraction performance should be attributed to the strong driving force produced by the potential-responsive ion-pumping effect in the ESIX process,as well as the low ion transfer resistance of the film electrode which is caused by the special crystal structure of NiHCF.In addition,the NiHCF film electrode was implemented to work together with the bismuth oxybromide(BiOBr)film electrode to accomplish the simultaneous extraction of Cs^(+)and Br^(-).And the adsorption capacity and removal percentage of Br^(-)ions on the BiOBr film electrode reached 69.53 mg·g^(-1)and 77.32%,correspondingly.It is expected that such a potential-responsive ion-pump system based on NiHCF and BiOBr film electrodes could be used for the selective extraction and concentration of Cs^(+)and Br^(-)ions from salt lake brine.