“In-N-out” design enabling high-content triethyl phosphate-based non-flammable and high-conductivity electrolytes for lithium-ion batteries

Safety issues related to flammable electrolytes in lithium-ion batteries(LIBs) remain a major challenge for their extended applications.The use of non-flammable phosphate-based electrolytes has proved the validity in inhibiting the combustion of LIBs.However,the strong interaction between Li^(+) and phosphate leads to a dominant solid electrolyte interphase(SEI) with limited electronic shielding,resulting in the poor Li^(+) intercalation at the graphite(Gr) anode when using high-phosphate-content electrolytes.To mitigate this issue and improve Li^(+) insertion,we propose an “In-N-Out” strategy to render phosphates “noncoordinative”.By employing a combination of strongly polar solvents for a “block effect” and weakly polar solvents for a “drag effect”,we reduce the Li^(+)–phosphate interaction.As a result,phosphates remain in the electrolyte phase(“In”),minimizing their impact on the incompatibility with the Gr electrode(“Out”).We have developed a non-flammable electrolyte with high triethyl phosphate(TEP) content(>60 wt.%),demonstrating the excellent ion conductivity(5.94 mS cm^(-1) at 30 ℃) and reversible Li^(+) intercalation at a standard concentration(~1 mol L^(-1)).This approach enables the manipulation of multiple electrolyte functions and holds the promise for the development of safe electrochemical energy storage systems using non-flammable electrolytes.

Novel 2D/2D NiCo_(2)O_(4)/ZnCo_(2)O_(4)@rGO/CNTs self-supporting composite electrode with high hydroxyl ion adsorption capacity for asymmetric supercapacitor

The energy storage device has been urgently studied and developed to meet the increasing demand for energy and sustainable development.Due to the excellent conductivity of graphene and high performance of ZnCo_(2)O_(4)and NiCo_(2)O_(4),we design a self-supporting electrode based on vertically grown twodimensional/two-dimensional(2D/2D)NiCo_(2)O_(4)/ZnCo_(2)O_(4)hierarchical flakes on the carbon-based conductive substrate(NiCo_(2)O_(4)/ZnCo_(2)O_(4)@graphene/carbon nanotubes,NZ@GC).The density functional theory calculations indicate that the high OH-adsorption capacity of the NiCo_(2)O_(4)/ZnCo_(2)O_(4)nanosheets can significantly enhance the electrochemical reaction activity.NZ@GC shows a high capacitance of 1128.6 F g^(-1)at 1 A g^(-1).The capacitance retains 84.0%after 6000 cycles even at 10 A g^(-1).A hybrid supercapacitor is fabricated using NZ@GC and activated carbon,exhibiting a large energy density of 50.8 W h kg^(-1)at the power density of 800 W kg^(-1).After 9000 charge/discharge cycles,the supercapacitor still has 86.1%capacitance retention.The NZ@GC film has showed the potential as promising electrodes in high efficiency electrochemical energy storage devices.