Pomegranate-shaped silicon oxide-nitrogen doped carbon composite material, synthesis method thereof and lithium ion capacitor

Abstract

The invention discloses a pomegranate-shaped silicon oxide-nitrogen doped carbon composite material, a synthesis method thereof and a lithium ion capacitor, and the synthesis method comprises the steps: a) mixing lysine and water, adding tetrapropyl orthosilicate, and stirring to obtain a silicon oxide-based dispersion liquid; b) adding melamine and formaldehyde into water, and stirring to obtain a precursor solution; c) pouring the silicon oxide-based dispersion liquid into the precursor solution to obtain a mixed solution; d) adjusting the pH value of the mixed solution to 4.5-5, filtering, washing and drying; and e) curing in air, and carbonizing in a nitrogen atmosphere to obtain the pomegranate-shaped silicon oxide-nitrogen doped carbon composite material. The pomegranate-shaped silicon oxide surface of the composite material prepared by adopting the synthesis method is coated with a layer of carbon material, pomegranate-shaped spheres of the silicon oxide are prevented from directly contacting electrolyte, only lithium ions are allowed to pass through, the cycle performance is greatly improved, and the capacity of a lithium ion capacitor prepared by adopting the composite material as a negative electrode material is not obviously attenuated.

Description

technical field [0001] The invention belongs to the technical field of lithium ion capacitors, and in particular relates to a pomegranate silicon oxide-nitrogen-doped carbon composite material, a synthesis method thereof and a lithium ion capacitor. Background technique [0002] With the widespread use of various mobile electronic devices, such as smartphones, laptops, etc., lithium-ion capacitors have thus received extensive attention. However, the energy density and power density of commercial lithium-ion capacitors are difficult to meet the requirements of technological development for energy storage devices. Therefore, it is imminent to develop high-capacity electrode materials. [0003] For lithium-ion capacitors, the theoretical specific capacity of the traditional negative electrode material graphite is only 372mAh / g. As far as the current technical level and process conditions are concerned, the actual capacity of graphite is very close to its theoretical capacity, ...

AI Technical Summary

Problems solved by technology

However, there are some problems with the pure silicon oxide material as the negative electrode material of lithium ion capacitors. On the one hand, its inherent poor electrical conductivity limits its large-scale use; There will be obvious volume expansion and contraction, this volume change will lead to the rupture of the structure and then failure, or excessive formation of SEI film, consumption of lithium ions, resulting in a decrease in capacity, in addition, the loss of electrons due to volume expansion The contact also makes its capacity decay during the cycle, specifically: the volume expansion effect (200%) of the silicon oxide-based negative electrode material in the charge and discharge process can easily cause its capacity decay, and one of the most important points is due to the volume expansion- The island effect of the active material caused by the loss of electronic contact between the active material particles caused by shrinkage. Once the active material loses electronic contact, it will no longer be able to extract / intercalate lithium, which will eventually lead to the capacity decay of the material.

[0005] At present, in view of the poor conductivity of silicon oxide-based negative electrode materials and the capacity attenuation caused by the loss of contact between the active material particles caused by volume changes, researchers have proposed to use one-dimensional nanomaterials to construct three-dimensional conductive networks, such as carbon nanotubes and carbon nanotubes. Physical mixing of silicon oxide materials [Facile Synthesis and High AnodePerformance of Carbon Fiber Interwoven Amorphous Nano-SiOx / Graphene for Rechargeable Lithium Batteries, ACS Appl. Mater. Interfaces 2013,5,11234]; but this simple physical mixing method cannot Combining particles with one-dimensional nanomaterials, after several charge-discharge cycles, it is still easy to cause the electrons of the active material to lose contact

Another example is that Yoo et al. used metal platinum to catalyze and synthesized a silicon-based anode material with a sea urchin-like structure in the process of high-temperature heat treatment, in which nanowires with a silicon / silicon oxide core-shell structure grow and protrude on the surface of micron-scale silicon particles, and interact with each other. A three-dimensional network [Helical Silicon / Silicon Oxide CoreShell Anodes Grown onto the Surface of BulkSilicon, Nano Letters, 2011, 11, 4324]; however, the preparation process of this method is complicated, and it needs to be catalyzed by precious metals such as platinum, and the preparation cost is high and difficult to realize. actual production application

The prior art also discloses the direct preparation of one-dimensional silicon nanomaterials as negative electrode materials [Self-sacrificed synthesis of carbon-coated SiOxnanowires for high capacity lithiumion batteries, J.Mater.Chem.A, 2017,5,4183]; but this method It mainly uses noble metal catalysis, the preparation process is complicated, the cost is high, and the actual industrial application cannot be realized, and the tap density of the electrode prepared by silicon nanowires is low, which seriously affects its volumetric energy density in practical applications.

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