Graphene quantum dot modified electrolyte and preparation method thereof

Abstract

The invention provides a graphene quantum dot modified electrolyte and a preparation method thereof, and belongs to the field of lithium metal battery electrolytes. By adding graphene quantum dots anda polymer in the commercial electrolyte, the graphene quantum dots can continuously provide nucleation sites, and the polymer enables uniform dispersion of the graphene quantum dots in the electrolyte, thereby obtaining simple process and obviously improving cycling and multiplying performance of lithium metal batteries under operating conditions of high current and high capacity. When the lithium metal batteries in the graphene quantum dot modified electrolyte have a current density reaching 4mA / cm2 and a cycling capacity reaching 4mAh / cm2, there is still no short circuit caused by lithium dendrites, and good charging and discharging performance is kept, thereby having potential application in the field of lithium metal batteries, and realizing the purpose of lithium negative protectionunder high current and high capacity.

Description

technical field [0001] The invention belongs to the field of electrolytes for lithium metal batteries, and in particular relates to an electrolyte modified with graphene quantum dots and a preparation method thereof. Background technique [0002] With the rapid development of fields such as portable electronic devices and electric vehicles, society's demand for high-energy-density energy storage batteries has shown explosive growth. Metal lithium electrodes have a theoretical capacity (3860mAh / g) ten times that of carbon-based lithium-ion electrodes, and the resulting lithium metal batteries, such as lithium-sulfur batteries (Li-S) and lithium-oxygen batteries (Li-O 2 ), considered to be the most promising energy storage device with high energy density. However, lithium metal electrodes will generate a large number of dendrites during the charging and discharging process, which not only affects the cycle performance, but also punctures the separator, short-circuits the batt...

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Problems solved by technology

However, existing technical solutions, such as Kim et al. (Kim, et al. Controlled Lithium Dendrite Growth by a Synergistic Effect of Multilayered Graphene Coating and an Electrolyte Additive. Chem. Ma ter. 2015, 27 (8), 2780-2787.), Zhang .R et al (Zhang.R, etal.Conductive Nanostructured Scaffolds Render Low Local Current Density toInhibit Lithium Dendrite Growth.Adv.Mater.2016,28(11),2155-62.) and Zheng.G et al (Zheng. G, etal.Interconnected hollow carbon nano spheres for stable lithiummetal anodes.Nat.Nanotech.2014,9(8),618-623.), are limited to small current (≤2mA / cm 2 ) and low capacity (≤2mAh / cm 2 Li dendrite inhibition study under )

As the load and rate of the positive electrode of lithium metal batteries (such as Li-S batteries) continue to increase, the lithium metal negative electrode will face a greater current density (≥3mA / cm 2 ) and working capacity (≥3mAh / cm 2 ), relying solely on the existing modulation strategy has been unable to meet the needs of high-performance lithium metal batteries for lithium anode protection

In addition, common electrolyte additives (Ding.F, et al.Dendrite-free lithium de position via self-healing electrostatic shield mechanism.J.Am.Chem.Soc.2013,135(11),4450-6.) cannot control Nucleation to inhibit the formation of lithium dendrites at the root; and the existing scheme to control the nucleation of lithium deposition (Liu.Y, et al. Pre-planted nucleation seeds for rechargeable metallic lithiumanodes.J.Mater.Chem.A 2017, 5(35), 18862-18869.) The process is complicated, which is not conducive to scale and commercialization

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