A kind of composite of graded structure glass fiber and metal lithium and preparation method thereof

Abstract

The invention discloses a composite of hierarchical structure glass fiber and lithium metal and a preparation method thereof, and relates to the technical field of negative electrodes of batteries. Covered in the lithium layer, the top is exposed on the outside of the lithium layer, the middle and lower surfaces of the glass fiber are provided with a conductive layer, and the upper end is exposed. The conductive layer has lithium affinity and electronic conductivity, and the exposed top of the glass fiber layer has no electrons or ionic conductivity. The deposited lithium ions can only obtain electrons on the glass fiber with a modified layer on the surface of the composite electrode, and cannot obtain electrons at the top of the glass fiber, so as not to form lithium dendrites and dead lithium exceeding the thickness of the surface glass fiber, making the electrode overall The thickness is controllable and the battery safety is high. The top surface of the glass fiber is electronically insulated, and will not cause a short circuit in the battery after the separator is attached to the battery. The metal lithium in the lower half of the glass fiber is responsible for supplementing the lithium source, and the battery cycle performance is guaranteed.

Description

technical field [0001] The invention relates to the technical field of lithium battery negative electrodes, more specifically, it relates to a composite of hierarchical glass fiber and lithium metal and a preparation method thereof. Background technique [0002] Compared with graphite anodes currently commercially used in lithium-ion batteries, lithium metal anodes can theoretically provide more capacity (3860mAh / g, graphite anode: 372mAh / g) and the most negative potential (-3 .040V vs . Standard hydrogen electrode), is expected to achieve greater applications in the next generation of portable electronic devices and electric vehicles. Lithium-sulfur batteries and lithium-air batteries using metallic lithium as the negative electrode have gradually attracted the attention of researchers, and have become a hot spot in academic and industrial research in recent years. However, there are still many problems in the research of lithium metal anodes, the most important of which i...

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Problems solved by technology

[0003]Dendrite growth will cause three problems: (1) Dendrites will pierce the separator and cause a short circuit in the battery, and the short-circuit current inside the positive and negative electrodes is inside the battery Heat generation will cause thermal runaway of the battery system, which will lead to a series of safety issues such as battery fire or even explosion; (2) dendrites will increase the side reaction between the electrolyte and lithium metal, consume lithium active materials, and reduce battery utilization; (3) When depositing / stripping lithium, there is a large volume deformation for the thin metal lithium negative electrode, which makes the battery negative electrode as a whole in an uncontrollable dynamic change, which will cause the battery cycle capacity to decline

Because when the lithium ions of the counter electrode are deposited on the negative electrode, (1) the surface of the negative electrode undergoing bulk phase three-dimensional skeleton modification has no space for the deposited metal lithium layer, and lithium dendrites will preferentially nucleate on the lithium surface, especially at high current densities Even if there is some space, in the middle and late steps of the deposition process, preferential deposition may be carried out on special sites on the lithium surface, such as the skeleton position, and continuous and uniform deposition cannot be carried out.

(2) The negative electrode modified with the surface three-dimensional skeleton does not have a hierarchical structure. When the three-dimensional skeleton is a non-electronic conductor, lithium ions need to pass through the skeleton to reach the metal lithium surface, and the diffusion path is long, resulting in an exchange current on the electrode surface. Small density, high polarization, easy to form non-uniform deposition; when the three-dimensional framework is an electronic conductor, metal lithium has no preferential nucleation tendency, and it is very likely to preferentially deposit on the surface of the three-dimensional framework to form lithium dendrites

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