Hierarchical structure glass fiber and lithium metal compound and preparation method thereof

Abstract

The invention discloses a hierarchical structure glass fiber and lithium metal compound and a preparation method thereof, and relates to the technical field of battery cathodes. The hierarchical structure glass fiber and lithium metal compound comprises a lithium layer, a glass fiber layer is arranged in the lithium layer, and the bottom end of the glass fiber layer is completely wrapped in the lithium layer. The top end of the glass fiber layer is exposed outside the lithium layer, conductive layers are arranged on the middle and lower surfaces of glass fibers, and the upper ends of the glassfibers are exposed. The conductive layers have lithium affinity and electronic conductivity, and the exposed top end of the glass fiber layer has no electronic or ionic conductivity. The deposited lithium ions can only obtain the electrons on the glass fiber with a modification layer on the surface of a composite electrode, and cannot obtain the electrons at the topmost end of the glass fibers, so that the lithium dendrites and dead lithium exceeding the thickness of the glass fiber on the surface cannot be formed, the overall thickness of the electrode is controllable, and the battery safetyis high. The surface of the topmost end of the glass fiber is electronically insulated, and battery short circuit cannot be caused after a diaphragm is attached in the battery. The metal lithium at the lower half part of the glass fiber is responsible for supplementing a lithium source, so that the battery cycle performance is guaranteed.

Description

technical field [0001] The invention relates to the technical field of negative electrodes of lithium batteries, and more particularly, to a composite of graded structure glass fiber and metal lithium and a preparation method thereof. Background technique [0002] Compared with the graphite anodes currently used commercially in Li-ion batteries, Li metal anodes can theoretically provide more capacity (3860mAh / g, graphite anodes: 372mAh / g) and the most negative potentials (-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 with lithium metal 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 anode, the most important one is the growth o...

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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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