Alkali metal composite negative electrode material and preparation method thereof

Abstract

The invention discloses an alkali metal composite negative electrode material and a preparation method thereof. The alkali metal composite negative electrode material comprises a carbon-based materialand alkali metal loaded on the carbon-based material, wherein the surface of the carbon-based material is coated with an affinity substance. The preparation method comprises the following steps of: (1) preparing a modification solution, and adding the carbon-based material into the modification solution to be heated and infiltrated, wherein the modification solution is one of a soluble zinc saltsolution, a soluble copper salt solution, a soluble silver salt solution, a soluble gold salt solution and a soluble compound solution containing nitrogen and phosphorus elements; (2) calcining the infiltrated carbon-based material to obtain a carbon-based material of which the surface is coated with the affinity substance; and (3) loading alkali metal on the surface of the carbon-based material of which the surface is coated with the affinity substance to obtain the alkali metal composite negative electrode material. The alkali metal composite negative electrode material disclosed by the invention is good in electrochemical performance, long in cycle life and small in overpotential; and the preparation method is simple to operate and easy to implement.

Description

technical field [0001] The invention belongs to the field of negative electrode materials for batteries, and in particular relates to an alkali metal composite negative electrode material and a preparation method thereof. Background technique [0002] Due to its high theoretical discharge capacity (3860mAh / g) and lowest potential (-3.040Vvs. standard hydrogen electrode), lithium metal is expected to become the most ideal anode material for lithium-ion batteries in the next generation. When metal lithium is used as the negative electrode of Li / S battery and Li-O2 battery, its energy density is expected to reach 650Wh / kg and 950Wh / kg respectively, which is 2 to 3 times the energy density of commercialized lithium-ion batteries. Broad prospects. [0003] However, in the actual application of batteries with lithium metal as the negative electrode, the following problems often exist: [0004] (1) During the charging and discharging process of lithium metal batteries, due to the...

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Problems solved by technology

[0004] (1) During the charging and discharging process of lithium metal batteries, due to the uneven reaction on the surface of the lithium negative electrode, dendrites are easily generated, which triggers the growth of lithium dendrites, which will not only induce the thickening of the SEI film but even lead to the formation of "dead lithium", causing the battery Impedance and overpotential increase, Coulombic efficiency fluctuations and declines seriously affect the electrochemical performance of lithium metal batteries; what's more, there will be a risk of piercing the separator, causing battery short circuit, bringing irreversible capacity loss and safety hazards

[0005] (2) During the cycle, metal lithium is also accompanied by almost unlimited volume expansion, which also leads to the extreme instability of the surface SEI film, which further aggravates the formation of metal lithium dendrites.

This infinite volume expansion due to dendrite formation greatly limits the practical application of lithium metal anodes.

[0006] (3) Lithium metal has high reactivity, and it is easy to react with the electrolyte to form an interface film, which consumes the electrolyte and lithium metal, resulting in low utilization of lithium and low coulombic efficiency of the battery

[0007] (4) The interfacial film is unstable. The interfacial film formed by metal lithium and electrolyte dendrites is relatively fragile, and it is prone to rupture during charging and discharging, and continues to consume exposed fresh lithium; at the same time, the composition of the interfacial film is not evenly distributed. It leads to the difference in lithium ion transmission coefficient, and it is easy to form a local excessive lithium ion concentration on the electrode surface, which promotes the growth of dendrites and reduces the coulombic efficiency and stability of the battery.

This technical scheme adopts the melting method to deposit the alkali metal on the carbon cloth to obtain the alkali metal composite negative electrode, but the affinity of the carbon cloth to metal lithium is poor, and the alkali metal is difficult to deposit on the surface and the gap of the carbon cloth fiber, resulting in charging and discharging. In the process, the control effect of the uniformity of the surface reaction of the negative electrode is poor, and the effect of inhibiting lithium dendrites is not ideal

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