CN108448106B

CN108448106B - Preparation method of modified lithium metal negative electrode

Info

Publication number: CN108448106B
Application number: CN201810213657.4A
Authority: CN
Inventors: 朱业; 程君; 王玉虎
Original assignee: Shanghai Lixin Energy Technology Co ltd
Current assignee: Lixin Jiangsu Energy Technology Co ltd
Priority date: 2018-03-15
Filing date: 2018-03-15
Publication date: 2021-04-20
Anticipated expiration: 2038-03-15
Also published as: CN108448106A

Abstract

The invention discloses a preparation method of a modified lithium metal cathode, which comprises the steps of oxidizing metal lithium for 0.5-2h in a gas atmosphere, and reacting the metal lithium with steam flow of a silane coupling agent and silicate ester for 4-16h at the temperature of 60-200 ℃; finally heating the lithium metal anode for 0.5 to 2 hours at the temperature of between 60 and 200 ℃ to obtain the modified lithium metal anode. Compared with the prior art, the method has the following advantages: the preparation process is simple, the material cost is low, the formation and growth of lithium dendrites are effectively inhibited, the safety of the battery is enhanced, and the probability of potential safety hazards is reduced; the prepared modified lithium metal negative electrode has the advantages of long cycle and high stability; compared with a lithium-sulfur full battery prepared from a sulfur positive electrode, the lithium-sulfur full battery has longer service life and more stable cycle compared with an unmodified lithium metal negative electrode.

Description

Preparation method of modified lithium metal negative electrode

Technical Field

The invention relates to the field of lithium metal electrodes, in particular to a preparation method of a modified lithium metal negative electrode.

Background

In recent years, with the rapid development of portable electronic devices, electric vehicles and power grid energy storage technologies, the demand of batteries and energy storage systems with high energy density and high safety is more and more urgent. Among the electrochemical energy storage devices that have been commercialized, lithium ion batteries have become the best choice because of their high energy density and long cycle life. However, due to the limitation of electrode materials, the work of increasing the energy density of lithium ion batteries has been progressing slowly in recent years. Graphite is the most widely used lithium ion battery cathode material at present, the theoretical capacity of graphite is only 372mAh/g, and the demand of people on the high energy density lithium ion battery is more and more difficult to meet. Compared with a graphite cathode, the theoretical capacity of the lithium metal cathode is obviously higher, the lithium metal cathode reaches 3860mAh/g, and meanwhile, the lithium metal electrode has the most negative potential which reaches-3.040V vs. standard hydrogen electrode, so that the lithium battery using the lithium metal cathode is expected to be applied in the next generation electrochemical energy storage field on a large scale.

However, there are still many problems to be overcome in order to completely replace the graphite negative electrode with the lithium metal negative electrode, and the problem of inhibiting the formation and growth of lithium dendrites in the lithium metal negative electrode is always difficult to solve. The formation and growth of lithium dendrites mainly pose the following two hazards: firstly, the lithium dendrites can pierce through a diaphragm, so that the internal short circuit of the battery is caused, and a serious potential safety hazard is formed; secondly, the formation and growth of lithium dendrites can lead to the increase of the contact area between the electrolyte and the lithium metal, the lithium dendrites continuously grow, the electrolyte is continuously decomposed, and the coulomb efficiency and the cycle life of the lithium battery are rapidly reduced.

How to prepare a safe and reliable lithium metal cathode and effectively inhibit the formation and growth of lithium dendrites is worthy of research.

Disclosure of Invention

The purpose of the invention is as follows: in order to overcome the defects in the prior art, the invention provides a preparation method of a modified lithium metal negative electrode, which can effectively inhibit the formation and growth of lithium dendrites and improve the safety of a battery.

The technical scheme is as follows: in order to solve the technical problems, the technical scheme adopted by the invention is as follows: a preparation method of a modified lithium metal negative electrode comprises the following steps:

(1) oxidizing metal lithium at room temperature for 0.5-2h in a gas atmosphere to obtain a substance A;

(2) reacting the substance A with steam flow of silane coupling agent and silicate ester for 4-16h at 60-200 ℃;

(3) and (3) heating the reaction product obtained in the step (2) at the temperature of 60-200 ℃ for 0.5-2h to obtain the modified lithium metal negative electrode.

Furthermore, the metallic lithium in the step (1) is present in the form of one or more of lithium sheet, lithium ribbon, lithium rod, lithium particle and lithium powder.

The gas atmosphere in the step (1) is gas with oxygen volume concentration of 20-100%; the oxidation effect is optimal at this oxygen concentration.

More preferably, in the step (2), the substance a is one or a mixture of several of metallic lithium, lithium oxide, lithium peroxide, lithium hydroxide and lithium carbonate.

Furthermore, the silicate in the step (2) is one or a mixture of methyl silicate, ethyl orthosilicate, propyl orthosilicate, butyl orthosilicate and methyl triethoxysilane.

More preferably, the silane coupling agent in step (2) is a compound represented by formula (I):

wherein, X is selected from one of halogen group, substituted or unsubstituted C1-C10 alkoxy and substituted or unsubstituted C1-C10 acyloxy, and Y is selected from one of mercapto and substituted or unsubstituted C1-C20 mercaptoalkyl.

In order to obtain the best quality of the finished product, the volume ratio of the silane coupling agent to the silicate ester in the steam flow is 0.25:1-4: 1.

Has the advantages that: the preparation method of the modified lithium metal negative electrode provided by the invention has the following advantages: the preparation process is simple, the material cost is low, the formation and growth of lithium dendrites are effectively inhibited, the safety of the battery is enhanced, and the probability of potential safety hazards is reduced; the prepared modified lithium metal negative electrode has the advantages of long cycle and high stability; compared with a lithium-sulfur full battery prepared from a sulfur positive electrode, the lithium-sulfur full battery has longer service life and more stable cycle compared with an unmodified lithium metal negative electrode.

Drawings

FIG. 1 is a SEM diagram of a modified lithium metal negative electrode prepared in example 1;

FIG. 2 is a SEM illustration of an unmodified lithium metal negative electrode of comparative example 1;

fig. 3 is a schematic diagram showing the cycle test results of the button cell prepared in example 1 and comparative example 1.

Detailed Description

The present invention will be described in further detail with reference to the following examples:

example 1:

a preparation method of a modified lithium metal negative electrode comprises the following steps:

(1) oxidizing the metal lithium sheet for 0.5h at room temperature in the atmosphere of pure oxygen gas to obtain a substance A;

(2) reacting the substance A with steam flow of gamma-mercaptopropyltrimethoxysilane and butyl orthosilicate in a volume ratio of 1:1 at 100 ℃ for 4 hours;

(3) and (3) heating the reaction product obtained in the step (2) at 120 ℃ for 0.5h to obtain the modified lithium metal cathode.

Example 2:

(1) oxidizing metal lithium powder for 2 hours at room temperature in the air atmosphere to obtain a substance A;

(2) reacting the substance A with steam flow of gamma-mercaptopropyltrimethoxysilane and tetraethoxysilane in a volume ratio of 1:2 at 150 ℃ for 8 hours;

(3) and (3) heating the reaction product obtained in the step (2) at 100 ℃ for 1h to obtain the modified lithium metal negative electrode.

Example 3:

(1) oxidizing a metal lithium belt for 1h in an atmosphere with a volume ratio of nitrogen to oxygen of 1:1 to obtain a substance A;

(2) reacting the substance A with steam flow of gamma-mercaptopropyltrimethoxysilane and methyltriethoxysilane in a volume ratio of 2:1 at 200 ℃ for 12 hours;

(3) and (3) heating the reaction product obtained in the step (2) at 80 ℃ for 2h to obtain the modified lithium metal negative electrode.

Example 4:

(1) oxidizing the metal lithium particles for 1h in the air to obtain a substance A;

(2) reacting the substance A with steam flow of gamma-mercaptopropyltrimethoxysilane and methyl silicate in a volume ratio of 4:1 at 60 ℃ for 16 hours;

(3) and (3) heating the reaction product obtained in the step (2) at 150 ℃ for 1h to obtain the modified lithium metal negative electrode.

Example 5:

(1) oxidizing a metal lithium rod for 1h in the air to obtain a substance A;

(2) reacting the substance A with gamma-mercaptopropyltrimethoxysilane, ethyl orthosilicate and butyl orthosilicate for 10 hours at 100 ℃ in steam flow with the volume ratio of 1:1: 1;

(3) and (3) heating the reaction product obtained in the step (2) at 100 ℃ for 0.8h to obtain the modified lithium metal cathode.

Comparative example 1:

unmodified lithium metal negative electrodes were tested using commercially available commercial, 100 g/can lithium metal sheets of phi 15.6 x 1.00 mm.

(1) SEM image comparison:

referring to fig. 1-2, fig. 1 is an SEM picture of a modified lithium metal negative electrode prepared in example 1 of the present invention, and fig. 2 is a comparison result, which shows that, compared with an unmodified lithium negative electrode, the modified lithium negative electrode has a significant silicon grain layer on the surface thereof, and the silicon grain layer can effectively restrict the formation of lithium dendrites, thereby effectively enhancing the cycle stability of the lithium negative electrode.

(2) Battery assembly performance test

Assembling a CR2016 button cell, namely preparing a lithium-sulfur cell positive electrode by using a sulfur/activated carbon composite material (sulfur load is 70%), acetylene black and polyvinylidene fluoride according to a mass ratio of 7:2:1, taking 1mol/L lithium bistrifluoromethanesulfonylimide as a lithium salt, taking 1, 3-dioxolane and dimethyl ether according to a volume ratio of 1:1 as solutes, adding 1% by mass of lithium nitrate electrolyte, taking Cellgard 2400 as a diaphragm, and simultaneously taking the embodiment 1 and the comparative example 1 as button cell negative electrodes. The assembled lithium-sulfur button cells were cycled at 0.5C (1C 1675mAh/g) rate with comparative data as shown in fig. 3.

As can be seen from fig. 3, after 200 cycles, the capacity of the lithium-sulfur battery made of the unmodified lithium metal negative electrode is attenuated by about 54%, while the capacity of the lithium-sulfur battery made of the modified lithium metal negative electrode is attenuated by only 14%, and the modified lithium metal negative electrode prepared by the preparation method of the modified lithium metal negative electrode has the advantages of long cycle and high stability; compared with a lithium-sulfur full battery prepared from a sulfur positive electrode, the lithium-sulfur full battery has longer service life and more stable cycle compared with an unmodified lithium metal negative electrode.

It should be noted that the above-mentioned embodiments illustrate rather than limit the scope of the invention, and that those skilled in the art will be able to modify the invention in its various equivalent forms after reading the present disclosure without departing from the scope of the invention as defined by the appended claims.

Claims

1. A preparation method of a modified lithium metal negative electrode is characterized by comprising the following steps:

(1) oxidizing metal lithium at room temperature for 0.5-2h in a gas atmosphere to obtain a substance A; the gas atmosphere is gas with oxygen volume concentration of 20-100%; the existing form of the metal lithium is one or a mixture of a plurality of lithium sheets, lithium strips, lithium rods, lithium particles and lithium powder;

(2) reacting the substance A with steam flow of silane coupling agent and silicate ester for 4-16h at 60-200 ℃; the volume ratio of the silane coupling agent to the silicate ester in the vapor stream is 0.25:1 to 4: 1; the substance A is one or a mixture of more of lithium oxide, lithium peroxide, lithium hydroxide and lithium carbonate; the silicate is one or a mixture of methyl silicate, ethyl orthosilicate, propyl orthosilicate and butyl orthosilicate; the silane coupling agent is a compound shown as a formula (I):

（I）

wherein, X is selected from one of halogen group, substituted or unsubstituted C1-C10 alkoxy and substituted or unsubstituted C1-C10 acyloxy, and Y is selected from one of mercapto and substituted or unsubstituted C1-C20 mercaptoalkyl;