CN114373891A - Composite Lithium Anode and Its Application - Google Patents

Abstract

The invention provides a composite lithium negative electrode and application thereof, wherein the composite lithium negative electrode comprises lithium metal and functionalized inorganic particles; the functional group of the functionalized inorganic particle comprises any one or the combination of at least two of carboxyl, carbonyl, hydroxyl, sulfydryl, aldehyde group, peptide bond, carbon-carbon double bond, carbon-carbon triple bond or nitro; the invention solves the problems of volume expansion and lithium dendritic crystal growth of lithium metal in the circulation process by adding functionalized inorganic particles in the lithium metal.

Description

Composite Lithium Anode and Its Application

technical field

The invention belongs to the technical field of batteries, and relates to a lithium negative electrode, in particular to a composite lithium negative electrode and an application thereof.

Background technique

The lithium metal negative electrode has a high theoretical specific capacity (3860mAh/g), which is ten times the theoretical specific capacity (372mAh/g) of the current commercial graphite negative electrode. Therefore, the use of lithium metal as the negative electrode of power batteries has been widely concerned.

The high reactivity of the lithium metal anode leads to a large amount of lithium consumption, which makes the lithium ion deintercalation process prone to lithium dendrite growth, which pierces the separator, and the volume expansion of the lithium anode during cycling occurs. Although lithium anodes have great potential for development, only using pure lithium metal as anodes cannot achieve long battery cycles.

Based on the above research, how to provide a composite lithium negative electrode, which can solve the problems of excessive volume expansion of lithium metal during charge and discharge cycles, and lithium dendrite growth piercing the separator.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a composite lithium negative electrode and its application, especially a composite lithium negative electrode supported by an inorganic framework and its application. Medium volume expansion, inhibiting the growth of lithium dendrites.

In order to achieve this object of the invention, the present invention adopts the following technical solutions:

In a first aspect, the present invention provides a composite lithium negative electrode, the composite lithium negative electrode includes lithium metal and functionalized inorganic particles;

The functional groups of the functionalized inorganic particles include any one or a combination of at least two of the carboxyl group, carbonyl group, hydroxyl group, thiol group, aldehyde group, peptide bond, carbon-carbon double bond, carbon-carbon triple bond or nitro group, typical but non-limiting Combinations include carboxyl and carbonyl, hydroxyl and sulfhydryl, aldehyde and carbon-carbon double bond, or carbon-carbon triple bond and nitro.

The functionalized inorganic particles of the present invention play the role of an inorganic framework in the composite lithium negative electrode. Since pure lithium metal is used as the negative electrode, during the cycle process, the lithium metal will react with the electrolyte, and a passive layer will be formed on its surface. The ionic conductivity becomes poorer and the strength becomes lower, resulting in the continuous consumption of the electrolyte, and at the same time, the interface resistance between the lithium metal and the electrolyte will become higher and higher; therefore, the application uses functionalized inorganic particles to support the lithium metal, which can It accelerates the conduction of lithium ions, improves the ion conduction rate of the composite lithium negative electrode, reduces the uneven deposition of lithium ions, improves the ability to resist the expansion of the negative electrode, and can inhibit the growth of lithium dendrites.

The bonding mechanism of the functionalized inorganic particles of the present invention and lithium metal includes: carboxyl group, carbonyl group, hydroxyl group, sulfhydryl group, aldehyde group and peptide bond can undergo substitution reaction with lithium metal, so that inorganic particles are bonded to lithium metal; carbon Carbon double bonds and carbon-carbon triple bonds will undergo addition reaction bonding with lithium metal; lithium metal and nitro groups will generate inorganic substances such as lithium nitrite or lithium nitride.

In the functionalized inorganic particles of the present invention, the number of functional groups is one or more, such as 3, 5, 10, 15, 20, 25, 30 or 35, but not limited to For the recited values, other unrecited positive integers within the numerical range also apply.

The molar ratio of any two functional groups of the functionalized inorganic particles is 1:(0.1 to 10), for example, it can be 1:0.1, 1:1, 1:5 or 1:10, but not limited to the listed numerical values, the numerical value range The same applies to other non-recited values.

The molar ratio of any three functional groups of the functionalized inorganic particles is 1:(0.1 to 10):(0.1 to 10), for example, it can be 1:0.1:0.1, 1:1:1, 1:5:10 or 1: 10:10, but not limited to the recited values, other non-recited values within the numerical range also apply.

Preferably, the Young's modulus of the functionalized inorganic particles is above 1GPa, for example, it may be 1GPa, 1.5GPa, 2GPa, 2.5GPa, 3GPa, 3.5GPa, 4GPa, 4.5Gpa, 5Gpa, 6Gpa or 8GPa, but not Limited to the recited values, other non-recited values within the range of values also apply, preferably 1 GPa to 6 GPa.

The functionalized inorganic particles of the present invention have a Young's modulus of more than 1 GPa, thereby inhibiting the growth of lithium dendrites, stabilizing lithium metal, reducing the expansion effect of the lithium negative electrode in the inorganic particle network, and inhibiting the volume expansion of the lithium negative electrode. When the Young's modulus of the functionalized inorganic particles is less than 1 GPa, it is difficult to inhibit the formation of lithium dendrites and the expansion of lithium metal.

Preferably, the ionic conductivity of the functionalized inorganic particles is 10 ^-5 S/cm to 10 ^-3 S/cm, such as 10 ^-5 S/cm, 10 ^-4 S/cm or 10 ^-3 S /cm, but not limited to the recited values, other unrecited values within the numerical range are equally applicable.

The functionalized inorganic particles of the present invention have high ionic conductivity, so as to avoid uneven deposition of lithium ions during the charge-discharge cycle, which leads to the growth of lithium dendrites.

Preferably, the particle size D ₅₀ of the functionalized inorganic particles is 100 nm to 600 nm, for example, it can be 100 nm, 200 nm, 300 nm, 400 nm, 500 nm or 600 nm, but is not limited to the listed numerical values, and other unlisted values within the numerical range The same applies to numerical values.

Preferably, the inorganic particles include silicon-based inorganic particles.

Preferably, the silicon-based inorganic particles comprise silicon dioxide and/or LiSixOy, wherein _x >0, _y >0.

The silicon-based inorganic particles include _LiSixOy , wherein _x >0, for example, may be 0.1, 0.3, 0.5, 0.7, 0.9, 1.1 or 1.3, but not limited to the listed values, and other unlisted values within the numerical range The same applies, preferably 0<x<1.

The silicon-based inorganic particles include _LiSixOy , wherein _y >0, for example, may be 0.1, 0.3, 0.5, 0.7, 0.9, 1.1 or 1.3, but not limited to the listed values, and other unlisted values within the numerical range The same applies, preferably 0<x<3.

The preparation method of the composite lithium negative electrode of the present invention comprises the following steps:

Under the condition of inert gas, lithium metal and functionalized inorganic particles are mixed to obtain the composite lithium negative electrode.

Preferably, the lithium metal is in molten state.

Preferably, the inert gas includes helium, argon, krypton or radon, with typical but non-limiting combinations including a combination of helium and argon, or a combination of krypton and radon.

Preferably, the mixing is stirring mixing.

Preferably, after the mixing is completed, the temperature is lowered to obtain the composite lithium negative electrode.

In a second aspect, the present invention provides an electrochemical device comprising the composite lithium negative electrode according to the first aspect.

Preferably, the electrochemical device comprises a lithium-ion battery.

In a third aspect, the present invention provides an electronic device comprising the electrochemical device according to the second aspect.

Compared with the prior art, the present invention has the following beneficial effects:

The invention adopts functionalized inorganic particles as the skeleton of the lithium negative electrode to improve the ion conduction rate of the composite lithium negative electrode, accelerate the conduction of lithium ions, reduce the uneven deposition of lithium ions, improve the anti-expansion ability of the negative electrode, and inhibit the formation of lithium dendrites. growth, resulting in a lithium-ion battery with excellent cycle performance.

Description of drawings

FIG. 1 is a schematic diagram of the surface state of the composite lithium negative electrode described in Example 1 after 100 cycles.

2 is a schematic diagram of the surface state of the negative electrode described in Comparative Example 2 after 100 cycles.

Detailed ways

The technical solutions of the present invention are further described below through specific embodiments. It should be understood by those skilled in the art that the embodiments are only for helping the understanding of the present invention, and should not be regarded as a specific limitation of the present invention.

The method for functionalizing inorganic particles according to the present invention includes: using inorganic particles to combine with polymers through adsorption force, hydrogen bond or covalent bond, etc., using different functional groups (including carboxyl, carbonyl, hydroxyl, mercapto, aldehyde, The silane coupling agent of peptide bond, carbon-carbon double bond, carbon-carbon triple bond or nitro neutralization or at least two combinations) can modify the surface of inorganic particles with different functional groups in an acidic or alkaline environment, The functionalized inorganic particles are obtained; the present invention does not specifically limit the modification method, as long as the inorganic particles can be modified with functional groups; the above description of the method for functionalized inorganic particles is for the purpose of more completely explaining the present invention. The technical solution should not be regarded as a specific limitation to the present invention.

Example 1

This embodiment provides a composite lithium negative electrode, the lithium negative electrode includes lithium metal and functionalized silica;

The functionalized silica is a silica functionalized with a carboxyl group, a carbonyl group and a hydroxyl group, and the molar ratio of the carboxyl group, the carbonyl group and the hydroxyl group is 1:1:1;

The Young's modulus of the functionalized silica is 2.9 GPa, the ionic conductivity is 2.4×10 ^-4 S/cm, and the particle size D ₅₀ is 300 nm;

The preparation method of the composite lithium negative electrode comprises the following steps:

In an argon atmosphere, the molten lithium metal and the functionalized silica are stirred and mixed, and the composite lithium negative electrode is obtained after cooling.

The schematic diagram of the surface state of the composite lithium negative electrode described in this embodiment after 100 cycles is shown in FIG. 1 .

Example 2

This embodiment provides a composite lithium negative electrode, the lithium negative electrode includes lithium metal and functionalized silica;

The functionalized silica is a functionalized silica using carbon-carbon double bonds and nitro groups, and the molar ratio of the carbon-carbon double bonds and nitro groups is 1:3;

The Young's modulus of the functionalized silica is 2GPa, the ionic conductivity is 1.1×10 ^-4 S/cm, and the particle size _D50 is 100nm;

The preparation method of the composite lithium negative electrode comprises the following steps:

In an argon atmosphere, the molten lithium metal and the functionalized silica are stirred and mixed, and the composite lithium negative electrode is obtained after cooling.

Example 3

This embodiment provides a composite lithium negative electrode, the lithium negative electrode includes lithium metal and functionalized silica;

The functionalized silica is a functionalized silica using a carbon-carbon triple bond and an aldehyde group, and the molar ratio of the carbon-carbon triple bond and the aldehyde group is 1:10;

The Young's modulus of the functionalized silica is 1.2 GPa, the ionic conductivity is 1.3×10 ^-4 S/cm, and the particle size D ₅₀ is 600 nm;

The preparation method of the composite lithium negative electrode comprises the following steps:

Under a helium atmosphere, the molten lithium metal and the functionalized silica are stirred and mixed, and the composite lithium negative electrode is obtained after cooling.

Example 4 and Example 5 are the same as Example 1 except that the types of functionalized inorganic particles are changed as shown in Table 2.

Example 6 and Example 7 are the same as Example 1 except that the functionalized inorganic particles with Young's modulus shown in Table 3 are used.

Example 8 and Example 9 are the same as Example 1 except that the ionic conductivity of the functionalized inorganic particles is changed as shown in Table 4.

Comparative Example 1 is the same as Example 1 except that as shown in Table 5, silica without functional grouping is used.

In Comparative Example 2, pure lithium metal was used as the negative electrode, and the schematic diagram of the surface state after 100 cycles is shown in Figure 2.

Performance Testing:

The composite lithium negative electrode provided in the above-mentioned embodiment and the negative electrode provided in the comparative example are assembled with the positive electrode, the separator, and the electrolyte to form a lithium ion battery according to the general process for preparing lithium ion batteries; wherein, the positive electrode is coated with the positive electrode slurry on the aluminum foil. and drying, the positive electrode slurry includes LNCM (LiNi _0.8 Co _0.1 Mn _0.1 O ₂ ), acetylene black, polyvinylidene fluoride and N-methylpyrrolidone with a mass ratio of 95:3:2:50; Polypropylene microporous membrane (Celgard-2400); the electrolyte adopts 1mol/L LiPF ₆ /EC+DMC+EMC (EC is ethylene carbonate, EMC is ethyl methyl carbonate, DMC is dimethyl carbonate, EC, DMC and EMC in a volume ratio of 1:1:1).

The above assembled lithium-ion batteries were tested for cycle performance, as well as for ionic conductivity and Young's modulus after cycling.

Test of cycle performance: At 25°C, using the battery performance test system (BTS05/10C8D-HP) of Shenghong Electric Co., Ltd., the above-mentioned lithium-ion battery was discharged at 1C/1C. Divide by the discharge capacity of the first cycle to obtain the 100 cycle retention rate.

Ionic conductivity test after cycling: Ionic conductivity test by AC impedance method.

Young's modulus test after cycling: The test was performed using a nanoindenter (Nano Indenter XP, Keysight Technologies).

The test results are shown in Table 1 to Table 5:

Table 1

Table 2

table 3

Table 4

table 5

The following points can be seen from Table 1:

(1) It can be seen from Example 1 and Examples 6 to 7 that when the Young's modulus of the functionalized inorganic particles gradually decreases, the cycle performance of the provided composite lithium negative electrode gradually decreases, and when it is less than 1 GPa, it is difficult to achieve The effect of inhibiting lithium dendrites piercing the separator and inhibiting the expansion of lithium negative electrodes; it can be seen that when the functionalized inorganic particles of the present invention have a Young's modulus of 1 GPa or more, the growth of lithium dendrites can be inhibited, and lithium metal can be stabilized. Reduce the swelling effect of lithium anode in inorganic particle network.

(2) It can be seen from Example 1 and Examples 8 to 9 that when the ionic conductivity of the functionalized inorganic particles gradually decreases, the cycle performance of the provided composite lithium negative electrode also decreases gradually. When the ionic conductivity is less than 10 ^-5 S /cm, it is difficult to achieve the purpose of inhibiting the growth of lithium dendrites; it can be seen that the functionalized inorganic particles of the present invention have high ionic conductivity, so as to avoid uneven deposition of lithium ions during the charge-discharge cycle. A phenomenon that leads to the growth of lithium dendrites.

(3) It can be seen from Example 1 and Comparative Example 1 that in the lithium negative electrode of Comparative Example 1, the inorganic particles are not functionalized, so the lithium metal cannot be bonded to the inorganic particles, so that it cannot play a skeleton role, nor can it be modified. A good inhibition of the expansion of the lithium negative electrode can significantly reduce the cycle performance of the lithium-ion battery.

(4) It can be seen from Example 1 and Comparative Example 2 that the comparative example uses pure lithium metal as the negative electrode, and its cycle performance is significantly reduced. It can be seen from Figure 1 and Figure 2 that there are obvious lithium branches on the surface of the lithium negative electrode in Comparative Example 2. However, in Example 1, since the composite lithium negative electrode is used, there is no obvious lithium dendrite formation on the surface after the cycle; it can be seen that the composite lithium negative electrode of the present invention can suppress the formation of lithium dendrites and reduce the expansion of lithium metal negative electrode. , to improve the cycle performance of lithium-ion batteries.

In summary, the present invention provides a composite lithium negative electrode and its application, which can solve the problems of volume expansion of lithium metal and growth of lithium dendrites during cycling through the composite of lithium metal and functionalized inorganic particles.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any person skilled in the art is within the technical scope disclosed by the present invention, Changes or substitutions that can be easily conceived fall within the scope of protection and disclosure of the present invention.

Claims (10)

1. A composite lithium negative electrode, characterized in that the composite lithium negative electrode comprises lithium metal, and functionalized inorganic particles; The functional groups of the functionalized inorganic particles include any one or a combination of at least two of a carboxyl group, a carbonyl group, a hydroxyl group, a thiol group, an aldehyde group, a peptide bond, a carbon-carbon double bond, a carbon-carbon triple bond, or a nitro group. 2 . The composite lithium negative electrode according to claim 1 , wherein the Young's modulus of the functionalized inorganic particles is 1 GPa or more. 3 . 3 . The composite lithium negative electrode according to claim 2 , wherein the Young's modulus of the functionalized inorganic particles is 1 GPa to 6 GPa. 4 . 4 . The composite lithium negative electrode according to claim 3 , wherein the ionic conductivity of the functionalized inorganic particles is 10 ^-5 S/cm to 10 ^-3 S/cm. 5 . 5 . The composite lithium negative electrode according to claim 1 , wherein the particle size D ₅₀ of the functionalized inorganic particles is 100 nm to 600 nm. 6 . 6 . The composite lithium negative electrode according to claim 4 , wherein the inorganic particles comprise silicon-based inorganic particles. 7 . 7 . The composite lithium negative electrode according to claim 6 , wherein the silicon-based inorganic particles comprise silicon dioxide and/or LiSixOy, wherein _x >0 and _y >0. 8 . 8 . The composite lithium negative electrode according to claim 7 , wherein the silicon-based inorganic particles comprise LiSixOy, wherein 0< _x <1, 0< _y <3. 9 . 9 . An electrochemical device, characterized in that, the electrochemical device comprises the composite lithium negative electrode according to any one of claims 1 to 8 . 10 . 10 . An electronic device, wherein the electronic device comprises the electrochemical device of claim 9 . 11 .

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