Three-dimensional lithium alloy negative electrode for long-circulation low-expansion-force high-specific-energy battery

Abstract

A preparation method of the three-dimensional lithium alloy negative electrode for the high-specific-energy battery comprises the following steps that S1, a certain amount of solute is taken and dissolved in a first solvent, and etching liquid is obtained; s2, soaking the lithium alloy pole piece in an etching solution; and S3, taking out the etched lithium alloy pole piece, washing with a second solvent, and drying to obtain the three-dimensional lithium alloy negative electrode, the lithium battery has the advantages that more space is provided for lithium storage, volume expansion is effectively relieved, and growth of lithium dendrites is inhibited, so that the cycle life of the battery is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium batteries, and in particular relates to a three-dimensional lithium alloy negative electrode for a high specific energy battery with a long cycle and low expansion force. Background Art

[0002] As the demand for energy storage continues to grow, traditional battery materials have gradually failed to meet market demand in terms of energy density, cycle stability and safety. Lithium metal is regarded as an ideal negative electrode material for the next generation of high energy density batteries due to its extremely high theoretical capacity and lowest electrochemical potential. However, lithium metal has serious problems such as volume expansion and lithium dendrite growth during the charging and discharging process, which seriously restrict the practical application of lithium metal batteries.

[0003] In order to overcome these challenges, the inventors began to explore various new lithium negative electrode materials and accidentally discovered that three-dimensional porous lithium alloys have unique structural advantages, which can effectively alleviate the volume expansion during lithium deposition and provide three-dimensional structural support for the electrode after delithiation, thereby improving the stability of the electrode structure. The large-area three-dimensional porous structure can significantly reduce the local current density, inhibit the growth of lithium dendrites, and extend the service life of the battery. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a three-dimensional lithium alloy negative electrode for a high-energy-density battery with a long cycle and low expansion force, which provides more space for the storage of lithium, effectively alleviates volume expansion and inhibits the growth of lithium dendrites, thereby improving the battery cycle life.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a method for preparing a three-dimensional lithium alloy negative electrode for a high specific energy battery with a long cycle and low expansion force, comprising the following steps:

[0006] S1, taking a certain amount of solute and dissolving it in a first solvent to obtain an etching solution;

[0007] S2, immersing the lithium alloy electrode in an etching solution;

[0008] S3, taking out the etched lithium alloy electrode sheet, washing it with a second solvent, and drying it to obtain a three-dimensional lithium alloy negative electrode.

[0009] Preferably, in step S1, the solute is naphthol, iodic acid, K 2 ZF 6 , bromic acid, lithium nitrate or a mixture of at least two of them.

[0010] Preferably, in step S1, the first solvent is one of DMF, DMSO, DME, THF, G4, and G2, or a mixture of at least two of them.

[0011] Preferably, in step S1, the content of the solute is 0.02-5 mol / L.

[0012] Preferably, in step S2, the soaking time is 5-30 min and the soaking temperature is 20-30°C.

[0013] Preferably, in step S3, the second solvent is one of DMC, n-heptane and DME.

[0014] And a three-dimensional lithium alloy negative electrode for a high-energy-density battery with a long cycle and low expansion force, which is prepared by the preparation method of the three-dimensional lithium alloy negative electrode for a high-energy-density battery with a long cycle and low expansion force.

[0015] Compared with the prior art, the advantages of the present invention are:

[0016] 1. The three-dimensional lithium alloy negative electrode of the high-energy-density battery is etched to form a three-dimensional porous structure. The three-dimensional porous structure can alleviate the volume expansion during lithium deposition and provide three-dimensional structural support for the electrode after lithium removal, thereby improving the stability of the electrode structure, preventing the lithium alloy negative electrode from pulverizing during long-term operation, achieving excellent cycle stability, and helping to extend the service life of the battery;

[0017] 2. The three-dimensional lithium alloy negative electrode for the high specific energy battery has a three-dimensional porous structure with a large specific surface area, which can significantly reduce the local current density, provide uniformly distributed lithium nucleation sites, and improve the uniformity of lithium deposition, thereby effectively inhibiting the growth of lithium dendrites;

[0018] 3. The preparation method of the three-dimensional lithium alloy negative electrode for the high specific energy battery is simple and easy to operate. The obtained three-dimensional lithium alloy negative electrode has good consistency and is convenient for mass production;

[0019] 4. Compared with conventional powder metallurgy methods, the cost is lower. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the expansion change of the soft-pack battery composed of Example 3 and Comparative Example 1. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0022] Example:

[0023] A method for preparing a three-dimensional lithium alloy negative electrode for a high specific energy battery with a long cycle and low expansion force comprises the following steps:

[0024] S1, taking a certain amount of solute and dissolving it in the first solvent to obtain an etching solution with a solute content of 0.02-5 mol / L;

[0025] S2, immersing the lithium alloy electrode in the etching solution for 5-30 minutes at a temperature of 20-30°C;

[0026] S3, taking out the etched lithium alloy electrode sheet, washing it with a second solvent, and drying it to obtain a three-dimensional lithium alloy negative electrode.

[0027] In step S1, the solutes are naphthol, iodic acid, K 2 ZF 6 , bromic acid, lithium nitrate, or a mixture of at least two thereof; the first solvent is one of DMF (N,N-dimethylformamide), DMSO (dimethyl sulfoxide), DME (dimethyl ether), THF (tetrahydrofuran), G4 (tetraethylene glycol dimethyl ether), and G2 (diethylene glycol dimethyl ether), or a mixture of at least two thereof.

[0028] In step S3, the second solvent is one of DMC (dimethyl carbonate), n-heptane, and DME (dimethyl ether), and the washing times are preferably three times, and then dried.

[0029] Embodiment 1,

[0030] A method for preparing a three-dimensional lithium alloy negative electrode for a high specific energy battery with a long cycle and low expansion force comprises the following steps:

[0031] S1. Take a certain amount of K 2 ZF 6 The solute is dissolved in DMF solvent to obtain an etching solution with a solute content of 0.0706 mol / L;

[0032] S2, immersing the Li-30B lithium alloy electrode in the etching solution for 8 minutes at a temperature of 25°C;

[0033] S3. Take out the etched Li-30B lithium alloy electrode, rinse it three times with n-heptane solvent, and obtain a three-dimensional lithium alloy negative electrode after drying.

[0034] Embodiment 2,

[0035] A method for preparing a three-dimensional lithium alloy negative electrode for a high specific energy battery with a long cycle and low expansion force comprises the following steps:

[0036] S1. Take a certain amount of iodic acid and dissolve it in DMSO solvent to obtain an etching solution with a solute content of 0.025 mol / L;

[0037] S2, immersing the Li-30B lithium alloy electrode in the etching solution for 8 minutes at a temperature of 25°C;

[0038] S3. Take out the etched Li-30B lithium alloy electrode, rinse it three times with DMSO solvent, and obtain a three-dimensional lithium alloy negative electrode after drying.

[0039] Embodiment 3,

[0040] A method for preparing a three-dimensional lithium alloy negative electrode for a high specific energy battery with a long cycle and low expansion force comprises the following steps:

[0041] S1, taking a certain amount of naphthol and dissolving it in DME solvent to obtain an etching solution with a solute content of 2 mol / L;

[0042] S2, immersing the Li-30B lithium alloy electrode in the etching solution for 8 minutes at a temperature of 25°C;

[0043] S3. Take out the etched Li-30B lithium alloy electrode, rinse it three times with DME solvent, and obtain a three-dimensional lithium alloy negative electrode after drying.

[0044] Embodiment 4,

[0045] The rest is the same as Example 1, except that the solute content is 0.02 mol / L.

[0046] Embodiment 5,

[0047] The rest is the same as Example 1, except that the solute content is 0.5 mol / L.

[0048] Embodiment 6,

[0049] The rest is the same as in Example 1, except that the soaking time is 5 min.

[0050] Embodiment 7,

[0051] The rest is the same as in Example 1, except that the soaking time is 30 min.

[0052] Embodiment 8,

[0053] The rest is the same as in Example 1, except that the soaking temperature is 20°C.

[0054] Embodiment 9,

[0055] The rest is the same as in Example 1, except that the soaking temperature is 30°C.

[0056] Embodiment 10

[0057] The rest is the same as Example 2, except that the solute content is 0.02 mol / L.

[0058] Embodiment 11,

[0059] The rest is the same as Example 2, except that the solute content is 0.5 mol / L.

[0060] Embodiment 12

[0061] The rest is the same as in Example 2, except that the soaking time is 5 min.

[0062] Embodiment 13

[0063] The rest is the same as in Example 2, except that the soaking time is 30 min.

[0064] Embodiment 14

[0065] The rest is the same as in Example 2, except that the soaking temperature is 20°C.

[0066] Embodiment 15

[0067] The rest is the same as in Example 2, except that the soaking temperature is 30°C.

[0068] Example 16

[0069] The rest is the same as Example 3, except that the solute content is 0.02 mol / L.

[0070] Embodiment 17

[0071] The rest is the same as Example 3, except that the solute content is 5 mol / L.

[0072] Embodiment 18

[0073] The rest is the same as in Example 3, except that the soaking time is 5 min.

[0074] Embodiment 19,

[0075] The rest is the same as in Example 3, except that the soaking time is 30 min.

[0076] Embodiment 20,

[0077] The rest is the same as in Example 3, except that the soaking temperature is 20°C.

[0078] Embodiment 21,

[0079] The rest is the same as in Example 3, except that the soaking temperature is 30°C.

[0080] Comparative Example 1

[0081] The Li-30B lithium alloy electrode was used as the negative electrode.

[0082] The three-dimensional lithium alloy negative electrode of Examples 1-21 and the Li-30B lithium alloy pole piece of Comparative Example 1 were respectively combined with a 6-series (NCM) positive electrode, an electrolyte, etc. to form a soft-pack battery. The capacity of the soft-pack battery was about 10Ah. All soft-pack batteries were subjected to constant gap expansion test and charge-discharge cycle test. The test environment was 25°C, the voltage test range was 3.0V to 4.35V, and the charge-discharge ratio was 0.33C. First, a constant gap expansion force test was performed. The soft-pack battery was placed between two clamping plates with an initial pressure of 240kg. The soft-pack battery was charged and discharged for three cycles, and the maximum expansion force was recorded. Then, a conventional charge-discharge cycle test was performed, and the number of cycles when the capacity retention rate was less than 80% was recorded. The test data is as shown in the following table:

[0083]

[0084]

[0085] According to Examples 1-3, Comparative Example 1 and Figure 1 It can be seen that compared with the conventional Li-30B lithium alloy electrode, the three-dimensional lithium alloy negative electrode obtained by etching can increase the number of cycles of the soft-pack battery by more than 50%, reaching up to 61.5%, and the cycle performance is significantly improved. At the same time, the expansion force of the soft-pack battery has a small range of variation, and the maximum expansion force is reduced by more than 30%, reaching up to 38.1%. It can be seen that the three-dimensional lithium alloy negative electrode obtained by etching can effectively inhibit the volume change of lithium metal and has good stability.

[0086] According to Examples 1-21, it can be seen that there are certain differences in the etching effects of etching solutions formed by different solutes and solvents on lithium alloy pole pieces. If excessive etching is performed, although sufficient lithium nucleation sites can be provided, the structural strength of the constructed three-dimensional structure may be insufficient. However, if less etching is performed, although the structural strength of the three-dimensional structure can be guaranteed, fewer lithium nucleation sites are formed, which cannot provide sufficient growth space for subsequent lithium deposition and is not conducive to inhibiting the volume change of lithium metal. The present technical solution configures a suitable etching solution and adjusts parameters such as solute content, immersion time and immersion temperature to a suitable parameter range, which helps the etching solution to form a large number of lithium nucleation sites with good uniformity on the surface of the lithium alloy pole piece, and to construct a stable three-dimensional structure, thereby significantly improving the cycle performance of a battery prepared with the three-dimensional lithium alloy negative electrode as the negative electrode.

[0087] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the implementation of the present invention is not limited to the above-mentioned method. As long as various improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for preparing a three-dimensional lithium alloy negative electrode for a high specific energy battery with long cycle and low expansion force, characterized in that The following steps are involved: S1, taking a certain amount of solute and dissolving it in a first solvent to obtain an etching solution; S2, immersing the lithium alloy electrode in an etching solution; S3, taking out the etched lithium alloy electrode sheet, washing it with a second solvent, and drying it to obtain a three-dimensional lithium alloy negative electrode.

2. The method for preparing a three-dimensional lithium alloy negative electrode for a high specific energy battery with a long cycle and low expansion force according to claim 1, characterized in that In step S1, the solute is one of naphthol, iodic acid, K2ZrF6, bromic acid, and lithium nitrate, or a mixture of at least two of them.

3. The method for preparing a three-dimensional lithium alloy negative electrode for a high specific energy battery with a long cycle and low expansion force according to claim 1, characterized in that In the step S1, the first solvent is one of DMF, DMSO, DME, THF, G4, and G2, or a mixture of at least two of them.

4. The method for preparing a three-dimensional lithium alloy negative electrode for a high specific energy battery with a long cycle and low expansion force according to claim 1, characterized in that In the step S1, the content of the solute is 0.02-5 mol / L.

5. The method for preparing a three-dimensional lithium alloy negative electrode for a high specific energy battery with a long cycle and low expansion force according to claim 1, characterized in that In step S2, the soaking time is 5-30 minutes and the soaking temperature is 20-30°C.

6. The method for preparing a three-dimensional lithium alloy negative electrode for a high specific energy battery with a long cycle and low expansion force according to claim 1, characterized in that In the step S3, the second solvent is one of DMC, n-heptane and DME.

7. A three-dimensional lithium alloy negative electrode for a high specific energy battery with long cycle and low expansion force, characterized in that: The three-dimensional lithium alloy negative electrode is prepared by the method for preparing a three-dimensional lithium alloy negative electrode for a high specific energy battery with a long cycle and low expansion force as described in any one of claims 1 to 6.

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