Self-adhesive lithium alloy negative electrode, preparation method thereof and all-solid-state lithium metal battery

Abstract

The invention discloses a self-adhesive lithium alloy negative electrode, a preparation method thereof and an all-solid-state lithium metal battery, the alloy negative electrode capable of inhibiting the lithium dendritic crystal effect is prepared from an ion conducting polymer, a three-dimensional porous carbon material and lithium metal, so that a negative electrode layer and an electrolyte layer can be stably combined under low pressure, and the self-adhesive lithium alloy negative electrode can be used for inhibiting the lithium dendritic crystal effect. And moreover, the growth of lithium dendrites is effectively inhibited, and the practical progress of the all-solid-state battery is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery manufacturing, in particular to a self-adhesive lithium alloy negative electrode, a preparation method thereof and a full-solid-state lithium metal battery. BACKGROUND

[0002] With the advent of the intelligent interconnection era, the performance requirements of batteries for electric vehicles and 3C products are continuously increasing. However, with the continuous increase of the energy density of batteries, the safety problem of batteries gradually emerges. The full-solid-state battery using solid-state electrolyte gradually becomes the development direction of the next generation of batteries due to its safety. However, at present, the full-solid-state battery needs to operate under a pressure of hundreds of megapascals, and lithium metal still faces the problem of dendrite growth in the full-solid-state battery, which seriously restricts the commercial application of the full-solid-state battery.

[0003] At present, the full-solid-state battery usually operates under a pressure of hundreds of megapascals. The reason is that there is no liquid in the full-solid-state battery, and the ion and electron conduction in the battery must be transmitted through solid-solid contact. Because the positive electrode electrolyte of the full-solid-state battery is prepared integrally, the contact between the positive electrode layer and the electrolyte layer is good, so the good contact between the electrolyte layer and the negative electrode layer in the full-solid-state battery is the key to realizing the normal operation of the full-solid-state battery under low pressure in actual working conditions.

[0004] In addition, lithium metal is the key to realizing high-energy-density batteries due to its high specific capacity and low potential. However, it still faces the problem of dendrite growth in the full-solid-state battery. The reason is that lithium ions have no suitable deposition site and can only deposit on the surface of lithium metal. Such uneven deposition can easily lead to dendrite growth problems, thereby causing the battery to fail.

[0005] For example, the prior art ZL202210704736.1 discloses an activated negative electrode with lithium dendrite inhibition effect to inhibit the growth of lithium dendrites in a full-solid-state battery. However, although it has a certain inhibitory effect on dendrite growth, the battery still needs to rely on a pressure of hundreds of megapascals to operate, and the carbon layer on the negative electrode side uses PTFE as a binder. The binder will undergo harmful decomposition reactions at low potentials, hindering its practical application in full-solid-state batteries. SUMMARY

[0006] In view of the problems existing in the prior art, the present application provides a self-adhesive lithium alloy negative electrode, a preparation method thereof and a full-solid-state lithium metal battery, which overcomes the deficiencies of high pressure and easy short circuit of the existing full-solid-state lithium metal battery, helps the stable combination between the electrolyte layer and the negative electrode interface, and the lithium alloy negative electrode prepared therefrom has spontaneous adhesion and three-dimensional ion transport deposition holes, which can effectively and tightly combine with the electrolyte layer while inhibiting the growth of lithium dendrites, thereby providing protection for realizing stable circulation of the low-pressure full-solid-state lithium metal battery.

[0007] The present application is achieved in that a self-adhesive lithium alloy negative electrode is pressed from a three-dimensional porous carbon layer coated with an ion-conducting polymer and lithium metal, taking three-dimensional porous carbon material as the core, and then coating a layer of ion-conducting polymer on the surface, so that the negative electrode layer has spontaneous adhesion, and the electrolyte layer and the negative electrode layer form a close interface contact.

[0008] The ion-conducting polymer is at least one of polyethylene oxide, carboxymethyl cellulose, polyvinylidene fluoride, polyvinylpyrrolidone, polymethyl methacrylate, polyvinyl chloride, and polyvinylidene chloride.

[0009] The three-dimensional porous carbon material is at least one of soft carbon, hard carbon, graphite, silicon-carbon, and silicon-oxygen.

[0010] The mass ratio of the three-dimensional porous carbon material to the ion-conducting polymer coating layer is (90-98):(2-10).

[0011] The preparation method of the above-mentioned self-adhesive lithium alloy negative electrode comprises the following steps:

[0012] (1) adding an ion-conducting polymer into a solvent and mixing to obtain a polymer solution;

[0013] (2) adding three-dimensional porous carbon material into the polymer solution and mixing thoroughly with a high-speed mixer to obtain a mixed solution;

[0014] (3) coating the mixed solution on a PET substrate and then performing heat treatment until all the solvent in the mixed solution is volatilized, to obtain a three-dimensional porous carbon layer coated with an ion-conducting polymer;

[0015] (4) obtaining a self-adhesive lithium alloy negative electrode by heating and pressing the three-dimensional porous carbon layer coated with an ion-conducting polymer and lithium metal in a flat hot press.

[0016] The solvent is at least one of deionized water, tetrahydrofuran, and ethanol.

[0017] The mass percentage of the ion-conducting polymer in the polymer solution is 2%-10%.

[0018] The pressure in the flat hot press is 10 MPa or higher, and the heating temperature is 50-60°C.

[0019] A full-solid-state lithium metal battery comprises a positive electrode, a negative electrode, and an electrolyte material, wherein the negative electrode is the above-mentioned self-adhesive lithium alloy negative electrode or the self-adhesive lithium alloy negative electrode prepared by the above-mentioned preparation method.

[0020] The positive electrode material used by the positive electrode includes but is not limited to a ternary system (NCM, NCA), a lithium cobaltate system (LCO), a lithium iron phosphate system (LFP), and a lithium manganate system (LMO); and the electrolyte material includes but is not limited to a sulfide solid-state electrolyte and an oxide solid-state electrolyte.

[0021] The present application has the advantages and technical effects that: the present application coats a layer of ion-conducting polymer on the surface of the three-dimensional conductive carbon material, and then generates an alloy negative electrode by pressing the lithium metal, so that the negative electrode layer has spontaneous adhesion, the electrolyte layer and the negative electrode layer can form a close interface contact, and therefore the assembled all-solid-state battery can be stably operated under low pressure, and the three-dimensional conductive carbon material provides a good site for the deposition of lithium metal and inhibits the growth of lithium dendrites, thereby providing a new solution for the practical application of all-solid-state batteries. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The present application has the advantages and technical effects that: the present application coats a layer of ion-conducting polymer on the surface of the three-dimensional conductive carbon material, and then generates an alloy negative electrode by pressing the lithium metal, so that the negative electrode layer has spontaneous adhesion, the electrolyte layer and the negative electrode layer can form a close interface contact, and therefore the assembled all-solid-state battery can be stably operated under low pressure, and the three-dimensional conductive carbon material provides a good site for the deposition of lithium metal and inhibits the growth of lithium dendrites, thereby providing a new solution for the practical application of all-solid-state batteries. DETAILED DESCRIPTION

[0023] In order to facilitate the understanding of the present application, the present application will be described more fully below, and preferred embodiments of the present application will be given. However, it should be understood that these embodiments are only used for more detailed description, and should not be understood as limiting the present application in any form, i.e. not intended to limit the protection scope of the present application.

[0024] As shown in Figure 1 The present application has the advantages and technical effects that: the present application coats a layer of ion-conducting polymer on the surface of the three-dimensional conductive carbon material, and then generates an alloy negative electrode by pressing the lithium metal, so that the negative electrode layer has spontaneous adhesion, the electrolyte layer and the negative electrode layer can form a close interface contact, and therefore the assembled all-solid-state battery can be stably operated under low pressure, and the three-dimensional conductive carbon material provides a good site for the deposition of lithium metal and inhibits the growth of lithium dendrites, thereby providing a new solution for the practical application of all-solid-state batteries.

[0025] Specifically, the self-adhesive lithium alloy negative electrode of the present application includes a three-dimensional porous carbon material with three-dimensional ion and electron conductivity coated with an ion-conducting polymer and lithium metal.

[0026] In the above technical solution, the three-dimensional porous carbon material is used as the core, and then a layer of ion-conducting polymer is coated on the surface of the three-dimensional porous carbon material. The coating can make the negative electrode layer have spontaneous adhesion, and the electrolyte layer and the negative electrode layer can form a close interface contact.

[0027] Preferably, the ionically conductive polymer coating layer is selected from at least one of polyethylene oxide, carboxymethyl cellulose, polyvinylidene fluoride, polyvinylpyrrolidone, polymethyl methacrylate, polyvinyl chloride and polyvinylidene chloride.

[0028] Preferably, the three-dimensional porous carbon material is selected from at least one of silicon-oxygen, silicon-carbon, graphite, soft carbon and hard carbon.

[0029] Preferably, the mass ratio of the three-dimensional porous carbon material and the ionically conductive polymer coating layer is (90-98):(2-10).

[0030] In the above technical solution, the mass ratio of the three-dimensional porous carbon material and the ionically conductive polymer coating layer is limited within a specific range, so that the ionically conductive polymer coating layer has a suitable coating thickness, and the increase in interface impedance caused by the increase in thickness can be minimized while the negative electrode has spontaneous adhesion.

[0031] In a second aspect, the present application provides a preparation method of a three-dimensional porous carbon material with an ionically conductive polymer coating layer, comprising the following steps:

[0032] The ionically conductive polymer material is dissolved in a specific solvent, and the solvent is selected from at least one of deionized water, tetrahydrofuran and ethanol, to obtain a polymer solution.

[0033] The three-dimensional porous carbon material is added to the polymer solution in a certain proportion, and a high-speed mixer is used for sufficient mixing.

[0034] The mixed solution is coated on a smooth substrate such as PET, and then subjected to heat treatment until all the solvent in the mixed solution is volatilized, to obtain a three-dimensional porous carbon material film with an ionically conductive polymer coating.

[0035] In the above technical solution, the preparation is carried out according to a specific process, so that a three-dimensional porous carbon material with a uniform ionically conductive polymer coating on the surface can be obtained. The ionically conductive polymer coating layer not only enables the negative electrode to have spontaneous adhesion, but also enables lithium ions to migrate and deposit normally.

[0036] Preferably, the mass percentage of the ionically conductive polymer in the polymer solution is 2-10%.

[0037] In the above technical solution, by controlling the mass ratio of the ionically conductive polymer and the three-dimensional porous carbon material in the solution, the speed and time of the high-speed mixer can greatly improve the uniformity of the coating layer.

[0038] In a third aspect, the present application provides a preparation method of a self-adhesive lithium alloy negative electrode, which adopts a three-dimensional carbon layer film with an ionically conductive polymer coating and lithium metal for roll pressing and compounding, and then alloying under the heating and pressing of a flat plate hot press to prepare an alloy negative electrode.

[0039] Preferably, the alloy negative electrode is prepared by heating and pressing the lithium metal and the ion conductive polymer-coated carbon layer film in a flat plate hot press, preferably at a pressure of 10 MPa or more and at a heating temperature of 50-60°C.

[0040] The application also provides a battery comprising the above negative electrode.

[0041] The battery provided by the application, the battery positive electrode material battery positive electrode includes but is not limited to ternary system (NCM, NCA), lithium cobaltate system (LCO), lithium iron phosphate system (LFP), lithium manganate system (LMO) and the like.

[0042] The battery provided by the application, the electrolyte material used in the battery includes but is not limited to sulfide solid electrolyte, oxide solid electrolyte and the like.

[0043] Example 1

[0044] Preparation of ion conductive polymer-coated three-dimensional porous carbon material: 10 g of polyethylene oxide was dissolved in 90 g of deionized water to a concentration of 10%, then 98 g of soft carbon was mixed with 20 g of polymer mixed solution in a high homogenizer at a ratio of 98:20 for 12 h to form a uniform dispersion, then a coating machine was used to coat it on a PET film according to the design surface density of 20 mg / cm 2 , and then dried until all the solvent was dried.

[0045] Preparation of composite negative electrode: lithium metal with a thickness of 35 μm and ion conductive polymer-coated three-dimensional porous carbon material were pressed in a flat plate hot press at 60°C for 1 h, and then the PET film was removed.

[0046] Battery assembly: match the positive electrode composed of 20 wt% solid electrolyte and 80 wt% LiCoO2, 20 mg, and the above composite negative electrode to form an LCO / LPSCl / Li structure battery, wherein the electrolyte layer is 80 mg LPS. During self-preparation, the assembled layers in the battery are assembled together at a pressure of 300 MPa, but are kept at 2 MPa during testing.

[0047] Example 2

[0048] Preparation of ion conductive polymer-coated three-dimensional porous carbon material: 10 g of polyethylene oxide was dissolved in 90 g of deionized water to a concentration of 10%, then 98 g of soft carbon was mixed with 20 g of polymer mixed solution in a high homogenizer at a ratio of 98:20 for 12 h to form a uniform dispersion, then a coating machine was used to coat it on a PET film according to the design surface density of 20 mg / cm 2 , and then dried until all the solvent was dried.

[0049] Preparation of composite anode: Lithium metal and ionically conductive polymer coated three-dimensional porous carbon material with thickness of 35 pm was pressed under a flat-bed hot press at 60 °C for 1 h, then the PET film was peeled off.

[0050] Assembly of battery: A positive electrode composed of 20 wt% of solid electrolyte and 80 wt% of LiCoO2, total 20 mg, was assembled with the above composite anode as a LCO / LPSCl / Li structured battery, where the electrolyte layer was 80 mg LPS. Pressurization during self-assembly, the assembled layers in the battery were assembled together with a pressurization pressure of 300 MPa, but maintained at 2 MPa during the test.

[0051] Example 3

[0052] Preparation of ionically conductive polymer coated three-dimensional porous carbon material: Polyethylene oxide 10 g was dissolved in deionized water 90 g with a concentration of 10%, then silicon carbon 98 g was mixed with the polymer mixed solution 20 g in proportion in a high homogenizer for 12 h to form a uniform dispersion, then it was coated on the PET film according to the design surface density of 20 mg / cm 2 and then dried until all the solvents were dried.

[0053] Preparation of composite anode: Lithium metal and ionically conductive polymer coated three-dimensional porous carbon material with thickness of 35 pm was pressed under a flat-bed hot press at 60 °C for 1 h, then the PET film was peeled off.

[0054] Assembly of battery: A positive electrode composed of 20 wt% of solid electrolyte and 80 wt% of LiCoO2, total 20 mg, was assembled with the above composite anode as a LCO / LPSCl / Li structured battery, where the electrolyte layer was 80 mg LPS. Pressurization during self-assembly, the assembled layers in the battery were assembled together with a pressurization pressure of 300 MPa, but maintained at 2 MPa during the test.

[0055] Example 4

[0056] Preparation of ionically conductive polymer coated three-dimensional porous carbon material: Polyethylene oxide 10 g was dissolved in deionized water 90 g with a concentration of 10%, then silicon carbon 98 g was mixed with the polymer mixed solution 20 g in proportion in a high homogenizer for 12 h to form a uniform dispersion, then it was coated on the PET film according to the design surface density of 20 mg / cm 2 and then dried until all the solvents were dried.

[0057] Preparation of composite anode: Lithium metal and ionically conductive polymer coated three-dimensional porous carbon material with thickness of 35 pm was pressed under a flat-bed hot press at 60 °C for 1 h, then the PET film was peeled off.

[0058] Battery assembly: The positive electrode consisting of 20 wt% of solid electrolyte and 80 wt% of LiCoO2, total 20 mg, was assembled with the above composite negative electrode as a structural battery of LCO / LPSCl / Li, where the electrolyte layer was 80 mg LPS. The battery was assembled with a pressure of 300 MPa during the self- fabrication process, but was maintained at 2 MPa during the test.

[0059] Example 5

[0060] Preparation of ionically conductive polymer-coated three-dimensional porous carbon material: Polyethylene oxide 10 g was dissolved in deionized water 90 g at a concentration of 10%, and then graphite 98 g was mixed with the polymer mixed solution 20 g in a ratio in a high homogenizer for 12 h to form a uniform dispersion, and then it was coated on a PET film according to the designed areal density of 20 mg / cm 2 and then dried until all the solvents were dried.

[0061] Preparation of composite negative electrode: Lithium metal and ionically conductive polymer-coated three-dimensional porous carbon material with a thickness of 35 μm were pressed at 60°C for 1 h under a flat plate hot press, and then the PET film was removed.

[0062] Battery assembly: The positive electrode consisting of 20 wt% of solid electrolyte and 80 wt% of LiCoO2, total 20 mg, was assembled with the above composite negative electrode as a structural battery of LCO / LPSCl / Li, where the electrolyte layer was 80 mg LPS. The battery was assembled with a pressure of 300 MPa during the self- fabrication process, but was maintained at 2 MPa during the test.

[0063] Comparative Example 1

[0064] Preparation of composite negative electrode: Lithium metal and ionically conductive polymer-coated three-dimensional porous carbon material with a thickness of 35 μm were pressed at 60°C for 1 h under a flat plate hot press, and then the PET film was removed. 2 and then dried until all the solvents were dried.

[0065] Battery assembly: The positive electrode consisting of 20 wt% of solid electrolyte and 80 wt% of LiCoO2, total 20 mg, was assembled with the above composite negative electrode as a structural battery of LCO / LPSCl / Li, where the electrolyte layer was 80 mg LPS. The battery was assembled with a pressure of 300 MPa during the self- fabrication process, but was maintained at 2 MPa during the test.

[0066] Comparative Example 2

[0067] Battery assembly: 20 mg of 35 pm lithium metal negative electrode matched with 20 wt% solid electrolyte and 80 wt% LiCoO2, consisting of a positive electrode, was assembled with the above composite negative electrode into a battery with the structure of LCO / LPSCl / Li, where the electrolyte layer was 80 mg LPS. During self-made process, the assembled layers in the battery were assembled together with a pressure of 300 MPa, but maintained at 2 MPa during the test.

[0068] Battery test method is as follows:

[0069] At 50°C, the battery was charged at 0.5C constant current to 4.25V, then rested for 5 minutes, then discharged at 0.5C constant current to 2.8V, then rested for 5 minutes, which was one charge-discharge cycle. The battery monomer was tested by multiple cycles of charge-discharge in the above manner, the charge-discharge capacity of the 100th cycle was detected, and the capacity retention rate of the battery monomer after cycling was calculated by the following formula. The capacity retention rate of the battery after 500 cycles (%) = [discharge capacity of the 500th cycle / discharge capacity of the 1st cycle] x 100%.

[0070] Table 1 Electrochemical performance statistics

[0071]

[0072] Referring to Table 1, from the test results of Examples 1-5 and Comparative Example 1, the alloy negative electrode prepared by the carbon material coated with the ion conductive polymer provided by the embodiments of the present application has spontaneous adhesion due to the surface coating of the ion conductive polymer, which can form a stable interfacial bonding between the negative electrode and the electrolyte layer under low pressure, and the corresponding battery has excellent initial discharge capacity, initial efficiency and cycle performance compared with the existing alloy negative electrode without coating modification.

[0073] From the test results of Examples 1-5 and Comparative Example 2, the alloy negative electrode prepared by the present application has great advantages in inhibiting dendrite growth and preventing battery short circuit compared with pure lithium metal.

[0074] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A self-adhesive lithium alloy negative electrode, characterized in that, It is made by pressing a three-dimensional porous carbon layer coated with an ion-conducting polymer and lithium metal. The three-dimensional porous carbon material is used as the core, and then an ion-conducting polymer is coated on its surface. The negative electrode layer has self-adhesion, which makes the electrolyte layer and the negative electrode layer form a tight interfacial contact.

2. The self-adhesive lithium alloy negative electrode according to claim 1, characterized in that, The ion-conducting polymer is at least one of polyethylene oxide, carboxymethyl cellulose, polyvinylidene fluoride, polyvinylpyrrolidone, polymethyl methacrylate, polyvinyl chloride, and polyvinylidene chloride.

3. The self-adhesive lithium alloy negative electrode according to claim 1, characterized in that, The three-dimensional porous carbon material is at least one of soft carbon, hard carbon, graphite, silicon carbon, and silicon oxide.

4. The self-adhesive lithium alloy negative electrode according to any one of claims 1 to 3, characterized in that, The mass ratio of the three-dimensional porous carbon material to the ion-conducting polymer coating layer is (90-98):(2-10).

5. The method for preparing the self-adhesive lithium alloy negative electrode according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Add the ion-conducting polymer to the solvent and mix to obtain a polymer solution; (2) Add the three-dimensional porous carbon material to the polymer solution and mix thoroughly using a high-speed mixer to obtain a mixed solution; (3) The mixed solution is coated on a PET substrate and then heat-treated until all the solvent in the mixed solution evaporates to obtain a three-dimensional porous carbon layer coated with an ion-conductive polymer. (4) A self-adhesive lithium alloy anode is prepared by heating and pressurizing a three-dimensional porous carbon layer coated with an ion-conductive polymer and lithium metal under a flat plate hot press.

6. The method for preparing the self-adhesive lithium alloy negative electrode according to claim 5, characterized in that, The solvent is at least one of deionized water, tetrahydrofuran, and ethanol.

7. The method for preparing the self-adhesive lithium alloy negative electrode according to claim 5, characterized in that, The ion-conducting polymer accounts for 2% to 10% of the polymer solution by mass.

8. The method for preparing the self-adhesive lithium alloy negative electrode according to claim 5, characterized in that, The pressure applied during heating and pressurization in the flatbed hot press is above 10 MPa, and the heating temperature is 50℃~60℃.

9. An all-solid-state lithium metal battery, comprising a positive electrode, a negative electrode, and an electrolyte material, characterized in that, The negative electrode is a self-adhesive lithium alloy negative electrode as described in any one of claims 1-4 or a self-adhesive lithium alloy negative electrode prepared by the preparation method described in any one of claims 5-8.

10. The all-solid-state lithium metal battery according to claim 9, characterized in that, The cathode material used includes, but is not limited to, ternary systems (NCM, NCA), lithium cobalt oxide systems (LCO), lithium iron phosphate systems (LFP), and lithium manganese oxide systems (LMO); the electrolyte material includes, but is not limited to, sulfide solid electrolytes and oxide solid electrolytes.

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