Method for directly regenerating garnet type oxide solid electrolyte from waste solid battery

Abstract

The invention belongs to the technical field of battery recovery, discloses a method for directly regenerating a garnet type oxide solid electrolyte from a waste solid battery, and aims to solve the problem that the cycle life of a regenerated battery is relatively short due to short circuit caused by non-uniform deposition of solid electrolyte lithium in an existing regeneration process. According to the method, the solid electrolyte is separated from the waste solid battery, crushing treatment is firstly carried out, then lithium dendrites are removed through a water immersion method and are converted into lithium carbonate, finally, regeneration of the electrolyte is realized by adopting a high-temperature sintering process, and the obtained garnet type oxide solid electrolyte can be directly used for preparing the solid lithium battery. According to the method, redundant lithium in the solid electrolyte is effectively recycled, the electrochemical performance of the solid electrolyte can be recovered to the level before short circuit, and repeated utilization of the solid electrolyte is achieved. The whole recovery process does not need to add other chemical reagents, and does not generate harmful gas and wastewater, so that secondary pollution is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of battery recycling, and in particular to a method for directly regenerating garnet-type oxide solid electrolyte from waste solid-state batteries. Background Art

[0002] Solid-state lithium metal batteries have gradually become a potential alternative to lithium-ion batteries due to their high safety and high energy density (>500Wh / kg), and have received widespread attention from academia and industry. As an important component of solid-state lithium metal batteries, solid electrolytes can not only effectively solve the safety hazards caused by flammable organic solvents, but also provide the possibility for lithium-based batteries to achieve high energy density. Among them, garnet-type oxide solid electrolytes are regarded as strong candidates for the next generation of electrolyte materials due to their excellent chemical and electrochemical stability. However, at lower current densities (<1.5mA / cm 2 ), lithium dendrites may still penetrate the solid electrolyte and cause a short circuit. In addition, due to the lack of effective recycling methods, the solid electrolyte after short circuit is often discarded, resulting in resource waste and potential environmental pollution. Therefore, it is crucial to develop economical and sustainable recycling technologies before the large-scale commercial application of solid-state lithium metal batteries.

[0003] The direct regeneration technology of the positive and negative electrodes of lithium-ion batteries has been verified on a laboratory scale and can be used for the recycling of solid-state batteries. For example, Chinese invention patent CN115441080A discloses a direct recovery and regeneration method for oxide solid electrolytes, which first pre-treats the surface of the oxide-based solid electrolyte after short circuit, then performs heat treatment, and finally grinds and polishes its surface to complete the recovery and regeneration of the electrolyte. This process eliminates lithium dendrites and restores the electrochemical properties of the solid electrolyte to the level before the short circuit. However, this method may lead to local lithium-rich problems and increase the risk of short circuit in the regenerated battery. In addition, the cracks generated in the solid electrolyte during the recycling process cannot be repaired, resulting in an increase in the impedance of the regenerated electrolyte.

[0004] Therefore, developing technologies and processes that can achieve complete regeneration and multiple reuse of solid electrolytes has become a key issue that needs to be urgently addressed. Summary of the invention

[0005] In view of this, the present invention provides a method for directly regenerating garnet-type oxide solid electrolytes from waste solid-state batteries to solve the problem in the existing regeneration process that the short circuit problem caused by uneven deposition of solid electrolyte lithium cannot be completely solved, thereby resulting in a low cycle life of the regenerated battery.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] The present application provides a method for directly regenerating garnet-type oxide solid electrolyte from waste solid-state batteries, comprising the following steps:

[0008] (1) dismantling the waste solid-state battery and placing it in ethanol to separate the solid electrolyte from the positive and negative electrode materials; then crushing the separated solid electrolyte into powder, adding deionized water to the powder to perform a dissolution reaction to dissolve lithium dendrites, and filtering to obtain a lithium-containing filtrate and a filter residue;

[0009] (2) evaporating and concentrating the lithium-containing filtrate obtained in step (1), adding a sodium carbonate solution to precipitate lithium carbonate, filtering to obtain a lithium carbonate precipitate, washing the precipitate and drying to obtain lithium carbonate, and recycling the filtrate for further lithium precipitation;

[0010] (3) The filter residue obtained in step (1), the lithium carbonate obtained in step (2) and the solvent are uniformly mixed by wet grinding to prepare a mixed slurry; the mixed slurry is dried and subjected to a primary calcination reaction to obtain a garnet-type oxide solid electrolyte powder; the solid electrolyte powder is wet-ground to be finely ground, dried and pressed into tablets, and subjected to a secondary calcination reaction to obtain a garnet-type oxide solid electrolyte sheet.

[0011] Preferably, in step (1), the solid electrolyte is Li7La3Zr2O 12 , Li 7-x Ln3Z 2-x Ta x O 12 and Li 7- x Ln3Z 2-x Nb x O 12 One of them; Li 7-x Ln3Z 2-x Ta x O 12 Where x is the doping amount of Ta, 0 <x<2;Li 7-x Ln3Z 2-x Nb x O 12 Where x is the doping amount of Nb, 0 <x<2。

[0012] Preferably, in the dissolution reaction of step (1), the solid-liquid ratio is 30 to 50 g / L, and the reaction time is 10 to 60 min.

[0013] Preferably, in step (2), the lithium-containing filtrate is evaporated and concentrated at 90-98° C. for 30-120 min.

[0014] Preferably, in step (2), the concentration of the sodium carbonate solution is 100 to 300 g / L.

[0015] Preferably, in step (2), the obtained lithium carbonate precipitate is washed with hot water at 90 to 98° C. and then dried at 100 to 350° C.

[0016] Preferably, in step (3), the mass ratio of the filter residue to the lithium carbonate is 1:(0.1-0.3).

[0017] Preferably, in step (3), the solvent is one or more of water, ethanol, propanol, ethylene glycol, propylene glycol, allyl alcohol, isopropanol, dimethyl carbonate, diethyl carbonate, propylene carbonate, and vinyl carbonate mixed in any proportion.

[0018] Preferably, in step (3), the wet grinding speed is 100 to 500 r / min, the wet grinding time is 2 to 12 h, and the solid-liquid ratio during the wet grinding process is 1:1 to 1:3.

[0019] Preferably, in step (3), the primary calcination is carried out in a muffle furnace or a tubular furnace, with a heating rate of 2 to 10° C. / min, a reaction temperature of 500 to 1200° C., and a reaction time of 2 to 6 h.

[0020] Preferably, in step (3), the secondary calcination is carried out in a muffle furnace or a tubular furnace, the heating rate is 2 to 10° C. / min, the reaction temperature is 1000 to 1500° C., and the reaction time is 10 to 60 min.

[0021] The present invention separates solid electrolytes from waste solid-state batteries, first performs crushing treatment, then removes lithium dendrites through water immersion and converts them into lithium carbonate, and finally uses a high-temperature relithiation process to achieve electrolyte regeneration.

[0022] Compared with the prior art, this application has the following advantages and beneficial effects:

[0023] (1) The method of the present invention not only effectively recovers the excess lithium in the solid electrolyte, but also restores its electrochemical performance to the level before the short circuit, and reduces the risk of the regenerated electrolyte short-circuiting again.

[0024] (2) The method of the present invention can repair cracks generated during the recycling process of the electrolyte, thereby achieving its repeated use.

[0025] (3) The garnet-type oxide solid electrolyte obtained by the method of the present invention can be directly used in the preparation of solid-state lithium batteries. The battery prepared with the regenerated solid electrolyte has excellent battery performance and battery cycle life. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0027] Figure 1 It is a process flow chart of the method of the present invention.

[0028] Figure 2 This is the XRD diagram of lithium carbonate in Example 1 of the present invention.

[0029] Figure 3 Li7La3Zr2O after regeneration in Example 1 of the present invention 12 Powder XRD pattern.

[0030] Figure 4 These are pictures of the solid electrolyte of Example 1 of the present invention before cycling, after short circuiting, and after regeneration.

[0031] Figure 5 The lithium content of the electrolyte sheet before cycling, after short circuit and after regeneration in Example 1 of the present invention.

[0032] Figure 6 This is a graph showing the cycle performance of a lithium-lithium symmetric battery in Example 1 of the present invention.

[0033] Figure 7 The lithium content of the electrolyte sheet before cycling, after short circuit and after regeneration in Example 2 of the present invention.

[0034] Figure 8 This is a graph showing the cycle performance of a lithium-lithium symmetric battery according to Example 2 of the present invention.

[0035] Fig. 9 The lithium content of the electrolyte sheet before cycling, after short circuit and after regeneration in Example 3 of the present invention.

[0036] Fig.10 This is a graph showing the cycle performance of a lithium-lithium symmetric battery in Example 3 of the present invention. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Example 1

[0039] like Figure 1As shown, this embodiment provides a method for directly regenerating garnet-type oxide solid electrolyte from waste solid-state batteries, which is specifically carried out in the following steps:

[0040] (1) Dismantle the waste solid-state battery and place it in ethanol to separate the solid electrolyte from the positive and negative electrodes. Then crush the solid electrolyte into powder and pass it through a 200-mesh sieve to obtain Li7La3Zr2O 12 Solid electrolyte powder, add deionized water to the powder to dissolve lithium dendrites, solid-liquid ratio 30g / L, dissolution time 60min. Use Buchner funnel to filter to obtain lithium-containing filtrate and filter residue.

[0041] (2) The lithium-containing filtrate obtained in step (1) was heated to 90°C and kept warm for 60 min until the solution was free of Li + The content is ≥30g / L, and then 300g / L sodium carbonate solution is added to the solution to precipitate lithium, wherein sodium carbonate and Li + The molar ratio of is 1.5: 1. The lithium precipitated product is poured into the Buchner funnel again and filtered for the second time. The filter residue is washed three times with hot water at 90°C and dried to obtain lithium carbonate. Figure 2 This is the XRD diagram of lithium carbonate. The characteristic peaks of the obtained lithium carbonate are completely consistent with those of the standard card.

[0042] (3) The filter residue obtained in step (1) and the lithium carbonate obtained in step (2) are mixed in a mass ratio of 1:0.1, and isopropanol is added, and the mass ratio of (filter residue + lithium carbonate): isopropanol is 1:1. Place it in a zirconia ball mill and grind and mix it evenly. The wet grinding speed is 500r / min and the wet grinding time is 2h to obtain a mixed slurry. After the mixed slurry is dried, it is placed in a muffle furnace and the furnace temperature is raised from room temperature to 900℃ at a heating rate of 10℃ / min and kept warm for 4h to obtain Li7La3Zr2O 12 Solid electrolyte powder. Figure 3 Li7La3Zr2O 12 The XRD pattern of Li7La3Zr2O 12 The characteristic peaks are completely consistent with those of the standard card. The solid electrolyte powder is then wet-ground, dried, pressed into tablets, and then sintered for the second time. The calcination conditions are heating to 1300°C at a heating rate of 5°C / min and sintering for 10 minutes to prepare Li7La3Zr2O 12 Solid electrolyte sheet.

[0043] The photos of the solid electrolyte before cycling, after short circuit and after regeneration in Example 1 are as follows Figure 4 As shown in the figure, the solid electrolyte is a light yellow uniform ceramic sheet before the cycle. After the cycle, black lithium dendrites and cracks appear on the surface of the solid electrolyte. After regeneration, the solid electrolyte recovers the morphology before the cycle. Figure 5 As shown, it can be seen that the lithium content of the regenerated electrolyte sheet is restored to the level before cycling.

[0044] The solid electrolyte sheet prepared in Example 1 was made into a lithium-lithium symmetrical battery and subjected to relevant electrochemical tests. The cycle performance of the battery is as follows: Figure 6 As shown, at a current density of 0.2 mA / cm -2 , capacity is 0.2mAh / cm -2 Under the given conditions, it can circulate stably for 800h.

[0045] Example 2

[0046] like Figure 1 As shown, this embodiment provides a method for directly regenerating garnet-type oxide solid electrolyte from waste solid-state batteries, which is specifically carried out in the following steps:

[0047] (1) Dismantle the waste solid-state battery and place it in ethanol to separate the solid electrolyte from the positive and negative electrodes. Then crush the solid electrolyte into powder and pass it through a 200-mesh sieve to obtain Li 6.5 Ln3Z 1.5 Ta 0.5 O 12 Solid electrolyte powder, add deionized water to the powder to dissolve lithium dendrites, solid-liquid ratio 40g / L, dissolution time 30min. Use Buchner funnel to filter to obtain lithium-containing filtrate and filter residue.

[0048] (2) The lithium-containing filtrate obtained in step (1) was heated to 95°C and kept warm for 120 min until the solution was free of Li + The content is ≥30g / L, and then 100g / L sodium carbonate solution is added to the solution to precipitate lithium, wherein sodium carbonate and Li + The molar ratio of is 1.5: 1. The lithium precipitated product is poured into the Buchner funnel again and filtered for the second time. The filter residue is washed three times with hot water at 95°C and dried to obtain lithium carbonate.

[0049] (3) Mix the filter residue obtained in step (1) and the lithium carbonate obtained in step (2) in a mass ratio of 1:0.2, add propanol, and the solid-liquid ratio is 1:2. Place in a zirconia ball mill and grind and mix evenly, the wet grinding speed is 300r / min, the wet grinding time is 6h, and a mixed slurry is obtained. After the mixed slurry is dried, place it in a muffle furnace, and raise the furnace temperature from room temperature to 500°C at a heating rate of 2°C / min and keep it warm for 6h to obtain Li 6.5 Ln3Z 1.5 Ta 0.5 O 12Solid electrolyte powder. The solid electrolyte powder is then wet-ground, dried, pressed into tablets, and then sintered for the second time. The calcination conditions are heating at a rate of 2°C / min to 1000°C for 30 minutes to prepare Li 6.5 Ln3Z 1.5 Ta 0.5 O 12 Solid electrolyte sheet.

[0050] Example 2 The lithium content of the solid electrolyte before circulation, after short circuit and after regeneration is as follows Figure 7 As shown, it can be seen that the lithium content of the regenerated electrolyte sheet is restored to the level before cycling.

[0051] The solid electrolyte sheet prepared in Example 2 was made into a lithium-lithium symmetrical battery and subjected to relevant electrochemical tests. The cycle performance of the battery is as follows: Figure 8 As shown, at a current density of 0.2 mA / cm -2 , capacity is 0.2mAh / cm -2 Under the given conditions, it can circulate stably for 1000h.

[0052] Example 3

[0053] like Figure 1 As shown, this embodiment provides a method for directly regenerating garnet-type oxide solid electrolyte from waste solid-state batteries, which is specifically carried out in the following steps:

[0054] (1) Dismantle the waste solid-state battery and place it in ethanol to separate the solid electrolyte from the positive and negative electrodes. Then crush the solid electrolyte into powder and pass it through a 200-mesh sieve to obtain Li 6.5 Ln3Z 1.5 Nb 0.5 O 12 Solid electrolyte powder, add deionized water to the powder to dissolve lithium dendrites, solid-liquid ratio 50g / L, dissolution time 10min. Use Buchner funnel to filter to obtain lithium-containing filtrate and filter residue.

[0055] (2) The lithium-containing filtrate obtained in step (1) was heated to 98°C and kept warm for 30 min until the solution was free of Li + The content is ≥30g / L, and then 200g / L sodium carbonate solution is added to the solution to precipitate lithium, wherein sodium carbonate and Li + The molar ratio of is 1.5: 1. The lithium precipitated product is poured into the Buchner funnel again and filtered for the second time. The filter residue is washed three times with hot water at 98°C and dried to obtain lithium carbonate.

[0056] (3) Mix the filter residue obtained in step (1) and the lithium carbonate obtained in step (2) in a mass ratio of 1:0.3, add ethylene carbonate, and the solid-liquid ratio is 1:3. Place in a zirconia ball mill and grind and mix evenly, the wet grinding speed is 100r / min, and the wet grinding time is 12h to obtain a mixed slurry. After the mixed slurry is dried, place it in a muffle furnace, and raise the furnace temperature from room temperature to 1200℃ at a heating rate of 5℃ / min and keep it warm for 2h to obtain Li 6.5 Ln3Z 1.5 Nb 0.5 O 12 Solid electrolyte powder. The solid electrolyte powder is then wet-ground, dried, pressed into tablets, and then sintered for a second time. The calcination conditions are heating at a rate of 10°C / min to 1500°C for 60 minutes to prepare Li 6.5 Ln3Z 1.5 Nb 0.5 O 12 Solid electrolyte sheet.

[0057] Example 3 The lithium content of the solid electrolyte before circulation, after short circuit and after regeneration is as follows Fig. 9 As shown, it can be seen that the lithium content of the regenerated electrolyte sheet is restored to the level before cycling.

[0058] The solid electrolyte sheet prepared in Example 3 was made into a lithium-lithium symmetrical battery and subjected to relevant electrochemical tests. The cycle performance of the battery is as follows: Fig.10 As shown, at a current density of 0.2 mA / cm -2 , capacity is 0.2mAh / cm -2 Under the given conditions, it can circulate stably for 900h.

[0059] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0060] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for directly regenerating garnet-type oxide solid electrolyte from waste solid-state batteries, characterized in that: The following steps are involved: (1) dismantling the waste solid-state battery and placing it in ethanol to separate the solid electrolyte from the positive and negative electrode materials; then crushing the separated solid electrolyte into powder, adding deionized water to the powder to perform a dissolution reaction to dissolve lithium dendrites, and filtering to obtain a lithium-containing filtrate and a filter residue; (2) evaporating and concentrating the lithium-containing filtrate obtained in step (1), adding a sodium carbonate solution to precipitate lithium carbonate, filtering to obtain a lithium carbonate precipitate, washing the precipitate and drying to obtain lithium carbonate, and recycling the filtrate for further lithium precipitation; (3) The filter residue obtained in step (1), the lithium carbonate obtained in step (2) and the solvent are uniformly mixed by wet grinding to prepare a mixed slurry; the mixed slurry is dried and subjected to a primary calcination reaction to obtain a garnet-type oxide solid electrolyte powder; the solid electrolyte powder is wet-ground to be finely ground, dried and pressed into tablets, and subjected to a secondary calcination reaction to obtain a garnet-type oxide solid electrolyte sheet.

2. The method for directly regenerating garnet-type oxide solid electrolyte from waste solid-state batteries according to claim 1, characterized in that: In step (1), the solid electrolyte is Li7La3Zr2O 12 , Li 7-x Ln3Z 2-x Ta x O 12 and Li 7- x Ln3Z 2-x Nb x O 12 One of them; Li 7-x Ln3Z 2-x Ta x O 12 Where x is the doping amount of Ta, 0 <x<2;Li 7-x Ln3Z 2-x Nb x O 12 Where x is the doping amount of Nb, 0 <x<2。 3. The method for directly regenerating garnet-type oxide solid electrolyte from waste solid-state batteries according to claim 1, characterized in that: The solid-liquid ratio in the dissolution reaction of step (1) is 30-50 g / L, and the reaction time is 10-60 min.

4. The method for directly regenerating garnet oxide solid electrolyte from waste solid batteries according to claim 1, characterized in that: In step (2), the lithium-containing filtrate is evaporated and concentrated at 90-98° C. for 30-120 min.

5. The method for directly regenerating garnet-type oxide solid electrolyte from waste solid-state batteries according to claim 1, characterized in that: In step (2), the concentration of the sodium carbonate solution is 100-300 g / L, and the obtained lithium carbonate precipitate is washed with 90-98° C. hot water and then dried at 100-350° C.

6. The method for directly regenerating garnet-type oxide solid electrolyte from waste solid-state batteries according to claim 1, characterized in that: In step (3), the mass ratio of the filter residue to the lithium carbonate is 1:(0.1-0.3).

7. The method for directly regenerating garnet oxide solid electrolyte from waste solid batteries according to claim 1, characterized in that: In step (3), the solvent is one or more of water, ethanol, propanol, ethylene glycol, propylene glycol, allyl alcohol, isopropanol, dimethyl carbonate, diethyl carbonate, propylene carbonate, and vinyl carbonate mixed in any proportion.

8. The method for directly regenerating garnet oxide solid electrolyte from waste solid batteries according to claim 1, characterized in that: In step (3), the wet grinding speed is 100 to 500 r / min, the wet grinding time is 2 to 12 h, and the solid-liquid ratio during the wet grinding process is 1:1 to 1:

3.

9. The method for directly regenerating garnet oxide solid electrolyte from waste solid batteries according to claim 1, characterized in that: In step (3), the primary calcination is carried out in a muffle furnace or a tubular furnace, the heating rate is 2 to 10° C. / min, the reaction temperature is 500 to 1200° C., and the reaction time is 2 to 6 hours.

10. A method for directly regenerating garnet-type oxide solid electrolyte from waste solid-state batteries according to any one of claims 1 to 9, characterized in that: In step (3), the secondary calcination is carried out in a muffle furnace or a tubular furnace, the heating rate is 2 to 10°C / min, the reaction temperature is 1000 to 1500°C, and the reaction time is 10 to 60 min.

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