Lithium battery interface buffer layer and preparation method thereof
The lithium battery interface buffer layer prepared by electrospinning utilizes polyvinylidene fluoride, graphene, and cerium ammonium sulfate dihydrate to form a uniform fiber structure, which solves the problems of uneven deposition and dendrite growth of lithium metal anode and improves the safety and stability of lithium battery.
Patent Information
- Application Number
- CN202310843119.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-07-11
- Publication Date
- 2026-02-10
- Estimated Expiration
- 2043-07-11
AI Technical Summary
In lithium-ion batteries, lithium metal anodes are prone to uneven lithium deposition and dendrite growth due to the fragility of the solid electrolyte interlayer, which poses a safety hazard. Existing technologies such as electrolyte additives and artificial SEI layers cannot effectively solve this problem.
A lithium battery interface buffer layer was prepared by electrospinning using polyvinylidene fluoride, graphene, and cerium ammonium sulfate dihydrate as raw materials. Through high-voltage polarization treatment, a uniform fiber structure was formed to alleviate stress accumulation and volume expansion, and to promote uniform lithium deposition.
It improves the mechanical properties and conductivity of the interface buffer layer, suppresses uneven lithium deposition and dendrite growth, and enhances the safety and stability of lithium batteries.
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Figure CN116864689B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of lithium ion batteries, in particular to a lithium battery interface buffer layer and a preparation method thereof. BACKGROUND
[0002] The rapid development of electric vehicles and portable electronic products has put forward higher requirements for the energy density of secondary batteries. Limited by the low theoretical capacity (372 mAh / g) of graphite, the energy density of lithium ion batteries with graphite as the negative electrode material has reached the limit of its theoretical energy density. Therefore, it is urgent to replace the graphite negative electrode with a negative electrode material with higher theoretical capacity to meet the requirements of high specific energy secondary batteries. The theoretical specific capacity of lithium metal negative electrode is as high as 3860 mAh / g, which is 10 times that of graphite, and has a very low electrode potential (-3.04 V vs. standard hydrogen electrode), which can be matched with many positive electrode materials to assemble full batteries, and is considered to be one of the most potential negative electrode materials.
[0003] However, lithium metal has very active chemical properties, and as soon as it comes into contact with the electrolyte, a solid electrolyte interphase (SEI) layer is generated. The interphase layer is very thin and brittle, and is easily broken during the cycle process, thereby causing continuous consumption of the electrolyte. In addition, the broken interphase layer exposes the underlying negative electrode substrate, becoming a "hot spot" for lithium deposition, causing uneven lithium deposition and leading to dendrite growth. Dendrite growth can pierce the separator and contact the positive electrode, causing internal short circuit of the battery, and triggering fire or explosion and other safety accidents.
[0004] The existing technical solutions to solve the problem of easy breaking of the solid electrolyte interphase mainly include electrolyte additives and artificial SEI layers. The interface layer generated by the electrolyte additive is very thin and has poor mechanical properties, and is also easily broken during long cycle process. The artificial SEI layer has good mechanical properties and can relieve stress concentration and volume expansion during lithium deposition, but cannot control the lithium deposition behavior and still causes uneven lithium deposition and leads to dendrite growth. SUMMARY
[0005] To solve the above technical problems, the present application provides a lithium battery interface buffer layer and a preparation method thereof.
[0006] The technical scheme adopted by the present application is:
[0007] A lithium battery interface buffer layer is made of the following raw materials by weight:
[0008]
[0009] As a preferred, the interface buffer layer is arranged between the lithium battery negative electrode and the positive electrode, and the thickness is 2-10 μm.
[0010] The preparation method of any one of the above lithium metal interface buffer layers comprises the following steps:
[0011] (1) 20-80 parts by weight of polyvinylidene fluoride and 0.1-1 parts by weight of cerium ammonium sulfate dihydrate are added to a mixed solution of 10-50 parts by weight of acetone and 2-20 parts by weight of N,N-dimethylformamide, heated in a water bath and magnetically stirred for a certain time to obtain a clear solution, then 0.5-2 parts by weight of graphene is added to the clear solution, heated in a water bath and magnetically stirred for a certain time again to obtain an electrospinning precursor solution;
[0012] (2) The obtained electrospinning precursor solution is transferred to a needle tube for electrospinning to obtain an electrospinning fiber membrane;
[0013] (3) The obtained electrospinning fiber membrane is subjected to high-voltage polarization to obtain an interface buffer layer.
[0014] Preferably, in step (1), the first heating temperature is 40-80℃, and the first stirring time is 2-5h; the second heating temperature is 50-60℃, and the second stirring time is 4-8h.
[0015] Preferably, in step (2), the needle tip diameter of the needle tube is 0.2-0.8mm, the electrospinning speed is 0.02-0.15mL / min, the electrospinning voltage is 15-25kV, and the distance between the emitting needle tip and the collecting plate is 15-25cm.
[0016] Preferably, in step (3), the polarization mode is direct current high-voltage polarization.
[0017] Preferably, the high-voltage polarization temperature is 60-120℃, the voltage is 15-25kV / mm, and the polarization time is 2-5h.
[0018] The beneficial effects of the present application are:
[0019] 1) The interface buffer layer is prepared by electrospinning method, which is simple, repeatable, controllable and good.
[0020] 2) After adding cerium ammonium sulfate dihydrate, the fiber diameter and distribution inside the prepared buffer layer are uniform, the fiber arrangement is orderly, and the pore uniformity is improved. This allows the fibers inside the buffer layer to uniformly disperse stress when under tension, thereby improving its mechanical properties. Furthermore, the addition of graphene increases the conductivity of the solution, making it easier for the electric field force on the solution to overcome the surface tension during electrospinning, resulting in a stronger stretching of the solution jet and thus obtaining more uniform fibers. Under the combined effect of cerium ammonium sulfate dihydrate and graphene, the interface buffer layer prepared in this invention exhibits superior mechanical properties, effectively mitigating stress accumulation and volume expansion during lithium deposition and maintaining the interfacial stability of the lithium metal anode. Moreover, the prepared interface buffer layer can convert the stress generated during deposition into an electric field, thereby achieving uniform lithium deposition and suppressing dendrite growth. Attached Figure Description
[0021] Figure 1 (a) is a surface topography diagram of interface buffer layer A in Example 1.
[0022] Figure 1 (b) is a surface morphology diagram of the interface buffer layer B in Example 2.
[0023] Figure 1 (c) is a surface morphology diagram of the interface buffer layer C in Example 3.
[0024] Figure 2 The stress-strain curves of the interface buffer layers prepared in Examples 1, 2 and 3 of the present invention are shown.
[0025] Figure 3(a) shows the lithium deposition morphology of the lithium battery B assembled in Example 1.
[0026] Figure 3(b) shows the lithium deposition morphology of the lithium battery A assembled in Example 1.
[0027] Figure 3(c) is Figure 1 (b) Cross-sectional view.
[0028] Figure 4 The image shows the lithium deposition morphology of the interface buffer layer without polarization treatment prepared in Comparative Example 1 of the present invention.
[0029] Figure 5 The lithium deposition morphology of the interface buffer layer prepared in Comparative Examples 2 and 3 of the present invention is shown in the figure.
[0030] Figure 6 The surface morphology diagrams are of the interface buffer layers prepared in Examples 2 and 3 of the present invention.
[0031] Figure 7 The lithium deposition morphology of the interface buffer layer prepared in Examples 2 and 3 of the present invention is shown in the figure. Detailed Implementation
[0032] The present invention will be further illustrated below with specific examples to facilitate understanding of the invention, but this does not limit the invention.
[0033] The principles used in the following examples and comparative examples are all commercially available.
[0034] Example 1
[0035] A method for preparing a lithium battery interface buffer layer A includes the following steps:
[0036] (1) Take 20g of N,N-dimethylformamide (DMF) and 12g of acetone and add them to a beaker. Then add 16g of polyvinylidene fluoride (PVDF) and 0.2g of cerium ammonium sulfate dihydrate (CAS) powder to the solution and stir magnetically at 80℃ for 4h. Then add 0.5g of graphene to the well mixed solution and stir magnetically at 60℃ for 6h to obtain an electrospinning precursor solution.
[0037] (2) The well-stirred precursor solution was transferred to a syringe for electrospinning. The needle tip diameter was 0.6 mm, the distance between the emitting needle tip and the collecting plate was 20 cm, the electrospinning speed was 0.05 mL / min, and the voltage was set to 20 kV; an electrospinned fiber membrane was obtained.
[0038] (3) The obtained electrospun fiber membrane was subjected to DC high voltage polarization with a polarization voltage of 20kV / mm, a polarization temperature of 80℃, and a polarization time of 3h; an interface buffer layer A was obtained.
[0039] The surface morphology of interface buffer layer A is as follows Figure 1 As shown in (a), from Figure 1 As shown in (a), the fiber diameter and fiber distribution are uniform. Tensile testing was performed on it; see [reference needed]. Figure 2 It was found that it has excellent mechanical properties, with a tensile strength of 6.5 MPa.
[0040] Assemble lithium battery A in the following order: lithium iron phosphate sheet, electrolyte, separator, electrolyte, interface buffer layer A, copper current collector, gasket, and spring.
[0041] The lithium battery B is assembled in the following order: lithium iron phosphate sheet, electrolyte, separator, electrolyte, copper current collector, gasket, and spring.
[0042] Lithium deposition tests were performed on assembled lithium battery A and lithium battery B:
[0043] At 0.1mAh / cm 2 The capacity is 0.5 mA / cm 2Lithium was deposited on the surface of the copper current collector at a current density of 1000 ppm. The differences in lithium deposition morphology are compared, as shown in Figure 3.
[0044] As can be seen from Figure 3(a), the lithium deposited on the surface of the blank copper current collector is dendritic and unevenly distributed.
[0045] As can be seen from Figure 3(b), the lithium deposited on the surface of the copper current collector covered with the interface buffer layer A is uniformly distributed, and all the lithium is deposited at the bottom of the interface buffer layer.
[0046] As can be seen from Figure 3(c), the structure of the interface buffer layer remains intact even after a large amount of lithium has been deposited.
[0047] Comparative Example 1
[0048] A method for preparing a lithium battery interface buffer layer A1 includes the following steps:
[0049] (1) Take 20g of N,N-dimethylformamide (DMF) and 12g of acetone and add them to a water bath. Then add 6g of polyvinylidene fluoride (PVDF) and 0.2g of cerium ammonium sulfate dihydrate (CAS) powder to the solution and stir magnetically at 80℃ for 4h. Then add 0.5g of graphene to the well mixed solution and stir magnetically at 60℃ for 6h to obtain an electrospinning precursor solution.
[0050] (2) The well-stirred precursor solution was transferred to a syringe for electrospinning. The needle tip diameter was 0.6 mm, the distance between the emitting needle tip and the collecting plate was 20 cm, the electrospinning speed was 0.05 mL / min, and the voltage was set to 20 kV. An electrospinned fiber membrane was obtained. The electrospinned fiber membrane was used as the interface buffer layer A1.
[0051] The lithium battery C is assembled in the following order: lithium iron phosphate sheet, electrolyte, separator, electrolyte, interface buffer layer A1, copper current collector, gasket, and spring.
[0052] Lithium deposition test on lithium battery C:
[0053] At 0.1mAh / cm 2 The capacity is 0.5 mA / cm 2 The current density was used to electrodeposit lithium on the surface of a copper current collector covered with an unpolarized interface buffer layer A1. The differences in lithium deposition morphology were compared. Figure 4 It can be seen that the interface buffer layer A1 has a poor ability to regulate lithium deposition behavior, and some lithium is deposited on the surface of the interface buffer layer.
[0054] Comparative Example 2
[0055] A method for preparing a lithium battery interface buffer layer A2 includes the following steps:
[0056] (1) Take 10g DMF and 5g acetone and add them to a beaker. Then add 8g PVDF and 0.5g CAS powder to the solution. Stir magnetically in a water bath at 80℃ for 4h. Then add 0.8g graphene to the well mixed solution and stir magnetically again in a water bath at 60℃ for 6h. The electrospinning precursor solution is obtained.
[0057] (2) The well-stirred solution was transferred to a syringe for electrospinning. The needle tip diameter was 0.6 mm, the distance between the emitting needle tip and the collecting plate was 20 cm, the electrospinning speed was 0.05 mL / min, and the high voltage was set to 20 kV; an electrospinned fiber membrane was obtained.
[0058] (3) The obtained electrospun fiber membrane was subjected to DC high voltage polarization with a polarization voltage of 20kV / mm, a polarization temperature of 80℃, and a polarization time of 3h; an interface buffer layer A2 was obtained.
[0059] The surface morphology of interface buffer layer A2 is as follows Figure 1 As shown in (b), the fiber diameter is small and unevenly distributed. A small number of fibers have broken. This is because the amount of PVDF added is too low, resulting in insufficient solution viscosity and inadequate ability to overcome the surface tension at the needle tip exit. Therefore, the fibers produced by electrospinning are uneven, with varying thicknesses. Tensile tests were performed on them; see [reference needed]. Figure 2 It was found that its mechanical properties were slightly lower than those of Example 1, with a tensile strength of 4 MPa.
[0060] The lithium battery C is assembled in the following order: lithium iron phosphate sheet, electrolyte, separator, electrolyte, interface buffer layer A2, copper current collector, gasket, and spring.
[0061] Lithium deposition tests were performed on the assembled lithium battery C:
[0062] At 0.1mAh / cm 2 The capacity is 0.5 mA / cm 2 Lithium was deposited on the surface of a copper current collector covered with an interface buffer layer A2 at a current density of [value missing]. The effect of the interface buffer layer on suppressing volume expansion was compared. Figure 5 (a) It can be seen that the interface buffer layer with poor mechanical properties cannot alleviate the stress accumulation and volume expansion during the deposition process, and a large number of fibers break during lithium deposition.
[0063] Comparative Example 3
[0064] A method for preparing a lithium metal anode interface buffer layer A3 includes the following steps:
[0065] (1) Measure 30g of DMF and 80g of acetone and add them to a beaker. Then add 100g of PVDF and 2g of CAS powder to the solution. Stir magnetically in a water bath at 80℃ for 4 hours. Then add 2.5g of graphene to the well-mixed solution and stir magnetically again in a water bath at 60℃ for 6 hours to obtain an electrospinning precursor solution.
[0066] (2) The well-stirred solution was transferred to a syringe for electrospinning. The needle tip diameter was 0.6 mm, the distance between the emitting needle tip and the collecting plate was 20 cm, the electrospinning speed was 0.05 mL / min, and the high voltage was set to 20 kV; an electrospinned fiber membrane was obtained.
[0067] (3) The obtained electrospun fiber membrane was subjected to DC high voltage polarization with a polarization voltage of 20kV / mm, a polarization temperature of 80℃, and a polarization time of 3h; an interface buffer layer A3 was obtained.
[0068] The surface morphology of interface buffer layer A3 is as follows Figure 1 As shown in (C), the fiber diameter and distribution are extremely uneven, and a large number of fibers have broken. This is due to the increased PVDF content, which increases the viscosity of the precursor solution, leading to frequent needle blockage during electrospinning. Furthermore, the increased CAS and graphene content causes agglomeration (forming cone-shaped structures within the fibers). Tensile testing was performed; see [reference needed]. Figure 2 It was found that it had the worst mechanical properties, with a tensile strength of only 2 MPa.
[0069] The lithium battery D is assembled in the following order: lithium iron phosphate sheet, electrolyte, separator, electrolyte, interface buffer layer A3, copper current collector, gasket, and spring.
[0070] Lithium deposition tests were performed on the assembled lithium battery D:
[0071] At 0.1mAh / cm 2 The capacity is 0.5 mA / cm 2 Lithium was deposited on the surface of a copper current collector covered with an interface buffer layer A3 at a current density of [value missing]. The effect of the interface buffer layer on suppressing volume expansion was compared. Figure 5 (b) It can be seen that the interface buffer layer with poor mechanical properties cannot alleviate the stress accumulation and volume expansion during the deposition process. Therefore, a large number of dendrites are generated and accumulate on the surface of the buffer layer.
[0072] Example 2
[0073] A method for preparing a lithium metal anode interface buffer layer B includes the following steps:
[0074] (1) Measure 15g of DMF and 30g of acetone and add them to a beaker. Then add 25 parts of PVDF and 0.3g of CAS powder to the solution. Stir magnetically in a water bath at 80℃ for 4 hours. Then add 0.8g of graphene to the well-mixed solution and stir magnetically again in a water bath at 60℃ for 6 hours to obtain an electrospinning precursor solution.
[0075] (2) The well-stirred solution was transferred to a syringe for electrospinning. The needle tip diameter was 0.6 mm, the distance between the emitting needle tip and the collecting plate was 20 cm, the electrospinning speed was 0.05 mL / min, and the spinning voltage was set to 20 kV; an electrospinned fiber membrane was obtained.
[0076] (3) The obtained electrospun fiber membrane was subjected to DC high voltage polarization with a polarization voltage of 20kV / mm, a polarization temperature of 80℃, and a polarization time of 3h; thus, an interface buffer layer B was obtained.
[0077] The surface morphology of interface buffer layer B is as follows Figure 6 As shown in (a), the fiber diameter and fiber distribution are relatively uniform, the fiber surface is smooth, and there is no breakage.
[0078] Lithium deposition tests were performed using the same method as in Example 1:
[0079] At 0.1mAh / cm 2 The capacity is 0.5 mA / cm 2 Lithium was deposited on the surface of a copper current collector covered with an interface buffer layer B at a current density of [value missing]. The effect of the interface buffer layer on suppressing volume expansion was compared. Figure 7 (a) It can be seen that the interface buffer layer B has a certain conductivity, which can induce lithium deposition inside its fiber filament. At the same time, due to its excellent mechanical properties, the fiber filament is not damaged and can still maintain its original morphology, thereby inhibiting dendrite growth.
[0080] Example 3
[0081] A method for preparing a lithium metal anode interface buffer layer C includes the following steps:
[0082] (1) Measure 18g of DMF and 40g of acetone and add them to a beaker. Then add 40g of PVDF and 0.6g of CAS powder to the solution. Stir magnetically in a water bath at 80℃ for 4 hours. Then add 1.5g of graphene to the well-mixed solution and stir magnetically again in a water bath at 60℃ for 6 hours to obtain the electrospinning precursor solution.
[0083] (2) The well-stirred solution was transferred to a syringe for electrospinning. The needle tip diameter was 0.6 mm, the distance between the emitting needle tip and the collecting plate was 20 cm, the electrospinning speed was 0.05 mL / min, and the high voltage was set to 20 kV; an electrospinned fiber membrane was obtained.
[0084] (3) The obtained electrospun fiber membrane was subjected to DC high voltage polarization with a polarization voltage of 20kV / mm, a polarization temperature of 80℃, and a polarization time of 3h; an interface buffer layer C was obtained.
[0085] The surface morphology of the interface buffer layer C is as follows Figure 6 As shown in (b), the fiber diameter and fiber distribution are relatively uniform, the fiber surface is smooth, and there is no breakage.
[0086] Lithium deposition tests were performed using the same method as in Example 1:
[0087] At 0.1mAh / cm 2 The capacity is 0.5 mA / cm 2 Lithium was deposited on the surface of a copper current collector covered with an interface buffer layer C at a current density of [value missing]. The effect of the interface buffer layer on suppressing volume expansion was compared. Figure 7 (b) It can be seen that the interface buffer layer C has a certain conductivity, which can induce lithium deposition inside its fiber filament. At the same time, due to its excellent mechanical properties, the fiber filament is not damaged and can still maintain its original morphology, thereby inhibiting dendrite growth.
[0088] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also within the protection scope of the present invention.
Claims
1. A lithium battery interface buffer layer, characterized in that, Made from the following parts by weight of raw materials: 20-80 parts of polyvinylidene fluoride; 10-50 parts acetone; 2-20 parts of N,N-dimethylformamide; 0.1-1 part of cerium ammonium sulfate dihydrate; 0.5-2 parts of graphene; The method for preparing the lithium battery interface buffer layer includes the following steps: (1) Add 20-80 parts by weight of polyvinylidene fluoride and 0.1-1 parts by weight of cerium ammonium sulfate dihydrate to a mixed solution of 10-50 parts by weight of acetone and 2-20 parts by weight of N,N-dimethylformamide, heat in a water bath and stir magnetically for a certain time to obtain a clear solution, then add 0.5-2 parts by weight of graphene to the clear solution, heat in a water bath and stir magnetically for a certain time again to obtain an electrospinning precursor solution; (2) The obtained electrospinning precursor solution was transferred to a syringe for electrospinning to obtain an electrospinned fiber membrane. (3) The obtained electrospun fiber membrane is subjected to high voltage polarization at a voltage of 15-25kV / mm to obtain an interface buffer layer.
2. The lithium battery interface buffer layer according to claim 1, characterized in that, An interface buffer layer is placed between the negative and positive electrodes of the lithium battery, and its thickness is 2-10µm.
3. A method for preparing a lithium battery interface buffer layer according to claim 1 or 2, characterized in that, Includes the following steps: (1) Add 20-80 parts by weight of polyvinylidene fluoride and 0.1-1 parts by weight of cerium ammonium sulfate dihydrate to a mixed solution of 10-50 parts by weight of acetone and 2-20 parts by weight of N,N-dimethylformamide, heat in a water bath and stir magnetically for a certain time to obtain a clear solution, then add 0.5-2 parts by weight of graphene to the clear solution, heat in a water bath and stir magnetically for a certain time again to obtain an electrospinning precursor solution; (2) The obtained electrospinning precursor solution was transferred to a syringe for electrospinning to obtain an electrospinned fiber membrane. (3) The obtained electrospun fiber membrane is subjected to high voltage polarization to obtain an interface buffer layer.
4. The preparation method according to claim 3, characterized in that, In step (1), the first heating temperature is 40-80℃ and the first stirring time is 2-5h; the second heating temperature is 50-60℃ and the second stirring time is 4-8h.
5. The preparation method according to claim 3, characterized in that, In step (2), the needle tip diameter of the needle tube is 0.2-0.8 mm, the electrospinning speed is 0.02-0.15 mL / min, the electrospinning voltage is 15-25 kV, and the distance between the emitting needle tip and the collecting plate is 15-25 cm.
6. The preparation method according to claim 3, characterized in that, In step (3), the polarization mode is DC high voltage polarization.
7. The preparation method according to claim 6, characterized in that, The high-voltage polarization temperature is 60-120℃, and the polarization time is 2-5h.
Citation Information
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