Battery based on expansion self-adaptive slow-release film-forming additive and preparation method thereof

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a battery based on an expansion self-adaptive slow-release film-forming additive and a preparation method of the battery. Comprising at least two roll cores; the air bag is fixed between the at least two roll cores, the air bag is filled with a film forming additive, and micron-sized through holes which are distributed in a gradient manner are formed in the surface of the air bag; wherein the air bag is configured to respond to expansive force generated in the battery circulation process, and when the expansive force reaches a preset threshold value, the air bag deforms and releases the film-forming additive in a gradient mode through the micron-sized through holes. According to the invention, the expansion force increasing curve in the self-circulation process of the battery cell is utilized, the film-forming agent air bag is mechanically extruded, the film-forming additive is released as required, the uniform thin SEI film is formed, and the interface impedance of the negative electrode is obviously reduced.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a battery based on an expansion-adaptive slow-release film-forming additive and its preparation method. Background Technology

[0002] Rechargeable batteries, due to their advantages such as high energy density, long cycle life, safety, reliability, and no memory effect, have been widely used in various digital products, portable devices, electric vehicles, and energy storage power supplies. With the widespread application of rechargeable batteries in recent years, higher demands have been placed on them. Rechargeable batteries strive for ultra-high energy density and ultra-long cycle life. However, during the charging process of rechargeable batteries, the volume expansion of the negative electrode graphite and the repeated rupture and recombination of the SEI film lead to the continuous consumption of active lithium and film-forming additives in the electrolyte, resulting in significant SOH decay. To ensure battery cycle life, a certain proportion of film-forming additives is usually added to the electrolyte.

[0003] Existing film-forming additives are typically added to the battery electrolyte in a single step or added to the battery a second time after the initial SEI film formation. Insufficient addition cannot meet the continuous SEI degradation throughout the battery's lifespan, while excessive addition can lead to too much additive in the core immersed in electrolyte, resulting in an overly thick and uneven SEI film at the bottom of the core, increased lithium-ion transport impedance, and significant lithium plating at the bottom of the core, leading to significant cell capacity decay. Therefore, the method and amount of film-forming additive addition are crucial factors affecting the cycle life of lithium-ion batteries. Based on this, a battery with an expansion-adaptive slow-release film-forming additive and its preparation method are proposed. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the aforementioned background technology and provide a battery based on an expansion-adaptive slow-release film-forming additive and its preparation method.

[0005] The technical solution adopted in this invention is: a battery based on an expansion-adaptive slow-release film-forming additive, comprising: At least two cores; An airbag is fixed between at least two cores, the airbag is filled with a film-forming additive, and the surface of the airbag is provided with gradient-distributed micron-sized through holes. The airbag is configured to respond to the expansion force generated during battery cycling. When the expansion force reaches a preset threshold, the airbag deforms and releases the film-forming additive through the micron-level through-hole gradient.

[0006] Preferably, the airbag is made of any one of rubber, silicone, or thermoplastic polyurethane; the area of ​​the airbag is not less than the actual compression area of ​​the large surface of the core.

[0007] Preferably, the pore size of the micron-sized through-holes exhibits a gradient distribution, ranging from Φ50μm, Φ100μm, to Φ200μm, with a pore density of 5-250 pores / mm². 2 .

[0008] Preferably, the film-forming additive is at least one of vinylene carbonate, fluorovinyl carbonate, or 1,3-propanesulfonic acid lactone, with a purity ≥99.9%.

[0009] Preferably, the substrate of the airbag is further doped with graphene thermal conductive sheet and film-forming agent microcapsules, wherein the mass fraction of graphene thermal conductive sheet is 3wt%, the mass fraction of film-forming agent microcapsules is 10wt%, and the particle size is 3-10μm; the surface of the airbag is coated with a paraffin phase change material layer with a thickness of 1-5μm.

[0010] Preferably, when the expansion force is greater than 0.13 MPa, the deformation rate of the airbag is ≥33%; the airbag is configured to release film-forming additives according to different expansion force gradients: When the expansion force is 0.10 MPa, the release rate of the film-forming additive is 0. When the expansion force is 0.13 MPa, the release rate of the film-forming additive is 6.3 ± 0.5 μg / h; When the expansion force is 0.21 MPa, the release rate of the film-forming additive is 15.1 ± 0.6 μg / h; When the expansion force is 0.35 MPa, the release rate of the film-forming additive is 32.8 ± 2.1 μg / h; When the expansion force is 0.45 MPa, the release rate of the film-forming additive is 62.4 ± 3.5 μg / h.

[0011] Preferably, the airbag is fixed to the surface of the core by double-sided adhesive, and the double-sided adhesive is made of acrylic adhesive.

[0012] Preferably, the micron-sized through-hole is a tapered through-hole, and the diameter of the through-hole increases along the direction of electrolyte flow.

[0013] The present invention also provides a method for preparing the battery based on the expansion-adaptive sustained-release film-forming additive, comprising the following steps: S1: Prepare the airbag by using rubber, silicone or thermoplastic polyurethane material and making the airbag body through precision injection molding process; S2: Ultraviolet laser is used to drill holes on the surface of the airbag to form micron-level through holes with a gradient distribution of Φ50-100-200μm. S3: Fill the airbag with a film-forming additive; S4: Coat the surface of the airbag with a layer of paraffin phase change material; S5: Apply double-sided tape to the large surface of the airbag; S6: In the cell assembly process, the airbag with adhesive backing is bonded to one of the cores between at least two cores, and the cores are symmetrically arranged with the center line of the large surface of the core centered.

[0014] Preferably, the precision injection molding process in step S1 includes: Injection temperature: Barrel temperature 170-200℃, mold temperature 40-60℃; Injection pressure: 100-150MPa; Pressure holding time: 5-10 seconds; Cooldown time: 15-25 seconds; It adopts a conformal water channel design to fit the curved surface of the airbag, with a temperature difference of ≤5℃; Vacuum adsorption is used for demolding, with an adsorption force of -0.08 MPa.

[0015] Preferably, the wavelength range of the ultraviolet laser used in step S2 is 300-355nm, and the micron-sized through hole is a tapered through hole with the diameter of the through hole increasing along the direction of electrolyte flow.

[0016] Preferably, step S7 is also included: The battery cell equipped with the airbag is baked at a temperature of 90-110°C to melt the paraffin phase change material layer and open the micron-sized through-holes. A battery based on an expansion-adaptive slow-release film-forming additive was produced by sequentially performing liquid injection, high-temperature settling, formation, and capacity testing.

[0017] Compared with the prior art, the beneficial effects of the present invention are: Conventional battery film-forming additives are typically added to the electrolyte in a single step, which can easily lead to an excessively thick SEI film in parts of the battery core immersed in the electrolyte, thus hindering lithium-ion transport. This invention utilizes the increasing expansion force curve during the battery cell's own cycling process to mechanically compress the film-forming agent bladder, releasing the additive as needed to form a uniform, thin SEI film, significantly reducing the negative electrode interface impedance.

[0018] The airbag surface of this invention has micron-sized through holes with the diameter of the through holes increasing along the electrolyte flow direction. As the number of cycles increases, the core expansion force increases, and the airbag is slowly squeezed to release additives, repair the SEI film, avoid excessive consumption of active lithium, avoid excessive reaction between the electrolyte and graphite due to SEI damage, and extend the cycle life of the battery cell. Detailed Implementation

[0019] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0020] Example 1 This embodiment provides a battery based on an expansion-adaptive slow-release film-forming additive, comprising: Two cores, with the main surface dimensions of each core being 100mm × 200mm; An airbag is fixedly disposed between the two cores. The airbag is filled with a film-forming additive (ethylene carbonate VC, purity ≥99.9%), and the surface of the airbag is provided with gradient-distributed micron-sized through holes. The airbag is made of thermoplastic polyurethane (TPU, hardness 80A); the airbag has dimensions of 95mm × 195mm × 2mm, and its area is not less than the actual extrusion area of ​​the large surface of the core. The pore size of the micron-sized through-holes exhibits a gradient distribution: the pore size in the central region of the airbag is Φ50μm, and the pore density is 80-250 pores / mm. 2 The central region of the airbag has a pore diameter of Φ100μm and a pore density of 20-60 pores / mm. 2 The pore size at the edge of the airbag is Φ200μm, with a pore density of 5-15 pores / mm. 2 ; The airbag is configured to respond to the expansion force generated during battery cycling. When the expansion force reaches 0.13 MPa, the airbag deforms and releases the film-forming additive through the micron-sized through-hole gradient.

[0021] Example 2 This embodiment, based on Embodiment 1, further provides an optimized structure for the airbag: The airbag's substrate is thermoplastic polyurethane (TPU, hardness 80A), and the substrate is doped with: graphene thermal conductive sheet, with a mass fraction of 3wt%, to improve thermal diffusivity; and film-forming agent microcapsules (ethylene carbonate microcapsules), with a mass fraction of 10wt% and a particle size of 5μm. The surface of the airbag is covered with a paraffin phase change material layer with a thickness of 3μm; The micron-sized through-hole is a tapered through-hole, and the diameter of the through-hole increases along the direction of electrolyte flow; The airbags are bonded to the surface of the roll core with acrylic double-sided adhesive, and are symmetrically arranged with the center line of the large surface of the roll core in the center.

[0022] Example 3 This embodiment provides a method for preparing a battery based on an expansion-adaptive sustained-release film-forming additive, including the following steps: S1: The airbag is made of thermoplastic polyurethane (TPU, hardness 80A), which is doped with graphene thermal conductive sheet (3wt%) and vinylene carbonate microcapsules (10wt%, particle size 5μm). The airbag body is made by precision injection molding process. Injection molding process parameters: Plasticizing stage: barrel temperature 170℃ / 180℃ / 190℃ / 200℃ (four-stage temperature control) to prevent VC microcapsule rupture; microcapsule wall material is made of high-temperature resistant material to ensure no VC leakage during injection molding; Injection stage: pressure 120MPa, speed 80mm / s, segmented pressure holding curve control to prevent flash; Cooling stage: mold temperature 40℃, time 8s, rapid shaping to avoid uneven crystallinity; Demolding stage: ejection force 0.5kN, vacuum adsorption demolding (adsorption force -0.08MPa), surface film protection to prevent scratches; S2: Using an ultraviolet laser (wavelength 355nm), perforations are created on the surface of the airbag to form gradient-distributed conical micropores: the pore diameter in the central region of the airbag is Φ50μm, and the pore density is 150 pores / mm. 2 The central region of the airbag has a pore diameter of Φ100μm and a pore density of 40 pores / mm. 2 The airbag edge region has a pore diameter of Φ200μm and a pore density of 10 pores / mm. 2 The diameter of the through-hole increases along the direction of electrolyte flow. S3: Fill the airbag with vinylene carbonate (VC, purity ≥99.9%), the filling volume is 2ml, and seal it; S4: Coat the surface of the airbag with a paraffin phase change material layer with a thickness of 3μm; S5: Apply double-sided acrylic tape resistant to electrolyte corrosion to the large surface of the airbag; S6: In the cell assembly and core-fitting process, the airbag with adhesive backing is bonded to one of the two cores, symmetrically arranged with the center line of the core's large surface centered. S7: The battery cell equipped with the airbag is baked at a temperature of 100°C to melt the paraffin phase change material layer and open the micron-sized through holes; the processes of liquid injection, high-temperature standing, formation, and capacity testing are performed in sequence to obtain a battery based on expansion adaptive slow-release film-forming additive.

[0023] Example 4 The lithium-ion battery prepared in Example 3 was subjected to cycle performance testing: Test conditions: 25℃ environment, 1000 cycles of 1C charge-discharge. The pressure response test results are as follows: Test results show that when the expansion force reaches 0.13 MPa or higher, the airbag begins to release film-forming additives. As the number of cycles increases, the expansion force increases, and the release rate of the film-forming additives increases accordingly, achieving on-demand release. When the expansion force is greater than 0.13 MPa, the airbag deformation rate reaches more than 33%, ensuring the effective release of film-forming additives.

[0024] Example 5 This embodiment provides a method for preparing a battery based on an expansion-adaptive sustained-release film-forming additive, including the following steps: S1: The airbag is made of thermoplastic polyurethane (TPU, hardness 80A), doped with graphene thermal conductive sheets (3wt%) and vinylene carbonate microcapsules (10wt%, particle size 3μm). The airbag body is made by precision injection molding. Injection molding parameters: barrel temperature 170℃ (initial stage) during plasticizing stage, injection pressure 100MPa; mold temperature 40℃, holding time 5s, cooling time 15s; vacuum adsorption demolding is used during demolding (adsorption force -0.08MPa). S2: Using an ultraviolet laser (wavelength 300nm), perforations are created on the surface of the airbag to form gradient-distributed conical micropores: the pore diameter in the central region of the airbag is Φ50μm, and the pore density is 80 pores / mm. 2 The central region of the airbag has a pore diameter of Φ100μm and a pore density of 20 pores / mm. 2 The airbag edge region has a pore diameter of Φ200μm and a pore density of 5 pores / mm. 2 The diameter of the through-hole increases along the direction of electrolyte flow. S3: Fill the airbag with vinylene carbonate (VC, purity ≥99.9%), the filling volume is 2ml, and seal it; S4: Coat the surface of the airbag with a paraffin phase change material layer with a thickness of 1μm; S5: Apply acrylic double-sided adhesive to the large surface of the airbag; S6: In the cell assembly and core-fitting process, the airbag with adhesive backing is bonded to one of the two cores, symmetrically arranged with the center line of the core's large surface centered. S7: The battery cell equipped with the airbag is baked at a temperature of 90°C to melt the paraffin phase change material layer and open the micron-sized through holes; the battery is then subjected to liquid injection, high-temperature standing, formation, and capacity testing processes to obtain a battery based on expansion adaptive slow-release film-forming additives.

[0025] Example 6 This embodiment provides a method for preparing a battery based on an expansion-adaptive sustained-release film-forming additive, including the following steps: S1: The airbag is made of thermoplastic polyurethane (TPU, hardness 80A), doped with graphene thermal conductive sheets (3wt%) and vinylene carbonate microcapsules (10wt%, particle size 10μm). The airbag body is made by precision injection molding. Injection molding parameters: plasticizing stage barrel temperature 200℃ (terminal stage), injection stage pressure 150MPa; mold temperature 60℃, holding time 10s, cooling time 25s; demolding stage uses vacuum adsorption demolding (adsorption force -0.08MPa). S2: Using an ultraviolet laser (wavelength 355nm), perforations are created on the surface of the airbag to form gradient-distributed conical micropores: the pore diameter in the central region of the airbag is Φ50μm, and the pore density is 250 pores / mm. 2 The central region of the airbag has a pore diameter of Φ100μm and a pore density of 60 pores / mm. 2 The airbag edge region has a pore diameter of Φ200μm and a pore density of 15 pores / mm. 2 The diameter of the through-hole increases along the direction of electrolyte flow. S3: Fill the airbag with vinylene carbonate (VC, purity ≥99.9%), the filling volume is 2ml, and seal it; S4: Coat the surface of the airbag with a paraffin phase change material layer with a thickness of 5μm; S5: Apply acrylic double-sided adhesive to the large surface of the airbag; S6: In the cell assembly and core-fitting process, the airbag with adhesive backing is bonded to one of the two cores, symmetrically arranged with the center line of the core's large surface centered. S7: The battery cell equipped with the airbag is baked at a temperature of 110°C to melt the paraffin phase change material layer and open the micron-sized through holes; the battery is then subjected to liquid injection, high-temperature settling, formation, and capacity testing processes to obtain a battery based on expansion adaptive slow-release film-forming additives.

[0026] Comparative Example 1 The only difference from Example 3 is that, instead of using a gasbag-based sustained-release structure, an equal amount of vinylene carbonate (VC, 2 ml) is added to the electrolyte in a single step. All other preparation conditions and process parameters are the same as in Example 3.

[0027] Comparative Example 2 The only difference from Example 3 is that the airbag surface does not have gradient-distributed micropores, but rather uniformly distributed Φ100μm micropores with a uniform pore density of 60 pores / mm. 2 The remaining preparation conditions and process parameters are the same as in Example 3. The deformation rate and expansion force trigger threshold of the airbag are the same as in Example 3, that is, the deformation rate is ≥33% when the expansion force is greater than 0.13MPa.

[0028] Comparative Example 3 The only difference from Example 3 is that the airbag surface is not coated with a paraffin phase change material layer, and the micron-sized through-holes remain open at all times. All other preparation conditions and process parameters are the same as in Example 3. The airbag's deformation rate and expansion force trigger threshold are the same as in Example 3, i.e., the deformation rate is ≥33% when the expansion force is greater than 0.13 MPa.

[0029] Performance comparison test The batteries prepared in Example 3 and Comparative Examples 1-3 were subjected to cycle performance tests. Interfacial impedance was measured using electrochemical impedance spectroscopy (EIS). Test conditions included: a test frequency range of 0.01 Hz to 100 kHz, an AC excitation signal amplitude of 5 mV, a test temperature of 25 °C, 1C charge-discharge, and testing after 1000 cycles. The results are shown in the table below. Comparative analysis of results: 1. Compared with Comparative Example 1, Example 3 showed that after adopting the airbag sustained-release structure, the capacity retention rate after 1000 cycles increased from 70% to 88%, an increase of 18 percentage points; the interfacial impedance decreased from 35mΩ to 15mΩ, a decrease of 57%. This indicates that the airbag sustained-release structure can effectively release film-forming additives on demand, avoiding the problem of increased impedance caused by excessive SEI film thickness.

[0030] 2. Compared with Comparative Example 2, Example 3 showed that after adopting a gradient-distributed micropore design, the capacity retention rate after 1000 cycles increased from 78% to 88%, an improvement of 10 percentage points; the interfacial impedance decreased from 22mΩ to 15mΩ. This indicates that the gradient-distributed micropore design can achieve more precise controlled release, making the release of film-forming additives more matched with SEI film loss.

[0031] 3. Compared with Comparative Example 3, Example 3 showed that after using the paraffin phase change material layer, the capacity retention rate after 1000 cycles increased from 75% to 88%, an increase of 13 percentage points. This indicates that the paraffin phase change material layer can effectively seal micropores before battery baking, preventing premature leakage of film-forming additives during assembly and ensuring that the film-forming additives only begin to be released when the battery is actually used.

[0032] 4. Examples 5 and 6, using the lower and upper limits of the respective process parameter ranges, exhibit performance comparable to Example 3, with a capacity retention rate exceeding 86% after 1000 cycles and an interface impedance below 18 mΩ. This demonstrates that within the parameter range defined in this invention, the battery achieves excellent cycle performance and low interface impedance, verifying the rationality and effectiveness of the parameter ranges described in the claims.

[0033] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Contents not described in detail in this specification belong to prior art known to those skilled in the art.

Claims

1. A battery based on an expansion-adaptive slow-release film-forming additive, characterized in that, include: At least two cores; An airbag is fixed between at least two cores, the airbag is filled with a film-forming additive, and the surface of the airbag is provided with gradient-distributed micron-sized through holes. The airbag is configured to respond to the expansion force generated during battery cycling. When the expansion force reaches a preset threshold, the airbag deforms and releases the film-forming additive through the micron-level through-hole gradient.

2. The battery based on expansion-adaptive slow-release film-forming additive according to claim 1, characterized in that, The airbag is made of any one of rubber, silicone, or thermoplastic polyurethane; the area of ​​the airbag is not less than the actual extrusion area of ​​the large surface of the core.

3. The battery based on expansion-adaptive slow-release film-forming additive according to claim 1, characterized in that, The micron-sized through-holes have a gradient distribution in pore size, ranging from Φ50μm, Φ100μm, to Φ200μm, with a pore density of 5-250 pores / mm². 2 .

4. The battery based on expansion-adaptive slow-release film-forming additive according to claim 1, characterized in that, The film-forming additive is at least one of vinylene carbonate, fluorovinyl carbonate, or 1,3-propanesulfonic acid lactone, with a purity ≥99.9%.

5. The battery based on expansion-adaptive slow-release film-forming additive according to claim 1, characterized in that, The substrate of the airbag is also doped with graphene thermal conductive sheet and film-forming agent microcapsules, wherein the mass fraction of graphene thermal conductive sheet is 3wt%, the mass fraction of film-forming agent microcapsules is 10wt%, and the particle size is 3-10μm; the surface of the airbag is coated with a paraffin phase change material layer with a thickness of 1-5μm.

6. The battery based on expansion-adaptive slow-release film-forming additive according to claim 1, characterized in that, When the expansion force is greater than 0.13 MPa, the deformation rate of the airbag is ≥33%; the airbag is configured to release film-forming additives according to different expansion force gradients: When the expansion force is 0.10 MPa, the release rate of the film-forming additive is 0. When the expansion force is 0.13 MPa, the release rate of the film-forming additive is 6.3 ± 0.5 μg / h; When the expansion force is 0.21 MPa, the release rate of the film-forming additive is 15.1 ± 0.6 μg / h; When the expansion force is 0.35 MPa, the release rate of the film-forming additive is 32.8 ± 2.1 μg / h; When the expansion force is 0.45 MPa, the release rate of the film-forming additive is 62.4 ± 3.5 μg / h.

7. A method for preparing a battery based on an expansion-adaptive slow-release film-forming additive as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1: Prepare the airbag by using rubber, silicone or thermoplastic polyurethane material and making the airbag body through precision injection molding process; S2: Ultraviolet laser is used to drill holes on the surface of the airbag to form micron-level through holes with a gradient distribution of Φ50-100-200μm. S3: Fill the airbag with a film-forming additive; S4: Coat the surface of the airbag with a layer of paraffin phase change material; S5: Apply double-sided tape to the large surface of the airbag; S6: In the cell assembly process, the airbag with adhesive backing is bonded to one of the cores between at least two cores, and the cores are symmetrically arranged with the center line of the large surface of the core centered.

8. The method for preparing a battery based on an expansion-adaptive slow-release film-forming additive according to claim 7, characterized in that, The precision injection molding process in step S1 includes: Injection temperature: Barrel temperature 170-200℃, mold temperature 40-60℃; Injection pressure: 100-150MPa; Pressure holding time: 5-10 seconds; Cooldown time: 15-25 seconds; It adopts a conformal water channel design to fit the curved surface of the airbag, with a temperature difference of ≤5℃; Vacuum adsorption is used for demolding, with an adsorption force of -0.08 MPa.

9. The method for preparing a battery based on an expansion-adaptive slow-release film-forming additive according to claim 7, characterized in that, In step S2, the wavelength range of the ultraviolet laser used is 300-355nm, and the micron-sized through hole is a tapered through hole with the diameter of the through hole increasing along the direction of electrolyte flow.

10. The method for preparing a battery based on an expansion-adaptive slow-release film-forming additive according to claim 7, characterized in that, It also includes step S7: The battery cell equipped with the airbag is baked at a temperature of 90-110°C to melt the paraffin phase change material layer and open the micron-sized through-holes. A battery based on an expansion-adaptive slow-release film-forming additive was produced by sequentially performing liquid injection, high-temperature settling, formation, and capacity testing.

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