Deep-sea high-magnification lithium ion battery electrode material electric infiltration microfluidic method

Abstract

This invention relates to a microfluidic method for electrowetting electrode materials of deep-sea high-rate lithium-ion batteries, comprising the following steps: (1) assembling the electrode materials and separator of a lithium-ion battery, and injecting electrolyte after assembly; (2) applying an external electric field between the electrodes to complete the wetting of the lithium-ion battery electrode materials by the electrolyte. This invention employs an electrowetting microfluidic method to apply an external electric field between the electrodes, resulting in an induced electric field in the dielectric layer at the electrode-electrolyte interface. This alters the electrostatic interaction between charged ions in the dielectric layer, thereby improving the wetting ability of the liquid electrolyte within the porous electrode, accelerating the wetting between the positive and negative electrodes and the electrolyte, controlling the uniform wetting distribution of the electrolyte on the electrode sheet, and accelerating the wetting rate of the deep-sea high-rate lithium-ion battery electrode materials. The method of this invention exhibits excellent wetting performance and high efficiency.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, and specifically to a microfluidic method for electrowetting electrode materials in deep-sea high-rate lithium-ion batteries. Background Technology

[0002] In deep-sea environments, pressures can reach up to 100 MPa, which ordinary commercial lithium-ion batteries cannot directly withstand. Furthermore, to meet the demands of deep-sea applications, batteries typically need to discharge at high rates, such as 20–30C. However, for batteries operating at high power, the wettability of the electrode material to the electrolyte becomes crucial. Wettability refers to the ability of a liquid to spread or penetrate a solid surface. For batteries, good wettability means that the electrolyte can effectively contact the electrode material, thereby improving ion transport efficiency, which is essential for ensuring battery performance at high power. If wettability is poor, the electrolyte may not uniformly cover the electrode surface, leading to limited electrochemical reactions in localized areas, thus affecting the overall battery performance, especially electrode conductivity.

[0003] Deep-sea lithium-ion batteries with a high rate of 20-30C are typically high-capacity, high-energy-density pouch batteries with a capacity of 40Ah or more. Compared to conventional lithium-ion batteries, these batteries have higher compaction density, thicker electrode thickness, and a three-dimensional elastic separator to meet the pressure and high discharge rate requirements of the deep sea at depths of 10,000 meters. Therefore, the electrodes require a longer wetting time in the electrolyte; otherwise, the battery electrode materials will have poor wetting performance with the electrolyte.

[0004] Therefore, there is a need to provide a method to improve the wettability of lithium-ion battery electrode materials in order to solve the problem that the poor wettability of battery electrode materials to electrolytes affects the electrode conductivity of the battery at high power in the deep-sea high-rate discharge environment of 20-30C. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a microfluidic method for electrowetting of electrode materials for deep-sea high-rate lithium-ion batteries, solving the technical problem that the battery electrode materials have poor wetting performance or low wetting efficiency in the high-rate discharge environment of deep sea at 20-30C.

[0006] To achieve the above-mentioned technical objectives, the technical solution provided by this invention is as follows:

[0007] In a first aspect, the present invention provides a microfluidic method for electrowetting electrode materials of deep-sea high-rate lithium-ion batteries, comprising the following steps:

[0008] (1) The electrode materials and separators of lithium-ion batteries are used for assembly, and electrolyte is injected after assembly;

[0009] (2) An external electric field is applied between the electrodes to complete the wetting of the lithium-ion battery electrode material by the electrolyte.

[0010] Preferably, the voltage of the external electric field is between 100 and 300 mV.

[0011] Preferably, the soaking time is 2 to 3 hours.

[0012] Preferably, the lithium-ion battery is a lithium iron phosphate pouch battery.

[0013] Preferably, the electrolyte includes lithium salt and organic solvent.

[0014] More preferably, the lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(oxalato)borate, lithium bis(trifluoromethanesulfonate)imide, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, and lithium perchlorate; the organic solvent includes one or a mixture of two or more of cyclic carbonates, linear carbonates, carboxylic acid esters, and cyclic lactones in any proportion.

[0015] Further preferably, the electrolyte also includes one or more of the following: functional additives, SEI film-forming agents, anti-overcharge additives, flame retardants, and stabilizers; wherein the functional additives are a mixture of lithium (perfluorobutyl sulfonyl)imide and cucurbitacin in a mass ratio of 10:1; and the SEI film-forming agents are one or more of the following: vinylene carbonate, fluoroethylene ester, chloroethylene ester, propane sulfonate lactone, butane sulfonate lactone, tetraalkyl-dienylsiloxane, and (p-vinylbenzenesulfonyl) (perfluoroalkyl sulfonyl)imide salts.

[0016] Preferably, the diaphragm is a polypropylene-based porous composite diaphragm with a thickness of 20–35 micrometers.

[0017] More preferably, the membrane includes a coating, which may be an inorganic coating or an organic coating; the coating does not contain graphene, graphite, or carbon nanotubes.

[0018] More preferably, the inorganic coating includes one or more of Al2O3, Mg(OH)2, SiO2, ZrO2, TiO2 and boehmite.

[0019] More preferably, the organic coating includes one or more of PVDF, PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene), PEO (polyethylene oxide), PAN (polyacrylonitrile), PMMA, PVB (polyvinyl butyral), PDA (polydopamine), and polystyrene-acrylate.

[0020] Compared with the prior art, the beneficial effects of the present invention include:

[0021] This invention employs an electrowetting microfluidic method, applying an external electric field between the electrodes. This induces an electric field in the dielectric layer at the electrode-electrolyte interface, altering the electrostatic interaction between charged ions in the dielectric layer. By regulating the electrostatic interaction between the double-layer charge and the ions in the electrolyte, the interaction between the electrodes and the electrolyte is increased, resulting in a significant rise in the electrolyte level within the electrode capillary. This enhances the wetting ability of the liquid electrolyte within the porous electrode, accelerates the wetting between the positive and negative electrodes and the electrolyte, controls a uniform wetting distribution of the electrolyte on the electrode sheet, and accelerates the wetting rate of electrode materials for high-rate deep-sea lithium-ion batteries. The method of this invention exhibits excellent wetting performance and high efficiency. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] High-rate lithium-ion batteries operating at 20-30C in the deep sea are typically high-capacity, high-energy-density pouch cells with a capacity of 40Ah or more. Compared to conventional lithium-ion batteries, these batteries feature higher compaction density, thicker electrode sheets, and three-dimensional elastic separators to meet the pressure requirements and high discharge rates at depths of tens of thousands of meters. Therefore, the electrodes require longer immersion times in the electrolyte. The porous electrodes of these 20-30C high-rate lithium-ion batteries are characterized by high compaction density, uneven pore size, high pore tortuosity, random pore distribution, and thick electrodes. Furthermore, significant differences in surface energy exist between the active materials, binders, conductive agents, and current collectors. These factors can all lead to poor electrolyte wetting performance and low wetting efficiency. Poor wetting performance can prevent the electrolyte from uniformly covering the electrode surface, limiting electrochemical reactions in localized areas and affecting the overall battery performance, especially electrode conductivity.

[0024] To address the aforementioned problems, this invention utilizes an electrowetting microfluidic method to significantly improve electrolyte wetting efficiency and enhance high-rate discharge capability.

[0025] In a first aspect, the present invention provides a microfluidic method for electrowetting electrode materials of deep-sea high-rate lithium-ion batteries, comprising the following steps:

[0026] (1) The electrode materials and separators of lithium-ion batteries are used for assembly, and electrolyte is injected after assembly;

[0027] (2) An external electric field is applied between the electrodes to complete the wetting of the lithium-ion battery electrode material by the electrolyte.

[0028] Preferably, the voltage of the external electric field is between 100 and 300 mV. If the voltage of the external electric field is too low, it will not be conducive to improving the wetting efficiency, while if the voltage of the external electric field is too high, the improvement on the wetting efficiency will not be significant.

[0029] Preferably, the soaking time is 2 to 3 hours.

[0030] Preferably, the lithium-ion battery is a lithium iron phosphate pouch battery.

[0031] Preferably, the electrolyte includes lithium salt and organic solvent.

[0032] More preferably, the lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(oxalato)borate, lithium bis(trifluoromethanesulfonate)imide, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, and lithium perchlorate; the organic solvent includes one or a mixture of two or more of cyclic carbonates, linear carbonates, carboxylic acid esters, and cyclic lactones in any proportion.

[0033] The electrolyte of this invention may also contain other raw materials, such as functional additives, SEI film-forming agents, anti-overcharge additives, flame retardants and / or stabilizers, etc., composed of a mixture of lithium (perfluorobutyl sulfonyl)imide and cucurbitacin in a mass ratio of 10:1; wherein the SEI film-forming agent is one or more of vinylene carbonate, fluoroethylene ester, chloroethylene ester, propane sulfonate lactone, butane sulfonate lactone, tetraalkyl-dienylsiloxane and (p-vinylbenzenesulfonyl) (perfluoroalkyl sulfonyl)imide salts.

[0034] Preferably, the diaphragm is a polypropylene-based porous composite diaphragm with a thickness of 20–35 micrometers.

[0035] More preferably, the membrane includes a coating, which may be an inorganic coating or an organic coating; the coating does not contain three-dimensional conductive structures or particles such as graphene, graphite, or carbon nanotubes.

[0036] More preferably, the inorganic coating includes inorganic materials such as Al2O3, Mg(OH)2, SiO2, ZrO2, TiO2, and boehmite.

[0037] More preferably, the organic coating includes polymers such as PVDF, PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene), PEO (polyethylene oxide), PAN (polyacrylonitrile), PMMA, PVB (polyvinyl butyral), PDA (polydopamine), and polystyrene-acrylate.

[0038] Main mechanism of action and advantages of this invention:

[0039] The positive and negative electrode materials of high-voltage lithium batteries contain a large number of micro- and nano-pores, forming capillaries. This invention employs an electro-wetting microfluidic method, in which an external electric field is applied between the electrodes. An induced electric field appears in the dielectric layer at the electrode-electrolyte interface, changing the charge state of the electrode particles and thus altering the electrostatic interaction between charged ions in the dielectric layer. Through electric field microfluidic control, the electrolyte level in the electrode capillaries rises significantly, thereby increasing the penetration / wetting rate of the electrolyte inside the electrode when the battery is activated by injecting electrolyte. This improves the electrode conductivity, which is beneficial for high-power battery discharge and is suitable for the wetting of electrode materials for high-rate lithium-ion batteries in deep sea applications.

[0040] The present invention will be further described in detail below through specific embodiments.

[0041] Example 1

[0042] A microfluidic method for electrowetting electrode materials in deep-sea high-rate lithium-ion batteries includes the following steps:

[0043] (1) The electrode materials and separators of lithium-ion batteries are used for assembly, and the electrolyte is injected after assembly. The lithium-ion battery used is a lithium iron phosphate soft pack battery, which can meet the requirements of high capacity and high energy density discharge of 100MPa, 20-30C high rate and more than 40Ah. The electrolyte is a 1mol / L lithium hexafluorophosphate ethylene carbonate solution (with 10wt%FEMC and 3%EC added). The separator is a deep-sea special polypropylene-based porous composite separator.

[0044] (2) An external electric field is applied between the electrodes, and the lithium-ion battery electrode material is immersed in the electrolyte for 2 hours; wherein the applied external field voltage is 100mV.

[0045] Example 2

[0046] The only difference from Example 1 is that the applied external field voltage is adjusted to 150 mV, while the other steps and conditions are the same as in Example 1.

[0047] Example 3

[0048] The only difference from Example 1 is that the applied external field voltage is adjusted to 200 mV, while the other steps and conditions are the same as in Example 1.

[0049] Example 4

[0050] The only difference from Example 1 is that the applied external voltage is adjusted to 250 mV, while the other steps and conditions are the same as in Example 1.

[0051] Example 5

[0052] The only difference from Example 1 is that the applied external voltage is adjusted to 300 mV, while the other steps and conditions are the same as in Example 1.

[0053] Comparative Example 1

[0054] The only difference from Example 1 is that the applied external field voltage is adjusted to 0 mV (i.e. no external electric field is applied), while the other steps and conditions are the same as in Example 1.

[0055] An electric field was applied to the positive and negative electrodes using an electrochemical workstation. The effect of different external electric fields on the wetting rate of the positive electrode sheet of the pressure-resistant lithium iron phosphate battery was tested. The results are shown in Table 1.

[0056] Table 1. Wetting effect under different external voltages

[0057]

[0058] As shown in Table 1, under the same conditions, after applying an external electric field, the wetting area of ​​the present invention increases with increasing voltage, from 3.61 cm² in Comparative Example 1. 2 The wetted area increased significantly, reaching 8.94 cm² at an external voltage of 100 mV. 2 It is 2.5 times that of Comparative Example 1; after further increasing the external field voltage, the growth rate of the immersion area slows down. Therefore, the external field voltage of the present invention is preferably 100-300mV, and more preferably 100-200mV.

[0059] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A microfluidic method for electrowetting electrode materials in deep-sea high-rate lithium-ion batteries, characterized in that, Includes the following steps: (1) The electrode materials and separators of lithium-ion batteries are used for assembly, and electrolyte is injected after assembly; (2) An external electric field is applied between the electrodes to complete the wetting of the lithium-ion battery electrode material by the electrolyte; The voltage of the external electric field is between 100 and 200 mV; The soaking time is 2 to 3 hours; The lithium-ion battery is a high-rate lithium iron phosphate soft-pack battery with a capacity of over 40Ah and a high rate of 20-30C. The electrolyte comprises lithium salt and organic solvent.

2. The electrowetting microfluidic method for electrode materials in deep-sea high-rate lithium-ion batteries according to claim 1, characterized in that, The lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(oxalato)borate, lithium bis(trifluoromethanesulfonate)imide, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, and lithium perchlorate; the organic solvent includes one or a mixture of two or more of cyclic carbonates, linear carbonates, carboxylic acid esters, and cyclic lactones in any proportion.

3. The electrowetting microfluidic method for electrode materials in deep-sea high-rate lithium-ion batteries according to claim 1, characterized in that, The electrolyte also includes one or more of the following: functional additives, SEI film-forming agents, anti-overcharge additives, flame retardants, and stabilizers; wherein the functional additives are a mixture of lithium (perfluorobutyl sulfonyl)imide and cucurbitacin in a mass ratio of 10:1; the SEI film-forming agents are one or more of the following: vinylene carbonate, fluoroethylene ester, chloroethylene ester, propane sulfonate lactone, butane sulfonate lactone, tetraalkyl-dienylsiloxane, and (p-vinylbenzenesulfonyl) (perfluoroalkyl sulfonyl)imide salts.

4. The microfluidic method for electrowetting electrode materials in deep-sea high-rate lithium-ion batteries according to claim 1, characterized in that, The diaphragm is a polypropylene-based porous composite diaphragm with a thickness of 20–35 micrometers.

5. The electrowetting microfluidic method for electrode materials in deep-sea high-rate lithium-ion batteries according to claim 4, characterized in that, The membrane includes a coating, which may be an inorganic coating or an organic coating; the coating does not contain graphene, graphite, or carbon nanotubes.

6. The electrowetting microfluidic method for electrode materials in deep-sea high-rate lithium-ion batteries according to claim 5, characterized in that, The inorganic coating includes one or more of Al2O3, Mg(OH)2, SiO2, ZrO2, TiO2, and boehmite; the organic coating includes one or more of PVDF, PVDF-HFP, PEO, PAN, PMMA, PVB, PDA, and polystyrene-acrylate.

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