An electrolyte suitable for lithium primary batteries

Abstract

This invention relates to an electrolyte suitable for lithium primary batteries. To address the problems of poor safety performance under high-temperature conditions, high-rate discharge performance, and poor discharge performance of existing lithium primary battery electrolytes, the electrolyte of this invention comprises an electrolyte lithium salt, additives, and an organic solvent. The electrolyte lithium salt includes one or more of lithium trifluoromethanesulfonate, lithium di(trifluoromethanesulfonyl)imide, lithium difluorophosphate, and lithium difluoroborate oxalate; the additives include one or more of (2-trimethylsilylethyl)-2-acrylonitrile acetate, diphenyldimethoxysilane, and citrate anhydride; and the organic solvents include carbonate solvents and alcohol ether solvents. Through the selection and combination of the above-mentioned electrolyte lithium salt, additives, and solvents, this invention allows for simultaneous room-temperature discharge in lithium primary batteries, enabling them to simultaneously achieve high-temperature performance, high-rate discharge performance, and safety performance, thereby facilitating the wider application of lithium primary batteries.

Description

Technical Field

[0001] This invention belongs to the field of lithium primary battery technology, and specifically relates to an electrolyte suitable for lithium primary batteries. Background Technology

[0002] With the development of science and technology, lithium primary batteries have become a key supporting product and important technological foundation for weapons and electronic equipment, and are one of the important factors restricting their development. Countries around the world attach great importance to the research and development of lithium primary batteries. For example, the U.S. Department of Defense regards energy technology (including battery technology) as a key defense technology and a typical dual-use technology. In existing weapons and electronic equipment, a wide variety of lithium primary batteries are used. Based on the different cathode materials, they are mainly divided into lithium sulfur dioxide batteries, lithium thionyl chloride batteries, lithium manganese dioxide batteries, lithium iron disulfide batteries, and lithium fluoride carbon batteries, etc.

[0003] Lithium-manganese dioxide (Li / MnO2) batteries were the first commercially available lithium / solid cathode system battery and are also the most widely used type of lithium primary battery, with an actual specific energy exceeding 260–400 Wh / kg. These batteries have a rated voltage greater than 3V, an operating voltage plateau of around 2.7V, an operating temperature range of -40 to 75℃, and a storage life of over 10 years. Lithium-manganese dioxide batteries use manganese dioxide as the cathode and a mixture of lithium perchlorate and various organic solvents as the electrolyte. Their structural types mainly include button, cylindrical, prismatic, and pouch cells.

[0004] The traditional electrolyte lithium salt used in lithium manganese primary batteries is lithium perchlorate. Due to its strong oxidizing properties, it is listed as a chemical that is prone to explosion. In actual application, it also poses safety hazards under high temperature conditions. Its high-temperature discharge performance is not ideal, its high-rate discharge performance is limited, and its conductivity is also limited.

[0005] Therefore, there is an urgent need to provide an electrolyte suitable for lithium primary batteries, so that lithium primary batteries can simultaneously achieve high-temperature performance, high-rate discharge performance, and safety performance, thereby enabling lithium primary batteries to be better promoted and applied. Summary of the Invention

[0006] The purpose of this invention is to provide an electrolyte suitable for lithium primary batteries. This electrolyte not only has excellent discharge performance at room temperature, but also improves the high-temperature performance, high-rate discharge performance, and safety performance of lithium primary batteries.

[0007] Another objective of this invention is to provide a lithium primary battery with excellent performance at room temperature and high temperature, as well as high-rate discharge performance.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] An electrolyte suitable for lithium primary batteries comprises an electrolyte lithium salt, additives, and an organic solvent. The electrolyte lithium salt includes one or more of lithium trifluoromethanesulfonate, lithium di(trifluoromethanesulfonyl)imide, lithium difluorophosphate, and lithium difluoroborate oxalate. The additives include one or more of (2-trimethylsilylethyl)-2-acrylonitrile acetate, diphenyldimethoxysilane, and citrate anhydride. The organic solvents include carbonate solvents and alcohol ether solvents.

[0010] This invention, through the selection and combination of electrolyte lithium salt, additives and solvents, can simultaneously meet the requirements of room temperature discharge, high rate discharge and high temperature discharge performance when applied in lithium primary batteries. Among them, lithium trifluoromethanesulfonate and lithium di(trifluoromethanesulfonyl)imide, compared with lithium perchlorate, do not have strong oxidizing properties and have higher ionic conductivity; lithium difluorophosphate and lithium difluoroborate oxalate can react with metal aluminum foil on the positive electrode current collector of the cylindrical lithium manganese primary battery to form a passivation film on its surface, thereby preventing other corrosive substances from corroding the aluminum foil and avoiding battery failure caused by low voltage and high internal resistance; (2-trimethylsilylethyl)2-acrylonitrile acetate, diphenyldimethoxysilane, and citrate anhydride can participate in the formation process of the passivation film on the manganese dioxide positive electrode material to improve the film quality and high-temperature performance; combined with the optimized selection of solvents, while improving the dissociation degree of lithium salt and conductivity, it can also play a certain role in flame retardancy; thus optimizing the comprehensive performance of the electrolyte in lithium primary batteries, it has broad application prospects in future lithium manganese primary batteries.

[0011] Preferably, the concentration of the electrolyte lithium salt is 0.1 mol / L to 2 mol / L, for example, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, or 2 mol / L.

[0012] Preferably, the additive accounts for 0.5% to 15% of the total mass of the electrolyte, for example, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%.

[0013] More preferably, the additive includes at least two of (2-trimethylsilylethyl)-2-cyanoacetate, diphenyldimethoxysilane, and citrate anhydride.

[0014] Preferably, the electrolyte lithium salt further includes other electrolyte lithium salts, including one or more of lithium tetrafluoroborate, lithium perchlorate, lithium dioxaborate, lithium bis(fluorosulfonyl)imide, and lithium hexafluorophosphate.

[0015] More preferably, the concentration of the other electrolyte lithium salt is 0.01 mol / L to 1 mol / L, for example 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, or 1 mol / L.

[0016] Preferably, the additive further includes other additives, namely 2,6-di-tert-butyl-p-methylphenol and / or 3,5-dimethylisoxazole.

[0017] More preferably, the other additives account for 0.001% to 5% of the total mass of the electrolyte, for example, 0.001%, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and 5%.

[0018] Preferably, the carbonate solvent is selected from one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0019] Preferably, the alcohol ether solvent is selected from one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0020] Preferably, the mass ratio of the carbonate solvent to the alcohol ether solvent is 1:(0.5-2), for example 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, or 1:2.

[0021] Preferably, the organic solvent further includes other organic solvents selected from one or more of acetonitrile, γ-butyrolactone, 1,3-dioxolane, 1,4-dioxane, 1,3-dioxane, sulfolane, tetrahydrofuran, methyl butyrate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and propyl propionate.

[0022] More preferably, the other organic solvent is selected from one or more of acetonitrile, 1,3-dioxolane, sulfolane, and methyl butyrate.

[0023] More preferably, the mass of the other organic solvents is 10% to 40% of the total mass of the organic solvents, for example, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, or 40%.

[0024] The present invention also provides a lithium primary battery, which includes a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte is the electrolyte described above.

[0025] Preferably, the positive electrode material of the lithium primary battery is manganese dioxide, the negative electrode material is metallic lithium, and the shape is button, cylindrical, square, or pouch.

[0026] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0027] This invention, through the selection and combination of electrolyte lithium salt, additives and solvents, can simultaneously meet the requirements of room temperature discharge, high rate discharge, high temperature discharge performance and safety performance when applied in lithium primary batteries, and has broad application prospects in future lithium manganese primary batteries. Detailed Implementation

[0028] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific applications, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0029] In existing lithium primary batteries, the electrolyte lithium salt is typically lithium perchlorate. While it exhibits relatively good electrochemical performance at room temperature, its strong oxidizing properties result in suboptimal discharge performance at high temperatures, limited high-rate discharge capabilities, and safety hazards such as potential explosion, thus restricting the widespread application of lithium primary batteries. Replacing lithium perchlorate with other lithium salts offering better high-temperature safety further limits its discharge performance and high-rate discharge capabilities. To overcome these problems in the existing technology, the inventors of this invention, through long-term research and extensive practical experience, have proposed the technical solution of this invention.

[0030] Specifically, the electrolyte lithium salt in this invention is selected from one or more of lithium trifluoromethanesulfonate, lithium di(trifluoromethanesulfonyl)imide, lithium difluorophosphate, and lithium difluoroborate oxalate, and one or more of (2-trimethylsilylethyl)-2-acrylonitrile acetate, diphenyldimethoxysilane, and citrate anhydride as additives. At the same time, an organic solvent composed of carbonate solvents and alcohol ether solvents is used to optimize the comprehensive performance of the electrolyte in lithium primary batteries. This electrolyte has excellent discharge performance at room temperature, and can also suppress gas expansion and internal resistance increase of lithium primary batteries under high temperature conditions, thereby improving the high temperature performance, high rate discharge performance, and safety performance of lithium primary batteries.

[0031] The following will provide a further explanation of the technical solution, its implementation process, and its principles.

[0032] To provide a more intuitive comparison of the electrolyte's performance, the following comparative examples and embodiments use lithium manganese button cell 2032 and lithium manganese cylindrical CR123A batteries.

[0033] Comparative Example 1

[0034] The organic solvents are propylene carbonate and ethylene glycol dimethyl ether (mass ratio of 30:70); the electrolyte lithium salt is lithium trifluoromethanesulfonate with a concentration of 1 mol / L, and no other additives are added.

[0035] Comparative Example 2

[0036] The organic solvent is propylene carbonate, diethylene glycol dimethyl ether, and 1,3-dioxolane (in a mass ratio of 20:30:50); the electrolyte lithium salt is lithium perchlorate with a concentration of 1.1 mol / L.

[0037] Comparative Example 3

[0038] The organic solvents are propylene carbonate, ethylene glycol dimethyl ether, and 1,3-dioxolane (in a mass ratio of 40:30:30); the electrolyte lithium salt is lithium perchlorate with a concentration of 0.9 mol / L, and 1% citrate anhydride is added by mass.

[0039] Comparative Example 4

[0040] The organic solvents are ethylene carbonate, propylene carbonate, and triethylene glycol dimethyl ether (in a mass ratio of 5:25:70); the electrolyte lithium salt is lithium trifluoromethanesulfonate with a concentration of 0.8 mol / L, and no other additives are added.

[0041] Comparative Example 5

[0042] The organic solvents are ethylene carbonate, propylene carbonate, and ethylene glycol dimethyl ether (in a mass ratio of 8:32:60); the electrolyte lithium salts are 0.5 mol / L lithium trifluoromethanesulfonate and 0.2 mol / L lithium hexafluorophosphate, with no other additives added.

[0043] Example 1

[0044] The organic solvents are ethylene carbonate, propylene carbonate, and ethylene glycol dimethyl ether (in a mass ratio of 5:25:70); the electrolyte lithium salts are 0.5 mol / L lithium trifluoromethanesulfonate and 0.3 mol / L lithium bis(trifluoromethanesulfonyl)imide; and the additive is 0.5% (2-trimethylsilylethyl)2-nitrile acetate.

[0045] Example 2

[0046] The organic solvents are ethylene carbonate, propylene carbonate, ethylene glycol dimethyl ether, and 1,3-dioxolane (in a mass ratio of 8:25:27:40); the electrolyte lithium salts are 0.7 mol / L lithium bis(trifluoromethanesulfonyl)imide and 0.1 mol / L lithium difluoroborate oxalate; the additives are 0.5% (2-trimethylsilylethyl)2-acrylonitrile acetate and 0.5% diphenyldimethoxysilane.

[0047] Example 3

[0048] The organic solvents are ethylene carbonate, propylene carbonate, diethylene glycol dimethyl ether, and sulfolane (in a mass ratio of 8:35:47:10); the electrolyte lithium salts are 0.5 mol / L lithium bis(trifluoromethanesulfonyl)imide and 0.05 mol / L lithium difluorophosphate; the additives are 1% (2-trimethylsilylethyl)2-acrylic acid acetate and 0.5% citrate anhydride.

[0049] Example 4

[0050] The organic solvents are acetonitrile, propylene carbonate, diethylene glycol dimethyl ether, and methyl butyrate (in a mass ratio of 8:35:47:10); the electrolyte lithium salts are 0.8 mol / L lithium bis(trifluoromethanesulfonyl)imide and 0.05 mol / L lithium difluorophosphate; the additives are 1% (2-trimethylsilylethyl)2-acrylonitrile acetate, 0.5% diphenyldimethoxysilane, and 0.3% citrate anhydride.

[0051] Example 5

[0052] The organic solvents are propylene carbonate, ethylene glycol dimethyl ether, 1,3-dioxolane, and sulfolane (in a mass ratio of 25:35:25:15); the electrolyte lithium salts are 0.6 mol / L lithium trifluoromethanesulfonate, 0.4 mol / L lithium difluorosulfonylimide, and 0.1 mol / L lithium dioxolaneborate; the additives are 0.02% 2,6-di-tert-butyl-p-methylphenol, 1.5% diphenyldimethoxysilane, and 3% citrate anhydride.

[0053] Example 6

[0054] The organic solvents are ethylene carbonate, propylene carbonate, ethylene glycol dimethyl ether, 1,3-dioxolane, and sulfolane (in a mass ratio of 5:20:35:25:15); the electrolyte lithium salts are 0.5 mol / L lithium trifluoromethanesulfonate, 0.3 mol / L lithium di(trifluoromethanesulfonyl)imide, 0.1 mol / L lithium difluorophosphate, and 0.05 mol / L lithium difluoroborate oxalate; the additives are 0.05% 3,5-dimethylisoxazole, 3% (2-trimethylsilylethyl)2-acrylic acid acetate, 2% diphenyldimethoxysilane, and 0.1% citrate anhydride.

[0055] Example 7

[0056] The organic solvents are ethylene carbonate, propylene carbonate, ethylene glycol dimethyl ether, and 1,3-dioxolane (in a mass ratio of 10:20:35:35); the electrolyte lithium salts are 0.5 mol / L lithium di(trifluoromethanesulfonyl)imide, 0.1 mol / L lithium perchlorate, and 0.1 mol / L lithium difluorophosphate; the additives are 0.01% 3,5-dimethylisoxazole, 0.5% citrate anhydride, and 3% (2-trimethylsilylethyl)2-cyanoacetate.

[0057] Example 8

[0058] The organic solvents are ethylene carbonate, propylene carbonate, ethylene glycol dimethyl ether, and methyl butyrate (in a mass ratio of 10:20:35:35); the electrolyte lithium salts are 0.5 mol / L lithium di(trifluoromethanesulfonyl)imide, 0.1 mol / L lithium perchlorate, and 0.1 mol / L lithium difluoroborate oxalate; the additives are 1% diphenyldimethoxysilane and 5% citrate anhydride.

[0059] Example 9

[0060] The organic solvents are ethylene carbonate, propylene carbonate, and ethylene glycol dimethyl ether (in a mass ratio of 10:50:40); the electrolyte lithium salts are 1.2 mol / L lithium di(trifluoromethanesulfonyl)imide, 0.1 mol / L lithium hexafluorophosphate, and 0.1 mol / L lithium difluoroborate oxalate; the additives are 3% citrate anhydride, 1% diphenyldimethoxysilane, and 2% (2-trimethylsilylethyl)-2-cyanoacetate.

[0061] Example 10

[0062] The organic solvents are propylene carbonate, ethylene glycol dimethyl ether, and sulfolane (in a mass ratio of 55:35:10); the electrolyte lithium salts are 0.8 mol / L lithium trifluoromethanesulfonate, 0.6 mol / L lithium di(trifluoromethanesulfonyl)imide, and 0.1 mol / L lithium difluorophosphate; the additives are 1.5% (2-trimethylsilylethyl)2-acrylonitrile acetate and 5% diphenyldimethoxysilane.

[0063] Experimental results

[0064] Constant resistance discharge, high-temperature post-discharge, high-current discharge and flame retardant testing:

[0065] The discharge performance of the battery was tested using a Shenzhen Xinwei battery tester.

[0066] Five comparative examples and twelve exemplary examples were formulated into electrolytes according to the recipes and injected into CR2032 coin cell batteries and CR123A cylindrical lithium manganese primary batteries. The electrolytes were subjected to constant resistance discharge at room temperature, discharge after being placed at 60 degrees Celsius for 20 days, high current pulse discharge, and flame retardancy tests, respectively.

[0067] The test method for constant resistance discharge at room temperature is as follows: under room temperature conditions, with a resistance of 1KΩ, discharge at constant resistance until the cutoff voltage of 2.0V;

[0068] The test method for discharge after being placed at 60 degrees Celsius for 20 days is as follows: place it in a 60°C oven for 20 days, then remove it and discharge it at room temperature with a constant current of 1000mA to 2.0V.

[0069] The test method for high-current pulse discharge is as follows: under normal temperature conditions, discharge at a constant current of 3A for 3s, rest for 27s, and cycle until the voltage reaches 1.8V and then stop.

[0070] The flame retardant test method is as follows: absorb sufficient electrolyte with degreased cotton and ignite it directly with a flame source.

[0071] The test results for all comparative examples and embodiment examples are shown in Table 1.

[0072] Table 1

[0073]

[0074]

[0075] The flame retardant test results are shown in Table 2:

[0076] Table 2

[0077] Comparative examples and embodiments Electrolyte ignition experiment Comparative Example 1 on fire Comparative Example 2 on fire Comparative Example 3 on fire Comparative Example 4 on fire Comparative Example 5 on fire Example 1 on fire Example 2 on fire Example 3 on fire Example 4 on fire Example 5 on fire Example 6 No fire Example 7 on fire Example 8 on fire Example 9 No fire Example 10 No fire

[0078] Table 1 shows that the coin-type CR2032 lithium manganese primary batteries of each embodiment and comparative example have little difference in discharge capacity at a constant resistance of 1KΩ at room temperature. This indicates that under room temperature and low current conditions, all electrolyte formulations can release a certain capacity, and the conductivity requirement is not high. However, there are significant differences in the discharge performance of the column-type CR123A pulse discharge and after high-temperature storage. The optimization of the electrolyte lithium salt and the selection of additives have a positive impact on the discharge capacity of the lithium primary battery after high-temperature storage and the high-current 3A pulse discharge capacity. The optimized electrolyte lithium salt combination can form a passivation film to prevent other corrosive substances from corroding the aluminum foil. The added citralic anhydride, diphenyldimethoxysilane, and (2-trimethylsilylethyl)2-cyanoacetate can participate in the formation of the interface film on the positive electrode surface, which has a positive impact on the discharge capacity of the battery. In addition, the ignition test results of the electrolytes of some embodiments show that they do not ignite, that is, the flame retardant performance is significantly improved, and they have better safety performance.

[0079] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A lithium primary battery, characterized in that, The positive electrode material of the lithium primary battery is manganese dioxide, and the negative electrode material is metallic lithium. The electrolyte of the lithium primary battery comprises an electrolyte lithium salt, additives, and an organic solvent. The electrolyte lithium salt includes one or more of lithium trifluoromethanesulfonate, lithium di(trifluoromethanesulfonyl)imide, lithium difluorophosphate, and lithium difluoroborate oxalate. The additives include one or more of (2-trimethylsilylethyl)-2-acrylonitrile acetate, diphenyldimethoxysilane, and citrate anhydride. The organic solvents include carbonate solvents and alcohol ether solvents. The carbonate solvents are selected from one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. The alcohol ether solvents are selected from one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. The concentration of the electrolyte lithium salt is 0.1 mol / L to 2 mol / L. The additives account for 0.5% to 15% of the total mass of the electrolyte.

2. The lithium primary battery according to claim 1, characterized in that, The electrolyte lithium salt also includes other electrolyte lithium salts, including one or more of lithium tetrafluoroborate, lithium perchlorate, lithium dioxaborate, lithium bis(fluorosulfonyl)imide, and lithium hexafluorophosphate.

3. The lithium primary battery according to claim 2, characterized in that, The concentration of the other electrolyte lithium salt is 0.01 mol / L to 1 mol / L.

4. The lithium primary battery according to claim 1, characterized in that, The additives also include other additives, namely 2,6-di-tert-butyl-p-methylphenol and / or 3,5-dimethylisoxazole.

5. The lithium primary battery according to claim 4, characterized in that, The other additives mentioned account for 0.001% to 5% of the total mass of the electrolyte.

6. The lithium primary battery according to claim 1, characterized in that, The organic solvents also include other organic solvents selected from one or more of acetonitrile, γ-butyrolactone, 1,3-dioxolane, 1,4-dioxane, 1,3-dioxane, sulfolane, methyl butyrate, tetrahydrofuran, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and propyl propionate.

7. The lithium primary battery according to claim 1, characterized in that, The lithium primary battery can be in the shape of a button cell, cylinder, square cell, or pouch cell.

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