Lithium carbon fluoride primary battery electrolyte and preparation method and application thereof

Abstract

The invention discloses a lithium carbon fluoride primary battery electrolyte, which is composed of a lithium salt, a mixed solvent and In (OTf) 3 as an additive, the mass fraction of In (OTf) 3 is 0.01%-5%, the mixed solvent is an organic solvent composed of methyl acetate, a carbonic ester solvent and an ether solvent, the mass fraction of methyl acetate is 20%-50%, the mass fraction of carbonic ester solvent is 20%-50%, and the mass fraction of ether solvent is 20%-50%. The invention also discloses a preparation method thereof and a lithium carbon fluoride primary battery. Methyl acetate (MA) is introduced as a solvent, and In (OTf) 3 is added as a functional additive, so that the high-rate discharge capacity of the battery can be improved, the low-temperature performance can be improved, and the long-term storage stability can be enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium primary batteries, and in particular relates to a lithium carbon fluoride primary battery electrolyte, a preparation method thereof, and a method for using the electrolyte in the lithium carbon fluoride primary battery. Background Art

[0002] Lithium carbon fluoride (LCF) batteries are high-energy primary lithium batteries that have attracted widespread attention due to their ultra-high theoretical specific energy (2180 Wh / kg). However, existing LCF battery technology still has some key issues that limit its effectiveness in specific application scenarios.

[0003] First, existing lithium-carbon fluoride batteries (LCF) perform poorly under high-rate discharge conditions. On the one hand, the poor electronic conductivity of CF materials leads to high resistance in the material and electrodes. On the other hand, CF generates insoluble LiF during discharge, which deposits on the surface of the positive electrode material, further increasing the resistance of the material and electrode and hindering the lithium insertion process. Consequently, LCF batteries exhibit poor high-rate discharge capability, accompanied by voltage drop and high heat generation.

[0004] Secondly, the performance of lithium-carbon fluoride batteries decreases significantly in low-temperature environments. Under low-temperature conditions, the viscosity of the electrolyte increases and the ionic conductivity decreases, which leads to an increase in the internal resistance of the battery, thereby affecting the battery's discharge efficiency and output power.

[0005] In addition, the low temperature environment further slows down the chemical reaction rate inside the battery, further deteriorating battery performance.

[0006] Finally, insufficient long-term storage stability is another significant issue facing existing lithium-carbon fluoride batteries. During long-term storage, reactions such as self-discharge and electrolyte decomposition may occur within the battery, leading to capacity degradation and shortened battery life. This is particularly true for primary batteries, as their non-rechargeable nature renders them unusable once they fail, increasing operational costs and maintenance difficulties.

[0007] Chinese patent CN116525953A discloses a low-temperature electrolyte for lithium carbon fluoride batteries. Dimethylformamide (DMF) and dioxolane (DOL) are used as the main components of the electrolyte. The low viscosity and high dielectric constant of DMF and DOL ensure that the electrolyte has high lithium ion conductivity under low temperature conditions. At the same time, the high number of electron donors in DMF can effectively induce the dissociation of carbon-fluoride bonds, thereby reducing the reaction energy barrier of carbon fluoride and improving the reaction kinetics. However, DMF is unstable towards the metallic lithium negative electrode, which is not conducive to the battery after long-term storage.

[0008] Chinese patent CN116666674A discloses a high-energy-density lithium / carbon fluoride primary battery electrolyte and its applications. From an electrolyte perspective, the invention introduces FEC, a commonly used film-forming additive, into the Li / CFx battery electrolyte as a cosolvent to form the electrolyte. FEC participates in the battery's discharge process, improving the electrode / electrolyte interface while boosting the battery's discharge capacity, thereby achieving high energy density. However, FEC requires electrochemical reactions to participate in interfacial processes and cannot react in an undischarged storage state to form an effective protective layer, thus failing to effectively extend the battery's storage life. Summary of the Invention

[0009] In order to overcome the above technical difficulties, one of the objectives of the present invention is to propose a lithium carbon fluoride primary battery to solve the problems of poor high-rate discharge capability, performance degradation in low-temperature environments, and insufficient long-term storage stability in the existing technology.

[0010] The technical solution adopted by the present invention to solve its technical problem is: a lithium fluoride carbon primary battery electrolyte, composed of a lithium salt, a mixed solvent and In(OTf)3 as an additive, wherein the mass fraction of In(OTf)3 in the electrolyte is 0.01% to 5%, and the mixed solvent is an organic solvent composed of methyl acetate, a carbonate solvent and an ether solvent, wherein the mass fraction of methyl acetate in the mixed solvent is 20% to 50%.

[0011] Furthermore, the lithium salt is lithium hexafluorophosphate (LiPF6) or lithium perchlorate (LiClO4) or a mixture of the two.

[0012] Furthermore, the carbonate solvent is propylene carbonate (PC).

[0013] Furthermore, the ether solvent is ethylene glycol dimethyl ether (DME).

[0014] The second object of the present invention is to propose a method for preparing the above-mentioned lithium fluorinated carbon primary battery electrolyte, the steps of which are: in a glove box filled with argon, propylene carbonate, ethylene glycol dimethyl ether and methyl acetate are weighed on a balance and mixed evenly, and then lithium salt is added to the mixed solvent. After the lithium salt is completely dissolved, a lithium salt electrolyte with a concentration of 0.8 to 1.4 mol / L is obtained, and then the additive In(OTf)3 is added to obtain a lithium fluorinated carbon primary battery electrolyte.

[0015] Furthermore, in the glove box, H2O≤0.1ppm, O2≤0.1ppm, and a 4Å molecular sieve was used to purify the corresponding organic solvent and remove water at room temperature to obtain a pure solvent.

[0016] The third object of the present invention is to propose that the above electrolyte be used in lithium carbon fluoride primary batteries to achieve simultaneous improvement in the high-rate discharge capability, low-temperature performance, and storage stability of lithium carbon fluoride primary batteries.

[0017] The beneficial effects of the present invention are: by introducing methyl acetate (MA) as a solvent and adding In(OTf)3 as a functional additive to the electrolyte, the battery's high-rate discharge capability, low-temperature performance, and long-term storage stability can be improved. Specifically, MA can effectively reduce the viscosity of the electrolyte, significantly improving the ionic conductivity and low-temperature performance of the electrolyte; In(OTf)3 as a functional additive has multiple functions. 3+ It can form an alloy layer with the negative electrode metal lithium to protect the lithium negative electrode and thus increase the storage life of the battery; the Lewis acidity of In(OTf)3 helps dissolve the discharge product LiF, promotes the rapid reaction of the positive electrode, and improves the high-rate discharge energy of the battery.

[0018] The present invention introduces 20% to 50% by mass of MA into the solvent, which can effectively reduce the viscosity of the electrolyte, improve the conductivity of the electrolyte, and facilitate the ion conduction of the electrolyte at low temperatures. At the same time, the low viscosity electrolyte also provides a basis for the dissolution of LiF in the electrolyte. The additive In(OTf)3 can remove the inert LiF generated during the discharge process of the positive electrode, promote the rapid reaction of the positive electrode, and improve the high-rate discharge capability of the battery. In addition, In 3+ It can form an alloy layer with the negative electrode metal lithium to protect the lithium negative electrode and thus increase the storage life of the battery.

[0019] In summary, the present invention can improve the low-temperature performance, rate performance and storage stability of lithium carbon fluoride primary batteries by introducing co-solvent MA and functional In(OTf)3. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 1 is a discharge curve diagram of Example 1 and Comparative Example 1 at the same rate. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Example 1

[0022] This embodiment provides an electrolyte for a lithium carbon fluoride primary battery. The electrolyte is composed of a carefully selected lithium salt, a non-aqueous organic solvent, and functional additives, prepared in specific proportions. Specifically, the lithium salt is LiPF6 at a concentration of 1.2 mol / L, the mixed solvent is PC, DME, and MA in a mass ratio of PC:DME:MA = 4:4:2, and the additive In(OTf)3 accounts for 1% by mass of the electrolyte.

[0023] The present invention introduces methyl acetate (MA) into the solvent and adds the additive In(OTf)3 into the electrolyte. MA can reduce the viscosity of the electrolyte, improve the ionic conductivity and low-temperature performance of the electrolyte; In(OTf)3 can remove the inert LiF generated during the discharge process of the positive electrode, promote the rapid reaction of the positive electrode, and improve the high-rate discharge capability of the battery. 3+ It can form an alloy layer with the negative electrode metal lithium, protecting the lithium negative electrode and thus extending the battery's storage life. In summary, the electrolyte of the present invention, through its unique combination of components and synergistic mechanism, provides an innovative solution for improving the overall performance and application range of batteries. It is particularly suitable for application scenarios requiring high energy output, low temperature resistance, and long storage life. This electrolyte can be applied to lithium carbon fluoride primary batteries.

[0024] The preparation steps are as follows: in a glove box filled with argon, use a balance to weigh 40% PC, 40% DME and 40% MA by mass and mix them evenly, then add LiPF6 to the mixed solvent, and after it is completely dissolved, a lithium salt electrolyte with a concentration of 1.2 mol / L is obtained, and then the additive In(OTf)3 is added, and the mass fraction of the additive is 1%.

[0025] The electrolyte was prepared in a glove box due to its extreme sensitivity to water and oxygen. In a glove box filled with high-purity argon (H2O ≤ 0.1 ppm, O2 ≤ 0.1 ppm), the corresponding organic solvent was purified using 4Å molecular sieves at room temperature to remove water and obtain pure solvent.

[0026] Preparation of the positive electrode: The active material (CFx), conductive carbon black (Super P), carbon nanotubes (CNTs), and polyvinylidene fluoride (PVDF) were weighed in a mass ratio of 8:0.8:0.2:1 and placed in an agate mortar. The mixture was then thoroughly ground for 30 minutes. 2-4 mL of N-methylpyrrolidone (NMP) was then added to the mortar and ground again until a smooth, fine slurry was obtained. The slurry was then evenly coated onto carbon-coated aluminum foil using a 100 μm blade on an electrode coater. The foil was then transferred to an 80°C constant-temperature forced-air drying oven and dried for 4 hours. The dried electrode was removed and punched into 12 mm diameter discs using a manual slicer. The discs were then transferred to a vacuum drying oven at 100°C and dried for 12 hours. After complete drying, the discs were weighed on an electronic analytical balance and recorded. The discs were then placed in an 80°C vacuum drying oven for later use.

[0027] Battery assembly and testing: A CR2032 button-type battery case was used. The carbon fluoride positive electrode sheet was placed in the center of the positive electrode case. 50 μL of electrolyte was added, and a Celgard 2400 separator was placed. Another 50 μL of electrolyte was added. A lithium metal sheet (0.5 mm), a gasket, a spring, and the negative electrode case were then placed in sequence. The button-type battery was then sealed using a battery sealing machine. The assembled battery was allowed to rest for 12 hours to ensure sufficient infiltration between the electrolyte and the electrodes. A constant current discharge test was performed on a LANDCT2001A battery test system, with a discharge cutoff voltage of 1.5 V.

[0028] After testing, the lithium carbon fluoride battery using the electrolyte of this embodiment has a discharge specific capacity of 853 mAh / g when discharged at a current density of 800 mA / g; a discharge specific capacity of 720 mAh / g at -20°C when discharged at a current density of 800 mA / g; and a discharge specific capacity of 790 mAh / g when discharged at a current density of 800 mA / g after storage at 55°C for 30 days. Example 2

[0029] This embodiment provides an electrolyte for lithium fluoride carbon primary batteries. The electrolyte comprises a lithium salt, a mixed solvent, and an additive. The lithium salt is LiPF6 at a concentration of 0.8 mol / L. The mixed solvent comprises PC, DME, and MA in a mass ratio of PC:DME:MA = 4:5:1. The mass fraction of the additive In(OTf)6 in the electrolyte is 0.01%. This electrolyte can be used in lithium fluoride carbon primary batteries.

[0030] The preparation steps are as follows: in a glove box filled with argon, use a balance to weigh 40% PC, 50% DME and 10% MA by mass and mix them evenly, then add LiPF6 to the mixed solvent, and after it is completely dissolved, a lithium salt electrolyte with a concentration of 1.2 mol / L is obtained, and then the additive In(OTf)3 is added, and the mass fraction of the additive is 0.01%.

[0031] After testing, the lithium carbon fluoride battery using the electrolyte of this embodiment has a discharge specific capacity of 845 mAh / g when discharged at a current density of 800 mA / g; a discharge specific capacity of 730 mAh / g at -20°C when discharged at a current density of 800 mA / g; and a discharge specific capacity of 790 mAh / g when discharged at a current density of 800 mA / g after storage at 55°C for 30 days. Example 3

[0032] This embodiment provides an electrolyte for lithium fluoride carbon primary batteries. The electrolyte consists of a lithium salt, a mixed solvent, and an additive. The lithium salt is LiPF6 at a concentration of 1.4 mol / L. The mixed solvent is PC, DME, and MA in a mass ratio of PC:DME:MA = 3:2:5. The additive, In(OTf)3, accounts for 5% by mass of the electrolyte. This electrolyte can be used in lithium fluoride carbon primary batteries.

[0033] The preparation steps are as follows: in a glove box filled with argon, use a balance to weigh 30% PC, 20% DME and 50% MA by mass and mix them evenly, then add LiPF6 to the mixed solvent, and after it is completely dissolved, a lithium salt electrolyte with a concentration of 1.2 mol / L is obtained, and then the additive In(OTf)3 is added, and the mass fraction of the additive is 5%.

[0034] After testing, the lithium carbon fluoride battery using the electrolyte of this embodiment has a discharge specific capacity of 855 mAh / g when discharged at a current density of 800 mA / g; a discharge specific capacity of 725 mAh / g at -20°C when discharged at a current density of 800 mA / g; and a discharge specific capacity of 782 mAh / g when discharged at a current density of 800 mA / g after storage at 55°C for 30 days.

[0035] Comparative Example 1: This comparative example provides an electrolyte for a lithium fluoride carbon primary battery, wherein the lithium salt is LiPF6 with a concentration of 1.2 mol / L, the mixed solvent is PC and DME, the mass ratio of the mixed solvent is PC:DME=1:1, and the mass fraction of the additive In(OTf)3 in the electrolyte is 1%.

[0036] In an argon-filled glove box, 50% PC and 50% DME were weighed on a balance. LiPF6 was then added to the mixed solvent. After complete dissolution, a lithium salt electrolyte with a concentration of 1.2 mol / L was prepared. In(OTf)3 was then added with an additive mass fraction of 1%.

[0037] After testing, the lithium fluoride carbon battery using the electrolyte of Comparative Example 1, when discharged at a current density of 800 mA / g, the discharge specific capacity can reach 760 mAh / g; when discharged at a current density of 800 mA / g, the discharge specific capacity at -20°C can reach 550 mAh / g; after being stored at 55°C for 30 days, the discharge specific capacity can reach 760 mAh / g when discharged at a current density of 800 mA / g. The discharge curves of Example 1 and Comparative Example 1 at the same rate are shown in Figure 1. Figure 1 shown.

[0038] Comparative Example 2: This comparative example provides an electrolyte for a lithium fluoride carbon primary battery, wherein the lithium salt is LiPF6 with a concentration of 1.2 mol / L, the mixed solvent is PC, DME, and MA, and the mass ratio of the mixed solvent is PC:DME:MA=4:4:2.

[0039] In an argon-filled glove box, 40% PC, 40% DME, and 40% MA were weighed on a balance and mixed evenly. LiPF6 was then added to the mixed solvent and a lithium salt electrolyte with a concentration of 1.2 mol / L was prepared after it was completely dissolved.

[0040] After testing, the lithium carbon fluoride battery using the electrolyte of Comparative Example 2, when discharged at a current density of 800 mA / g, has a discharge capacity of 800 mAh / g at room temperature; when discharged at a current density of 800 mA / g, the discharge capacity at -20°C can reach 680 mAh / g; after storage at 55°C for 30 days, the discharge capacity can reach 750 mAh / g when discharged at a current density of 800 mA / g.

[0041] The above embodiments illustrate that the electrolyte of a lithium carbon fluoride primary battery provided by the present invention has excellent high-rate discharge capability, low-temperature performance and storage stability, and can be used to construct high-performance lithium carbon fluoride primary batteries.

[0042] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A lithium carbon fluoride primary battery electrolyte, characterized in that: The invention is composed of lithium salt, a mixed solvent and In(OTf)3 as an additive, wherein the mass fraction of In(OTf)3 is 0.01% to 5%, and the mixed solvent is an organic solvent composed of methyl acetate, a carbonate solvent and an ether solvent, wherein the mass fraction of methyl acetate is 20% to 50%.

2. The lithium carbon fluoride primary battery electrolyte according to claim 1, characterized in that: The lithium salt is lithium hexafluorophosphate or lithium perchlorate.

3. The lithium carbon fluoride primary battery electrolyte according to claim 1, characterized in that: The carbonate solvent is propylene carbonate.

4. The lithium fluoride carbon primary battery electrolyte according to claim 1, characterized in that: The ether solvent is ethylene glycol dimethyl ether.

5. A method for preparing the lithium carbon fluoride primary battery electrolyte as claimed in claim 1, characterized in that: The steps are as follows: in a glove box filled with argon, propylene carbonate, ethylene glycol dimethyl ether and methyl acetate are weighed and mixed evenly, then lithium salt is added and completely dissolved to obtain a lithium salt electrolyte with a concentration of 0.8 to 1.4 mol / L, and then the additive In(OTf)3 is added to obtain a lithium fluoride carbon primary battery electrolyte.

6. The method for preparing a lithium carbon fluoride primary battery electrolyte according to claim 5, characterized in that: In the glove box, H2O≤0.1ppm, O2≤0.1ppm, and 4Å molecular sieves were used to purify the organic solvent and remove water at room temperature.

7. An electrolyte as claimed in claim 1 for a lithium carbon fluoride primary battery.

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