A lithium / carbon fluoride battery electrolyte and its application in batteries

Abstract

The present invention provides a lithium / carbon fluoride battery electrolyte and its application in a battery. The electrolyte includes a lithium salt, a lipid solvent, a nitrile solvent, an ether solvent, and an electrolyte additive. The lithium / carbon fluoride battery electrolyte prepared by the present invention can form a stable passivation layer on the surfaces of the carbon fluoride positive electrode and the lithium metal negative electrode through pre-discharge, solves the problem of voltage hysteresis in the initial stage of discharge of the lithium / carbon fluoride battery, and finally reduces the self-discharge rate of the lithium / carbon fluoride battery during high-temperature storage, thereby significantly improving the shelf stability (capacity retention rate) of the lithium / carbon fluoride battery at a high temperature of 55 °C, as well as the discharge performance at high temperature (85 °C) and low temperature (-40 °C), and can be widely applied to lithium / carbon fluoride batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode material preparation, and particularly to the application of nitrogen-doped carbon-coated carbon fluoride electrode materials in lithium / carbon fluoride batteries. Background Art

[0002] With the technological progress in fields such as mobile communication, aerospace, transportation, and military equipment, the development of various high specific energy power batteries has become an urgent need for the development of the national economy. Due to the characteristics of light mass and negative electrode potential of metallic lithium, the development of primary lithium batteries with lithium as the negative electrode has received great attention. Primary lithium batteries mainly include lithium-manganese dioxide (Li / MnO2), lithium-sulfur dioxide (Li / SO2), lithium-thionyl chloride (Li / SOCl2), and lithium-carbon fluoride (Li / CF x ) and other battery systems. Compared with other primary batteries, the Li / CFx battery has the highest theoretical specific energy value (2180 Wh / kg). At the same time, the Li / CF x battery also has advantages such as high safety, stable discharge voltage, and environmental friendliness, and is particularly suitable as a power source for instrument equipment used in unmanned or enclosed environments. Such as cardiac pacemakers, missile ignition systems, radio transmitters, underwater electronic detectors, etc., especially as a communication power source for military long-range reconnaissance and soldiers to carry with them, it has great application potential.

[0003] The Li / CFx battery is a primary chemical power source with the highest theoretical specific energy. Inevitably, it needs to be stored and shelved during actual use, especially in application fields such as aviation and military. During storage, especially under high temperature (such as 55 °C) conditions, the self-discharge of the Li / CF x battery is serious, resulting in a decrease in its discharge capacity, and the voltage hysteresis phenomenon becomes more obvious, and it will further intensify with the increase of the external temperature and storage time. Therefore, it is crucial to improve the high-temperature storage performance of the Li / CFx battery. The reasons for the self-discharge of the Li / CF x battery include: on the one hand, during the storage of the Li / CF x battery, part of the fluorine on the surface of the positive electrode CF x spontaneously reacts, consuming part of the fluorine, resulting in a reduction in the final capacity of the Li / CF x battery; on the other hand, during high-temperature storage or use of the Li / CF x battery, due to the high activity of the lithium negative electrode, a large amount of electrolyte decomposes on the surface of the lithium negative electrode, resulting in irreversible attenuation of the capacity of the Li / CF x battery. Summary of the Invention

[0004] The present invention aims at the above-mentioned situations that may cause Li / CF xReasons for self-discharge and capacity reduction of the battery. By improving the electrolyte formulation and introducing a pre-discharge method, the self-discharge problem of Li / CF x batteries during storage has been significantly improved. The electrolyte of the lithium / carbon fluoride battery of the present invention has been improved. After the improved electrolyte is pre-discharged, a stable passivation layer can be formed on the surfaces of the carbon fluoride positive electrode and the lithium metal negative electrode; this method solves the voltage hysteresis problem in the initial stage of discharge of the lithium / carbon fluoride battery, and finally reduces the self-discharge rate of the lithium / carbon fluoride battery during high-temperature storage, significantly improving the shelf stability (capacity retention rate) of the lithium / carbon fluoride battery at high temperature, and the discharge performance at high and low temperatures, and can be widely applied to lithium / carbon fluoride batteries.

[0005] The technical solution of the present invention is as follows:

[0006] On the one hand, the present invention provides an electrolyte for a lithium / carbon fluoride battery, and the electrolyte includes a lithium salt, an organic solvent, and an electrolyte additive; the organic solvent simultaneously includes a lipid solvent, a nitrile solvent, and an ether solvent, and the volume ratio of the lipid solvent, the ether solvent, and the nitrile solvent is (65-80):(15-25):(5-10); the electrolyte additive simultaneously includes vinylene sulfate, lithium difluorophosphate, and lithium nitrate.

[0007] Preferably, the electrolyte additive (vinylene sulfate, lithium difluorophosphate, and lithium nitrate) accounts for 0.5-5% of the total mass of the lithium salt and the organic solvent.

[0008] Preferably, vinylene sulfate, lithium difluorophosphate, and lithium nitrate respectively account for 0.2-2 wt%, 0.1-1.5 wt%, and 0.1-3 wt% of the total mass of the lithium salt and the organic solvent.

[0009] Preferably, the concentration of the lithium salt in the organic solvent is 0.5-1.5 M, preferably 1 M.

[0010] Preferably, the lithium salt includes one or more of lithium perchlorate and lithium tetrafluoroborate.

[0011] Preferably, the nitrile solvent is at least one of acetonitrile, propionitrile, and succinonitrile.

[0012] Preferably, the lipid solvent is a mixture of two or more of ethyl acetate, propylene carbonate, 1,4-butyrolactone, and diethyl carbonate.

[0013] Preferably, the ether solvent is one or more of diethylene glycol dimethyl ether, tetrahydrofuran, and 1,3-dioxolane.

[0014] On the other hand, the present invention provides an application of the above electrolyte in a primary lithium / carbon monofluoride battery. Specifically: before the primary lithium / carbon monofluoride battery is stored or before it is discharged, the lithium / carbon monofluoride battery filled with the above electrolyte is first pre-discharged at a rate of 0.01-0.5C for 1-300 minutes. The purpose is to form a uniform passivation layer on the surfaces of the positive and negative electrodes of the electrolyte, so as to protect the above battery to exhibit excellent shelf stability during actual use; after the pre-discharge is completed, a part of the lithium / carbon monofluoride batteries are discharged at a rate of 0.1C to 1V at -40°C - 85°C (such as normal temperature 25°C or low temperature -40°C or high temperature 85°C); another part of the lithium / carbon monofluoride batteries are placed in a high-temperature oven at 55°C - 65°C, taken out after 30-90 days, and their discharge performance (0.1C) at normal temperature is tested. The capacity before and after storage is compared, and the capacity retention rate is calculated; at the same time, the rate performance of the corresponding batteries is also investigated.

[0015] Beneficial effects

[0016] 1. Through the design of the types of solvents and additives in the electrolyte and the matching of the content relationships between various substances, the present application finally obtains an electrolyte system suitable for lithium / carbon monofluoride batteries.

[0017] 2. By improving the electrolyte for lithium / carbon monofluoride batteries, that is, the electrolyte includes a lithium salt, three organic solvents and three additives. When the three organic solvents have appropriate ratios, they can play a synergistic role, enabling it to have good solubility for the lithium salt and good compatibility with the three additives. At the same time, the electrolyte has excellent conductivity. The simultaneous use of the three additives makes the negative lithium in the lithium / carbon monofluoride battery have good stability and makes the interface between the electrode and the electrolyte stable. The above electrolyte enables the lithium / carbon monofluoride battery to simultaneously have excellent shelf stability, rate performance, high temperature (85°C) and low temperature (-40°C) performance.

[0018] 3. When using the electrolyte of the present application, the capacity retention rate of the lithium / carbon monofluoride battery can reach 98% after being stored at 55°C for 30 days and 95% after being stored for 90 days; the capacity retention rate can reach 97% after being stored at 65°C for 30 days and 91% after being stored for 90 days. At the same time, the lithium / carbon monofluoride battery has excellent high temperature (85°C), low temperature (-40°C) performance and rate performance, that is, the battery does not swell during discharge at high temperature, and can be discharged at low temperature and high rate (5C).

[0019] 4. The preparation process of the present invention is simple and easy to realize large-scale production and application. Specific embodiments

[0020] The present application will be described in detail below in conjunction with embodiments, but the present application is not limited to these embodiments. Unless otherwise specified, the raw materials in the embodiments of the present application are all purchased through commercial channels. The LAND-CT2001A charge and discharge tester is used to test the electrochemical performance of lithium / carbon fluoride batteries.

[0021] Example 1:

[0022] In a glove box filled with nitrogen, propylene carbonate, diethyl carbonate, tetrahydrofuran, and succinonitrile are used as solvents, and lithium perchlorate is dissolved in the above solvents at a molar concentration of 1 mol / L. The volume ratio of the solvents propylene carbonate, diethyl carbonate, tetrahydrofuran, and succinonitrile is: 35∶30∶25∶10. The additives are vinylene sulfate, lithium difluorophosphate, and lithium nitrate. The mass fractions of the above additives in the total mass of the lithium salt and organic solvents are 0.5%, 1.5%, and 2% respectively.

[0023] Using carbon fluoride (CF 1.01 ) as the positive electrode material and lithium metal (Li) as the negative electrode material, a soft-pack lithium / carbon fluoride battery is assembled. The number of batteries is 9, and the above-prepared electrolyte is used as the electrolyte of the battery. The following tests are carried out on the above batteries: First, pre-discharge at a rate of 0.01C for 300 min; after the pre-discharge is completed, take 3 lithium / carbon fluoride batteries and discharge them to 1V at a rate of 0.1C at room temperature of 25°C, low temperature of -40°C, and high temperature of 85°C respectively; take 4 lithium / carbon fluoride batteries and place them in a high-temperature oven at 55°C and 65°C (2 batteries are placed at each temperature condition). The 2 batteries at each temperature condition are left standing for 30 and 90 days respectively, and then taken out to test their discharge performance (0.1C) at room temperature. Compare the capacity before and after standing, and calculate the capacity retention rate; take 2 lithium / carbon fluoride batteries and discharge them to 1V at rates of 1C and 5C respectively (at room temperature of 25°C). The test data under each condition are shown in Table 2-5.

[0024] Example 2:

[0025] In a glove box filled with nitrogen, propylene carbonate, diethyl carbonate, diethylene glycol dimethyl ether, and acetonitrile are used as solvents, and lithium perchlorate is dissolved in the above solvents at a molar concentration of 1 mol / L. The volume ratio of the solvents propylene carbonate, diethyl carbonate, diethylene glycol dimethyl ether, and acetonitrile is: 45∶35∶15∶5. The additives are vinylene sulfate, lithium difluorophosphate, and lithium nitrate. The mass fractions of the above additives in the total mass of the lithium salt and organic solvents are 1%, 1.2%, and 2% respectively.

[0026] Using carbon fluoride (CF 1.01) Using carbon monofluoride (CF

[0027] Take 2 lithium / carbon monofluoride batteries and discharge them to 1V at 1C and 5C rates (at room temperature of 25°C); the test data under each condition are shown in Table 2-5 in detail.

[0028] Example 3:

[0029] In a glove box filled with nitrogen, using propylene carbonate, ethyl acetate, 1,3-dioxolane, and propionitrile as solvents, dissolve lithium perchlorate at a molar concentration of 1 mol / L in the above solvents, where the volume ratio of the solvents propylene carbonate, ethyl acetate, 1,3-dioxolane, and propionitrile is: 42∶30∶20∶8. The additives are vinylene sulfate, lithium difluorophosphate, and lithium nitrate, and the mass fractions of the above additives in the total mass of the lithium salt and organic solvents are 1%, 1.2%, and 3% respectively.

[0030] Using carbon monofluoride (CF 1.01 ) as the positive electrode material and lithium metal (Li) as the negative electrode material, assemble a soft-pack lithium / carbon monofluoride battery with 9 batteries, and use the above-prepared electrolyte as the electrolyte of the battery. Conduct the following tests on the above batteries: First, perform a pre-discharge for 5 minutes at a rate of 0.1C; after the pre-discharge is completed, take 3 lithium / carbon monofluoride batteries and discharge them to 1V at a rate of 0.1C under the conditions of room temperature of 25°C, low temperature of -40°C, and high temperature of 85°C respectively; take 4 lithium / carbon monofluoride batteries and place them in a high-temperature oven at 55°C and 65°C (2 batteries are placed at each temperature condition), and the 2 batteries at each temperature condition are left standing for 30 and 90 days respectively. After taking them out, test their discharge performance at room temperature (0.1C), compare the capacities before and after standing, and calculate the capacity retention rate;

[0031] Take 2 lithium / carbon monofluoride batteries and discharge them to 1V at 1C and 5C rates (at room temperature of 25°C); the test data under each condition are shown in Table 2-5 in detail.

[0032] Example 4:

[0033] In a glove box filled with nitrogen, lithium perchlorate was dissolved in the above solvents at a molar concentration of 1 mol / L using propylene carbonate, diethyl carbonate, tetrahydrofuran, and succinonitrile as solvents. The volume ratio of the solvents propylene carbonate, diethyl carbonate, tetrahydrofuran, and succinonitrile was 45∶30∶15∶10. The additives were vinylene sulfate, lithium difluorophosphate, and lithium nitrate, and the mass fractions of the above additives in the total mass of the lithium salt and organic solvents were 1%, 1%, and 2% respectively.

[0034] Using carbon fluoride (CF 1.01 ) as the positive electrode material and lithium metal (Li) as the negative electrode material, a soft-pack lithium / carbon fluoride battery was assembled with 9 batteries, and the above-prepared electrolyte was used as the electrolyte of the battery. The following tests were conducted on the above batteries: First, pre-discharge was carried out at a rate of 0.1 for 10 min; after the pre-discharge was completed, 3 lithium / carbon fluoride batteries were taken and discharged at a rate of 0.1C to 1V at room temperature of 25°C, low temperature of -40°C, and high temperature of 85°C respectively; 4 lithium / carbon fluoride batteries were taken and placed in a high-temperature oven at 55°C and 65°C (2 batteries were placed at each temperature condition). The 2 batteries at each temperature condition were left for 30 and 90 days respectively, and after being taken out, their discharge performance at room temperature (0.1C) was tested, the capacity before and after storage was compared, and the capacity retention rate was calculated; 2 lithium / carbon fluoride batteries were taken and discharged at rates of 1C and 5C (at room temperature of 25°C) to 1V; the test data under each condition are shown in Table 2-5.

[0035] Comparative Example 1:

[0036] A commercial electrolyte 1 was used, in which the solvents were propylene carbonate and diethyl carbonate (the volume ratio of the two was 70∶30), the additive was vinylene sulfate, and the mass fractions of the above additives in the total mass of the lithium salt and organic solvents were 3% respectively; the lithium salt was lithium perchlorate with a concentration of 1 mol / L.

[0037] Using carbon fluoride (CF 1.01) Using carbon fluoride (CF

[0038] Comparative Example 2:

[0039] ) as the positive electrode material and lithium metal (Li) as the negative electrode material, 9 soft-pack lithium / carbon fluoride batteries were assembled, and the above commercial electrolyte was used as the electrolyte of the batteries. The following tests were conducted on the above batteries: First, pre-discharge at a rate of 0.01 C for 300 min; after the pre-discharge, take 3 lithium / carbon fluoride batteries and discharge them to 1 V at a rate of 0.1 C at room temperature of 25 °C, low temperature of -40 °C, and high temperature of 85 °C respectively; take 4 lithium / carbon fluoride batteries and place them in a high-temperature oven at 55 °C and 65 °C (2 batteries are placed at each temperature condition), and the 2 batteries at each temperature condition are left standing for 30 and 90 days respectively. After taking them out, test their discharge performance at room temperature (0.1 C), compare the capacities before and after standing, and calculate the capacity retention rate; take 2 lithium / carbon fluoride batteries and discharge them to 1 V at rates of 1 C and 5 C respectively (at room temperature of 25 °C); the test data under each condition are shown in Table 2-5 in detail.

[0040] Using commercial electrolyte 2, where the solvents are propylene carbonate, 1,3-dioxolane, and tetrahydrofuran (with a volume ratio of 80:10:10), and the additives are vinylene sulfate and lithium nitrate. The mass fractions of the above additives in the total mass of the lithium salt and organic solvents are 3% and 5% respectively; the lithium salt is lithium perchlorate with a concentration of 1 mol / L. 1.01 ) as the positive electrode material and lithium metal (Li) as the negative electrode material, 9 soft-pack lithium / carbon fluoride batteries were assembled, and the above commercial electrolyte was used as the electrolyte of the batteries. The following tests were conducted on the above batteries: First, pre-discharge at a rate of 0.5 C for 1 min; after the pre-discharge, take 3 lithium / carbon fluoride batteries and discharge them to 1 V at a rate of 0.1 C at room temperature of 25 °C, low temperature of -40 °C, and high temperature of 85 °C respectively; take 4 lithium / carbon fluoride batteries and place them in a high-temperature oven at 55 °C and 65 °C (2 batteries are placed at each temperature condition), and the 2 batteries at each temperature condition are left standing for 30 and 90 days respectively. After taking them out, test their discharge performance at room temperature (0.1 C), compare the capacities before and after standing, and calculate the capacity retention rate

[0041] Take 2 lithium / carbon fluoride batteries and discharge them to 1 V at rates of 1 C and 5 C respectively (at room temperature of 25 °C); the test data under each condition are shown in Table 2-5 in detail.

[0042] Comparative Example 3:

[0043] Use commercial electrolyte 3, where the solvents are propylene carbonate, ethylene glycol dimethyl ether, 1,3-dioxolane, and fluoroether (with a volume ratio of 40:20:30:10), the additives are lithium difluorophosphate and lithium nitrate, and the mass fractions of the above additives in the total mass of the lithium salt and organic solvents are 2% and 5% respectively; the lithium salt is lithium tetrafluoroborate with a concentration of 1 mol / L.

[0044] Use carbon fluoride (CF 1.01 ) as the positive electrode material and lithium metal (Li) as the negative electrode material to assemble a soft-pack lithium / carbon fluoride battery. The number of batteries is 9, and the above commercial electrolyte is used as the electrolyte of the battery. The following tests are carried out on the above battery: First, perform a pre-discharge at a rate of 0.1 for 5 minutes; after the pre-discharge is completed, take 3 lithium / carbon fluoride batteries and discharge them to 1V at a rate of 0.1C at room temperature of 25°C, low temperature of -40°C, and high temperature of 85°C respectively; take 4 lithium / carbon fluoride batteries and place them in a high-temperature oven at 55°C and 65°C (2 batteries are placed at each temperature condition). The 2 batteries at each temperature condition are left standing for 30 and 90 days respectively, and then taken out to test their discharge performance (0.1C) at room temperature, compare the capacity before and after standing, and calculate the capacity retention rate.

[0045] Take 2 lithium / carbon fluoride batteries and discharge them to 1V at rates of 1C and 5C respectively (at room temperature of 25°C); the test data under each condition are shown in Table 2-5.

[0046] Comparative Example 4:

[0047] Use commercial electrolyte 4, where the solvents are propylene carbonate and acetonitrile (with a volume ratio of 80:20), the additives are vinylene sulfate and lithium difluorophosphate, and the mass fractions of the above additives in the total mass of the lithium salt and organic solvents are 3% and 2% respectively; the lithium salt is lithium perchlorate with a concentration of 1 mol / L.

[0048] Use carbon fluoride (CF 1.01) is used as the positive electrode material, and lithium metal (Li) is used as the negative electrode material to assemble a soft-pack lithium / carbon fluoride battery. The number of batteries is 9, and the above commercial electrolyte is used as the electrolyte of the battery. The following tests are carried out on the above batteries: First, perform a pre-discharge for 300 min at a rate of 0.01 C; after the pre-discharge is completed, take 3 lithium / carbon fluoride batteries and discharge them to 1 V at a rate of 0.1 C under the conditions of normal temperature 25 °C, low temperature -40 °C, and high temperature 85 °C respectively; take 4 lithium / carbon fluoride batteries and place them in a high-temperature oven at 55 °C and 65 °C (2 batteries are placed at each temperature condition). The 2 batteries at each temperature condition are left standing for 30 and 90 days respectively, and after taking them out, test their discharge performance at normal temperature (0.1 C), compare the capacity before and after standing, and calculate the capacity retention rate; take 2 lithium / carbon fluoride batteries and discharge them to 1 V at rates of 1 C and 5 C respectively (at normal temperature 25 °C); the test data under each condition are shown in Table 2-5 in detail.

[0049] Comparative Example 5:

[0050] Use commercial electrolyte 5, where the solvents are propylene carbonate, 1,3-dioxolane, and acetonitrile (the volume ratio is 70∶10∶20), and the additives are vinylene sulfate, lithium difluorophosphate, and lithium nitrate. The mass fractions of the above additives in the total mass of the lithium salt and organic solvents are 3%, 2%, and 5% respectively; the lithium salt is lithium perchlorate, and the concentration is 1 mol / L.

[0051] Using carbon fluoride (CF 1.01 ) as the positive electrode material, and lithium metal (Li) as the negative electrode material to assemble a soft-pack lithium / carbon fluoride battery. The number of batteries is 9, and the above commercial electrolyte is used as the electrolyte of the battery. The following tests are carried out on the above batteries: First, perform a pre-discharge for 1 min at a rate of 0.5 C; after the pre-discharge is completed, take 3 lithium / carbon fluoride batteries and discharge them to 1 V at a rate of 0.1 C under the conditions of normal temperature 25 °C, low temperature -40 °C, and high temperature 85 °C respectively; take 4 lithium / carbon fluoride batteries and place them in a high-temperature oven at 55 °C and 65 °C (2 batteries are placed at each temperature condition). The 2 batteries at each temperature condition are left standing for 30 and 90 days respectively, and after taking them out, test their discharge performance at normal temperature (0.1 C), compare the capacity before and after standing, and calculate the capacity retention rate; take 2 lithium / carbon fluoride batteries and discharge them to 1 V at rates of 1 C and 5 C respectively (at normal temperature 25 °C); the test data under each condition are shown in Table 2-5 in detail.

[0052] Comparative Example 6:

[0053] A commercial electrolyte 6 is adopted, where the solvents are propylene carbonate, ethylene glycol dimethyl ether, 1,3-dioxolane and succinonitrile (with a volume ratio of 50∶10∶15∶25), and the additives are vinylene sulfate, lithium difluorophosphate and lithium nitrate. The mass fractions of the above additives in the total mass of the lithium salt and the organic solvent are 0.1%, 0.05% and 0.05% respectively; the lithium salt is lithium tetrafluoroborate with a concentration of 1 mol / L.

[0054] Using carbon fluoride (CF 1.01 ) as the positive electrode material and lithium metal (Li) as the negative electrode material, a soft-pack lithium / carbon fluoride battery is assembled with 9 batteries, and the above commercial electrolyte is used as the electrolyte of the battery. The following tests are carried out on the above battery: First, perform a pre-discharge at a rate of 0.1 for 5 min; after the pre-discharge is completed, take 3 lithium / carbon fluoride batteries and discharge them to 1 V at a rate of 0.1C at room temperature of 25°C, low temperature of -40°C and high temperature of 85°C respectively; take 4 lithium / carbon fluoride batteries and place them in a high-temperature oven at 55°C and 65°C (2 batteries are placed at each temperature condition). The 2 batteries at each temperature condition are left standing for 30 and 90 days respectively, and then taken out to test their discharge performance (0.1C) at room temperature, compare the capacities before and after standing, and calculate the capacity retention rate; take 2 lithium / carbon fluoride batteries and discharge them to 1 V at rates of 1C and 5C respectively (at room temperature of 25°C); the test data under each condition are shown in Table 2-5.

[0055] Comparative example 7:

[0056] A commercial electrolyte 7 is adopted, where the solvents are propylene carbonate, 1,3-dioxolane and succinonitrile (with a volume ratio of 90∶5∶5), and the additives are vinylene sulfate, lithium difluorophosphate and lithium nitrate. The mass fractions of the above additives in the total mass of the lithium salt and the organic solvent are 0.1%, 2% and 4% respectively; the lithium salt is lithium perchlorate with a concentration of 1 mol / L.

[0057] Using carbon fluoride (CF 1.01) As the positive electrode material and lithium metal (Li) as the negative electrode material, 9 soft-pack lithium / carbon fluoride batteries are assembled, and the above commercial electrolyte is used as the electrolyte of the batteries. The following tests are carried out on the above batteries: First, perform a pre-discharge for 300 min at a rate of 0.01 C; after the pre-discharge is completed, take 3 lithium / carbon fluoride batteries and discharge them to 1 V at a rate of 0.1 C under the conditions of normal temperature 25 °C, low temperature -40 °C, and high temperature 85 °C respectively; take 4 lithium / carbon fluoride batteries and place them in a high-temperature oven at 55 °C and 65 °C respectively (2 batteries are placed in each temperature condition). The 2 batteries in each temperature condition are left standing for 30 and 90 days respectively, and then taken out to test their discharge performance (0.1 C) at normal temperature, compare the capacity before and after standing, and calculate the capacity retention rate; take 2 lithium / carbon fluoride batteries and discharge them to 1 V at rates of 1 C and 5 C respectively (at normal temperature 25 °C); The test data under each condition are shown in Table 2-5 in detail.

[0058] Comparative Example 8:

[0059] Use commercial electrolyte 8, where the solvents are propylene carbonate, tetrahydrofuran, and acetonitrile (the volume ratio is 80∶5∶15); the additives are vinylene sulfate, lithium difluorophosphate, and lithium nitrate, and the mass fractions of the above additives in the total mass of the lithium salt and organic solvents are 3%, 2%, and 5% respectively; the lithium salt is lithium perchlorate with a concentration of 1 mol / L.

[0060] Using carbon fluoride (CF 1.01 ) as the positive electrode material and lithium metal (Li) as the negative electrode material, 9 soft-pack lithium / carbon fluoride batteries are assembled, and the above commercial electrolyte is used as the electrolyte of the batteries. The following tests are carried out on the above batteries: First, perform a pre-discharge for 1 min at a rate of 0.5 C; after the pre-discharge is completed, take 3 lithium / carbon fluoride batteries and discharge them to 1 V at a rate of 0.1 C under the conditions of normal temperature 25 °C, low temperature -40 °C, and high temperature 85 °C respectively; take 4 lithium / carbon fluoride batteries and place them in a high-temperature oven at 55 °C and 65 °C respectively (2 batteries are placed in each temperature condition). The 2 batteries in each temperature condition are left standing for 30 and 90 days respectively, and then taken out to test their discharge performance (0.1 C) at normal temperature, compare the capacity before and after standing, and calculate the capacity retention rate; take 2 lithium / carbon fluoride batteries and discharge them to 1 V at rates of 1 C and 5 C respectively (at normal temperature 25 °C); The test data under each condition are shown in Table 2-5 in detail.

[0061] Comparative Example 9: The difference from Example 1 is the solvent ratio of the electrolyte. The organic solvent composition does not contain nitrile solvents, and the others are the same as in Example 1. The specific composition is shown in Table 1 for details.

[0062] Comparative Example 10: The difference from Example 1 is the solvent ratio of the electrolyte. The organic solvent composition does not contain ester solvents, and the others are the same as in Example 1. The specific composition is shown in Table 1 for details.

[0063] Comparative Example 11: Different from Example 1 in the solvent ratio of the electrolyte, the organic solvent composition does not contain ether solvents, and the others are the same as in Example 1. For the specific composition, see Table 1.

[0064] Comparative Example 12: Different from Example 1 in the type of additive, without the additive lithium nitrate, and the others are the same as in Example 1. For the specific composition, see Table 1.

[0065] Comparative Example 13: Different from Example 1 in the type of additive, without the additive lithium difluorophosphate, and the others are the same as in Example 1. For the specific composition, see Table 1.

[0066] Comparative Example 14: Different from Example 1 in the type of additive, without the additive vinylene sulfate, and the others are the same as in Example 1. For the specific composition, see Table 1.

[0067] Analysis of test results: The electrolyte components and matching conditions designed in the present invention enable it to have good solubility for lithium salts and good compatibility with the three additives. At the same time, the electrolyte has excellent conductivity. The simultaneous use of the three additives makes the negative lithium in the lithium / carbon fluoride battery have good stability and enables the electrode and the electrolyte to have a stable interface.

[0068] In addition, the present invention introduces a method for pre-discharging lithium / carbon fluoride batteries, which solves the problem of voltage hysteresis in the initial stage of discharging lithium / carbon fluoride batteries. The electrolyte designed in the present invention significantly improves the shelf stability (capacity retention rate) of lithium / carbon fluoride batteries at a high temperature of 55°C, the discharge performance at high temperatures (85°C) and low temperatures (-40°C), and the normal temperature rate performance, and can be widely applied to lithium / carbon fluoride batteries.

[0069] The electrolyte in the present invention simultaneously uses three solvents and three additives, and optimizes the ratio between the three solvents and the percentage of the three additives in the total mass of the electrolyte. The test results are shown in Tables 2-5.

[0070] As can be seen from the data in Table 2-5, when the method of pre-discharge is introduced simultaneously with the electrolyte of the present invention, lithium / carbon fluoride has better shelf stability (as shown in Tables 2 and 3), high and low temperature discharge performance (as shown in Table 4), and rate performance (as shown in Table 5). As in Examples 1-4, after being stored at 55 °C for 30 days, the highest capacity retention rate reaches 98%, and after being stored for 90 days, the highest capacity retention rate reaches 95%; after being stored at 65 °C for 30 days, the highest capacity retention rate reaches 97%, and after being stored for 90 days, the highest capacity retention rate reaches 90%. In contrast, when using commercial electrolytes (Comparative Examples 1-4: containing 1-2 solvents and 1-2 additives; Comparative Examples 5-8: containing 3 solvents and 3 additives, but the dosage is not within the scope of the present invention), after being stored at 55 °C for 30 days, the highest capacity retention rate is only 93%, and after being stored for 90 days, the highest capacity retention rate is only 88%; after being stored at 65 °C for 30 days, the highest capacity retention rate is only 89%, and after being stored for 90 days, the highest capacity retention rate is only 76%. It is worth mentioning that when the method of pre-discharge is introduced simultaneously with the electrolyte of the present invention, when the lithium / carbon fluoride battery discharges at a high temperature of 85 °C, the battery does not swell, which makes it have practical application value in soft-packaged batteries. At the same time, it has a high discharge specific capacity at low temperature (-40 °C), up to 486.4 mAh / g. In addition, as shown in Table 5, when using the electrolyte of the present invention (Examples 1-4: containing 3 solvents and 3 additives, and the two have appropriate proportions), the lithium / carbon fluoride battery exhibits excellent rate performance, that is, when discharging at a rate of 1C, the discharge specific capacity is above 810 mAh / g, and when discharging at a rate of 5C, the discharge specific capacity is above 620 mAh / g. When using commercial electrolytes (Comparative Examples 1-4: containing 1-2 solvents and 1-2 additives; Comparative Examples 5-8: containing 3 solvents and 3 additives, but not within the scope of the present invention), when discharging at a rate of 1C, the discharge specific capacity is only about 615 mAh / g, and when discharging at a rate of 5C, the discharge specific capacity is only about 420 mAh / g.

[0071] Table 1. Components and proportions of solvents and electrolyte additives in each example and comparative example

[0072]

[0073]

[0074] Table 2. Performance of lithium / carbon fluoride batteries with different electrolytes before and after being stored at 55 °C and 65 °C for 30 days

[0075]

[0076]

[0077] Table 3 Performance of Lithium / Carbon Fluoride Batteries with Different Electrolytes before and after 90-day Storage at 55°C and 65°C

[0078]

[0079]

[0080] Table 4 Discharge Performance of Lithium / Carbon Fluoride Batteries with Different Electrolytes at Room Temperature (25°C), High Temperature (85°C), and Low Temperature (-40°C)

[0081]

[0082] Table 5 Rate (0.1C, 1C, and 5C) Performance of Lithium / Carbon Fluoride Batteries with Different Electrolytes at Room Temperature (25°C)

[0083]

Claims

1. A lithium / carbon fluoride battery electrolyte, characterized in that, The electrolyte includes a lithium salt, an organic solvent, and an electrolyte additive; the organic solvent simultaneously includes an ester solvent, an ether solvent, and a nitrile solvent, and the volume ratio of the ester solvent, the ether solvent, and the nitrile solvent is (65-80):(15-25):(5-10); the electrolyte additive simultaneously includes vinylene sulfate, lithium difluorophosphate, and lithium nitrate.

2. The lithium / carbon fluoride battery electrolyte according to claim 1, characterized in that, The electrolyte additive accounts for 0.5-5% of the total mass of the lithium salt and the organic solvent.

3. The lithium / carbon fluoride battery electrolyte according to claim 1, wherein Vinylene sulfate, lithium difluorophosphate, and lithium nitrate respectively account for 0.2-2%, 0.1-1.5%, and 0.1-3% of the total mass of the lithium salt and the organic solvent.

4. The lithium / carbon fluoride battery electrolyte according to claim 1, wherein, The concentration of the lithium salt in the organic solvent is 0.5-1.5 M; the lithium salt is one or both of lithium perchlorate and lithium tetrafluoroborate.

5. The lithium / carbon fluoride battery electrolyte according to claim 1, wherein The nitrile solvent is at least one of acetonitrile, propionitrile, and succinonitrile.

6. The lithium / carbon fluoride battery electrolyte according to claim 1, wherein, The ester solvent is two or more of ethyl acetate, propylene carbonate, 1,4-butyrolactone, and diethyl carbonate.

7. The electrolyte of the lithium / carbon fluoride battery according to claim 1, wherein The ether solvent is one or more of diethylene glycol dimethyl ether, tetrahydrofuran, and 1,3-dioxolane.

8. Use of the electrolyte according to any one of claims 1-7 in a primary lithium / carbon monofluoride battery, characterized in that: Inject the electrolyte into the lithium / carbon monofluoride primary battery, and perform a pre-discharge at a rate of 0.01-0.5 C for 1-300 min before the battery is stored or discharged.

9. The application according to claim 8, characterized in that, The storage temperature of the battery is 55°C-65°C; the discharge temperature of the battery is -40°C-85°C.

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