Lithium-carbon fluoride battery electrolyte containing redox medium as well as preparation method and application of lithium-carbon fluoride battery electrolyte

Abstract

The invention discloses a lithium-carbon fluoride battery electrolyte containing a redox medium as well as a preparation method and application of the lithium-carbon fluoride battery electrolyte, and belongs to the technical field of lithium primary batteries. By adding 0.005-0.1 mol / L of redox medium into the electrolyte of the lithium-carbon fluoride battery, compared with the traditional solid-phase reaction, the redox medium in the electrolyte can participate in the reaction and promote the generation of LiF in the liquid phase, so that the discharge voltage platform is greatly improved, the voltage lag is delayed, and the discharge capacity of the lithium-carbon fluoride battery is also improved. In addition, the lithium-carbon fluoride battery electrolyte containing the oxidation-reduction medium also has the characteristic of being easy to prepare, and large-scale production can be realized. The technology not only improves the overall performance of the battery, but also enhances the operability and economical efficiency of the battery in practical application.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium primary batteries, and in particular relates to a lithium-carbon fluoride battery electrolyte containing a redox medium, and a preparation method and application thereof. Background Art

[0002] As the primary battery system with the highest known energy density, the lithium-carbon fluoride battery has a theoretical energy density of up to 2180Wh / kg, significantly surpassing the lithium-thionyl chloride battery (1470Wh / kg) and the lithium-manganese dioxide battery (1005Wh / kg), showing excellent energy storage potential. Thanks to the extremely high chemical stability of carbon fluoride materials, the battery of this system has an extremely low annual self-discharge rate, thus ensuring its ultra-long storage life. Therefore, lithium-carbon fluoride batteries can not only work stably in extreme or special environments, but are also widely used in high-tech fields such as medical, aerospace, and military, becoming an indispensable power solution.

[0003] However, with the rapid development of science and technology, the demand for high-energy primary batteries in various fields is becoming increasingly urgent. Although lithium-carbon fluoride batteries have many advantages, further improving their energy density faces severe challenges. Specifically, the low conductivity of carbon fluoride materials is one of the main constraints, which can lead to severe polarization. In addition, LiF produced during the discharge process is an insulating substance, which will significantly reduce the actual energy output of lithium-carbon fluoride batteries.

[0004] To overcome this bottleneck, researchers have actively explored and implemented a variety of innovative strategies. These include preparing high-specific-capacity and high-conductivity carbon fluoride cathode materials by optimizing the selection of carbon and fluorine sources; introducing efficient electrolyte additives to improve the discharge voltage platform and discharge capacity of the battery; and developing ultra-thin lithium metal anode technology to reduce the anode-to-cathode capacity ratio (N / P ratio), thereby maximizing the energy density of the battery without sacrificing safety. Although these efforts have alleviated the problem of increasing energy density to a certain extent, they are still insufficient in the face of growing application needs, and more breakthrough solutions are urgently needed.

[0005] Therefore, the present invention focuses on developing a lithium-carbon fluoride battery electrolyte containing a redox medium, aiming to effectively improve the conductivity of the carbon fluoride positive electrode through an innovative electrolyte formula, inhibit the formation of a LiF passivation layer, make the formed LiF particles smaller in size and further improve the discharge performance and energy density of the battery, and open up new ways for the application of lithium-carbon fluoride batteries in the field of high energy density and long life. Summary of the invention

[0006] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0007] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0008] Therefore, the object of the present invention is to overcome the deficiencies in the prior art and provide a lithium-carbon fluoride battery electrolyte containing a redox medium.

[0009] In order to solve the above technical problems, the present invention provides the following technical solution: It is composed of a lithium salt, a redox medium and a solvent;

[0010] Wherein, the concentration of lithium salt is 0.5-5 mol / L, and the concentration of redox medium is 0.005-0.1 mol / L;

[0011] The redox mediator includes one or more of lithium halide, 2,5-dimethyl-p-benzoquinone, 2,6-dimethylbenzoquinone, 2,6-dimethoxy-1,4-benzoquinone, and 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl free radical.

[0012] As a preferred embodiment of the lithium-carbon fluoride battery electrolyte containing redox media according to the present invention, the lithium salt includes one or more of LiBF4, LiPF6, LiBOB, LiTFSI, LiFSI, and LiClO4.

[0013] As a preferred embodiment of the lithium-carbon fluoride battery electrolyte containing a redox medium according to the present invention, the solvent includes one or more of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, y-butyrolactone, dimethyl sulfite, ethylene glycol dimethyl ether, dimethyl sulfoxide, tetraethylene glycol dimethyl ether, tetrahydrofuran, cyclopentane sulfone, methyl phenyl sulfone, 1,3-dioxolane, and acetonitrile.

[0014] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a lithium-carbon fluoride battery electrolyte containing a redox medium.

[0015] In order to solve the above technical problems, the present invention provides the following technical solutions: comprising:

[0016] Weigh a lithium salt and dissolve it in a solvent. After stirring until the lithium salt is completely dissolved, add a redox medium to the solution and continue stirring until the redox medium is completely dissolved to obtain a lithium-carbon fluoride battery electrolyte containing a redox medium.

[0017] The purpose of the present invention is to overcome the deficiencies in the prior art and provide an application of a lithium-carbon fluoride battery electrolyte containing a redox medium in the preparation of a lithium-carbon fluoride battery.

[0018] In order to solve the above technical problems, the present invention provides the following technical solutions: comprising:

[0019] In an argon atmosphere, a lithium sheet was used as a negative electrode, a carbon fluoride sheet was used as a positive electrode, and a PP film was used as a separator. 100 μL of the electrolyte was injected to assemble a battery;

[0020] Wherein, the electrolyte is left to stand for more than 12 hours.

[0021] As a preferred embodiment of the method for preparing the lithium-carbon fluoride battery of the present invention, the method for preparing the carbon fluoride sheet comprises:

[0022] Carbon fluoride, conductive carbon, and binder are mixed and evenly dispersed in N-methylpyrrolidone solvent to form a uniform slurry. Subsequently, the slurry is coated on the current collector using a coating machine to control the surface density to 1-20 mg / cm 2 After coating, place the electrode in an oven to dry. Use a punching machine to cut the dried electrode into carbon fluoride sheets with a diameter of 12 mm;

[0023] Wherein, the mass ratio of the carbon fluoride, the conductive carbon and the binder is 92:6:2.

[0024] As a preferred embodiment of the method for preparing the lithium-carbon fluoride battery of the present invention, the conductive carbon includes one or more of Super P, acetylene black, carbon black, carbon nanotubes, graphene and Ketjen black.

[0025] As a preferred solution of the method for preparing the lithium-carbon fluoride battery of the present invention, the binder includes one or more of polyvinylidene fluoride and sodium alginate.

[0026] As a preferred solution of the preparation method of the lithium-carbon fluoride battery of the present invention, the electrolyte effectively improves the conductivity of the carbon fluoride positive electrode, inhibits the formation of the LiF passivation layer, makes the formed LiF particles smaller in size and further improves the discharge performance and energy density of the battery.

[0027] Beneficial effects of the present invention:

[0028] In the traditional electrolyte system, lithium fluoride (LiF) is difficult to dissolve as an insulating product, and its crystallization rate increases with the increase of discharge rate, which not only destroys the conductive network structure of the carbon fluoride positive electrode, but also hinders the subsequent discharge of the battery, thereby reducing the actual discharge capacity of the battery and causing the internal resistance of the battery to increase, increasing heat, and seriously reducing the specific energy of the lithium-carbon fluoride battery. In addition, due to the poor conductivity of the carbon fluoride material itself, the voltage hysteresis of the lithium-carbon fluoride battery is further aggravated.

[0029] The present invention introduces a redox medium and utilizes its higher reduction potential to significantly increase the discharge voltage of the lithium-carbon fluoride battery, effectively improving the phenomenon of discharge voltage hysteresis. At the same time, the redox medium can also participate in the discharge process, promote the formation of LiF in the liquid phase, reduce the size of the formed LiF crystal particles, and avoid the passivation of the carbon fluoride positive electrode, thereby significantly increasing the discharge capacity and discharge specific energy of the lithium-carbon fluoride battery.

[0030] The present invention not only improves the discharge capacity of the lithium-carbon fluoride battery by optimizing the electrolyte composition, but also solves the voltage hysteresis problem. In addition, since the redox medium has a wide source and is easy to prepare, it provides the possibility of large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0032] Figure 1 This is the morphology of the positive electrode discharge product of the lithium-carbon fluoride battery obtained in Example 1 of the present invention;

[0033] Figure 2 is the discharge curve of the lithium-carbon fluoride battery obtained in Example 1 of the present invention;

[0034] Figure 3 This is the morphology of the positive electrode discharge product of the lithium-carbon fluoride battery obtained in Comparative Example 1;

[0035] Figure 4 This is the discharge curve of the lithium-carbon fluoride battery obtained in Comparative Example 1;

[0036] Figure 5 is the discharge curve of the lithium-carbon fluoride battery obtained in Example 5 of the present invention;

[0037] Figure 6 is the discharge curve of the lithium-carbon fluoride battery obtained in Example 6 of the present invention;

[0038] Figure 7 This is the discharge curve of the lithium-carbon fluoride battery obtained in Example 7 of the present invention. DETAILED DESCRIPTION

[0039] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0040] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0041] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0042] The raw materials used in the present invention are all commercially available unless otherwise specified.

[0043] The electrochemical performance of the material prepared in the embodiment of the present invention was tested as follows:

[0044] The positive electrode material is prepared as follows: carbon fluoride, conductive carbon black, and polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 92:6:2 and evenly dispersed in N-methylpyrrolidone solvent to form a uniform slurry. Subsequently, the slurry is coated on the current collector using a coating machine, and the surface density is controlled to be 10 mg / cm 2 . After coating, place the electrode in an oven for drying. Use a punching machine to cut the dried electrode into electrode sheets with a diameter of 12 mm. In a glove box filled with argon, use a lithium sheet as the negative electrode and a PP film as the separator, inject 100 microliters of electrolyte, and assemble into a button battery. After standing for 8 hours, use a blue electric tester CT2001A to discharge to 1.5V at a discharge current of 0.1C, and record the data.

[0045] Example 1

[0046] This embodiment provides a lithium-carbon fluoride battery electrolyte containing a redox medium, specifically:

[0047] An electrolyte was prepared by dissolving 0.05 mol / L 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl radical and 1 mol / L LiBF4 in a mixed solvent of propylene carbonate and ethylene glycol dimethyl ether (volume ratio 1:1).

[0048] Figure 1 The discharge product morphology of the positive electrode of a lithium-carbon fluoride battery prepared using the electrolyte obtained in Example 1 of the present invention. Figure 2 is the discharge curve of the lithium-carbon fluoride battery obtained in Example 1 of the present invention;

[0049] Comparative Example 1

[0050] The difference between this comparative example and Example 1 is that no redox medium is added, and the rest of the preparation process is the same as that of Example 1 to prepare an electrolyte.

[0051] Figure 3 The morphology of the discharge product of the positive electrode of the lithium-carbon fluoride battery obtained in this comparative example is as follows: Figure 4 It is the discharge curve of the lithium-carbon fluoride battery obtained in this comparative example.

[0052] and Figure 1 , 2 By comparison, it can be clearly observed that under 0.1C discharge conditions, the lithium-carbon fluoride battery prepared by the electrolyte containing redox media exhibits a significantly higher discharge voltage and discharge specific capacity than the battery without any redox media. This shows that such redox media as additives to lithium-carbon fluoride battery electrolytes can not only significantly improve the discharge capacity of lithium-carbon fluoride primary batteries, but also maintain a relatively high discharge voltage, solving the voltage hysteresis problem of lithium-carbon fluoride batteries to a certain extent.

[0053] Example 2

[0054] The difference between this embodiment and embodiment 1 is that the concentration of the redox medium is adjusted to 0.005 mol / L, and the rest of the preparation process is the same as that of embodiment 1 to prepare an electrolyte.

[0055] Example 3

[0056] The difference between this embodiment and embodiment 1 is that the concentration of the redox medium is adjusted to 0.075 mol / L, and the rest of the preparation process is the same as that of embodiment 1 to prepare an electrolyte.

[0057] Example 4

[0058] The difference between this embodiment and embodiment 1 is that the concentration of the redox medium is adjusted to 0.1 mol / L, and the rest of the preparation process is the same as that of embodiment 1 to prepare an electrolyte.

[0059] The electrochemical performance of the lithium-carbon fluoride battery prepared by the electrolyte obtained in the above example was tested, and the comparison results with those in Example 1 are shown in Table 1.

[0060] Table 1 Effect of the presence or absence of redox mediator and its concentration on battery performance

[0061]

[0062] As can be seen from the table above, adjusting the concentration of the redox medium has a significant effect on the performance of the prepared lithium-carbon fluoride battery. This is because the redox medium participates in the discharge process, promotes the formation of LiF in the liquid phase, slows down the accumulation of inert product LiF on the positive electrode surface, and increases the discharge capacity and discharge voltage. However, when the concentration of the redox medium increases, the discharge capacity of the battery does not increase significantly, which may be related to the fact that the excess redox medium changes the Li + According to the results in the above table, the best technical effect can be obtained when the concentration of the redox medium in the present invention is 0.05 mol / L.

[0063] Example 5

[0064] The difference between this embodiment and embodiment 1 is that the type of redox medium is adjusted to 2,5-dimethyl-p-benzoquinone, and the rest of the preparation process is the same as that of embodiment 1 to prepare an electrolyte.

[0065] Figure 5 This is the discharge curve of the lithium-carbon fluoride battery obtained in Example 5 of the present invention.

[0066] Example 6

[0067] The difference between this embodiment and embodiment 1 is that the type of redox medium is adjusted to 2,6-dimethylbenzoquinone, and the rest of the preparation process is the same as that of embodiment 1 to prepare an electrolyte.

[0068] Figure 6 This is the discharge curve of the lithium-carbon fluoride battery obtained in Example 6 of the present invention.

[0069] Example 7

[0070] The difference between this embodiment and embodiment 1 is that the type of redox medium is adjusted to 2,6-dimethoxy-1,4-benzoquinone, and the rest of the preparation process is the same as that of embodiment 1 to prepare an electrolyte.

[0071] Figure 7 This is the discharge curve of the lithium-carbon fluoride battery obtained in Example 7 of the present invention.

[0072] The electrochemical performance of the material prepared in the above embodiment was tested, and the comparison results with those in Example 1 are shown in Table 2.

[0073] Table 2 Effect of different redox mediators on battery performance

[0074]

[0075]

[0076] Combined with the above table Figures 5 to 7 It can be seen that adjusting the type of redox medium has a significant effect on the performance of the prepared lithium-carbon fluoride battery, which is determined by the redox potential of the redox medium itself and its dispersion in the electrolyte. According to the results in the above table, the best technical effect can be obtained when the type of redox medium in the present invention is 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl free radical.

[0077] Example 8

[0078] The difference between this embodiment and embodiment 1 is that LiBF4 is adjusted to LiPF6, and the rest of the preparation process is the same as that of embodiment 1 to obtain an electrolyte.

[0079] Example 9

[0080] The difference between this embodiment and embodiment 1 is that LiBF4 is adjusted to LiBOB, and the rest of the preparation process is the same as that of embodiment 1 to prepare an electrolyte.

[0081] Example 10

[0082] The difference between this embodiment and embodiment 1 is that LiBF4 is adjusted to LiTFSI, and the rest of the preparation process is the same as that of embodiment 1 to obtain an electrolyte.

[0083] Embodiment 11

[0084] The difference between this embodiment and embodiment 1 is that LiBF4 is adjusted to LiFSI, and the rest of the preparation process is the same as that of embodiment 1 to obtain an electrolyte.

[0085] Example 12

[0086] The difference between this embodiment and embodiment 1 is that LiBF4 is adjusted to LiClO4, and the rest of the preparation process is the same as that of embodiment 1 to obtain an electrolyte.

[0087] The electrochemical performance of the material prepared in the above embodiment was tested, and the comparison results with those in Example 1 are shown in Table 3.

[0088] Table 3 Effect of different lithium salts on battery performance

[0089]

[0090]

[0091] It can be seen from the above table that the adjustment of the lithium salt has a significant effect on the performance of the prepared lithium-carbon fluoride battery. This is due to the different solubilities of different lithium salts in the mixed solvent of propylene carbonate and ethylene glycol dimethyl ether (volume ratio 1:1). According to the results in the above table, the best technical effect can be obtained when the lithium salt in the present invention is LiBF4.

[0092] Comparative Example 2

[0093] The difference between this comparative example and Example 1 is that the addition amount of the redox medium (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl free radical) is adjusted to 0.2 mol / L, and the rest of the preparation process is the same as that of Example 1 to obtain an electrolyte.

[0094] Comparative Example 3

[0095] The difference between this comparative example and Example 1 is that the addition amount of the redox medium (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl free radical) is adjusted to 0.15 mol / L, and the rest of the preparation process is the same as that of Example 1 to obtain an electrolyte.

[0096] Comparative Example 4

[0097] The difference between this comparative example and Example 1 is that the addition amount of the redox medium (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl free radical) is adjusted to 0.001 mol / L, and the rest of the preparation process is the same as that of Example 1 to obtain an electrolyte.

[0098] Comparative Example 5

[0099] The difference between this comparative example and Example 1 is that the addition amount of the redox medium (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl free radical) is adjusted to 0.004 mol / L, and the rest of the preparation process is the same as that of Example 1 to obtain an electrolyte.

[0100] The electrochemical performance of the material obtained in the above comparative example was tested, and the comparison results with those of Example 1 are shown in Table 4.

[0101] Table 4 Effect of different redox mediator concentrations on battery performance

[0102]

[0103]

[0104] As can be seen from the table above, the electrolyte with added redox media increases the discharge voltage platform compared to the electrolyte without added redox media. The concentration of redox media has an impact on the discharge voltage platform of the battery. Too low or too high a concentration will cause the battery capacity to decay.

[0105] In summary, the positive electrode of the lithium-carbon fluoride battery has poor conductivity and large voltage polarization, and the generated discharge products will passivate the positive electrode and affect the energy utilization. The present invention changes the reaction path of the discharge product LiF or adjusts the morphology of LiF by adding a redox medium, thereby improving the energy density. The present invention reduces the crystal size of the discharge product, which is more conducive to high-rate discharge and increased specific capacity. The present invention not only improves the discharge capacity of the lithium-carbon fluoride battery by optimizing the electrolyte composition, but also solves the voltage hysteresis problem, and because the redox medium is widely available and easy to prepare, it provides the possibility of large-scale production.

[0106] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A lithium-carbon fluoride battery electrolyte containing a redox medium, characterized in that: It is composed of a lithium salt, a redox medium and a solvent; Wherein, the concentration of lithium salt is 0.5-5 mol / L, and the concentration of redox medium is 0.005-0.1 mol / L; The redox mediator includes one or more of lithium halide, 2,5-dimethyl-p-benzoquinone, 2,6-dimethylbenzoquinone, 2,6-dimethoxy-1,4-benzoquinone, and 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl free radical.

2. The lithium-carbon fluoride battery electrolyte containing a redox medium according to claim 1, characterized in that: The lithium salt includes one or more of LiBF4, LiPF6, LiBOB, LiTFSI, LiFSI, and LiClO4.

3. The lithium-carbon fluoride battery electrolyte containing a redox medium according to claim 1, characterized in that: The solvent includes one or more of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, y-butyrolactone, dimethyl sulfite, ethylene glycol dimethyl ether, dimethyl sulfoxide, tetraethylene glycol dimethyl ether, tetrahydrofuran, cyclopentane sulfone, methyl phenyl sulfone, 1,3-dioxolane, and acetonitrile.

4. The method for preparing a lithium-carbon fluoride battery electrolyte containing a redox medium according to claim 1, characterized in that: include, Weigh a lithium salt and dissolve it in a solvent. After stirring until the lithium salt is completely dissolved, add a redox medium to the solution and continue stirring until the redox medium is completely dissolved to obtain a lithium-carbon fluoride battery electrolyte containing a redox medium.

5. Use of the lithium-carbon fluoride battery electrolyte containing a redox medium as claimed in claim 1 in the preparation of a lithium-carbon fluoride battery.

6. The method for preparing a lithium-carbon fluoride battery according to claim 5, characterized in that: include, In an argon atmosphere, a lithium sheet was used as a negative electrode, a carbon fluoride sheet was used as a positive electrode, and a PP film was used as a separator. 100 μL of the electrolyte was injected to assemble a battery; Wherein, the electrolyte is left to stand for more than 12 hours.

7. The method for preparing a lithium-carbon fluoride battery according to claim 6, characterized in that: The method for preparing the carbon fluoride positive electrode sheet, include, The carbon fluoride, conductive carbon and binder are mixed and evenly dispersed in N-methylpyrrolidone solvent to form a uniform slurry. Subsequently, the slurry is coated on the current collector to control the surface density to 1-20 mg / cm 2 After coating, drying and cutting are performed to obtain carbon fluoride positive electrode sheets; Wherein, the mass ratio of the carbon fluoride, the conductive carbon and the binder is 92:6:

2.

8. The method for preparing a lithium-carbon fluoride battery according to claim 6, characterized in that: The conductive carbon includes one or more of SuperP, acetylene black, carbon black, carbon nanotubes, graphene and Ketjen black.

9. The method for preparing a lithium-carbon fluoride battery according to claim 6, characterized in that: The binder includes one or more of polyvinylidene fluoride and sodium alginate.

10. The method for preparing a lithium-carbon fluoride battery according to claim 6, characterized in that: The electrolyte effectively improves the conductivity of the carbon fluoride positive electrode, reduces the size of the formed LiF particles, inhibits the formation of the LiF passivation layer, and further improves the discharge performance and energy density of the battery.

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