A secondary lithium battery and a method of manufacturing the same

Abstract

This invention relates to lithium battery electrolytes, and discloses a cross-linked interpenetrating composite electrolyte for secondary lithium batteries and its preparation method. The composite electrolyte includes a polymer electrolyte and an anhydrous electrolyte. A membrane, which is a flexible inorganic SiO2 nanofiber membrane, is disposed within the secondary lithium battery. The composite electrolyte is located between the electrodes and the membrane of the lithium battery. The polymer electrolyte is polymerized from tetraethylene glycol diacrylate monomer and 2,2,3,3-tetrafluoropropyl methacrylate monomer. The polymer electrolyte is in a three-dimensional network structure, and the anhydrous electrolyte fills within the network of polymer electrolyte, forming a gel-like composite electrolyte. The anhydrous electrolyte is composed of an organic solvent and a lithium salt. By in-situ polymerization of tetraethylene glycol diacrylate monomer and 2,2,3,3-tetrafluoropropyl methacrylate monomer between the membrane and the electrodes of the secondary lithium battery, a network-like polymer electrolyte encapsulating the anhydrous electrolyte is formed, exhibiting excellent cycle performance and rate performance.

Description

Technical Field

[0001] This invention relates to lithium battery electrolytes, and more particularly to a secondary lithium battery and its preparation method. Background Technology

[0002] With the advancement of technology, the popularity of personal smart devices is increasing, and at the same time, rechargeable lithium batteries used in smart devices are also being widely applied.

[0003] Existing secondary lithium batteries sometimes use electrolytes as the conductive medium. These electrolytes contain volatile and flammable carbonate solutions, which generate heat during charging and discharging, leading to safety hazards such as leakage, fire, and even explosion. Others use solid polymer electrolytes, whose matrix includes polyethers, polycarbonates, and polyacrylates. While solid polymer electrolytes have better safety performance, they are not conducive to lithium-ion conduction, resulting in low discharge specific capacity and poor charge-discharge efficiency in secondary lithium batteries using solid polymer electrolytes. After a period of use, excessive lithium-ion deposition can easily occur, leading to short circuits. Summary of the Invention

[0004] To address the aforementioned problems, the primary objective of this invention is to provide a secondary lithium battery in which the cross-linked interpenetrating composite electrolyte contains a polymer electrolyte in a network structure, exhibiting advantages such as high conductivity and electrochemical stability, and possessing excellent cycle performance and rate performance.

[0005] Another objective of this invention is to provide a method for preparing a secondary lithium battery, in which an in-situ polymerized composite electrolyte is formed within the secondary lithium battery.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] A secondary lithium battery, the secondary lithium battery comprising a cross-linked interpenetrating composite electrolyte, the composite electrolyte comprising a polymer electrolyte and an anhydrous electrolyte;

[0008] The secondary lithium battery contains a separator made of flexible inorganic SiO2 nanofiber membrane; the composite electrolyte is located between the electrodes of the secondary lithium battery and the separator.

[0009] The polymer electrolyte is polymerized from tetraethylene glycol diacrylate monomer and 2,2,3,3-tetrafluoropropyl methacrylate monomer;

[0010] The polymer electrolyte is in the form of a three-dimensional network, and the anhydrous electrolyte fills the network of the polymer electrolyte, making the composite electrolyte as a whole form a gel.

[0011] The anhydrous electrolyte is composed of an organic solvent and a lithium salt.

[0012] Preferably, the mass ratio of the tetraethylene glycol diacrylate monomer to the 2,2,3,3-tetrafluoropropyl methacrylate monomer is (1-3):(1-3).

[0013] The molecular chain of 2,2,3,3-tetrafluoropropyl methacrylate contains a large number of strong electron-withdrawing groups (–C–F), thus exhibiting excellent electrochemical stability.

[0014] Preferably, the lithium salt includes at least one of LiPF6, LiBOB, LiFSI, LiTFSI, LiSbF6, LiAlO2, and LiAlCl4.

[0015] The tetraethylene glycol diacrylate monomer and the 2,2,3,3-tetrafluoropropyl methacrylate monomer are chemically stable and do not produce side reactions with lithium salts. They can also effectively dissociate different lithium salts, which is beneficial for lithium-ion transport.

[0016] Preferably, the organic solvent includes at least one of carbonate solvents, ester solvents, ether solvents, alcohol solvents, and nitrile solvents.

[0017] Preferably, the concentration of the lithium salt in the anhydrous electrolyte is 0.1-5M.

[0018] Furthermore, a method for preparing a secondary lithium battery includes the step of preparing a cross-linked interpenetrating composite electrolyte for the aforementioned secondary lithium battery. The step of preparing the cross-linked interpenetrating composite electrolyte includes:

[0019] S1) Weigh out tetraethylene glycol diacrylate monomer, 2,2,3,3-tetrafluoropropyl methacrylate monomer and anhydrous electrolyte in proportion, mix them evenly, then add powdered 2,2-azobisisobutyronitrile, stir evenly, and obtain the precursor of polymer electrolyte.

[0020] S2) Flexible inorganic SiO2 nanofiber membranes were prepared by electrospinning and high-temperature calcination in a muffle furnace using ethyl silicate as raw material.

[0021] S3) The flexible inorganic SiO2 nanofiber membrane is installed as a separator in a secondary lithium battery, and the precursor is injected between the electrode and the separator of the secondary lithium battery. Then, it is placed in a low temperature chamber to stand.

[0022] S4) The secondary lithium battery, after being left to stand, is placed in a high-temperature chamber and heated to allow the tetraethylene glycol diacrylate monomer and the 2,2,3,3-tetrafluoropropyl methacrylate monomer to undergo a polymerization reaction between the surface of the flexible inorganic SiO2 nanofiber membrane and the electrode. After the reaction is completed, the mixture is cooled to room temperature to obtain the composite electrolyte.

[0023] Preferably, in step S1), the total mass of the tetraethylene glycol diacrylate monomer and the 2,2,3,3-tetrafluoropropyl methacrylate monomer is 3-20% of the mass of the precursor of the polymer electrolyte.

[0024] Preferably, in step S1), the content of the powdered 2,2-azobisisobutyronitrile is 0.1-5% of the total mass of the tetraethylene glycol diacrylate monomer and the 2,2,3,3-tetrafluoropropyl methacrylate monomer.

[0025] Preferably, in step S3), the temperature of the low-temperature chamber is 0-30°C, and the settling time is 3-24 hours.

[0026] Preferably, in step S4), the temperature after heating is 40-90℃ and the reaction time is 3-12h.

[0027] The beneficial effects of the above-mentioned technical solution of the present invention are as follows: The cross-linked interpenetrating composite electrolyte for secondary lithium batteries uses a flexible inorganic SiO2 nanofiber membrane as a support. Tetraethylene glycol diacrylate monomer and 2,2,3,3-tetrafluoropropyl methacrylate monomer are polymerized in situ between the membrane and the electrodes of the secondary lithium battery to form a network-like polymer electrolyte rich in ester and fluorine groups. Anhydrous electrolyte is then encapsulated within this network-like polymer electrolyte. Firstly, the fluorine groups in the composite electrolyte have strong electronegativity and carbon-fluorine bond energy, which can improve the dissociation of lithium salts. Furthermore, the composite electrolyte has good compatibility with the electrode materials, enabling the secondary lithium battery to have advantages such as high conductivity and a stable electrochemical window, preventing leakage and explosion. The inorganic SiO2 nanofiber membrane used as a separator provides abundant Lewis acid-base sites and forms continuous ion transport pathways. The combination of this separator and the composite electrolyte can further improve the dissociation efficiency of lithium salts and the transport speed of lithium ions.

[0028] Furthermore, the composite electrolyte preparation method proposed in this invention uses in-situ polymerization to form a composite electrolyte inside the battery, which enables the secondary lithium battery to have excellent cycle performance and rate performance, fast charging efficiency, and long service life. Attached Figure Description

[0029] Figure 1 This is an electron microscope scanning image of the composite electrolyte of Example 1 of the present invention;

[0030] Figure 2 An optical photograph of the composite electrolyte of Embodiment 1 of the present invention;

[0031] Figure 3 This is a long-cycle performance diagram of a lithium symmetric coin cell using a composite electrolyte in Embodiment 2 of the present invention;

[0032] Figure 4 The rate performance diagram of a high-nickel ternary coin cell using a composite electrolyte in Example 2 of the present invention is shown.

[0033] Figure 5 This is a graph showing the long-cycle performance of a high-nickel ternary coin cell using a composite electrolyte in Example 3 of the present invention.

[0034] Figure 6 This is a graph showing the long-cycle performance of the lithium symmetric coin cell of Comparative Example 1 of the present invention.

[0035] Figure 7 This is a graph showing the long-cycle performance of the lithium symmetric coin cell of Comparative Example 2 of the present invention. Detailed Implementation

[0036] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0037] In the description of this specification, references to terms such as "embodiment," "example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0038] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

[0039] A secondary lithium battery, wherein the composite electrolyte comprises a polymer electrolyte and an anhydrous electrolyte;

[0040] The secondary lithium battery contains a separator made of flexible inorganic SiO2 nanofiber membrane; the composite electrolyte is located between the electrodes of the secondary lithium battery and the separator.

[0041] The polymer electrolyte is polymerized from tetraethylene glycol diacrylate monomer and 2,2,3,3-tetrafluoropropyl methacrylate monomer;

[0042] The polymer electrolyte is in the form of a three-dimensional network, and the anhydrous electrolyte fills the network of the polymer electrolyte, making the composite electrolyte as a whole form a gel.

[0043] The anhydrous electrolyte is composed of an organic solvent and a lithium salt.

[0044] The cross-linked interpenetrating composite electrolyte of the present invention for use in secondary lithium batteries uses a flexible inorganic SiO2 nanofiber membrane as a support. It is formed by in-situ polymerization of tetraethylene glycol diacrylate monomer and 2,2,3,3-tetrafluoropropyl methacrylate monomer between the membrane and the electrode of the secondary lithium battery, forming a network polymer electrolyte rich in acrylate groups and fluorine groups. The anhydrous electrolyte is encapsulated in the network polymer electrolyte, hence the name cross-linked interpenetrating composite electrolyte.

[0045] First, the fluorine groups contained in the composite electrolyte have strong electronegativity and carbon-fluorine bond energy, which can improve the dissociation performance of lithium salt. Furthermore, the composite electrolyte has good compatibility with electrode materials, which enables the secondary lithium battery to have the advantages of high conductivity and stable electrochemical window, and will not cause leakage or explosion.

[0046] Secondly, the inorganic SiO2 nanofiber membrane used provides abundant Lewis acid-base sites and forms a continuous ion transport path. When combined with the composite electrolyte, this membrane can further improve the dissociation efficiency of lithium salt and the transport speed of lithium ions, enabling the secondary lithium battery to have excellent cycle performance and rate performance, fast charging efficiency, and long service life.

[0047] Preferably, the mass ratio of the tetraethylene glycol diacrylate monomer to the 2,2,3,3-tetrafluoropropyl methacrylate monomer is (1-3):(1-3).

[0048] Tetraethylene glycol diacrylate contains an ionic carbonyl group, which facilitates lithium ion transfer. Tetraethylene glycol diacrylate also has good cross-linking ability, providing excellent liquid absorption capacity and interfacial compatibility.

[0049] The molecular chain of 2,2,3,3-tetrafluoropropyl methacrylate contains a large number of strong electron-withdrawing groups (–C–F), thus exhibiting excellent electrochemical stability.

[0050] Preferably, the lithium salt includes at least one of LiPF6, LiBOB, LiFSI, LiTFSI, LiSbF6, LiAlO2, and LiAlCl4.

[0051] The lithium salts mentioned above dissociate in the electrolyte to provide lithium ions.

[0052] The tetraethylene glycol diacrylate monomer and the 2,2,3,3-tetrafluoropropyl methacrylate monomer are chemically stable, do not produce side reactions with lithium salts, and can effectively dissociate lithium salts, which helps lithium ion transport.

[0053] Preferably, the organic solvent includes at least one of carbonate solvents, ester solvents, ether solvents, alcohol solvents, and nitrile solvents.

[0054] Used to dissolve lithium salts to form an electrolyte.

[0055] Preferably, the concentration of the lithium salt in the anhydrous electrolyte is 0.1-5M.

[0056] The higher the lithium salt concentration, the higher the conductivity of lithium ions in the electrolyte. When the lithium salt concentration is below 0.1M, there are too few lithium ions, resulting in insufficient conductivity of the electrolyte. When the lithium salt concentration is above 5M, lithium ions are more likely to form dendrites.

[0057] Furthermore, this invention proposes a method for preparing a secondary lithium battery, characterized by including the step of preparing a cross-linked interpenetrating composite electrolyte for the aforementioned secondary lithium battery. The step of preparing the cross-linked interpenetrating composite electrolyte includes:

[0058] S1) Weigh out tetraethylene glycol diacrylate monomer, 2,2,3,3-tetrafluoropropyl methacrylate monomer and anhydrous electrolyte in proportion, mix them evenly, then add powdered 2,2-azobisisobutyronitrile, stir evenly, and obtain the precursor of polymer electrolyte.

[0059] S2) Flexible inorganic SiO2 nanofiber membranes were prepared by electrospinning and high-temperature calcination in a muffle furnace using ethyl silicate as raw material.

[0060] S3) The flexible inorganic SiO2 nanofiber membrane is installed as a separator in a secondary lithium battery, and the precursor is injected between the electrode and the separator of the secondary lithium battery. Then, it is placed in a low temperature chamber to stand.

[0061] S4) The secondary lithium battery, after being left to stand, is placed in a high-temperature chamber and heated to allow the tetraethylene glycol diacrylate monomer and the 2,2,3,3-tetrafluoropropyl methacrylate monomer to undergo a polymerization reaction between the surface of the flexible inorganic SiO2 nanofiber membrane and the electrode. After the reaction is completed, the mixture is cooled to room temperature to obtain the composite electrolyte.

[0062] Step S2), the SiO2 nanofiber membrane prepared by electrospinning using the above in-situ polymerization method has the characteristics of being flexible and thinner.

[0063] Step S3) allows the precursor to fully wet the positive and negative electrodes and separator of the secondary lithium battery, thereby enabling the prepared composite electrolyte to have better contact performance with the electrodes.

[0064] In step S4), the two monomers are polymerized in situ on the surface and inside of the flexible inorganic SiO2 nanofiber membrane to form a network polymer electrolyte. The network polymer electrolyte is filled with anhydrous electrolyte to form the composite electrolyte. The polymer electrolyte has both the good electrochemical performance of the organic liquid electrolyte system with good ionic conductivity and the safety performance of the solid polymer electrolyte.

[0065] Preferably, in step S1), the total mass of the tetraethylene glycol diacrylate monomer and the 2,2,3,3-tetrafluoropropyl methacrylate monomer is 3-20% of the mass of the precursor of the polymer electrolyte.

[0066] If the monomer ratio is too low, the anhydrous electrolyte cannot be completely encapsulated within the polymer electrolyte network. If the monomer ratio is too high, the polymer chain density will be too high, thus hindering polymer chain movement and adversely affecting lithium-ion transport.

[0067] The molecular weights of both tetraethylene glycol diacrylate monomer and 2,2,3,3-tetrafluoropropyl methacrylate monomer are 100-1000.

[0068] Preferably, in step S1), the content of the powdered 2,2-azobisisobutyronitrile is 0.1-5% of the total mass of the tetraethylene glycol diacrylate monomer and the 2,2,3,3-tetrafluoropropyl methacrylate monomer.

[0069] Add 0.1-5% of 2,2-azobisisobutyronitrile initiator to ensure that both polymer monomers can be fully polymerized.

[0070] Preferably, in step S3), the temperature of the low-temperature chamber is 0-30°C, and the settling time is 3-24 hours.

[0071] The initiator used is a thermal initiator. Before initiating the polymerization reaction, a low-temperature standing period is used to avoid polymerization between the two monomers, thereby ensuring the wettability of the precursor to the electrode and the diaphragm.

[0072] Preferably, in step S4), the temperature after heating is 40-90℃ and the reaction time is 3-12h.

[0073] When heated to 40-90℃, the initiator decomposes, generating free radical molecules that attack the unsaturated carbon-carbon double bonds in the monomer, initiating a polymerization reaction. The higher the temperature, the faster the reaction rate and the shorter the required reaction time.

[0074] Examples 1-3 and Comparative Examples 1-2

[0075] Example 1

[0076] 1. Weigh 0.6g of TGD monomer (tetraethylene glycol diacrylate monomer) and 0.2g of TFM monomer (2,2,3,3-tetrafluoropropyl methacrylate monomer), and add them to glass bottles respectively. Then, add 4.5g of liquid electrolyte to the glass bottle and stir magnetically for 30min at a stirring speed of 500rpm. Next, weigh 0.8mg of AIBN (2,2-azobisisobutyronitrile) initiator powder and add it to the glass bottle. Stir magnetically for another 1h to obtain the precursor.

[0077] 2. Preparation of SiO2 membrane by electrospinning: TEOS (tetraethyl orthosilicate) and H2O were prepared in a 1:1 ratio, and 1M HCl was added and stirred for 24 hours. Then, 10wt% PVA solution was added and stirred until homogeneous to obtain a mixed solution. Using a 5ml syringe, 4mL of spinning solution was drawn in, the distance between the syringe and the collector was adjusted to 15cm, the flow rate was controlled at 1ml / h, and a high voltage of 18kV was applied to the syringe. Under the action of a strong electric field, the spinning solution was sprayed into filaments and collected in the collector to form a spun membrane. The spun membrane was then placed in a muffle furnace and heated to 800℃ at a heating rate of 5℃ / min, and sintered at high temperature for 2 hours to obtain a SiO2 membrane. The SiO2 membrane was cut into 19mm diameter sheets and placed in a glove box for later use.

[0078] 3. The precursor was injected into a 2032 coin cell with SiO2 membrane as separator, the cell was assembled, and the cell was placed in a low temperature chamber at 20°C for 3 hours. After standing, the cell was transferred to an oven, heated to 60°C and maintained for 12 hours to obtain a cross-linked interpenetrating composite electrolyte.

[0079] 4. The prepared composite electrolyte was subjected to SEM scanning analysis and optical analysis. The obtained electron microscope scan images are shown below. Figure 1 The obtained optical photographs, such as Figure 2 ;from Figure 1 As can be seen in Example 1, the polymer electrolyte in the composite electrolyte is in a network structure. The space between the network polymer electrolyte and the SiO2 nanofiber membrane is filled with electrolyte, which helps to uniformly transport lithium ions in the electrolyte. The composite electrolyte is formed as a whole. Figure 2 The gel-like substance shown.

[0080] Example 2

[0081] 1. Same as step 1 of Example 1, except that in Example 2, both TGD monomer and TFM monomer are 0.4g.

[0082] 2. Same as step 2 in Example 1.

[0083] 3. Similar to step 3 of Example 1, the battery used is a symmetrical coin cell lithium battery.

[0084] 4. Similar to step 3 of Example 1, the battery used is a high-nickel ternary coin cell.

[0085] 5. The symmetrical coin cell lithium battery obtained in step 3 was subjected to long-cycle performance testing. The test results are as follows: Figure 3 As shown, from Figure 3 It can be seen that the symmetrical coin cell lithium battery in Example 2 can maintain a stable polarization voltage for 1600 hours without any short circuit.

[0086] 6. The high-nickel ternary coin cells prepared in step 4 were subjected to rate performance tests at discharge rates of 0.5C, 1C, 3C, 5C, 7C, and 10C. The test results are as follows: Figure 4 As shown, the corresponding discharge capacities reached 193.6 mAh / g, 188 mAh / g, 172.6 mAh / g, 154.3 mAh / g, 129.6 mAh / g and 96.1 mAh / g, respectively. When the rate returned to 0.5C, the discharge capacity of the high-nickel ternary coin cell in Example 2 remained at 197.5 mAh / g, demonstrating excellent rate performance.

[0087] Therefore, it can be seen that the TFM and TGD in the composite electrolyte of Example 2 work together to introduce fluorine groups with high bond strength CF bonds into the polymer chain, which stabilizes the structure of the polymer chain and accelerates the conduction of lithium ions.

[0088] Example 3

[0089] 1. Same as step 1 of Example 1, except that the TGD monomer and TFM monomer in Example 3 are 0.2g and 0.6g respectively.

[0090] 2. Same as step 2 in Example 1.

[0091] 3. Similar to step 3 of Example 1, the battery used is a high-nickel ternary coin cell.

[0092] 4. The high-nickel ternary coin cell prepared in step 3 was subjected to a long-cycle performance test at 1C rate. The test results are as follows: Figure 5 As shown, from Figure 5 It can be seen that the high-nickel ternary button cell of Example 3 still retains 98.6% of its capacity after 200 cycles.

[0093] Comparative Example 1

[0094] 1. Same as step 1 of Example 1, except that Comparative Example 1 only added 0.8g of TGD monomer.

[0095] 2. Same as step 2 in Example 1.

[0096] 3. Similar to step 3 of Example 1, the battery used is a symmetrical coin cell lithium battery.

[0097] 4. The symmetrical coin cell lithium battery obtained in step 3 was subjected to long-cycle performance testing. The test results are as follows: Figure 6 As shown, from Figure 6 It can be seen that the symmetrical coin cell lithium battery in Comparative Example 1 experienced a short circuit after approximately 600 hours.

[0098] The polymer chain of the composite electrolyte with only TGD monomer has abundant ester groups, which can help transport lithium ions. However, its polymer structure is unstable during chain movement, which can lead to uniform lithium ion deposition and the formation of lithium dendrites. The growth of lithium dendrites can puncture the composite electrolyte and cause the battery to short circuit.

[0099] Comparative Example 2

[0100] 1. Same as step 1 of Example 1, except that Comparative Example 2 only added 0.8g of TMF monomer.

[0101] 2. Same as step 2 in Example 1.

[0102] 3. Similar to step 3 of Example 1, the battery used is a symmetrical coin cell lithium battery.

[0103] 4. The symmetrical coin cell lithium battery obtained in step 3 was subjected to long-cycle performance testing. The test results are as follows: Figure 7 As shown, from Figure 7 It can be seen that the symmetrical coin cell lithium battery in Comparative Example 2 experienced a short circuit after approximately 185 hours.

[0104] The polymer chain of the composite electrolyte with only TGD monomer has too many fluorinated segments, resulting in high electronegativity and excessive binding capacity for lithium ions, thus hindering lithium ion transport. During long-cycle operation of the symmetrical coin lithium battery in Comparative Example 2, lithium ions concentrate near the polar groups, leading to excessively high local voltage, unstable lithium ion transport, lithium dendrite formation and growth, and ultimately, short circuits.

[0105] In summary, the cross-linked interpenetrating composite electrolyte for secondary lithium batteries described in the above embodiments uses a flexible inorganic SiO2 nanofiber membrane as a support. Tetraethylene glycol diacrylate monomer and 2,2,3,3-tetrafluoropropyl methacrylate monomer are polymerized in situ between the membrane and the electrodes of the secondary lithium battery to form a network-like polymer electrolyte rich in ester and fluorine groups. Anhydrous electrolyte is then encapsulated within this network. Firstly, the fluorine groups in the composite electrolyte possess strong electronegativity and carbon-fluorine bond energy, which can improve the dissociation performance of lithium salts. Furthermore, the composite electrolyte has good compatibility with the electrode materials, enabling the secondary lithium battery to have advantages such as high conductivity and a stable electrochemical window, preventing leakage and explosion. The inorganic SiO2 nanofiber membrane provides abundant Lewis acid-base sites and forms continuous ion transport pathways. The combination of this membrane and the composite electrolyte further improves the dissociation efficiency of lithium salts and the transport rate of lithium ions.

[0106] Furthermore, the composite electrolyte preparation method proposed in this invention uses in-situ polymerization to form a composite electrolyte inside the battery, which enables the secondary lithium battery to have excellent cycle performance and rate performance, fast charging efficiency, and long service life.

[0107] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A secondary lithium battery, characterized in that, The secondary lithium battery includes a cross-linked interpenetrating composite electrolyte, which includes a polymer electrolyte and an anhydrous electrolyte. The secondary lithium battery contains a separator made of flexible inorganic SiO2 nanofiber membrane; the composite electrolyte is located between the electrodes of the secondary lithium battery and the separator. The polymer electrolyte is polymerized from tetraethylene glycol diacrylate monomer and 2,2,3,3-tetrafluoropropyl methacrylate monomer; The polymer electrolyte is in the form of a three-dimensional network, and the anhydrous electrolyte fills the network of the polymer electrolyte, making the composite electrolyte as a whole form a gel. The anhydrous electrolyte is composed of an organic solvent and a lithium salt; The mass ratio of the tetraethylene glycol diacrylate monomer to the 2,2,3,3-tetrafluoropropyl methacrylate monomer is (1-3):(1-3).

2. A secondary lithium battery according to claim 1, characterized in that, The lithium salt includes at least one of LiPF6, LiBOB, LiFSI, LiTFSI, LiSbF6, LiAlO2, and LiAlCl4.

3. A secondary lithium battery according to claim 1, characterized in that, The organic solvent includes at least one of carbonate solvents, ester solvents, ether solvents, alcohol solvents, and nitrile solvents.

4. A secondary lithium battery according to claim 1, characterized in that, The concentration of the lithium salt in the anhydrous electrolyte is 0.1-5M.

5. A method for preparing a secondary lithium battery, characterized in that, The step includes preparing the cross-linked interpenetrating composite electrolyte of the secondary lithium battery according to any one of claims 1-4, wherein the step of preparing the cross-linked interpenetrating composite electrolyte includes: S1) Weigh out tetraethylene glycol diacrylate monomer, 2,2,3,3-tetrafluoropropyl methacrylate monomer and anhydrous electrolyte in proportion, mix them evenly, then add powdered 2,2-azobisisobutyronitrile, stir evenly, and obtain the precursor of polymer electrolyte. S2) Flexible inorganic SiO2 nanofiber membranes were prepared by electrospinning and high-temperature calcination in a muffle furnace using ethyl silicate as raw material. S3) The flexible inorganic SiO2 nanofiber membrane is installed as a separator in a secondary lithium battery, and the precursor is injected between the electrode and the separator of the secondary lithium battery. Then, it is placed in a low temperature chamber to stand. S4) The secondary lithium battery, after being left to stand, is placed in a high-temperature chamber and heated to allow the tetraethylene glycol diacrylate monomer and the 2,2,3,3-tetrafluoropropyl methacrylate monomer to undergo a polymerization reaction on the surface of the flexible inorganic SiO2 nanofiber membrane and between the electrodes. After the reaction is completed, the mixture is cooled to room temperature to obtain the composite electrolyte. In step S3), the temperature of the low-temperature chamber is 0-30℃, and the settling time is 3-24 hours; In step S4), the temperature after heating is 40-90℃, and the reaction time is 3-12h.

6. The method for preparing a secondary lithium battery according to claim 5, characterized in that, In step S1), the total mass of the tetraethylene glycol diacrylate monomer and the 2,2,3,3-tetrafluoropropyl methacrylate monomer is 3-20% of the mass of the precursor of the polymer electrolyte.

7. The method for preparing a secondary lithium battery according to claim 5, characterized in that, In step S1), the content of the powdered 2,2-azobisisobutyronitrile is 0.1-5% of the total mass of the tetraethylene glycol diacrylate monomer and the 2,2,3,3-tetrafluoropropyl methacrylate monomer.

Images