Secondary battery and electric device

Abstract

Embodiments of the present application provide a secondary battery, including: a positive electrode, a negative electrode, and a sulfide solid electrolyte, a molecular formula of the sulfide solid electrolyte being: Li a P 1‑b M b S c O d X e wherein 5

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the field of batteries, in particular, to secondary batteries and power consuming devices. BACKGROUND

[0002] With the development of new energy field, the performance of battery becomes more and more important. In the field of battery, the development of all-solid-state battery is particularly important, because compared with traditional lithium ion battery, all-solid-state battery (ASSB) using inorganic solid electrolyte (SE) has higher safety and excellent energy density. For practical application, sulfide solid electrolyte shows high ionic conductivity of more than 1 mS cm -1 at room temperature (R.T.) and has deformable mechanical properties, which can realize scalable cold stamping manufacturing, and is a potential solid electrolyte candidate system. However, the commonly used sulfide solid electrolyte is unstable in air and will react with water to degrade. And the sulfide solid electrolyte is unstable with lithium metal and will be reduced by lithium metal, which limits the matching of the negative electrode with the solid electrolyte, and further limits the further improvement of the energy density of the battery, and the following shortcomings exist in the current technology:

[0003] When the sulfide solid electrolyte is exposed to air, problems such as generation of toxic gas H2S (hydrogen sulfide), complete destruction of electrolyte structure, and decay of electrochemical performance will occur, and when matching with lithium metal negative electrode, chemical reaction with lithium metal will easily cause short circuit of the battery. SUMMARY

[0004] The present application solves the problems of instability of sulfide solid electrolyte in air and reaction with lithium metal by designing the chemical structure of sulfide solid electrolyte and using lithium metal surface modification technology, and improves the cycle performance of lithium metal battery.

[0005] Some embodiments of the present application provide a secondary battery, comprising: a positive electrode, a negative electrode and a sulfide solid electrolyte, wherein the molecular formula of the sulfide solid electrolyte is:

[0006] Li a P 1-b M b S c O d X e ,

[0007] wherein 5 < a < 6, 0 < b < 1, 1.5 < c < 5, 0 < d < 2.5, 4 < c + d < 5, and 1 < e < 2; M is selected from one or more of Al, Ga, In, Ti, Sc, As, Sb, Bi, V, Nb; and X is selected from one or more of Cl, Br, I, and the surface of the negative electrode comprises a fluorinated silane coating. In some preferred embodiments, M is Sb, In, or Bi, and in some embodiments, X is Cl.

[0008] In the present application, by introducing one or more of Al, Ga, In, Ti, Sc, As, Sb, Bi, V, Nb and O element in the halogen-rich sulfide solid electrolyte, it forms P-O and Sb-S / Bi-S / In-S / Al-S / Ga covalent bonds in the crystal structure of the sulfide solid electrolyte, thereby increasing the intrinsic resistance to atmospheric degradation and effectively reducing the generation of H2S, thereby enhancing the air stability of the sulfide solid electrolyte.

[0009] In addition, the negative electrode comprises lithium metal, by modifying a fluorinated silane coating on the surface of the lithium metal of the negative electrode, a stable inorganic substance such as LiF (lithium fluoride) can be formed in situ, which can homogenize the electric field, balance the local current density, and thereby regulate the nucleation and growth process of Li. In addition, LiF has a high interfacial energy, which can partially alleviate the rapid growth of lithium dendrites at the interface.

[0010] In some embodiments, 0 < b < 0.1. In further embodiments, when the valence of M is +5, b is 0.04, and when the valence of M is +3, b is 0.02. This is because the M element cannot be doped too much, and too much doping will cause changes in the sulfide crystal structure, thereby affecting the stability of the electrical conductivity, etc., so when b is 0.04 or 0.02, the performance is the most balanced.

[0011] In some embodiments, the fluorinated silane coating is a triethyl(trifluoromethyl)silane coating. In the present application, due to the low surface energy of triethyl(trifluoromethyl)silane, it can quickly spread on the surface of the lithium metal, and the fluorinated silane such as triethyl(trifluoromethyl)silane can react with lithium metal to generate LiF, which can accelerate the lithium ion transport kinetics, promote the uniform deposition of lithium on the surface of the lithium metal, and inhibit the growth of lithium dendrites.

[0012] In some embodiments, the triethyl(trifluoromethyl)silane coating has a thickness of 1-10 μm, such as a corresponding volume of 10-100 μL. In some embodiments, when the triethyl(trifluoromethyl)silane coating has a thickness of 1-10 μm, such as a corresponding volume in the range of 10-100 μL, the triethyl(trifluoromethyl)silane coating can generate an SEI film in situ with lithium metal, while having high capacity and good battery cycle stability. In some embodiments, the triethyl(trifluoromethyl)silane coating has a thickness of 6 μm, such as a corresponding volume of 60 μL, and when the triethyl(trifluoromethyl)silane coating has a thickness of 6 μm, a stable and moderately thick SEI film can be generated in situ with lithium metal, and the battery has the best and most balanced performance.

[0013] Some embodiments of the present application also provide a power consumption device comprising the secondary battery.

[0014] In the present application, by introducing one or more of Al, Ga, In, Ti, Sc, As, Sb, Bi, V, Nb and O elements into the sulfide solid electrolyte, P-O and Sb-S / Bi-S / In-S… bonds are formed in the crystal structure of the sulfide solid electrolyte, thereby increasing the intrinsic resistance to atmospheric degradation and effectively reducing the generation of H2S, thereby enhancing the air stability of the sulfide solid electrolyte.

[0015] In addition, the fluorinated silane coating on the surface of the lithium metal of the negative electrode can in situ form stable inorganic substances such as LiF (lithium fluoride), uniformize the electric field, balance the local current density, and thereby regulate the nucleation and growth process of Li. In addition, LiF has a high interface energy, which can partially alleviate the rapid growth of lithium dendrites at the interface. DETAILED DESCRIPTION

[0016] The secondary battery provided by the present application has both advantages, the sulfide solid electrolyte is designed by chemical structure to be stable with air and the metal lithium of the negative electrode, and the fluorinated silane coating on the surface of the lithium metal of the negative electrode is used to improve the stability between the lithium metal and the sulfide solid electrolyte, thereby solving the problems of instability of the sulfide solid electrolyte in air and reaction with the lithium metal of the negative electrode, and improving the cycle performance of the secondary battery.

[0017] Specifically, some embodiments of the present application provide a secondary battery, which comprises: a positive electrode, a negative electrode, and a sulfide solid electrolyte, the molecular formula of the sulfide solid electrolyte is:

[0018] Li a P 1-b M b S c O d Xe ,

[0019] wherein 5 < a < 6, 0 < b < 1, 1.5 < c < 5, 0 < d < 2.5, 4 < c + d < 5, and 1 < e < 2; M is selected from one or more of Al, Ga, In, Ti, Sc, As, Sb, Bi, V, Nb; and X is selected from one or more of Cl, Br, I, and the surface of the negative electrode comprises a fluorinated silane coating.

[0020] In the present application, by introducing one or more of Al, Ga, In, Ti, Sc, As, Sb, Bi, V, Nb and O element in the halogen-rich sulfide solid electrolyte, P-O and Sb-S / Bi-S / In-S / Al-S / Ga… bonds are formed in the crystal structure of the sulfide solid electrolyte, thereby increasing the inherent resistance to atmospheric degradation and effectively reducing the generation of H2S, thereby enhancing the air stability of the sulfide solid electrolyte.

[0021] In addition, the negative electrode comprises lithium metal, by modifying a fluorinated silane coating on the surface of the lithium metal of the negative electrode, a stable inorganic substance such as LiF (lithium fluoride) can be formed in situ, the electric field is homogenized, the local current density is balanced, and the nucleation and growth process of Li is adjusted. In addition, LiF has a high interfacial energy, which can partially alleviate the rapid growth of lithium dendrites at the interface.

[0022] In some embodiments, M is Sb, In or Bi, and in some embodiments, X is Cl. In the present application, when X is Cl, a chlorine-rich sulfide solid electrolyte is formed, and by introducing Sb / Bi / In and O elements in the chlorine-rich sulfide solid electrolyte, P-O and Sb-S / Bi-S / In-S bonds are formed in the crystal structure of the sulfide solid electrolyte, thereby increasing the inherent resistance to atmospheric degradation and effectively reducing the generation of H2S, thereby enhancing the air stability of the sulfide solid electrolyte.

[0023] In some embodiments, 0 < b < 0.1. In further embodiments, when the valence of M is +5, b is 0.04, and when the valence of M is +3, b is 0.02. This is because the M element cannot be doped too much, and doping too much will cause changes in the sulfide crystal structure, thereby affecting the stability of the electrical conductivity, etc., and therefore when b is 0.04 or 0.02, the performance is the most balanced.

[0024] In some embodiments, the fluorinated silane coating is a triethyl(trifluoromethyl)silane coating. In the present application, due to the low surface energy of triethyl(trifluoromethyl)silane, it can quickly spread on the surface of lithium metal, and the fluorinated silane such as triethyl(trifluoromethyl)silane can react with lithium metal to generate LiF, which can accelerate the lithium ion transmission kinetics, promote the uniform deposition of lithium on the surface of lithium metal, and inhibit the growth of lithium dendrites.

[0025] In some embodiments, the thickness of the triethyl(trifluoromethyl)silane coating is 1-10 μm, and in some cases, it is 10-100 μL. In some embodiments, when the thickness of the triethyl(trifluoromethyl)silane coating is in the range of 1-10 μm, the triethyl(trifluoromethyl)silane coating can generate an SEI film in situ with lithium metal, while the capacity is high and the battery cycle stability is good. In some embodiments, the thickness of the triethyl(trifluoromethyl)silane coating is 6 μm, and in some cases, it is 60 μL. When the thickness of the triethyl(trifluoromethyl)silane coating is 6 μm, a stable and moderately thick SEI film can be generated in situ with lithium metal, and the battery performance is the best and most balanced.

[0026] Some embodiments of the present application also provide a power utilization device comprising the secondary battery.

[0027] In the present application, the secondary battery comprises a positive electrode, a negative electrode, and a sulfide solid electrolyte, and the related preparation method is as follows.

[0028] The positive electrode active material, the positive electrode conductive agent, and the positive electrode binder are dispersed in the solvent in a mass ratio of 95:2:3 to form a uniform positive electrode slurry. The positive electrode slurry is coated on the surface of the positive electrode current collector, and after processes such as drying and cold pressing, a positive electrode active material layer is formed on the positive electrode current collector, thereby serving as the positive electrode in the present technical solution. The ratio between the components in the positive electrode slurry can be set according to the conventional ratio, which is not limited herein. The positive electrode active material is a positive electrode active material conventionally understood in the art and coated on the positive electrode current collector. The type of the positive electrode active material can be one or more of lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), lithium nickel cobalt manganese oxide (NCM), or lithium nickel cobalt aluminum oxide (NCA). The positive electrode conductive agent is selected from one or a combination of two or more of carbon black, acetylene black, graphene, carbon nanotubes, carbon nanofibers, etc. in any proportion. The positive electrode binder is selected from one of PVDF and its derivatives. In some embodiments, the positive electrode current collector can be an aluminum foil.

[0029] 10-100 μL of triethyl(trifluoromethyl)silane is added dropwise on a polished lithium metal surface, and the thickness of the formed triethyl(trifluoromethyl)silane is 1 μm-10 μm, so as to form a lithium metal (such as ≤0.6 mm thick lithium metal, commonly used lithium metal) with a fluorinated silane coating modified on the surface as the negative electrode in the technical solution.

[0030] The preparation method of the sulfide solid electrolyte in the application comprises the following steps:

[0031] 1) The chemical formula of the sulfide solid electrolyte is Li a P 1-b M b S c O d X e , wherein 5 < a < 6, 0 < b < 1, 1.5 < c < 5, 0 < d < 2.5, 4 < c + d < 5, and 1 < e < 2; M is selected from one or more of Al, Ga, In, Ti, Sc, As, Sb, Bi, V, Nb; and X is selected from one or more of Cl, Br, I; the raw materials are uniformly mixed according to the stoichiometric ratio, and then placed in a ball milling tank for ball milling for 24 h, wherein the ball milling speed is 600 rpm, and the ball-to-material ratio is 40:1, to obtain a sulfide solid electrolyte precursor powder, wherein the raw materials include Li2S, LiX, P2S5, and the oxide MxOy corresponding to the element M, X is selected from one or more of Cl, Br, or I, M is selected from one or more of Al, Ga, In, Ti, Sc, As, Sb, Bi, V, or Nb, and the stoichiometric ratio is determined according to the molar ratio of each element in Li a P 1-b M b S c O d X e ;

[0032] 2) The precursor powder is annealed and sintered at a high temperature of 500 ℃ for 24 h to obtain a sulfide solid electrolyte.

[0033] Finally, the positive electrode, the sulfide solid electrolyte, and the negative electrode are sequentially placed in a mold for assembly; after assembly, the pressure is applied and the nut at the top end of the stand is tightened to a constant pressure, and a secondary battery is obtained. The assembly process is completed in an argon atmosphere glove box.

[0034] Those skilled in the art will understand that the preparation method of the battery described above is only an example. Other methods commonly used in the art can be used without departing from the content disclosed in the application.

[0035] The reagents and raw materials used in the application are commercially available.

[0036] The present application does not have special requirements for the assembly method of the above-mentioned battery, and the assembly method known to those skilled in the art can be used. In addition, the above-mentioned technical solution can be applied not only to commonly used all-solid-state lithium ion batteries, but also to all-solid-state sodium ion batteries, all-solid-state potassium ion batteries and various kinetic batteries. The above-mentioned secondary battery can be applied to any suitable electric device, including but not limited to electric vehicles and the like.

[0037] Some specific examples and comparative examples are listed below to better illustrate the present application.

[0038] Example 1

[0039] Preparation of sulfide solid electrolyte:

[0040] The raw materials Li2S, LiCl, P2S5 and In2O3 were mixed uniformly according to the stoichiometric ratio of 1.5:2:0.49:0.01, and then placed in a ball mill pot for ball milling for 24 h at a speed of 600 rpm and a ball-to-material ratio of 40:1. After ball milling, the sulfide solid electrolyte precursor powder was obtained. Then, the precursor powder was annealed and sintered at a high temperature of 500°C for 24 h, thereby obtaining the sulfide solid electrolyte Li 5.5 P 0.98 In 0.02 S 4.45 O 0.03 Cl 1.5 .

[0041] Preparation of lithium metal electrode:

[0042] On the polished surface of the lithium metal, 60 μL of triethyl(trifluoromethyl)silane was added to form a lithium metal electrode with a fluorinated silane coating layer with a thickness of 6 μm as the negative electrode, wherein the fluorinated silane was triethyl(trifluoromethyl)silane.

[0043] The sulfide solid electrolyte and lithium metal electrode prepared by the above method were further assembled into lithium-lithium symmetric batteries and full batteries for cycle and discharge retention rate performance tests.

[0044] Example 2

[0045] The preparation method of Example 1 was consistent, except that 10 μL of triethyl(trifluoromethyl)silane was added to the polished surface of the lithium metal in Example 2, and the thickness of the triethyl(trifluoromethyl)silane coating layer formed was 1 μm.

[0046] Example 3

[0047] The preparation method of Example 1 was followed except that in Example 3, 100 μΐ^of triethyl(trifluoromethyl)silane was added dropwise on the polished lithium metal surface, and the thickness of the triethyl(trifluoromethyl)silane coating formed was 10 μιη.

[0048] Example 4

[0049] The preparation method of Example 1 was followed except that in Example 4, 30 μΐ^of triethyl(trifluoromethyl)silane was added dropwise on the polished lithium metal surface, and the thickness of the triethyl(trifluoromethyl)silane coating formed was 3 μιη.

[0050] Example 5

[0051] The preparation method of Example 1 was followed except that in Example 5, 80 μΐ^of triethyl(trifluoromethyl)silane was added dropwise on the polished lithium metal surface, and the thickness of the triethyl(trifluoromethyl)silane coating formed was 8 μιη.

[0052] Example 6

[0053] The preparation method of Example 1 was followed except that in Example 6, the sulfide solid-state electrolyte was Li 5.5 P 0.98 Sb 0.02 S 4.45 O 0.03 Cl 1.5 .

[0054] Example 7

[0055] The preparation method of Example 1 was followed except that in Example 7, the sulfide solid-state electrolyte was Li 5.5 P 0.98 Bi 0.02 S 4.45 O 0.03 Cl 1.5 .

[0056] Example 8

[0057] The preparation method of Example 1 was followed except that in Example 8, the sulfide solid-state electrolyte was Li 5.5 P 0.96 V 0.04 S 4.4 O 0.1 Cl 1.5 .

[0058] Comparative Example 1

[0059] The preparation method of Example 1 was followed except that in Comparative Example 1, 1 μΐ^of triethyl(trifluoromethyl)silane was added dropwise on the polished lithium metal surface, and the thickness of the triethyl(trifluoromethyl)silane coating formed was 0.1 μιη.

[0060] Comparative Example 2

[0061] The preparation method was consistent with that of Example 1, except that 200 μL of triethyl(trifluoromethyl)silane was dropped on the polished lithium metal surface in Comparative Example 2, and the thickness of the triethyl(trifluoromethyl)silane coating formed was 20 μm.

[0062] Comparative Example 3

[0063] The preparation method was consistent with that of Example 1, except that no fluorinated silane coating was modified on the lithium metal surface in Comparative Example 3.

[0064] Comparative Example 4

[0065] The preparation method was consistent with that of Example 1, except that the sulfide solid-state electrolyte in Comparative Example 4 was Li6PS5Cl, and no fluorinated silane coating was modified on the lithium metal surface.

[0066] Performance test method

[0067] Lithium-lithium symmetric battery test: Li 5.5 P 0.98 In 0.02 S 4.45 O 0.03 Cl 1.5 / Li 5.5 P 0.98 Sb 0.02 S 4.45 O 0.03 Cl 1.5 / Li 5.5 P 0.98 Bi 0.02 S 4.45 O 0.03 Cl 1.5 / Li 5.5 P 0.96 V 0.04 S 4.4 O 0.1 Cl 1.5 The lithium metal piece modified with fluorinated silane was used as the lithium metal symmetric electrode. The symmetric battery prepared above was subjected to long cycle charging and discharging at 25°C, and the charge-discharge rate was measured to be 0.5 mA / cm 2 , and the charge-discharge time was 1 h.

[0068] Full battery test: LiNi 0.8 Co 0.1 Mn 0.1 O2 as the positive electrode, lithium metal modified with fluorinated silane as the negative electrode, and Li 5.5 P0.98 In 0.02 S 4.45 O 0.03 Cl 1.5 / Li 5.5 P 0.98 Sb 0.02 S 4.45 O 0.03 Cl 1.5 / Li 5.5 P 0.98 Bi 0.02 S 4.45 O 0.03 Cl 1.5 / Li 5.5 P 0.96 V 0.04 S 4.4 O 0.1 Cl 1.5 The electrolyte is an electrolyte. The full battery prepared above is subjected to long cycle charging and discharging at 25°C environment, and the capacity retention rate under 1C / 1C charging and discharging rate is measured. The specific preparation method of the positive and negative electrodes of the full battery is as follows.

[0069] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, positive electrode conductive agent Super P, positive electrode binder polyvinylidene fluoride, and the corresponding sulfide electrolyte are mixed and dispersed in xylene in a mass ratio of 75:1:1:23, stirred to uniformity under the action of a vacuum stirrer, and a positive electrode slurry is obtained. The positive electrode slurry is uniformly coated on an aluminum foil, and the aluminum foil is dried at room temperature after air drying, then transferred to a glove box vacuum transition cabin for drying, and then cold-pressed and cut to obtain a positive electrode.

[0070] A porous polyethylene (PE) film is used as a separator.

[0071] Finally, the positive electrode, the separator, and the lithium metal negative electrode and the sulfide solid electrolyte prepared in each example and the comparative example are sequentially placed in a mold for assembly. After assembly, the nut at the top of the stand is tightened to constant pressure, and a full battery is obtained.

[0072] The test results are shown in Table 1 below.

[0073] Table 1. Secondary battery performance test results of Examples 1-18 and Comparative Examples 1-12

[0074]

[0075] Comparing Examples 1-8 above with Comparative Examples 3-4 shows that the secondary battery provided by the application has a high capacity retention rate and a long cycle life by using a halogen-rich sulfide solid electrolyte (Li a P 1-bM b S c O d X e ) one or more of Al, Ga, In, Ti, Sc, As, Sb, Bi, V, Nb and O elements are introduced, so that they form P-O and Sb-S / Bi-S / In-S / V-S covalent bonds in the crystal structure of the sulfide solid-state electrolyte, thereby increasing the inherent resistance to atmospheric degradation and effectively reducing the generation of H2S, thereby enhancing the air stability of the sulfide solid-state electrolyte. In addition, a fluorinated silane coating is modified on the surface of the lithium metal of the negative electrode, which can in situ form stable inorganics such as LiF (lithium fluoride) to homogenize the electric field, balance the local current density, and thereby regulate the nucleation and growth process of Li. In addition, LiF has a high interfacial energy, which can partially alleviate the rapid growth of lithium dendrites at the interface. As can be seen from Examples 1-8, the lithium-lithium symmetric battery in the above Examples 1-8 can be stably cycled for more than 1000h at a large current density of 0.5mA / cm 2 In the following, the battery cycle number is doubled compared to the unmodified lithium metal assembled full battery of Comparative Examples 3-4. In addition, as can be seen from Comparative Examples 3-4, the battery capacity and cycle life of Li6PS5Cl are increased compared to the ordinary sulfide in Comparative Example 4, but there are still side reactions with unmodified lithium metal. As can be further seen from Comparative Example 4, the side reaction between Li6PS5Cl and lithium metal is relatively severe, resulting in a decrease in the cycle performance of the battery.

[0076] As can be seen from Examples 1-5 and Comparative Examples 1-2, the thickness of the triethyl(trifluoromethyl)silane coating layer is 1-10 μm, and the corresponding volume is 10-100 μL. When the thickness of the triethyl(trifluoromethyl)silane coating layer is in the range of 1-10 μm, the triethyl(trifluoromethyl)silane coating layer can form an SEI film in situ with lithium metal, and the capacity is high and the battery cycle stability is good. In some embodiments, the thickness of the triethyl(trifluoromethyl)silane coating layer is 6 μm, and the corresponding volume is 60 μL. When the thickness of the triethyl(trifluoromethyl)silane coating layer is 6 μm, a stable and moderately thick SEI film can be formed in situ with lithium metal, and the battery performance is the best and most balanced. As can be seen from Example 3 and Example 5, when the volume of the triethyl(trifluoromethyl)silane coating layer is 100 μL and 80 μL, a large amount of SEI film can be formed in situ with lithium metal, and the battery cycle stability is good. As can be seen from Comparative Example 1, when the triethyl(trifluoromethyl)silane coating layer is too small (e.g., 1 μL), it hardly protects the lithium metal, and the battery performance is poor. As can be seen from Comparative Example 5, when the triethyl(trifluoromethyl)silane coating layer is too large (e.g., 200 μL), it has too great an impact on the battery capacity, and the capacity is low.

[0077] The foregoing summary of some embodiments has been presented for the purposes of illustration and description. It is, of course, not intended to be an exhaustive overview of the aspects of the application. It is also not intended to be limiting as to the scope of the application. Persons skilled in the relevant art will recognize that many modifications and changes in light of the teachings herein can be made without deviating from the spirit and scope of the application.

Claims

1. A secondary battery, characterized in that, Comprising: a positive electrode, a negative electrode, and a sulfide solid electrolyte, the molecular formula of the sulfide solid electrolyte being: Li a P 1-b M b S c O d X e , where 5 < a < 6, 0 < b < 1, 1.5 < c < 5, 0 < d < 2.5, 4 < c + d < 5, and 1 < e < 2; M is selected from one or more of Al, Ga, In, Ti, Sc, As, Sb, Bi, V, Nb; and X is selected from one or more of Cl, Br, I, the negative electrode includes lithium metal, and the surface of the lithium metal is modified with a fluorinated silane coating.

2. The secondary battery according to claim 1, characterized in that, The M is Sb, In or Bi.

3. The secondary battery according to claim 1 or 2, characterized in that, The X is Cl.

4. The secondary battery according to claim 1, characterized in that, 0＜b＜0.1。 5. The secondary battery according to claim 4, characterized in that, The valence of M is +5, and b is 0.

04.

6. The secondary battery according to claim 4, characterized in that, The valence of M is +3, and b is 0.

02.

7. The secondary battery according to claim 1, characterized in that, The fluorinated silane coating is a triethyl(trifluoromethyl)silane coating.

8. The secondary battery according to claim 1, characterized in that, The thickness of the fluorinated silane coating is 1 µm - 10 µm.

9. The secondary battery according to claim 8, characterized in that, The thickness of the fluorinated silane coating is 6 µm.

10. An electrical appliance, characterized in that, Comprising a secondary battery according to any one of claims 1 - 9.

Images