A solid-state electrolyte, a preparation method thereof, a polymer composite solid-state electrolyte, and a solid-state lithium battery

Abstract

The application discloses a kind of solid electrolyte and preparation method thereof, polymer composite solid electrolyte and solid lithium battery, belong to solid lithium battery technical field, solid electrolyte includes lithium-containing transition metal oxide and doped element doped in lithium-containing transition metal oxide;The chemical formula of the solid electrolyte is Li x M (1‑y) N y O z ;Wherein, M is any one of transition metal, and the transition metal includes any one of Co, Ni or Mn, N is any one or more of doped element, x>0, 0.001≤y≤0.5, z>0.The solid electrolyte provided by the application has high ionic conductivity, controllable electronic conductivity, good interface compatibility, strong environmental stability and low cost, and is suitable for existing solid lithium battery system.

Description

Technical Field

[0001] This invention belongs to the field of solid-state lithium battery technology, specifically relating to a solid electrolyte and its preparation method, a polymer composite solid electrolyte, and a solid-state lithium battery. Background Technology

[0002] With the rapid development of electric vehicles, large-scale energy storage, and other fields, people have placed higher demands on the energy density and safety of rechargeable batteries. Traditional lithium-ion batteries use organic liquid electrolytes, which pose safety risks such as easy leakage, flammability, and explosion, and their energy density is gradually approaching its theoretical limit. All-solid-state lithium batteries use non-flammable solid electrolytes instead of liquid electrolytes and are considered one of the ideal ways to fundamentally solve battery safety issues and break through the energy density bottleneck.

[0003] Solid electrolytes are the core component of all-solid-state batteries, and their performance directly determines the overall performance of the battery. Currently researched solid electrolytes all have inherent drawbacks: PEO-based polymer solid electrolytes have low room-temperature ionic conductivity and a narrow electrochemical window, limiting their compatibility with high-voltage cathodes (Zhe Xiong et al., 4.2V polymer all-solid-state lithium batteries enabled by high-concentration PEO solid electrolytes, Energy Storage Mater., 2023, 57, 171; CN11220184A). Li7La3Zr2O 12 and Li 1.3 Al 0.3 Ti 1.7(PO4)3 and other oxide solid electrolytes are typically hard, resulting in poor physical contact and high solid-solid interface impedance (Yang Zhang et al., Garnet-Type Solid-State Electrolyte with Tailored Lithium Compatibility for High Performance All-Solid-State Lithium Batteries, Adv. Mater., 2026, 38, e09828). Li6PS5Cl sulfide solid electrolytes possess extremely high ionic conductivity comparable to liquid electrolytes, but their chemical stability is extremely poor. They react with moisture in the air to produce toxic hydrogen sulfide gas, placing extremely stringent requirements on production and usage environments. Furthermore, their compatibility with high-voltage cathodes is also problematic (Sijie Liu et al., Sulfide / Polymer Composite Solid-State Electrolytes for All-Solid-State Lithium Batteries, Adv. Energy Mater., 2024, 14, 2403602; CN111293354A).

[0004] In summary, existing solid-state electrolyte materials struggle to simultaneously achieve ideal performance across multiple key parameters, including ionic conductivity, interfacial compatibility, and electrochemical stability. Therefore, there is an urgent need in this field for a novel material design approach that can overcome the limitations of existing solid-state electrolyte materials. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a solid electrolyte and its preparation method, a polymer composite solid electrolyte and a solid lithium battery. This invention transforms layered cathode materials into solid electrolytes by doping with cationic elements, thus expanding the application scenarios of the materials. The solid electrolyte provided by this invention has high ionic conductivity, controllable electronic conductivity, good interface compatibility, strong environmental stability and low cost, and is suitable for existing solid lithium battery systems.

[0006] This invention provides the following technical solution: In a first aspect, a solid electrolyte is provided, the solid electrolyte comprising a lithium-containing transition metal oxide and a doping element doped in the lithium-containing transition metal oxide; The chemical formula of the solid electrolyte is Li x M (1-y) N y O z ; Wherein, M is any one of the transition metals, including Co, Ni or Mn, N is any one or more of the doping elements, x > 0, 0.001 ≤ y ≤ 0.5, z > 0; preferably, 0.01 ≤ y ≤ 0.1.

[0007] Furthermore, the average valence state of N is consistent with the valence state of M.

[0008] Furthermore, the lithium-containing transition metal oxide includes one of LiCoO2, LiNiO2, LiMnO2, or Li2MnO3.

[0009] Furthermore, the doping element includes one or more of Al, Ga, In, Ti, Mg, Ca, Sr, Si, Ge, Sn, or La-based elements.

[0010] In a second aspect, a method for preparing the solid electrolyte as described in any one of the first aspects is provided, including any one of the solid-phase method or the sol-gel method.

[0011] Furthermore, the solid-state method includes the following steps: The lithium source, doped element precursor and transition metal precursor were weighed separately, anhydrous ethanol was added, and they were ground thoroughly at 350-450 rpm for 8-24 h and then dried to obtain powder. The powder is sintered in a gas atmosphere at 500~1000℃ for 6~24 h, cooled, ground and sieved, pressed into sheets and annealed at 700~1000℃ to obtain a solid electrolyte.

[0012] Furthermore, the sol-gel method includes the following steps: The lithium source, doped element precursor and transition metal precursor were weighed separately, dissolved in a solvent, and a chelating agent was added to obtain a sol. The solvent in the sol was evaporated to dryness to obtain a gel; The gel was pre-calcined at 300-600℃ for 4-10 h, then calcined at 700-900℃ for 6-24 h, cooled, ground and sieved, pressed into sheets and annealed at 700-1000℃ to obtain a solid electrolyte.

[0013] Thirdly, a polymer composite solid electrolyte is provided, comprising a polymer and an inorganic filler, wherein the inorganic filler is prepared by the preparation method of the solid electrolyte according to any one of the first aspects or the solid electrolyte according to any one of the second aspects; The polymer includes any one or more of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyacrylonitrile, polycarbonate, polymethyl methacrylate, polysiloxane, polyphosphazene, or polyvinyl chloride.

[0014] Furthermore, the mass of the solid electrolyte accounts for 30% to 90% of the mass of the polymer composite solid electrolyte.

[0015] Fourthly, a solid-state lithium battery is provided, comprising a positive electrode, a negative electrode, and a solid electrolyte membrane between the positive electrode and the negative electrode, wherein the solid electrolyte membrane is a polymer composite solid electrolyte as described in any of the third aspects.

[0016] Furthermore, the thickness of the polysolid electrolyte membrane is 20~40 μm.

[0017] Furthermore, the positive electrode includes any one of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, vanadium pentoxide, lithium vanadium oxide, or lithium titanate, and the negative electrode includes any one of lithium metal or lithium alloy.

[0018] Compared with the prior art, the beneficial effects of the present invention are: (1) This invention provides an element-doped modified lithium-containing transition metal oxide. The lithium-containing transition metal oxide uses layered cathode material as raw material. Unmodified layered cathode material is mainly electron-conducting. Directly using it as a solid electrolyte will cause internal short circuits in the battery. This invention uses element doping. The doped element occupies the transition metal sites in the layered cathode material, which can significantly suppress the electronic conductivity of the layered cathode material. It effectively utilizes the intrinsic lithium-ion fast transport channel and transforms the layered cathode material from an electronic conductor to a highly efficient ion conductor. The prepared solid electrolyte has high ionic conductivity and low electronic conductivity. The raw materials used in this invention are inexpensive and the preparation method is simple and efficient, and it can be applied to solid-state lithium batteries. (2) By doping elements, the present invention effectively improves the oxidation potential of the layered cathode material, enabling it to withstand higher operating voltages and thus possessing excellent electrochemical stability. (3) The solid electrolyte provided by the present invention has good interfacial compatibility, which is due to the element doping that isolates electronic conduction. The doped solid electrolyte material can operate stably in lithium symmetric batteries and lithium metal full batteries. Attached Figure Description

[0019] Figure 1 This is a comparison chart of the electronic conductivity of the solid electrolytes in Examples 1-3 of the present invention and Comparative Example 1; Figure 2 This is a comparison chart of the ionic conductivity and activation energy of the solid electrolytes in Examples 1-3 of the present invention and Comparative Example 1; Figure 3 The figures show the 200-h cycle diagrams of the lithium symmetric batteries of Example 1 and Comparative Example 1 of this invention; Figure 4 The figures show the 20-hour cycle diagrams of the lithium symmetric batteries of Example 1 and Comparative Example 1 of this invention. Figure 5 This is a comparison chart of the cycle performance of lithium metal full batteries in Example 23 of the present invention and Comparative Examples 1 to 4. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0021] In the description of this invention, unless otherwise stated, "multiple" means two or more. The terms "comprising," "including," "having," "containing," etc., as used herein are open-ended, meaning they include but are not limited to.

[0022] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0023] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0024] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0025] This invention provides a solid electrolyte, which is used as an inorganic filler to prepare a polymer composite solid electrolyte and is applied in a solid lithium battery. The solid electrolyte is prepared by either the solid phase method or the sol-gel method.

[0026] The preparation of solid electrolytes using a solid-phase method includes the following steps.

[0027] 1. Weigh the lithium source, doped element precursor and transition metal precursor separately, add anhydrous ethanol, grind thoroughly at 350~450 rpm for 8~24 h and dry to obtain powder.

[0028] 2. Sinter the powder in a gas atmosphere at 500~1000℃ for 6~24 h, cool, grind and sieve, press into sheets and anneal at 700~1000℃ to obtain solid electrolyte.

[0029] Solid electrolytes are prepared using the sol-gel method, which includes the following steps.

[0030] 1. Weigh out the lithium source, doped element precursor and transition metal precursor respectively, dissolve them in a solvent, and add a chelating agent to obtain a sol.

[0031] 2. Evaporate the solvent in the sol to obtain a gel.

[0032] 3. Pre-calcine the gel at 300~600℃ for 4~10 h, then calcine it at 700~900℃ for 6~24 h, cool it, grind and sieve it, press it into sheets and anneal it at 700~1000℃ to obtain a solid electrolyte.

[0033] In some possible embodiments, the gas atmosphere used in the solid-phase process includes one of air, argon, or nitrogen.

[0034] In some possible embodiments, the lithium source used in the solid-state method or sol-gel method includes any one of lithium oxide, lithium hydroxide, lithium carbonate, or lithium nitrate, and the lithium source is weighed in stoichiometric excess of 5% to 10%. The transition metal precursor is an oxide, hydroxide, or nitrate corresponding to cobalt, nickel, or manganese.

[0035] The solid-phase electrolyte comprises a lithium-containing transition metal oxide and doping elements doped into the lithium-containing transition metal oxide. The lithium-containing transition metal oxide uses a layered cathode material as a raw material. The doping elements, in the form of doping compounds, are used to modify the lithium-containing transition metal oxide through solid-state methods or sol-gel methods, occupying the transition metal sites. In the solid-phase electrolyte of this invention, the doping element can be a single element or multiple elements co-doped. The average valence state of the doping element is consistent with the valence state of the transition metal in the lithium-containing transition metal oxide. While ensuring the stability of the doped material, the electronic conductivity and ionic conductivity of the lithium-containing transition metal oxide are controlled, thereby transforming the layered cathode material from an electronic conductor into a highly efficient ionic conductor.

[0036] In some possible embodiments, the doping amount of the dopant element accounts for 0.1 to 50% of the total molar number of transition metal sites in the lithium-containing transition metal oxide, preferably 1 to 10%.

[0037] In some possible embodiments, the doped element precursor used in the solid-state method or sol-gel method includes one of the following: aluminum source, gallium source, indium source, titanium source, magnesium source, calcium source, silicon source, germanium source, tin source, or lanthanide compound; aluminum source includes any one of aluminum oxide or aluminum hydroxide; gallium source includes any one of gallium oxide or gallium hydroxide; indium source includes any one of indium oxide, indium hydroxide, or indium nitrate; titanium source includes any one of titanium dioxide, titanium nitrate, or isopropyl titanate; magnesium source includes any one of magnesium oxide, magnesium hydroxide, magnesium carbonate, or magnesium oxalate; silicon source, germanium source, and tin source include any one of silicon dioxide, germanium oxide, or tin oxide; and lanthanide compound includes any one of lanthanum trioxide or lanthanum hydroxide.

[0038] In some possible embodiments, the chelating agent includes any one or more of citric acid, oxaloacetic acid, tartaric acid, or oxalic acid.

[0039] Example 1

[0040] This embodiment provides a solid-state method for preparing LiCo. 0.9 Al 0.1 O2 solid electrolyte. Using Li2CO3, Co3O4, and Al2O3 as raw materials, according to LiCo... 0.9 Al 0.1 The stoichiometric amount of O2 was weighed, with lithium carbonate added in 5% excess of the theoretical stoichiometric amount to compensate for lithium volatilization during sintering. The weighed raw material was mixed with anhydrous ethanol as a grinding aid and ball-milled in a planetary ball mill at 400 rpm for 10 h. The milled slurry was dried at 80 °C. The dried powder was sintered in air at 900 °C for 12 h, and after cooling, LiCo was obtained. 0.9 Al 0.1 O2 blocks were ground, sieved, pressed into sheets, and annealed at 1000°C to obtain electrolyte sheets for testing.

[0041] Examples 2 to 6

[0042] Examples 2 to 6 prepared solid electrolytes based on the solid electrolyte preparation method provided in Example 1. The difference is that the doping elements and doping amounts are different in Examples 2 to 6, as detailed in Table 1.

[0043] Example 7

[0044] This embodiment uses the sol-gel method to synthesize In and Ti co-doped LiNi. 0.88 In 0.02 Ti 0.1O2 material. LiNO3, Ni(NO3)2, In(NO3)3, and Ti(OCH(CH3)2)4 were weighed and dissolved in a solvent according to the theoretical stoichiometric ratio. Citric acid was added to form a sol, which was then evaporated to form a gel. The gel was pre-calcined at 500℃ for 6 h to remove organic matter, and then calcined at 700℃ for 12 h to obtain LiNi. 0.88 In 0.02 Ti 0.1 O2 was then ground, sieved, pressed into sheets, and annealed at 720°C to obtain electrolyte sheets for testing.

[0045] Examples 8 to 12

[0046] Examples 8-12 prepared solid electrolytes based on the solid electrolyte preparation method provided in Example 7. The difference is that the doping elements and doping amounts in Examples 8-12 are different, as detailed in Table 1.

[0047] Example 9

[0048] This embodiment uses a solid-state method to synthesize LiMn. 0.99 Al 0.01 O2 material. Li2CO3, Mn3O4, and Al2O3 were weighed according to the theoretical stoichiometric ratio and ball-milled in a planetary ball mill at 400 rpm for 10 h. The resulting slurry was dried at 80 °C. The dried powder was sintered at 750 °C for 10 h in an argon atmosphere, and LiMn was obtained after cooling. 0.99 Al 0.01 O2. LiMn 0.99 Al 0.01 O2 is ground and sieved, pressed into sheets and annealed at 800℃ to obtain electrolyte sheets for testing.

[0049] Examples 14-15

[0050] Examples 14 and 15 prepared solid electrolytes based on the solid electrolyte preparation method provided in Example 13. The difference is that the doping elements and doping amounts in Examples 14 and 15 are different, as detailed in Table 1.

[0051] Example 16

[0052] This embodiment uses a solid-state method to synthesize Li₂Mn. 0.99 Ti 0.01 O3 was used as the solid electrolyte. Li2CO3, Mn3O4, and TiO2 were weighed according to their theoretical stoichiometric ratio and ball-milled in a planetary ball mill at 400 rpm for 20 h. The resulting slurry was dried at 80 °C. The dried powder was sintered in air at 700 °C for 24 h, and after cooling, Li2Mn was obtained. 0.99 Ti0.01 O3. Grind and sieve, press into sheets and anneal at 720°C to obtain electrolyte sheets for testing.

[0053] Examples 17-18

[0054] Examples 17 and 18 prepared solid electrolytes based on the solid electrolyte preparation method provided in Example 16. The difference is that the doping elements and doping amounts in Examples 17 and 18 are different, as detailed in Table 1.

[0055] Examples 19 to 22

[0056] Based on the solid electrolyte prepared in Example 3, Examples 19 to 22 each provide a polymer composite solid electrolyte membrane.

[0057] Polymers used were polymethyl methacrylate (PMMA) and polyvinylidene fluoride (PVDF). The inorganic filler was the solid electrolyte prepared in Example 3. The mass percentage of the inorganic filler was 30% to 90%. The specific mass percentages of the inorganic filler in Examples 19 to 22 are shown in Table 2.

[0058] The preparation method adopts a common method for polymer solid electrolytes in the existing technology. Inorganic filler, PMMA and PVDF are dissolved in N,N-dimethylacetamide (DMAC), stirred thoroughly, cast into a film, and dried to obtain a polymer composite electrolyte membrane.

[0059] Example 23

[0060] This embodiment provides a solid-state lithium battery, with lithium iron phosphate as the positive electrode, lithium metal as the negative electrode, and the solid electrolyte being the polymer composite solid electrolyte (denoted as PMMA-PVDF-LiCo) prepared in Example 21. 0.5 Al 0.5 O2-70%).

[0061] Comparative Example 1

[0062] Based on the solid electrolyte preparation method provided in Example 1, this comparative example prepares LiCoO2 as a solid electrolyte, the difference being that aluminum oxide is not added, and lithium carbonate and cobalt tetroxide are weighed according to the stoichiometric ratio of LiCoO2.

[0063] LiCoO2, PMMA and PVDF were dissolved in DMAC and stirred thoroughly. The mixture was then cast into a film and dried to obtain a polymer composite electrolyte membrane, denoted as PMMA-PVDF-LiCoO2-70%.

[0064] LiCoO2 is used as an inorganic filler, accounting for 70% by mass.

[0065] Comparative Example 2

[0066] Based on the solid electrolyte preparation method provided in Example 7, this comparative example prepares LiNiO2 as a solid electrolyte, the difference being that no titanium source and indium source are added, and the lithium source and nickel source are weighed according to the stoichiometric ratio of LiNiO2.

[0067] LiNiO2, PMMA and PVDF were dissolved in DMAC and stirred thoroughly. The mixture was then cast into a film and dried to obtain a polymer composite electrolyte membrane, denoted as PMMA-PVDF-LiNiO2-70%.

[0068] LiNiO2 is used as an inorganic filler, accounting for 70% by mass.

[0069] Comparative Example 3

[0070] Based on the solid electrolyte preparation method provided in Example 16, this comparative example prepares LiMnO2 as a solid electrolyte, the difference being that no titanium source is added, and the lithium source and manganese source are weighed according to the theoretical stoichiometric ratio of LiMnO2.

[0071] LiMnO2, PMMA and PVDF were dissolved in DMAC and stirred thoroughly. The mixture was then cast into a film and dried to obtain a polymer composite electrolyte membrane, denoted as PMMA-PVDF-LiMnO2-70%.

[0072] LiMnO2 is used as an inorganic filler, accounting for 70% by mass.

[0073] Comparative Example 4

[0074] Based on the solid electrolyte preparation method provided in Example 16, this comparative example prepares Li2MnO3 as a solid electrolyte. The difference is that no titanium source is added, and the lithium source and manganese source are weighed according to the theoretical stoichiometric ratio of Li2MnO3.

[0075] Li2MnO3, PMMA and PVDF were dissolved in DMAC and stirred thoroughly. The mixture was then cast into a film and dried to obtain a polymer composite electrolyte membrane, denoted as PMMA-PVDF-LiMnO3-70%.

[0076] LiMnO3 is used as an inorganic filler, accounting for 70% by mass.

[0077] Comparative Example 5

[0078] Based on the solid electrolyte preparation method provided in Example 1, this comparative example prepares LiZn 0.1 Co 0.9 O2 is used as a solid electrolyte, the only difference being that the doping element is replaced by Zn instead of Al.

[0079] Comparative Example 6

[0080] Based on the solid electrolyte preparation method provided in Example 1, this comparative example prepares LiCo. 0.3 Al 0.7 O2 is used as a solid electrolyte, but the difference lies in that only the amount of Al doping is adjusted.

[0081] The following analysis is based on specific data.

[0082] Based on the solid electrolytes prepared in Examples 1-18 and Comparative Examples 1-6, the electronic conductivity of the solid electrolytes was tested using the DC polarization method. Symmetrical cells with blocking electrodes were prepared, a small DC bias voltage of 0.2 V was applied, and the steady-state current was recorded. The electronic conductivity test results for Examples 1-18 and Comparative Examples 1-6 are shown in Tables 1 and 2.

[0083] Electronic conductivity is calculated using the following formula: ; in, L For sample thickness, S The electrode contact area, R For electronic resistance, U For the applied DC bias voltage, I This is the steady-state current.

[0084] Based on the solid electrolytes prepared in Examples 1-18 and Comparative Examples 1-6, the ionic conductivity of the solid electrolytes was tested using the AC impedance method. Symmetrical cells with blocking electrodes were prepared, and the impedance response of the samples at different frequencies was measured by applying a small-amplitude sinusoidal AC voltage signal, thereby obtaining the bulk resistance of the material. The ionic conductivity test results of Examples 1-18 and Comparative Examples 1-6 are shown in Tables 1 and 2.

[0085] Ionic conductivity is calculated using the following formula: ; in, L For sample thickness, R 体 For volume impedance, S This represents the electrode contact area.

[0086] Based on the solid electrolytes prepared in Examples 1-18 and Comparative Examples 1-6, the electrochemical stability window of the materials was tested using linear sweep voltammetry at a scan rate of 10 mV / s. The cycle life of the lithium-ion symmetric battery was tested using a galvanostatic cycling method at a test condition of 0.5 mA / cm². 2 The test results are shown in Tables 1 and 2. The cells were charged and discharged for 1 hour at a current density.

[0087] Table 1. Electrochemical test results of Examples 1 to 18

[0088] Table 2 Electrochemical test results for comparisons 1 through 6

[0089] like Figure 1 and Figure 2 As shown in Table 1, taking Al doping as an example, elemental doping significantly reduces the electronic conductivity of the layered cathode material LiCoO2, while maintaining the ionic conductivity at a relatively high level (approximately 10⁻⁶). -3 S / cm). For example... Figure 3 and Figure 4 As shown, taking the solid electrolytes of Example 1 and Comparative Example 1 as examples, Example 1 was assembled into a lithium symmetric battery, denoted as Li-LiCo. 0.9 Al 0.1 O2-Li was used to assemble Comparative Example 1 into a lithium-symmetric battery, denoted as Li-LiCoO2-Li. A 200-hour cycle performance test was conducted. The battery in Example 1 maintained good performance after 200 hours of cycle testing, while the battery in Comparative Example 1 experienced internal circuitry and showed no cycle performance. As shown in Table 1, Examples 1-6 demonstrate that elemental doping can significantly reduce electronic conductivity while maintaining high ionic conductivity (achieving "functional decoupling"), and synergistically improve oxidation potential and interface stability, thus fully meeting the performance requirements of solid-state electrolytes. Examples 7-18 further confirm that this method is universally applicable to layered cathode materials of different systems (such as LiNiO2, LiMnO2, and Li2MnO3). As shown in Table 2, although the undoped original cathode materials used in Comparative Examples 1-4 possess high ionic conductivity, directly using them as solid-state electrolytes would cause internal short circuits due to their extremely high electronic conductivity, making them unsuitable for direct use as solid-state electrolytes. However, the electronic conductivity of Comparative Example 5 (Zn doped) and Comparative Example 6 (Al overdoped) remained high, leading to short circuits in the batteries and preventing the transformation of the layered cathode material into a solid electrolyte. This further demonstrates that the present invention achieves a functional transformation of the material from an "electrode" to a "solid electrolyte" through the regulation of doping elements and the amount of doping.

[0090] Based on the polymeric composite solid electrolyte membranes of Examples 19 to 22, the above-described methods for testing electronic conductivity and ionic conductivity were used for testing, and the results are shown in Table 3.

[0091] Table 3. Results of membrane physical state, electronic conductivity, and ionic conductivity in Examples 19-22

[0092] As shown in Tables 2 and 3, the polymer composite solid electrolytes provided in Examples 19 to 22 exhibit high ionic conductivity and extremely low electronic conductivity. Furthermore, while Example 22 shows high ionic conductivity, its membrane becomes rigid and brittle, making it difficult to self-support. This is because in polymer composite solid electrolyte membranes, the polymer provides a mechanical and flexible support framework for the electrolyte. When the proportion of inorganic fillers is too high, the polymer proportion is insufficient, failing to form a complete support framework, leading to a decrease in flexibility and self-support.

[0093] Based on the solid-state lithium batteries of Examples 23 and Comparative Examples 1-4, constant current charge-discharge tests were performed using a battery testing system. The charge-discharge capacity and coulombic efficiency of the batteries were recorded. The test results are shown in Table 4 and... Figure 5 As shown.

[0094] Table 4 compares the cycle performance of solid lithium metal batteries in Example 3 and Comparative Examples 1-4.

[0095] From Table 4 and Figure 5 As shown, Comparative Examples 1-4 suffered from short-circuit failure due to their high electronic conductivity. The solid-state lithium metal battery provided in Example 23 exhibited excellent cycle performance, demonstrating that the elemental doping modification method provided by this invention can transform layered cathode materials into solid electrolytes suitable for solid-state lithium batteries, thus verifying the practical application value of this invention.

[0096] This invention achieves functional decoupling of electron transport and ion transport by using metal cations to dope layered cathode materials. While suppressing electron transport capability, it retains lithium-ion conduction characteristics, realizing the functional transformation from "energy storage" to "ion transport", which has high application value in solid-state lithium batteries.

[0097] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A solid electrolyte, characterized in that, The solid electrolyte includes a lithium-containing transition metal oxide and doping elements doped into the lithium-containing transition metal oxide. The chemical formula of the solid electrolyte is Li x M (1-y) N y O z ; Wherein, M is any one of the transition metals, including any one of Co, Ni or Mn, N is any one or more doping elements, x > 0, 0.001 ≤ y ≤ 0.5, z > 0.

2. The solid electrolyte according to claim 1, characterized in that, The average valence state of N is consistent with the valence state of M.

3. The solid electrolyte according to claim 1, characterized in that, The lithium-containing transition metal oxide includes one of LiCoO2, LiNiO2, LiMnO2, or Li2MnO3; And / or, the doping element includes one or more of Al, Ga, In, Ti, Mg, Ca, Sr, Si, Ge, Sn, or La-based elements.

4. A method for preparing a solid electrolyte according to any one of claims 1 to 3, characterized in that, It can be prepared by any of the following methods: solid-phase method or sol-gel method.

5. The method for preparing a solid electrolyte according to claim 4, characterized in that, The solid-state method includes the following steps: The lithium source, doped element precursor and transition metal precursor were weighed separately, anhydrous ethanol was added, and they were ground thoroughly at 350~450 rpm for 8~24 h and then dried to obtain powder. The powder is sintered in a gas atmosphere at 500~1000℃ for 6~24 h, cooled, ground and sieved, pressed into sheets and annealed at 700~1000℃ to obtain a solid electrolyte.

6. The method for preparing a solid electrolyte according to claim 4, characterized in that, The sol-gel method includes the following steps: The lithium source, doped element precursor and transition metal precursor were weighed separately, dissolved in a solvent, and a chelating agent was added to obtain a sol. The solvent in the sol was evaporated to dryness to obtain a gel; The gel was pre-calcined at 300-600℃ for 4-10 h, then calcined at 700-900℃ for 6-24 h, cooled, ground and sieved, pressed into sheets and annealed at 700-1000℃ to obtain a solid electrolyte.

7. A polymer composite solid electrolyte, comprising a polymer and an inorganic filler, characterized in that, The inorganic filler is prepared using the solid electrolyte preparation method according to any one of claims 1 to 3 or the solid electrolyte preparation method according to any one of claims 4 to 6; The polymer includes one or more of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyacrylonitrile, polycarbonate, polymethyl methacrylate, polysiloxane, polyphosphazene, or polyvinyl chloride.

8. The polymer composite solid electrolyte according to claim 7, characterized in that, The mass of the solid electrolyte accounts for 30% to 90% of the mass of the polymer composite solid electrolyte.

9. A solid-state lithium battery, comprising a positive electrode, a negative electrode, and a solid electrolyte membrane situated between the positive and negative electrodes, characterized in that, The solid electrolyte membrane is a polymer composite solid electrolyte as described in any one of claims 7 to 9.

10. The polymer composite solid electrolyte according to claim 9, characterized in that, The thickness of the solid electrolyte membrane is 20~40 μm.

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