Composite conductor, method for manufacturing the same, positive electrode sheet, secondary battery, and electric device

Abstract

This application relates to the field of solid-state battery technology, and discloses a composite conductor with the molecular formula Li. 1+x Al x Ti 2‑x (PO4)3, 0.1 ≤ x ≤ 0.5; the Ti element includes Ti 4+ Ti 3+ And metallic Ti, by mass percentage, 62% < Ti 4+ <79%, 6% < metallic Ti < 22%, balance is Ti 3+ The total is 100%. This application achieves efficient electronic and ionic mixed conductivity by precisely controlling the valence state distribution of titanium, thereby optimizing the transport performance of the cathode material in a thick electrode structure. It solves the bottleneck of ion and electron transport dynamics in the thick electrode structure of all-solid-state batteries, improves rate performance and fast charge and discharge capability, while reducing production costs and process complexity, avoiding impurity problems caused by external additives, and improving material stability and compatibility.

Description

Technical Field

[0001] This application relates to the field of solid-state battery technology, and in particular to a composite conductor and its preparation method, as well as a positive electrode, a secondary battery, and an electrical device. Background Technology

[0002] As the global energy structure accelerates its transition towards cleaner and more sustainable energy, the large-scale deployment of electric vehicles and renewable energy storage systems places higher demands on high-performance energy storage technologies. All-solid-state batteries, with their innovative design that uses solid electrolytes instead of traditional liquid electrolytes, have demonstrated significant advantages in eliminating electrolyte leakage risks, suppressing thermal runaway, and increasing energy density, and are considered a key direction for energy storage technology development. However, in practical engineering applications, the rate performance and fast charge / discharge capabilities of all-solid-state batteries still face severe challenges, mainly due to the bottleneck of ion and electron transport dynamics in thick electrode structures. To achieve higher energy density, the thickness of the positive electrode active material layer typically needs to be increased to the hundreds of micrometers level, but this structure significantly prolongs the diffusion path of lithium ions in the solid electrolyte, while simultaneously exacerbating the conduction resistance of electrons within the positive electrode material. Traditional solutions rely on adding solid electrolytes and conductive agents to the positive electrode to improve transport performance. However, in thick electrodes, this addition not only occupies the effective space of the active material, leading to a decrease in volumetric energy density, but also causes tortuous charge transport paths due to poor solid-solid interface contact, resulting in severe battery polarization and capacity decay, which is particularly prominent under high-rate conditions.

[0003] To address the aforementioned issues, existing technologies attempt to optimize the conductivity of cathode materials through various approaches. Some studies employ metal-organic frameworks (MOFs) as carriers to embed ion-conducting materials, constructing porous transport networks; others focus on generating an electronically conductive phase in situ within inorganic materials, such as introducing elemental metals into inorganic materials through lithium reduction or chemical lithiation to form an electronically conductive phase. However, these methods reveal systemic drawbacks in practical applications. First, the introduction of auxiliary materials such as MOFs or lithium metal significantly increases production costs and resource consumption, and the synthesis process often involves toxic organic solvents, posing a threat to environmental safety. Second, doping of the second-phase material inevitably introduces impurity elements, which may induce side reactions or disrupt the material's structural stability, while also significantly increasing process complexity, requiring extremely high precision in reaction condition control, making it difficult to meet the demands of large-scale industrial production. Furthermore, existing technological routes generally lack compatibility with mainstream battery production equipment; for example, liquid-phase reaction processes require dedicated reactors, while high-temperature reduction processes require customized furnaces, resulting in high equipment investment costs and difficulties in technology transfer. Furthermore, liquid-phase synthesis methods struggle to ensure uniform component distribution during material mixing, and microscale inconsistencies can accumulate into macroscopic performance fluctuations, impacting product reliability and batch stability. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a composite conductor and its preparation method, which enables the composite conductor to solve the bottleneck problem of ion and electron transport dynamics under the thick electrode structure of all-solid-state batteries, improve rate performance and fast charge and discharge capability, while reducing production cost and process complexity, avoiding impurity problems caused by external additives, and improving the material stability and compatibility.

[0005] Another object of this application is to provide a positive electrode, a secondary battery, and an electrical device based on the composite conductor described in this application.

[0006] To achieve all or part of the above objectives, as a first aspect of this application, a composite conductor with the molecular formula Li is provided. 1+x Al x Ti 2-x (PO4)3, 0.1 ≤ x ≤ 0.5; the Ti element includes Ti 4+ Ti 3+ And metallic Ti, by mass percentage, 62% < Ti 4+ <79%, 6% < metallic Ti < 22%, balance is Ti 3+ Total: 100%.

[0007] Optionally, by mass percentage, 65% ≤ Ti 4+ ≤75%, 8%≤metallic Ti≤20%, balance is Ti 3+ Total: 100%.

[0008] As a second aspect of this application, a method for preparing a composite conductor as described in this application is provided, comprising: Lithium, aluminum, titanium, and phosphorus sources were obtained according to stoichiometric ratios, mixed, and then sintered to form Li. 1+x Al x Ti 2-x (PO4)3, 0.1 ≤ x ≤ 0.5; The Li 1+x Al x Ti 2-x The composite conductor is obtained by annealing (PO4)3 in a mixed atmosphere of hydrogen and protective gas; the proportion of hydrogen in the mixed atmosphere is 15% < hydrogen volume percentage < 25%.

[0009] Optionally, the lithium source includes Li2CO3 and / or LiOH; the aluminum source includes Al2O3 and / or Al2(CO3)3; the titanium source includes TiO2; and the phosphorus source includes NH4H2PO4 and / or (NH4)2HPO4.

[0010] Optionally, the sintering temperature is 700-900℃.

[0011] Optionally, the protective gas includes argon.

[0012] Optionally, the annealing treatment is performed at a temperature of 200-400℃ for 1-3 hours.

[0013] Optionally, the proportion of hydrogen in the mixed atmosphere is 18% ≤ hydrogen volume percentage ≤ 22%.

[0014] As a third aspect of this application, a positive electrode sheet is provided, including a current collector and a positive electrode material coated on the surface of the current collector; the positive electrode material includes the composite conductor described in this application, or a composite conductor prepared by the preparation method described in this application.

[0015] Optionally, the positive electrode material includes a positive electrode active material, a binder, and the composite conductor described in this application or the composite conductor prepared by the preparation method described in this application.

[0016] As a fourth aspect of this application, a secondary battery is provided, including a negative electrode, a positive electrode as described in this application, and a solid electrolyte.

[0017] Optionally, the solid electrolyte includes an oxide-polymer composite electrolyte.

[0018] As a fifth aspect of this application, an electrical device is provided, including the secondary battery described in this application, wherein the secondary battery provides electrical energy to the electrical device or serves as an energy storage unit for the electrical device.

[0019] This application achieves highly efficient electronic and ionic mixed conductivity by precisely controlling the valence state distribution of titanium, thereby optimizing the transport performance of the cathode material under a thick electrode structure. It solves the bottleneck of ion and electron transport dynamics under a thick electrode structure in all-solid-state batteries, improves rate performance and fast charge and discharge capability, while reducing production costs and process complexity, avoiding impurity problems caused by external additives, and improving material stability and compatibility. Detailed Implementation

[0020] This application discloses a composite conductor and its preparation method, as well as a positive electrode sheet, a secondary battery, and electrical equipment. Those skilled in the art can refer to the content of this application and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this application. The products and processes described in this application have been described through preferred embodiments. Those skilled in the art can obviously modify or appropriately change and combine the products and processes described herein without departing from the content, spirit, and scope of this application to realize and apply the technology of this application. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0021] It should be noted that, in this document, relational terms such as "first" and "second," "step 1" and "step 2," and "(1)" and "(2)" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Moreover, the embodiments and features described in this application can be combined with each other without conflict.

[0022] Traditional all-solid-state batteries, with their thick electrode structures, suffer from insufficient electronic and ionic conductivity in the cathode materials, limiting battery rate performance and charge / discharge efficiency. Existing solutions generally suffer from high production costs, resource waste, environmental pollution, complex processes, poor equipment compatibility, difficulty in ensuring material mixing uniformity, and limited conductivity improvement, especially in terms of capacity enhancement with thick electrodes, making it difficult to meet the needs of large-scale industrial production and practical applications.

[0023] Therefore, in the first aspect of this application, a composite conductor with the molecular formula Li is proposed. 1+x Al x Ti 2-x (PO4)3, where x takes values ​​in the range of 0.1 ≤ x ≤ 0.5. The Ti element in this composite conductor includes Ti... 4+ Ti 3+And metallic Ti, and by mass percentage, 62% < Ti 4+ <79%, 6% < metallic Ti < 22%, balance is Ti 3+ The total efficiency is 100%. The composite conductor provided in this application constructs a highly efficient electron and ion transport network through its specific molecular formula and the synergistic effect of the multiple valence states of titanium. Therefore, this composite conductor can significantly improve the electronic and ion conductivity of the cathode material in all-solid-state batteries with thick electrode structures, effectively reduce battery polarization, and thus improve the rate performance and charge / discharge efficiency of the battery.

[0024] The composite conductor of this application possesses both excellent ionic and electronic conductivity to meet the high charge transport requirements of thick electrodes in all-solid-state batteries. For example, the composite conductor can be prepared as a powder and mixed with the positive electrode active material to form a positive electrode material with a good conductive network. As another implementation, the composite conductor can also be coated on the surface of the positive electrode active material to form a core-shell structure, providing a more direct charge transport path.

[0025] The molecular formula of the composite conductor in this application is Li. 1+x Al x Ti 2-x (PO4)3, where x ranges from 0.1 to 0.5, belongs to the NASICON type structure, which is conducive to the rapid migration of lithium ions. For example, x can be set to 0.1, in which case the lithium ion concentration in the material is relatively low, but the lattice stability is high. As another implementation, x can also be set to 0.5, in which case the lithium ion concentration in the material is relatively high, which is conducive to ion transport. By adjusting the value of x, such as 0.1, 0.2, 0.3, 0.4, 0.5, or any value between two points, the ionic conductivity of the material can be controlled.

[0026] In some embodiments of this application, the Ti element in the composite conductor includes Ti 4+ Ti 3+ And metallic Ti. Ti 4+ As a key component of the material framework, Ti maintains the stability of the NASICON-type structure. 3+ The presence of Ti introduces electronic defects, thereby creating electron transport paths within the material. Metallic Ti, acting as an independent electronically conductive phase, significantly enhances the overall electronic conductivity of the material. For example, Ti... 4+ Ti can be obtained by sintering a titanium source under an oxidizing atmosphere. 3+ Ti can be processed under a reducing atmosphere 4+ It is formed through partial reduction. Metallic Ti can be achieved through stronger reduction conditions or by introducing a metallic reducing agent.

[0027] In other embodiments of this application, the valence states of Ti in the composite conductor, by mass percentage, are 62% < Ti 4+ <79%, 6% < metallic Ti < 22%, balance is Ti 3+ The total is 100%. And the sum of the three is 100%. This specific ratio configuration is designed to achieve a synergistic balance between electronic and ionic conductivity. For example, Ti 4+ The content of Ti can be controlled at 70%. 3+ The content of Ti can be controlled at 10%, and the content of metallic Ti can be controlled at 20%. As another implementation method, Ti... 4 + The content of Ti can be controlled at 75%. 3+ The content of α can be controlled at 15%, and the content of metallic Ti can be controlled at 10%. By precisely controlling the ratio of these three valence states, the electronic and ion transport characteristics of the composite conductor can be optimized to meet the needs of different application scenarios.

[0028] In some other embodiments of this application, the valence distribution of titanium in the composite conductor, expressed as a mass percentage, is specifically 65% ​​≤ Ti. 4+ ≤75%, 8%≤metallic Ti≤20%, balance is Ti 3+ A total of 100%. Within this range, the electronic and ion transport properties of the composite conductor can be optimally optimized. Ti 4+ Controlling the content of [Ti] within this range, such as 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 72%, 74%, 75%, or any value between any two, ensures that the composite conductor has sufficient ion transport capability while avoiding excessive content that would dilute the effectiveness of the electronically conductive phase. Controlling the content of metallic Ti within this range, such as 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any value between any two, ensures the formation of efficient electron transport paths, significantly improving the overall electronic conductivity of the composite conductor, while avoiding structural instability or agglomeration problems that may be caused by excessive metallic titanium content. The balance is Ti. 3+ The percentage content can be 5-27%, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 27%, or any value between any two, by determining Ti 4+ The content of metallic Ti further affects Ti 3+ The content of Ti is kept within a suitable range to maximize electron transport efficiency while avoiding the negative effects of Ti.3+ The conductivity decreases due to excessively high or low content.

[0029] In a second aspect of this application, a method for preparing a composite conductor as described in this application is provided, comprising: First, lithium, aluminum, titanium, and phosphorus sources are obtained according to stoichiometric ratios, mixed, and then sintered to form Li. 1+x Al x Ti 2-x (PO4)3, 0.1 ≤ x ≤ 0.5; This step aims to precisely control the composition of the composite conductor precursor, laying a uniform and stable foundation for subsequent valence state regulation. Specifically, the lithium source can be one or more of lithium carbonate, lithium hydroxide, lithium nitrate, or lithium fluoride; the aluminum source can be one or more of alumina, aluminum hydroxide, aluminum carbonate, aluminum nitrate, or aluminum chloride; the titanium source can be one or more of titanium dioxide, titanium hydroxide, or titanium tetrachloride; the phosphorus source can be one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, phosphoric acid, or phosphorus pentoxide; more specifically, the lithium source includes Li2CO3 and / or LiOH; the aluminum source includes Al2O3 and / or Al2(CO3)3; the titanium source includes TiO2; and the phosphorus source includes NH4H2PO4 and / or (NH4)2HPO4. After obtaining these raw materials, the stoichiometric ratio of each component needs to be accurately calculated according to the target molecular formula to ensure that the chemical composition of the final product meets the design requirements. Subsequently, these raw materials are thoroughly mixed. Mixing methods can include dry mixing, such as planetary ball milling, or wet mixing, such as dispersing the raw materials in a suitable solvent and then stirring or ultrasonically treating them, to ensure uniform dispersion of the components. The mixed precursor is then sintered at a high temperature, typically within the range of 600℃ to 1000℃, for example, between 700℃ and 900℃, to promote the formation of Li with a specific crystal structure in the precursor. 1+x Al x Ti 2-x (PO4)3 compound.

[0030] Secondly, the Li 1+x Al x Ti 2-x The composite conductor is obtained by annealing (PO4)3 in a mixed atmosphere of hydrogen and protective gas; the proportion of hydrogen in the mixed atmosphere is 15% < hydrogen volume percentage < 25%.

[0031] This step is the core of achieving precise control of the valence state of Ti. By controlling the composition of the reducing atmosphere, Li... 1+x Al x Ti 2-x Part of Ti in (PO4)3 4+ Restore to Ti3+ The presence of metallic Ti imparts excellent electronic and ionic conductivity to the composite conductor. Specifically, the sintered Li... 1+x Al x Ti 2-x (PO4)3 is annealed in a mixed atmosphere containing hydrogen and a protective gas. Hydrogen, acting as a reducing agent, has its volume percentage in the mixed atmosphere precisely controlled between 15% and 25%, for example, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, or any value between these two ranges. This can be further optimized to a range of 18% ≤ hydrogen volume percentage ≤ 22% to achieve fine control over the valence state distribution of Ti. The protective gas provides an inert environment to prevent unwanted oxidation or other side reactions during the high-temperature reduction process. It can be one or more inert gases such as argon, nitrogen, or helium. The annealing temperature is typically selected within the range of 200°C to 600°C, for example, between 200°C and 400°C; the annealing time is typically selected within the range of 0.5 hours to 5 hours, for example, between 1 hour and 3 hours. By precisely controlling the annealing temperature, time, and atmosphere composition, composite conductors with specific Ti valence state distributions can be obtained efficiently and stably.

[0032] Compared to existing technologies, the composite conductor prepared in this application does not require the introduction of additional auxiliary materials or the use of toxic solvents, thus significantly reducing production costs, minimizing environmental pollution, and simplifying the process. Through integrated sintering and reduction annealing steps, the introduction of second-phase impurities is avoided, improving the purity and uniformity of the material and solving problems such as complex processes, poor equipment compatibility, and unstable material properties in existing methods. This preparation method can efficiently and stably achieve a specific valence state distribution of Ti, thereby producing a composite conductor with excellent electronic and ionic conductivity.

[0033] In a third aspect of this application, a positive electrode sheet is provided, comprising a current collector and a positive electrode material coated on the surface of the current collector; the positive electrode material comprises the composite conductor described in this application, or a composite conductor prepared by the preparation method described in this application.

[0034] In some embodiments of this application, the positive electrode material includes a positive electrode active material, a binder, and a composite conductor as described in this application or a composite conductor prepared by the preparation method described in this application. The ratio of the three components can be selected as 80-98:1-10:1-10, for example 90:2:8, 95:2.5:2.5, 85:5:10, etc.

[0035] The positive electrode active material can be a lithium-ion positive electrode active material, including but not limited to layered oxides, such as lithium cobalt oxide (LiCoO2), lithium nickel manganese cobalt oxide (LiNiMnCoO2, NMC) or lithium nickel cobalt aluminum oxide (LiNiCoAlO2, NCA); spinel-type oxides, such as lithium manganese oxide (LiMn2O4); and olivine-type phosphates, such as lithium iron phosphate (LiFePO4) or lithium manganese phosphate (LiMnPO4).

[0036] Commonly used adhesives include, but are not limited to, polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), or combinations thereof.

[0037] In some embodiments of this application, the positive electrode active material, binder and composite conductor of this application are mixed evenly and then subjected to fiberization treatment; finally, the fiberized material is placed in a roller press to form a high-load thick positive electrode sheet.

[0038] This application achieves internal Ti in the material by combining composite conductors with optimized electrode formulations (reducing or eliminating the addition of external conductive agents). 4+ Ti 3+ The balance between the metal and Ti metal can take into account both electronic and ionic conductivity, ultimately achieving a significant improvement in the 1C capacity retention rate of thick electrodes to 89.9%.

[0039] In a fourth aspect of this application, a secondary battery is provided, comprising a negative electrode, a positive electrode as described in this application, and a solid electrolyte. The secondary battery is a rechargeable battery capable of recovering its active material through charging after discharge, thereby enabling multiple cycles of use. This secondary battery can be a lithium-ion battery. The negative electrode can be prepared using conventional negative electrode preparation processes in the art, and this application does not limit this. In some embodiments of this application, the negative electrode is a lithium metal negative electrode.

[0040] In some embodiments of this application, the positive electrode, the negative electrode, and the solid electrolyte can be fabricated into an electrode assembly by a winding process or a stacking process.

[0041] In some embodiments of this application, the secondary battery may include an outer packaging. This outer packaging can be used to encapsulate the aforementioned electrode assembly. In other embodiments of this application, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging of the secondary battery may also be a soft package, such as a pouch.

[0042] In some embodiments of this application, the solid electrolyte includes an oxide-polymer composite electrolyte. An oxide-polymer composite electrolyte is a hybrid solid electrolyte that combines the advantages of inorganic oxide solid electrolytes and organic polymer electrolytes. Its basic structure typically includes inorganic oxide particles as an ion transport framework and a polymer as a flexible matrix and interfacial binder. This composite structure aims to overcome the limitations of single solid electrolytes; inorganic oxides typically have high ionic conductivity and good electrochemical stability but are brittle and have poor interfacial contact with electrodes, while polymers have excellent flexibility, processability, and good wettability with electrodes but relatively low ionic conductivity. By combining the two, a combination of high ionic conductivity, good interfacial contact, excellent flexibility, and mechanical strength can be achieved. In practical applications, the inorganic oxide component can be selected from materials with high lithium-ion conductivity, such as, but not limited to, garnet-type oxides (e.g., Li7La3Zr2O). 12 ), NASICON type oxides (such as Li) 1.4 Al 0.4 Ge 1.6 (PO4)3) or perovskite oxides (such as Li) 0.33 La 0.56 (e.g., TiO3). These oxides act as fast channels for ion transport, ensuring the high ionic conductivity of the overall composite electrolyte. Simultaneously, the polymer component can be selected from polymer matrices with good flexibility and electrochemical stability, such as, but not limited to, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), or polymethyl methacrylate (PMMA). These polymers not only provide mechanical support and flexibility but also improve interfacial contact with electrode materials. The preparation methods of the composite electrolyte can include, but are not limited to, solution casting, in-situ polymerization, melt blending, or electrospinning. For example, by dispersing inorganic oxide particles in a polymer solution and then performing solvent evaporation or in-situ polymerization, a uniform composite film can be formed.

[0043] In a fifth aspect of this application, an electrical device is provided, including the secondary battery described in this application, the secondary battery providing electrical energy to the electrical device or serving as an energy storage unit for the electrical device.

[0044] The secondary battery provides electrical energy to electrical devices by converting stored chemical energy into electrical energy through a discharge process and supplying it to the devices to power their normal operation. For example, in electric vehicles, the secondary battery powers the drive motor; in portable electronic devices, the secondary battery directly supplies power to the internal circuitry.

[0045] The secondary battery, used as an energy storage unit in electrical equipment, refers to a battery that not only provides electrical energy but also acts as an energy buffer and storage medium. It can be charged when powered by an external power source and released when needed. For example, in smart grids or home energy storage systems, secondary batteries can be charged during off-peak electricity periods and discharged during peak periods, achieving peak shaving and valley filling, thus optimizing energy utilization. In hybrid vehicles, secondary batteries can recover and store braking energy, providing auxiliary power during acceleration and improving fuel efficiency.

[0046] The electrical equipment may include, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0047] In the comparative experiments provided in this application, unless otherwise specified, all experimental conditions and materials remain consistent to ensure comparability. Furthermore, all materials used in this application are commercially available.

[0048] The following provides a further description of a composite conductor, its preparation method, a positive electrode sheet, a secondary battery, and an electrical device provided in this application.

[0049] Example 1: Preparation of LATP-X, an electron-ion mixed conductor: according to the stoichiometric ratio of Li 1.1 Al 0.1 Ti 1.9 Weigh out lithium, aluminum, titanium, and phosphorus source powders (PO4)3 (i.e., x=0.1) in a molar ratio of Li:Al:Ti:P = 1.1:0.1:1.9:3. Perform a first ball milling (300 r / min, 8 h), drying (80℃, 8 h), and high-temperature sintering (800℃, 6 h), followed by a second ball milling (300 r / min, 8 h) to obtain LATP-based powder. Place the obtained LATP-based powder in a tube furnace and anneal it in a H2 / Ar2 mixed atmosphere (20% H2 volume fraction) at 300℃ for 2 h to obtain an electron-ion hybrid conductor material, denoted as LATP-M-1.1.

[0050] Preparation of high-load thick electrode: The obtained LATP-Li was used as the positive electrode additive, and a thick electrode (area loading of 40 mg / cm²) was prepared according to the basic formula (positive electrode active material NCM811: binder PTFE: LATP = 85: 2: 13), and a solid-state battery was assembled for testing.

[0051] An oxide-polymer composite electrolyte membrane (PVDF+LATP+LiTFSI in a ratio of 50%:10%:40%) was placed between the lithium metal anode and the high-load thick cathode to assemble a solid-state lithium battery. The assembled battery was placed in a glove box and fitted with stainless steel positive and negative electrode cases to form a button cell for electrochemical performance testing.

[0052] Example 2: Preparation of LATP-X, an electron-ion mixed conductor: according to the stoichiometric ratio of Li 1.3 Al 0.3 Ti 1.7 Weigh out lithium, aluminum, titanium, and phosphorus source powders (PO4)3 (i.e., x=0.3) in a molar ratio of Li:Al:Ti:P = 1.3:0.3:1.7:3. Follow the same steps as in Example 1 to obtain the electron-ion hybrid conductor material, denoted as LATP-M-1.3. Prepare the electrode using the same steps and formulation as in Example 1, and simultaneously assemble a solid-state battery for testing.

[0053] Example 3: Preparation of LATP-X, an electron-ion mixed conductor: according to the stoichiometric ratio of Li 1.5 Weigh out lithium, aluminum, titanium, and phosphorus source powders (i.e., x=0.5) into Al0.5Ti1.5(PO4)3 (i.e., x=0.5), with a molar ratio of Li:Al:Ti:P = 1.5:0.5:1.5:3. Follow the same steps as in Example 1 to obtain the electron-ion hybrid conductor material, denoted as LATP-M-1.5. Prepare the electrode using the same steps and formula as in Example 1, and simultaneously assemble a solid-state battery for testing.

[0054] Example 4: Preparation of the electron-ion hybrid conductor LATP-X: LATP powder was prepared according to the process in Example 2, except that the volume fraction of H2 in the H2 / Ar2 mixed atmosphere was 18%, denoted as LATP-1.3-18H. The electrode was prepared using the same electrode preparation steps and formulation as in Example 1, and a solid-state battery was assembled for testing.

[0055] Example 5: Preparation of the electron-ion hybrid conductor LATP-X: LATP powder was prepared according to the process in Example 2, except that the volume fraction of H2 in the H2 / Ar2 mixed atmosphere was 22%, denoted as LATP-1.3-22H. The electrode was prepared using the same electrode preparation steps and formulation as in Example 1, and a solid-state battery was assembled for testing.

[0056] Comparative Example 1: LATP powder was prepared according to the process in Example 2, except that it was not subjected to annealing in a H2 / Ar2 mixed atmosphere (named LATP-0). The obtained LATP-0 was used as a positive electrode additive, and a thick electrode (area loading 40 mg / cm²) was prepared according to the basic formula (positive electrode active material NCM811: binder PTFE: conductive agent conductive carbon black: LATP = 85:2:2:11; since the H2 / Ar2 mixed atmosphere treatment was not performed, a conductive agent needs to be added). Solid-state batteries were then assembled and tested.

[0057] Comparative Example 2: LATP powder was prepared according to the process in Example 2, except that the volume fraction of H2 in the H2 / Ar2 mixed atmosphere was 3% (named LATP-3H). The obtained LATP-3H was used as a positive electrode additive to prepare a thick electrode (area loading 40 mg / cm²) according to the basic formula, and a solid-state battery was assembled for testing.

[0058] Comparative Example 3: LATP powder was prepared according to the process in Example 2, except that the volume fraction of H2 in the H2 / Ar2 mixed atmosphere was 10% (named LATP-10H). The obtained LATP-10H was used as a positive electrode additive to prepare a thick electrode (area loading 40 mg / cm²) according to the basic formula, and a solid-state battery was assembled for testing.

[0059] Comparative Example 4: LATP powder was prepared according to the process in Example 2, except that the volume fraction of H2 in the H2 / Ar2 mixed atmosphere was 15% (named LATP-15H). The obtained LATP-15H was used as a positive electrode additive to prepare a thick electrode (area loading 40 mg / cm²) according to the basic formula, and a solid-state battery was assembled for testing.

[0060] Comparative Example 5: LATP powder was prepared according to the process in Example 2, except that the volume fraction of H2 in the H2 / Ar2 mixed atmosphere was 25% (named LATP-25H). The obtained LATP-25H was used as a positive electrode additive to prepare a thick electrode (area loading 40 mg / cm²) according to the basic formula, and a solid-state battery was assembled for testing.

[0061] Comparative Example 6: Tristyrene and zirconium nitrate were dissolved in a mixed solvent of DMF (N,N-dimethylformamide) and formic acid, and reacted in a reactor at 130°C for 24 h. The product was washed with DMF, exchanged with methanol, and dried under vacuum to obtain the MOF-808 support. Precursor impregnation: Li 1.3 Al 0.3 Ti 1.7A precursor solution of (PO4)3 (lithium, aluminum, titanium, and phosphorus sources dissolved in DMF) was used to impregnate the MOF-808 support. The solution was ultrasonically treated for 30 min and allowed to stand for 12 h to allow the precursor to fully penetrate the MOF channels. Heat treatment: The impregnated MOF support was placed in a tube furnace and heat-treated at 500℃ for 3 h under a N2 atmosphere. This caused the precursor to decompose and form a conductive phase, while simultaneously carbonizing the MOF framework, resulting in a MOF-derived electron-ion hybrid conductor material, denoted as LATP-MOF.

[0062] The obtained LATP-MOF was used as a positive electrode additive to prepare a thick electrode (area loading 40 mg / cm²) according to the basic formulation of Example 2, and a solid-state battery was assembled for testing.

[0063] Comparative Example 7: LATP powder was prepared according to the process in Example 2, using 9 g of Li 1.3 Al 0.3 Ti 1.7 (PO4)3 powder was mixed with 1 g of lithium metal powder and then ball-milled for 1 hour at a rate of 300 r / min. The milled powder was then placed in anhydrous ethanol to remove the lithium metal, and after filtration and drying, LATP-Li material was obtained.

[0064] The obtained LATP-Li was used as a positive electrode additive to prepare a thick electrode (area loading 40 mg / cm²) according to the basic formulation of Example 2, and a solid-state battery was assembled for testing.

[0065] Experimental example: (1) XPS analysis Table 1 XPS analysis results of each group of materials Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Example 1 Example 2 Example 3 Example 4 Example 5 LATP-0 LATP-3H LATP-10H LATP-15H LATP-25H LATP-1.1 LATP-1.3 LATP-1.5 LATP-1.3-18H LATP-1.3-22H <![CDATA[Ti 4+ Percentage 100 94.3 86.1 79.6 61.5 71.7 70.4 69.8 74.2 67.9 <![CDATA[Ti 3+ Percentage 0 5.7 13.9 15.1 16.4 11.1 14 16.3 17.4 13.8 Ti percentage 0 0 0 5.3 22.1 17.2 15.6 13.9 8.4 18.3 As shown in Table 1, the valence state distribution of titanium in the LATP materials prepared in each group changed accordingly with the change in the hydrogen volume percentage. The material in Comparative Example 1 was not subjected to any gas atmosphere treatment, and all titanium in its material was in the form of Ti. 4+ The materials in Comparative Examples 2 and 3 were treated with 3% and 10% hydrogen atmospheres, respectively, and the Ti in the materials... 4+ Gradually transforming into part of Ti 3+ However, metallic Ti still did not appear. When the hydrogen volume percentage was 15%, the titanium in the material prepared in Comparative Example 4 began to show partial metallic Ti. As the proportion of hydrogen was further increased, the metallic Ti gradually increased. 4+ The levels gradually decreased. Ti was not detected in any of the XPS analysis results. 2+ The reason is speculated to be that the current reducing power of hydrogen by volume percentage is insufficient to reduce titanium to Ti.2+ Moreover, Ti 2+ Ti is the most unstable of all valence states, and it is extremely easy for it to transform into other valence states. 3+ Because it has half full 3D 1 Configuration, relative to Ti² + (3d) 2 It is more stable.

[0066] (2) Performance testing Table 2 Performance test results of each group of materials and assembled batteries

[0067] Note: The 1C capacity retention rate is obtained by using constant current charge and discharge (CC), that is, first test 0.1C / 0.1C charge and discharge, then test 0.1C / 1C charge and discharge. By following this charge and discharge strategy, the 1C capacity retention rate can be obtained by dividing the 1C discharge specific capacity by the 0.1C discharge specific capacity. The retention rate was tested over 100 cycles using a charge / discharge strategy of 0.33C / 1C.

[0068] Combining the results in Tables 1 and 2, it can be seen that the comparative examples as a whole failed to obtain LATP materials with both good ionic and electronic conductivity. In particular, Comparative Example 1, due to the lack of any gas atmosphere treatment, has almost no electronic conduction channels within its material, and its electronic conductivity is only 5.2 × 10⁻⁶. -8 S / cm. In the thick electrode structure, electron transport is severely impeded, leading to a significant increase in polarization and extremely poor rate performance. The battery's 1C capacity retention is only 34.9%, and the 100-cycle retention is only 58.4%. Comparative Example 1 shows that LATP without reduction treatment cannot meet the basic requirements for electronic conductivity of thick electrodes.

[0069] Comparative Examples 2 through 4 gradually increased the volume percentage of hydrogen, causing Ti to gradually appear inside the material. 3+ While the electrode contains metallic Ti, the lack of electronic conductivity channels limits the improvement in electronic conductivity. The charge transport dynamics of the thick electrode are not substantially improved, and the 1C capacity retention remains at 35-55%, with a 100-cycle retention of 65-75%. These results indicate that excessively low H2 concentrations have limited impact on improving electronic conductivity and still cannot meet the electronic conductivity requirements of thick electrodes.

[0070] Comparative Example 5 increased the volume percentage of hydrogen to 25%, which directly resulted in a surge in electronic conductivity to 215.1 S / cm (far exceeding that of conventional conductive agents), but a direct drop in ionic conductivity to 5.5 × 10⁻⁶. -6The S / cm ratio showed a significant decrease in ion transport performance, resulting in a severe deterioration in the overall battery performance (1C capacity retention was 41.3%, and 100-cycle retention was 65.7%). Comparative Example 5 demonstrates that higher H2 concentrations are not always better; appropriate reduction is necessary while maintaining the ion conduction structure.

[0071] Comparative Examples 6 and 7 were modified with MOF-808 and Li using conventional methods. Compared with Comparative Examples 1-5, both comparative examples showed higher electronic and ionic conductivity. However, this resulted in a negative impact: the impurity content exceeded 100 ppm. Although the two existing modification methods improved electronic conductivity while maintaining ionic conductivity, the electronic conductivity COV increased significantly. Furthermore, they sacrificed material purity, extended the preparation cycle, used organic solvents, and significantly increased costs. The test results of the materials obtained in the example group show that they have a good balance of ionic conductivity and electronic conductivity, which are maintained at a high level. In addition, the impurity content is low, the process does not use organic solvents, the cycle is short, and the cost is low.

[0072] Among them, the LATP materials prepared in Examples 1-3 under the same 20% hydrogen volume percentage showed that as the Al doping amount gradually increased, the ionic conductivity first increased and then decreased, but the overall change was not significant; the electronic conductivity gradually decreased, but still remained above 110 S / cm.

[0073] Examples 4 and 5 were based on Example 2, with the volume percentage of hydrogen reduced and increased respectively. The results showed that the electronic conductivity of Example 4 was significantly improved compared to Comparative Examples 1-4. However, the metallic Ti content in the LATP material of Example 4 was still at a low level, and the electronic conductivity was still lower than that of the other examples and the comparative examples with higher hydrogen volume percentages. In contrast, the electronic conductivity of Example 5 was significantly increased to 200 S / cm, accompanied by a corresponding decrease in ionic conductivity, but it still remained at a good level.

[0074] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A composite conductor, characterized in that, The molecular formula is Li 1+x Al x Ti 2-x (PO4)3, 0.1 ≤ x ≤ 0.5; the Ti element includes Ti 4+ Ti 3+ And metallic Ti, by mass percentage, 62% < Ti 4+ <79%, 6% < metallic Ti < 22%, balance is Ti 3+ Total: 100%.

2. The composite conductor according to claim 1, characterized in that, By mass percentage, 65% ≤ Ti 4+ ≤75%, 8%≤metallic Ti≤20%, balance is Ti 3+ Total: 100%.

3. A method for preparing a composite conductor as described in claim 1, characterized in that, include: Lithium, aluminum, titanium, and phosphorus sources were obtained according to stoichiometric ratios, mixed, and then sintered to form Li. 1+x Al x Ti 2-x (PO4)3, 0.1 ≤ x ≤ 0.5; The Li 1+x Al x Ti 2-x The composite conductor is obtained by annealing (PO4)3 in a mixed atmosphere of hydrogen and protective gas; the proportion of hydrogen in the mixed atmosphere is 15% < hydrogen volume percentage < 25%.

4. The preparation method according to claim 3, characterized in that, The lithium source includes Li2CO3 and / or LiOH; the aluminum source includes Al2O3 and / or Al2(CO3)3; the titanium source includes TiO2; and the phosphorus source includes NH4H2PO4 and / or (NH4)2HPO4.

5. The preparation method according to claim 3, characterized in that, The sintering temperature is 700-900℃.

6. The preparation method according to claim 3, characterized in that, The protective gas includes argon.

7. The preparation method according to claim 3, characterized in that, The annealing process is carried out at a temperature of 200-400℃ for 1-3 hours.

8. The preparation method according to claim 3, characterized in that, The proportion of hydrogen in the mixed atmosphere is 18% ≤ hydrogen volume percentage ≤ 22%.

9. A positive electrode sheet, characterized in that, It includes a current collector and a positive electrode material coated on the surface of the current collector; the positive electrode material includes the composite conductor according to claim 1 or 2, or the composite conductor prepared by the preparation method according to any one of claims 3-8.

10. The positive electrode sheet according to claim 9, characterized in that, The positive electrode material includes a positive electrode active material, a binder, and a composite conductor as described in claim 1 or 2, or a composite conductor prepared by any one of the preparation methods described in claims 3-8.

11. A secondary battery, characterized in that, It includes a negative electrode, a positive electrode as described in claim 9, and a solid electrolyte.

12. The secondary battery according to claim 11, characterized in that, The solid electrolyte includes an oxide-polymer composite electrolyte.

13. An electrical appliance, characterized in that, Includes the secondary battery as described in claim 11 or 12, wherein the secondary battery provides electrical energy to the electrical device or serves as an energy storage unit for the electrical device.

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