Conductive agent, preparation method thereof, positive electrode and solid-state battery

Abstract

This invention discloses a conductive agent, its preparation method, a positive electrode, and a solid-state battery, belonging to the field of solid-state battery technology. The conductive agent provided by this invention includes a conductive agent matrix and a coating layer covering the surface of the conductive agent matrix; the coating layer contains Li and O elements, and at least one element selected from Zr, Nb, Al, Ti, and P; the coating layer has a multilayer structure in the thickness direction. This invention constructs a uniform and dense multilayer interfacial coating layer on the surface of the conductive agent through atomic layer deposition, effectively improving the dispersibility of the conductive agent in the positive electrode and significantly suppressing its interfacial side reactions with the sulfide electrolyte.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery technology, and in particular to a conductive agent and its preparation method, a positive electrode, and a solid-state battery. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] In the composite cathode of sulfide-based solid-state batteries, the conductive agent is a key component in constructing the electronic conductivity network. However, the introduction of this component brings two significant challenges. First, due to their surface characteristics, conductive agent particles are prone to electrostatic aggregation, leading to uneven dispersion in the cathode slurry. This, in turn, results in a non-uniform microstructure and unbalanced charge distribution in the prepared electrode, ultimately affecting the cycle stability of the battery. Second, and more critically, there is thermodynamic instability between the conductive agent (especially carbon materials) and the sulfide solid electrolyte. Direct contact between the two can induce continuous interfacial side reactions, leading to irreversible electrolyte decomposition, a significant increase in interfacial impedance, and accelerated capacity decay.

[0004] To alleviate the aforementioned interface problems, existing technologies typically employ modification methods by constructing a coating layer on the surface of the conductive agent. These methods aim to reduce contact through physical isolation or improve compatibility by introducing a functional interface layer. However, common coating strategies, such as solution-based impregnation coating, ball milling followed by heat treatment, or coaxial spinning, often struggle to achieve uniform, dense, and controllable thickness coating on the surface of conductive agent particles at the nano or submicron scale. Process limitations can easily lead to poor coating layer continuity, localized exposure, or uneven thickness, failing to completely and stably isolate side reactions. Furthermore, some coating layer materials themselves lack sufficient chemical or electrochemical stability at high voltages, or their thermal processing temperature is mismatched with the conductive agent matrix, further limiting their practical application and process feasibility. Therefore, developing a highly uniform, dense conductive agent compatible with sulfide electrolyte systems and its preparation method is of great significance for improving the overall electrochemical performance of sulfide-based solid-state batteries. Summary of the Invention

[0005] In view of this, the present invention provides a conductive agent and its preparation method, a positive electrode and a solid-state battery. The present invention constructs a uniform and dense multilayer interfacial coating layer on the surface of the conductive agent, which effectively improves the dispersibility of the conductive agent in the positive electrode and significantly suppresses its interfacial side reactions with the sulfide electrolyte.

[0006] In a first aspect, the present invention provides a conductive agent, comprising a conductive agent matrix and a coating layer covering the surface of the conductive agent matrix; The coating layer contains Li and O elements, as well as at least one element selected from Zr, Nb, Al, Ti, and P; The coating layer has a multi-layer structure in the thickness direction.

[0007] Preferably, the coating layer contains at least two elements selected from Zr, Nb, Al, Ti, and P.

[0008] Preferably, the multilayer structure consists of 2 to 20 sublayers, and the thickness of the coating layer is 0.2 to 5 nm.

[0009] Preferably, the conductive agent matrix is ​​at least one of conductive carbon black, vapor-grown carbon fiber, superconducting carbon, conductive graphite, or carbon nanotubes.

[0010] Secondly, the present invention provides a method for preparing the above-mentioned conductive agent, comprising the following steps: Surface pretreatment of the conductive agent matrix; The coating layer is constructed on the surface of a pretreated conductive agent substrate by atomic layer deposition (ALD) through multiple deposition cycles; wherein each deposition cycle includes: introducing a selected precursor, followed by introducing an oxidant for reaction; The precursor includes a lithium source, and also includes at least one of a zirconium source, a niobium source, an aluminum source, a titanium source, and a phosphorus source.

[0011] Preferably, the surface pretreatment is plasma treatment.

[0012] Furthermore, the plasma treatment includes: first cleaning the conductive agent matrix with inert gas plasma, and then activating it with oxygen plasma.

[0013] Preferably, the oxidant is selected from water or ozone; the deposition temperature of the atomic layer deposition process is 180~250℃.

[0014] Preferably, in the first deposition cycle, a lithium source is introduced, followed by the introduction of an oxidant for reaction.

[0015] Thirdly, the present invention provides a positive electrode, comprising a positive electrode active material, a sulfide solid electrolyte, and the above-described conductive agent or a conductive agent prepared by the above-described preparation method.

[0016] Fourthly, the present invention provides a solid-state battery, including the above-described positive electrode.

[0017] Compared with the prior art, the present invention has achieved the following beneficial effects: (1) The conductive agent provided by the present invention has a coating layer containing specific types of elements and forming a multilayer structure in the thickness direction. This precisely designed interface layer constructs a stable and complete physical barrier for the conductive carbon matrix at the nanoscale. Experimental data show that the specific surface area of ​​the coated conductive agent is reduced, thus reducing the direct contact area with the sulfide electrolyte; at the same time, as a lithium-containing composite oxide, the coating layer has better chemical compatibility with the sulfide electrolyte, which can thermodynamically suppress the side reactions between the two and reduce the irreversible decomposition of the electrolyte.

[0018] (2) The present invention uses atomic layer deposition technology to precisely control the order of introduction and the number of cycles of different precursors, thereby constructing a multi-layer structure, fundamentally overcoming the problems of uneven coating, single composition or complex process caused by wet chemical method, ball milling method or sintering method in the prior art.

[0019] (3) Applying the conductive agent of the present invention to the cathode of a sulfide solid-state battery can improve the overall electrochemical performance of the battery. On the one hand, the coating layer neutralizes the static charge on the surface of the conductive carbon, greatly improving its dispersibility in the electrode slurry or dry electrode preparation process, which is beneficial to building a uniform and continuous conductive network. On the other hand, the stable interface and excellent dispersibility work together to bring significant performance gains at the battery level. Experimental data show that the battery using this conductive agent not only has a higher first-cycle discharge capacity, but also exhibits better cycle stability. Attached Figure Description

[0020] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation thereof. Obviously, those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0021] Figure 1 These are the first 0.1C charge-discharge curves of the batteries assembled in Examples 1-3 and Comparative Example 1 of this invention; Figure 2 These are cycle performance diagrams of the batteries assembled in Examples 1-3 and Comparative Example 1 of the present invention after a first charge-discharge cycle at 0.1C and a long cycle cycle at 0.5C. Figure 3 These are scanning electron microscope images of dry-process positive electrode sheets prepared by conductive agent (A) of Comparative Example 1 and conductive agent (B) of Example 1 of the present invention. Figure 4 This is a cycle performance diagram of the solid-state batteries assembled in Embodiment 1 and Comparative Example 1 of the present invention under 1C charge-discharge conditions for 150 cycles. Detailed Implementation

[0022] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0023] The present invention provides a conductive agent, comprising a conductive agent matrix and a coating layer covering the surface of the conductive agent matrix; The coating layer contains Li and O elements, as well as at least one element selected from Zr, Nb, Al, Ti, and P; The coating layer has a multi-layer structure in the thickness direction.

[0024] The coating layer of this invention must contain lithium (Li), oxygen (O), and at least one element selected from zirconium (Zr), niobium (Nb), aluminum (Al), titanium (Ti), and phosphorus (P), more preferably at least two elements selected from zirconium (Zr), niobium (Nb), aluminum (Al), titanium (Ti), and phosphorus (P). The introduction of lithium ensures that the coating layer itself has the potential for lithium-ion conduction, avoiding severe blockage of ion transport at the interface. The selected elements such as Zr, Nb, Al, Ti, and P, in their oxides or composite oxides, generally have high chemical and electrochemical stability, and some (such as oxides containing P and Al) have better thermodynamic compatibility with sulfide electrolytes. Through the combination and interaction of elements, composite functional materials with a wider electrochemical window, higher ionic conductivity, or stronger interfacial bonding can be formed, which are superior to single-component materials.

[0025] The multi-layer structure design in this invention achieves functional gradient and optimization, thereby enhancing adhesion to conductive agents and optimizing interfacial contact and ion transport kinetics with electrolytes.

[0026] In optional embodiments of the present invention, the multilayer structure comprises 2 to 20 sublayers, more preferably 3 to 10 sublayers, and even more preferably 3 to 5 layers. The thickness of the coating layer is 0.2 to 5 nm, more preferably 0.5 to 2 nm. A coating layer of suitable thickness can effectively isolate the conductive agent matrix from the sulfide electrolyte while maintaining the electronic conductivity of the conductive agent.

[0027] In an optional embodiment of the present invention, the conductive agent matrix is ​​at least one of conductive carbon black, vapor-grown carbon fiber, superconducting carbon, conductive graphite, or carbon nanotubes.

[0028] The present invention also provides a method for preparing the above-mentioned conductive agent, comprising the following steps: Surface pretreatment of the conductive agent matrix; The coating layer is constructed on the surface of a pretreated conductive agent substrate by atomic layer deposition (ALD) through multiple deposition cycles; wherein each deposition cycle includes: introducing a selected precursor, followed by introducing an oxidant for reaction; The precursor includes a lithium source, and also includes at least one of a zirconium source, a niobium source, an aluminum source, a titanium source, and a phosphorus source; by setting the order of deposition cycles containing different precursors, a multilayer structure is constructed in the coating thickness direction.

[0029] This invention utilizes atomic layer deposition (ALD) to construct the coating layer. In a single deposition cycle, precursor molecules chemically adsorb onto active sites on the conductive agent matrix surface until saturation, after which excess molecules are purged. Subsequently, an oxidant is introduced, reacting with the adsorbed precursor to generate the target oxide and regenerate active sites, completing a monolayer growth. This process is repeated cyclically. By adjusting the types and order of precursor introduction, multilayer structures with compositional gradients or alternations can be constructed along the thickness direction (deposition direction). This method can construct ultrathin, uniform coating layers on the surface of complex nano-conductive agents, which helps reduce the specific surface area of ​​the conductive agent, improves its dispersibility, and mitigates the decomposition effect of the conductive agent on sulfide electrolytes. Furthermore, this multilayer stacked structure composed of various stable oxides synergistically enhances the overall chemical and mechanical stability of the interfacial region.

[0030] In an optional embodiment of the present invention, the surface pretreatment is plasma treatment. Further, the plasma treatment includes: first cleaning the conductive agent substrate with inert gas plasma, and then activating it with oxygen plasma. The inherent chemical inertness and potential contamination layer on the surface of carbon materials can severely hinder the effective chemical adsorption of precursor molecules during subsequent atomic layer deposition (ALD), leading to uneven film growth and poor adhesion. Inert gas (such as argon) plasma cleaning mainly removes the physical contamination layer such as adsorbed organic matter and water vapor from the surface through the physical bombardment (sputtering) of high-energy particles, thus cleaning the surface. Based on this cleaning, oxygen-containing functional groups such as hydroxyl (-OH) and carboxyl (-COOH) groups are introduced onto the carbon surface through the chemical action of oxygen plasma. These polar groups can serve as active sites for the chemical adsorption of ALD precursors, greatly improving nucleation uniformity and are key to achieving subsequent ultrathin, continuous, and robust coating.

[0031] The present invention does not impose any special restrictions on the process of cleaning the conductive agent matrix using inert gas plasma. The preferred conditions of the present invention are as follows: power of 5~100 W, more preferably 5~20 W, and even more preferably 8~15 W; pressure of 2~10 mbar, more preferably 3~8 mbar; gas flow rate of 20~100 sccm, more preferably 40~60 sccm; and processing time of 5~30 s, more preferably 5~20 s.

[0032] The present invention does not impose any special restrictions on the activation process using oxygen plasma. The preferred conditions of the present invention are as follows: power of 5~100 W, more preferably 5~20 W, and even more preferably 8~15 W; pressure of 0.2~1 mbar, more preferably 0.3~0.8 mbar; gas flow rate of 20~300 sccm, more preferably 100~150 sccm; and processing time of 30~100 s, more preferably 40~60 s.

[0033] In optional embodiments of the present invention, the lithium source is at least one of lithium tert-butoxide or lithium cyclopentadienyl; the zirconium source is at least one of tetra(dimethylamino)zirconium, tetra(ethylmethylamino)zirconium, or zirconium tetrachloride; the niobium source is at least one of penta(ethylmethylamino)niobium or penta(dimethylamino)niobium; the aluminum source is trimethylaluminum; the titanium source is at least one of tetramethyltitanium or triethyltitanium chloride; and the phosphorus source is one of trimethyl phosphate or tri(dimethylamino)phosphorus.

[0034] In an optional embodiment of the present invention, the oxidant is selected from water or ozone; more preferably, ozone. The deposition temperature of the atomic layer deposition process is 180~250℃, more preferably 200~230℃.

[0035] In an optional embodiment of the present invention, a lithium source is introduced in the first deposition cycle, followed by the introduction of an oxidant for reaction. This facilitates the initial formation of a lithium-rich initial layer on the conductive agent matrix, which has better adhesion to the conductive agent matrix and lays the foundation for rapid lithium-ion transport throughout the coating layer.

[0036] In an optional embodiment of the present invention, the gas flow rate introduced for each precursor or oxidant is 80~300 sccm, more preferably 80~230 sccm. The introduction time is 0.05~5s, more preferably 0.1~2s.

[0037] In the atomic layer deposition process of this invention, after each precursor or oxidant introduction is completed, an inert gas is introduced for purging to thoroughly remove unreacted precursor molecules, gaseous byproducts, and excess reactants from the reaction chamber. The purging uses an inert gas, including but not limited to nitrogen, argon, or helium.

[0038] The present invention also provides a positive electrode, comprising a positive electrode active material, a sulfide solid electrolyte, and the above-described conductive agent or a conductive agent prepared by the above-described preparation method.

[0039] In an optional embodiment of the present invention, the mass ratio of the positive electrode active material, the sulfide solid electrolyte, and the conductive agent is (75~85): (10~20): (1~3).

[0040] In an optional embodiment of the present invention, the positive electrode further includes a binder, and the mass ratio of the positive electrode active material, the sulfide solid electrolyte, the binder and the conductive agent is (75~85): (10~20): (1~3): (1~3).

[0041] In optional embodiments of the present invention, the positive electrode active material includes, but is not limited to, LiCoO2 and Li(Ni) a Co b X c One or more of O2 (a+b+c=1, X is Al or Mn) or LiMn2O4. Sulfide solid electrolytes include, but are not limited to, LGPS, Li3PS, and Li7P3S. 114 Li 5.5 PS 4.5 Cl 1.5 One or more of Li6PS5Cl or Li8PS5Br. The binder includes, but is not limited to, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), etc.

[0042] The present invention also provides a solid-state battery, including the above-described positive electrode.

[0043] This invention does not impose any special limitations on the preparation method of the above-mentioned solid-state battery; any solid-state battery preparation method commonly used in the field can be used.

[0044] The technical solution of the present invention will be further described below with reference to specific embodiments. The present invention does not impose any special restrictions on the source of reagents used in the following embodiments; commercially available products well known to those skilled in the art can be used.

[0045] Example 1 This embodiment provides a conductive agent, which includes a conductive agent matrix and a coating layer. The specific preparation method is as follows: (1) Plasma pretreatment: Ten grams of vapor-grown carbon fiber (VGCF) was used as the conductive agent matrix and subjected to plasma pretreatment. First, argon plasma cleaning was performed: power 10 W, pressure 5 mbar, argon flow rate 50 sccm, and treatment time 10 s. Subsequently, oxygen plasma activation was performed: power 10 W, pressure 0.5 mbar, oxygen flow rate 120 sccm, and treatment time 50 s.

[0046] (2) Atomic layer deposition (ALD) coating: An ALD coating layer was formed on the surface of the conductive agent substrate after plasma pretreatment in step (1). Lithium tert-butoxide was used as the lithium source, tetrakis(dimethylamino)zirconium as the zirconium source, trimethylaluminum as the aluminum source, ozone as the oxidant, and high-purity nitrogen as the purge gas. The deposition temperature was 200℃, and the total purge gas flow rate was 300 sccm.

[0047] The specific ALD coating process is as follows: a) Introduce a lithium source at a flow rate of 200 sccm for 0.5 s, followed by nitrogen purging for 60 s; b) Introduce ozone at a flow rate of 100 sccm for 0.5 s, followed by nitrogen purging for 60 s; c) Introduce a zirconium source at a flow rate of 100 sccm for 0.5 s, followed by nitrogen purging for 60 s; d) Introduce ozone at a flow rate of 100 sccm for 0.5 s, followed by nitrogen purging for 60 s; e) Introduce a lithium source at a flow rate of 200 sccm for 0.5 s, followed by nitrogen purging for 60 s; f) Introduce ozone at a flow rate of 100 sccm for 0.5 s, followed by nitrogen purging for 60 s; g) Introduce an aluminum source at a flow rate of 200 sccm for 0.5 s. After 60 seconds, nitrogen was purged for 60 seconds to complete the preparation of the conductive agent.

[0048] Through the above ALD process, a multilayer composite oxide coating layer is formed on the surface of the conductive agent matrix. The coating layer mainly contains lithium (Li), zirconium (Zr), aluminum (Al) and oxygen (O) elements, forming a stacked structure containing lithium-rich zirconium oxide and lithium-rich aluminum oxide.

[0049] Example 2 This embodiment provides a conductive agent, which includes a conductive agent matrix and a coating layer. The specific preparation method is as follows: (1) Plasma pretreatment: Ten grams of vapor-grown carbon fiber (VGCF) was used as the conductive agent matrix and subjected to plasma pretreatment. First, argon plasma cleaning was performed: power 10 W, pressure 5 mbar, argon flow rate 50 sccm, and treatment time 10 s. Subsequently, oxygen plasma activation was performed: power 10 W, pressure 0.5 mbar, oxygen flow rate 120 sccm, and treatment time 50 s.

[0050] (2) Atomic layer deposition (ALD) coating: An ALD coating layer was formed on the surface of the conductive agent substrate after plasma pretreatment in step (1). Lithium tert-butoxide was used as the lithium source, tetramethyltitanium as the titanium source, trimethylaluminum as the aluminum source, trimethyl phosphate as the phosphorus source, ozone as the oxidant, and high-purity nitrogen as the purge gas. The deposition temperature was 200℃, and the total purge gas flow rate was 300 sccm.

[0051] The specific ALD encapsulation process is as follows: a) Introduce a lithium source at a flow rate of 200 sccm for 0.5 s, followed by nitrogen purging for 60 s; b) Introduce ozone at a flow rate of 100 sccm for 0.5 s, followed by nitrogen purging for 60 s; c) Introduce an aluminum source at a flow rate of 100 sccm for 0.5 s, followed by nitrogen purging for 60 s; d) Introduce ozone at a flow rate of 100 sccm for 0.5 s, followed by nitrogen purging for 60 s; e) Introduce a titanium source at a flow rate of 200 sccm for 0.5 s, followed by nitrogen purging for 60 s; f) Introduce ozone at a flow rate of 100 sccm for 0.5 s, followed by nitrogen purging for 60 s; g) Introduce a phosphorus source at a flow rate of 200 sccm for 0.5 s, followed by nitrogen purging for 60 s. s, complete the preparation of the conductive agent.

[0052] Through the above ALD process, a multilayer composite oxide coating layer is formed on the surface of the conductive agent matrix. The coating layer mainly contains lithium (Li), aluminum (Al), titanium (Ti), phosphorus (P) and oxygen (O) elements. The three elements of aluminum, titanium and phosphorus appear in enriched regions in the thickness direction of the coating layer, forming a gradient composite structure that transitions from lithium-rich aluminum oxide to titanium oxide and finally covers phosphorus-containing oxide.

[0053] Example 3 This embodiment provides a conductive agent, which includes a conductive agent matrix and a coating layer. The specific preparation method is as follows: (1) Plasma pretreatment: Ten grams of vapor-grown carbon fiber were first dried in a vacuum atmosphere at 150°C for 2 hours, followed by argon plasma cleaning: power 10 W, pressure 5 mbar, argon flow rate 50 sccm, and treatment time 10 s. Then, oxygen plasma treatment was performed: power 20 W, pressure 0.5 mbar, time 50 s, and gas flow rate 120 sccm.

[0054] (2) Atomic layer deposition (ALD) coating: An ALD coating layer was formed on the surface of the conductive agent substrate after plasma pretreatment in step (1), using lithium tert-butoxide as the lithium source, trimethylaluminum as the aluminum source, and ozone as the oxidant. The deposition temperature was 220℃, and the total flow rate of the purge gas was 300 sccm.

[0055] The deposition process for one cycle is as follows: a) Introduce a lithium source at a flow rate of 300 sccm for 0.5 s, followed by nitrogen purging for 60 s; b) Introduce ozone at 200 sccm for 0.5 s, followed by nitrogen purging for 60 s; c) Introduce an aluminum source at 300 sccm for 0.5 s, followed by nitrogen purging for 60 s; d) Introduce ozone at 200 sccm for 0.5 s, followed by nitrogen purging for 60 s. Repeat this deposition process five times to complete the material preparation. At this point, the main component of the coating layer on the material surface is lithium-rich aluminum oxide.

[0056] The material prepared in this embodiment was tested by inductively coupled plasma spectroscopy (ICP), and its aluminum content was 235 ppm, which proved the successful introduction of aluminum.

[0057] Comparative Example 1 Compared with Example 1, this comparative example did not perform plasma pretreatment and atomic layer deposition coating on VGCF.

[0058] Test case 1. Conductive agent performance testing The specific surface area of ​​the conductive agents in Examples 1-3 and Comparative Example 1 was tested by nitrogen adsorption-desorption (BET method), and the resistivity of the conductive agents in Examples 1-3 and Comparative Example 1 was tested by four-probe resistance testing method. The test results are summarized in Table 1.

[0059] Table 1. Test results of conductive agent parameters in Examples 1-3 and Comparative Example 1 serial number <![CDATA[Specific surface area (m 2 / g)]]> Resistivity (Ω·cm) Example 1 18.2 <![CDATA[1.55×10 -4 ]]> Example 2 18.3 <![CDATA[1.6×10 -4 ]]> Example 3 18 <![CDATA[1.7×10 -4 ]]> Comparative Example 1 18.5 <![CDATA[1.5×10 -4 ]]> 2. Battery performance based on simplified composite cathode (1) Composite cathode and battery preparation: LiNi, the positive electrode active material 0.92 Co 0.05 Mn 0.03 O2, sulfide solid electrolyte Li 5.5 PS 4.5 Cl 1.5 The conductive agent from Examples 1-3 or Comparative Example 1 was dry-mixed with the conductive agent at a mass ratio of 80:18:2 to obtain a composite cathode material. 120 mg of Li was taken... 5.5 PS 4.5 Cl 1.5 Electrolyte powder was pressed in a mold at 400 MPa for 10 minutes to form an electrolyte layer. Subsequently, 20 mg of the aforementioned composite positive electrode material was added to the positive electrode side, using carbon-coated aluminum foil as the positive electrode current collector and graphite as the negative electrode (N / P ratio of 1.5). The mixture was then pressed again at 400 MPa for 10 minutes to assemble a simplified model battery without binder. Battery testing was conducted at 25°C and an external stacking pressure of 100 MPa.

[0060] (2) Electrochemical performance test results: The first-cycle 0.1C charge-discharge curves of the batteries assembled in Examples 1, 2, 3, and Comparative Example 1 are shown below. Figure 1 As shown, the initial discharge specific capacities were 218.0, 216.6, 204.4, and 200.0 mAh / g, respectively, and the initial charge-discharge efficiencies were 92.8%, 95.8%, 88.9%, and 88.5%, respectively. The improvement in initial efficiency directly proves that the coated conductive agent effectively reduced the irreversible decomposition of the sulfide electrolyte.

[0061] After the battery undergoes its first charge-discharge cycle at 0.1C, it is then subjected to a long-term cycle at 0.5C. Figure 2 As shown, after 50 cycles, the specific capacities of the batteries in Examples 1, 2, 3, and Comparative Example 1 were 200.6, 176.2, 161.9, and 152.5 mAh / g, respectively. The capacity retention rates after 50 cycles were 98.8%, 98.5%, 90.5%, and 85.5%, respectively. The high specific capacity at 0.5 C discharge indicates that the coated conductive agent can improve the battery's rate performance, and the high capacity retention rate indicates improved battery stability.

[0062] 2. Electrode and battery performance based on dry electrode technology Preparation of dry-process positive electrode sheet: 8.0g LiNi 0.92 Co 0.05 Mn 0.03 O2, 1.6g Li 5.5 PS 4.5 Cl 1.5 0.2g of polytetrafluoroethylene and 0.2g of the conductive agent prepared in Example 1 or the VGCF conductive agent of Comparative Example 1 were mixed and fiberized by a high-speed mixer; carbon-coated aluminum foil was used as the positive current collector, and then rolled by a multi-stage roller press to obtain a dry positive electrode sheet.

[0063] Preparation of solid-state batteries: Take 120 mg Li 5.5 PS 4.5 Cl 1.5 The electrolyte powder was pressed at 400 MPa for 10 min, and then 20 mg of dry-processed positive electrode sheet was added to the positive electrode side. The negative electrode was a graphite negative electrode with an N / P ratio of 1.5. It was then pressed at 400 MPa for 10 min.

[0064] Scanning electron microscope (SEM) images of the dry-process positive electrode sheets prepared using the conductive agent of Comparative Example 1 and the conductive agent of Example 1 are shown below. Figure 3As shown in A and B in the figure, it can be seen that the dry-process positive electrode sheet prepared from untreated VGCF in Comparative Example 1 exhibits obvious agglomeration, while the dry-process positive electrode sheet prepared with the conductive agent in Example 1 shows good dispersibility and no obvious agglomeration. This indicates that the conductive agent coating layer in Example 1 neutralizes the static charge on the surface of VGCF, reduces charge accumulation, improves material dispersibility, and is beneficial for constructing a uniform and continuous conductive network.

[0065] The solid-state battery was tested at a pressure of 100 MPa and a temperature of 25°C. The cycle performance of the battery after 150 cycles under 1C charge / discharge conditions is shown in the graph. Figure 4 As shown, the solid-state battery assembled in Example 1, which has better dispersion, has higher capacity and stability because its conductive network is more complete and more conducive to capacity utilization.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A conductive agent, characterized in that, It includes a conductive agent matrix and a coating layer covering the surface of the conductive agent matrix; The coating layer contains Li and O elements, as well as at least one element selected from Zr, Nb, Al, Ti, and P; The coating layer has a multi-layer structure in the thickness direction.

2. The conductive agent as described in claim 1, characterized in that, The coating layer contains at least two elements selected from Zr, Nb, Al, Ti, and P.

3. The conductive agent as described in claim 1, characterized in that, The multilayer structure consists of 2 to 20 sublayers, and the thickness of the coating layer is 0.2 to 5 nm.

4. The conductive agent as described in claim 1, characterized in that, The conductive agent matrix is ​​at least one of conductive carbon black, vapor-grown carbon fiber, superconducting carbon, conductive graphite, or carbon nanotubes.

5. The method for preparing the conductive agent according to any one of claims 1 to 4, characterized in that, The steps include the following: Surface pretreatment of the conductive agent matrix; The coating layer is constructed on the surface of a pretreated conductive agent substrate by atomic layer deposition (ALD) through multiple deposition cycles; wherein each deposition cycle includes: introducing a selected precursor, followed by introducing an oxidant for reaction; The precursor includes a lithium source, and also includes at least one of a zirconium source, a niobium source, an aluminum source, a titanium source, and a phosphorus source.

6. The preparation method according to claim 5, characterized in that, The surface pretreatment is plasma treatment; the plasma treatment includes: first cleaning the conductive agent matrix with inert gas plasma, and then activating it with oxygen plasma.

7. The preparation method according to claim 5, characterized in that, The oxidant is selected from water or ozone; the deposition temperature of the atomic layer deposition process is 180~250℃.

8. The preparation method according to claim 5, characterized in that, In the first deposition cycle, a lithium source is introduced, followed by an oxidant to carry out the reaction.

9. A positive electrode, characterized in that, It includes positive electrode active materials, sulfide solid electrolytes, and conductive agents as described in any one of claims 1 to 4 or prepared by any one of claims 5 to 8.

10. A solid-state battery, characterized in that, Includes the positive electrode as described in claim 9.

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