High-conductivity positive electrode material for lithium battery and preparation method of high-conductivity positive electrode material

Abstract

The invention relates to the technical field of lithium ion battery materials, and discloses a high-conductivity positive electrode material for a lithium battery and a preparation method of the high-conductivity positive electrode material for the lithium battery, and the preparation method comprises the following steps: a network is composed of carbon nanotubes which are connected in a rooted manner and fast ion conductors which are distributed in a nano island shape, and an integrated structure without interface resistance is formed. The preparation method comprises the following steps: uniformly mixing a lithium transition metal oxide precursor, a lithium source, an organic metal compound containing a catalyst element and an ion channel inducer by adopting a one-pot process; and then in the continuous heat treatment process, low-temperature decomposition, catalyst activation in the high-temperature sintering process and final synchronous construction steps are sequentially carried out through accurate time sequence atmosphere regulation and control. According to the invention, by constructing an integrated double-conduction network, the problems of high interface resistance and poor structural stability in a traditional modification method are fundamentally solved, so that the prepared positive electrode material has excellent rate capability and excellent long-cycle stability.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery materials technology, and in particular to highly conductive cathode materials for lithium batteries and their preparation methods. Background Technology

[0002] With the rapid development of portable electronic devices, electric vehicles, and large-scale energy storage systems, the market has placed increasingly stringent demands on the energy density, power density, and cycle life of lithium-ion batteries. Among numerous cathode material systems, layered transition metal oxides, represented by lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide, have become the mainstream choice for high-energy-density lithium-ion batteries due to their high operating voltage and theoretical specific capacity.

[0003] However, the commercial application of these cathode materials, especially high-nickel systems, still faces inherent technical bottlenecks. A core issue is the relatively low intrinsic electronic conductivity and lithium-ion diffusion coefficient of these materials. This sluggish charge and ion transport kinetics leads to severe electrochemical polarization during high-rate charge and discharge, which not only limits the battery's power performance but also causes safety hazards such as localized overheating and accelerates the structural degradation of the material, thus affecting the battery's long-term cycle stability.

[0004] To alleviate these problems, existing technologies typically employ surface modification strategies. A common approach is to coat the active material particles with chemically stable oxides such as alumina and zirconium oxide, or ionic conductors such as phosphates and fluorides, to form a protective film on the particle surface. While this method can suppress side reactions between the cathode and electrolyte to some extent, many coating layers are themselves electronic insulators, which undoubtedly further hinders electron transport. Even with ionicly conductive coating layers, it is difficult to achieve uniform and complete nanoscale coverage of the particle surface, and the physical interface formed between the coating layer and the active material may itself become an additional obstacle for lithium ions to cross.

[0005] Another technical approach involves adding additional conductive agents, such as conductive carbon black, graphite, or even carbon nanotubes, through physical mixing during electrode fabrication to create a conductive network between the active material particles. However, this conductive network formed through mechanical blending has a discrete, point-to-point contact mechanism. The physical interface between the active material and the conductive agent exhibits high contact resistance, and this fragile connection is easily disrupted during repeated charge-discharge cycles due to the volume expansion and contraction of the active material, leading to gradual network failure and rapid capacity degradation. To achieve acceptable conductivity, the amount of conductive agent added often needs to be increased, but this sacrifices the overall energy density of the battery, as the conductive agent itself does not contribute to capacity.

[0006] In summary, existing technologies, whether employing surface coating or physical mixing of conductive agents, struggle to fundamentally address the synergistic optimization of electron and ion transport simultaneously. Furthermore, they often introduce new physical interfaces, becoming bottlenecks limiting further improvements in battery performance. Therefore, there is an urgent need to develop a novel cathode material and its preparation method that can construct an integrated, barrier-free internal dual-conductivity network, thereby simultaneously improving the material's rate performance and cycle stability without sacrificing energy density. Summary of the Invention

[0007] The purpose of this invention is to provide a high-conductivity cathode material for lithium batteries and its preparation method, which solves the problem that the rate performance and cycle life of existing lithium battery cathode materials are limited due to insufficient intrinsic conductivity and the introduction of high-resistivity interfaces by traditional modification methods.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] This invention provides a highly conductive cathode material for lithium batteries and its preparation method.

[0010] The first aspect of the present invention provides a highly conductive positive electrode material for lithium batteries. This material is a composite material that integrates a functionalized electronic conductive network and an ion conductive channel.

[0011] In one specific embodiment, the composite material comprises the following components: lithium transition metal oxide active material, in-situ generated carbon nanotubes, in-situ generated boron- or phosphorus-containing lithium salt fast ion conductor phase, and catalyst residues.

[0012] By mass fraction, the lithium transition metal oxide active material comprises 95-99 parts; the in-situ generated carbon nanotubes comprise 0.5-2.5 parts; the in-situ generated boron- or phosphorus-containing lithium salt fast ion conductor phase comprises 0.1-1.5 parts; and the catalyst residue comprises 0.1-1.0 parts.

[0013] Unlike existing technologies that add conductive agents through physical mixing, the composite material provided by this invention possesses a unique microstructure. The carbon nanotubes are not simply attached to the surface of the active material, but rather their roots are integrated with the surface of the active material particles, forming a three-dimensional, interconnected electron transport network extending outward from the bulk of the active material without physical interfaces. This "rooted" structure ensures that electrons can be efficiently and unimpededly injected into the active material from the conductive network.

[0014] Meanwhile, the lithium salt fast ion conductor phase does not completely coat the active material, but rather is selectively distributed in the areas of the active material surface not covered by carbon nanotubes, especially in the interstitial spaces at the roots of the carbon nanotube network, in the form of nano-islands. This structure provides a rapid transport path for lithium ions across the particle interface, forming an "ion ferry station" that works in conjunction with the electron transport network.

[0015] In a preferred embodiment, the lithium transition metal oxide active material is lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide with a layered crystal structure. The catalyst residue is one or more metals selected from iron, cobalt, and nickel, or their carbides. The lithium salt fast ion conductor phase is an amorphous lithium borate glass phase or a lithium phosphate glass phase. This combination achieves a combination of excellent electrochemical lithium storage performance and structural stability.

[0016] The second aspect of the present invention provides a method for preparing the above-mentioned high-conductivity cathode material for lithium batteries. The core of this method is to achieve the in-situ and simultaneous occurrence of multiple chemical reactions in a continuous heat treatment process by using a "one-pot" process and precise timing atmosphere control.

[0017] The method includes the following steps:

[0018] A. Mixing step: The lithium source, transition metal precursor, organometallic compound containing the catalyst element, and boron- or phosphorus-containing organic compound are uniformly mixed to obtain a mixed precursor. This step provides a uniformly distributed material basis for all subsequent in-situ reactions.

[0019] b. Pre-decomposition step: Under an inert atmosphere, the mixed precursor obtained in step a undergoes a first-stage heat treatment. In this step, heat promotes the decomposition of the organometallic compound and the organic compound, forming in-situ nanoscale dispersed particles of catalyst precursor (such as metal oxide) and ion channel inducer precursor on the surface of the transition metal precursor particles.

[0020] c. Activation Step: Under a weakly reducing atmosphere, the product obtained in step b undergoes a second-stage heat treatment. The purpose of this step is to selectively reduce the catalyst precursor distributed on the surface into catalytically active metallic or carbide sites without destroying the main structure of the lithium transition metal oxide to be formed. This step is a crucial prerequisite for subsequent catalytic growth.

[0021] d. Simultaneous Construction Step: Under a carbon-source-containing atmosphere, the product obtained in step c undergoes a third-stage heat treatment. This step is the core technology of this invention, where three concerted reactions occur simultaneously on an isothermal platform:

[0022] 1. The lithium source and transition metal oxide undergo a solid-phase reaction to form a well-crystallized lithium transition metal oxide active material.

[0023] 2. The activated catalytic active sites in step c catalyze the cracking of carbon source gas, and carbon nanotubes integrated with the surface of the active material are grown in situ using these sites as growth points.

[0024] 3. The ion channel inducer precursor formed in step b undergoes a solid-phase reaction with the surface-excess lithium generated during sintering, generating a lithium salt fast ion conductor phase in situ.

[0025] In one specific embodiment, the transition metal precursor in step a is nickel cobalt manganese hydroxide or nickel cobalt aluminum hydroxide; the organometallic compound containing the catalyst element is iron acetylacetonate; and the boron-containing organic compound is triphenylboron.

[0026] In a preferred embodiment, the temperature range for the first stage heat treatment in step b is 480–520°C. The weakly reducing atmosphere in step c is a mixture of hydrogen and an inert gas, and this step is performed while heating to the final sintering temperature. The carbon source atmosphere in step d is a mixture of acetylene and an inert gas, and this step is performed at an isothermal sintering temperature of 780–820°C.

[0027] The method also includes step e: after the third stage heat treatment is completed, switching to an inert atmosphere and performing controlled cooling to protect the product structure and prevent it from being oxidized at high temperatures.

[0028] The beneficial effects of this invention are as follows: Through the above technical solution, this invention provides a cathode material with a highly integrated structure and function. Its integrated electronic and ion dual-conductivity network fundamentally eliminates the physical interface and the resulting interface resistance problems existing in traditional modification methods. Simultaneously, the "rooted" conductive network endows the material with excellent structural stability, effectively buffering volume changes during cycling and preventing conductive network failure. Furthermore, the integrated preparation method provided by this invention integrates multiple modification steps into a continuous process flow, significantly simplifying the production process, reducing preparation costs, and possessing high industrial application value.

[0029] In summary, the present invention has at least one of the following beneficial technical effects:

[0030] 1. This invention utilizes an integrated preparation method to construct an in-situ electron / ion dual-conductivity network on the surface of active material particles. In this network, embedded carbon nanotubes provide a "highway" for electrons, while nano-island-like fast ion conductors establish a "ferry station" for lithium ions. The synergistic effect of these two elements significantly reduces the resistance to charge and ion transport within the material and at the interface, thereby ensuring that the battery can still efficiently output capacity under high-current charge and discharge conditions.

[0031] 2. This invention utilizes an in-situ generated carbon nanotube network, which acts like a robust skeleton to tightly encapsulate and fix the active material particles. This effectively buffers and dissipates the internal stress generated by the repeated insertion and extraction of lithium ions during cycling, suppressing microcracks and even pulverization of the particles. This structural reinforcement maintains the integrity of the electrode during long-term cycling, thereby achieving excellent capacity retention and long cycle life.

[0032] 3. This invention employs an innovative "one-pot" process, integrating traditionally multi-step processes such as material synthesis, surface coating, and conductive agent lamination into a single continuous heat treatment flow. This highly integrated preparation method not only shortens the production cycle and reduces equipment investment and energy consumption, but also avoids batch variations and material losses that may result from multi-step transfers.

[0033] 4. Unlike the "point-to-point" high-resistance contact formed by traditional physical mixing of conductive agents, this invention achieves seamless connection and integration between carbon nanotubes and active material particles through catalytic growth under a specific atmosphere. This "rooted" three-dimensional conductive network eliminates interfacial contact resistance, creating an unobstructed pathway for electron transport within the composite material, resulting in a macroscopic conductivity far exceeding that of traditional mixed materials.

[0034] 5. By introducing specific ion channel inducers, this invention can transform harmful residual lithium compounds on the material surface into a stable phase with high lithium-ion conductivity in situ. This not only purifies the particle surface and reduces side reactions with the electrolyte, but more importantly, it constructs rapid channels at key ion transport nodes, significantly reducing charge transfer resistance and improving interfacial kinetics. Detailed Implementation

[0035] This invention provides a highly conductive cathode material for lithium batteries and a method for preparing the same.

[0036] Example 1

[0037] This embodiment provides a method for preparing a highly conductive positive electrode material.

[0038] 1. Precursor mixing: Accurately weigh spherical Ni 0.8 Co 0.1 Mn 0.1 93.1 g of (OH)2 precursor, 3.6 g of LiOH·H2O, 3.5 g of acetylacetone iron(III), and 1.2 g of triphenylborone were mixed in a high-speed mixer at 350 rpm for 25 minutes under argon protection to obtain a homogeneous mixture.

[0039] 2. Low-temperature heat treatment: The mixture is placed in a tube furnace and heated from room temperature to 250°C at a rate of 5.0°C / min under N2 atmosphere, and held for 60 minutes; then the temperature is increased to 500°C at a rate of 5.0°C / min and held for 120 minutes.

[0040] 3. High-temperature sintering and activation: The temperature is increased from 500℃ at a rate of 5.0℃ / min. When the furnace temperature reaches 700℃, the atmosphere is switched to a mixture of 5.0 vol% H2 / 95.0 vol% Ar, and the temperature is continued to rise to 800℃.

[0041] 4. Synchronous construction: When the furnace temperature stabilizes at 800℃, immediately switch the atmosphere to a mixture of 2.0 vol% C2H2 / 98.0 vol% Ar, and sinter at a constant temperature for 5 hours under these conditions.

[0042] 5. Cooling and Post-processing: After the isothermal period, switch the atmosphere back to high-purity N2 and allow the furnace to cool naturally to room temperature. Remove the product, lightly grind it, and pass it through a 200-mesh sieve to obtain the final cathode composite powder.

[0043] Example 2

[0044] This embodiment provides a method for preparing a highly conductive positive electrode material.

[0045] 1. Precursor mixing: Accurately weigh spherical Ni 0.8 Co 0.1 Mn 0.1 93.1 g of (OH)2 precursor, 2.8 g of Li OH·H2O4, 1.8 g of acetylacetone iron(III), and 0.5 g of triphenylborone were placed in a high-speed mixer and mixed at 300 rpm for 20 minutes under argon protection to obtain a homogeneous mixture.

[0046] 2. Low-temperature heat treatment: The mixture is placed in a tube furnace and heated from room temperature to 240°C at a rate of 4.0°C / min under N2 atmosphere, and held for 50 minutes; then the temperature is increased to 480°C at a rate of 4.0°C / min and held for 110 minutes.

[0047] 3. High-temperature sintering and activation: The temperature is increased from 480℃ at a rate of 4.0℃ / min. When the furnace temperature reaches 680℃, the atmosphere is switched to a mixture of 5.0 vol% H2 / 95.0 vol% Ar, and the temperature is continued to rise to 780℃.

[0048] 4. Synchronous construction: When the furnace temperature stabilizes at 780℃, immediately switch the atmosphere to a mixture of 2.0 vol% C2H2 / 98.0 vol% Ar, and sinter at a constant temperature for 4 hours under these conditions.

[0049] 5. Cooling and Post-processing: After the isothermal period, switch the atmosphere back to high-purity N2 and allow the furnace to cool naturally to room temperature. Remove the product, lightly grind it, and pass it through a 200-mesh sieve to obtain the final cathode composite powder.

[0050] Example 3

[0051] This embodiment provides a method for preparing a highly conductive positive electrode material.

[0052] 1. Precursor mixing: Accurately weigh spherical Ni 0.8 Co 0.1 Mn 0.1 93.1 g of (OH)2 precursor, 44.0 g of LiOH·H2O, 5.3 g of acetylacetone iron(III), and 1.9 g of triphenylborone were placed in a high-speed mixer and mixed at 400 rpm for 30 minutes under argon protection to obtain a homogeneous mixture.

[0053] 2. Low-temperature heat treatment: The mixture is placed in a tube furnace and heated from room temperature to 260°C at a rate of 6.0°C / min under N2 atmosphere, and held for 70 minutes; then the temperature is further increased to 520°C at a rate of 6.0°C / min and held for 130 minutes.

[0054] 3. High-temperature sintering and activation: The temperature is increased from 520℃ at a rate of 6.0℃ / min. When the furnace temperature reaches 720℃, the atmosphere is switched to a mixture of 5.0 vol% H2 / 95.0 vol% Ar, and the temperature is continued to rise to 820℃.

[0055] 4. Synchronous construction: When the furnace temperature stabilizes at 820℃, immediately switch the atmosphere to a mixture of 2.0 vol% C2H2 / 98.0 vol% Ar and sinter at a constant temperature for 6 hours under these conditions.

[0056] 5. Cooling and Post-processing: After the isothermal period, switch the atmosphere back to high-purity N2 and allow the furnace to cool naturally to room temperature. Remove the product, lightly grind it, and pass it through a 200-mesh sieve to obtain the final cathode composite powder.

[0057] Comparative Example 1: Compared with Example 1, the difference is that iron acetylacetonate (III) as a bifunctional dopant was not added in the precursor mixing step. The remaining component ratios, equipment and process steps are the same as in Example 1.

[0058] Comparative Example 2: Compared with Example 1, the difference is that triphenylborone, as an ion channel inducer, was not added in the precursor mixing step. The remaining component ratios, equipment, and process steps are the same as in Example 1.

[0059] Comparative Example 3: Compared to Example 1, the difference lies in omitting the catalyst activation step during the high-temperature sintering process. Specifically, during the temperature rise from 500°C to 800°C, an N2 atmosphere is maintained throughout, without switching to an H2 / Ar mixture. Upon reaching 800°C, the atmosphere is directly switched to a mixture of 2.0 vol% C2H2 / 98.0 vol% Ar. All other aspects remain the same.

[0060] Comparative Example 4: Compared with Example 1, the difference is that the carbon source atmosphere in the synchronous construction step was omitted. That is, the entire heat treatment process was carried out according to the temperature and atmosphere program of Example 1, but after reaching 800°C, instead of switching to a C2H2 / Ar mixed gas, isothermal sintering was completed in an H2 / Ar mixed gas atmosphere. Everything else was the same.

[0061] Comparative Example 5: Compared with Example 1, the difference lies in that the amount of the bifunctional dopant iron acetylacetone (III) added exceeds the preferred range of the present invention. That is, in the precursor mixing step, the amount of iron acetylacetone (III) added is increased to a corresponding Fe / Me molar ratio of 5.0 mol%. All other aspects are the same.

[0062] Comparative Example 6: This comparative example aims to simulate traditional physical mixing methods. First, a reference cathode material without any additives was prepared according to the steps of Example 1, i.e., iron(III) acetylacetonate and triphenylboron were not added in the precursor mixing step, and the entire heat treatment process was carried out under a N2 atmosphere to obtain a reference lithium transition metal oxide powder. Then, the obtained reference powder was mixed with commercially available carbon nanotube powder and lithium borate powder at a mass ratio of 97:1.5:1.5 using a high-speed mechanical dry mixing process to obtain the final product.

[0063] Test Example 1: Powder Conductivity Test

[0064] Experimental steps

[0065] 1. Sample preparation: Take the positive electrode material powders prepared in Example 1, Comparative Example 1, Comparative Example 3 and Comparative Example 6 respectively, and dry them in a vacuum oven at 80°C for 4 hours to remove the surface adsorbed moisture.

[0066] 2. Tableting: Accurately weigh 1.0g of each dried sample powder. Place the powder into a cemented carbide tablet mold with an inner diameter of 10mm, and use a hydraulic press to hold the pressure at 20MPa for 2 minutes to form a round tablet sample for testing.

[0067] 3. Size measurement: Using a micrometer with an accuracy of 0.001 mm, the thickness of each pressed disc sample was measured at three different locations, and the average value was taken as the recorded thickness value of the sample.

[0068] 4. Conductivity Measurement: Place the pressed disc sample on the test platform of the four-probe tester. Adjust the four probes to ensure good contact with the sample surface, start the test program at room temperature (25℃), and the instrument will automatically measure and record the resistance of the sample.

[0069] 5. Data Calculation: Based on the measured resistance value, sample thickness, and the instrument's built-in geometric correction factor, the instrument software automatically calculates and obtains the material's conductivity, in units of S·cm. -1 Each sample was measured three times, and the average value was recorded in the result.

[0070] Experimental data

[0071] Table 1: Conductivity test results of cathode material powders prepared in different embodiments and comparative examples

[0072] Sample Name Tablet thickness (mm) <![CDATA[Conductivity (S·cm -1 )]]> Example 1 1.02 <![CDATA[5.12x10 -1 ]]> Comparative Example 1 0.98 <![CDATA[3.71x10 -6 ]]> Comparative Example 3 1.05 <![CDATA[9.58x10 -5 ]]> Comparative Example 6 0.99 8.45x10-3

[0073] Summary of Experimental Results

[0074] The data in Table 1 clearly show that the cathode material prepared by the method of this invention (Example 1) exhibits significantly higher powder conductivity than all comparative materials. This superior electronic conductivity stems from the integrated electronic conductivity network constructed by the unique composition design and preparation method of this invention. In Example 1, by introducing an organometallic compound containing a catalyst element and precisely controlling the atmosphere during subsequent heat treatment, a "rooted" carbon nanotube network was successfully generated in situ on the surface of the active material particles. This network forms a seamless and continuous interface with the active material, providing an efficient and low-resistance pathway for electron transport, thus exhibiting extremely high macroscopic conductivity.

[0075] In stark contrast, Comparative Example 1, lacking the addition of a catalyst component, failed to form a conductive network, and its conductivity exhibited only the extremely low intrinsic conductivity of the lithium transition metal oxide itself. While Comparative Example 3 added a catalyst component, it omitted the crucial weakly reducing atmosphere activation step, resulting in the catalyst failing to be effectively reduced to a catalytically active metallic state and thus failing to efficiently catalyze the growth of carbon nanotubes; consequently, its conductivity improvement was minimal. This clearly demonstrates that the synergistic effect between specific components and specific process steps is a necessary condition for achieving high-performance materials in the method of this invention.

[0076] Furthermore, the comparison between Example 1 and Comparative Example 6 highlights the fundamental advantages of the "in-situ integration" method of this invention over the traditional "physical blending" method. Although Comparative Example 6 introduced carbon nanotubes through physical mixing, its conductivity was still nearly two orders of magnitude lower than that of Example 1. This is because the conductive network formed by physical mixing involves "point-to-point" mechanical contact between particles, resulting in significant interfacial resistance and poor network continuity. In contrast, this invention, through in-situ growth, constructs a continuous conductive framework extending from the inside of the particles outward, completely eliminating these harmful physical interfaces and enabling unimpeded electron transport within the composite material. This is the core innovation of this invention in improving the conductivity of materials.

[0077] Test Example 2: Electrochemical AC Impedance Spectroscopy Test

[0078] Experimental steps

[0079] 1. Battery Assembly and Activation: Using the cathode materials prepared in Example 1, Comparative Example 2, and Comparative Example 6, respectively, CR2032 coin cells were assembled according to the aforementioned "General Method for Battery Preparation". The assembled cells were left to stand at room temperature for 12 hours to ensure that the electrolyte fully wetted the electrodes. Subsequently, the cells were subjected to three charge-discharge cycles at a constant rate of 0.1C using a battery testing system to complete the activation of the cells and form a stable SEI / CEI film.

[0080] 2. Test State Setting: After activation, charge the battery at a constant current rate of 0.1C to 4.3V, then switch to constant voltage charging mode until the charging current drops below 0.01C. Subsequently, let the battery rest in an open-circuit state for 1 hour to allow it to reach a quasi-equilibrium state.

[0081] 3. EIS Spectrum Acquisition: Connect the battery in the aforementioned quasi-equilibrium state to the electrochemical workstation. Apply a sinusoidal AC voltage signal with an amplitude of 5mV at the open-circuit potential, with the scan frequency range set from 100kHz to 0.01Hz. The electrochemical workstation automatically records and plots the Nyquist spectrum.

[0082] 4. Data Fitting and Analysis: Using the accompanying analysis software, an equivalent circuit model was fitted to the obtained Nyquist spectrum. The diameter of the semicircle in the high-frequency region of the spectrum corresponds to the charge transfer resistance. The Rct values ​​of different sample cells were recorded and compared.

[0083] Experimental data

[0084] Table 2: Charge transfer resistance test results of batteries prepared in different embodiments and comparative examples

[0085] Sample Name Charge transfer resistance (Rct) (Ω) Example 1 24.8 Comparative Example 2 135.6 Comparative Example 6 117.2

[0086] Summary of Experimental Results

[0087] The test results in Table 2 clearly demonstrate that the battery assembled using the material of Example 1 of this invention has a charge transfer resistance (Rct) value that is significantly lower than that of Comparative Examples 2 and 6. Charge transfer resistance is a key indicator of the ease with which lithium ions can be extracted / intercalated at the cathode / electrolyte interface; a lower value indicates faster ion transport kinetics at the interface. The low Rct value exhibited in Example 1 strongly demonstrates the significant effect of this invention in improving interfacial lithium ion transport. This effect is achieved through the introduction of boron-containing organic compounds and the in-situ generation of nano-island-like lithium salt fast ion conductor phases under specific processes.

[0088] Comparative Example 2, lacking the addition of boron-containing organic compounds during preparation, suffers from a lack of fast channels specifically designed for lithium-ion transport on its active material surface. Lithium ions, when crossing the solid-liquid interface, must overcome a traditional hysteresis layer composed of surface residual lithium and byproducts, thus exhibiting high charge transfer resistance. This directly confirms the indispensability of this specific component in the composition of the present invention for constructing efficient ion channels. The amorphous lithium borate glass phase generated in situ in Example 1, as an excellent lithium-ion conductor, forms numerous "ion ferry stations" on the surface of the active material, providing a low-barrier transport shortcut for lithium ions.

[0089] By comparing Example 1 and Comparative Example 6, the innovative concept of "dual-conductivity network synergy" in this invention can be further clarified. Although Comparative Example 6 also attempted to add ionic conductors through physical mixing, its Rct value remained high. This is because simple physical mixing cannot achieve precise and uniform distribution of ionic conductors on the surface of the active material, nor can it form effective synergy with the electronic conduction network. In contrast, the method of this invention can simultaneously construct the electronic conduction network and "embed" ion channels in situ at the root gaps of the network and on the exposed active surface, forming an optimized spatial layout and highly efficient functional synergy of electron and ion transport paths. This unique microstructure allows for rapid charge injection and a fast lithium-ion response, jointly contributing to extremely low interfacial impedance.

[0090] Test Example 3: Battery Rate Performance Test

[0091] Experimental steps

[0092] 1. Battery assembly and activation: Using the positive electrode materials prepared in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 4 and Comparative Example 6 respectively, CR2032 coin cells were assembled according to the aforementioned "General Method for Battery Preparation" and left to stand at room temperature for 12 hours.

[0093] 2. Capacity Testing Procedure: Place the battery in the battery testing system and first charge it to 4.3V at a constant current (CC) of 0.1C. Then switch to constant voltage (CV) charging mode until the current is less than 0.01C; this constitutes one complete charge. Subsequently, discharge the battery to 2.8V at constant current rates of 0.2C, 0.5C, 1.0C, 2.0C, and 5.0C, respectively, and record the discharge specific capacity (mAh·g) at each rate. -1 Before each change of discharge rate, fully charge the battery according to the CC-CV mode described above and let it stand for 10 minutes.

[0094] Experimental data

[0095] Table 3: Rate performance test results of batteries prepared in different embodiments and comparative examples

[0096]

[0097]

[0098] Summary of Experimental Results

[0099] Table 3 shows the rate performance test results, comprehensively demonstrating that the cathode material prepared in Example 1 of this invention exhibits superior capacity performance across the entire test range from low to high rates. Particularly under high-current discharge conditions of 5.0C, its capacity retention capability far surpasses that of all comparative examples. This is directly attributed to the internally integrated electron and ion dual-conductivity network constructed in this invention. This synergistic network ensures that charge and lithium ions can be rapidly and unimpededly transported to the reaction sites of the active material during high-current charge and discharge, significantly reducing battery polarization and thus maintaining high capacity output.

[0100] The performance degradation of Comparative Examples 1, 2, and 4 reveals the importance of different functional components in this invention. Comparative Examples 1 and 4, lacking an effective electronic conductivity network, suffer severe obstruction of electron transport at high rates, leading to significant ohmic and electrochemical polarization and a sharp decrease in capacity. Comparative Example 2 illustrates that even with some electronic conductivity, the lack of efficient interfacial ion channels makes lithium-ion transport at the solid-liquid interface a bottleneck, also resulting in severe polarization and capacity degradation. These comparisons fully demonstrate that excellent rate performance is not determined by a single conductivity factor, but rather is the inevitable result of the synergistic optimization of both electron and ion transport pathways in this invention.

[0101] Finally, the comparison between Example 1 and Comparative Example 6 profoundly reveals the superiority of the "in-situ integrated" preparation method of this invention. Comparative Example 6 introduced a conductive agent through physical mixing, which improved performance, but still lagged far behind Example 1. This is because the conductive component formed by physical mixing has high-resistance mechanical contact points with the active material, resulting in a fragile and discontinuous network connection. In contrast, the method of this invention grows "rooted" carbon nanotubes in situ on the surface of the active material and "embeds" ionic conductors, forming a seamless, integrated composite structure. This structure fundamentally eliminates interfacial resistance, constructing a stable, efficient, and conductive architecture that permeates the entire material system—this is the core technical advantage of this invention.

[0102] Test Example 4: Battery Long Cycle Performance Test

[0103] Experimental steps

[0104] 1. Battery Assembly and Activation: Using the positive electrode materials prepared in Examples 1, 1, 5, and 6 respectively, CR2032 coin cells were assembled according to the aforementioned "General Method for Battery Preparation" and allowed to stand at room temperature for 12 hours. The cells were then activated by performing three charge-discharge cycles (voltage range 2.8–4.3V) at a constant rate of 0.1C using a battery testing system.

[0105] 2. Long-cycle testing procedure: After activation, place the battery in the battery testing system and set the constant current charge / discharge rate to 1.0C. The charging procedure is as follows: charge at a constant current of 1.0C to 4.3V, then switch to constant voltage charging mode until the current is less than 0.01C. The discharging procedure is as follows: discharge at a constant current of 1.0C to 2.8V. Repeat this charge / discharge process for 200 cycles.

[0106] 3. Data Recording and Calculation: Record the discharge specific capacity at the 1st and 200th cycles. The capacity retention rate is calculated as: (Discharge specific capacity at the 200th cycle / Discharge specific capacity at the 1st cycle) × 100%.

[0107] Experimental data

[0108] Table 4: Long-cycle performance test results of batteries prepared in different embodiments and comparative examples at 1.0C rate.

[0109]

[0110] Summary of Experimental Results

[0111] Table 4 clearly shows that the cathode material prepared in Example 1 of this invention maintains an extremely high capacity retention rate after 200 high-rate cycles, exhibiting excellent cycle stability, far exceeding that of all comparative examples. This superior stability stems directly from the highly structurally resilient integrated composite structure constructed in this invention. The in-situ generated carbon nanotube network acts like an "elastic skeleton," firmly "rooted" on the surface of the active material particles, effectively buffering and adapting to the volumetric stress generated during repeated lithium-ion insertion / extraction, thereby inhibiting the generation of microcracks and particle pulverization in the active material and maintaining the long-term integrity of the electrode structure.

[0112] The rapid capacity decay observed in Comparative Examples 1 and 5 serves as a stark reminder of the importance of specific components and precise proportions in this invention. Comparative Example 1 lacks the mechanical support of a conductive network, leaving the active particles isolated and vulnerable to structural damage and electrical contact failure during cycling. In Comparative Example 5, excessive catalyst residue not only fails to improve performance but may also form harmful impurities or structural defects on the surface of the active material. These defects become stress concentration points during cycling, accelerating material degradation and irreversible capacity loss. This demonstrates that precise control of the dosage of each component is a crucial prerequisite for achieving stable cycling performance in this invention.

[0113] The significant difference between Example 1 and Comparative Example 6 profoundly reveals the fundamental advantage of the "in-situ integrated" preparation method compared to the traditional "physical blending." In Comparative Example 6, the physically mixed carbon nanotubes and the active material are only connected by weak van der Waals forces. This connection is vulnerable to the drastic volume changes during cycling, and the conductive network gradually peels off and fails, leading to a continuous increase in electrode internal resistance and a sustained capacity decay. In contrast, this invention achieves chemical bonding or metallurgical-level bonding between carbon nanotubes and the active material through in-situ catalytic growth. This "integrated" and robust connection ensures that the conductive network remains stable and efficient throughout long-term cycling, thus endowing the material with an exceptional cycle life. This is the core innovation of this invention in terms of structural stability.

[0114] The preparation method of the high conductivity positive electrode material for lithium batteries described below can be referred to in correspondence with the high conductivity positive electrode material for lithium batteries described above.

[0115] Preparation method of high conductivity positive electrode material for lithium batteries:

[0116] a. A lithium source, a transition metal precursor, an organometallic compound containing a catalyst element, and an organic compound containing boron or phosphorus are mixed to obtain a mixed precursor.

[0117] b. The mixed precursor described in step a is subjected to a first-stage heat treatment under an inert atmosphere to decompose the organometallic compound and the organic compound;

[0118] c. The product after the first stage heat treatment in step b is subjected to a second stage heat treatment under a weak reducing atmosphere to reduce the catalyst elements to catalytic active sites.

[0119] d. The product after the second stage heat treatment in step c is subjected to a third stage heat treatment under a carbon source atmosphere to complete the sintering of lithium transition metal oxide and simultaneously generate carbon nanotubes and lithium salt fast ion conductor phase in situ.

[0120] e. After the third stage of heat treatment is completed, switch to an inert atmosphere and cool to room temperature.

[0121] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-conductivity positive electrode material for lithium batteries, characterized in that, It is a composite material containing the following components in parts by mass: Lithium transition metal oxide active material: 95–99 parts; In-situ generated carbon nanotubes: 0.5–2.5 parts; In-situ generated boron- or phosphorus-containing lithium salt fast ion conductor phase: 0.1–1.5 parts; Catalyst residue: 0.1–1.0 parts; wherein the root of the carbon nanotube is integrally connected to the surface of the lithium transition metal oxide active material, and the lithium salt fast ion conductor phase is distributed in nano-islands in the area of ​​the active material surface not covered by carbon nanotubes.

2. The high conductivity positive electrode material for lithium batteries according to claim 1, characterized in that, The lithium transition metal oxide active material is lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide with a layered structure.

3. The high conductivity positive electrode material for lithium batteries according to claim 1, characterized in that, The catalyst residue is one or more metals selected from iron, cobalt, and nickel, or their carbides.

4. The high conductivity positive electrode material for lithium batteries according to claim 1, characterized in that, The lithium salt fast ion conductor phase is an amorphous lithium borate glass phase or a lithium phosphate glass phase.

5. The method for preparing a high-conductivity positive electrode material for lithium batteries according to any one of claims 1-4, characterized in that, Includes the following steps: a. A lithium source, a transition metal precursor, an organometallic compound containing a catalyst element, and an organic compound containing boron or phosphorus are mixed to obtain a mixed precursor. b. The mixed precursor described in step a is subjected to a first-stage heat treatment under an inert atmosphere to decompose the organometallic compound and the organic compound; c. The product after the first stage heat treatment in step b is subjected to a second stage heat treatment under a weak reducing atmosphere to reduce the catalyst elements to catalytic active sites. d. The product after the second stage heat treatment in step c is subjected to a third stage heat treatment under a carbon source atmosphere to complete the sintering of lithium transition metal oxide and simultaneously generate carbon nanotubes and lithium salt fast ion conductor phase in situ.

6. The method for preparing the high-conductivity positive electrode material for lithium batteries according to claim 5, characterized in that, The transition metal precursor mentioned in step a is nickel cobalt manganese hydroxide or nickel cobalt aluminum hydroxide, the organometallic compound containing the catalyst element is iron acetylacetonate, and the boron-containing organic compound is triphenylboron.

7. The method for preparing the high-conductivity positive electrode material for lithium batteries according to claim 5, characterized in that, The temperature range for the first stage heat treatment described in step b is 480–520°C.

8. The method for preparing the high-conductivity positive electrode material for lithium batteries according to claim 5, characterized in that, The weakly reducing atmosphere mentioned in step c is a mixture of hydrogen and an inert gas, and this step is carried out during the process of heating to the final sintering temperature.

9. The method for preparing a high-conductivity positive electrode material for lithium batteries according to claim 5, characterized in that, The atmosphere containing the carbon source in step d is a mixture of acetylene and inert gas, and this step is carried out at a constant temperature of 780-820°C.

10. The method for preparing a high-conductivity positive electrode material for lithium batteries according to claim 5, characterized in that, It also includes step e: after the third stage of heat treatment is completed, switch to an inert atmosphere and cool to room temperature.

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