A reverse interface engineering treatment lithium cobaltate positive electrode material, and a preparation method and application thereof

Abstract

The application belongs to the field of lithium ion batteries, and discloses a reverse interface engineering treatment lithium cobaltate positive electrode material and a preparation method and application thereof. The application uses the reducing property and acidity of phosphoric acid to treat the surface of bare sample lithium cobaltate, reversely generates and forms a coating layer on the original cobalt trioxide raw material for synthesizing the bare sample lithium cobaltate positive electrode material, and simultaneously generates a lithium phosphate fast ion conductor layer, thereby well solving the serious interface reaction between the solid-state battery positive electrode material and the electrolyte. The lithium cobaltate positive electrode material treated by the method has good long cycle stability, excellent rate performance and high performance under high conditions in a full solid-state lithium ion battery based on lithium phosphorus sulfur chloride (LPSCl) sulfide electrolyte, and provides a new idea for the modification method of the solid-state battery positive electrode interface and future industrialization.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion batteries, and specifically relates to a reverse interface engineering process for lithium cobalt oxide cathode materials, its preparation method, and its application. Background Technology

[0002] Since Sony first commercialized lithium-ion batteries in 1991, liquid lithium-ion batteries have been considered a promising technology for new energy storage. Since the beginning of the 21st century, the electric vehicle industry has gradually developed, especially in the last decade, showing explosive growth, and the future market for electric vehicles is expected to expand further. However, the energy density of liquid lithium-ion batteries is currently limited, and issues such as fast charging and cycle life at lower temperatures remain to be addressed. Furthermore, liquid batteries use organic electrolytes, which pose risks of evaporation, fire, and even explosion during operation. Current cutting-edge battery technology has shifted towards all-solid-state lithium-ion batteries (ASSLIB) using non-flammable solid electrolytes. ASSLIB batteries not only have the advantage of being non-flammable but also offer higher energy density, potentially even meeting the performance requirements of current gasoline-powered electric vehicles. Therefore, ASSLIB technology is considered one of the key technologies for future battery development.

[0003] Although all-solid-state lithium-ion batteries (ASSLIB) have promising development prospects, they still face significant challenges in practical applications. Solid-state batteries mainly consist of three parts: the negative electrode, the positive electrode, and the electrolyte. The positive electrode is the most crucial component. For the positive electrode, high-voltage, high-load, and high-capacity layered oxide positive electrodes, such as lithium cobalt oxide (LCO) and high-nickel materials like NCM811, can maximize energy density and meet commercial requirements. However, high-capacity layered oxide positive electrodes and sulfide electrolytes currently face a series of problems in application, most of which stem from the interface between the electrolyte and the positive and negative electrodes. These problems include severe interfacial reactions, space charge layers, element diffusion, and poor contact. These issues lead to high interfacial impedance and continuous capacity decay in solid-state batteries. Therefore, there is an urgent need to develop a method for surface modification of layered materials for lithium cobalt oxide positive electrodes. Currently, LiNbO3 and Li4Ti5O3 are commonly used methods for surface modification. 12 Oxides such as LiNbO3 and Li3BO3-Li2CO3, used to modify the cathode of solid-state batteries, have been extensively studied for stabilizing the oxide cathode / electrolyte interface and have achieved good results. However, current modification methods are relatively complex, and there are few methods to directly generate an oxide layer on the surface of lithium cobalt oxide. Summary of the Invention

[0004] To overcome the shortcomings and deficiencies of existing solid-state batteries, the primary objective of this invention is to provide a method for preparing lithium cobalt oxide cathode materials through reverse interface engineering. This method uses phosphoric acid to reduce a portion of cobalt tetroxide and lithium phosphate to the surface of a bare lithium cobalt oxide cathode material. Cobalt tetroxide forms the main framework of the interface, and lithium phosphate fills it to form a coating layer that coats the surface of the lithium cobalt oxide cathode material, thereby solving the serious interfacial reaction problem between the cathode material and the electrolyte in solid-state batteries. This method is an in-situ modification method that can process lithium cobalt oxide cathode materials in large quantities at low cost.

[0005] Another objective of this invention is to provide a lithium cobalt oxide cathode material prepared by the above-described preparation method through reverse interface engineering.

[0006] Another object of the present invention is to provide an application of the lithium cobalt oxide cathode material subjected to the above-mentioned reverse interface engineering treatment.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for preparing lithium cobalt oxide cathode material through reverse interface engineering includes the following steps:

[0009] (1) Weigh the bare lithium cobalt oxide sample and place it in a beaker. Then weigh the phosphoric acid solution and ultrapure water and add them to the beaker. Place the beaker in a water bath and heat it in the water bath with magnetic stirring.

[0010] (2) After the sample is heated in a water bath, filter it and then put it in an oven to dry it.

[0011] (3) Place the dried sample into a muffle furnace for high-temperature sintering;

[0012] (4) Take out the sintered sample, cool it to room temperature and then grind it to obtain the lithium cobalt oxide cathode material with reverse interface engineering treatment.

[0013] The mass of the phosphoric acid solution added in step (1) is 5-80% of the mass of the bare lithium cobalt oxide sample.

[0014] The amount of ultrapure water used in step (1) is not less than 150 ml.

[0015] The water bath heating temperature in step (1) is 40-80℃, and the water bath heating time is 4-6h.

[0016] The drying temperature in step (2) shall not be less than 60°C and the drying time shall not be less than 6 hours.

[0017] The filtration in step (2) is performed using a vacuum filter, and the drying is performed using a blower drying oven.

[0018] The high-temperature sintering temperature in step (3) is 400-600℃, and the sintering time is 4-6h.

[0019] The grinding time in step (4) shall not be less than 30 minutes.

[0020] A lithium cobalt oxide cathode material prepared by the above-described preparation method and subjected to reverse interface engineering.

[0021] The application of the aforementioned reverse interface engineering treated lithium cobalt oxide cathode material in the preparation of solid-state lithium-ion batteries.

[0022] The present invention has the following advantages and beneficial effects compared with the prior art:

[0023] (1) This invention utilizes the reducing and acidic properties of phosphoric acid to treat the surface of bare lithium cobalt oxide cathode material, thereby reverse-generating the cobalt tetroxide raw material originally used to synthesize lithium cobalt oxide cathode material and forming a coating layer. At the same time, a lithium phosphate fast ion conductor layer is generated, which effectively solves the serious interfacial reaction between the cathode material and the electrolyte in solid-state batteries. The lithium cobalt oxide cathode material treated by this method exhibits good long-cycle stability, excellent rate performance and high performance under high conditions in all-solid-state lithium-ion batteries based on lithium phosphorus sulfide chloride (LPSCl) sulfide electrolyte, providing a new approach for the modification of the cathode interface of solid-state batteries and its future industrialization.

[0024] (2) This invention does not require the introduction of other coating materials. It utilizes the reducing and corrosive properties of phosphoric acid to generate a coating layer in situ on the surface of the bare lithium cobalt oxide cathode material.

[0025] (3) The process of this invention is simple, green and safe, pollution-free, and easy to operate on a large scale.

[0026] (4) The reaction of this invention is sufficient and conducive to stable output. Attached Figure Description

[0027] Figure 1 The images show the XRD patterns of the cathode materials obtained in Examples 1-3 and Comparative Example 1.

[0028] Figure 2 The graph shows the long-cycle test results of the cathode materials obtained in Examples 1-3 and Comparative Example 1 on all-solid-state lithium-ion batteries based on LPSCL electrolyte at a rate of 0.2C.

[0029] Figure 3 The graph shows the long-cycle test results of the cathode materials obtained in Examples 1-3 and Comparative Example 1 on all-solid-state lithium-ion batteries based on LPSCL electrolyte at a rate of 0.5C.

[0030] Figure 4The graph shows the long-cycle test results of the cathode materials obtained in Examples 1-3 and Comparative Example 1 with LPSCL electrolyte in all-solid-state lithium-ion batteries under 1C rate conditions.

[0031] Figure 5 The graphs show the rate performance of all-solid-state lithium-ion batteries based on LPSCL electrolyte using the cathode materials obtained in Examples 1-3 and Comparative Example 1 under conditions of 0.1C, 0.2C, 0.5C, 1C, and 2C.

[0032] Figure 6 Impedance test diagrams of all-solid-state lithium-ion batteries based on LPSCL electrolyte after cycling, based on the cathode materials obtained in Examples 1-3 and Comparative Example 1, after 10 cycles.

[0033] Figure 7 The figures show the GITT test results of the cathode materials obtained in Examples 1-3 and Comparative Example 1 based on LPSCL electrolyte for all-solid-state lithium-ion charge-discharge. The results show that Example 2 exhibits a smaller polarization voltage, highlighting the superior performance of Example 2.

[0034] Figure 8 The cathode materials obtained in Examples 1-3 and Comparative Example 1 were subjected to a high loading of 14 mg / cm². 2 Long-cycle test diagram of an all-solid-state lithium-ion battery based on LPSCL electrolyte under certain conditions.

[0035] Figure 9 The images show the Raman spectra of the cathode materials obtained in Examples 1-3 and Comparative Example 1.

[0036] Figure 10 Transmission electron microscopy (TEM) of the cathode materials obtained in Examples 1-3 and Comparative Example 1. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0038] Example 1: Preparation process of lithium cobalt oxide (LCO) battery with reverse interface engineering and its assembly as an all-solid-state battery

[0039] (1) Weigh 1g of bare lithium cobalt oxide (Bare-LCO) into a beaker using a balance, and then weigh 10% of the mass of the bare lithium cobalt oxide phosphoric acid solution and 150ml of ultrapure water into the beaker.

[0040] (2) Place a stirring magnet in a beaker containing the mixed sample and heat it in a water bath at 65°C for 5 hours.

[0041] (3) Remove the beaker from the water bath after the water bath is complete, and filter the sample in the beaker using a vacuum filter.

[0042] (4) Place the filtered powder sample into a beaker, and then place the beaker into a 70°C forced-air drying oven to dry for 10 hours.

[0043] (5) After the dried sample is placed in the crucible, it is placed in the muffle furnace for sintering. The temperature is raised to 600℃ at a heating rate of 5℃ / min for a total of 120min. After the heating is completed, the sample is sintered at 600℃ for 6h.

[0044] (6) After the sintered sample is cooled to room temperature, it is taken out and poured into a mortar for grinding for 30 minutes to obtain lithium cobalt oxide cathode material (LCO) treated by reverse interface engineering; take out the lithium cobalt oxide cathode material and grind it in a mortar for 30 minutes according to the mass ratio of lithium cobalt oxide cathode material (LCO): lithium phosphorus sulfur chlorine electrolyte (LSPCL): conductive carbon (Super P) = 150:100:5 to make mixed cathode material; then add 5mg of mixed cathode material, 250mg of LPSCL, and lithium indium alloy as negative electrode into a mold to press into a solid battery.

[0045] Example 2

[0046] (1) Weigh 1g of bare lithium cobalt oxide (Bare-LCO) into a beaker using a balance, and then weigh 40% of the mass of the bare lithium cobalt oxide phosphoric acid solution and 150ml of ultrapure water into the beaker.

[0047] (2) Place a stirring magnet in a beaker containing the mixed sample and heat it in a water bath at 65°C for 5 hours.

[0048] (3) Remove the beaker from the water bath after the water bath is complete, and filter the sample in the beaker using a vacuum filter.

[0049] (4) Place the filtered powder sample into a beaker, and then place the beaker into a 70°C forced-air drying oven to dry for 10 hours.

[0050] (5) After the dried sample is placed in the crucible, it is placed in the muffle furnace for sintering. The temperature is raised to 600℃ at a heating rate of 5℃ / min for a total of 120min. After the heating is completed, the sample is sintered at 600℃ for 6h.

[0051] (6) After the sintered sample is cooled to room temperature, it is taken out and poured into a mortar for grinding for 30 minutes to obtain lithium cobalt oxide cathode material (LCO) treated by reverse interface engineering; take out the lithium cobalt oxide cathode material and grind it in a mortar for 30 minutes according to the mass ratio of lithium cobalt oxide cathode material (LCO): lithium phosphorus sulfur chlorine electrolyte (LSPCL): conductive carbon (Super P) = 150:100:5 to make mixed cathode material; then add 5mg of mixed cathode material, 250mg of LPSCL, and lithium indium alloy as negative electrode into a mold to press into a solid battery.

[0052] Example 3

[0053] (1) Weigh 1g of bare lithium cobalt oxide (Bare-LCO) into a beaker using a balance, and then weigh 60% of the mass of the bare lithium cobalt oxide phosphoric acid solution and 150ml of ultrapure water into the beaker.

[0054] (2) Place a stirring magnet in a beaker containing the mixed sample and heat it in a water bath at 65°C for 5 hours.

[0055] (3) Remove the beaker from the water bath after the water bath is complete, and filter the sample in the beaker using a vacuum filter.

[0056] (4) Place the filtered powder sample into a beaker, and then place the beaker into a 70°C forced-air drying oven to dry for 10 hours.

[0057] (5) After the dried sample is placed in the crucible, it is placed in the muffle furnace for sintering. The temperature is raised to 600℃ at a heating rate of 5℃ / min for a total of 120min. After the heating is completed, the sample is sintered at 600℃ for 6h.

[0058] (6) After the sintered sample is cooled to room temperature, it is taken out and poured into a mortar for grinding for 30 minutes to obtain lithium cobalt oxide cathode material (LCO) treated by reverse interface engineering; take out the lithium cobalt oxide cathode material and grind it in a mortar for 30 minutes according to the mass ratio of lithium cobalt oxide cathode material (LCO): lithium phosphorus sulfur chlorine electrolyte (LSPCL): conductive carbon (Super P) = 150:100:5 to make mixed cathode material; then add 5mg of mixed cathode material, 250mg of LPSCL, and lithium indium alloy as negative electrode into a mold to press into a solid battery.

[0059] Comparative Example 1: Preparation process of Bare-LCO and assembly of its all-solid-state battery

[0060] (1) Weigh 1g of bare lithium cobalt oxide (Bare-LCO) into a beaker using a balance;

[0061] (2) Place a stirring magnet in the beaker containing the sample and heat it in a water bath at 65°C for 5 hours.

[0062] (3) Remove the beaker from the water bath after the water bath is complete, and filter the sample in the beaker using a vacuum filter.

[0063] (4) Place the filtered powder sample into a beaker, and then place the beaker into a 70°C forced-air drying oven to dry for 10 hours.

[0064] (5) After the dried sample is placed in the crucible, it is placed in the muffle furnace for sintering. The temperature is raised to 600℃ at a heating rate of 5℃ / min for a total of 120min. After the heating is completed, the sample is sintered at 600℃ for 6h.

[0065] (6) After the sintered sample is cooled to room temperature, it is taken out and poured into a mortar for grinding for 30 minutes to obtain lithium cobalt oxide cathode material (LCO) without reverse interface engineering treatment; take out the lithium cobalt oxide cathode material and grind it in a mortar for 30 minutes according to the mass ratio of lithium cobalt oxide cathode material (LCO): lithium phosphorus sulfur chlorine electrolyte (LSPCL): conductive carbon (Super P) = 150:100:5 to make mixed cathode material; then add 5 mg of mixed cathode material, 250 mg of LPSCL, and lithium indium alloy as negative electrode into a mold to press into a solid battery.

[0066] The present invention conducted the following tests on Example 1, Example 2, Example 3 and Comparative Example 1.

[0067] like Figure 1 As shown, XRD (X-ray diffraction) tests were performed on the lithium cobalt oxide electrodes prepared in Examples 1, 2, 3, and Comparative Example 1 after reverse interface engineering. Compared with Comparative Example 1, new cobalt tetroxide peaks appeared in the XRD patterns of Examples 1, 2, and 3, proving that cobalt tetroxide was generated in the treated samples. Furthermore, as the amount of phosphoric acid added increased, the concentration of cobalt tetroxide in Examples 1, 2, and 3 continuously increased, indicating that the amount of cobalt tetroxide generated continuously increased.

[0068] like Figure 2 As shown, the lithium cobalt oxide electrodes prepared in Examples 1, 2, 3, and Comparative Example 1 underwent long-term cycling tests at 0.2C rate in all-solid-state lithium-ion batteries based on LPSCL electrolyte. It was found that compared with Comparative Example 1, Examples 1, 2, and 3 exhibited superior long-term cycling stability and coulombic efficiency, with Example 2 showing the best performance.

[0069] like Figure 3As shown, the lithium cobalt oxide electrodes prepared in Example 2 and Comparative Example 1 underwent long-term cycling tests at 0.5C rate in all-solid-state lithium-ion batteries based on LPSCL electrolyte. It was found that Example 2 exhibited superior long-term cycling stability and coulombic efficiency compared to Comparative Example 1.

[0070] like Figure 4 As shown, the lithium cobalt oxide electrode prepared in Example 2 underwent long-term cycling tests in an all-solid-state lithium-ion battery with LPSCL electrolyte at 1C rate. Example 2 was found to exhibit excellent long-term cycling performance under high-rate conditions.

[0071] like Figure 5 As shown, the reverse interface engineering treated lithium cobalt oxide cathodes prepared in Examples 1, 2, 3, and Comparative Example 1 were used to test the rate performance of all-solid-state lithium-ion batteries based on LPSCL electrolyte under conditions of 0.1C, 0.2C, 0.5C, 1C, and 2C. It was found that compared to Comparative Example 1, Examples 1, 2, and 3 all exhibited superior rate performance. Example 2 showed the most outstanding performance.

[0072] like Figure 6 As shown, the lithium cobalt oxide cathodes prepared in Example 2 and Comparative Example 1 underwent 10 cycles of reverse interface engineering followed by impedance testing in an all-solid-state lithium-ion battery based on LPSCL electrolyte. It was found that Example 2 exhibited lower impedance compared to Comparative Example 1, indicating superior performance of Example 2.

[0073] like Figure 7 As shown, the lithium cobalt oxide cathodes prepared in Example 2 and Comparative Example 1 underwent all-solid-state lithium-ion charge-discharge GITT tests based on LPSCL electrolyte. The results show that Example 2 exhibits a smaller polarization voltage, highlighting the superior performance of Example 2.

[0074] like Figure 8 As shown, the lithium cobalt oxide electrode prepared in Example 2 underwent high loading of 14 mg / cm². 2 Long-cycle tests were conducted on all-solid-state lithium-ion batteries based on LPSCL electrolyte under certain conditions. The results showed that Example 2 exhibited excellent cycle performance under high load conditions.

[0075] like Figure 9 As shown, Raman spectroscopy was performed on the lithium cobalt oxide cathodes prepared in Example 2 and Comparative Example 1, which underwent reverse interface engineering treatment. The results showed that, compared with Comparative Example 1, peaks of cobalt tetroxide and phosphate were observed in Example 2, confirming the presence of cobalt tetroxide and lithium phosphate.

[0076] like Figure 10 As shown, the lithium cobalt oxide electrode prepared in Example 2 underwent transmission electron microscopy (TEM) testing. Clear lattice fringes belonging to the cobalt tetroxide coating and lithium cobalt oxide were observed at the interface, indicating that the cobalt tetroxide coating had been successfully applied in Example 2.

[0077] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing lithium cobalt oxide cathode material through reverse interface engineering, characterized in that... The following steps are included: (1) Weigh the bare lithium cobalt oxide sample and place it in a beaker. Then weigh the phosphoric acid solution and ultrapure water and add them to the beaker. Place the beaker in a water bath and heat it in the water bath with magnetic stirring. The mass of the phosphoric acid solution added is 5-80% of the mass of the bare lithium cobalt oxide sample. The temperature of the water bath is 40-80℃ and the heating time is 4-6h. (2) After the sample is heated in a water bath, filter it and then put it in an oven to dry. (3) Place the dried sample into a muffle furnace for high-temperature sintering; (4) Take out the sintered sample, cool it to room temperature and then grind it to obtain the lithium cobalt oxide cathode material with reverse interface engineering treatment; the surface of the lithium cobalt oxide cathode material is formed with a coating layer containing cobalt tetroxide and lithium phosphate.

2. The preparation method according to claim 1, characterized in that: The amount of ultrapure water used in step (1) is no less than 150 ml.

3. The preparation method according to claim 1, characterized in that: The drying temperature in step (2) shall not be less than 60°C and the drying time shall not be less than 6 hours.

4. The preparation method according to claim 1, characterized in that: The filtration in step (2) is performed using a vacuum filter, and the drying is performed using a forced-air drying oven.

5. The preparation method according to claim 1, characterized in that: The high-temperature sintering temperature in step (3) is 400-600℃, and the sintering time is 4-6h.

6. The preparation method according to claim 1, characterized in that: The grinding time in step (4) shall not be less than 30 minutes.

7. A lithium cobalt oxide cathode material with reverse interface engineering prepared by the preparation method according to any one of claims 1-6.

8. The application of the lithium cobalt oxide cathode material with reverse interface engineering treatment according to claim 7 in the preparation of solid-state lithium-ion batteries.

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