Negative electrode material, lithium ion battery containing negative electrode material and preparation method of negative electrode material
By constructing a dual continuous coating structure of amorphous carbon and solid electrolyte on the surface of lithium-ion battery anode material, the problem of poor contact between the anode material and solid electrolyte interface is solved, improving the electronic and ion conduction performance of the battery, and enhancing the battery's cycle performance and energy density.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-26
- Publication Date
- 2026-04-03
AI Technical Summary
Existing lithium-ion battery anode materials have poor interfacial contact with solid electrolytes, resulting in high interfacial impedance and poor electrochemical stability. Furthermore, existing modification methods cannot simultaneously achieve electronic and ion conduction performance, resulting in weak interfacial bonding and easy detachment during cycling.
An in-situ uniform coating process is adopted, and a dual continuous coating structure of amorphous carbon and solid electrolyte is simultaneously constructed on the surface of the matrix material by pre-sintering and sintering a mixture of carbon source (such as asphalt), dispersant (such as hydrophilic polymer) and solid electrolyte, thereby improving interfacial bonding and conductivity.
It significantly improves the electronic and ion conduction properties of the anode material, enhances the overall electrochemical performance of lithium-ion batteries, especially their cycle performance, and also features low cost and ease of operation.
Smart Images
Figure CN121790348A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a negative electrode material, a lithium-ion battery containing the same, and a method for preparing the same. Background Technology
[0002] With the rapid development of electric vehicles, energy storage, electric aviation, and smart terminals, the market demand for high-energy-density, high-safety, long-life, and low-cost lithium batteries is becoming increasingly urgent. However, existing lithium-ion batteries face significant challenges in meeting these performance requirements due to their use of flammable liquid electrolytes. Against this backdrop, solid-state batteries, with their unique advantages of solid-state electrolytes, have demonstrated enormous market potential and technological prospects. Solid-state batteries not only promise to simultaneously achieve high energy density, high safety, long life, and low cost, but are also globally recognized as the key to disrupting existing lithium-ion battery technology. In recent years, research on solid-state batteries has sparked a surge of interest in academia and industry, with governments worldwide increasing investment and viewing it as the future direction of advanced battery technology. They consider it a crucial pathway to achieving next-generation high-performance batteries, potentially leading to revolutionary changes in industries such as electric vehicles and energy storage, and injecting strong momentum into the optimization of the global energy structure and sustainable development.
[0003] All-solid-state batteries have become a key research direction for the next generation of energy storage technology. However, the electrode-electrolyte interface problem in solid-state batteries has seriously restricted its commercialization process. In particular, the poor solid-solid contact between the negative electrode material (such as graphite and silicon-based materials) and the solid electrolyte has led to the following key problems: (1) High interface impedance. Traditional liquid electrolytes can wet the electrode surface, but the physical contact between the solid electrolyte and the negative electrode is poor, and the interface ion transport resistance is large, resulting in severe battery polarization and poor rate performance; (2) Poor electrochemical stability. The negative electrodes such as graphite and silicon undergo significant volume changes during cycling and are prone to mechanical stripping from the solid electrolyte.
[0004] To address the above issues, even though there are already various methods to improve the negative electrode-solid electrolyte interface (such as coating modification), there are still certain technical limitations: it is impossible to balance electronic and ion conduction performance, and the coating is uneven, the interfacial bonding is weak, and it is easy to fall off during cycling.
[0005] Therefore, there is an urgent need for an effective coating modification process to effectively improve the various properties of the obtained anode material and the overall performance of the battery. Summary of the Invention
[0006] To overcome the technical shortcomings of existing modification methods for materials such as graphite and silicon-carbon, such as the inability to simultaneously achieve electronic and ionic conductivity, uneven coating, and weak interfacial bonding, this invention provides an anode material, a lithium-ion battery containing the anode material, and a method for preparing the same. This preparation method achieves in-situ uniform coating while effectively improving the electronic and ionic conductivity of the resulting anode material. When applied to lithium-ion batteries, this effectively enhances the overall electrochemical performance of the battery, such as rate performance, energy density, and cycle performance, especially cycle performance.
[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows.
[0008] This invention provides a method for preparing a negative electrode material, the method comprising the following steps:
[0009] The negative electrode material is prepared by pre-sintering and sintering a mixed slurry containing a matrix material, a carbon source, a solid electrolyte, a dispersant, and water; wherein,
[0010] The carbon source includes bitumen;
[0011] The dispersant includes a hydrophilic polymer;
[0012] The pre-sintering temperature is lower than the sintering temperature.
[0013] In this invention, amorphous carbon and solid electrolyte can be simultaneously and in-situ coated onto the surface of a matrix material through the above steps, achieving a dual continuous coating structure. Furthermore, research has shown that when specific carbon sources (asphalt) and dispersants (hydrophilic polymers) are used, along with a pre-sintering step, the coating uniformity during sintering can be effectively improved. When used in batteries, this significantly enhances the interfacial bonding strength and stability of the resulting negative electrode material, mitigating volume expansion during charge and discharge. Simultaneously, it effectively improves electron and ion conduction performance, thereby enhancing the overall electrochemical performance of the resulting battery, especially its cycle performance.
[0014] In this invention, the matrix material can be a matrix material of conventional anode materials in the art, such as one or more of graphite materials, pure carbon materials and silicon carbide materials.
[0015] In some embodiments, the graphite material is untreated graphite raw material or obtained by acid treatment of the graphite raw material. Studies have found that acid treatment can remove impurities from the surface of the graphite raw material while simultaneously etching the surface, thereby further improving the bonding strength between the substrate material and the coating layer during simultaneous in-situ coating and effectively promoting uniform coating.
[0016] The graphite raw material is, for example, artificial graphite and / or natural graphite. The particle size D50 of the graphite raw material is, for example, 8-35 μm, and more specifically, 13.2 μm.
[0017] The acid treatment is preferably performed using acid.
[0018] Furthermore, the acid can be an acid with etching properties conventional in the art, and generally refers to a mixed solution of acid and water; for example, it includes one or more of hydrochloric acid, nitric acid and sulfuric acid.
[0019] Furthermore, the concentration of the acid is preferably 0.5-1.5 mol / L, for example 1 mol / L.
[0020] Furthermore, the preferred mass ratio of the acid to the graphite raw material is (2-5):1.
[0021] Furthermore, the acid treatment step includes adding the graphite raw material to the acid, followed by stirring and washing.
[0022] The stirring time is preferably 20-40 minutes, for example 30 minutes.
[0023] Preferably, the cleaning is performed with deionized water until the pH reaches 7.0.
[0024] The number of times the cleaning is performed is preferably 2-3 times.
[0025] Furthermore, the acid treatment also includes a drying step.
[0026] The drying method may include, for example, vacuum drying.
[0027] The drying temperature is preferably 70-90°C, for example 80°C.
[0028] The drying time is preferably 10-20 hours, for example 12 hours.
[0029] The pure carbon material is, for example, hard carbon and / or soft carbon; the particle size D50 of the pure carbon material is, for example, 8-35 μm.
[0030] Preferably, the silicon-carbon material is a CVD silicon-carbon material; the CVD silicon-carbon material means a silicon-carbon material prepared by chemical vapor deposition (CVD) technology.
[0031] The particle size D50 of the silicon-carbon material is, for example, 3-15 μm, and more specifically, 8.3 μm.
[0032] In some embodiments, the mass percentage of the carbon source and the matrix material is 0.5%-10%, for example 2% or 4%.
[0033] In some embodiments, the solid electrolyte includes sulfide-based electrolytes and / or oxide-based electrolytes conventional in the art.
[0034] In some embodiments, the solid electrolyte includes NASICON-type electrolytes, preferably including one or more of LATP (lithium aluminum titanium phosphate), LAGP (lithium aluminum germanium phosphate), and LAGTP (lithium aluminum germanium titanium phosphate). The LATP, LAGP, and LAGTP are all common NASICON-type solid electrolytes in the art; those skilled in the art can understand their specific meanings. It has been found through research that if other conventional solid electrolytes in the art such as LLZO-type electrolytes are selected, they are prone to react with water in the system, thereby affecting the relevant properties of the obtained negative electrode material to a certain extent.
[0035] Specifically, the composition of the LATP may be Li (1+x) Al (x) Ti (2-x) (PO4)3, where 0 < x ≤ 0.6, for example, Li 1.3 Al 0.3 Ti[[ID=##**ERROR**##]] 1.7 (PO4)3.
[0036] Specifically, the composition of the LAGP may be Li (1+x) Al (x) Ge (2-x) (PO4)3, where 0 < x ≤ 0.6, for example, Li 1.5 Al 0.5 Ge 1.5 (PO4)3.
[0037] Specifically, the composition of the LAGTP may be Li 1.5 Al 0.5 Ti x Ge 1.5-x (PO4)3, where 0 < x ≤ 0.4, for example, Li 1.5 Al 0.5 Ti 0.1 Ge 1.4 (PO4)3.
[0038] In some specific embodiments, the solid electrolyte is LATP and LAGP, and the mass ratio of LATP to LAGP is, for example, 1:1. [[ID=##**ERROR**##]] [[ID=##**ERROR**##]]
[0039] In some embodiments, the mass percentage of the solid electrolyte and the matrix material is 0.5% - 10%, for example, 1% or 2%. [[ID=##**ERROR**##]] [[ID=##**ERROR**##]]
[0040] In some embodiments, the particle size D50 of the solid electrolyte is 5 - 100 nm, for example, 20 nm, 21.6 nm, or 23.4 nm. Please note that there seem to be some errors in the original text where some tags are repeated in the translation requirements but not in the expected way for proper translation. Also, the translation process was carried out as accurately as possible based on the given rules despite these potential confusions. If you have any further clarifications regarding the text or translation requirements, it would be helpful for a more precise translation.
[0041] In some embodiments, the dispersant is one or more of sodium carboxymethyl cellulose (CMC), polyvinylpyrrolidone (PVP), hydroxyethyl cellulose (HEC), sodium polyacrylate (PAAS), polyethylene glycol (PEG), and polyacrylamide (PAM).
[0042] In some embodiments, the mass percentage of the dispersant and the matrix material is 0.5%-10%, for example, 1%.
[0043] In some embodiments, the preparation of the mixed slurry includes the following steps:
[0044] (1) Mix the dispersant with water to obtain solution a;
[0045] (2) Take a portion of the adhesive solution a and the carbon source and mix them to obtain slurry b;
[0046] (3) Take the remaining adhesive solution a and the solid electrolyte and mix them to obtain slurry c;
[0047] (4) Mix the slurry b and slurry c to obtain slurry d;
[0048] (5) Mix the matrix material and the slurry d to obtain the final product.
[0049] In step (1), the water is preferably heated to 60°C-80°C first, and then the dispersant is added while maintaining this temperature.
[0050] In steps (1) to (4), the mixing can be carried out independently according to conventional mixing steps in the art, for example, by using a dispersing disc to stir; the mixing speed can be independently, for example, 1000 r / min.
[0051] In step (1), the mixing time is preferably 4-6 hours, for example 5 hours.
[0052] In step (2), the mixing time is preferably 0.5-2 hours, for example, 1 hour.
[0053] In step (3), the mixing time is preferably 0.5-2 hours, for example, 1 hour.
[0054] In step (4), the mixing time is preferably 1-3 hours, for example 2 hours.
[0055] In step (5), the mixing is performed, for example, in a VC mixing device (vertical axis forced circulation mixing device).
[0056] In step (5), the mixing time is preferably 20-60 min, for example 25 min.
[0057] In step (5), the mixing speed is preferably 400-1200 r / min.
[0058] In some specific implementations, in step (5), the mixing is performed by mixing at a speed of 400 r / min for 5 min, and then mixing at a speed of 1200 r / min for 20 min.
[0059] In this invention, the pre-sintering and sintering steps may each include a heating step independently, that is, when the temperature is raised to the holding temperature, pre-sintering or sintering begins; the temperatures of pre-sintering and sintering each independently refer to the holding temperature. Those skilled in the art will understand their specific meaning.
[0060] In some embodiments, the pre-sintering temperature is 150-200°C.
[0061] In some embodiments, the heating rate before pre-sintering is 5-10 °C / min.
[0062] In some implementations, the pre-sintering time is 0.5-2 hours.
[0063] In some embodiments, the sintering temperature is 600-1500°C, for example 700°C.
[0064] In some embodiments, the heating rate before sintering is 5-10 °C / min.
[0065] In some implementations, the sintering time is 1-4 hours, for example, 2 hours.
[0066] In some embodiments, the pre-sintering and sintering steps are each performed independently in an inert atmosphere, such as nitrogen and / or argon.
[0067] In some embodiments, the sintering step is followed by a grinding step.
[0068] The present invention also provides a negative electrode material, which is prepared by the method for preparing negative electrode materials as described above.
[0069] In this invention, the negative electrode material, prepared by the method described above, may include a matrix material and a coating layer covering the surface of the matrix material, wherein the coating layer includes amorphous carbon and a solid electrolyte.
[0070] In some embodiments, the content of the amorphous carbon is 1%-10%, for example 2%; the percentage is the mass percentage of the amorphous carbon and the negative electrode material.
[0071] In some embodiments, the content of the solid electrolyte is 0.5%-10%, for example 1% or 2%; the percentage is the mass percentage of the solid electrolyte and the negative electrode material.
[0072] In some implementations, the thickness of the coating layer is 1-100 nm.
[0073] The present invention also provides a lithium-ion battery comprising the negative electrode material as described above.
[0074] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.
[0075] The reagents and raw materials used in this invention are all commercially available.
[0076] The positive and progressive effects of this invention are as follows:
[0077] This invention employs a one-step co-coating process to directly mix and pyrolyze asphalt (carbon source) with solid electrolyte and matrix material. This simultaneously constructs a dual-continuous "carbon layer-solid electrolyte" coating structure on the matrix material surface, achieving in-situ uniform coating while effectively improving the electronic and ionic conductivity of the resulting anode material. When applied to lithium-ion batteries, this ensures excellent interfacial adhesion, thereby significantly enhancing the battery's overall electrochemical performance, such as rate performance, energy density, and cycle performance. Furthermore, this preparation method is characterized by low cost, simple operation, and high adaptability, significantly solving the core problems of poor contact and high impedance at the anode-solid electrolyte interface in solid-state batteries, and possessing both high performance and large-scale production potential. Attached Figure Description
[0078] Figure 1 This is a SEM image of the negative electrode material obtained in Example 5.
[0079] Figure 2 The image shows the EDS diagram of the negative electrode material obtained in Example 5.
[0080] Figure 3 This is a TEM image of the negative electrode material obtained in Example 7.
[0081] Figure 4 The graph shows the cyclic specific capacity volatilization results of the battery obtained from the graphite-silicon-carbon hybrid material in the effect embodiment.
[0082] Figure 5 The graph shows the cycle capacity retention of the battery obtained from the graphite-silicon-carbon hybrid material in the effect embodiment. Detailed Implementation
[0083] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.
[0084] The specific information of the raw materials used in the following examples and comparative examples is as follows:
[0085] Graphite material: artificial graphite with a particle size D50 of 13.2 μm.
[0086] Silicon-carbon material: CVD silicon-carbon material with a particle size D50 of 8.3 μm.
[0087] LATP: Its specific composition is Li 1.3 Al 0.3 Ti 1.7 (PO4)3, with a particle size D50 of 20 nm.
[0088] LAGP: Its specific composition is Li 1.5 Al 0.5 Ge 1.5 (PO4)3, with a particle size D50 of 23.4 nm.
[0089] LAGTP: Its specific composition is Li 1.5 Al 0.5 Ti 0.1 Ge 1.4 (PO4)3, with a particle size D50 of 21.6 nm.
[0090] Example 1
[0091] (1) Take 995g of water, heat it to 60℃, then add 10g of CMC to the water, stir in a dispersion pan for 5h at a speed of 1000r / min to obtain transparent liquid a.
[0092] (2) Take 20g of asphalt and add it to 500g of adhesive solution a. Stir in a dispersing pan for 1 hour at a speed of 1000r / min until it is completely dispersed and uniform to obtain slurry b.
[0093] (3) Take 10g of solid electrolyte LATP powder and add it to the remaining 500g of gel solution a. Stir in a dispersion pan for 1 hour at a speed of 1000r / min until it is completely dispersed and uniform to obtain slurry c.
[0094] (4) Mix slurry b and slurry c and stir for 2 hours at a speed of 1000 r / min to obtain mixed slurry d.
[0095] (5) Immerse 1 kg of graphite raw material in 2 kg of 1 mol / L dilute hydrochloric acid and stir in a dispersion pan for 30 min to remove metal impurities. Wash with deionized water 2-3 times until neutral (pH=7), and vacuum dry at 80℃ for 12 h to obtain dried graphite material. Then add 1 kg of dried graphite material to slurry d and mix in a VC high-speed mixing device (vertical axis forced circulation mixing device). Mix at low speed for 5 min at a speed of 400 r / min, and then mix at high speed for 20 min at a speed of 1800 r / min to obtain a mixed slurry.
[0096] (6) The mixed slurry was pre-sintered and sintered under an argon atmosphere: pre-sintered at 200°C for 30 min to completely remove the solvent (water), and sintered at 700°C for 4 h with the heating rate always maintained at 5°C / min; the resulting black blocky material was ground to obtain a powder material with amorphous carbon (coating amount of 1%, mass percentage) and solid electrolyte LATP (coating amount of 1%, mass percentage) on the surface, which is the negative electrode material of this embodiment.
[0097] The coating amount of amorphous carbon can be measured using conventional methods in the field, specifically based on the cracking rate of the carbon source at the sintering temperature of 700°C; the coating amount of solid electrolyte can be calculated based on the theoretical ratio of the amount of solid electrolyte fed to the negative electrode material, as follows.
[0098] Example 2
[0099] Compared to Example 1, the only difference is that in step (3), the solid electrolyte is LAGP.
[0100] A negative electrode material with a surface coated with amorphous carbon (coating amount of 1%, mass percentage) and solid electrolyte LAGP (coating amount of 1%, mass percentage) was prepared.
[0101] Example 3
[0102] Compared to Example 1, the only difference is that in step (3), the solid electrolyte is 5g LATP and 5g LAGP.
[0103] Anode materials were prepared by coating amorphous carbon (1% by mass) and solid electrolytes (LATP and LAGP, 0.5% by mass, respectively).
[0104] Example 4
[0105] Compared to Example 1, the only difference is that in step (3), the solid electrolyte is LAGTP.
[0106] A negative electrode material with a surface coated with amorphous carbon (coating amount of 1%, mass percentage) and solid electrolyte LAGTP (coating amount of 1%, mass percentage) was prepared.
[0107] Example 5
[0108] Compared to Example 1, the only difference is that in step (1), the dispersant is PVP; and in step (2), the amount of asphalt used is 40g.
[0109] A negative electrode material was prepared by coating amorphous carbon (2% by mass) and solid electrolyte LATP (1% by mass) on its surface.
[0110] Example 6
[0111] Compared to Example 1, the only difference is that: in step (1), the dispersant is PVP; in step (2), the amount of asphalt used is 40g; and in step (3), the amount of solid electrolyte LATP used is 20g.
[0112] A negative electrode material with a surface coated with amorphous carbon (coating amount of 2%, mass percentage) and solid electrolyte LATP (coating amount of 2%, mass percentage) was prepared.
[0113] Example 7
[0114] Compared to Example 1, the only difference is that in step (5), no acid treatment is performed. Instead, 1 kg of graphite raw material is washed with deionized water 2-3 times and vacuum dried at 80°C for 12 hours to obtain dried graphite material.
[0115] A negative electrode material with surface-coated carbon (coating amount of 1%, mass percentage) and solid electrolyte LATP (coating amount of 1%, mass percentage) was prepared.
[0116] Example 8
[0117] (1) Take 995g of water, heat it to 60℃, then add 10g of PVP to the water, stir in a dispersion pan for 5h at a speed of 1000r / min to obtain transparent liquid a.
[0118] (2) Take 40g of asphalt and add it to 500g of adhesive a. Stir in a dispersing pan for 1 hour at a speed of 1000r / min until it is completely dispersed and uniform to obtain slurry b.
[0119] (3) Take 20g of solid electrolyte LATP powder and add it to the remaining 500g of gel solution a. Stir in a dispersion pan for 1 hour at a speed of 1000r / min until it is completely dispersed and uniform to obtain slurry c.
[0120] (4) Mix slurry b and slurry c and stir for 2 hours at a speed of 1000 r / min to obtain mixed slurry d.
[0121] (5) Add 1 kg of silicon carbide material to slurry d and mix it in a VC high-mixing device (vertical axis forced circulation mixing device). Mix at low speed for 5 min at a speed of 400 r / min, and then mix at high speed for 20 min at a speed of 1200 r / min to obtain a mixed slurry.
[0122] (6) The mixed slurry is sintered under an argon atmosphere. It is pre-sintered at 200°C for 30 min to completely remove the solvent (water). It is then sintered at 700°C for 2 h. The resulting black blocky material is ground to obtain a powder material with amorphous carbon (coating amount of 2%, mass percentage) and solid electrolyte LATP (coating amount of 2%, mass percentage) on the surface. This is the negative electrode material of this embodiment.
[0123] Comparative Example 1
[0124] The acid-treated graphite material from Example 1 was directly used as the negative electrode material.
[0125] Comparative Example 2
[0126] Compared to Example 1, the only difference is that step (3) is not involved, and step (1) is:
[0127] Take 495g of water, heat it to 60℃, then add 5g of CMC to the water, stir in a dispersion pan for 5 hours at a speed of 1000r / min to obtain a transparent gel a.
[0128] A negative electrode material with a surface coated with amorphous carbon (coating amount of 1%, mass percentage) was obtained.
[0129] Comparative Example 3
[0130] Compared to Example 1, the only difference is that step (2) is not involved, and step (1) is:
[0131] Take 495g of water, heat it to 60℃, then add 5g of CMC to the water, stir in a dispersion pan for 5 hours at a speed of 1000r / min to obtain a transparent gel a.
[0132] A negative electrode material with a surface coating of solid electrolyte LATP (coating amount of 1%, mass percentage) was prepared.
[0133] Comparative Example 4
[0134] Compared to Example 1, the only difference is that in step (2), the carbon source pitch is replaced with polymethyl methacrylate, and the amount used is 50g.
[0135] A negative electrode material with surface-coated carbon (coating amount of 1%, mass percentage) and solid electrolyte LATP (coating amount of 1%, mass percentage) was prepared.
[0136] Comparative Example 5
[0137] Compared to Example 1, the only difference is that: no dispersant is used, that is, there is no step (1), and the asphalt and solid electrolyte are directly mixed with 500g of water in steps (2) and (3).
[0138] A negative electrode material with surface-coated carbon (coating amount of 1%, mass percentage) and solid electrolyte LATP (coating amount of 1%, mass percentage) was prepared.
[0139] Comparative Example 6
[0140] Compared to Example 1, the only difference is that in step (6), no pre-sintering is performed, and the black blocky material is directly sintered at 700°C for 4 hours, and then ground.
[0141] A negative electrode material with surface-coated carbon (coating amount of 1%, mass percentage) and solid electrolyte LATP (coating amount of 1%, mass percentage) was prepared.
[0142] Comparative Example 7
[0143] The untreated silicon-carbon material from Example 8 was used directly as the negative electrode material.
[0144] Effect Example
[0145] The following performance tests were conducted on the negative electrode materials obtained in Examples 1-8 and Comparative Examples 1-7, respectively:
[0146] 1. Characterization of its own physicochemical parameters
[0147] (1) Morphological characteristics
[0148] The morphology of the negative electrode material obtained in Example 5 was characterized using scanning electron microscopy. The results are as follows: Figure 1 As shown in the figure, the solid electrolyte (white particles) is uniformly coated on the surface of the graphite material.
[0149] (2) Element characterization
[0150] The anode material obtained in Example 5 was characterized by elemental analysis using EDS. The results are as follows: Figure 2 As shown in the figure, the graphite material surface is uniformly coated with LATP solid electrolyte and amorphous carbon (corresponding elements are C, Ti, Al and P).
[0151] In addition, such as Figure 3The image shown is a TEM image of the negative electrode material obtained in Example 7. In the image, the amorphous region on the silicon-carbon surface is the carbon layer, and the lattice fringes are the solid electrolyte. This result indicates that the coating layer is within 100 nm.
[0152] 2. Electrochemical performance characterization
[0153] (1) Preparation of negative electrode
[0154] ① The negative electrode materials obtained from Comparative Examples 1-6 and Implementation Cases 1-7 were respectively made into negative electrode sheets, wherein the formulation of the negative electrode sheet is: negative electrode material: SP: CMC: SBR = 95.6%: 1.0%: 1.6%: 1.8%, and the coating density is 5 mg / cm². 2 The compaction density is 1.6 mg / cm³. 3 .
[0155] ② The negative electrode materials obtained in Comparative Example 7 and Example 8 were respectively made into negative electrode sheets, wherein the formulation of the negative electrode sheet is: negative electrode material: SP:SWCNT:CMC:SBR:PAA = 80.9%:2%:0.1%:2%:5%:10%, and the coating density is 3mg / cm². 2 The compaction density is 1.1 mg / cm³. 3 .
[0156] ③ By mass percentage, 85% untreated graphite (or graphite-containing anode material) and 15% untreated silicon-carbon (or silicon-carbon-containing anode material) are mixed to prepare a negative electrode sheet. The formulation of the negative electrode sheet is: main material: SP:SWCNT:CMC:SBR:PAA = 94.9%:1%:0.1%:0.3%:1.2%:2.5%, and the coating density is 3 mg / cm². 2 The compaction density is 1.6 mg / cm³. 3 Formula 1 consists of 85% of the negative electrode material (containing graphite) from Example 1 and the negative electrode material (containing silicon carbon) from Example 8. Formula 2 consists of the negative electrode material (i.e., graphite material) from Comparative Example 1 and the negative electrode material (i.e., silicon carbon material) from Comparative Example 7.
[0157] (2) Surface density and compaction density test
[0158] Areal density test method: The obtained negative electrode sheet is punched into a disc with a diameter of 16mm using a button punching machine, and the mass is weighed. The areal density of the coating is calculated using the following formula: Coating areal density = (mass of coated disc - mass of copper foil disc) / 2.0096;
[0159] Compaction density test method: Measure the thickness of the negative electrode sheet and the thickness of the copper foil after rolling, and calculate the electrode sheet compaction density using the following formula: Electrode sheet compaction density = Coating surface density / (Electrode sheet thickness - Copper foil thickness).
[0160] (3) Button assembly
[0161] The corresponding negative electrode sheets are assembled into corresponding lithium-ion batteries, wherein: the counter electrode is a lithium metal disc with a diameter of 18mm; the solid electrolyte membrane is a polymer / oxide composite film (PVDF-HFP-75% / LLZO-25%).
[0162] (4) Electrical performance test
[0163] The lithium-ion batteries obtained in (3) were subjected to the following parameter measurements:
[0164] Specific capacity test: Discharge 0.1C to 50mV, cut-off current 0.05C, charge 0.1C to 2V, and divide the obtained capacity by the mass of graphite in the negative electrode.
[0165] First-efficiency test: Using the above capacity test method, measure the charging capacity and discharging capacity, and calculate the first-efficiency according to the formula: First-efficiency = Charging capacity / Discharging capacity;
[0166] Capacity retention rate test: 1C retention rate = 1C charging capacity / 0.1C charging capacity; 2C retention rate = 2C charging capacity / 0.1C charging capacity; 0.33C retention rate = 0.33C charging capacity / 0.1C charging capacity; 0.5C retention rate = 0.5C charging capacity / 0.1C charging capacity.
[0167] The test results are shown in Tables 1-2 and Figures 4-5 As shown.
[0168] Table 1
[0169]
[0170] Table 2
[0171]
[0172] The results show that:
[0173] When graphite is used as the matrix material, the negative electrode material obtained in the examples, when used in a battery, can simultaneously guarantee: a 0.1C specific capacity of not less than 345 mAh / g, an initial efficiency of not less than 93%, a 1C capacity retention rate of not less than 88.5%, and a 2C capacity retention rate of not less than 86%. Preferably, when the graphite material involves acid treatment, the resulting negative electrode material, when used in a battery, can simultaneously guarantee: a 0.1C specific capacity of not less than 350 mAh / g, an initial efficiency of not less than 93%, a 1C capacity retention rate of not less than 97%, and a 2C capacity retention rate of not less than 94%.
[0174] Compared to Example 1, in Comparative Example 1, when only untreated graphite material was used as the negative electrode material, the specific capacity, initial efficiency, 1C capacity retention rate, and 2C capacity retention rate of the resulting battery were all significantly reduced; in Comparative Example 2, when only carbon-coated negative electrode material was used in the battery, the 1C capacity retention rate and 2C capacity retention rate were still significantly reduced; in Comparative Example 3, when only solid electrolyte-coated negative electrode material was used in the battery, the specific capacity, initial efficiency, 1C capacity retention rate, and 2C capacity retention rate were all significantly reduced; in Comparative Examples 4-6, when the type of carbon source was changed and no dispersant was involved, the specific capacity, initial efficiency, 1C capacity retention rate, and 2C capacity retention rate were all significantly reduced.
[0175] When silicon-carbon material is used as the matrix material, the negative electrode material obtained in the example can simultaneously guarantee the following when used in a battery: 0.1C specific capacity not less than 1900mAh / g, first efficiency not less than 92%, 0.33C capacity retention rate not less than 84%, and 0.5C capacity retention rate not less than 80%.
[0176] Compared to Example 8, in Comparative Example 7, when only untreated silicon-carbon material was used as the negative electrode material, the specific capacity, initial efficiency, 0.33C capacity retention rate, and 0.5C capacity retention rate of the resulting battery were significantly reduced.
[0177] In addition, such as Figures 4-5 The results showed that the cycle stability of the battery obtained by Formula 2 (the negative electrode material in Example 1 and the negative electrode material in Example 8) was significantly higher than that of Formula 1 (the negative electrode material in Comparative Example 1 and the negative electrode material in Comparative Example 7).
[0178] In summary, the coating modification method of the present invention can simultaneously construct a "carbon layer-solid electrolyte" dual continuous coating structure and achieve in-situ uniform coating, while effectively improving the electronic and ion conduction properties of the obtained negative electrode material. When applied to lithium-ion batteries, it improves the interfacial bonding force and thus effectively enhances the comprehensive electrochemical performance of the obtained battery, such as rate performance, energy density, and cycle performance, especially cycle performance.
Claims
1. A method for preparing a negative electrode material, characterized in that, The preparation method of the negative electrode material includes the following steps: The negative electrode material is prepared by pre-sintering and sintering a mixed slurry containing a matrix material, a carbon source, a solid electrolyte, a dispersant, and water; wherein, The carbon source includes bitumen; The dispersant includes a hydrophilic polymer; The pre-sintering temperature is lower than the sintering temperature.
2. The method for preparing the negative electrode material as described in claim 1, characterized in that, The matrix material includes one or more of graphite materials, pure carbon materials, and silicon carbide materials; Preferably, the method for preparing the negative electrode material satisfies one or more of the following conditions: (1) The graphite material is a graphite raw material without any surface treatment or is obtained by acid treatment of the graphite raw material; The graphite raw material is, for example, artificial graphite and / or natural graphite; the particle size D50 of the graphite raw material is, for example, 8-35 μm; Preferably, the acid treatment is performed using an acid; Furthermore, the acid preferably includes one or more of hydrochloric acid, nitric acid, and sulfuric acid; Furthermore, the concentration of the acid is preferably 0.5-1.5 mol / L, for example 1 mol / L; Furthermore, the preferred mass ratio of the acid to the graphite material is (2-5):1; Preferably, the acid treatment step includes adding the graphite raw material to the acid, followed by stirring and washing; Preferably, the acid treatment also includes a drying step; (2) The pure carbon material is hard carbon and / or soft carbon; (3) The particle size D50 of the pure carbon material is 8-35 μm; (4) The silicon-carbon material is a CVD silicon-carbon material; (5) The particle size D50 of the silicon carbide material is 8-10 μm.
3. The method for preparing the negative electrode material as described in claim 1, characterized in that, The preparation method of the negative electrode material satisfies one or more of the following conditions: (1) The mass percentage of the carbon source and the matrix material is 0.5%-10%, for example 2% or 4%; (2) The solid electrolyte includes sulfide-type electrolytes and / or oxide-type electrolytes; (3) The solid electrolyte includes NASICON-type electrolytes, preferably one or more of LATP, LAGP and LAGTP; Among them, the composition of the LATP is preferably Li 1.7 Al (x) Ti (2-x) (PO4)3, 0 < x ≤ 0.6, for example, Li 1.3 Al 0.3 Ti 1.7 (PO4)3; Among them, the composition of the LAGP is preferably Li (1+x) Al (x) Ge (2-x) (PO4)3, 0 < x ≤ 0.6, for example, Li 1.5 Al 0.5 Ge 1.5 (PO4)3; Among them, the composition of the LAGTP is preferably Li 1.5 Al 0.5 Ti x Ge 1.5-x (PO4)3, 0 < x ≤ 0.4, for example Li 1.5 Al 0.5 Ti 0.1 Ge 1.4 (PO4)3; When the solid electrolyte is LATP and LAGP, the mass ratio of LATP to LAGP is, for example, 1:
1. (4) The mass percentage of the solid electrolyte and the matrix material is 0.5%-10%, for example 1% or 2%; (5) The particle size of the solid electrolyte is 5-100 nm.
4. The method for preparing the negative electrode material as described in claim 1, characterized in that, The preparation method of the negative electrode material satisfies one or two of the following conditions: (1) The dispersant is one or more of sodium carboxymethyl cellulose, polyvinylpyrrolidone, hydroxyethyl cellulose, sodium polyacrylate, polyethylene glycol and polyacrylamide; (2) The mass percentage of the dispersant and the matrix material is 0.5%-10%, for example 1%.
5. The method for preparing the negative electrode material as described in claim 1, characterized in that, The preparation of the mixed slurry includes the following steps: (1) Mix the dispersant with water to obtain solution a; (2) Take a portion of the adhesive solution a and the carbon source and mix them to obtain slurry b; (3) Take the remaining adhesive solution a and the solid electrolyte and mix them to obtain slurry c; (4) Mix the slurry b and slurry c to obtain slurry d; (5) Mix the matrix material and the slurry d to obtain the final product.
6. The method for preparing the negative electrode material as described in claim 1, characterized in that, The preparation method of the negative electrode material satisfies one or more of the following conditions: (1) The pre-sintering temperature is 150-200℃; (2) The heating rate before pre-sintering is 5-10℃ / min; (3) The pre-sintering time is 0.5-2 hours; (4) The pre-sintering step is carried out in an inert atmosphere, such as nitrogen and / or argon.
7. The method for preparing the negative electrode material as described in claim 1, characterized in that, The preparation method of the negative electrode material satisfies one or more of the following conditions: (1) The sintering temperature is 600-1500℃, for example 700℃; (2) The heating rate before sintering is 5-10℃ / min; (3) The sintering time is 1-4 hours, for example, 2 hours; (4) The sintering step is carried out in an inert atmosphere; the inert atmosphere is, for example, nitrogen and / or argon. (5) The sintering step is followed by a grinding step.
8. A negative electrode material, characterized in that, The negative electrode material is prepared by the method for preparing the negative electrode material as described in any one of claims 1-7.
9. The negative electrode material as described in claim 8, characterized in that, The negative electrode material includes a matrix material and a coating layer covering the surface of the matrix material, wherein the coating layer includes amorphous carbon and solid electrolyte; Preferably, the method for preparing the negative electrode material satisfies one or more of the following conditions: (1) The content of the amorphous carbon is 1%-10%, for example 2%; the percentage is the mass percentage of the amorphous carbon and the negative electrode material; (2) The content of the solid electrolyte is 0.5%-10%, for example 1% or 2%; the percentage is the mass percentage of the solid electrolyte and the negative electrode material; (3) The thickness of the coating layer is 1-100 nm.
10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the negative electrode material as described in claim 8 or 9.