Graphite composite negative electrode material and preparation method thereof, negative electrode sheet and lithium battery
By preparing silver-doped graphite composite materials, combined with alumina coating and amorphous carbon, a composite structure is formed with silver-doped graphite as the core and lithium aluminate and amorphous carbon as the shell. This solves the problem of balancing fast-charging performance, conductivity, energy density and cycle performance of lithium-ion battery anode materials, and achieves high conductivity and efficient electrolyte absorption capacity of the material.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JEREH NEW ENERGY TECH CO LTD
- Filing Date
- 2023-01-09
- Publication Date
- 2026-06-05
AI Technical Summary
Existing lithium-ion battery anode materials, while improving fast charging performance, struggle to simultaneously maintain conductivity, energy density, cycle performance, and rate performance.
A silver-doped graphite composite material was formed by hydrothermal reaction of silver ammonia solution with porous graphite, and then coated with aluminum salt solution to form aluminum oxide coating. Combined with amorphous carbon and inorganic lithium compounds, a composite structure with silver-doped graphite as the core and lithium aluminate and amorphous carbon as the shell was prepared.
It significantly improves the electronic conductivity and tap density of graphite composite anode materials, enhances the electrolyte absorption rate and retention rate, and improves cycle performance, rate performance and first charge-discharge performance.
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Figure CN115954455B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of lithium-ion batteries, and in particular to a graphite composite anode material and its preparation method, as well as an anode sheet and a lithium battery. Background Technology
[0002] As the market demands higher fast-charging performance for lithium-ion batteries, the negative electrode materials used in lithium-ion batteries must not only have fast-charging performance, but also good conductivity, energy density, and cycle performance.
[0003] Currently, the main measures to improve the fast-charging performance of materials are as follows: 1) Reducing the primary particle size / finished particle size of the material to control particle size distribution, but this affects energy density; 2) Coating the material surface with amorphous carbon to improve the diffusion rate of the material, but this reduces energy density and high-temperature performance; 3) Doping the material with metals, oxides, and fast ion conductors with high electronic conductivity to improve the lithium-ion exchange rate during charging and discharging, thereby improving rate performance. However, due to the poor electronic conductivity of inorganic lithium compounds, they often need to be mixed with amorphous carbon with high electronic conductivity to improve ionic and electronic conductivity and improve the rate performance of the material. However, the above improvements have limited effect on the conductivity, energy density, rate performance, and cycle performance of anode materials, and still cannot meet the requirements of lithium battery anode materials. Summary of the Invention
[0004] In view of this, the purpose of this application is to provide a graphite composite anode material and a method for preparing the same, so that the graphite composite anode material can improve the conductivity and tap density.
[0005] The purpose of this application is to provide a graphite composite anode material and its preparation method, which enables the graphite composite anode material to improve the electrolyte absorption rate and electrolyte retention rate.
[0006] The purpose of this application is to provide a graphite composite anode material and its preparation method, so that the graphite composite anode material can improve the cycle performance, rate performance and first charge-discharge performance of the battery.
[0007] Another objective of this application is to provide a negative electrode sheet and a lithium battery based on the above-mentioned graphite composite negative electrode material.
[0008] To solve the aforementioned technical problems / achieve the aforementioned objectives, or at least partially solve the aforementioned technical problems / achieve the aforementioned objectives, as a first aspect of this application, a method for preparing a graphite composite anode material is provided, comprising:
[0009] A silver-doped graphite composite material was obtained by hydrothermal reaction of silver ammonia solution and porous graphite solution.
[0010] The aluminum salt solution and the silver-doped graphite composite material are evenly dispersed, filtered, and then sintered to obtain an alumina-coated silver-doped graphite composite material.
[0011] The alumina-coated silver-doped graphite composite material, amorphous carbon source, inorganic lithium compound, and conductive agent are uniformly dispersed in an organic solvent, spray-dried, and then carbonized to obtain the graphite composite anode material.
[0012] Optionally, the mass ratio of silver ions to porous graphite in the silver ammonia solution is (4.65-7.45):100.
[0013] Optionally, the mass-to-volume ratio of aluminum salt to solvent in the aluminum salt solution is (1-10) g: 100 mL; further optionally, the aluminum salt includes one or more of aluminum nitrate, aluminum sulfate, and aluminum chloride.
[0014] Optionally, the mass ratio of the alumina-coated silver-doped graphite composite material to the amorphous carbon source, inorganic lithium compound, and conductive agent is 100:(1-5):(1-10):(0.5-2); further optionally, the amorphous carbon source includes one or more of petroleum asphalt, coal tar pitch, phenolic resin, furfural resin, and epoxy resin, the inorganic lithium compound includes one or more of lithium oxide, lithium hydroxide, and lithium carbonate, and the conductive agent includes carbon nanotubes.
[0015] As a second aspect of this application, a graphite composite anode material prepared by the preparation method described in this application is provided, which includes a core and a shell, wherein the core is a silver-doped graphite composite material and the shell includes lithium aluminate and amorphous carbon.
[0016] As a third aspect of this application, a negative electrode sheet is provided, which is a graphite composite negative electrode material prepared by the preparation method described in this application or uses the graphite composite negative electrode material described in this application as an active material.
[0017] As a fourth aspect of this application, a lithium battery is provided, which includes a positive electrode, a separator, an electrolyte, and the negative electrode described in this application.
[0018] This application improves the electronic conductivity of graphite by uniformly depositing silver on the surface and inside of porous graphite through a silver-ammonia reaction. On the one hand, it leverages the high specific capacity and high porosity of the core graphite, and on the other hand, silver has high electronic conductivity. Filling the pores of porous graphite reduces side reactions and improves electronic conductivity, resulting in a silver-doped graphite composite.
[0019] In addition, this application first coats the surface of silver-doped graphite composite material with alumina by liquid phase coating method, and then reacts it with inorganic lithium compound at high temperature to obtain lithium aluminate, which has the characteristics of high ionic conductivity. At the same time, carbonization of carbon source to obtain amorphous carbon can improve the electronic conductivity of lithium aluminate, so that it can give full play to the characteristics of high outer electron and ionic conductivity, and improve the fast charging performance of the material. Attached Figure Description
[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application.
[0021] Figure 1 The diagram shown is a structural schematic of the graphite composite anode material described in this application.
[0022] Figure 2 The image shown is a SEM image of the graphite composite anode material described in this application. Detailed Implementation
[0023] This application discloses a graphite composite anode material and its preparation method, as well as an anode sheet and a lithium battery. Those skilled in the art can refer to the content of this application and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this application. The products, processes, and applications described in this application have been described through preferred embodiments. Those skilled in the art can obviously modify or appropriately change and combine the methods described herein without departing from the content, spirit, and scope of this application to realize and apply the technology of this application. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.
[0024] It should be noted that, in this document, relational terms such as "first" and "second," "step 1" and "step 2," and "(1)" and "(2)" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Moreover, the embodiments and features described in this application can be combined with each other without conflict.
[0025] In the first aspect of this application, a method for preparing a graphite composite anode material is provided, comprising:
[0026] A silver-doped graphite composite material was obtained by hydrothermal reaction of silver ammonia solution and porous graphite solution.
[0027] The aluminum salt solution and the silver-doped graphite composite material are evenly dispersed, filtered, and then sintered to obtain an alumina-coated silver-doped graphite composite material.
[0028] The alumina-coated silver-doped graphite composite material, amorphous carbon source, inorganic lithium compound, and conductive agent are uniformly dispersed in an organic solvent, spray-dried, and then carbonized to obtain the graphite composite anode material.
[0029] In some embodiments of this application, the mass ratio of silver ions to porous graphite in the silver ammonia solution is (4.65-7.45):100.
[0030] In some embodiments of this application, the silver ammonia solution is obtained by reacting silver oxide and ammonia in an organic solvent, such as ethanol, with the mass ratio of silver oxide:ammonia:organic solvent being (5-8):200:(1000-5000), specifically 6:200:3000, 2:200:1000, or 8:200:5000.
[0031] In some embodiments of this application, the porous graphite solution is prepared using an organic solvent, including formaldehyde. In other embodiments of this application, the porous graphite can be prepared as follows:
[0032] Mix 100 parts of graphite with 1-10 parts of ferric acetate evenly, heat to 600-800℃ under a protective gas and hold for 1-6 hours, then cool naturally to room temperature, acid wash, and wash with deionized water to obtain porous graphite.
[0033] In some embodiments of this application, the hydrothermal reaction is performed using a microwave hydrothermal method; in other embodiments of this application, the microwave heating parameters are 650W-850W.
[0034] In some embodiments of this application, the silver-doped graphite composite material is first prepared by reacting silver oxide and ammonia in ethanol to obtain a silver ammonia solution, which is then mixed with a formaldehyde solution of porous graphite and subjected to a microwave hydrothermal reaction at a temperature of 150-240°C for 180-240 min. After centrifugation for 2-3 h, the mixture is washed with deionized water and dried to obtain the silver-doped graphite composite material. The mass ratio of silver oxide to porous graphite is (5-8):100, and the molar ratio of silver oxide to formaldehyde is 1:(1-2).
[0035] In some embodiments of this application, the mass-to-volume ratio of aluminum salt to solvent in the aluminum salt solution is (1-10) g:100 mL, for example, 1 g:100 mL, 5 g:100 mL, or 10 g:100 mL; in other embodiments of this application, the aluminum salt includes one or more of aluminum nitrate, aluminum sulfate, and aluminum chloride; and the solvent includes one or more of chloroform, acetone, diethyl ether, n-hexane, and trichloroethylene.
[0036] In some embodiments of this application, the mass ratio of the alumina-coated silver-doped graphite composite material to the amorphous carbon source to the inorganic lithium compound to the conductive agent is 100:(1-5):(1-10):(0.5-2); in other embodiments of this application, the mass ratio of the alumina-coated silver-doped graphite composite material to the amorphous carbon source to the inorganic lithium compound to the conductive agent is 100:5:10:2, 100:1:1:0.5, or 100:3:5:1.
[0037] In some embodiments of this application, the sintering is performed at 400-600℃ for 1-10 hours, wherein the temperature can be selected from 400℃, 450℃, 500℃, 550℃ or 600℃, and the sintering time can be selected from 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours.
[0038] In some embodiments of this application, the alumina-coated silver-doped graphite composite material, the amorphous carbon source, the inorganic lithium compound, and the conductive agent are uniformly dispersed in one or more organic solvents selected from chloroform, acetone, diethyl ether, n-hexane, and trichloroethylene. In other embodiments of this application, the total weight percentage of the alumina-coated silver-doped graphite composite material and the amorphous carbon source to the organic solvent is 1-10%, for example, 1%, 2%, 3%, 4%, 4.9%, 5%, 6%, 7%, 8%, 9%, or 10%.
[0039] In some embodiments of this application, the amorphous carbon source includes one or more of petroleum asphalt, coal tar pitch, phenolic resin, furfural resin, and epoxy resin, and the inorganic lithium compound includes one or more of lithium oxide, lithium hydroxide, and lithium carbonate.
[0040] In some embodiments of this application, the conductive agent includes carbon nanotubes. Compared with other conductive agents, carbon nanotubes can significantly reduce the internal resistance of the battery, improve the fast charging efficiency and high-rate discharge performance of the battery; enable the battery electrode to have higher liquid absorption and better liquid retention capacity; uniformly coat the surface of the active material to build a rich three-dimensional conductive network with better conductivity; and achieve the same conductivity as other conductive agents with a smaller amount.
[0041] In some embodiments of this application, the carbonization treatment temperature is 950-1250℃, and the holding time is 2-3 hours. In other embodiments of this application, the carbonization treatment temperature can be selected as 950℃, 1150℃, or 1250℃, and the holding time is 2 hours or 3 hours.
[0042] As a second aspect of this application, a graphite composite anode material prepared by the preparation method described in this application is provided, comprising a core and a shell. The core is a silver-doped graphite composite material, and the shell comprises lithium aluminate and amorphous carbon, which are interleaved to form the shell. A schematic diagram of the structure is shown below. Figure 1 SEM image (see) Figure 2 The particle size is between 10-15 μm, with a reasonable particle size distribution, and a small number of bright spots are present on the material surface, exhibiting a slight granulation structure. In some embodiments of this application, multiple comparative tests have demonstrated that the graphite composite anode material described in this application can significantly improve conductivity and tap density, while also possessing high liquid absorption rate, liquid retention rate, initial charge-discharge performance, rate performance (fast charging performance), and cycle performance.
[0043] In a third aspect of this application, a negative electrode sheet is provided, which is a graphite composite negative electrode material prepared by the preparation method described in this application, or uses the graphite composite negative electrode material described in this application as an active material.
[0044] In some embodiments of this application, the negative electrode sheet includes a current collector and an active material coated on the current collector; wherein, the current collector may be selected from a metal foil with good conductivity, such as copper foil or aluminum foil; the active material includes the graphite composite negative electrode material described in this application, as well as a binder and a conductive agent, etc., and the binder, conductive agent and solvent and their amounts are selected in accordance with conventional methods, and this application does not impose specific limitations, for example, the binder is styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC), and the conductive agent is conductive carbon black (SP).
[0045] In a fourth aspect of this application, a lithium battery is provided, including a positive electrode, a separator, an electrolyte, and the negative electrode described in this application; in some embodiments of this application, the lithium-ion battery is a full cell, a pouch cell, or a button cell.
[0046] In some embodiments of this application, the positive electrode is a lithium metal sheet or an electrode made of lithium iron phosphate, high-nickel ternary, lithium-rich manganese-based material, or ternary lithium material; the separator is a Celegard separator; the electrolyte is a LiPF6 solution, for example, an electrolyte with a volume ratio of 1:1 of ethylene carbonate (EC) and diethyl carbonate (DEC) as solvents and a LiPF6 concentration of 1.0-1.5 mol / L; or an electrolyte with a volume ratio of 1:1:1 of ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) as solvents and a LiPF6 concentration of 1.0-1.5 mol / L.
[0047] In the comparative experiments provided in this application, unless otherwise specified, all experimental conditions and materials remain consistent to ensure comparability. Furthermore, all materials used in this application are commercially available.
[0048] The following provides a further description of a graphite composite anode material, its preparation method, anode sheet, and lithium battery provided in this application.
[0049] Example 1:
[0050] 100g of artificial graphite and 5g of ferric acetate were mixed evenly and heated to 700℃ for 3h under argon atmosphere. The mixture was then allowed to cool naturally to room temperature, and the mixture was acid-washed with 0.1mol / L acetic acid and washed with deionized water to obtain porous graphite material.
[0051] Weigh 6g of silver oxide and 200g of ammonia water and mix with 3000g of ethanol to obtain a silver ammonia solution; mix this silver ammonia solution with 100g of porous graphite and 1.56g of formaldehyde solution (formaldehyde mass percentage 50%) and microwave heat (parameters 750w, heating to 200℃, reaction for 210min), centrifuge for 3h, wash and dry to obtain silver-doped graphite composite material.
[0052] 5g of aluminum nitrate was added to 100ml of chloroform to prepare a 5% (W / V) aluminum nitrate solution. Then, 100g of silver-doped graphite composite material was added, dispersed evenly, filtered, and sintered at 500℃ for 1h to obtain silver-doped graphite composite material coated with alumina.
[0053] 100g of alumina-coated silver-doped graphite composite material and 3g of petroleum asphalt were added to 2000g of chloroform and dispersed evenly to prepare a 4.9wt% solution. Then, 5g of lithium carbonate and 1g of carbon nanotubes were added and dispersed evenly. The mixture was then spray-dried and carbonized at 1150℃ for 3h under an argon atmosphere to obtain a lithium aluminate / amorphous carbon-coated silver-doped graphite composite material.
[0054] Example 2:
[0055] 100g of artificial graphite and 1g of ferric acetate were mixed evenly and then heated to 600℃ for 6h under an argon atmosphere. The mixture was then allowed to cool naturally to room temperature, and the mixture was acid-washed with 0.1mol / L acetic acid and washed with deionized water to obtain porous graphite material.
[0056] 5g of silver oxide, 200g of ammonia water and 1000g of ethanol were mixed evenly to obtain a silver ammonia solution; then this silver ammonia solution was mixed with 100g of porous graphite and 2.42g of formaldehyde solution (formaldehyde mass percentage 50%) and microwave heated (parameters 650w, heated to 150℃, reaction for 240min), centrifuged for 2h, washed and dried to obtain silver-doped graphite composite material.
[0057] 5g of aluminum sulfate was added to 500ml of acetone organic solvent to prepare a 1% (W / V) aluminum salt solution. Then, 100g of silver-doped graphite composite material was added, dispersed evenly, filtered, and sintered at 400℃ for 6h to obtain silver-doped graphite composite material coated with alumina.
[0058] Then, 100g of alumina-coated silver-doped graphite composite material and 1g of coal tar pitch were added to 9999g of acetone organic solvent and dispersed evenly to prepare 1wt%. Then, 1g of lithium hydroxide and 0.5g of carbon nanotubes were added and dispersed evenly. After spray drying, the mixture was carbonized at 950℃ for 3h under argon atmosphere to obtain lithium aluminate / amorphous carbon-coated silver-doped graphite composite material.
[0059] Example 3:
[0060] 100g of artificial graphite and 10g of ferric acetate were mixed evenly and heated to 800℃ for 1 hour under an argon atmosphere. The mixture was then allowed to cool naturally to room temperature, and the mixture was acid-washed with 0.1mol / L acetic acid and washed with deionized water to obtain porous graphite material.
[0061] Silver ammonia solution was obtained by mixing 8g of silver oxide, 200g of ammonia solution, and 5000g of ethanol. This silver ammonia solution was then mixed with 100g of porous graphite and 3.9g of formaldehyde solution (formaldehyde mass percentage 50%) and microwaved (parameters: 850w, heated to 240℃, reaction time: 180min). After centrifugation for 3h, the mixture was washed and dried to obtain silver-doped graphite composite material.
[0062] 5g of aluminum chloride was added to 50ml of n-hexane organic solvent to prepare a 10% (W / V) aluminum salt solution. Then, 100g of silver-doped graphite composite material was added, dispersed evenly, filtered, and sintered at 600℃ for 1h to obtain silver-doped graphite composite material coated with alumina.
[0063] Then, 100g of alumina-coated silver-doped graphite composite material and 5g of furfural resin were added to 945g of n-hexane organic solvent and dispersed evenly to prepare 10wt%. Then, 10g of lithium oxide and 2g of carbon nanotubes were added and dispersed evenly. After spray drying, the mixture was carbonized at 1250℃ for 2h under an inert atmosphere to obtain lithium aluminate / amorphous carbon-coated silver-doped graphite composite material.
[0064] Comparative Example 1:
[0065] Take 100g of the silver-doped graphite composite material prepared in Example 3, add 5g of furfural resin to 945g of n-hexane organic solvent and disperse evenly to prepare 10wt%, then add 2g of carbon nanotubes, disperse evenly, spray dry, and carbonize at 1250℃ for 2h under an inert atmosphere to obtain amorphous carbon-coated silver-doped graphite composite material.
[0066] Comparative Example 2:
[0067] Referring to the process in Example 1, the difference lies in using artificial graphite instead of silver-doped graphite composite material to prepare alumina-coated graphite composite material:
[0068] 5g of aluminum nitrate was added to 100ml of chloroform to prepare a 5% aluminum nitrate solution. Then, 100g of artificial graphite was added, dispersed evenly, filtered, and sintered at 500℃ for 1h to obtain an alumina-coated graphite composite material.
[0069] 100g of alumina-coated silver-doped graphite composite material and 3g of petroleum pitch were added to 2000g of chloroform and dispersed evenly to prepare a 4.9wt% solution. Then, 5g of lithium carbonate and 1g of carbon nanotubes were added and dispersed evenly. The mixture was then spray-dried and carbonized at 1150℃ for 3h under an argon atmosphere to obtain a lithium aluminate / amorphous carbon-coated graphite composite material.
[0070] Comparative Example 3:
[0071] The process is the same as in Example 3, except that 5.5g of aluminum chloride is added to 50ml of n-hexane organic solvent to prepare an 11% aluminum salt solution, while the rest remains the same.
[0072] Comparative Example 4:
[0073] Referring to the process in Example 1, the difference is that zinc oxide is used instead of silver oxide to form a zinc ammonia solution to prepare a zinc-doped graphite composite material, which then participates in subsequent preparation processes. All other aspects remain the same.
[0074] Weigh 6g Zn(OH)2 and 200g ammonia solvent and mix with 3000g ethanol to obtain a zinc-ammonia complex solution; mix this zinc-ammonia solution with 100g porous graphite and 1.56g formaldehyde solution (formaldehyde mass percentage 50%) and microwave heat (parameters 750w, heating to 200℃, reaction for 210min), centrifuge, wash, and dry to obtain zinc-doped graphite composite material.
[0075] Experimental Example 1:
[0076] 1. SEM testing
[0077] The lithium aluminate / amorphous carbon-coated silver-doped graphite composite material prepared in Example 1 was subjected to SEM testing, and the results are as follows: Figure 2 As shown. By Figure 2 It can be seen that the particle size is between 10-15μm, the particle size distribution is reasonable, and there are a few bright spots on the surface of the material, as well as a slight granulation structure.
[0078] 2. Physicochemical property testing
[0079] The conductivity, tap density, specific surface area, and particle size of the graphite composite anode materials in Examples 1-3 and Comparative Examples 1-4 were tested according to the test methods in standard GB / T-24533-2019 "Graphite Anode Materials for Lithium-ion Batteries". The test results are shown in Table 1.
[0080] Table 1
[0081]
[0082]
[0083] As can be seen from Table 1, the electrical conductivity of the lithium aluminate / amorphous carbon-coated silver-doped graphite composite materials prepared in Examples 1-3 is significantly higher than that of Comparative Examples 1-4 by an order of magnitude. This may be because the surface of the materials in the examples is coated with silver, which has high electronic conductivity, reducing impedance and increasing specific surface area. At the same time, the outer lithium aluminate has a high tap density, which increases the tap density of the composite material.
[0084] Furthermore, the comparison results of Examples 1-3 and Comparative Example 3 show that when the concentration of aluminum salt solution exceeds 10%, the silver doping to improve the electronic conductivity of the core graphite and the lithium aluminate of the outer shell to improve the ionic conductivity of the material cannot exert the best synergistic effect between the two, and the conductivity is significantly lower than that of the materials in the examples.
[0085] 3. Button cell battery test
[0086] The lithium aluminate-coated silver-doped graphite composite materials prepared in Examples 1-3 and the graphite composite anode materials of Comparative Examples 1, 2, and 4 were assembled into coin cells according to the following methods:
[0087] The graphite composite anode materials prepared in Examples 1-3 and Comparative Examples 1, 2, and 4 were used as anodes and assembled into coin cells with lithium sheets, electrolytes, and separators in a glove box with argon and water contents both below 0.1 ppm. The separator was Celegard 2400; the electrolyte was a LiPF6 solution with a LiPF6 concentration of 1 mol / L, and the solvent was a mixed solution of ethylene carbonate (EC) and diethyl carbonate (DMC) at a weight ratio of 1:1.
[0088] The fabricated coin cells were tested using a blue-light tester. The test conditions were: 0.1C charge-discharge rate, voltage range of 0.05-2V, 3 cycles, followed by testing the discharge capacity at 1C, and the 1C / 0.1C rate performance was calculated. The test results are shown in Table 2.
[0089] Table 2
[0090] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 4 Initial discharge capacity (mAh / g) 365.9 362.6 366.3 355.9 353.2 354.6 First-time efficiency (%) 96.9 96.5 97.1 92.3 94.4 94.3 Rate performance (1C / 0.1C) 59.7％ 57.8％ 54.9％ 36.8％ 42.5％ 46.3％
[0091] As shown in Table 2, the coin cells prepared using the lithium aluminate / amorphous carbon-coated silver-doped graphite composite materials of Examples 1-3 exhibit significantly higher discharge capacity and efficiency than those of Comparative Examples 1, 2, and 4. The experimental results demonstrate that the lithium aluminate / amorphous carbon-coated silver-doped graphite composite material of this application enables the battery to possess excellent discharge capacity and efficiency. This is because the high lithium-ion conductivity of lithium aluminate coated on the graphite surface reduces its irreversible capacity, improving the initial efficiency and specific capacity. Simultaneously, silver doping enhances the electronic conductivity of the material, thereby improving rate performance.
[0092] 4. Soft-pack battery test
[0093] Using the graphite composite anode materials of Examples 1-3 and Comparative Examples 1-4 as the anode active materials, and the positive electrode active material ternary material (LiNi) 1 / 3 Co 1 / 3 Mn 1 / 3 O2), electrolyte, and separator are assembled into a 5Ah pouch battery.
[0094] The diaphragm is Celegard 2400, and the electrolyte is a LiPF6 solution (the solvent is a 1:1 volume ratio of EC and DEC, and the concentration of LiPF6 is 1.3 mol / L).
[0095] In Examples 1-3 and Comparative Examples 1-4, 5Ah soft-pack batteries and their corresponding negative electrode sheets were prepared, and their liquid absorption and retention capacity and cycle performance were tested. The results are shown in Tables 3-4.
[0096] The testing method is as follows:
[0097] 1) Liquid absorption capacity:
[0098] Using a 1 mL burette, a volume of electrolyte (V mL) was drawn and a drop was added to the electrode surface. Timing was maintained until the electrolyte was completely absorbed, and the time (t) was recorded. The absorption rate of the electrode (V / t) was then calculated. The test results are shown in Table 3.
[0099] 2) Liquid retention rate test:
[0100] The theoretical liquid absorption capacity m1 of the electrode was calculated based on the electrode parameters, and the weight m2 of the electrode was measured. The electrode was then immersed in the electrolyte for 24 hours, and its weight m3 was measured. The liquid absorption capacity m3-m2 was calculated, and the liquid retention rate was calculated using the following formula: Liquid retention rate = (m3-m2)*100% / m1. The test results are shown in Table 3.
[0101] 1) Cyclic performance: The cycle performance of the battery was tested at a charge / discharge rate of 1C / 1C and a voltage range of 2.5V-4.2V at a temperature of 25±3℃; the test results are shown in Table 4.
[0102] 2) Rate performance: The battery was charged to 100% SOC using a 2C rate and constant current + constant voltage mode. The constant current ratio was then calculated as constant current capacity / (constant current capacity + constant voltage capacity). The test results are shown in Table 4.
[0103] Table 3
[0104] Negative electrode sheet Aspiration rate (mL / min) Electrolyte retention rate (24h electrolyte volume / 0h electrolyte volume) Example 1 5.1 93.3％ Example 2 4.9 92.8％ Example 3 5.2 93.8％ Comparative Example 1 2.8 87.8％ Comparative Example 2 3.3 89.6％ Comparative Example 4 4.1 90.2％
[0105] As can be seen from Table 3, the liquid absorption and retention capabilities of the lithium aluminate / amorphous carbon-coated silver-doped graphite composite materials obtained in Examples 1-3 are significantly higher than those in Comparative Examples 1, 2, and 4, indicating that the graphite composite anode material of this application has a high specific surface area and a porous structure, which enhances the liquid absorption capability of the material.
[0106] Table 4
[0107]
[0108]
[0109] As shown in Table 4, the cycle performance of the battery in the example is significantly better than that of Comparative Examples 1, 2, and 4, and better than that of Comparative Example 3. The reason is that the graphite composite negative electrode material obtained in the example is coated with lithium aluminate, which reduces the consumption of lithium ions during charging and discharging and has high liquid retention performance, thus improving its cycle performance. At the same time, the material in the example has high electronic conductivity and good rate performance, which improves the rate performance of the material.
[0110] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.
Claims
1. A method for preparing a graphite composite anode material, characterized in that, include: A silver-doped graphite composite material was obtained by hydrothermal reaction of silver ammonia solution and porous graphite solution. The aluminum salt solution and the silver-doped graphite composite material are evenly dispersed, filtered, and then sintered to obtain an alumina-coated silver-doped graphite composite material. The alumina-coated silver-doped graphite composite material, amorphous carbon source, inorganic lithium compound, and conductive agent are uniformly dispersed in an organic solvent, spray-dried, and then carbonized to obtain the graphite composite anode material. The graphite composite anode material is a lithium aluminate / amorphous carbon-coated silver-doped graphite composite material. The carbonization temperature is 950-1250℃.
2. The preparation method according to claim 1, characterized in that, The mass ratio of silver ions to porous graphite in the silver ammonia solution is (4.65-7.45):
100.
3. The preparation method according to claim 1, characterized in that, The mass-to-volume ratio of aluminum salt to solvent in the aluminum salt solution is (1-10) g: 100 mL.
4. The preparation method according to claim 1 or 3, characterized in that, The aluminum salt includes one or more of aluminum nitrate, aluminum sulfate, and aluminum chloride.
5. The preparation method according to claim 1, characterized in that, The mass ratio of the alumina-coated silver-doped graphite composite material to the amorphous carbon source, inorganic lithium compound, and conductive agent is 100:(1-5):(1-10):(0.5-2).
6. The preparation method according to claim 1 or 5, characterized in that, The amorphous carbon source includes one or more of petroleum asphalt, coal tar pitch, phenolic resin, furfural resin, and epoxy resin.
7. The preparation method according to claim 1 or 5, characterized in that, The inorganic lithium compound includes one or more of lithium oxide, lithium hydroxide, and lithium carbonate, and the conductive agent includes carbon nanotubes.
8. The graphite composite anode material prepared by the preparation method according to any one of claims 1-7, characterized in that, It includes a core and a shell, wherein the core is a silver-doped graphite composite material and the shell comprises lithium aluminate and amorphous carbon.
9. A negative electrode sheet, characterized in that, The graphite composite anode material prepared by any one of claims 1-7 or the graphite composite anode material described in claim 8 is used as the active material.
10. A lithium battery, characterized in that, It includes a positive electrode, a separator, an electrolyte, and the negative electrode as described in claim 9.