Composite negative electrode and lithium-ion battery using same
By introducing medium-temperature pitch with a specific coking value into lithium-ion batteries to prepare artificial graphite and combining it with hard carbon, the problem of insufficient rate performance of lithium-ion batteries in ultra-low temperature environments was solved, and high-rate charging and low-temperature performance improvement of batteries were achieved.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- EVE ENERGY CO LTD
- Filing Date
- 2025-08-22
- Publication Date
- 2026-06-25
Smart Images
Figure PCTCN2025116451-APPB-I100001 
Figure PCTCN2025116451-APPB-I100002
Abstract
Description
A composite negative electrode and a lithium-ion battery using it
[0001]
[0002] Priority information
[0003] This application claims priority to patent application No. 202411874543.6, filed with the China National Intellectual Property Administration on December 18, 2024, the entire contents of which are incorporated herein by reference as if copied herein. Technical Field
[0004] This invention belongs to the field of batteries, and particularly relates to a composite negative electrode and a lithium-ion battery using the same. Background Technology
[0005] Whether in electronic devices or lithium-ion battery vehicles, the demand for fast charging is becoming increasingly common, and some products prefer to operate for extended periods at lower temperatures. Therefore, with the rapid development of lithium-ion batteries, the requirements for rate performance and low-temperature performance are gradually increasing. The negative electrode, as a key component of a lithium-ion cell, is the core factor determining the cell's fast-charging performance. Technical issues
[0006] Currently, mid-to-high-end synthetic graphite can achieve charging rates of 10C or even higher from the material level, but the charging window is significantly reduced in ultra-low temperature environments. Therefore, some researchers are using silicon-based anodes. The high specific capacitance of silicon materials can achieve low areal density, thereby reducing charging impedance and improving rate performance. However, the expansion and high-temperature cycling defects of silicon-based anodes prevent their widespread adoption in some products. Technical solutions
[0007] To improve the rate performance and low-temperature performance of batteries, this invention provides a composite negative electrode and a lithium-ion battery using the same.
[0008] According to one aspect of this application, a composite negative electrode is provided, comprising artificial graphite and biomass hard carbon; the artificial graphite is prepared by the following method: S1. raw coke is mixed with auxiliary materials and subjected to weak granulation treatment to obtain a first solid; S2. the first solid is subjected to high-temperature graphitization treatment and then mixed with a solid phase coating agent to obtain a second solid; the solid phase coating agent is medium-temperature asphalt, and the coking value of the medium-temperature asphalt is ≥58%; S3. the second solid is subjected to carbonization treatment to obtain artificial graphite.
[0009] According to a second aspect of this application, a lithium-ion battery is provided, the lithium-ion battery comprising the composite negative electrode as described above. Beneficial effects
[0010] This invention prepares artificial graphite by introducing medium-temperature pitch with a specific coking value as a coating agent, which can improve the lithium-ion transport rate. This is because, at high temperatures, medium-temperature pitch with a specific coking value can be converted into coke with a high fixed carbon content and good structural strength, giving artificial graphite good fast-charging performance and cycle stability. Furthermore, by combining artificial graphite and hard carbon in the negative electrode, both the rate performance and low-temperature performance of the battery can be achieved. This is due to the complementary effect between artificial graphite and hard carbon. On the one hand, artificial graphite can provide conductive channels for hard carbon, compensating for the low initial efficiency of hard carbon; on the other hand, hard carbon can alleviate the expansion of artificial graphite, significantly improving the anti-lithium plating characteristics during high-rate charging. Therefore, this invention, by preparing artificial graphite by introducing medium-temperature pitch with a specific coking value and combining it with hard carbon, can better balance energy-power density and give the battery good low-temperature performance. Embodiments of the present invention
[0011] To enable those skilled in the art to better understand the technical solutions of this application, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.
[0012] Example 1
[0013] 1. Preparation of composite negative electrode
[0014] (1) Preparation of artificial graphite
[0015] The artificial graphite provided in this embodiment is prepared according to the following method:
[0016] S1. Raw coke is mixed with medium-temperature asphalt (coke value 60%) and subjected to weak granulation treatment at a reaction temperature of 900℃ and a granulation time of 6 hours to obtain the first solid (calculated by mass ratio, primary particles: secondary particles = 3:7).
[0017] S2. After reacting the first solid at 900℃ for 7 hours, it is mixed with medium-temperature asphalt to obtain the second solid; wherein, the mass content of medium-temperature asphalt with a coking value of 58% is 3%; the mass content of medium-temperature asphalt with a coking value of 60% is 5%; and the mass content of medium-temperature asphalt with a coking value of 60.5% is 2%.
[0018] S3. The second solid is reacted at 1000℃ for 8 hours to obtain the artificial graphite.
[0019] (2) Preparation of biomass hard carbon
[0020] The biomass hard carbon provided in this embodiment is prepared by the following method: imported coconut shell raw materials are subjected to carbonization treatment, grinding treatment, alkaline solution impregnation, pyrolysis and polycondensation treatment in sequence, and reacted at 850°C for 7 hours in a hydrocarbon or protective gas atmosphere to obtain the biomass hard carbon.
[0021] (3) Preparation of composite negative electrode
[0022] The artificial graphite and biomass hard carbon prepared above were mixed at a mass ratio of 99:1 to obtain the negative electrode main material. Then, the negative electrode main material, carbon black, and binder were mixed at a mass ratio of 96.0:1.3:2.7, and deionized water was added to obtain the negative electrode slurry. Subsequently, the negative electrode slurry was coated onto a copper foil current collector through a coating process, and after vacuum drying and cold pressing, a composite negative electrode was obtained.
[0023] 2. Preparation of lithium-ion batteries
[0024] The positive electrode (commercial lithium cobalt oxide), separator, and composite negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained. The electrolyte is a conventional carbonate-based electrolyte.
[0025] Example 2
[0026] This embodiment refers to the formulation and method provided in Example 1 to prepare a composite negative electrode and a lithium-ion battery using it. The difference from Example 1 is that, in the preparation of artificial graphite, the solid phase coating agent used in this embodiment is: 5% by mass of medium-temperature pitch with a coking value of 58%; and 5% by mass of medium-temperature pitch with a coking value of 60%. Apart from the above differences, the operation steps for preparing the composite negative electrode and the lithium-ion battery using it in this embodiment are strictly consistent with those in Example 1.
[0027] Example 3
[0028] This embodiment refers to the formulation and method provided in Example 1 to prepare a composite negative electrode and a lithium-ion battery using it. The difference from Example 1 is that in this embodiment, when preparing artificial graphite, the material used as the solid phase coating agent is: medium-temperature pitch with a coking value of 58% and a mass content of 10%. Apart from the above differences, the operation steps for preparing the composite negative electrode and the lithium-ion battery using it in this embodiment are strictly consistent with those in Example 1.
[0029] Example 4
[0030] This embodiment refers to the formulation and method provided in Example 1 to prepare a composite negative electrode and a lithium-ion battery using it. The difference from Example 1 is that in this embodiment, when preparing artificial graphite, the material used as the solid phase coating agent is: medium-temperature pitch with a coking value of 63% and a mass content of 10%. Apart from the above differences, the operation steps for preparing the composite negative electrode and the lithium-ion battery using it in this embodiment are strictly consistent with those in Example 1.
[0031] Example 5
[0032] This embodiment refers to the formulation and method provided in Example 1 to prepare a composite negative electrode and a lithium-ion battery using it. The difference from Example 1 is that in this embodiment, when preparing artificial graphite, the mass ratio of primary particles to secondary particles in the first solid is calculated as 1:1. Apart from the above differences, the operation steps for preparing the composite negative electrode and the lithium-ion battery using it in this embodiment are strictly consistent with those in Example 1.
[0033] Example 6
[0034] This embodiment refers to the formulation and method provided in Example 1 to prepare a composite negative electrode and a lithium-ion battery using it. The difference from Example 1 is that in this embodiment, when preparing artificial graphite, the mass ratio of primary particles to secondary particles in the first solid is 2:8. Apart from the above differences, the operation steps for preparing the composite negative electrode and the lithium-ion battery using it in this embodiment are strictly consistent with those in Example 1.
[0035] Example 7
[0036] This embodiment refers to the formulation and method provided in Example 1 to prepare a composite negative electrode and a lithium-ion battery using it. The difference from Example 1 is that in this embodiment, when preparing artificial graphite, the mass ratio of primary particles to secondary particles in the first solid is calculated as 4:6. Apart from the above differences, the operation steps for preparing the composite negative electrode and the lithium-ion battery using it in this embodiment are strictly consistent with those in Example 1.
[0037] Example 8
[0038] This embodiment refers to the formulation and method provided in Example 1 to prepare a composite negative electrode and a lithium-ion battery using it. The difference from Example 1 is that in this embodiment, when preparing the composite negative electrode, the mass ratio of artificial graphite to biomass hard carbon in the main negative electrode material is calculated as 98:2. Apart from the above differences, the operation steps for preparing the composite negative electrode and the lithium-ion battery using it in this embodiment are strictly consistent with those in Example 1.
[0039] Example 9
[0040] This embodiment refers to the formula and method provided in Example 1 to prepare a composite negative electrode and a lithium-ion battery using it. The difference from Example 1 is that in this embodiment, when preparing the composite negative electrode, the mass ratio of artificial graphite to biomass hard carbon in the main negative electrode material is calculated as 97:3. Apart from the above differences, the operation steps for preparing the composite negative electrode and the lithium-ion battery using it in this embodiment are strictly consistent with those in Example 1.
[0041] Example 10
[0042] This embodiment refers to the formula and method provided in Example 1 to prepare a composite negative electrode and a lithium-ion battery using it. The difference from Example 1 is that in this embodiment, when preparing the composite negative electrode, the mass ratio of artificial graphite to biomass hard carbon in the main negative electrode material is calculated as 96:4. Apart from the above differences, the operation steps for preparing the composite negative electrode and the lithium-ion battery using it in this embodiment are strictly consistent with those in Example 1.
[0043] Example 11
[0044] This embodiment refers to the formulation and method provided in Embodiment 1 to prepare a composite negative electrode and a lithium-ion battery using it. The difference from Embodiment 1 is that, in this embodiment, when preparing the composite negative electrode, the mass ratio of artificial graphite to biomass hard carbon in the main negative electrode material is 96:4; and the conductive agent used in the composite negative electrode is high specific surface area carbon black with a specific surface area ≥150m². 2 / g, the oil absorption value decreases. Apart from the differences mentioned above, the operational steps for preparing the composite negative electrode and the lithium-ion battery using it in this embodiment are strictly consistent with those in Example 1.
[0045] Example 12
[0046] This embodiment refers to the formulation and method provided in Example 1 to prepare a composite negative electrode and a lithium-ion battery using it. The difference from Example 1 is that, in this embodiment, when preparing the composite negative electrode, the mass ratio of artificial graphite to biomass hard carbon in the main negative electrode material is 95:5. Apart from the above differences, the operational steps for preparing the composite negative electrode and the lithium-ion battery using it in this embodiment are strictly consistent with those in Example 1.
[0047] Comparative Example 1
[0048] This comparative example prepares a composite negative electrode and a lithium-ion battery using the same formulation and method as in Example 1. The difference between this comparative example and Example 1 is that, in preparing the negative electrode, an equal mass fraction of natural graphite is used instead of artificial graphite. Apart from the above differences, the operational steps for preparing the composite negative electrode and the lithium-ion battery using the same in this comparative example are strictly consistent with those in Example 1.
[0049] Comparative Example 2
[0050] This comparative example prepares a composite negative electrode and a lithium-ion battery using the same formulation and method as in Example 1. The difference from Example 1 is that, in preparing the negative electrode active material, an equal mass fraction of artificial graphite is used instead of biomass hard carbon. Apart from the above differences, the operational steps for preparing the composite negative electrode and the lithium-ion battery using the same in this comparative example are strictly consistent with those in Example 1.
[0051] Comparative Example 3
[0052] This comparative example prepares a composite negative electrode and a lithium-ion battery using the same formulation and method as in Example 1. The difference from Example 1 is that, in preparing the negative electrode active material, an equal mass fraction of biomass hard carbon is used instead of artificial graphite. Apart from the above differences, the operational steps for preparing the composite negative electrode and the lithium-ion battery using the same in this comparative example are strictly consistent with those in Example 1.
[0053] Test case
[0054] 1. Test Object
[0055] Composite anodes prepared in Examples 1-12 and Comparative Examples 1-3, and lithium-ion batteries using them.
[0056] 2. Testing Methods
[0057] (1) 5C charging constant current ratio: The ratio of the charging capacity to the total charging capacity during the constant current stage under the 5C fast charging setting is used for cell testing in the Xinwei cabinet, which reflects the fast charging performance.
[0058] (2) 5C charging temperature rise: A temperature sensor is used to test the highest temperature on the surface of the battery cell at a 5C fast charging rate. The difference between the temperature and the room temperature represents the temperature rise under fast charging.
[0059] (3) -20℃ discharge / 25℃ discharge capacity: The ratio of the capacity discharged by the cell at -20 degrees Celsius after standard charging to the capacity discharged at 0.2C at 25℃.
[0060] (4) 25℃ 5C / 1C cycle 800 times: At room temperature, the battery cell is charged at 5C constant current and constant voltage on the Xinwei test cabinet. The upper limit voltage is 4.5V, 0.025C cutoff, rest for 5min, 1C discharge to 3.0V, and the remaining capacity and thickness expansion after 800 cycles are used as the cycle performance evaluation indicators.
[0061] (5) 0℃ 3C / 1C cycle 400 times: In the 0℃ temperature chamber, the battery cell is charged with 3C constant current and constant voltage on the Xinwei test cabinet. The upper limit voltage is 4.5V, 0.025C cutoff, rest for 5min, 1C discharge to 3.0V, and the remaining capacity and thickness expansion after 400 cycles are used as the cycle performance evaluation indicators.
[0062] 3. Test Results and Analysis
[0063] The test results for this test case are shown in Tables 1 and 2.
[0064] As shown in Table 1, the negative electrode active material provided in this application can significantly improve the fast-charging performance and low-temperature performance of the battery. Furthermore, based on the data in Table 2, it can be seen that by controlling the raw materials in the preparation of artificial graphite and the mass ratio of artificial graphite to biomass hard carbon in the main negative electrode material, the battery's cycle performance at high rates and its low-temperature rate performance can be improved. Specifically, by comparing the data from Example 1 and Comparative Examples 1-3, it can be seen that the combination of artificial graphite and hard carbon can significantly balance the relationship between energy density and power density.
[0065] Furthermore, data from Examples 1-4 show that the coking value of the solid coating agent (medium-temperature pitch) used in the preparation of artificial graphite affects the low-temperature performance of the battery. Also, data from Example 5 shows that the type of auxiliary materials used also affects battery performance.
[0066] Secondly, based on the data from Examples 5-7, it is known that the mass ratio between primary and secondary particles in the first solid can improve system compaction and specific capacity utilization, thereby balancing the energy density and rate performance of the battery cell. Furthermore, data from Examples 1 and 8-11 show that the mass ratio between artificial graphite and biomass hard carbon in the composite negative electrode affects the battery's cycle performance and low-temperature performance. And data from Example 12 shows that, combined with the use of a highly efficient conductive agent, the battery's fast-charging performance and low-temperature performance can be further improved.
[0067] Table 1. Test results of fast charging performance and low temperature performance
[0068]
[0069] Table 2. Test results of cycle performance
[0070]
[0071] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the substance and scope of the technical solutions of this application.
Claims
1. A composite negative electrode, characterized in that, The composite negative electrode comprises artificial graphite and biomass hard carbon; the artificial graphite is prepared by the following method: S1. Raw coke is mixed with auxiliary materials and subjected to weak granulation to obtain the first solid. S2. The first solid is subjected to high-temperature graphitization treatment and then mixed with a solid phase coating agent to obtain a second solid; the solid phase coating agent is medium-temperature asphalt, and the coking value of the medium-temperature asphalt is ≥58%; S3. The second solid is subjected to carbonization treatment to obtain the artificial graphite.
2. The composite negative electrode as described in claim 1, characterized in that, In the second solid, the mass content of the medium-temperature asphalt is ≥10% by percentage.
3. The composite negative electrode as described in claim 2, characterized in that: The mass content of the medium-temperature asphalt with a coking value of 58-59% is 2-3.5%; And / or, the mass content of the medium-temperature asphalt with a coking value of 59-60% is 4-5%; And / or, the mass content of medium-temperature asphalt with a coking value of 60-60.5% is 2-3%.
4. The composite negative electrode as described in claim 1, characterized in that, The auxiliary materials include at least one of medium-temperature asphalt and epoxy resin.
5. The composite negative electrode as described in claim 1, characterized in that, The first solid comprises primary particles and secondary particles, wherein the D50 of the primary particles is 5~7μm and the D50 of the secondary particles is 6~8μm.
6. The composite negative electrode as described in claim 5, characterized in that, Based on the mass ratio, the ratio of primary particles to secondary particles is 2~4:6~8.
7. The composite negative electrode as described in claim 1, characterized in that, In S1, the reaction conditions for weak granulation treatment are: granulation temperature of 800~950℃ and granulation time of less than 9 hours.
8. The composite negative electrode as described in claim 1, characterized in that, The preparation method of the biomass hard carbon includes the following steps: carbonizing, grinding, alkaline impregnation, pyrolysis and polycondensation, and high-temperature treatment of the biomass raw materials to obtain the biomass hard carbon.
9. The composite negative electrode according to any one of claims 1 to 8, characterized in that, The mass ratio of the artificial graphite to the biomass hard carbon is 94-97% to 3-6%.
10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the composite negative electrode as described in any one of claims 1 to 9.