Patent Application
20240282965
This application claims the benefit of Chinese Patent Application 202110646868.9 filed on Jun. 10, 2021, the disclosure of which is incorporated herein by reference.
The present invention relates to the field of carbon materials, and particularly relates to a graphite negative electrode material, and a preparation method and application thereof.
A negative electrode of a lithium ion battery is mainly a carbon material, including amorphous carbon, natural graphite, and artificial graphite. Graphite has a regular layered structure and excellent electrical conductivity, has a theoretical specific capacity of 372 m·h/g, is high in efficiency, and is a mainstream negative electrode material at present. At present, raw materials for developing the artificial graphite mainly include three types: isotropic coke, bituminous adhesive and needle coke. The isotropic coke-based artificial graphite is low in crystallinity, high in isotropy, low in capacity and high in power. The needle coke-based artificial graphite is high in capacity, but relatively poor in rate capability, and the bituminous adhesive is generally between the two.
CN104681786A discloses a coal-based negative electrode material. The coal-based negative electrode material is composed of a coal-based material graphitized inner layer, an intermediate layer, and an outer layer distributed on a surface. A preparation method of the material includes: crushing the coal-based material; adding a binder, or a mixer of a binder and a modifier; and then performing compression and high-temperature graphitization to obtain a finished product.
CN109319757A discloses a method for preparing a negative electrode material of an onion carbon lithium ion battery with a hollow opening. A coal material is used as a raw material and is mixed and heated with a nickel salt or a nickel elementary substance as a catalyst, so that the nickel salt or the nickel elementary substance is evenly distributed on a surface of the coal-based material particle, formed an opening graphite onion carbon layer on the spherical surface after cooling, and finally graphite onion carbon with a hollow opening spherical structure is obtained after acid-base treatment and purification.
CN107528053A discloses a negative electrode material for a lithium ion secondary battery, a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery. The negative electrode material for the lithium ion secondary battery contains a carbon material, the carbon material has an average interplanar spacing d002 as determined by X-ray diffraction of from 0.335 nm to 0.340 nm, a volume average particle size (50% D) of from 1 μm to 40 μm, a maximum particle size Dmax of 74 μm or less, and at least two exothermic peaks within a temperature range of from 300° C. to less than 1,000° C. while performing differential thermal analysis in an air flow.
The negative electrode material provided by the above prior art is complex in structure and process and high in cost; moreover, acid, base and the like are adopted for purification treatment in the treatment process, which is not friendly to environment. More importantly, a rate capability of single-phase graphite in the negative electrode material in the prior art is insufficient, which cannot meet actual requirements.
In order to overcome the problems of complex structure, insufficient rate capability of single-phase graphite, complex preparation process and high cost of a graphite negative electrode material in the prior art, the present invention provides a coal-based graphite negative electrode material, a preparation method and application thereof. The coal-based graphite negative electrode material has high charge-discharge capacity, high initial coulombic efficiency and excellent rate capability, and the preparation method is simple in process and low in cost.
In order to achieve the above objects, one aspect of the present invention provides a graphite negative electrode material, wherein a crystal size Lc in a c-axis direction and a crystal size La in an a-axis direction, which are obtained by XRD, of the graphite negative electrode material, satisfy the following conditions:
and
A second aspect of the present invention provides a preparation method of the graphite negative electrode material, wherein the method includes the following steps of:
A third aspect of the present invention provides a graphite negative electrode material prepared by the preparation method above.
A fourth aspect of the present invention provides an application of the graphite negative electrode material above in at least one of a lithium ion battery, an energy storage material, a mechanical component and a graphite electrode.
According to the above technical solutions, the graphite negative electrode material and the preparation method and application thereof provided by the present invention have the following beneficial effects:
The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, which should be understood to include values close to those ranges or values. For numerical ranges, one or more new numerical ranges can be obtained by combining the endpoint values of various ranges, endpoint values of various ranges and individual point values, and individual point values, and these numerical ranges should be regarded as specifically disclosed herein.
A first aspect of the present invention provides a graphite negative electrode material, wherein a crystal size Lc in a c-axis direction and a crystal size La in an a-axis direction, which are obtained by XRD, of the graphite negative electrode material, satisfy the following conditions:
and
In the present invention, the graphite negative electrode material meeting the above conditions has the characteristics of high isotropy and small crystal particle size, so that lithium ions can be intercalated and desorbed in many channels with short paths, and the rate capability of a battery including the graphite negative electrode material can be significantly improved on the premise of maintaining relatively high charge-discharge capacity and initial coulombic efficiency, thereby achieving the best balance of the three.
In the present invention, the graphite negative electrode material is a coal-based graphite negative electrode material.
In the present invention, a graphitization degree G of the graphite negative electrode material is calculated according to the following formula:
G=(0.344−d002)/(0.344−0.3354), wherein d002 value is calculated by Bragg equation.
In the present invention, as shown in
Further, when 30 nm≤Lc≤50 nm, the rate capability, the charge-discharge capacity and the initial coulombic efficiency of the graphite negative electrode material are further improved.
Further, when 55 nm≤La≤100 nm, the rate capability, the charge-discharge capacity and the initial coulombic efficiency of the graphite negative electrode material are further improved.
Further, when 86≤graphitization degree≤92, the rate capability, the charge-discharge capacity and the initial coulombic efficiency of the graphite negative electrode material are further improved.
According to the present invention, interplanar spacing d002 of a (002) crystal plane, which is obtained by XRD, of the graphite negative electrode material meets the following condition:
According to the present invention, when the interplanar spacing d002 of the (002) crystal plane meets that 0.3360 nm≤d002≤0.3370 nm, the graphite negative electrode material has more excellent comprehensive performance.
According to the present invention, a peak intensity I110 of a (110) crystal plane and a peak intensity I004 of a (004) crystal plane, which are obtained by XRD, of the graphite negative electrode material, meet the following condition:
In the present invention, the isotropy of the graphite negative electrode material meeting the above conditions is further increased, such that the rate capability of the graphite negative electrode material is further improved.
Further, when 0.35≤I110/I004≤0.85, the graphite negative electrode material has more excellent rate capability.
According to the present invention, an ash content of the graphite negative electrode material is less than or equal to 1000 ppm.
In the present invention, the ash content of graphite negative electrode material is measured by the method in GB/T3521. The graphite negative electrode material provided by the present invention has low ash content, which can significantly improve the overall homogeneity of the graphite negative electrode material.
Further, the ash content of the graphite negative electrode material is less than or equal to 500 ppm.
A second aspect of the present invention provides a preparation method of a graphite negative electrode material, wherein the method includes the following steps of:
In the present invention, the graphitizing device may be a graphitizing device commonly used in industry in the art, and specifically, the graphitizing device may be selected from at least one of an Acheson furnace, a box-type furnace, an inner-series furnace, a vertical graphitizing furnace, and a horizontal graphitizing furnace.
According to the present invention, the coal is used as the raw material to develop the graphite negative electrode material having low cost and unique micro-nano structure, and when the graphite negative electrode material is prepared according to the method provided by the present invention, high additional value utilization as well as clean and efficient conversion of the coal can be achieved.
In the present invention, when the coal meeting the above conditions is selected as the raw material for preparing the graphite negative electrode material, the prepared graphite negative electrode material has a moderate graphitization degree, and has the characteristics of small crystal particle size and high isotropy, thereby significantly improving the rate capability, the charge-discharge capacity, and the initial coulombic efficiency of the graphite negative electrode material.
In the present invention, a vitrinite reflectance of the coal is measured by method GB/T 6948 in the national standard, and the volatile constituent content and the ash content of the coal are both measured by method GB/T 30732 in the national standard.
According to the present invention, the coal meets the following conditions: a vitrinite reflectance greater than or equal to 2.35; a volatile constituent less than or equal to 10 wt %; and an ash content less than or equal to 6 wt %.
In the present invention, a conventional device in the art, such as a jet mill, may be used to crush the coal.
According to the present invention, in step (1), a particle size D50 of the coal particles is 1 μm to 100 μm, preferably 5 μm to 30 μm.
According to the present invention, the method further includes a step of shaping and/or grading the coal particles.
According to the present invention, step (2) includes the following steps of:
In the present invention, before the graphitizing treatment, carbonizing the coal particles can remove the volatile constituents or ash in the coal particles to avoid agglomeration caused by escape of the volatile constituents or ash in the graphitizing process; meanwhile, the graphitization degree of the product can be improved, such that the charge-discharge capacity and the initial coulombic efficiency of a battery including the graphite negative electrode material are higher, and therefore the best balance of the capacity, the efficiency and the rate capacity is achieved.
According to the present invention, in step (2-1), the carbonizing condition includes: a carbonizing temperature of 400° C. to 1,800° C., and a carbonizing time of 1 hour to 10 hours.
In the present invention, the carbonizing is performed in the presence of an inert atmosphere.
According to the present invention, in step (2), the graphitizing condition includes: controlling an actual maximum supply power of a transformer in a graphitizing device to be 5,000 kW to 50,000 kW, and a continuous power transmission time of the actual maximum power transmission power being 5 hours to 50 hours.
Further, the graphitizing condition includes: controlling the actual maximum supply power of the transformer in the graphitizing device 10,000 kW to 30,000 kW, and the continuous power transmission time of the actual maximum power transmission power being 8 hours to 40 hours.
A third aspect of the present invention provides a graphite negative electrode material prepared by the preparation method above.
A fourth aspect of the present invention provides an application of the graphite negative electrode material above in at least one of a lithium ion battery, an energy storage material, a mechanical component and a graphite electrode.
In the present invention, the lithium ion battery including the graphite negative electrode material above has excellent electrochemical performance, and specifically, the lithium ion battery including the graphite negative electrode material above has charge-discharge capacity greater than or equal to 330 mAh/g, initial coulombic efficiency greater than equal to 90%, and capacity retention rate at 2 C/0.2 C greater than equal to 35%.
The present invention is described in detail hereinafter with reference to the embodiments.
D50 was obtained by a Malvern Mastersizer 2000 laser particle size meter of Malvern Instruments Ltd.
The charge-discharge capacity and the initial coulombic efficiency of the battery were subjected to charge-discharge tests through a CT2001A battery tester of a battery test system of Wuhan Land Electronics Co., Ltd. at a current of 0.1 C (1 C=350 mAh/g) and a voltage of 0 V to 3 V.
(1) Coal (vitrinite reflectance of 2.445; volatile content of 7.7 wt %; and ash content of 2.6 wt %) was crushed by a crusher to obtain powder with D50 of 10 μm and then the powder was graded to obtain coal particles;
(2-1) the coal particles were carbonized at 1000° C. in an inert gas for 2 hours to obtain an intermediate; and
(2-2) the intermediate was graphitized in a graphitizing furnace, wherein in the graphitizing furnace, an actual maximum supply power of a transformer was 22,000 kW, and a continuous power transmission time of the actual maximum transmission power was 20 hours; a graphite negative electrode material was obtained, and was sieved to obtain product A1.
A TEM photograph of the graphite negative electrode material was as shown in
(1) Coal (vitrinite reflectance of 2.445; volatile content of 7.7 wt %; and ash content of 2.6 wt %) was crushed by a crusher to obtain coal powder with D50 of 10 μm;
(2-1) the coal particles were carbonized at 1000° C. in an inert gas for 2 hours to obtain an intermediate; and
(2-2) the intermediate was graphitized in a graphitizing furnace, wherein in the graphitizing furnace, an actual maximum supply power of a transformer was 22,000 kW, and a continuous power transmission time of the actual maximum transmission power was 35 hours; a graphite negative electrode material was obtained, and sieved to obtain product A2.
(1) Coal (vitrinite reflectance of 2.445; volatile content of 7.7 wt %; and ash content of 2.6 wt %) was crushed by a crusher to obtain coal powder with D50 of 10 μm;
(2-1) the coal particles were carbonized at 1,000° C. in an inert gas for 2 hours to obtain an intermediate; and
(2-2) the intermediate was graphitized in a graphitizing furnace, wherein in the graphitizing furnace, an actual maximum supply power of a transformer was 22,000 kW, and a continuous power transmission time of the actual maximum transmission power was 10 hours; a graphite negative electrode material was obtained, and sieved to obtain product A3.
(1) Coal (vitrinite reflectance of 2.445; volatile content of 7.7 wt %; and ash content of 2.6 wt %) was crushed by a crusher to obtain coal powder with D50 of 10 μm;
(2-1) the coal particles were carbonized at 1000° C. in an inert gas for 2 hours to obtain an intermediate; and
(2-2) the intermediate was graphitized in a graphitizing furnace, wherein in the graphitizing furnace, an actual maximum supply power of a transformer was 10,000 kW, and a continuous power transmission time of the actual maximum transmission power was 20 hours; a graphite negative electrode material was obtained, and sieved to obtain product A4.
(1) Coal (vitrinite reflectance of 2.269; volatile content of 6.83 wt %; and ash content of 9.3 wt %) was crushed by a crusher to obtain powder with D50 of 10 μm and then the powder was graded to obtain coal particles;
(2-1) the coal particles were carbonized at 1000° C. in an inert gas for 2 hours to obtain an intermediate; and
(2-2) the intermediate was graphitized in a graphitizing furnace, wherein in the graphitizing furnace, an actual maximum supply power of a transformer was 22,000 kW, and a continuous power transmission time of the actual maximum transmission power was 20 hours; a graphite negative electrode material was obtained, and sieved to obtain product A5.
(1) Coal (vitrinite reflectance of 2.269; volatile content of 6.83 wt %; and ash content of 9.3 wt %) was crushed by a crusher to obtain powder with D50 of 10 μm and then the powder was graded to obtain coal particles;
(2-1) the coal particles were carbonized at 1000° C. in an inert gas for 2 hours to obtain an intermediate; and
(2-2) the intermediate was graphitized in a graphitizing furnace, wherein in the graphitizing furnace, an actual maximum supply power of a transformer was 5,000 kW, and a continuous power transmission time of the actual maximum transmission power was 20 hours; a graphite negative electrode material was obtained, and sieved to obtain product A6.
(1) Coal (vitrinite reflectance of 2.269; volatile content of 6.83 wt %; and ash content of 9.3 wt %) was crushed by a crusher to obtain powder with D50 of 10 μm and then the powder was graded to obtain coal particles;
(2-1) the coal particles were carbonized at 1000° C. in an inert gas for 2 hours to obtain an intermediate; and
(2-2) the intermediate was graphitized in a graphitizing furnace, wherein in the graphitizing furnace, an actual maximum supply power of a transformer was 22,000 kW, and a continuous power transmission time of the actual maximum transmission power was 5 hours; a graphite negative electrode material was obtained, and sieved to obtain product A7.
A graphite negative electrode material was prepared according to the method of Example 1, except that in the step (2-1), the carbonizing condition was different from that in Example 1. Specifically, the carbonizing temperature was 400° C., and the time was 0.5 hour.
A graphite negative electrode material was prepared according to the method of Example 1, except that in the step (2-1), the carbonizing condition was different from that in Example 1. Specifically, the carbonizing temperature was 2200° C., and the time was 15 hours.
(1) Coal (vitrinite reflectance of 2.445; volatile content of 7.7 wt %; and ash content of 2.6 wt %) was crushed by a crusher to obtain coal powder with D50 of 10 μm;
(2) the coal particles were graphitized in a graphitizing furnace, wherein in the graphitizing furnace, an actual maximum supply power of a transformer was 22,000 kW, and a continuous power transmission time of the actual maximum transmission power was 20 hours; a graphite negative electrode material was obtained, and sieved to obtain product A10.
(1) Coal (vitrinite reflectance of 1.947; volatile content of 12.5 wt %; and ash content of 9.4 wt %) was crushed by a jet mill to obtain coal powder with D50 of 10 μm;
(2-1) the coal particles were carbonized at 1000° C. in an inert gas for 2 hours to obtain an intermediate; and
(2-2) the intermediate was graphitized in a graphitizing furnace, wherein in the graphitizing furnace, an actual maximum supply power of a transformer was 22,000 kW, and a continuous power transmission time of the actual maximum transmission power was 20 hours; a graphite negative electrode material was obtained, and sieved to obtain product D1.
(1) Coal (vitrinite reflectance of 2.445; volatile content of 7.7 wt %; and ash content of 2.6 wt %) was crushed by a jet mill to obtain coal powder with D50 of 10 μm;
(2-1) the coal particles were carbonized at 1000° C. in an inert gas for 2 hours to obtain an intermediate; and
(2-2) the intermediate was graphitized in a graphitizing furnace, wherein in the graphitizing furnace, an actual maximum supply power of a transformer was 600 kW, and a continuous power transmission time of the actual maximum transmission power was 20 hours; a graphite negative electrode material was obtained, and sieved to obtain product D2.
A negative electrode material was prepared according to the method of Example 1, except that the coal was replaced by pitch coke. Negative electrode material D3 was prepared.
The graphite negative electrode materials prepared in the examples and the comparative examples were characterized, and the results can be seen in Table 1 below.
The negative electrode materials prepared in the examples and the comparative examples were evenly mixed with conductive carbon black Super P and binder poly(vinylidene fluoride) (PVDF) in a mass ratio of 92:3:5, and then added with a solvent N-methyl pyrrolidone (NMP), stirred into a uniform negative electrode slurry, which was evenly coated on an aluminum foil with a scraper, dried to obtain a negative electrode plate, the plate was cut into pieces, and then transferred to an MBraun 2000 glove box (Ar atmosphere, H2O and O2 concentration being less than 0.1×10−6 vol %), and then assembled into a button battery by using a metal lithium plate as a reference electrode. Electrochemical performances of the button battery were tested, and the test results can be seen in Table 2.
It can be seen from the results of Table 1 and Table 2 that the charge-discharge capacity and the initial coulombic efficiency of the battery made of the coal-based negative electrode materials prepared in Examples 1-10 of the present invention are better, and the best balance of the charge-discharge capacity, the initial coulombic efficiency and the rate capability of the battery can be achieved.
Those described above are preferred embodiments of the present invention, but the present invention is not limited to the embodiments. Within the scope of the technical concept of the present invention, many simple modifications can be made to the technical solutions of the present invention, including the combination of various technical features in any other suitable way. These simple modifications and combinations shall also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202110646868.9 | Jun 2021 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2021/133965 | 11/29/2021 | WO |
