CN112670445A - Lithium ion battery cathode, preparation method thereof and lithium ion battery - Google Patents
Lithium ion battery cathode, preparation method thereof and lithium ion battery Download PDFInfo
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 108
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 108
- 238000002360 preparation method Methods 0.000 title claims abstract description 10
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 149
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 133
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims abstract description 133
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 133
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 131
- 239000010439 graphite Substances 0.000 claims abstract description 131
- 239000006258 conductive agent Substances 0.000 claims abstract description 40
- 239000000725 suspension Substances 0.000 claims description 63
- 239000011230 binding agent Substances 0.000 claims description 24
- 239000002904 solvent Substances 0.000 claims description 22
- 239000013078 crystal Substances 0.000 claims description 14
- 239000007787 solid Substances 0.000 claims description 14
- 239000002033 PVDF binder Substances 0.000 claims description 13
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 13
- 239000003273 ketjen black Substances 0.000 claims description 11
- 239000006230 acetylene black Substances 0.000 claims description 9
- 239000002041 carbon nanotube Substances 0.000 claims description 9
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 9
- 238000000576 coating method Methods 0.000 claims description 9
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical group CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 8
- 239000011248 coating agent Substances 0.000 claims description 8
- 239000002245 particle Substances 0.000 claims description 8
- 229920003048 styrene butadiene rubber Polymers 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical group [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- 238000007756 gravure coating Methods 0.000 claims description 5
- 239000011889 copper foil Substances 0.000 claims description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 3
- 229910052782 aluminium Inorganic materials 0.000 claims description 3
- 238000007765 extrusion coating Methods 0.000 claims description 3
- 239000011888 foil Substances 0.000 claims description 3
- 238000012546 transfer Methods 0.000 claims description 3
- 238000000034 method Methods 0.000 abstract description 12
- 230000002427 irreversible effect Effects 0.000 abstract description 8
- 238000007086 side reaction Methods 0.000 abstract description 7
- 238000006243 chemical reaction Methods 0.000 abstract description 5
- 230000009286 beneficial effect Effects 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 239000003792 electrolyte Substances 0.000 description 3
- HNJBEVLQSNELDL-UHFFFAOYSA-N pyrrolidin-2-one Chemical compound O=C1CCCN1 HNJBEVLQSNELDL-UHFFFAOYSA-N 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000007773 negative electrode material Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- OTYYBJNSLLBAGE-UHFFFAOYSA-N CN1C(CCC1)=O.[N] Chemical group CN1C(CCC1)=O.[N] OTYYBJNSLLBAGE-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000004626 scanning electron microscopy Methods 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention provides a lithium ion battery cathode, a preparation method thereof and a lithium ion battery. The lithium ion battery negative electrode includes: the lithium ion battery comprises a negative current collector, a lithium titanate layer and a graphite layer which are coated on the surface of the negative current collector, and conductive agents which are respectively and independently dispersed in the lithium titanate layer and the graphite layer, wherein the graphite layer is arranged between the negative current collector and the lithium titanate layer. The negative electrode of the lithium ion battery is used for the lithium ion battery, and the electrode potential of lithium titanate is relatively higher than that of graphite, so that lithium ions and lithium titanate are subjected to chemical reaction firstly, the rate of lithium ions being embedded into lithium titanate is higher than the rate of lithium ions being embedded into graphite, the amount of graphite participating in side reaction in the charging process of the battery is reduced, the irreversible capacity loss of graphite is reduced, and the cycle performance and the rate capability of the lithium ion battery are further improved.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a lithium ion battery cathode, a preparation method thereof and a lithium ion battery.
Background
In recent years, lithium ion batteries have been greatly developed, and among them, the graphite negative electrode material has a gram capacity of about 345mAh/g, which is one of the highest gram capacities among the mainstream negative electrode materials, and is cheap, about 3 to 5 ten thousand yuan per ton, so the graphite negative electrode is popular due to the advantages of low price, high gram capacity, and easy processing. However, during formation and charge and discharge processes of the graphite negative electrode, negative reactions involving lithium ions can cause irreversible capacity loss, and as a result, the cycle performance and rate performance of the battery cell can be affected.
Disclosure of Invention
The invention mainly aims to provide a lithium ion battery cathode, a preparation method thereof and a lithium ion battery, and aims to solve the problem that the cycle performance and the rate performance of the lithium ion battery in the prior art are poor.
In order to achieve the above object, according to one aspect of the present invention, there is provided a lithium ion battery anode including: the lithium ion battery comprises a negative current collector, a lithium titanate layer and a graphite layer which are coated on the surface of the negative current collector, and conductive agents which are respectively and independently dispersed in the lithium titanate layer and the graphite layer, wherein the graphite layer is arranged between the negative current collector and the lithium titanate layer.
Further, the thickness of the lithium titanate layer is 15 to 30 μm.
Further, the graphite layer has a thickness of 50 to 125 μm.
Further, the thickness ratio of the graphite layer to the lithium titanate layer is 2-6.25: 1.
The conductive agent is selected from one or more of acetylene black, Ketjen black and carbon nanotubes, the mass ratio of lithium titanate in the lithium titanate layer to the conductive agent dispersed in the lithium titanate layer is preferably 19.2-28: 0.4-1, and the mass ratio of graphite in the graphite layer to the conductive agent dispersed in the graphite layer is preferably 48-50: 1-2.
Further, the negative electrode current collector is a copper foil or an aluminum foil.
According to another aspect of the present invention, there is provided a method of preparing a negative electrode for a lithium ion battery, the method comprising: step S1, carrying out first mixing on graphite, a first conductive agent, a first binder and a first solvent to obtain a graphite suspension; step S2, performing second mixing on lithium titanate, a second conductive agent, a second binder and a second solvent to obtain a lithium titanate suspension; step S3, arranging the graphite suspension on the surface of the negative current collector to obtain a pole piece containing a graphite layer; and step S4, arranging the lithium titanate suspension on the surface of the graphite layer to obtain the lithium ion battery cathode.
Further, a graphite suspension is coated on the surface of the negative current collector in a squeezing coating or transfer coating mode, the solid content of the graphite suspension is preferably 50-52%, the viscosity of the graphite suspension is preferably 2000-6000 mPas, the first conductive agent is preferably selected from one or more of acetylene black, Ketjen black and carbon nano tubes, the first binder is preferably polyvinylidene fluoride and/or styrene butadiene rubber, the first solvent is preferably azomethyl pyrrolidone and/or water, and the mass ratio of the graphite, the first conductive agent and the first binder is preferably 48-50: 1-2: 48-50.
Further, a lithium titanate suspension is coated on the surface of the graphite layer by adopting a gravure coating mode, preferably, the lithium titanate is a lithium titanate single crystal, the D50 particle size of the lithium titanate single crystal is 20-500 nm, the fineness of the lithium titanate suspension is 0.5-12 mu m, the solid content of the lithium titanate suspension is 39-41%, the viscosity of the lithium titanate suspension is 2000-4500 mPas, the second conductive agent is selected from one or more of acetylene black, Ketjen black and carbon nano tubes, the second binder is polyvinylidene fluoride and/or styrene butadiene rubber, the second solvent is azomethyl pyrrolidone and/or water, and the mass ratio of the lithium titanate, the second conductive agent, the second binder and the second solvent is 19.2-28: 0.4-1: 70-80.
According to another aspect of the present invention, there is provided a lithium ion battery, comprising a positive electrode and a negative electrode, wherein the negative electrode is the aforementioned lithium ion battery negative electrode.
By applying the technical scheme of the invention, the lithium ion battery cathode has the structure that the upper layer is the lithium titanate layer, the middle layer is the graphite layer and the lower layer is the cathode current collector, so that the lithium ion battery cathode is used for the lithium ion battery, on one hand, the gram capacity of the lithium titanate layer can be more fully exerted by the indirect contact of the lithium titanate layer and the cathode current collector through the graphite layer. On the other hand, when the lithium ion battery is formed for the first time, lithium ions are in contact with the lithium titanate layer and the graphite layer through the electrolyte, and the electrode potential of the lithium titanate is relatively higher than that of the graphite, so that the lithium ions and the lithium titanate are subjected to chemical reaction, the rate of lithium ions being embedded into the lithium titanate is higher than the rate of lithium ions being embedded into the graphite, the amount of the graphite participating in side reaction in the charging process of the battery is further reduced, the irreversible capacity loss of the graphite is reduced, and the cycle performance and the rate capability of the lithium ion battery are further improved.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.
As analyzed by the background art, the problem of poor cycle performance and rate performance of the lithium ion battery exists in the prior art, and in order to solve the problem, the invention provides a lithium ion battery cathode, a preparation method thereof and the lithium ion battery.
In an exemplary embodiment of the present application, there is provided a lithium ion battery anode including: the lithium ion battery comprises a negative current collector, a lithium titanate layer and a graphite layer which are coated on the surface of the negative current collector, and conductive agents which are respectively and independently dispersed in the lithium titanate layer and the graphite layer, wherein the graphite layer is arranged between the negative current collector and the lithium titanate layer.
Because the lithium ion battery negative pole of this application has the upper strata and is the lithium titanate layer, the centre is the graphite layer, the lower floor is the structure of negative current collector, consequently, is used for the lithium ion battery negative pole of this application, and the gram capacity on performance lithium titanate layer that can be more abundant is through the indirect and negative current collector's of graphite layer contact on the one hand lithium titanate layer. On the other hand, when the lithium ion battery is formed for the first time, lithium ions are in contact with the lithium titanate layer and the graphite layer through the electrolyte, and the electrode potential of the lithium titanate is relatively higher than that of the graphite, so that the lithium ions and the lithium titanate are subjected to chemical reaction, the rate of lithium ions being embedded into the lithium titanate is higher than the rate of lithium ions being embedded into the graphite, the amount of the graphite participating in side reaction in the charging process of the battery is further reduced, the irreversible capacity loss of the graphite is reduced, and the cycle performance and the rate capability of the lithium ion battery are further improved.
In order to allow lithium ions deintercalated from the lithium titanate layer to smoothly reach the graphite layer and act thereon, the thickness of the lithium titanate layer is preferably 15 to 30 μm. And due to the characteristic of low conductivity of lithium titanate, the thickness of the lithium titanate layer does not influence the overall excellent conductivity of the negative electrode of the lithium ion battery.
In order to improve the conductivity of the graphite layer and improve the gram capacity of the negative electrode of the lithium ion battery, the thickness of the graphite layer is preferably 50-125 μm.
In order to further improve the synergistic effect of the lithium titanate layer and the graphite layer, the speed of lithium ions being inserted into the lithium titanate is fully utilized to be faster than the speed of lithium ions being inserted into the graphite, so that the quantity of the graphite participating in side reaction in the charging process of the battery is reduced, the irreversible capacity loss of the graphite is reduced, and the cycle performance and the rate capability of the lithium ion battery are improved. The thickness ratio of the graphite layer to the lithium titanate layer is preferably 2 to 6.25: 1.
Since the lithium titanate has almost no conductivity, in order to reduce the influence of the lithium titanate layer on the conductivity of the lithium ion battery negative electrode and ensure the excellent conductivity of the lithium ion battery negative electrode as much as possible, the conductive agent is preferably selected from one or more of acetylene black, ketjen black and carbon nano tubes, the mass ratio of the lithium titanate in the lithium titanate layer to the conductive agent dispersed in the lithium titanate layer is preferably 19.2-28: 0.4-1, and the mass ratio of the graphite in the graphite layer to the conductive agent dispersed in the graphite layer is preferably 48-50: 1-2.
In order to meet the requirements of various lithium ion battery cathodes, the current collector of the cathode is preferably copper foil or aluminum foil.
In another exemplary embodiment of the present application, there is provided a method of preparing a negative electrode for a lithium ion battery, the method including: step S1, carrying out first mixing on graphite, a first conductive agent, a first binder and a first solvent to obtain a graphite suspension; step S2, performing second mixing on lithium titanate, a second conductive agent, a second binder and a second solvent to obtain a lithium titanate suspension; step S3, arranging the graphite suspension on the surface of the negative current collector to obtain a pole piece containing a graphite layer; and step S4, arranging the lithium titanate suspension on the surface of the graphite layer to obtain the lithium ion battery cathode.
The graphite suspension and the lithium titanate suspension are convenient to be respectively arranged on the surface of the negative current collector, for example, by coating and other modes, so that a more uniform graphite layer and a more uniform lithium titanate layer are obtained, and the addition of the second conductive agent in the lithium titanate suspension is particularly beneficial to improving the conductivity of the lithium titanate layer, so that the conductivity of the whole lithium ion battery negative electrode is more uniform. The first binder and the second binder may make the bonding between the graphite layer and the lithium titanate layer and the negative electrode current collector more firm. The lithium ion battery cathode with the structure that the upper layer is a lithium titanate layer, the middle layer is a graphite layer and the lower layer is a cathode current collector is obtained, and the rate of lithium ions to be embedded into lithium titanate is higher than the rate of lithium ions to be embedded into graphite, so that the amount of the graphite participating in side reaction in the charging process of the battery is reduced, the irreversible capacity loss of the graphite is reduced, and the cycle performance and the rate capability of the lithium ion battery are further improved.
In one embodiment of the application, a graphite suspension is coated on the surface of a negative current collector by extrusion coating or transfer coating, preferably, the solid content of the graphite suspension is 50-52%, preferably, the viscosity of the graphite suspension is 2000-6000 mPas, preferably, the first conductive agent is selected from one or more of acetylene black, ketjen black and carbon nanotubes, preferably, the first binder is polyvinylidene fluoride and/or styrene butadiene rubber, preferably, the first solvent is nitrogen methyl pyrrolidone and/or water, and preferably, the mass ratio of the graphite, the first conductive agent and the first solvent is 48-50: 1-2: 48-50.
The control of the solid content and the viscosity is beneficial to coating the graphite suspension on the surface of the negative current collector more conveniently to obtain an even graphite layer, the selection of the first conductive agent is beneficial to improving the conductivity of the graphite layer, the selection of the first binder and the first solvent is beneficial to improving the uniformity of the graphite suspension, and the graphite suspension is better attached to the negative current collector, and the mass ratio of the graphite, the first conductive agent, the first binder and the first solvent is beneficial to obtaining a tighter graphite layer which has better conductivity and is combined with the negative current collector.
In one embodiment of the application, a lithium titanate suspension is coated on the surface of the graphite layer by means of gravure coating, preferably, the lithium titanate is a lithium titanate single crystal, the D50 particle size of the lithium titanate single crystal is 20-500 nm, the fineness of the lithium titanate suspension is 0.5-12 μm, the solid content of the lithium titanate suspension is 39-41%, the viscosity of the lithium titanate suspension is 2000-4500 mPas, the second conductive agent is selected from one or more of acetylene black, ketjen black and carbon nanotubes, the second binder is polyvinylidene fluoride and/or styrene butadiene rubber, the second solvent is azomethyl pyrrolidone and/or water, and the mass ratio of the lithium titanate, the second conductive agent, the second binder and the second solvent is 19.2-28: 0.4-1: 70-80.
The D50 particle size of the lithium titanate single crystal and the fineness of the lithium titanate suspension are more favorable for improving the rate of lithium ion intercalation and lithium ion deintercalation, thereby better reducing the amount of graphite participating in side reaction in the battery charging process so as to reduce the irreversible capacity loss of the graphite. The gravure coating mode is adopted, and the solid content and the viscosity of the lithium titanate suspension are controlled, so that the lithium titanate suspension can be uniformly coated on the surface of the graphite layer, and a uniform lithium titanate layer can be obtained. The selection of the second conductive agent can make up the defect of insufficient conductivity of the lithium titanate, and the mass ratio of the lithium titanate, the second conductive agent, the second binder and the second solvent is more favorable for enabling the lithium titanate layer and the graphite layer to be combined more tightly.
In yet another exemplary embodiment of the present application, there is provided a lithium ion battery including a positive electrode and a negative electrode, the negative electrode being the lithium ion battery negative electrode described above.
The lithium ion battery comprising the lithium ion battery cathode has better cycle performance and rate capability.
The advantageous effects of the present application will be described below with reference to specific examples and comparative examples.
Example 1
Firstly, graphite, carbon black (SP), polyvinylidene fluoride (PVDF) and N-methyl pyrrolidone (NMP) are placed into a stirring tank according to the mass ratio of 48:1.5:1.5:50 to be dispersed into uniform graphite suspension, the solid content of the graphite suspension is about 50%, and the viscosity is controlled to be about 5000 mPas. And then placing the lithium titanate single crystal, SP, PVDF and NMP into a stirring tank according to the mass ratio of 25:0.4:0.4:70, dispersing at the high dispersion disc speed, and obtaining a uniform lithium titanate suspension after dispersion, wherein the solid content of the lithium titanate suspension is about 39%, the viscosity is controlled at 3000mPas, the fineness is controlled at 10 mu m, and the D50 particle size of the lithium titanate single crystal is 110 nm. The preparation method comprises the steps of enabling a graphite suspension to pass through a double-layer 160-mesh filter screen to obtain a filtered graphite suspension, enabling a lithium titanate suspension to pass through a 500-mesh filter screen to obtain a filtered lithium titanate suspension, preparing a copper foil, coating the filtered graphite suspension uniformly on a copper current collector in an extrusion coating mode, heating and baking the copper current collector in a multi-layer oven, controlling the thickness of a graphite layer to be about 60 mu m, and rolling a dried graphite negative electrode plate for later use. And uniformly coating the filtered lithium titanate suspension on a dry graphite layer by adopting a gravure coating mode, controlling the thickness of the lithium titanate layer to be 30 mu m, and baking the lithium titanate layer by using an oven to obtain the lithium ion battery cathode.
Example 2
The difference between the embodiment 2 and the embodiment 1 is that the mass ratio of graphite, SP, PVDF and NMP is 49:1:1:48, the solid content of the graphite suspension is about 51%, the viscosity of the graphite suspension is controlled to be about 6000mPas, and finally the lithium ion battery negative electrode is obtained.
Example 3
The difference between the embodiment 3 and the embodiment 1 is that the mass ratio of the graphite, the SP, the PVDF and the NMP is 50:2:2:49, the solid content of the graphite suspension is about 52 percent, the viscosity of the graphite suspension is controlled to be about 2000mPas, and finally the lithium ion battery negative electrode is obtained.
Example 4
Example 4 is different from example 1 in that the mass ratio of lithium titanate single crystal, SP, PVDF and NMP is 19.2:0.7:0.7:75, the solid content of lithium titanate suspension is about 40%, the viscosity of lithium titanate suspension is controlled to be about 2000mPas, and finally the negative electrode of the lithium ion battery is obtained.
Example 5
The difference between the example 5 and the example 1 is that the mass ratio of the lithium titanate single crystal to the SP, the PVDF and the NMP is 28:1:1:80, the solid content of the lithium titanate suspension is about 41%, the viscosity of the lithium titanate suspension is controlled to be about 4500mPas, and finally the lithium ion battery cathode is obtained.
Example 6
Example 6 is different from example 1 in that the fineness of the lithium titanate suspension is controlled to 0.5 μm, and finally a lithium ion battery negative electrode is obtained.
Example 7
Example 7 is different from example 1 in that the fineness of the lithium titanate suspension is controlled to 12 μm, and finally a lithium ion battery negative electrode is obtained.
Example 8
Example 8 is different from example 1 in that the fineness of the lithium titanate suspension is controlled to 15 μm, and finally the lithium ion battery negative electrode is obtained.
Example 9
Example 9 differs from example 1 in that the lithium titanate single crystal had a D50 particle size of 20nm, and a lithium ion battery negative electrode was finally obtained.
Example 10
Example 10 differs from example 1 in that the lithium titanate single crystal had a D50 particle size of 500nm, and a lithium ion battery negative electrode was finally obtained.
Example 11
Example 11 differs from example 1 in that the lithium titanate single crystal had a D50 particle size of 550nm, and a lithium ion battery negative electrode was finally obtained.
Example 12
The difference between the embodiment 12 and the embodiment 1 is that the lithium ion battery negative electrode is finally obtained by using the ketjen black as the first conductive agent, styrene butadiene rubber as the first binder and deionized water as the first solvent.
Example 13
The difference between the embodiment 13 and the embodiment 1 is that the second conductive agent is ketjen black, the second binder is styrene butadiene rubber, and the second solvent is deionized water, so that the negative electrode of the lithium ion battery is finally obtained.
Comparative example 1
Comparative example 1 differs from example 1 in that a lithium titanate layer is not coated on the surface of a graphite layer, and the mass of the graphite layer is equal to the total mass of the graphite layer and the lithium titanate layer of example 1, and a lithium ion battery negative electrode is finally obtained.
The thicknesses of the graphite layer and the lithium titanate layer and the ratio of the graphite layer to the lithium titanate layer (denoted as a), the mass ratio of the graphite layer to the conductive agent dispersed therein (denoted as B), and the mass ratio of the lithium titanate layer to the conductive agent dispersed therein (denoted as C) in the negative electrodes of the lithium ion batteries obtained in the above examples 1 to 13 and comparative example 1 were measured by scanning electron microscopy of the cut surfaces of the coatings, and are shown in table 1.
TABLE 1
The lithium ion battery cathodes obtained in examples 1 to 13 and comparative example 1 were respectively used to prepare coin cells 1 to 14 from the lithium ion positive electrode, and the capacity, the first discharge efficiency, and the capacity retention rate after 25 weeks of cycle of the coin cells 1 to 14 were respectively tested at 1C, and the test results are shown in table 2.
TABLE 2
| Button cell | capacity/mAh | First discharge efficiency/%) | @25 weeks of capacity retention% |
| Button cell 1 | 2.226 | 86.8 | 94.6 |
| Button cell 2 | 2.219 | 87.5 | 94.0 |
| Button cell 3 | 2.292 | 88.5 | 93.6 |
| Button cell 4 | 2.299 | 91.6 | 93.5 |
| Button cell 5 | 2.211 | 87.5 | 94.8 |
| Button cell 6 | 2.328 | 94.5 | 94.5 |
| Button cell 7 | 2.247 | 92.1 | 94.5 |
| Button cell 8 | 2.229 | 88.6 | 94.4 |
| Button cell 9 | 2.219 | 92.9 | 94.0 |
| Button cell 10 | 2.257 | 92.6 | 94.1 |
| Button cell 11 | 2.218 | 92.1 | 93.9 |
| Button cell 12 | 2.155 | 91.9 | 94.8 |
| Button cell 13 | 2.145 | 92.8 | 92.6 |
| Button cell 14 | 2.028 | 75.0 | 84.0 |
From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:
because the lithium ion battery negative pole of this application has the upper strata and is the lithium titanate layer, the centre is the graphite layer, the lower floor is the structure of negative current collector, consequently, is used for the lithium ion battery negative pole of this application, and the gram capacity on performance lithium titanate layer that can be more abundant is through the indirect and negative current collector's of graphite layer contact on the one hand lithium titanate layer. On the other hand, when the lithium ion battery is formed for the first time, lithium ions are in contact with the lithium titanate layer and the graphite layer through the electrolyte, and the electrode potential of the lithium titanate is relatively higher than that of the graphite, so that the lithium ions and the lithium titanate are subjected to chemical reaction, the rate of lithium ions being embedded into the lithium titanate is higher than the rate of lithium ions being embedded into the graphite, the amount of the graphite participating in side reaction in the charging process of the battery is further reduced, the irreversible capacity loss of the graphite is reduced, and the cycle performance and the rate capability of the lithium ion battery are further improved.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A lithium ion battery negative electrode, comprising: the lithium ion battery comprises a negative current collector, a lithium titanate layer and a graphite layer, wherein the lithium titanate layer and the graphite layer are coated on the surface of the negative current collector, and conductive agents are respectively and independently dispersed in the lithium titanate layer and the graphite layer, and the graphite layer is arranged between the negative current collector and the lithium titanate layer.
2. The negative electrode for a lithium ion battery according to claim 1, wherein the thickness of the lithium titanate layer is 15 to 30 μm.
3. The negative electrode for a lithium ion battery according to claim 2, wherein the graphite layer has a thickness of 50 to 125 μm.
4. The negative electrode for a lithium ion battery according to claim 3, wherein a thickness ratio of the graphite layer to the lithium titanate layer is 2 to 6.25: 1.
5. The lithium ion battery negative electrode according to any one of claims 1 to 4, wherein the conductive agent is selected from any one or more of acetylene black, Ketjen black and carbon nanotubes, preferably, the mass ratio of lithium titanate in the lithium titanate layer to the conductive agent dispersed in the lithium titanate layer is 19.2-28: 0.4-1, and preferably, the mass ratio of graphite in the graphite layer to the conductive agent dispersed in the graphite layer is 48-50: 1-2.
6. The lithium ion battery negative electrode of any one of claims 1 to 4, wherein the negative electrode current collector is a copper foil or an aluminum foil.
7. A preparation method of a lithium ion battery cathode is characterized by comprising the following steps:
step S1, carrying out first mixing on graphite, a first conductive agent, a first binder and a first solvent to obtain a graphite suspension;
step S2, performing second mixing on lithium titanate, a second conductive agent, a second binder and a second solvent to obtain a lithium titanate suspension;
step S3, arranging the graphite suspension on the surface of a negative current collector to obtain a pole piece containing a graphite layer; and
and step S4, arranging the lithium titanate suspension on the surface of the graphite layer to obtain the lithium ion battery cathode.
8. The preparation method according to claim 7, wherein the graphite suspension is coated on the surface of the negative current collector by extrusion coating or transfer coating, preferably the solid content of the graphite suspension is 50-52%, preferably the viscosity of the graphite suspension is 2000-6000 mPas, preferably the first conductive agent is selected from one or more of acetylene black, Ketjen black and carbon nanotubes, preferably the first binder is polyvinylidene fluoride and/or styrene butadiene rubber, preferably the first solvent is N-methyl pyrrolidone and/or water, and preferably the mass ratio of the graphite, the first conductive agent, the first binder and the first solvent is 48-50: 1-2: 48-50.
9. The preparation method according to claim 7, characterized in that the lithium titanate suspension is coated on the surface of the graphite layer by gravure coating, preferably the lithium titanate is a lithium titanate single crystal, preferably the lithium titanate single crystal has a D50 particle size of 20-500 nm, preferably the fineness of the lithium titanate suspension is 0.5-12 μm, preferably the solid content of the lithium titanate suspension is 39-41%, preferably the viscosity of the lithium titanate suspension is 2000-4500 mPas, preferably the second conductive agent is selected from one or more of acetylene black, Ketjen black and carbon nanotubes, preferably the second binder is polyvinylidene fluoride and/or styrene butadiene rubber, preferably the second solvent is azomethylpyrrolidone and/or water, preferably, the mass ratio of the lithium titanate, the second conductive agent, the second binder and the second solvent is 19.2-28: 0.4-1: 70-80.
10. A lithium ion battery comprising a positive electrode and a negative electrode, wherein the negative electrode is the lithium ion battery negative electrode of any one of claims 1 to 6.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113346043A (en) * | 2021-06-04 | 2021-09-03 | 江西安驰新能源科技有限公司 | Low-temperature lithium ion battery positive pole piece and preparation method thereof, and lithium ion battery |
| WO2023202289A1 (en) * | 2022-04-20 | 2023-10-26 | 宁德时代新能源科技股份有限公司 | Negative electrode plate and preparation method therefor, secondary battery, battery module, battery pack, and electric device |
| WO2023240595A1 (en) * | 2022-06-17 | 2023-12-21 | 宁德时代新能源科技股份有限公司 | Negative electrode plate and manufacturing method therefor, electrode assembly, and secondary battery |
| WO2024055188A1 (en) * | 2022-09-14 | 2024-03-21 | 宁德时代新能源科技股份有限公司 | Negative electrode sheet, secondary battery and electric apparatus |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113346043A (en) * | 2021-06-04 | 2021-09-03 | 江西安驰新能源科技有限公司 | Low-temperature lithium ion battery positive pole piece and preparation method thereof, and lithium ion battery |
| WO2023202289A1 (en) * | 2022-04-20 | 2023-10-26 | 宁德时代新能源科技股份有限公司 | Negative electrode plate and preparation method therefor, secondary battery, battery module, battery pack, and electric device |
| WO2023240595A1 (en) * | 2022-06-17 | 2023-12-21 | 宁德时代新能源科技股份有限公司 | Negative electrode plate and manufacturing method therefor, electrode assembly, and secondary battery |
| WO2024055188A1 (en) * | 2022-09-14 | 2024-03-21 | 宁德时代新能源科技股份有限公司 | Negative electrode sheet, secondary battery and electric apparatus |
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