CN112331826A - Modified lithium ion battery positive electrode material and preparation method and application thereof - Google Patents
Modified lithium ion battery positive electrode material and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a modified lithium ion battery anode material and a preparation method and application thereof, wherein the modified lithium ion battery anode material has a core-shell structure and sequentially comprises a lithium ion battery anode material core, a polycation polymer layer and a graphene oxide layer from inside to outside, and the surface of the lithium ion battery anode material is electronegative; if the surface of the lithium ion battery anode material is electropositive, a polyanion polymer layer is arranged between the lithium ion battery anode material core and the polycation polymer layer. The modified lithium ion battery anode material has excellent cycle stability, stable charge and discharge, and low capacity reduction degree after multiple charge and discharge; the lithium ion battery anode material can be modified by using trace graphene oxide, so that the cycle stability of the anode material can be effectively improved; the invention is suitable for various lithium ion battery anode materials, has wide coating range and strong applicability; and can carry out multilayer cladding as required, the cladding thickness can be regulated and control.
Description
Technical Field
The invention relates to the technical field of lithium ion battery materials, in particular to a modified lithium ion battery anode material and a preparation method and application thereof.
Background
With the rapid development of high and new technologies and the excessive consumption of traditional primary energy, a series of environmental problems are derived, and the contradiction between energy supply and demand gradually becomes a great challenge for human beings. Among all renewable clean energy sources, lithium ion batteries dominate the electrochemical energy storage field due to the advantages of slow self-discharge, long cycle life, no memory effect, high energy/power density and the like. At present, research aiming at lithium ion batteries mainly focuses on developing novel high-energy density electrode materials, developing high-safety solid polymers, cathode metal protection technology, battery management systems and the like. The positive electrode material is a core factor which directly influences the overall performance of the battery, and an ideal lithium ion battery needs to have high energy density, stable cycle performance and rate capability, good safety and lower economic cost. However, the layered positive electrode materials currently in wide use, while capable of providing higher specific capacities, dissolution of the surface active material and formation of the CEI film cause rapid decay in subsequent cycles.
In view of the above-mentioned drawbacks of the cathode material, researchers have tried many modification methods, for example, a cationic polymer modified graphene oxide and a lithium-rich manganese-based cathode material are self-assembled by electrostatic interaction, the charge-discharge cycling effect of the lithium-rich manganese-based cathode material modified by the method is not stable, and the modified material has instability in the cycling process, which results in significant fluctuation of the capacity around 30 cycles. Moreover, the modification method needs to consume a large amount of graphene oxide, and the cost is high.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art. To this end, a first object of the present invention is to provide a modified lithium ion battery positive electrode material having good cycle stability.
The modified lithium ion battery positive electrode material has a core-shell structure and sequentially comprises a lithium ion battery positive electrode material core, a polycationic polymer layer and a graphene oxide layer from inside to outside, and the surface of the lithium ion battery positive electrode material is electronegative.
Compared with the prior art, the graphene oxide is coated on the surface of the lithium ion battery anode material through the polycation polymer, so that the electron circulation path is improved, and the cycle performance of the lithium ion battery anode material is effectively improved.
The lithium ion battery anode material is a lithium ion battery layered anode material, such as LiNi0.8Co0.1Mn0.1O2、LiNi0.5Co0.2Mn0.3O2、LiNi0.5Co0.5O2、LiNiO2。
The polycation polymer is selected from one or more of polydiallyl ammonium chloride (PDDA), polyethyleneimine, polyvinylamine and polyvinylpyridine. The polycation polymer is used as a positive charge matrix and can be coated on the surface of a lithium ion battery positive electrode material with negative electricity through electrostatic action to form a polycation polymer layer with positive charge; meanwhile, as the graphene oxide is negatively charged, the polycation polymer layer can adsorb the graphene oxide on the surface of the graphene oxide layer through electrostatic action to form the graphene oxide layer.
The mass ratio of the lithium ion battery anode material core to the polycation polymer layer and the graphene oxide layer is 1 (0.01-0.2) to 0.001-0.02.
Or the modified lithium ion battery anode material has a core-shell structure and sequentially comprises a lithium ion battery anode material core, a polyanion polymer layer, a polycation polymer layer and a graphene oxide layer from inside to outside, and the surface of the lithium ion battery anode material is electropositive.
The polyanion polymer is selected from any one or more of polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, polyvinyl sulfonic acid and polyvinyl phosphoric acid.
The above-mentionedThe lithium ion battery anode material is selected from LiCoO2And the like.
The mass ratio of the lithium ion battery anode material core, the polyanionic polymer layer, the polycationic polymer layer and the graphene oxide layer is 1 (0.005-0.1) to (0.01-0.2) to (0.001-0.02).
The second purpose of the invention is to provide a preparation method of the modified lithium ion battery anode material.
Specifically, the preparation method of the modified lithium ion battery anode material comprises the following steps:
(1) detecting the electrical property of the surface of the lithium ion battery anode material;
(2) when the surface of the lithium ion battery anode material is negative, coating the lithium ion battery anode material with a polycation polymer to obtain a polycation polymer layer on the surface of the lithium ion battery anode material; then coating a graphene oxide layer on the surface of the polycation polymer layer;
(3) when the surface of the lithium ion battery anode material is positive, coating the lithium ion battery anode material with a polyanion polymer to obtain a polyanion polymer layer on the surface of the lithium ion battery anode material; then coating a polycation polymer layer on the surface of the polyanion polymer layer, and finally coating a graphene oxide layer on the surface of the polycation polymer layer.
More specifically, in the step (2), the polycationic polymer layer is prepared by dispersing the lithium ion battery cathode material in a polycationic polymer solution to obtain the polycationic polymer layer.
The concentration of the polycation polymer solution is 0.5-2 g/L.
The preparation method of the graphene oxide layer comprises the steps of mixing the lithium ion battery anode material coated with the polycation polymer layer with a graphene oxide solution, and forming the graphene oxide layer on the surface of the polycation polymer layer through electrostatic action. In order to increase the coating amount of graphene oxide, a multilayer graphene oxide can be prepared by repeating this step.
The concentration of the graphene oxide solution is 0.01-0.05 g/L.
In the step (2), a drying and/or sintering step is further included after the graphene oxide layer is coated.
The drying temperature is 60-100 ℃.
The sintering temperature is 200-500 ℃, and the sintering time is 1-3 h. The crystallinity of the modified lithium ion battery anode material can be optimized through low-temperature sintering.
The polyanionic polymer layer, the polycationic polymer layer and the graphene oxide layer in the step (3) are also prepared by a similar method, and the same drying and sintering steps can also be included after the graphene oxide layer is coated. When preparing the polyanionic polymer layer, 0.01-0.2 g/L polyanionic polymer solution is used, preferably 0.1-0.2 g/L polyanionic polymer solution.
The third purpose of the invention is to provide the application of the modified lithium ion battery anode material. Specifically, the lithium ion battery comprises the modified lithium ion battery cathode material.
Compared with the prior art, the invention has the following beneficial effects:
(1) the modified lithium ion battery anode material has excellent cycle stability, stable charge and discharge and low capacity reduction degree after multiple charge and discharge.
(2) According to the invention, the lithium ion battery anode material can be modified only by a very trace amount of graphene oxide, so that the cycle stability of the anode material can be effectively improved, the use amount of the graphene oxide is greatly reduced compared with that of the prior art, the material is saved, and the cost is reduced.
(3) The modification method is suitable for various lithium ion battery anode materials, and has wide coating range and strong applicability; and can carry out multilayer cladding as required, the cladding thickness can be regulated and control.
Drawings
FIG. 1 is a schematic structural diagram of a modified lithium ion battery positive electrode material according to the present invention;
FIG. 2 is an XRD pattern of 811 and 811-GO;
FIG. 3 is a scanning electron micrograph of 811(a, b) and 811-GO (c, d);
FIG. 4 shows Raman test results for 811 and 811-GO;
FIG. 5 shows the results of thermogravimetric analysis of 811 and 811-GO;
FIG. 6 is a graph comparing the first charge and discharge performance of 811 and 811-GO;
FIG. 7 is a graph comparing charge and discharge cycle performance of 811 and 811-GO;
FIG. 8 shows the results of the charge and discharge tests of 811 and 811-GO at different currents;
FIG. 9 is LiCoO2(a) And LiCoO2-scanning electron micrographs of go (b);
FIG. 10 is LiCoO2And LiCoO2-raman test results of GO;
FIG. 11 is LiCoO2And LiCoO2-a comparison graph of charge-discharge cycle performance of GO;
FIG. 12 is LiCoO2And LiCoO2-GO charge and discharge test results at different currents.
Detailed Description
The invention provides a modified lithium ion battery anode material which has a core-shell structure and sequentially comprises a lithium ion battery anode material (layered anode material) core, a polycation polymer (positive charge substrate) layer and a graphene oxide layer from inside to outside, wherein the surface of the lithium ion battery anode material is electronegative, and the structure of the lithium ion battery anode material is shown in figure 1 a.
Or, the modified lithium ion battery positive electrode material has a core-shell structure, and sequentially comprises a lithium ion battery positive electrode material (layered positive electrode material) core, a polyanion polymer (negative charge matrix) layer, a polycation polymer (positive charge matrix) layer and a graphene oxide layer from inside to outside, wherein the surface of the lithium ion battery positive electrode material is electropositive, and the structure of the lithium ion battery positive electrode material is shown in fig. 1 b.
The technical solution of the present invention is further described below with reference to specific examples.
Example 1
The modified lithium ion battery anode material has a core-shell structure and sequentially comprises a lithium ion battery ternary electrode material LiNi from inside to outside0.8Co0.1Mn0.1O2A core, a polydiallylammonium chloride (PDDA) layer, and a graphene oxide layer.
The preparation method of the modified lithium ion battery cathode material comprises the following steps:
ni synthesis by coprecipitation method0.8Co0.1Mn0.1C2O4·2H2O, vacuum drying at 80 ℃ overnight, reacting with LiOH & H2O according to LiNi0.8Co0.1Mn0.1O2The mixture with the excess of 15 percent of the calculated coefficient is uniformly mixed and annealed for 6 hours at 500 ℃. Fully mixing the reactants, and annealing at 750 ℃ for 6h to obtain the active material LiNi0.8Co0.1Mn0.1O2(labeled 811). Weighing 1g of the active material, respectively carrying out ultrasonic cleaning for 3 times by using ethanol and deionized water, removing supernatant, and testing that the surface electric property is negative.
Uniformly dispersing the treated active material in 100mL of 1g/L PDDA solution, performing ultrasonic treatment for 20min, stirring for 20min, coating the surface of the active material, namely successfully coating a PDDA positive charge layer on the surface of the active material, and then washing with deionized water.
And then mixing 100mL of 0.02g/L Graphene Oxide (GO) solution with the active material coated with the positive charge layer by utilizing the electrostatic action, carrying out ultrasonic treatment for 20min, stirring for 1h to enable the GO to be uniformly adsorbed on the surface of the target material, standing, removing supernatant, washing for 3 times by using deionized water, carrying out suction filtration, centrifuging, and drying in an oven at the temperature of 80 ℃ overnight to obtain the modified lithium ion battery positive electrode material (marked as 811-GO).
The modified lithium ion battery anode material is subjected to size mixing, coating and packaging to obtain the lithium ion battery.
Material characterization and performance testing:
(1) XRD, SEM, Raman and thermogravimetric test results of 811 and 811-GO are respectively shown in figures 2-5, and it can be seen from figure 2 that the GO coating layer does not affect the intrinsic crystal structure of the material.
Fig. 3 reflects GO creases appear on the surface after coating.
It can be seen from FIG. 4 that some disordered sp appears after coating GO2Bond and sp3A key.
As can be seen from fig. 5, the coating of GO is about 0.57% of the material mass.
(2) The initial charge and discharge performance of 811 and 811-GO is tested under the conditions that the voltage range is 2.8-4.5V and the charge and discharge current density is 0.2C, as shown in figure 6. Test results show that the first charge capacity of 811-GO is 180.2mAh/g, and the first discharge capacity is 179.3 mAh/g; 811 had a first charge capacity of 164.9mAh/g and a first discharge capacity of 163.2 mAh/g.
The charge-discharge cycle performance of 811 and 811-GO is tested in the voltage range of 2.8-4.5V under the charge-discharge current density of 0.2C. Test results show that the discharge capacity of 811-GO is kept at 91.6% of the first discharge capacity after 100 cycles, the cycle curve is stable, the phenomenon of sudden high and sudden low in the prior art is avoided, the discharge capacity of 811 without coating is reduced to 48.2% of the first discharge capacity after 100 cycles, and as shown in FIG. 7, the cycle stability of the anode material is obviously improved by coating with the polycation polymer and GO.
The charge and discharge test results of 811 and 811-GO under different currents are shown in FIG. 8, and the rate capability of the modified 811-GO under large current is superior to that of the unmodified 811, which shows that the rate capability of the material is successfully improved and the capacity is improved to a certain extent.
Example 2
The modified lithium ion battery anode material has a core-shell structure and sequentially comprises a lithium ion battery ternary electrode material LiNi from inside to outside0.5Co0.2Mn0.3O2A core, a polydiallylammonium chloride (PDDA) layer, and a graphene oxide layer.
The preparation method of the modified lithium ion battery cathode material comprises the following steps:
the ratio of the configured measurement coefficients is 5: 3: 2 NiSO4·6H2O、CoSO4·7H2O、MnSO4·H2Solution of O, at a concentration ratio of 1: 1.05 of Na2C2O4Synthesis of Ni by coprecipitation0.5Co0.2Mn0.3C2O4·2H2O, vacuum drying at 80 ℃ overnight, reacting with LiOH & H2O according to LiNi0.5Co0.2Mn0.3O2MeteringThe mixture with the coefficient more than 15 percent is evenly mixed and annealed for 6 hours at 500 ℃. Fully mixing the reactants, and annealing at 850 ℃ for 6h to obtain the active material LiNi0.5Co0.2Mn0.3O2Weighing 1g of the active material, respectively carrying out ultrasonic cleaning for 3 times by using ethanol and deionized water, removing supernatant, and testing that the surface electric property is negative.
And uniformly dispersing the treated active material in 100mL of 2g/L PDDA solution, performing ultrasonic treatment for 20min, stirring for 20min, and coating the surface of the active material, namely successfully coating the surface of the active material with a PDDA positive charge layer.
And then mixing 100mL of 0.05g/L Graphene Oxide (GO) solution with the active material coated with the positive charge layer by utilizing the electrostatic action, carrying out ultrasonic treatment for 20min, stirring for 1h to enable the GO to be uniformly adsorbed on the surface of the target material, standing, removing supernatant, washing for 3 times by using deionized water, carrying out suction filtration, centrifuging, and drying in an oven at 80 ℃ overnight to obtain the GO-coated modified lithium ion battery positive electrode material.
The modified lithium ion battery anode material is subjected to size mixing, coating and packaging to obtain the lithium ion battery.
Example 3
A modified lithium ion battery anode material has a core-shell structure and sequentially comprises a lithium ion battery binary electrode material LiNi from inside to outside0.5Co0.5O2A core, a polydiallylammonium chloride (PDDA) layer, and a graphene oxide layer.
The preparation method of the modified lithium ion battery cathode material comprises the following steps:
ni synthesis by coprecipitation method0.5Co0.5C2O4·2H2O, vacuum drying at 80 ℃ overnight, reacting with LiOH & H2O according to LiNi0.5Co0.5O2The mixture with the excess of 15 percent of the calculated coefficient is uniformly mixed and annealed for 6 hours at 500 ℃. Fully mixing the reactants, and annealing at 850 ℃ for 6h to obtain the active material LiNi0.5Co0.5O2The surface electrical property is tested to be negative.
Weighing 1g of the active material, firstly ultrasonically cleaning for 3 times by ethanol and deionized water respectively, removing supernatant, and carrying out suction filtration and drying for later use.
And uniformly dispersing the treated active material in 100mL of 0.5g/L PDDA solution, performing ultrasonic treatment for 20min, stirring for 20min, and coating the surface of the active material, namely successfully coating the surface of the active material with a PDDA positive charge layer.
Then, mixing 100mL of 0.01g/L Graphene Oxide (GO) solution with the active material coated with the positive charge layer by utilizing the electrostatic action, carrying out ultrasonic treatment for 20min, stirring for 1h to enable GO to be uniformly adsorbed on the surface of a target material, standing, removing supernatant, washing for 3 times by using deionized water, carrying out suction filtration, centrifuging, and drying in an oven at 80 ℃ overnight; and then annealing for 2h at 350 ℃ in the air atmosphere to obtain the modified lithium ion battery anode material.
The modified lithium ion battery anode material is subjected to size mixing, coating and packaging to obtain the lithium ion battery.
Example 4
The modified lithium ion battery anode material has a core-shell structure and sequentially comprises a lithium ion battery unitary electrode material LiCoO from inside to outside2An inner core, a sodium polyacrylate layer, a polydiallylammonium chloride (PDDA) layer, and a graphene oxide layer.
The preparation method of the modified lithium ion battery cathode material comprises the following steps:
CoC synthesis by coprecipitation method2O4·2H2O, vacuum drying at 80 ℃ overnight, reacting with LiOH & H2O according to LiCoO2The mixture with the excess of 15 percent of the calculated coefficient is uniformly mixed and annealed for 6 hours at 500 ℃. Fully mixing the reactants, and annealing at 850 ℃ for 6h to obtain an active material LiCoO2. Weighing 1g of the active material, respectively carrying out ultrasonic cleaning for 3 times by using ethanol and deionized water, removing supernatant, and testing the surface electric property to be positive.
Uniformly dispersing the treated active material in 100mL of 0.1g/L sodium polyacrylate solution, performing ultrasonic treatment for 20min, stirring for 20min, and coating the surface of the active material, namely successfully coating the surface of the active material with a sodium polyacrylate negative charge layer.
Uniformly dispersing the treated material in 100mL of 1g/L PDDA solution, performing ultrasonic treatment for 20min, stirring for 20min, and coating the surface of the active material, namely coating the surface of the material coated with the negative charge layer with a PDDA positive charge layer.
Then, mixing 100mL of 0.02g/L Graphene Oxide (GO) solution with the active material by utilizing electrostatic action, carrying out ultrasonic treatment for 20min, stirring for 1h to enable GO to be uniformly adsorbed on the surface of a target material, standing, removing supernatant, washing for 3 times by using deionized water, carrying out suction filtration and centrifugation, and drying in an oven at 80 ℃ overnight; then annealing for 2h at 350 ℃ in the air atmosphere to obtain the modified lithium ion battery anode material which is marked as LiCoO2-GO。
The modified lithium ion battery anode material is subjected to size mixing, coating and packaging to obtain the lithium ion battery.
Material characterization and performance testing:
(1)LiCoO2and LiCoO2SEM and Raman test results of GO are respectively shown in FIGS. 9-10, and it can be seen from FIG. 9 that GO coating layer is successfully coated on LiCoO2The surface of the single crystal particle.
It can be seen from FIG. 10 that some disordered sp appears after coating GO2Bond and sp3Bonds corresponding to the G and D bonds of the GO material, respectively.
(2) Under the conditions of voltage range of 2.8-4.5V and charge-discharge current density of 0.2C, LiCoO is treated2And LiCoO2The charge-discharge cycle performance of GO is tested, and the test result shows that LiCoO2The discharge capacity of GO is kept at 80.7 percent of the first discharge capacity after 200 cycles of cycling, the cycling curve is smooth, and the phenomenon of suddenly rising and suddenly falling in the prior art does not occur, but the LiCoO which is not coated does not occur2The discharge capacity after 200 cycles was reduced to 47.6% of the first discharge capacity, as shown in fig. 11, which illustrates that the cycle stability of the positive electrode material was significantly improved by coating with a polyanionic polymer, a polycationic polymer and GO.
LiCoO in the voltage range of 2.8-4.5V2And LiCoO2The results of the charge and discharge tests of-GO at different currents are shown in FIG. 12, modified LiCoO2The rate capability of-GO is superior to that of unmodified LiCoO2The method successfully improves the rate capability of the material and has certain capacity improvement.
Example 5
A modified lithium ion battery anode material has a core-shell structure and sequentially comprises a lithium ion battery unitary electrode material LiNiO from inside to outside2A core, a polydiallylammonium chloride (PDDA) layer, and a graphene oxide layer.
The preparation method of the modified lithium ion battery cathode material comprises the following steps:
synthesizing NiC by coprecipitation method2O4·2H2O, vacuum drying at 80 ℃ overnight, reacting with LiOH & H2O according to LiNiO2The mixture with the excess of 15 percent of the calculated coefficient is uniformly mixed and annealed for 6 hours at 500 ℃. Fully mixing the reactants, and annealing at 750 ℃ for 6h to obtain an active material LiNiO2.1g of the active material is weighed, firstly, ultrasonic cleaning is carried out for 3 times respectively through ethanol and deionized water, supernatant liquor is removed, and the surface electric property is tested to be negative.
And uniformly dispersing the treated active material in 100mL of 1g/L PDDA solution, performing ultrasonic treatment for 20min, stirring for 20min, and coating the surface of the active material, namely successfully coating the surface of the active material with a PDDA positive charge layer.
Then, mixing 100mL of 0.05g/L Graphene Oxide (GO) solution with the active material coated with the positive charge layer by utilizing the electrostatic action, carrying out ultrasonic treatment for 20min, stirring for 1h to enable GO to be uniformly adsorbed on the surface of a target material, standing, removing supernatant, washing for 3 times by using deionized water, carrying out suction filtration, centrifuging, and drying in an oven at 80 ℃ overnight; and then annealing for 2h at 350 ℃ in the air atmosphere to obtain the modified lithium ion battery anode material.
The modified lithium ion battery anode material is subjected to size mixing, coating and packaging to obtain the lithium ion battery.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (10)
1. A modified lithium ion battery anode material is characterized in that: the modified lithium ion battery anode material has a core-shell structure and sequentially comprises a lithium ion battery anode material core, a polycation polymer layer and a graphene oxide layer from inside to outside, and the surface of the lithium ion battery anode material is electronegative.
2. The modified lithium ion battery cathode material according to claim 1, wherein: the lithium ion battery anode material is selected from LiNi0.8Co0.1Mn0.1O2、LiNi0.5Co0.2Mn0.3O2、LiNi0.5Co0.5O2、LiNiO2Any one or more of them.
3. The modified lithium ion battery cathode material according to claim 1, wherein: the polycation polymer is selected from one or more of polydiallyl ammonium chloride, polyethyleneimine, polyvinylamine and polyvinyl pyridine.
4. The modified lithium ion battery positive electrode material according to any one of claims 1 to 3, characterized in that: the mass ratio of the lithium ion battery anode material core to the polycation polymer layer and the graphene oxide layer is 1 (0.01-0.2) to 0.001-0.02.
5. A modified lithium ion battery anode material is characterized in that: the modified lithium ion battery anode material has a core-shell structure and sequentially comprises a lithium ion battery anode material core, a polyanion polymer layer, a polycation polymer layer and a graphene oxide layer from inside to outside, and the surface of the lithium ion battery anode material is electropositive.
6. The modified lithium ion battery cathode material according to claim 5, wherein: the polyanion polymer is selected from any one or more of polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, polyvinyl sulfonic acid and polyvinyl phosphoric acid.
7. The modified lithium ion battery cathode material according to claim 5, wherein: the mass ratio of the lithium ion battery anode material core, the polyanionic polymer layer, the polycationic polymer layer and the graphene oxide layer is 1 (0.005-0.1) to (0.01-0.2) to (0.001-0.02).
8. A preparation method of a modified lithium ion battery anode material is characterized by comprising the following steps: the method comprises the following steps:
(1) detecting the electrical property of the surface of the lithium ion battery anode material;
(2) when the surface of the lithium ion battery anode material is negative, coating the lithium ion battery anode material with a polycation polymer to obtain a polycation polymer layer on the surface of the lithium ion battery anode material; then coating a graphene oxide layer on the surface of the polycation polymer layer;
(3) when the surface of the lithium ion battery anode material is positive, coating the lithium ion battery anode material with a polyanion polymer to obtain a polyanion polymer layer on the surface of the lithium ion battery anode material; then coating a polycation polymer layer on the surface of the polyanion polymer layer, and finally coating a graphene oxide layer on the surface of the polycation polymer layer.
9. The method of claim 8, wherein: a drying and/or sintering step is also included after coating the graphene oxide layer.
10. A lithium ion battery, characterized by: the modified lithium ion battery cathode material comprises the modified lithium ion battery cathode material as claimed in any one of claims 1 to 4 or 5 to 7.
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