CN109768274B - Battery positive electrode material precursor, battery positive electrode material, preparation method and application thereof - Google Patents
Battery positive electrode material precursor, battery positive electrode material, preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a battery anode materialThe preparation method of the material precursor comprises the following steps: dissolving Ni-based nitrate, Co-based nitrate, Mn-based nitrate and Cd-based nitrate in absolute ethyl alcohol to obtain a mixed solution; and carrying out solvothermal reaction on the mixed solution to precipitate Ni, Co, Mn and Cd elements together, and carrying out post-treatment on the obtained precipitate to obtain the Ni-Co-Mn-Cd-based battery positive electrode material precursor. The invention utilizes K of four elements of Ni, Co, Mn and CdspSimilar to the characteristic, the four elements are precipitated together in the solvothermal synthesis process by utilizing a solvothermal method to obtain a Ni-Co-Mn-Cd-based battery anode material precursor, and then the Cd-doped ternary battery anode material is synthesized by a high-temperature solid-phase roasting method. The Cd is an inactive element with good conductivity, can stabilize the structure of the material after doping, and improves the electronic conductivity of the material.
Description
Technical Field
The invention relates to a battery anode material, in particular to a battery anode material precursor, a battery anode material, a preparation method and an application thereof.
Background
The layered high nickel cathode material is considered to be one of the most promising lithium ion battery cathode materials due to its high capacity and low cost, however, its commercial utilization is limited due to its undesirable cycling performance, storage performance, low coulombic efficiency and thermal instability. The main reasons for this phenomenon are:
(1) due to Ni2+(0.069nm) and Li+The radius of (0.076nm) is the same, Li occurs in the layered structure+/Ni2+Mixed arrangement of (1);
(2) edge reaction of electrode and electrolyte interface to produce Li2CO3Or LiOH, which has a great influence on the electrochemical performance.
In view of this, modification is often used to suppress these factors affecting electrochemical performance. Ion doping, which is considered to be one of the most effective methods for overcoming these difficulties, is considered to be a simple method for improving the structure and thermal stability of the layered high-nickel cathode material, and the doping ions reported so far are mainly Al3+，Mg2+，Ti4+，Mo6+，Nd3+And Na+And the like. Although the current ion doping mode has great progress in stabilizing the structure and improving the electrochemical performance, most of the doping modification methods are to dope the material with elements in the lithium-mixed high-temperature roasting stage after the precursor is synthesized, and few reports are made on in-situ doping modification of the material in the precursor synthesis stage.
Compared with in-situ doping modification, ex-situ doping modification is difficult to dope doping elements into a material main body to occupy positions of transition metals, and simultaneously, the ex-situ doping mode also makes the modification process more complicated.
Disclosure of Invention
The invention mainly aims to provide a battery anode material precursor, a battery anode material, a preparation method and application thereof, so as to overcome the defects in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of a battery positive electrode material precursor comprises the following steps:
dissolving Ni-based nitrate, Co-based nitrate, Mn-based nitrate and Cd-based nitrate in absolute ethyl alcohol to obtain a mixed solution;
and carrying out solvothermal reaction on the mixed solution to precipitate Ni, Co, Mn and Cd elements together, and carrying out post-treatment on the obtained precipitate to obtain the Ni-Co-Mn-Cd-based battery positive electrode material precursor.
The embodiment of the invention also provides a battery positive electrode material precursor prepared by the method.
The embodiment of the invention also provides a preparation method of the battery anode material, which comprises the following steps:
and mixing the precursor of the battery positive electrode material with lithium salt, and then sequentially carrying out pre-roasting and roasting to obtain the Cd-doped battery positive electrode material.
The embodiment of the invention also provides the battery cathode material prepared by the method.
The embodiment of the invention also provides the application of the battery anode material precursor or the battery anode material in the preparation of a lithium ion battery.
Compared with the prior art, the invention has the beneficial effects that:
(1) the invention utilizes K of four elements of Ni, Co, Mn and CdspThis property is similar to that of the previous one (Ksp of Ni, Co, Mn, Cd is 2.0 × 10-15，1.9×10-15，1.6×10-13，3.2×10-14) And Cd is used as a modifying element. The method comprises the steps of taking absolute ethyl alcohol as a solvent and nitrate as a transition metal salt, utilizing a solvothermal method to jointly precipitate four elements in a solvothermal synthesis process to obtain a Ni-Co-Mn-Cd-based battery anode material precursor, and then synthesizing a Cd-doped ternary battery anode material by a high-temperature solid-phase roasting method.
(2) The Cd is an inactive element with good conductivity, can stabilize the structure of the material after doping, and improves the electronic conductivity of the material.
(3) CdO has a high carrier concentration and oxygen vacancies, and is therefore considered to be an n-type semiconductor with a resistivity of 10-2-10-4Omega, which is beneficial to reducing the impedance of the material.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 shows XRD diffraction patterns of the positive electrode materials of the batteries of examples 1, 2, 3 and 1.
Fig. 2 is an SEM photograph of the battery positive electrode material precursor at a Cd doping amount of 0.01mol in example 1.
FIG. 3 is an SEM photograph of the positive electrode material of the battery in example 1 at a Cd doping amount of 0.01 mol.
Fig. 4 is an SEM photograph of the cell positive electrode material precursor at a Cd doping amount of 0.02mol in example 2.
Fig. 5 is an SEM photograph of the battery positive electrode material at a Cd doping amount of 0.02mol in example 2.
Fig. 6 is an SEM photograph of the battery positive electrode material precursor at a Cd doping amount of 0.03mol in example 3.
Fig. 7 is an SEM photograph of the battery positive electrode material at a Cd doping amount of 0.03mol in example 3.
Fig. 8 is an SEM photograph of the Cd-undoped battery positive electrode material precursor synthesized in comparative example 1.
Fig. 9 is an SEM photograph of the Cd-undoped battery cathode material synthesized in comparative example 1.
Fig. 10 is a graph showing the first charge/discharge performance of the positive electrode material of the batteries of examples 1, 2, 3 and 1.
Fig. 11 is a graph showing the cycle performance analysis of the positive electrode materials of the batteries of examples 1, 2, 3 and 1.
Fig. 12 is a graph showing rate performance analysis of the positive electrode materials of the batteries of examples 1, 2, 3 and 1.
Detailed Description
In view of the deficiencies in the prior art, the inventors of the present invention have made extensive studies and extensive practices to propose the technical solution of the present invention, and further explain the technical solution, the implementation process and the principle thereof, etc.
The modified elements in the synthesis stage of the precursor have K similar to Ni, Co and MnspSo that the Ksp of Ni, Co, Mn and Cd is 2.0 × 10-15，1.9×10-15，1.6×10-13，3.2×10-14Of which K isspClose. In the invention, Cd is used as a modification element, four elements of Ni, Co, Mn and Cd are jointly precipitated in the solvothermal reaction synthesis process by a solvothermal method to synthesize a Ni-Co-Mn-Cd-based battery anode material precursor, and then the Cd-doped battery anode material is synthesized by lithium mixing and roasting.
As one aspect of the technical scheme of the invention, the invention relates to a preparation method of a precursor of a battery positive electrode material, which comprises the following steps:
dissolving Ni-based nitrate, Co-based nitrate, Mn-based nitrate and Cd-based nitrate in absolute ethyl alcohol to obtain a mixed solution;
and carrying out solvothermal reaction on the mixed solution to precipitate Ni, Co, Mn and Cd elements together, and carrying out post-treatment on the obtained precipitate to obtain the Ni-Co-Mn-Cd-based battery positive electrode material precursor.
In the invention, the material is subjected to in-situ doping modification in the synthesis stage of the precursor of the battery anode material, and the specific reaction principle is shown in the following equation:
7CH3CH2OH+4NO3 -→7CH3CHO+2NO↑+N2O+4OH-+5H2O； (1)
3Ni2++6OH-+2H2O→3Ni(OH)2·2H2O↓； (2)
2Co2++Mn2++6OH-→MnCo2O4↓+3H2O； (3)
Co2++2Mn2++6OH-→CoMn2O4↓+3H2O； (4)
Cd2++6OH-+2H2O→3Cd(OH)2·2H2O↓； (5)
in some embodiments, specifically including: adding 0.1 to 0.3mol of Ni (NO) in total3)2·6H2O、Co(NO3)2·6H2O、Mn(NO3)2Aqueous solution and Cd (NO)3)2·4H2Dissolving O in 100-200 mL of absolute ethanol to obtain a mixed solution.
Among them, it is preferable to dissolve in 140 to 160mL of anhydrous ethanol.
In some embodiments, the molar ratio n of the elements Ni, Co, Mn, Cd (Ni) in the mixed solutionxCoyMnz) nCd is 0.97-1: 0-0.03, wherein x + y + z is 1, nCd is not equal to 0.
In some more preferred embodiments, the molar ratio n (Ni) of the Ni, Co, Mn, Cd elements in the mixed solutionxCoyMnz) nCd is 0.98-1: 0-0.02, wherein x + y + z is 1, nCd is not equal to 0.
In some embodiments, the temperature of the solvothermal reaction is 150-160 ℃, and the time of the solvothermal reaction is 10-14 h.
Wherein, the mixed solution is placed in a polytetrafluoroethylene reaction kettle for solvothermal reaction.
In some embodiments, the post-treatment specifically comprises: and (3) washing the precipitate obtained after the Ni, Co, Mn and Cd elements are jointly precipitated by adopting absolute ethyl alcohol for more than one time, and then drying and roasting.
In some preferred embodiments, the drying temperature is 70-90 ℃ and the drying time is 10-14 h.
In some more preferable embodiments, the roasting temperature is 440-460 ℃, and the roasting time is 4-6 h
The embodiment of the invention also provides a battery positive electrode material precursor prepared by the method.
As another aspect of the technical solution of the present invention, a method for preparing a positive electrode material of a battery includes:
and mixing the precursor of the battery positive electrode material with lithium salt, and then sequentially carrying out pre-roasting and roasting to obtain the Cd-doped battery positive electrode material.
In some embodiments, the pre-baking temperature is 480-520 ℃ and the time is 4-6 h.
In some embodiments, the temperature of the roasting is 830-870 ℃ and the time is 9-12 h.
In some embodiments, the mass ratio of the battery positive electrode material precursor to the lithium salt is 1: 1.03-1.06.
In some embodiments, the lithium salt comprises lithium carbonate.
The embodiment of the invention also provides a battery cathode material prepared by the method.
In some specific embodiments, a method of making a battery positive electrode material comprises:
s1, adding Ni (NO) in an amount of 0.2mol3)2·6H2O，Co(NO3)2·6H2O，Mn(NO3)2(50 wt% aqueous solution) and Cd (NO)3)2·4H2Dissolving O in 150ml of absolute ethyl alcohol according to a proper ratio respectively to obtain mixed solution;
s2, stirring the mixed solution at room temperature until the mixed solution is completely dissolved, and then averagely dividing the solution into three parts and transferring the three parts to three 100mL polytetrafluoroethylene reaction kettles; the amount of the mixed solution added into the 100mL reaction kettle can be controlled between 1/2 and 2/3;
s3, transferring the reaction kettle into an oven, and standing for 12 hours at 150-160 ℃;
s4, finally washing the precipitate for 4 to 5 times by using absolute ethyl alcohol, and then drying the precipitate in an oven at the temperature of 80 ℃ for 12 hours, wherein in order to ensure that the precipitate has good appearance after high-temperature roasting, the precipitate is roasted at the temperature of 450 ℃ for 5 hours in a muffle furnace before lithium mixing;
s5, mixing Cd doped precursor prepared in S4 with Li2CO3Uniformly mixing according to the proportion of 1: 1.05, placing the mixture into a muffle furnace, pre-roasting for 5 hours at 500 ℃, and then roasting for 10 hours at 850 ℃ to finally obtain the Cd-doped battery cathode material.
As another aspect of the technical solution of the present invention, it relates to an application of the foregoing battery positive electrode material precursor or the foregoing battery positive electrode material in the preparation of a lithium ion battery.
The technical solutions of the present invention will be described in further detail with reference to several preferred embodiments, and it should be apparent that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention. The test methods in the following examples, which are not specified under specific conditions, are generally carried out under conventional conditions.
Example 1
The preparation and test method of the lithium ion battery anode material precursor doped with 0.01mol Cd, the battery anode material (NCM-1) and the lithium ion battery comprises the following steps:
(1) 34.545852g of Ni (NO)3)2·6H2O，11.524788g Co(NO3)2·6H2O，14.17284g Mn(NO3)2(50 wt% aqueous solution) and 0.61692g of Cd (NO)3)2·4H2Dissolving O in 150mL of absolute ethyl alcohol, stirring the mixed solution at room temperature until the mixed solution is completely dissolved, and then averagely dividing the solution into three parts and transferring the three parts to three 100mL polytetrafluoroethylene reaction kettles; the reaction kettle is moved into an oven and placed for 12 hours at the temperature of 150 ℃; finally, washing the precipitate for 4-5 times by using absolute ethyl alcohol, then drying the precipitate in an oven at 80 ℃ for 12h, and roasting the precipitate for 5h at 450 ℃ in a muffle furnace before mixing lithium to obtain a 622 battery positive electrode material precursor with the doping amount of 0.01mol Cd so that the precipitate has good appearance after high-temperature roasting;
(2) the prepared battery anode material precursor and Li2CO3Uniformly mixing the materials according to the mass ratio of 1: 1.05, placing the materials into a muffle furnace, pre-roasting the materials for 5 hours at 500 ℃, and then roasting the materials for 10 hours at 850 ℃ to finally obtain the Li (Ni) with the doping amount of 0.01mol Cd0.6Co0.2Mn0.2)0.99Cd0.01O2A battery positive electrode material (NCM-1);
(3) li (Ni) to be produced0.6Co0.2Mn0.2)0.99Cd0.01O2Uniformly mixing a battery positive electrode material (NCM-1), conductive carbon black super P and a binder PVDF according to the mass ratio of 8: 1, adding a proper amount of 1-methyl-2 pyrrolidone, ball-milling for 15min to prepare slurry, uniformly coating the slurry on an aluminum sheet current collector by using a coating machine, and drying for 2 hours at 70 ℃; then moving to a vacuum drying oven to dry for 12 hours at 120 ℃, and finally tabletting to obtain an electrode slice;
(4) taking the electrode plate obtained in the step (3) as a positive electrode, a lithium plate as a counter electrode, a porous polymer film as a diaphragm (Celgard 2400), and 1mol/L LiPF6And mixed solution of EC, DEC and EMC (volume ratio of 1: 1) is used as electrolyte and assembled into the button cell in a glove box.
Tests show that the first discharge capacity of the battery anode material (NCM-1) under 0.01mol Cd doping amount at 0.1C multiplying power is 186.3mAh/g, and the capacity retention rate can reach 82.8% after 100 times of circulation at 1C.
X-ray diffraction (XRD) pair is used for preparing Li (Ni) as a battery cathode material0.6Co0.2Mn0.2)0.99Cd0.01O2(NCM-1) was subjected to X-ray diffraction, and the diffraction pattern is shown in FIG. 1.
The SEM image of the precursor of the battery cathode material doped with 0.01mol of Cd is shown in figure 2, the shape of the precursor is still spherical, the petal shape of the spherical surface begins to disappear, the surface begins to become compact, and the SEM image of the corresponding battery cathode material is shown in figure 3.
The first charge and discharge performance of the battery cathode material at 0.1C is shown in fig. 10, and the cycle curve of the battery cathode material at 1C rate after 100 cycles is shown in fig. 11. The rate performance curves of the battery cathode material at different rates are shown in fig. 12.
Example 2
The preparation and test method of the lithium ion battery anode material precursor doped with 0.02mol Cd, the battery anode material (NCM-2) and the lithium ion battery comprises the following steps:
(1) 34.197g of Ni (NO)3)2·6H2O，11.408g Co(NO3)2·6H2O，14.0296g Mn(NO3)2(50 wt% aqueous solution) and 1.234g of Cd (NO)3)2·4H2Dissolving O in 100mL of absolute ethyl alcohol, stirring the mixed solution at room temperature until the mixed solution is completely dissolved, and then averagely dividing the solution into three parts and transferring the three parts to three 100mL polytetrafluoroethylene reaction kettles; the reaction kettle is moved into an oven and placed for 10 hours at the temperature of 150 ℃; finally, washing the precipitate for 4-5 times by using absolute ethyl alcohol, then drying the precipitate for 14h in an oven at 70 ℃, and roasting the precipitate for 6h at 440 ℃ in a muffle furnace before mixing lithium so as to obtain a 622 battery anode material precursor with the doping amount of 0.02mol Cd, wherein the high-temperature roasting is carried out for the precipitate to obtain a good appearance;
(2) the prepared battery anode material precursor and Li2CO3Uniformly mixing the materials according to the mass ratio of 1:1.03, placing the materials into a muffle furnace, pre-roasting the materials for 6 hours at 480 ℃, and then roasting the materials for 9 hours at 830 ℃ to finally obtain the Li (Ni) with the doping amount of 0.02mol Cd0.6Co0.2Mn0.2)0.98Cd0.02O2A battery positive electrode material (NCM-2);
(3) li (Ni) to be produced0.6Co0.2Mn0.2)0.98Cd0.02O2Uniformly mixing a battery positive electrode material (NCM-2), conductive carbon black super P and a binder PVDF according to the mass ratio of 8: 1, adding a proper amount of 1-methyl-2 pyrrolidone, ball-milling for 15min to prepare slurry, uniformly coating the slurry on an aluminum sheet current collector by using a coating machine, and drying for 2 hours at 70 ℃; then moving to a vacuum drying oven to dry for 12 hours at 120 ℃, and finally tabletting to obtain an electrode slice;
(4) in the step (3)The obtained electrode plate is used as a positive electrode, a lithium plate is used as a counter electrode, a porous polymer film is used as a diaphragm (Celgard 2400), and 1mol/L LiPF6And mixed solution of EC, DEC and EMC (volume ratio of 1: 1) is used as electrolyte and assembled into the button cell in a glove box.
Tests show that the first discharge capacity of the 0.02mol Cd-doped battery positive electrode material (NCM-2) at the rate of 0.1C is 179.5mAh/g, and the capacity retention rate can reach 81.8% after 100 cycles at 1C.
X-ray diffraction (XRD) pair is used for preparing Li (Ni) as a battery cathode material0.6Co0.2Mn0.2)0.98Cd0.02O2(NCM-2) was subjected to X-ray diffraction, and the diffraction pattern was as shown in FIG. 1.
The SEM image of the battery cathode material precursor doped with 0.02mol Cd is shown in FIG. 4, it can be clearly seen from the image that the shape of the precursor is still spherical, the petal shape of the spherical surface almost disappears, the surface starts to become very dense, and the SEM image of the corresponding battery cathode material is shown in FIG. 5.
The first charge and discharge characteristics at 0.1C are shown in fig. 10. The cycling curve for 100 cycles of the battery positive electrode material at 1C rate is shown in fig. 11. The rate performance curves of the battery cathode material at different rates are shown in fig. 12.
Example 3
The preparation and test method of the lithium ion battery anode material precursor doped with 0.03mol of Cd, the battery anode material (NCM-3) and the lithium ion battery comprises the following steps:
(1) 33.848g of Ni (NO)3)2·6H2O，11.292g Co(NO3)2·6H2O，14.887g Mn(NO3)2(50 wt% aqueous solution) and 1.851g of Cd (NO)3)2·4H2Dissolving O in 200mL of absolute ethyl alcohol, stirring the mixed solution at room temperature until the mixed solution is completely dissolved, and then averagely dividing the solution into three parts and transferring the three parts to three 100mL polytetrafluoroethylene reaction kettles; the reaction kettle is moved into an oven and placed for 14 hours at 160 ℃; finally washing the precipitate with anhydrous ethanol for 4-5 times, and drying the precipitate in an oven at 90 deg.C for 10 hr to obtainThe precursor is enabled to have good appearance after high-temperature roasting, and is roasted for 4 hours at 460 ℃ in a muffle furnace before lithium mixing to obtain a 622 battery anode material precursor with the doping amount of 0.03mol Cd;
(2) the prepared battery anode material precursor and Li2CO3Uniformly mixing the materials according to the mass ratio of 1: 1.06, placing the mixture into a muffle furnace, pre-roasting the mixture for 4 hours at 520 ℃, and then roasting the mixture for 12 hours at 870 ℃ to finally obtain the Li (Ni) with the doping amount of 0.03mol Cd0.6Co0.2Mn0.2)0.97Cd0.03O2A battery positive electrode material (NCM-3);
(3) li (Ni) to be produced0.6Co0.2Mn0.2)0.97Cd0.03O2Uniformly mixing a battery positive electrode material (NCM-3), conductive carbon black super P and a binder PVDF according to the mass ratio of 8: 1, adding a proper amount of 1-methyl-2 pyrrolidone, ball-milling for 15min to prepare slurry, uniformly coating the slurry on an aluminum sheet current collector by using a coating machine, and drying for 2 hours at 70 ℃; then moving to a vacuum drying oven to dry for 12 hours at 120 ℃, and finally tabletting to obtain an electrode slice;
(4) and (3) taking the electrode plate obtained in the step (3) as a positive electrode, taking a lithium plate as a counter electrode, taking a porous polymer film as a diaphragm (Celgard 2400), taking a mixed solution of 1mol/L LiPF6 and EC: DEC: EMC (volume ratio of 1: 1) as an electrolyte, and assembling the button cell in a glove box.
Tests show that the first discharge capacity of 0.03mol of Cd-doped battery positive electrode material (NCM-3) at the rate of 0.1C is 166.1mAh/g, and the capacity retention rate can reach 67.3% after 100 cycles at 1C.
X-ray diffraction (XRD) pair is used for preparing Li (Ni) as a battery cathode material0.6Co0.2Mn0.2)0.97Cd0.03O2(NCM-3) was subjected to X-ray diffraction, and the diffraction pattern was as shown in FIG. 1.
The SEM image of the precursor of the battery cathode material doped with 0.03mol of Cd is shown in FIG. 6, and it can be clearly seen from the SEM image that the shape of the precursor is still spherical, the petal shape of the spherical surface disappears, the surface becomes dense and small particles exist, and the SEM image of the corresponding battery cathode material is shown in FIG. 7.
The first charge and discharge characteristics at 0.1C are shown in fig. 10. The cycling curve for 100 cycles of the battery positive electrode material at 1C rate is shown in fig. 11. The rate performance curves of the battery cathode material at different rates are shown in fig. 12.
Comparative example 1
The preparation methods of the battery positive electrode material precursor, the battery positive electrode material and the lithium ion battery in the comparative example 1 are basically the same as those of the battery positive electrode material precursor, the battery positive electrode material and the lithium ion battery in the example 1, except that the battery positive electrode material precursor and the battery positive electrode material in the comparative example 1 are not doped with Cd.
The preparation method of the Cd-undoped lithium ion battery positive electrode material precursor, the battery positive electrode material (NCM-P) and the lithium ion battery comprises the following steps:
(1) 34.8948g of Ni (NO)3)2·6H2O，11.6412g Co(NO3)2·6H2O，14.316g Mn(NO3)2Dissolving (50 wt% aqueous solution) in 150mL of anhydrous ethanol, stirring the mixed solution at room temperature until the mixed solution is completely dissolved, and then averagely dividing the solution into three parts and transferring the three parts to three 100mL polytetrafluoroethylene reaction kettles; the reaction kettle is moved into an oven and placed for 12 hours at the temperature of 150 ℃; finally, washing the precipitate for 4-5 times by using absolute ethyl alcohol, then drying the precipitate in an oven at 80 ℃ for 12h, and roasting the precipitate for 5h at 450 ℃ in a muffle furnace before mixing lithium so as to obtain a 622 battery anode material precursor not doped with Cd in order to ensure that the precipitate has good appearance after high-temperature roasting;
(2) the prepared battery anode material precursor and Li2CO3Uniformly mixing the raw materials according to the ratio of 1: 1.05, placing the mixture into a muffle furnace, pre-roasting the mixture for 5 hours at 500 ℃, and then roasting the mixture for 10 hours at 850 ℃ to finally obtain the LiNi which is not doped with Cd0.6Co0.2Mn0.2O2A battery positive electrode material (NCM-P);
(3) the obtained LiNi0.6Co0.2Mn0.2O2Uniformly mixing a battery positive electrode material (NCM-P), conductive carbon black super P and a binder PVDF according to the mass ratio of 8: 1, adding a proper amount of 1-methyl-2 pyrrolidone, and ball-milling for 15min preparing slurry, uniformly coating the slurry on an aluminum sheet current collector by using a coating machine, and drying the slurry for 2 hours at the temperature of 70 ℃; then moving to a vacuum drying oven to dry for 12 hours at 120 ℃, and finally tabletting to obtain an electrode slice;
(4) taking the electrode plate obtained in the step (3) as a positive electrode, a lithium plate as a counter electrode, a porous polymer film as a diaphragm (Celgard 2400), and 1mol/L LiPF6And mixed solution of EC, DEC and EMC (volume ratio of 1: 1) is used as electrolyte and assembled into the button cell in a glove box.
Tested, the battery anode material LiNi which is not doped with Cd0.6Co0.2Mn0.2O2(NCM-P) the first discharge capacity at 0.1C rate was 173.2mAh/g, and the capacity retention rate after 100 cycles at 1C was 69.3%.
X-ray diffraction (XRD) is used for preparing LiNi which is a battery positive electrode material and is not doped with Cd0.6Co0.2Mn0.2O2(NCM-P) and the diffraction pattern is shown in FIG. 1, all diffraction peaks can be indexed to the layered α -NaFeO with R-3m space group2And (5) structure.
An SEM image of the precursor of the Cd-undoped battery cathode material is shown in figure 8, and the shape of the precursor is spherical and the spherical surface is petal-shaped clearly. An SEM image of the corresponding battery cathode material is shown in fig. 9.
The first charge and discharge characteristics at 0.1C are shown in fig. 10. The cycling curve for 100 cycles of the battery positive electrode material at 1C rate is shown in fig. 11. The rate performance curves of the battery cathode material at different rates are shown in fig. 12.
Referring to FIG. 1, it can be seen that the positive electrode material (NCM-1) of the cell doped with 0.01mol of Cd and the positive electrode material LiNi of the cell not doped with Cd in example 10.6Co0.2Mn0.2O2(NCM-P) compared with the prior art, the two are not different, and the doping of Cd does not change the main body structure of the material. The battery positive electrode material (NCM-2) doped with 0.02mol of Cd in example 2 and the battery positive electrode material (NCM-3) doped with 0.03mol of Cd in example 3 and the battery positive electrode material LiNi not doped with Cd0.6Co0.2Mn0.2O2Compared with (NCM-P), the two are not greatly different, which shows that the doping of Cd has no influence on the material structure, but a small peak appears around 33 degrees, and the peak corresponds to the crystal face of CdO.
Referring to fig. 10, the initial coulombic efficiencies of the positive electrode materials of the batteries of example 1, example 2, example 3 and comparative example 1 were 86.09%, 85.18%, 85.56% and 84.39%, respectively.
Referring to fig. 11, the cycle retention rates of the battery positive electrode materials in examples 1, 2, 3 and 1 were 82.8%, 81.8%, 67.3% and 69.3%.
Referring to fig. 12, which is a graph illustrating the rate performance analysis of the battery cathode materials in examples 1, 2, 3 and 1, it can be seen that the rate performance of the battery cathode materials in examples 1 and 2 under different rates is better than that of the battery cathode material in comparative example 1 under different rates, but the rate performance of the battery cathode material in example 3 under different rates is lower than that of the battery cathode material in comparative example 1 under different rates, which indicates that the doping of a proper amount of Cd is beneficial to stabilizing the structure of the material and improving the electrochemical performance of the material, but when the doping amount is too high, the content of inactive elements in the material increases, and the diffusion of lithium ions is hindered, so that the electrochemical performance of the battery cathode material is deteriorated.
In addition, the inventor also carries out corresponding experiments by using other raw materials and other process conditions listed above to replace various raw materials and corresponding process conditions in the examples 1 to 3, and the contents to be verified are similar to the products in the examples 1 to 3. Therefore, the contents of the verification of the respective examples are not described herein, and the excellent points of the present invention will be described only by examples 1 to 3 as representative examples.
It should be noted that, in the present document, in a general case, an element defined by the phrase "includes.
It should be understood that the above preferred embodiments are only for illustrating the present invention, and other embodiments of the present invention are also possible, but those skilled in the art will be able to adopt the technical teaching of the present invention and equivalent alternatives or modifications thereof without departing from the scope of the present invention.
Claims (7)
1. A preparation method of a precursor of a battery positive electrode material is characterized by comprising the following steps:
mixing Ni (NO)3)2·6H2O、Co(NO3)2·6H2O、Mn(NO3)2Aqueous solution and Cd (NO)3)2·4H2Dissolving O in absolute ethanol to obtain mixed solution, and adding Ni (NO)3)2·6H2O、Co(NO3)2·6H2O、Mn(NO3)2And Cd (NO)3)2·4H2The volume ratio of the total molar amount of O to the absolute ethyl alcohol is (0.1-0.3) mol: (100-200) mL, and the molar ratio n (Ni) of Ni, Co, Mn and Cd elements in the mixed solutionxCoyMnz) nCd = 0.97-1: 0-0.03, wherein x + y + z =1, nCd ≠ 0;
and carrying out solvothermal reaction on the mixed solution at the reaction temperature of 150-160 ℃ for 10-14 h to precipitate Ni, Co, Mn and Cd elements together, washing the obtained precipitate for more than one time by adopting absolute ethyl alcohol, drying and roasting, wherein the drying temperature is 70-90 ℃ for 10-14 h, the roasting temperature is 440-460 ℃ for 4-6 h, and the post-treatment on the precipitate is completed to obtain the Ni-Co-Mn-Cd-based battery positive electrode material precursor.
2. The method of claim 1, wherein: the molar ratio n (Ni) of Ni, Co, Mn and Cd elements in the mixed solutionxCoyMnz):nCd=0.98~1: 0~0.02，nCd≠0。
3. A battery positive electrode material precursor prepared by the method of any one of claims 1-2.
4. A preparation method of a battery positive electrode material is characterized by comprising the following steps:
mixing the battery positive electrode material precursor as defined in claim 3 with lithium salt, and then sequentially carrying out pre-roasting and roasting to obtain a Cd-doped battery positive electrode material;
the pre-roasting temperature is 480-520 ℃, the roasting time is 4-6 hours, the roasting temperature is 830-870 ℃, the roasting time is 9-12 hours, and the mass ratio of the battery positive electrode material precursor to the lithium salt is 1: 1.03-1.06.
5. The method of claim 4, wherein: the lithium salt includes lithium carbonate.
6. A battery positive electrode material prepared by the method of any one of claims 4-5.
7. Use of the battery positive electrode material precursor as claimed in claim 3 or the battery positive electrode material as claimed in claim 6 for the preparation of a lithium ion battery.
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