CN109768274B - Battery positive electrode material precursor, battery positive electrode material, preparation method and application thereof - Google Patents

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 Cd_spSimilar 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

Battery positive electrode material precursor, battery positive electrode material, preparation method and application thereof

technical field

The invention relates to a battery positive electrode material, in particular to a battery positive electrode material precursor, a battery positive electrode material, a preparation method and application thereof.

Background technique

Layered high-nickel cathode materials are considered as one of the most promising cathode materials for Li-ion batteries due to their high capacity and low cost, however, due to their unsatisfactory cycle performance, storage performance, low Coulombic efficiency and thermal Instability limits its commercial use. The main reasons for this phenomenon are:

(1) Since the radii of Ni ²⁺ (0.069nm) and Li ⁺ (0.076nm) are the same, the mixing of Li ⁺ /Ni ²⁺ occurs in the layered structure;

(2) The edge reaction occurs at the interface between the electrode and the electrolyte to generate by _- products such as Li2CO3 or _LiOH , and these shortcomings have a great impact on its electrochemical performance.

In view of this, people often suppress these factors that affect the electrochemical performance by means of modification. Ion doping is considered to be one of the most effective ways to overcome these difficulties. It is considered to be a simple method to improve the structure and thermal stability of layered high-nickel cathode materials. The doping ions that have been reported so far are mainly Al ³ . ⁺ , Mg ²⁺ , Ti ⁴⁺ , Mo ⁶⁺ , Nd ³⁺ and Na ⁺ etc. Although the current ion doping methods have made great progress in stabilizing the structure and improving the electrochemical performance, most of these doping modification methods are to perform elemental modification on the material in the high temperature calcination stage of mixed lithium after the synthesis of the precursor. Doping, there are few reports of in situ doping modification of materials at the precursor synthesis stage.

Compared with in-situ doping modification, ex-situ doping modification is difficult to dopant elements into the material body to occupy the position of transition metal, and ex-situ doping also makes modification difficult. The process is more complicated.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to provide a battery positive electrode material precursor, a battery positive electrode material, a preparation method and application thereof, so as to overcome the deficiencies in the prior art.

In order to realize the above-mentioned purpose of the invention, the present invention has adopted the following technical solutions:

A preparation method of a battery positive electrode material precursor, comprising:

Dissolving Ni-based nitrate, Co-based nitrate, Mn-based nitrate and Cd-based nitrate in absolute ethanol to obtain a mixed solution;

The mixed solution is subjected to a solvothermal reaction to co-precipitate Ni, Co, Mn and Cd elements, and the obtained precipitate is post-treated to obtain a Ni-Co-Mn-Cd-based battery positive electrode material precursor.

The embodiment of the present invention also provides a battery positive electrode material precursor prepared by the foregoing method.

The embodiment of the present invention also provides a method for preparing a positive electrode material for a battery, comprising:

The battery positive electrode material precursor is mixed with lithium salt, and then pre-baking and calcining are sequentially performed to obtain a Cd-doped battery positive electrode material.

The embodiment of the present invention also provides a battery positive electrode material prepared by the foregoing method.

The embodiments of the present invention also provide the application of the battery positive electrode material precursor or the battery positive electrode material in preparing a lithium ion battery.

Compared with the prior art, the beneficial effects of the present invention at least include:

(1) The present invention utilizes the characteristic that the Ksp of the four elements Ni, Co, Mn, and Cd are similar (the _Ksp of Ni, Co, Mn, and Cd are 2.0×10 ^-15 , 1.9×10 ^-15 , 1.6×10 , respectively). ^-13 , 3.2×10 ^-14 ), with Cd as the modifying element. Using absolute ethanol as the solvent and nitrate as the transition metal salt, the four elements were co-precipitated in the solvothermal synthesis process by the solvothermal method to obtain a Ni-Co-Mn-Cd-based battery cathode material precursor, which was then passed through The Cd-doped ternary battery positive electrode material is synthesized by a high-temperature solid-phase roasting method, and the preparation method is simple and the cost is low.

(2) Cd, as an inactive element with good electrical conductivity, can stabilize the structure of the material after doping and improve the electronic conductivity of the material.

(3) CdO has high carrier concentration and oxygen vacancies, so it is considered to be an n-type semiconductor with a resistivity of 10 ^-2 -10 ^-4 Ω, which is beneficial to reduce the resistance of the material.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments described in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

FIG. 1 is the XRD diffraction pattern of the battery cathode material in Example 1, Example 2, Example 3, and Comparative Example 1. FIG.

FIG. 2 is a SEM photograph of the battery cathode material precursor under the doping amount of 0.01 mol Cd in Example 1. FIG.

FIG. 3 is a SEM photograph of the battery cathode material under the doping amount of 0.01 mol Cd in Example 1. FIG.

FIG. 4 is a SEM photograph of the battery cathode material precursor under the doping amount of 0.02 mol Cd in Example 2. FIG.

FIG. 5 is a SEM photograph of the battery cathode material under the doping amount of 0.02 mol Cd in Example 2. FIG.

FIG. 6 is a SEM photograph of the battery cathode material precursor under the doping amount of 0.03 mol Cd in Example 3. FIG.

FIG. 7 is a SEM photograph of the battery cathode material under the doping amount of 0.03 mol Cd in Example 3. FIG.

FIG. 8 is a SEM photograph of the undoped Cd battery cathode material precursor synthesized in Comparative Example 1. FIG.

FIG. 9 is a SEM photograph of the undoped Cd battery positive electrode material synthesized in Comparative Example 1. FIG.

10 is a graph showing the first charge-discharge performance of the positive electrode materials of the batteries in Example 1, Example 2, Example 3, and Comparative Example 1.

11 is an analysis diagram of the cycle performance of the battery cathode materials in Example 1, Example 2, Example 3, and Comparative Example 1.

12 is an analysis diagram of the rate performance of the positive electrode material of the battery in Example 1, Example 2, Example 3, and Comparative Example 1.

Detailed ways

In view of the deficiencies in the prior art, the inventor of the present invention has been able to propose the technical solution of the present invention after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained below.

The modified elements in the precursor synthesis stage must have similar _Ksp with Ni, Co, Mn, so that they can be co-precipitated during the synthesis process. Among them, the Ksp of Ni, Co, Mn, and Cd are 2.0×10 ^{- 15} , 1.9×10 ^-15 , 1.6×10 ^-13 , 3.2×10 ^-14 , and their K _sp is similar. In the present invention, Cd is used as a modifying element, and four elements Ni, Co, Mn and Cd are co-precipitated in the solvothermal reaction synthesis process by a solvothermal method to synthesize a Ni-Co-Mn-Cd-based battery cathode material The precursor, and then the Cd-doped battery cathode material is synthesized by mixed lithium calcination.

As an aspect of the technical solution of the present invention, it relates to a preparation method of a battery positive electrode material precursor, including:

Dissolving Ni-based nitrate, Co-based nitrate, Mn-based nitrate and Cd-based nitrate in absolute ethanol to obtain a mixed solution;

The mixed solution is subjected to a solvothermal reaction to co-precipitate Ni, Co, Mn and Cd elements, and the obtained precipitate is post-treated to obtain a Ni-Co-Mn-Cd-based battery positive electrode material precursor.

The present invention performs in-situ doping modification on the material during the synthesis stage of the battery cathode material precursor, and the specific reaction principle is shown in the following equation:

7CH ₃ CH ₂ OH+4NO ₃ ^- →7CH ₃ CHO+2NO↑+N ₂ O+4OH ^- +5H ₂ O; (1)

3Ni ²⁺ +6OH ^- +2H ₂ O→3Ni(OH) ₂ ·2H ₂ O↓; (2)

2Co ²⁺ +Mn ²⁺ +6OH ^- →MnCo ₂ O ₄ ↓+3H ₂ O; (3)

Co ²⁺ +2Mn ²⁺ +6OH ^- →CoMn ₂ O ₄ ↓+3H ₂ O; (4)

Cd ²⁺ +6OH ^- +2H ₂ O→3Cd(OH) ₂ ·2H ₂ O↓; (5)

In some embodiments, it specifically includes: Ni(NO ₃ ) ₂ .6H ₂ O, Co(NO ₃ ) ₂ .6H ₂ O, Mn(NO ₃ ) ₂ aqueous solution, and Cd(NO ₃ ) ₂ ·4H ₂ O is dissolved in 100-200 mL of absolute ethanol to obtain a mixed solution.

Among them, it is preferable to dissolve in 140 to 160 mL of absolute ethanol.

In some embodiments, the molar ratio of Ni, Co, Mn, and Cd elements in the mixed solution is n(Ni _x Co _y M _z ):nCd=0.97～1:0～0.03, wherein x+y+z=1 , nCd≠0.

In some more preferred embodiments, the molar ratio of Ni, Co, Mn and Cd elements in the mixed solution is n(Ni _x Co _y M _z ):nCd=0.98～1:0～0.02, wherein x+y+ z=1, nCd≠0.

In some embodiments, the temperature of the solvothermal reaction is 150˜160° C., and the time of the solvothermal reaction is 10˜14 h.

Wherein, the mixed solution is placed in a polytetrafluoroethylene reactor for solvothermal reaction.

In some embodiments, the post-treatment specifically includes: washing the precipitate after co-precipitation of Ni, Co, Mn and Cd elements with absolute ethanol more than once, and then drying and calcining.

In some more preferred embodiments, the drying temperature is 70-90° C., and the drying time is 10-14 hours.

In some more preferred embodiments, the calcination temperature is 440-460°C, and the calcination time is 4-6h

The embodiment of the present invention also provides a battery positive electrode material precursor prepared by the foregoing method.

As another aspect of the technical solution of the present invention, it relates to a preparation method of a battery positive electrode material, comprising:

The battery positive electrode material precursor is mixed with lithium salt, and then pre-baking and calcining are sequentially performed to obtain a Cd-doped battery positive electrode material.

In some embodiments, the temperature of the pre-baking is 480-520° C., and the time is 4-6 h.

In some embodiments, the roasting temperature is 830-870° C., and the time is 9-12 h.

In some embodiments, the mass ratio of the battery cathode material precursor to the lithium salt is 1:1.03-1.06.

In some embodiments, the lithium salt includes lithium carbonate.

The embodiment of the present invention also provides a battery positive electrode material prepared by the foregoing method.

In some specific embodiments, the preparation method of the positive electrode material of the battery includes:

S1. Ni(NO ₃ ) ₂ .6H ₂ O, Co(NO ₃ ) ₂ .6H ₂ O, Mn(NO ₃ ) ₂ (50wt% aqueous solution) and Cd(NO ₃ ) ₂ . 4H ₂ O was dissolved in 150 ml of absolute ethanol according to a suitable ratio to obtain a mixed solution;

S2, the mixed solution is stirred at room temperature until it is completely dissolved, then the solution is evenly divided into three parts and moved to three 100mL polytetrafluoroethylene reactors; the amount of the mixed solution added in the 100mL reactor can be controlled in the reactor 1/2 to 2/3 of the volume;

S3. The reaction kettle is moved into an oven and placed at 150-160°C for 12h;

S4. Finally, wash the precipitate with absolute ethanol for 4 to 5 times, and then dry the precipitate in an oven at 80°C for 12 hours. Roast at 450℃ for 5h;

S5. Mix the Cd-doped precursor prepared in S4 with Li ₂ CO ₃ at a ratio of 1:1.05, and then put it into a muffle furnace for pre-baking at 500° C. for 5 hours, and then at 850° C. After calcining for 10h, a Cd-doped battery cathode material was finally obtained.

As another aspect of the technical solution of the present invention, it relates to the application of the foregoing battery positive electrode material precursor or the foregoing battery positive electrode material in preparing a lithium ion battery.

The technical solutions of the present invention will be described in further detail below with reference to several preferred embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention. In the following examples, the test methods without specific conditions are generally in accordance with conventional conditions.

Example 1

Lithium-ion battery cathode material precursor doped with 0.01mol Cd, battery cathode material (NCM-1), preparation and testing method of lithium-ion battery, including the following:

(1) 34.545852g Ni( _NO3 ) _2.6H2O , 11.524788g Co( _NO3 ) _2.6H2O , _14.17284g Mn( _{NO3 )2 (} 50wt% aqueous solution) and 0.61692g Cd(NO3) ₃ ) _{2.4H 2} O was dissolved in 150ml absolute ethanol, the mixed solution was stirred at room temperature until completely dissolved, then the solution was evenly divided into three parts and moved to three 100mL polytetrafluoroethylene reactors; It was moved into an oven and placed at 150°C for 12h; finally, the precipitate was washed 4 to 5 times with absolute ethanol, and then the precipitate was dried in an oven at 80°C for 12h, in order to make it have a good morphology after high temperature roasting, Before mixing lithium, calcined in a muffle furnace at 450 °C for 5 h to obtain a 622 battery cathode material precursor with a doping amount of 0.01 mol Cd;

(2) The prepared battery cathode material precursor and Li ₂ CO ₃ were uniformly mixed in a mass ratio of 1:1.05, and then placed in a muffle furnace for pre-baking at 500 °C for 5 h, followed by calcination at 850 °C. After calcining for 10h, a Li(Ni _0.6 Co _0.2 Mn _0.2 ) _0.99 Cd _0.01 O ₂ battery cathode material (NCM-1) with a doping amount of 0.01mol Cd was finally obtained;

(3) The obtained Li(Ni _0.6 Co _0.2 Mn _0.2 ) _0.99 Cd _0.01 O ₂ battery cathode material (NCM-1), the conductive carbon black super P, and the binder PVDF were uniform in a mass ratio of 8:1:1 Mix, add an appropriate amount of 1-methyl-2-pyrrolidone, and ball mill for 15 minutes to prepare a slurry, which is uniformly coated on the aluminum sheet current collector with a coater, and dried at 70°C for 2 hours; then moved to a vacuum drying oven at 120°C Dry for 12 hours, and finally press to obtain an electrode sheet;

(4) The electrode sheet obtained in step (3) was used as the positive electrode, the lithium sheet was used as the counter electrode, the porous polymer film was used as the separator (Celgard 2400), and 1 mol/L LiPF ₆ and EC:DEC:EMC (volume ratio of 1:1:1) mixed solution was used as electrolyte, and a button cell was assembled in a glove box.

After testing, the battery cathode material (NCM-1) with 0.01mol Cd doping amount has an initial discharge capacity of 186.3mAh/g at 0.1C rate, and the capacity retention rate can reach 82.8% after 100 cycles at 1C.

The prepared battery cathode material Li(Ni _0.6 Co _0.2 Mn _0.2 ) _0.99 Cd _0.01 O ₂ (NCM-1) was subjected to X-ray diffraction by X-ray diffraction (XRD). The diffraction pattern is shown in FIG. 1 .

The SEM image of the precursor of the battery cathode material doped with 0.01mol Cd is shown in Figure 2. It can be clearly seen from the figure that the morphology of the precursor is still spherical, the petal shape of the spherical surface begins to disappear, and the surface begins to become dense , and the corresponding SEM image of the battery cathode material is shown in Figure 3.

The first charge-discharge performance of the battery cathode material at 0.1C is shown in Figure 10, and the cycle curve of the battery cathode material under 1C rate for 100 cycles is shown in Figure 11. The rate performance curves of the battery cathode material at different rates are shown in Figure 12.

Example 2

Lithium-ion battery cathode material precursor doped with 0.02mol Cd, battery cathode material (NCM-2), preparation and testing method of lithium-ion battery, including the following:

(1) 34.197g Ni(NO ₃ ) ₂ .6H ₂ O, 11.408g Co(NO ₃ ) ₂ .6H ₂ O, 14.0296g Mn(NO ₃ ) ₂ (50wt% aqueous solution) and 1.234g Cd(NO ) ₃ ) _{2.4H 2} O was dissolved in 100ml absolute ethanol, the mixed solution was stirred at room temperature until completely dissolved, then the solution was evenly divided into three parts and moved to three 100mL polytetrafluoroethylene reactors; It was moved into an oven and placed at 150°C for 10h; finally, the precipitate was washed 4 to 5 times with anhydrous ethanol, and then the precipitate was dried in an oven at 70°C for 14h. Before mixing lithium, it was calcined in a muffle furnace at 440 °C for 6 h to obtain a 622 battery cathode material precursor with a doping amount of 0.02 mol Cd;

(2) The prepared battery cathode material precursor and Li ₂ CO ₃ were uniformly mixed in a mass ratio of 1:1.03, and then placed in a muffle furnace for pre-baking at 480°C for 6 hours, followed by calcination at 830°C for 6 hours. After calcination for 9 hours, a Li(Ni _0.6 Co _0.2 Mn _0.2 ) _0.98 Cd _0.02 O ₂ battery cathode material (NCM-2) with a doping amount of 0.02mol Cd was finally obtained;

(3) The obtained Li(Ni _0.6 Co _0.2 Mn _0.2 ) _0.98 Cd _0.02 O ₂ battery positive electrode material (NCM-2), conductive carbon black super P, and binder PVDF were uniform in a mass ratio of 8:1:1 Mix, add an appropriate amount of 1-methyl-2-pyrrolidone, and ball mill for 15 minutes to prepare a slurry, which is uniformly coated on the aluminum sheet current collector with a coater, and dried at 70°C for 2 hours; then moved to a vacuum drying oven at 120°C Dry for 12 hours, and finally press to obtain an electrode sheet;

(4) The electrode sheet obtained in step (3) was used as the positive electrode, the lithium sheet was used as the counter electrode, the porous polymer film was used as the separator (Celgard 2400), and 1 mol/L LiPF ₆ and EC:DEC:EMC (volume ratio of 1:1:1) mixed solution was used as electrolyte, and a button cell was assembled in a glove box.

After testing, the first discharge capacity of 0.02mol Cd-doped battery cathode material (NCM-2) at 0.1C rate is 179.5mAh/g, and the capacity retention rate can reach 81.8% after 100 cycles at 1C.

The prepared battery cathode material Li(Ni _0.6 Co _0.2 Mn _0.2 ) _0.98 Cd _0.02 O ₂ (NCM-2) was subjected to X-ray diffraction by X-ray diffraction (XRD). The diffraction pattern is shown in FIG. 1 .

The SEM image of the precursor of the battery cathode material doped with 0.02mol Cd is shown in Figure 4. It can be clearly seen from the figure that the morphology of the precursor is still spherical, the petal shape of the spherical surface almost disappears, and the surface begins to become very Dense, and the corresponding SEM image of the battery cathode material is shown in Figure 5.

The first charge-discharge performance graph at 0.1C is shown in Figure 10. Figure 11 shows the cycle curve of the battery cathode material for 100 cycles at a rate of 1C. The rate performance curves of the battery cathode material at different rates are shown in Figure 12.

Example 3

Lithium-ion battery cathode material precursor doped with 0.03mol Cd, battery cathode material (NCM-3), preparation and testing method of lithium-ion battery, including the following:

(1) 33.848g Ni( _NO3 ) ₂ ·6H2O, 11.292g Co( _NO3 ) _{2 ·} 6H2O, 14.887g Mn( _{NO3 )2 (} 50wt% aqueous solution) and 1.851g Cd(NO3) ₃ ) _{2.4H 2} O was dissolved in 200ml absolute ethanol, the mixed solution was stirred at room temperature until completely dissolved, then the solution was evenly divided into three parts and moved to three 100mL polytetrafluoroethylene reactors; It was moved into an oven and placed at 160°C for 14h; finally, the precipitate was washed 4 to 5 times with absolute ethanol, and then the precipitate was dried in an oven at 90°C for 10h, in order to make it have a good morphology after high temperature roasting, Before mixing lithium, it was calcined in a muffle furnace at 460 °C for 4 h to obtain a 622 battery cathode material precursor with a doping amount of 0.03 mol Cd;

(2) The prepared battery cathode material precursor and Li ₂ CO ₃ were uniformly mixed in a mass ratio of 1:1.06, and then placed in a muffle furnace for pre-baking at 520 °C for 4 h, followed by calcination at 870 °C. After calcining for 12h, a Li(Ni _0.6 Co _0.2 Mn _0.2 ) _0.97 Cd _0.03 O ₂ battery cathode material (NCM-3) with a doping amount of 0.03mol Cd was finally obtained;

(3) The obtained Li(Ni _0.6 Co _0.2 Mn _0.2 ) _0.97 Cd _0.03 O ₂ battery cathode material (NCM-3), the conductive carbon black super P, and the binder PVDF were uniform in a mass ratio of 8:1:1 Mix, add an appropriate amount of 1-methyl-2-pyrrolidone, and ball mill for 15 minutes to prepare a slurry, which is uniformly coated on the aluminum sheet current collector with a coater, and dried at 70°C for 2 hours; then moved to a vacuum drying oven at 120°C Dry for 12 hours, and finally press to obtain an electrode sheet;

(4) The electrode sheet obtained in step (3) was used as the positive electrode, the lithium sheet was used as the counter electrode, the porous polymer film was used as the separator (Celgard 2400), and 1 mol/L LiPF6 and EC:DEC:EMC (volume ratio of 1:1:1) mixed solution was used as electrolyte, and a button cell was assembled in a glove box.

After testing, the first discharge capacity of 0.03mol Cd-doped battery cathode material (NCM-3) at 0.1C rate is 166.1mAh/g, and the capacity retention rate can reach 67.3% after 100 cycles at 1C.

The prepared battery cathode material Li(Ni _0.6 Co _0.2 Mn _0.2 ) _0.97 Cd _0.03 O ₂ (NCM-3) was subjected to X-ray diffraction by X-ray diffraction (XRD). The diffraction pattern is shown in FIG. 1 .

The SEM image of the precursor of the battery cathode material doped with 0.03mol Cd is shown in Figure 6. It can be clearly seen from the figure that the morphology of the precursor is still spherical, the petal shape of the spherical surface disappears, and the surface becomes dense and has Small particles exist, and the corresponding SEM image of the battery cathode material is shown in Figure 7.

The first charge-discharge performance graph at 0.1C is shown in Figure 10. Figure 11 shows the cycle curve of the battery cathode material for 100 cycles at a rate of 1C. The rate performance curves of the battery cathode material at different rates are shown in Figure 12.

Comparative Example 1

The preparation methods of the battery positive electrode material precursor, battery positive electrode material, and lithium ion battery in Comparative Example 1 and Example 1 are basically the same, except that the battery positive electrode material precursor and the battery positive electrode material in Comparative Example 1 are not doped with Cd.

Undoped Cd lithium ion battery cathode material precursor, battery cathode material (NCM-P), preparation and testing method of lithium ion battery, including the following:

(1) Dissolve 34.8948g Ni(NO ₃ ) ₂ ·6H ₂ O, 11.6412g Co(NO ₃ ) ₂ ·6H ₂ O, 14.316g Mn(NO ₃ ) ₂ (50wt% aqueous solution) in 150ml absolute ethanol , the mixed solution was stirred at room temperature until completely dissolved, then the solution was equally divided into three parts and moved into three 100 mL PTFE reaction kettles; the reaction kettles were moved into an oven and placed at 150 ° C for 12 hours; The precipitate was washed 4 to 5 times with water ethanol, and then the precipitate was dried in an oven at 80 °C for 12 h. In order to make it have a good morphology after high temperature calcination, it was first calcined at 450 °C in a muffle furnace before mixing with lithium. 5h, the undoped Cd 622 battery cathode material precursor was obtained;

(2) The prepared battery cathode material precursor and Li ₂ CO ₃ were mixed uniformly in a ratio of 1:1.05, and then placed in a muffle furnace for pre-baking at 500 °C for 5 h, followed by calcination at 850 ° C for 10 h , and finally obtained an undoped Cd LiNi _0.6 Co _0.2 Mn _0.2 O ₂ battery cathode material (NCM-P);

(3) The prepared LiNi _0.6 Co _0.2 Mn _0.2 O ₂ battery cathode material (NCM-P), the conductive carbon black super P, and the binder PVDF were uniformly mixed in a mass ratio of 8:1:1, and an appropriate amount of 1 -Methyl-2-pyrrolidone ball milled for 15 minutes to prepare a slurry, which was uniformly coated on the aluminum sheet current collector with a coating machine, and dried at 70 °C for 2 hours; then moved to a vacuum drying box and dried at 120 °C for 12 hours, and finally Compression to obtain electrode sheets;

(4) The electrode sheet obtained in step (3) was used as the positive electrode, the lithium sheet was used as the counter electrode, the porous polymer film was used as the separator (Celgard 2400), and 1 mol/L LiPF ₆ and EC:DEC:EMC (volume ratio of 1:1:1) mixed solution was used as electrolyte, and a button cell was assembled in a glove box.

After testing, the battery cathode material LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM-P) without Cd doping has an initial discharge capacity of 173.2mAh/g at a rate of 0.1C, and a capacity retention rate after 100 cycles at 1C was 69.3%.

X-ray diffraction (XRD) was performed on the prepared undoped Cd battery cathode material LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM-P), the diffraction pattern is shown in Figure 1, all diffraction peaks can all be indexed to the layered α-NaFeO ₂ structure with R-3m space group.

The SEM image of the precursor of the undoped Cd battery cathode material is shown in Figure 8. It can be clearly seen from the figure that the precursor is spherical in shape, and the spherical surface is in the shape of a petal. The SEM image of the corresponding battery cathode material is shown in FIG. 9 .

The first charge-discharge performance graph at 0.1C is shown in Figure 10. Figure 11 shows the cycle curve of the battery cathode material for 100 cycles at a rate of 1C. The rate performance curves of the battery cathode material at different rates are shown in Figure 12.

Referring to Figure 1, it can be seen that the battery cathode material (NCM-1) doped with 0.01 mol Cd in Example 1 and the battery cathode material not doped with Cd LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM-P) In comparison, there is no difference between the two, indicating that the doping of Cd does not change the host structure of the material. The battery positive electrode material (NCM-2) doped with 0.02 mol Cd in Example 2 and the battery positive electrode material (NCM-3) doped with 0.03 mol Cd in Example 3 and the battery positive electrode material without Cd doping LiNi _0.6 Co _0.2 Compared with Mn _0.2 O ₂ (NCM-P), there is no great difference between the two, indicating that the doping of Cd has no effect on the material structure, but a small peak appears around 33°, which corresponds to the crystal plane of CdO.

As shown in FIG. 10 , the initial coulombic efficiencies of the battery cathode materials in Example 1, Example 2, Example 3, and Comparative Example 1 are 86.09%, 85.18%, 85.56%, and 84.39%, respectively.

As shown in FIG. 11 , the cycle retention rates of the battery cathode materials in Example 1, Example 2, Example 3, and Comparative Example 1 were 82.8%, 81.8%, 67.3%, and 69.3%.

Referring to Figure 12, it is an analysis chart of the rate performance of the battery positive electrode materials in Example 1, Example 2, Example 3, and Comparative Example 1. It can be seen that the rate performance of the battery positive electrode materials in Example 1 and Example 2 under different rates The performance is better than the rate performance of the battery cathode material in Comparative Example 1 at different rates. However, 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. The rate performance at different rates shows that an appropriate amount of The doping of Cd is conducive 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 will increase, hindering the diffusion of lithium ions, which will deteriorate the battery cathode material. electrochemical performance.

In addition, the inventors of the present case also used other raw materials and other process conditions listed above to replace the various raw materials and corresponding process conditions in Examples 1-3 and carried out corresponding experiments. 3 products are close. Therefore, the verification contents of each embodiment will not be described one by one here, and only embodiments 1 to 3 will be used as a representative to describe the advantages of the application of the present invention.

It should be noted that, in this article, in general, the elements defined by the sentence "comprising..." do not exclude the existence of other elements in the steps, processes, methods or experimental equipment including the elements. of the same elements.

It should be understood that the above preferred embodiments are only used to illustrate the content of the present invention. In addition, the present invention also has other embodiments. However, those skilled in the art use equivalent replacements or equivalents due to the technical inspiration involved in the present invention. The technical solutions formed by the effective deformation method all fall within the protection scope of the present invention.

Claims (7)

1. a preparation method of battery positive electrode material precursor, is characterized in that, comprises: Dissolve Ni(NO ₃ ) ₂ .6H ₂ O, Co(NO ₃ ) ₂ .6H ₂ O, Mn(NO ₃ ) ₂ aqueous solution and Cd(NO ₃ ) ₂ .4H ₂ O in absolute ethanol to obtain a mixed solution. solution, the total molar amounts of the Ni(NO ₃ ) ₂ .6H ₂ O, Co(NO ₃ ) ₂ .6H ₂ O, Mn(NO ₃ ) ₂ and Cd(NO ₃ ) ₂ .4H ₂ O with anhydrous The volume ratio of ethanol is (0.1～0.3) mol: (100～200) mL, and the molar ratio of Ni, Co, Mn, Cd elements in the mixed solution n (Ni _x Co _y Mn _z ): nCd=0.97～ 1: 0~0.03, where x+y+z=1, nCd≠0; The mixed solution is subjected to a solvothermal reaction, the reaction temperature is 150-160 ° C, and the time is 10-14 h, so that Ni, Co, Mn and Cd elements are co-precipitated, and then the obtained precipitate is washed with anhydrous ethanol more than once, Then drying and roasting, wherein the drying temperature is 70~90°C and the time is 10~14h, and the roasting temperature is 440~460°C and the time is 4~6h, and the post-treatment of the precipitate is completed to obtain Ni-Co -Mn-Cd-based battery cathode material precursor. 2. preparation method as claimed in claim 1, is characterized in that: the mol ratio n (Ni _x Co _y Mn _z ) of Ni, Co, Mn, Cd element in described mixed solution: nCd=0.98～1: 0～ 0.02, nCd≠0. 3. The battery positive electrode material precursor prepared by the method of any one of claims 1-2. 4. a preparation method of battery positive electrode material, is characterized in that, comprises: Mixing the battery positive electrode material precursor described in claim 3 with a lithium salt, and then performing pre-baking and roasting in sequence to obtain a Cd-doped battery positive electrode material; Wherein, the temperature of the pre-baking is 480-520°C and the time is 4-6h, the temperature of the baking is 830-870°C and the time is 9-12h, and the mass ratio of the battery cathode material precursor to the lithium salt is is 1:1.03~1.06. 5. The preparation method of claim 4, wherein the lithium salt comprises lithium carbonate. 6. The battery cathode material prepared by the method of any one of claims 4-5. 7. The application of the battery positive electrode material precursor described in claim 3 or the battery positive electrode material described in claim 6 in the preparation of lithium ion batteries.

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