Co-doped modified single-crystal cathode material and preparation method thereof

Abstract

The disclosure discloses a phase-doped modified single-crystal positive electrode material and a preparation method thereof. The modified single-crystal positive electrode material is M q -LiNi x Co y Mn z O2; wherein M is a La4[LiTM]O8(TM=Ni, Co, Mn) phase. The preparation method comprises the following steps: mixing raw materials for preparing a positive electrode precursor material, preparing a precursor of the modified single-crystal positive electrode material by using a coprecipitation method, mixing the single-crystal positive electrode material raw material and a modifier, and preparing the phase-doped modified single-crystal positive electrode material by using a solid-phase method, wherein the modifier comprises a transition metal salt, and the positive electrode material is lithium nickel cobalt manganese oxide. The disclosure performs phase-doped modification and single-crystallization on lithium nickel cobalt manganese oxide precursor and its positive electrode material by using a transition metal salt, can effectively relieve lattice strain accumulation and volume change of the positive electrode material in the charging and discharging process, and improves the working life of the lithium nickel cobalt manganese positive electrode material.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of lithium ion battery cathode material, and in particular to a preparation method of phase-doped modified single crystal cathode material. BACKGROUND

[0002] LiNi x Co y Mn 1-x-y 02 is a promising lithium ion battery cathode material, which achieves a good balance in multiple dimensions such as economy, safety, energy density, cycle life, etc. For example, the 8-system lithium nickel cobalt manganese oxide LiNi 0.8 Co 0.1 Mn 0.1 02 has a theoretical specific capacity of 277.4 mAh / g and an actual specific capacity of 210 mAh / g, and has an application energy density of 669.6 Wh / kg (applicable voltage 4.35 V, relative to Li / Li + ), but the fast capacity decay and poor thermal stability of the ternary nickel cobalt manganese cathode material limit its practical application.

[0003] Compared with polycrystalline, single crystal ternary nickel cobalt manganese cathode material has higher specific surface area and better ion transport performance, which can provide higher specific capacity and faster charge and discharge rate. However, the anisotropic lattice strain and stress-related volume change generated during the (de) intercalation process of single crystal ternary nickel cobalt manganese cathode material will cause serious structural instability and electrochemical decay of the cathode material.

[0004] Phase doping is an important means to improve the stability of ternary nickel cobalt manganese cathode material. The doped phase usually needs to have a stable physical structure and good lattice matching with the layered structure oxide, and the doped phase can alleviate the accumulation of lattice strain and volume change during the charge and discharge process of the ternary nickel cobalt manganese cathode material, thereby improving the stability of the ternary nickel cobalt manganese cathode material.

[0005] During phase doping, impurities and unstable phase structures are usually introduced, which reduces the stability of the ternary nickel cobalt manganese cathode material, so it is particularly important to provide a stable phase doping idea and realize the modification of the single crystal cathode material. SUMMARY

[0006] To solve the above technical problems, the present disclosure provides a preparation method of a modified cathode material.

[0007] In a first aspect, the present disclosure provides a preparation method of a phase-doped modified single crystal cathode material, which comprises: mixing a preparation raw material of a cathode precursor material, preparing a precursor of the modified single crystal cathode material by a coprecipitation method, mixing a single crystal cathode material raw material with a modifier, and preparing the phase-doped modified single crystal cathode material by a solid phase method.

[0008] The modifier includes transition metal oxides or transition metal salts, and the cathode material is lithium nickel cobalt manganese oxide.

[0009] This disclosure uses transition metal salts as doping precursors to modify the phase of lithium nickel cobalt manganese oxide (LCO) cathode materials and achieves single-crystal formation of the LCO cathode materials via a high-temperature solid-state method. This effectively alleviates lattice strain accumulation and volume changes during charge-discharge processes, thereby improving the service life of the LCO cathode materials. Specifically:

[0010] In the preparation method disclosed herein, phase doping modification and single crystallization of cathode material are achieved by co-precipitation and solid-state methods. The La4[LiTM]O8 (TM=Ni,Co,Mn) phase can alleviate the accumulation of lattice strain and volume change during the charging and discharging process of ternary nickel-cobalt-manganese cathode material, thereby improving the stability of ternary nickel-cobalt-manganese cathode material. Compared with polycrystalline materials, single crystal has a higher specific surface area and better ion transport performance, and can provide higher specific capacity and faster charging and discharging rate.

[0011] As a preferred technical solution of this disclosure, the modified cathode material is M. q -LiNi x Co y Mn z O2.

[0012] Where M is the La4[LiTM]O8 (TM=Ni,Co,Mn) phase, 0.001≤x≤0.999, x can be 0.60, 0.65, 0.70, 0.73, 0.75, 0.77, 0.8, 0.9, etc.; 0.001≤y≤0.999, y can be 0.10, 0.15, 0.20, 0.23, 0.25, 0.27, 0.3, 0.4, etc.; 0.001≤z≤0.999, z can be 0.10, 0.15, 0.20, 0.23, 0.25, 0.27, 0.3, 0.4, etc.;

[0013] As a preferred technical solution of this disclosure, 0.8≤x≤0.999.

[0014] As a preferred technical solution of this disclosure, 0.001≤q≤0.003, where q can be 0.001, 0.002, 0.003, etc.

[0015] Currently, there are not many reports on stable phase-doped single-crystal cathode materials for lithium nickel cobalt manganese oxide. This disclosure fills this gap by using transition metal salts as doping materials to modify and single-crystalize lithium nickel cobalt manganese oxide cathode materials through phase doping.

[0016] As a preferred technical solution of this disclosure, when performing the co-precipitation synthesis, the raw materials for preparing the cathode precursor material include a nickel source, a cobalt source, a manganese source, an alkali source, and a complexing agent; when performing the solid-phase doping modification, the raw materials for the single-crystal cathode material include the precursor of the modified single-crystal cathode material and a lithium source, and the modifier is a transition metal salt.

[0017] In the preparation method disclosed herein, La4[LiTM]O8 (LLMO,TM=Ni,Co,Mn) phase doping and single crystallization are performed by co-precipitation and solid-state methods to obtain the phase-doped modified single-crystal cathode material. Phase doping can alleviate the lattice strain accumulation and volume change during the charge and discharge process of the ternary nickel-cobalt-manganese cathode material, improve the stability of the ternary nickel-cobalt-manganese cathode material, and the single crystal has a higher specific surface area and better ion transport performance than the polycrystalline material, which can provide higher specific capacity and faster charge and discharge rate.

[0018] As a preferred technical solution of this disclosure, the molar ratio of Ni:Co:Mn:Li:M in the nickel source, cobalt source, manganese source, lithium source, and transition metal salt is x:y:z:1:q.

[0019] As a preferred technical solution of this disclosure, the nickel source is selected from any one or a combination of at least two of nickel hydroxide, nickel nitrate, nickel sulfate or nickel chloride;

[0020] As a preferred technical solution of this disclosure, the manganese source is selected from any one or a combination of at least two of manganese carbonate, manganese acetate, manganese sulfate or manganese chloride;

[0021] As a preferred technical solution of this disclosure, the cobalt source is selected from any one or a combination of at least two of cobalt nitrate, cobalt sulfate, cobalt carbonate, or cobalt chloride;

[0022] As a preferred technical solution of this disclosure, the lithium source is selected from any one or a combination of at least two of lithium carbonate, lithium hydroxide, lithium acetate or lithium dihydrogen phosphate.

[0023] As a preferred technical solution of this disclosure, the alkali source is sodium hydroxide;

[0024] As a preferred technical solution of this disclosure, the complexing agent is selected as ammonia monohydrate;

[0025] As a preferred embodiment of this disclosure, the transition metal salt is selected as lanthanum nitrate hexahydrate;

[0026] As a preferred embodiment of this disclosure, the co-precipitation method is carried out in a nitrogen atmosphere, the pH of the co-precipitation method is 11-12, and the reaction time is 12-15 hours.

[0027] As a preferred technical solution of this disclosure, the solid-phase method is carried out in an air atmosphere, and the reaction temperature of the solid-phase method is 700-1000℃, and the reaction time is 10-18h.

[0028] As a specific implementation of this disclosure, the preparation method of the phase-doped modified cathode material includes: mixing nickel source, manganese source, cobalt source, alkali source, complexing agent and transition metal salt in proportion, reacting in a nitrogen atmosphere at pH 11-12 for 12-15 h to obtain a cathode material precursor, mixing it in proportion with lithium source and transition metal salt, annealing in an air atmosphere at 700-1000℃ for 10-18 h to obtain a phase-doped modified single-crystal nickel cobalt manganese oxide cathode material.

[0029] Secondly, this disclosure provides a modified cathode material prepared by the preparation method described in the first aspect, wherein the phase-doped modified single-crystal lithium nickel cobalt manganese oxide cathode material has excellent electrochemical performance.

[0030] Thirdly, this disclosure provides a positive electrode sheet, which includes the modified positive electrode material described in the second aspect.

[0031] Fourthly, this disclosure provides an electrochemical device comprising the modified cathode material described in the second aspect or the cathode sheet described in the third aspect.

[0032] The beneficial effects of this invention are as follows:

[0033] This disclosure uses transition metal salts as doping precursors to modify lithium nickel cobalt manganese oxide cathode materials through phase doping and achieves single crystallization of lithium nickel cobalt manganese oxide cathode materials through a high-temperature solid-state method. This can effectively alleviate the accumulation of lattice strain and volume change of the cathode material during the charging and discharging process, and improve the working life of the lithium nickel cobalt manganese oxide cathode material. Attached Figure Description

[0034] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0035] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0036] Figure 1 This is a SEM image of the modified cathode material prepared in Example 1 of this disclosure.

[0037] Figure 2The image shows the EIS diagram of the modified cathode material prepared in Example 1 of this disclosure.

[0038] Figure 3 The image shows the XRD pattern of the modified cathode material prepared in Example 1 of this disclosure. Detailed Implementation

[0039] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0040] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.

[0041] Example 1

[0042] This embodiment provides a La 0.01 -LiNi 0.801 Co 0.098 Mn 0.101 O2 phase doped modified single crystal cathode material and its preparation method are as follows:

[0043] 12.390g NiSO4 (0.801mol), 1.525g MnSO4 (0.101mol), and 1.519g CoSO4 (0.112mol) were weighed and mixed. Under a nitrogen atmosphere, NaOH and ammonia were added to maintain the pH at 11.5 and the mixture was reacted for 15h. Then, 3.695g Li2CO3 (0.100mol) and 0.433g La(NO3)3·6H2O (0.001mol) were mixed and ball-milled for 1h. The mixture was then annealed at 900℃ for 12h in an air atmosphere in a tube furnace to obtain the modified cathode material.

[0044] Example 2

[0045] This embodiment provides a phase-doped modified single-crystal cathode material and its preparation method. The difference from Embodiment 1 is that the modified cathode material is La. 0.02 -LiNi 0.801 Co 0.098 Mn 0.101 O2. The annealing temperature was changed to 900℃, and the annealing time was 12 hours. The preparation method is as follows:

[0046] 12.390g NiSO4 (0.801mol), 1.525g MnSO4 (0.101mol), and 1.519g CoSO4 (0.112mol) were weighed and mixed. Under a nitrogen atmosphere, NaOH and ammonia were added to maintain the pH at 11.5 and the mixture was reacted for 15h. Then, 3.695g Li2CO3 (0.100mol) and 0.866g La(NO3)3·6H2O (0.002mol) were mixed and ball-milled for 1h. The mixture was then annealed at 900℃ for 12h in an air atmosphere in a tube furnace to obtain the modified cathode material.

[0047] Example 3

[0048] This embodiment provides a phase-doped modified single-crystal cathode material and its preparation method. The difference from Embodiment 1 is that the modified cathode material is La. 0.03 -LiNi 0.801 Co 0.098 Mn 0.101 O2. The annealing temperature was changed to 900℃, and the annealing time was 12 hours. The preparation method is as follows:

[0049] 12.390g NiSO4 (0.801mol), 1.525g MnSO4 (0.101mol), and 1.519g CoSO4 (0.112mol) were weighed and mixed. Under a nitrogen atmosphere, NaOH and ammonia were added to maintain the pH at 11.5 and the mixture was reacted for 15h. Then, 3.695g Li2CO3 (0.100mol) and 0.866g La(NO3)3·6H2O (0.002mol) were mixed and ball-milled for 1h. The mixture was then annealed at 900℃ for 12h in an air atmosphere in a tube furnace to obtain the modified cathode material.

[0050] Example 4

[0051] This embodiment provides a phase-doped modified single-crystal cathode material and its preparation method. The difference from Embodiment 1 is that the modified cathode material is La. 0.005 -LiNi 0.801 Co 0.098 Mn 0.101 O2. The annealing temperature was changed to 900℃, and the annealing time was 12 hours. The preparation method is as follows:

[0052] 12.390g NiSO4 (0.801mol), 1.525g MnSO4 (0.101mol), and 1.519g CoSO4 (0.112mol) were weighed and mixed. Under a nitrogen atmosphere, NaOH and ammonia were added to maintain the pH at 11.5 and the mixture was reacted for 15h. Then, 3.695g Li2CO3 (0.100mol) and 0.2165g La(NO3)3·6H2O (0.0005mol) were mixed and ball-milled for 1h. The mixture was then annealed at 900℃ for 12h in an air atmosphere in a tube furnace to obtain the modified cathode material.

[0053] Example 5

[0054] This embodiment provides a phase-doped modified single-crystal cathode material and its preparation method. The difference from Embodiment 1 is that the modified cathode material is La. 0.01 -LiNi 0.801 Co 0.098 Mn 0.101 O2. The annealing temperature was changed to 880℃, and the annealing time was 12 hours. The preparation method is as follows:

[0055] 12.390g NiSO4 (0.801mol), 1.525g MnSO4 (0.101mol), and 1.519g CoSO4 (0.112mol) were weighed and mixed. Under a nitrogen atmosphere, NaOH and ammonia were added to maintain the pH at 11.5 and the reaction was carried out for 15h. Then, 3.695g Li2CO3 (0.100mol) and 0.433g La(NO3)3·6H2O (0.002mol) were mixed and ball-milled for 1h. The mixture was then annealed in a tube furnace at 880℃ for 12h under an air atmosphere to obtain the modified cathode material.

[0056] Comparative Example 1

[0057] This comparative example provides a single-crystal cathode material and its preparation method, which differs from Example 1 in that La(NO3)3·6H2O is not added. The preparation method is as follows:

[0058] 12.390 g NiSO4 (0.801 mol), 1.525 g MnSO4 (0.101 mol) and 1.519 g CoSO4 (0.112 mol) were weighed and mixed. Under a nitrogen atmosphere, NaOH and ammonia were added to maintain the pH at 11.5 and the mixture was reacted for 15 h. Then, it was mixed with 3.695 g Li2CO3 (0.100 mol) and ball-milled for 1 h. The mixture was then annealed at 900 °C for 12 h in an air atmosphere in a tube furnace to obtain the modified cathode material.

[0059] Comparative Example 2

[0060] This embodiment provides a cathode material and its preparation method, differing from Embodiment 1 in that the annealing temperature is changed to 750°C. The preparation method is as follows:

[0061] 12.390g NiSO4 (0.801mol), 1.525g MnSO4 (0.101mol), and 1.519g CoSO4 (0.112mol) were weighed and mixed. Under a nitrogen atmosphere, NaOH and ammonia were added to maintain the pH at 11.5 and the mixture was reacted for 15h. Then, it was mixed with 3.695g Li2CO3 (0.100mol) and ball-milled for 1h. Finally, it was annealed in a tube furnace at 750℃ for 12h under an air atmosphere to obtain the modified cathode material.

[0062] Performance Test 1

[0063] SEM tests were performed on the cathode materials obtained in Examples 1-4 and Comparative Examples 1-2. The SEM image of the cathode material obtained in Example 1 is shown below. Figure 1 As shown.

[0064] Performance Test 2

[0065] EIS impedance testing was performed on the cathode materials obtained in Examples 1-4 and Comparative Examples 1-2. The testing method was the three-electrode method, and the results are shown in Table 1. The EIS plot of the cathode material obtained in Example 1 is shown below. Figure 2 As shown. The XRD pattern of the cathode material obtained in Example 1 is shown below. Figure 3 As shown.

[0066] Table 1

[0067]

[0068] As shown in Table 1, the resistance of the cathode material decreases after phase doping and single crystallization, which is beneficial for rapid charging and discharging.

[0069] Performance Test 3

[0070] The cathode materials obtained in Examples 1-4 and Comparative Examples 1-2 were subjected to constant current charge-discharge tests. The test conditions were 1C (1C = 200 mAH), and the results are shown in Table 2.

[0071] Table 2

[0072]

[0073] As shown in Table 2, phase doping and single crystallization improve the stability of the cathode material and enhance its cycle performance.

[0074] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0075] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A phase-doped modified single-crystal cathode material, characterized in that, The modified single-crystal cathode material is M q -LiNi x Co y Mn z O2; where M is the La4[LiTM]O8 (TM=Ni,Co,Mn) phase or the La2Sr2[LiTM]O8 phase, 0.8≤x≤0.999, 0.001≤y≤0.999, 0.001≤z≤0.999, 0.001≤q≤0.

003.

2. A method for preparing a phase-doped modified single-crystal cathode material, characterized in that, This method is used to prepare the phase-doped modified single-crystal cathode material as described in claim 1, specifically comprising: mixing raw materials for preparing the cathode precursor material, preparing the precursor of the modified single-crystal cathode material using a co-precipitation method, mixing the single-crystal cathode material raw materials with a modifier, and preparing the phase-doped modified single-crystal cathode material using a solid-state method, wherein: the modifier includes a transition metal salt, and the cathode material is lithium nickel cobalt manganese oxide.

3. The preparation method according to claim 2, characterized in that, The transition metal salt is selected from either La(NO3)3·6H2O or Sr(NO3)2.

4. The preparation method according to claim 2, characterized in that, When performing the co-precipitation reaction, the raw materials for preparing the cathode precursor material include a nickel source, a cobalt source, a manganese source, an alkali source, and a complexing agent; when performing the solid-phase doping modification, the raw materials for the single-crystal cathode material include the precursor of the modified single-crystal cathode material and a lithium source, and the modifier is a transition metal salt.

5. The preparation method according to claim 4, characterized in that, The nickel source is selected from any one or a combination of at least two of nickel hydroxide, nickel nitrate, nickel sulfate, or nickel chloride. And / or, the manganese source is selected from any one or a combination of at least two of manganese carbonate, manganese acetate, manganese sulfate or manganese chloride; And / or, the cobalt source is selected from any one or a combination of at least two of cobalt nitrate, cobalt sulfate, cobalt carbonate, or cobalt chloride; And / or, the lithium source is selected from any one or a combination of at least two of lithium carbonate, lithium hydroxide, lithium acetate or lithium dihydrogen phosphate; And / or, the alkali source is selected from sodium hydroxide; And / or, the complexing agent is selected as ammonium monohydrate.

6. A positive electrode sheet, characterized in that, The positive electrode sheet comprises the modified positive electrode material as described in claim 1.

7. An electrochemical device, characterized in that, The electrochemical device includes the modified cathode material of claim 1 or the cathode sheet of claim 6.

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