Ternary positive electrode material and preparation method thereof

Abstract

The invention provides a ternary positive electrode material and a preparation method thereof, and the method comprises the following steps: obtaining a tungsten and boron double-doped ternary positive electrode material through a mixed sintering method, introducing a Co element to react with free lithium during secondary sintering, and generating an ionic conductive compound LiCoO2 on the surface of the ternary material, and finally, coating a layer of nano CaCO3 on the ternary material of which the surface is coated with LiCoO2, so as to obtain the ternary positive electrode material with a doped coating structure. The ternary positive electrode material prepared by the invention has excellent conductivity and can effectively inhibit the growth of lithium dendrites, and meanwhile, the structural stability of the material can be enhanced through doping modification, so that the low-temperature power, high-temperature storage and cycle performance of the ternary lithium ion battery are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and in particular relates to a ternary positive electrode material and a preparation method thereof. Background Art

[0002] The development of new energy vehicles is a powerful measure for my country to seek new economic growth points and promote industrial transformation and upgrading. More importantly, new energy vehicles are in line with the current trend of green travel and will help the international community strive to achieve the goal of carbon neutrality. Among them, the cruising range of a car is an important factor in whether it can be quickly and widely popularized, and this depends to a large extent on the energy density of the positive electrode material of lithium-ion batteries. In recent years, nickel-cobalt-manganese ternary positive electrode materials have been favored by many car companies due to their advantages such as high capacity and high voltage, and have become the development focus of the industry at this stage. However, there are some common problems with nickel-cobalt-manganese ternary materials that need to be solved urgently. First, ternary materials have high voltage and energy storage capacity, and are prone to structural evolution during cyclic charging and discharging, resulting in rapid degradation of capacity; second, ternary lithium batteries are prone to degradation and failure at high temperatures, and their power performance at low temperatures still needs to be further optimized. Summary of the invention

[0003] In view of the deficiencies in the prior art, the object of the present invention is to provide a modified ternary positive electrode material, which has excellent conductivity and can effectively inhibit the growth of lithium dendrites, while enhancing the structural stability of the material through doping modification, thereby improving the low-temperature power, high-temperature storage and cycle performance of the ternary lithium-ion battery.

[0004] To achieve the above object, the technical solution adopted by the present invention is:

[0005] A modified ternary cathode material, comprising a tungsten- and boron-doped ternary cathode material located in an inner core and LiCoO 2 Coating layer and / or nano-CaCO 3 Coating layer.

[0006] The present invention enhances the stability of the material by adding tungsten and boron elements to the ternary positive electrode material. At the same time, the free lithium provided reacts with the subsequently introduced Co to generate an ion conductive compound LiCoO on the surface of the material. 2 , reducing the internal resistance of the material surface while improving the low-temperature power performance of the ternary battery, and finally coating with nano-CaCO 3 layer, avoiding the growth of lithium dendrites and improving the high-temperature storage and cycle performance of ternary lithium-ion batteries.

[0007] In the ternary positive electrode material, the LiCoO 2 Coating layer and / or nano-CaCO 3 The coating layer is sequentially coated on the surface of the ternary positive electrode material from inside to outside;

[0008] The LiCoO 2 The thickness of the coating layer is 100-500nm;

[0009] The nano-CaCO 3 The thickness of the coating layer is 50-200 nm.

[0010] The present invention also proposes a method for preparing the above-mentioned ternary positive electrode material, comprising the following steps:

[0011] 1) Preparation of tungsten and boron doped ternary cathode material: x Co y Mn (1-x-y) (OH) 2 ) is mixed with a lithium source, a tungsten source and a boron source, and then the mixed material is sintered in an oxygen atmosphere to obtain a tungsten and boron dual-doped ternary positive electrode material;

[0012] 2) Preparation of LiCoO 2 Coating layer: After the ternary cathode material prepared in step 1) is uniformly mixed with the cobalt source, the mixture is sintered in an oxygen atmosphere to obtain a surface-coated LiCoO 2 Ternary cathode materials;

[0013] 3) Preparation of nano-CaCO 3 Coating layer: The product obtained in step 2) is mixed with nano-CaCO 3 After uniform mixing, the mixture is sintered in an oxygen atmosphere to obtain a ternary positive electrode material with a double-doping and double-coating structure.

[0014] In step 1) of the above method, the lithium source is selected from at least one of lithium carbonate and LiOH; the tungsten source is selected from at least one of tungsten oxide and tungstic acid; the boron source is boric acid;

[0015] In step 2), the cobalt source is selected from at least one of cobalt oxyhydroxide CoOOH and cobalt hydroxide.

[0016] In step 1), the amount of tungsten added is 0.1%-0.3% of the mass of the ternary precursor; the amount of boron added is 0.01%-0.05% of the mass of the ternary precursor;

[0017] The molar ratio of the ternary precursor to Li in the lithium source may be 1:1.02-1.06;

[0018] The sintering temperature may be 900-930°C and the sintering time may be 10-20h;

[0019] During the sintering process, oxygen with a purity of more than 95% is introduced;

[0020] After sintering, crushing is also carried out.

[0021] In step 2) of the above method, the mass of the cobalt element in the cobalt source accounts for 0.5-1.5% of the mass of the ternary positive electrode material obtained in step 1);

[0022] The sintering temperature may be 700-800°C and the sintering time may be 4-6h;

[0023] After sintering, crushing is also carried out.

[0024] In step 3) of the above method, the nano-CaCO 3 The amount of addition accounts for the surface-coated LiCoO prepared in step 2) 2 0.05-0.15% of the mass of the ternary positive electrode material;

[0025] The sintering temperature may be 600-700°C and the sintering time may be 4-6h;

[0026] After sintering, the final product is obtained by crushing, screening and demagnetization, that is, a ternary positive electrode material with a double-doped and double-coated structure.

[0027] The use of the above-mentioned ternary positive electrode material as a positive electrode material for a lithium-ion battery or in the preparation of a positive electrode material for a lithium-ion battery also falls within the protection scope of the present invention.

[0028] The present invention also provides a lithium-ion battery, which contains the above-mentioned ternary positive electrode material.

[0029] The present invention also provides an electrical device, wherein the electrical device contains the lithium ion battery.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention can enhance the structural stability of the material by doping with functional elements that can increase the residual alkali on the surface of the first sintered material (the material after sintering in step 1), and also provide sufficient free lithium for the Co element introduced in the second sintering process. The two are sintered at high temperature to form an ion conductive compound, thereby reducing the internal resistance of the material surface, thereby improving the low-temperature power performance of the ternary battery cell; in addition, nano-CaCO 3 The coating layer can stabilize the crystal structure of the ternary material, while the nano-CaCO 3 It can continuously adsorb HF, a byproduct of the electrolyte, inhibit the acidification of the electrolyte at high temperatures, and avoid the growth of lithium dendrites caused by acidity, thereby improving the high-temperature storage and cycle performance of ternary lithium-ion batteries.

[0032] The ternary positive electrode material with a double-doping and double-coating structure prepared by the present invention has excellent low-temperature power performance, and also has good high-temperature storage and cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The low temperature power performance diagram of four groups of battery cells;

[0034] Figure 2 This is a graph of high temperature storage performance of four groups of batteries;

[0035] Figure 3 This is the high temperature cycle performance diagram of four groups of battery cells;

[0036] Figure 4 This is a scanning electron microscope image of the ternary positive electrode material prepared in Example 4. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below in conjunction with specific embodiments, and the examples provided are only for illustrating the present invention, rather than for limiting the scope of the present invention. The examples provided below can be used as a guide for further improvements by those of ordinary skill in the art, and do not constitute a limitation of the present invention in any way.

[0038] The experimental methods in the following examples, unless otherwise specified, are all conventional methods, and are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial channels.

[0039] Example 1

[0040] A method for preparing a modified ternary positive electrode material comprises the following steps:

[0041] S1. Preparation of ternary cathode materials with dual doping structure:

[0042] The ternary precursor (Ni 0.68 Co 0.08 Mn 0.24 (OH) 2 ) is mixed with lithium carbonate, tungsten oxide and boric acid. The ternary material precursor and lithium carbonate (Li 2 CO 3 ) wherein the molar ratio of Li is 1:1.04, the amount of tungsten added is 0.1% of the mass of the ternary precursor, and the amount of boron added is 0.03% of the mass of the ternary precursor; the mixed material is then sent to a sintering furnace at 925° C. and calcined for 15 hours, oxygen with a purity of more than 95% is introduced during the sintering process, and the material is crushed after sintering to obtain a tungsten and boron dual-doped ternary positive electrode material;

[0043] S2. Preparation of LiCoO 2 Cladding:

[0044] The ternary cathode material prepared by S1 was uniformly mixed with cobalt oxyhydroxide CoOOH, and the mixture was sintered at 700 °C for 5 h in an oxygen atmosphere. After crushing, the surface-coated LiCoO 2 (LiCoO can be judged by the SEM state of the material surface 2 The formation of LiCoO 2 A ternary positive electrode material having a wrinkled state coated on the surface of the ternary material; wherein the mass of the cobalt element in the cobalt oxyhydroxide CoOOH accounts for 0.5% of the mass of the ternary positive electrode material prepared by S1;

[0045] S3. Preparation of Nano-CaCO 3 Cladding:

[0046] The product obtained in step S2 is mixed with nano-CaCO 3 (particle size 100nm) were evenly mixed, and then the mixed material was sent to a 650℃ sintering furnace for calcination for 5h, and oxygen was introduced into the furnace during sintering; finally, the sintered material was crushed, sieved, and demagnetized to obtain the final product, that is, a ternary positive electrode material with a double-doped and double-coated structure; among them, nano-CaCO 3 The addition amount accounts for 0.1% of the ternary positive electrode material prepared by S2.

[0047] Example 2

[0048] A method for preparing a modified ternary positive electrode material comprises the following steps:

[0049] S1. Preparation of ternary cathode materials with dual doping structure:

[0050] The ternary precursor (Ni 0.68 Co 0.08 Mn 0.24 (OH) 2 ) is mixed with lithium carbonate, tungsten oxide and boric acid, the molar ratio of the ternary material precursor to Li in the lithium carbonate is 1:1.04, the addition amount of tungsten element accounts for 0.1% of the mass of the ternary precursor, and the addition amount of boron element accounts for 0.03% of the mass of the ternary precursor; and then the mixed material is sent to a 925°C sintering furnace for calcination for 15h, and oxygen with a purity of more than 95% is introduced during the sintering process. After the sintering is completed, it is crushed to obtain a tungsten and boron dual-doped ternary positive electrode material;

[0051] S2. Preparation of LiCoO 2 Cladding:

[0052] The ternary cathode material prepared by S1 was uniformly mixed with cobalt oxyhydroxide CoOOH, and the mixture was sintered at 750 °C for 5 h in an oxygen atmosphere. After crushing, the surface-coated LiCoO 2The mass of the cobalt element in the cobalt oxyhydroxide CoOOH accounts for 0.5% of the ternary positive electrode material prepared by S1;

[0053] S3. Preparation of Nano-CaCO 3 Cladding:

[0054] The product obtained in step S2 is mixed with nano-CaCO 3 (particle size 100nm) were evenly mixed, and then the mixed material was sent to a 650℃ sintering furnace for calcination for 5h, and oxygen was introduced into the furnace during sintering; finally, the sintered material was crushed, sieved, and demagnetized to obtain the final product, that is, a ternary positive electrode material with a double-doped and double-coated structure; among them, nano-CaCO 3 The addition amount accounts for 0.1% of the ternary positive electrode material prepared by S2.

[0055] Example 3

[0056] A method for preparing a modified ternary positive electrode material comprises the following steps:

[0057] S1. Preparation of ternary cathode materials with dual doping structure:

[0058] The ternary precursor (Ni 0.68 Co 0.08 Mn 0.24 (OH) 2 ) is mixed with lithium carbonate, tungsten oxide and boric acid, the molar ratio of the ternary material precursor to Li in the lithium carbonate is 1:1.04, the addition amount of tungsten element accounts for 0.1% of the mass of the ternary precursor, and the addition amount of boron element accounts for 0.03% of the mass of the ternary precursor; and then the mixed material is sent to a 925°C sintering furnace for calcination for 15h, and oxygen with a purity of more than 95% is introduced during the sintering process. After the sintering is completed, it is crushed to obtain a tungsten and boron dual-doped ternary positive electrode material;

[0059] S2. Preparation of LiCoO 2 Cladding:

[0060] The ternary cathode material prepared by S1 was uniformly mixed with cobalt oxyhydroxide CoOOH, and the mixture was sintered at 750 °C for 5 h in an oxygen atmosphere. After crushing, the surface-coated LiCoO 2 The mass of the cobalt element in the cobalt oxyhydroxide CoOOH accounts for 1% of the ternary positive electrode material prepared by S1;

[0061] S3. Preparation of Nano-CaCO 3 Cladding:

[0062] The product obtained in step S2 is mixed with nano-CaCO 3(100nm) were uniformly mixed, and then the mixed material was sent to a 650℃ sintering furnace for calcination for 5h, and oxygen was introduced into the furnace during sintering; finally, the sintered material was crushed, sieved, and demagnetized to obtain the final product, that is, a ternary positive electrode material with a double-doped and double-coated structure; among them, nano-CaCO 3 The addition amount accounts for 0.1% of the ternary positive electrode material prepared by S2.

[0063] Example 4

[0064] A method for preparing a modified ternary positive electrode material comprises the following steps:

[0065] S1. Preparation of ternary cathode materials with dual doping structure:

[0066] The ternary precursor (Ni 0.68 Co 0.08 Mn 0.24 (OH) 2 ) is mixed with lithium carbonate, tungsten oxide and boric acid, the molar ratio of the ternary material precursor to Li in the lithium carbonate is 1:1.04, the addition amount of tungsten element accounts for 0.1% of the mass of the ternary precursor, and the addition amount of boron element accounts for 0.03% of the mass of the ternary precursor; and then the mixed material is sent to a 925°C sintering furnace for calcination for 15h, and oxygen with a purity of more than 95% is introduced during the sintering process. After the sintering is completed, it is crushed to obtain a tungsten and boron dual-doped ternary positive electrode material;

[0067] S2. Preparation of LiCoO 2 Cladding:

[0068] The ternary cathode material prepared by S1 was uniformly mixed with cobalt oxyhydroxide CoOOH, and the mixture was sintered at 750 °C for 5 h in an oxygen atmosphere. After crushing, the surface-coated LiCoO 2 The mass of the cobalt element in the cobalt oxyhydroxide CoOOH accounts for 1% of the ternary positive electrode material prepared by S1;

[0069] S3. Preparation of Nano-CaCO 3 Cladding:

[0070] The product obtained in step S2 is mixed with nano-CaCO 3 (100nm) were uniformly mixed, and then the mixed material was sent to a 650℃ sintering furnace for calcination for 5h, and oxygen was introduced into the furnace during sintering; finally, the sintered material was crushed, sieved, and demagnetized to obtain the final product, that is, a ternary positive electrode material with a double-doped and double-coated structure; among them, nano-CaCO 3 The addition amount accounts for 0.05% of the ternary positive electrode material prepared by S2.

[0071] Figure 4The scanning electron microscope image of the prepared ternary positive electrode material. 0.68 Co 0.08 Mn 0.24 O 2 ) is sample A0, the ternary positive electrode material for dual doping and uncoated is sample A1 (the ternary positive electrode material for dual doping of tungsten and boron obtained by S1 in Example 4), the ternary positive electrode material for dual doping and single coating of LiCoO 2 The ternary positive electrode material is sample A2 (sample prepared by S2 in Example 4), and the ternary positive electrode material with dual doping and dual coating structure prepared in Example 4 is sample A3. Under the same proportion of active materials, samples A0, A1, A2, and A3 are used to prepare corresponding ternary lithium-ion batteries (the positive electrode is slurried according to NCM: CNTs: PVDF = 98:1:1, and the double-sided surface density of the positive electrode coating is 330g / m 2 , the positive electrode roller compaction is 3.5g / cc; the negative electrode is slurried according to graphite: SP: CMC: SBR = 96.2: 0.8: 1.2: 1.8, the negative electrode coating double-sided density is 216g / m2, and the negative electrode roller compaction is 1.6g / cc; Xinzhoubang E8A-2 high-voltage electrolyte and Enjie 9+2+2+1+1 type diaphragm are used). Except for the positive electrode material, the other materials, dosages, and battery preparation methods of the four groups of lithium-ion batteries are the same. The following are the test results of the performance of the four groups of batteries:

[0072] (1) Battery low temperature power performance test

[0073] The specific test method is: take four groups of batteries and charge them from 2.8V to 4.4V at 0.33C at 25℃, keep charging at 4.4V, and cut off current 0.05C; then discharge them to 2.8V at 0.33C, cycle for three weeks, and take the average of the three-week discharge capacity as the battery capacity C0; adjust the battery to 20% SOC at 25℃ according to the C0 value, then place the battery at -25℃ for 10h, and discharge at 1.1C for 30S. The test results are shown in Table 1. Figure 1 .

[0074] Table 1 -25℃ low temperature DCR performance of four groups of cells

[0075]

[0076] From Table 1 and Figure 1 It can be seen that the dual-doping modification can slightly reduce the low-temperature DCR of the ternary material. 2 The coating layer can significantly reduce the low-temperature DCR of the ternary material. The coated nano-CaCO 3The low-temperature DCR performance of the latter ternary material can be maintained unchanged; this shows that the low-temperature power performance of the battery is greatly improved when the double-doped and double-coated ternary cathode material prepared by the present invention is applied to lithium-ion batteries. (The lower the low-temperature DCR value of the battery cell, the better its low-temperature power performance).

[0077] (2) Battery high temperature storage performance test

[0078] The specific test method is: take four groups of batteries and charge them from 2.8V to 4.4V at 1C at 25℃, keep charging at 4.4V, and cut off the current at 0.05C; then discharge them to 2.8V at 1C constant current for three cycles, and take the average of the three-week discharge capacity as the initial capacity C0 of the battery; charge the battery to full power at 1C and place it in a 60℃ constant temperature box for 7 days, and resume charging and discharging 3 times at 25℃. The test results are shown in Table 2 and Figure 2 .

[0079] Table 2 High shelf capacity retention rate and recovery rate (average) of four groups of batteries

[0080] Material Name Capacity retention rate Capacity recovery rate A0 88.45％ 94.89％ A1 90.07％ 95.22％ A2 90.58％ 95.69％ A3 93.99％ 98.70％

[0081] From Table 2 and Figure 2 It can be seen that the dual doping modification and single coating LiCoO 2 The high-temperature storage performance of ternary materials can be slightly improved. On this basis, nano-CaCO 3 The high-temperature storage performance of the ternary material is significantly improved after the coating layer; this shows that when the double-doped and double-coated ternary positive electrode material prepared by the present invention is applied to lithium-ion batteries, the high-temperature storage performance of the battery is greatly improved.

[0082] (3) Battery high temperature cycle performance test

[0083] The specific test method is: take four groups of batteries and charge them from 2.8V to 4.4V at a constant current of 0.5C, maintain a constant voltage of 4.4V, and cut off the current at 0.05C; then discharge them to 2.8V at a constant current of 1C, and cycle the charge and discharge for 1500 cycles. The test results are shown in Table 3. Figure 3 shown.

[0084] From Table 3 and Figure 3 It can be seen that the capacity retention rate of A0 sample has dropped to 81.72% after 764 cycles; the cycle performance of ternary materials can be slightly improved after double doping modification, and the battery has a capacity retention rate of 83.99% after 889 cycles; LiCoO is introduced on the basis of double doping. 2 The coating layer can significantly improve the high-cycle performance of the material, and the high-cycle life of the battery cell is about 1170 weeks; the coating of nano-CaCO 3After that, the high-cycling performance of the ternary material was further improved. After 1230 cycles, the capacity retention rate was still above 84%. This shows that when the double-doped and double-coated ternary positive electrode material prepared by the present invention is applied to lithium-ion batteries, the high-temperature cycling performance of the battery is also significantly improved.

[0085] Table 3 High temperature cycle capacity retention rate of four groups of batteries

[0086]

[0087]

[0088] In summary, the ternary positive electrode material with a dual-doping and dual-coating structure prepared in the present invention has excellent low-temperature power performance, as well as good high-temperature storage and cycle performance.

[0089] The present invention has been described in detail above. For those skilled in the art, without departing from the purpose and scope of the present invention, and without the need to carry out unnecessary experimental conditions, the present invention can be implemented in a wide range under equivalent parameters, concentrations and conditions. Although the present invention provides specific embodiments, it should be understood that the present invention can be further improved. In a word, according to the principles of the present invention, the application is intended to include any changes, uses or improvements to the present invention, including departure from the disclosed scope in the application, and changes made with conventional techniques known in the art.

Claims

1. A ternary positive electrode material, comprising a ternary positive electrode material doped with tungsten and boron located in an inner core and a LiCoO2 coating layer and / or a nano-CaCO3 coating layer.

2. The ternary cathode material according to claim 1, characterized in that: The LiCoO2 coating layer and / or the nano-CaCO3 coating layer are sequentially coated on the surface of the ternary positive electrode material from the inside to the outside; The thickness of the LiCoO2 coating layer is 100-500nm; The thickness of the nano-CaCO3 coating layer is 50-200nm.

3. A method for preparing the ternary cathode material according to claim 1 or 2, comprising the following steps: 1) preparing a ternary cathode material doped with tungsten and boron: mixing a ternary precursor with a lithium source, a tungsten source and a boron source, and then sintering the mixed material in an oxygen atmosphere to obtain a ternary cathode material doped with tungsten and boron; 2) preparing a LiCoO2 coating layer: uniformly mixing the ternary cathode material prepared in step 1) with a cobalt source, and sintering the mixture in an oxygen atmosphere to obtain a ternary cathode material with a surface coated with LiCoO2; 3) Preparation of nano-CaCO3 coating layer: The product obtained in step 2) is uniformly mixed with nano-CaCO3, and then sintered in an oxygen atmosphere to obtain a ternary positive electrode material with a double-doping and double-coating structure.

4. The method according to claim 3, characterized in that In step 1), the lithium source is selected from at least one of lithium carbonate and LiOH; the tungsten source is selected from at least one of tungsten oxide and tungstic acid; the boron source is boric acid; In step 2), the cobalt source is selected from at least one of cobalt oxyhydroxide CoOOH and cobalt hydroxide.

5. The method according to claim 3, characterized in that: In step 1), the amount of tungsten added is 0.1%-0.3% of the mass of the ternary precursor; the amount of boron added is 0.01%-0.05% of the mass of the ternary precursor; The molar ratio of the ternary precursor to Li in the lithium source is 1:1.02-1.06; The sintering temperature is 900-930° C. and the sintering time is 10-20 hours.

6. The method according to claim 3, characterized in that In step 2), the cobalt source accounts for 0.5-1.5% of the mass of the ternary positive electrode material obtained in step 1); The sintering temperature is 700-800° C. and the sintering time is 4-6 hours.

7. The method according to claim 3, characterized in that In step 3), the amount of the nano-CaCO3 added is 0.05-0.15% of the mass of the surface-coated LiCoO2 ternary positive electrode material obtained in step 2); The sintering temperature is 600-700° C. and the sintering time is 4-6 hours.

8. Use of the ternary positive electrode material according to claim 1 or 2 as a positive electrode material for a lithium ion battery or in the preparation of a positive electrode material for a lithium ion battery.

9. A lithium-ion battery, comprising the ternary positive electrode material according to claim 1 or 2.

10. An electrical device comprising the lithium-ion battery according to claim 9.

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