Lithium ion battery positive electrode material and lithium ion battery

Abstract

The invention discloses a lithium ion battery positive electrode material and a lithium ion battery thereof. The chemical composition of the positive electrode material is LimConn-x-y-zTexMyAzO2, m is larger than or equal to 0.8 and smaller than or equal to 1.02, n is larger than or equal to 0.98 and smaller than or equal to 1.02, x is larger than 0 and smaller than or equal to 0.1, y is larger than 0 and smaller than or equal to 0.1, z is larger than or equal to 0 and smaller than or equal to 0.1, M is one or more of Ni, Cu, Zn, Cr, Mn, Ga, Fe and Mg, and A is one or more of conventional doped elements except the M. Co and Te elements in the material are locally and orderly distributed, and besides a LiCoO2 first phase with a space group of R-3m, a second phase with a space group of C2 / m is formed; meanwhile, the M element, Li, Te and O form a compound with a superlattice structure, the compound and lithium cobalt oxide grow in a coherent manner, and the M element and the Te element are locally and orderly distributed, so that the thermodynamic stability of the material is enhanced. The element A coats the surfaces of the particles in an oxide form or acts on the bulk phase of the material in a doped element form, so that the stability of the surface or the bulk phase is further improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery materials and electrochemistry, and specifically relates to a cathode material with a novel structure and its lithium-ion battery. Background Technology

[0002] As an energy storage and conversion device, lithium-ion batteries play a vital role in modern society. Lithium-ion batteries are mainly composed of positive electrode materials, electrolytes, and negative electrode materials, with the cost and performance of the positive electrode material limiting the overall performance of the battery. Lithium cobalt oxide positive electrode materials have always attracted attention due to their high volumetric energy density, and have mature applications in the 3C digital field, showing broad application prospects in electric vehicles and energy storage systems. However, with the rapid growth of the electric vehicle market and the increasing demand for high-performance batteries in electronic products, the performance requirements for lithium cobalt oxide materials are also becoming increasingly stringent.

[0003] Increasing the charging cutoff voltage is the most direct and effective way to improve the energy density of lithium cobalt oxide. When charged to 4.6V, lithium cobalt oxide can provide a maximum energy density of 886Wh / kg (based on the cathode), which can significantly improve the battery life of 3C electronic products. However, when charged to higher voltages above 4.55V, the capacity decay and performance degradation problems exhibited by traditional lithium cobalt oxide materials become increasingly prominent. After cycling at high voltages, the lattice structure of lithium cobalt oxide undergoes irreversible changes, and its stability is greatly reduced, which will lead to a decline in battery performance and even safety hazards. Therefore, how to improve the structural stability of lithium cobalt oxide cathode materials while maintaining high capacity at high voltages is an important problem that urgently needs to be solved in this field. Summary of the Invention

[0004] To address the above problems and improve the structural stability of lithium cobalt oxide lithium-ion batteries under high voltage, this invention provides a novel cathode material and its lithium-ion battery.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] A lithium-ion battery cathode material, the general chemical formula of which is Li m Co n-x-y-z Te x M y A z O2, where 0.8≤m≤1.02, 0.98≤n≤1.02, 0<x≤0.1, 0<y≤0.1, 0≤z≤0.1, element M is one or more of elements such as Ni, Cu, Zn, Cr, Mn, Ga, Fe, Mg, etc., and element A is one or more of conventional doping elements other than element M, such as Al, Ti, Zr, La, Y, B, P, Ce, Na, K, F.

[0007] In addition to the conventional layered structure of lithium cobalt oxide, the M element in the novel cathode material described in this invention is selected because M can form a compound with Li, Te, and O that has a superlattice structure, such as Li4MTeO6 and Li8M2Te2O. 12 Li 4.5 Compounds in any form, such as MTeO6, Li2M2TeO6, and Li4M3TeO8 (with Te in a +6 valence), are coherently grown with lithium cobalt oxide, resulting in a novel structure. Compared to LiCoO2 materials doped only with Te, the M and Co elements exhibit a locally ordered distribution, further enhancing material stability and improving electrochemical performance. X-ray photoelectron spectroscopy (XPS) analysis of this material or a cathode formed from it revealed a peak for +6 Te at 576.7 ± 0.3 eV.

[0008] Element A can be coated on the surface of material particles in the form of an oxide, or it can be doped into the bulk structure of the material as a dopant element, further stabilizing the new structure cathode material. The morphology of the novel structure cathode material of this invention can be single-crystal or polycrystalline, with a volumetric particle size distribution Dv50 of 12–20 μm and a relatively obvious bimodal distribution, such as… Figure 7 As shown, the particle size distribution curve of the material has two peaks, located at 0.8 μm and 6 μm, respectively.

[0009] This invention also provides a method for preparing the above-mentioned novel cathode material, comprising the following steps:

[0010] Step 1: Mix cobalt source, tellurium source, lithium source, M element source and A element source to be doped into the bulk phase in a certain stoichiometric ratio until homogeneous, and then perform a first calcination in air to obtain a first calcination product;

[0011] Step 2: The product from the first calcination is uniformly crushed, mixed evenly with the A element source to be coated on the surface, and then calcined a second time in air to obtain the cathode material.

[0012] The first calcination process is as follows: starting at room temperature, under an air atmosphere, the temperature is increased to 900–1100℃ at a rate of 2–10℃ / min and held for 8–15 hours, then cooled to room temperature at a rate of 2–10℃ / min or cooled to room temperature in the furnace. The second calcination process is as follows: starting at room temperature, under an air atmosphere, the temperature is increased to 800–1000℃ at a rate of 2–10℃ / min and held for 8–15 hours, then cooled to room temperature at a rate of 2–10℃ / min or cooled to room temperature in the furnace.

[0013] Preferably, in step 1, the solid cobalt source, tellurium source, lithium source, M element source and A element source to be doped into the bulk phase are first mixed by wet ball milling and then dried, and then calcined in air atmosphere.

[0014] In the above preparation method, the cobalt source, tellurium source, lithium source, element M source, and element A source are all solids. The cobalt source can be selected from one or more of cobalt(II) oxide, cobalt(III) oxide, cobalt(III) oxide, cobalt carbonate, and cobalt hydroxide. The tellurium source can be selected from one or more of telluric acid, lithium tellurite, tellurium dioxide, and tellurium trioxide. The lithium source can be selected from one or more of lithium oxide, lithium hydroxide, lithium carbonate, lithium acetate, and lithium oxalate. The element M source can be selected from one or more of the oxide, hydroxide, carbonate, acetate, and oxalate of element M. The element A source can be selected from one or more of the oxide, hydroxide, carbonate, acetate, and oxalate of element A.

[0015] The present invention also provides a lithium-ion battery incorporating the novel cathode material. By assembling the novel cathode material as the cathode of a lithium-ion battery, a lithium-ion battery with superior performance can be obtained.

[0016] The principle of this invention is as follows:

[0017] The novel cathode material prepared in this invention exhibits a locally ordered distribution of Co and Te elements. Besides the first phase, LiCoO2 with space group R-3m, the locally ordered distribution of Co and Te forms a second phase with space group C2 / m (X-ray diffraction patterns show diffraction peaks in the range of 18–22°). Simultaneously, the material also contains M element, which forms a compound with Li, Te, and O, exhibiting a superlattice structure. The locally ordered distribution of M and Te elements, along with this multi-element local order and superlattice structure, creates a thermodynamically stable structure that enhances the stability of the lithium cobalt oxide cathode material. During electrochemical cycling, this structure can control the distribution of Li… + Release, inhibit Co 3+ Migration alleviates stress accumulation caused by structural phase transformation and increases the stability of the system. Element A, in the form of oxides, coats the particle surface or acts on the bulk phase of the material as a dopant, further enhancing the stability of the surface or bulk phase.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] This invention provides a novel cathode material structure through a simple solid-state sintering method, offering a solution for improving the cycle stability of lithium cobalt oxide at charging cutoff voltages above 4.55V. While maintaining high capacity, the cycle stability is significantly improved compared to the comparative sample. Furthermore, this invention does not introduce new processes and is perfectly compatible with existing production equipment, facilitating industrial production and scale-up. Attached Figure Description

[0020] Figure 1XPS image of the novel cathode material prepared in Example 1 of this invention.

[0021] Figure 2 This is the XRD pattern of the novel cathode material described in Embodiment 1 of the present invention.

[0022] Figure 3 This is a charge-discharge curve of the novel cathode material described in Embodiment 1 of the present invention.

[0023] Figure 4 This is a SEM image (polycrystalline) of the novel cathode material with the new structure described in Embodiment 1 of the present invention.

[0024] Figure 5 This is a SEM image (single crystal) of the novel cathode material with the new structure described in Embodiment 5 of the present invention.

[0025] Figure 6 This is a SEM image (single crystal) of the novel cathode material with the new structure described in Comparative Example 1 of this invention.

[0026] Figure 7 This is a particle size distribution diagram of the novel cathode material described in Embodiment 1 of the present invention. Detailed Implementation

[0027] The present invention will be further described in detail below through embodiments, but those skilled in the art should understand that the scope of the present invention is not limited thereto. Any modifications or equivalent substitutions to the technical solutions of the present invention that do not depart from the spirit and scope of the technical solutions of the present invention should be covered by the protection of the present invention.

[0028] Example 1

[0029] Weigh 3.973g Co3O4, 0.057g H6TeO6, 0.019g NiO, and 1.939g Li2CO3, pour them into a ball mill, and ball mill with ethanol at 300 r / min for 4 hours. After removing and drying, calcine the product in a tube furnace. The calcine process is as follows: starting at room temperature, heating at a rate of 2℃ / min, holding at 1000℃ for 10 hours, and then cooling to room temperature with the furnace to obtain the first-calcined product. Grind the first-calcined product and place it in a tube furnace for a second calcination. The calcination process is as follows: starting at room temperature, heating at a rate of 2℃ / min, holding at 900℃ for 10 hours, and then cooling to room temperature with the furnace to obtain a new structural material doped with Te and Ni, with the chemical formula LiCo. 0.99 Te 0.005 Ni 0.005 O2 has a polycrystalline morphology.

[0030] Example 2

[0031] Weigh 3.973g Co3O4, 0.057g H6TeO6, 0.019g NiO, and 1.939g Li2CO3, pour them into a ball mill, and ball mill with ethanol at 300 r / min for 4 hours. After drying, calcine the mixture in a tube furnace. The calcine process is as follows: starting at room temperature, heating at a rate of 2℃ / min, holding at 1000℃ for 10 hours, and then cooling to room temperature with the furnace to obtain the first-calcined product. Weigh 0.026g Al2O3, mix it with the first-calcined product, grind it evenly, and then place it in a tube furnace for a second calcination. The calcination process is as follows: starting at room temperature, heating at a rate of 2℃ / min, holding at 900℃ for 10 hours, and then cooling to room temperature with the furnace to obtain a new structural material doped with Te and Ni and coated with Al, with the chemical formula Li. 1.01 Co 0.99 Te 0.005 Ni 0.005 Al 0.01 O2 has a polycrystalline morphology.

[0032] Example 3

[0033] Weigh 3.973g Co3O4, 0.057g H6TeO6, 0.019g NiO, and 1.939g Li2CO3, pour them into a ball mill, and ball mill with ethanol at 300 r / min for 4 hours. After removing and drying, calcine them in a tube furnace. The calcine process is as follows: starting at room temperature, heating at a rate of 2℃ / min, holding at 1000℃ for 10 hours, and then cooling to room temperature with the furnace to obtain the first-calcined product. Weigh 0.056g Y2O3, mix it with the first-calcined product, grind it evenly, and then place it in a tube furnace for a second calcination. The calcination process is as follows: starting at room temperature, heating at a rate of 2℃ / min, holding at 900℃ for 10 hours, and then cooling to room temperature with the furnace to obtain a new structural material doped with Te and N and coated with Y, with the chemical formula Li. 1.01 Co 0.99 Te 0.005 Ni 0.005 Y 0.01 O2 has a polycrystalline morphology.

[0034] Example 4

[0035] Weigh 3.973g Co3O4, 0.038g H6TeO6, 0.012g NiO, 0.019g Y2O3, and 1.939g Li2CO3, pour them into a ball mill, and ball mill with ethanol at 300 r / min for 4 hours. After removing and drying, calcine the product in a tube furnace. The calcine process is as follows: starting at room temperature, heating at a rate of 2℃ / min, holding at 1000℃ for 10 hours, and then cooling to room temperature with the furnace to obtain the first-calcined product. Grind the first-calcined product and place it in a tube furnace for a second calcination. The calcination process is as follows: starting at room temperature, heating at a rate of 2℃ / min, holding at 900℃ for 10 hours, and then cooling to room temperature with the furnace to obtain a new structural material doped with Te, Ni, and Y, with the chemical formula LiCo. 0.99 Te 0.003 Ni 0.003 Y 0.003 O2 has a polycrystalline morphology.

[0036] Example 5

[0037] Weigh 3.973g Co3O4, 0.038g H6TeO6, 0.012g NiO, 0.006g B2O3, and 1.939g Li2CO3, pour them into a ball mill, and ball mill with ethanol at 300 r / min for 4 hours. After removing and drying, calcine the product in a tube furnace. The calcine process is as follows: starting at room temperature, heating at a rate of 2℃ / min, holding at 1000℃ for 10 hours, and then cooling to room temperature with the furnace to obtain the first-calcined product. Grind the first-calcined product and place it in a tube furnace for a second calcination. The calcination process is as follows: starting at room temperature, heating at a rate of 2℃ / min, holding at 900℃ for 10 hours, and then cooling to room temperature with the furnace to obtain a new structural material doped with Te, Ni, and B, with the chemical formula LiCo. 0.99 Te 0.003 Ni 0.003 B 0.003 O2 has a single crystal morphology.

[0038] Example 6

[0039] Weigh 3.973g Co3O4, 0.038g H6TeO6, 0.012g NiO, 0.006g B2O3, and 1.939g Li2CO3, pour them into a ball mill, and ball mill with ethanol at 300 r / min for 4 hours. After drying, calcine the mixture in a tube furnace. The calcine process is as follows: starting at room temperature, heating at a rate of 2℃ / min, holding at 1000℃ for 10 hours, and then cooling to room temperature with the furnace to obtain the first-calcined product. Weigh 0.062g ZrO2, mix it with the first-calcined product, grind it evenly, and then place it in a tube furnace for a second calcination. The calcination process is as follows: starting at room temperature, heating at a rate of 2℃ / min, holding at 900℃ for 10 hours, and then cooling to room temperature with the furnace to obtain a new structural material doped with Te, Ni, and B and coated with Zr, with the chemical formula Li. 1.01 Co 0.99 Te 0.003 Ni 0.003 Y 0.003 Zr 0.01 O2 has a single crystal morphology.

[0040] Comparative Example 1

[0041] Comparative Example 1 was carried out in accordance with Example 1, except that Te element was not doped, and its chemical formula was LiCoO2, and its morphology was single crystal.

[0042] Comparative Example 2

[0043] Weigh 3.973g Co3O4, 0.025g Al2O3, and 1.939g Li2CO3, pour them into a ball mill, and ball mill with ethanol at 300 r / min for 4 hours. After drying, calcine the mixture in a tube furnace. The calcine process is as follows: starting at room temperature, heating at a rate of 2℃ / min, holding at 1000℃ for 10 hours, and then cooling to room temperature in the furnace to obtain the first-calcined product. Grind the first-calcined product and place it in a tube furnace for a second calcination. The calcination process is as follows: starting at room temperature, heating at a rate of 2℃ / min, holding at 900℃ for 10 hours, and then cooling to room temperature in the furnace to obtain conventionally doped lithium cobalt oxide cathode material with the chemical formula LiCo. 0.99 Al 0.01 O2 has a single crystal morphology.

[0044] Comparative Example 3

[0045] Weigh 3.997g Co3O4, 0.046g H6TeO6, and 1.939g Li2CO3, pour them into a ball mill, and ball mill with ethanol at 300 r / min for 4 hours. After removing and drying, calcine the mixture in a tube furnace. The calcine process is as follows: starting at room temperature, heating at a rate of 2℃ / min, holding at 1000℃ for 10 hours, and then cooling to room temperature with the furnace to obtain the first-calcined product. Grind the first-calcined product and place it in a tube furnace for a second calcination. The calcination process is as follows: starting at room temperature, heating at a rate of 2℃ / min, holding at 900℃ for 10 hours, and then cooling to room temperature with the furnace to obtain a new Te-doped structural material with the chemical formula LiCo. 0.995 Te 0.005 O2 has a polycrystalline morphology.

[0046] Test case

[0047] (1) XPS test

[0048] The cathode material prepared in Example 1 was subjected to XPS testing, and the test results are as follows: Figure 1 As shown, a peak for Te at 576.7 eV is observed, indicating that the Te element in the material has a +6 valence state.

[0049] (2) XRD test

[0050] The cathode material prepared in Example 1 was subjected to XRD testing, and the test results are as follows: Figure 2 As shown, the material is mainly the first phase of LiCoO2 in the R-3m space group, and there are diffraction peaks in the range of 18 to 22°, which is a manifestation of the superstructure formed between the transition metal and Te.

[0051] (3) SEM testing

[0052] The morphology of the cathode materials prepared in Examples 1-6 and Comparative Examples 1-3 was observed by SEM testing, as shown in Table 1. The morphologies of the cathode materials prepared in Examples 1, 5, and Comparative Example 1 are shown in Table 1. Figure 4 , Figure 5 and Figure 6 As shown, both undoped and conventionally doped LiCoO2 are single-crystal morphologies, while LiCoO2 doped with Te and M elements are mostly polycrystalline morphologies, with the specific morphology depending on the type of A element.

[0053] (4) Electrochemical performance testing

[0054] The positive electrode materials prepared in Examples 1-6 and Comparative Examples 1-3 were mixed with conductive agent carbon black and binder PVDF (polyvinylidene fluoride) at a mass ratio of 8:1:1. The mixture was ground uniformly using NMP (N-methylpyrrolidone) as a solvent, then coated onto aluminum foil and dried in a 100°C oven for 24 hours. After drying, the mixture was cut into electrode discs and rolled several times on a roller press to obtain the positive electrode sheet. The above positive electrode sheet was then combined with a lithium metal negative electrode to form a button cell in a glove box. The cells were tested at room temperature using a Newway battery testing system. The initial discharge capacity at a current density of 20 mA / g was recorded, and the capacity retention rate after 50 cycles at 1C was calculated. The test results are recorded in Table 2. The first charge-discharge curve of the positive electrode material prepared in Example 1 is shown below. Figure 3 As shown.

[0055] Table 1

[0056] Example plan Chemical formula Appearance Example 1 Te-doped, Ni <![CDATA[LiCo 0.99 The 0.005 Yes 0.005 O2]]> polycrystalline Example 2 Te- and Ni-doped Al <![CDATA[Li 1.01 Co 0.99 Tea 0.005 Ni 0.005 Al 0.01 O2]]> polycrystalline Example 3 Te, Ni-doped Y <![CDATA[Li 1.01 Co 0.99 Tea 0.005 Neither 0.005 AND 0.01 O2]]> polycrystalline Example 4 Te-doped, Ni-doped, Y-doped <![CDATA[LiCo 0.99 Tea 0.003 Neither 0.003 AND 0.003 O2]]> polycrystalline Example 5 Te-doped, Ni-doped, B-doped <![CDATA[LiCo 0.99 Tea 0.003 of 0.003 B 0.003 O2]]> single crystal Example 6 Te-doped, Ni-doped, B-doped, Zr-doped <![CDATA[Li 1.01 Co 0.99 For 0.003 It’s 0.003 Y 0.003 Zr 0.01 O2]]> single crystal Comparative Example 1 Undoped <![CDATA[LiCoO2]]> single crystal Comparative Example 2 Conventional doping <![CDATA[LiCo 0.99 Al 0.01 O2]]> single crystal Comparative Example 3 Te-doped <![CDATA[LiCo 0.995 At 0.005 O2]]> polycrystalline

[0057] Table 2

[0058] Example Chemical formula Initial capacity (mAh / g) Capacity retention rate (%) after 500 weeks Example 1 <![CDATA[LiCo 0.99 The 0.005 Yes 0.005 O2]]> 216.3 88.3 Example 2 <![CDATA[Li 1.01 Co 0.99 Tea 0.005 Ni 0.005 Al 0.01 O2]]> 219.5 96.3 Example 3 <![CDATA[Li 1.01 Co 0.99 Tea 0.005 Neither 0.005 AND 0.01 O2]]> 221.3 95.5 Example 4 <![CDATA[LiCo 0.99 Tea 0.003 Neither 0.003 AND 0.003 O2]]> 210.8 88.5 Example 5 <![CDATA[LiCo 0.99 Tea 0.003 of 0.003 B 0.003 O2]]> 208.4 90.2 Example 6 <![CDATA[Li 1.01 Co 0.99 For 0.003 It’s 0.003 Y 0.003 Zr 0.01 O2]]> 213.8 94.5 Comparative Example 1 <![CDATA[LiCoO2]]> 218.3 49.7 Comparative Example 2 <![CDATA[LiCo 0.99 Al 0.01 O2]]> 210.5 77.8 Comparative Example 3 <![CDATA[LiCo 0.995 At 0.005 O2]]> 218.6 83.2

Claims

1. A lithium-ion battery cathode material, the general chemical formula of which is Li m Co n-x-y-z Te x M y A z O2, where 0.8≤m≤1.02, 0.98≤n≤1.02, 0<x≤0.1, 0<y≤0.1, 0≤z≤0.1, element M is one or more of Ni, Cu, Zn, Cr, Mn, Ga, Fe, and Mg, and element A is one or more of conventional doping elements other than element M.

2. The lithium-ion battery cathode material as described in claim 1, characterized in that, The element A is selected from one or more of Al, Ti, Zr, La, Y, B, P, Ce, Na, K, and F.

3. The lithium-ion battery cathode material as described in claim 1, characterized in that, In the lithium-ion battery cathode material. Element M forms a compound with Li, Te, and O that has a superlattice structure and grows coherently with lithium cobalt oxide.

4. The lithium-ion battery cathode material as described in claim 3, characterized in that, The compounds with superlattice structures are Li4MTeO6 and Li8M2Te2O. 12 Li 4.5 Compounds in any of the following forms: MTeO6, Li2M2TeO6, and Li4M3TeO8.

5. The lithium-ion battery cathode material as described in claim 1, characterized in that, Element A can be coated on the surface of material particles in the form of an oxide, or doped into the bulk structure of the material as a dopant element.

6. The lithium-ion battery cathode material as described in claim 1, characterized in that, The lithium-ion battery cathode material is a single crystal or polycrystalline material with a volumetric particle size distribution Dv50 of 12–20 μm and exhibits a bimodal distribution.

7. A method for preparing the lithium-ion battery cathode material according to any one of claims 1 to 6, comprising the following steps: 1) Mix cobalt source, tellurium source, lithium source, M element source and A element source to be doped into the bulk phase in a certain stoichiometric ratio, and then perform a first calcination in air to obtain a first calcination product. 2) The product from the first calcination is uniformly crushed, mixed evenly with the A element source to be coated on the surface, and then calcined a second time in air to obtain the lithium-ion cathode material.

8. The preparation method according to claim 7, characterized in that, Step 1) First, mix the solid cobalt source, tellurium source, lithium source, M element source and A element source to be doped into the bulk phase by wet ball milling and then dry them. Then, calcine them in air atmosphere. The temperature of the first calcination is 900-1100℃ and the temperature of the second calcination is 800-1000℃.

9. The preparation method according to claim 7, characterized in that, The cobalt source is selected from one or more of cobalt(II) oxide, cobalt(III) oxide, cobalt(IV) tetroxide, cobalt carbonate, and cobalt hydroxide; the tellurium source is selected from one or more of telluric acid, lithium tellurite, tellurium dioxide, and tellurium trioxide; and the lithium source is selected from one or more of lithium oxide, lithium hydroxide, lithium carbonate, lithium acetate, and lithium oxalate. The source of element M is selected from one or more of the oxides, hydroxides, carbonates, acetates, and oxalates of element M; the source of element A is selected from one or more of the oxides, hydroxides, carbonates, acetates, and oxalates of element A.

10. A lithium-ion battery, characterized in that, The positive electrode of the lithium-ion battery comprises the lithium-ion battery positive electrode material according to any one of claims 1 to 6.

Images