CN106784676A - Lithium-enriched cathodic material of lithium ion battery of fluorine element doping vario-property and preparation method thereof - Google Patents

Abstract

The invention relates to a fluorine-doped and modified lithium-ion battery lithium-rich cathode material and a preparation method thereof, belonging to the field of lithium-ion batteries. The positive electrode material is Li[Li _0.2 Ni _{0.2-0.5b+ 0.5a} Co _b Mn _{0.6-0.5b-0.5a} ]O _2-a F _a ; wherein, 0<a≤0.1, 0≤b≤0.13; lithium Grind salt, nickel salt, manganese salt, cobalt salt, lithium fluoride and combustion accelerant into fine powder, add solvent and mix evenly, and then burn it. The lithium-rich cathode material of the lithium ion battery of the present invention not only has a high discharge specific capacity, but also has excellent cycle stability, excellent rate performance, and high and low temperature performance, and can meet the requirements of power batteries. The fluorine salt used for doping is rich in sources, low in price, and environmentally friendly. The synthesis process is simple and easy, the manufacturing cost is low, and it is convenient for large-scale industrial production and has a high degree of practicality.

Description

Fluorine-doped modified lithium-ion battery lithium-rich cathode material and preparation method thereof

technical field

The invention relates to a fluorine-doped and modified lithium-ion battery lithium-rich cathode material and a preparation method thereof, belonging to the field of lithium-ion batteries.

Background technique

As a secondary green battery, lithium-ion batteries have been widely used in many fields such as portable electronic devices, and have begun to expand the market for large-capacity batteries such as electric vehicles. LiCoO ₂ is still the mainstream positive electrode material used in lithium-ion secondary batteries at present, but LiCoO ₂ has low capacity utilization, high cost, and serious environmental pollution. These shortcomings force people to seek its substitutes. In recent years, lithium-rich cathode material Li[Li _x Ni _{y Mnz} Co _1-xyz ]O ₂ has become a research hotspot due to its advantages of high relative capacity and low price.

Li[Li _x Ni _y Mn _z Co _1-xyz ]O ₂ is mainly a solid solution formed by Li ₂ MnO ₃ and layered material LiMO ₂ (M=Ni, Mn, Co and other transition group metal elements), which can also be written as xLi ₂ MnO ₃ ·(1-x)LiMO ₂ . The lithium-rich material has a platform of delithiation and deoxidation at about 4.5V. During the delithiation and deoxidation process, the Li ₂ MnO ₃ component is activated, so that it can show a higher specific capacity during the discharge process. At the same time, the Li The ₂ MnO ₃ component can also play a role in stabilizing the structure of the electrode material during the charging and discharging process.

However, this type of lithium-rich cathode materials also has the problems of rapid initial specific capacity decline and poor rate performance. Li[Li _0.2 Ni _0.1 Co _0.2 Mn _0.5 ]O ₂ synthesized by ChiHoon Song et al. by sol-gel method, at room temperature in the voltage range of 2-4.8V, the first discharge capacity at 0.2C current is 274.13mAh/g , but the capacity retention after 20 cycles was only 83.9%. Wu et al. used AlPO ₄ to coat Li _1.2 Mn _0.54 Co _0.13 Ni _0.13 O ₂ , but this coating can only improve the first Coulombic efficiency and discharge capacity, and has not improved the rate performance.

Contents of the invention

The purpose of the present invention is to solve the problems of the existing lithium-rich positive electrode materials with rapid initial specific capacity decline and poor rate performance, and to provide a lithium-rich positive electrode material for a high-capacity lithium ion battery and a preparation method thereof.

According to the technical solution provided by the present invention, a fluorine-doped modified lithium-ion battery lithium-rich cathode material, the cathode material is Li[Li _0.2 Ni _{0.2-0.5b+0.5a} Co _b Mn _{0.6-0.5b- 0.5a} ]O _2-a F _a ; Wherein, 0<a≤0.1, 0≤b≤0.13;

Grind lithium salt, nickel salt, manganese salt, cobalt salt, lithium fluoride and combustion accelerant into fine powder in molar ratio, add solvent and mix evenly, and then burn to obtain the product chlorine-doped modified lithium-ion battery lithium-rich Cathode material.

A method for preparing a lithium-rich cathode material for lithium-ion batteries doped and modified by chlorine element, the steps are as follows:

(1) Mixing: Weigh according to the molar ratio of lithium salt, nickel salt, manganese salt, cobalt salt, lithium fluoride and combustion accelerant 1.21～1.26:0.13～0.25:0.49～0.6:0～0.13:0～0.1:0.8 , grind them in a mortar and mix them evenly, then add 3-5mL of solvent, and continue grinding until the mixture is uniform and fine paste;

(2) Burning: take the paste mixture obtained in step (1) and bake it at 110-130°C for 11-13 hours, and pre-burn the obtained precursor at 450-550°C for 5-8 hours, cool and grind it, and then heat it at 850°C. After calcination at ~950°C for 12-20 hours, a lithium-rich cathode material for lithium-ion batteries with the molecular formula Li[Li _0.2 Ni _{0.2-0.5b+0.5a} Co _b Mn _{0.6-0.5b-0.5a} ]O _2-a F _a is obtained ; Wherein, 0<a≤0.1, 0≤b≤0.13.

The lithium salt is at least one of LiNO ₃ , CH ₃ COOLi and LiOH, and the nickel salt is one or a mixture of Ni(NO ₃ ) ₂ and Ni(CH ₃ COO) ₂ .

The manganese salt is one or a mixture of Mn(NO ₃ ) ₂ and Mn(CH ₃ COO) ₂ .

The cobalt salt is one or a mixture of Co(NO ₃ ) ₂ and Co(CH ₃ COO) ₂ .

The chloride salt is one or a mixture of LiF, NiF ₂ , MnF ₂ and CoF ₂ .

The combustion enhancer is one or a mixture of tartaric acid, sucrose, urea, citric acid and oxalic acid.

The solvent is deionized water and/or ethanol.

The invention has the following advantages: the lithium-rich positive electrode material of the lithium ion battery not only has a high discharge specific capacity, but also has excellent cycle stability, excellent rate performance, and high and low temperature performance, and can meet the requirements of power batteries. The fluorine salt used for doping is rich in sources, low in price, and environmentally friendly. The synthesis process is simple and easy, the manufacturing cost is low, and it is convenient for large-scale industrial production and has a high degree of practicality.

Description of drawings

FIG. 1 is an XRD characterization diagram of the cathode material Li[Li _0.2 Ni _0.155 Co _0.13 Mn _0.515 ]O _1.95 F _0.05 prepared in Example 1.

Fig. 2 is a cycle graph of Li _1.2 Mn _0.54 Ni _0.13 Co _0.13 O ₂ and the positive electrode material of Example 1 at 15°C and 0.2C current.

Fig. 3 is a cycle diagram of Li _1.2 Mn _0.54 Ni _0.13 Co _0.13 O ₂ and the positive electrode material of Example 1 at 55°C at different rates.

detailed description

The technical solution of the present invention will be further described below in conjunction with the embodiments.

Example 1

Weigh according to the molar ratio of LiNO ₃ , Ni(NO ₃ ) ₂ , Mn(CH ₃ COO) ₂ , Co(NO ₃ ) ₂ , LiF, and citric acid: 1.21:0.155:0.515:0.13:0.05:0.8, respectively Grind in a mortar and mix evenly, then add 5mL of deionized water and continue grinding until the mixture becomes a uniform and fine paste. Then bake the mixture at 120°C for 12 hours to obtain a precursor. The precursor is pre-calcined at 500°C for 6 hours, cooled and ground, then calcined at 850°C for 20 hours and cooled to obtain Li[Li _0.2 Ni _0.155 Co _0.13 Mn _0.515 ]O _1.95 F _0.05 cathode material.

Weigh it according to the molar ratio of LiNO ₃ , Ni(NO ₃ ) ₂ , Mn(CH ₃ COO) ₂ , Co(NO ₃ ) ₂ , and citric acid is 1.26:0.13:0.54:0.13:0.8, and then weigh it in the same way as above Li _1.2 Mn _0.54 Ni _0.13 Co _0.13 O ₂ can be synthesized by following steps.

Example 2

Weigh according to the molar ratio of LiNO ₃ , Ni(NO ₃ ) ₂ , Mn(CH ₃ COO) ₂ , Co(NO ₃ ) ₂ , LiF, and citric acid is 1.23:0.145:0.525:0.13:0.03:0.8, respectively Grind in a mortar and mix evenly, then add 5mL of deionized water and continue grinding until the mixture becomes a uniform and fine paste. Then bake the mixture at 120°C for 12 hours to obtain a precursor. The precursor is pre-calcined at 500°C for 6 hours, then cooled and ground, then calcined at 850°C for 20 hours and then cooled to obtain Li[Li _0.2 Ni _0.145 Co _0.13 Mn _0.525 ]O _1.97 F _0.03 cathode material.

Example 3

Weigh according to the molar ratio of LiNO ₃ , Ni(NO ₃ ) ₂ , Mn(CH ₃ COO) ₂ , Co(CH ₃ COO) ₂ , LiF, and citric acid is 1.16:0.18:0.49:0.13:0.1:0.8, Grind them in a mortar and mix well, then add 5mL of deionized water, and continue grinding until the mixture is uniform and fine paste. Then bake the mixture at 120°C for 12 hours to obtain a precursor. The precursor is pre-calcined at 550°C for 5 hours, then cooled and ground, then calcined at 850°C for 20 hours and then cooled to obtain Li[Li _0.2 Ni _0.18 Co _0.13 Mn _0.49 ]O _1.9 F _0.1 cathode material.

Example 4

Weigh according to the amount of LiNO ₃ , Ni(NO ₃ ) ₂ , Mn(CH ₃ COO) ₂ , LiF, and citric acid with a molar ratio of 1.21:0.225:0.575:0.05:0.8, grind them in a mortar and mix well , then add 3mL of deionized water, continue to grind until the mixture is uniform and fine mud paste. Then bake the mixture at 120°C for 12 hours to obtain a precursor. The precursor is pre-calcined at 450°C for 8 hours, then cooled and ground, then calcined at 950°C for 12 hours and then cooled to obtain Li[Li _0.2 Ni _0.225 Mn _0.575 ]O _1.95 F _0.05 cathode material.

Weigh LiNO ₃ , Ni(NO ₃ ) ₂ , Mn(CH ₃ COO) ₂ , and citric acid with a molar ratio of 1.26:0.2:0.6:0.8, and then synthesize Li[Li _0.2 Ni _0.2 Mn _0.6 ]O ₂ .

Example 5

Weigh according to the amount of LiOH, Ni(NO ₃ ) ₂ , Mn(CH ₃ COO) ₂ , Co(CH ₃ COO) ₂ , CoF ₂ , and citric acid in a molar ratio of 1.26:0.185:0.535:0.055:0.025:0.8, Grind them in a mortar and mix well, then add 4mL of ethanol and continue grinding until the mixture is uniform and fine paste. Then the mixture was baked at 120°C for 12 hours to obtain a precursor. The precursor was pre-calcined at 500°C for 7 hours, cooled and ground, then calcined at 900°C for 15 hours and then cooled to obtain Li[Li _0.2 Ni _0.185 Mn _0.535 Co _0.08 ]O _1.95 F _0.05 cathode material.

Weigh according to the amount of LiOH, Ni(NO ₃ ) ₂ , Mn(CH ₃ COO) ₂ , Co(CH ₃ COO) ₂ , and citric acid in a molar ratio of 1.26:0.16:0.56:0.08:0.8, and then carry out the same method as above Li[Li _0.2 Ni _0.16 Mn _0.56 Co _0.08 ]O ₂ can be synthesized by following steps.

As shown in Figure 1, XRD characterization shows that Li[Li _0.2 Ni _0.155 Co _0.13 Mn _0.515 ]O _1.95 F _0.05 has a typical layered hexagonal structure, that is, the α-NaFeO ₂ configuration, and the space group is R-3m, which does not appear in the figure other miscellaneous peaks.

Application Example 1

The anode material prepared in Examples 1-5, carbon black, and binder PVDF are mixed in N-methylrolidone (NMP) in a mass ratio of 8:1:1 to form a slurry, and then the slurry The material is uniformly coated on the aluminum foil current collector, dried at 80°C, and pressed under a pressure of 18MPa, used as the positive electrode, metal lithium as the negative electrode, Celgard2325 as the separator, and the electrolyte as 1mol/L LiPF ₆ solution (solvent ethylene carbonate: dimethyl carbonate volume ratio of 1:1 mixture), assembled into a CR2032 button cell in an argon atmosphere glove box. The assembled CR2032 button cell was characterized by a charge-discharge tester LAND-CT2001A, and the charge-discharge range was 2-4.8V.

It should be noted that when the present invention is implemented in detail, since the Li element in the obtained lithium-rich positive electrode material is volatile during high-temperature calcination, about 5% of Li will be lost, so the actual molar amount of the lithium salt is 5% higher than the theoretical amount. %about.

The electrochemical performance characterization results of different materials at a current of 0.2C are shown in Table 1, and the discharge capacity after 50 cycles at a current of 1C at a temperature of 55°C is shown in Table 2.

Li _1.2 Mn _0.54 Ni _0.13 Co _0.13 O ₂ and the positive electrode material of Example 1, the cycle curve at 0.2C current at 15°C is shown in Figure 1; Li _1.2 Mn _0.54 Ni _0.13 Co _0.13 O ₂ and Example 1 The positive electrode material of Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 and the positive electrode material of Example 1 are shown in Figure 2 at 55 ° C at different rates; the cycle charts of Li _1.2 Mn _0.54 Ni _0.13 Co _0.13 O ₂ and the positive electrode material of Example 1 are at 55 ° C at different rates. As shown in Figure 3.

Table 1 The electrochemical performance characterization results of different materials at 0.2C current are as follows:

Table 2 The temperature is 55°C, and the discharge capacity after 50 cycles at 1C current is shown in the table below:

Material Discharge capacity (mAh/g) Li _1.2 Mn _{0 54} Ni _{0 13} Co _{0 13} O ₂ 166.6 Example 1 200.3 Example 2 191.7 Example 3 188.6 Li _{1 2} Ni _{0 2} Mn _{0 6} O ₂ 155.7 Example 4 172.6 Li[Li _{0 2} Ni _{0 16} Mn _{0 56} Co _{0 08} ]O ₂ 160 Example 5 181.8

Claims (8)

1. A lithium-rich cathode material for a lithium-ion battery modified by fluorine doping, characterized in that: the cathode material is Li[Li _0.2 Ni _{0.2-0.5b+0.5a} Co _b Mn _{0.6-0.5b-0.5a} ]O _2-a F _a ; where, 0<a≤0.1, 0≤b≤0.13; Grind lithium salts, nickel salts, manganese salts, cobalt salts, lithium fluoride, and combustion accelerants into fine powders in molar ratios, add solvents, mix them evenly, and burn them to obtain the lithium-rich lithium-ion battery modified by fluorine element doping Cathode material. 2. A preparation method of a fluorine-doped modified lithium-ion battery lithium-rich positive electrode material, characterized in that the steps are as follows: (1) Mixing: Weigh according to the molar ratio of lithium salt, nickel salt, manganese salt, cobalt salt, lithium fluoride and combustion accelerant 1.21～1.26:0.13～0.25:0.49～0.6:0～0.13:0～0.1:0.8 , grind them in a mortar and mix them evenly, then add 3-5mL of solvent, and continue grinding until the mixture is uniform and fine paste; (2) Burning: take the paste mixture obtained in step (1) and bake it at 110-130°C for 11-13 hours, and pre-burn the obtained precursor at 450-550°C for 5-8 hours, cool and grind it, and then heat it at 850°C. After calcination at ~950°C for 12-20 hours, a product with the molecular formula Li[Li _0.2 Ni _{0.2-0.5b+0.5a} Co _b Mn _{0.6-0.5b-0.5a} ]O _2-a F _a is obtained Lithium-rich cathode for lithium-ion batteries Material; where, 0<a≤0.1, 0≤b≤0.13. 3. The preparation method of the fluorine-doped modified lithium-ion battery lithium-rich cathode material as claimed in claim 2, characterized in that: the lithium salt is at least one of LiNO ₃ , CH ₃ COOLi and LiOH, and the The nickel salt is one or a mixture of Ni(NO ₃ ) ₂ and Ni(CH ₃ COO) ₂ . 4. The preparation method of the fluorine-doped modified lithium-ion battery lithium-rich cathode material as claimed in claim 2, characterized in that: the manganese salt is Mn(NO ₃ ) ₂ and Mn(CH ₃ COO) ₂ one or a mixture of two. 5. The preparation method of the fluorine-doped modified lithium-ion battery lithium-rich cathode material as claimed in claim 2, characterized in that: the cobalt salt is Co(NO ₃ ) ₂ and Co(CH ₃ COO) ₂ one or a mixture of two. 6. The preparation method of the fluorine-doped modified lithium-ion battery lithium-rich cathode material as claimed in claim 2, characterized in that: the chloride salt is one of LiF, NiF ₂ , MnF ₂ and CoF ₂ or A mixture of several. 7. The preparation method of the fluorine-doped modified lithium-ion battery lithium-rich cathode material as claimed in claim 2, wherein the combustion enhancer is one of tartaric acid, urea, sucrose, citric acid and oxalic acid or A mixture of several. 8 . The method for preparing the fluorine-doped modified lithium-ion battery lithium-rich cathode material according to claim 2 , wherein the solvent is deionized water and/or ethanol.