CN104253265A - Cation-doped and modified lithium ion battery (4:4:2)type ternary cathode material and preparation method thereof - Google Patents

Abstract

The invention relates to a cation-doped and modified lithium-ion battery (4:4:2) type ternary cathode material and a preparation method thereof, belonging to the field of lithium-ion batteries. The general chemical formula of the cathode material is LiNi _0.4-x M ¹ _x Co _0.2-y M ² _y Mn _0.4-z M ³ _z O ₂ , M ¹ is Mg, Zn or Cu; M ² is Al or Cr; M ³ is Ti, Zr or Mo, 0≤x≤0.15; 0≤y≤0.15; 0≤z≤0.15; weigh soluble lithium source, nickel source, manganese source, cobalt source and metal M according to molar ratio ¹ salt, M ² salt and M ³ salt were dissolved in deionized water respectively, then mixed with citric acid solution and stirred evenly, the pH was adjusted with concentrated ammonia water, and then heated and evaporated to obtain a gel. After the gel is heated and dried, it is burned and ground twice to obtain a cation-doped modified lithium-ion battery (4:4:2) type ternary positive electrode material. The ternary positive electrode material for lithium ion batteries of the present invention has fine and uniform particles reaching the nanoscale level, so it has high discharge capacity, excellent cycle stability and rate capability, and its performance can be maintained under high and low temperature conditions, which is convenient for large-scale industrial production , high degree of practicality.

Description

Lithium-ion battery (4:4:2) type ternary cathode material modified by cation doping and preparation method thereof

technical field

The invention relates to a cation-doped and modified lithium-ion battery (4:4:2) type ternary cathode material and a preparation method thereof, belonging to the field of lithium-ion batteries.

Background technique

At present, LiCoO ₂ has become the most widely used cathode material in commerce because of its high operating voltage, large capacity, stable discharge, suitable for high current discharge, and good cycle performance. However, cobalt is a rare metal, which is expensive and pollutes the environment to a certain extent. Therefore, people's research focus turns to replace _LiCoO2 materials with cheap and environmentally friendly other transition metal compounds. LiNiO ₂ has a similar structure to LiCoO ₂ , has a higher actual discharge capacity, and nickel reserves are much more abundant and cheaper than cobalt. However, its preparation is difficult, non-stoichiometric products are easily generated during the preparation process, and the crystal structure will change during the charge and discharge process, resulting in rapid capacity decay, poor cycle performance and thermal stability. For these reasons, the application fields of LiNiO ₂ are greatly limited. LiMn ₂ O ₄ has a spinel crystal structure. Compared with LiCoO ₂ and LiNiO ₂ , LiMn ₂ O ₄ has many advantages: large manganese reserves, low cost, environmental friendliness, and easy preparation. However, its discharge capacity is low (about 120mAh/g), and the distortion of the crystal lattice caused by the Jahn-Teller effect of Mn ³⁺ leads to an irreversible phase change in the crystal structure during charge and discharge, which makes LiMn ₂ O ₄ The capacity fades quickly, especially at high temperatures higher than 45°C. This slows down the process of its industrialization.

LiNi _x Co _y Mn _1-xy O ₂ ternary cathode material combines the characteristics of LiCoO ₂ , LiNiO ₂ , and LiMn ₂ O ₄ materials, and has the advantages of high capacity, stable structure, good safety, and low cost. One of the cathode materials with the most potential for commercialization. The patent of the present invention selects the molar ratio n(Ni):n(Co):n(Mn)=4:2:4 as the research system, in the advantage of the original LiNi _1/3 Mn _1/3 Co _1/3 O ₂ material Under the premise, the content of expensive Co is reduced, which can reduce the cost of materials and the environmental pollution of the production process to a certain extent. Ni contributes the most to the capacity, and the relative increase of Ni content can make the material have higher theoretical specific capacity. At the same time, increasing the content of Mn can further improve its safety performance. Therefore LiNi _0.4 Co _0.2 Mn _0.4 O ₂ is a ternary cathode material with more research value. However, the current ternary materials still have shortcomings such as insufficient cycle performance and insufficient rate performance. Doping is an important means to improve the performance of lithium-ion battery cathode materials, and this means has been widely used in LiNiO ₂ , LiMn ₂ O ₄ and other materials. The invention patent, on the basis of cation doping, adopts sol-gel method to synthesize nano-scale modified lithium-ion battery (4:4:2) type ternary positive electrode material, and improves its particle morphology and electrochemical performance.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, to provide a nano-scale cation doping modified lithium ion battery (4:4:2) type ternary positive electrode material preparation method, the positive electrode material particles are small and uniform , smooth surface, good crystallization performance, high capacity, high Coulombic efficiency, good cycle performance under high and low temperature conditions, and good rate performance.

According to the technical scheme provided by the present invention, a cation-doped modified lithium-ion battery (4:4:2) type ternary positive electrode material, the chemical general formula of the positive electrode material is LiNi _0.4-x M ¹ _x Co _{0.2 -y} M ² _y Mn _0.4-z M ³ _z O ₂ , M ¹ is Mg, Zn or Cu; M ² is Al or Cr; M ³ is Ti, Zr or Mo, 0≤x≤0.15; 0≤y≤ 0.15; 0≤z≤0.15;

Weigh soluble lithium source, nickel source, manganese source, cobalt source and metal M ¹ salt, M ² salt, M ³ salt according to the molar ratio, dissolve them in deionized water respectively, add citric acid solution and mix well, then use concentrated ammonia water After adjusting the pH, the product was heated and evaporated to obtain a gel. After the gel is heated and dried, it is burned and ground twice to obtain a cation-doped modified lithium-ion battery (4:4:2) type ternary positive electrode material.

A cation-doped modified lithium-ion battery (4:4:2) type ternary positive electrode material, the steps are as follows:

(1) Preparation of gel: Weigh analytically pure lithium source, nickel source, manganese source, cobalt source and metal M ¹ salt, M ² salt, M ³ salt, respectively dissolved in deionized water, add citric acid solution, the amount added is equal to the sum of molar amounts of transition metal ions, mix and stir evenly, adjust the pH value to 7-8 with concentrated ammonia water, 60-100°C Evaporate by heating in a water bath, and keep stirring until a dark purple gel is obtained;

(2) Ignition: take the gel prepared in step (1) and dry it at 80-150°C for 8-15 hours, then place it at 300-600°C for pre-burning treatment for 4-8 hours; naturally cool to room temperature and grind to obtain the precursor body; the ground powder is baked at 700-1000°C for 10-20 hours, and then ground after cooling to obtain the product cation-doped modified lithium-ion battery (4:4:2) type ternary positive electrode material.

Further, the lithium source is one or more of LiNO ₃ , CH ₃ COOLi, and LiOH, and the nickel source is one or more of Ni(NO ₃ ) ₂ and Ni(CH ₃ COO) ₂ , The manganese source is one or both of Mn(NO ₃ ) ₂ and Mn(CH ₃ COO) ₂ , and the cobalt source is one of Co(NO ₃ ) ₂ and Co(CH ₃ COO) ₂ or two, the metal M ¹ salt is Mg(NO ₃ ) ₂ ·6H ₂ O, Zn(NO ₃ ) ₂ ·6H ₂ O or Cu(NO ₃ ) ₂ ·3H ₂ O, the metal M ² salt Al(NO ₃ ) ₂ ·9H ₂ O or Cr(NO ₃ ) ₂ ·9H ₂ O; the metal M ³ salt is C ₁₆ H ₃₆ O ₄ Ti, Zr(NO ₃ ) ₂ ·5H ₂ O or MoO ₃ .

The present invention has the following advantages:

(1) The particle size distribution of the positive electrode material prepared by the present invention is uniform, the crystallinity is high, the surface is smooth, and the particle dispersion is good;

(2) The positive electrode material provided by the present invention has a more stable material structure due to the doping modification of cations. As a result, the material has high discharge capacity, excellent cycle performance and rate performance under high and low temperature conditions. Moreover, the raw materials required for doping modification are cheap, which further reduces the cost required for the production of positive electrode materials, and is conducive to promoting the process of commercialization.

Description of drawings

Fig. 1 is the X-ray diffraction pattern of the positive electrode materials prepared in Comparative Example and Examples 1 and 5.

Fig. 2 is the scanning electron micrograph of the anode material prepared in Examples 1, 5, 6, and 7 (a in the figure is Example 1, b is Example 5, c is Example 6, and d is Example 7).

Fig. 3 is a cycle graph of positive electrode materials prepared in Comparative Example and Examples 1 and 5 at room temperature under a current of 0.2C, and the charging and discharging voltage range is 2.0-4.6V.

Fig. 4 is the cycle curves of positive electrode materials prepared in Comparative Example and Examples 1 and 5 at different rates at 55°C, and the charge and discharge voltage range is 2.0-4.6V.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

Comparative Example Preparation of undoped LiNi _0.4 Co _0.2 Mn _0.4 O ₂ cathode material.

Weigh analytically pure CH ₃ COOLi·2H ₂ O, Ni(CH ₃ COO) ₂ ·4H ₂ O, Co(CH ₃ COO) ₂ ·4H ₂ O, Mn(CH ₃ COO)·4H ₂ O, fully dissolved in deionized water, add citric acid solution, the amount added is equal to the sum of molar amounts of transition metal ions, mix well and adjust the pH value of the solution to about 7.5 with concentrated ammonia water , heated and stirred in a water bath at 80°C to fully complex the various ions and evaporate the water to form a deep purple gel; dry the gel at 120°C for 10 hours, then pretreat it at 500°C for 6 hours, and cool Grinding afterward, and then roasting at 850°C for 20 hours to obtain the desired product.

Example 1

(1) Preparation of gel: Weigh analytically pure CH ₃ COOLi·2H ₂ O, Ni(CH ₃ COO) ₂ ·4H ₂ O, Co( CH ₃ COO) ₂ 4H ₂ O, Mn(CH ₃ COO) 4H ₂ O, Mg(NO ₃ ) ₂ 6H ₂ O were completely dissolved in deionized water respectively, and then added citric acid solution in an amount equal to the transition metal The sum of the molar amounts of ions, after mixing evenly, adjust the pH value to about 7 with concentrated ammonia water, heat in a water bath at 60°C and keep stirring until a deep purple gel is obtained;

(2) Burning: take the gel prepared in step (1) and heat and dry at 80°C for 8 hours, pre-burn the resulting product at 300°C for 4 hours, cool and grind, then calcinate at 700°C for 10 hours, cool and grind , to obtain the product LiNi _0.35 Co _0.2 Mn _0.4 Mg _0.05 O ₂ cathode material.

Example 2

(1) Preparation of gel: Weigh analytically pure LiNO ₃ , Ni(NO ₃ ) ₂ ·6H ₂ O, Co(NO ₃ ) ₂ ·6H according to the stoichiometric ratio (1.05:0.3:0.2:0.4:0.1) ₂ O, Mn(NO ₃ ) ₂ 4H ₂ O, Cu(NO ₃ ) ₂ 3H ₂ O were completely dissolved in deionized water respectively, and then citric acid solution was added in an amount equal to the sum of molar amounts of transition metal ions. After mixing evenly, adjust the pH value to about 7.5 with concentrated ammonia water, heat in a water bath at 80°C and keep stirring until a dark purple gel is obtained;

(2) Burning: Burning: Take the gel prepared in step (1) and heat and dry at 100°C for 10 hours, pre-burn the resulting product at 400°C for 5 hours, cool and grind, and then calcinate at 850°C for 15 hours After cooling and grinding, the product LiNi _0.3 Co _0.2 Mn _0.4 Cu _0.1 O ₂ cathode material was obtained.

Example 3

(1) Preparation of gel: Weigh analytically pure LiOH·H ₂ O, Ni(NO ₃ ) ₂ ·6H ₂ O, Co(NO ₃ ) according to the stoichiometric ratio (1.05:0.25:0.2:0.4:0.15) ₂ · 6H ₂ O, Mn(NO ₃ ) ₂ · 4H ₂ O, Zn(NO ₃ ) ₂ · 6H ₂ O, dissolve completely with deionized water respectively, add citric acid solution, the amount equal to the molar amount of transition metal ions After mixing evenly, adjust the pH value to about 8 with concentrated ammonia water, heat in a water bath at 90°C and keep stirring until a deep purple gel is obtained;

(2) Burning: 2) Burning: take the gel prepared in step (1) and heat and dry at 120°C for 12 hours, pre-burn the resulting product at 500°C for 6 hours, then cool and grind, and then calcined at 900°C After cooling and grinding for 18 hours, the product LiNi _0.25 Co _0.2 Mn _0.4 Zn _0.15 O ₂ cathode material was obtained.

Example 4

(1) Preparation of gel: Weigh analytically pure CH ₃ COOLi·2H ₂ O, Ni(CH ₃ COO) ₂ ·4H ₂ O, Co( CH ₃ COO) ₂ 4H ₂ O, Mn(CH ₃ COO) 4H ₂ O, Al(NO ₃ ) ₂ 9H ₂ O were completely dissolved in deionized water respectively, then added citric acid solution, the amount equal to transition metal The sum of molar amounts of ions, after mixing evenly, adjust the pH value to about 7.5 with concentrated ammonia water, heat in a water bath at 100°C and keep stirring until a deep purple gel is obtained;

(2) Burning: take the gel prepared in step (1) and heat and dry at 150°C for 15 hours, pre-burn the resulting product at 600°C for 8 hours, cool and grind, then calcinate at 1000°C for 20 hours, cool and grind , to obtain the product LiNi _0.4 Co _0.1 Mn _0.4 Al _0.1 O ₂ cathode material.

Example 5

(1) Preparation of gel: Weigh analytically pure LiNO ₃ , Ni(NO ₃ ) ₂ ·6H ₂ O, Co(NO ₃ ) ₂ according to the stoichiometric ratio (1.05:0.35:0.15:0.4:0.05:0.05) · 6H ₂ O, Mn(NO ₃ ) ₂ · 4H ₂ O, Mg(CH ₃ COO) · 4H ₂ O, Cr(NO ₃ ) ₂ · 9H ₂ O, respectively dissolved completely in deionized water, add citric acid solution , the input amount is equal to the sum of the molar amounts of transition metal ions, after mixing evenly, adjust the pH value to about 7.5 with concentrated ammonia water, heat in a water bath at 90°C and keep stirring until a deep purple gel is obtained;

(2) Burning: Take the gel prepared in step (1) and heat and dry at 100°C for 14 hours, pre-burn the resulting product at 600°C for 8 hours, cool and grind, then calcinate at 950°C for 20 hours, cool and grind , to obtain the product LiNi _0.35 Co _0.15 Mn _0.4 Mg _0.05 Cr _0.05 O ₂ cathode material.

Example 6

(1) Preparation of gel: Weigh analytically pure LiNO ₃ , Ni(NO ₃ ) ₂ ·6H ₂ O, Co(NO ₃ ) ₂ 6H ₂ O, Mn(NO ₃ ) ₂ 4H ₂ O, Zn(NO ₃ ) ₂ 6H ₂ O, Cr(NO ₃ ) ₂ 9H ₂ O, respectively dissolved in deionized water completely, add lemon Acid solution, the addition amount is equal to the sum of the molar amounts of transition metal ions, then add the stoichiometric ratio of n-butyl orthotitanate, mix well, adjust the pH value to about 7.5 with concentrated ammonia water, heat in a water bath at 80°C and Stir continuously until a dark purple gel is obtained;

(2) Burning: The prepared gel was heated and dried at 100°C for 14 hours, the product obtained was pre-fired at 600°C for 6 hours, cooled and ground, then calcined at 850°C for 18 hours, cooled and ground to obtain the product LiNi _0.37 Co _0.17 Mn _0.37 Zn _0.03 Cr _0.03 Ti _0.03 O ₂ cathode material.

Example 7

(1) Preparation of gel: Weigh analytically pure CH ₃ COOLi·2H ₂ O, Ni(CH ₃ COO) ₂ ·4H ₂ O, Co( CH ₃ COO) ₂ 4H ₂ O, Mn(CH ₃ COO) 4H ₂ O, Zr(NO ₃ ) ₂ 5H ₂ O were completely dissolved in deionized water, and then added citric acid solution, the amount of which was equal to the transition metal The sum of the molar amounts of ions, after mixing evenly, adjust the pH value to about 7.5 with concentrated ammonia water, heat in a water bath at 70°C and keep stirring until a deep purple gel is obtained;

(2) Burning: take the gel prepared in step (1) and heat and dry it at 120°C for 13 hours, pre-burn the product at 600°C for 8 hours, then cool and grind it, then calcinate it at 900°C for 20 hours, then cool and grind it , to obtain the product LiNi _0.4 Co _0.2 Mn _0.3 Zr _0.1 O ₂ cathode material.

Example 8

(1) Preparation of gel: Weigh analytically pure LiNO ₃ , Ni(NO ₃ ) ₂ ·6H ₂ O, Co(NO ₃ ) ₂ ·6H according to the stoichiometric ratio (1.05:0.4:0.2:0.25:0.15) ₂ O and Mn(NO ₃ ) ₂ ·4H ₂ O were dissolved completely in deionized water respectively, then added citric acid solution, the amount of which was equal to the sum of the molar amounts of transition metal ions, then dissolved MoO ₃ in NH ₄ OH and added In the mixed solution obtained above, after mixing evenly, adjust the pH value to about 8 with concentrated ammonia water, heat in a water bath at 90°C and keep stirring until a dark purple gel is obtained;

(2) Burning: take the gel prepared in step (1) and heat and dry at 100°C for 15 hours, pre-burn the resulting product at 500°C for 6 hours, cool and grind, then calcinate at 850°C for 15 hours, cool and grind , to obtain the product LiNi _0.4 Co _0.2 Mn _0.25 Mo _0.15 O ₂ cathode material.

As can be seen from the X-ray diffraction patterns of the comparative example in the accompanying drawing 1 and the examples 1 and 5, the positive electrode material synthesized in the examples 1 and 5 has a highly ordered two-dimensional hexagonal layered structure, and no The impurity peaks of doping elements indicate that doping does not cause changes in the crystal structure of the material.

As can be seen from the scanning electron microscope figure of embodiment 1-4 in accompanying drawing 2 (a among the figure is the material synthesized in embodiment 1, and b is the material synthesized in embodiment 2, and c is the material synthesized in embodiment 3, d It is the material synthesized in the embodiment 4), and the materials synthesized in the embodiment all have the advantages of finer particles and uniform particle size distribution, smooth surface and better crystallinity.

Application Example 1

Mix the positive electrode material powder, acetylene black, and polyvinylidene fluoride (PVDF) synthesized in Examples 1-8 at a mass fraction ratio of 80:12:8, add an appropriate amount of pyrrolidone, grind it into a uniform slurry, and evenly coat it on aluminum foil On, dry at 100°C, gun-cut (diameter 14mm), roll at 3MPa to make a pole piece, vacuum-dry at 80°C for 12 hours before use, assemble a button-type (CR2032) test battery in a glove box filled with argon , the negative electrode is a lithium sheet, the electrolyte is LB315[m(DMC):m(EMC):m(EC)=1:1:1] solution, and the separator is a Celgard2325 porous film. The assembled battery is charged and discharged with LAND-CT2001A. The charging and discharging range is 2.0-4.6V.

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

Table 1 shows the electrochemical performance characterization results of batteries assembled from the cathode materials synthesized in Comparative Examples and Examples 1-8 at a current density of 0.2C at room temperature and at 55°C.

The assembled battery of the positive electrode material of comparative example and embodiment 1,5, the cycle curve graph under 0.2C electric current when normal temperature is as shown in Figure 3; The battery assembled of the positive electrode material of comparative example and embodiment 1,5, in The cycle curves at different rate currents at 55°C are shown in Figure 4.

Table 10.2 Under the current density of 2C, the test results of charge and discharge performance of each embodiment are shown in the following table:

Claims (7)

1. lithium ion battery (4:4:2) type tertiary cathode material for cation doping modification, is characterized in that: described positive electrode is LiNi _0.4-xm ¹ _xco _0.2-ym ² _ymn _0.4-zm ³ _zo ₂, M ¹for Mg, Zn or Cu; M ²for Al or Cr; M ³for Ti, Zr or Mo, 0≤x≤0.15; 0≤y≤0.15; 0≤z≤0.15.

Solubility lithium source, nickel source, manganese source, cobalt source and metal M is taken according to mol ratio ¹salt, M ²salt, M ³salt, respectively with after deionized water dissolving, adds citric acid solution mixing and stirring, and after regulating pH with concentrated ammonia liquor, heating evaporation obtains gel.After gel heat drying, obtain lithium ion battery (4:4:2) the type tertiary cathode material of product cation doping modification through twice calcination grinding.

2. lithium ion battery (4:4:2) type tertiary cathode material for cation doping modification, step is as follows:

(1) preparation of gel: according to stoichiometric proportion (1.05: 0.4: 0.4: 0.2: x: y: z) take analytically pure lithium source, nickel source, manganese source, cobalt source and metal M ¹salt, M ²salt, M ³salt, is dissolved in respectively in deionized water, adds citric acid solution, addition equals the mole sum of transition metal ions, mixing and stirring, by concentrated ammonia liquor adjust ph to 7-8,60-100 DEG C of heating water bath evaporation, and constantly stir, until obtain darkviolet gel;

(2) calcination: get gel dry 8-15 hour at 80-150 DEG C prepared by step (1), and be placed on 300-600 DEG C of pre-calcination process 4-8 hour; Naturally cool to grinding at room temperature and obtain presoma; Powder after grinding is placed in roasting 10-20 hour under 700-1000 DEG C of condition, continues lithium ion battery (4:4:2) the type tertiary cathode material that grinding obtains the modification of product cation doping after cooling.

3. the preparation method of the ternary cathode material of lithium ion battery of cation doping modification as claimed in claim 2, is characterized in that: described lithium salts is LiNO ₃, CH ₃one or more in COOLi, LiOH.

4. the preparation method of the ternary cathode material of lithium ion battery of cation doping modification as claimed in claim 2, is characterized in that: described nickel salt is Ni (NO ₃) ₂, Ni (CH ₃cOO) ₂in one or both.

5. the preparation method of the ternary cathode material of lithium ion battery of cation doping modification as claimed in claim 2, is characterized in that: described manganese salt is Mn (NO ₃) ₂, Mn (CH ₃cOO) ₂in one or both.

6. the preparation method of the ternary cathode material of lithium ion battery of cation doping modification as claimed in claim 2, is characterized in that: described cobalt salt is Co (NO ₃) ₂, Co (CH ₃cOO) ₂in one or both.

7. the preparation method of the ternary cathode material of lithium ion battery of cation doping modification as claimed in claim 2, is characterized in that: described metal M ¹salt is Mg (NO ₃) ₂6H ₂o, Zn (NO ₃) ₂6H ₂o or Cu (NO ₃) ₂3H ₂o, described metal M ²salt is Al (NO ₃) ₂9H ₂o or Cr (NO ₃) ₂9H ₂o; Described metal M ³salt is C ₁₆h ₃₆o ₄ti, Zr (NO ₃) ₂5H ₂o or MoO ₃.