CN102403496B - Composite cathode material of high-content lithium-ion battery and synthesis method for composite cathode material - Google Patents

Abstract

The present invention belongs to the field of lithium ion batteries. Provide a high-capacity lithium-ion battery composite cathode material, the composite cathode material contains 3 to 20% by mass of γ-MnO ₂ and 80 to 97% by mass of a molecular formula of Li _1.2 Ni _(0.2-x) Mn _{(0.6-x )} Co _2X O ₂ composite metal oxide, wherein, x=0～0.07. Also provide a kind of method for preparing this composite cathode material, first prepare the composite metal oxide of Li and transition metal element, then composite metal oxide and gamma-MnO Mix and grind _evenly according to proportioning amount, promptly obtain the present invention's high Capacitive lithium-ion battery composite cathode material. The composite positive electrode material has high high-temperature specific capacity, excellent rate performance, and high first-time Coulombic efficiency, which can meet the requirements of power batteries. The synthesis method is simple and feasible, and is suitable for large-scale industrial production.

Description

A kind of high-capacity lithium-ion battery composite cathode material and its synthesis method

technical field

The invention belongs to the field of lithium-ion batteries, and in particular relates to a high-capacity lithium-ion battery composite cathode material and a synthesis method thereof.

Background technique

Lithium-ion batteries have become the main choice of rechargeable power supplies for today's portable electronic products due to their high specific energy, high power density, long cycle life, low self-discharge, and high cost performance. In the development process of lithium-ion batteries, the battery cathode material has become a bottleneck restricting its large-scale promotion and application, and the production of a cathode with superior performance and low price is a key factor for the commercialization of lithium-ion batteries.

At present, the existing commercial lithium-ion battery cathode materials include LiCoO ₂ , LiMn ₂ O ₄ and LiFePO ₄ , but the capacity of these cathode materials is relatively low, and it is difficult to meet the needs of high-capacity, high-energy-density electronic products. In particular, it is difficult to meet the development needs of electric vehicles. It has been reported in the literature that a lithium-rich cathode material such as Li[Li _0.2 Ni _0.2 Mn _0.6 ]O ₂ has an initial discharge capacity of 270mAh/g at a voltage of 2.0-4.6V and a constant current of 0.1C, and the capacity retention rate after 50 cycles It is 92%, showing high discharge capacity and cycle stability, and has become a research hotspot. This type of lithium-rich cathode material is mainly a solid solution formed by Li ₂ MnO ₃ and layered material LiMO (M=Ni, Mn, Co and other transition group metal elements). It has a layered structure similar to LiMnO ₂ and is in the ɑ-NaFeO ₂ configuration, belonging to the hexagonal crystal system and the R-3m space group.

Although the above lithium-rich cathode materials have high capacity and cycle stability, such lithium-rich cathode materials also suffer from low initial Coulombic efficiency and poor rate capability.

Contents of the invention

The purpose of the present invention is to solve the problems of low initial coulombic efficiency and poor rate performance in the existing lithium-rich positive electrode materials, and provide a high-capacity lithium-ion battery composite positive electrode material.

Another object of the present invention is to provide a synthesis method of the high-capacity lithium-ion battery composite cathode material.

The technical scheme that the present invention realizes above-mentioned object is as follows:

A high-capacity lithium-ion battery composite positive electrode material, the composite positive electrode material contains 3 to 20% by mass of γ-MnO ₂ and 80 to 97% by mass of a molecular formula of Li _1.2 Ni _(0.2-x) Mn _(0.6-x) A composite metal oxide of Co _2X O ₂ , where x=0-0.07.

The synthetic method of above-mentioned high-capacity lithium-ion battery composite cathode material comprises the steps:

(1) Dissolve soluble lithium salts, nickel salts, manganese salts, cobalt salts and gelling agents in water according to the ratio, then adjust the pH of the solution to neutral or slightly alkaline, and react at a temperature of 70-80°C for 6- A sol was generated after 10 hours;

(2) Dry the sol, pre-calcine the obtained precursor at 450-550°C for 5-8 hours, cool and grind, and then calcinate at 800-950°C for 6-15 hours to obtain the molecular formula Li _1.2 Ni _{(0.2-x )} Mn _(0.6-x) Co _2X O ₂ composite metal oxides;

(3) Heat treatment of γ-MnO ₂ at a temperature of 130-350°C for 5-25 hours;

(4) Mixing the composite metal oxide obtained in the step (2) with the γ-MnO ₂ after the heat treatment in the step (3) according to the ratio, and grinding them uniformly to obtain a composite positive electrode material for a high-capacity lithium-ion battery.

Further, the lithium salt is at least one of LiNO ₃ , LiCl, CH ₃ COOLi and LiOH, and the nickel salt is at least one of Ni(NO ₃ ) ₂ , NiCl ₂ and Ni(CH ₃ COO) ₂ , the manganese salt is at least one of Mn(NO ₃ ) ₂ , MnCl ₂ and Mn(CH ₃ COO) ₂ , and the cobalt salt is Co(NO ₃ ) ₂ , CoCl2 and Co(CH ₃ COO) ₂ at least one of the

Further, the molar dosage of the gel-forming agent is equal to the sum of the molar dosages of nickel salt, manganese salt and cobalt salt.

Further, the gelling agent is tartaric acid and/or citric acid.

Further, in the step (1), the pH of the solution is adjusted to 7-7.5 with ammonia water.

Beneficial effects of the present invention:

(1) The high-capacity lithium-ion battery composite positive electrode material of the present invention has high high-temperature specific capacity and excellent rate performance, which can meet the requirements of power batteries. It can be charged and discharged at 2-4.8V and 55°C, and the initial discharge capacity is the highest at 0.1C. It can reach 281mAh/g, and the discharge capacity can reach 180 mAh/g at 1C; while the composite metal oxide of Li _1.2 Ni _(0.2-x) Mn _(0.6-x) Co _2X O ₂ is charged and discharged at 55°C, 1C The discharge capacity is only about 110 mAh/g.

(2) The high-capacity lithium-ion battery composite cathode material of the present invention has a high initial Coulombic efficiency, which can reach up to 90% when charging and discharging at 20°C, and 98% when charging and discharging at 55°C; while Li _1.2 Ni The first Coulombic efficiency of _(0.2-x) Mn _(0.6-x) Co _2X O ₂ composite metal oxide is only 82% at 20°C and only 88% at 55°C.

(3) The cyclic voltammetry curve shows that the composite positive electrode material of the present invention is not mixed with γ-MnO ₂ Li _1.2 Ni _0.17 Mn _0.56 Co _0.07 O ₂ Comparing the composite metal oxide, the structure of the composite positive electrode material is more stable when charging and discharging. Less variation and correspondingly better stability.

(4) The γ-MnO ₂ raw material used is rich in sources and low in price, and the cost of the positive electrode material can be reduced after adding this raw material in the lithium-rich positive electrode material.

(5) The synthesis method of the composite cathode material of the present invention is simple and feasible, suitable for large-scale industrial production, and has a high degree of practicality.

Description of drawings

FIG. 1 is an XRD characterization diagram of the Li _1.2 Ni _0.17 Mn _0.56 Co _0.07 O ₂ composite metal oxide prepared in Example 1.

Fig. 2 is the initial charge and discharge graphs of Li _1.2 Ni _0.17 Mn _0.56 Co _0.07 O ₂ (a) and the composite positive electrode material (b) of Example 1 at 20°C under 0.1C current.

Fig. 3 is the first charge and discharge diagram of Li _1.2 Ni _0.17 Mn _0.56 Co _0.07 O ₂ (a) and the composite positive electrode material (b) of Example 1 at 55°C under 0.1C current.

Fig. 4 is the cycle diagram of Li _1.2 Ni _0.17 Mn _0.56 Co _0.07 O ₂ (a) and the composite cathode material of Example 1 (b) at different rates.

Fig. 5 is a cyclic voltammetry curve of Li _1.2 Ni _0.17 Mn _0.56 Co _0.07 O ₂ .

FIG. 6 is a graph of cyclic voltammetry of the composite cathode material of Example 1. FIG.

Detailed ways

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

The electrochemical performance characterization method of the high-capacity lithium-ion battery composite cathode material of the present invention is as follows: the consumption of positive electrode material and carbon black, binding agent PVDF is 8:1:1 in N-methylrolidone ( NMP) was mixed to make a slurry, and then the slurry was 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, and Celgard2325 as the separator. The electrolyte is 1mol/L LiPF ₆ solution (the solvent is a mixture of ethylene carbonate: dimethyl carbonate with a volume ratio of 1:1), and a CR2032 button battery is assembled in a glove box with an argon atmosphere. 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 specifically implemented, since the volatility of the Li element in the obtained Li _1.2 Ni _0.17 Mn _0.56 Co _0.07 O ₂ composite metal oxide is much higher than that of Ni, Mn, Co and other elements during high-temperature calcination, it contains The actual molar amount of Li raw materials is about 5% higher than the theoretical amount to compensate for the Li content deviation caused by volatilization.

Example 1

Weigh it according to the amount of LiNO ₃ , Ni(NO ₃ ) ₂ , Mn(CH ₃ COO) ₂ , Co(NO ₃ ) ₂ , and citric acid in a molar ratio of 1.26:0.17:0.56:0.07:0.8, and dissolve it in water , then adjust the pH of the solution to 7 with ammonia water, then heat at 80°C for 9 hours to form a sol, and then dry the sol at 120°C for 15 hours to obtain a precursor, which is pre-calcined at 500°C for 6 hours, After cooling and grinding, calcining at 950°C for 6 hours and then cooling, Li _1.2 Ni _0.17 Mn _0.56 Co _0.07 O ₂ composite metal oxide was obtained. The γ- _MnO2 was heat-treated at 300°C for 15 hours and cooled. According to the mass percentage of γ-MnO2 and Li _1.2 Ni _0.17 Mn _0.56 Co _0.07 O ₂ of 8%:92%, they are mixed and ground evenly to obtain the composite cathode material.

Example 2

Weigh it according to the amount of LiNO ₃ , Ni(NO ₃ ) ₂ , Mn(CH ₃ COO) ₂ , and citric acid in a molar ratio of 1.26:0.2:0.6:0.8, dissolve it in water, and adjust the pH of the solution to 7.2, and then heated at 70°C for 10 hours to form a sol, and then dried the sol at 120°C for 15 hours to obtain a precursor, which was pre-calcined at 500°C for 7 hours, cooled and ground, and then calcined at 950°C Cooling after 6 hours affords Li _1.2 Ni _0.2 Mn _0.6 O ₂ . The γ- _MnO2 was heat-treated at 350°C for 6 hours and cooled. Mix and grind evenly according to the mass percentage of γ-MnO ₂ and Li _1.2 Ni _0.2 Mn _0.6 O ₂ at 8%:92% to obtain a composite positive electrode material.

Example 3

Weigh it according to the amount of LiNO ₃ , Ni(NO ₃ ) ₂ , Mn(CH ₃ COO) ₂ , Co(NO ₃ ) ₂ , and citric acid in a molar ratio of 1.26:0.13:0.54:0.13:0.8, and dissolve it in water , then adjust the pH of the solution to 7.3 with ammonia water, then heat at 75°C for 10 hours to form a sol, and then dry the sol at 120°C for 15 hours to obtain a precursor, which is pre-calcined at 500°C for 8 hours, After cooling and grinding, calcining at 900°C for 8 hours and then cooling to obtain Li _1.2 Ni _0.13 Mn _0.54 Co _0.13 O ₂ . Heat-treat γ-MnO2 at 250°C for 18 hours and cool down. Mix and grind evenly according to the mass percentage of γ-MnO ₂ and Li _1.2 Ni _0.13 Mn _0.54 Co _0.13 O ₂ at 8%:92% to obtain a composite positive electrode material.

Example 4

Weigh it according to the amount of LiNO ₃ , Ni(NO ₃ ) ₂ , Mn(CH ₃ COO) ₂ , Co(NO ₃ ) ₂ , and citric acid in a molar ratio of 1.26:0.17:0.56:0.07:0.8, and dissolve it in water , then adjust the pH of the solution to 7 with ammonia water, then heat at 75°C for 8 hours to form a sol, and then dry the sol at 120°C for 15 hours to obtain a precursor, which is pre-calcined at 550°C for 5 hours, After cooling and grinding, calcining at 950°C for 7 hours and then cooling, Li _1.2 Ni _0.17 Mn _0.56 Co _0.07 O ₂ was obtained. γ- _MnO2 was heat-treated at 300°C for 10 hours and cooled. Mix and grind evenly according to the mass percentage of γ-MnO ₂ and Li _1.2 Ni _0.17 Mn _0.56 Co _0.07 O ₂ at 3%:97% to obtain a composite positive electrode material.

Example 5

Weigh it according to the molar ratio of CH ₃ COOLi, Ni(CH ₃ COO) ₂ , Mn(CH ₃ COO) ₂ , Co(CH ₃ COO) ₂ , and citric acid is 1.26:0.17:0.56:0.07:0.8, and weigh it Dissolve in water, adjust the pH of the solution to 7 with ammonia water, then heat at 80°C for 6 hours to form a sol, and then dry the sol at 120°C for 15 hours to obtain a precursor, which is pre-calcined at 450°C for 8 After 1 hour, it was cooled and ground, then calcined at 850°C for 10 hours and then cooled to obtain Li _1.2 Ni _0.17 Mn _0.56 Co _0.07 O ₂ . The γ- _MnO2 was heat-treated at 170°C for 25 hours and cooled. Mix and grind evenly according to the mass percentage of γ-MnO ₂ and Li _1.2 Ni _0.17 Mn _0.56 Co _0.07 O ₂ at 10%:90% to obtain a composite positive electrode material.

Example 6

Weigh it according to the amount of LiOH, Ni(NO ₃ ) ₂ , Mn(CH ₃ COO) ₂ , Co(NO ₃ ) ₂ , and tartaric acid in a molar ratio of 1.26:0.17:0.56:0.07:0.8, dissolve it in water, and then Adjust the pH of the solution to 7 with ammonia water, then heat at 80°C for 7 hours to form a sol, and then dry the sol at 120°C for 15 hours to obtain a precursor, which is pre-calcined at 550°C for 6 hours, then cooled and ground , then calcined at 850°C for 12 hours and then cooled to obtain Li _1.2 Ni _0.17 Mn _0.56 Co _0.07 O ₂ . γ- _MnO2 was heat-treated at 200°C for 20 hours and cooled. Mix and grind evenly according to the mass percentage of γ-MnO ₂ and Li _1.2 Ni _0.17 Mn _0.56 Co _0.07 O ₂ at 20%:80% to obtain a composite positive electrode material.

As shown in Figure 1, XRD characterization shows that the Li _1.2 Ni _0.17 Mn _0.56 Co _0.07 O ₂ composite metal oxide has a typical layered hexagonal structure, that is, the ɑ-NaFeO ₂ configuration, and the space group is R-3m. of miscellaneous peaks.

At 0.1C current, the electrochemical performance characterization results of different materials are as follows:

.

The temperature is 55°C, and the discharge capacity after 30 cycles at 1C current is shown in the table below:

.

The cyclic voltammetry curves of the lithium-rich cathode material Li _1.2 Ni _0.17 Mn _0.56 Co _0.07 O ₂ (as shown in Figure 5) and the composite cathode material of Example 1 (as shown in Figure 6) both showed 2 There are two peaks, that is, the peak less than 4.5V and the peak greater than 4.5V, and in the subsequent cycle, the peak greater than 4.5V disappears. During the discharge process, the lithium-rich cathode material Li _1.2 Ni _0.17 Mn _0.56 Co _0.07 O ₂ The peak at around 3.75V shifts to the left and the peak shape changes greatly, while the peak of the Li _1.2 Ni _0.17 Mn _0.56 Co _0.07 O ₂ composite metal oxide mixed with γ-MnO ₂ also shifts to the left but the peak shape changes relatively Smaller, indicating that the positive electrode material structure mixed with γ-MnO ₂ has smaller structural changes and is more stable during charge and discharge.

Claims (5)

1. a synthetic method of high-capacity lithium-ion battery composite positive electrode material, is characterized in that, described composite positive electrode material comprises the gamma- _MnO of 3～20 mass % and the molecular formula of 80～97 mass % is Li _1.2 Ni _{( 0.2-x)} Mn _(0.6-x) Co _2X O ₂ composite metal oxide, wherein, x=0～0.07, Including the following steps: (1) Dissolve soluble lithium salts, nickel salts, manganese salts, cobalt salts and gelling agents in water according to the ratio, then adjust the pH of the solution to neutral or slightly alkaline, and react at a temperature of 70-80°C for 6- A sol was generated after 10 hours; (2) Dry the sol, pre-calcine the obtained precursor at 450-550°C for 5-8 hours, cool and grind it, and then calcinate at 850-950°C for 6-15 hours to obtain the molecular formula Li _1.2 Ni _{(0.2-x )} Mn _(0.6-x) Co _2X O ₂ composite metal oxides; (3) Heat treatment of γ-MnO ₂ at a temperature of 130-350°C for 5-25 hours; (4) Mixing the composite metal oxide obtained in the step (2) with the γ-MnO ₂ after the heat treatment in the step (3) according to the ratio, and grinding them uniformly to obtain a composite positive electrode material for a high-capacity lithium-ion battery. 2. the synthetic method of high-capacity lithium-ion battery composite cathode material according to claim 1, is characterized in that: described lithium salt is at least one in LiNO ₃ , LiCl, CH ₃ COOLi and LiOH, and described nickel salt is at least one of Ni(NO ₃ ) ₂ , NiCl ₂ and Ni(CH ₃ COO) ₂ , and the manganese salt is at least one of Mn(NO ₃ ) ₂ , MnCl ₂ and Mn(CH ₃ COO) ₂ species, the cobalt salt is at least one of Co(NO ₃ ) ₂ , CoCl ₂ and Co(CH ₃ COO) ₂ . 3. The synthetic method of high-capacity lithium-ion battery composite cathode material according to claim 1, characterized in that: the molar dosage of the gelling agent is equal to the sum of the three molar dosages of nickel salt, manganese salt and cobalt salt. 4. the synthetic method of high-capacity lithium-ion battery composite cathode material according to claim 1, is characterized in that: described gelling agent is tartaric acid and/or citric acid. 5 . The method for synthesizing composite cathode materials for high-capacity lithium-ion batteries according to claim 1 , characterized in that in step (1), the pH of the solution is adjusted to 7-7.5 with ammonia water.