JP2016139583A - Metal gradient dope positive electrode material for lithium ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal gradient dope positive electrode material for a lithium ion battery.SOLUTION: A metal gradient dope positive electrode material for a lithium ion battery is an active unit of positive electrode material powder which contains a hexagonal crystal positive electrode main body and modified metal, and comprises, as main component, any type oxide of single metal of nickel or cobalt, two kinds of metal of nickel and cobalt, nickel and magnesium or cobalt and magnesium, or three kinds of metal of nickel, cobalt and magnesium. The modified metal is an active metal element different from nickel, cobalt and manganese. Particularly, the modified metal relatively concentrates on the surface of the positive electrode material powder, and gradually decreases to a core, whereby the modified metal forms a continuous concentration gradient dope distribution and has no boundary and no divided layer in the material powder. The modified metal has a relatively high concentration on the surface of the positive electrode material powder, the reactivity of the surface of the positive material to electrolyte liquid is lowered, the stability and safety of a lithium ion battery are enhanced, the material amount of the modified metal is small and the energy density and the use-life can be increased.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a kind of metal gradient doped positive electrode material for lithium ion batteries, and in particular, magnesium (Mg), calcium (Ca), strontium (Sr), boron (B), aluminum (Al), gallium (Ga), indium. By doping one of the modifier elements (In), titanium (Ti), silicon (Si), and tin (Sn) into the hexagonal positive electrode material structure in a continuous concentration gradient distribution method, The present invention relates to a device that improves electric capacity, service life and safety, and thereby promotes higher energy of a positive electrode material.

  In recent years, with the global warming phenomenon becoming increasingly severe and the energy resource crisis of petroleum gradually decreasing, mankind has been forced to develop more energy-saving, carbon-reduced, and environmentally-friendly electric vehicles. Researching and developing lithium-ion batteries that can be used in electric vehicles with high safety and high energy density is now an extremely important part of environmental protection and energy saving. The United States, Europe, Japan, South Korea, Mainland China and Taiwan have all been actively engaged in R & D and mass production of electric vehicle and power lithium-ion battery technologies. In addition, with the rise of 3C consumer electronics industry, smart phones and tablet PCs are already hot products, and people can use mobile smart functions such as wireless online, audio video broadcasting, and cloud data reception at any time. Therefore, it is necessary to extend the power usage time of the 3C electronic product. As a result, it is necessary to develop a lithium ion battery having a high energy density so that it can be applied to electric vehicles and 3C products. The energy density of a lithium ion battery is related to the electrode active material adopted by the battery. Yes, the positive electrode material is the key.

The influence of the positive electrode material on the performance of the lithium-ion battery is very large, and as a result, the selection of the positive electrode material has requirements such as low cost, high capacity, high cycle life, and high current charge / discharge capability, More importantly, the material itself has good thermal stability and can increase the safety of the battery. Among many positive electrode materials, the hexagonal positive electrode material has a relatively high energy density, which Research is emphasized. Among the positive electrode materials for lithium ion batteries, lithium cobalt oxide (LiCoO ₂ ) has been the longest developed and is a hexagonal positive electrode material (single positive electrode material) that is relatively commonly used in the market today. However, Co is a strategic material, high in price, not easy to acquire and toxic. Therefore, lithium nickel oxide (LiNiO ₂ ) having high energy density, relatively low cost, and relatively non-toxicity is used. It has been studied instead of lithium cobalt oxide (LiCoO ₂ ). However, lithium nickel oxide (LiNiO ₂ ) hexagonal positive electrode material (unitary positive electrode material) also has problems such as difficulty in synthesis measurement, low thermal stability and poor structural stability, to improve these problems, the addition of Co by replacing a part of Ni in LiNiO _2, to increase the structural stability of LiNiO _2. This gives rise to the LiNi _x Co _1-x O ₂ hexagonal positive electrode material (binary positive electrode material), which has a higher capacitance (actual capacitance> 180 mAhg ⁻¹ ) than LiCoO ₂ , Moreover, it has better thermal stability than LiNiO ₂ and is a positive electrode material that is the key to the next-generation lithium ion battery. Although two source primary electrode material has many advantages, in view of the material cost of the market, ternary hexagonal AkiraTadashikyoku material _{(LiNi X Co y Mn 1-} Xy O 2) was developed. Although the ternary material has a lower capacitance than the binary material, it can reduce the material cost by adding and replacing Mn, and can increase the stability and safety of the material structure.

  The industry currently has two major development directions for high energy density cathode materials, one of which is nickel (Ni), assuming that the high capacitance of the material itself is increased. By adopting binary and ternary positive electrode materials as components, the other is to increase the positive electrode material working voltage (greater than 4.2V) and increase the capacitance of the material.

  Hexagonal lithium ion battery positive electrode material has a relatively high capacitance and is the most widely used lithium ion battery positive electrode material. The material life is shortened, and there is a concern about safety in use.

  To improve the stability of hexagonal lithium-ion battery cathode materials in a well-known technology, many researchers add relatively stable modifiers in the material structure, thereby increasing the stability of the cathode material surface. Among them, the modifiers used are three kinds of active metal elements, nickel (Ni), cobalt (Co), and manganese (Mn), which are mainly composed of a hexagonal positive electrode material.

  Specifically, there are two types of modification methods commonly used: a material surface modification method and a metal dope modification method.

  With respect to the material surface modification method, the outside of the positive electrode material is coated with a single nano-sized non-electrochemically active substance, thereby reducing the reactivity with the electrolyte on the surface of the positive electrode material and increasing the service life of the material. However, it is necessary to uniformly coat the entire material with a nano-sized protective layer, which is technically difficult and difficult to control, which greatly reduces industrial applicability.

  The metal doping method improves the stability of the material structure itself by uniformly doping a non-electrochemically active metal in the positive electrode material structure, but if it attempts to significantly suppress the reaction with the electrolyte on the material surface If so, it is necessary to dope a high dosage of modifier, which can result in a significant reduction in the capacitance of the material, which in turn causes the high energy density characteristics of the material to be lost.

  For this reason, it is a kind of new metal gradient doped positive electrode material for lithium-ion batteries, and the material modification can improve the stability and safety of the material, and also consider the energy density performance of the material, What is needed is a solution that can achieve the production of a lithium ion battery that takes both capacity and high safety into account, and that solves the above-mentioned problems of the known technology.

The present invention provides a kind of metal gradient doped positive electrode material for lithium ion batteries, and the material powder is composed mainly of a hexagonal positive electrode material and a modified metal that is mainly doped with a concentration gradient of the hexagonal positive electrode material and has an interface. a powder structure without the layer separation without the metal gradient doped lithium ion battery positive electrode material total agent amount may be displayed by using the formula _{f mol% doped Li z Ni a} Co b Mn c O 2, of which, Li _z Ni _a Co _b Mn _c O ₂ represents the main component of the hexagonal positive electrode material, M represents the modified metal, and the molar content of the modified metal is the total mol of nickel, cobalt and manganese in the hexagonal positive electrode material. 0.5% or more of the content and 10% or less of the total molar content of nickel, cobalt and manganese in the hexagonal positive electrode material, and 0.5% (a + b + c) ≦ f ≦ 10% ( a + + C) may be displayed using.

The hexagonal positive electrode material mainly contained in the metal gradient doped positive electrode material of the lithium ion battery described above is nickel, cobalt single metal or nickel and cobalt, nickel and manganese, cobalt and manganese, two kinds of metals or nickel, cobalt and manganese. A positive electrode material active unit composed of any type of oxides of the three types of metals, and represented by the chemical formula Li _z Ni _a Co _b Mn _c O ₂ , and its chemical dosage range Satisfies {0.9 ≦ z ≦ 1.2; a + b + c = 1; 0 ≦ a ≦ 1; 0 ≦ b ≦ 1; 0 ≦ c ≦ 0.6}, and the modified metals are magnesium (Mg), calcium (Ca), strontium (Sr), boron (B), aluminum (Al), gallium (Ga), indium (In), titanium (Ti), silicon (Si), and tin (Sn) One kind of metal element or similar metal element, and the modified metal is relatively concentrated on the surface of the positive electrode material powder, and the continuity concentration gradually decreases toward the core. Form. The metal gradient doped positive electrode material powder surface of the lithium ion battery has a relatively high concentration of the modified metal, effectively reducing the reactivity of the material to the electrolyte, thereby improving the overall operational stability of the lithium ion battery and Safety is improved. In particular, the effect can be achieved only by using a low amount of the modified metal, and it is possible to prevent the problem that the capacitance is greatly lowered by doping an excessive amount of the modified metal in the well-known technique, and as a result, the entire lithium ion The battery energy density can be increased and the service life can be extended.

  Specifically, the positive electrode material of the present invention has both good electrochemical characteristics and thermal stability, in addition to the feature of reducing the reactivity to the electrolyte by using a relatively low amount of the modified metal. , Greatly increase the overall operation efficiency of the lithium ion battery, extend the service life, and improve the industrial utility.

It is a structure display figure of the metal gradient dope positive electrode material of the lithium ion battery of the Example of this invention. It is a material surface form and aluminum element distribution ratio graph of Al (GD) -LNCO of the 1st example of the present invention. It is a charging / discharging curve figure of 1st Example of this invention and a 1st comparative example. It is a charging / discharging curve figure of the various electric current of 1st Example of this invention and a 1st comparative example. It is a cycle life curve figure of the 1st example of the present invention, and the 1st comparative example. It is a DSC test figure of the 1st example and 1st comparative example of the present invention. It is a material surface form and magnesium element distribution ratio graph of Mg (GD) -LNCMO of 2nd Example of this invention. It is a charging / discharging curve figure of 2nd Example of this invention, and a 2nd comparative example. It is a charging / discharging curve figure of the various electric current of 2nd Example of this invention, and a 2nd comparative example. It is a cycle life curve figure of the 2nd example of the present invention, and the 2nd comparative example. It is a DSC test figure of 2nd Example of this invention, and a 2nd comparative example.

  The technical contents, structural features, objects to be achieved, and operational effects of the present invention will be described in detail below with reference to examples and drawings.

Please refer to FIG. FIG. 1 is a structural display diagram of a metal gradient doped positive electrode material of a lithium ion battery according to an embodiment of the present invention. As shown in FIG. 1, the metal gradient-doped positive electrode material 1 of the lithium ion battery of the present invention is a powder, and the modified metal is a hexagonal positive electrode material mainly and a hexagonal positive electrode material that is continuously doped with a gradient concentration. wherein the powder inside is no minute layer with no interface, metal gradient doped cathode material agent of the lithium-ion battery, can be displayed by using the formula _{f mol% dopedLi z Ni a Co} b Mn c O 2, of which , Li _z Ni _a Co _b Mn _c O ₂ represents the main component of the hexagonal positive electrode material, M represents the modified metal, and the molar content of the modified metal is the total of nickel, cobalt and manganese in the hexagonal positive electrode material. 0.5% or more of the molar content and 10% or less of the total molar content of nickel, cobalt and manganese in the hexagonal positive electrode material, 0.5% (a + b + c) ≦ f ≦ 10% (a + b + c) ) Can be displayed.

The hexagonal positive electrode material mainly contained in the above-described metal gradient doped positive electrode material of lithium ion battery is nickel, cobalt single metal or nickel and cobalt, nickel and manganese, cobalt and manganese, two kinds of metals or nickel, cobalt and manganese A positive electrode material active unit composed of any type of oxides of the three types of metals, and represented by the chemical formula Li _z Ni _a Co _b Mn _c O ₂ , and its chemical dosage range Satisfies the following conditions: {0.9 ≦ z ≦ 1.2; a + b + c = 1; 0 ≦ a ≦ 1; 0 ≦ b ≦ 1; 0 ≦ c ≦ 0.6} and is doped with the concentration gradient Is doped in the main material of hexagonal positive electrode in a continuously decreasing distribution system, and in particular, the modified metal is a metal element different from the three active metal elements of nickel (Ni), cobalt (Co), and manganese (Mn). It is a relatively inert metal with respect to the and and electrolyte.

  Relatively preferred modified metals are magnesium (Mg), calcium (Ca), strontium (Sr), boron (B), aluminum (Al), gallium (Ga), indium (In), titanium (Ti), silicon (Si ) And tin (Sn), or a metal element similar to these metals. In particular, the modified metal is doped so as to concentrate on the surface A of the hexagonal positive electrode material powder, and continuously decreases toward the core B of the hexagonal positive electrode material powder, and the direction of decreasing the concentration of the modified metal is C in the figure. This forms the required continuous concentration gradient distribution.

In addition, the space group of the metal gradient doped positive electrode material of the lithium ion battery of the present invention is R-3m, the powder particle diameter D50 is between 0.5 and 25 μm, and the metal gradient concentration is powder in the material. It changes at half of the body particle size, that is, a change interval of about 0.25 to 12.5 μm. In particular, the tap density of the positive electrode material of the present invention is at least 1.5 gcm ⁻³ or more, and the surface area is between 0.1 and 25 m ² g ⁻¹ .

  The improved performance of the present invention will be elucidated below with examples and comparative examples, as well as with physical and electrochemical property analyses.

[Example 1]
1. Synthesis of aluminum gradient doped lithium nickel cobalt oxide cathode material:
Spherical nickel cobalt hydroxide (Ni _0.82 Co _0.18 (OH) ₂ ) was synthesized using the chemical coprecipitation method, and lithium hydroxide was added and mixed. The dose ratio of lithium salt to nickel cobalt metal content 1.02: 1.00, and this mixture is fired at 750 ° C. for 10 hours in an oxygen gas atmosphere to obtain a LiNi _0.82 Co _0.18 O ₂ positive electrode material (LNCO). Further, lithium nickel cobalt oxide (LNCO) was placed in the reaction tank, and the coprecipitation method was used to uniformly coat the surface of the lithium nickel cobalt oxide with an appropriate amount of aluminum hydroxide, followed by 750 ° C. in an oxygen gas atmosphere. To obtain an aluminum metal gradient-doped lithium nickel cobalt oxide positive electrode material (designated code: Al (GD) -LNCO).

2. Manufacturing and testing of button-type batteries:
Production of positive electrode plate: As a positive electrode material, graphite: carbon black: PVdF (polyvinylidene fluoride) = 90: 6: 4 is measured in proportion, and then a certain ratio of NMP is added and mixed uniformly to form a slurry. The slurry is applied on aluminum foil (18 μm) using a 150 μm knife. The electrode plate is first heat-dried on a heating platform, and further vacuum-heated to remove the NMP solvent. Before battery assembly, the electrode plate is first rolled, and the electrode plate is further cut into a coin-type electrode plate having a diameter of about 12 mm. Assume that lithium metal is used as a negative electrode, an Al (GD) -LNCO electrode plate is used as a positive electrode, and 1 M LiPF ₆ is dissolved in a mixed solvent of EC and DMC in a volume ratio of 1: 1. The charge / discharge ranges are set to 2.8-4.3V and 2.8-4.5V, respectively, the charge / discharge current is set to 0.1C, and various electrochemical characteristics of the Al (GD) -LNCO positive electrode material are measured. Furthermore, charge / discharge ranges were set to 2.8-4.3V and 2.8-4.5V, respectively, and various electrochemical characteristics of Al (GD) -LNCO positive electrode materials were measured at various charge / discharge currents (C-rate). To do.

3. Differential scanning calorimetry (DSC) measurement of Al (GD) -LNCO positive electrode material:
Configure the button type battery, charge to 4.3V, disassemble the button type battery with forceps, take out the positive electrode plate, scrape the positive electrode material, take 3 mg of the positive electrode material, put it in the aluminum crucible, In addition, 3 μL electrolytic solution is added, and an aluminum crucible is further caulked and bonded, and the heating rate is 5 ° C. min ⁻¹ , and the scanning temperature range of the measuring device is 180-280 ° C.

[Comparative Example 1]
The synthesis method of Comparative Example 1 used for the comparison of this example, that is, an unmodified lithium nickel cobalt oxide positive electrode material (indicated by the symbol LNCO) is as follows. That is, spherical nickel cobalt hydroxide (Ni _0.82 Co _0.18 (OH) ₂ ) is synthesized using a chemical coprecipitation method, lithium hydroxide is added and mixed, and the lithium salt and nickel cobalt metal content agent are mixed. The quantity ratio is 1.02: 1.00, and this mixture is fired at 750 ° C. for 13 hours in an oxygen gas atmosphere to obtain a LiNi _0.82 Co _0.18 O ₂ positive electrode material (LNCO). Subsequent button-type lithium batteries were manufactured and tested in the same manner as Example Al (GD) -LNCO, and differential scanning calorimetry (DSC) measurements of the LNCO positive electrode material were also the same as in Example Al (GD) -LNCO.

  The test results of Example 1 and Comparative Example 1 are as follows, and the test results are as shown in FIGS.

  For physical property analysis, the whole, surface and cross-section for the positive electrode material of Example Al (GD) -LNCO using inductively coupled plasma emission spectroscopy (ICP / OES) and energy dispersive X-ray analysis (EDS) Quantitative elemental analysis. In ICP / OES, the molar ratio of the doping of the aluminum element to the entire lithium nickel cobalt oxide is 2.55%. 2A is a surface form of the Al (GD) -LNCO positive electrode material, and FIG. 2B is an aluminum element distribution map on the surface of the Al (GD) -LNCO positive electrode material, and the Al (GD) -LNCO positive electrode. It shows that a high amount of aluminum element is surely present on the material surface. In addition, FIG. 2 (c) shows a cross-sectional form of the Al (GD) -LNCO positive electrode material, showing that there is no interface and no layered structure in the Al (GD) -LNCO material powder, FIG. 2D is a quantitative analysis graph of the aluminum element distribution ratio on the material fracture surface, where the aluminum element doping ratio on the surface of the Al (GD) -LNCO material is 8.48%, and the inside of the Al (GD) -LNCO material. The aluminum element doping molar ratio in the portion whose distance from the surface is 8.5 μm is reduced to 0.83%, and the aluminum element distribution of the Al (GD) -LNCO positive electrode material exhibits a continuously decreasing gradient from the surface toward the core. .

Regarding the electrochemical property analysis, the difference in the electrochemical property between the Al (GD) -LNCO of this example and the LNCO material of Comparative Example 1 is the charge / discharge curve property of the material charge / discharge (0.1C) in FIG. By comparing, it can be clearly seen. In the voltage range 2.8-4.3V, the discharge capacitance of the Al (GD) -LNCO of the example is 182.7 mAhg ⁻¹ and the irreversible capacitance is 33.2 mAhg ⁻¹ . If the voltage range is raised to 2.8-4.5 V, the discharge capacitance of Al (GD) -LNCO of the example is 197.8 mAhg ⁻¹ and the irreversible capacitance is 54.3 mAhg ^{−. 1}

  In addition, FIG. 4 is a charge / discharge curve diagram when the discharge current conditions are changed to those in Example 1 and Comparative Example 1 of the present invention. Among them, the constant current charge / discharge conditions are set to charge 0.2C, discharge 0.5C to 7C, and the working voltage is between 2.8 to 4.3V. It is clearly observed in the figure that the example Al (GD) -LNCO has a relatively high discharge voltage platform, ie, a high capacitance of 82.06% under a discharge current of 7C. The LNCO of Comparative Example 1 only has a capacitance of 71.10%.

  The cycle life curves of Example 1 of the present invention and Comparative Example 1 in FIG. 5 show that the material is charged and discharged 70 times in a voltage range of 2.8-4.3 V at a constant current of 0.5 C. And calculated that the example Al (GD) -LNCO still maintains 91.11% of the original capacitance, while the LNCO of Comparative Example 1 has a slightly lower 85. Only 75% remains. If the voltage range is changed to 2.8-4.5 V, the material is charged / discharged at a constant current of 0.5 C, and 40 charge / discharge tests are performed, the calculation results in Example Al (GD). It can be seen that -LNCO still maintains a capacitance of 89.98% of the original capacitance, while LNCO of Comparative Example 1 remains only 79.23% of the original capacitance.

  Thus, when the above results are combined, it can be proved that the example Al (GD) -LNCO surely has superior electrochemical characteristics as compared with the LNCO of Comparative Example 1.

See further FIG. FIG. 3 is a differential scanning calorimeter (DSC) measurement diagram of Example 1 and Comparative Example 1; as shown, the heat dissociation temperature of Comparative Example 1 is about 214.3 ° C., but Example Al (GD) -LNCO has a clearly increased decomposition temperature, its heat dissociation temperature is increased to about 229.9 ° C., and the heat dissipation is reduced from 855.06 Jg ⁻¹ to 591.76 Jg ⁻¹ , thereby Al (GD) -LNCO has proven to have a relatively good thermal stability.

[Example 2]
1. Synthesis of magnesium gradient doped lithium nickel cobalt manganese oxide cathode material:
After synthesizing spherical nickel cobalt manganese hydroxide (Ni _0.51 Co _0.29 Mn _0.20 (OH) ₂ ) using a chemical coprecipitation method, first, spherical nickel cobalt manganese hydroxide is synthesized at 600 ° C. under an oxygen gas atmosphere. After sintering for a while to obtain spherical nickel cobalt manganese oxide, lithium hydroxide was further added and mixed, and the dose ratio of lithium salt to nickel cobalt manganese metal content was set to 1.02: 1.00. The mixture is calcined at 850 ° C. for 18 hours under an oxygen gas atmosphere to obtain a LiNi _0.51 Co _0.29 Mn _0.20 O ₂ positive electrode material (LNCMO). Further, lithium nickel cobalt manganese oxide (LNCMO) is put in a reaction tank, and after coprecipitation is used, the lithium nickel cobalt manganese oxide surface is uniformly coated on a suitable amount of magnesium hydroxide, and then in an oxygen gas atmosphere. Calcination is performed at 850 ° C. for 2 hours to obtain a magnesium gradient-doped lithium nickel cobalt manganese oxide positive electrode material (indicated by Mg (GD) -LNCMO).

2. Manufacturing and testing of button-type batteries:
Production of positive electrode plate: As a positive electrode material, graphite: carbon black: PVdF (polyvinylidene fluoride) = 91: 6: 3 is measured in proportion, and then a certain ratio of NMP is added and mixed uniformly to form a slurry. The slurry is applied on aluminum foil (18 μm) using a 150 μm knife. The electrode plate is first heat-dried on a heating platform, and further vacuum-heated to remove the NMP solvent. Before battery assembly, the electrode plate is first rolled, and the electrode plate is further cut into a coin-type electrode plate having a diameter of about 12 mm. The lithium metal is used as the negative electrode, the Mg (GD) -LNCMO electrode plate is used as the positive electrode, and the electrolyte solution is prepared by dissolving 1M LiPF ₆ in a mixed solvent of EC and DMC in a volume ratio of 1: 1. The charge / discharge ranges are 2.8-4.3V and 2.8-4.5V, respectively, and various electrochemical characteristics of the Mg (GD) -LNCMO positive electrode material are measured at various charge / discharge currents (C-rate).

3. Differential scanning calorimetry (DSC) measurement of Mg (GD) -LNCMO positive electrode material:
Configure the button type battery, charge to 4.5V, disassemble the button type battery with forceps, take out the positive electrode plate, scrape the positive electrode material, take 3 mg of the positive electrode material, put it in the aluminum crucible, In addition, 3 μL electrolyte is added, and an aluminum crucible is caulked and sealed, and the heating rate is 5 ° C. min ⁻¹ , and the scanning temperature range of the measuring device is 220-300 ° C.

[Comparative Example 2]
In Comparative Example 2, that is, an unmodified lithium nickel cobalt manganese oxide positive electrode material (indicated by symbol LNCMO), the synthesis method is as follows. That is, spherical nickel cobalt manganese hydroxide (Ni _0.51 Co _0.29 Mn _0.20 (OH) ₂ ) was synthesized using a chemical coprecipitation method, and the spherical nickel cobalt manganese hydroxide was synthesized at a temperature of 600 ° C. in an oxygen atmosphere. Sinter for 10 hours to obtain spherical nickel cobalt manganese oxide. Further, lithium hydroxide was added and mixed, and the dose ratio of lithium salt to nickel cobalt manganese content was set to 1.02: 1.00. This mixture was calcined at 850 ° C. for 20 hours in an oxygen gas atmosphere, and LiNi. _0.51 Co _0.29 Mn _0.20 O ₂ cathode material (LNCMO) is obtained. Subsequent button-type lithium batteries are manufactured and tested in the same manner as Example Mg (GD) -LNCMO, and differential scanning calorimetry (DSC) measurements of the LNCMO cathode material are also the same as Example Mg (GD) -LNCMO.

  The test results of Example 2 and Comparative Example 2 are as follows, and the test results are as shown in FIGS.

  For physical property analysis, inductively coupled plasma emission spectroscopy (ICP / OES) and energy dispersive X-ray analysis (EDS) are used for the cathode material of Example Mg (GD) -LNCMO as a whole, surface and cross section. Quantitative elemental analysis. The molar ratio of the magnesium element to the entire lithium nickel cobalt manganese oxide measured by ICP / OES is 1.7%. 7A is a surface form of the Mg (GD) -LNCMO positive electrode material, and FIG. 7B is a magnesium element distribution diagram on the surface of the Mg (GD) -LNCMO positive electrode material. Mg (GD) -LNCMO positive electrode It shows that a high amount of magnesium element is surely present on the material surface. In addition, FIG. 7C shows a cross-sectional form of the Mg (GD) -LNCMO positive electrode material, showing that there is no interface and no layered structure in the Mg (GD) -LNCMO material powder, FIG. 7 (d) is a quantitative analysis graph of the magnesium element distribution ratio on the material fracture surface, where the magnesium element doping ratio on the surface of the Mg (GD) -LNCMO material is 2.5%, and the Mg (GD) -LNCMO material inside The magnesium element doping molar ratio of the portion whose distance from the surface is 6.5 μm is reduced to 0.5%, and the magnesium element distribution of the Mg (GD) -LNCMO positive electrode material exhibits a decreasing gradient from the surface toward the core. .

Regarding the electrochemical property analysis, the difference between the electrochemical properties of the Mg (GD) -LNCMO of this example and the LNCMO material of Comparative Example 2 is the charge / discharge curve property of the material charge / discharge (0.1C) in FIG. By comparing, it can be clearly seen. In the voltage range 2.8-4.3 V, the discharge capacitance of the Mg (GD) -LNCMO of the example is 160.3 mAhg ⁻¹ and the irreversible capacitance is 30.2 mAhg ⁻¹ . If the voltage range is between 2.8 and 4.5 V, the discharge capacitance of Mg (GD) -LNCMO in the example is 189.9 mAhg ⁻¹ and the irreversible capacitance is 29.2 mAhg ^{−. 1} Furthermore, as can be seen from the various charge / discharge curve diagrams of FIG. 9, when the constant current condition is charge 0.2C and discharge 0.5C-7C, the working voltage is between 2.8-4.3V. The example Mg (GD) -LNCMO has a relatively high discharge voltage platform, ie it can have a high capacitance of 78.4% under a discharge current of 7C, ie 78.4%, while the LNCMO of Comparative Example 2 is 72 Only 5% capacitance remains.

  Further, as shown in the cycle life curve diagram of FIG. 10, the material was charged and discharged 70 times in the voltage range of 2.8 to 4.3 V at a constant current of 0.5 C. It can be seen that the example Mg (GD) -LNCMO still maintains 91.7% of the original capacitance, and the LNCMO of Comparative Example 2 remains only 83.6% of the original capacitance. . If the voltage range is changed to 2.8-4.5V, the material is charged / discharged at a constant current of 0.5C, and the charge / discharge test is performed 70 times, the calculation results in the example Mg (GD ) -LNCMO still maintains a capacitance of 86.7% of the original capacitance, and it can be seen that LNCMO of Comparative Example 2 remains only 71.3% of the original capacitance.

  Taking the above results together, it can be proved that the example Mg (GD) -LNCMO surely has superior electrochemical properties as compared with the LNCMO of Comparative Example 2.

See further FIG. It is a differential scanning calorimeter (DSC) measurement diagram of the present Example 2 and Comparative Example 2. As shown in the figure, the heat dissipation decomposition temperature of LNCMO of Comparative Example 2 is about 254 ° C., but Example Mg (GD ) -LNCMO has an apparently increased decomposition temperature, its heat dissociation decomposition temperature is increased to about 266 ° C., and the heat dissipation amount is reduced from 227.3 Jg ⁻¹ to 115.9 Jg ⁻¹ , thus (GD) -LNCMO has been shown to have relatively good thermal stability.

  In general, the lithium secondary battery manufactured using the positive electrode material of the present invention can include any circular and square stainless steel, aluminum and aluminum alloy can-covered lithium batteries, and any aluminum foil. It can be applied to polymer lithium batteries packaged with a pouch hot-pressure sealing method and lithium batteries with a related exterior design, thereby improving battery safety and capacitance.

  In summary, the features of the present invention provide a hexagonal positive electrode material doped with metal to have a concentration gradient, and the reaction of the material to the electrolyte using a relatively high metal doping concentration on the powder surface. The metal doping concentration that reduces the properties and continuously and gradually decreases toward the core, reduces the total content of the doped metal, considers both the high capacitance and service life of the material under high voltage, and use Improves the above safety, increases the practicality and industrial applicability by increasing the energy of the positive electrode material, and is very suitable for application to the positive electrode plate necessary for lithium battery fabrication.

  The foregoing is only a description of the preferred embodiment of the present invention, and is not intended to limit the present invention. Other equivalent effect modifications or substitutions that may be accomplished without departing from the spirit of the present invention are not Are also within the scope of the claims of the present invention.

1 Lithium-ion battery metal gradient doped cathode material A Surface B Core C Modified metal concentration reduction direction

Claims (7)

A metal gradient-doped positive electrode material for a lithium ion battery, used as a powder in a lithium ion battery, comprising a hexagonal positive electrode material main body and a modified metal, wherein the modified metal has a continuous concentration gradient distribution and the hexagonal crystal The overall composition of the metal gradient-doped positive electrode material of the lithium ion battery, doped into the main body of the positive electrode material, is represented by the chemical formula f mol% doped Li _z Ni _a Co _b Mn _c O ₂ , of which Li _z Ni _a Co _b Mn _c O ₂ represents a hexagonal positive electrode material main body, the hexagonal positive electrode material main body is lithium and nickel, a single metal of cobalt, or nickel and cobalt, nickel and manganese, cobalt and manganese, Or a positive electrode material active unit composed of an oxide of any type of three metals of nickel, cobalt and manganese, wherein a, b in the chemical formula The chemical agent amount ranges of c and z are 0.9 ≦ z ≦ 1.2, a + b + c = 1, 0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ c ≦ 0.6, respectively. Modified metal or similar metal element, magnesium (Mg), calcium (Ca), strontium (Sr), boron (B), aluminum (Al), gallium (Ga), indium (In), titanium (Ti), silicon (Si) and at least one of tin (Sn), and the molar content of the modified metal or the similar metal element is denoted by f, and the nickel, cobalt, and manganese in the hexagonal positive electrode material 0.5% or more of the total molar content, 10% or lower of the total molar content of nickel, cobalt and manganese in the hexagonal positive electrode material, 0.5% (a + b + c) ≦ f ≦ 10% Displayed as (a + b + c) A metal gradient doped positive electrode material for a lithium ion battery.   The metal gradient doped positive electrode material for a lithium ion battery according to claim 1, wherein the powder has no interface and no layered structure. .   2. The metal gradient doped positive electrode material for a lithium ion battery according to claim 1, wherein the concentration of the modified metal on the surface of the powder is higher than the concentration of the modified metal in the core of the powder, and the concentration of the modified metal is the powder. The total chemical amount of nickel, cobalt, and manganese metal elements on the surface of the powder decreases from the body surface toward the core of the powder. The amount of nickel, cobalt, and manganese metal elements is less than the total chemical amount of the element, and the concentration of nickel, cobalt, and manganese metal elements increases in a continuous gradient from the surface of the powder toward the core of the powder. Metal gradient doped cathode material.   2. The metal gradient doped positive electrode material for lithium ion batteries according to claim 1, comprising an R-3m space group. In the metal gradient doping positive electrode material of the lithium ion battery of claim 1, wherein the average particle size of the powder granules (D ₅₀₎ is being in the range of 0.5 to 25, and lithium-ion batteries Gradient doped cathode material. 2. The metal gradient doped positive electrode material for lithium ion batteries according to claim 1, wherein the powder has a tap density of at least 1.5 g cm ⁻³ or more. 2. The metal gradient-doped positive electrode material for a lithium ion battery according to claim 1, wherein the specific surface area of the powder is in the range of 0.1 to 25 m ² g ^−1. Doped cathode material.

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