JP2015037069A - Lithium nickel cobalt positive electrode material powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide lithium nickel cobalt positive electrode material powder.SOLUTION: Lithium nickel cobalt positive electrode material powder comprises powder granules. The powder granules consist of nano particles. The powder granules each include a lithium nickel cobalt oxide, of which the chemical composition is given by: LiNiCoO. The average chemical composition of the powder granules satisfies the following conditions: 0.9≤a≤1.2; and 0.1≤b≤0.5. The nano particles located in the surface of each powder granule to its core have structures differing from each other in chemical composition. With the aid of the high cobalt content of the nano particles located in the surface of each granule of the lithium nickel cobalt manganese positive electrode material powder of the present invention, and the high nickel content of the nano particles in the core of the powder granule, the lithium nickel cobalt positive electrode material powder of the present invention is allowed to have both the advantages of a high level of safety and a high electrostatic capacitance.

Description

  The present invention relates to a kind of lithium nickel cobalt cathode material powder, more specifically, lithium nickel cobalt oxide having different chemical composition ratios from nanoparticles on the powder granule surface to nanoparticles on the powder granule core. Related to things.

  With the rise of 3C technology and the rise of environmental protection awareness, electric vehicles are becoming more and more important every day. However, the main goal of any battery application system is the pursuit of a lithium ion battery having a high energy density, and its volumetric energy density requirement is already larger than 400 Wh / L. The lithium battery volume energy density of the lithium cobalt positive electrode material system is only 320 to 350 Wh / L, and there is no room for performance improvement. Finally, the energy density is high, the manufacturing cost is relatively low, and the toxicity is high. No lithium nickel cathode material has been studied instead of lithium cobalt cathode material. However, its thermal stability and structural stability are not good, which makes the safety unsatisfactory and very difficult to operate on lithium batteries. The positive electrode material of a lithium battery not only affects battery performance, but is an important factor that determines battery safety. For this reason, a good lithium battery positive electrode material must have a high capacitance, and most importantly, the material has good thermal stability, that is, good material stability. Therefore, it can be applied to positive electrode materials. In order to improve the problem of lithium nickel positive electrode material, some scholars dope some lithium ions into the lithium nickel oxide by doping relatively stable structural cobalt ions into the lithium nickel cobalt positive electrode material. This improves the structural stability and thermal stability of the lithium nickel positive electrode material, and the higher the cobalt content in the material, the better the safety of the material. The capacity will decline, and the goal of the lithium ion battery with the high energy density originally pursued will be lost.

  The main key to the current lack of commercialized lithium nickel cobalt cathode materials in large quantities worldwide is that the safety issue has not been solved, and research has been conducted to solve this problem. Unit or material manufacturers can choose to increase the stability of the material structure by implanting other types of metal ions into the structure of the lithium nickel cobalt cathode material, but the capacitance is due to the increased electrical resistance in the material. Obviously lower.

  In recent years, one scholar has modified the surface of a lithium nickel cobalt cathode material with a single nano-level protective layer to prevent the material and electrolyte from reacting to form a structural collapse. Although the method can reduce the heat dissipation amount of the material, the heat dissipation temperature cannot be increased, and the mass production of the material and the stratification technique are relatively difficult to operate.

  At present, some scholars use lithium nickel cobalt oxide as the core of the positive electrode material, and further coat the surface of the material with a single layer of heat-stable positive electrode material such as lithium nickel cobalt manganese oxide or lithium nickel manganese oxide. The protective shell layer has a thickness of about 1 to 2 μm to form a composite cathode material having a core-shell structure. Such a structure can effectively increase the safety of the material. The internal interfacial resistance increases, the material's performance at high current discharge decreases, and the material of such a structure is difficult to grasp the synthetic quality in mass production.

The main object of the present invention is to provide a kind of lithium nickel cobalt cathode material powder, which includes a plurality of powder granules, each powder granule being composed of a plurality of nanoparticles, The body granule includes lithium nickel cobalt oxide, and its average chemical composition is expressed as Li _a Ni _1-b Co _b O ₂ , of which 0.9 ≦ a ≦ 1.2, 0.1 ≦ b The composition satisfying the condition of ≦ 0.5 and the nanoparticles on the surface of the powder granule to the core nanoparticles of the powder granule have different composition ratios.

The present invention provides a kind of lithium nickel cobalt cathode material powder, which includes a plurality of powder granules, each powder granule is composed of a plurality of nanoparticles, and each powder granule is lithium nickel cobalt Including oxides, the average chemical composition is expressed as Li _a Ni _1-b Co _b O ₂ , of which 0.9 ≦ a ≦ 1.2 and 0.1 ≦ b ≦ 0.5 Filling and from the nanoparticles on the surface of the powder granules to the core nanoparticles of the powder granules have different composition ratio structures.

  The structure of the above-described lithium nickel cobalt positive electrode material powder having different composition ratios is such that the Li content is uniformly distributed from the nanoparticles on the powder granule surface toward the nanoparticles on the powder granule core, and the Ni content is The nanoparticles on the surface of the powder granule increase toward the nanoparticle on the powder granule core, and the Co content decreases from the nanoparticle on the surface of the powder granule toward the nanoparticle on the powder granule core.

The chemical composition of the nanoparticles on the surface of the above-described lithium nickel cobalt positive electrode material powder is expressed as Li _x Ni _1-y Co _y O ₂ , of which 0.9 ≦ x ≦ 1.2 and 0.15 ≦ y ≦. 1.0, and the chemical composition of the nanoparticles of the powder granule core is expressed as Li _{x ′} Ni _{1-y ′} Co _{y ′} O ₂ , of which 0.9 ≦ x ′ ≦ 1. 2, 0 ≦ y ′ ≦ 0.3 is satisfied, and x = x ′ and y> y ′.

Among the above-mentioned lithium nickel cobalt positive electrode material powder, the particle size of these nanoparticles is in the range of 30 to 700 nm. The average particle diameter (D ₅₀ ) of the powder granules is in the range of 0.5 to 25 μm. In addition, the powder granule is an R-3m rhombohedron, the powder density is at least greater than 1.5 g / cm ³ , and the specific surface area is in the range of 0.1 to ²⁰ m ² / g. is there.

  As a result, the lithium nickel cobalt cathode material of the present invention is composed of nanoparticles with different composition ratios, the Co content of the nanoparticles on the surface of the powder granules is relatively high, and the powder granule outer layer nanoparticles have a high thermal stability. The Ni content of the powder granule core nanoparticles is relatively high, and thus has a high capacitance form. Therefore, the lithium nickel cobalt positive electrode material powder of the present invention has a sufficiently high stability. Can have the advantages of high capacitance at the same time, thereby achieving the purpose of having both high safety and high energy density, and suitable for the positive electrode material of lithium battery.

It is a structure display figure of the lithium nickel cobalt positive electrode material powder granule of this invention. It is a diagram showing the elemental quantitative analysis of DC-LiNi _0.72 Co _0.28 O ₂ cathode material of Example of the present invention. It is an electrical characteristic figure in the small electric current charge / discharge of the Example and comparative example of this invention. It is an electrical property figure in various current discharges of an example and a comparative example of the present invention. It is a cycle life electrical characteristic figure of the Example and comparative example of this invention. It is a DSC test figure of the Example and comparative example of this invention.

  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. It is a structure display diagram of the lithium nickel cobalt cathode material powder granule of the present invention. The lithium nickel cobalt positive electrode material powder of the present invention includes a plurality of powder granules, each powder granule is composed of a plurality of nanoparticles, and each powder granule includes a lithium nickel cobalt oxide. The average chemical composition is expressed as Li _a Ni _1-b Co _b O _2, and the average chemical composition of the powder granules is 0.9 ≦ a ≦ 1.2, 0.1 ≦ b ≦ 0.5. The nanoparticle on the surface of the powder granule and the core nanoparticle of the powder granule have structures having different composition ratios.

  In FIG. 1, A represents any one nanoparticle on the surface of the lithium nickel cobalt cathode material powder granule of the present invention, and B represents any one nanoparticle in the powder granule core.

  According to the lithium nickel cobalt positive electrode material powder of the present invention, the structure of different composition ratio is such that the Li content is uniformly distributed from the nanoparticles on the powder granule surface toward the nanoparticles on the powder granule core, Ni The content increases from the nanoparticles on the powder granule surface to the nanoparticles on the powder granule core, and the Co content increases from the nanoparticle on the powder granule surface to the nanoparticles on the powder granule core. Decrease.

  As a result, in the example shown in FIG. 1, the Li content is uniformly distributed from A to B, the Ni content is increased from A to B, and the Co content is decreased from A to B.

Of the lithium nickel cobalt positive electrode material powder of the present invention, the chemical composition of the nanoparticles on the powder surface, for example, the chemical composition of A in FIG. 1 is expressed as Li _x Ni _1-y Co _y O ₂ , Among them, a 0.9 ≦ x ≦ 1.2,0.15 ≦ y ≦ 1.0, the chemical composition of the nanoparticles of the powder granule core, for example, the chemical composition of B in FIG. 1, Li _{x '} Ni _{1-y ′} Co _{y ′} O ₂ , of which 0.9 ≦ x ′ ≦ 1.2, 0 ≦ y ′ ≦ 0.3, and x = x ′ and y> y ′ Meet.

In the lithium nickel cobalt positive electrode material powder of the present invention, the particle size of these nanoparticles is in the range of 30 to 700 nm. The average particle diameter (D ₅₀ ) of the powder granules is in the range of 0.5 to 25 μm.

In addition, in the lithium nickel cobalt positive electrode material powder of the present invention, the powder granules are R-3m rhomboids, the powder density is at least greater than 1.5 g / cm ³ , and the specific surface area is In the range of 0.1 to ²⁰ m ² / g.

  In the following, the improved performance of the present invention will be clarified by one each of the experimental example and the comparative example, and by physical and electrochemical property analysis.

[Example]
1. Synthesis of lithium nickel cobalt cathode material composed of nanoparticles of different chemical composition Spherical nickel cobalt hydroxide was synthesized by chemical coprecipitation method, nickel cobalt hydroxide was put into the reaction vessel, and further coprecipitation method was used. Cobalt hydroxide can uniformly coat the surface of spherical nickel cobalt hydroxide, and then lithium hydroxide is added and mixed, the ratio of lithium salt to nickel cobalt content being 1.02: This mixture is sintered at 750 degrees Celsius for 12 hours in an oxygen gas atmosphere, and finally, a lithium nickel cobalt cathode material composed of nanoparticles having different composition ratio structures according to the present invention is obtained. . For convenience of explanation, the lithium nickel cobalt positive electrode material synthesized in this experimental example is indicated below with the symbol DC-LiNi _0.72 Co _0.28 O ₂ .

2. Production of button-type battery The production of the positive electrode plate is made of lithium nickel cobalt positive electrode material: (graphite + carbon black): polyvinylidene fluoride (PVDF) = 89: 6: 5, then at a constant ratio. N-methylpyrrolidinone (NMP) is uniformly mixed to form a thick liquid, and a paste material is applied onto a 20 μm aluminum foil using a 200 μm knife. The electrode plate is first heat-dried on a heating platform and then vacuum-heated to remove the NMP solvent.
The electrode plate is extruded first, and further cut into a coin-type electrode plate having a diameter of about 12 mm. Subsequently, lithium metal is used as the negative electrode, DC-LiNi _0.72 Co _0.28 O ₂ electrode plate is used as the positive electrode, and the electrolyte solution is 1M LiPF ₆ -EC + EC / PC / EMC / DMC (volume ratio 3: 1: 4: 2). Configure a button-type battery.
About the button type battery described above, various electrochemical characteristics of the DC-LiNi _0.72 Co _0.28 O ₂ positive electrode material were measured in a charge / discharge range of 2.8 to 4.3 V and a charge / discharge current of 0.1 C.

3. DSC test of DC-LiNi _0.72 Co _0.28 O ₂ positive electrode material Charge the above button type battery to 4.3 V, disassemble the button type battery using tweezers, remove the positive electrode plate, cut out the positive electrode material, 3 mg The positive electrode material was put into an aluminum crucible, 3 μl of electrolyte was added, the aluminum crucible was riveted and sealed, heated at a rate of 5 degrees Celsius / minute, and the measuring instrument was set within a temperature range of 150 to 300 degrees Celsius. Use to scan.

[Comparative example]
1. Synthesis of lithium nickel cobalt cathode material composed of nanoparticles with uniform composition ratio Spherical nickel cobalt hydroxide was synthesized by chemical coprecipitation method, and further mixed with lithium hydroxide, of which lithium salt and nickel cobalt contained The quantity ratio was 1.02: 1.00, and this mixture was sintered at 750 degrees Celsius for 12 hours under an oxygen gas atmosphere, and finally composed of nanoparticles with a uniform composition ratio structure. A lithium nickel cobalt positive electrode material is obtained. For convenience of explanation, the lithium nickel cobalt positive electrode material synthesized in this comparative example is indicated below with the symbol AC-LiNi _0.72 Co _0.28 O ₂ .

2. Manufacture of button-type battery The manufacture of the positive electrode plate is the same as the experimental example except that AC-LiNi _0.72 Co _0.28 O ₂ is used, and the various methods of AC-LiNi _0.72 Co _0.28 O ₂ positive electrode material are the same. Test chemical properties.

3. DSC test of AC-LiNi _0.72 Co _0.28 O ₂ positive electrode material Charge the above button type battery to 4.3 V, disassemble the button type battery using tweezers, remove the positive electrode plate, cut out the positive electrode material, 3 mg The positive electrode material was put into an aluminum crucible, 3 μl of electrolyte was added, the aluminum crucible was riveted and sealed, heated at a rate of 5 degrees Celsius / minute, and the measuring instrument was set within a temperature range of 150 to 300 degrees Celsius. Use to scan.

[result of analysis]
1. Physical Property Analysis See FIG. It is the result of elemental quantitative analysis of the DC-LiNi _0.72 Co _0.28 O ₂ cathode material of the experimental example. Elemental analysis of the surface and cross section of DC-LiNi _0.72 Co _0.28 O ₂ positive electrode material is performed with an inductively coupled plasma (ICP) and an energy dispersive X-ray analyzer (Energy Dispersive Spectrometer, EDS). . Of (a) is 2, a surface morphology and elemental analysis ratio graph of DC-LiNi _0.72 Co _0.28 O ₂ cathode material, (b), FIG. 2, cross-sectional configuration of the DC-LiNi _0.72 Co _0.28 O ₂ cathode material It is an element analysis ratio graph.
When the molar ratio of Ni: Co of the entire DC-LiNi _0.72 Co _0.28 O ₂ positive electrode material was measured by ICP, it was 72.77: 27.23, which was observed in FIG. The Ni: Co molar ratio of the surface nanoparticles of the _0.72 Co _0.28 O ₂ cathode material is 68.74: 31.26, and the DC-LiNi _0.72 Co _0.28 O ₂ cathode material observed in FIG. After high temperature sintering, Co diffuses into the material, thereby changing the elemental ratio of Ni: Co, and Ni: Co of the core nanoparticles of this portion of the DC-LiNi _0.72 Co _0.28 O ₂ cathode material The molar ratio is 80.13: 19.87.

2. Electrochemical characterization See FIG. It is an electrical property diagram of an example material and a comparative example material with small current charge / discharge. Curve (a) represents the comparative material AC-LiNi _0.72 Co _0.28 O ₂ , and curve (b) represents the example material DC-LiNi _0.72 Co _0.28 O ₂ . The difference in electrochemical properties between the example material DC-LiNi _0.72 Co _0.28 O ₂ and the comparative material AC-LiNi _0.72 Co _0.28 O ₂ can be compared by the material small current charge / discharge (0.1 C), and the voltage range 2.8 Between ˜4.3V, the example material DC-LiNi _0.72 Co _0.28 O ₂ discharge capacity is 194.3 mAh / g and the irreversible capacity is 9.4 mAh / g. The discharge capacity of the comparative example material AC-LiNi _0.72 Co _0.28 O ₂ is 185.7 mAh / g and the irreversible capacity is 10.8 mAh / g.

Please refer to FIG. It is an electrical characteristic diagram of Examples and Comparative Examples with various current discharges. Curve (a) represents the comparative material AC-LiNi _0.72 Co _0.28 O ₂ , and curve (b) represents the example material DC-LiNi _0.72 Co _0.28 O ₂ . Current conditions are charge 0.2C, discharge 1C-7C, and working voltage is between 2.8-4.3V. From FIG. 4 it is clear that the example material DC-LiNi _0.72 Co _0.28 O ₂ has a relatively high discharge platform, has a high capacity of 78% under a discharge current of 7C, and the comparative material AC-LiNi It is observed that _0.72 Co _0.28 O ₂ leaves only 74% capacity.

Please refer to FIG. It is a cycle life electric characteristic figure of an example material and a comparative example material. Curve (a) represents the comparative material AC-LiNi _0.72 Co _0.28 O ₂ , and curve (b) represents the example material DC-LiNi _0.72 Co _0.28 O ₂ . Using a constant current of 0.5 C, the material was charged and discharged 60 times in the voltage range of 2.8 to 4.3 V, and then the example material DC-LiNi _0.72 Co _0.28 O _{2 was} calculated. However, 83.5% of the starting electricity amount is still maintained, and it can be seen that the comparative material AC-LiNi _0.72 Co _0.28 O ₂ remains only 78.5% of the starting electricity amount, and the above results are summarized. It can be seen that the example material DC-LiNi _0.72 Co _0.28 O ₂ has relatively good charge / discharge characteristics.

See FIG. It is a DSC test diagram of the example material and the comparative example material. Curve (a) represents the comparative material AC-LiNi _0.72 Co _0.28 O ₂ , and curve (b) represents the example material DC-LiNi _0.72 Co _0.28 O ₂ . From the results in FIG. 6, the heat release decomposition temperature of the comparative material AC-LiNi _0.72 Co _0.28 O ₂ is about 227.6 degrees Celsius, but the example material DC-LiNi _0.72 Co _0.28 O ₂ is clearly heat release decomposition. The temperature is increased, the temperature is increased to about 236.7 degrees Celsius, and the heat radiation amount is decreased from 222.07 J / g to 148.73 J / g. Therefore, the example material DC-LiNi _0.72 Co _0.28 O ₂ has better thermal stability than the comparative example.

  The main feature of the present invention is to design a kind of lithium nickel cobalt cathode material powder composed of nanoparticles of different chemical composition ratios, as well as not doped or modified with dissimilar metals, which makes it obvious There is no problem of interface resistance or storage active region. By design, the nanoparticle Co content on the surface of the material powder granule is relatively high, so that the outer layer nanoparticle of the material powder granule is biased to a highly heat-stable form and the Ni content of the nanoparticle of the material powder granule core The rate is relatively high, which is a high capacity form. Therefore, the lithium nickel cobalt positive electrode material powder of the present invention has the advantages of high stability and high capacity at the same time, the surface structure of the powder granule can be stabilized, safety can be increased, and the material itself per gram. Without reducing the capacity, the purpose of simultaneously providing high safety and high energy density is achieved, and the high energy content and high safety requirements of the lithium battery positive electrode material are met.

  Another feature of the present invention is to design a lithium nickel cobalt cathode material powder composed of nanoparticles having different composition ratios of chemical components so that the powder can be applied to the manufacture of a lithium secondary battery. Includes lithium batteries in rectangular stainless steel, aluminum and aluminum alloy can packages, and can be applied to polymer lithium batteries packaged in any aluminum foil bag thermocompression bonding method and lithium batteries in related package designs. It is to improve safety and capacity.

  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.

A Powder nanoparticles surface nanoparticles B Powder granules core nanoparticles

The present invention relates to a kind of lithium nickel cobalt positive electrode material powder, more specifically, the ratio of chemical composition components from the nanoparticles on the powder granule surface to the nanoparticles on the powder granule core are different from each other. The present invention relates to a lithium nickel cobalt oxide having a continuously changing structure .

  With the rise of 3C technology and the rise of environmental protection awareness, electric vehicles are becoming more and more important every day. However, the main goal of any battery application system is the pursuit of a lithium ion battery having a high energy density, and its volumetric energy density requirement is already larger than 400 Wh / L. The lithium battery volume energy density of the lithium cobalt positive electrode material system is only 320 to 350 Wh / L, and there is no room for performance improvement. Finally, the energy density is high, the manufacturing cost is relatively low, and the toxicity is high. No lithium nickel cathode material has been studied instead of lithium cobalt cathode material. However, its thermal stability and structural stability are not good, which makes the safety unsatisfactory and very difficult to operate on lithium batteries. The positive electrode material of a lithium battery not only affects battery performance, but is an important factor that determines battery safety. For this reason, a good lithium battery positive electrode material must have a high capacitance, and most importantly, the material has good thermal stability, that is, good material stability. Therefore, it can be applied to positive electrode materials. In order to improve the problem of lithium nickel positive electrode material, some scholars dope some lithium ions into the lithium nickel oxide by doping relatively stable structural cobalt ions into the lithium nickel cobalt positive electrode material. This improves the structural stability and thermal stability of the lithium nickel positive electrode material, and the higher the cobalt content in the material, the better the safety of the material. The capacity will decline, and the goal of the lithium ion battery with the high energy density originally pursued will be lost.

  The main key to the current lack of commercialized lithium nickel cobalt cathode materials in large quantities worldwide is that the safety issue has not been solved, and research has been conducted to solve this problem. Unit or material manufacturers can choose to increase the stability of the material structure by implanting other types of metal ions into the structure of the lithium nickel cobalt cathode material, but the capacitance is due to the increased electrical resistance in the material. Obviously lower.

  In recent years, one scholar has modified the surface of a lithium nickel cobalt cathode material with a single nano-level protective layer to prevent the material and electrolyte from reacting to form a structural collapse. Although the method can reduce the heat dissipation amount of the material, the heat dissipation temperature cannot be increased, and the mass production of the material and the stratification technique are relatively difficult to operate.

  At present, some scholars use lithium nickel cobalt oxide as the core of the positive electrode material, and further coat the surface of the material with a single layer of heat-stable positive electrode material such as lithium nickel cobalt manganese oxide or lithium nickel manganese oxide. The protective shell layer has a thickness of about 1 to 2 μm to form a composite cathode material having a core-shell structure. Such a structure can effectively increase the safety of the material. The internal interfacial resistance increases, the material's performance at high current discharge decreases, and the material of such a structure is difficult to grasp the synthetic quality in mass production.

The main object of the present invention is to provide a kind of lithium nickel cobalt cathode material powder, which includes a plurality of powder granules, and there is no boundary surface in the powder and it is not divided into layers. each powder granules are composed of a plurality of nanoparticles, each powder granules encompasses a lithium nickel cobalt oxide, the average chemical composition is displayed as _{Li a Ni 1-b Co b} O 2, of which 0.9 ≦ a ≦ 1.2, 0.1 ≦ b ≦ 0.5, and the powder granules surface to the core nanoparticles of the powder granules are all different It has a continuously changing structure of the component ratio, which is the component ratio of the chemical composition .

The present invention provides a kind of lithium nickel cobalt cathode material powder, which includes a plurality of powder granules, each powder granule is composed of a plurality of nanoparticles, and each powder granule is lithium nickel cobalt Including oxides, the average chemical composition is expressed as Li _a Ni _1-b Co _b O ₂ , of which 0.9 ≦ a ≦ 1.2 and 0.1 ≦ b ≦ 0.5 The nanoparticle on the surface of the powder granule to the core nanoparticle of the powder granule has a continuously changing structure of the component ratio, which is a component ratio of different chemical compositions .

The structure of the above-described lithium nickel cobalt positive electrode material powder having different component ratios is such that the Li content is uniformly distributed from the nanoparticles on the powder granule surface toward the nanoparticles on the powder granule core, and the Ni content is from nanoparticles of the powder granule surface toward the nanoparticle powder granules core increases continuously, Co content continuously decreases towards the nanoparticle powder granule core from nanoparticles of the powder surface of the granules.

The chemical composition of the nanoparticles on the surface of the above-described lithium nickel cobalt positive electrode material powder is expressed as Li _x Ni _1-y Co _y O ₂ , of which 0.9 ≦ x ≦ 1.2 and 0.15 ≦ y ≦. 1.0, and the chemical composition of the nanoparticles of the powder granule core is expressed as Li _{x ′} Ni _{1-y ′} Co _{y ′} O ₂ , of which 0.9 ≦ x ′ ≦ 1. 2, 0 ≦ y ′ ≦ 0.3 is satisfied, and x = x ′ and y> y ′.

Among the above-mentioned lithium nickel cobalt positive electrode material powder, the particle size of these nanoparticles is in the range of 30 to 700 nm. The average particle diameter (D ₅₀ ) of the powder granules is in the range of 0.5 to 25 μm. In addition, the powder granule is an R-3m rhombohedron, the powder density (tap density) is at least greater than 1.5 g / cm ³ , and the specific surface area is 0.1 to 20 m 2. / G.

  As a result, the lithium nickel cobalt cathode material of the present invention is composed of nanoparticles with different composition ratios, the Co content of the nanoparticles on the surface of the powder granules is relatively high, and the powder granule outer layer nanoparticles have a high thermal stability. The Ni content of the powder granule core nanoparticles is relatively high, and thus has a high capacitance form. Therefore, the lithium nickel cobalt positive electrode material powder of the present invention has a sufficiently high stability. Can have the advantages of high capacitance at the same time, thereby achieving the purpose of having both high safety and high energy density, and suitable for the positive electrode material of lithium battery.

It is a structure display figure of the lithium nickel cobalt positive electrode material powder granule of this invention. It is a figure which shows the element quantitative analysis result of the DC-LiNi0.72Co0.28O2 positive electrode material of the Example of this invention. It is an electrical characteristic figure in the small electric current charge / discharge of the Example and comparative example of this invention. It is an electrical property figure in various current discharges of an example and a comparative example of the present invention. It is a cycle life electrical characteristic figure of the Example and comparative example of this invention. It is a DSC test figure of the Example and comparative example of this invention.

  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. It is a structure display diagram of the lithium nickel cobalt cathode material powder granule of the present invention. The lithium nickel cobalt cathode material powder of the present invention includes a plurality of powder granules, each of which is composed of a plurality of nanoparticles , and is observed or defined in the composed powder. The powder granules contain lithium nickel cobalt oxide, the average chemical composition is expressed as LiaNi1-bCobO2, and the average chemical composition of the powder granules is 0. The conditions of 9 ≦ a ≦ 1.2 and 0.1 ≦ b ≦ 0.5 are satisfied, and from the nanoparticle on the surface of the powder granule to the core nanoparticle of the powder granule, both have different chemical compositions. It has a component ratio, continuously changing structure of component ratio .

  In FIG. 1, A represents any one nanoparticle on the surface of the lithium nickel cobalt cathode material powder granule of the present invention, and B represents any one nanoparticle in the powder granule core.

According to the lithium nickel cobalt positive electrode material powder of the present invention, the continuous change structure of the component ratio is such that the Li content is uniformly distributed from the nanoparticles on the powder granule surface toward the nanoparticles on the powder granule core, The Ni content continuously increases from the nanoparticles on the powder granule surface toward the nanoparticles on the powder granule core, and the Co content rate increases from the nanoparticles on the powder granule surface to the nanoparticles on the powder granule core. It decreases continuously toward.

Accordingly, in the example shown in FIG. 1, the Li content is uniformly distributed from A to B, the Ni content is continuously increased from A to B, and the Co content is continuously decreased from A to B. To do.

Of the lithium nickel cobalt positive electrode material powder of the present invention, the chemical composition of the nanoparticles on the powder surface, for example, the chemical composition of A in FIG. 1 is expressed as Li _x Ni _1-y Co _y O ₂ , Among them, a 0.9 ≦ x ≦ 1.2,0.15 ≦ y ≦ 1.0, the chemical composition of the nanoparticles of the powder granule core, for example, the chemical composition of B in FIG. 1, Li _{x '} Ni _{1-y ′} Co _{y ′} O ₂ , of which 0.9 ≦ x ′ ≦ 1.2, 0 ≦ y ′ ≦ 0.3, and x = x ′ and y> y ′ Meet.

In the lithium nickel cobalt positive electrode material powder of the present invention, the particle size of these nanoparticles is in the range of 30 to 700 nm. The average particle diameter (D ₅₀ ) of the powder granules is in the range of 0.5 to 25 μm.

In addition, the lithium nickel cobalt cathode material powder of the present invention has an R-3m rhombohedral powder granule, a powder tap density of at least 1.5 g / cm 3 and a specific surface area of 0. Within the range of 1 to 20 m @ 2 / g.

  In the following, the improved performance of the present invention will be clarified by one each of the experimental example and the comparative example, and by physical and electrochemical property analysis.

[Example]
1. Synthesis of lithium nickel cobalt cathode material composed of nanoparticles of different chemical composition Spherical nickel cobalt hydroxide was synthesized by chemical coprecipitation method, nickel cobalt hydroxide was put into the reaction vessel, and further coprecipitation method was used. Cobalt hydroxide can uniformly coat the surface of spherical nickel cobalt hydroxide, and then lithium hydroxide is added and mixed, the ratio of lithium salt to nickel cobalt content being 1.02: This mixture is sintered at 750 degrees Celsius for 12 hours in an oxygen gas atmosphere, and finally, a lithium nickel cobalt cathode material composed of nanoparticles having different composition ratio structures according to the present invention is obtained. . For convenience of explanation, the lithium nickel cobalt positive electrode material synthesized in this experimental example is indicated below with the symbol DC-LiNi _0.72 Co _0.28 O ₂ .

2. Production of button-type battery The production of the positive electrode plate is made of lithium nickel cobalt positive electrode material: (graphite + carbon black): polyvinylidene fluoride (PVDF) = 89: 6: 5, then at a constant ratio. N-methylpyrrolidinone (NMP) is uniformly mixed to form a thick liquid, and a paste material is applied onto a 20 μm aluminum foil using a 200 μm knife. The electrode plate is first heat-dried on a heating platform and then vacuum-heated to remove the NMP solvent.
The electrode plate is extruded first, and further cut into a coin-type electrode plate having a diameter of about 12 mm. Subsequently, lithium metal is used as the negative electrode, DC-LiNi _0.72 Co _0.28 O ₂ electrode plate is used as the positive electrode, and the electrolyte solution is 1M LiPF ₆ -EC + EC / PC / EMC / DMC (volume ratio 3: 1: 4: 2). Configure a button-type battery.
About the button type battery described above, various electrochemical characteristics of the DC-LiNi _0.72 Co _0.28 O ₂ positive electrode material were measured in a charge / discharge range of 2.8 to 4.3 V and a charge / discharge current of 0.1 C.

3. DSC test of DC-LiNi _0.72 Co _0.28 O ₂ positive electrode material Charge the above button type battery to 4.3 V, disassemble the button type battery using tweezers, remove the positive electrode plate, cut out the positive electrode material, 3 mg The positive electrode material was put into an aluminum crucible, 3 μl of electrolyte was added, the aluminum crucible was riveted and sealed, heated at a rate of 5 degrees Celsius / minute, and the measuring instrument was set within a temperature range of 150 to 300 degrees Celsius. Use to scan.

[Comparative example]
1. Synthesis of lithium nickel cobalt cathode material composed of nanoparticles with uniform composition ratio Spherical nickel cobalt hydroxide was synthesized by chemical coprecipitation method, and further mixed with lithium hydroxide, of which lithium salt and nickel cobalt contained The quantity ratio was 1.02: 1.00, and this mixture was sintered at 750 degrees Celsius for 12 hours under an oxygen gas atmosphere, and finally composed of nanoparticles with a uniform composition ratio structure. A lithium nickel cobalt positive electrode material is obtained. For convenience of explanation, the lithium nickel cobalt positive electrode material synthesized in this comparative example is indicated below with the symbol AC-LiNi _0.72 Co _0.28 O ₂ .

2. Manufacture of button-type battery The manufacture of the positive electrode plate is the same as the experimental example except that AC-LiNi _0.72 Co _0.28 O ₂ is used, and the various methods of AC-LiNi _0.72 Co _0.28 O ₂ positive electrode material are the same. Test chemical properties.

3. DSC test of AC-LiNi _0.72 Co _0.28 O ₂ positive electrode material Charge the above button type battery to 4.3 V, disassemble the button type battery using tweezers, remove the positive electrode plate, cut out the positive electrode material, 3 mg The positive electrode material was put into an aluminum crucible, 3 μl of electrolyte was added, the aluminum crucible was riveted and sealed, heated at a rate of 5 degrees Celsius / minute, and the measuring instrument was set within a temperature range of 150 to 300 degrees Celsius. Use to scan.

[result of analysis]
1. Physical Property Analysis See FIG. It is the result of elemental quantitative analysis of the DC-LiNi _0.72 Co _0.28 O ₂ cathode material of the experimental example. Elemental analysis of the surface and cross section of DC-LiNi _0.72 Co _0.28 O ₂ positive electrode material is performed with an inductively coupled plasma (ICP) and an energy dispersive X-ray analyzer (Energy Dispersive Spectrometer, EDS). . Of (a) is 2, a surface morphology and elemental analysis ratio graph of DC-LiNi _0.72 Co _0.28 O ₂ cathode material, (b), FIG. 2, cross-sectional configuration of the DC-LiNi _0.72 Co _0.28 O ₂ cathode material It is an element analysis ratio graph.
When the molar ratio of Ni: Co of the entire DC-LiNi _0.72 Co _0.28 O ₂ positive electrode material was measured by ICP, it was 72.77: 27.23, which was observed in FIG. The Ni: Co molar ratio of the surface nanoparticles of the _0.72 Co _0.28 O ₂ cathode material is 68.74: 31.26, and the DC-LiNi _0.72 Co _0.28 O ₂ cathode material observed in FIG. After high temperature sintering, Co diffuses into the material, thereby changing the elemental ratio of Ni: Co, and Ni: Co of the core nanoparticles of this portion of the DC-LiNi _0.72 Co _0.28 O ₂ cathode material The molar ratio is 80.13: 19.87.

2. Electrochemical characterization See FIG. It is an electrical property diagram of an example material and a comparative example material with small current charge / discharge. Curve (a) represents the comparative material AC-LiNi _0.72 Co _0.28 O ₂ , and curve (b) represents the example material DC-LiNi _0.72 Co _0.28 O ₂ . The difference in electrochemical properties between the example material DC-LiNi _0.72 Co _0.28 O ₂ and the comparative material AC-LiNi _0.72 Co _0.28 O ₂ can be compared by the material small current charge / discharge (0.1 C), and the voltage range 2.8 Between ˜4.3V, the example material DC-LiNi _0.72 Co _0.28 O ₂ discharge capacity is 194.3 mAh / g and the irreversible capacity is 9.4 mAh / g. The discharge capacity of the comparative example material AC-LiNi _0.72 Co _0.28 O ₂ is 185.7 mAh / g and the irreversible capacity is 10.8 mAh / g.

Please refer to FIG. It is an electrical characteristic diagram of Examples and Comparative Examples with various current discharges. Curve (a) represents the comparative material AC-LiNi _0.72 Co _0.28 O ₂ , and curve (b) represents the example material DC-LiNi _0.72 Co _0.28 O ₂ . Current conditions are charge 0.2C, discharge 1C-7C, and working voltage is between 2.8-4.3V. From FIG. 4 it is clear that the example material DC-LiNi _0.72 Co _0.28 O ₂ has a relatively high discharge platform, has a high capacity of 78% under a discharge current of 7C, and the comparative material AC-LiNi It is observed that _0.72 Co _0.28 O ₂ leaves only 74% capacity.

Please refer to FIG. It is a cycle life electric characteristic figure of an example material and a comparative example material. Curve (a) represents the comparative material AC-LiNi _0.72 Co _0.28 O ₂ , and curve (b) represents the example material DC-LiNi _0.72 Co _0.28 O ₂ . Using a constant current of 0.5 C, the material was charged and discharged 60 times in the voltage range of 2.8 to 4.3 V, and then the example material DC-LiNi _0.72 Co _0.28 O _{2 was} calculated. However, 83.5% of the starting electricity amount is still maintained, and it can be seen that the comparative material AC-LiNi _0.72 Co _0.28 O ₂ remains only 78.5% of the starting electricity amount, and the above results are summarized. It can be seen that the example material DC-LiNi0.72Co0.28O2 has relatively good charge / discharge characteristics.

See FIG. It is a DSC test diagram of the example material and the comparative example material. Curve (a) is representative of a comparative example material AC-LiNi0.72Co0.28O2, curve (b) is representative of EXAMPLES Materials _{DC-LiNi 0.72 Co 0.28 O 2} . From the results in FIG. 6, the heat release decomposition temperature of the comparative material AC-LiNi _0.72 Co _0.28 O ₂ is about 227.6 degrees Celsius, but the example material DC-LiNi _0.72 Co _0.28 O ₂ is clearly heat release decomposition. The temperature is increased, the temperature is increased to about 236.7 degrees Celsius, and the heat radiation amount is decreased from 222.07 J / g to 148.73 J / g. Therefore, the example material DC-LiNi _0.72 Co _0.28 O ₂ has better thermal stability than the comparative example.

  The main feature of the present invention is to design a kind of lithium nickel cobalt cathode material powder composed of nanoparticles of different chemical composition ratios, as well as not doped or modified with dissimilar metals, which makes it obvious There is no problem of interface resistance or storage active region. By design, the nanoparticle Co content on the surface of the material powder granule is relatively high, so that the outer layer nanoparticle of the material powder granule is biased to a highly heat-stable form and the Ni content of the nanoparticle of the material powder granule core The rate is relatively high, which is a high capacity form. Therefore, the lithium nickel cobalt positive electrode material powder of the present invention has the advantages of high stability and high capacity at the same time, the surface structure of the powder granule can be stabilized, safety can be increased, and the material itself per gram. Without reducing the capacity, the purpose of simultaneously providing high safety and high energy density is achieved, and the high energy content and high safety requirements of the lithium battery positive electrode material are met.

  Another feature of the present invention is to design a lithium nickel cobalt cathode material powder composed of nanoparticles having different composition ratios of chemical components so that the powder can be applied to the manufacture of a lithium secondary battery. Includes lithium batteries in rectangular stainless steel, aluminum and aluminum alloy can packages, and can be applied to polymer lithium batteries packaged in any aluminum foil bag thermocompression bonding method and lithium batteries in related package designs. It is to improve safety and capacity.

  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.

A Powder nanoparticles surface nanoparticles B Powder granules core nanoparticles

Claims (8)

The lithium nickel cobalt positive electrode material powder includes a plurality of powder granules, each powder granule is composed of a plurality of nanoparticles, each powder granule includes lithium nickel cobalt oxide, and has an average chemical composition. The composition is expressed as Li _a Ni _1-b Co _b O ₂ , of which 0.9 ≦ a ≦ 1.2, 0.1 ≦ b ≦ 0.5, and the surface of the powder granule Lithium nickel cobalt positive electrode material powder characterized by having a structure with different composition ratios from the nanoparticle to the core nanoparticle of the powder granule.   The lithium nickel cobalt positive electrode material powder according to claim 1, wherein the structure having the different composition ratio is such that the Li content is uniformly distributed from the nanoparticle on the surface of the powder granule toward the nanoparticle on the powder granule core. The content increases from the nanoparticles on the powder granule surface toward the nanoparticles in the powder granule core, and the Co content decreases from the nanoparticles on the powder granule surface toward the nanoparticles in the powder granule core Lithium nickel cobalt positive electrode material powder characterized by. The lithium nickel cobalt positive electrode material powder according to claim 2, wherein the chemical composition of the nanoparticles on the surface of the lithium nickel cobalt positive electrode material powder is expressed as Li _x Ni _1-y Co _y O ₂ . 9 ≦ x ≦ 1.2, 0.15 ≦ y ≦ 1.0, and the chemical composition of the nanoparticles of the powder granule core is expressed as Li _{x ′} Ni _{1-y ′} Co _{y ′} O _2. Of these, 0.9 ≦ x ′ ≦ 1.2, 0 ≦ y ′ ≦ 0.3, and x = x ′ and y> y ′, wherein the lithium nickel cobalt positive electrode material powder .   The lithium nickel cobalt positive electrode material powder according to claim 3, wherein the particle diameter of these nanoparticles is in the range of 30 to 700 nm. 5. The lithium nickel cobalt positive electrode material powder according to claim 4, wherein the powder granules have an average particle diameter (D ₅₀ ) in the range of 0.5 to 25 μm. body.   The lithium nickel cobalt positive electrode material powder according to any one of claims 1 to 5, wherein the powder granule is an R-3m rhombohedron. The lithium nickel cobalt positive electrode material powder according to any one of claims 1 to 5, wherein an actual density of the powder is at least greater than 1.5 g / cm ^3. . The lithium nickel cobalt positive electrode material powder according to any one of claims 1 to 5, wherein the specific surface area of the powder is in a range of 0.1 to ²⁰ m ² / g. Material powder.

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