CN105895910A - Multi-core structured positive electrode material of lithium ion battery and fabrication method of positive electrode material - Google Patents

Abstract

The invention provides a lithium-ion battery positive electrode material with a multi-core structure, which includes a casing and a core disposed in the casing, the core includes at least two core particles that are in contact with each other and are independent of each other, and each core particle The material is selected from a layered structure positive electrode active material, a spinel structure positive electrode active material and an olivine structure positive electrode active material, and the material of the shell is selected from materials that are inert to the electrolyte, and the layered structure positive electrode active material includes xLi ₂ MO ₃ ·(1-x)LiMO ₂ , wherein, 0≤x<1; the positive electrode active material with spinel structure includes LiM ₂ O ₄ ; the positive electrode active material with olivine structure includes LiMPO ₄ , wherein, M is one or more of metal elements with an atomic number of 6 or more. The invention also provides a preparation method of the positive electrode material of the lithium ion battery with the multi-core structure.

Description

Lithium-ion battery cathode material with multi-core structure and preparation method thereof

technical field

The invention relates to a lithium-ion battery cathode material with a multi-core structure and a preparation method thereof.

Background technique

As lithium-ion batteries are more and more widely used in various portable electrical equipment and as power batteries in electric bicycles, electric vehicles, aerospace and other fields, and the further expansion of their application fields, the anode materials for lithium-ion batteries New requirements have also been put forward, such as higher specific capacity, high voltage, high energy density, better thermal stability, rate performance and safety performance, longer cycle life and lower cost, etc.

From the history of the development and replacement of cathode materials for lithium batteries, it can be seen that the purpose is to seek a material that has the above-mentioned advantages as much as possible. The materials that have been commercialized include nickel cobalt lithium manganate, nickel cobalt aluminum oxide, lithium cobalt oxide, and titanium sulfide lithium with layered structure; lithium manganese oxide with spinel structure; and phosphoric acid with olivine structure. Lithium iron etc. Among them, layered structure materials are the most commercialized, the reason is that they have a higher specific capacity; and spinel structure materials usually have a higher voltage above 4V and because of the Li ⁺ from the positive electrode material structure It has a relatively stable structure and excellent charge-discharge cycle performance during intercalation and deintercalation; materials with an olivine structure such as lithium iron phosphate have many advantages such as low price, safety and environmental protection, but their specific capacity is very low and because of its The extremely low electronic conductivity (10 ^-9 -10 ^-10 S cm ^-1 ) and lithium ion diffusivity (1.8×10 ^-14 cm ² s ^-1 ) lead to poor rate capability. It can be seen from this that it is difficult to obtain excellent performances from a single material.

At present, the most commonly used method is coating and doping modification, but usually simple coating and doping of a material cannot achieve very satisfactory results. US Patent Application No. US2014/0377655A1 discloses a doping of less than 1.9% garnet oxide to improve the ionic conductivity of the material. Chinese Patent Application No. 201510640646.0 and Chinese Patent Application No. 201110160960.0 disclose a core-shell structure in which the core is a single-core particle whose core is lithium vanadium phosphate coated with lithium manganese phosphate. Chinese Patent Application No. 201410120066.4 discloses a method for preparing a core-shell structure phosphate-based composite cathode material with a multilayer core. Sometimes in the industry, two or more positive electrode materials are directly mixed and coated on the electrode sheet according to specific needs, and the advantages of the materials are used to complement each other in order to achieve the purpose of optimizing various electrochemical indicators and saving costs. However, the disadvantage of this method is that they are all independent substances, which are only macro-mixed, which may lead to the inhomogeneity of various performance indicators, and may not meet expectations.

Contents of the invention

The object of the present invention is to provide a lithium-ion battery cathode material with a multi-core structure and a preparation method thereof, so as to solve the above-mentioned problems.

The invention provides a lithium-ion battery positive electrode material with a multi-core structure, which includes a casing and a core disposed in the casing, the core includes at least two core particles that are in contact with each other and are independent of each other, and each core particle The material is selected from a layered structure positive electrode active material, a spinel structure positive electrode active material and an olivine structure positive electrode active material, and the material of the shell is selected from materials that are inert to the electrolyte, and the layered structure positive electrode active material includes xLi ₂ MO ₃ ·(1-x)LiMO ₂ , wherein, 0≤x<1; the positive electrode active material with spinel structure includes LiM ₂ O ₄ ; the positive electrode active material with olivine structure includes LiMPO ₄ , wherein, M is one or more metal elements with an atomic number of 6 or more, preferably selected from Co, Ni, Mn, V, Fe, Cr, and Al.

Preferably, the layered positive electrode active material includes nickel-cobalt lithium manganate, lithium-rich nickel-cobalt lithium manganate, nickel-cobalt lithium aluminate, lithium cobaltate, lithium manganate (layered structure) and lithium nickel-cobaltate.

Preferably, the spinel positive electrode active material includes lithium manganese oxide (spinel structure) and lithium nickel manganese oxide.

Preferably, the positive electrode active material with olivine structure includes lithium iron phosphate, lithium manganese phosphate, lithium vanadium phosphate and lithium cobalt phosphate.

Preferably, there are gaps between the core particles, which are used to provide a buffer space for the change of lattice size during the Li+ intercalation process.

Preferably, the total particle diameter of the core is 100 nm-10 μm.

Preferably, the shell has a thickness of 10nm-200nm.

The present invention also provides a kind of preparation method of the lithium-ion battery cathode material of multi-core structure, and it comprises the following steps:

S1, providing at least two kinds of core particles (the structure of the material can be the same or different), and uniformly mixing the at least two kinds of core particles to form a mixture, wherein the material of each core particle is selected from the layered structure positive electrode active material , a spinel structure positive electrode active material and an olivine structure positive electrode active material, the layered structure positive electrode active material includes xLi ₂ MO ₃ ·(1-x)LiMO ₂ , wherein, 0≤x<1; the spinel The stone structure positive electrode active material includes LiM ₂ O ₄ ; the olivine structure positive electrode active material includes LiMPO ₄ , wherein, M is one or more metal elements with an atomic number of 6 or more, preferably selected from Co, Ni, Mn , V, Fe, Cr, Al;

S2, spray drying the mixture to form multiple cores;

S3, immersing the core in a solution containing shell material components, after fully stirring, filtering, washing and drying;

S4, under the desired atmosphere, calcining the material obtained in step S3 at high temperature, then cooling, pulverizing, and sieving.

Preferably, gaps exist between the core particles in the core to provide a buffer space for the change of lattice size during the Li+ intercalation process.

Preferably, the calcination temperature is 500-800°C.

Compared with the prior art, the lithium-ion battery positive electrode material with multi-core structure and the preparation method thereof of the present invention have the following advantages:

(1) The core contains a variety of materials, and the components and properties are evenly distributed at the nanoscale, which can make the structure and performance complement each other and make up for defects at the nanoscale level. Compared with simple mixed use (micron-scale) smearing It can give full play to its due advantages on the pole piece.

(2) In the multi-nuclear structure proposed by the present invention, since the inner cores are independent of each other, there is no reaction. Therefore, there are tiny gaps between the inner cores, and the shape and size of the gaps are determined by the shape and size of the particles. This more evenly distributed space can provide a buffer space for the change of Li+ lattice size during the intercalation and deintercalation process, which can reduce the deformation of the structure during charging and discharging, and reduce the possibility of forming a dead zone (partial collapse of the structure) inside the structure, thereby further The cycle performance of the material is improved.

(3) Since there are tiny gaps between the cores in this multi-core structure, it can also provide a buffer for the volume change caused by the expansion and contraction of the material when the temperature changes, thereby improving the thermal stability and safety of the material.

(4) These tiny voids also increase the transport channels for Li+ on the grain surface, increasing the transport rate, thereby improving the electrochemical performance, especially the rate performance of the material.

Description of drawings

FIG. 1 is a schematic structural view of a lithium-ion battery positive electrode material with a multi-core structure provided by an embodiment of the present invention.

Fig. 2 is a flow chart of a method for preparing a cathode material for a lithium-ion battery with a multi-core structure provided by an embodiment of the present invention.

FIG. 3 is a first charge and discharge curve diagram of the lithium-ion battery positive electrode material with a multi-core structure in Example 1. FIG.

FIG. 4 is a cycle charge and discharge curve diagram of the lithium-ion battery cathode material with a multi-core structure in Example 1. FIG.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the implementation manners in the present invention, all other implementation manners obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Please refer to FIG. 1 , an embodiment of the present invention provides a lithium-ion battery positive electrode material 100 with a multi-core structure, including a casing 10 and a core 11 disposed in the casing 10, the core 11 includes at least two kinds of materials that are in contact with each other and The core particles 111/112/113 are independent of each other, and the material of each core particle 111/112/113 is selected from layered structure positive electrode active materials, spinel structure positive electrode active materials and olivine structure positive electrode active materials. For example, the core 11 may include at least two layered structure positive electrode active materials with different compositions, at least two spinel structure positive electrode active materials with different compositions, at least two olivine structure positive electrode active materials with different compositions, or a mixture thereof . The material of the housing 10 is selected from materials that are inert to the electrolyte, and the layered positive electrode active material includes xLi ₂ MO ₃ ·(1-x)LiMO ₂ , wherein, 0≤x<1; The spar structure positive electrode active material includes LiM ₂ O ₄ ; the olivine structure positive electrode active material includes LiMPO ₄ , wherein M is one or more metal elements with an atomic number of 6 or more, preferably selected from Co, Ni, Mn, V, Fe, Cr, Al.

The shell 10 has a thickness of 10nm-200nm. More preferably, the thickness of the casing 10 is 30nm-60nm. It can be understood that when the thickness of the casing 10 is too large, it is not conducive to the rapid transmission of lithium ions, thereby affecting the rate performance of the material.

There is a gap between the core particles 111/112/113, which is used to provide a buffer space for the change of the lattice size during the Li+ intercalation process. Preferably, the gaps between the core particles 111 / 112 / 113 account for 3%-20% of the total space of the casing 10 . Preferably, the gaps between the core particles 111 / 112 / 113 account for 3-8% of the total space of the casing 10 . It can be understood that when the buffer space is too large, it is not conducive to improving the compaction density of the material, and if it is too small, it is difficult to meet the change of lattice size during the Li+ intercalation process.

The total particle diameter of the core 11 is 100nm-10μm. Preferably, the total particle diameter of the core 11 is 100nm-500nm. More preferably, the total particle diameter of the core 11 is 100nm-200nm. Preferably, the layered positive electrode active material includes lithium manganese oxide (layered structure) lithium nickel cobalt manganese oxide, lithium-rich nickel cobalt lithium manganese oxide, lithium nickel cobalt aluminate, lithium cobalt oxide and lithium nickel cobalt oxide. Preferably, the spinel positive electrode active material includes lithium manganese oxide (spinel structure) and lithium nickel manganese oxide. Preferably, the positive electrode active material with olivine structure includes lithium iron phosphate, lithium manganese phosphate, lithium vanadium phosphate and lithium cobalt phosphate. For example, the core 11 includes three core particles 111/112/113 that are independent of each other, namely the layered structure positive electrode active material core particle 111, the spinel structure positive electrode active material core particle 112 and the olivine structure positive electrode active material core particle 113. The particle diameter of each core particle 111/112/113 is nanoscale, preferably, the particle diameter of each core particle 111/112/113 is 20nm-100nm.

The mass ratio of various core particles in the core particles 111/112/113 is not limited, and can be adjusted according to actual needs. Preferably, the layered structure positive electrode active material core particle 111, the spinel structure positive electrode active material The stoichiometric ratio between the core particle 112 and the positive electrode active material core particle 113 with an olivine structure is 1:0.05˜0.5:0.05˜0.5. More preferably, the stoichiometric ratio between the layered structure positive active material core particle 111, the spinel structure positive active material core particle 112 and the olivine structure positive active material core particle 113 is 1:0.2 ~0.4:0.1~0.3.

Please refer to Fig. 2, the embodiment of the present invention provides a kind of preparation method of the cathode material of lithium-ion battery of multi-core structure, and it comprises the following steps:

S1, providing at least two kinds of core particles, and uniformly mixing the at least two kinds of core particles to form a mixture, wherein the material of each core particle is selected from layered structure positive electrode active materials, spinel structure positive electrode active materials and olive Stone structure positive electrode active material, the layered structure positive electrode active material includes xLi ₂ MO ₃ ·(1-x)LiMO ₂ , wherein, 0≤x<1; the spinel structure positive electrode active material includes LiM ₂ O ₄ ; The olivine structure positive electrode active material includes LiMPO ₄ , wherein M is one or more metal elements with an atomic number of 6 or more, preferably selected from Co, Ni, Mn, V, Fe, Cr, Al;

S2, spray drying the mixture to form multiple cores;

S3, immersing the core in a solution containing shell material components, after fully stirring, filtering, washing and drying;

S4, under the desired atmosphere, calcining the material obtained in step S3 at high temperature, then cooling, pulverizing, and sieving. The composition of the required atmosphere is not limited, and can be selected according to the prior art in combination with specific materials and growth environment, and usually includes oxygen.

In step S2, core particles of different materials are physically bonded together to form a core composed of multiple cores. It will be appreciated that the size of the core can be controlled by adding an appropriate amount of binder.

In step S3, after fully stirring, the shell material will be evenly wrapped on the surface of the core. It will be appreciated that the thickness of the final shell can be controlled by controlling the concentration of shell material in solution, temperature and time.

In step S4, the calcination temperature should be selected enough to remove the moisture in the mixture and ensure that the multinuclei are independent from each other and do not react with each other. Preferably, the calcination temperature is 500-800°C.

Example 1:

Fully mix the layered lithium nickel cobalt aluminate LiNi _0.8 Co _0.15 Al _0.05 O ₂ and the spinel lithium manganese oxide LiMn ₂ O ₄ nanoscale material according to the stoichiometric ratio of 1:0.1, and spray dry After nucleation, disperse in an ethanol solution containing aluminum isopropoxide with a concentration of 5wt.%, and after continuous stirring for 3 hours, filter, wash and dry, and place the resulting mixture in an oxygen or air atmosphere at a temperature of 600°C After calcination for 6 hours, the cathode material was obtained after cooling.

Please refer to Figure 3-4, the electrochemical performance test of the material is tested at 25°C with the blue electric battery test system, the test voltage range is 3V ~ 4.2V; specific capacity test conditions: 0.1C charge and discharge once;; cycle performance test Conditions: Charge and discharge at a rate of 1C, cycle for 100 cycles, and investigate the capacity retention rate. The specific discharge capacity of the material at 0.1C rate is 185mAh/g. The capacity retention rate of 1C charge-discharge cycle for 100 cycles is greater than 97%, and the cycle performance is good.

The above description is a preferred embodiment of the present invention, it should be pointed out that for those skilled in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also considered Be the protection scope of the present invention.

Claims (10)

1. the anode material for lithium-ion batteries of a coenocytism, it is characterised in that include housing and setting Core in described housing, described core bag at least two contacts with each other and core granule independent of each other, The material of each core granule is selected from layer structure positive electrode active materials, spinel structure positive electrode active materials And olivine structural positive electrode active materials, the material of described housing is inert material selected from relative electrolyte, Layered structure positive electrode active materials includes xLi₂MO₃·(1-x)LiMO₂, wherein, 0≤x < 1；Described point is brilliant Stone structure positive electrode active materials includes LiM₂O₄；Described olivine structural positive electrode active materials includes LiMPO₄, Wherein, M be atomic number be one or more in more than 6 metallic elements.

2. an anode material for lithium-ion batteries as claimed in claim 1, it is characterised in that layered Positive electrode active materials includes nickle cobalt lithium manganate, rich lithium nickel cobalt manganese acid lithium, nickel cobalt lithium aluminate, cobalt acid lithium, mangaic acid Lithium and lithium nickel cobalt dioxide.

3. an anode material for lithium-ion batteries as claimed in claim 1, it is characterised in that described point is brilliant Stone positive electrode active materials includes LiMn2O4 and nickel ion doped.

4. an anode material for lithium-ion batteries as claimed in claim 1, it is characterised in that described Fructus Canarii albi Stone structure positive electrode active materials includes LiFePO4, lithium manganese phosphate, phosphoric acid vanadium lithium and cobalt phosphate lithium.

5. an anode material for lithium-ion batteries as claimed in claim 1, it is characterised in that described core There is gap between granule, the change for lattice dimensions during Li+ deintercalation provides cushion space.

6. an anode material for lithium-ion batteries as claimed in claim 1, it is characterised in that described core Total particle diameter be 100nm-10 μm.

7. an anode material for lithium-ion batteries as claimed in claim 1, it is characterised in that described housing Thickness be 10nm-200nm.

8. a preparation method for the anode material for lithium-ion batteries of coenocytism, it comprises the following steps:

S1, it is provided that at least two core granule, and described at least two core granule is uniformly mixed to form mixed Compound, wherein, the material of each core granule is selected from layer structure positive electrode active materials, spinel structure Positive electrode active materials and olivine structural positive electrode active materials, layered structure positive electrode active materials includes xLi₂MO₃·(1-x)LiMO₂, wherein, 0≤x < 1；Described spinel structure positive electrode active materials includes LiM₂O₄； Described olivine structural positive electrode active materials includes LiMPO₄, wherein, M be atomic number be more than 6 gold Belong to one or more in element；

S2, carries out described mixture being spray-dried the multiple cores of formation；

S3, is immersed in described core in the solution of case material composition, after being sufficiently stirred for, filters, washes Wash and dry；

S4, under required atmosphere atmosphere, material step S3 obtained at high temperature is calcined, then cooling, Pulverize, sieve.

9. a preparation method as claimed in claim 8, it is characterised in that the core in described core Gap is there is between Li.

10. a preparation method as claimed in claim 8, it is characterised in that described calcining heat is 500-800℃。