JP5223166B2 - Battery active material and secondary battery - Google Patents

Description

  The present invention relates to a battery active material, and more particularly to a positive electrode active material of a lithium ion secondary battery.

  In recent years, hybrid vehicles, electric vehicles, and fuel cell vehicles have been manufactured and sold from the viewpoints of environment and fuel efficiency, and new developments are continuing. In these so-called electric vehicles, it is indispensable to use a power supply device capable of discharging and charging. As the power supply device, a secondary battery such as a lithium ion battery or a nickel metal hydride battery, an electric double layer capacitor, or the like is used.

  In particular, lithium ion secondary batteries are considered suitable for electric vehicles because of their high energy density and high durability against repeated charging and discharging, and various developments have been intensively advanced. Among electric vehicles, a so-called hybrid vehicle using both an internal combustion engine and a battery requires high output in a short time such as during acceleration. Therefore, countermeasures such as reducing the average particle size of the active material, for example, increasing the effective surface area to several μm or less, are being studied.

Conventionally, composite oxides of lithium and various metal elements have been used as positive electrode active materials for lithium ion batteries. In addition, a method of using a combination of these composite oxides (for example, see Patent Document 1) has been proposed.
Japanese Patent No. 3610943

  However, the technique considered in the conventional lithium ion secondary battery as described in Patent Document 1 is mixing active material particles, and the characteristics of each active material having different output performance and capacity performance are sufficiently utilized. There was a problem of not being.

  Therefore, the present invention has been made in view of the above-described problems of the prior art. That is, an object of the present invention is to provide a battery active material that can fully utilize the characteristics of each active material having different output performance and capacity performance, and a lithium ion secondary battery using the battery active material.

  The inventor has a core-shell structure composed of materials having different performances as active material particles, the core portion is made of a material that emphasizes capacity performance, and the shell portion is made of a material that emphasizes output performance. The present inventors have found that the above characteristics can be fully utilized and completed the present invention.

  An object of the present invention is a battery active material, which is composed of at least two types of active material, the material in the particles has a core-shell type structure, and the shell portion with respect to the active material of the core portion. It can be achieved by a battery active material characterized in that the active material is high output.

  According to the battery active material of the present invention, the material in the active material particles has a core-shell structure, and the material of the shell part has a high output relative to the material of the core part. High performance materials can be used effectively.

  The present invention is a battery active material, which is composed of at least two types of active material, the material in the particles has a core-shell type structure, and the active part material of the core part has an active part of the shell part. The material is characterized by high output. Hereinafter, although embodiment of the battery active material of this invention is described using drawing, this invention is not limited to these embodiment. FIG. 1A is a schematic cross-sectional view of active material particles according to an embodiment of the battery active material of the present invention, showing a state in which the inside of the particle has a core-shell structure with different active material materials. FIG. 1B shows another embodiment of the battery active material of the present invention, which has a core-shell type structure with active material materials having different inside particles, and a structure in which an elution preventing layer is further provided outside the shell portion. It is a cross-sectional schematic diagram of the active material particle showing a state of becoming.

  As shown in FIG. 1A, in the battery active material of the present invention, the shell part (surface layer part) 1 of the core-shell type particle 3 is composed of an active material having a higher output than the core part (inside) 2. Has been. Furthermore, as shown in FIG. 1B, in the battery active material of the present invention, an elution preventing layer 4 may be provided outside the shell portion 1.

  The electrode reaction is a so-called electrochemical reaction, and the easiness of the reaction differs between the surface layer portion and the inside of the active material particles. For this reason, when high output is taken out in a short time, the shell part 1 of the particles, in which the electrolyte components and Li ions are easily inserted and desorbed quickly and the reaction is likely to occur, is mainly used, and many of the core parts 2 remain unused. is there. Therefore, as in Patent Document 1, when particles having excellent output performance and particles having excellent capacity performance are mixed and used, none of the characteristics can be fully utilized. That is, even if a high output is to be taken out in a short time, the output of the entire electrode obtained is a weighted average of these due to variations in output characteristics between particles having different characteristics. Therefore, it is difficult to provide a high output as in the case where only particles having excellent output performance are used. On the other hand, even if it is attempted to take out a predetermined capacity (medium to low output) stably for a relatively long period of time, the capacity of the entire electrode obtained is excellent in output performance with a small capacity due to variation in capacity between particles having different characteristics. It is limited by the capacity of the particles. That is, when the capacity of the particles having excellent output performance with a small capacity is exhausted, the output of the entire electrode is lowered, and it becomes difficult to supply a predetermined output with only the remaining particles having excellent capacity performance. Therefore, it is difficult to provide a high capacity as in the case where only particles having excellent capacity performance are used.

  On the other hand, in the present invention, by using particles of a core-shell type structure in which the material of the shell part is composed of an active material having a higher output than that of the core part, the characteristics of both output performance and capacity performance can be fully utilized. Can do. That is, even when it is necessary to take out a high output in a short time, there is no variation in output characteristics between particles, and a high-power active material with a shell portion that easily reacts with all particles can be used effectively. Therefore, it is possible to provide a high output equivalent to the case where only particles having excellent output performance are used. Further, even when an attempt is made to provide as much capacity as possible over a long period of time, there is little variation in the volume characteristics between particles, and all particles can be efficiently subjected to reaction up to a high-capacity core portion. Therefore, a battery having a high capacity can be provided without much difference from the case where only particles having excellent capacity performance are used.

  Hereinafter, description will be made by dividing into a core part, a shell part, and an elution preventing layer, which are main constituents of the battery active material of the present invention.

(I) Core part The core part in a particle | grain may be one layer (single layer), and may be comprised by two or more layers.

  In the aspect in which the core part is composed of two or more layers, (1) a plurality of layers in which performance (material) such as capacity and output changes from the surface of the core part toward the center part are stacked concentrically, for example. Structure. In addition, (2) a structure in which the performance such as capacity and output continuously changes from the surface of the core portion toward the center portion is also included. In these cases, for example, by changing the material for each layer or changing the mixing ratio of two or more active material materials, the performance such as capacity and output increases from the surface of the core toward the center. Or it can be changed (functional gradient) to decrease. Furthermore, in this invention, what can be manufactured with the granulation technique using 2 or more types of materials may be contained. For example, (3) a sea-island structure in which different materials are scattered and arranged in an island shape in the matrix material may be used. Further, (4) a structure in which different materials are arranged for each hemispherical portion of the core particle may be used. Further, (5) a secondary particle (aggregation) structure in which fine particle groups made of different materials are gathered together, consolidated and granulated may be used. Furthermore, the structure etc. which combined said (1)-(5) suitably are mentioned. However, it is not limited to these. From the viewpoint of ease of manufacturing, reduction in the number of materials and manufacturing man-hours (reduction in materials and manufacturing costs), etc., it is desirable to configure with one layer (single layer). In addition, for example, from the viewpoint of suppressing a sudden change in capacity performance or output performance at the boundary portion with the share portion, and suppressing an increase in internal resistance at the boundary portion, it is desirable to configure with two or more layers. I can say that.

  As described above, it is desirable to use an active material having an excellent capacity performance as compared with the active material of the shell as the active material of the core. Specifically, a lithium metal composite oxide, a lithium metal composite phosphate compound, a lithium metal composite sulfate compound, a metal oxide, a metal sulfide, a conductive polymer, or a material obtained by mixing these materials is preferable. Used.

In particular, the core active material is preferably a layered nickel-based lithium metal composite oxide (hereinafter abbreviated as LiNiO ₂ ). At this time, it is more preferable to partially substitute a part of nickel in LiNiO ₂ with another element. Examples of substitution elements include lithium, boron, phosphorus, nitrogen, magnesium, aluminum, calcium, vanadium, titanium, chromium, manganese, iron, cobalt, copper, zinc, strontium, zirconium, niobium, molybdenum, tin, or These combinations are preferred. These LiNiO ₂ , a material in which a part thereof is substituted, or a mixture thereof is desirable because it has a layered crystal structure with a relatively high Li ratio and is excellent in capacity performance. In particular, it is excellent in that the stability of the layered material (particularly, stability at high voltage charging) can be improved by partially replacing the metal element of the lithium metal composite oxide such as LiNiO ₂ . In addition to this, by appropriately selecting a substitution element, it is possible to improve the cycle characteristics during charging while maintaining capacity performance, increase the storage stability at high temperatures, and more inexpensively. It is excellent in that characteristics suitable for the purpose of use and application can be imparted, such as cost reduction by a simple alternative element.

  These active material materials for the core may be used alone or in combination of two or more. When the core portion is composed of two or more layers, the active material may be used alone for each layer, or two or more types may be mixed and used.

  The shape of the core part is not particularly limited, and examples thereof include a spherical shape, a cubic shape, a rectangular parallelepiped shape, an elliptical spherical shape, a needle shape, a plate shape, a square shape, a column shape, and an indefinite shape. Spherical and elliptical spheres are preferred.

  The average particle size of the core part is not particularly limited, but is preferably 20 μm or less. More preferably, it is the range of 0.1-2 micrometers. When the average particle diameter of the core part is 20 μm or less, especially 2 μm or less, the material characteristics of the core part can be sufficiently exhibited, and the average particle diameter of the whole battery active material particles can be reduced (for example, several μm or less). The effective surface area can be increased. Furthermore, it is possible to sufficiently secure a shell portion having a desired thickness. Therefore, even when high response performance such as acceleration is required, high output can be quickly supplied, and high tracking performance (response performance) can be realized. Note that the lower limit is not particularly limited, but in the case of 0.1 μm or more, the handling for the creation of the particles and the creation of the electrode is not performed as a conventional powder without special management. It is excellent in that it can be done in the same way.

(II) Shell part The shell part should just be formed in the outer side (outer layer) of a core part, and may be 1 layer (single layer), and may be comprised by two or more layers. .

  The shell portion may be arranged in a layer so as to cover the entire surface of the core portion (see FIG. 1A), or the entire surface of the core portion is covered (attached) with a large number of fine particles (powder). ) (See FIG. 1C). That is, by covering the entire surface of the core part with the material of the shell part, it is possible to increase the ratio of the share part material occupying the particle surface (surface area that effectively contributes to higher output). Therefore, when a high output is taken out in a short time such as during acceleration, the high-power active material material of the share part of the particle surface can be used very effectively. However, if the desired high output can be sufficiently taken out in a short time, it is not always necessary to cover the entire particle surface with the active material of the shell portion. That is, the active material material (for example, granular material) of the share part may be disposed so as to be scattered on the surface of the core part (core particle), and a part of the surface of the core part may be left exposed.

  In the aspect in which the shell part is composed of two or more layers, (1) a plurality of layers in which performance (material) such as output and capacity changes from the shell part surface to the inside of the particle are concentrically stacked, for example. Structure is mentioned. In addition, (2) a structure in which the performance such as capacity and output continuously changes from the shell surface to the inside of the particle is also included. In these cases, for example, by changing the material for each layer or changing the mixing ratio of two or more active material materials, the performance such as output and capacity increases from the surface of the shell part to the inside of the particle. Or it can be changed (functional gradient) to decrease. Furthermore, in this invention, what can be manufactured with the granulation technique using 2 or more types of materials may be contained. For example, (3) a sea-island structure in which another material is arranged in an island shape in the matrix material may be used. Further, (4) a structure in which different materials are arranged for each outer shell portion of the hemisphere may be used. Further, (5) a structure in which fine particle groups made of different materials are attached or coated on the surface of the core particle may be used. Furthermore, the structure etc. which combined said (1)-(5) suitably are mentioned. However, it is not limited to these. From the viewpoint of ease of manufacturing, reduction in the number of materials and manufacturing man-hours (reduction in materials and manufacturing costs), etc., it is desirable to configure with one layer (single layer). In addition, for example, from the viewpoint of suppressing an abrupt change in output performance or capacity performance at the boundary portion with the core portion, and suppressing an increase in internal resistance at the boundary portion, it is desirable to configure with two or more layers. I can say that.

  As described above, as the active material for the shell, it is desirable to use a high-power active material that has higher output performance than the active material for the core. Specifically, a lithium metal composite oxide, a lithium metal composite phosphate compound, a lithium metal composite sulfate compound, a metal oxide, a metal sulfide, a conductive polymer, or a material obtained by mixing these materials is preferable. Used.

In particular, the active material of the shell portion is preferably a spinel manganese-based lithium metal composite oxide (hereinafter abbreviated as LiMn ₂ O ₄ ). At this time, it is more preferable to partially substitute a part of manganese in LiMn ₂ O ₄ with another element. Examples of substitution elements include lithium, boron, phosphorus, nitrogen, magnesium, aluminum, calcium, vanadium, titanium, chromium, nickel, iron, cobalt, copper, zinc, strontium, zirconium, niobium, molybdenum, tin, or These combinations are preferred. These LiMn ₂ O ₄ , a material in which a part thereof is substituted, or a mixture thereof is desirable in terms of excellent output performance because it has a spinel structure and Li can easily move regardless of the Li content. In particular, it is excellent in that the safety (especially storage stability at high temperature) of a spinel material can be improved by partially replacing a metal element of an oxide such as LiMn ₂ O ₄ . In addition to this, by properly selecting the substitution element, the cycle characteristics during charging can be improved while maintaining the output performance, and the safety during high temperature and overcharge can be improved. It is excellent in that it can provide properties suitable for the purpose of use and application, such as cost reduction by a cheaper alternative element.

  These active material materials for the shell part may be used singly or in combination of two or more. When the shell portion is constituted by two or more layers, the active material may be used alone for each layer, or two or more types may be mixed and used.

Regarding the combination of the active material of the core part and the shell part described above, it is sufficient that the active material of the shell part has a higher output than the active material of the core part. Therefore, it is limited to the combination of the above-described LiMn ₂ O ₄ of the shell part, a material substituted part thereof, or a mixture thereof, and the above-described LiNiO _{2 of} the core part, material substituted part of the core part, or a mixture thereof. It is not a thing. For example, even in the case of a lithium metal composite oxide assuming a positive electrode active material of a lithium ion battery, a combination of various materials as shown in Table 1 below can be used, and an optimum material should be selected from various design factors for the battery. Is possible.

  In the battery active material having such a core-shell structure, the volume of the shell part is preferably 40% or less of the whole. More preferably, it is 5% or more and 30% or less. If it exceeds 40%, the thickness ratio of the shell portion increases, and the core portion relatively decreases. Therefore, by setting it to 40% or less, the high-capacity material of the core part can be used more effectively. The lower limit is not particularly limited, but when it is 5% or more, the shell material can be dispersed substantially uniformly on the core grains. Thereby, the high output performance and the capacity performance can be fully utilized, and both can be optimized.

  Further, the average thickness of the shell portion is 1 μm or less, preferably 0.2 μm or less. More preferably, it is 0.01 μm or more and 0.2 μm or less. By setting the thickness to 1 μm or less, the lithium diffusion distance of the shell portion does not become too long, and effective use can be achieved for the entire volume of the high-capacity core portion. That is, it can be effectively utilized (provided for charge / discharge reaction) from the center part to the deepest part of the core part, and charge / discharge efficiency can be increased. The lower limit is not particularly limited, but in the case of 0.01 μm or more, one shell part (or two or more layers) can be uniformly formed on the core part (core particle) surface. it can. As a result, a high output can be taken out in a short time with a very responsive response when accelerating the shell part. As a result, when applied to a hybrid vehicle or the like, it is excellent in that an excellent high acceleration performance that is not much different from that of an existing internal combustion engine (gasoline engine) can be realized.

(III) Elution prevention layer The elution prevention layer should just be formed in the outer side (outer layer) of a shell part, and may be 1 layer (single layer), and is comprised by two or more layers. Also good.

  This elution preventing layer is intended to suppress detachment of the material (particles) forming the shell portion. Therefore, as shown in FIG. 1B, the elution preventing layer is disposed in a layered manner so as to cover the entire surface of the shell portion 1, or the entire surface of the shell portion is covered (attached) with a large number of fine particles (powder). It is desirable to arrange as follows. That is, by covering the entire surface of the shell portion with the elution preventing layer, the detachment of the material (particles) forming the shell portion can be further remarkably suppressed.

  The aspect which comprises an elution prevention layer by two or more layers is the same as the aspect which comprises the said shell part by two or more layers. That is, (1) a structure in which a plurality of layers in which performance (material) such as elution prevention changes from the surface of the elution prevention layer to the inside of the particle is concentrically stacked, for example. In addition, (2) a structure in which performance such as elution prevention continuously changes from the surface of the elution prevention layer toward the inside of the particle is also included. In these cases, for example, by changing the material for each layer or changing the mixing ratio of two or more materials, the performance such as elution prevention increases or decreases from the surface of the elution prevention layer toward the inside of the particle. It can be changed (function inclination). Furthermore, in this invention, what can be manufactured with the granulation technique using 2 or more types of materials may be contained. For example, (3) a sea-island structure in which another material is arranged in an island shape in the matrix material may be used. Further, (4) a structure in which different materials are arranged for each outer shell portion of the hemisphere may be used. Further, (5) a structure in which fine particle groups made of different materials are attached to the surface of core-shell type particles or formed into a film may be employed. Furthermore, the structure etc. which combined said (1)-(5) suitably are mentioned. However, it is not limited to these. From the viewpoint of ease of manufacturing, reduction in the number of materials and manufacturing man-hours (reduction in materials and manufacturing costs), etc., it is desirable to configure with one layer (single layer). In addition, for example, it can be said that it is desirable to configure with two or more layers from the viewpoint of suppressing an increase in resistance at the boundary with the shell.

The material constituting the elution prevention layer is not particularly limited as long as it can suppress the separation (elution) of the material (particles) forming the shell portion. Preferably, it has the function of preventing elution and can be effectively used as an active material. The material constituting the elution preventing layer, specifically, for example, in the shell portion of the LiMn ₂ O _4, a portion of the metal substituted LiMn ₂ O ₄ and a lithium ion conducting polymer or a mixture thereof, Preferably used. However, it is not limited to these.

  The average thickness of the elution preventing layer is 0.2 μm or less, more preferably 0.01 μm or more and 0.1 μm or less. By making it 0.2 μm or less, the lithium diffusion distance of the elution preventing layer does not become too long, and effective use can be achieved for both the high-power shell portion and the high-capacity core portion. In other words, the high-capacity core part can be effectively utilized in the charge / discharge reaction as well as the high output due to the high response speed in the share part without interfering with the lithium diffusion rate and diffusion amount to the shell part and core part. Charge / discharge efficiency can be improved. In addition, although it does not restrict | limit especially about a lower limit, in the case of 0.01 micrometer or more, an elution prevention layer can be uniformly formed in the shell part surface. As a result, the elution of the shell material required for the elution prevention layer in the charge / discharge environment can be effectively suppressed, and the deterioration of the output performance due to the progress of the charge / discharge cycle is effectively suppressed. It is excellent in that it can maintain high output performance stably.

As described above, various materials are used as the battery active material of the present invention. For example, as a positive electrode active material of lithium ions, a material having an action of releasing lithium ions during charging and occluding lithium ions during discharging is used. For example, spinel manganese-based lithium metal composite oxides have a layered crystal structure in which the lithium ion migration direction is limited because the sites where lithium ions enter and exit the crystal exist regardless of the orientation. The output is higher (see FIG. 2A). In addition, in a manganese-based lithium metal composite oxide, a low-cost material called Mn can be used as a transition metal, and heat stability is excellent. On the other hand, for example, layered lithium nickel composite oxide (LiNiO ₂ ) and lithium / cobalt / aluminum composite oxide, which are composite oxides having a layered crystal structure, are spinel oxides such as manganese and other layered oxides. Has a higher capacity (see FIG. 2B). This is because spinel manganese-based lithium metal composite oxide (spinel-based lithium manganese oxide) has the same three-dimensional channel structure as spinel ore (mineral name), and 0.5 Li atoms are active per Mn atom. Contained in the substance (see FIG. 2A). On the other hand, layered lithium nickel composite oxide (LiNiO ₂ ; nickel-based lithium metal composite oxide), or a part of nickel in the LiNiO ₂ partially substituted with other elements (for example, Co or Mn), etc. Then, it has a layered crystal structure in which lithium atomic layers and transition metals (M: Ni only or Mn, Ni, and Co are arranged in an orderly manner) atomic layers are alternately stacked via oxygen atomic layers (see FIG. 2A). .), One Li atom is included per atom of the transition metal M, and the amount of Li that can be taken out is twice that of the spinel-based lithium manganese oxide, that is, the supply capacity is doubled, so that a high capacity can be obtained. .

  According to the present invention, by using these two active material materials having different characteristics in combination with the core-shell type structure, the output performance and capacity performance of each material can be fully utilized. Generally, the output performance required for a hybrid vehicle or the like is that a large current can be discharged in a short time. In such a case, it is not necessary that the output performance is good in all portions of the active material particles, and it is sufficient if the portion close to the surface necessary for short-time discharge is high performance. However, capacity performance is required up to the inside of the active material particles. In other words, by arranging a material with high output performance in the shell part to cope with short-time large current discharge, and arranging a material with high capacity performance in the core part to cope with long-time discharge where capacity performance is required The characteristics of the active material can be fully utilized.

  The composition of the core part, shell part, and elution prevention layer can be measured, for example, by inductively coupled plasma (ICP) emission analysis. In addition, it can be measured by, for example, ICP mass spectrometry, atomic absorption, fluorescent X-ray, Raman spectroscopy, chelate titration, and particle analyzer.

  The average particle diameter of the core part particles and active material particles (particles having a core-shell structure, particles provided with an elution preventing layer outside the shell part) can be measured by, for example, a laser diffraction method. In addition, it can be measured by, for example, a dynamic light scattering method, a standard sieving method, SEM observation, and TEM observation. In addition, although the shape of a core part particle | grain or an active material particle becomes a substantially spherical shape when using the manufacturing method mentioned later, shapes other than a spherical shape (for example, indefinite shape) may be included as mentioned above. Therefore, the average particle diameter is expressed as an absolute maximum length because the particle shape is not uniform. Here, the absolute maximum length is assumed to be, for example, the maximum length among the distances between any two points on the outline of the particle when SEM observation or TEM observation is performed.

  The average thickness of the shell part can be calculated from the average particle diameter of the particles composed of the core particles and the core-shell type structure. Similarly, the average thickness of the elution preventing layer can be calculated from the average particle diameter of particles having a core-shell type structure and particles having an elution preventing layer provided outside the shell portion. The average volume of the shell part can also be calculated from the average particle diameter of the core part and the average thickness of the shell part.

  Next, the method for producing a battery active material having a core-shell type structure according to the present invention is not particularly limited. The material for the shell portion relative to the material for the core portion, and further the material for the elution prevention layer It is possible to apply a technique for attaching / coating. Specifically, as a technique for attaching / covering the material of the shell portion and further the material of the elution prevention layer to the material of the core portion, both (a) wet method and (b) dry method should be applied. Can do.

(A) Wet method Examples of the wet method include a method of forming the shell part by applying the raw material of the shell part onto the core part particles formed in advance and sintering again. For example, the core material is prepared by a coprecipitation method, and the shell material is again coprecipitated by the coprecipitation method on the surface of the core particle, and the surface of the particle having a core-shell type structure as necessary. A battery active material (particles) having a core-shell structure can be obtained by co-precipitation of the material of the elution preventing layer by co-precipitation method, thermal decomposition, and firing (see FIGS. 1A and 1B). Of that.) Hereinafter, specific examples of the method for producing the core-shell type battery active material (particles) shown in FIG. 1A will be briefly described, but the present invention is not limited to these ranges.

(I) Preparation of core part particles by coprecipitation method The raw materials of the core part are mixed (mixing step A), coprecipitated (coprecipitation step A), pyrolyzed (pyrolysis step A), and fired (firing step). A) The core part particles are thus produced.

(Mixing process A)
The raw material of the core part, for example, Li compound, Ni compound or the like is dissolved in an appropriate solvent such as water so as to have a desired composition of the active material of the core part.

  Examples of the Li compound (powder) include, but are not limited to, lithium hydroxide or hydrates thereof, lithium peroxide, lithium nitrate, and lithium carbonate.

  Examples of the Ni compound (powder) include, but are not limited to, nickel hydroxide, nickel oxide, nickel nitrate, and the like.

  The solvent is preferably pure water, but is not limited thereto.

  In this process, if necessary, as a metal element that replaces a part of the layered lithium metal composite oxide constituting the active material of the core part so that the composition of the active material of the core part is further desired. , For example, at least one metal element such as lithium, boron, phosphorus, nitrogen, magnesium, aluminum, calcium, vanadium, titanium, chromium, manganese, iron, cobalt, copper, zinc, strontium, zirconium, niobium, molybdenum, tin You may mix further the compound containing this. Alternatively, the Ni compound may contain a metal element that substitutes a part of the lithium metal composite oxide that constitutes the active material of the core part, if necessary.

  In the present invention, it is desirable to coprecipitate the above-described Li compound, Ni compound, etc. as a hydroxide. Other elements (metal element to be substituted) other than Li and Ni elements can be added by coprecipitation as hydroxides. In addition to hydroxides, metals, oxides, nitrates, and sulfates can be added.

(Coprecipitation process A)
The aqueous solution obtained in the mixing step is heated from room temperature to a range of 100 to 110 ° C. at a heating rate of 1 to 20 ° C./min, and in that heating temperature range (preferably a constant temperature within the temperature range), The mixture is stirred for 12 to 48 hours in air or in an oxygen atmosphere while being heated to evaporate water by 90% or more and dehydrate. The size of the core particle can be controlled by the heating temperature condition here.

(Pyrolysis process A)
The powder obtained in the coprecipitation step A is transferred to a suitable ceramic container (such as a crucible) and heated up to 200 to 400 ° C. at a heating rate of 5 to 30 ° C./min. Thermal decomposition (preliminary firing) is preferably performed for 1 to 10 hours in air or in an oxygen atmosphere at a certain temperature within the temperature range.

(Baking step A)
The temperature is raised from the temperature of the thermal decomposition (preliminary calcination) to a range of 500 to 900 ° C. at a rate of temperature increase of 5 to 30 ° C./min, and in that temperature range (preferably a constant temperature within the temperature range), Bake for 3-15 hours in 2% or oxygen atmosphere while homogenizing. After firing, the temperature is lowered from the firing temperature to a range of 200 to 400 ° C. at a rate of temperature reduction of 0.5 to 5 ° C./min, and in the temperature range (preferably a constant temperature within the temperature range), in the air or oxygen Desired core part particles can be produced by annealing in an atmosphere for 1 to 5 hours. In this step, the material constituting the particles grows into a lithium metal composite oxide having a layered structure that is an active material.

  ICP (inductive ion plasma method) is used as the quantitative method for the metal element in the core particle, and TOF-MASS (time-of-flight mass spectrometry) and TOF-SIMS (time-of-flight type 2) are used as the quantitative methods for the non-metallic and metallic elements. Secondary ion mass spectrometry) can be used.

(Ii) Production of active material particles by coprecipitation method The raw materials of the shell part are mixed again by the coprecipitation method (mixing step B), and the shell part obtained in the mixing step B is mixed on the surface of the obtained core part particles. A battery active material (particles) having a core-shell structure can be obtained by co-precipitation of raw materials (co-precipitation step B), thermal decomposition (thermal decomposition step B), and firing (firing step B). .

(Mixing process B)
A raw material of the shell part, for example, a Li compound, a Mn compound, or the like is dissolved in an appropriate solvent such as water so as to become a desired active material of the shell part.

  Examples of the Li compound (powder) include, but are not limited to, lithium hydroxide or hydrates thereof, lithium peroxide, lithium nitrate, and lithium carbonate.

  Examples of the Mn compound (powder) include, but are not limited to, manganese dioxide, manganese carbonate, manganese nitrate, manganese hydroxide, and the like.

  The solvent is preferably pure water, but is not limited thereto.

  In this process, if necessary, as a metal element for substituting a part of the spinel-based lithium metal composite oxide constituting the active material of the shell part so as to become a desired active material of the shell part, For example, at least one metal element such as lithium, boron, phosphorus, nitrogen, magnesium, aluminum, calcium, vanadium, titanium, chromium, nickel, iron, cobalt, copper, zinc, strontium, zirconium, niobium, molybdenum, tin, etc. You may mix the compound which contains further. Or the metal element which substitutes a part of lithium metal complex oxide which comprises the active material material of a shell part as needed may be contained in the said Mn compound.

  In the present invention, it is desirable to coprecipitate the aforementioned Li compound, Mn compound, etc. as a hydroxide. Other elements (metal element to be substituted) other than Li and Mn elements can be added by being coprecipitated as hydroxides. In addition to hydroxides, metals, oxides, nitrates, and sulfates can be added.

(Coprecipitation process B)
The core particles obtained in the firing step A are mixed and stirred in the aqueous solution obtained in the mixing step B, and heated from room temperature to a range of 100 to 110 ° C. at a temperature increase rate of 1 to 20 ° C./min. In a heating temperature range (preferably a constant temperature within the temperature range), the mixture is stirred for 12 to 48 hours in the air or in an oxygen atmosphere while heating to evaporate water by 90% or more and dehydrate. Thereby, the raw material of a shell part can be co-precipitated on the surface of a core particle. The thickness of the shell part formed on the surface of the core part particle can be controlled by the heating temperature condition here.

(Pyrolysis process B)
The particles obtained in the coprecipitation step B are transferred to a suitable ceramic container (such as a crucible) and heated to a temperature of 200 to 400 ° C. at a temperature rising rate of 5 to 30 ° C./min. Thermal decomposition (preliminary firing) is performed in air or in an oxygen atmosphere for 1 to 10 hours (preferably at a constant temperature within the temperature range). The porosity of the secondary particles can be controlled by the temperature of thermal decomposition.

(Baking step B)
The temperature is raised from the temperature of the thermal decomposition (preliminary calcination) to a range of 500 to 900 ° C. at a rate of temperature increase of 5 to 30 ° C./min, and in that temperature range (preferably a constant temperature within the temperature range), Bake for 3-15 hours in 2% or oxygen atmosphere while homogenizing. After firing, the temperature is lowered from the firing temperature to a range of 200 to 400 ° C. at a rate of temperature reduction of 0.5 to 5 ° C./min, and in the temperature range (preferably a constant temperature within the temperature range), in the air or oxygen Annealing may be performed in an atmosphere for 1 to 5 hours, or the temperature may be lowered to room temperature within 5 minutes (without quenching) while flowing oxygen. Thereby, a battery active material (particle) having a desired core-shell type structure can be produced. In this step, the material constituting the shell portion in the particle grows into a spinel-based lithium metal composite oxide that is an active material. The particle shape and size (aspect ratio) can be controlled by adjusting the firing temperature condition.

  ICP (inductive ion plasma method) is used as a quantification method for metal elements in the shell, and TOF-MASS (time-of-flight mass spectrometry) and TOF-SIMS (time-of-flight secondary method) are used as quantification methods for non-metal and metal elements. Ion mass spectrometry) and the like can be used.

  The wet method that can be used in the production method of the present invention is not limited to the method using the coprecipitation method, and the core part particles are formed by another method, for example, the wet slurry method. Alternatively, the raw material of the shell part and further the material of the elution preventing layer may be applied onto the particles of the core part and sintered again.

(B) Dry Method On the other hand, as an embodiment of the dry method, for example, the material (powder) of the shell portion is mixed in the particles of the core portion and dry-mixed. Hybridization systems (Nara Machinery Co., Ltd.), Cosmos (Kawasaki Heavy Industries), Mechano-Fusion (Hosokawa Micron), Surfing System (Nihon Pneumatic Kogyo), MechanoMill / Speed Kneader / Speed Mill / Spiracoater Any known method and apparatus such as Okada Seiko can be used. If necessary, then heat. Thereby, the battery active material of a core-shell type structure can be obtained.

  Other embodiments of the dry method include, for example, chemical vapor deposition (CVD), physical vapor deposition (PVD), pulsed laser deposition (PLD), and the like on the core particles. A method of forming a shell portion and further an elution preventing layer by sputtering or the like can also be applied.

  Here, the core particles may be formed using the coprecipitation method described in the above-described wet method, or the core material (powder) may be preliminarily used using the mixing device. The material formed by granulating the body) to an appropriate size is not particularly limited.

  Furthermore, in the dry method using the above-described CVD, PVD, PLD, sputtering, etc., the surface of the positive electrode directly (here, the current collector previously supporting (forming) the particles of the core part) the surface of the shell part material, Furthermore, it is possible to coat with an elution preventing layer.

  Next, in the lithium ion secondary battery of the present invention, the battery active material of the present invention that can fully utilize the characteristics of each active material having different output performance and capacity performance is used for a part or all of the positive electrode active material. It is characterized by this.

That is, in the lithium ion secondary battery of the present invention, in addition to the battery active material of the present invention, the positive electrode material may include other positive electrode active materials that can be used within the range that does not impair the effects of the present invention. Good. As such another positive electrode active material, a positive electrode active material used in a conventionally known non-aqueous electrolyte lithium ion battery can be used. Specifically, a composite oxide of lithium and transition metal (lithium-transition metal composite oxide) can be preferably used. For example, Li · Mn composite oxides such as LiMn ₂ O ₄ , Li · Ni composite oxides such as LiNiO ₂ , Li · Co composite oxides such as LiCoO ₂ , Li ₂ Cr ₂ O ₇ , Li ₂ CrO such as Li · Cr based composite oxides such as _4, those obtained by substituting Li · Fe-based composite oxides and another element some of these transition metals, such as LiFeO ₂ (e.g., lithium nickel manganese oxide, or the like) Can be selected and used from Li metal oxides, but is not limited to these materials. These lithium-transition metal composite oxides are excellent in reactivity and cycle durability and are low-cost materials. In addition to these, transition metal and lithium phosphate compounds and sulfuric acid compounds such as LiFePO ₄ ; transition metal oxides and sulfides such as V ₂ O ₅ , MnO ₂ , TiS ₂ , MoS ₂ , and MoO ₃ ; PbO ₂ , AgO, NiOOH, etc. can be used together.

  Although the average particle diameter of the positive electrode active material depends on the production method, it is 0.1 to 50 μm, preferably 0. It can be said that the range of 1 to 5 μm is desirable. However, the present invention is not necessarily limited to the above range. However, it goes without saying that, depending on the manufacturing method, the positive electrode active material particles may not be secondary particles formed by aggregation, agglomeration, or the like. The particle size of the positive electrode active material particles and the particle size of the primary particles can be measured, for example, by observation with a scanning electron microscope (SEM) or transmission electron microscope (TEM).

  The method for producing the positive electrode active material is not particularly limited, and conventionally known production techniques for various composite oxides can be applied. In detail, since it is as having already demonstrated as a manufacturing method of the battery active material of this invention, description here is abbreviate | omitted. That is, other positive electrode active materials other than the battery active material of the present invention can be produced in the same manner as the battery active material production method of the present invention.

  The positive electrode material of the lithium ion secondary battery of this invention should just contain the said positive electrode active material. Further, as the positive electrode material, other constituent components that can be used in addition to the positive electrode active material include a conductive auxiliary agent for increasing electron conductivity, a binder, and an electrolyte supporting salt (lithium salt) for increasing ion conductivity. In addition, a polymer gel or a solid electrolyte (host polymer, electrolytic solution, etc.) may be included. In the case of using a polymer gel electrolyte for the battery electrolyte layer, it is sufficient that a conventionally known binder, a conductive auxiliary agent for enhancing electronic conductivity, etc. are contained. Lithium salt or the like may not be contained. Even when a solution electrolyte is used for the battery electrolyte layer, the positive electrode material may not contain a host polymer, an electrolytic solution, a lithium salt, or the like as a raw material of the polymer electrolyte.

  Examples of the conductive aid include acetylene black, carbon black, graphite, and vapor grown carbon fiber (VGCF). However, it is not necessarily limited to these.

  As the binder, polyvinylidene fluoride (PVdF), SBR, polyimide, or the like can be used. However, it is not necessarily limited to these.

  The polymer gel electrolyte includes a solid polymer electrolyte having ion conductivity and an electrolyte used in a conventionally known non-aqueous electrolyte lithium ion battery, and further has lithium ion conductivity. A structure in which a similar electrolyte solution is held in a non-polymeric skeleton is also included.

Here, the electrolytic solution (electrolyte supporting salt and plasticizer) contained in the polymer gel electrolyte is not particularly limited, and various conventionally known electrolytic solutions can be appropriately used. For example, inorganic acid anion salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiTaF ₆ , LiAlCl ₄ , Li ₂ B ₁₀ Cl ₁₀ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, Li (C 2 _F 5 _{SO 2)} selected from organic acid anion salts such as 2 _N, wherein at least one lithium salt (electrolyte support salt), propylene carbonate, cyclic carbonates such as ethylene carbonate; dimethyl carbonate , Chain carbonates such as methyl ethyl carbonate and diethyl carbonate; ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-dibutoxyethane; γ-butyrolactone, etc. Lactones; Nitto such as acetonitrile Lyls; Esters such as methyl propionate; Amides such as dimethylformamide; Plasticizers such as aprotic solvents (organic) mixed with at least one selected from methyl acetate and methyl formate Those using a solvent) can be used. However, it is not necessarily limited to these.

  Examples of the solid polymer electrolyte having ion conductivity include known solid polymer electrolytes such as polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof.

  For example, polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), etc. are used as the polymer having no lithium ion conductivity used in the polymer gel electrolyte. it can. However, it is not necessarily limited to these. Note that PAN, PMMA, etc. are in a class that has almost no ionic conductivity, and therefore can be a polymer having the above ionic conductivity, but here, they are used for a polymer gel electrolyte. This is exemplified as a polymer having no lithium ion conductivity.

As an electrolyte support salt to increase the ionic conductivity, for _{example, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10 inorganic acid anion salts such as, Li ( An organic acid anion salt such as CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N, or a mixture thereof can be used. However, it is not necessarily limited to these.

  The ratio (mass ratio) between the host polymer and the electrolytic solution in the polymer gel electrolyte may be determined according to the purpose of use, but is in the range of 2:98 to 90:10. That is, in the present invention, particularly from the viewpoint of suppressing the decomposition of the electrolytic solution due to the release of radical oxygen from the LiNi oxide, among nonaqueous electrolytes, a solution electrolyte or a polymer gel electrolyte that uses an electrolytic solution is particularly used. It works effectively against. Therefore, regarding the ratio (mass ratio) between the host polymer and the electrolytic solution in the polymer gel electrolyte, it is not necessary to limit the amount of the electrolytic solution for the purpose of preventing the swelling of the battery due to the decomposition of the electrolytic solution, and priority is given to the battery characteristics. It is something that can be done.

  Hereinafter, a typical embodiment of a lithium ion secondary battery using the battery active material of the present invention as a part or all of the positive electrode active material will be described separately for each component. However, the lithium ion secondary battery of the present invention should not be limited to these.

[Current collector]
The current collector that can be used in the present invention is not particularly limited, and conventionally known current collectors can be used. For example, aluminum foil, stainless steel (SUS) foil, nickel-aluminum clad material, copper-aluminum clad material, SUS-aluminum clad material, or a plated material of a combination of these metals can be preferably used. Further, a current collector in which a metal surface is coated with aluminum may be used. Moreover, you may use the electrical power collector which bonded 2 or more metal foil depending on the case. When the composite current collector is used, as a material for the positive electrode current collector, for example, a conductive metal such as aluminum, an aluminum alloy, SUS, or titanium can be used, and aluminum is particularly preferable. On the other hand, as the material of the negative electrode current collector, for example, conductive metals such as copper, nickel, silver, and SUS can be used, and SUS and nickel are particularly preferable. Further, in the composite current collector, the positive electrode current collector and the negative electrode current collector may be electrically connected to each other directly or via a conductive intermediate layer made of a third material. In addition to the flat plate (foil), the positive electrode current collector and the negative electrode current collector are constituted by a lath plate, that is, a plate in which a mesh space is formed by expanding a plate with a cut. Can also be used.

  Although the thickness of a collector is not specifically limited, Usually, it is about 1-100 micrometers.

[Positive electrode (also referred to as positive electrode active material layer)]
Here, as a constituent material of the positive electrode active material layer, a positive electrode material containing the battery active material of the present invention as a positive electrode active material is used. Description is omitted.

  The thickness of the positive electrode active material layer is not particularly limited, and should be determined in consideration of the purpose of use of the battery (output importance, energy importance, etc.) and ion conductivity. The thickness of the general positive electrode active material layer (referring to the thickness of the positive electrode active material layer formed on one side of the current collector) is about 1 to 500 μm, and this range is sufficient for the present invention. However, in order to effectively express the function of the positive electrode material of the present invention, it is particularly preferable that the range is 4 to 60 μm.

[Negative electrode (also referred to as negative electrode active material layer)]
As a constituent material of the negative electrode active material layer, any material using a negative electrode material may be used. The negative electrode material only needs to include a negative electrode active material. In addition to this, conductive aids to enhance electronic conductivity, binders, electrolyte supporting salts (lithium salts) to enhance ionic conductivity, polymer gels or solid electrolytes (host polymers, electrolytes, etc.), etc. Can be. Except for the type of the negative electrode active material, the content is basically the same as the content described in the section “Positive electrode material of lithium ion secondary battery of the present invention”, and thus the description thereof is omitted here.

  As a negative electrode active material, the negative electrode active material used also in a conventionally well-known solution-type lithium ion battery can be used. Specifically, a negative electrode mainly composed of at least one selected from carbon materials such as natural graphite, artificial graphite, amorphous carbon, coke and mesophase pitch carbon fiber, graphite, and hard carbon which is amorphous carbon. Although it is desirable to use an active material, it is not particularly limited. In addition, a metal oxide (particularly a transition metal oxide, specifically titanium oxide), a composite oxide of a metal (particularly a transition metal, specifically titanium) and lithium, or the like can also be used.

[Electrolyte layer]
In the present invention, depending on the purpose of use, (a) a separator is impregnated with an electrolyte, (b) a polymer gel electrolyte alone, or a separator impregnated with and supporting the polymer gel electrolyte (C) The present invention can be applied to either a polymer solid electrolyte alone or a separator in which the polymer solid electrolyte is supported.

(A) Electrolyte solution soaked in separator As electrolyte solution that can be soaked in separator, electrolyte solution contained in polymer gel electrolyte of the above-mentioned “positive electrode material of lithium ion battery of the present invention” The same as (electrolyte salt and plasticizer) can be used. Therefore, a preferred example of the electrolytic solution is shown here, and a detailed description thereof is omitted. As a preferable example of such an electrolytic solution, the concentration of the electrolyte is adjusted to 0.5 to 2 mol / liter by dissolving the following electrolyte in the following solvent. However, the present invention should not be limited to these. Here, as the electrolyte, for example, at least one of LiClO ₄ , LiAsF ₆ , LiPF ₅ , LiBOB, LiCF ₃ SO ₃ and Li (CF ₃ SO ₂ ) ₂ can be suitably used. Examples of the solvent include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1, At least one of ethers composed of 3-dioxolane and γ-butyllactone can be suitably used.

  The separator is not particularly limited, and a conventionally known separator can be used. For example, a porous sheet made of a polymer that absorbs and holds the electrolytic solution (for example, a polyolefin microporous material). Separator, etc.), a nonwoven fabric separator, etc. can be used. The polyolefin microporous separator having the property of being chemically stable to an organic solvent has an excellent effect that the reactivity with the electrolyte (electrolytic solution) can be kept low.

  Examples of the material for the porous sheet such as the polyolefin-based microporous separator include a laminate having a three-layer structure of polyethylene (PE), polypropylene (PP), PP / PE / PP, and polyimide.

  As the material of the nonwoven fabric separator, for example, conventionally known materials such as cotton, rayon, acetate, nylon, polyester, polypropylene, polyethylene and other polyolefins, polyimide, and aramid can be used, and the purpose of use (machines required for the electrolyte layer) Depending on strength, etc., they are used alone or in combination.

  The bulk density of the nonwoven fabric separator is not particularly limited as long as sufficient battery characteristics can be obtained by the impregnated polymer gel electrolyte. That is, if the bulk density of the nonwoven fabric separator is too large, the proportion of the non-electrolyte material in the electrolyte layer becomes too large, and the ionic conductivity and the like in the electrolyte layer may be impaired.

  The thickness of the separator cannot be unambiguously defined because it varies depending on the application, but in applications such as a secondary battery for driving a motor such as a hybrid vehicle, an electric vehicle, and a fuel cell vehicle, it is 5 to 200 μm. It is desirable that When the thickness of the separator is within such a range, it is possible to suppress increase in retention and resistance. In addition, there is an effect of securing mechanical strength in the thickness direction and ensuring high output performance because it is desirable to prevent a short circuit caused by fine particles entering the separator and to narrow the space between the electrodes for high output. . In addition, when a plurality of batteries are connected, the electrode area increases, so that it is desirable to use a thick separator in the above range in order to increase the reliability of the battery.

  It is desirable that the fine pore diameter of the separator (polyolefin-based microporous separator or the like) is 1 μm or less (usually a pore diameter of about several tens of nm). Due to the fact that the average diameter of the micropores in the separator is within the above range, the “shutdown phenomenon” that the separator melts due to heat and the micropores close quickly occurs, resulting in higher reliability during abnormalities, resulting in heat resistance. Has the effect of improving. In other words, when the battery temperature rises due to overcharging (in an abnormal state), the “shutdown phenomenon” that the separator melts and closes the micropores occurs quickly, so that the positive electrode (+) of the battery (electrode) Li ions cannot pass through to the negative electrode (−) side, and no further charge is possible. As a result, overcharging cannot be performed and overcharging is eliminated. As a result, the heat resistance (safety) of the battery is improved, and it is possible to prevent gas from being released and the heat fusion part (seal part) of the battery exterior material from being opened. Here, the average diameter of the micropores of the separator is calculated as an average diameter obtained by observing the separator with a scanning electron microscope or the like and statistically processing the photograph with an image analyzer or the like.

  The porosity of the separator (such as a polyolefin microporous separator) is desirably 20 to 50%. The separator's porosity is within the above range, preventing output from being reduced due to the resistance of the electrolyte (electrolyte), and preventing the short circuit due to fine particles penetrating the separator's pores (micropores). It has the effect of securing both sexes. Here, the porosity of the separator is a value obtained as a volume ratio from the density of the raw material resin and the density of the separator of the final product.

  The porosity of the nonwoven fabric separator is preferably 50 to 90%. If the porosity is less than 50%, the electrolyte retention deteriorates, and if it exceeds 90%, the strength is insufficient.

  The amount of the electrolytic solution impregnated in the separator may be impregnated to the range of the liquid retention capacity of the separator, but may be impregnated beyond the liquid retention capacity range. This can prevent impregnation of the electrolyte from the electrolyte layer by injecting a resin into the electrolyte seal portion, and therefore can be impregnated as long as the electrolyte layer can be retained. The electrolyte can be impregnated in the separator by a conventionally known method, for example, the electrolyte can be completely sealed after being injected by a vacuum injection method or the like.

(B) A polymer gel electrolyte alone or a separator impregnated and supported with the polymer gel electrolyte and (c) A polymer solid electrolyte alone or a separator with the polymer solid electrolyte supported High Regarding the molecular gel electrolyte and the solid polymer electrolyte, since the same polymer gel electrolyte and solid polymer electrolyte as the positive electrode material of the lithium ion battery of the present invention described above can be used, the description here Is omitted. Further, regarding the separator, since the same separator as that described in the section (a) where the separator is impregnated with the electrolytic solution can be used, description thereof is omitted here.

  The above (b) includes those obtained by impregnating and supporting a polymer gel electrolyte in a separator. In this case, the amount of the polymer gel electrolyte impregnated / supported in the separator may be impregnated / supported up to the range of the liquid retention / retention capacity of the separator. May be. This is because resin can be injected into the electrolyte seal portion to prevent the electrolyte solution from leaking out from the electrolyte layer (mainly polymer gel electrolyte), so that the electrolyte layer can be impregnated and supported as long as it can be retained and retained. Is possible. The polymer gel electrolyte is a polymer electrolyte raw material host polymer, an electrolytic solution or a lithium salt applied to and impregnated in the separator, and then heated to crosslink the host polymer, and the separator is impregnated with the polymer gel electrolyte. What is necessary is just to carry | support, and it does not restrict | limit in particular.

  The above (c) also includes those in which a polymer solid electrolyte is supported on a separator. In this case, the amount of the solid polymer electrolyte supported on the separator may be supported up to the holding capacity range of the separator, but may be supported beyond the holding capacity range. Since there is no electrolyte solution that causes the electrolyte layer to bleed out, there is no risk of liquid junction. Therefore, the electrolyte layer can be supported as long as it can be held in the electrolyte layer. The polymer solid electrolyte is applied to the separator with the host polymer, solvent (mainly viscosity adjusting solvent) or lithium salt as the raw material of the polymer electrolyte, and heated to crosslink the host polymer and remove the solvent. The separator is not particularly limited, for example, a polymer solid electrolyte may be supported on the separator.

  The electrolyte layers (a) to (c) may be used in one battery.

  In addition, the polymer electrolyte may be included in the polymer gel electrolyte layer, the positive electrode active material layer, and the negative electrode active material layer, but the same polymer electrolyte may be used, or different polymer electrolytes may be used depending on the layer. Good.

  By the way, a host polymer for a polymer gel electrolyte that is preferably used at present is a polyether polymer such as PEO and PPO. For this reason, the oxidation resistance on the positive electrode side under high temperature conditions is weak. Therefore, when using a positive electrode material having a high oxidation-reduction potential, the capacity of the negative electrode (active material layer) is preferably smaller than the capacity of the positive electrode (active material layer) opposed via the polymer gel electrolyte layer. When the capacity of the negative electrode (active material layer) is less than the capacity of the opposing positive electrode (active material layer), it is possible to prevent the positive electrode potential from rising excessively at the end of charging. In addition, the capacity | capacitance of a positive electrode (active material layer) and a negative electrode (active material layer) can be calculated | required from manufacturing conditions as theoretical capacity | capacitance at the time of manufacturing a positive electrode (active material layer) and a negative electrode (active material layer). You may measure the capacity | capacitance of a finished product directly with a measuring device. However, if the capacity of the negative electrode (active material layer) is smaller than the capacity of the opposing positive electrode (active material layer), the negative electrode potential will drop too much and the durability of the battery may be impaired. There is a need. For example, care should be taken not to lower the durability by setting the average charge voltage of one cell (single cell layer) to an appropriate value for the oxidation-reduction potential of the positive electrode active material.

  The thickness of the electrolyte layer constituting the battery is not particularly limited. However, in order to obtain a compact battery, it is preferable to make it as thin as possible within a range in which the function as an electrolyte can be ensured, and the thickness of the electrolyte layer is preferably 5 to 200 μm.

[Positive electrode and negative electrode terminal plate]
When using positive and negative terminal plates, in addition to having a function as a terminal, it is better to be as thin as possible from the viewpoint of thinning, but the laminated electrode, electrolyte and current collector all have mechanical strength. Since it is weak, it is desirable to have strength to sandwich and support these from both sides. Furthermore, it can be said that the thickness of the positive electrode and the negative electrode terminal plate is usually preferably about 0.1 to 2 mm from the viewpoint of suppressing the internal resistance at the terminal portion.

  As materials for the positive electrode and the negative electrode terminal plate, materials used in a conventionally known lithium ion battery can be used. For example, aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof can be used. Aluminum is preferably used from the viewpoints of corrosion resistance, ease of production, economy, and the like.

  The material of the positive electrode terminal plate and the negative electrode terminal plate may be the same material or different materials. Furthermore, the positive electrode and the negative electrode terminal plate may be a laminate of different materials.

[Positive electrode and negative electrode lead]
Regarding the positive electrode and the negative electrode lead, the same lead as that used in a conventionally known lithium ion battery can be used. In addition, the part taken out from the battery exterior material (battery case) does not affect the product (for example, automobile parts, especially electronic devices, etc.) by contacting with peripheral devices or wiring and leaking electricity. It is preferable to coat with a heat-resistant insulating heat shrinkable tube or the like.

[Battery exterior material (battery case)]
In a lithium ion battery, in order to prevent external impact and environmental degradation during use, it is desirable to accommodate the entire battery stack or battery winding body, which is the battery body, in a battery exterior material or battery case. From the viewpoint of weight reduction, a polymer-metal composite laminate film in which both surfaces of metals (including alloys) such as aluminum, stainless steel, nickel, and copper are covered with an insulator (preferably a heat-resistant insulator) such as a polypropylene film. It is preferable that the battery stack is housed and sealed by joining a part or all of the peripheral part thereof by heat fusion using a conventionally known battery exterior material. In this case, the positive electrode and the negative electrode lead may be structured to be sandwiched between the heat-sealed portions and exposed to the outside of the battery exterior material. In addition, it is preferable to use a polymer-metal composite laminate film having excellent thermal conductivity because heat can be efficiently transmitted from a heat source of an automobile and the inside of the battery can be quickly heated to the battery operating temperature.

  The polymer-metal composite laminate film is not particularly limited, and a conventionally known film in which a metal film is disposed between polymer films and the whole is laminated and integrated can be used. As specific examples, for example, an outer protective layer made of a polymer film (laminate outermost layer), a metal film layer, a heat-sealing layer made of a polymer film (laminate innermost layer), and the whole is laminated and integrated. The thing which becomes. Specifically, in the polymer-metal composite laminate film used for the exterior material, a heat-resistant insulating resin film is first formed as a polymer film on both surfaces of the metal film, and heat fusion is performed on at least one heat-resistant insulating resin film. An insulating insulating film is laminated. Such a laminate film is heat-sealed by an appropriate method, whereby the heat-welding insulating film portion is fused and joined to form a heat-sealing portion. An example of the metal film is an aluminum film. Moreover, as said insulating resin film, a polyethylene tetraphthalate film (heat-resistant insulating film), a nylon film (heat-resistant insulating film), a polyethylene film (heat-bonding insulating film), a polypropylene film (heat-bonding insulating film) ) Etc. can be illustrated. However, the exterior material of the present invention should not be limited to these.

  In such a laminate film, it is possible to easily and surely join one to one (bag-like) laminate films by heat fusion using a heat fusion insulating film by ultrasonic welding or the like. In order to maximize the long-term reliability of the battery, metal films that are constituent elements of the laminate sheet may be directly joined. Ultrasonic welding can be used to join the metal films by removing or destroying the heat-fusible resin between the metal films.

  The lithium ion secondary battery of the present invention may be a bipolar lithium ion secondary battery (also referred to as a bipolar battery) or a non-bipolar lithium ion secondary battery (also referred to as a non-bipolar battery). Also good.

  Next, as the use of the lithium ion secondary battery of the present invention, for example, as a large-capacity power source such as a hybrid vehicle, an electric vehicle or a hybrid electric vehicle, a fuel cell vehicle or a hybrid fuel cell vehicle, a high energy density and a high output density. Therefore, it can be suitably used for a vehicle driving power source and an auxiliary power source that require the above. In this case, it is desirable that the assembled battery is constructed by connecting a plurality of lithium ion secondary batteries of the present invention. That is, in the present invention, a plurality of the lithium ion secondary batteries are used as an assembled battery (vehicle submodule) using at least one of a parallel connection, a series connection, a parallel-series connection, or a series-parallel connection. it can. This makes it possible to meet the demands for capacity and voltage for various types of vehicles by combining basic batteries. As a result, it becomes possible to facilitate the design selectivity of required energy and output. For this reason, it is not necessary to design and produce different batteries for various vehicles, and it becomes possible to mass-produce basic batteries and to reduce costs by mass production.

  The other constituent requirements of the assembled battery should not be limited at all, and the same constituent requirements as the assembled battery using the existing lithium ion secondary battery can be applied as appropriate. Since conventionally known components and manufacturing techniques for assembled batteries can be used, the description thereof is omitted here.

  Next, by forming at least two or more of the above assembled batteries in series, parallel, or a composite battery in which the series and parallel are connected in combination, a new assembled battery is produced to meet the battery capacity and output requirements for each purpose of use. Therefore, it becomes possible to cope with relatively low cost. That is, the composite battery pack of the present invention is characterized in that at least two or more battery packs are connected in series, in parallel, or in series and parallel, and a reference battery pack is manufactured and combined. By using an assembled battery, the specifications of the assembled battery can be tuned. Thereby, since it is not necessary to manufacture many assembled battery types with different specifications, the composite assembled battery cost can be reduced. Further, the assembled battery of the present invention is not particularly limited, such as a battery composed of only the bipolar battery or non-bipolar battery of the present invention, or a combination of the bipolar battery of the present invention and a non-bipolar battery. . Furthermore, if necessary, the lithium ion secondary battery of the present invention and an existing lithium ion secondary battery can be used in appropriate combination.

  Moreover, in the said composite assembled battery, it is desirable to connect the some assembled battery which comprises this so that attachment or detachment is possible respectively. As described above, in the composite assembled battery in which a plurality of assembled batteries are connected in series and parallel, even if some of the batteries and the assembled battery fail, the repair can be performed only by replacing the failed part.

  The vehicle according to the present invention is characterized in that the assembled battery and / or the composite assembled battery is mounted. This makes it possible to meet a large vehicle demand for space by using a light and small battery. By reducing the battery space, the weight of the vehicle can be reduced.

  For example, in order to mount the composite assembled battery on a vehicle such as a hybrid car, an electric vehicle, or a fuel cell, the composite assembled battery is mounted under a seat (seat) at the center of the vehicle body of the vehicle. This is because if it is installed under the seat, the interior space and the trunk room can be widened. The place where the battery is mounted is not limited to under the seat, but may be under the floor of the vehicle, behind the seat back, under the rear trunk room, or in the engine room in front of the vehicle.

  In the present invention, not only the composite battery pack but also the battery pack may be mounted on the vehicle depending on the intended use, or the composite battery pack and the battery pack may be mounted in combination. In addition, as a vehicle in which the assembled battery and / or the composite assembled battery of the present invention can be mounted as, for example, a driving power supply or an auxiliary power supply, an ordinary hybrid car (a gasoline engine and the assembled battery of the present invention and / or Combinations of composite assembled batteries), electric vehicles, hybrid electric vehicles, fuel cell vehicles, hybrid fuel cell vehicles and the like are preferable, but are not limited thereto.

  Hereinafter, the content of the present invention will be described with reference to examples and comparative examples, but the present invention is not limited to these examples.

Reference example 1
I. Preparation of positive electrode active material First, a positive electrode active material was prepared by the following procedure.

(Preparation of positive electrode active material core)
LiNiO ₂ was produced by a coprecipitation method. Specifically, an aqueous solution of lithium hydroxide LiOH (H ₂ O) and nickel hydroxide Ni (OH) ₂ was prepared so that the molar ratio of Li and Ni was 1: 1, and stirred while heating at 200 ° C. More than 95% of the total was evaporated. After that, it was transferred to a ceramic crucible, heated in air at 100 ° C./h, and pre-baked at 400 ° C. for 12 hours. After the preliminary firing, firing was performed at 800 ° C. in oxygen 2% or oxygen atmosphere for 24 hours to obtain a layered lithium nickel composite oxide (LiNiO ₂ ) having an average particle diameter of 10 μm as core part particles.

(Preparation of positive electrode active material shell)
An aqueous solution of lithium nitrate LiCO ₃ and manganese nitrate Mn (CO ₃ ) ₂ was prepared so that the molar ratio of Li and Mn was 1: 2, and the above core part particles were added and stirred while heating at 200 ° C. % Or more was evaporated. After that, it was transferred to a ceramic crucible, heated in air at 100 ° C./h, and pre-baked at 400 ° C. for 12 hours. After preliminary firing, active material particles having an average thickness of spinel-based lithium nickel composite oxide (LiMn ₂ O ₄ ) of 0.5 μm are fired at 600 ° C., 2% oxygen or in an oxygen atmosphere for 24 hours. Was obtained (see FIG. 1A). The average particle diameter of the obtained active material particles was 11.0 μm.

II. Production of Lithium Ion Secondary Battery Next, a lithium ion secondary battery was produced by the following procedure.

(Formation of positive electrode)
The above active material particles (85% by mass) were used as the positive electrode active material, acetylene black (5% by mass) was used as the conductive additive, and polyvinylidene fluoride (10% by mass) was used as the binder. These were dispersed in a solvent (N-methylpyrrolidone) to obtain a positive electrode slurry. The slurry was applied to one side of an aluminum foil having a thickness of 20 μm, and pressurized and dried to form a positive electrode having a thickness of 40 μm.

(Formation of negative electrode)
Graphite (85% by mass) having an average particle diameter of 10 μm as a negative electrode active material and polyvinylidene fluoride (10% by mass) as a binder were used. These were dispersed in a solvent (N-methylpyrrolidone) to obtain a negative electrode slurry. The slurry was applied to one side of a 20 μm thick copper foil, and pressed and dried to form a negative electrode having a thickness of 40 μm.

(Production of battery)
The formed positive electrode and negative electrode are overlapped with a separator (polypropylene porous membrane, thickness 25 μm) and stored in a laminate cell, and then an electrolytic solution (ethylene carbonate containing 1 mol / L of LiPF ₆ and diethyl carbonate 1: 1). (Mixed solution of (volume ratio)) was poured, and the opening of the laminate film was sealed under reduced pressure to prepare a lithium ion secondary battery (unit cell).

III. Battery performance evaluation Next, the performance evaluation of the obtained lithium ion secondary battery (unit cell) was performed according to the following procedure.

(Initial charge)
The produced unit cell was charged with a constant current (CC) to 2.7 V, and then charged with a constant voltage (CV) for a total of 15 hours.

(Measurement of resistance)
The so-called “high output battery” is a battery that can output for a certain time (for example, 5 seconds) at a large current, in other words, a battery having a small voltage drop, that is, a resistance. Therefore, the produced single cell was discharged for 5 seconds from full charge (potential V ₀ [V]) at a current density I [A / cm ² ] equivalent to 50 CA (per electrode area) calculated from the theoretical capacity of the active material. The resistance value R [Ωcm ² ] was calculated from the potential V ₅ [V] and I after 5 seconds. Ie

1 / R was used as an index of output characteristics.

(Capacity measurement)
In the produced unit cell, discharge was performed from full charge to 2.7 V with a 0.2 CA current value calculated from the active material theoretical capacity, and the value obtained by dividing the product of the discharge time and current by the active material weight was defined as the capacity.

Reference example 2
A lithium ion secondary battery was prepared in the same manner as in Reference Example 1 except that the average thickness of the shell portion was 0.75 μm and the average particle diameter of the active material particles was 11.5 μm. And the capacity were measured.

Reference example 3
A lithium ion secondary battery was prepared in the same manner as in Reference Example 1 except that the average thickness of the shell portion was 0.3 μm and the average particle diameter of the active material particles was 10.6 μm. And the capacity were measured.

Example 4
A lithium ion secondary battery was prepared in the same manner as in Reference Example 1, except that the average particle diameter of the core part particles was 5 μm, the average thickness of the shell part was 0.25 μm, and the average particle diameter of the active material particles was 5.5 μm. The initial charge was performed, the resistance was measured, and the capacity was measured.

Example 5
A lithium ion secondary battery was prepared in the same manner as in Reference Example 1 except that the average particle diameter of the core part particles was 3 μm, the average thickness of the shell part was 0.15 μm, and the average particle diameter of the active material particles was 3.3 μm. The initial charge was performed, the resistance was measured, and the capacity was measured.

Reference Example 6
A lithium ion secondary battery was prepared in the same manner as in Reference Example 1 except that the average thickness of the shell portion was 1.3 μm and the average particle diameter of the active material particles was 12.6 μm. And the capacity were measured.

Comparative Example 1
In the step of (preparation of positive electrode active material core part), LiMn ₂ O ₄ particles having an average particle diameter of 10 μm are prepared by coprecipitation method, and the obtained core part particles are used as a positive electrode active material, and (positive electrode active material shell part) A lithium ion secondary battery was produced in the same manner as in Reference Example 1 except that the step of (Production) was omitted, and the initial charge was performed, the resistance was measured, and the capacity was measured.

Specifically, the LiMn ₂ O ₄ particles are prepared by preparing an aqueous solution of lithium nitrate LiCO ₃ and manganese nitrate Mn (CO ₃ ) ₂ so that the molar ratio of Li and Mn is 1: 2, and heating at 200 ° C. Stirring was performed to evaporate more than 95% of the water. After that, it was transferred to a ceramic crucible, heated in air at 100 ° C./h, and pre-baked at 400 ° C. for 12 hours. After the preliminary firing, firing was performed at 600 ° C. in oxygen 2% or in an oxygen atmosphere for 24 hours to obtain spinel-based lithium manganese composite oxide (LiMn ₂ O ₄ ) having an average particle size of 10 μm as core part particles.

Comparative Example 2
In the step of (preparation of positive electrode active material core portion), LiNiO ₂ particles having an average particle diameter of 10 μm are prepared, and the obtained core portion particles are used as the positive electrode active material, and the step of (preparation of positive electrode active material shell portion) is performed. A lithium ion secondary battery was produced in the same manner as in Reference Example 1 except that the description was omitted, and the initial charge was performed, the resistance was measured, and the capacity was measured.

Comparative Example 3
In the step of (preparation of positive electrode active material core part), LiMn ₂ O ₄ particles having an average particle diameter of 10 μm and LiNiO ₂ particles having an average particle diameter of 10 μm are respectively prepared, and these core part particles are used as the LiMn ₂ O ₄ particles. A lithium ion secondary battery was prepared in the same manner as in Reference Example 1 except that the mixture of LiNiO ₂ particles in a volume ratio of 3: 7 was used as the positive electrode active material, and the step of (preparation of positive electrode active material shell) was omitted. The first charge was made, the resistance was measured, and the capacity was measured.

Table 2 shown below shows the relative output and capacity based on Comparative Example 1 for each Example , Reference Example, and Comparative Example.

  Note) The volume ratio of the core active material and the shell active material is a ratio to the whole active material particles.

As shown in Table 2, the capacity of each of Examples 4 to 5 and Reference Examples 1 to 3 and 6 was improved as compared with Comparative Example 1. In Reference Example 6, the capacity improvement margin was slightly reduced as compared with other Examples 4 to 5 and Reference Examples 1 to 3 . This is presumably because the specific volume of the active material layer in the shell part is large and relatively thick, so that the improvement in capacity derived from LiNiO ₂ is small. Note improvement margin of capacity in each of Examples 4-5 and the Reference Examples 1 to 3 and 6, from simply capacity determined from the capacitance and the volume ratio of LiMn ₂ O ₄ and LiNiO ₂ are slightly below. This is considered because there is resistance when lithium ions move between LiNiO ₂ in the core part and LiMn ₂ O _{4 in the} shell part.

  Further, in Examples 4 and 5, by reducing the average particle size, the effective surface area due to the high-power active material (material) of the shell portion covering the particle surface increases, so that the apparent output performance is improved. It is thought that there is. The output performance was considered to be almost equivalent when the particle size was about 10 μm.

FIG. 1A is an embodiment of a battery active material according to the present invention, which has a core-shell type structure with different active material materials in the particles, and the shell portion is layered so as to cover the entire surface of the core portion. It is a cross-sectional schematic diagram of the active material particle showing a mode that it is arrange | positioned. FIG. 1B is another embodiment of the battery active material of the present invention, and has a structure in which an elution preventing layer is further provided in a layer form on the outside of the shell portion of FIG. 1A so as to cover the entire surface of the shell portion. It is the cross-sectional schematic diagram of the active material particle showing a mode that it has become. FIG. 1C shows still another embodiment of the battery active material of the present invention, which has a core-shell type structure with different active material materials inside the particles, and the shell portion uses a large number of fine particles (powder). It is a cross-sectional schematic diagram of the active material particle showing a mode that it is arrange | positioned so that it may cover (attach). FIG. 2A is an embodiment of the battery active material of the present invention, and is a layered nickel-based lithium ion metal composite that is a suitable kind of material of the core part constituting the core-shell type structure of the active material particles. it is a schematic view showing the crystal structure of; _(M = Ni LiMO 2) oxide. FIG. 2BA is an embodiment of the battery active material of the present invention, and is a spinel manganese-based lithium metal composite oxide, which is a suitable kind of material of the shell part constituting the core-shell type structure of the active material particles. it is a schematic view showing the crystal structure _{of; (M = Mn LiM 2 O} 4).

Explanation of symbols

1 Shell portion of positive electrode active material particles,
2 core part of positive electrode active material particles,
3 The whole positive electrode active material particles,
4 Elution prevention layer.

Claims (11)

A positive electrode active material for a lithium ion secondary battery, composed of at least two or more active materials, the material core in particles - has a shell structure, the shell relative to the active material of the core portion Part of the active material is high power,
Active material of the core portion is a lithium-metal composite oxide,
Active material of the shell portion is a lithium-metal composite oxide having a spinel manganese,
The active material of the core part has a higher capacity than the active material of the shell part,
The average particle diameter of the core portion is 3 to 5 [mu] m, the positive electrode active material for a lithium ion secondary battery, wherein the average thickness of the shell portion is 0.15～0.25Myuemu. A positive electrode active material for a lithium ion secondary battery according to claim 1, the active material of the shell portion, partially replacing some of the manganese lithium-metal composite oxide of the spinel manganese another element the positive electrode active material for you ruri lithium ion secondary battery and characterized in that to those were. A positive electrode active material for a lithium ion secondary battery as claimed in claim 2, the element substituting a part of manganese lithium-metal composite oxide of the spinel manganese is lithium, boron, phosphorus, nitrogen, magnesium, For lithium ion secondary batteries characterized by being any one of aluminum, calcium, vanadium, titanium, chromium, nickel, iron, cobalt, copper, zinc, strontium, zirconium, niobium, molybdenum, tin, or a combination thereof The positive electrode active material. A positive electrode active material for a lithium ion secondary battery according to claims 1 to 3, the active material of the core portion, for a lithium ion secondary battery which is a lithium-metal composite oxide of nickel-based The positive electrode active material. A positive electrode active material for a lithium ion secondary battery according to claim 4, the active material of the core portion was partially substituted part of nickel of lithium-metal composite oxide of nickel to other elements the positive electrode active material for lithium ion secondary battery, characterized in that. A positive electrode active material for a lithium ion secondary battery according to claim 5, the element substituting a part of nickel of lithium-metal composite oxide of nickel-based is selected from the group consisting of lithium, boron, phosphorus, nitrogen, magnesium, aluminum , Calcium, vanadium, titanium, chromium, manganese, iron, cobalt, copper, zinc, strontium, zirconium, niobium, molybdenum, tin, or a combination thereof, and a positive electrode for a lithium ion secondary battery Active material. A positive electrode active material for a lithium ion secondary battery according to claims 1 to 6, the average volume of the shell portion, the positive electrode active material for lithium ion secondary batteries, characterized by more than 40% of the total. A positive electrode active material for a lithium ion secondary battery according to claims 1 to 7, and elution preventing layer is provided on the outside of the shell portion,
The material forming the pre-Symbol elution preventing layer, a lithium metal composite oxide partially substituted metal spinel manganese, lithium ion conductive polymer or a lithium ion secondary battery which is a mixture thereof, use the positive electrode active material. A method of manufacturing a lithium ion secondary battery positive electrode active material according to claims 1 to 8, the shell portion by sintering applied again raw shell portion onto the preformed core portion of the particles method for producing a positive electrode active material for a lithium ion secondary battery, and forming. A method of manufacturing a lithium ion secondary battery positive electrode active material according to claim 1 to 8, the positive electrode for a lithium ion secondary battery, characterized by forming the shell portion by CVD on the particles of the core portion A method for producing an active material. Part or lithium ion secondary battery using the whole of the claims 1 to 10 a positive electrode active material for a lithium ion secondary battery positive electrode active material.