JP2013054418A - Simulation method for particle filling structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reproduce a particle filling structure constituting a whole solid battery by simulation.SOLUTION: The simulation method for particle filling structure includes: a mass point arrangement step for arranging, on respective surfaces of a plurality of particles, the same number of mass points (200) despite the dimension of each of the plurality of particles (100); and a repulsive force setting step for setting a repulsive force (E) of mass points that are arranged on the surface of one particle of the plurality of particles with respect to mass points that are arranged on the surface of another particle of the plurality of particles, according to an interval (AS) between the mass points arranged on the surface of the one particle.

Description

  The present invention relates to a technical field of a particle packed structure simulation method for performing a simulation related to a packed structure of particles packed in a certain space.

  As a method of this kind, for example, a particle aggregate is placed in a space of a predetermined size, is allowed to fall freely from a particle having a low center of gravity, and in the dropping process, the degree of freedom in the horizontal direction or existing particles is transmitted. A method has been proposed in which a particle permeation coefficient is given as a condition and a particle packing structure is simulated by placing particles at the bottom (see Patent Document 1). Alternatively, there has been proposed a powder behavior calculation method based on an individual element method in consideration of interparticle contact and electrostatic and magnetic interaction (see Patent Document 2).

JP-A-8-190576 JP 2005-122354 A

  By the way, for example, in order to improve the safety of a battery mounted on a vehicle such as a hybrid vehicle or an electric vehicle, development of an all-solid battery using, for example, a solid electrolyte or the like has been advanced. The all-solid-state battery is produced, for example, by pressing and solidifying an active material and electrolyte particles after placing them in a mold. In the field of handling particles such as powders and granules, it is one of the important issues to grasp the behavior of the particles, and the above-described simulation is used to grasp the behavior of the particles. There are many cases.

  However, Patent Document 1 has a technical problem that the repulsive force acting between the particles is not considered. Moreover, in the said patent document 2, since the particle | grain is handled as a point when calculating the interaction which acts between particle | grains, there exists a technical problem that sufficient accuracy may not be acquired.

  The present invention has been made in view of the above problems, for example, and an object of the present invention is to propose a particle-packed structure simulation method capable of reproducing the packed structure of particles constituting an all-solid battery.

  In order to solve the above problems, the particle packed structure simulation method of the present invention includes a mass point arranging step of arranging the same number of mass points on the surface of each of the plurality of particles regardless of the size of each of the plurality of particles, The repulsive force of the mass arranged on the surface of one of the particles to the mass arranged on the surface of the other of the plurality of particles is determined between the masses arranged on the surface of the one of the particles. And a repulsive force setting step that is set according to the interval.

  According to the particle packing structure simulation method of the present invention, in the mass point arranging step, the same number of mass points are arranged on the surface of each of the plurality of particles regardless of the size of each of the plurality of particles. The mass points arranged on the surface of each particle may be arbitrarily arranged on the surface of the particle, but are desirably arranged at equal intervals. The number of mass points arranged on the surface of one particle is desirably large to some extent (for example, several tens) so that the particle filling structure simulation method can be applied to relatively large particles.

  In the repulsive force setting step, the repulsive force of the mass point arranged on the surface of one of the plurality of particles to the mass point arranged on the surface of the other particle of the plurality of particles is the surface of the one particle It is set according to the interval between the mass points arranged in.

  In the present invention, as described above, the same number of mass points are arranged on all particles regardless of the size of the particles. For this reason, the smaller the size of the particles, the higher the surface density of the mass points related to the particles. If the repulsive force of all the mass points is set to a constant value, the repulsive force against other particles increases as the particle size decreases.

  On the other hand, when the number of mass points arranged according to the size of the particles is changed, for example, the same number of particles having the same aspect ratio (that is, similar-shaped particles) having the same density but different particle representative dimensions are used. It has been found by the inventor's research that there is a possibility that threshold values of percolation that should be essentially the same may be different in the arranged similarity model.

  However, in the present invention, the repulsive force related to the mass point arranged on the surface of the one particle is set according to the interval between the mass points arranged on the surface of the one particle. For this reason, repulsive force against other particles can be similar between similar-shaped particles. Then, percolation thresholds can be made to coincide with each other in the similarity model. Therefore, according to the particle filling structure simulation method of the present invention, the particle filling structure constituting the all-solid-state battery can be accurately reproduced.

  The effect | action and other gain of this invention are clarified from the form for implementing demonstrated below.

It is a flowchart which shows the process of the simulation method which concerns on embodiment of this invention. It is a conceptual diagram which shows the concept of the main processes of the simulation method which concerns on embodiment of this invention. It is a figure which shows an example of the simulation result which concerns on embodiment of this invention. It is a figure which shows an example of the relationship between the value which divided the mass point distance r which concerns on embodiment of this invention by the particle | grain internal mass point distance AS, and the potential energy E between mass points. It is a figure which shows an example of the relationship between the volume density of the particle | grains which concern on embodiment of this invention, and the ratio of a coupling | bonding particle | grain. It is a figure which shows an example of the relationship between the distance between the mass points which concerns on a comparative example, and the potential energy between mass points. It is a figure which shows an example of the relationship between the volume density of the particle | grains concerning a comparative example, and the ratio of a coupling | bonding particle | grain.

  Hereinafter, an embodiment of a particle filling structure simulation method according to the present invention will be described with reference to the drawings.

  First, an overall processing flow of the particle packing structure simulation method according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a flowchart showing the process of the simulation method according to this embodiment, and FIG. 2 is a conceptual diagram showing the concept of the main process of the simulation method according to this embodiment.

  In FIG. 1, first, a plurality of ellipsoids 100 (see FIG. 2) as an example of “particles” according to the present invention simulating an active material constituting a compacted all-solid battery are generated (step S101). Here, for the ellipsoid 100, for example, the major axis radius of the ellipsoid 100, the standard deviation of the major axis radius, the aspect ratio of the ellipsoid 100, the standard deviation of the aspect ratio, the number of ellipsoids 100, and the like are designated. Is generated. The values of various parameters such as the major axis radius of the ellipsoid 100 may be obtained by measuring an actual active material, or may be arbitrarily determined by an analyst (that is, a user).

  Next, as shown in FIG. 2A, in the mass point arranging step, a plurality of mass points 200 are arranged on the surface of the ellipsoid 100 at regular intervals, for example (step S102). At this time, the number of mass points 200 arranged on the surface of the ellipsoid 100 is constant regardless of the size of the ellipsoid 100.

  In order to avoid the overlapping of the ellipsoids 100 at the time of compression, the distance between the mass points 200 should be narrow, but since the number of the mass points 200 increases, the time spent for the compression process is long. Become. For this reason, the number of mass points 200 may be adjusted according to, for example, required accuracy of the simulation result, analysis time, and the like.

  Next, as shown in FIG. 2B, in the particle arrangement step, each of the plurality of ellipsoids 100 is arranged in the space 1 so as not to overlap each other (step S103). Here, the “space 1” is set to have a volume sufficiently larger than the total volume that is the sum of the volumes of the plurality of particles.

  In order to avoid the occurrence of overlapping of the ellipsoids 100, for example, among the major axis radii of each of the plurality of ellipsoids 100 generated in step S101, the space 1 has a longer interval than the longest major axis radius. The plurality of ellipsoids 100 may be arranged at regular intervals.

  Next, as shown in FIG. 2 (c), in the compression process, one ellipse is formed in a state where the relative positions of the mass points 200 of each of the plurality of ellipsoids 100 are fixed (that is, the ellipsoid 100 is a rigid body). A repulsive potential energy (ie, repulsive force) acting between the mass point of the body and the mass point of another ellipsoid different from the one ellipsoid is set. The space is compressed to the density 1 '(step S104).

  The volume of the space 1 ′ after compression is determined by, for example, an ellipsoid total volume that is the sum of the volumes of the plurality of ellipsoids 100 and a preset volume density. Further, in the compression process, the motion speed of the ellipsoids 100 is reduced, and the system temperature is cooled in order to avoid overlapping of the ellipsoids 100.

  As a result of the processing in steps S101 to S104 described above, for example, an active material model as shown in FIG. 3 is obtained. FIG. 3 is a diagram illustrating an example of a simulation result according to the present embodiment. FIG. 3A is an example of a simulation result when the particle (that is, the ellipsoid 100) is relatively small, and FIG. 3B is an example of the simulation result when the particle is relatively large. Here, the particles according to FIG. 3A and the particles according to FIG. 3B are similar to each other.

  Particularly in the present embodiment, the repulsive potential energy is set as follows. That is, the distance r between one mass point of one ellipsoid and one mass point of another ellipsoid is defined as an interval between adjacent mass points in the one ellipsoid (hereinafter referred to as “particle internal mass point interval” as appropriate). If the value divided by AS is the same between similar ellipsoids, the repulsive potential energy of one mass point of the one ellipsoid to the mass point of the other ellipsoid is Set to be the same regardless of body size.

  Specifically, in this embodiment, the potential energy is obtained using the following formula (1).

(1)
Here, “E” is a potential energy between mass points, and “r _c ” is a cutoff value. The above equation (1) is a Morse-type potential function, and the parameters “D ₀ ”, “α”, and “r ₀ ” are “depth of well of potential curve”, “curvature of potential curve” and It means “minimum point of potential curve”.

Particularly in this embodiment, the cut-off value r _c is set as (between particles in mass distance AS) × (coefficient 1). The parameter r ₀ is set as (particle internal point distance AS) × (coefficient 2). “Coefficient 1” and “Coefficient 2” are, for example, “3” and “5”, respectively.

Each of the parameters “D ₀ ” and “α” is adjusted by trial and error repeatedly so that particle overlap does not occur in a region where the particle density is relatively high (for example, 70% or more). This is a common practice in the field of molecular dynamics.

When indicated particles is relatively small in FIG. 3 (a), the distance between the particles in the mass points AS, parameter _{D 0,} the parameter alpha, the parameter _{r 0} and the cutoff value _{r c,} respectively, for example, "0.23" , “10”, “3.78”, “1.36”, and “1.2”. On the other hand, if the larger particles shown in FIG. 3 (b), between the particles in the mass range AS, parameter _{D 0,} the parameter alpha, the parameter _{r 0} and the cutoff value _{r c,} respectively, for example, "0. “5”, “10”, “1.90”, “2.71”, and “2.5” are set.

  When the potential energy E is calculated using the parameters set in this way and the above equation (1), the similar particles are as shown in FIG. 4, for example. FIG. 4 is a diagram illustrating an example of a relationship between a value obtained by dividing the distance r according to the present embodiment by the inter-particle mass point distance AS and the potential energy E between the mass points.

  Then, when the processing of steps S101 to S104 is performed using the potential energy E between the mass points set as described above, the ratio of the coupled particles becomes, for example, as shown in FIG. FIG. 5 is a diagram illustrating an example of the relationship between the volume density of particles and the ratio of bonded particles according to the present embodiment.

  In FIG. 5, regardless of the size of the particles, the proportion of bound particles increases rapidly at the same particle density (here between 65% and 70%). Here, according to the particle coupling theory, the percolation threshold is said to be the same if the particles are similar to each other.

  As shown in FIG. 5, according to the particle packing structure simulation method according to the present embodiment, a simulation result consistent with the particle coupling theory can be obtained. As a result, according to the particle filling structure simulation method according to the present embodiment, the particle filling structure constituting the all-solid-state battery can be suitably reproduced.

<Comparative example>
Next, a comparative example of this embodiment will be described with reference to FIGS. In the comparative example, the cut-off value r _c and the parameter r _0, are set independently of the distance AS between the particles in the mass.

The calculation of the potential energy between the mass points, but using Equation (1) above, the parameter _{D 0,} the parameter alpha, the parameter _{r 0} and the cutoff value _{r c,} respectively, for example, "10", "5.0" , “1.11” and “1.0”. The calculated potential energy E between the mass points is, for example, as shown in FIG. FIG. 6 is a diagram showing an example of the relationship between the mass-point distance according to the comparative example and the potential energy between the mass points, which has the same concept as in FIG. 4.

  Using the potential energy E between the mass points shown in FIG. 6 and performing the above-described steps S101 to S104 on the small particle model and the large particle model that are similar to each other, the ratio of the coupled particles is, for example, As shown in FIG. FIG. 7 is a diagram showing an example of the relationship between the volume density of particles and the ratio of bonded particles according to a comparative example having the same meaning as in FIG. 5.

  As shown in FIG. 7, in the comparative example, although the particles are similar to each other, the percolation thresholds are different from each other. That is, in the simulation method according to the comparative example, it can be said that it is extremely difficult to sufficiently reproduce the packed structure of the particles constituting the all solid state battery.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. Simulation methods are also included in the technical scope of the present invention.

  1, 1 '... space, 100 ... ellipsoid, 200 ... mass point

Claims (2)

Regardless of the size of each of the plurality of particles, a mass point arrangement step of arranging the same number of mass points on the surface of each of the plurality of particles,
The repulsive force of the mass point arranged on the surface of one of the plurality of particles with respect to the mass point arranged on the surface of another particle of the plurality of particles, the mass point arranged on the surface of the one particle A repulsive force setting step to set according to the interval between each other;
A particle-packed structure simulation method comprising: A particle generating step for generating each of the plurality of particles;
A particle disposing step of disposing the plurality of particles in space so as not to overlap each other;
The particle packed structure simulation method according to claim 1, further comprising: