Patent ID: 12255310

MODE FOR INVENTION

Hereinafter, embodiments of the present invention will be described on detail with reference to the accompanying drawing so that those skilled in the art may easily practice the present invention. The present invention may be implemented in various different forms and is not limited to exemplary embodiments provided herein.

Portion unrelated to the description will be omitted to obviously describe the present disclosure, and same or similar portions will be denoted by same or similar reference numerals throughout the specification.

FIG.3is a conceptual diagram illustrating an apparatus for producing a precursor having a concentration gradient according to an exemplary embodiment of the present invention.FIG.4is a graph illustrating an injection amount of a material depending on a reaction time ideal for the apparatus for producing a precursor having a concentration gradient.FIG.5is a graph illustrating an injection amount of a material depending on a reaction time ideal for the apparatus for producing a precursor according to an exemplary embodiment of the present invention.FIG.6is a graph illustrating an injection amount of a material depending on a reaction time when a feed amount of a material of a Q1feed tank is simply calculated in a pattern in which it gradually decreases during a total process time.

Referring toFIG.3, the apparatus for producing a precursor having a concentration gradient according to an exemplary embodiment of the present invention includes two feed tanks Q1and Q2storing metal solutions having different composition ratios, a plurality of mixers Q3mixing the metal solutions having different a composition ratios injected from the two feed tanks Q1and Q2, and a plurality of reactors A, B, C, and D connected to the plurality of mixers Q3in a one-to-one corresponding manner and receiving the mixed metal solutions from the mixer Q3. In the present exemplary embodiment, the mixer Q3and the reactors A, B, C, and D are illustrated as four, respectively, but the number of them may be increased or decreased as necessary. In the apparatus for producing a precursor having a concentration gradient, the metal solutions having different composition ratios injected from the two feed tanks Q1and Q2are mixed in the mixer Q3in advance and then injected into the reactors A, B, C and D to perform the process. In the apparatus, a production capacity may be effectively increased or decreased only with the increase or decrease in the number of the mixer Q3and the reactors A, B, C and D.

In the apparatus for producing a precursor having a concentration gradient, an injection amount of the mixed materials injected from the mixer Q3into the reactors A, B, C, and D is constant, but in the feed flow rate injected from the two feed tanks Q1and Q2into the mixer Q3, the injection amount is required to be sequentially changed in a opposite pattern to each other in order to create a concentration gradient. The flow rate injected from the mixer Q3into the reactor may be simply expressed as Equation 1 below:
Feed flow rate ofQ3=(total amount ofQ1+total amount ofQ2)/reaction time  Equation 1

The feed flow rate of the mixer Q3is always constantly injected throughout the reaction time, but the feed flow rate injected from the two feed tanks Q1and Q2to the mixer Q3is to be the mixing ratio at which the concentration gradient is created in the mixer (Q3), and thus the injection schedules thereof are different from each other.FIG.4is a graph showing the most ideal schedule of the feed flow rate injected from the two feed tanks Q1and Q2to the mixer Q3.

However, in the mixer Q3, the reaction starts in a state in which the metal solution of the first feed tank Q1is filled at a predetermined amount (500 kg in the embodiment) in advance. As a result, during the reaction, the injection amount of the material of the first feed tank Q1is 500 kg or less than that of a second feed tank Q2, and after all the materials contained in the first feed tank Q1are consumed, 500 kg of the material contained in the mixer Q3is injected into the reactor. Thus, a graph for material feeding, as shown inFIG.5, is to be created.

However, in order to change a precursor concentration, as shown inFIG.1, a core portion of the precursor has a constant composition, without change in the composition, and a shell portion thereof has a specific slope for the change in concentration for each metal solution. In order to ensure that the injection amount of the material of the first feed tank Q1is constantly changed for each time zone, the injection amount of the material of the first feed tank Q1is calculated to be in a pattern that it gradually decreases for a total reaction time. However, due to 500 kg of the initial material of the first feed tank Q1injected into the mixer Q3in advance, as shown inFIG.6, the difference between an injection flow rate for 1 hour in the first injection step and an injection flow rate for 1 hour in the second injection step, and the difference in the injection flow rate for 1 hour between the injection steps after the second injection step are differently calculated. This difference causes the concentration of the portion in contact with the core of the precursor formed by the initial reaction to change rapidly compared to other portions. In detail,FIG.6shows a material injection schedule for 30-hour reaction, and the feed flow rate from the mixer Q3into the reactors A, B, C, and D is fixed at 221.77 kg/h. In order to initially fix a composition ratio of the core portion of the precursor, only the core composition solution is to be injected for 1 hour, and thereafter, the injection amount of the core composition solution is to be decreased by a constant flow rate difference. Herein, in calculating the decreased injection amount of the core composition solution, the flow rate of the core composition solution to be injected for 1 hour in the second injection step is calculated by using the feed flow rate per hour of the mixer Q3, 221.77 kg/h, and an injection amount of the core composition solution obtained by subtracting 500 kg injected into the mixer Q3in advance from the total amount of the core composition solution (an amount of the material injected from the first feed tank Q1) as a basis for the calculation. However, the feed flow rate per hour of the mixer Q3, 221.77 kg/h is an amount calculated based on the total amount of the core composition solution, not based on the amount of the material injected from the first feed tank Q1. Thus, a degree of decrease in the flow rate of the core composition solution injected for 2 hours may be calculated to be large compared to a degree of decrease in the flow rate of the core composition solution after 2 hours. Table 1 below shows the detailed values of the flow rate for the injection schedule up to the initial 6 hours inFIG.6.

TABLE 1InjectiontimeGradientFinal injection amount of core(Hour)DifferenceQ1Q2Q3129.51221.770221.7727.80192.2629.51221.7737.80184.4637.31221.7747.80176.6545.11221.7757.80168.8552.92221.7767.80161.0460.72221.7777.80153.2468.53221.77

Referring to Table 1, the difference between the first injection flow rate and the second injection flow rate is 29.51 kg/h, and after the second flow rate, it constantly decrease at a slope of 7.80 kg/h. However, this rapid change in the first injection flow rate and the second injection flow rate causes the concentration of the portion in contact with the core of the precursor to change rapidly compared to that of other portions. In order to solve this problem, in an exemplary embodiment of the present invention, the following material injection scheduling method is provided.

FIG.7is a flow chart of a material injection scheduling method for producing a precursor having a concentration gradient according to an exemplary embodiment of the present invention.FIG.8is a graph illustrating a process of modifying an injection schedule of a feed amount of a material of a Q1feed tank through the material injection scheduling method for producing a precursor having a concentration gradient according to an exemplary embodiment of the present invention.

ReferringFIG.7, first, the total process time (Tr), the total amount of the material of Q1(total amount of the core material, a mixed solution of nickel and cobalt is used in this embodiment), the total amount of the material of Q2(a mixed solution of nickel, cobalt and manganese is used in this embodiment), and the amount of the material of Q1stored in Q3in advance are checked (S1).

Next, the feed flow rate of Q3is calculated by dividing the sum of the total amount of the material of Q1and the total amount of the material of Q2by the total process time (Tr) (S2).

Next, the time (TQ1) required for feeding the entire materials of the Q1feed tank is calculated by subtracting the time required to consume the material of Q1stored in Q3in advance from the total process time (Tr) (value obtained by dividing the amount of the material of Q1stored in Q3in advance by the feed flow rate of Q3) (S3).

Next, during the total process time (Tr), the flow rate of the material to be fed from the Q1feed tank into the Q3feed tank is calculated in a pattern in which it gradually decreases (S4). Herein, the flow rate of Q1(FQ1t) for each time (for feeding step) is calculated using Equation 2 below.
FQ1t=2×(total amount of material ofQ1−amount of material ofQ1 stored inQ3 in advance−amount of material ofQ1 injected in advance)/(time required for feeding entire materials ofQ1 feed tank(TQ1)−time already taken for injection intoQ1)  Equation 2

The change in the flow rate of the material to be fed from the Q1feed tank into the Q3calculated through the above process may be represented as B in the graph ofFIG.8.

Next, it is determined whether or not the difference in the flow rate of the material to be fed from the Q1feed tank into the Q3feed tank is the same between feeding steps other than between the first feeding step and the second feeding step (for 1 hour and 2 hours after starting material feed of Q1) and between the last feeding step and the feeding step just before the last feeding step (S5). Herein, if it is determined to be ‘NO’, step (S4) is performed again, and if it is determined to be ‘YES’, the material injection scheduling method proceeds to next step (S6).

Next, the flow rate of Q1(FQ1t) for each time (for each feeding step) calculated in step (S4) is summed (S6).

Next, it is determined whether or not the sum of the flow rate of Q1(FQ1t) calculated in step (S6) is greater than the total amount of feeding of Q1(total amount of material of Q1−amount of material of Q1stored in Q3in advance) (S7). Here, if it is determined to be ‘NO’, the flow rate of Q1(FQ1t) calculated in step (S6) is determined as a feeding schedule of Q1and the material injection scheduling method proceeds to step (S11), and if it is determined to be ‘YES’, the material injection scheduling method proceeds to step (S8).

Next, an optimum amount making the difference in the flow rate of Q1(FQ1t) constant even in the first and second feed steps (for 1 hour and 2 hours after starting material feeding of Q1) is calculated (S8). These optimum amounts may be calculated by repeatedly inputting estimation values, or by creating an Equation representing a line L shown inFIG.8and substituting each time values.

Next, a difference between the optimum amount calculated in step (S8) and the flow rate of Q1(FQ1t) for each time (for each feeding step) calculated in step (S4) is calculated, and the values of the difference are arranged to feeding step in reverse order to be subtracted from the optimum amount calculated in step (S8), such that a corrected flow rate of Q1in each feeding step is obtained (S9). The corrected flow rate of Q1in each feeding step may be represented as W in the graph ofFIG.8.

Next, it is determined whether or not the value obtained by subtracting the total amount of feeding of Q1from the sum of the corrected flow rates of Q1in each feeding step is smaller than a predetermined value set in advance (S10). Herein, if it is determined to be ‘NO’, steps (S8and S9) are performed again, and if it is determined to be ‘YES’, the corrected flow rate of Q1is determined as the feeding schedule of Q1and the material injection scheduling method proceeds to step (S11).

Next, the feed flow rate of Q2is calculated by subtracting the feed schedule of Q1determined in step S10from the feed flow rate of Q3(S11).

When the material injection scheduling method as described above is used, a precursor having a uniform concentration gradient may be produced even though the reaction time is changed.FIG.9A,FIG.10A, andFIG.11Ashow the results obtained by calculating the material injection schedule of the co-precipitation process with reaction times of 22 hours, 25 hours, and 30 hours, respectively, according to an embodiment of the present invention. As can be seen inFIG.9B,FIG.10B, andFIG.11B, when the schedule obtained through the material injection scheduling method according to the embodiment of the present invention is used, a precursor may be formed to have a uniform concentration gradient even in the vicinity of the core.

Although embodiments of the present invention have been described in detail hereinabove, the scope of the present invention is not limited thereto, but may include several modifications and alterations made by those skilled in the art using a basic concept of the present invention as defined in the claims.