JP6341517B2 - Evaluation method for positive electrode material for lithium ion secondary battery, evaluation device for positive electrode material for lithium ion secondary battery, and evaluation device for lithium ion secondary battery - Google Patents

Description

  The present invention relates to a method for evaluating a positive electrode material for a lithium ion secondary battery, an evaluation apparatus therefor, and an evaluation apparatus for a lithium ion secondary battery.

As a positive electrode material of a lithium ion secondary battery (hereinafter sometimes simply referred to as a battery), lithium iron phosphate (LiFePO ₄ ), lithium manganese phosphate (LiMnPO ₄ ), lithium lithium cobalt phosphate (LiCoPO ₄ ), nickel phosphate lithium (LiNiPO ₄₎ general formula, such as _{LiMPO 4 (M = Fe, Mn} , Co, Ni) transition metal phosphate lithium compound represented by the like.

Among them, lithium iron phosphate having an olivine type crystal structure has a large theoretical capacity (170 mAh / g) and has a relatively high electromotive force (vs. Li / Li ⁺ about 3.4 to 3.5 V at the negative electrode). Furthermore, since it is thermodynamically stable and hardly releases oxygen or generates heat up to about 400 ° C., it can be said to be a preferable positive electrode material from the viewpoint of safety.
Further, since it can be produced at low cost from resource-rich iron, phosphorus, etc., it is expected as a promising positive electrode material.

By the way, the performance and quality of the above-listed compounds as a positive electrode material for a lithium ion secondary battery are generally evaluated by actually producing a battery using the positive electrode material to be evaluated and its battery performance. .
For example, in Patent Document 1, charge / discharge of a predetermined number of cycles (100 cycles in Patent Document 1) is performed with one charge / discharge as one cycle for a lithium ion secondary battery made using a positive electrode material to be evaluated. A test (charging / discharging test) is repeated, and the positive electrode material is evaluated based on the discharge capacity retention rate (cycle characteristics) after the test.

JP 2007-134274 A

Here, for example, even when the discharge capacity retention rate in the charge / discharge test of about 50 to 100 cycles is about the same, when the number of cycles is repeatedly charged and discharged, there may be a difference in the discharge capacity retention rate. is there. In other words, even if there is no difference in the discharge capacity maintenance rate in the charge / discharge test of 50 to 100 cycles, a difference in battery life may occur.
The battery life is determined based on when the discharge capacity maintenance rate reaches a predetermined value (for example, 60% or less).

  In order to clarify the difference in the battery life, the charge / discharge test may be performed up to the number of cycles that will result in the battery life. Usually, the life required for the lithium ion secondary battery is 1000 cycles or more. When one cycle takes 2 hours, a test period of about 3 months is required.

  Accordingly, an object of the present invention is to provide a highly reliable evaluation method and apparatus for a positive electrode material for a lithium ion secondary battery in a short time and in a simple manner. Moreover, it is providing the evaluation apparatus of a lithium ion secondary battery.

In view of the above problems, the evaluation method of the positive electrode material for a lithium ion secondary battery according to the first aspect of the present invention is a lithium ion secondary represented by the general formula LiMPO ₄ (M is Fe, Mn, Co or Ni). A method for evaluating a positive electrode material for a battery, wherein a lithium ion secondary battery produced using the positive electrode material for a lithium ion secondary battery is held in a charged state by a constant current / constant voltage method for a predetermined period of time. A measuring step for measuring the charging current value A over a predetermined period, and an output step for outputting the data relating to the fluctuation of the charging current value A in the predetermined period in an evaluable manner.

Based on the earnest research of the present inventors, a lithium ion secondary battery produced using a positive electrode material for a lithium ion secondary battery to be evaluated is kept in a charged state by a constant current / constant voltage method, and a predetermined The charging current value A is measured over a period (measurement process), and based on data relating to fluctuations in the charging current value A (for example, fluctuation width, rate of change, etc. of the charging current value A), It was found that durability can be predicted.
More specifically, it was found that the smaller the fluctuation of the charging current value A in the predetermined period, the better the durability of the battery, and the larger the fluctuation, the lower the durability of the battery.
The reason why the charging current value A fluctuates in a state where the lithium ion secondary battery is held in a charged state will be described in detail in the following description of the test example.

  According to this aspect, the durability of the lithium ion secondary battery can be predicted based on the data output in the output step, and the performance of the positive electrode material for the lithium ion secondary battery to be evaluated can be evaluated. That is, the performance of the positive electrode material for a lithium ion secondary battery can be evaluated in a short time and simply without charging and discharging the battery until the battery life.

In the output step, “output the data relating to the fluctuation of the charging current value A during the predetermined period in an evaluable manner” means that the charging current value A increases or decreases during the predetermined period and the charging current value A fluctuates. Outputs the width, rate of change, etc. so that it can be analyzed, for example, outputs the maximum value and minimum value of the charging current value A in the predetermined period, which is output by digitizing the value of the charging current value A over time And so on.
In addition, the “output” indicates the measured numerical value itself and the change in the charging current value A in addition to the case where the measurement data in the measurement process is sent to an evaluation unit that analyzes and evaluates the data by a program such as a computer. This includes cases in which what is shown in a table or graph is output and displayed so as to be visible.

  Further, as shown in a test example to be described later, according to this aspect, the durability of each battery is determined for a plurality of batteries in which the conventional charge / discharge test (the number of cycles is 50 to 100) does not show a difference in discharge capacity retention rate. Difference in battery performance (battery life) and positive electrode material for lithium ion secondary battery can be performed with higher reliability.

In this specification, the general formula LiMPO ₄ (M is Fe, Mn, Co or Ni) is lithium (Li), transition metal (M = Fe, Mn, Co or Ni) and phosphoric acid (PO ₄ ). In the stoichiometric ratio, it means that it is contained at a ratio of approximately 1: 1: 1, and is not limited to the case where each component is strictly contained at 1: 1: 1. Moreover, it does not require that no other components or impurities are contained.

  The evaluation method of the positive electrode material for a lithium ion secondary battery according to the second aspect of the present invention is the method for evaluating the positive electrode material for a lithium ion secondary battery in the first aspect, receiving data output in the output step. It has the evaluation process which evaluates performance, It is characterized by the above-mentioned.

  According to this aspect, the evaluation result of the positive electrode material for a lithium ion secondary battery can be obtained by the evaluation process performed by receiving the data output in the output process.

  The evaluation method of the positive electrode material for a lithium ion secondary battery according to the third aspect of the present invention is the method according to the first aspect or the second aspect, wherein the data relating to the fluctuation of the charging current value A is transferred to constant voltage charging Is the ratio (Amax / Amin) of the maximum charging current value Amax to the minimum charging current value Amin.

  According to this aspect, it is possible to quantitatively evaluate the positive electrode material for a lithium ion secondary battery based on the data relating to the fluctuation of the charging current value A.

  The evaluation method of the positive electrode material for a lithium ion secondary battery according to the fourth aspect of the present invention is characterized in that, in any one of the first to third aspects, the measurement step is performed at a temperature higher than room temperature. It is what.

  According to this aspect, the temporal change of the lithium ion secondary battery can be accelerated by performing the measurement step at a temperature higher than room temperature. That is, an accelerated test can be performed. Therefore, an effective evaluation result can be obtained in a shorter period.

The method for evaluating a positive electrode material for a lithium ion secondary battery according to a fifth aspect of the present invention is the method for evaluating a positive electrode material for a lithium ion secondary battery according to any one of the first aspect to the fourth aspect, wherein the positive electrode material for a lithium ion secondary battery has the general formula LiFePO ₄ is a lithium iron phosphate positive electrode material represented by ₄ .

The evaluation apparatus for a positive electrode material for a lithium ion secondary battery according to the sixth aspect of the present invention is a positive electrode material for a lithium ion secondary battery represented by the general formula LiMPO ₄ (M is Fe, Mn, Co or Ni). An evaluation device, a charging unit for charging a lithium ion secondary battery produced using the positive electrode material for a lithium ion secondary battery by a constant current / constant voltage method, and the lithium ion secondary battery in the charging unit A current measuring unit that measures a charging current value A over a predetermined period in a state where the charging state is maintained, and data relating to fluctuations in the charging current value A during the predetermined period can be evaluated from the current measuring unit. And an output unit.

  According to this aspect, the method for evaluating a positive electrode material for a lithium ion secondary battery according to the first aspect is executed, and a highly reliable positive electrode material for a lithium ion secondary battery can be evaluated in a short time and easily. it can.

  The evaluation apparatus for a positive electrode material for a lithium ion secondary battery according to a seventh aspect of the present invention, in the sixth aspect, receives the data output from the output unit and evaluates the performance of the lithium ion secondary battery. It is characterized by providing the evaluation part which performs.

  According to this aspect, the method for evaluating a positive electrode material for a lithium ion secondary battery according to the second aspect is executed, and a highly reliable positive electrode material for a lithium ion secondary battery can be evaluated in a short time and easily. it can.

  An evaluation apparatus for a positive electrode material for a lithium ion secondary battery according to an eighth aspect of the present invention, in the sixth aspect or the seventh aspect, the evaluation unit, as the data relating to the fluctuation of the charging current value A, is fixed. The ratio (Amax / Amin) of the maximum charging current value Amax to the minimum charging current value Amin after the transition to voltage charging is used.

  According to this aspect, since the evaluation of the positive electrode material for a lithium ion secondary battery is performed by a quantitative method, the evaluation unit can be configured with a relatively simple program.

  The apparatus for evaluating a positive electrode material for a lithium ion secondary battery according to a ninth aspect of the present invention is the temperature control unit for controlling the temperature at the time of charging in the charging unit in any of the sixth to eighth aspects. It is characterized by providing.

  According to this aspect, since the temperature at the time of charging in the charging unit can be increased, so-called acceleration that accelerates the change over time of the test object (battery manufactured using the positive electrode material for a lithium ion secondary battery). A test can be performed.

The evaluation apparatus for a positive electrode material for a lithium ion secondary battery according to a tenth aspect of the present invention is the positive electrode material for a lithium ion secondary battery according to any of the sixth aspect to the ninth aspect, wherein the positive electrode material for a lithium ion secondary battery has the general formula LiFePO ₄ is a lithium iron phosphate positive electrode material represented by ₄ .

The evaluation apparatus for a lithium ion secondary battery according to the eleventh aspect of the present invention includes a positive electrode material for a lithium ion secondary battery represented by the general formula LiMPO ₄ (M is Fe, Mn, Co, or Ni) as a constituent element. An evaluation apparatus for a lithium ion secondary battery including a charging unit for charging the lithium ion secondary battery by a constant current / constant voltage method, and a charging state of the lithium ion secondary battery held in the charging unit A current measuring unit that measures a charging current value A over a predetermined period, and an output unit that outputs data relating to fluctuations in the charging current value A during the predetermined period from the current measuring unit so that the data can be evaluated. It is characterized by comprising.

According to this aspect, the positive electrode for a lithium ion secondary battery represented by the general formula LiMPO ₄ (M is Fe, Mn, Co or Ni) in a short time and easily based on the data output from the output unit. The durability (life) of the lithium ion secondary battery containing the material as a constituent element can be evaluated with high reliability.

  The evaluation apparatus for a lithium ion secondary battery according to a twelfth aspect of the present invention, in the eleventh aspect, receives data output from the output part and evaluates the performance of the lithium ion secondary battery. It is characterized by providing.

  According to this aspect, evaluation can be performed by the evaluation unit based on the data output from the output unit, and the durability (life) of the lithium ion secondary battery can be evaluated in a short time and simply. .

An evaluation apparatus for a lithium ion secondary battery according to a thirteenth aspect of the present invention is the lithium ion secondary battery positive electrode material according to the eleventh aspect or the twelfth aspect, wherein the positive electrode material for a lithium ion secondary battery is a phosphorus represented by the general formula LiFePO _4. It is a lithium iron oxide positive electrode material.

The figure which shows the fluctuation | variation of the charging current value A measured in the test of Example 1. FIG. The schematic block diagram which shows an example of the evaluation apparatus of the positive electrode material for lithium ion secondary batteries which concerns on this invention. The schematic block diagram which shows the other example of the evaluation apparatus of the positive electrode material for lithium ion secondary batteries which concerns on this invention. The schematic block diagram which shows an example of the evaluation apparatus of the lithium ion secondary battery which concerns on this invention.

  Hereinafter, a method for evaluating a positive electrode material for a lithium ion secondary battery and a device for evaluating a positive electrode material for a lithium ion secondary battery according to the present invention will be described.

<About the positive electrode material for lithium ion secondary batteries to be evaluated>
The positive electrode material for a lithium ion secondary battery to be evaluated in the evaluation method and evaluation apparatus for a positive electrode material for a lithium ion secondary battery according to the present invention is represented by the general formula LiMPO ₄ (M is Fe, Mn, Co or Ni). Examples thereof include lithium iron phosphate (LiFePO ₄ ), lithium manganese phosphate (LiMnPO ₄ ), lithium cobalt phosphate (LiCoPO ₄ ), and lithium nickel phosphate (LiNiPO ₄ ).

For example, lithium iron phosphate (LiFePO ₄ ) includes lithium carbonate (Li ₂ CO ₃ ), ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ), and iron (II) oxalate dihydrate as examples of raw materials. It can be obtained by a general method of firing a mixture and pulverized (FeC ₂ O ₄ .2H ₂ O).
It may be lithium iron phosphate in which a bitumen such as coal pitch or a carbon precursor such as saccharide is added during the calcination, and conductive carbon is deposited on the surface of LiFePO ₄ . The positive electrode material having conductive carbon deposited on the surface can exhibit even higher charge / discharge characteristics than when no carbon is deposited.

<Outline of Evaluation Method for Positive Electrode Material for Lithium Ion Secondary Battery According to the Present Invention>
As described above, according to the fluctuation data of the charging current value A in a state where the lithium ion secondary battery manufactured using the positive electrode material for the lithium ion secondary battery to be evaluated is held in a charged state by a constant current / constant voltage method. It was found that the durability of the lithium ion secondary battery can be predicted.
Based on this knowledge, the evaluation method of the positive electrode material for a lithium ion secondary battery according to the present invention includes the following (1) measurement step and (2) output step.

(1) Measurement process The measurement process is performed in a state where a lithium ion secondary battery manufactured using a positive electrode material for a lithium ion secondary battery to be evaluated is held in a charged state by a constant current / constant voltage method. This is a step of measuring the charging current value A over a period.

(2) Output Step The output step is a step of outputting “data relating to fluctuations in the charging current value A” in a predetermined period of the measurement step so that it can be evaluated.
Examples of the “data related to fluctuations in the charging current value A” include increase / decrease, fluctuation width, rate of change, and the like of the charging current value A in the predetermined period.

  In the output step, “output the data relating to the fluctuation of the charging current value A in the predetermined period in an evaluable manner” means the fluctuation of the charging current value A in the predetermined period, that is, the charging current value A In addition to outputting numerical values or graphs so that the fluctuation of charging current, fluctuation range of charging current value A, rate of change, etc. can be seen visually, it is directly output to an evaluation unit that can automatically analyze data by a program such as a computer May be.

(3) Evaluation process An evaluation process is a process of receiving the data output in the said output process, and evaluating the performance of the positive electrode material for lithium ion secondary batteries. The evaluation step can be performed by using an evaluation unit that performs evaluation by a program or the like based on the data, in addition to the case where a person analyzes and evaluates the data output as a figure such as a numerical value or a graph.

Here, the relationship between the fluctuation | variation of the charging current value A in the state which hold | maintained the lithium ion secondary battery in the charge state, and durability of the said lithium ion secondary battery is demonstrated.
In the positive electrode material for a lithium ion secondary battery represented by the general formula LiMPO ₄ (M is Fe, Mn, Co or Ni), a ferromagnetic component derived from a raw material for introducing the transition metal M is an impurity during the production thereof. May be generated as
For example, in a lithium iron phosphate positive electrode material represented by the general formula LiFePO ₄ , iron-based impurities such as iron, iron oxide, and iron phosphide may be generated during production. When a lithium ion secondary battery made of a positive electrode material for a lithium ion secondary battery containing such a ferromagnetic component (iron impurities in the lithium iron phosphate positive electrode material) is charged, the ferromagnetic component is deposited on the negative electrode. . Then, a part of the separator may be damaged by the ferromagnetic component deposited on the negative electrode, and stable ionic conductivity between the positive electrode and the negative electrode may not be maintained.
If the ionic conductivity between the positive electrode and the negative electrode is not stable, the charging current value A during charging is not stable.

Therefore, when the fluctuation of the charging current value A is large, it is considered that the separator is damaged due to precipitation of the ferromagnetic component on the negative electrode, and the durability as a battery is considered low. On the other hand, if the fluctuation of the charging current value A is small, the influence of precipitation of the ferromagnetic component on the negative electrode is low, and the durability of the battery is considered good.
From the above, the durability of the lithium ion secondary battery can be evaluated based on the “data on the fluctuation of the charging current value A” and the positive electrode material for the lithium ion secondary battery used in the lithium ion secondary battery can be evaluated. Performance can be evaluated.

According to this evaluation method, the durability of the lithium ion secondary battery is predicted without charging / discharging the battery until the battery life, and thus the performance of the positive electrode material for the lithium ion secondary battery to be evaluated is evaluated. Can do. That is, the positive electrode material for a lithium ion secondary battery can be evaluated with higher reliability by a simple method in a short time.
In addition, the effect of this evaluation method is explained in full detail in the test example shown later.

In addition, the measurement step can be performed at a temperature higher than room temperature, thereby performing an accelerated test that accelerates the change over time of the charged lithium ion secondary battery. In particular, it is desirable to carry out at 40 to 70 ° C.
As a result, an effective evaluation result can be obtained in a shorter period of time.

[Test example]
Example 1
As an example of a positive electrode material for a lithium ion secondary battery represented by the general formula LiMPO ₄ (M is Fe, Mn, Co or Ni), a lithium iron phosphate (LiFePO ₄ ) positive electrode material (test material 1 to test material 4) A lithium ion secondary battery was prepared using the above, and an evaluation test was performed by the evaluation method of the positive electrode material for a lithium ion secondary battery of the present invention.
The conditions of the manufactured lithium ion secondary battery are shown below. Table 1 shows the magnetization values (emu / g) of the test materials 1 to 4 measured by VSM (sample vibration type magnetometer). In addition, it has shown that the iron-type impurity mentioned above is contained much in the lithium iron phosphate positive electrode material of a test material, so that a magnetization value is large.

<Lithium ion secondary battery>
Cell type: CR2032
Positive electrode composition: LFP: AB: PVdF = 91: 4: 5
Cathode loading: 16 mg / cm ²
Negative electrode: Li-Metal
Electrolyte: 1M LiPF ₆ in EC / EMC
LFP = lithium iron phosphate, AB = acetylene black, PVdF = polyvinylidene fluoride, LiPF ₆ = lithium hexafluorophosphate, EC = ethylene carbonate, and EMC = ethyl methyl carbonate.

以下に示す充電条件で充電状態を保持したまま、充電電流値Ａを測定した。

The charging current value A was measured while maintaining the charging state under the following charging conditions.

Charging condition: 0.1C 4.3V cc-cv charge mode
Retention time: Up to 300 hours
Temperature: 60 ° C
The variation of the charging current value A measured in the test of Example 1 is shown in FIG.

(Comparative example)
As a comparative example, an evaluation test using a charge / discharge test (50 cycles), which is a conventional method, was performed on a lithium ion secondary battery that was similarly manufactured using the same test materials 1 to 4 as in Example 1. The conditions for the charge / discharge test are shown below.
Temperature: 25 ° C
Charging conditions: 2C charging
Discharge condition: 2C discharge
1 charge / discharge cycle: 1 hour
Table 2 shows the results of a conventional charge / discharge test as a comparative example.

表２に示すように、比較例の充放電試験では、試験材料１（磁化値0.020emu/g）と試験材料２（磁化値0.202emu/g）において、５０サイクル目（50th）における放電容量および放電容量維持率（％）にほとんど差はなく、試験材料１と試験材料２の電池性能はほぼ同じと評価される。

As shown in Table 2, in the charge / discharge test of the comparative example, in the test material 1 (magnetization value 0.020 emu / g) and the test material 2 (magnetization value 0.202 emu / g), the discharge capacity and the 50th cycle (50th) There is almost no difference in the discharge capacity retention rate (%), and the battery performances of the test material 1 and the test material 2 are evaluated to be substantially the same.

On the other hand, in the test of Example 1, there is a difference in the fluctuation of the charging current value A after shifting to the constant voltage charge in each test material, and in the comparative example, the test material 1 and the test material 2 in which the evaluation was not different. A large difference was also observed.
As shown in FIG. 1, the test material 1 has a small variation in the charging current value A. In the test material 2 and the test material 3, the charging current value A starts to increase from the time when the charging time is 80 to 90 hours. Fluctuated more than test material 1.
Table 3 shows the minimum charging current value Amin and the maximum charging current value Amax after shifting to constant voltage charging, and the ratio (Amax / Amin) of the maximum charging current value Amax to the minimum charging current value Amin.

最小充電電流値Ａminに対する最大充電電流値Ａmaxの比（Ａmax／Ａmin）の値には、各試験材料の磁化値と相関性が見られた。
すなわち、試験材料の磁化値が小さい程（試験材料１＜試験材料２＜試験材料３＜試験材料４）、Ａmax／Ａminの値も小さくなる（表３を参照）。

The ratio of the maximum charging current value Amax to the minimum charging current value Amin (Amax / Amin) was correlated with the magnetization value of each test material.
That is, the smaller the magnetization value of the test material (test material 1 <test material 2 <test material 3 <test material 4), the smaller the value of Amax / Amin (see Table 3).

The smaller the magnetization value, the smaller the iron-based impurities contained in the lithium iron phosphate positive electrode material. Therefore, the amount of iron-based impurities deposited on the negative electrode during charging is reduced, leading to a separator due to precipitation of the iron-based impurities on the negative electrode. (For example, the possibility of breakage of the separator) is reduced. Accordingly, the ionic conductivity between the positive electrode and the negative electrode is stabilized, and the durability of the battery is improved. Therefore, it can be said that the smaller the Amax / Amin, the better the durability of the battery.
The test material 4 did not shift from constant current charging to constant voltage charging and could not be charged, so Amax / Amin could not be calculated.

  As described above, according to the evaluation method according to the present invention, the performance of the lithium iron phosphate positive electrode material is evaluated more reliably and in a shorter time than the time for charging and discharging the battery until the battery life by a simple method. be able to.

  Moreover, as shown in Table 3, by evaluating using the ratio (Amax / Amin) of the maximum charging current value Amax to the minimum charging current value Amin after shifting to constant voltage charging, the lithium iron phosphate positive electrode material Evaluation can be performed quantitatively. For example, when the value of Amax / Amin is a predetermined value or less, it can be evaluated that the durability as a lithium ion secondary battery is good.

As mentioned above, although the evaluation example was given and the evaluation method of the positive electrode material for lithium ion secondary batteries which concerns on this invention was demonstrated, the said positive electrode material for lithium ion secondary batteries was used by performing the said measurement process and the said output process. The performance of the lithium ion secondary battery produced in this way can also be evaluated.
In the above it has been described test examples of lithium iron phosphate as a cathode material for a lithium ion secondary battery (LiFePO _4), lithium manganese phosphate (LiMnPO _4), lithium cobalt phosphate (LiCoPO _4), phosphoric acid lithium nickel (LiNiPO ₄₎ general formula, such as _{LiMPO 4 (M = Fe, Mn} , Co, Ni) can be also similarly evaluated the performance of the positive electrode material for other lithium ion secondary battery represented by.

<Outline of evaluation apparatus for positive electrode material for lithium ion secondary battery>
Next, a schematic configuration of an evaluation apparatus for a positive electrode material for a lithium ion secondary battery will be described with reference to the drawings. FIG. 2 is a schematic configuration diagram illustrating an example of an evaluation apparatus for a positive electrode material for a lithium ion secondary battery.
An evaluation apparatus 1 for a positive electrode material for a lithium ion secondary battery includes a charging unit 2 for charging a lithium ion secondary battery by a constant current / constant voltage method, and a current measuring unit 3 for measuring a charging current value A of the charging unit 2. I have. The current measuring unit 3 includes an output unit 4 and is configured to output data relating to the fluctuation of the charging current value A in the predetermined period so as to be evaluated.
Data output from the output unit 4 is sent to an evaluation unit 5 that evaluates the performance of the positive electrode material for a lithium ion secondary battery.

In the charging part 2, the lithium ion secondary battery produced using the positive electrode material for lithium ion secondary batteries to be evaluated is charged.
The current measuring unit 3 is configured to measure the charging current value A over a predetermined period in a state where the charging unit 2 maintains the charged state of the lithium ion secondary battery.
The charging unit 2 and the current measuring unit 3 can execute the measurement step in the above-described method for evaluating the positive electrode material for a lithium ion secondary battery.

  The charging unit 2 is provided with a temperature control unit 6 that controls the temperature of the charging unit 2. An acceleration test can be performed by setting the temperature when the measurement step is performed by the temperature controller 6 to a temperature higher than room temperature (for example, 40 ° C. to 70 ° C.).

As described above, the evaluation unit 5 is configured to receive the data output from the output unit 4 and evaluate the performance of the positive electrode material for a lithium ion secondary battery.
In the present embodiment, the charging current value A measured by the current measuring unit 3 is configured to be sent from the output unit 4 to the evaluation unit 5. As a result, the evaluation unit 5 obtains “data relating to fluctuations in the charging current value A”.
Examples of the “data relating to fluctuations in the charging current value A” include values such as the fluctuation width and rate of change of the charging current value A. In particular, it is desirable to use the ratio (Amax / Amin) of the maximum charging current value Amax to the minimum charging current value Amin after shifting to constant voltage charging.
In the evaluation apparatus 1 of this embodiment, the evaluation result in the evaluation unit 5 is configured to be displayed on the first display unit 7.

Further, the evaluation apparatus 1 of the present embodiment can be provided with a second display unit 8 that displays the measurement result measured by the current measuring unit 3. Data is sent from the output unit 4 to the second display unit 8.
As the second display unit 8, for example, a display unit that displays the value of the charging current value A over time by a digital display method or a needle display method can be employed. Moreover, the change of the charging current value A can also be displayed as a graph. Further, the value or graph of the charging current value A can be configured to be displayed on a paper medium or the like in addition to being displayed on a display panel or the like.

<Other aspects of evaluation apparatus for positive electrode material for lithium ion secondary battery>
In addition to the evaluation device that performs evaluation by the evaluation unit 5 as in the evaluation device 1 illustrated in FIG. 2, for example, the user (evaluation tester) visually confirms the measurement result output to the second display unit 8, and the result Based on the above, the user can also evaluate the test material (the positive electrode material for a lithium ion secondary battery).
In that case, as shown in FIG. 3, it is also possible to use an evaluation apparatus 11 for a positive electrode material for a lithium ion secondary battery that does not have an evaluation unit.

<Evaluation equipment for lithium ion secondary batteries>
A lithium ion secondary battery represented by the general formula LiMPO ₄ (M is Fe, Mn, Co or Ni) by an apparatus having the same configuration as the evaluation apparatus 1 or the evaluation apparatus 11 (evaluation apparatus 21, see FIG. 4). The performance of a lithium ion secondary battery that includes the positive electrode material for use as a constituent element can be evaluated.

For example, the evaluation device 21 for a lithium ion secondary battery includes a charging unit 22 for charging a lithium ion secondary battery by a constant current / constant voltage method, a current measuring unit 23 for measuring a charging current value A of the charging unit 22, The output unit 24 that outputs the data related to the fluctuation of the charging current value A in the predetermined period from the current measuring unit 23 so that the data can be evaluated, and the data output from the output unit 24, and the performance of the lithium ion secondary battery The evaluation part 25 which evaluates is provided.
The evaluation device 21 further includes a temperature control unit 26 that controls the temperature of the charging unit 22, a first display unit 27 that displays an evaluation result in the evaluation unit 25, and a second display that displays the measurement result measured in the current measurement unit 23. A display unit 28 is provided.

With the above configuration, a lithium ion secondary battery including a positive electrode material for a lithium ion secondary battery represented by the general formula LiMPO ₄ (M is Fe, Mn, Co, or Ni) as a constituent element can be obtained in a short time and simply. It can be evaluated with high reliability. Of course, the evaluation apparatus for a lithium ion secondary battery can be configured not to include the evaluation unit 25 as in the evaluation apparatus 11 for the positive electrode material for a lithium ion secondary battery described above.

  As mentioned above, although the evaluation method of the positive electrode material for lithium ion secondary batteries which concerns on this invention, its evaluation apparatus, and an example of the evaluation apparatus of a lithium ion secondary battery were demonstrated, this invention is not limited to these, Various modifications are possible within the scope of the invention described in the claims, and these are also included in the scope of the present invention.

1 Evaluation device for positive electrode material for lithium ion secondary battery, 2 charging section,
3 current measurement unit, 4 output unit, 5 evaluation unit,
6 temperature control unit, 7 first display unit, 8 second display unit,
11 Evaluation apparatus of positive electrode material for lithium ion secondary battery,
21 lithium ion secondary battery evaluation device, 22 charging unit,
23 current measurement unit, 24 output unit, 25 evaluation unit,
26 temperature control unit, 27 first display unit, 28 second display unit

Claims (13)

An evaluation method of a positive electrode material for a lithium ion secondary battery represented by a general formula LiMPO4 (M is Fe, Mn, Co or Ni),
A measurement step of measuring a charging current value A over a predetermined period in a state in which a lithium ion secondary battery manufactured using the positive electrode material for a lithium ion secondary battery is held in a charged state by a constant current / constant voltage method. When,
An output step of outputting the data relating to the fluctuation of the charging current value A in the predetermined period so that it can be evaluated;
The evaluation method of the positive electrode material for lithium ion secondary batteries characterized by having. In the evaluation method of the positive electrode material for lithium ion secondary batteries according to claim 1,
A method for evaluating a positive electrode material for a lithium ion secondary battery, comprising an evaluation step of receiving data output in the output step and evaluating the performance of the positive electrode material for a lithium ion secondary battery. In the evaluation method of the positive electrode material for a lithium ion secondary battery according to claim 1 or 2,
The data relating to the fluctuation of the charging current value A is a ratio (Amax / Amin) of the maximum charging current value Amax to the minimum charging current value Amin after shifting to the constant voltage charging. Evaluation method for positive electrode materials. In the evaluation method of the positive electrode material for a lithium ion secondary battery according to any one of claims 1 to 3,
A method for evaluating a positive electrode material for a lithium ion secondary battery, wherein the measuring step is performed at a temperature higher than room temperature. In the evaluation method of the positive electrode material for a lithium ion secondary battery according to any one of claims 1 to 4,
The method for evaluating a positive electrode material for a lithium ion secondary battery, wherein the positive electrode material for a lithium ion secondary battery is a lithium iron phosphate positive electrode material represented by a general formula LiFePO4. An evaluation apparatus for a positive electrode material for a lithium ion secondary battery represented by a general formula LiMPO4 (M is Fe, Mn, Co or Ni),
A charging unit for charging a lithium ion secondary battery produced using the positive electrode material for a lithium ion secondary battery by a constant current / constant voltage method,
A current measuring unit that measures a charging current value A over a predetermined period in a state where the charging state of the lithium ion secondary battery is maintained in the charging unit;
An output unit that outputs data relating to fluctuations in the charging current value A in the predetermined period from the current measuring unit so that the data can be evaluated;
An evaluation apparatus for a positive electrode material for a lithium ion secondary battery. In the evaluation apparatus of the positive electrode material for a lithium ion secondary battery according to claim 6,
An evaluation apparatus for a positive electrode material for a lithium ion secondary battery, comprising: an evaluation section that receives data output from the output section and evaluates the performance of the lithium ion secondary battery. In the evaluation apparatus for the positive electrode material for a lithium ion secondary battery according to claim 6 or 7,
As the data for changes in previous SL charging current value A, after transition to the constant voltage charging, which comprises using the ratio of the maximum charging current value Amax to the minimum charging current value Amin (Amax / Amin), the lithium ion secondary Evaluation apparatus for positive electrode materials for batteries. In the evaluation apparatus of the positive electrode material for a lithium ion secondary battery according to any one of claims 6 to 8,
An evaluation apparatus for a positive electrode material for a lithium ion secondary battery, comprising: a temperature control unit that controls a temperature during charging in the charging unit. In the evaluation apparatus of the positive electrode material for a lithium ion secondary battery according to any one of claims 6 to 9,
The positive electrode material for lithium ion secondary batteries is a lithium iron phosphate positive electrode material represented by the general formula LiFePO4. An evaluation apparatus for a lithium ion secondary battery including a positive electrode material for a lithium ion secondary battery represented by a general formula LiMPO4 (M is Fe, Mn, Co, or Ni) as a component,
A charging unit for charging the lithium ion secondary battery by a constant current / constant voltage method;
A current measuring unit that measures a charging current value A over a predetermined period in a state where the charging state of the lithium ion secondary battery is maintained in the charging unit;
An output unit that outputs data relating to fluctuations in the charging current value A in the predetermined period from the current measuring unit so that the data can be evaluated;
An evaluation apparatus for a lithium ion secondary battery, comprising: In the evaluation apparatus of the lithium ion secondary battery according to claim 11,
An evaluation device for a lithium ion secondary battery, comprising: an evaluation unit that receives data output from the output unit and evaluates the performance of the lithium ion secondary battery. In the evaluation apparatus of the lithium ion secondary battery according to claim 11 or 12,
The evaluation apparatus for a lithium ion secondary battery, wherein the positive electrode material for a lithium ion secondary battery is a lithium iron phosphate positive electrode material represented by a general formula LiFePO4.

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