Molded and sintered body of cathode active material and secondary battery made from same

Abstract

The present invention provides: a molded and sintered body of a cathode active material in which a plurality of cathode active material particles are aggregated and maintain the shape of the molded and sintered body; and a secondary battery made from same. The molded and sintered body of a cathode active material is manufactured by sintering after feeding into a sintering furnace without using a sintering vessel, and thus has high productivity. In addition, the reactivity of the molded and sintered body is high due to the high conversion energy and large amount of contact with a fluid during sintering, and thus it is possible to produce a cathode active material having excellent physical properties.

Description

Positive electrode active material molded sintered body and secondary battery manufactured therefrom

[0001] The present invention relates to a positive electrode active material molded sintered body that is pulverized for manufacturing a positive electrode active material, and more specifically, to a positive electrode active material molded sintered body in which a plurality of positive electrode active material particles are aggregated to maintain a shape, and a secondary battery manufactured therefrom.

[0002] Typically, cathode active materials are produced using a roller hearth kiln (RHK), i.e., a continuous kiln. This continuous kiln places a ceramic kiln filled with cathode raw materials, including transition metal precursors and lithium raw materials, on a Si-C driven roller, and then places the kiln into a horizontal furnace where temperatures are set for each zone, where sintering is performed.

[0003] Since the above transition metal precursors and lithium raw materials are in powder form, they must be transported in a sintering vessel. These sintering vessels are moved tens of meters along a conveyor belt, where continuous sintering occurs. The high-temperature heat supplied from within the horizontal furnace causes the cathode raw materials to react with each other, leading to diffusion and crystal growth.

[0004] In this type of continuous kiln method, a large number of kilns are arranged horizontally and stacked to improve productivity. At this time, a large load is applied to the Si-C drive roller, and to prevent its damage, the number of horizontal arrangements and the number of stacking stages are limited, so there is a limit to improving productivity.

[0005] To overcome these limitations, a technology has been proposed in the art that allows cathode material to be compressed and shaped independently, thereby allowing it to be fed into a kiln without a kiln container. This compressed cathode material can be stacked in multiple layers, and the pressure-molding process increases density per unit volume, thereby improving production yield and enhancing reactivity by ensuring close particle contact.

[0006] However, these technologies have not been commercialized in practice for the following reasons:

[0007] When cathode material raw materials are shaped and fired, the particles sinter together to form a single mass. Therefore, after firing, the molded product must be pulverized into powder again. During this process, the cathode active material particles that were previously attached to each other are crushed, and the intact cathode active material particle shape is not maintained. In particular, in the case of cathode active materials in the form of secondary particles, the primary particle units or primary particles are partially shattered into agglomerates during the pulverization, which causes a problem in that the characteristics of the cathode active material are degraded.

[0008] Due to the above problem, efforts have been made in the industry to solve it by controlling the pressure during pressure molding and the crushing strength after firing.

[0009] When the pressure is weak during the pressure molding of the positive electrode material raw material, the area where the particles come into contact and sinter with each other is reduced, resulting in the molded body not being able to maintain its shape after firing and collapsing. In addition, when the pressure is strong, the particles are excessively sintered, resulting in the problem of the particles shattering rather than maintaining their desired shape during subsequent crushing. In addition, when the positive electrode active material molded body that has gone through the firing process is crushed, if the crushing strength is strong, the particle shape is broken, and if the crushing strength is weak, the particles are not completely separated.

[0010] Therefore, in a technology using a sintered molded body as one of the methods for manufacturing a positive electrode active material, there is a high need in the art for developing a technology for obtaining intact active material particles that are separated from each other without being crushed during pulverization.

[0011] The present invention aims to solve the problems of the prior art as described above and the technical tasks requested from the past.

[0012] The inventors of the present invention, after repeated in-depth research and various experiments, have developed a novel positive electrode active material molded sintered body in which a plurality of positive electrode active material particles are aggregated to maintain their shape, and since such a molded sintered body can be manufactured by firing it in a sintering furnace in a laminated state without using a sintering vessel, they have confirmed that a positive electrode active material with excellent physical properties can be manufactured through high productivity and reactivity, and have completed the present invention.

[0013] Accordingly, the present invention is a positive electrode active material molded sintered body that is pulverized (disintegrated) for manufacturing a positive electrode active material, and the positive electrode active material molded sintered body is characterized in that a plurality of positive electrode active material particles are aggregated to maintain a shape.

[0014]

[0015] The positive electrode active material molded sintered body of the present invention is manufactured by molding a positive electrode raw material including a transition metal precursor and a lithium raw material into a predetermined shape and then firing it. For example, a paste is manufactured by adding deionized water (DIW) to the positive electrode raw material, and this is placed in a mold of a predetermined shape and pressurized to produce a green body, and then fired. When manufacturing the paste, a binder may be used instead of DIW, if necessary. In addition, the size and shape of the green body are not particularly limited as long as it can be introduced into a sintering furnace and effectively perform a sintering process. For example, a shape that can be laminated into multiple layers, as in Fig. 1a, may be more preferable.

[0016] FIG. 1a discloses a structure in which a plurality of green bodies (100) for manufacturing a positive electrode active material molded sintered body according to the present invention are stacked and horizontally arranged on a drive roller (30) for feeding into a sintering furnace (not shown), and FIG. 1b schematically illustrates a structure in which a plurality of sintering containers (10) containing positive electrode material raw materials (20) are stacked and horizontally arranged on a drive roller (30). According to the present invention, since a sintering container (10) as in FIG. 1b is not used, the load applied to the drive roller (30) is reduced, and a relatively large amount of loading is possible under the same conditions, and there is no need to use consumables (sintering containers), so that overall productivity can be improved.

[0017] The effect obtained by not using a sintering vessel is not only cost reduction, but also, as seen in FIG. 2, when viewed from above, the area where an oxidizing gas such as air or oxygen can directly contact the cathode raw material (20) during the sintering process can be maximized, thereby improving reactivity. For reference, (A) in FIG. 2 is a schematic diagram when viewed from the top of the single body of FIG. 1a, and (B) in FIG. 2 is a schematic diagram when viewed from the top of the single body of FIG. 1b.

[0018] In addition, as shown in Fig. 3, during the compression process for manufacturing a green body, residual stress is generated inside the molded body, and during firing, this stress acts as energy in the crystal phase formation reaction, which can further improve reactivity.

[0019]

[0020] In a preferred embodiment, the positive electrode active material particles may be at least partially sintered with adjacent particles to maintain shape.

[0021] Here, 'partially sintered' means a sintered state in which the sintering strength for forming a molded structure is minimized, and the sintering strength for separating single particles from each other is maximized while the breakage of the particles themselves is suppressed when pulverizing for manufacturing a positive electrode active material.

[0022] Therefore, when the molded sintered body for manufacturing the positive electrode active material powder is pulverized, the positive electrode active material particles that maintain their shape can be separated from each other and converted into powder.

[0023] The magnitude of the pressure applied for crushing may be similar to or slightly greater than the magnitude of the pressure applied when crushing the cathode material raw material conventionally contained in a sintering vessel after firing. In other words, even if the material is fired in the form of a molded body, there is no need to apply a significantly greater pressure compared to the conventional crushing process.

[0024] As mentioned above, "the positive electrode active material particles maintain their shape" means that even if the edges of the molded sintered body are partially broken or crumbled, the molded sintered body can maintain its overall molded structure to the extent that it can be stacked and transported. Accordingly, the stacked molded sintered body can be prevented from collapsing.

[0025]

[0026] In one specific example, the positive electrode active material particles may be configured to include a single particle.

[0027] Typically, the positive electrode active material particles used in lithium secondary batteries have a secondary particle structure of several micrometers in size, formed by agglomeration of fine, submicron-sized primary particles. This secondary particle structure presents a problem in that the secondary particles break apart as the aggregated primary particles separate during repeated charge and discharge cycles, degrading battery performance. To address this issue, single-body particle positive electrode active materials have been proposed in the art.

[0028] These single particle active materials have a structure of a 'non-agglomerated single particle' rather than the conventional 'secondary particle structure of aggregated primary particles', and since there is 'almost' no particle agglomeration, there is no particle separation due to charge / discharge, thus solving the problems that occur in secondary particle active materials. Here, the term 'almost' means that some aggregated lumps that inevitably exist during the manufacturing of single particle / powder are allowed. That is, since it is impossible for all particles to exist in a perfectly separated state due to technical limitations, some unintended aggregated lumps may be generated, and the proportion of some aggregated particles may be within 30% of the entire active material powder. These some aggregated particles do not correspond to conventional secondary particles.

[0029] A single particle in the positive electrode active material molded body according to the present invention can be understood as being converted into a single particle or single particle as described above when single particles that are mutually aggregated to form a molded structure as defined above are pulverized to form a positive electrode active material.

[0030] Therefore, from a morphological perspective, a 'single particle' refers to a particle that can be 'recognized as a single independent particle by a person skilled in the art in a SEM or TEM'. Conversely, a 'secondary particle' refers to a particle that is 'difficult for a person skilled in the art to recognize as a single independent particle by a SEM or TEM, and is an aggregate of multiple particles'.

[0031] Additionally, a 'single particle' recognized in the art is a particle that exists alone and has an average particle diameter of at least 1 ㎛. When primary particles less than 1 ㎛ included in 'secondary particles' are crushed and separated, problems such as deterioration of structural stability, electrolyte side reactions, and shortened lifespan occur due to the generation of fine particles. In other words, a 'single particle' can function as a positive electrode active material when it exists alone, but a 'primary particle' with an average particle diameter of less than 1 ㎛ separated from a 'secondary particle' cannot function as a normal positive electrode active material. Such problems caused by fine particles are already widely recognized in the art, and efforts are being made to control fine particles.

[0032]

[0033] According to the present invention, the powder (crushed material) obtained by crushing a molded sintered body contains single particles, and optionally may further contain aggregates in which single particles are aggregated.

[0034] That is, in some cases, the powder may contain aggregates, which are agglomerates of some single particles. This is because it may be difficult to separate all single particles during the grinding process, and rather, applying excessive pressure to achieve complete separation may result in some of the single particles being crushed, which is undesirable. Generally, the aggregates are confirmed to not exceed 30%, and preferably 20%, of the total volume.

[0035]

[0036] For example, to enhance reactivity in the firing process for manufacturing a molded body, the molded structure may be formed with patterns and / or holes through which fluid can flow during firing.

[0037]

[0038] The single particles included in the molded sintered body of the positive electrode active material according to the present invention can be formed under different firing conditions than those of conventional molded sintered bodies. To create highly crystalline particles, such as single particles, the amount of heat applied must be dependent, and this can be typically controlled by the firing temperature and firing time.

[0039] Regarding the above-mentioned sintering temperature, in order to manufacture a single particle, not only a certain amount of heat is required, but also an absolute temperature is required for the elements forming the crystal to react smoothly with each other. In other words, even if a certain amount of heat is applied over a long sintering time at a low sintering temperature, a single particle with high crystallinity cannot be produced if the specified sintering temperature is not satisfied. This appropriate sintering temperature may vary depending on the content of the elements constituting the positive electrode active material, and in particular, the appropriate sintering temperature may decrease as the nickel content increases.

[0040] Specifically, when manufacturing a cathode active material having a Ni content in the range of 50 to 80 mol% relative to the total transition metal, a firing condition of 900°C or higher for 5 hours or longer can be applied to manufacture a single particle, and when manufacturing a cathode active material having a Ni content exceeding 80 mol% relative to the total transition metal, a firing condition of 800°C or higher for 10 hours or longer can be applied to manufacture a single particle, but it is not necessarily limited to the above conditions depending on conditions such as a firing profile.

[0041]

[0042] The positive electrode active material molded sintered body according to the present invention exhibits the following differences that are not seen in the prior art due to the characteristic that positive electrode active material particles or single particles are aggregated to form a molded structure as defined above.

[0043]

[0044] In the first specific example, the positive electrode active material particle or single particle may have a grain size of the (003) plane in the range of 100 nm or more when measured by XRD.

[0045] As can be confirmed from the experimental results thereafter, the cathode active material molded sintered body according to the present invention may have a crystal grain size of the (003) plane of at least 100 nm or more, preferably 120 nm or more, more preferably 130 nm or more, and particularly preferably 160 nm or more, and in a specific example based on the experiment, it falls within the range of 160 to 250 nm. This is presumed to be because the crystals of the corresponding plane grow significantly during the sintering process performed at a higher temperature for a long time to form the particles.

[0046]

[0047] In a second specific example, in the FE-SEM image of the powder obtained after pulverization, in a square image area of ​​5 μm × 5 μm in size set to focus on at least one single particle, seven or fewer single particles may be distributed.

[0048] The above rectangular image area is selected from any area in the FE-SEM image of the powder as a pulverized product, and an area can be selected in which at least one single particle is focused, or preferably one single particle is focused in the center. In addition, the single particle included in the area can only be recognized as one in which the entire particle is completely included in the area. Accordingly, the number of single particles distributed in the rectangular image area can be in the range of 1 to 7, preferably in the range of 1 to 5.

[0049]

[0050] In a third specific example, a single particle may have a minimum width of at least 2 μm.

[0051] In the positive electrode active material where primary particles are aggregated to form secondary particles, the primary particles do not satisfy the above conditions, so it can be seen that they are clearly different from single particles.

[0052]

[0053] In one specific example, the positive electrode active material molded sintered body of the present invention may include an elemental composition represented by the following chemical formula 1.

[0054] A x M 1-y D y O 2-z Q z (1)

[0055] In the above formula,

[0056] A is at least one element selected from alkali metals;

[0057] M is one or more transition metal elements that are stable in the four- or six-coordinate configuration;

[0058] D is a dopant, which is at least one element selected from alkaline earth metals, transition metals, and non-metals;

[0059] Q is an anion containing one or more elements selected from F, S, and P;

[0060] 0.35≤x≤1.1, 0≤y≤0.1, 0≤z≤0.2.

[0061] Representative examples of the above alkali metal (A) include Li, Na, etc., and preferably Li.

[0062] Representative examples of the above transition metal (M) include one or more of Ni, Co, Mn, etc., and preferably, Ni may be 50 mol% or more. When the Ni content is at least 50 mol% or more based on the total transition metal content, it may be preferable that the positive electrode active material be a single particle or a single particle when considering the efficiency, life characteristics, etc., of the positive electrode active material, and this is because the positive electrode active material molded sintered body of the present invention having a molded structure in which single particles are aggregated can be preferably manufactured.

[0063]

[0064] Representative examples of the above dopant (D) include Al, Zr, Mg, B, Ti, P, Si, Zn, Sn, Ca, Ge, Ga, Nb, Mo, W, etc.

[0065] In one specific example, it may be more effective if the dopant D includes at least one element selected from the group consisting of Al, Zr, Ti, and B.

[0066] Among them, Al is 6-coordinated to Ni in the transition metal layer of the active material. 3+ Elements with similar ionic radii, for example Al 3+ The ionic radius of (6-coordinated) is 0.535Å and that of Ni is 0.56Å. 3+ (6-coordination) has a similar value, so it can be seen that substitution is easy. Since Ni has an unstable structure in terms of electron configuration when it exists in the oxidation state of 3+, the above Al 3+ Go Ni 3+ When doped on the site, it can be effective in improving life characteristics.

[0067] In the case of Zr, 6-coordinated Li in the transition metal layer of the active material+ Elements with similar ionic radii, for example, Zr with an ionic radius of 0.72Å 4+ (6-coordination) can be applied. The above ion can be doped into the 3a Octahedral site of the Li layer to improve structural stability, and thus can be more effective in achieving the effects of the present invention.

[0068] The positive electrode active material in the molded sintered body according to the present invention may have various crystal structures, and may be formed, for example, of an α-NaFeO2 layered crystal structure.

[0069]

[0070] In addition, based on the above, the present invention provides a molded sintered body comprising a plurality of molded sintered bodies that are laminated and / or horizontally arranged, each of the molded sintered bodies characterized in that a plurality of positive electrode active material particles are aggregated to maintain a shape. Here, the positive electrode active material particles may preferably include single particles.

[0071] The structure and composition of these molded aggregates have unique characteristics that cannot be found in conventional technologies.

[0072]

[0073] The present invention also provides a positive electrode active material manufactured by crushing the positive electrode active material molded sintered body and a secondary battery including the positive electrode active material.

[0074] The method of producing a positive electrode active material, specifically a positive electrode active material powder, by crushing a sintered material and the method of configuring and manufacturing a secondary battery are known in the art, and therefore, a detailed description thereof is omitted herein.

[0075] As described above, the positive electrode active material molded sintered body according to the present invention is manufactured by being fed into a sintering furnace without using a sintering vessel and then sintered, and thus has high productivity. In addition, the internal stress generated by the pressure applied during the process of manufacturing the molded body for sintering increases the conversion energy during sintering, and the contact of the fluid during sintering is turned on, so that a positive electrode active material with excellent physical properties can be manufactured by high reactivity.

[0076] FIG. 1a is a schematic diagram of a structure in which a plurality of molded sintered bodies are stacked and horizontally arranged according to one embodiment of the present invention;

[0077] Figure 1b is a schematic diagram of a structure in which multiple sintering vessels containing cathode material are stacked and horizontally arranged;

[0078] (A) of Fig. 2 is a schematic diagram when viewed from the top surface of the single body of Fig. 1a, and (B) is a schematic diagram when viewed from the top surface of the single body of Fig. 1b;

[0079] Figure 3 is a schematic diagram showing the phenomenon of residual stress occurring inside a molded body during the compression process for manufacturing a green body;

[0080] Figure 4a is an SEM image of the positive electrode active material powder of Comparative Example 1;

[0081] Figure 4b is a SEM image of the positive electrode active material powder of Comparative Example 2;

[0082] Figure 5 shows SEM images of the positive electrode active material powder of Example 1 (A: 10,000 times magnification, B: 3,000 times magnification);

[0083] Figure 6 shows SEM images of the positive electrode active material powder of Example 2 (A: 10,000 times magnification, B: 3,000 times magnification);

[0084] Figure 7a is an FE-SEM image of the positive electrode active material powder of Comparative Example 1 and an enlarged view of a square image area measuring 5 μm × 5 μm;

[0085] Figure 7b is an FE-SEM image of the positive electrode active material powder of Comparative Example 2 and an enlarged view of a square image area measuring 5 μm × 5 μm;

[0086] Figure 8a is an FE-SEM image of the positive electrode active material powder of Example 1 and an enlarged view of a square image area measuring 5 μm × 5 μm;

[0087] Figure 8b is an FE-SEM image of the positive electrode active material powder of Example 2 and an enlarged view of a square image area measuring 5 μm × 5 μm.

[0088] Hereinafter, the present invention will be described in more detail with reference to embodiments of the present invention, but the scope of the present invention is not limited thereto.

[0089]

[0090] [Example 1]

[0091] A precursor solution was prepared by adding NiSO4 as a nickel raw material, CoSO4 as a cobalt raw material, and MnSO4 as a manganese raw material to water in a molar ratio of 0.96:0.01:0.03. The precursor solution was slowly added dropwise to ammonia water and NaOH water while stirring at 1000 rpm and 50-60°C in a reactor so that the pH became 10-12, and stirring was performed until the D50 of the precursor particles reached the desired size. Then, the synthesized precursor was washed and separated from the filtrate, and dried at 120°C for 20 hours to obtain Ni. 0.96 Co 0.01 Mn 0.03 A precursor of (OH)2 was prepared.

[0092] The precursor and lithium raw material LiOH were weighed at a molar ratio of 1.01 to the precursor and introduced into a 10 L cylindrical reactor, and 0.1 mol Al(OH)3 as the Al raw material and 0.1 mol ZrO2 as the Zr raw material were mixed, and then 3 to 6 wt% of water based on the total mixture was additionally introduced and mixed. Then, a predetermined pressure was applied to 50 g of the mixture using a compression molding machine (Hantech Co., Ltd., HLP) to obtain a molded precursor.

[0093] The above molding precursor was transferred into the RHK sintering furnace in a state of being laminated in multiple layers on a sagger, and then the temperature was raised to 700 to 900°C in an oxygen atmosphere and maintained for 8 to 10 hours to be sintered, resulting in a Ni doped with Zr and Al. 0.96 Co 0.01 Mn 0.03 A molded sintered body containing the positive active material of O2 was manufactured.

[0094] The above-mentioned molded body was placed in a jet-mill crushing device and crushed at a strength of 1.2 to 2 bar to finally obtain a positive electrode active material powder.

[0095]

[0096] [Comparative Example 1]

[0097] A sintered body and positive electrode active material powder were manufactured in the same manner as in Example 1, except that the sintering temperature was 600 to 700°C, the sintering holding time was 2 to 3 hours, and the crushing strength was 0.7 to 1 bar.

[0098]

[0099] [Comparative Example 2]

[0100] A sintered body and positive electrode active material powder were manufactured in the same manner as in Comparative Example 1, except that the crushing strength was 1.2 to 2 bar.

[0101]

[0102] [Example 2]

[0103] A sintered body and a positive electrode active material powder were manufactured in the same manner as in Example 1, except that the element molar ratio of transition metals (Ni:Co:M) was 88:09:03 and the sintering temperature was 800 to 900°C.

[0104]

[0105] [Comparative Example 3]

[0106] A sintered body and positive electrode active material powder were manufactured in the same manner as in Example 2, except that the sintering temperature was 700 to 800°C, the sintering holding time was 2 to 3 hours, and the crushing strength was 0.7 to 1 bar.

[0107]

[0108] [Comparative Example 4]

[0109] A sintered body and positive electrode active material powder were manufactured in the same manner as in Comparative Example 3, except that the crushing strength was 1.2 to 2 bar.

[0110]

[0111] [Comparative Example 5]

[0112] A sintered body and positive electrode active material powder were manufactured in the same manner as in Comparative Example 3, except that the sintering time was 3 to 4 hours and the crushing strength was 1.2 to 2 bar.

[0113]

[0114] [Example 3]

[0115] A sintered body and a positive electrode active material powder were manufactured in the same manner as in Example 1, except that the element molar ratio of transition metals (Ni:Co:M) was 70:15:15, the sintering temperature was 950 to 1050°C, and the sintering holding time was 10 to 12 hours.

[0116]

[0117] [Comparative Example 6]

[0118] A sintered body and positive electrode active material powder were manufactured in the same manner as in Example 3, except that the sintering temperature was 800 to 900°C, the sintering holding time was 5 to 7 hours, and the crushing strength was 0.7 to 1 bar.

[0119]

[0120] [Comparative Example 7]

[0121] A sintered body and positive electrode active material powder were manufactured in the same manner as in Comparative Example 6, except that the crushing strength was 1.2 to 2 bar.

[0122]

[0123] [Example 4]

[0124] A sintered body and a positive electrode active material powder were manufactured in the same manner as in Example 1, except that the element molar ratio of transition metals (Ni:Co:M) was 60:20:20, the sintering temperature was 950 to 1050°C, and the sintering holding time was 10 to 12 hours.

[0125]

[0126] [Comparative Example 8]

[0127] A sintered body and positive electrode active material powder were manufactured in the same manner as in Example 4, except that the sintering temperature was 800 to 900°C, the sintering holding time was 5 to 7 hours, and the crushing strength was 0.7 to 1 bar.

[0128]

[0129] [Comparative Example 9]

[0130] A sintered body and positive electrode active material powder were manufactured in the same manner as in Comparative Example 8, except that the crushing strength was 1.2 to 2 bar.

[0131]

[0132] [Example 5]

[0133] A sintered body and a positive electrode active material powder were manufactured in the same manner as in Example 1, except that the element molar ratio of transition metals (Ni:Co:M) was 50:20:30, the sintering temperature was 950 to 1050°C, and the sintering holding time was 10 to 12 hours.

[0134]

[0135] [Comparative Example 10]

[0136] A sintered body and positive electrode active material powder were manufactured in the same manner as in Example 4, except that the sintering temperature was 800 to 900°C, the sintering holding time was 5 to 7 hours, and the crushing strength was 0.7 to 1 bar.

[0137]

[0138] [Comparative Example 11]

[0139] A sintered body and positive electrode active material powder were manufactured in the same manner as in Comparative Example 10, except that the crushing strength was 1.2 to 2 bar.

[0140]

[0141] [Experimental Example 1]

[0142] SEM images were obtained for the positive electrode active material powders manufactured in Comparative Examples 1 and 2 and Examples 1 and 2, respectively, under the following measurement conditions, and the results are shown in Figures 4 to 8.

[0143]

[0144] SEM measurement conditions

[0145] - Model: HITACHI (S-4800)

[0146] - Resolution: 1.0㎚ 15㎸, 1.5㎚ 1㎸

[0147] - Magnification: x10,000

[0148] - Electron gun: Cold-cathode field emission type electron gun

[0149] - Accelerating voltage: 15㎸

[0150] - Detector: SE (BSE)

[0151]

[0152] PSD measurement conditions

[0153] - Measuring equipment: Microtrac S3500 Extended

[0154] - Circulation speed: 45% / sec

[0155] - Refractive index ratio: 1.55

[0156] - Equipment input solvent: distilled water

[0157] - Cell Sample: 0665

[0158] - Calculation Logic: X100

[0159] - Sample amount: 0.0025 g

[0160] - Sample dispersant: 1 ml of 10% Sodium Hexamethaphosphate

[0161] - Sample solvent: 40 ml of distilled water

[0162] - Sample ultrasonic dispersion: 40 KHz, 1 min

[0163]

[0164] First, referring to FIG. 4a for the positive electrode active material powder of Comparative Example 1 and FIG. 4b for the positive electrode active material powder of Comparative Example 2, the strength for crushing ('crushing strength') is relatively small in Comparative Example 1 (FIG. 4a) and relatively large in Comparative Example 2 (FIG. 4b). Due to the small crushing strength, both a broken particle state and a particle agglomeration state are confirmed in the positive electrode active material powder of Comparative Example 1, and the broken particle state is a broken spherical secondary particle. On the other hand, due to the large crushing strength, it can be confirmed that the crushing phenomenon is confirmed in many cases in the positive electrode active material powder of Comparative Example 2 and the generation of fine particles is very large.

[0165] For reference, in a separate experiment, in order to prevent this particle breakage state, the sintering process was performed by minimizing the applied pressure during the process of manufacturing the molded body, but the result was that the sintered product was unable to maintain the molded state and completely collapsed.

[0166] In contrast, when looking at the positive electrode active material powder of Example 1 (Fig. 5) and the positive electrode active material powder of Example 2 (Fig. 6), it can be confirmed that there is almost no particle breakage and that the agglomeration is also very small.

[0167]

[0168] Meanwhile, FIGS. 7a and 7b provide FE-SEM images of the positive electrode active material powders of Comparative Examples 1 and 2, respectively. It can be confirmed that a large number of particles, i.e., primary particles, are present in a square image area measuring 5 ㎛ × 5 ㎛.

[0169] In contrast, looking at Figs. 8a and 8b, which provide FE-SEM images of the positive electrode active material powders of Examples 1 and 2, respectively, it can be confirmed that there are three single particles in each square image area measuring 5 μm × 5 μm. In addition, it is confirmed that the single particles have a size of 2 μm or more.

[0170] For reference, the particle counting above, in both the comparative example and the exemplary embodiment, targeted only particles that were entirely contained in the rectangular image area, i.e., particles whose outer surface did not extend over the area boundary.

[0171]

[0172] [Experimental Example 2]

[0173] XRD measurements were performed on the positive electrode active material powders manufactured in Examples 1 to 5 and Comparative Examples 1 to 11, respectively, under the following conditions, and the crystal grain size (nm) of the (003) plane is shown in Table 1 below.

[0174]

[0175] XRD measurement conditions

[0176] - Power source: CuKα (pre-focus), wavelength: 1.541836Å

[0177] - Operating axis: 2θ / θ, Measurement method: Continuous, Counting unit: cps

[0178] - Start angle: 10.0°, End angle: 80.0°, Number of accumulations: 1

[0179] - Sampling width: 0.01°, Scan speed: 2.0° / min

[0180] - Voltage: 40kV, Current: 40mA

[0181] - Divergence slit: 0.2mm, divergence species limiting slit: 10mm

[0182] - Scatter slit: open, receiving slit: open

[0183] - Offset angle: 0°

[0184] - Goniometer radius: 285mm, optical system: focusing method

[0185] - Attachment: ASC-48

[0186] - Slit: Slit for D / teX Ultra

[0187] - Detector: D / teX Ultra

[0188] - Incident Monochrome: CBO

[0189] - Ni-Kβ filter: None

[0190] - Rotation speed: 30 rpm

[0191]

[0192] As shown in Table 1 above, the positive electrode active materials of the examples satisfy the condition that the grain size of the (003) plane is at least 100 nm or more, specifically 160 nm to 250 nm, when measured by XRD, whereas the positive electrode active materials of most of the comparative examples all have a size of less than 100 nm.

[0193] Comparative Example 5, compared to Comparative Example 4, allowed the crystals to grow further by setting a longer firing time, resulting in a grain size of 115 nm. However, the appropriate firing temperature for forming a single particle was not satisfied, and thus a cathode active material in the form of secondary particles with a relatively large grain size was produced. Therefore, it can be confirmed that the battery characteristics are inferior when compared to the examples according to the present invention in Experimental Example 3 described below.

[0194]

[0195] [Experimental Example 3]

[0196] The positive electrode active material powders manufactured in Comparative Examples 1 to 11 and Examples 1 to 5 were mixed with Super-P as a conductive agent and PVdF as a binder in a solvent, N-methylpyrrolidone, at a weight ratio of 96:2:2 to manufacture a positive electrode active material slurry, which was applied onto an aluminum current collector, dried at 120°C, and then rolled to manufacture a positive electrode.

[0197] An electrode assembly was manufactured using lithium metal as an anode together with the positive electrode manufactured above and a porous polyethylene film as a separator between them. After positioning the electrode assembly inside a battery case, an electrolyte was injected into the inside of the battery case to manufacture a CR2032 type coin cell. At this time, the electrolyte used was lithium hexafluorophosphate (LiPF6) dissolved at a concentration of 1.0 M in an organic solvent composed of ethylene carbonate / dimethyl carbonate (EC / DMC mixing volume ratio = 1 / 1).

[0198] The coin cell manufactured above was subjected to charge and discharge evaluation at 25℃ in the voltage range of 4.25~2.5V, and after applying a current density of 0.2C, a 0.05C constant voltage section was given. The voltage range for the life evaluation was 4.25~2.5V, and after applying a charge and discharge current density of 0.5C / 1C, a 0.05C constant voltage section was given, and a life evaluation was performed after 50 cycles. The results are shown in Table 2 below.

[0199]

[0200] As shown in Table 2 above, the secondary batteries of the examples have relatively excellent charge / discharge efficiency and, in particular, excellent life characteristics when compared with the secondary batteries of the comparative examples having the same transition metal element composition (for example, the secondary battery of example 1 is compared with the secondary batteries of comparative examples 1 and 2 having the same transition metal element composition).

[0201] Specifically, Comparative Examples 1, 3, 6, 8, and 10, in which the crushing strength was weak and some of the secondary particles were crushed or agglomerated, showed lower charge / discharge efficiency and, in particular, significantly lower life characteristics compared to the examples of the same composition. In addition, Comparative Examples 2, 4, 7, 9, and 11, in which the crushing strength was strong and most of the secondary particles were crushed, showed lower charge / discharge efficiency compared to the examples of the same composition and, in particular, showed a greater decrease than Comparative Examples 1, 3, 6, 8, and 10. This is expected to be because the secondary particles were destroyed and a large amount of fine powder was generated, which lowered the structural stability during charge / discharge, resulting in lower life characteristics.

[0202] In the case of Comparative Example 5, the grain size was formed to be larger than that of other Comparative Examples, as in Experimental Example 2, but as it was formed into secondary particles and a large amount of fine powder was generated after pulverization, the lifespan was shown to be reduced to a level very similar to that of Comparative Example 4 of the same composition. In other words, if it is not formed into a single particle, it can be seen that even if the grain size is larger than that of general secondary particle active materials, the battery characteristics may be deteriorated due to the problem of particles being crushed during pulverization.

[0203]

[0204] The present invention is not limited to the above-described embodiments, but can be manufactured in a variety of different forms. Those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. A positive electrode active material molded sintered body characterized in that a plurality of positive electrode active material particles are aggregated and maintain their shape.

2. A positive electrode active material molded sintered body, characterized in that in the first paragraph, at least a portion of the positive electrode active material particles are partially sintered with adjacent particles to maintain the shape.

3. A positive electrode active material molded sintered body according to claim 1, characterized in that the positive electrode active material particles comprise a single particle.

4. A positive electrode active material molded sintered body, characterized in that, when the molded sintered body is pulverized for manufacturing positive electrode active material powder in the first paragraph, positive electrode active material particles that maintain their shape are separated from each other and converted into powder.

5. A positive electrode active material molded sintered body, characterized in that in the fourth paragraph, the powder contains single particles and optionally further contains aggregates in which single particles are aggregated.

6. In the 4th paragraph, a positive electrode active material molded sintered body characterized in that in a square image area of ​​5 ㎛ × 5 ㎛ in size set to focus on at least one single particle in the FE-SEM image of the powder, 7 or fewer single particles are distributed.

7. In the third paragraph, the single particle is characterized in that the shortest width is at least 2 ㎛ or more, and is a positive electrode active material molded sintered body.

8. A positive electrode active material molded sintered body according to claim 1 or claim 3, characterized in that the positive electrode active material particles have a grain size of 100 nm or more on the (003) plane as measured by XRD.

9. A positive electrode active material molded sintered body, characterized in that in the 8th paragraph, the positive electrode active material particles have a crystal grain size of 120 nm or more on the (003) plane when measured by XRD.

10. A positive electrode active material molded sintered body, characterized in that in the first paragraph, a pattern and / or hole through which a fluid can flow is formed in the molded structure during sintering.

11. A positive electrode active material molded sintered body characterized in that the Ni content in the first paragraph is at least 50 mol% based on the total transition metal content.

12. Contains a plurality of molded sintered bodies that are stacked and / or horizontally arranged, A molded sintered body, each of which is characterized in that a plurality of positive electrode active material particles are aggregated to maintain a shape.

13. A cathode active material characterized by being manufactured by crushing a cathode active material molded body according to Article 1.

14. A secondary battery characterized by including a positive electrode active material according to Article 13.

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