Molded precursor for preparation of cathode active material

Abstract

The present invention provides a molded precursor comprising a transition metal precursor and an alkali metal / alkaline earth metal precursor, wherein the transition metal precursor contains Fe, and the precursors are aggregated to maintain a shape.

Description

Molded precursor for manufacturing positive electrode active material

[0001] The present invention relates to a molded precursor for manufacturing an anode active material, and more specifically, to a molded precursor in which a transition metal precursor containing Fe and an alkali metal / earth metal precursor aggregate to maintain a stable shape.

[0002] The manufacturing of cathode active materials using precursors as raw materials necessarily involves a calcination process. The Roller Hearth Kiln (RHK) calcination method is well known in the industry as a representative method for calcining electrode active materials and is applied in the mass production of products in industrial settings.

[0003] This RHK calcination method consists of a process in which powdered raw materials are mixed, placed into a calcination vessel, and then inserted into a horizontal furnace with temperature settings for each zone. The vessel is then moved along a conveyor for tens of meters to carry out continuous calcination. Inside the calcination vessel moving on the conveyor, the raw materials are contained in a mixed state, and diffusion and crystal growth occur as they react with each other due to the high-temperature heat supplied from within the horizontal furnace.

[0004] Since the RHK calcination furnace can only load the positive active material up to the internal volume of the calcination vessel, it has the disadvantage that if the bulk density of the raw material is high, a large amount of positive active material cannot be calcined at once.

[0005] Consequently, a method is sometimes used in which raw material powder is placed in firing vessels and stacked in multiple layers to improve productivity while moving through the kiln for firing; however, there is a problem in that firing vessels cannot be stacked above a certain height because the load is limited to prevent damage to the rollers supporting the vessels.

[0006] Therefore, to increase productivity, a technology is being attempted to improve productivity by forming precursors for manufacturing cathode active materials and stacking the molded bodies themselves without stacking the firing vessels, thereby producing more cathode active material equivalent to the weight of the firing vessels; however, when making molded bodies using a pressing method, if the molding method is not optimized according to the characteristics of the precursors, problems such as the molded bodies breaking after molding or firing, or non-uniform reactions, may occur.

[0007] For example, in the case of commonly used NCM cathode active materials, when a molded body is prepared from raw materials and fired, the NCM cathode active material molded body discharged from the kiln fails to maintain its shape intact or collapses during firing, preventing it from being discharged from the kiln. Even if it is discharged while maintaining its shape, problems arise such as a degradation of the electrochemical properties of the cathode active material. This is because, in the case of NCM cathode active materials, primary particles are aggregated to form secondary particles in a spherical shape; however, when pressure is applied for molding, these secondary particles fail to maintain their shape and break, thereby degrading the properties of the cathode active material.

[0008] In the case of lithium iron phosphate (LFP) cathode active materials, the raw materials—FePO4, Li, and carbon sources—have low powder densities and small particle sizes, resulting in significant scattering during the reaction process in the calcination. These scattered particles are collected by exhaust fans, causing loss. For these LFP cathode active materials, pellet density is crucial for improving power density; however, since this pellet density is lowered by the nano-sized particle size distribution, attempts are being made to improve this characteristic. Furthermore, as LFP cathode active materials have the advantage of being inexpensive, increasing production efficiency to enhance price competitiveness is also a critical task; thus, a differentiated manufacturing method compared to NCM cathode active materials is required.

[0009] Therefore, there is a high need in the industry for new technologies capable of manufacturing cathode active materials, such as LFP, with excellent productivity while providing high density.

[0010] The present invention aims to solve the problems of the prior art described above and technical challenges that have been requested over time.

[0011] After conducting in-depth research and various experiments, the inventors of this application developed a new type of molded precursor in which an Fe-containing transition metal precursor and an alkali metal / earth metal precursor maintain an aggregated shape. Since this molded precursor maintains a stable shape due to high structural stability, it can be fired by stacking multiple layers without using a firing vessel, thereby enabling the realization of high productivity. Based on this, the inventors have completed the present invention.

[0012] Therefore, the molding precursor of the present invention is,

[0013] It includes transition metal precursors and alkali metal / earth metal precursors,

[0014] The above transition metal precursor includes Fe,

[0015] The above precursors are characterized by being aggregated and maintaining their shape.

[0016] As defined above, the molded precursor of the present invention has a form in which a transition metal precursor containing Fe as an essential element and an alkali metal / earth metal precursor are aggregated, and this can be introduced into a calcination device such as an RHK calcination furnace without using a separate calcination vessel to manufacture a positive electrode active material with high productivity through calcination.

[0017] In the above, "maintaining shape" refers to a state in which the overall molding structure can be maintained to the extent that the molding precursor itself can be stacked and transported, even if the edges of the molding precursor are partially broken or crumbled. Accordingly, the stacked molding precursor may not collapse.

[0018]

[0019] Such molding precursors can be manufactured, for example, through a process including the following steps.

[0020] (a) A process of preparing a wettable mixture by mixing a transition metal precursor and an alkali metal / earth metal precursor and adding water;

[0021] (b) a process of drying the above wettable mixture to produce a powder composite; and

[0022] (c) A process of placing the above powder composite into a molding mold and applying pressure to produce a molding precursor.

[0023] As experimentally confirmed by the inventors, when preparing a "powder composite" from a "wet mixture" in process (b), if the precursors are aggregated into a form close to spherical during the drying process, the flowability of the powder composite is improved, so that when pressure is applied in process (c), the powder composites are evenly dispersed and compressed, and a uniform pressure is applied overall, thereby producing a molded product with a desired pressure. To this end, drying methods such as spray drying or drum drying may be preferably used.

[0024] In addition, it was confirmed that the pressure applied to produce the molded precursor in the above process (c) needs to be set differently depending on the precursor.

[0025] For example, in the case of Ni-based active materials such as NCM active materials, there is a problem where characteristics such as structural stability and lifespan deteriorate as the amount of fine particles increases, so it may be desirable to manufacture them as single particles with relatively large particle sizes, and when the applied pressure is increased, the particles aggregate better, which may be advantageous for manufacturing single particles.

[0026] In the case of LFP active materials, it is advantageous to form particles in the nano-sized range with a small particle size as much as possible due to reasons such as low electronic conductivity. However, as explained above, if the powder aggregate is formed into a near-spherical aggregate during the drying process for excellent moldability, the springback phenomenon is intensified, and a problem may occur where the molded body is damaged by the restoring force of the particles when excessive pressure is applied, so it is necessary to apply a relatively low pressure. For example, the applied pressure for manufacturing the molded precursor of the LFP active material may preferably be in the range of 30K to 60K.

[0027]

[0028] In one specific example, the precursors may be physically bonded.

[0029] This distinguishes the precursors from a state where they are simply mixed, implying that they are physically bonded through the action of factors capable of providing interparticle fixation, such as electrostatic attraction, van der Waals forces, partial chemical bonding, and jamming due to surface shape. This physical bonding enables the formation of a molded body with excellent structural stability.

[0030]

[0031] The molding precursor of the present invention may preferably not include a binder for inducing adhesion between precursor particles.

[0032] While the inclusion of binders such as polymers improves structural stability, if the binder remains in some of the active material, it acts as an impurity, making it difficult to achieve the desired battery characteristics. Furthermore, the amount of cathode active material that can be produced per unit volume decreases proportionally to the amount of binder added, which can directly impact productivity. In particular, given the nature of LFP active materials, which must be manufactured at a low cost by minimizing unit expenses, a decrease in productivity—that is, an increase in costs—can significantly diminish the advantages of LFP active materials.

[0033] In addition, even when a certain amount of water is included as a binder, the moisture inside evaporates and escapes during firing, causing cracks in the molded body and potentially leading to its collapse after firing; therefore, stacking and firing molded bodies to improve productivity may also be practically difficult.

[0034]

[0035] In one preferred example, the molding precursor of the present invention may further include a carbon precursor.

[0036] In the case of LFP active materials, carbon coating is essential due to issues such as low electronic conductivity, so it may be desirable to include a carbon precursor in the molding precursor.

[0037] The method of including a carbon precursor in the molding precursor can be selected from two methods as follows, depending on the process.

[0038] (i) A method of forming a molded precursor by mixing a carbon precursor into a powder composite prepared by drying a wettable mixture of a transition metal precursor and an alkali metal / earth metal precursor.

[0039] (ii) A method for preparing a wettable mixture in which a carbon precursor is pre-mixed with a transition metal precursor and an alkali metal / earth metal precursor, and the preparation of a powder composite by drying and the formation of a molded precursor by applying pressure.

[0040] In the above method (i), calcination proceeds in a form where a carbon precursor is in contact with the outer surface of a powder composite, which is a secondary particle composed of a transition metal precursor and an alkali metal / earth metal precursor. When the mixture is crushed after calcination, the carbon is coated only on the primary particles located on the outer surface of the secondary particles, and the primary particles located in the center of the secondary particles have less opportunity to come into contact with the carbon and may not be coated. In other words, the carbon coating may be uneven, which can cause a relative deterioration of battery characteristics.

[0041] On the other hand, in the case of method (ii), when disintegrating after firing, the carbon coating is uniformly formed on all primary particles, which may be more desirable.

[0042]

[0043] In one specific example, the bulk density is 0.85 to 1.4 g / cm³ 3 The range may be, and the bulk density increase rate before / after pressing may be in the range of 130 to 210%.

[0044] Bulk density is directly related to press pressure, and a bulk density of 0.85 g / cm³ 3 If it is too small, it means that the press pressure is applied too weakly, and the manufactured molded body may break; conversely, 1.4 g / cm³ 3 If the value is excessively large, it implies that the press pressure has been applied too strongly; this is undesirable as it may lead to cracking or breakage in the manufactured molded body due to the springback phenomenon. The preferred bulk density is 1 to 1.3 g / cm³. 3 The range may be, and the desirable increase rate of bulk density after pressing may be in the range of 175 to 190%.

[0045] Such bulk density can vary depending on characteristics such as particle size resulting from differences in composition (e.g., NCM, NCA, LFP) and manufacturing methods, as well as the appropriate bulk density and the rate of increase in bulk density before and after pressing. In other words, the desirable bulk density and the rate of increase in bulk density before and after pressing may be closely related to the particle composition.

[0046]

[0047] The above transition metal precursor may have a composition represented by, for example, Chemical Formula 1 below.

[0048] (Fe x M 1-x )P y O 4-z (1)

[0049] In the above formula,

[0050] 0 <x≤1, 0≤y≤2, 0<z≤4이고,

[0051] M is one or more selected from alkaline earth metals, transition metals, post-transition metals, metalloids, nonmetals, lanthanides, and actinides.

[0052] The above "alkaline earth metals" may be, for example, Be, Mg, Ca, Sr, Ba, Ra, etc.

[0053] The above "transition metal" is a "transition metal of Group 3 to Group 12 excluding Fe," and may be, for example, Ni, Co, Mn, Sc, Ti, V, Cr, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, etc.

[0054] The above "post-transition metals" and "metalloids" are "post-transition metals and metalloids in groups 13 to 15," and may be, for example, Al, Ga, In, Sn, Tl, Pb, Bi, Po, B, Si, Ge, As, Sb, Te, At, etc.

[0055] The above "nonmetal" may be "nonmetal elements in groups 14 to 16," such as C, P, S, Se, etc.

[0056] The P content is preferably 0 <y≤2일 수 있고, 그에 따른 바람직한 전이금속 전구체는 FePO4또는 FePO4에 알칼리 금속, 전이금속, 전이후금속, 준금속, 비금속, 란탄족, 악티늄족 중 1종 이상이 도핑된 형태일 수 있다.

[0057]

[0058] The above alkali metal / earth metal precursor may have a composition represented by, for example, Chemical Formula 2 below.

[0059] (1-fghi)A a CO3* fA b OH * gA c O2* hA d SO4*iA e PO4(2)

[0060] In the above formula,

[0061] 0 <a≤4, 0<b≤4, 0<c≤4, 0<d≤4, 0<e≤4, 0≤f≤1, 0≤g≤1, 0≤h≤1, 0≤i≤1, 0≤1-f-g-h-i≤1이고,

[0062] A is one or more selected from alkali metals and alkaline earth metals.

[0063] Above A a A desirable example of CO3 is Li2CO3, and A b Preferred examples of OH include LiOH, but are not limited to these. Such compounds may exist alone or in a mixed state as shown in Chemical Formula 2 above, and Li2CO3 may be used alone to reduce the production cost of the LFP active material.

[0064]

[0065] The above carbon precursor may have a composition represented by, for example, Chemical Formula 3 below.

[0066] C h H i O j (3)

[0067] In the above formula,

[0068] 0 <h≤20, 0≤i≤42, 0≤j≤10이다.

[0069] Preferable examples of carbon precursors include sugars such as glucose, sucrose, galactose, and lactose, general hydrocarbon polymers, and pitch, but are not limited to these.

[0070]

[0071] In one specific example, the molding precursor of the present invention may additionally include a doping element, which may be included in one or more of the following ways.

[0072] (i) Transition metal precursors containing additional doping elements,

[0073] (ii) Including a doping precursor in addition to the transition metal precursor.

[0074] The above method (i) is a case where the doping element is already added when manufacturing the transition metal precursor so that the doping element is included in the transition metal precursor as a constituent element, and the method (ii) is a case where the doping element is added when manufacturing the wettable mixture as described above, and / or added by mixing with the powder composite.

[0075]

[0076] In some cases, a surfactant for uniform molding may be further included, and examples of such surfactants include polyethylene glycol (PEG), but are not limited to that.

[0077] When a surfactant is added during the spray drying process, it adheres to the interface of the droplets, making them more spherical and potentially increasing the flowability of the resulting dried particles (powder aggregate).

[0078]

[0079] The present invention also provides a stacked assembly of molding precursors characterized by having the molding precursors described above stacked in multiple stages.

[0080] As explained above, since the molding precursor of the present invention can maintain a stable shape not only before but also after firing, it is possible to introduce a stacked assembly formed by stacking the molding precursors in multiple stages into the firing furnace based on this structural stability.

[0081] The number of stacked layers is not specifically limited and can be determined by considering, for example, the maximum support load of the rollers in the kiln device to which the present invention is applied.

[0082]

[0083] The present invention also provides a positive active material prepared from the above-mentioned molded precursor and a secondary battery comprising such positive active material.

[0084] The technology for manufacturing a positive electrode active material from a molded precursor and thereby manufacturing a secondary battery is known in the art and is exemplified in the experimental details described below; therefore, a detailed description thereof is omitted in this specification.

[0085] As explained above, the molded precursor of the present invention can be introduced into a firing device such as an RHK firing furnace without using a separate firing container to manufacture an anode active material through firing, and also has excellent structural stability, allowing firing even in a multi-layered stacked state, thereby enabling high productivity.

[0086] FIG. 1 shows photographs of the powder composite placed in a mold (A) and the green body (B) produced by applying pressure in Example 2;

[0087] Figure 2 is a photograph of the green body of Example 4;

[0088] Figure 3 is a photograph of the green body of Comparative Example 3;

[0089] Fig. 4 is a photograph of the green body of Comparative Example 4;

[0090] FIG. 5 is a photograph (A) of the powder composites of Example 3 and an enlarged photograph (B) of one of the powder composites;

[0091] FIG. 6 shows photographs of the shape (A) of an exemplary laminated assembly produced by stacking the molding precursors produced in Example 2 in multiple stages, and the shape (B) after firing.

[0092] The present invention will be described further below with reference to embodiments thereof, but the scope of the invention is not limited by them.

[0093]

[0094] [Example 1]

[0095] FePO4 (transition metal precursor) and Li2CO3 (alkali metal precursor) were weighed at a molar ratio of 1.01 Li / Fe and introduced into a 10L cylindrical reactor to be mixed. The wettable mixture thus obtained was dried using a spray dryer device to produce a powder composite with an average particle size of 30 μm.

[0096] About 5% by weight of glucose (carbon precursor) based on the total solid weight was added to the above powder mixture and placed in a mold, and a pressure of about 40K was applied using a pressure molding machine to produce a green body (molding precursor) with dimensions of 116 mm × 65 mm × 15 mm. Here, the pressure unit K can be replaced with MPa.

[0097] The above green bodies were arranged in 10 rows on each side and stacked in 10 rows vertically and transferred into an RHK kiln, and then fired for about 9 hours at a temperature raised to about 800°C in an inert atmosphere (N2 gas) to produce a molded fired body containing a positive electrode active material of LiFePO4.

[0098] The above-mentioned molded sintered body was fed into a Jet-mill grinding device and ground with a strength of 1.2 to 2 bar to finally produce a positive electrode active material powder.

[0099]

[0100] [Example 2]

[0101] A powder composite was prepared by adding glucose, a carbon precursor, in a mixed manner with FePO4 and Li2CO3, and an anode active material powder was prepared in the same manner as in Example 1, except that the applied pressure was changed to 30K.

[0102]

[0103] [Example 3]

[0104] A positive electrode active material powder was prepared in the same manner as in Example 2, except that the magnitude of the applied pressure was changed to 40K.

[0105]

[0106] [Example 4]

[0107] A powder composite was prepared by adding PEG, a surfactant, in a manner that mixed it with glucose, FePO4, and Li2CO3, and an anode active material powder was prepared in the same manner as in Example 2, except that the applied pressure was changed to 50K.

[0108]

[0109] [Example 5]

[0110] A positive electrode active material powder was prepared in the same manner as in Example 2, except that the magnitude of the applied pressure was changed to 60K.

[0111]

[0112] [Example 6]

[0113] A positive electrode active material powder was prepared in the same manner as in Example 3, except that a transition metal precursor containing 200 to 700 ppm of Ti was used.

[0114]

[0115] [Example 7]

[0116] Except for the addition of Mn during the preparation of the transition metal precursor, Fe was prepared in the same manner as in Example 3. 1-x Mn x A positive electrode active material powder of PO4 (x = 0.001 ~ 0.005) was prepared.

[0117]

[0118] [Comparative Example 1]

[0119] Ni instead of FePO4 0.96 Co 0.01 Mn 0.03 Except for using LiOH instead of (OH)2 and Li2CO3, not adding a carbon precursor, and changing the applied pressure to 70K to fabricate a green body, followed by calcination in an oxidizing atmosphere, LiNi was prepared in the same manner as in Example 1. 0.96 Co 0.01 Mn 0.03 O2 positive active material powder was prepared.

[0120] The above Ni 0.96 Co 0.01 Mn 0.03 (OH)2 was prepared through the following process.

[0121] First, an aqueous precursor solution was prepared by adding NiSO4 as a nickel source, CoSO4 as a cobalt source, and MnSO4 as a manganese source to water in a molar ratio of 0.96:0.01:0.03. The aqueous precursor solution was stirred in a reactor at 50–60°C and 1000 rpm while slowly adding aqueous ammonia water and NaOH solution dropwise to adjust the pH to 10–12, stirring until the D50 of the precursor particles reached the desired size. Then, the synthesized precursor was dried at 120°C for 20 hours following washing and filtrate separation, and Ni 0.96 Co 0.01 Mn 0.03 A precursor of (OH)2 was prepared.

[0122]

[0123] [Comparative Example 2]

[0124] The positive active material powder was prepared in the same manner as in Example 2, except that no pressure was applied when making the green body.

[0125]

[0126] [Comparative Example 3]

[0127] A positive electrode active material powder was prepared in the same manner as in Example 2, except that the magnitude of the applied pressure was changed to 20K.

[0128]

[0129] [Comparative Example 4]

[0130] A positive electrode active material powder was prepared in the same manner as in Example 2, except that the magnitude of the applied pressure was changed to 70K.

[0131]

[0132] [Comparative Example 5]

[0133] The positive electrode active material powder was prepared in the same manner as in Example 2, except that the method was changed from spray drying to powder drying.

[0134]

[0135] [Comparative Example 6]

[0136] A positive electrode active material powder was prepared in the same manner as in Example 2, except that approximately 5 wt% of water (binder) relative to the total mixture was additionally added to the powder composite and glucose mixture and mixed.

[0137]

[0138] [Experimental Example 1]

[0139] In the process of manufacturing the cathode active material powder in Examples 1 to 7 and Comparative Examples 1 to 6 above, damage after molding and firing was visually observed, and the density increase rate (%) was calculated by measuring the bulk density before and after pressing. In addition, the pellet density (PD) was measured in the following manner, and the relative production volume was measured when the production volume of Comparative Example 2 was set to 100%. The above results are shown in Table 1 below.

[0140]

[0141] Pellet Density (PD) Measurement Method

[0142] The equipment used was the CARVER Auto pellet press 3887NE.L model. Approximately 1.0 g of the finished pulverized active material was placed in a dedicated mold, and the initial height (mm) was measured using the equipment's vernier caliper. Then, a pressure of 2.5 ton was applied to the mold for 30 seconds and then released. Afterward, the height (mm) of the sample was measured after compression using the equipment's vernier caliper.

[0143] Then, the thickness of the compressed sample was calculated according to the following formula, and

[0144] A. Sample thickness (cm) = [Sample height after compression (mm) - Initial height (mm)] * 0.1

[0145] The pellet density was calculated according to the following formula.

[0146] B. Pellet density (g / cm³) 3 ) = Weight of active material (g) / Volume of pellet (cm³) 3) = Weight of active material (g) / [Mold radius (cm)] 2 * 3.141592 * Sample thickness (cm).

[0147]

[0148] The following items can be confirmed through the results of Table 1 above and Figures 1 to 6.

[0149]

[0150] (1) As shown in FIG. 1, the powder composite in Example 2 is placed in a mold (A) and the green body (B) produced by applying pressure is shown. It can be seen that the green body (molding precursor) maintains a stable shape while maintaining structural stability.

[0151]

[0152] (2) Figure 2 shows a photograph of the green body of Example 4, and Figure 3 shows a photograph of the green body of Comparative Example 3. While the green body of Example 4 maintains a stable shape, the green body of Comparative Example 3 is severely damaged due to the excessively weak press pressure. The green body of Comparative Example 4 was also damaged due to the springback effect caused by the excessively strong press pressure.

[0153]

[0154] (3) Figure 4 shows a photograph (A) of the powder composites of Example 3 and an enlarged photograph (B) of one of the powder composites. Overall, it shows a shape that is very close to a sphere. This high sphericity increases the flowability of the powder composite and improves the bulk density through dense filling.

[0155]

[0156] (4) In the case of Comparative Example 5, the fluidity of the dried particles was reduced using a general powder drying method, and as a result, pressure deviation occurred in some parts during press molding, and as a result, uneven molding proceeded and the strength of the molded body was partially weakened and broke.

[0157]

[0158] (5) In the case of Comparative Example 1, the precursor contains Ni as the main transition metal and is not spray-dried, so the appropriate press pressure is formed to be significantly high, and in the case of Comparative Example 5, the precursor has an LFP composition and is not spray-dried, so the molded body is damaged due to the application of partially uneven pressure during pressing.

[0159]

[0160] (6) In Comparative Example 3, the press pressure was weak, so the bulk density after pressing was low and the molded body was damaged. In Comparative Example 4, the press pressure was too strong, so the molded body was damaged due to the spring back phenomenon despite the high bulk density after pressing.

[0161]

[0162] (7) In the case of Comparative Example 6, the molded body contained a binder (water), so the binder inside was vaporized by firing, causing a void and crack, and the molded body was damaged after firing.

[0163]

[0164] (8) In the case of Example 1, the molded precursor was prepared by adding a carbon precursor to a powder composite composed of FePO4 and Li2CO3, which is different from Examples 2 to 6 in which the carbon precursor is included in a wettable mixture. As a result, the uniformity of the carbon coating on the active material is somewhat lower, and as shown in Table 2 of Experimental Example 2 described later, the electrical properties are somewhat inferior to those of Examples 2 to 6.

[0165]

[0166] (9) In the case of Example 4, it can be seen that the droplets during spray drying are made more spherical by the use of a surfactant, and the resulting powder composite provides high bulk density due to excellent fluidity.

[0167]

[0168] (10) Example 6 is a case where the doping precursor is mixed separately, and Example 7 is a case where the dopant is included in the transition metal precursor beforehand, so the doping element is consequently included in the precursor for manufacturing the positive active material.

[0169]

[0170] (11) FIG. 5 shows the shape (A) of an exemplary stacked assembly produced by stacking the molding precursors produced in Example 2 in multiple stages, and the shape (B) after firing. It can be seen that the stacked state remains stable even after firing, and that each molding precursor does not undergo significant changes in shape after firing.

[0171]

[0172] [Experimental Example 2]

[0173] The positive active materials prepared in Examples 1 to 7 and Comparative Examples 1 to 6, respectively, were mixed with PVdF (KF1100) as a binder and Super-P as a conductive material in a weight ratio of 95:2:3, and added to an NMP solvent to prepare a positive active material slurry. The slurry was coated onto an aluminum foil (Al foil, thickness: 20 μm) serving as a positive current collector, dried at 120°C, and then rolled to produce a positive electrode plate. The loading level of the rolled positive was 12 mg / cm². 2 The rolled density is 2.40 g / cm³ 3 The above positive electrode plate was stamped to 13.8Φ, and a 2032 coin-type half cell was fabricated using a 15Φ lithium metal negative electrode and an electrolyte (1M LiPF6 in EC / DMC / DEC 1:2:1).

[0174] After aging the above coin-type half cell at room temperature for 10 hours, charge-discharge tests were performed, and the results are shown in Table 2 below. Capacity evaluation was based on a standard of 150 mAh / g at a 0.1C rate, and charge-discharge conditions were executed under constant current (CC) / constant voltage (CV) within a voltage range of 3.7 to 2.5.

[0175]

[0176] As shown in Table 2 above, it can be seen that there is no significant difference in charge / discharge capacity between the secondary batteries of all embodiments and the secondary battery of Comparative Example 2. As shown in Table 1 of Experimental Example 1, the secondary battery of Comparative Example 2 has a production volume that is only about 30% to 50% of that of the embodiments, so it can be said that the manufacturing cost is significantly higher than that of the embodiments.

[0177] The remaining comparative examples could not perform charge-discharge tests because they failed to maintain their shape in the molded body state before firing or in the fired body state after firing, and consequently, proper firing could not proceed.

[0178] As seen in the above results, in particular, it can be seen that the secondary battery of Example 4 exhibits the best charge-discharge efficiency.

[0179]

[0180] The present invention is not limited to the above embodiments and can be manufactured in various different forms, and those skilled in the art will understand that the invention can be implemented in other specific forms without changing the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. Includes transition metal precursors and alkali metal / earth metal precursors, The above transition metal precursor includes Fe, A molding precursor characterized by the above precursors aggregating to maintain their shape.

2. A molding precursor according to claim 1, characterized by being manufactured through a process comprising the following steps: (a) A process of preparing a wettable mixture by mixing a transition metal precursor and an alkali metal / earth metal precursor and adding water; (b) a process of drying the above wettable mixture to produce a powder composite; and (c) A process of placing the above powder composite into a molding mold and applying pressure to produce a molding precursor.

3. A molded precursor according to claim 2, characterized in that, when manufacturing the powder composite in the above process (b), the precursors are aggregated into a form close to a sphere during the drying process.

4. A molded precursor according to claim 2, characterized in that the pressure applied to produce the molded precursor in the above process (c) is set differently depending on the transition metal composition of the precursor.

5. A molding precursor according to claim 1, characterized in that the precursors are physically bonded.

6. A molding precursor according to claim 1, characterized by not including a binder for inducing adhesion between precursor particles.

7. A molding precursor according to claim 1, characterized by further comprising a carbon precursor.

8. In claim 1, the bulk density is 0.85 to 1.4 g / cm³ 3 A molding precursor characterized by being.

9. A molding precursor according to claim 1, characterized in that the bulk density increase rate before and after pressing is 130 to 210%.

10. A molded precursor according to claim 1, characterized in that the transition metal precursor comprises a composition represented by Chemical Formula 1: (Fe x M 1-x )P y O 4-z (1) In the above formula, 0 <x≤1, 0≤y≤2, 0<z≤4이고, M is one or more selected from alkaline earth metals, transition metals, post-transition metals, metalloids, nonmetals, lanthanides, and actinides.

11. A molding precursor according to claim 1, characterized in that the alkali metal / earth metal precursor comprises a composition represented by Chemical Formula 2: (1-f-g-h-i)A a CO3* fA b OH * gA c O2* hA d SO4*iA e PO4(2) In the above formula, 0 <a≤4, 0<b≤4, 0<c≤4, 0<d≤4, 0<e≤4, 0≤f≤1, 0≤g≤1, 0≤h≤1, 0≤i≤1, 0≤1-f-g-h-i≤1이고, A is one or more selected from alkali metals and alkaline earth metals.

12. A molding precursor according to claim 7, characterized in that the carbon precursor comprises a composition represented by Chemical Formula 3: C h H i O j (3) In the above formula, 0 <h≤20, 0≤i≤42, 0≤j≤10이다.

13. A molded precursor according to claim 1, characterized in that it comprises a doping element and / or a doping precursor in one or more of the following ways: (i) Transition metal precursors containing additional doping elements, (ii) Including a doping precursor in addition to the transition metal precursor.

14. A molding precursor according to claim 1, further comprising a surfactant for uniform molding.

15. Includes transition metal precursors and alkali metal / earth metal precursors, The above transition metal precursor includes Fe, The above precursors are aggregated to form a molding precursor that maintains its shape, and A stacked assembly of molding precursors characterized by the above-mentioned molding precursors being stacked in multiple stages 16. A positive active material characterized by being manufactured from a molded precursor according to claim 1.

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