Preparation method of high-compaction low-magnetic-foreign-matter lithium iron phosphate

Abstract

The application provides a preparation method of high-compaction low-magnetic-foreign-matter lithium iron phosphate, which comprises the following steps: adding a phosphorus iron source, a lithium source, a carbon source and an additive into water to mix uniformly to obtain slurry A; making the slurry A pass through coarse sand grinding and fine sand grinding in sequence to obtain slurry B; spray drying the slurry B to separate out large-particle powder C and small-particle powder D; sintering the large-particle powder C at high temperature to obtain powder E; sintering the small-particle powder D at high temperature to obtain powder F; screening the powder F to obtain sieve-up material G and sieve-down material H; crushing the powder E and the sieve-up material G to obtain powder I; and mixing the powder H and the powder I uniformly to obtain the high-compaction low-magnetic-foreign-matter lithium iron phosphate. The technical scheme of the application has great improvement in magnetic substances, and all the above schemes maintain certain electrochemical performance.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of lithium ion batteries, in particular to a preparation method of high-compaction low-magnetic-foreign-matter lithium iron phosphate. BACKGROUND

[0002] Lithium ion batteries are regarded as the most important representatives of new energy storage devices due to their high energy density, long cycle life and environmental friendliness. With the gradual development of the new energy industry, the lithium battery material industry is booming and highly competitive, and downstream manufacturers have higher requirements for the performance of materials. Olivine-type lithium iron phosphate is the first choice for power and energy storage batteries due to its high theoretical capacity and flat working voltage, stable structure, and low cost and pollution-free characteristics. With the rapid development of the new energy industry and the support of new energy industry policies, the market share and market demand of lithium iron phosphate are also increasing.

[0003] The energy density of the battery directly affects the cruising range of the electric vehicle and the capacity of the energy storage station, and the energy density of the lithium battery material is particularly important. Increasing the energy density of the battery has become the common goal of the industry. For lithium iron phosphate batteries, the voltage platform is determined by the types of positive and negative electrode materials and cannot be changed. To increase the energy density, the gram capacity and compaction density of the material need to be improved. The current industry lithium iron phosphate material has a discharge gram capacity of 160+ / -3 mAh / g at 0.1C, which is limited compared to the theoretical capacity of 170 mAh / g. The theoretical compaction density of lithium iron phosphate is 3.6 g / cm3, and the average level of lithium iron phosphate powder compaction density in the industry is only 2.4-2.5 g / cm3, which still has a large room for improvement.

[0004] The traditional method for improving the compaction density of lithium iron phosphate is to increase the sintering temperature and prolong the holding time. However, there are differences in the sintering resistance of large and small particles. Large particles have strong sintering resistance, while small particles have weak sintering resistance. At higher temperatures and longer holding times, some side reactions will occur, producing iron phosphide, iron pyrophosphate and other magnetic substances and some by-products. Since magnetic substances seriously affect the safety performance of the battery, it is particularly important to strictly control the content of magnetic substances in the material.

[0005] Therefore, it is of great significance to provide a high-compaction low-magnetic-foreign-matter lithium iron phosphate positive material and a preparation method thereof, which is beneficial to improve the energy density and safety performance of the battery. In view of this, the present application is proposed. SUMMARY

[0006] Therefore, the application provides a preparation method of high-compaction low-magnetic-foreign-matter lithium iron phosphate.

[0007] To achieve the above-mentioned purpose, the application adopts the following technical scheme:

[0008] A preparation method of high-compaction low-magnetic-foreign-matter lithium iron phosphate comprises the following steps:

[0009] adding a phosphorus iron source, a lithium source, a carbon source and an additive into deionized water to mix uniformly to obtain slurry A with a certain solid content;

[0010] subjecting the slurry A to coarse sand grinding and fine sand grinding in sequence to obtain slurry B with a certain standard particle size;

[0011] subjecting the slurry B to spray drying and then sorting out large-particle powder C and small-particle powder D;

[0012] subjecting the large-particle powder C to high-temperature sintering under an inert atmosphere to obtain powder E;

[0013] subjecting the small-particle powder D to high-temperature sintering under an inert atmosphere to obtain powder F;

[0014] subjecting the powder F to sieving to obtain sieve-up material G and sieve-down material H;

[0015] subjecting the powder E and the sieve-up material G to crushing and sieving to obtain powder I with a certain particle size;

[0016] fully mixing and uniformly mixing the powder H and the powder I at a certain proportion to obtain the high-compaction low-magnetic-foreign-matter lithium iron phosphate.

[0017] Further, the phosphorus iron source is selected from iron phosphate, and the iron-phosphorus ratio of the iron phosphate is Fe:P=0.97±0.02;

[0018] the lithium source is lithium carbonate;

[0019] the carbon source is glucose and polyethylene glycol;

[0020] the additive is selected from one or more of titanium dioxide, tetrabutyl titanate and titanium oxychloride.

[0021] Further, the mass fraction of the carbon source / the phosphorus iron source is 10±5%.

[0022] Further, in the slurry A, the content of the lithium source is added according to the molar ratio Li:Fe=1.03±0.02.

[0023] Further, the additive is added in a mass fraction of 0.05-0.5% of the additive / iron phosphate source.

[0024] Further, the particle size D50 of the slurry B is 0.5±0.2um.

[0025] Further, the particle size D50 of the large-particle powder C is 30±20um, and the particle size D50 of the small-particle powder D is 10±5um.

[0026] Further, the sintering temperature of the large-particle powder C is 770±30℃, and the holding time is 8±2h, the sintering temperature of the small-particle powder D is 740±30℃, and the holding time is 6±2h, and the sintering temperature of the large-particle powder C is 30-60℃ higher than that of the small-particle powder D, and the holding time is 2-4h longer.

[0027] In some embodiments, the sintering temperature of the large-particle powder C is 770℃, and the holding time is 8h, the sintering temperature of the small-particle powder D is 730℃, and the holding time is 6h.

[0028] In some embodiments, the sintering temperature of the large-particle powder C is 790℃, and the holding time is 8h, the sintering temperature of the small-particle powder D is 730℃, and the holding time is 6h.

[0029] In some embodiments, the sintering temperature of the large-particle powder C is 790℃, and the holding time is 8h, the sintering temperature of the small-particle powder D is 750℃, and the holding time is 6h.

[0030] Since the degree of side reactions will greatly increase when the sintering temperature is greater than 800℃, and the crystallinity of the lithium iron phosphate crystal will not be enough when the sintering temperature is less than 700℃, the capacity and the tap density will be affected, and considering the difference in the sintering resistance of large and small particles, the sintering process of the above several embodiments is selected.

[0031] Further, the particle size D50 of the powder I is 1.5±1um.

[0032] Further, the mixing mass ratio of the powders H and I is H:I=0.1-0.9.

[0033] Since the large particle lithium iron phosphate does not affect the homogenate, sieving and coating process of battery preparation when it is not crushed, the processing performance of the product is poor, so the existing conventional process needs to crush and sieve the product after sintering. However, the small particle material in the scheme has a small particle size, has little effect on the subsequent processing performance, and can well retain the carbon coating layer without crushing, thereby maintaining its good electrochemical performance. Therefore, the powder H selected in the scheme is only sieved, and the undersize material is directly mixed with other crushed powder I in a certain proportion. The particle size of the powder I is small, and the voids between the powder H are filled during the mixing process, thereby enhancing the compaction performance of the product.

[0034] Further, the size particle sorting device is as shown in Figure 1 The principle and process are as follows: after spraying, the powder enters the cutting surface of the cyclone through the feeding pipe, the large particles rotate along the wall and fall into the first material collection, and the small particles are sucked into the material collection tower by the suction device, and the second material collection is carried out through the pulse trap. By adjusting the up-down position of the suction device and the frequency and size of the Roots blower, the particle size and collection rate of the two-stage collected powder are realized.

[0035] The high-pressure compacted lithium iron phosphate material prepared by the preparation method also has a low magnetic foreign matter. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 It is a front view of the spray material grading and collecting device in the application.

[0037] Figure 2 It is a top view of the spray material grading and collecting device in the application.

[0038] Figure 3 It is a SEM image of the large particle powder C in examples 1-7 in the application.

[0039] Figure 4 It is a SEM image of the small particle powder D in examples 1-7 in the application. DETAILED DESCRIPTION

[0040] In order to facilitate the understanding of the present application, the present application will be described more fully below with specific examples. However, the present application can be realized in many different forms, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application herein are only for the purpose of describing the specific embodiments and are not intended to limit the present application.

[0042] The application discloses a preparation method of high-compaction low-magnetic-foreign-matter lithium iron phosphate, and comprises the following steps:

[0043] Phosphorus iron source, lithium source, carbon source and additives are added into deionized water and uniformly mixed to obtain slurry A with a certain solid content, and the solid content of the slurry A is 40±10%;

[0044] The slurry A is sequentially subjected to coarse sand grinding and fine sand grinding to obtain slurry B with a certain standard particle size, and the particle size D50 of the slurry B is 0.5±0.2 um;

[0045] The slurry B is spray-dried, and large-particle powder C and small-particle powder D are sorted out, and the sorting method comprises but is not limited to the following methods: sieving and grading, and the purpose is to separate the particle sizes of the powder after spraying.

[0046] The large-particle powder C is sintered at high temperature under an inert atmosphere to obtain powder E, and the small-particle powder D is sintered at high temperature under an inert atmosphere to obtain powder F, and the sintering equipment comprises common sintering equipment such as a box furnace, a rotary furnace and a roller furnace; the inert atmosphere is commonly used in the field, such as nitrogen, argon and helium.

[0047] The powder F is sieved to obtain sieve-up material G and sieve-down material H, and the mesh number of the sieve is 200-500 meshes.

[0048] The powder E and the sieve-up material G are crushed and sieved to obtain powder I with a certain particle size, and the particle size D50 of the powder I is 1.5±1 um.

[0049] The powder H and the powder I are fully mixed in a certain proportion to obtain the high-compaction low-magnetic-foreign-matter lithium iron phosphate, and the mixing mass ratio is H:I=0.1-0.9.

[0050] The traditional process for preparing high-compaction-density lithium iron phosphate usually increases the sintering temperature and prolongs the holding time, but the change of the sintering process will cause the occurrence of a side reaction, and magnetic foreign matters are easily generated. After the improvement of the traditional process, different sintering processes are adopted for different particle powders, the over-sintering condition is prevented, the occurrence of the side reaction is avoided, the compaction density is improved by matching the large and small particles, and the content of the magnetic foreign matters in the material is reduced. The method is simple in operation, and can be realized on the basis of slight modification of the existing carbon thermal reduction method equipment, so that large-scale industrialization is realized.

[0051] The technical solutions of the application will be described more clearly and completely in combination with specific embodiments.

[0052] Embodiment 1

[0053] Iron phosphate, lithium carbonate, glucose, polyethylene glycol, titanium dioxide are added into deionized water to mix uniformly to obtain slurry A with a certain solid content, and the solid content is 35%;

[0054] The slurry A is subjected to sand milling to obtain slurry B, so that the particle size D50 thereof is 0.45 um;

[0055] The slurry B is spray dried to sort out large-particle powder C and small-particle powder D, the particle size D50 of the large-particle powder C is 36 um, and the particle size D50 of the small-particle powder D is 6 um;

[0056] The large-particle powder C is subjected to high-temperature sintering under an inert atmosphere to obtain powder E, the sintering temperature is 770 DEG C, and the holding time is 8 h;

[0057] The small-particle powder D is subjected to high-temperature sintering under an inert atmosphere to obtain powder F, the sintering temperature is 730 DEG C, and the holding time is 6 h;

[0058] The powder F is subjected to sieving to obtain sieve-up material G and sieve-down material H, and the sieve mesh is 400 mesh;

[0059] The powder E and the sieve-up material G are subjected to crushing and sieving to obtain powder I with a certain particle size, and the particle size D50 of the powder I is 1.0 um;

[0060] The powder H and the powder I are mixed uniformly at a certain proportion, and the mixing mass ratio is H:I = 0.1.

[0061] Example 2

[0062] Iron phosphate, lithium carbonate, glucose, polyethylene glycol, titanium dioxide are added into deionized water to mix uniformly to obtain slurry A with a certain solid content, and the solid content is 35%;

[0063] The slurry A is subjected to sand milling to obtain slurry B, so that the particle size D50 thereof is 0.45 um;

[0064] The slurry B is spray dried to sort out large-particle powder C and small-particle powder D, the particle size D50 of the large-particle powder C is 36 um, and the particle size D50 of the small-particle powder D is 6 um;

[0065] The large-particle powder C is subjected to high-temperature sintering under an inert atmosphere to obtain powder E, the sintering temperature is 770 DEG C, and the holding time is 8 h;

[0066] The small-particle powder D is subjected to high-temperature sintering under an inert atmosphere to obtain powder F, the sintering temperature is 730 DEG C, and the holding time is 6 h;

[0067] The powder F is subjected to sieving to obtain sieve-up material G and sieve-down material H, and the sieve mesh is 400 mesh;

[0068] The powder E and the oversize powder G are crushed and sieved to obtain a powder I with a certain particle size, and the particle size D50 of the powder I is 1.0 um;

[0069] The powder H and the powder I are mixed in a certain proportion to obtain a mixture, and the mixing mass ratio of H:I is 0.2.

[0070] Example 3

[0071] Iron phosphate, lithium carbonate, glucose, polyethylene glycol, and titanium dioxide are added into deionized water and uniformly mixed to obtain a slurry A with a certain solid content, and the solid content is 35%;

[0072] The slurry A is sand-milled to obtain a slurry B with a particle size D50 of 0.45 um;

[0073] The slurry B is spray-dried to obtain a large-particle powder C and a small-particle powder D, the particle size D50 of the large-particle powder C is 36 um, and the particle size D50 of the small-particle powder D is 6 um;

[0074] The large-particle powder C is sintered at a high temperature in an inert atmosphere to obtain a powder E, the sintering temperature is 770 DEG C, and the holding time is 8 h;

[0075] The small-particle powder D is sintered at a high temperature in an inert atmosphere to obtain a powder F, the sintering temperature is 730 DEG C, and the holding time is 6 h;

[0076] The powder F is sieved to obtain an oversize powder G and an undersize powder H, and the sieve mesh is 400 mesh;

[0077] The powder E and the oversize powder G are crushed and sieved to obtain a powder I with a certain particle size, and the particle size D50 of the powder I is 1.0 um;

[0078] The powder H and the powder I are mixed in a certain proportion to obtain a mixture, and the mixing mass ratio of H:I is 0.3.

[0079] Example 4

[0080] Iron phosphate, lithium carbonate, glucose, polyethylene glycol, and titanium dioxide are added into deionized water and uniformly mixed to obtain a slurry A with a certain solid content, and the solid content is 35%;

[0081] The slurry A is sand-milled to obtain a slurry B with a particle size D50 of 0.45 um;

[0082] The slurry B is spray-dried to obtain a large-particle powder C and a small-particle powder D, the particle size D50 of the large-particle powder C is 36 um, and the particle size D50 of the small-particle powder D is 6 um;

[0083] The large particle powder C is placed in an inert atmosphere for high temperature sintering to obtain powder E, the sintering temperature is 770 DEG C, and the holding time is 8h;

[0084] The small particle powder D is placed in an inert atmosphere for high temperature sintering to obtain powder F, the sintering temperature is 730 DEG C, and the holding time is 6h;

[0085] The powder F is sieved to obtain sieve-up material G and sieve-down material H, and the sieve mesh is 400 meshes;

[0086] The powder E and the sieve-up material G are crushed and sieved to obtain powder I with a certain particle size, and the particle size D50 of the powder I is 1.0um;

[0087] The powder H and the powder I are mixed uniformly at a certain proportion, and the mixing mass ratio is H:I = 0.4.

[0088] Example 5

[0089] Iron phosphate, lithium carbonate, glucose, polyethylene glycol, and titanium dioxide are added into deionized water and mixed uniformly to obtain slurry A with a certain solid content, and the solid content is 35%;

[0090] The slurry A is sand-milled to obtain slurry B, so that the particle size D50 thereof is 0.45um;

[0091] The slurry B is spray-dried and sorted to obtain large particle powder C and small particle powder D, the particle size D50 of the large particle powder C is 36um, and the particle size D50 of the small particle powder D is 6um;

[0092] The large particle powder C is placed in an inert atmosphere for high temperature sintering to obtain powder E, the sintering temperature is 770 DEG C, and the holding time is 8h;

[0093] The small particle powder D is placed in an inert atmosphere for high temperature sintering to obtain powder F, the sintering temperature is 730 DEG C, and the holding time is 6h;

[0094] The powder F is sieved to obtain sieve-up material G and sieve-down material H, and the sieve mesh is 400 meshes;

[0095] The powder E and the sieve-up material G are crushed and sieved to obtain powder I with a certain particle size, and the particle size D50 of the powder I is 1.0um;

[0096] The powder H and the powder I are mixed uniformly at a certain proportion, and the mixing mass ratio is H:I = 0.5.

[0097] Example 6

[0098] Iron phosphate, lithium carbonate, glucose, polyethylene glycol, and titanium dioxide are added into deionized water and mixed uniformly to obtain slurry A with a certain solid content, and the solid content is 35%;

[0099] The slurry A is sand milled to obtain slurry B, so that the particle size D50 thereof is 0.45 um;

[0100] The slurry B is spray dried to sort out large-particle powder C and small-particle powder D, the particle size D50 of the large-particle powder C is 36 um, and the particle size D50 of the small-particle powder D is 6 um;

[0101] The large-particle powder C is sintered at high temperature under an inert atmosphere to obtain powder E, the sintering temperature is 790 DEG C, and the holding time is 8 h;

[0102] The small-particle powder D is sintered at high temperature under an inert atmosphere to obtain powder F, the sintering temperature is 730 DEG C, and the holding time is 6 h;

[0103] The powder F is sieved to obtain sieve-up material G and sieve-down material H, the sieve mesh is 400 mesh;

[0104] The powder E and the sieve-up material G are crushed and sieved to obtain powder I with a certain particle size, and the particle size D50 of the powder I is 1.0 um;

[0105] The powder H and the powder I are mixed at a certain proportion to obtain a mixture, and the mixing mass ratio is H:I = 0.4.

[0106] Example 7

[0107] Iron phosphate, lithium carbonate, glucose, polyethylene glycol, and titanium dioxide are added into deionized water to obtain slurry A with a certain solid content, and the solid content is 35%;

[0108] The slurry A is sand milled to obtain slurry B, so that the particle size D50 thereof is 0.45 um;

[0109] The slurry B is spray dried to sort out large-particle powder C and small-particle powder D, the particle size D50 of the large-particle powder C is 36 um, and the particle size D50 of the small-particle powder D is 6 um;

[0110] The large-particle powder C is sintered at high temperature under an inert atmosphere to obtain powder E, the sintering temperature is 790 DEG C, and the holding time is 8 h;

[0111] The small-particle powder D is sintered at high temperature under an inert atmosphere to obtain powder F, the sintering temperature is 750 DEG C, and the holding time is 6 h;

[0112] The powder F is sieved to obtain sieve-up material G and sieve-down material H, the sieve mesh is 400 mesh;

[0113] The powder E and the sieve-up material G are crushed and sieved to obtain powder I with a certain particle size, and the particle size D50 of the powder I is 1.0 um;

[0114] The powder H and powder I are mixed in a certain proportion to be uniform, and the mixing mass ratio is H: I = 0.4.

[0115] Comparative Example 1

[0116] Iron phosphate, lithium carbonate, glucose, polyethylene glycol, and titanium dioxide are added to deionized water and mixed uniformly to obtain a slurry with a certain solid content, and the solid content is 35%;

[0117] The slurry is subjected to sand milling to make the particle size D50 of the slurry 0.45 um;

[0118] The particle size D50 of the slurry spray dried is 32 um;

[0119] The spray material is placed in an inert atmosphere for high-temperature sintering, the temperature is set to 750 DEG C, and the holding time is 8 h;

[0120] The sintered material is crushed and sieved to make the crushed particle size D50 1.3 um.

[0121] Comparative Example 2

[0122] Iron phosphate, lithium carbonate, glucose, polyethylene glycol, and titanium dioxide are added to deionized water and mixed uniformly to obtain a slurry with a certain solid content, and the solid content is 35%;

[0123] The slurry is subjected to sand milling to make the particle size D50 of the slurry 0.45 um;

[0124] The particle size D50 of the slurry spray dried is 32 um;

[0125] The spray material is placed in an inert atmosphere for high-temperature sintering, the temperature is set to 790 DEG C, and the holding time is 8 h;

[0126] The sintered material is crushed and sieved to make the crushed particle size D50 1.3 um.

[0127] The above materials are tested for compaction density by a powder compaction density tester, the test pressure is set to 3T, and the pressure holding time is set to 30S; a certain mass of powder is dissolved in water, adsorbed by a 6000GS magnetic rod and tank mill, and the magnetic material is tested by ICP; in addition, the above materials are prepared for discharge, and the electrical performance is tested on a blue electric test system, the voltage interval is selected (2.0-3.75V), and the discharge rate is set to 0.1C.

[0128]

[0129] As can be seen from the above table, examples 1-7 have greater improvement in compaction density relative to comparative example 1, and greater improvement in magnetic substance relative to comparative example 2, while all of the above solutions maintain certain electrochemical performance. Thus, the prepared lithium iron phosphate of the present application can effectively solve the existing technical barriers, both improving the compaction density of the material and maintaining a lower magnetic substance, while also exhibiting good electrochemical performance.

[0130] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described, but it should be considered that any combination of the technical features is within the scope of the present disclosure, as long as the combination does not result in contradictions.

[0131] Although the present application has been illustrated and described with reference to specific embodiments, it should be recognized that the embodiments are merely illustrative of the present application and should not be considered restrictive. It should be understood that modifications and variations of the embodiments described herein can be made by those of ordinary skill in the art without departing from the spirit or scope of the present application. Such modifications and variations are intended to be within the scope of the present application. Accordingly, the disclosure is intended to embrace all such alternatives, modifications and variations as fall within the scope of the appended claims.

Claims

1. A method for preparing high-pressure, low-magnetic lithium iron phosphate, characterized in that, Includes the following steps: Phosphorus iron source, lithium source, carbon source and additives are added to deionized water and mixed evenly to obtain slurry A; The slurry A is sequentially subjected to a coarse sand mill and a fine sand mill to obtain slurry B; After spray drying, the slurry B is separated into large particle powder C and small particle powder D. The particle size D50 of the large particle powder C is 30±20um, and the particle size D50 of the small particle powder D is 10±5um. The large-particle powder C is sintered at high temperature under an inert atmosphere to obtain powder E; The small particle powder D is sintered at high temperature under an inert atmosphere to obtain powder F; The sintering temperature of the large particle powder C is 770±30℃, and the holding time is 8±2h. The sintering temperature of the small particle powder D is 730±30℃, and the holding time is 6±2h. The sintering temperature of the large particle powder C is 30-60℃ higher than that of the small particle powder D, and the holding time is 2-4h longer. The powder F is sieved to obtain oversize material G and undersize material H. The powder E and the sieve material G are crushed and sieved to obtain powder I with a certain particle size; The high-pressure, low-magnetic foreign matter lithium iron phosphate is prepared by thoroughly mixing powder H and powder I.

2. The preparation method according to claim 1, characterized in that, The phosphorus iron source is selected from iron phosphate; The lithium source is one or more of lithium carbonate, lithium hydroxide, and lithium oxalate; the carbon source is one or more of glucose, starch, sucrose, polyethylene glycol, and carbon nanotubes. The additive is a metal cation dopant, and the doped metal ion is one or more of titanium ions, aluminum ions, vanadium ions, or molybdenum ions.

3. The preparation method according to claim 1, characterized in that, In the slurry B, the lithium source content is added according to the molar ratio Li:Fe = 1.03 ± 0.

02.

4. The preparation method according to claim 1, characterized in that, The particle size D50 of the slurry B is 0.5±0.2um.

5. The preparation method according to claim 1, characterized in that, The sorting method after spray drying includes the following methods: sieving or grading.

6. The preparation method according to claim 1, characterized in that, The powder F is sieved through a sieve with a mesh size of 200-500.

7. The preparation method according to claim 1, characterized in that, The particle size D50 of the powder I is 1.5±1um.

8. The preparation method according to claim 1, characterized in that, The mixing mass ratio of powders H and I is H:I = 0.1-0.9.

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