Electrolyte for lithium-rich manganese-based lithium ion battery

Abstract

The invention relates to an electrolyte for a lithium-rich manganese-based lithium ion battery, in order to solve the problems of too fast voltage drop and cycle attenuation of the electrolyte for the lithium-rich manganese-based lithium ion battery and the lithium ion battery, the invention adopts a high-voltage-resistant electrolyte for the lithium-rich manganese-based lithium ion battery, and the high-voltage-resistant electrolyte comprises an electrolyte lithium salt, a non-aqueous organic solvent and an additive, wherein the non-aqueous organic solvent is a mixture of carbonates, fluorocarbonates and fluoroethers, and the additive comprises a vinyl-containing malonic acid lithium borate derivative and lithium tetrafluoro oxalate phosphate. According to the lithium ion battery electrolyte, the voltage drop of the lithium-rich manganese battery under high voltage can be inhibited, the cycle life of the battery is prolonged, the thickness expansion of the battery is reduced, and the development of the electrolyte is expected to provide a basis for commercial application of the lithium-rich manganese battery.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium-rich manganese-based lithium ion batteries, and specifically relates to an electrolyte for lithium-rich manganese-based lithium ion batteries. Background Art

[0002] The continuous innovation of new energy technologies has provided a strong impetus for sustainable economic development. Among them, lithium-ion batteries have become the representative of new energy technologies due to their high energy density, good cycle performance, high safety and reliability, and strong environmental adaptability. They are widely used in various mobile tools, automobiles, equipment drives, energy storage and other fields.

[0003] Li-rich manganese cathode material (LMCM) has a high specific capacity (>250mAh g -1 ) and low cost, and is considered the most promising cathode material for the next generation of lithium-ion batteries. However, during the cycle of the cathode material using the existing conventional electrolyte, there are problems such as irreversible structural transformation, active oxygen precipitation, and electrolyte oxidation decomposition under high voltage, resulting in high first irreversible capacity loss, poor rate performance, energy decay and voltage decay, which hinder the development and further commercial application of lithium-rich manganese-based lithium-ion batteries. Therefore, it is necessary to develop an electrolyte that is beneficial to the performance of lithium-rich manganese-based lithium-ion batteries for lithium-rich manganese-based cathode materials. Summary of the invention

[0004] The object of the present invention is to provide an electrolyte for a lithium-rich manganese-based lithium-ion battery, so as to improve the electrochemical performance and service life of the lithium-rich manganese-based lithium-ion battery.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] An electrolyte for a lithium-rich manganese-based lithium ion battery, comprising an electrolyte lithium salt, a non-aqueous organic solvent and an additive, wherein the non-aqueous organic solvent is a mixture of carbonates, fluorocarbons and fluoroethers, and the additive comprises a vinyl-containing lithium malonic acid borate salt derivative and lithium tetrafluorooxalate phosphate, wherein the structure of the vinyl-containing lithium malonic acid borate derivative is shown in general formula A and / or B:

[0007]

[0008] Among them, R 1 , R 2 , R 3 , R 4 , R 5 They are independently selected from H, a halogen atom, an unsubstituted or fluorine-substituted alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a cyano group.

[0009] Preferably, the volume ratio of the carbonates, fluorocarbons and fluoroethers is (2.5-8):1:(1.5-5).

[0010] More preferably, the volume ratio of the carbonates, fluorocarbons and fluoroethers is (4-8):1:(2-4).

[0011] More preferably, the volume ratio of the carbonates, fluorocarbons and fluoroethers is (5-8):1:(2-3).

[0012] Preferably, the carbonates are one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

[0013] Preferably, the fluorinated carbonates are one or more of fluoroethylene carbonate, difluoroethylene carbonate, and tetrafluoroethylene carbonate.

[0014] Preferably, the fluoroether is one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether or 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether.

[0015] According to some specific embodiments, the non-aqueous organic solvent is dimethyl carbonate, fluoroethylene carbonate and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in a volume ratio of (4-8):1:(1-4).

[0016] Preferably, the mass of the vinyl-containing lithium malonic acid borate derivative accounts for 0.1% to 8% of the total mass of the electrolyte.

[0017] Further preferably, the feed mass of the vinyl-containing lithium malonic acid borate derivative accounts for 0.1% to 5% of the total mass of the electrolyte.

[0018] Still more preferably, the mass of the vinyl-containing lithium malonic acid borate derivative accounts for 0.1% to 3% of the total mass of the electrolyte.

[0019] More preferably, the mass of the vinyl-containing lithium malonic acid borate derivative accounts for 1% to 2% of the total mass of the electrolyte.

[0020] Preferably, the mass of the lithium tetrafluorooxalate phosphate feed accounts for 0.5% to 5% of the total mass of the electrolyte.

[0021] Further preferably, the feed mass of the lithium tetrafluorooxalate phosphate accounts for 0.5% to 2% of the total mass of the electrolyte.

[0022] More preferably, the mass of the lithium tetrafluorooxalate phosphate feed accounts for 1% to 2% of the total mass of the electrolyte.

[0023] Preferably, the mass ratio of the vinyl-containing lithium malonic acid borate derivative to lithium tetrafluorooxalate phosphate is 1:(0.3-5).

[0024] Further preferably, the feed mass ratio of the vinyl-containing lithium malonic acid borate derivative to lithium tetrafluorooxalate phosphate is 1:(0.3-4).

[0025] More preferably, the mass ratio of the vinyl-containing lithium malonic acid borate derivative to lithium tetrafluorooxalate phosphate is 1:(0.5-2).

[0026] Preferably, the lithium salt is LiPF 6 and other lithium salts, wherein the other lithium salts are LiBF 4 、LiClO 4 , LiTFSI, LiFSI.

[0027] Preferably, the concentration of the lithium salt in the electrolyte is 1-3 mol / L, for example, 1 mol / L, 1.5 mol / L, 21 mol / L, 2.5 mol / L, 3 mol / L.

[0028] Preferably, the LiPF 6 The concentration ratio to other lithium salts is (2-8):1.

[0029] Further preferably, the LiPF 6 The concentration ratio to other lithium salts is (3-5):1.

[0030] More preferably, the LiPF 6 The concentration ratio to other lithium salts is (4-5):1.

[0031] According to some specific and preferred embodiments, the other lithium salt is LiTFSI and / or LiFSI.

[0032] Preferably, the additives also include other additives, and the other additives are one or more of succinonitrile, adiponitrile, 1,3-propane sultone, vinyl sulfate, methylene disulfonate, propylene sulfate, tris(trimethylsilyl)borate, tris(trimethylsilyl)phosphite, tris(trimethylsilyl)phosphate, vinyl ethylene carbonate, maleic anhydride, and glutaric anhydride.

[0033] Further preferably, the feeding mass of the other additives accounts for 0.01% to 5% of the total mass of the electrolyte, such as 0.01%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 0.5.

[0034] According to some embodiments, the other additives are a combination of trimethylsilyl phosphate and any one or more of glutaric anhydride, ethylene sulfite, and lithium difluorobis(oxalate)phosphate.

[0035] The second aspect of the present invention further provides a lithium-rich manganese-based lithium-ion battery, including a positive electrode, a separator, a negative electrode, and an electrolyte, and the electrolyte is the electrolyte for the lithium-rich manganese-based lithium-ion battery described above.

[0036] Preferably, the positive electrode includes a positive electrode active material, and the positive electrode active material is xLi 2 MnO 3 ·(1-x)LiMO 2 , where 0 < x < 1, M = Ni, Co, Mn and their combinations, the negative electrode includes a negative electrode active material, and the negative electrode active material is graphite and / or silicon, silicon-oxygen material.

[0037] In the present invention, the core manufacturing method of the lithium-ion battery is winding or stacking.

[0038] According to a specific embodiment, the lithium-ion battery is a lithium-rich manganese-based positive electrode and graphite negative electrode battery.

[0039] Due to the application of the above technical solutions, the present invention has the following advantages compared with the prior art:

[0040] The electrolyte for the lithium-rich manganese-based lithium-ion battery of the present invention has excellent high-temperature resistance performance, can inhibit the voltage drop of the lithium-rich manganese battery under high voltage, improve the cycle life of the lithium-rich manganese battery, reduce the thickness expansion of the lithium-rich manganese battery, provide a basis for the commercial application of the lithium-rich manganese battery, and has broad application prospects. Specific Embodiments

[0041] Although the lithium-rich manganese-based positive electrode material has the advantages of high specific capacity and low cost, due to some insurmountable problems of the lithium-rich manganese-based positive electrode material itself, the lithium-rich manganese battery using the existing conventional electrolyte has a high voltage drop and rapid cycle decay under high voltage, a short service life, and thus the commercial application process of the current lithium-rich manganese battery is slow. To solve the above problems, the present invention obtains an electrolyte that can inhibit the voltage drop of the lithium-rich manganese battery under high voltage, improve the cycle life of the battery, and reduce the thickness expansion of the battery by optimizing the selected solvent, additives, and lithium salt through appropriate dosage adjustment. The solution of the present invention is as follows:

[0042] The solvent used in the present invention is a mixture of carbonates, fluorocarbons and fluoroethers in a certain volume ratio, which can improve the oxidation resistance of the electrolyte under high voltage, avoid the occurrence of excessive side reactions, reduce flammability, improve the safety performance of the battery, and at the same time reduce the overall viscosity of the electrolyte, improve the wettability of the electrode, and improve the conductivity of the electrolyte.

[0043] The vinyl-containing lithium malonate borate derivatives (lithium bis(vinyl malonate) borate, 2-vinyl malonate difluoroborate) used in the present invention not only have similar properties to lithium oxalate borate, i.e. similar conductivity and reduction potential, but also contain carbon-carbon double bonds in their structures, so that they cross-link with each other while undergoing oxidation and reduction at the positive and negative electrodes, forming a denser and more ductile SEI film, thereby reducing the dissolution of metal ions in the lithium-manganese-rich material. Compared with lithium malonate borate, alkenyl-substituted lithium malonate borate has a higher HOMO orbital, is more likely to bind to oxygen precipitated in the lithium-manganese-rich material, reduce its oxidative decomposition of the electrolyte, and ensure the stable cycle of the battery. Lithium tetrafluorooxalate phosphate (LiTFOP) can synergistically act with lithium bis(vinyl malonate) borate and / or lithium 2-vinyl malonate difluoroborate in the electrolyte to form a more stable SEI. At the same time, it also has the functions of improving the shelf performance of the battery, reducing gas production, and reducing impedance.

[0044] On the one hand, the composite lithium salt used in the present invention can form a solid interface film rich in inorganic components such as LiF on the electrode surface, thereby increasing the stability of the interface film. On the other hand, the two lithium salts have a high donor number and are easily dissociated in the electrolyte to release more free lithium ions, thereby increasing the conductivity of the electrolyte and avoiding excessive capacity loss of the battery from a small current to a large current, thereby contributing to the improvement of the battery's kinetic performance.

[0045] In the electrolyte of the present invention, each solvent component, additive component, composite lithium salt and the additive can exert their respective advantages and suppress their respective disadvantages after being properly proportioned. Through their synergistic effect, the lithium-rich manganese-based lithium ion battery containing the electrolyte of the present invention has excellent cycle performance, thus having good application prospects.

[0046] The present invention is further described below in conjunction with the examples. However, the present invention is not limited to the following examples. The implementation conditions used in the examples can be further adjusted according to the different requirements of specific use, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in each embodiment of the present invention can be combined with each other as long as they do not conflict with each other.

[0047] The experimental methods in the following embodiments and comparative examples are conventional methods unless otherwise specified; the experimental materials used are purchased from conventional biochemical reagent manufacturers unless otherwise specified.

[0048] Embodiment 1:

[0049] In a glove box filled with argon (water and oxygen contents were less than 0.1 ppm), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC) and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether were mixed in a volume ratio of 6:1:3, and 0.9 M lithium hexafluorophosphate (LiPF 6 ) and 0.2M lithium bis(fluorosulfonyl)imide (LiFSi), stirred evenly, added 1% of lithium bis(vinylmalonate)borate (LiBMB-A), 2% of lithium tetrafluoro(oxalate)phosphate (LiTFOP), 1% of trimethylsilyl phosphate (TMSP) and 0.8% of glutaric anhydride (GA) accounting for 2% of the total mass of the electrolyte, and obtained the electrolyte of Example 1.

[0050] The positive electrode sheet, the separator and the negative electrode sheet are wound or stacked to form a battery cell, and the battery cell is placed in a battery housing, and the lithium-ion battery electrolyte in this embodiment is injected, and then the formation, degassing, secondary sealing and constant capacity are performed according to conventional operations to obtain the final lithium-ion battery. 1.13 Mn 0.517 Ni 0.256 Co 0.097 O 2 The negative electrode is artificial graphite, the diaphragm is a double-layer composite diaphragm of polyethylene (PE) and polypropylene (PP), and the battery cell is designed to have a capacity of 1000mAh.

[0051] Examples 2 to 16 and Comparative Examples 1 to 16:

[0052] In Examples 2 to 16 and Comparative Examples 1 to 16, the electrolyte solvent, electrolyte lithium salt and additive components involved are added in the proportions shown in Table 1, and the rest are the same as in Example 1.

[0053] Table 1

[0054]

[0055]

[0056] In Table 1, “%” refers to mass percentage, and “ / ” means not used.

[0057] DMC: dimethyl carbonate; FEC: fluoroethylene carbonate; HFE: 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether; LiPF 6: lithium hexafluorophosphate; LiFSi: lithium bis(fluorosulfonyl)imide; LiBMB-A: lithium bis(vinylmalonate)borate; LiBMB-B: lithium 2-vinylmalonate difluoroborate; LiBOB: lithium dioxalatoborate; LiTFOP: lithium tetrafluoro(oxalate)phosphate; LiDFOP: lithium difluorobis(oxalate)phosphate; TMSP: trimethylsilyl phosphate; GA: glutaric anhydride; DTD: ethylene sulfate.

[0058] The performance of the lithium-ion batteries prepared in the above embodiments and comparative examples was tested, and the test items and methods were as follows:

[0059] 400-cycle performance test at room temperature: Under room temperature conditions, charge at 0.5C rate, cut-off current is 0.02C, discharge at 0.5C rate, voltage range is 2.0-4.8V, cycle for 5 weeks, the test battery thickness is recorded as T1, and then cycle for 400 weeks under the above conditions, the test battery thickness is recorded as T2.

[0060] Normal temperature cycle capacity retention rate = normal temperature 400-cycle discharge capacity / normal temperature first-cycle discharge capacity × 100%.

[0061] Thickness expansion ratio = (T2-T1) / T1×100%.

[0062] Voltage drop test: At room temperature, charge at 0.5C rate, cut-off current is 0.02C, discharge at 0.5C rate, voltage range is 2.0-4.8V, cycle under this condition for 5 weeks, then charge to 4.8V at 0.5C rate, cut-off current is 0.02C, leave at room temperature for 48 hours, test the battery voltage, recorded as V1.

[0063] Voltage drop = 4.8 - V1, in volts.

[0064] The relevant test results are shown in Table 2:

[0065] Table 2

[0066]

[0067]

[0068] From the data in the above table, it can be seen that for the lithium-rich manganese-based graphite high-voltage 4.8V battery system, compared with the traditional carbonate electrolyte (Comparative Example 1), the electrolyte of the solvent system of the embodiment has better matching with the high-voltage positive electrode material, and the gas production behavior of the battery is obviously reduced on the surface. The solvent system of the embodiment has good high-voltage tolerance, which effectively inhibits the occurrence of electrolyte side reactions, especially inhibits the oxidation and decomposition of solvents such as EC, which causes the increase in SEI film thickness and the increase in battery thickness. At the same time, it is of great help to reduce the voltage drop of the battery in the full state and improve the cycle performance. Further, the combination and ratio of the solvents in the present invention have a great influence on the performance of the battery. It can be seen from the embodiments and comparative examples 7 to 14 that the batteries with the two solvent combinations of DMC / FEC and TTE / FEC are poor in terms of circulation and expansion. In addition, the present invention also optimizes the formula of the solvent system in detail. The results show that the battery has the best cycle performance when the ratio of DMC, FEC, and HFE is 6:1:3. By simulating and calculating the radial distribution function of the electrolyte, it can be seen that the total coordination number of lithium ions in the solvation structure of the electrolytes of Comparative Examples 2 to 4 is basically around 5, but when the ratio is 6:1:3, the solvation structure contains more PF 6 - anion (about 0.7), while other ratios of solvation structures have only 0.4, more PF 6 - Entering the solvation shell will greatly help improve the stability of the electrolyte.

[0069] In the present invention, LiPF is added 6 LiFSi as the electrolyte lithium salt of the electrolyte can improve the kinetic properties of the electrolyte and, to a certain extent, alleviate the irreversible capacity loss of the lithium-rich manganese-based material itself caused by poor rate performance.

[0070] The lithium bis(vinylmalonate)borate (LiBMB-A) and lithium 2-vinylmalonate difluoroborate (LiBMB-B) used in the present invention not only have similar properties to lithium oxalate borate, i.e., similar conductivity and reduction potential, but also contain carbon-carbon double bonds in their structures, which cross-link each other during oxidation and reduction at the positive and negative electrodes to form a denser and more ductile SEI film, thereby reducing the dissolution of metal ions in the lithium-manganese-rich material; furthermore, the alkenyl-substituted lithium malonate borate is more Lithium tetrafluoroborate has a higher HOMO orbital and is more likely to bind to oxygen precipitated in lithium-manganese-rich materials, reducing its oxidative decomposition of the electrolyte and ensuring stable battery cycling; lithium tetrafluorooxalate phosphate (LiTFOP) can synergistically work with lithium bis(vinylmalonate) borate (LiBMB-A) and / or lithium 2-vinylmalonate difluoroborate (LiBMB-B) in the electrolyte to form a more stable SEI. At the same time, it also has the functions of improving the shelf performance of the battery, reducing gas production, and lowering impedance.

[0071] It can be seen from Examples 1 to 16 that when the mass ratio of LiBMB-A or LiBMB-B to LiTFOP is 1:0.3 to 1:4, and the mass percentage of LiBMB-A or LiBMB-B is in the range of 0.5% to 3%, and the mass percentage of LiTFOP is in the range of 0.5% to 2%, the performance of the electrolyte is better. If the amount added is too small, the performance of the additive cannot be fully exerted, and if the amount added is too large, the battery impedance will increase, thereby causing the cycle performance to decrease. Therefore, there is an optimal value for the amount of additive added. The most preferred amounts of LiBMB-A and LiTFOP and LiBMB-B and LiTFOP are 1% and 2% and 1% and 1%, respectively.

[0072] The present invention has also conducted certain research on the combination of other additives, such as adding TMSP and any one of GA, LiDFOP and DTD at the same time. The results show that the electrolyte based on the present invention, combined with other additives, can also make the battery have better performance.

[0073] Through the above-mentioned embodiments and comparative experiments, it can be found that the battery with lithium-rich manganese-based positive electrode material using the electrolyte of the present invention can work normally in a high voltage system, and suppresses the gas production of the battery during the cycle process, effectively reduces the expansion degree of the battery, and also has a good improvement effect on the voltage drop of the battery.

[0074] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes made according to the spirit of the present invention.

Claims

1. An electrolyte for a lithium-rich manganese-based lithium-ion battery, comprising an electrolyte lithium salt, a non-aqueous organic solvent, and an additive, Characterized in that: The non-aqueous organic solvent is a mixture of carbonates, fluorinated carbonates, and fluoroethers, and the additive includes a vinyl-containing lithium malonate borate derivative and lithium tetrafluoroxalate phosphate, and the structure of the vinyl-containing lithium malonate borate derivative is shown by general formula A and / or B: Among them, R 1 , R 2 , R 3 , R 4 , R 5 are independently selected from H, a halogen atom, an alkyl group having 1-3 carbon atoms which is unsubstituted or substituted with a fluorine atom, an alkoxy group having 1-3 carbon atoms, or a cyano group.

2. The electrolyte for a lithium-rich manganese-based lithium-ion battery according to claim 1, Characterized in that: The volume ratio of the carbonates, fluorinated carbonates, and fluoroethers is (2.5 to 8):1:(1.5 to 5).

3. The electrolyte for a lithium-rich manganese-based lithium-ion battery according to claim 1, Characterized in that: The carbonates are one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate; the fluorinated carbonates are one or more of fluorinated ethylene carbonate, difluorinated ethylene carbonate, and tetrafluorinated ethylene carbonate; and the fluoroethers are one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, or 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether.

4. The electrolyte for a lithium-rich manganese-based lithium-ion battery according to claim 1, Characterized in that: The feeding mass of the vinyl-containing lithium malonate borate derivative accounts for 0.1% to 8% of the total mass of the electrolyte, and the feeding mass of the lithium tetrafluoroxalate phosphate accounts for 0.5% to 5% of the total mass of the electrolyte.

5. The electrolyte for a lithium-rich manganese-based lithium-ion battery according to claim 4, Characterized in that: The feeding mass ratio of the vinyl-containing lithium malonate borate derivative to the lithium tetrafluoroxalate phosphate is 1:(0.3 to 5).

6. The electrolyte for a lithium-rich manganese-based lithium-ion battery according to claim 1, Characterized in that: The lithium salt is LiPF 6 and other lithium salts, and the other lithium salts are LiBF 4 , LiClO 4 , LiTFSI, LiFSI, or at least one of them; and / or, the concentration of the lithium salt in the electrolyte is 1 to 3 mol / L; and / or the concentration ratio of the LiPF 6 to other lithium salts is (2 to 8):

1.

7. The electrolyte for a lithium-rich manganese-based lithium-ion battery according to claim 6, Characterized in that: The other lithium salt is LiTFSI and / or LiFSI.

8. The electrolyte for a lithium-rich manganese-based lithium-ion battery according to claim 1, Characterized in that: The additive further includes other additives, and the other additives are one or more of succinonitrile, adiponitrile, 1,3-propane sultone, ethylene sulfate, methylene methanedisulfonate, propylene sulfate, tris(trimethylsilyl) borate, tris(trimethylsilyl) phosphite, tris(trimethylsilyl) phosphate, vinylene ethylene carbonate, maleic anhydride, and glutaric anhydride; and / or, the feeding mass of the other additives accounts for 0.01% to 5% of the total mass of the electrolyte.

9. A lithium-rich manganese-based lithium-ion battery, comprising a positive electrode, a separator, a negative electrode, and an electrolyte, Characterized in that, The electrolyte is the electrolyte for a lithium-rich manganese-based lithium-ion battery according to any one of claims 1 to 8.

10. The lithium-rich manganese-based lithium-ion battery according to claim 9, wherein, The positive electrode includes a positive electrode active material, and the positive electrode active material is xLi 2 MnO 3 ·(1-x)LiMO 2 , where 0 < x < 1, M = Ni, Co, Mn and combinations thereof. The negative electrode includes a negative electrode active material, and the negative electrode active material is graphite and / or silicon, silicon oxide materials.

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