Acidic Aqueous All-Organic Symmetric Battery Based on Dihydroxynaphthoquinone Derivatives

Abstract

The present invention belongs to the field of new energy materials, and particularly relates to an acidic aqueous all-organic symmetric battery based on dihydroxynaphthalenedione derivatives. An acidic aqueous supporting electrolyte system is adopted, and the dihydroxynaphthalenedione derivative serves as both the positive and negative electrode active materials to assemble an aqueous all-organic symmetric battery. The aqueous all-organic symmetric battery designed by the present invention has the advantages of simple design, low cost, reversible battery polarity, high energy density, and high cycle stability, and has broad prospects in future large-scale energy storage applications.

Description

Technical Field

[0001] The present invention belongs to the field of new energy materials, and particularly relates to an acidic aqueous all-organic symmetric battery based on dihydroxynaphthalenedione derivatives. Background Art

[0002] Aqueous secondary batteries are widely used in various fields of society due to their safety, environmental friendliness and low cost. Compared with non-aqueous secondary batteries, their electrolytes have higher ionic conductivity and can withstand overcharging (Electrochim. Acta, 2000, 45, 2467). Among various aqueous secondary batteries, lead-acid batteries have the largest market share due to their wide availability and competitive price. However, the high toxicity of heavy metal lead and the problem of sulfation on the electrode during cycling (i.e., the accumulation of lead sulfate crystals) are inevitable. Nickel-metal hydride batteries have the problem of volume expansion, resulting in less than ideal cycling. Emerging aqueous lithium (sodium) ion batteries (especially the positive electrode) use electrode materials similar to those of non-aqueous lithium (sodium) ion batteries, but the specific capacities of these electrode materials are relatively low, resulting in limited energy density.

[0003] Organic electrode materials are composed of light elements with high abundance in the earth's crust (such as carbon, hydrogen, oxygen and nitrogen, etc.), and are rich in sources and low in cost. Moreover, the synthesis temperature of organic materials is usually much lower than that of inorganic materials (Nat. Chem. 2015, 7, 19). The molecular structure of organic compounds has high designability, that is, the key properties such as potential, theoretical specific capacity and electrochemical kinetics can be effectively regulated by the design and modification of the parent structure and groups. Quinones are one of the most common electroactive organic molecules, which not only exist widely in nature, but can also be synthesized from petrochemical raw materials. The reversible interconversion of the quinone-phenol structure usually has a very small reorganization energy and exhibits high reversibility in redox reactions. Therefore, in recent years, quinone molecules have been widely used as electrode materials for various battery systems (Nature 2014, 505, 195; Nat. Mater. 2017, 16, 841; ACS Appl. Energy Mater. 2019, 2, 4016; Angew. Chem. 2020, 132, 9718). However, the theoretical specific capacity of the existing battery systems with quinone-phenol structure is relatively low.

[0004] In addition, the positive and negative electrodes of common secondary batteries use different electrode materials, and the battery polarity cannot be reversed. Therefore, not only the battery installation is more complex, but also there are certain potential safety hazards. Summary of the Invention

[0005] To solve the problem that the current battery installation needs to consider polarity, simplify the installation process, and improve fault tolerance, the present invention designs an aqueous symmetric battery with electrically reversible polarity using quinone molecule dihydroxynaphthalenedione derivatives as both the positive and negative electrode materials. The organic electrode material dihydroxynaphthalenedione derivatives can either act as the negative electrode and undergo redox reactions in the low potential region or act as the positive electrode and undergo redox reactions in the high potential region. This symmetric battery has the advantages of simple design and reversible electrode polarity, and has important research significance and application value. Moreover, the battery of the present invention has the advantages of high specific capacity, long cycle life, safety, environmental protection, and easy synthesis.

[0006] The object of the present invention is to use dihydroxynaphthalenedione derivatives with multiple groups of redox reactions as the positive and negative electrode materials to construct a high-performance aqueous all-organic symmetric battery, and solve problems such as performance degradation, safety hazards, and shortened cycle life caused by possible reverse installation of the battery polarity. To achieve the above object, the present invention provides a synthesis method of dihydroxynaphthalenedione derivatives that can be used in aqueous all-organic symmetric batteries, and also provides an aqueous all-organic symmetric battery based on dihydroxynaphthalenedione derivatives. The dihydroxynaphthalenedione derivatives provided by the present invention have redox-active conjugated structural units, can undergo at least two groups of reversible redox reactions, and such organic electrode materials have the advantages of wide raw material sources, scalable synthesis, low cost, high energy density, and long cycle life. Moreover, the problem of considering polarity in battery installation is solved, and it has broad prospects in future large-scale energy storage applications. Compared with organic electrolytes, aqueous electrolytes have higher ionic conductivity.

[0007] The technical solution adopted by the present invention to solve its technical problems is: an aqueous all-organic symmetric battery based on dihydroxynaphthalenedione derivatives. Dihydroxynaphthalenedione derivatives with redox-active conjugated structural units are selected, which can either act as the negative electrode and undergo redox reactions in the low potential region or act as the positive electrode and undergo redox reactions in the high potential region. Using the same dihydroxynaphthalenedione derivatives as the positive and negative active materials, an aqueous all-organic symmetric battery with reversible polarity and high energy density is assembled.

[0008] The electrode active material of the aqueous all-organic symmetric battery is dihydroxynaphthalenedione derivatives with redox-active conjugated structural units, and its structural formula is as follows:

[0009]

[0010] Among them, each of R1 - R4 independently selects from H, optionally substituted C1-6 alkyl, halogen, carboxyl, cyano, nitro, aldehyde group, and trifluoromethyl.

[0011] The construction steps of the aqueous all-organic symmetric battery are as follows: First, synthesize or select a dihydroxynaphthalenedione derivative that can undergo at least two sets of reversible redox reactions, and then use it as the active material for both the positive and negative electrodes, and use an acidic electrolyte as the supporting electrolyte solution to assemble a symmetric battery.

[0012]

[0013] Preferably, the electrode active material is 5,8-dihydroxy-2,3,6,7-tetramethyl-1,4-naphthalenedione (DHTMNDO), 2,3,6,7-tetrabromo-5,8-dihydroxy-1,4-naphthalenedione (TBDHNDO), 2,3-dichloro-5,8-dihydroxy-1,4-naphthalenedione (DCDHNDO), 5,8-dihydroxy-2-isopropyl-1,4-naphthalenedione (DHINDO), 1,4-dihydroxyanthraquinone (DHAQ), 2,3-dichloro-1,4-dihydroxyanthraquinone (DCDHAQ), 1,4-dihydroxy-2,3-bis(hydroxymethyl)anthraquinone (DHBHAQ) or 6,11-dihydroxy-5,12-benzoperylenequinone (DHNCDO).

[0014]

[0015] Preferably, the pH value of the supporting electrolyte solution is 0-6.

[0016] Preferably, the acid contained in the supporting electrolyte solution is acetic acid, sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, phosphoric acid or a mixture thereof; the salts contained are potassium chloride, sodium chloride, lithium chloride, potassium sulfate, potassium nitrate, potassium perchlorate, sodium sulfate, sodium nitrate, sodium perchlorate, lithium sulfate, lithium nitrate, sodium acetate, potassium acetate or a mixture thereof.

[0017] Preferably, the total concentration of cations in the supporting electrolyte solution is 0.5-8 mol / L.

[0018] The beneficial effects of the present invention are as follows: In the present invention, a dihydroxynaphthalenedione derivative that can undergo at least two sets of reversible redox reactions is used as the active material for both the positive and negative electrodes, and an acidic supporting electrolyte solution is used to construct an aqueous all-organic symmetric battery with reversible polarity. The battery also has the advantages of low cost, simple structure, high energy density and long cycle life, and has broad prospects in future large-scale energy storage applications.

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0020] Figure 1 is the nuclear magnetic resonance hydrogen spectrum of 5,8-dihydroxy-2,3,6,7-tetramethyl-1,4-naphthalenedione (DHTMNDO) synthesized in Example 1 (1 1H NMR, A) and carbon nuclear magnetic resonance ( 13 13C NMR, B) spectra.

[0021] Figure 2 It is the cyclic voltammogram of DHTMNDO synthesized in Example 1.

[0022] Figure 3 It is the charge-discharge curve of the aqueous symmetric battery with DHTMNDO synthesized in Example 1 as the positive and negative electrodes.

[0023] Figure 4 It is the cycle life diagram of the aqueous symmetric battery with DHTMNDO synthesized in Example 1 as the positive and negative electrodes.

[0024] Figure 5 It is of 2,3-dichloro-5,8-dihydroxy-1,4-naphthoquinone (DCDHNDO) synthesized in Example 2 1 1H NMR and 13 13C NMR spectra.

[0025] Figure 6 It is the cyclic voltammogram of DCDHNDO synthesized in Example 2.

[0026] Figure 7 It is the cycle life diagram of the aqueous symmetric battery with DCDHNDO prepared in Example 2 as the positive and negative electrodes.

[0027] Figure 8 It is of 2,3,6,7-tetrabromo-5,8-dihydroxy-1,4-naphthoquinone (TBDHNDO) synthesized in Example 3 13 13C NMR spectrum.

[0028] Figure 9 It is the cyclic voltammogram of TBDHNDO synthesized in Example 3.

[0029] Figure 10 It is the cycle life diagram of the aqueous symmetric battery with TBDHNDO synthesized in Example 3 as the positive and negative electrodes.

[0030] Figure 11 It is the structural schematic diagram of the aqueous symmetric battery based on dihydroxy naphthoquinone derivatives. Detailed implementation mode

[0031] The present invention will be described in more detail through examples, but the protection scope of the present invention is not limited to these examples.

[0032] Example 1

[0033] Synthesis of 5,8-dihydroxy-2,3,6,7-tetramethyl-1,4-naphthalenedione (DHTMNDO) and Aqueous Symmetric Battery with It as Positive and Negative Electrodes

[0034] (1) Synthesis of DHTMNDO

[0035] Weigh 2,3-dimethyl-1,4-benzenediol (7.5 mmol, 1.0362 g), 2,3-dimethylmaleic anhydride (45 mmol, 5.6748 g), anhydrous aluminum chloride (22.5 mmol, 3.001 g) and sodium chloride (22.5 mol, 1.314 g), add them to a Schlenk tube purged with nitrogen, mix evenly, evacuate with a double-tube, and heat to 180 °C in an oil bath for 5 hours. After the reaction, perform the metathesis of aluminum with 6 mol L -1 hydrochloric acid, stir at room temperature for 2 days, extract the crude product with anhydrous diethyl ether, dry it with anhydrous sodium sulfate to remove water, rotary evaporate, and vacuum dry at 60 °C for 6 hours to obtain a black solid (3.45 g, yield 94%).

[0036] (2) Assembly and Performance Testing of Aqueous Symmetric Battery with DHTMNDO as Positive and Negative Electrodes

[0037] The battery uses graphite plates as current collectors. Mix DHTMNDO, carbon black and binder PTFE evenly at a mass ratio of 8:1:1, and then coat it on Toray carbon paper (TGP-H-060), which are used as the positive and negative electrodes respectively. The loading of DHTMNDO in the electrode layer is 1 mg cm -2 . The active area of the electrode is 5 cm 2 . Inject a 1 mol L -1 sodium acetate - acetic acid solution with pH 5 as the supporting electrolyte solution between the positive and negative electrodes, and use a cation exchange membrane to separate the positive and negative electrodes.

[0038] Figure 1 is the 1 H NMR and 13 C NMR spectra of DHTMNDO synthesized in Example 1. Figure 1 The proton peak at 2.01 ppm in chemical shift in A belongs to the hydrogen atom on the methyl group of DHTMNDO. There are four types of carbon atoms in the DHTMNDO structure, which are labeled with letters a - d. Among them, the methyl carbon atom is labeled as a, the benzene ring carbon atom connected to the methyl group is labeled as b, the benzene ring carbon atom connected to the oxygen is labeled as c, and the carbon atom connecting the two benzene rings is d. Specifically, Figure 1The peak at 166.96 ppm in B corresponds to the carbon atom connected to oxygen, the peak at 140.87 ppm corresponds to the benzene ring carbon atom connected to the methyl group and the carbon atom connecting two benzene rings, while the peak at 9.74 ppm corresponds to the methyl carbon atom. No impurity peaks were observed, indicating that the DHTMNDO synthesized by this method has high purity.

[0039] Figure 2 It is the cyclic voltammogram of the DHTMNDO electrode in Example 1. The CV diagrams of the DHTMNDO electrode at different scan rates in the sodium acetate - acetic acid mixed solution (pH = 5) show that three sets of reversible redox reactions (labeled as ET1, ET2, and ET3 respectively) can occur, and the corresponding standard potentials are 0.12, 0.58, and 1.16 V respectively. The standard potential difference between the ET1 and ET3 reactions is 1.04 V.

[0040] Figure 3 It is the charge - discharge curve of the aqueous symmetric battery with the DHTMNDO synthesized in Example 1 as the positive and negative electrodes. The discharge specific capacity of this battery can reach 68 mAh g -1 When the positive and negative electrodes of this battery are reversed, the discharge specific capacity can still reach 60 mAh g -1 .

[0041] Figure 4 It is the cycle life diagram of the aqueous symmetric battery with the DHTMNDO synthesized in Example 1 as the positive and negative electrodes. After 1000 continuous charge - discharge cycles of this battery at 2 A·g -1 , the discharge capacity retention rate is 83.4%, and the average Coulombic efficiency is 98.8%.

[0042] Example 2: Synthesis of 2,3 - dichloro - 5,8 - dihydroxy - 1,4 - naphthoquinone (DCDHNDO) and aqueous symmetric battery with it as the positive and negative electrodes

[0043] (1) Synthesis of DCDHNDO

[0044] Add anhydrous aluminum chloride (708 mg, 5.3 mmol), sodium chloride (142 mg, 2.4 mmol), 1,4 - dimethoxybenzene (82 mg, 0.6 mmol) and 2,3 - dichloromaleic anhydride (200 mg, 1.2 mmol) into a Schlenk tube respectively, and mix evenly. Heat to 170 - 175 °C and react for 5 minutes. Cool the obtained dark red melt, add 8 mL of H2O and 500 μL of 12 molL -1 hydrochloric acid for hydrolysis, and stir overnight at room temperature. Extract with ethyl acetate, dry the organic layer with anhydrous sodium sulfate, filter and perform rotary evaporation to obtain a red solid.

[0045] (2) Assembly and performance test of an aqueous symmetric battery with DCDHNDO as the positive and negative electrodes

[0046] The steps for the assembly and performance test of the aqueous symmetric battery with DCDHNDO as the positive and negative electrodes are the same as those in Example 1. Figure 5 It is the 1 H NMR and 13 C NMR spectra of DCDHNDO synthesized in Example 2. Figure 5 For 1 all proton signals in the H NMR spectrum of A can correspond to the hydrogen atoms in the molecular structure of DCDHNDO, Figure 5 For 13 all nuclear magnetic carbon peaks in the C NMR spectrum of B can correspond to the carbon atoms in the molecular structure of DCDHNDO, and no obvious impurity peaks are observed, indicating that the DCDHNDO synthesized by this method has high purity.

[0047] Figure 6 It is the cyclic voltammogram of DCDHNDO synthesized in Example 2. There are also three groups of redox peak signals in the CV diagrams of the DCDHNDO electrode in a sodium acetate - acetic acid mixed solution (pH = 5) at different scanning rates, and their standard potentials are 0.06, 0.22, and 0.80 V respectively, indicating that DCDHNDO can undergo three groups of redox reactions.

[0048] Figure 7 It is the cycle life diagram of the aqueous symmetric battery with the DCDHNDO synthesized in Example 2 as the positive and negative electrodes. After 1000 charge - discharge cycles, the capacity retention rate of the battery is still 85.7%. The discharge specific capacity of the aqueous symmetric battery with the DCDHNDO synthesized in Example 2 as the positive and negative electrodes can reach 52 mAh g -1 , and when the positive and negative electrodes of the battery are reversed, the discharge specific capacity can still reach 44 mAh g -1 .

[0049] Example 3: Synthesis of 2,3,6,7 - tetrabromo - 5,8 - dihydroxy - 1,4 - naphthoquinone (TBDHNDO) and an aqueous symmetric battery with it as the positive and negative electrodes

[0050] (1) Synthesis of TBDHNDO

[0051] Add 0.2 g (0.0008 mol) of DCDHNDO to 50 mL of glacial acetic acid, heat to reflux the reactants, then dropwise add 1.032 mL (0.02 mol) of bromine, and continue to reflux the resulting solution for 10 hours. Cool to room temperature, filter by suction, and dry at 60 °C for 12 h to obtain a dark red solid.

[0052] (2) Assembly and performance test of an aqueous symmetric battery with TBDHNDO as the positive and negative electrodes

[0053] The assembly and performance test of the aqueous symmetric battery with TBDHNDO as the positive and negative electrodes are the same as those in Example 1. Figure 8 It is the 13 C NMR spectrum of TBDHNDO synthesized in Example 3. The peak at 108.22 ppm corresponds to the carbon atom connecting two benzene rings in TBDHNDO, the peak at 134.69 ppm corresponds to the benzene ring carbon atom connecting the chlorine atom in TBDHNDO, and the peak at 166.58 ppm corresponds to the benzene ring carbon atom connecting the oxygen atom.

[0054] Figure 9 It is the cyclic voltammogram of the TBDHNDO electrode synthesized in Example 3. TBDHNDO has two pairs of redox peaks, and their standard potentials are -0.1 V (ET1) and 0.8 V (ET2) respectively.

[0055] Figure 10 It is the cycle life diagram of the aqueous symmetric battery with TBDHNDO synthesized in Example 3 as the positive and negative electrodes. After 1000 charge-discharge cycles, the capacity retention rate is 98.3%. The discharge specific capacity of the aqueous symmetric battery with TBDHNDO synthesized in Example 3 as the positive and negative electrodes can reach 76 mAh g -1 , when the positive and negative electrodes of the battery are reversed, the discharge specific capacity can still reach 68 mAh g -1 .

[0056] Example 4: Synthesis of 5,8-dihydroxy-2-isopropyl-1,4-naphthoquinone (DHINDO) and aqueous symmetric battery with it as the positive and negative electrodes

[0057] (1) Synthesis of DHINDO

[0058] Under nitrogen protection, anhydrous aluminum chloride, sodium chloride, maleic anhydride and hydroquinone were mixed at a molar ratio of 3:3:6:1 at 140 °C, and the reaction temperature was raised to 180 °C within 3 h. Then the aluminum complex was decomposed with cold 6 mol L -1 hydrochloric acid, and stirred at room temperature for 2 days. The crude product was extracted with ether, and then purified by chromatography and eluted with chloroform to obtain the product DHINDO.

[0059] (2) Assembly and performance test of the aqueous symmetric battery with DHINDO as the positive and negative electrodes

[0060] The assembly and performance test of the aqueous symmetric battery with DHINDO as the positive and negative electrodes are the same as those in Example 1. After 1000 charge-discharge cycles, the capacity retention rate is 95.4%. The discharge specific capacity of the aqueous symmetric battery with DHINDO synthesized in Example 4 as the positive and negative electrodes can reach 82 mAh g -1 , when the positive and negative electrodes of the battery are reversed, the discharge specific capacity can still reach 76 mAh g-1 。

[0061] Example 5: Assembly and Performance Testing of an Aqueous Symmetric Battery with 1,4-Dihydroxyanthraquinone (DHAQ) as the Positive and Negative Electrodes

[0062] DHAQ is sourced from commercial products. The assembly and performance testing of an aqueous symmetric battery with DHAQ as the positive and negative electrodes are the same as in Example 1. After 600 charge-discharge cycles, the capacity retention rate is 86.1%. The discharge specific capacity of the aqueous symmetric battery with the DHAQ synthesized in Example 5 as the positive and negative electrodes can reach 42 mAh g -1 , and when the positive and negative electrodes of this battery are reversed, the discharge specific capacity can still reach 34 mAh g -1 。

[0063] Example 6: Assembly and Performance Testing of an Aqueous Symmetric Battery with 2,3-Dichloro-1,4-dihydroxyanthraquinone (DCDHAQ) as the Positive and Negative Electrodes

[0064] DCDHAQ is sourced from commercial products. The assembly and performance testing of an aqueous symmetric battery with DCDHAQ as the positive and negative electrodes are the same as in Example 1. After 800 charge-discharge cycles, the capacity retention rate is 83.9%. The discharge specific capacity of the aqueous symmetric battery with the DCDHAQ synthesized in Example 6 as the positive and negative electrodes can reach 38 mAh g -1 , and when the positive and negative electrodes of this battery are reversed, the discharge specific capacity can still reach 33 mAh g -1 。

[0065] Example 7: Assembly and Performance Testing of an Aqueous Symmetric Battery with 1,4-Dihydroxy-2,3-bis(hydroxymethyl)anthraquinone (DHBHAQ) as the Positive and Negative Electrodes

[0066] DHBHAQ is sourced from commercial products. The assembly and performance testing of an aqueous symmetric battery with DHBHAQ as the positive and negative electrodes are the same as in Example 1. After 1000 charge-discharge cycles, the capacity retention rate is 85.2%. The discharge specific capacity of the aqueous symmetric battery with the DHBHAQ synthesized in Example 7 as the positive and negative electrodes can reach 43 mAh g -1 , and when the positive and negative electrodes of this battery are reversed, the discharge specific capacity can still reach 37 mAh g -1 。

[0067] Example 8: Assembly and Performance Testing of an Aqueous Symmetric Battery with 6,11-Dihydroxy-5,12-benzoperylenequinone (DHNCDO) as the Positive and Negative Electrodes

[0068] DHNCDO is derived from commercial products. The assembly and performance test of the aqueous symmetric battery with DHNCDO as the positive and negative electrodes are the same as those in Example 1. After 600 charge-discharge cycles, the capacity retention rate is 89.6%. The discharge specific capacity of the aqueous symmetric battery with the DHNCDO synthesized in Example 8 as the positive and negative electrodes can reach 64 mAh g -1 , and when the positive and negative electrodes of the battery are reversed, the discharge specific capacity can still reach 56 mAh g -1 .

Claims

1. An acidic aqueous all-organic symmetric battery based on dihydroxynaphthalenedione derivatives, characterized in that, The battery uses a dihydroxynaphthalenedione derivative as both the positive electrode and the negative electrode of the battery, and an acidic aqueous electrolyte solution as the supporting electrolyte solution; The dihydroxynaphthalenedione derivative has a molecular structure of the following formula: wherein, R1-R4 are independently selected from H, optionally substituted C1-6 alkyl, halogen, carboxyl, cyano, nitro, aldehyde or trifluoromethyl.

2. The acidic aqueous all-organic symmetric battery based on the dihydroxynaphthalenedione derivative according to claim 1, wherein The dihydroxynaphthalenedione derivative is selected from: 5,8-dihydroxy-2,3,6,7-tetramethyl-1,4-naphthalenedione DHTMNDO, 2,3,6,7-tetrabromo-5,8-dihydroxy-1,4-naphthalenedione TBDHNDO, 2,3-dichloro-5,8-dihydroxy-1,4-naphthalenedione DCDHNDO, 5,8-dihydroxy-2-isopropyl-1,4-naphthalenedione DHINDO, 1,4-dihydroxyanthraquinone DHAQ, 2,3-dichloro-1,4-dihydroxyanthraquinone DCDHAQ, 1,4-dihydroxy-2,3-bis(hydroxymethyl)anthraquinone DHBHAQ or 6,11-dihydroxy-5,12-benzotetracene dione DHNCDO.

3. The acidic aqueous all-organic symmetric battery based on dihydroxynaphthalenedione derivatives according to claim 1, wherein The pH range of the acidic aqueous electrolyte solution as the supporting electrolyte solution is 0-6.

4. The acidic aqueous all-organic symmetric battery based on the dihydroxynaphthalenedione derivative according to claim 1, wherein The total concentration of cations in the supporting electrolyte solution is 0.5-8 mol / L.

5. The acidic aqueous all-organic symmetric battery based on the dihydroxynaphthalenedione derivative according to claim 1, wherein The supporting electrolyte is a mixture of an acid and salts.

6. The acidic aqueous all-organic symmetric battery based on the dihydroxynaphthalenedione derivative according to claim 5, wherein The salts are potassium chloride, sodium chloride, lithium chloride, potassium sulfate, potassium nitrate, potassium perchlorate, sodium sulfate, sodium nitrate, sodium perchlorate, lithium sulfate, lithium nitrate, sodium acetate, potassium acetate or a mixture thereof.

7. The acidic aqueous all-organic symmetric battery based on the dihydroxynaphthalenedione derivative according to claim 5, wherein The acid is acetic acid, sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, phosphoric acid or a mixture thereof.

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