Solid or semi-solid electrolyte for Na-ion battery

Abstract

Electrolyte for Na-ion battery, comprising hyaluronic acid and at least one ionic conductive compound comprising sodium. Figure for abstract: Fig 1

Description

Title of the invention: Solid or semi-solid electrolyte for Na-ion battery Technical field

[0001] The present invention relates to the field of Na-ion batteries and electrolytes incorporating a polymer.

[0002] More particularly, the present invention relates to a solid or semi-solid electrolyte for a Na-ion battery and a method for manufacturing such an electrolyte. The invention also relates to a Na-ion battery cell comprising said electrolyte, to a Na-ion battery incorporating such a cell, as well as to a method for recycling such a Na-ion battery. Previous techniques

[0003] Since 2006, the European Union has required its member states to recycle at least 50% of batteries by mass, including the automotive sector and electric vehicle batteries. At the end of 2020, new European regulations on batteries and their waste were proposed, aimed at strengthening the initial measures adopted, with an obligation to achieve 65% recycling efficiency by 2024 and 70% by 2030.

[0004] This regulation strongly encourages the development of more efficient recycling processes. At the same time, it also forces car manufacturers to review the design of batteries to facilitate dismantling and recycling, for example by modifying their design or composition.

[0005] However, several aspects block the development of current systems.

[0006] Access to the active material is often difficult so that it is generally necessary to grind the entire battery modules. In particular, access to the battery cells is impossible without causing safety problems.

[0007] The cells of an electric battery comprise several materials, in particular the active materials forming the electrodes, the separators and the polymeric binders, and their separation is difficult.

[0008] The binders conventionally used, such as polyvinylidene fluoride, PVDF, limit the detachment of the active material of the electrodes from their support, the collectors. The binders need to be burned by pyrolysis at high temperature, around 500°C, before recycling the battery.

[0009] The composition of these binders, based on fluorine, also results in the presence of impurities that are difficult to remove from recycled materials.

[0010] There is therefore a need to develop a new battery cell, particularly for electric vehicles, making it possible to overcome the above drawbacks.

[0011] An electrolyte for a Na-ion battery is therefore proposed, comprising hyaluronic acid and at least one ionic conductive compound comprising sodium.

[0012] According to one embodiment, said ionic conductive compound may comprise one or more sodium salts, more preferably chosen from NaBF4, NaClO4, NaPF6, NaTFSI, NaFSI, NaODFB or a mixture thereof.

[0013] Preferably, the sodium salt(s) are dissolved in water.

[0014] Advantageously, the electrolyte may comprise one or more solvents chosen from aprotic polar solvents, such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl and ethyl carbonate or a mixture thereof.

[0015] According to another embodiment, said ionic conductive compound may comprise a solid ionic conductor, preferably an inorganic conductor such as a glass-ceramic conductor.

[0016] Preferably, the electrolyte comprises a content of between 5 and 50% by weight of hyaluronic acid, preferably between 5 and 30% by weight, more preferably between 5 and 20% by weight. These percentages are considered relative to the total weight of the electrolyte.

[0017] The invention also relates to the use of an electrolyte as described above in a solid or semi-solid Na-ion battery.

[0018] The invention also relates to a method for preparing an electrolyte for a Na-ion battery, comprising mixing hyaluronic acid with at least one ionic conductive compound comprising sodium.

[0019] According to one embodiment, said ionic conductive compound may comprise one or more sodium salts, preferably chosen from NaBF4, NaC104, NaPF6, NaTFSI, NaFSI, NaODFB or a mixture thereof.

[0020] Preferably, the method for preparing an electrolyte for a Na-ion battery comprises a step of dissolving the sodium salt(s) in water.

[0021] Advantageously, one or more solvents are added to the mixture of hyaluronic acid and said ionic conductive compound, chosen from aprotic polar solvents, such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl and ethyl carbonate or a mixture thereof.

[0022] According to another embodiment, said ionic conductive compound of the mixture may comprise a solid ionic conductor, preferably an inorganic conductor such as a glass-ceramic conductor.

[0023] Preferably, the mixture comprises a content of between 5 and 50% by weight of hyaluronic acid, preferably between 5 and 30% by weight, more preferably between 5 and 20% by weight. These percentages are considered relative to the total weight of the electrolyte.

[0024] The invention further relates to a solid or semi-solid Na-ion battery cell, comprising a positive electrode, a negative electrode, an anode current collector, a cathode current collector, a separator and an electrolyte as described above.

[0025] Advantageously, the electrolyte and the separator can form a single structure.

[0026] Preferably, the positive electrode and / or the negative electrode comprises hyaluronic acid.

[0027] Preferably, the thickness of the electrolyte is between 20 and 60 μm, preferably between 25 and 35 μm.

[0028] The invention also relates to a method for manufacturing a Na-ion battery cell, in which an electrolyte as previously described is deposited on a negative electrode or on a positive electrode by liquid coating.

[0029] Preferably, the liquid coating step is preferably carried out using a solvent which is mainly water.

[0030] By predominantly, we mean a percentage greater than 50% by weight of the solvent used to carry out the coating.

[0031] Advantageously, the method for manufacturing a Na-ion battery cell may comprise a prior step of forming hyaluronic acid by fermentation, preferably by fermentation of plants or by bacterial fermentation.

[0032] The invention also relates to a solid or semi-solid Na-ion battery comprising at least one cell as described above.

[0033] The invention also relates to a method for manufacturing a Na-ion battery, said method comprising a step of assembling one or more cells as described previously.

[0034] The invention further relates to a method for recovering hyaluronic acid from a Na-ion battery as described above, comprising a step of dissolving in water the hyaluronic acid from the Na-ion battery, including the hyaluronic acid from the electrolyte.

[0035] Preferably, the recovery method comprises a preliminary step of determining the state of charge of the Na-ion battery.

[0036] Advantageously, the recovery method comprises, when the state of charge of the Na-ion battery is zero, a step of opening the cell(s) 1 forming the Na-ion battery.

[0037] Preferably, the recovery method comprises a step of dissolving in water the hyaluronic acid from the Na-ion battery, and in particular the hyaluronic acid from the electrolyte as previously described.

[0038] Preferably, the dissolution step is carried out in the presence of ultrasound.

[0039] Advantageously, the recovery method may comprise, after dissolution, a filtration step to separate the hyaluronic acid dissolved in the water from the rest of the Na-ion battery.

[0040] Preferably, the recovery method comprises a step of recycling the remainder of the Na-ion battery separated from the hyaluronic acid, such as active materials of the positive and negative electrodes. Statement of the invention

[0041] Other aims, advantages and characteristics will emerge from the description which follows, given purely for illustrative purposes and with reference to the appended drawings in which:

[0042] [Fig-1] is a schematic sectional view of a Na-ion cell for an electric or hybrid motor vehicle according to one embodiment of the invention.

[0043] [Fig.2] is a detailed schematic view of an electrode of a Na-ion cell for an electric or hybrid motor vehicle according to one embodiment of the invention.

[0044] [Fig.3] illustrates a method for recovering hyaluronic acid from a Na-ion battery according to one embodiment of the invention.

[0045] In what follows, the limits of a domain of values are included in this domain, in particular in the expression “between”.

[0046] Furthermore, the expression "at least one" used in the present description is equivalent to the expression "one or more".

[0047] [Fig.l] illustrates a Na-ion battery cell 1 comprising a positive electrode 2, a negative electrode 3, an anode current collector 5, a cathode current collector 4, a separator and an electrolyte 6. The electrolyte 6 ensures the transport of the ions between the two electrodes 2 and 3.

[0048] In the illustrated example, the electrolyte 6 and the separator form a single structure.

[0049] Electrolyte 6 comprises hyaluronic acid and at least one ionic conductive compound comprising sodium.

[0050] In one embodiment, the electrolyte 6 may be semi-solid and form a polymeric gel.

[0051] In the case of the semi-solid electrolyte 6, the ionic conductive compound may then comprise one or more sodium salts, preferably chosen from NaBF4, NaC104, NaPF6, NaTFSI, NaFSI, NaODFB or a mixture thereof.

[0052] Preferably, the sodium salt(s) are dissolved in water.

[0053] Preferably, the electrolyte 6 further comprises one or more solvents chosen from aprotic polar solvents, such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl and ethyl carbonate or a mixture thereof.

[0054] According to an exemplary embodiment, the semi-solid electrolyte 6 can thus be formed, advantageously, by at least one sodium salt and at least one carbonate solvent mixed in a hyaluronic acid matrix.

[0055] According to another embodiment, the electrolyte 6 can be solid.

[0056] In the case of solid electrolyte 6, the ionic conductive compound may comprise a solid ionic conductor, preferably an inorganic conductor, such as a glass-ceramic conductor.

[0057] The glass-ceramic conductor may, for example, comprise Na3SbS4-Na2WS4. Advantageously, the Na3SbS4-Na2WS4 may be synthesized in demineralized water from Na2S, Sb2S3, S, NaOH and (NH4)2WS4.

[0058] According to an exemplary embodiment, the solid electrolyte 6 can thus be formed, advantageously, by at least one vitroceramic ionic conductive compound comprising sodium mixed in a hyaluronic acid matrix.

[0059] Preferably, the solid or semi-solid electrolyte 6 comprises a content of between 5 and 50% by weight of hyaluronic acid, more preferably between 5 and 30% by weight, and even more preferably between 5 and 20% by weight. These percentages are considered relative to the total weight of the electrolyte 6.

[0060] Preferably, the thickness of the solid or semi-solid electrolyte 6 in the cell 1 is between 20 and 60 μm, more preferably between 25 and 35 μm. According to one example, the thickness of the electrolyte 6 may be 30 μm.

[0061] Hyaluronic acid is a polymer of disaccharides so that it forms a polymeric matrix in electrolyte 6.

[0062] Hyaluronic acid is fluorine-free and has high mechanical properties. It is also water-soluble, and therefore easily recyclable by dissolving in water.

[0063] Hyaluronic acid also has the advantage of being bio-sourced, manufactured in particular by fermentation.

[0064] Preferably, the positive electrode 2 and the negative electrode 3 also comprise hyaluronic acid.

[0065] [Fig.2] illustrates a positive or negative electrode 2, 3 of a cell 1 for a Na-ion battery.

[0066] The positive and negative electrodes 2, 3 preferably comprise an active material 7, carbon 8, and hyaluronic acid 9.

[0067] The active material 7 of the positive electrode 2 is, for example, Na3V2(PO4)3, (NVP).

[0068] The active material 7 of the negative electrode 3 is, for example, hard carbon.

[0069] In addition, the positive and negative electrodes 2, 3 comprise a collector of current, respectively, cathodic and anodic 4 and 5.

[0070] The current collectors 4 and 5 are, for example, aluminum current collectors.

[0071] Preferably, the thickness of the positive electrode 2 is between 50 and 150 μm, more preferably between 90 and 110 μm. According to one example, the thickness of the positive electrode 2 may be 100 μm.

[0072] Preferably, the thickness of the negative electrode 3 is between 50 and 150 μm, more preferably between 90 and 110 μm. According to one example, the thickness of the negative electrode 3 may be 100 μm.

[0073] The electrolyte layer 6 allows both the conduction of the Na+ cations and the electronic insulation of the two electrodes 2, 3.

[0074] Another object of the invention is a Na-ion battery comprising one or more cells 1 incorporating the solid or semi-solid electrolyte 6 according to the invention.

[0075] Another object of the invention is a method for preparing an electrolyte 6 for a Na-ion battery, comprising a step of mixing hyaluronic acid with at least one ionic conductive compound comprising sodium.

[0076] According to one embodiment, and in order to obtain a semi-solid electrolyte 6, the ionic conductive compound may comprise one or more sodium salts, preferably chosen from NaBF4, NaC104, NaPF6, NaTFSI, NaFSI, NaODFB or a mixture thereof.

[0077] Preferably, the method for preparing an electrolyte 6 for a Na-ion battery comprises a step of dissolving the sodium salt(s) in water.

[0078] Advantageously, one or more solvents are added to the mixture comprising the hyaluronic acid and the ionic conductive compound.

[0079] Preferably, the solvent(s) are chosen from aprotic polar solvents, such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl and ethyl carbonate or a mixture thereof.

[0080] According to another alternative embodiment, and in order to obtain a solid electrolyte 6, the ionic conductive compound of said mixture may comprise a solid ionic conductor.

[0081] Preferably, the ionic conductive compound is an inorganic conductor such as a glass-ceramic conductor.

[0082] The glass-ceramic conductor may, for example, comprise Na3SbS4-Na2WS4.

[0083] Advantageously, prior to the step of forming the mixture of hyaluronic acid and the ionic conductive compound, the Na3SbS4-Na2WS4 can be synthesized in demineralized water from Na2S, Sb2S3, S, NaOH and (NH4)2WS4.

[0084] Preferably, said mixture comprises a content of between 5 and 50% by weight of hyaluronic acid, preferably between 5 and 30% by weight, more preferably between 5 and 20% by weight. These percentages are considered relative to the total weight of the electrolyte.

[0085] The invention also relates to a method for manufacturing a Na-ion battery cell 1 in which a solid or semi-solid electrolyte 6 as previously described is deposited on the negative electrode 3 or on the positive electrode 2 by liquid coating.

[0086] Preferably, the thickness of the solid or semi-solid electrolyte 6 formed is between 20 and 60 μm, more preferably between 25 and 35 μm. According to one example, the thickness of the electrolyte 6 may be 30 μm.

[0087] The step of coating the electrolyte 6 by liquid means is preferably carried out using a solvent which is mainly water.

[0088] By predominantly, we mean a percentage greater than 50% by weight of the solvent used to carry out the coating.

[0089] According to an exemplary implementation, the positive electrode 2, comprising carbon, hyaluronic acid and active material 7, such as Na3V2(PO4)3, is deposited by liquid coating on the aluminum collector 4.

[0090] Preferably, the thickness of the positive electrode 2 formed on the aluminum collector 4 is between 50 and 150 μm, more preferably between 90 and 110 μm. According to one example, the thickness of the positive electrode 2 may be 100 μm.

[0091] According to an exemplary implementation, the negative electrode 3, comprising carbon, hyaluronic acid and active material 7, such as hard carbon, is deposited by liquid coating on the aluminum collector 5.

[0092] Preferably, the thickness of the negative electrode 3 formed on the aluminum collector 5 is between 50 and 150 μm, more preferably between 90 and 110 μm. According to one example, the thickness of the negative electrode 3 may be 100 μm.

[0093] After deposition of the electrolyte layer 6 on one of the two positive electrodes 2 and negative 3, the method of manufacturing a Na-ion battery cell 1 may comprise a step of dry rolling of the assembly obtained with the other of the two positive 2 and negative 3 electrodes in order to obtain a cell 1.

[0094] Preferably, the electrolyte 6 is deposited by liquid coating on the positive electrode 2, then the assembly of the electrolyte layer 6 and the positive electrode 2 is dry laminated with the negative electrode 3.

[0095] Advantageously, the method for manufacturing a Na-ion battery cell may comprise a prior step of forming hyaluronic acid by fermentation, preferably by fermentation of plants or by bacterial fermentation.

[0096] Another object of the invention is a method for recovering hyaluronic acid from a Na-ion battery as described previously.

[0097] With reference to [Fig.3], the recovery method preferably comprises a preliminary step 100 of determining the state of charge of the Na-ion battery.

[0098] When the state of charge, SOC, expressed in %, of the Na-ion battery is zero, the recovery method comprises a step 200 of opening the cell(s) 1 forming the Na-ion battery.

[0099] The recovery method comprises a step 300 of dissolving in water the hyaluronic acid from the Na-ion battery, and in particular the hyaluronic acid from the electrolyte 6.

[0100] In the example illustrated in Figures 1 and 2, the electrolyte 6, as well as the positive 2 and negative 3 electrodes incorporate hyaluronic acid. Preferably, step 300 of the recovery method advantageously comprises the dissolution in water of the hyaluronic acid of the electrolyte, as well as the hyaluronic acid of the positive 2 and negative 3 electrodes.

[0101] In order to facilitate dissolution, step 300 is carried out in the presence of ultrasound.

[0102] After dissolution, the recovery method preferably comprises a filtration step 400 to separate the hyaluronic acid dissolved in the water from the remainder of the Na-ion battery. On one side, the aqueous phase 500 comprising the dissolved hyaluronic acid is recovered. On the other side, the remainder 600 of the Na-ion battery, called black mass 600 or “black mass”, comprising in particular the active materials 7 of the positive 2 and negative 3 electrodes, is recovered.

[0103] Filtration 400 thus makes it possible to recover the hyaluronic acid from the electrolyte 6 and the positive 2 and negative 3 electrodes after its dissolution in water.

[0104] Preferably, the recovery method comprises a step 700 of recycling the remainder of the Na-ion battery, in particular active materials 7 of the positive 2 and negative 3 electrodes, into a new use.

[0105] The polymeric agent in hyaluronic acid of the electrolyte 6 allows direct and facilitated aqueous recycling, without heat treatment being necessary, and without the release of hydrofluoric acid likely to degrade the active materials 7 of the cell 1. Examples

[0106] Example 1: Preparation of a Na-ion battery comprising a semi-solid electrolyte

[0107] NaBF4 was dissolved in water to obtain an aqueous solution with a molar concentration of 1 mol / l. In the solution obtained, hyaluronic acid was dissolved in an amount of 15% by weight, relative to the total weight of the electrolyte solution, in order to obtain a homogeneous polymer gel. 20% by weight of propylene carbonate, PC, as well as 30% by weight of ethylene carbonate, EC were then added.

[0108] After mixing, the obtained semi-solid electrolyte was cast to form a 100 μm thick film on a cathode substrate composed of a mixture of Na3V2(PO4)3, NVP, carbon additive and hyaluronic acid previously liquid-coated on an aluminum current collector. The resulting composite was dried at 50 °C for 5 h under vacuum. Finally, the composite was dry-rolled with a 100 μm thick negative electrode composed of a mixture of hard carbon, carbon additive and hyaluronic acid previously liquid-coated on an aluminum current collector. A Na-ion battery with a semi-solid electrolyte is thus obtained.

[0109] Example 2: Preparation of a Na-ion battery with a solid electrolyte

[0110] Na3SbS4-Na2WS4 was synthesized in demineralized water from Na2S, Sb2S3, S, NaOH and (NH4)2WS4, weighed in stoichiometric quantity. Hyaluronic acid was carefully added to this mixture in an amount of 10% by weight relative to the total weight of the mixture incorporating the hyaluronic acid. The resulting mixture is mixed.

[0111] The electrolyte was then cast to obtain a 100 μm thick film on a cathode substrate composed of a mixture of Na3V2(PO4)3, NVP, carbon additive and hyaluronic acid previously liquid-coated on an aluminum current collector. The resulting composite was dried at 50 °C for 5 h under vacuum. Finally, the composite is dry-rolled with the 100 μm thick negative electrode composed of a mixture of hard carbon, carbon additive and hyaluronic acid previously liquid-coated on an aluminum current collector. A Na-ion battery with a solid electrolyte is thus obtained.

Claims

Claims

1. Electrolyte for Na-ion battery, comprising hyaluronic acid and at least one ionic conductive compound comprising sodium, said ionic conductive compound comprising: one or more sodium salts selected from NaBF4, NaC104, NaPF6, NaTFSI, NaFSI, NaODFB or a mixture thereof, or a solid ionic conductor, preferably an inorganic conductor such as a glass-ceramic conductor.

2. An electrolyte according to claim 1, wherein the sodium salt(s) are dissolved in water.

3. Electrolyte according to claim 1 or 2, comprising one or more solvents chosen from polar aprotic solvents, such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl and ethyl carbonate or a mixture thereof.

4. Electrolyte according to any one of the preceding claims, comprising a content of between 5 and 50% by weight of hyaluronic acid, preferably between 5 and 30% by weight, more preferably between 5 and 20% by weight.

5. Use of an electrolyte as defined in any one of claims 1 to 4 in a solid or semi-solid Na-ion battery.

6. A method of preparing an electrolyte for a Na-ion battery, comprising mixing hyaluronic acid with at least one ionic conductive compound comprising sodium, said ionic conductive compound comprising: one or more sodium salts selected from NaBF4, NaC104, NaPF6, NaTFSI, NaFSI, NaODFB or a mixture thereof, or a solid ionic conductor, preferably an inorganic conductor such as a glass-ceramic conductor.

7. A method according to claim 6, comprising a step of dissolving the sodium salt(s) in water.

8. A solid or semi-solid Na-ion battery cell, comprising a positive electrode (2), a negative electrode (3), an anode current collector (5), a cathode current collector (4), a separator and an electrolyte (6) as defined in any one of claims 1 to 4.

9.

10.

11.

12.

13. Cell according to claim 8, in which the electrolyte (6) and the separator form a single structure. Cell according to claim 8 or 9, wherein the positive electrode (2) and / or the negative electrode (3) comprises hyaluronic acid. Solid or semi-solid Na-ion battery comprising at least one cell (1) as defined in any one of claims 8 to 10. A method of recovering hyaluronic acid from a Na-ion battery according to claim 11, comprising a step of dissolving in water the hyaluronic acid from the Na-ion battery, including the hyaluronic acid from the electrolyte (6). A method according to claim 12, comprising a step of recycling the remainder of the Na-ion battery separated from the hyaluronic acid, such as active materials of the positive and negative electrodes.

Images