treated electrode for battery

Abstract

Lithium-metal treated electrode for battery, comprising on the surface of the electrode: - a three-dimensional polymer network, and - at least one crown ether positioned between the surface of the electrode and said three-dimensional polymer network.

Description

Title of the invention: Treated electrode for battery technical field

[0001] The present invention relates, in general, to electric batteries, such as an electric battery for a motor vehicle and, more specifically, to the lifespan of an electric battery.

[0002] More specifically, the invention relates to a treated battery electrode, a battery electrochemical cell comprising such a treated electrode, an electric battery comprising such an electrochemical cell, and a motor vehicle comprising such an electrochemical cell. The invention also relates to a method for treating a battery electrode. Previous techniques

[0003] Classically, an electrochemical cell of an electric battery comprises a positive electrode called "cathode", a negative electrode called "anode", an electrolyte allowing the circulation of ions between the anode and the cathode, and anodic and cathodic current collectors carrying, respectively, the anode and the cathode and connecting them to the external circuit.

[0004] The performance of a battery depends on the ionic and electronic transport properties.

[0005] Reactions can be initiated during the first low-rate charging cycles of the electrochemical cell, and the first ion exchanges between the electrodes take place. Products resulting from these reactions accumulate on the surface of the electrodes to form a layer called the solid-electrolyte interface or SEI layer.

[0006] The quality of the SEI layer determines the battery life and its formation is therefore an important step.

[0007] Moreover, alkali metal anodes such as lithium are the most attractive candidates because of their high energy density.

[0008] However, their surface is prone to dendrite formation, which can lead to various mechanical problems in the electrochemical cell, or even induce a short circuit. Furthermore, the SEI layer is strongly bonded to the anode surface, so the SEI layer can be degraded during the cycle.

[0009] To limit the appearance of dendrites, it is known to add crown ether compounds as additives in the electrolyte.

[0010] Crown ether compounds, in the form of ethylene oxide macrocycles, form thin and flexible SEI layers in electrolytes. It has In particular, it has been reported that they can regulate the formation of lithium dendrites when added to carbonate-based liquid electrolytes.

[0011] Nevertheless, the presence of crown ether compounds affects certain properties of electrolytes, such as their transport properties, viscosity, thermal stability and chemical stability.

[0012] Crown ether, which has a greater affinity for the lithium cation than for simple carbonate molecules, can modify the solvation structure of lithium in electrolytes. This phenomenon is known as the macrocyclic effect. In particular, it has been reported that the Coulomb efficiency (CE) is strongly affected by the concentration of 18-crown-6 ether.

[0013] Thus, there is a need to develop new lithium-metal battery materials to overcome the drawbacks mentioned below. Description of the invention

[0014] The present invention therefore aims to overcome the aforementioned disadvantages and to improve the stability of a lithium-metal battery electrochemical cell during its charge and discharge cycles by limiting the negative side effects related to the presence of crown ether compounds, with a view to increasing its lifespan.

[0015] In the description of the invention which will be made, the expression "at least one" used shall be considered equivalent to the expression "one or more".

[0016] Furthermore, it is specified that the expression "between ... and ..." used in this description of the invention should be understood as including each of the limits mentioned.

[0017] The present invention relates to a lithium-metal treated electrode for a battery, comprising on the surface of the electrode:

[0018] - a three-dimensional polymer network, and

[0019] - at least one coronal ether positioned between the surface of the electrode and said network three-dimensional polymer.

[0020] By three-dimensional polymer network, we mean a structure developing in the three directions of space, forming a single macromolecule obtained by cross-linking the chains of the monomer or monomers from which it is derived.

[0021] Advantageously, the treated electrode can be used as an anode.

[0022] Alternatively, the treated electrode can be used for low operating voltage cathode materials, such as LFP.

[0023] The assembly formed by the three-dimensional polymer network and the crown ether compound forms an artificial SEI layer on the surface of the lithium metal.

[0024] The three-dimensional polymer network makes it possible to maintain a high concentration of crown ether molecules on the surface of the lithium metal.

[0025] These molecules, which nevertheless retain their mobility, can thus effectively control the formation of dendrites.

[0026] When such a treated electrode is incorporated into an electrochemical cell, it is possible to regulate dendrite formation while minimizing the negative effects of the crown ether on the electrolyte.

[0027] Preferably, the three-dimensional polymer network forms pores.

[0028] Preferably, the three-dimensional polymer network comprises pores of size molecular to selectively conduct the lithium cation Li+.

[0029] Advantageously, the pore size of the three-dimensional polymer network is between 0.5 and 2 Å, i.e. between 0.05 and 0.2 nm.

[0030] Advantageously, the crown ether can be selected from: 12-crown-4 ether, 15-crown-5 ether, 16-crown-4 ether, 18-crown-6 ether, 21-crown-7 ether, dibenzo-18-crown-6 ether and a mixture of these.

[0031] In one embodiment, the three-dimensional polymer network can be obtained from a single type of monomer comprising at least two polymerizable groups capable of reacting with each other to form said three-dimensional polymer network by polymerization.

[0032] Alternatively, the three-dimensional polymer network can result from the contact of at least two different monomers, capable of forming with each other said three-dimensional polymer network by polymerization.

[0033] In one embodiment, the three-dimensional polymer network may comprise at least motifs obtained from the following monomers:

[0034] (i) monomer comprising at least one unsaturated group, and

[0035] (ii) monomer comprising at least one thiol group.

[0036] The chemical bonds between the macromolecular chains are thus formed by click chemistry, and more particularly by thiol-ene reaction.

[0037] Such designs have the advantage of being easily created, using a simple and inexpensive process.

[0038] In one embodiment, the monomer comprising at least one thiol group may be selected from: pentaerythritol tetrakis(3-mercaptopropionate) (PTMP), 3,6-dioxa-l,8-octanedithiol (DODT) and mixtures thereof.

[0039] Preferably, the three-dimensional polymer network comprises at least motifs obtained from the following monomers: divinylbenzene, pentaerythritol tetrakis(3-mercaptopropionate) (PTMP) and 3,6-dioxa-l,8-octanedithiol (DODT).

[0040] In one embodiment, the three-dimensional polymer network consists of motifs obtained from the following monomers: divinylbenzene, pentaerythritol tetrakis(3-mercaptopropionate) (PTMP) and 3,6-dioxa-l,8-octanedithiol (DODT).

[0041] In one embodiment, the treated electrode for the battery comprises, on the surface of the electrode:

[0042] - a three-dimensional polymer network comprising motifs obtained from the the following monomers: divinylbenzene, pentaerythritol tetrakis(3-mercaptopropionate) (PTMP) and 3,6-dioxa-l,8-octanedithiol (DODT), and

[0043] - of 12-crown-4 ether positioned between the surface of the electrode and the network three-dimensional polymer.

[0044] In one embodiment, the treated electrode for the battery consists of:

[0045] - a lithium-metal electrode,

[0046] - a three-dimensional polymer network on the surface of said electrode consisting of motifs obtained from the following monomers: divinylbenzene, pentaerythritol tetrakis(3-mercaptopropionate) (PTMP) and 3,6-dioxa-l,8-octanedithiol (DODT), and

[0047] - of 12-crown-4 ether positioned between the surface of the electrode and the network three-dimensional polymer.

[0048] The invention also relates to a method for treating a battery electrode, comprising the following steps:

[0049] a) provide a lithium-metal electrode,

[0050] b) prepare a mixture comprising:

[0051] - at least one crown aether, and

[0052] - at least one compound comprising at least one polymerizable group capable of forming a three-dimensional polymer network after polymerization

[0053] c) deposit said mixture onto the surface of the lithium-metal electrode,

[0054] d) polymerize said compound to form said three-dimensional polymer network, and

[0055] e) recover the treated electrode obtained.

[0056] The treated electrode obtained can be incorporated into an electrochemical cell. The presence of the three-dimensional polymer network and the crown ether allows for the regulation of dendrite formation while minimizing the negative effects of the crown ether on the electrolyte.

[0057] The treated electrode obtained can be incorporated into an electrochemical cell as an anode comprising a SEL layer

[0058] The embodiments described for the treated electrode are applicable to said electrode treatment process.

[0059] Advantageously, in step b), the mixture may further comprise at least one solvent, preferably an aprotic organic solvent. The thickness of the layer formed by the three-dimensional polymer network and the ether compound crowns the surface of the lithium metal can be adjusted according to the amount of solvent incorporated into the mixture.

[0060] For example, in step c), the mixture can be applied to the surface of the lithium-metal electrode by dipping, spraying or chemical vapor deposition.

[0061] Dipping deposition has the advantage of being particularly simple and inexpensive.

[0062] Preferably, the compound(s) comprising at least one polymerizable group is / are capable of forming a three-dimensional polymer network incorporating pores.

[0063] Preferably, the compound(s) comprising at least one polymerizable group is / are capable of forming a three-dimensional polymer network comprising molecular-sized pores to selectively conduct the lithium cation Li+.

[0064] Advantageously, the crown ether may be selected from: 12-crown-4 ether, 15-crown-5 ether, 16-crown-4 ether, 18-crown-6 ether, 21-crown-7 ether, dibenzo-18-crown-6 ether and a mixture thereof

[0065] According to one feature, the three-dimensional polymer network can result from the contact of at least two different monomers, capable of forming with each other said three-dimensional polymer network by polymerization.

[0066] According to one feature, in step b), the mixture may comprise at least two different monomers, capable of forming with each other the three-dimensional polymer network by polymerization.

[0067] In one embodiment, the mixture may comprise at least the following monomers:

[0068] (i) monomer comprising at least one unsaturated group, and

[0069] (ii) monomer comprising at least one thiol group.

[0070] In one embodiment, the monomer comprising at least one thiol group may be selected from: pentaerythritol tetrakis(3-mercaptopropionate) (PTMP), 3,6-dioxa-l,8-octanedithiol (DODT) and mixtures thereof.

[0071] Preferably, in step b), the mixture comprises at least one of the following monomers: divinylbenzene, pentaerythritol tetrakis(3-mercaptopropionate) (PTMP) and 3,6-dioxa-l,8-octanedithiol (DODT).

[0072] In one embodiment, the mixture comprises the following monomers: divinylbenzene, pentaerythritol tetrakis(3-mercaptopropionate) (PTMP) and 3,6-dioxa-1,8-octanedithiol (DODT).

[0073] In one embodiment, the mixture comprises:

[0074] - the following monomers: divinylbenzene, pentaerythritol tetrakis(3- mercaptopropionate) (PTMP) and 3,6-dioxa-l,8-octanedithiol (DODT), and

[0075] - of 12-crown-4 ether.

[0076] In one embodiment, the mixture consists of:

[0077] - the following monomers: divinylbenzene, pentaerythritol tetrakis(3- mercaptopropionate) (PTMP) and 3,6-dioxa-l,8-octanedithiol (DODT), and

[0078] - 12-crown-4 ether.

[0079] The present invention also relates to an electrochemical battery cell comprising an electrode treated as described above.

[0080] The invention also relates to a battery comprising at least one electrochemical cell as previously described.

[0081] Advantageously, the battery can be a lithium-metal battery, a lithium-air battery, or a lithium-sulfur battery.

[0082] The invention also relates to a motor vehicle comprising at least one battery as previously described.

[0083] Example 1: Surface treatment of a lithium-metal electrode

[0084] 12-crown-4 ether, divinylbenzene, pentaerythritol tetrakis(3-mercaptopropionate) (PTMP), 3,6-dioxa-1,8-octanedithiol (DODT), and a photoinitiator are mixed together and stirred to obtain a homogeneous solution.

[0085] The resulting mixture can be diluted using aprotic organic solvents to adjust the desired thickness of the SEI layer on the surface of the plate.

[0086] The ratio between unsaturated groups and thiol groups is 1:1, and the ratio between PTMP and DODT is 25:75.

[0087] A lithium-metal plate is dipped into the mixture obtained so that the mixture covers the surface of the plate.

[0088] During soaking, the significant affinity of 12-crown-4 ether for lithium leads to the formation of a complex on the surface of the lithium metal.

[0089] After application of the solution, the lithium-metal plate is stabilized under a controlled atmosphere.

[0090] The preparation of the monomers and the polymerization were carried out according to a process described in the publication Macromolecules 2015, 48, 2098-2106.

[0091] Polymerization is carried out by irradiating the surface of the lithium-metal plate with UV light. The polymerization occurs via click chemistry according to a thiol-ene reaction. The three-dimensional polymer network formed on the surface of the plate after crosslinking maintains the 12-crown-4 ether compound in contact with the lithium-metal.

[0092] The lithium metal plate thus treated is dried under vacuum at 40°C to remove excess 12-crown-4 ether compound and unreacted monomers.

[0093] The treated electrode obtained can advantageously be used in an electrochemical battery cell as an anode comprising an artificial SEI layer.

Claims

Demands

1. Lithium-metal treated electrode for battery, comprising on the surface of the electrode: - a three-dimensional polymer network, and - at least one crown ether positioned between the surface of the electrode and said three-dimensional polymer network.

2. Electrode treated according to claim 1, wherein the three-dimensional polymer network comprises at least motifs obtained from the following monomers: (i) monomer comprising at least one unsaturated group, and (ii) monomer comprising at least one thiol group.

3. Electrode treated according to claim 2, wherein the monomer comprising at least one thiol group is selected from: pentaerythritol tetrakis(3-mercaptopropionate) (PTMP), 3,6-dioxa-l,8-octanedithiol (DODT) and mixtures thereof.

4. Electrode treated according to any one of the preceding claims, wherein the three-dimensional polymer network comprises at least motifs obtained from the following monomers: divinylbenzene, pentaerythritol tetrakis(3-mercaptopropionate) (PTMP) and 3,6-dioxa-l,8-octanedithiol (DODT).

5. Electrode treated according to any one of the preceding claims, wherein the crown ether is selected from: 12-crown-4 ether, 15-crown-5 ether, 16-crown-4 ether, 18-crown-6 ether, 21-crown-7 ether, dibenzo-18-crown-6 ether and a mixture thereof.

6. A method for treating a battery electrode to obtain a treated electrode as defined in any one of claims 1 to 5, comprising the following steps: a) providing a lithium-metal electrode, b) preparing a mixture comprising: - at least one crown ether, and - at least one compound comprising at least one polymerizable group capable of forming a three-dimensional polymer network after polymerization, c) depositing said mixture onto the surface of the lithium-metal electrode, d) polymerize said compound to form said three-dimensional polymer network, and e) recover the treated electrode obtained.

7. A method according to claim 6, wherein step c) is carried out by dipping, spraying or chemical vapor deposition.

8. A process according to claim 6 or 7, wherein the mixture in step b) further comprises a solvent, preferably an aprotic organic solvent.

9. Electrochemical battery cell comprising an electrode treated according to any one of claims 1 to 5.

10. Battery comprising at least one electrochemical cell according to claim 9.

11. Motor vehicle comprising at least one battery according to claim 10.