Process for manufacturing a composite powder for electric batteries

Abstract

A process for manufacturing a composite powder for an electric battery, comprising the following steps: a) placing at least one alkali metal, such as lithium, potassium, sodium or a mixture thereof, under an inert atmosphere, b) injecting sulfuryl fluoride (SO2F2) gas and, simultaneously, applying mechanical grinding to said alkali metal, until the formation of a powder comprising particles of said alkali metal having -F and -SO2F groups on the surface, and c) recovering the resulting powder.

Description

Title of the invention: Method for manufacturing a composite powder for an electric 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 method for manufacturing a composite powder for an electric battery, a composite powder for an electric battery, an electrochemical cell for an electric battery comprising such a composite powder, an electric battery comprising such an electrochemical cell, and a motor vehicle comprising such an electrochemical cell. 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 are initiated during the first charging cycles of the low-speed 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] In a lithium battery, this layer is an essential element for the proper functioning of the electric battery. An ideal SEI layer has high ionic conductivity to allow rapid ion exchange in the electrode-electrolyte interface, while being electrically insulating to prevent further electrochemical decomposition of the electrolyte components during the battery's charge and discharge cycles.

[0007] The quality of the SEI layer determines the battery life and its formation is therefore an important step.

[0008] The volume of alkali metal anodes such as lithium is considerably altered during the cycle. Limiting this radical change is the greatest challenge in achieving cycle stability in an alkali metal battery. Due to the A significant volume change destroys the previously formed SEI layer on the anode surface. Consequently, the electrolyte is continuously decomposed on the bare anode surface, accelerating battery aging.

[0009] Moreover, alkali metal anodes such as lithium are the most attractive candidates because of their high energy density.

[0010] Typically, lithium metal is present in significant excess in lithium metal batteries. In other words, the theoretical number of Li cells in the anode is much higher than the number of Li cells that can be accommodated by the cathode material. A huge amount of Li is therefore wasted in manufacturing Li metal batteries, leading to higher prices and reduced energy density.

[0011] It is known to form ultra-thin lithium anodes to minimize the amount of lithium metal wasted. However, the production cost increases exponentially as the thickness of the lithium metal decreases.

[0012] Also, high-potential cathodes are of interest for improving the energy density of electric batteries. However, due to their high operating potential, such cathodes suffer from electrochemical instability and problems with the dissolution of alkali metals. Description of the invention

[0013] The present invention therefore aims to overcome the aforementioned disadvantages and to improve the stability of an electrochemical cell during its charge and discharge cycles with a view to increasing its lifespan and the lifespan of the electric battery incorporating such an electrochemical cell according to a low-cost strategy.

[0014] In the description of the invention which will be given, the expression "at least one" used shall be considered equivalent to the expression "one or more".

[0015] 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.

[0016] The present invention relates to a method for manufacturing a composite powder for an electric battery, comprising the following steps:

[0017] a) place at least one alkali metal under an inert atmosphere, such as an argon atmosphere,

[0018] b) inject a sulfuryl fluoride (SO2F2) gas and, simultaneously, apply mechanical grinding to said alkali metal, until the formation of a powder comprising particles of said alkali metal having -F and -SO2F groups on its surface, and

[0019] c) recover the powder obtained.

[0020] Such a process for manufacturing composite powder is simple and inexpensive, not requiring complex equipment.

[0021] The composite powder obtained is particularly advantageous for manufacturing an artificial SEI layer on the surface of an anodic current collector, and for manufacturing a cathode forming an artificial CEI layer on the surface of a cathodic current collector.

[0022] Thanks to the presence of the -F and -SO2F groups, the stability of an electrochemical cell incorporating such an artificial SEI layer and / or such a cathode can be improved, extending its lifespan.

[0023] From such a composite powder, it is possible to form an electrochemical cell for an electric battery without damaging

[0024] In step a), the alkali metal can be lithium, potassium, sodium or a mixture of these.

[0025] Advantageously, the alkali metal is in the form of particles of average size between 1 mm and 1 cm, for example in the form of beads.

[0026] In step b), mechanical grinding can advantageously be carried out using SO2F2 gas inert balls, such as ceramic balls.

[0027] Preferably, the SO2F2 gas is injected until a constant SO2F2 concentration is obtained.

[0028] The cessation of the evolution of the concentration of the SO2F2 gas indicates a complete reaction between the SO2F2 gas and the alkali metal, and therefore a saturation of the surface of the alkali metal with -F and -SO2F groups.

[0029] Advantageously, at least one additive may be added to the alkali metal, either in step b), or after step c) in order to improve the electrochemical and / or mechanical stability of the composite powder.

[0030] The additive can be chosen from: an electrical conductor such as carbon black, metal particles, metalloid particles, a polymeric binder, organic particles, inorganic particles, and a mixture of these.

[0031] The average size of the alkali metal particles comprising the -F and -SO2F groups on the surface of the composite powder obtained is between 10 nm and 1000 sqm.

[0032] According to one embodiment, lithium metal beads and ceramic beads are introduced into a Teflon container having an inlet and an outlet. The atmosphere inside the container is an argon atmosphere.

[0033] The container is then rotated at low speed to start the mechanical grinding of the lithium metal from the ceramic beads and, simultaneously with the start of the mechanical grinding, SO2F2 gas is injected into the container at through the container inlet. As the SO2F2 gas is introduced, the argon atmosphere is replaced by the SO2F2 gas.

[0034] The SO2F2 gas concentration within the container is measured continuously.

[0035] Under the effect of mechanical grinding, the lithium metal cracks and breaks until it reaches a powder state and, simultaneously with this mechanical grinding, the SO2F2 gas reacts on the surface of the newly formed lithium metal as the lithium metal particles crack.

[0036] The reaction of SO2F2 gas on the surface of lithium metal produces a complex formed by LiF and LiSO2F. LiF and LiSO2F interact with each other in such a way that they cannot be easily separated from each other.

[0037] The SO2F2 gas is introduced continuously, at a constant flow rate, and the reaction continues to occur until all of the lithium metal is consumed.

[0038] When the concentration of SO2F2 gas within the container no longer changes, the reaction is complete and the introduction of SO2F2 gas into the container is then stopped. A composite powder of LiF and LiSO2F is obtained.

[0039] Argon is introduced through the inlet of the container until an argon atmosphere is formed again and replaces the SO2F2 gas. Then, the composite powder is recovered and stored under an argon atmosphere.

[0040] The invention also relates to a composite powder for electric battery, comprising alkali metal particles having -F and -SO2F groups on the surface.

[0041] Advantageously, the composite powder may further comprise at least one additive selected from: an electrical conductor such as carbon black, metal particles, metalloid particles, a polymeric binder, organic particles, inorganic particles, and a mixture thereof.

[0042] The invention also relates to a composite powder for electric battery, consisting of alkali metal particles having -F and -SO2 F groups on the surface, and optionally at least one additive selected from: an electrical conductor such as carbon black, metal particles, metalloid particles, a polymeric binder, organic particles, inorganic particles, and a mixture thereof.

[0043] The alkali metal of the composite powder can be lithium, potassium, sodium or a mixture of these.

[0044] Preferably, the average size of the alkali metal particles having -F and -SO2F groups on the surface of the composite powder is between 10 nm and 1000 sqm.

[0045] Preferably, the surface of the alkali metal particles of the composite powder is saturated with -F and -SO2F groups.

[0046] The invention also relates to an anodic current collector assembly for an electric battery. The anodic current collector assembly comprises an anodic current collector and an Al layer disposed on all or part of the surface of the anodic current collector. The Al layer comprises composite powder as described above.

[0047] Advantageously, such an anodic current collector assembly can be incorporated into an electrochemical cell of an electric battery without anode.

[0048] The Al layer incorporating the composite powder as described above forms an artificial SEI layer on the surface of the anodic current collector.

[0049] The Al layer can, in addition, incorporate at least one additive selected from: an electrical conductor such as carbon black, metal particles, metalloid particles, a polymeric binder, organic particles, inorganic particles, and a mixture of these.

[0050] The anodic current collector is, for example, made of copper.

[0051] The invention also relates to an anodic current collector assembly for an electric battery, consisting of an anodic current collector and an Al layer disposed on all or part of the surface of the anodic current collector, the Al layer consisting of composite powder as described above and, optionally at least one additive chosen from: an electrical conductor such as carbon black, metal particles, metalloid particles, a polymeric binder, organic particles, inorganic particles, and a mixture thereof.

[0052] The anodic current collector assembly for an electric battery can be manufactured by coating all or part of the surface of an anodic current collector, such as a copper current collector, with a powder as previously described, and optionally with at least one additive as previously described.

[0053] The additive can be added during the manufacture of the composite powder or mixed with the composite powder prior to the formation of the Al layer on the anodic current collector.

[0054] The additive allows, for example, to improve the electrochemical and / or mechanical stability of the anodic current collector assembly.

[0055] An Al layer forms on the surface of the anodic current collector. The Al layer can be applied by dry coating or wet coating.

[0056] Such an anodic current collector assembly incorporated in an electrochemical cell for an electric battery makes it possible to form an electrochemical cell without anode and to eliminate the problems associated with the waste of alkali metal, such as lithium metal, for a limited production cost.

[0057] In addition, the Al layer forms an artificial SEI layer on the anodic current collector SEI which allows a uniform transfer of Li+ in the plane of the SEI layer.

[0058] Through a synergistic effect, the -F and -SO2F groups confer significant stability to the alkali metal during cycling.

[0059] In the case of a lithium battery, the presence of LiF and LiSO2F compounds thus stabilizes the entire anodic collector assembly during charge and discharge cycles by inhibiting the formation of irregular structures and dendrites at the interface between the anodic current collector and the electrolyte. This results in a longer battery life.

[0060] On the one hand, LiF gives high mechanical properties to the SEI layer, which greatly contributes to improving the stability of the entire anodic current collector assembly.

[0061] On the other hand, LiSO2F compensates for the low ionic conductivity of LiF by contributing to a uniform transfer of Li+ in the plane of the SEI layer, while also participating in the stability of the entire anodic current collector assembly.

[0062] This results in significant stability of the Li metal during cycling, obtained thanks to the synergistic effect of LiF and LiSO2F.

[0063] The invention also relates to a cathode current collector assembly for an electric battery. The cathode current collector assembly comprises a cathode current collector and a Cl layer disposed on all or part of the surface of the cathode current collector. The Cl layer comprises composite powder as described above.

[0064] According to one feature, the Cl layer may further comprise a cathode active material, preferably the cathode active material being selected from lithium nickel manganese oxide (LiNi0.5Mni 5O4), NMC811 (LiNio.8Mn0.iCoo.iO2), high nickel cathode active materials from LiNiO2 and LiNixFeyAlzO2, and a mixture of these.

[0065] The Cl layer may further include at least one additive to improve the electrochemical and / or mechanical stability of the cathode current collector assembly.

[0066] The additive can be chosen from: an electrical conductor such as carbon black, metal particles, metalloid particles, a polymeric binder, organic particles, inorganic particles, and a mixture of these.

[0067] Advantageously, the Cl layer forms a cathode.

[0068] Advantageously, the cathode is a high-potential operating cathode, in particular a cathode operating at a potential greater than or equal to 3.8V.

[0069] The presence of the groups allows the Cl layer to form, in addition, an artificial cathode-electrolyte interface or artificial IEC layer from the English "Cathode-Electrolyte Interphase".

[0070] The cathode current collector assembly for an electric battery can be manufactured by coating all or part of the surface of a cathode current collector, such as an aluminum current collector, with a mixture of a powder as previously described, an active cathode material, and optionally at least one additive as previously described.

[0071] The additive can be added during the manufacture of the composite powder or mixed with the composite powder prior to the formation of the Cl layer on the cathode current collector.

[0072] The mixture forms a Cl layer on the surface of the cathode current collector. The Cl layer can be applied by dry coating or wet coating.

[0073] Such a cathode current collector assembly incorporated in an electrochemical cell for an electric battery allows a uniform transfer of Li+ in the plane of the IEC layer.

[0074] Through a synergistic effect, the -F and -SO2F groups confer significant stability to the alkali metal during cycling.

[0075] In the case of a lithium battery, the presence of LiF and LiSO2F compounds thus stabilizes the entire cathode collector during charge and discharge cycles by inhibiting the formation of irregular structures and dendrites at the interface between the cathode current collector and the electrolyte. This results in a longer battery life.

[0076] On the one hand, LiF confers high mechanical properties to the cathode and the IEC layer it contains, which greatly contributes to improving the stability of the entire cathode current collector assembly.

[0077] On the other hand, LiSO2F compensates for the low ionic conductivity of LiF by contributing to a uniform transfer of Li+ in the plane of the IEC layer, while also participating in cathode stability. It has been calculated that the oxidation potential of LiSO2F is higher than that of LiF, so the IEC layer is particularly advantageous for improving the electrochemical stability of high-voltage batteries. Furthermore, LiSO2F is involved in suppressing the dissolution of alkali metals.

[0078] This results in significant stability of the Li metal during cycling, obtained thanks to the synergistic effect of LiF and LiSO2F.

[0079] In parallel, the composite powder according to the invention can be used to form the anodic current collector assembly and the cathodic current collector assembly without risking damage to the latter.

[0080] The incorporation of such a composite powder into the anodic current collector assembly and into the cathodic current collector assembly can be carried out without this involving a change in the volume of the anode and the cathode, or an alteration by corrosion of the anodic and cathodic current collectors.

[0081] The invention also relates to an electrochemical cell for an electric battery comprising an anodic current collector assembly as described above and / or a cathodic current collector assembly as described above.

[0082] The invention also relates to an electric battery comprising at least one electrochemical cell as previously described.

[0083] Advantageously, the electric battery is a high voltage electric battery.

[0084] Advantageously, the electric battery is an anode-free electric battery, such as than a high-voltage electric battery.

[0085] The electric battery can be a lithium-ion battery, a lithium-air battery, a lithium-sulfur battery or a battery incorporating an anode of an alkali metal other than lithium, such as potassium or sodium.

[0086] The invention also relates to a motor vehicle comprising at least one electric battery as previously described.

Claims

Demands

1. A method for manufacturing a composite powder for an electric battery, comprising the following steps: a) placing at least one alkali metal, such as lithium, sodium, potassium, or a mixture thereof, under an inert atmosphere, b) injecting sulfuryl fluoride (SO2F2) gas and, simultaneously, applying mechanical grinding to said alkali metal, until the formation of a powder comprising particles of said alkali metal having -F and -SO2F groups on the surface, and c) recovering the resulting powder.

2. A method according to claim 1, wherein in step b), SO2F2 gas is injected until a constant SO2F2 concentration is obtained.

3. A method according to claim 1 or 2, wherein at least one additive is added to said alkali metal in step b) or after step c), the additive being selected from: an electrical conductor such as carbon black, metal particles, metalloid particles, a polymeric binder, organic particles, inorganic particles, and a mixture thereof.

4. Composite powder for electric battery, comprising particles of said alkali metal having -F and -SO2F groups on the surface.

5. Composite powder according to claim 4, wherein the surface of said particles is saturated with -F and -SO2F groups.

6. Composite powder according to claim 4 or 5, further comprising at least one additive selected from: an electrical conductor such as carbon black, metal particles, metalloid particles, a polymeric binder, and a mixture thereof.

7. An anodic current collector assembly for an electric battery, comprising an anodic current collector and an Al layer disposed on all or part of the surface of the anodic current collector and comprising composite powder according to any one of claims 4 to 6.

8. Cathode current collector assembly for an electric battery, comprising a cathode current collector and a Cl layer disposed on all or part of the collector surface cathodic current and comprising composite powder according to any one of claims 4 to 6.

9. Cathode current collector assembly according to claim 8, wherein the Cl layer further comprises a cathode active material, preferably the cathode active material being selected from: lithium nickel manganese oxide (LiNio.5Mn1.5O4), NMC811 (LiNi0.8Mn0.1Co0.1O2), LiNiO2, LiNiFeyAlZO2 and a mixture thereof.

10. Electrochemical cell for electric battery comprising an anodic current collector assembly according to claim 7 and / or a cathodic current collector assembly according to claim 8 or 9.

11. Electric battery comprising at least one electrochemical cell according to claim 10.

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