Method for making an all-solid-state lithium-metal or sodium-metal battery from a liquid electrolyte metal-ion electrochemical accumulator, for the purpose of thermal abuse testing.

Abstract

A method for producing an all-solid-state lithium-metal or sodium-metal battery from a liquid-electrolyte metal-ion electrochemical cell for thermal abuse testing. The invention relates to a method for producing an all-solid-state lithium-metal or sodium-metal battery directly from a fully manufactured liquid-electrolyte metal-ion cell that has a predetermined electrical charge level, preferably 100%. Figure for the abstract: Fig. 8

Description

Title of the invention: Method for producing an all-solid lithium-metal or sodium-metal battery from a metal-ion electrochemical accumulator with liquid electrolyte, for the purpose of thermal abuse tests. Technical field

[0001] The present invention relates to the field of electrochemical accumulators, and more particularly that of lithium-metal or sodium-metal accumulators with solid electrolyte, also referred to hereinafter as all-solid-state batteries.

[0002] More particularly, the invention relates to the production of an all-solid lithium-metal or sodium-metal battery, for the purposes of thermal abuse tests. Prior art

[0003] An electrochemical accumulator must operate within a defined temperature range, generally less than 70°C at the outer surface of its rigid packaging in the form of a case, otherwise its performance will be degraded, or even physically degraded to the point of destruction.

[0004] Examples include lithium iron-phosphate accumulators which have an operating range generally between -20°C and +60°C. Above 60°C, the materials can undergo significant degradation, reducing the performance of the cell. Above a so-called thermal runaway temperature which can be between 70°C and 110°C, exothermic internal chemical reactions begin.

[0005] When the accumulator is no longer able to evacuate enough heat, the temperature of the cell increases until it is destroyed, this phenomenon usually being referred to as thermal runaway.

[0006] In other words, thermal runaway occurs in a cell (accumulator) when the energy released by the exothermic reactions occurring inside it exceeds the capacity to dissipate it to the outside. This runaway may be followed by the generation of gas and explosion and / or fire.

[0007] Also, maintaining a temperature below 70°C makes it possible to increase the lifespan of an accumulator, because the higher the operating temperature of an accumulator, the more its lifespan will be reduced.

[0008] Furthermore, some battery chemistries require an operating temperature well above room temperature and therefore it is necessary necessary to regulate their temperature level by initial preheating of the accumulators, or even by permanently maintaining the temperature of the accumulators.

[0009] Furthermore, battery manufacturers have two major objectives: to constantly increase the energy density of their batteries in order to improve their performance and to improve the safety of their batteries.

[0010] Thus, the use of materials with high energy capacity but with highly exothermic behavior in the event of thermal runaway of an accumulator is becoming increasingly common: [1]. With regard to the phenomenon of thermal runaway, reference should be made to publication [1] and the protocol described in this publication. The so-called “self-heating” and “thermal runaway” temperatures are respectively denoted T1 and T2 in this publication.

[0011] The temperature Tl, typically 70°C, in figure 2 of the publication, is the temperature from which the accumulator heats up without an external source at a typical rate of 0.02°C / min in adiabatic conditions.

[0012] The temperature T2, typically 150°C, in Figure 2 of the publication, is the temperature from which the accumulator heats up at a typical heating rate of 10°C / min under adiabatic conditions, which leads to the melting of the separator in the electrochemical beam of the accumulator, to a short circuit and therefore to the collapse of the voltage.

[0013] By "thermal runaway", we can thus understand here and within the framework of the invention, a ratio between the value of the derivative of the heating temperature and that of the time at least equal to 0.02°C per min.

[0014] According to the literature, such as publication [2], the use of all-solid batteries would make it possible to increase the energy density while eliminating the elements which would be the cause of thermal runaways, namely the organic solvents of the liquid electrolyte and the polymers of the separator, likely to ignite or leak and therefore improve their safety [3].

[0015] Thus, if the energy density of a current lithium-ion battery is around 200 Wh / kg: [4], all-solid lithium-metal batteries would make it possible to achieve an energy density greater than 500 Wh / kg: [5]. Sodium-metal batteries could achieve an energy density equivalent to those of lithium: [6].

[0016] All-solid lithium-metal and sodium-metal technologies would therefore make it possible to at least double the energy density of batteries.

[0017] That being said, all-solid-state lithium-metal batteries are not commercialized because each solid electrolyte has at least one major development problem to solve:[5].

[0018] To date, several test solutions have been carried out at the material scale to evaluate the stability of lithium metal with solid electrolytes: [7].

[0019] Furthermore, thermal runaway models have been performed on all-solid-state lithium-metal batteries: [8].

[0020] On the other hand, since the technology of all-solid lithium-metal or sodium-metal batteries is not mature, no abusive test has been carried out on the scale of an all-solid battery to verify the aforementioned hypothesis from the literature on the improvement that an all-solid battery would bring to safety from a thermal point of view.

[0021] There is a need for a solution that allows abusive tests to be carried out on the scale of an all-solid lithium-metal or sodium-metal battery in order to validate it.

[0022] The general aim of the invention is then to respond at least in part to this need. Statement of the invention

[0023] To do this, the invention firstly relates to a method for producing an all-solid lithium-metal or sodium-metal battery comprising the following steps:

[0024] a / production of a lithium-metal or sodium-metal electrochemical accumulator comprising an electrochemical bundle comprising at least one electrochemical cell consisting of a cathode and an anode on either side of a separator impregnated with a liquid electrolyte, the cathode comprising a substrate, formed of a metal strip which supports in its central portion an active material for inserting lithium or sodium ions, the anode being constituted of a substrate, formed of a lithium or sodium metal strip and a packaging arranged to contain the electrochemical bundle with sealing;

[0025] b / electrical charge of the accumulator so that it reaches a predetermined electrical charge state;

[0026] c / piercing the packaging;

[0027] d / removal of the liquid electrolyte;

[0028] e / opening of the packaging;

[0029] f / separation of the anode, the cathode and the separator from each other;

[0030] g / deposition by coating of at least one layer of ink forming an all-electrolyte solid, on the electrode among the anode or the cathode, which is electrically charged to the predetermined state;

[0031] h / production of an electrochemical bundle comprising at least one electrochemical cell consisting of the cathode separated according to step f / and coated with the all-solid electrolyte layer deposited according to step g / and either the anode (3) separated according to step f / or a new anode consisting of a substrate, formed from a lithium or sodium metal foil.

[0032] According to an advantageous embodiment, the method comprises a step i / placing a package arranged to contain the electrochemical bundle (F') with sealing. This step i / makes it possible to represent an accumulator in real conditions of use.

[0033] The predetermined state of charge according to step b / is advantageously between 30 and 100%, preferably between 85 and 100%, more preferably 100%.

[0034] According to an advantageous configuration, the electrochemical bundles each consist of a single electrochemical cell wound on itself by winding.

[0035] Preferably, step d / is carried out by evaporation under vacuum.

[0036] More preferably, the vacuum evaporation is carried out at at least 70°C for a duration of at least 24 hours, preferably 48 hours.

[0037] According to an advantageous embodiment variant, the coating step g / is carried out by means of a coating scraper fixed above the electrode to be coated pulled at a substantially constant speed.

[0038] Advantageously, the coating step g / is carried out so that the thickness of the all-solid electrolyte layer on the electrode is between 10 and 20 μm.

[0039] According to another advantageous embodiment, the method comprises, between step f / and step g / , a step fl / of cleaning the cathode, and optionally the anode, with dimethyl carbonate (DMC).

[0040] In the configuration where the packages are boxes, steps a / and i / comprise the crimping of a box cover.

[0041] Advantageously, the material of the ink forming the all-solid electrolyte, deposited according to step g / , is chosen from polymers, oxides and sulfides or a mixture thereof.

[0042] Advantageously, the ink material is chosen from poly(oxyethylene) (POE), a ceramic of the Li7La3Zr20i2 (LLZO) type.

[0043] The invention also relates to a method for thermal abuse testing of an all-solid battery produced according to the method described above.

[0044] Thus, the invention essentially consists of producing an all-solid lithium-metal or sodium-metal battery directly from a fully produced lithium-ion or sodium-metal accumulator with liquid electrolyte and which has a predetermined electrical state of charge, preferably equal to 100%.

[0045] After having completely removed the liquid electrolyte, opened the accumulator and separated from each other the electrodes and the separator constituting the electrochemical cell of the accumulator, a layer of ink whose material is that of an all-solid electrolyte is deposited by coating directly onto the cathode electrically charged in the predetermined state.

[0046] After having reconstituted an “all-solid” electrochemical beam from the coated cathode and the separate anode or a new anode made of a substrate formed from a lithium or sodium metal foil, the setting in place of its packaging and we finally obtain an all-solid accumulator whose electrochemistry is active although not very efficient due to a very high internal resistance.

[0047] The primary advantage of an all-solid lithium-metal or sodium-metal battery obtained using the method according to the invention is that following an abusive thermal test, for example according to standard [3] with a temperature ramp of 5 to 20 °C / min, said battery behaves in thermal runaway like a real all-solid battery.

[0048] An all-solid lithium-metal or sodium-metal battery obtained according to the invention may be of cylindrical or prismatic geometry or stacked.

[0049] Other advantages and characteristics will become more apparent upon reading the detailed description, given for illustrative and non-limiting purposes, with reference to the following figures. Brief description of the drawings

[0050] [Fig-1] [Fig.l] is a perspective photographic view of an electro beam chemical structure of a lithium-metal or sodium-metal accumulator with liquid electrolyte, the bundle consisting of a single electrochemical cell wound on itself by winding.

[0051] [Fig.2A][Fig.2B] Figures 2A and 2B are side and top views respectively of a positive electrode of the electrochemical beam according to [Fig.l].

[0052] [Fig.3A][Fig.3B] Figures 3A and 3B are side and top views respectively of a negative electrode of the electrochemical beam according to [Fig.l].

[0053] [Fig.4][Fig.4A][Fig.4B][Fig.4C][Fig.4D] Figures 4 and 4A to 4D are views in perspective and top view of each of the two current collectors welded to one of the lateral ends of an electrochemical bundle according to the state of the art.

[0054] [Fig.5] [Fig.5] is an axial sectional view of a part of a state-of-the-art lithium-metal or sodium-metal accumulator with liquid electrolyte.

[0055] [Fig.6] [Fig.6] is a photographic reproduction of an electrically charged electrode to a predetermined state of charge from a lithium-metal or sodium-metal accumulator such as that of [Fig.5] from which the liquid electrolyte has previously been removed.

[0056] [Fig.7] [Fig.7] is a photographic reproduction of the electrode according to [Fig.6] coated with a layer of ink of an all-solid electrolyte.

[0057] [Fig.8] [Fig.8] is a photographic perspective view of an electrochemical bundle of an all-solid lithium-metal or sodium-metal battery according to the invention, the bundle consisting of a single electrochemical cell wound on itself by winding. Detailed description

[0058] For the sake of clarity, the same references designating the same elements of a lithium-metal or sodium-metal accumulator with liquid electrolyte according to the state of the art and an all-solid battery according to the invention are used for all figures 1 to 8.

[0059] It should be noted that the various elements according to the invention are shown solely for the sake of clarity and that they are not to scale.

[0060] It is also specified that the terms “length” and “lateral” relating to an electrode are to be considered when it is flat before being wound.

[0061] The terms “height” and “lateral” relating to the electrochemical beam are to be considered in a vertical configuration with its lateral ends respectively on the top and on the bottom.

[0062] In order to be able to validate the generally accepted hypothesis that all-solid battery technology improves safety, and in particular high energy density all-solid lithium-metal and sodium-metal technologies, the inventors thought of producing an all-solid battery from a lithium-metal or sodium-metal accumulator with liquid electrolyte such as directly used for thermal abuse tests.

[0063] Data for characterizing the safety of batteries / accumulators following thermal runaway include, for example, the energy released during runaway, the quantity, flow rate and type of gas.

[0064] The method for producing an all-solid lithium-metal and sodium-metal battery according to the invention is described.

[0065] Step a / : A lithium-metal or sodium-metal accumulator with liquid electrolyte is produced as according to the state of the art, with reference to figures 1 to 5.

[0066] [Fig.l] shows a photograph of an electrochemical bundle F of elongated shape along a longitudinal axis XI and comprising a single electrochemical cell C as it is usually wound by winding before the steps of housing in a case, electrical connection to the output terminals of the accumulator and its impregnation with an electrolyte. The cell C consists of an anode 3 and a cathode 2 on either side of a separator (not visible) adapted to be impregnated with the electrolyte. As can be seen, one 10 of its lateral ends of the bundle F is delimited by the strip 30 of the anode 3, while the other 11 of its lateral ends is delimited by the strip 20 of the uncoated cathode 2.

[0067] By "uncoated strip" or "edge" is meant here and within the scope of the invention, a lateral portion of a metal sheet, also called a strip, forming a current collector, which is not covered with a metal ion insertion material, such as lithium in the case of a lithium-metal accumulator or sodium for a sodium-metal accumulator.

[0068] In more detail, respectively, are shown in Figures 2A and 2B and in Figures 3A and 3B, a positive electrode or cathode 2 and a negative electrode or anode 3 from which a current electrochemical beam is produced by winding with a separator interposed between cathode 2 and anode 3.

[0069] The cathode 2 is made up of a substrate 2S formed from a metal strip which supports in its central portion 22, an active lithium or sodium insertion material 21, while its lateral strip (edge) 20 is devoid of active insertion material.

[0070] The anode 3 is constituted solely by a substrate 3S formed from a metallic lithium or sodium foil comprising a lateral strip 30.

[0071] From an electrochemical beam such as illustrated in [Fig.l], the electrode strips are generally compacted axially at their edges 20, 30.

[0072] Once the packing has been carried out, one of the lateral ends 11 of the bundle F is welded, preferably with a conventional current collector 12 in the form of a solid metal disc, itself intended to be subsequently welded with the bottom of the accumulator casing 6 (figures 4, 4A, 4B).

[0073] The same procedure is carried out between the other of the lateral ends 10 of the bundle, and a part of the usual current collector 13 in the form of a solid metal disc, pierced in its center and a tab 130 projecting laterally from the disc 13 (figures 4, 4C, 4D).

[0074] To finalize the definitive production of the accumulator, the procedure is usually as follows.

[0075] The bundle with the collector 13 is introduced into a rigid aluminum container forming only the lateral envelope of the housing 6. During this step, so that the tab 130 does not hinder the introduction, it is folded upwards.

[0076] The collector 12 is welded to the bottom of the housing 6.

[0077] The collector 13 is welded to a negative pole 50 forming a crossing of a cover 9 of box 6.

[0078] The cover 9 is then welded to the rigid metal container.

[0079] Then a step of filling the housing 6 is carried out using a liquid electrolyte, through a through opening (not shown) which is made in the cover 9.

[0080] The production of the accumulator ends with the plugging of the filling opening.

[0081] An example of a lithium-metal or sodium-metal accumulator with liquid electrolyte is shown in [Fig. 5]: one of the output terminals 50, generally the negative terminal, passes through the housing 6 in an electrically insulated manner and is electrically connected to an electrode of the same polarity of the electrochemical bundle F by means of the current collector 13, the flat tab 130 of which is folded back on itself. The other ... output 40, generally the positive terminal, is welded to the cover 9 of the housing 6 itself electrically connected to the electrode of the electrochemical bundle F of polarity opposite to that of terminal 50.

[0082] It is also possible not to permanently close the accumulator case 6 once the filling with the liquid electrolyte has been carried out. For example, an airtight adhesive tape can be positioned on the liquid electrolyte filling hole, in order to make the accumulator watertight. The fact of not permanently closing the case 6 at this zero charge state of the accumulator has the advantage that no thermal runaway can be triggered.

[0083] Step b / : The accumulator is electrically charged so that it reaches a predetermined electrical state of charge, advantageously 100%. No thermal runaway is possible at this state of charge. The negative electrode 3 is thus at the predetermined state of charge and the positive electrode 2 is completely discharged. Another state of charge lower than 100% can be chosen.

[0084] Step c / : The housing 6 is drilled. For example, the adhesive tape is removed from the filling hole.

[0085] Step d / : All the liquid electrolyte is then removed from the accumulator without opening it and in complete safety due to the prior electrical charge. To do this, the accumulator is placed in an airlock under vacuum and heated to 70°C for 48 hours. The liquid electrolyte is therefore removed by evaporation under vacuum without damaging the other components of the accumulator.

[0086] Step e / : The box 6 is then opened.

[0087] Step f / : The cathode 2 charged to the predetermined charge state is then separated from preferably equal to 100%, anode 3 and separator 1 from each other.

[0088] Step fl / (optional): The cathode 2 is cleaned at the predetermined charge state, preferably equal to 100%, in a bath of dimethyl carbonate (DMC), typically for a period of 3 minutes. Optionally, the anode 3 can also be cleaned in an identical manner.

[0089] Step g / : A layer of ink 14 forming an all-solid electrolyte is deposited by coating on the insertion material 21 of the cathode 2 electrically charged to the predetermined state of charge, preferably equal to 100%. Figures 6 and 7 show the cathode 2 respectively before and after such deposition.

[0090] Known methods of making all-solid electrolyte ink and coating are as follows: - the materials of the positive electrode and the solid electrolyte are mixed together in the form of ink and then this ink is coated on a current collector support [9], - solid electrolytes can be agglomerated in pellet form. The positive electrode may or may not contain solid electrolyte, such as LLZO:

[10] , - the solid electrolyte can be deposited according to a so-called solid reaction on a support where the positive electrode has been deposited before:

[11] .

[0091] The inventors have wisely thought from the first method cited [9].

[0092] And they started from an all-solid electrolyte ink but which does not contain any active ion insertion material. The viscosity of the ink is adapted according to the material 21 on which the ink is deposited.

[0093] The coating thickness can be set to 50 pm above that of the cathode 2, in order to obtain a final thickness of the layer 14 of 10 to 20 pm.

[0094] Advantageously, the coating is carried out with a fixed doctor blade while the cathode 2 is pulled at a constant speed, typically of the order of a few mm / s.

[0095] Step h / : An electrochemical beam (F') is then produced by winding, comprising from the cathode 2 coated with the all-solid electrolyte layer deposited according to step g / and either the anode 3 previously separated according to step f / , or a new metallic foil of lithium or sodium ([Fig.8]).

[0096] Step i / : The electrochemical bundle (F') is placed in the housing 6 and the procedure is as usual with a lithium-metal or sodium-metal accumulator as described previously but, of course, without any filling with liquid electrolyte.

[0097] The all-solid lithium-metal or sodium-metal battery thus obtained has active electrochemistry although it is not very efficient due to very high internal resistance.

[0098] It is noted that when this all-solid battery is subjected to a standardized thermal abuse test with a ramp of 5 to 20°C / min, it behaves in thermal runaway like a real all-solid battery, that is to say produced with the industrial processes currently planned.

[0099] Thus by reassembling all-solid-state batteries from liquid electrolyte Li-ion accumulators, according to steps a / to i / previously described, it is possible to evaluate the safety of any all-solid-state technology before its development is mature.

[0100] With the invention, it is therefore possible to envisage, when developing a new all-solid lithium-metal or sodium-metal battery technology, optimizing its safety alongside its performance.

[0101] This method can be applied to virtually all all-solid-state battery technologies. It is sufficient to produce an ink with the all-solid electrolyte and to coat a layer 14 of it on the cathode 2. The ink material can advantageously be POE, or a ceramic such as LLZO, or a sulfide.

[0102] Other advantages and improvements may be made without departing from the scope of the invention. List of cited references:

[0103] [1]: Xuning Feng, et al. “Thermal runaway mechanism of lithium-ion battery for electric vehicles: A review”, Energy Storage Materials, Volume 10, January 2018, Pages 246-267.

[0104] [2]: Wensheng Huang et al. « Questions and Answers Relating to Lithium-Ion Battery Safety Issues”, Cell Reports Physical Science, Volume 2, Issue 1, 20 January 2021, 100285.

[0105] [3]: Xiaolu Tian et al., “Design Strategies ofSafe Electrolytes for Preventing Thermal Runaway in Lithium-Ion Batteries” Chem. Mater. 2020, 32, 23, 9821-9848. November 20, 2020.

[0106] [4]: “A modeling framework to assess spécifie energy, costs and environmental impacts ofLi-ion and Na-ion batteries”, Sustainable Energy & Fuels, Issue 11, 2019.

[0107] [5] : ” Challenges for and Pathways toward Li-Metal-Based All-Solid-State Batteries”, ACS Energy Lett. 2021, 6, 1399-1404.

[0108] [6]: “On rechargeability and reaction kinetics of sodium-air batteries” Energy & En vironmental Science, Issue 11, 2014.

[0109] [7]: Rusong Chen et al., ”The Thermal Stability of Lithium Solid Electrolytes with Metallic Lithium”, Joule, Volume 4, ISSUE 4, P812-821, April 15, 2020.

[0110] [8]: Nathan Johnson et al., ”Modeling Thermal Behavior and Safety of Large Format All-Solid-State Lithium Métal Batteries under Thermal Ramp and Short Circuit Conditions” The Electrochemical Society, Volume 169, Number 6, June 29, 2022.

[0111] [9]: Zhijie Bia et al. « Interface engineering on cathode side for solid garnet batteries», Chemical Engineering Journal, Volume 387, 1 May 2020, 124089.

[0112]

[10] : Martin Finsterbusch et al., “High-Capacity Garnet-Based All-Solid-State Lithium Batteries: Fabrication and 3D-Microstructure Resolved Modeling” ACS Appl. Mater. Interfaces 2018, 10, 26, 22329-22339.

[0113] [H]: Jordi Sastre et al. “Aluminum-Assisted Densification of Cosputtered Lithium Garnet Electrolyte Films for Solid-State Batteries”, ACS Appl. Energy Mater. 2019, 2, 12, 8511-8524.

Claims

Claims

1. Method for producing an all-solid lithium-metal or sodium-metal battery comprising the following steps: a / producing a lithium-metal or sodium-metal electrochemical accumulator comprising an electrochemical bundle (F) comprising at least one electrochemical cell (C) consisting of a cathode (2) and an anode (3) on either side of a separator (4) impregnated with a liquid electrolyte, the cathode comprising a substrate, formed of a metal strip which supports in its central portion an active material for inserting lithium or sodium ions, the anode being constituted by a substrate, formed of a lithium or sodium metal strip and a packaging (6) arranged to contain the electrochemical bundle (F) with sealing, b / electrical charging of the accumulator so that it reaches a predetermined electrical charge state; c / piercing of the packaging; d / removing the liquid electrolyte; e / opening the packaging;f / separation of the anode, cathode and separator from each other; g / deposition by coating of at least one layer of ink (14) forming an all-solid electrolyte, on the cathode, which is electrically charged to the predetermined state; h / production of an electrochemical bundle (F') comprising at least one electrochemical cell (C) consisting of the cathode (2) separated according to step f / and coated with the all-solid electrolyte layer deposited according to step g / and either of the anode (3) separated according to step f / or of a new anode consisting of a substrate, formed of a lithium or sodium metal foil.;

2. Method according to claim 1, comprising a step i / of placing a package arranged to contain the electrochemical bundle (F') with sealing.

3. Method according to claim 1 or 2, the electrochemical bundles (F, F') each consisting of a single electrochemical cell (C) wound on itself by winding.

4. Method according to one of claims 1 to 3, step d / being carried out by evaporation under vacuum.

5. A method according to claim 4, the vacuum evaporation being carried out at at least 70°C for a period of at least 24 hours, preferably 48 hours.

6. Method according to one of the preceding claims, the coating step g / being carried out by means of a coating scraper fixed above the electrode to be coated pulled at a substantially constant speed.

7. Method according to claim 6, the coating step g / being carried out to obtain a thickness of the all-solid electrolyte layer on the electrode of between 10 and 20 μm.

8. Method according to one of the preceding claims, comprising, between step f / and step g / , a step fl / of cleaning the cathode, and optionally the anode, with dimethyl carbonate (DMC).

9. Method according to one of claims 2 to 8, the packages being boxes, steps a / and i / comprising the crimping of a box cover.

10. Method according to one of the preceding claims, the material of the ink forming the all-solid electrolyte, deposited according to step g / , being chosen from polymers, oxides and sulfides or a mixture thereof.

11. Method according to claim 10, the ink material being chosen from poly(oxyethylene) (POE), a ceramic of the Li7La3Zr20i2 (LLZO) type.

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