Use of 2,3,3,3 - tetrafluoropropene for heating a lithium battery

Abstract

The present invention relates to the use of a refrigerant comprising 2,3,3,3-tetrafluoropropene for heating a battery of an electric vehicle comprising at least one electrochemical cell comprising an anode, a cathode and an electrolyte, wherein the electrolyte comprises a lithium salt and the anode comprises metallic lithium as the electrochemically active material.

Description

Technical Field

[0001] The present invention relates to the use of 2,3,3,3-tetrafluoropropene for heating a lithium battery, i.e., a battery containing a lithium salt as an electrolyte.

Background Art

[0002] In vehicles, it is known to use a vapor compression circuit to provide heating or cooling. A refrigerant circulates through this circuit and thus, through evaporation, compression, condensation and expansion follow, completing the cycle.

[0003] 2,3,3,3-Tetrafluoropropene (HFO-1234yf) is a hydrofluoroolefin exhibiting thermodynamic and thermophysical properties that make it highly preferable for use as a refrigerant, particularly in cooling, air conditioning, power production (especially by means of a Rankine cycle) and heat pump applications. In addition, this product is particularly advantageous as it also exhibits a low global warming potential (GWP).

[0004] An electric vehicle includes a battery containing electrochemical cells. Each electrochemical cell includes a negative electrode, a positive electrode, a separator and an electrolyte. Depending on the nature of the materials present in the cell, the operation of the battery may be more or less affected by temperature and, in fact, the battery may even be more or less deteriorated.

[0005] Document FR2937906 describes a method for heating and / or air conditioning the passenger compartment of an electric vehicle using a reversible cooling loop through which a refrigerant containing 2,3,3,3-tetrafluoropropene circulates. This method is also suitable for hybrid vehicles designed to operate alternately on a heat engine and an electric motor.

[0006] Document EP2880739 discloses a system for charging an electric vehicle battery that enables simultaneous control of the temperature of the vehicle's battery and the temperature of the passenger compartment.

[0007] U.S. Patent No. 5,305,613 describes a system for heating and air - conditioning the passenger compartment of an electric vehicle that is operated before starting the vehicle to increase driver comfort.

[0008] U.S. Patent Application Publication No. 2015 / 0191072 describes a cooling cycle that enables the implementation of heating or air - conditioning functions, in particular enabling hot air to be blown onto a battery.

[0009] U.S. Patent Application Publication No. 2011 / 0139397 describes a method for controlling the temperature of the passenger compartment of an electric vehicle by means of a refrigerant circuit, which is in particular connected to a battery.

[0010] There is a need to ensure the optimal functioning of the battery of an electric vehicle and to prevent battery degradation. SUMMARY OF THE INVENTION

[0011] The present invention relates, firstly, to the use of a refrigerant containing 2,3,3,3 - tetrafluoropropene for heating a battery of an electric vehicle comprising at least one electrochemical cell including a negative electrode, a positive electrode and an electrolyte, wherein the electrolyte contains a lithium salt and the negative electrode contains metallic lithium as an electrochemically active material.

[0012] In some embodiments, the lithium salt of the electrolyte is selected from LiPF6, LiFSI, LiTDI, LiPOF2, LiB(C2O4)2, LiF2B(C2O4)2, LiBF4, LiNO3, LiClO4 and mixtures thereof.

[0013] In some embodiments, the battery is maintained at a temperature between a minimum temperature t1 and a maximum temperature t2.

[0014] In some embodiments, the minimum temperature t1 is 10 °C or higher and the maximum temperature t2 is 40 °C or lower, preferably the minimum temperature t1 is 15 °C or higher and the maximum temperature t2 is 30 °C or lower, and more preferably the minimum temperature t1 is 16 °C or higher and the maximum temperature t2 is 28 °C or lower.

[0015] In some embodiments, the refrigerant circulates through a vapor compression circuit.

[0016] In some embodiments, the vapor compression circuit is also suitable for heating the passenger compartment of a vehicle and / or air conditioning the passenger compartment of a vehicle and / or cooling the vehicle's battery.

[0017] In some embodiments, the refrigerant consists essentially of 2,3,3,3 - tetrafluoropropene.

[0018] In some embodiments, the refrigerant comprises about 78.5 wt% 2,3,3,3 - tetrafluoropropene and about 21.5 wt% difluoromethane.

[0019] The present invention also relates to a method for conditioning a battery of an electric vehicle, wherein the battery comprises at least one electrochemical cell comprising a negative electrode, a positive electrode and an electrolyte, the electrolyte comprises a lithium salt, the negative electrode comprises lead or a lithium - containing material as an electrochemically active material, and the method comprises - heating the battery using a refrigerant comprising 2,3,3,3 - tetrafluoropropene and relates to a method.

[0020] In some embodiments, the lithium salt of the electrolyte is selected from LiPF6, LiFSI, LiTDI, LiPOF2, LiB(C2O4)2, LiF2B(C2O4)2, LiBF4, LiNO3, LiClO4 and mixtures thereof.

[0021] In some embodiments, the method comprises - maintaining the vehicle's battery at a temperature between a minimum temperature t1 and a maximum temperature t2 and comprises.

[0022] In some embodiments, the minimum temperature t1 is 10 °C or higher and the maximum temperature t2 is 40 °C or lower, preferably the minimum temperature t1 is 15 °C or higher and the maximum temperature t2 is 30 °C or lower, and more preferably the minimum temperature t1 is 16 °C or higher and the maximum temperature t2 is 28 °C or lower.

[0023] In some embodiments, maintaining the vehicle's battery at a temperature between t1 and t2 is alternately performed by cooling the battery using a refrigerant and heating the battery.

[0024] In some embodiments, heating of the battery is also partially performed by electrical resistance.

[0025] In some embodiments, the refrigerant circulates in a vapor compression circuit.

[0026] In some embodiments, the refrigerant consists essentially of 2,3,3,3 - tetrafluoropropene.

[0027] In some embodiments, the refrigerant contains about 78.5 wt% of 2,3,3,3 - tetrafluoropropene and about 21.5 wt% of difluoromethane.

[0028] The present invention makes it possible to meet the above - mentioned needs. This is because the present invention ensures the optimal functioning of the battery of an electric vehicle, more specifically, the electrochemical cell of the battery, which includes a negative electrode containing an electrolyte based on a lithium salt and a carbon or metal - lithium - containing material as an electrochemically active material, and makes it possible to prevent the degradation of the battery. This material shows the advantage of imparting a higher energy density than conventional negative electrode materials. This is because metallic lithium has a capacity of about 3860 mAh / g.

[0029] In such cells, it has been observed that at relatively low temperatures, metallic lithium tends to deposit on the carbon of the negative electrode, or in the case of materials, tends to form dendrites. This phenomenon is likely to cause a short - circuit, bring irreversible damage to the battery, and even cause a fire or actually an explosion.

[0030] It has been found that the use of 2,3,3,3 - tetrafluoropropene as a refrigerant for heating such a battery is particularly effective in maintaining the function and maintainability of this battery.

Mode for Carrying Out the Invention

[0031] The present invention will be described in more detail and in a non - limiting manner in the following description.

[0032] The battery of an electric vehicle The term "electric vehicle" (optionally "hybrid") refers to an electric device capable of moving or transporting people or substances, and the motor of which is supplied with electrical energy by a motor battery (preferably all, but in some cases only partially in the case of a hybrid electric vehicle). The motor battery is more simply referred to as the "battery" in the context of this patent application.

[0033] The electric vehicle is preferably an electric car. Alternatively, the electric vehicle can be an electric truck or an electric bus.

[0034] The battery includes at least one electrochemical cell, preferably a plurality. Each electrochemical cell includes a negative electrode, a positive electrode, and an electrolyte inserted between the negative electrode and the positive electrode.

[0035] Each electrochemical cell can also include a separator impregnated with an electrolyte.

[0036] In the battery, the electrochemical cells can be assembled in series and / or in parallel.

[0037] The term "negative electrode" is understood to mean an electrode that acts as an anode when the battery carries current (i.e., when the battery is in the process of discharging) and acts as a cathode when the battery is in the process of charging.

[0038] The negative electrode typically includes an electrochemically active material, optionally an electronically conductive material, and optionally a binder.

[0039] The term "positive electrode" is understood to mean an electrode that acts as a cathode when the battery is carrying current (i.e., when the battery is in the process of discharging) and as an anode when the battery is in the process of charging.

[0040] The positive electrode typically includes an electrochemically active material, optionally an electronically conductive material, and optionally a binder.

[0041] The term "electrochemically active material" is understood to mean a material that can reversibly insert ions.

[0042] The term "electronically conductive material" is understood to mean a material that can conduct electrons.

[0043] The negative electrode of an electrochemical cell can specifically include metallic lithium as the electrochemically active material. This metallic lithium can be in an essentially pure form or in the form of an alloy. For example, among the lithium-based alloys that can be used, lithium-aluminum alloy, lithium-silica alloy, lithium-tin alloy, Li-Zn, Li3Bi, Li3Cd, and Li3SB can be mentioned. Mixtures of the above materials can also be used.

[0044] The negative electrode can be in the form of a film or a rod. An example of the negative electrode can include an active lithium film prepared by rolling a strip of lithium between rollers.

[0045] The positive electrode is preferably of the oxide type, preferably manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium / manganese composite oxide (e.g., Li x M n2 O4 or Li xMnO2), lithium / nickel composition oxide (e.g., Li x NiO2), lithium / cobalt composition oxide (e.g., Li x CoO2), lithium / nickel / cobalt composite oxide (e.g., LiNi 1-y Co y O2), lithium / nickel / cobalt / manganese composite oxide (e.g., LiNi x Mn y Co z O2) where x + y + z = 1), lithium-rich lithium / nickel / cobalt / manganese composite oxide (e.g., Li 1+x (Ni x Mn y Co z ) 1-x O2), lithium / transition metal composite oxide, spinel-structured lithium / manganese / nickel composite oxide (e.g., Li x Mn 2-y Ni y O4), vanadium oxide, and mixtures thereof.

[0046] Preferably, the positive electrode contains a lithium / nickel / manganese / cobalt composite oxide [LiNi x Mn y Co z O2 (where x + y + z = 1), abbreviated as NMC, x > y and x > z], or a lithium / nickel / cobalt / aluminum composite oxide [LiNi x’ Co y’ Al z’ (where x'+ y'+ z' = 1), abbreviated as NCA, x' > y' and x' > z'] containing an electrochemical active material.

[0047] Specific examples of these oxides are NMC532 (LiNi 0.5 Mn 0.3 Co 0.2 O2), NMC622 (LiNi 0.6 Mn 0.2 Co 0.2 O2) and NMC811 (LiNi0.8 Mn 0.1 Co 0.1 is O2).

[0048] In addition to the electrochemically active material, the material of each electrode can also include, for example, an electron-conductive material such as carbon black, Ketjen (registered trademark) carbon, Shawinigan carbon, graphite, graphene, carbon nanotubes, carbon fibers (e.g., vapor-grown carbon fibers or VGCF), non-powdery carbon obtained by carbonization of an organic precursor, or a combination of two or more of these. The material of the positive electrode may also contain other additives, such as lithium salts or ceramic or glass-type inorganic particles, or even other compatible active materials (e.g., sulfur).

[0049] The material of each electrode can also include a binder. Non-limiting examples of the binder include linear, branched, and / or cross-linked polyether polymer binders (e.g., polymers based on poly(ethylene oxide) (PEO), or poly(propylene oxide) (PPO) or a mixture of the two (or EO / PO copolymer) and optionally containing cross-linkable units), water-soluble binders (e.g., SBR (styrene / butadiene rubber), NBR (acrylonitrile / butadiene rubber), HNBR (hydrogenated NBR), CHR (epichlorohydrin rubber), ACM (acrylate rubber)), or fluoropolymer-type binders (e.g., PVDF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene)), and combinations thereof. Some binders, such as those soluble in water, can also contain additives such as CMC (carboxymethyl cellulose).

[0050] The separator can be a porous polymer membrane. As non-limiting examples, the separator can be a porous membrane of a polyolefin, such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, an ethylene / methacrylate copolymer, or a multilayer structure of the above polymers.

[0051] The electrolyte can consist of one or more lithium salts dissolved in a solvent or a mixture of a solvent and one or more additives.

[0052] As non-limiting examples, the lithium salt or salts can be selected from LiPF6 (lithium hexafluorophosphate), LiFSI (lithium bis(fluorosulfonyl)imide), LiTDI (lithium 2-trifluoromethyl-4,5-dicyanoimidazolate), LiPOF2, LiB(C2O4)2, LiF2B(C2O4)2, LiBF4, LiNO3 or LiClO4.

[0053] The solvent can be selected from the following non-exhaustive list: ethers, esters, ketones, alcohols, nitriles and carbonates.

[0054] Among the ethers, linear or cyclic ethers such as dimethoxyethane (DME), methyl ethers of oligoethylene glycol with 2 to 5 oxyethylene units, dioxolane, dioxane, dibutyl ether, tetrahydrofuran and mixtures thereof can be mentioned.

[0055] Among the esters, phosphate esters or sulfite esters can be mentioned. For example, methyl formate, methyl acetate, methyl propionate, ethyl acetate, butyl acetate, γ-butyrolactone or mixtures thereof can be mentioned.

[0056] Among the ketones, cyclohexanone is particularly mentioned.

[0057] Among the alcohols, for example, ethyl alcohol or isopropyl alcohol can be mentioned.

[0058] Among nitriles, for example, acetonitrile, pyruvonitrile, propionitrile, methoxypropionitrile, dimethylaminopropionitrile, butyronitrile, isobutyronitrile, valeronitrile, pivalonitrile, isovaleronitrile, glutaronitrile, methoxyglutaronitrile, 2-methylglutaronitrile, 3-methylglutaronitrile, adiponitrile, malononitrile, and mixtures thereof can be mentioned.

[0059] Among carbonates, for example, cyclic carbonates such as ethylene carbonate (EC) (CAS: 96-49-1), propylene carbonate (PC) (CAS: 108-32-7), butylene carbonate (BC) (CAS: 4437-85-8), dimethyl carbonate (DMC) (CAS: 616-38-6), diethyl carbonate (DEC) (CAS: 105-58-8), ethyl methyl carbonate (EMC) (CAS: 623-53-0), diphenyl carbonate (CAS 102-09-0), methyl phenyl carbonate (CAS: 13509-27-8), dipropyl carbonate (DPC) (CAS: 623-96-1), methyl propyl carbonate (MPC) (CAS: 1333-41-1), ethyl propyl carbonate (EPC), vinylene carbonate (VC) (CAS: 872-36-6), fluoroethylene carbonate (FEC) (CAS: 114435-02-8), trifluoropropylene carbonate (CAS: 167951-80-6), or mixtures thereof can be mentioned.

[0060] The additive can be selected from the group consisting of fluoroethylene carbonate (FEC), vinylene carbonate, 4-vinyl-1,3-dioxolan-2-one, pyridazine, vinylpyridazine, quinoline, vinylquinoline, butadiene, sebaconitrile, alkyldisulfide, fluorotoluene, 1,4-dimethoxytetrafluorotoluene, t-butylphenol, di(t-butyl)phenol, tris(pentafluorophenyl)borane, oxime, aliphatic epoxide, halogenated biphenyl, methacrylic acid, allylethyl carbonate, vinyl acetate, divinyl adipate, propane sultone, acrylonitrile, 2-vinylpyridine, maleic anhydride, methyl cinnamate, phosphonate, vinyl-containing silane compound, and 2-cyanofuran.

[0061] Refrigerant In the context of the present invention, "HFO-1234yf" refers to 2,3,3,3-tetrafluoropropene.

[0062] The term "refrigerant" is understood to mean a fluid that can absorb heat by evaporating at a low temperature and low pressure and release heat by condensing at a high temperature and high pressure in a vapor compression circuit according to the application under consideration. Generally, a refrigerant can consist essentially of a single compound or can be a mixture of several compounds.

[0063] The present invention uses a refrigerant containing HFO-1234yf. Other heat transfer compounds may or may not be present in the refrigerant in combination with HFO-1234yf.

[0064] The refrigerant can be combined with a lubricant and / or an additive to form a heat transfer composition.

[0065] The heat transfer composition is present and circulates in the vapor compression circuit.

[0066] In certain embodiments, the refrigerant of the present invention consists essentially of HFO-1234yf and in fact can even consist of HFO-1234yf.

[0067] In other embodiments, the refrigerant comprises HFO-1234yf as a mixture with one or more other heat transfer compounds, such as hydrofluorocarbons and / or hydrofluoroolefins and / or hydrocarbons and / or hydrochlorofluoroolefins and / or CO2.

[0068] Among the hydrofluorocarbons, difluoromethane (HFC-32), pentafluoroethane (HFC-125), 1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1-difluoroethane (HFC-152a), fluoroethane (HFC-161), 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), 1,1,1-trifluoropropane (HFC-263fb) and mixtures thereof are particularly mentioned.

[0069] Among the hydrofluoroolefins, cis and / or trans-forms, preferably the trans-form of 1,3,3,3-tetrafluoropropene (HFO-1234ze), and trifluoroethylene (HFO-1123) are particularly mentioned.

[0070] Among the hydrochlorofluoroolefins, cis and / or trans-forms, preferably the trans-form of 1-chloro-3,3,3-trifluoropropene (HCFO-1233zd) are particularly mentioned.

[0071] In certain embodiments, the refrigerant comprises at least 50 wt% of HFO-1234yf, or at least 60 wt% of HFO-1234yf, or at least 70 wt% of HFO-1234yf, or at least 80 wt% of HFO-1234yf, or at least 90 wt% of HFO-1234yf, or at least 95 wt% of HFO-1234yf.

[0072] In certain embodiments, the refrigerant consists essentially of HFO-1234yf and HFC-32, and in fact may even consist of HFO-1234yf and HFC-32. The content of HFO-1234yf is preferably about 60% to about 95% by weight, more preferably about 70% to about 90% by weight, more preferably about 75% to about 85% by weight, and more preferably about 78.5% by weight; the content of HFC-32 is preferably about 5% to about 40% by weight, more preferably about 10% to about 30% by weight, more preferably about 15% to about 25% by weight, and more preferably about 21.5% by weight.

[0073] To form the heat transfer composition, the additives that can be added to the refrigerant can be specifically selected from nanoparticles, stabilizers, surfactants, tracer agents, fluorescent agents, odorous agents, and solubilizing agents.

[0074] The total amount of the additives does not exceed 5% by weight of the refrigerant, particularly 4% by weight, more particularly 3% by weight, very particularly 2% by weight, and in fact may even not exceed 1% by weight.

[0075] In certain embodiments, HFO-1234yf contains impurities. If impurities are present, they can be shown to be less than 1% by weight, preferably less than 0.5% by weight, preferably less than 0.1% by weight, preferably less than 0.05% by weight, and preferably less than 0.01% by weight with respect to HFO-1234yf.

[0076] One or more lubricants can be present in the heat transfer composition. These lubricants can be selected from polyol esters (POE), polyalkylene glycols (PAG), or polyvinyl ethers (PVE).

[0077] The lubricant can represent 1% to 50% by weight, preferably 2% to 40% by weight, and more preferably 5% to 30% by weight of the heat transfer composition.

[0078] Vapor compression circuit Heating of the battery according to the present invention is preferably (at least partially) carried out by a facility, which includes a vapor compression circuit. The vapor compression circuit contains the above refrigerant, and the refrigerant provides heat conduction.

[0079] In certain embodiments, the vapor compression circuit is also suitable for cooling the vehicle's battery.

[0080] In certain embodiments, the vapor compression circuit is also suitable for heating the vehicle's passenger compartment.

[0081] In certain embodiments, the vapor compression circuit is also suitable for air-conditioning (cooling) the vehicle's passenger compartment.

[0082] For this purpose, the vapor compression circuit can include different branches with separate heat exchangers, and the refrigerant can circulate or not circulate through these branches depending on the operating mode. Optionally, the vapor compression circuit can alternatively or additionally include means for changing the direction of refrigerant circulation, for example, including one or more three-way or four-way valves.

[0083] The main stages of the heat conduction process are executed periodically, - Evaporation of the refrigerant in the evaporator; - Compression of the refrigerant in the compressor; - Condensation of the refrigerant in the condenser; - Expansion of the refrigerant in the expansion module including.

[0084] Evaporation of the refrigerant can start and be carried out from the liquid phase or from a two-phase liquid / vapor mixture.

[0085] The compressor can be hermetic, semi-hermetic or open type. A hermetic compressor includes a motor part and a compression part enclosed in a non-dismantlable hermetic housing. A semi-hermetic compressor includes a motor part and a compression part directly assembled with respect to each other. The coupling between the motor part and the compression part can be accessed when separating the two parts by dismantling. An open type compressor includes a separated motor part and compression part. They can be operated by belt transmission or by a direct coupling.

[0086] In particular, as the compressor, a dynamic compressor or a positive displacement compressor may be used.

[0087] Dynamic compressors include axial flow compressors and centrifugal compressors, which can have one or more stages. Small centrifugal compressors can also be used.

[0088] Positive displacement compressors include rotary compressors and reciprocating compressors.

[0089] Reciprocating compressors include diaphragm compressors and piston compressors.

[0090] Rotary compressors include screw compressors, lobe compressors, scroll (or spiral) compressors, liquid ring compressors and vane compressors. Screw compressors can preferably be twin-screw or single-screw.

[0091] The implementation of the present invention is particularly advantageous when using a scroll compressor due to its good efficiency under typical conditions of an electric vehicle.

[0092] In the equipment used, the compressor can include a device for injecting steam or liquid. The injection is achieved by introducing a refrigerant in a liquid or vapor state into the compressor at an intermediate level between the start and the end of compression.

[0093] In the equipment used, the compressor can be driven by an electric motor, or by a gas turbine (e.g., supplied by the exhaust gas of a vehicle) or by gearing.

[0094] The evaporator and the condenser are heat exchangers. In the present invention, any type of heat exchanger, in particular a parallel-flow heat exchanger, or preferably a counter-flow heat exchanger can be used.

[0095] The term "counter-flow heat exchanger" is understood to mean a heat exchanger in which the first fluid at the inlet of the exchanger exchanges heat with the second fluid at the outlet of the exchanger, and the first fluid at the outlet of the exchanger exchanges heat with the second fluid at the inlet of the exchanger, so that heat is exchanged between the first fluid and the second fluid.

[0096] For example, a counter-flow heat exchanger includes an apparatus in which the flow of the first fluid and the flow of the second fluid are in opposite or substantially opposite directions. Exchangers operating in a counter-current mode with a counter-flow tendency are also included within counter-flow heat exchangers.

[0097] The heat exchanger can in particular be an exchanger having U-shaped tubes, a bundle of horizontal or vertical tubes, a helix, plates or fins.

[0098] The equipment can optionally also include at least one heat-conducting fluid circuit used to transport heat (with or without a change of state) between the circuit of the heat-conducting composition and the battery. Preferably, the equipment does not include a heat-conducting fluid circuit used to transport heat between the heat-conducting composition circuit and the battery. It is also possible to provide a heat exchanger of the circuit containing the heat-conducting composition to ensure heat exchange between the refrigerant and the air, and subsequently the air is blown onto the battery to ensure heat exchange with the battery itself. However, preferably, the heat exchanger of the circuit containing the heat-conducting composition is in contact with or incorporated into the battery.

[0099] The equipment can also optionally include two (or more) vapor compression circuits containing the same or different heat transfer compositions. For example, the plurality of vapor compression circuits can be connected to each other. However, preferably, the equipment includes a single vapor compression circuit.

[0100] According to the present invention, the refrigerant can be superheated between evaporation and compression, that is, between evaporation and compression, the refrigerant can be brought to a temperature higher than the end temperature of evaporation.

[0101] The term "evaporation start temperature" is understood to mean the temperature of the refrigerant at the inlet of the evaporator.

[0102] The term "evaporation end temperature" is understood to mean the temperature of the refrigerant (saturated vapor temperature or dew point) during evaporation when the last drop of the refrigerant in liquid form evaporates.

[0103] When the refrigerant is HFO-1234yf alone or an azeotropic mixture containing HFO-1234yf, under a constant pressure, the evaporation start temperature is equal to the evaporation end temperature.

[0104] The term "superheat" (equivalent to "superheat in the evaporator" in this specification) means the temperature difference between the highest temperature reached by the refrigerant before compression (that is, the highest temperature reached by the refrigerant at the end of the superheat stage) and the evaporation end temperature. This highest temperature is generally the temperature of the refrigerant at the inlet of the compressor. It can correspond to the temperature of the refrigerant at the outlet of the evaporator. Instead, the refrigerant can be at least partially superheated between the evaporator and the compressor (for example, by an internal exchanger). Superheat can be adjusted by appropriate management of the parameters of the equipment, particularly by management of the expansion module.

[0105] In the method of the present invention, the superheat can be 1 to 25 °C, preferably 2 to 10 °C, preferably 3 to 7 °C, more preferably 4 to 6 °C.

[0106] According to the present invention, the refrigerant can be subcooled between condensation and expansion, that is, between condensation and expansion, the refrigerant can be brought to a temperature lower than the end temperature of condensation.

[0107] The term "condensation start temperature" is understood to mean the temperature of the refrigerant during the appearance of the first drop of the refrigerant in the condenser, and is called the vapor saturation temperature or the dew point.

[0108] The term "condensation end temperature" is understood to mean the temperature of the refrigerant during the condensation of the last bubble of the refrigerant in the gaseous form, and is called the liquid saturation temperature or the bubble point.

[0109] The term "subcooling" (equivalent to "subcooling in the condenser" in this specification) means the possible (in absolute value) temperature difference between the lowest temperature reached by the refrigerant before expansion (that is, the lowest temperature reached by the refrigerant at the end of the subcooling stage) and the condensation end temperature. This lowest temperature is generally the temperature of the refrigerant at the inlet of the expansion module. It may correspond to the temperature of the refrigerant at the outlet of the condenser. Instead, the refrigerant can be at least partially subcooled (for example, by an internal heat exchanger) between the condenser and the expansion module.

[0110] In the method of the present invention, when subcooling exists, the subcooling can be 1 to 50 °C, preferably 1 to 40 °C, preferably 1 to 30 °C, preferably 1 to 20 °C, 1 to 15 °C, preferably 1 to 10 °C, more preferably 1 to 5 °C.

[0111] The expansion module can be a thermostat valve called a thermostatic expansion valve or an electronic expansion valve having one or more orifices, or a pressostatic expansion valve that manages pressure. The expansion module can also be a capillary tube in which the expansion of the fluid is obtained by a pressure drop in the tube.

[0112] Use of the refrigerant The present invention relates to the use of a refrigerant containing HFO-1234yf for heating the above battery.

[0113] The term "temperature of the battery" is generally understood to mean the temperature of the outer wall of one or more electrochemical cells of the battery.

[0114] The temperature of the battery can be measured by a temperature sensor. If there are several temperature sensors in the battery, the temperature of the battery can be regarded as the average value of the different measured temperatures.

[0115] The above heating can be carried out when the vehicle's battery is charging. Instead, when the battery is discharging, especially when starting the vehicle's engine, the above heating can be carried out. By doing so, it is possible to prevent the temperature of the battery from being too low due to the outside temperature.

[0116] In one embodiment, the heating can raise the temperature of the battery by at least 5°C, or at least 10°C, or at least 15°C, or at least 20°C, or at least 25°C, or at least 30°C.

[0117] In one embodiment, the outside temperature during battery heating is 5°C or less, preferably 0°C or less, more preferably -10°C or less, more preferably -15°C or less, more preferably -20°C or less.

[0118] The term "outside temperature" is understood to mean the ambient temperature outside the vehicle.

[0119] In one embodiment, the electrical resistance contributes partially to the heating of the battery at a different moment or simultaneously with the heating by the vapor compression circuit.

[0120] In other embodiments, only the vapor compression circuit is responsible for heating the battery.

[0121] In one embodiment, the heating of the battery is continuous over a period of time.

[0122] In one embodiment, the heating of the battery is alternated with an interruption period and even a period during which the battery is actually cooled. When the battery is cooled, the battery can be cooled, in particular, by the above-described vapor compression circuit.

[0123] In one embodiment, by heating and optional cooling, in particular when the vehicle is in operation (engine running), and especially when the vehicle is moving, the temperature of the battery can be maintained within an appropriate temperature range. This is because if the temperature of the battery is too high, the battery performance deteriorates and the battery is prone to degradation.

[0124] In one embodiment, the temperature of the vehicle's battery is thus maintained between a minimum temperature t1 and a maximum temperature t2.

[0125] In one embodiment, the minimum temperature t1 is 10 °C or higher and the maximum temperature t2 is 40 °C or lower, preferably the minimum temperature t1 is 15 °C or higher and the maximum temperature t2 is 30 °C or lower, more preferably the minimum temperature t1 is 16 °C or higher and the maximum temperature t2 is 28 °C or lower.

[0126] For the purpose of reliably maintaining the desired temperature, it is advantageous to have a feedback loop for modifying the operating parameters of the equipment as a function of the measured battery temperature.

Claims

1. Use of a refrigerant containing 2,3,3,3 - tetrafluoropropene for heating a battery of an electric vehicle comprising at least one electrochemical cell including a negative electrode, a positive electrode and an electrolyte, wherein the electrolyte contains a lithium salt, the negative electrode contains metallic lithium as an electrochemically active material, and the battery is maintained at a temperature between a minimum temperature t １ and a maximum temperature t ２ therebetween. for use, wherein the minimum temperature t1 is 10 °C or higher and the maximum temperature t2 is 40 °C or lower; use.

2. The lithium salt of the electrolyte is LiPF ６ , LiFSI, LiTDI, LiPOF ２ , LiB(C ２ O ４ ), ２ , LiF ２ B(C ２ O ４ ), ２ , LiBF ４ , LiNO ３ , LiClO ４ and the use according to claim 1, selected from these mixtures.

3. The minimum temperature t １ is 15°C or higher and the maximum temperature t ２ is 30°C or lower, the use according to claim 1 or 2.

4. The use according to any one of claims 1 to 3, wherein the refrigerant circulates in a vapor compression circuit.

5. The use according to claim 4, wherein the vapor compression circuit is also suitable for heating the passenger compartment of a vehicle and / or air-conditioning the passenger compartment of a vehicle and / or cooling the battery of a vehicle.

6. The use according to any one of claims 1 to 5, wherein the refrigerant consists essentially of 2,3,3,3-tetrafluoropropene.

7. The use according to any one of claims 1 to 5, wherein the refrigerant contains about 78.5% by weight of 2,3,3,3-tetrafluoropropene and about 21.5% by weight of difluoromethane.

8. A method for conditioning a battery of an electric vehicle, wherein the battery includes at least one electrochemical cell including a negative electrode, a positive electrode, and an electrolyte, the electrolyte includes a lithium salt, the negative electrode includes graphite or a lithium-containing material as an electrochemically active material, and the method includes: - heating the battery using a refrigerant containing 2,3,3,3-tetrafluoropropene, and - Maintain the temperature of the vehicle's battery between the minimum temperature t １ and the maximum temperature t ２ ​ including, wherein the minimum temperature t1 is 10 °C or higher and the maximum temperature t2 is 40 °C or lower; method.

9. The lithium salt of the electrolyte is LiPF ６ , LiFSI, LiTDI, LiPOF ２ , LiB(C ２ O ４ ), ２ , LiF ２ B(C ２ O ４ ), ２ , LiBF ４ , LiNO ３ , LiClO ４ and a mixture thereof, the method according to claim 8.

10. The minimum temperature t １ is 15°C or higher and the maximum temperature t ２ is 30°C or lower. The method according to claim 8 or 9.

11. Maintaining the temperature of the vehicle battery between t １ and t ２ is alternately performed by cooling the battery using a refrigerant and by heating the battery, the method according to any one of claims 8 to 10.

12. The method according to claim 11, wherein the heating of the battery is also carried out partially by electrical resistance.

13. The method according to any one of claims 8 to 12, wherein the refrigerant circulates in a vapor compression circuit.

14. The method according to any one of claims 8 to 13, wherein the refrigerant consists essentially of 2,3,3,3-tetrafluoropropene.

15. The method according to any one of claims 8 to 13, wherein the refrigerant contains about 78.5% by weight of 2,3,3,3-tetrafluoropropene and about 21.5% by weight of difluoromethane.