Liquid electrolyte medium and its use in solid electrolyte lithium batteries

Abstract

A liquid electrolyte medium includes: a fluorinated ether; a dicarbonate; a lithium salt; wherein: the fluorinated ether and the dicarbonate are non-polar or low-polar solvents; and the lithium salt is non-lithium hexafluorophosphate, and the concentration is matched to not exceed the saturation concentration of the solvents; the liquid electrolyte medium provided by the application is compatible with sulfide solid electrolyte, and can avoid high-voltage decomposition, does not need to change the existing factory positive electrode production line process, can maintain the high conductivity of the positive electrode itself and the interface, and the solid electrolyte will not be attacked by the liquid electrolyte medium.

Description

Technical Field

[0001] This invention relates to a liquid electrolyte, and more particularly to a liquid electrolyte with compatibility with solid sulfide electrolytes.

[0002] The liquid electrolyte provided by this invention will primarily be used in solid-state lithium batteries containing sulfide electrolytes, and this primary application will be described and illustrated in detail below. However, this invention is not limited to this single application, and other applications that can perform the same or equivalent functions should be covered within the scope claimed by this invention. Background Technology

[0003] Commercially available lithium batteries typically contain an electrolyte, a polar solvent that wets the pores between the electrode powders and reduces interfacial impedance, increasing conductivity. However, when this polar electrolyte is used in solid-state lithium batteries with solid electrolytes, the solid electrolyte is attacked by the polar solvent, causing its surface and structure to decompose and be damaged, resulting in a loss of its intended characteristics and performance, and consequently, a decrease in the battery's efficiency.

[0004] On the other hand, polar solvents are used as electrolytes in the positive electrode of all-solid-state electrolyte lithium batteries and in the interface between the positive electrode and the solid electrolyte. They can even be used in the negative electrode of powder form. Since the electrolyte can easily form resistance in the electrode itself and at the interface with the solid electrolyte, many electrode processing steps need to be added in the processing technology, which undoubtedly increases the production cost. Summary of the Invention

[0005] To address the problem that existing polar electrolytes cause solid electrolytes to decompose, break down, and lose their intended properties, this invention provides a liquid electrolyte medium comprising: a fluorinated ether; a dicarbonate; and a lithium salt; wherein: the fluorinated ether and the dicarbonate are nonpolar or low-polar solvents, with molar ratios of 5-40%, 30-60%, and 5-35%, respectively; and the lithium salt is non-hexafluorophosphate, the concentration of which, when mixed with the nonpolar or low-polar solvent of the fluorinated ether and the dicarbonate at a temperature between -10 and 60°C, does not exceed the saturation concentration of the lithium salt in the nonpolar or low-polar solvent.

[0006] The fluorinated ethers include 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether; and the carbonates are fluoroethylene carbonate and methyl ethyl carbonate, respectively.

[0007] The lithium salt comprises at least one or a mixture of lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluoroantimonyate, lithium tetrachloroaluminate, lithium tetrachlorogallate, lithium nitrate, tri(trifluoromethanesulfonyl)methyl lithium, bis(trifluoromethanesulfonyl)imide, lithium thiocyanate, lithium pentafluorosulfonate, lithium trifluorocarbonate, lithium fluorosulfonate, lithium tetra(pentafluorophenyl)borate, lithium trifluoromethanesulfonate, and lithium difluorooxalateborate.

[0008] Preferably, when the lithium salt is mixed in the nonpolar or low-polar solvent of the fluorinated ether and the dicarbonate, the concentration is between 0.5M and 4M.

[0009] The present invention also provides the above-mentioned liquid electrolyte medium for use in solid electrolyte lithium batteries, comprising: a positive electrode, the positive electrode comprising a positive electrode material in contact with a solid electrolyte; the positive electrode material having a powder or granular structure and being filled with the liquid electrolyte medium as described above.

[0010] The solid electrolyte lithium battery further includes a negative electrode, in which the liquid electrolyte is filled.

[0011] The solid electrolyte includes either a sulfide solid electrolyte or an oxide solid electrolyte.

[0012] Preferably, the sulfur solid electrolyte comprises (100-x)Li₂S-xP₂S₅; a mixture of (100-x)Li₂S-xP₂S₅ and a lithium compound; a mixture of (100-x)Li₂S-xP₂S₅ and a sulfur compound; or a mixture of (100-x)Li₂S-xP₂S₅ and a lithium compound and a sulfur compound, wherein all x are positive integers less than 100.

[0013] Preferably, in the sulfide solid electrolyte, the lithium compound comprises lithium chloride, lithium bromide, lithium iodide or any combination thereof; and the sulfide comprises germanium disulfide, silicon disulfide, tin disulfide, molybdenum disulfide, aluminum sulfide, nickel sulfide or any combination thereof.

[0014] The cathode material comprises LiNixMnyCozO2, where x+y+z is the sum of any number = 1; LiNixAlyCozO2, where x+y+z is the sum of any number = 1; LiMPO4, where M is iron, cobalt, nickel, manganese or a combination thereof; LiMSO4F, where M is iron, cobalt, nickel, manganese, aluminum or a combination thereof; and Li2M, where M is sulfur, selenium, tellurium or a combination thereof.

[0015] Preferably, the cathode material comprises LiNi 0.8 Mn 0.1 Co 0.1 O2.

[0016] Compared with similar technologies, the present invention has the following beneficial effects and advantages: This invention provides an electrolyte containing a solvent with low free polarity. This liquid electrolyte is compatible with sulfide solid electrolytes and can avoid high-voltage decomposition. It does not require changes to the existing positive electrode production line process in the factory. It can maintain the high conductivity of the positive electrode itself and the interface. The solid electrolyte will not be attacked by the electrolyte, resulting in the decomposition and destruction of its surface and structure. Attached Figure Description

[0017] The present invention will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting, and in these embodiments, the same reference numerals denote the same structures, wherein: Figure 1 This is a schematic diagram of a preferred embodiment of the present invention, which applies the liquid electrolyte medium to an anode-free solid electrolyte lithium battery.

[0018] Figure 2A , 2B Electrochemical impedance analysis of preferred embodiment 1 and comparative example 2 of the present invention.

[0019] Figure 3 This shows the relationship between discharge capacitance and voltage for Comparative Example 1.

[0020] Figure 4A and Figure 4B The discharge capacitance and voltage relationship are shown in preferred embodiments 1 and 2 of the present invention.

[0021] Figure 5A This is a schematic diagram of a full cell after the cathode material of Example 1 is filled.

[0022] Figure 5B To correspond to Figure 5A The diagram shows a full battery cut directly with scissors.

[0023] Symbol explanation: 10 positive electrode 11 Cathode Materials 12 Liquid Electrolyte 13 Solid electrolyte Detailed Implementation

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of the present invention. For those skilled in the art, these drawings can be applied to other similar scenarios without creative effort. Unless obvious from the context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0025] It should be understood that the terms "system," "device," "unit," and / or "module" used herein are one method of distinguishing different components, parts, components, sections, or assemblies at different levels. However, if other terms can achieve the same purpose, they may be replaced by other expressions.

[0026] As indicated in this invention and the claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0027] This invention uses flowcharts to illustrate the operations performed by the system according to embodiments of the invention. It should be understood that the preceding or following operations are not necessarily performed precisely in sequence. Instead, the steps can be processed in reverse order or simultaneously. Furthermore, other operations can be added to these processes, or one or more steps can be removed from them.

[0028] Liquid Electrolyte The preferred embodiment of the liquid electrolytic medium of the present invention comprises a liquid solution formed from the following components: Monofluorinated ethers; Dicarbonates; The fluorinated ethers and dicarbonates are both nonpolar solvents, and are mixed in molar ratios of 5-40%, 30-60%, and 5-35%, respectively; and A lithium salt, the concentration of which, when mixed at a temperature between -10 and 60°C in a nonpolar or low-polar solvent of the fluorinated ether and the dicarbonate, does not exceed the saturation concentration of the lithium salt in the nonpolar or low-polar solvent, and is any lithium salt other than lithium hexafluorophosphate (LiPF6).

[0029] The fluorinated ethers include 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE); the carbonates are fluoroethylene carbonate (FEC) and ethyl methyl carbonate (EMC); and the lithium salt is preferably lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium hexafluoroantimonyate (LiSbF6), lithium tetrachloroaluminate (LiAlCl4), lithium tetrachlorogallium oxide (LiGaCl4), lithium nitrate (LiNO3), tris(trifluoromethanesulfonyl)methyllithium (LiC(SO2CF3)3), lithium di(trifluoromethanesulfonyl)imide (LiN(SO2CF3)2), lithium thiocyanate (LiSCN), LiO3SCF2CF3, lithium pentafluorosulfonate (LiC6F5SO3), lithium trifluorocarbonate (LiO2CCF3), lithium fluorosulfonate (LiSO3F), lithium tetra(pentafluorophenyl)borate (LiB(C6H5)4), lithium trifluoromethanesulfonate (LiCF3SO3), and lithium difluorooxalate borate (LiDFOB) at least one or a mixture thereof.

[0030] Wherein, TTE, FEC, and EMC are all non-polar solvents, and are mixed in the aforementioned molar ratio. Specifically, a ternary non-polar solvent can be formed by mixing and proportioning them at a preferred molar ratio of 3:5:2. The lithium salt is then added to this ternary non-polar solvent for mixing. The lithium salt is preferably any lithium salt other than lithium hexafluorophosphate (LiPF6), such as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The concentration is based on the saturation concentration that does not produce precipitates when mixed in the ternary non-polar solvent within the aforementioned temperature range, for example, preferably 0.5M to 4.0M, or more preferably 0.5M to 2.0M, in the aforementioned ternary non-polar solvent.

[0031] Solid-state electrolyte lithium battery (full cell) Please continue to refer to this. Figure 1 The present invention applies the above-mentioned liquid electrolyte medium to an anode-free solid electrolyte lithium battery in a preferred embodiment, which includes: A positive electrode 10, comprising a positive electrode material 11 in contact with a solid electrolyte 13, wherein the positive electrode material 11 is preferably in powder form and filled with the liquid electrolyte 12.

[0032] In this preferred embodiment, the solid electrolyte preferably comprises a sulfide solid electrolyte or an oxide solid electrolyte. The sulfide solid electrolyte is preferably (100-x)Li₂S-xP₂S₅, such as Li₇P₃S. 11 ; mixtures of (100-x)Li₂S⁻xP₂S₅ with lithium compounds (LiX), such as Li₆PS₅Cl; (100-x)Li₂S⁻xP₂S₅ with sulfur compounds (M x S y A mixture of (100-x)Li₂S-xP₂S₅ with lithium compounds (LiX) and sulfur compounds (M). x S y A mixture of ( ), wherein all x are positive integers less than 100. The lithium compound (LiX) comprises lithium chloride, lithium bromide, lithium iodide, or any combination thereof (X = Cl, Br, I, or combinations thereof); and the sulfide (M x S y ) includes germanium disulfide, silicon disulfide, tin disulfide, molybdenum disulfide, aluminum sulfide, nickel sulfide, or any combination thereof (M x S y =GeS2, SiS2, SnS2, MoS2, Al2S3, Ni3S2 or combinations thereof).

[0033] The cathode material 11 is preferably in powder or granular form, and more likely in a porous state, comprising LiNixMnyCozO2, where x+y+z is the sum of any number = 1; LiNixAlyCozO2, where x+y+z is the sum of any number = 1; LiMPO4, where M is iron, cobalt, nickel, manganese, or a combination thereof; LiMSO4F, where M is iron, cobalt, nickel, manganese, aluminum, or a combination thereof; Li2M, where M is sulfur, selenium, tellurium, or a combination thereof, and a preferred embodiment is LiNi. 0.8 Mn 0.1 Co 0.1 O2 (NMC811); On the other hand, since the liquid electrolyte 12 provided by the present invention is mainly applicable to the positive electrode material in powder or granular state, because solid powder or granular positive electrode materials have high interfacial impedance problems, the liquid electrolyte 12 provided by the present invention can effectively improve the interfacial impedance.

[0034] It should be noted that this embodiment uses an anode-free solid electrolyte lithium battery, so there is no negative electrode (no anode), or only a general current receiver (such as copper foil). However, the present invention can be used in general normal full battery applications where possible, that is, it also includes a negative electrode, and the liquid electrolyte 12 provided by the present invention can also be filled in the negative electrode at the same time, which can also reduce the problem of interface impedance and improve the full battery performance.

[0035] <Validity Test> Table 1 below lists the preferred embodiments of the present invention and comparative examples using LiPF6 as the lithium salt, and the performance of the above-described solid electrolyte lithium battery type was tested.

[0036]

[0037] Please refer to Figure 2A , 2B The above describes the electrochemical EIS impedance analysis of Example 1 and Comparative Example 2. Compared with Comparative Example 2, which did not add liquid electrolyte, the impedance of Example 1 is significantly smaller. The calculated impedance values ​​are 80 ohms and 275 ohms, respectively. This indicates that the non-polar solvent liquid electrolyte used in this invention can reduce the impedance of the electrode and the interface between it and the solid electrolyte.

[0038] Please refer to Figure 3 The discharge capacity and voltage relationship of Comparative Example 1: Because the addition of LiPF6 increases the polarity of the solvent in Comparative Example 1, the polar electrolyte attacks the sulfide solid electrolyte, so the full cell cannot show a normal electrical curve.

[0039] Please refer to Figure 4A and Figure 4B The figure shows the discharge capacity versus voltage relationship for Examples 1 and 2. As can be seen from the figure, the discharge capacity of Example 1 (155 mAh / g) is better than that of Example 2 (138 mAh / g), but both examples are better than Comparative Example 1. Figures 3-4B Full-cell tests with electrolytes of different polarities demonstrate that the low-free-polarity solvent electrolyte of this invention can reduce the attack of sulfide solid electrolytes by polar solvents while maintaining high electrode conductivity.

[0040] Please refer to Figure 5A and Figure 5B , Figure 5A This refers to the full battery formed by filling the positive electrode material 11 in Example 1. Figure 5B It is a full battery that has been cut directly with scissors. Figure 5A and Figure 5BThis invention demonstrates that even when a liquid electrolyte is added to a sulfide solid electrolyte lithium battery, the same battery can be directly cut with scissors during discharge without causing a short circuit due to the electrolyte, thus maintaining the performance of the all-solid-state electrolyte lithium battery.

[0041] Furthermore, unless expressly stated in the claims, the order of processing elements and sequences, the use of numbers and letters, or other names described in this invention are not intended to limit the order of the processes and methods of this invention. Although some currently considered useful embodiments of the invention have been discussed in the foregoing disclosure by way of various examples, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments. Rather, the claims are intended to cover all modifications and equivalent combinations that conform to the spirit and scope of the embodiments of this invention.

[0042] Similarly, it should be noted that, in order to simplify the description of the disclosed techniques and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of the embodiments of the invention sometimes combines multiple features into a single embodiment, drawing, or description thereof. However, this disclosure method does not imply that the features required for the object of protection claimed by the invention are more numerous than the features mentioned in the embodiments. In fact, without impairing the effectiveness of the invention, the features in the claims may be fewer than all the features of the single embodiment disclosed above.

[0043] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used in the description of embodiments are sometimes modified by the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant figures and employ a general method of preserving decimal places. Although the numerical ranges and parameters used to confirm their breadth of scope in some embodiments of the invention are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

[0044] Finally, it should be understood that the embodiments described in this invention are merely illustrative of the principles of the invention. Other modifications may also fall within the scope of this invention. Therefore, alternative configurations of the embodiments of this invention are considered as examples and not limitations, and are regarded as consistent with the teachings of this invention. Accordingly, the embodiments of this invention are not limited to those explicitly described and illustrated herein.

Claims

1. A solid-state electrolyte lithium battery, characterized in that, At least includes: A positive electrode comprising a positive electrode material and in contact with a solid electrolyte; the solid electrolyte comprising a sulfide solid electrolyte. The positive electrode material has a powder or granular structure and is filled with a liquid electrolyte; the liquid electrolyte comprises: Monofluorinated ethers; the fluorinated ethers include 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether; Dicarbonates; these dicarbonates are ethylene fluorocarbonate and ethyl methyl carbonate; A lithium salt; the lithium salt comprises at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluoroantimonyate, lithium tetrachloroaluminate, lithium tetrachlorogallium oxide, lithium nitrate, lithium thiocyanate, lithium fluorosulfonate, lithium tetra(pentafluorophenyl)borate, lithium trifluoromethanesulfonate, and lithium difluorooxalateborate. in: The molar ratios of the fluorinated ethers and dicarbonates are 5-40% fluorinated ethers, 30-60% fluoroethylene carbonate, and 5-35% methyl ethyl carbonate; and The lithium salt is non-hexafluorophosphate, and its concentration, when mixed with the fluorinated ether and dicarbonate at a temperature between -10 and 60°C, does not exceed the saturation concentration of the lithium salt in the fluorinated ether and dicarbonate.

2. The solid-state electrolyte lithium battery as described in claim 1, characterized in that: When the lithium salt is mixed with the fluorinated ether and the dicarbonate, the concentration is between 0.5M and 4M.

3. The solid-state electrolyte lithium battery as described in claim 1, characterized in that: The solid electrolyte lithium battery further includes a negative electrode.

4. The solid-state electrolyte lithium battery as described in claim 3, characterized in that: The liquid electrolyte fills the negative electrode.

5. The solid-state electrolyte lithium battery as described in claim 1, characterized in that: The sulfide solid electrolyte comprises (100-x)Li₂S₁₀P₂S₅, a mixture of (100-x)Li₂S₁₀P₂S₅ and a lithium compound, a mixture of (100-x)Li₂S₁₀P₂S₅ and a sulfur compound, or a mixture of (100-x)Li₂S₁₀P₂S₅ and a lithium compound and a sulfur compound, wherein x is a positive integer less than 100.

6. The solid-state electrolyte lithium battery as described in claim 5, characterized in that: In the sulfide solid electrolyte, the lithium compound comprises lithium chloride, lithium bromide, lithium iodide or any combination thereof; and the sulfide comprises germanium disulfide, silicon disulfide, tin disulfide, molybdenum disulfide, aluminum sulfide, nickel sulfide or any combination thereof.

7. The solid-state electrolyte lithium battery as described in claim 5 or 6, characterized in that: The sulfide solid electrolyte contains Li7P3S. 11 Or Li6PS5Cl.

8. The solid-state electrolyte lithium battery as described in claim 1 or 3, characterized in that: The cathode material comprises LiNixMnyCozO2, where x+y+z is the sum of any number = 1; LiNixAlyCozO2, where x+y+z is the sum of any number = 1; LiMPO4, where M is iron, cobalt, nickel, manganese or a combination thereof; LiMSO4F, where M is iron, cobalt, nickel, manganese or a combination thereof; or Li2M, where M is sulfur, selenium, tellurium or a combination thereof.

9. The solid-state electrolyte lithium battery as described in claim 8, characterized in that: The cathode material contains LiNi 0.8 Mn 0.1 Co 0.1 O2.

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