Non-aqueous electrolyte components

Abstract

The present invention relates to a non-aqueous electrolyte composition for an electrochemical cell comprising a pre-sodiumization reagent containing one or more sacrificial sodium salts. The present invention also relates to an electrochemical cell pre-sodiumized using the above non-aqueous electrolyte. Devices, methods, and uses comprising the above non-aqueous electrolyte are also disclosed.

Description

[Technical Field]

[0001] The present invention relates particularly to novel non-aqueous electrolyte compositions for electrochemical cells. Electrochemical cells comprising the above-mentioned non-aqueous electrolyte compositions, as well as methods and uses comprising the above-mentioned novel electrolyte compositions, are also disclosed. The present invention also relates to electrochemical cells using the above-mentioned non-aqueous electrolyte compositions. [Background technology]

[0002] Sodium-ion batteries are similar in many ways to the lithium-ion batteries that are currently in common use. They are both reusable secondary batteries that contain an anode (negative electrode), a cathode (positive electrode), and an electrolyte material, and both can store energy and charge and discharge by similar reaction mechanisms. When a sodium-ion (or lithium-ion) battery is charging, Na + (or Li + Ions deintercalate from the cathode and are inserted into the anode. Meanwhile, charge balancing electrons pass from the cathode to the anode of the battery through an external circuit containing a charger. During discharge, the same process occurs, but in the opposite direction.

[0003] Sodium-ion batteries have garnered significant interest and are considered one of the most promising candidates for next-generation battery technology. However, a more noteworthy area is the development of ways to increase the capacity and / or cycle life of sodium-ion batteries in order to compete with existing lithium-ion batteries.

[0004] For example, any capacity loss of the sodium ion cell, especially in the initial cycle, is clearly undesirable. As will be explained below, such capacity loss generally occurs because of the “renewable” Na consumed during the first cycle of operation. + This is caused by ion loss.

[0005] In a typical sodium-ion full cell, the cathode, which is the only sodium ion source, provides "rechargeable" Na + ions (i.e., the reversible Na + ions that move between the anode and the cathode as described above), and also provides "non-rechargeable" Na + ions (i.e., the irreversible Na + ions that are entirely consumed during the first cycle). In particular, Na + ions are typically consumed during the formation of the solid electrolyte interphase (SEI) on the anode surface and / or the cathode electrolyte interphase (CEI) on the cathode surface, especially during the first cycle of the sodium-ion cell. This is the very first cycle experienced by the sodium-ion cell, which typically occurs during the initial "formation" cycle of the sodium-ion cell.

[0006] It is known in the prior art that electrochemical performance can be improved by increasing the content of reversible Na + ions in a sodium-ion full cell to mitigate the loss of Na + ions consumed during SEI and / or CEI formation. This strategy of providing an additional sodium ion source to the electrochemical cell system (i.e., in addition to the cathode active material sodium ion source) is known in the art as "presodiation".

[0007] Since capacity loss is usually induced by the consumption of sodium ions limited by the sodium source in the cathode active material, by providing an additional sodium ion source, the electrochemical cell system is supplied with more Na + ions, and thus can compensate for the loss of "rechargeable" Na + ions and the subsequent capacity loss.

[0008] Prior art "presodiation" techniques are briefly summarized below from Mu et al., Energy Mater 2022; 2:200043, and take the following forms: 1) Self-sacrificing sodium-containing additive for cathodes These are sacrificial sodium-containing additives combined with the active cathode material in the cathode electrode. When released from the cathode electrode, they provide additional Na during the first cycle of the sodium ion cell. + It provides a source. Often provided as a salt, the accompanying anions are typically oxidized to a gas and then released from the sodium ion cell. Examples include Na2C4O4, CH3COONa, NaNO2, NaN3, and Na2O2, which can be found in the prior art described below. Na2C4O4 salt: Ilarduya et al., Electrochim.Acta, 2019, 321, 134693; Shanmukaraj et al., ChemSusChem, 2018, 11, 3286 Ch3COONa salt:Zou et al., Angew. Chem. Int. Ed., 2021, 60, 17070 NaNO2: Jo et al., J. Mater. Chem. A, 2019, 7, 3903 NaN3: Ilarduya et al., J.Power Sources, 2017, 337, 197 Na2O2:Guo et al., ACS Appl.Mater.Interfaces, 2021, 13, 2772

[0009] Certain examples are low-cost, environmentally friendly, and Na + Although it is claimed that no additional residue is left after extraction, the applicant has demonstrated the following shortcomings within this specification: a) Adding sacrificial sodium-containing additives to the cathode electrode composition reduces the amount of cathode active material that may be present in the composition. Therefore, mAh / g カソード活物質 Even if an increase in mAh is observed, the actual mAh of the cell may not increase.

[0010] b) Adding sacrificial sodium-containing additives to the cathode electrode composition reduces the integrity of the cathode electrode after the accompanying anions are oxidized. This has a significant impact on the performance of the sodium ion cell in subsequent charge-discharge cycles. Readers should refer to the experimental section of this specification for further technical explanations.

[0011] 2) Self-presodium-forming cathode materials These are Na-rich cathode active materials. One example is O3-type Na. 0.9 Cu 0.31 Ni 0.11 Fe 0.3 Mn 0.48 Ti 0.1 O2 cathode compounds were used, which were prepared by quenching to achieve a high sodium content (approximately 0.9). See Ding et al., Additive-Free Self-Presodiation Strategy for High-Performance Na-Ion Batteries. Adv.Funct.Mater.2021, 31, 2101475.

[0012] This example illustrates an alternative method to pre-sodiumization. However, the additional steps required to produce these Na-rich materials suggest that this method is unlikely to be successful in a commercial setting.

[0013] 3) Direct contact with sodium foil / sodium powder Another pre-sodiumization method involves using sodium foil or sodium powder in direct contact with the anode material. See Liu et al., ACS Appl. Mater. Interfaces 2019, 11, 26, 23207-23212. However, metallic sodium is extremely reactive and difficult to store safely in air; therefore, pre-sodiumization can only be carried out in an oxygen- and moisture-free environment (e.g., a glove box). In addition, the production of sodium powder is labor-intensive, and there is a risk of thermal runaway if the anode and metallic sodium powder are pressure-coated. For this reason, this method is also unlikely to be successful in a commercial setting.

[0014] 4) Chemical pre-sodium treatment of the anode Another presodiumization method involves directly contacting the anode with a sodium-containing solvent prepared by combining a solvent with metallic sodium. The sodium-containing solvent can then be sprayed onto a commercially available anode material. See Liu et al., *A Simple Electrode-Level Chemical Presodization Route by Solution Spraying to Improve Energy Density of Sodium-Ion Batteries*, Adv.Funct.Mater. 2019, 29, 1903795. This method avoids the use of metallic sodium to produce the pre-sodium anode, but still requires the use of metallic sodium to prepare the sodium-containing solvent. Therefore, this additional complexity in the manufacturing process means that this method is unlikely to be commercially viable.

[0015] 5) Electrochemical presodium treatment The final prior art sodiumization technique involves using an electrochemical process to provide a pre-sodium anode (often referred to as a "pre-charge-discharge cycle" in the prior art). See Liu et al., Enabling high-performance sodium metal anode via a presodiated alloy-induced interphase, Chemical Engineering Journal, vol. 417, 2021, 128997. This method involves the additional assembly and disassembly of half-cells to provide pre-sodium anodes that can be used in full sodium ion cells (specifically, first fabricating sodium half-cells, performing charge-discharge cycles on them, disassembling the cells, washing the electrode materials with a suitable solvent to remove unwanted decomposition products, drying the electrodes, and then using these electrodes to fabricate new cells). Therefore, these additional manufacturing steps mean that this method is unlikely to be commercially viable.

[0016] U.S. Patent Application Publication 20150064568 relates to the general disclosure that metal ion additives may be incorporated into (i) one or more electrodes, (ii) a separator, or (iii) an electrolyte. The metal ion additives provide additional donor ions corresponding to the metal ions stored and released by the anode active material particles and cathode active material particles. Paragraph

[0035] of U.S. Patent Application Publication 20150064568 proposes several sacrificial salts that may supply additional Na in sodium-ion batteries. However, because the focus of U.S. Patent Application Publication 20150064568 is lithium-containing sacrificial salts for use in lithium-ion batteries (see paragraphs

[0010] and

[0018] -

[0024] ), U.S. Patent Application Publication 20150064568 does not test or demonstrate any of these sacrificial salts in sodium-ion batteries.

[0017] Furthermore, U.S. Patent Application Publication 20150064568 does not specify which solvent systems should be used in conjunction with the sodium-containing sacrificial salt disclosed in paragraph

[0035] of U.S. Patent Application Publication 20150064568, nor does it specify a particular concentration of the sodium-containing sacrificial salt disclosed in paragraph

[0035] of U.S. Patent Application Publication 20150064568, nor does it specify when it may be used in a particular solvent system. In fact, only the concentration disclosed in paragraph

[0071] of U.S. Patent Application Publication 20150064568 is a lithium-containing material that has absolutely no resemblance to the sodium-containing sacrificial salt disclosed in paragraph

[0035] of U.S. Patent Application Publication 20150064568. [Overview of the Initiative] [Problems that the invention aims to solve]

[0018] Therefore, the present invention aims to mitigate or eliminate one or more of the aforementioned drawbacks of the known technology.

[0019] In particular, therefore, an object of the present invention is to provide a novel pre-sodiumization technique that can be used in electrochemical cells, especially sodium ion cells. The method of the present invention generally involves the "renewable" Na consumed during the first cycle of an electrochemical cell. + This reduces and / or eliminates capacity loss caused by ion loss. The pre-sodiumization method of the present invention is also commercially attractive by avoiding additional manufacturing complexities such as the direct use of metallic sodium and / or further cell assembly. In addition to reducing and / or eliminating capacity loss, the pre-sodiumization method of the present invention can also provide performance advantages, such as improved cell cycle life of the electrochemical cell. [Means for solving the problem]

[0020] The present invention (a) A solvent system comprising one or more organic carbonate solvents, (b) A pre-sodium reagent containing one or more sacrificial sodium salts, which may be less than 1.0 mol / kg These objectives are achieved by providing a novel non-aqueous electrolyte for electrochemical cells, including [specific component]. [Modes for carrying out the invention]

[0021] Pre-doping is the process of pre-doping with sodium ions. Therefore, in this disclosure, pre-doping reagents as defined herein mean any substance or compound (regardless of its state, such as solid or liquid) that, when exposed to an electrochemical cell environment, can chemically change to provide a sodium ion source. In particular, during the charge-discharge cycle of an electrochemical cell, pre-doping reagents can provide sodium ions to the reversibly active sodium ion content of the electrochemical cell.

[0022] In a typical sodium ion cell, the active sodium ion content is stored in the positive electrode (cathode). During the first charge (formation cycle) of the cell, a certain amount of active sodium is typically lost at the negative electrode (anode), mainly by SEI formation, and the amount of residual active sodium decreases after the first charge / discharge cycle (i.e., it is less). In the present invention, the strategy to overcome this problem is to store a certain amount of active sodium by pre-sodiumization using one or more sacrificial sodium salts in the non-aqueous electrolyte composition before further charge / discharge cycles.

[0023] This replenishes the lost active sodium, resulting in an increased sodium ion content after the first cycle, and thus improved residual cell energy. In fact, the present invention is in contrast to prior art methods, in which strategies to overcome the above problems have been to store a certain amount of active sodium in the negative and / or positive electrodes by pre-sodiumization before the charge / discharge cycle, for example, using one or more sacrificial sodium salts contained in the cathode.

[0024] More specifically, the present invention provides a novel non-aqueous electrolyte composition that, after the first cycle of operation, is used to perform reversible charge-discharge cycles in an electrochemical cell. + Surprisingly, the total amount increases. This is because the obtained mAh / g カソード活物質 This not only increases capacity but also the total capacity (mAh) of the electrochemical cell. As demonstrated by the detailed examples disclosed herein, this is in contrast to prior art pre-sodiumization methods, which store a certain amount of activated sodium by using one or more sacrificial sodium salts at the anode through pre-sodiumization before the charge / discharge cycle.

[0025] Furthermore, while the invention of suitable electrolyte compositions typically receives less attention than that of active materials (electrodes), their importance should not be overlooked, as they are largely key to battery life and are essential for achieving the practical performance that the cell can accomplish in terms of capacity, rate characteristics, safety, and so on.

[0026] However, in order to be a suitable electrolyte composition, it must satisfy a long list of characteristics, including the following: • Chemical stability - No reactions must occur during cell operation, or if a reaction occurs, it must occur within the electrolyte itself or together with the separator, including the electrodes, current collector, or packaging material used, in order to allow for an acceptable number of charge-discharge cycles (e.g., during SEI formation at the anode); • Electrochemical stability - A wide electrochemical stability range is required, i.e., a large gap must exist between high and low onset potentials for decomposition by oxidation or reduction; • Thermal stability - The electrolyte composition shall not decompose or chemically disintegrate during normal cell operation and at operating temperatures; • Physical properties - The electrolyte composition must be liquid, and therefore its melting and boiling points must be well outside the range of the cell's internal operating temperature; • High ionic conductivity and low electronic conductivity are, respectively, Na + This is necessary to maintain cell operation during transport and minimize cell self-discharge; • Low toxicity; • Based on sustainable chemistry, that is, produced through low-impact synthesis (energy, pollution, etc.) using abundant elements; • Cost-effective production.

[0027] It is clearly desirable to find novel pre-sodiumization techniques to mitigate and / or eliminate the drawbacks associated with the prior art methods detailed above. However, it is also desirable to provide an optimal electrolyte composition to promote high electrochemical cell performance.

[0028] In reality, electrochemical cells rely on how the electrolyte composition interacts with the components of the electrochemical cell (e.g., separator, positive electrode, and / or negative electrode). This interaction cannot be predicted based on the mosaic-like physical properties of the electrolyte composition. In particular, as shown above, Na + To maintain cell operation through transport, the electrolyte composition must have high ionic conductivity and, ideally, no electronic conductivity. However, this high ionic conductivity and low electronic conductivity must be at least compatible with the ability to maintain chemical and electrochemical stability, and therefore the electrochemical cell can be charged and discharged over many cycles, in some cases at various voltage profiles.

[0029] In the case of novel non-aqueous electrolyte compositions, the applicant has found, surprisingly, that the present invention not only provides an improved technique for pre-sodiumization, but also provides an electrolyte composition that promotes and / or maintains high electrochemical performance in electrochemical cells when compared with prior art electrolyte compositions. For example, rate performance and / or charge-discharge cycle stability were found to be equivalent to or better than prior art electrolyte compositions. This was not known from the prior art as of the priority date of this application, nor could it have been predicted therefrom.

[0030] As used herein, the term (phase) “sacrificial sodium salt” means a sodium salt or portion thereof intended to be consumed or disintegrated during the charging operation of an electrochemical cell for the purpose of providing additional capacity to the electrochemical cell, as discussed below.

[0031] In a preferred embodiment, one or more sacrificial sodium salts of the present invention irreversibly provide sodium ions to the anode (and / or the anode surface) during charging of an electrochemical cell. This is the anode of the electrochemical cell, since the electrochemical cell contains an anode. Pre-sodiumization using one or more sacrificial sodium salts in a non-aqueous electrolyte composition is advantageous, in particular, when the salt irreversibly donates sodium ions during charging of an electrochemical cell, as this eliminates the need for additional manufacturing steps, in contrast to the prior art techniques described above.

[0032] Therefore, in this context, the term "irreversibly" means that one or more sacrificial sodium salts are Na + It means that ions and their respective anions are provided, and at least a portion of them are consumed during the first charge (formation cycle) of the electrochemical cell. That is, they are Na in the non-aqueous electrolyte composition. + They are consumed in the sense that they do not return to their previous state as ions and their respective counter anions.

[0033] The applicant claims that in the examples disclosed herein, further Na is provided by one or more sacrificial salts of the present invention. + Therefore, Na at the cathode + This will be used to store additional capacity from an electrochemical cell (for example, the resulting mAh / g). カソード活物質 Demonstrate the capacity and / or total capacity (mAh).

[0034] Of course, as long as one or more of these sodium-containing salts irreversibly supply sodium ions to the anode (and / or the anode surface) during the charging of the electrochemical cell, these one or more sodium-containing salts also provide additional "renewable" Na + Ions (i.e., reversible Na ions moving between the anode and cathode as described above) + It can provide ions.

[0035] Preferably, one or more sacrificial sodium salts decompose during the charging of the electrochemical cell (e.g., the first cycle) (e.g., one or more anions of the sacrificial sodium salts are oxidized) to provide sodium ions to the anode. Therefore, it is preferable that the one or more sacrificial sodium salts contain one or more anions that are oxidized during the charging of the electrochemical cell, more preferably during the first charging of the electrochemical cell (i.e., the first cycle). This is the very first cycle experienced by the sodium ion cell and typically occurs during the initial "formation" cycle of the sodium ion cell. Therefore, the one or more sacrificial sodium salts of the present invention, ideally, typically during the charging of the electrochemical cell, substantially decompose (i.e., one or more anions of the sacrificial sodium salts are substantially oxidized) depending on the activation potential (i.e., voltage) applied between the anode and cathode electrodes of the electrochemical cell. Therefore, this causes the release of sodium ions to the anode electrode.

[0036] Regarding this, sufficient Na during the charging of the electrochemical cell, preferably during the first charge, + To provide this, the decomposition potential of one or more sacrificial sodium salts (i.e., the potential at which one or more anions are oxidized) should ideally be lower than the upper cutoff voltage of the electrochemical cell. The ideal upper cutoff voltage of an electrochemical cell (preferably a sodium ion cell) is about 4.5V or about 4.3V. The most preferred upper cutoff voltage of an electrochemical cell (preferably a sodium ion cell) is about 4.2V, and optionally about 3.75V. The ideal lower cutoff voltage of an electrochemical cell (preferably a sodium ion cell) is about 1.0V, or alternatively 2.5V.

[0037] The electrochemical cell (ideally a sodium ion cell) is preferably charged and discharged at 1.0V to 4.5V, more preferably at 1.0V to 4.2V.

[0038] In one embodiment, the decomposition potential of one or more sacrificial sodium salts is approximately 0V to approximately 5V. Ideally, this can be achieved using an electrochemical cell containing a reference electrode containing sodium metal (i.e., relative to Na / Na). + ) is required. This electrochemical cell is typically a three-electrode electrochemical cell, one of which contains sodium metal (as a reference electrode). Alternatively, the reference electrode may be another electrode active material (different from sodium metal), for example, Na 2+x V2(PO4)3 [where -0.5 ≤ x ≤ 0.5] can contain a typical Na / Na compound. + It has a redox pair at around 3.4V.

[0039] Depending on the case, the decomposition potential of one or more sacrificial sodium salts is Na / Na + The voltage is approximately 0.5V to 5V (i.e., Na / Na). + For redox pairs: Those skilled in the art will know Na / Na + For this, the absolute potential range is 0.5V to 5V, and that is Li / Li + (It will be understood that a set of potential values ​​using one scale, such as Na / Na, can be converted to another scale, such as the redox pair of a standard hydrogen electrode.) Preferably, the decomposition potential of one or more sacrificial sodium salts is Na / Na + The voltage is approximately 2.5V to 4.3V, and Na / Na is very preferred. + The voltage is approximately 2.75V to 3.9V.

[0040] Ideally, the decomposition potential of one or more sacrificial sodium salts should be Na / Na + It is approximately 2.5V to 3.75V. In fact, 3.26V (vs. Na / Na) + ) and 3.74V (vs. Na / Na) + ) A specific value of ) is also ideal.

[0041] In one embodiment, one or more sacrificial sodium salts are approximately 3.5V or less (relative to Na / Na). + Ideally, it should be approximately 3.2V or less (relative to Na / Na +It has a decomposition potential of ).

[0042] To enable the decomposition of one or more sacrificial sodium salts of the present invention in response to an activation potential (i.e., voltage) applied between the anode and cathode electrodes of the electrochemical cell, the electrochemical cell is charged to a voltage greater than the decomposition potential of the one or more sacrificial sodium salts. As described above, the decomposition potential of the one or more sacrificial sodium salts should ideally be lower than the upper cutoff voltage of the electrochemical cell. This means that the upper cutoff voltage of the electrochemical cell should ideally be greater than the decomposition potential of the one or more sacrificial sodium salts.

[0043] The decomposition potential of one or more sacrificial sodium salts should ideally be greater than the lower cutoff voltage of the electrochemical cell. Therefore, a preferred electrochemical cell may undergo charge-discharge cycles at 1V to 4.2V, and the preferred decomposition potential of one or more sacrificial sodium salts may be 2.5V to 3.75V. That is, the preferred one or more sacrificial sodium salts of the present invention substantially decompose at a potential of 2.5V to 3.75V. If the non-aqueous electrolyte composition according to the present invention contains one or more non-sacrificial sodium-containing salts, the preferred one or more non-sacrificial sodium-containing salts of the present invention do not substantially decompose at a potential of 2.5V to 3.75V, as will be discussed in more detail below.

[0044] In one embodiment, one or more sacrificial sodium salts substantially decompose during charging of the electrochemical cell at voltages of 1V to 4.3V, preferably 1V to 4.2V. That is, substantial oxidation of one or more anions of one or more sacrificial salts occurs when the electrochemical cell is operated within this voltage range. Typically, substantial oxidation of one or more anions of one or more sacrificial salts occurs when the cell is charged above 3V, and in some cases above 4V.

[0045] Therefore, one or more sacrificial sodium salts can substantially decompose during the charging of the electrochemical cell at voltages greater than 3V and up to 4.3V, preferably between 3V and 4.2V. In some cases, they can substantially decompose during the charging of the electrochemical cell at voltages between 4V and 4.3V, preferably between 4V and 4.2V. That is, substantial oxidation of one or more anions of one or more sacrificial salts occurs when the electrochemical cell is operated within this voltage range.

[0046] Ideally, during the charging of the electrochemical cell, the oxidation of one or more anions of one or more sacrificial sodium salts is about 25% or more, preferably about 50% or more, very preferably about 75% or more, even more preferably 95% or more, and most preferably about 100%.

[0047] The present invention may include one or more sacrificial sodium salts containing one or more anions, each containing an atom selected from the group consisting of sulfur, nitrogen, boron, oxygen, and halogen atoms (e.g., fluorine). Ideally, the one or more sacrificial sodium salts may include one or more anions, each containing an atom selected from oxygen and / or sulfur, and most ideally containing a sulfur atom.

[0048] The present invention may include one or more sacrificial sodium salts containing one or more anions, each containing at least one atom selected from the group consisting of sulfur, nitrogen, boron, oxygen, and halogen atoms (e.g., fluorine). Ideally, the present invention may include one or more sacrificial sodium salts containing one or more anions, each containing at least one atom selected from oxygen and / or sulfur, and most ideally containing a sulfur atom.

[0049] Preferably, one or more sacrificial sodium salts include thiocyanate-containing compounds, cyanate-containing compounds, sulfonate-containing compounds, sulfite-containing compounds, periodate-containing compounds, fluorosilicate-containing compounds, fluoroferrate-containing compounds, alkoxide-containing compounds, boron-containing compounds, and NaSb m X x The compounds are selected from one or more compounds from the group consisting of compounds containing thiolates, thiolates, thiosulfates, cyanamides (including dicyanamides), azides, carboxylates, ketones (including rhozonates), fluorotitanates, and arenes (including terephthalates).

[0050] Examples of terephthalate-containing compounds include terephthalate-containing compounds containing alkyl groups that may be linear, branched, or cyclic, such as dimethyl terephthalate, diethyl terephthalate, and diisopropyl terephthalate. In preferred arene-containing compounds (including terephthalate-containing compounds), the total number of carbon atoms may be 14 or less, optionally 10 or less, and even more optionally 9 or less.

[0051] The additional one or more sacrificial sodium salts may be selected from one or more compounds in the group consisting of triflate-containing compounds, difluorophosphate-containing compounds, and tetraphenylborate-containing compounds.

[0052] Preferred one or more formulas NaSb m X x In the sacrificial sodium salt of NaSb, Sb is antimony, and X is a group containing or composed of one or more halogens, preferably selected from fluorine, chlorine, bromine, and iodine, and more preferably selected from fluorine. The amount x of halogen X is preferably x=1 to 16, more preferably x=6. The amount m of antimony Sb is preferably m=1 to 3, more preferably m=1 to 2, and particularly preferably m=1. The most preferred is one or more of the formula NaSbm X x The sacrificial sodium salt is sodium hexafluoroantimonate (V) (NaSbF6).

[0053] For example, one or more sacrificial sodium salts, Sodium sulfite (Na2SO3), Sodium trifluoromethanesulfonate (NaSO3CF3) (also known as sodium triflate), Sodium thiocyanate (NaSCN), Sodium cyanate (NaOCN), Sodium periodate (NaIO4), Sodium 1-butene-2-oleate (C4H7NaO), Sodium heptafluorobutyrate (C4F7NaO2), Sodium tetraphenylborate (C6H5)4BNa), Sodium hexafluoroantimonate (V) (NaSbF6), Sodium methanethiolate (CH3NaS), Sodium thiosulfate (Na2S2O3), Sodium methoxide (CH3NaO), Sodium borohydride cyanohydride (NaBH3CN), Dicyanamide sodium (NaN(CN)2), Sodium azide (NaN3), Sodium hexafluorotianoate (Na2TiF6), Disodium terephthalate (C8H4Na2O4), Sodium terephthalate (C8H5NaO4), Disodium rhizonate (Na2C6O6), Sodium hexafluoroferrate(III) (Na3FeF6), Sodium hexafluorosilicate (Na2[SiF6]), and Sodium difluorophosphate (NaPO2F2) One or more compounds may be selected from the group consisting of the following:

[0054] Most preferably, one or more sacrificial sodium salts include a cyanate-containing compound or a thiocyanate-containing compound. Ideally, one or more sacrificial sodium salts have the general formula NaXCN [wherein X is a group 16 element (from the periodic table), optionally selected from oxygen and sulfur, preferably selected from sulfur]. In one most preferred embodiment, one or more sacrificial sodium salts include sodium thiocyanate (NaSCN).

[0055] Alternatively, or in addition, preferred sacrificial sodium salts may include one or more of sodium triflate (NaSO3CF3), sodium difluorophosphate (NaPO2F2), and sodium tetraphenylborate (NaBPh4).

[0056] It is convenient to express the amount of one or more sacrificial sodium salts of the present invention in terms of their molar concentration in the solvent system; that is, the total number of moles of one or more sacrificial sodium salts (i.e., solutes) per kilogram of solvent system - i.e., moles / kg.

[0057] One or more sacrificial sodium salts may be present in the non-aqueous electrolyte composition at a concentration of less than 1.0 mol / kg. Ideally, this concentration ranges from above 0 mol / kg to below 1.0 mol / kg.

[0058] In a preferred embodiment, one or more sacrificial sodium salts may be present in the non-aqueous electrolyte composition at a concentration of about 0.75 mol / kg or less. Ideally, this concentration ranges from above 0 mol / kg to about 0.75 mol / kg. Similarly, one or more sacrificial sodium salts may be present in the non-aqueous electrolyte composition at a concentration of about 0.50 mol / kg or less. Ideally, this concentration ranges from above 0 mol / kg to about 0.50 mol / kg.

[0059] In a very preferred embodiment, one or more sacrificial sodium salts may be present at concentrations of about 0.015 mol / kg to about 0.5 mol / kg. Increased capacity and / or excellent long-term charge-discharge cycles were observed at these concentrations. In particular, excellent long-term charge-discharge cycles were achieved at the ideal concentration of about 0.25 mol / kg. This was especially evident when charge-discharge cycles were performed to include a voltage range of about 3.75 V to about 2.5 V in the electrochemical cell. Increased capacity was also observed at concentrations of about 0.015 mol / kg to about 0.1 mol / kg.

[0060] In another very preferred embodiment, one or more sacrificial sodium salts may be present in the non-aqueous electrolyte composition at concentrations of about 0.020 mol / kg to about 0.025 mol / kg. Similarly, concentrations of about 0.020 mol / kg and about 0.025 mol / kg resulted in electrochemical cells with extended lifecycles.

[0061] The non-aqueous electrolyte composition of the present invention comprises a solvent system containing one or more organic carbonate-based solvents.

[0062] One or more organic carbonate solvents present in the solvent system may be cyclic or acyclic compounds characterized by containing a carbonate ester group, i.e., a carbonyl group with one or two alkoxy groups laterally positioned: R1O(C=O)OR2. When one or more cyclic organic carbonate solvents are present in the solvent system, R1 and R2 are understood to be able to combine to form a cyclic carbonate ester compound. The R1 and R2 groups are preferably hydrogen; or C1-C 20 Ring or C1~C 20 Acyclic, branched or unbranched, substituted or unsubstituted alkyl groups; or C1-C 20 Ring or C1~C 20 Acyclic, branched or unbranched, substituted or unsubstituted alkenyl groups; or C1-C 20 Branched chain or C1~C 20The unbranched, substituted or unsubstituted cycloalkyl-containing groups, phenyl-containing groups, or heterocyclic-containing groups are independently selected (i.e., they may be the same or different from one another).

[0063] A very suitable electrolyte solvent is C3-C 10 Examples of cycloalkyl organic carbonates include propylene carbonate (C4H6O3) (PC) and ethylene carbonate (C3H4O3) (EC). Propylene carbonate (C4H6O3) exhibits particularly good affinity and high solubility with electrode materials, a broad liquidus range, and its high boiling point also makes this solvent advantageous for use in sodium-ion batteries. Other very suitable organic carbonate compounds include diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylene carbonate (EC), ethylmethyl carbonate (EMC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC).

[0064] The advantageous electrolyte composition of the present invention may include a solvent system containing propylene carbonate in an amount of 20% by weight or more, preferably 25% by weight or more, of the solvent system.

[0065] Preferably, the non-aqueous electrolyte composition of the present invention comprises a mixture of solvents. Particularly preferred solvent systems may include a mixture of solvents comprising propylene carbonate (PC) and further solvents selected from the group consisting of ethylene carbonate (EC), diethyl carbonate (DEC), and hydrofluoroalkyl ethers, such as 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE).

[0066] Therefore, in a preferred embodiment, the solvent system includes a mixture of solvents comprising propylene carbonate and a further solvent selected from the group consisting of ethylene carbonate (EC) and diethyl carbonate (DEC). Thus, this includes a mixture of two solvent components (e.g., propylene carbonate and ethylene carbonate (EC), or propylene carbonate and diethyl carbonate (DEC)) or a mixture of three solvent components (e.g., propylene carbonate, ethylene carbonate (EC), and diethyl carbonate (DEC)).

[0067] Preferably, the solvent system comprises a mixture of ethylene carbonate (EC), diethyl carbonate (DEC), and propylene carbonate (PC), the mixture ideally having a weight ratio in the range of 1-4:1-10:1-10 wt / wt, more ideally 1-2:1-5:1-2 wt / wt, and most preferably 1:2:1 wt / wt (EC:DEC:PC).

[0068] In another embodiment, the solvent system comprises propylene carbonate (PC) and diethyl carbonate (DEC). Preferably in this embodiment, the solvent system contains propylene carbonate (PC) in an amount greater than 55% to less than 100% by weight of the solvent system, and diethyl carbonate (DEC) in an amount greater than 0% to less than 45% by weight of the solvent system. Most preferably in this embodiment, propylene carbonate (PC) is present in an amount of about 76% by weight of the solvent system. Ideally, diethyl carbonate (DEC) is present in an amount of about 20% by weight of the solvent system.

[0069] In a preferred alternative embodiment, the solvent system comprises a mixture of solvents including propylene carbonate (PC) and a hydrofluoroalkyl ether, such as 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE). Preferably in this embodiment, the solvent system contains propylene carbonate (PC) in an amount greater than 55% to less than 100% by weight of the solvent system, and a hydrofluoroalkyl ether, such as 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE), in an amount greater than 0% to less than 45% by weight of the solvent system. Most preferably in this embodiment, propylene carbonate (PC) is present in an amount of about 77% by weight of the solvent system, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE) is present in an amount of about 20% by weight of the solvent system.

[0070] In a more preferred alternative embodiment, the solvent system comprises fluoroethylene carbonate (FEC) and a phosphate solvent, such as triethyl phosphate (TEP). Preferably in this embodiment, the solvent system contains fluoroethylene carbonate (FEC) in an amount of more than 1% to less than 60% by weight of the solvent system, and a hydrofluoroalkyl ether, such as 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE) in an amount of more than 40% to less than 99% by weight of the solvent system. Most preferably in this embodiment, fluoroethylene carbonate (FEC) is present in an amount of about 5% by weight of the solvent system. The solvent system comprising fluoroethylene carbonate (FEC) and a phosphate solvent, such as triethyl phosphate (TEP), may also preferably contain a hydrofluoroalkyl ether, such as 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE). Most preferably in this embodiment, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE) is present in an amount of about 20% by weight of the solvent system.

[0071] In addition, the solvent system of the present invention may also include one or more performance additives, which are different from one or more sacrificial sodium salts. In particular, when the present invention includes one or more solvents as the first component of the solvent system, one or more performance additives may be included as the second component of the solvent system of the present invention.

[0072] One or more performance additives (in addition to one or more sacrificial salts of the present invention) enable the formation of a stable cathode-electrolyte interface (CEI) at the cathode and / or a stable solid-electrolyte interface (SEI) at the anode, or result in improved wettability of the electrolyte in the separator and / or electrode material by reducing the surface tension of the solvent system and / or by a surface adsorption effect that can efficiently form an artificial SEI / CEI layer, which results in advantages such as improved Coulomb efficiency and improved cathode discharge capacity. Addition of one or more performance additives (in addition to one or more sacrificial salts of the present invention) to the non-aqueous electrolyte composition of the present invention can further improve the electrolyte performance due to unexpected synergistic effects (e.g., with one or more sacrificial sodium salts of the present invention).

[0073] One or more performance additives as the second component of the solvent system are preferably selected from sulfur-containing compounds, boron-containing compounds, and surfactants. Ideally, these compounds are not sodium salts. Therefore, one or more performance additives are ideally sodium salt-free.

[0074] Furthermore, unlike the pre-sodium reagents of the present invention, which ideally include one or more sacrificial sodium salts that irreversibly provide sodium ions to the anode during the charging of the electrochemical cell, these one or more performance additives are not intended (i.e., do not provide) sodium ions to the anode during the charging of the electrochemical cell.

[0075] One or more performance additives may be present as a second component of the solvent system in an amount greater than 0.5% by weight but less than or equal to 10% by weight of the solvent system. To avoid any doubt, the term "weight of the solvent system" as used herein means the weight of the first component of the solvent system, combined with the weight of the second component of the solvent system.

[0076] The second component of the solvent system may include two or more performance additives. The addition of two or more performance additives (in addition to one or more sacrificial salts of the present invention) to the non-aqueous electrolyte composition of the present invention can further improve the electrolyte performance due to unexpected synergistic effects (e.g., with one or more sacrificial salts of the present invention). The two or more performance additives may be present as the second component of the solvent system in an amount greater than 0.5% by weight and less than or equal to 10% by weight of the solvent system.

[0077] For example, two or more performance additives, which are the second components of a solvent system, may include a mixture of boron-containing compounds and surfactants. That is, one or more boron-containing compounds can be mixed with one or more surfactants to produce a mixture of two or more performance additives. Alternatively, two or more performance additives, which are the second components of a solvent system, may include a mixture of sulfur-containing compounds and surfactants. That is, one or more sulfur-containing compounds can be mixed with one or more surfactants to produce a mixture of two or more performance additives.

[0078] The second component of the solvent system, consisting of two or more performance additives, may include a mixture of sulfur-containing compounds in an amount of about 2% by weight of the solvent system, and a surfactant in an amount of about 1% by weight of the solvent system. This combination of two or more performance additives as the second component of the solvent system is particularly preferred when used in combination with a solvent system containing propylene carbonate (PC) and diethyl carbonate (DEC).

[0079] Preferably, the second component of the solvent system may include three or more performance additives. The addition of three or more performance additives (in addition to one or more sacrificial salts of the present invention) to the non-aqueous electrolyte composition of the present invention can further improve the electrolyte performance due to unexpected synergistic effects (e.g., with one or more sacrificial salts of the present invention). The three or more performance additives may be present as the second component of the solvent system in an amount of more than 0.5% to 10% by weight of the solvent system.

[0080] For example, the three or more performance additives, which are the second components of the solvent system, may include sulfur-containing compounds, boron-containing compounds, and surfactants. That is, one or more sulfur-containing compounds can be mixed with one or more sulfur-containing compounds, one or more boron-containing compounds, and one or more surfactants to produce a mixture of three or more performance additives.

[0081] The second component of the solvent system, consisting of three or more performance additives, may include a mixture of sulfur-containing compounds in an amount of approximately 1% by weight of the solvent system, a boron-containing compound in an amount of approximately 1% by weight of the solvent system, and a surfactant in an amount of approximately 1% by weight of the solvent system.

[0082] The use of three or more performance additives as the second component of the solvent system is particularly preferred when used in conjunction with a solvent system that includes a mixture of solvents containing propylene carbonate (PC) and hydrofluoroalkyl ethers, such as 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE).

[0083] The second component of the solvent system, consisting of three or more performance additives, may alternatively include a mixture of sulfur-containing compounds in an amount of about 2% by weight of the solvent system, a boron-containing compound in an amount of about 1% by weight of the solvent system, and a surfactant in an amount of about 1% by weight of the solvent system. This combination of three or more performance additives as the second component of the solvent system is particularly preferred when used in conjunction with a solvent system containing propylene carbonate (PC) and diethyl carbonate (DEC).

[0084] One or more surfactants used in the second component of the solvent system according to the present invention are performance additives, preferably selected to enhance the ability of the electrolyte composition to wet separators (particularly polyolefin separators) and / or battery electrodes, which advantageously promotes a longer battery cycle life. Furthermore, it is known in the literature that surfactants can result in non-dendritic metal plating / metal elution (and also inhibit corrosion) due to their surface adsorption on various substrates. Preferred one or more surfactant additives are selected from anionic surfactants, cationic surfactants, nonionic (hydrophilic) surfactants, and amphoteric (zwitterionic) surfactants, with anionic and nonionic (hydrophilic) surfactants being particularly preferred. Ideally, one or more of these surfactant additives are selected from the following:

[0085] 1) Anionic (negatively charged) surfactants. Preferred examples include carboxylates (e.g., alkyl carboxylates (e.g., fatty acid salts)), fluorinated carboxylate surfactants; sulfates (e.g., alkyl sulfates (e.g., sodium lauryl sulfate), alkyl ether sulfates (e.g., sodium laureth sulfate)); sulfonates (e.g., docusate (e.g., sodium dioctyl sulfosuccinate) and alkylbenzene sulfonates); and monophosphate or diphosphate esters (e.g., alkylaryl ether phosphates and alkyl ether phosphates);

[0086] 2) A zwitterionic (amphoteric) surfactant that can be anionic, cationic, or nonionic depending on the pH of the solution in which the surfactant is present. An example is RN + H2CH2COO - , RN + (CH3)2CH2CH2SO3 - Examples include phospholipids (e.g., phosphatidylcholine (lecithin));

[0087] 3) Cationic surfactants that possess a positive charge, for example, RN + H3Cl- , RN + (CH3)3Cl - , diotadecyl dimethylammonium chloride, cetylpyridinium chloride, benzalkonium chloride, hexadecyltrimethylammonium hexafluorophosphate, hexadecyltrimethylammonium chloride (CTAC), and hexadecyltrimethylammonium bromide (CTAB); and 4) Nonionic surfactants. These are uncharged and include, for example, trialkyl phosphates, polyol esters (e.g., glycols, glycerol esters, sorbitan, and sorbitan derivatives, e.g., fatty acid esters of sorbitan (Spans) and their ethoxylated derivatives (Tweens)), polyoxyethylene esters, and poloxamers.

[0088] Poloxamers may include block copolymers, such as poloxamer 84, poloxamer 105, poloxamer 123, poloxamer 124, poloxamer 188, poloxamer 237, poloxamer 338, poloxamer 407, and poloxamer F127.

[0089] Most preferably, the one or more surfactants used in the second component of the solvent system according to the present invention contain one or more nonionic block copolymer-containing surfactants. A very preferred example is poloxamer. A very detailed example is poloxamer 123.

[0090] As described above, the second component of the solvent system according to the present invention may include one or more sulfur-containing compounds. The one or more sulfur-containing compounds of the present invention may be defined as described herein.

[0091] One or more sulfur-containing compounds used in the second component of the solvent system according to the present invention are performance additives, preferably selected to enable the formation of a stable cathode-electrolyte interface (CEI) at the cathode and / or a stable solid-electrolyte interface (SEI) at the anode, which results in advantages such as improved first-cycle Coulomb efficiency (FCE) and increased cycle life; or the additive may decompose significantly preferentially in the first cycle, which may result in lower first-cycle efficiency but improve subsequent charge-discharge cycle stability.

[0092] Suitable sulfur-containing compounds may include cyclic sulfur-containing compounds and / or acyclic sulfur-containing compounds. Preferably, the sulfur-containing compound is a sulfone-containing compound, a sulfate-containing compound, or a sulfonate-containing compound.

[0093] In other words, sulfur-containing compounds can have a sulfonyl functional group bonded to two carbon atoms (sulfone), a sulfonyl functional group bonded to two oxygen atoms (sulfate), or a sulfonyl functional group bonded to one carbon atom and one oxygen atom in a cyclic or acyclic structure (sulfonate). When the sulfonate is cyclic, the compound may be called a sultone.

[0094] As used herein, the term "sulfone" means that a central hexavalent sulfur atom is double-bonded to each of two oxygen atoms and has single bonds to each of two carbon atoms.

[0095] As used herein, the term "sulfate" means that the central hexavalent sulfur atom is double-bonded to two of the oxygen atoms and has single bonds to the other two oxygen atoms, each of which is further single-bonded to a carbon atom.

[0096] As used herein, the term "sulfonate" means a sultone in which a central hexavalent sulfur atom is double-bonded to two of the oxygen atoms, has a single bond to one carbon atom and another single bond to the other oxygen atom, which is further single-bonded to the carbon atom and cyclically linked to the other carbon atom bonded to the sulfur atom.

[0097] The general formula for such compounds is RY(S=O)2Y'R', where: Y and Y' are independently selected from C or O (i.e., they may be the same or different from each other); If Y and Y' are the same, R and R' may independently be selected from any linear or branched substituted or unsubstituted C1-C6 alkyl group; a linear or branched substituted or unsubstituted C1-C6 alkenyl group; or a linear or branched substituted or unsubstituted C1-C6 alkoxy group (i.e., they may be the same or different from each other); or R and R' may independently or together form a substituted or unsubstituted C3-C6 cycloalkyl-containing group, a phenyl-containing group, or a heterocyclic-containing group; If Y and Y' are different from each other, R' may independently be selected from any linear or branched substituted or unsubstituted C1-C6 alkyl group; a linear or branched substituted or unsubstituted C1-C6 alkenyl group; or a linear or branched substituted or unsubstituted C1-C6 alkoxy group; or R and R' may independently or together form a substituted or unsubstituted C3-C6 cycloalkyl-containing group, a cycloalkenyl-containing group, a phenyl-containing group, or a heterocyclic-containing group. In some embodiments, the general formula of such compounds is R-SO2-R', where R and R' may independently be selected from any linear or branched substituted or unsubstituted C1-C6 alkyl group; a linear or branched substituted or unsubstituted C1-C6 alkenyl group; or a linear or branched substituted or unsubstituted C1-C6 alkoxy group (i.e., they may be the same or different from one another); or R and R' may independently or together form a substituted or unsubstituted C3-C6 cycloalkyl-containing group, a phenyl-containing group, or a heterocyclic-containing group.

[0098] Preferably, the general formula of such compounds is RO(S=O)2OR', where R and R' may independently be selected from any linear or branched substituted or unsubstituted C1-C6 alkyl group; linear or branched substituted or unsubstituted C1-C6 alkenyl group; or linear or branched substituted or unsubstituted C1-C6 alkoxy group (i.e., they may be the same or different from each other); or R and R' may independently or together form a substituted or unsubstituted C3-C6 cycloalkyl-containing group, a phenyl-containing group, or a heterocyclic-containing group.

[0099] More preferably, the sulfur-containing compound is selected from cyclic sulfates (e.g., 1,3-propanediol cyclic sulfate (PCS), also known as 1,3,2-dioxathiane 2,2-dioxide (DTD or (CH2)3SO4)); 1,5,2,4-dioxadithiane 2,2,4,4-tetraoxide; or 1,3,2-dioxathiolane 2,2-dioxide.

[0100] Suitable examples of cyclic sulfones include sulfolane ((CH2)4SO2), 3-methylsulfolane ((CH3)CH(CH2)3SO2), and trimethylsulfone ((CH2)3SO2). A suitable example of an acyclic sulfone is methylphenylsulfone ((CH3)(C6H5)SO2).

[0101] Preferred examples of sultones include 1-propene-1,3-sultone ((CH)2CH2SO3) and 1,3-propane-sultone (CH2)3SO3.

[0102] Most preferably, the sulfur-containing compound is 1,3-propanediol cyclic sulfate (PCS).

[0103] As described above, the second component of the solvent system according to the present invention may include one or more boron-containing compounds. The one or more boron-containing compounds of the present invention may be defined as described herein.

[0104] The boron-containing compound used in the second solvent component of the solvent system according to the present invention is a performance additive, preferably selected to enable the formation of a stable cathode-electrolyte interface (CEI) at the cathode and / or a stable solid-electrolyte interface (SEI) at the anode, which results in advantages such as improved Coulomb efficiency and / or increased cycle life of the first cycle.

[0105] Suitable boron-containing compounds may include cyclic boron-containing compounds and / or acyclic boron-containing compounds. Preferably, one or more boron-containing compounds are borates or boroxines.

[0106] In other words, one or more boron-containing compounds can have a central boron atom bonded to three oxygen atoms, each of which is further single-bonded to a carbon or silicon atom (borate). Alternatively, one or more boron-containing compounds can include a six-membered heterocyclic structure composed of three alternating boron and oxygen atoms linked together by shared single bonds. Each boron atom is further single-bonded to an outer carbon or oxygen atom of the heterocyclic structure.

[0107] As used herein, the term "borate" means a central trivalent boron atom that is single-bonded to three oxygen atoms, each of which is further single-bonded to either a carbon or silicon atom.

[0108] As used herein, the term "boroxine" refers to a six-membered heterocyclic compound composed of alternating trivalent boron atoms and divalent oxygen atoms, each boron atom being further single-bonded to an outer oxygen or carbon atom of the heterocyclic structure.

[0109] The general formula for these borate compounds is B(OYR)3, where Y and R may be the same or may vary depending on the individual bond. For more details, see below. It may also be written as B(OYR)(OY'R')(OY''R''), and in the formula, Y, Y', and Y'' are independently selected from C or Si (i.e., they may be the same or different from one another), R, R', and R'' can be independently selected from: hydrogen; any linear or branched substituted or unsubstituted C1-C6 alkyl group; linear or branched substituted or unsubstituted C1-C6 alkenyl group; linear or branched substituted or unsubstituted C1-C6 alkoxy group; or a substituted or unsubstituted C3-C6 cycloalkyl-containing group, phenyl-containing group, or heterocyclic-containing group.

[0110] More preferably, the boron-containing compound is selected from acyclic borates. A suitable example is tris(trimethylsilyl) borate (TMSB), Tris(2,2,2-trifluoroethyl) borate, Trimethyl borate, and Triethyl borate These are some examples.

[0111] The general formula for these boroxine compounds is B3(YR)3O3, where Y and R may be the same or may vary depending on the individual bond. For more details, see below. B a (YR) b (O) c It may also be written as, during the ceremony, Y is independently selected from C or O (i.e., they may be the same or different from each other), R may be the same or may vary in each individual bond, and can be independently selected from: hydrogen; any linear or branched, substituted or unsubstituted C1-C6 alkyl group; linear or branched, substituted or unsubstituted C1-C6 alkenyl group; linear or branched, substituted or unsubstituted C1-C6 alkoxy group; or a substituted or unsubstituted C3-C6 cycloalkyl-containing group, phenyl-containing group, or heterocyclic-containing group. a=b=c, and a, b, and c are each 3.

[0112] Suitable examples include trimethoxyboroxine and trimethylboroxine. Most preferably, the boron-containing compound is tris(trimethylsilyl) borate (TMSB).

[0113] In a preferred embodiment, the non-aqueous electrolyte composition of the present invention further comprises one or more sodium-containing salts in addition to the pre-sodium reagent according to the present invention. Such additional salts may be considered as “primary salts”.

[0114] More specifically, unlike the pre-sodium treatment reagents of the present invention which ideally include one or more sacrificial sodium salts that irreversibly provide sodium ions to the anode during the charging of the electrochemical cell, these additional one or more sodium-containing salt anions are not (i.e., do not) intended to irreversibly provide sodium ions to the anode during the charging of the electrochemical cell. In particular, these additional one or more sodium-containing salt anions are not (i.e., do not) intended to decompose (e.g., be oxidized) to provide sodium ions to the anode during the charging of the electrochemical cell.

[0115] Instead, these additional sodium-containing salts are, ideally, intended to facilitate the movement of sodium ions in the electrochemical cell (e.g., from cathode to anode). More ideally, unlike the pre-sodium reagents of the present invention which include one or more sacrificial sodium salts containing one or more anions that oxidize during the charging of the electrochemical cell, one or more sodium-containing salts (in addition to the one or more sacrificial sodium salts of the present invention) are, ideally, substantially free of one or more anions that oxidize during the charging of the electrochemical cell. However, as long as such one or more sodium-containing salts contain one or more anions that do not oxidize during the charging of the electrochemical cell, they will not oxidize in the conventionally assumed amounts and thus benefit the electrochemical cell capacity.

[0116] Therefore, these additional (primary) sodium-containing salts may be described as one or more (primary) non-sacrificial sodium salts.

[0117] In one embodiment, one or more non-sacrificial sodium-containing salts do not substantially decompose during charging of the electrochemical cell at voltages of 1V to 4.3V, preferably 1V to 4.2V. That is, substantial oxidation of one or more anions of one or more non-sacrificial sodium-containing salts does not occur (ideally, no oxidation occurs at all) when the electrochemical cell is operated within this voltage range. Typically, substantial oxidation of non-sacrificial salts does not occur when the cell is charged above 3V, and in some cases above 4V.

[0118] Ideally, during the charging of the electrochemical cell, the oxidation of one or more anions of one or more non-sacrificial sodium-containing salts is limited to about 5% or less, preferably about 3% or less, very preferably about 1% or less, and most preferably 0% (no oxidation occurs).

[0119] Therefore, the anions of one or more non-sacrificial sodium-containing salts do not substantially decompose (ideally not decompose at all) during charging of the electrochemical cell at voltages greater than 3V and up to 4.3V, preferably between 3V and 4.2V. In some cases, the anions of one or more non-sacrificial sodium-containing salts do not substantially decompose during charging of the electrochemical cell at voltages between 4V and 4.3V, preferably between 4V and 4.2V.

[0120] These one or more non-sacrificial sodium-containing salts (in addition to the one or more sacrificial sodium salts of the present invention) are one or more of the formula NaM m X x Compounds of the formula NaXO4; sodium salts of one or more fluorosulfonyl-containing compounds; sodium salts of one or more fluorosulfonate-containing compounds; sodium salts of one or more oxalatoborate compounds; sodium salts of one or more difluoro-oxalatoborate compounds; and tetrakis[3,5-bis(trifluoromethyl)phenylborate anion (B[3,5-(CF3)2C6H3] - 4) Tris(pentafluorophenyl)borate anion (B(C6F5)- 4), and tetrakiscarboxy(trifluoromethyl)aluminate anion (Al[OC(CF3)3] - 4) One or more compounds containing tetrahedral anions can be selected.

[0121] Preferably, one or more non-sacrificial sodium-containing salts are one or more of the formula NaM m X x [wherein M is one or more metals and / or nonmetals, and X is selected from compounds comprising one or more halogens; sodium salts of one or more fluorosulfonyl-containing compounds; sodium salts of one or more fluorosulfonate-containing compounds; sodium salts of one or more oxalatoborate compounds; and sodium salts of one or more difluoro-oxalatoborate compounds or groups composed thereof].

[0122] Preferred one or more formulas NaM m X x In the non-sacrificial sodium-containing salt of NaM, M is one or more metals and / or nonmetals, and X is preferably a group containing or composed of one or more halogens selected from fluorine, chlorine, bromine, and iodine, and more preferably a group containing or composed of fluorine. The amount x of halogen X is preferably x=1 to 16, and more preferably x=4 or 6. The amount m of one or more metals M and / or nonmetals M is preferably m=1 to 3, more preferably m=1 to 2, and particularly preferably m=1. Ideally, one or more metals M and / or nonmetals M are preferably selected from aluminum, boron, gallium, indium, iridium, platinum, scandium, yttrium, lanthanum, antimony, arsenic, and phosphorus. Particularly preferably, M is selected from aluminum, boron, gallium, phosphorus, and arsenic. General formula NaM n X xThe most preferred sodium-containing salt is one or more selected from sodium tetrafluoroborate (NaBF4) and sodium hexafluorophosphate (NaPF6).

[0123] In preferred sodium compounds of the formula NaXO4, element X is preferably one or more halogens selected from fluorine, chlorine, bromine, and iodine. Chlorine is particularly preferred, and the most preferred sodium-containing salt of the formula NaXO4 is NaClO4.

[0124] Preferred non-sacrificial sodium salts of one or more fluorosulfonyl-containing compounds include sodium bis(fluorosulfonyl)imide, also known as NaFSI(NaN(SO2F)2), and sodium bis(trifluoromethanesulfonyl)imide, also known as NaTFSI(C2F6NNaO4S2). Preferred sodium salts of one or more fluorosulfonate-containing compounds include sodium trifluoromethanesulfonate, also known as sodium triflate or NaOTf(CF3NaSO3), when used in a cell at a voltage <4.0V. Preferred sodium salts of one or more oxalate borate compounds include sodium bis(oxalate), also known as borate NaBOB or NaB(C2O4)2, and sodium difluoro(oxalato)borate, also known as NaDFOB.

[0125] Very preferably, one or more non-sacrificial sodium-containing salts are selected from sodium hexafluorophosphate (NaPF6), sodium bis(fluorosulfonyl)imide (NaFSI), and sodium bis(trifluoromethanesulfonyl)imide (NaTFSI). Most preferably, one or more non-sacrificial sodium-containing salts include sodium hexafluorophosphate (NaPF6).

[0126] As an alternative or additional, highly preferred non-sacrificial sodium-containing salt may include sodium tetrafluoroborate (NaBF4).

[0127] Certain salts that are non-sacrificial when charge-discharge cycles are performed up to a certain maximum voltage are understood to be sacrificial when charge-discharge cycles are performed up to a voltage exceeding the operating voltage. One such example is sodium triflate or NaOTf(CF3NaSO3). For instance, substantial oxidation of the anion in NaOTf occurs when the electrochemical cell is charged above 4V, as demonstrated herein.

[0128] As used herein, the terms “non-sacrificial sodium-containing salt” or “primary sodium-containing salt” refer to any sodium-containing salt containing anions that are substantially non-decomposing (i.e., substantially non-oxidizing) (including not decomposing at all) at the cell potential as defined herein. In this regard, the decomposition potential of one or more non-sacrificial sodium salts should ideally be higher than the upper cutoff voltage of the electrochemical cell. As indicated above, the ideal upper cutoff voltage of an electrochemical cell (preferably a sodium ion cell) is about 4.5V or about 4.3V. The most preferred upper cutoff voltage of an electrochemical cell (preferably a sodium ion cell) is about 4.2V, and optionally about 3.75V.

[0129] Therefore, anions of non-sacrificial (primary) sodium-containing salts should not substantially decompose (e.g., not be oxidized) when undergoing charge-discharge cycles in an electrochemical cell up to an upper cutoff voltage of 3.75 V, ideally up to approximately 4.2 V. In some cases, anions of non-sacrificial (primary) sodium-containing salts should not decompose (e.g., not be oxidized) when undergoing charge-discharge cycles in an electrochemical cell up to an upper cutoff voltage of 4.3 V or approximately 4.5 V.

[0130] It is convenient to express the amount of one or more sodium-containing salts (in addition to the one or more sacrificial sodium salts of the present invention) in terms of their molar concentration in the solvent system; that is, the total number of moles of one or more sodium-containing salts (i.e., solutes) per kilogram of solvent system - i.e., moles / kg.

[0131] One or more sodium-containing salts (in addition to the one or more sacrificial sodium salts of the present invention) may be present at a concentration of about 0.1 mol / kg to about 5 mol / kg, more preferably about 0.3 mol / kg to about 5 mol / kg, more preferably about 0.1 mol / kg to about 2.5 mol / kg or less, and most preferably about 0.3 mol / kg to about 2.5 mol / kg. Very preferably, especially when the component is NaPF6, the molar concentration is about 0.1 mol / kg to about 2.5 mol / kg, ideally about 0.3 mol / kg to about 1.5 mol / kg, and most preferably about 0.5 mol / kg to about 1 mol / kg.

[0132] The total molar concentration of one or more sacrificial sodium salts of the present invention and one or more additional sodium-containing salts as defined above is preferably about 0.1 mol / kg to about 5 mol / kg, more preferably about 0.3 mol / kg to about 5 mol / kg, more preferably about 0.3 mol / kg to about 3 mol / kg, and most preferably about 0.4 mol / kg to about 1.5 mol / kg.

[0133] Very preferably, when the present invention comprises a mixture of NaSCN and NaPF6, the total molar concentration is about 0.3 mol / kg to about 2 mol / kg, ideally about 0.4 mol / kg to about 1.5 mol / kg, and most preferably less than about 0.5 mol / kg to 1.5 mol / kg.

[0134] Very preferably, when the present invention comprises a mixture of NaSCN and NaFSI, the total molar concentration is about 0.3 mol / kg to about 2 mol / kg, ideally about 0.4 mol / kg to about 1.5 mol / kg, and most preferably less than about 0.5 mol / kg to 1.5 mol / kg.

[0135] The non-aqueous electrolyte compositions of the present invention are particularly useful in electrochemical cells. Therefore, in a further embodiment, the present invention provides an electrochemical cell comprising a non-aqueous electrolyte composition as defined herein.

[0136] The electrolyte compositions of the present invention are particularly useful in sodium ion cells, most preferably in sodium ion full cells (not sodium metal half cells). Accordingly, in a further embodiment, the present invention provides a sodium ion cell comprising a non-aqueous electrolyte composition as defined herein. Preferably, the sodium ion cell comprises a negative electrode, a positive electrode, and a non-aqueous electrolyte composition as defined herein.

[0137] The sodium ion cell disclosed herein may also include an anode (negative) electrode comprising an anode current collector and / or a cathode (positive) electrode comprising a cathode current collector. The cathode current collector, the anode current collector, or both the cathode and anode current collectors may be formed from aluminum or an aluminum alloy (e.g., an alloy of aluminum with one or more of Mg, Mn, Cr, Zn, Si, Fe, and Ni). Preferably, the anode current collector comprises an aluminum current collector. Very preferably, both the cathode and anode current collectors comprise aluminum current collectors. Alternatively, copper, magnesium, carbon paper / carbon foil / carbon substrates, and tin may also be used as current collector materials.

[0138] Preferably, the anode (negative) current collector also includes one or more carbon-containing layers formed on one or more surfaces of the anode current collector prior to the first charging cycle of the sodium ion cell. These layers may ideally include amorphous carbon (e.g., carbon black such as TIMCAL Super C65) having a thickness of about 10 angstroms to about 1000 μm.

[0139] Alternatively, the anode (negative) current collector disclosed herein does not have one or more carbon-containing layers on one or more surfaces of the anode current collector prior to the first charging cycle of the sodium ion cell. Therefore, the anode current collector is in its "initial state" prior to the first charging cycle of the sodium ion cell. When used herein with respect to a current collector, the term "initial state" means that the current collector is in its "as-made" state prior to the first charging cycle of the sodium ion cell. In other words, the anode current collector is essentially the pure material on which it was formed, free from impurities (e.g., surface oxide layers). Therefore, the anode current collector is not coated with one or more carbon-containing layers (as described above), conventional active materials, binders, etc.

[0140] The sodium ion cell disclosed herein may also include a separator located between the cathode current collector and the anode current collector. A polyolefin separator is preferred.

[0141] The anode (negative) electrode of the sodium ion cell according to the present invention preferably further comprises a polymer binder. Typically, the polymer binder is selected from polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), and carboxymethylcellulose (CMC). Preferably, the polymer binder comprises carboxymethylcellulose (CMC). Very preferably, the polymer binder comprises a mixture of styrene-butadiene rubber (SBR) and carboxymethylcellulose (CMC).

[0142] The anode (negative) electrode of the sodium ion cell according to the present invention ideally comprises a negative electrode active material (A), one or more polymer binders (B), and one or more conductive additives (C). These mixtures are typically mixed with an aqueous or non-aqueous solvent (e.g., water or N-methylpyrrolidone (NMP)) and then deposited as a layer or thin film on one or more surfaces of the anode current collector by techniques such as the doctor blade method or the slot die method.

[0143] Typically, A:B:C exists in a weight ratio of (80-98):(1-19):(1-19), and ideally in a weight ratio of (85-98):(1-9):(1-9). When the polymer binder contains polyvinylidene fluoride (PVDF), A:B:C is preferably present in a weight ratio of about 88:9:3. When the polymer binder preferably contains carboxymethylcellulose (CMC), and very preferably contains a mixture of styrene-butadiene rubber (SBR) and carboxymethylcellulose (CMC), A:B:C is preferably in a weight ratio of about 95:3.5:1.5.

[0144] One or more conductive additives (C) may include one or more of carbon black, carbon nanotubes, graphene, acetylene black, and carbon nanofibers. Preferably, one or more conductive additives include carbon black such as TIMCAL Super C65.

[0145] The anode (negative) electrode of the sodium ion cell according to the present invention preferably further comprises a negative electrode active material. For example, the negative electrode comprising the negative electrode active material may include graphite materials, soft carbon, hard carbon, carbon fibers, mesocarbon microbeads, silicon-based materials, tin-based materials, P-based materials, Sb-based materials, SnSb-based materials, other types of materials that store charge by conversion and / or alloying reactions (e.g., oxides such as mono-system / binary / ternary systems of Fe, Cu, Ni, Mn, etc.), and materials that store charge by traditional intercalation reactions, such as lithium titanate, various types of sodium titanate, titania, etc.; as well as mixtures produced by physical blending (e.g., physical mixing such as ball milling or spray drying). Blended together by a method or chemical mixing method, as carbon and Sb, or by in-situ reaction (with or without subsequent heating / thermal decomposition steps, by appropriate synthesis routes such as solvothermal / hydrothermal reactions, sol-gel reactions, solution-system reactions, reflux reactions, coprecipitation reactions, or solid-state reactions), one or more of these precursor materials, such as carbon / Sb, carbon / P, carbon / Fe2O3, the latter may also result in doped materials (e.g., carbon doped with Sb, P, or Sn) and / or substitution materials (e.g., substitution of Fe2O3 with a small amount of TiO2). The anode electrode of the sodium ion cell according to the present invention preferably comprises a negative electrode active material containing hard carbon.

[0146] The non-aqueous electrolyte composition of the present invention is particularly useful in sodium ion cells that use an anode electrode containing a negative electrode active material including a non-graphite carbon-containing material such as hard carbon, or an anode containing a sodium insertion material, or a converted and / or alloyed anode material.

[0147] The cathode (positive) electrode of the sodium ion cell according to the present invention preferably further comprises a polymer binder. Typically, the polymer binder is selected from polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), and carboxymethylcellulose (CMC). Preferably, the polymer binder comprises polyvinylidene fluoride (PVDF).

[0148] The cathode (positive) electrode of the sodium ion cell according to the present invention ideally comprises a positive electrode active material (A), one or more polymer binders (B), and one or more conductive additives (C). These mixtures are typically mixed with an aqueous or non-aqueous solvent (e.g., water or N-methylpyrrolidone (NMP)) and deposited as a layer or thin film on one or more surfaces of the anode current collector by techniques such as the doctor blade method or the slot die method.

[0149] Typically, A:B:C exist in a weight ratio of (80-98):(1-19):(1-19). If the polymer binder contains polyvinylidene fluoride (PVDF), A:B:C are preferably present in a weight ratio of about 89:5:6, or alternatively, 92:4:4.

[0150] One or more conductive additives (C) may include one or more of carbon black, carbon nanotubes, graphene, acetylene black, and carbon nanofibers. Preferably, one or more conductive additives include carbon black such as TIMCAL Super C65.

[0151] The cathode (positive) electrode of the sodium-ion cell according to the present invention preferably further comprises a sodium-containing positive electrode active material tailored to enable insertion / extraction of sodium ions during charging / discharging. Examples of these include transition metal sodium oxides, polyanionic compounds (including fluorinated polyanionic compounds), Prussian blue analogue (PBA) compounds (e.g., Prussian white or Berlin green), substances that store sodium via conversion reactions, sodium transition metal fluorides, oxyfluorides, phosphates, sulfates, and silicates (and their fluorinated forms). A preferred example is transition metal sodium oxide.

[0152] Preferred transition metal sodium oxides have the general formula: A 1±δ M 1 V M 2 W M 3 X M 4 Y M 5 Z O 2-c [In the formula, A is one or more alkali metals selected from sodium, potassium, and lithium, M 1 preferably comprises one or more redox-active metals in the +2 oxidation state, selected from the group consisting of nickel, copper, cobalt, and manganese, M 2 comprises a metal in an oxidation state greater than 0 and up to +4, M 3 comprises a metal in the +2 oxidation state, M 4 comprises a metal in an oxidation state greater than 0 and up to +4, M 5 comprises a metal in the +3 oxidation state, 0≦δ≦1, V>0, W≧0, X≧0, Y≧0, At least one of W and Y is greater than 0, Z ≥ 0, C is in the range 0 ≤ c < 2, V, W, X, Y, Z, and C are selected to maintain electrochemical neutrality. It belongs to them.

[0153] Ideally, metal M 2 It comprises one or more transition metals, preferably selected from manganese, titanium, and zirconium; M 3 is preferably one or more selected from magnesium, calcium, copper, tin, zinc, and cobalt; M 4 preferably comprises one or more transition metals selected from manganese, titanium, and zirconium; M 5 Preferably, it is one or more selected from aluminum, iron, cobalt, tin, molybdenum, chromium, vanadium, scandium, and yttrium.

[0154] A particularly preferred cathode active material for use in sodium ion cells is a nickelate-based material. Sodium-containing active materials having any crystalline structure can be used, preferably the structure being O3 or P2 or a derivative thereof, however, in detail the cathode electrode active material may also contain a mixture of phases, i.e., a heterogeneous structure composed of several different crystalline forms. For example, the cathode active material may contain a compound having the general formula detailed above in a mixture of O3 and P2 phases. The ratio of O3 phase to P2 phase is preferably 1 to 99:99 to 1.

[0155] In another aspect, the present invention also provides the use of a non-aqueous electrolyte composition as defined herein in an electrochemical cell. Ideally, the electrochemical cell is a sodium ion cell, most ideally a sodium ion full cell.

[0156] The present invention also provides the use of one or more sacrificial sodium salts in an electrochemical cell, the use of one or more sacrificial sodium salts as defined herein. Ideally, the electrochemical cell is a sodium ion cell, and most ideally, a sodium ion full cell.

[0157] As described above, most preferably, one or more sacrificial sodium salts include a cyanate-containing compound or a thiocyanate-containing compound. Ideally, one or more sacrificial sodium salts have the general formula NaXCN [wherein X is a group 16 element (from the periodic table), optionally selected from oxygen and sulfur, preferably selected from sulfur]. In one most preferred embodiment, one or more sacrificial sodium salts include sodium thiocyanate (NaSCN).

[0158] Alternatively, or in addition, preferred sacrificial sodium salts may include one or more of sodium triflate (NaSO3CF3), sodium difluorophosphate (NaPO2F2), and sodium tetraphenylborate (NaBPh4).

[0159] In another aspect, the present invention also provides the use of one or more sacrificial sodium salts as defined herein as pre-sodiumization reagents, preferably for use in an electrochemical cell. Ideally, the electrochemical cell is a sodium ion cell, most ideally a sodium ion full cell.

[0160] In another aspect, the present invention also provides the use of a non-aqueous electrolyte composition as defined herein as a pre-sodiumization reagent, preferably for use in an electrochemical cell. Ideally, the electrochemical cell is a sodium ion cell, most ideally a sodium ion full cell.

[0161] The electrochemical cell of the present invention (ideally, the sodium ion cell of the present invention) can be used in energy storage devices, such as batteries, rechargeable batteries, electrochemical devices, and electrochromic devices.

[0162] In another embodiment, the present invention also provides an apparatus comprising an electrochemical cell (ideally a sodium ion cell) as disclosed herein. Typical apparatuses may include devices that can be used in either stationary or mobile applications, such as battery packs.

[0163] In another embodiment, the present invention also provides a method for producing a non-aqueous electrolyte composition as defined herein.

[0164] In another aspect, the present invention also provides an electrochemical cell pre-sodium-treated using a non-aqueous electrolyte composition as defined herein. This is an electrochemical cell pre-sodium-treated by charging with a non-aqueous electrolyte composition as defined herein. In practice, one or more sacrificial sodium salts present in the non-aqueous electrolyte composition as defined herein ideally provide sodium ions to the anode during charging of the electrochemical cell.

[0165] Therefore, more specifically, the present invention provides an electrochemical cell comprising a cathode, an electrolyte, and an anode, wherein the anode is pre-sodium-treated with a non-aqueous electrolyte composition as defined herein.

[0166] In this context, “electrolyte” is understood to mean either or not a non-aqueous electrolyte composition as defined herein. This is because one or more sacrificial sodium salts present in a non-aqueous electrolyte composition as defined herein ideally contain one or more anions that oxidize during the charging of the electrochemical cell. In practice, one or more of these sacrificial sodium salts or some of them are designed to be consumed or disintegrated during the charging of the electrochemical cell.

[0167] Therefore, it is conceivable that, after the anode has been pre-sodium-treated, a different electrolyte (i.e., one different from the non-aqueous electrolyte composition as defined herein) may be used in the electrochemical cell.

[0168] The electrochemical cell is ideally a sodium ion cell, preferably a full sodium ion cell. The ideal upper cutoff voltage for an electrochemical cell (preferably a sodium ion cell) is approximately 4.5V or 4.3V. The most preferred upper cutoff voltage for an electrochemical cell (preferably a sodium ion cell) is approximately 4.2V, and possibly approximately 3.75V.

[0169] The anode and cathode may be defined as shown above. Therefore, the cathode preferably comprises a positive electrode active material containing one or more transition metal sodium oxides. Similarly, the anode preferably comprises a negative electrode active material containing hard carbon. Therefore, the anode comprising the negative electrode active material containing hard carbon is very preferably pre-sodium-treated using a non-aqueous electrolyte composition as defined herein.

[0170] In another embodiment, the present invention also includes a method for forming an electrochemical cell, the method comprising the step of using a non-aqueous electrolyte composition as defined herein.

[0171] Ideally, the method for forming an electrochemical cell is: a) Providing an electrochemical cell with a non-aqueous electrolyte composition as defined herein, b) A step of charging the electrochemical cell to a voltage of 4.5V or less, if applicable. Includes. The electrochemical cell (preferably a sodium ion cell) provided in step a) is usually not pre-charged. That is, step a) usually occurs immediately after the electrochemical cell has been assembled by the manufacturer.

[0172] Step b) includes the step of charging the electrochemical cell from a first voltage to a second voltage, wherein the second voltage is preferably 4.5V or less. The second voltage is higher than the first voltage. The first voltage is usually -0.5V or higher. Ideally, the second voltage is about 2V to about 4.5V.

[0173] The charging step in step b) can be performed at a C rate of approximately 10C to approximately C / 50. The charging step in step b) can be performed at 5C (C / 0.2), 2C (C / 0.5), C / 1, C / 2, C / 5, or C / 50. Ideally, the C rate is approximately C / 1 to approximately C / 10.

[0174] The method may also include step c), which involves discharging the electrochemical cell from a second voltage to a third voltage. The third voltage is typically about 0V to about 3V. The discharging step in step c) may be carried out with a C rate of about C / 0.2(5C) to about C / 50. The discharging step in step c) may be carried out with C / 0.5(2C), C / 1(1C), C / 2, C / 5, or C / 50. Ideally, the C rate is about C / 1 to about C / 10.

[0175] The method may, depending on the circumstances, include a step in which steps b) and c) are repeated one or more times, perhaps two or more times.

[0176] Preferably, the electrochemical cell is charged to a voltage greater than the decomposition potential of one or more anions of one or more sacrificial sodium salts. Thus, one or more anions of one or more sacrificial sodium-containing salts can be substantially decomposed during charging.

[0177] An electrochemical cell can be charged to a voltage exceeding 2V. An electrochemical cell can be charged to a voltage exceeding 3V. An electrochemical cell can be charged to a voltage exceeding 3.5V. An electrochemical cell can be charged to a voltage exceeding 3.8V. An electrochemical cell can be charged to a voltage exceeding 4.0V. Ideally, an electrochemical cell should be charged to a voltage of 4.2V.

[0178] Preferably, the electrochemical cell is charged to a voltage greater than 3V and up to 4.3V, preferably greater than 3V and up to 4.2V. In some cases, the electrochemical cell is charged to a voltage of 4V to 4.3V, preferably 4V to 4.2V.

[0179] In another embodiment, the present invention also includes an electrochemical cell, ideally a sodium ion cell, fabricated by a method defined herein.

[0180] The purpose of the above formation method is to form a stable interface on the surface between the electrode and the electrolyte. Therefore, the formation method may produce gaseous byproducts, which are discharged in a step called the "degassing step" (in cylindrical or rectangular cells) or drawn out through appropriate notches in the packaging (for pouch cells).

[0181] The inventors of this application endeavor to utilize this formation method. In particular, the inventors have found, as shown in the examples disclosed herein, that the sacrificial salt according to the present invention is irreversibly oxidized during the first cycle (which is also the first formation cycle), and therefore any gaseous by-products (if formed) can be removed during the degassing step (which could occur in any case).

[0182] Therefore, it means that the present invention as defined herein exhibits excellent commercial utility without requiring any additional method steps.

[0183] The present invention is discussed herein with respect to the following drawings. [Brief explanation of the drawing]

[0184] [Figure 1]This figure shows a plot of cathode discharge capacity (mAh / g) versus number of cycles for cells using the electrolyte compositions of the present invention (samples TEL22, TEL25b, TEL25c, TEL25d, TEL25e, TEL25g, and TEL25h) compared to the charge-discharge cycle stability of cells using a control electrolyte composition (sample TEL0). [Figure 2] This figure shows a plot of the ratio dQ / dV (mAh / g / V) versus cathode potential (V vs. Na / Na+) for cells using the electrolyte compositions of the present invention (samples TEL25b, TEL25c, and TEL25d, respectively) compared to cells using a control electrolyte composition (sample TEL0). [Figure 3] This figure shows a plot of energy retention rate (%) versus number of cycles for a cell using the electrolyte composition of the present invention (sample TEL25b). [Figure 4] This figure shows a plot of discharge capacity (mAh / g active cathode) versus number of cycles for a cell using the electrolyte composition of the present invention (sample TEL25e) compared to the charge-discharge cycle stability of a cell using a control electrolyte composition (sample TEL0). [Figure 5] This figure shows a plot of discharge capacity (mAh / g) versus number of cycles for a cell using the electrolyte composition of the present invention (sample TEL25e) compared to the charge-discharge cycle stability of a cell using a control electrolyte composition (sample TEL0). [Figure 6] This figure shows a plot of discharge capacity (mAh / g active cathode) versus number of cycles for a cell using the electrolyte composition of the present invention (sample TEL45c) compared to the charge-discharge cycle stability of a cell using a control electrolyte composition (sample TEL42d). [Figure 7] This figure shows a plot of discharge capacity (mAh / g) versus number of cycles for a cell using the electrolyte composition of the present invention (sample TEL45c) compared to the charge-discharge cycle stability of a cell using a control electrolyte composition (sample TEL42d). [Figure 8]This figure shows a plot of cathode specific capacity (mAh / g) versus number of cycles for a cell using the electrolyte composition of the present invention (sample TEL76c) compared to the charge-discharge cycle stability of a cell using a control electrolyte composition (sample TEL67a). [Figure 9] This figure shows a plot of cathode specific capacity (mAh / g) versus number of cycles for a cell using the electrolyte composition of the present invention (sample TEL146a), compared to the charge-discharge cycle stability of a cell using a control electrolyte composition (sample TEL146). [Figure 10] This figure shows a plot of the ratio dQ / dV (mAh / g) versus voltage (V) for cells using the electrolyte composition of the present invention (TEL62a) compared to cells using a control electrolyte composition (sample TEL0). [Figure 11] This figure shows the plot of Figure 10 at cathode potentials of 3.5 to 4.2 V. [Figure 12] This figure shows a plot of the ratio dQ / dV (mAh / g) versus voltage (V) for cells using the electrolyte composition of the present invention (TEL67Ra) compared to cells using a control electrolyte composition (sample TEL67). [Figure 13] This figure shows the plots in Figure 12 at cathode potentials of 3.5 to 4.2 V. [Figure 14] This figure shows a plot of the ratio dQ / dV (mAh / g) versus voltage (V) for a cell using the electrolyte composition of the present invention (TEL79c) compared to a cell using a control electrolyte composition (sample TEL67a). [Examples]

[0185] The electrolyte compositions under study were prepared using the following general procedure. Appropriate amounts of solvent for the desired solvent system were mixed in a glass vial in the desired weight ratio. Depending on the circumstances, one or more performance additives (e.g., one or more surfactants, one or more boron-containing compounds, one or more sulfur-containing compounds, or combinations thereof) were also added to prepare the solvent system. Activated 4A molecular sieves were added to dry the formed solvent system, and finally the solvent system was dried for 18 hours.

[0186] In a separate glass bottle equipped with a magnetic pellet, a pre-sodiumization reagent containing the required weight of NaPF6 salt and one or more sacrificial sodium salts (e.g., NaSCN) was added, followed by the addition of the required amount of the desired solvent system prepared above.

[0187] Next, the electrolyte was stirred with magnetic pellets for more than 18 hours, after which the electrolyte became ready for use.

[0188] The exact composition of each of the electrolyte compositions investigated is detailed in Table 1 below.

[0189] [Table 1]

[0190] To avoid any ambiguity, the concentration expressed by "m" (molar concentration) above relates to the total number of moles of non-sacrificial or sacrificial sodium salts (e.g., NaPF6 or NaSCN) per 1 kg, or 1000 g, of solvent system.

[0191] Additionally, the percentages for various solvent components refer to the total solvent weight and do not include the weight of non-sacrificial or sacrificial sodium salts. Abbreviations used EC = ethylene carbonate, DEC = diethyl carbonate, PC = propylene carbonate, PCS = 1,3-propanediol cyclic sulfate, P123 = poloxamer (Pluronic®) P123, TMSB = tris(trimethylsilyl) borate, HFE = 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, NaSCN = sodium thiocyanate, and NaPF6 = sodium hexafluorophosphate; NaPO2F2 = sodium difluorophosphate; NaBPh4 = sodium tetraphenylborate; and NaFSI = sodium bis(fluorosulfonyl)imide; NaSO3CF3 = sodium triflate; TEP = triethyl phosphate; and FEC = fluoroethylene carbonate; Please note that in Table 1 above, the weight percentages of various solvents and / or performance additives refer to the total weight of the solvent system (which does not consider the weight(s) of one or more non-sacrificial or sacrificial sodium salts). General procedure for making a hard carbon sodium ion cell All cells were tested as Na ion pouch cells.

[0192] The electrolyte was prepared as follows: First, the cosolvent was mixed in a glass vial in the desired weight ratio. To dry the solvent mixture, activated 4A molecular sieves were added, and finally the solvent mixture was dried for 18 hours. In a separate glass vial equipped with a magnetic pellet, the required weight of the non-sacrificial salt (e.g., NaPF6) and sacrificial salt (e.g., NaSCN) was added, followed by the required amount of the required solvent mixture. The salt and solvent mixture was magnetically stirred for at least 18 hours, after which the resulting electrolyte was ready for use.

[0193] The cathode consisted of an O3 / P2 nickelate oxide material as the cathode active material, PVDF as the binder, and C65 as the conductive additive, coated onto a C-coated current collector, in a weight ratio of 89:06:05. This formulation was used for all cells shown in Experiments 1 and 2.

[0194] In an alternative embodiment, the cathode formulation was active material:PVDF binder:C65 = 92:04:04 wt / wt. This formulation was used for all cells shown in Experiments 0, 3, 4, and 5. The anode contained type 1 hard carbon as the active material, PVDF as the binder, and C65 as the conductive additive in a weight ratio of 88:09:03. This formulation was used for all cells shown in Experiments 1 and 2. In an alternative embodiment, the anode used an aqueous CMC-SBR binder, and in this embodiment, the weight ratio of type 1 hard carbon:(CMC-SBR):C65 was 95:3.5:1.5. This formulation was used for all cells shown in Experiments 0, 3, 4, and 5.

[0195] Aluminum tabs were connected to each electrode, and the cells were placed in polymer-coated aluminum pouches. After coating the cathode and anode, they were punched out to the desired dimensions. The coating weights of the cathode and anode are referred to as GSM values ​​(grams per square meter). "C / A" refers to the mass ratio of the cathode active material to the anode active material in each coating.

[0196] The separator used was a typical polyolefin separator commonly used in any type of rechargeable lithium-ion or sodium-ion battery, e.g., Celgard 2500. Inside the glove box, the cathode / separator / anode assembly was placed in a pouch with two Al-based connecting tabs that functioned as terminals, and filled with the above liquid electrolyte in amounts typical of lithium-ion or sodium-ion cells containing such polyolefin separators. These pouch cells were then sealed inside the glove box and taken out for cell testing.

[0197] In some examples (cells A3PC76, A3PC253, A3PC258, and A3PC272 in Experiment 1), three-electrode (3E) full cells were fabricated. These 3E cells are essentially the same as 2E full cells in that they include a cathode and anode, but also a third reference electrode to which a piece of Na metal is attached, allowing the individual potentials of the cathode and anode to be tracked (vs. Na / Na). + (Redox pair). This 3E cell was fabricated using two separator layers, with the Na metal inserted between the two separators outside the installation area of ​​the cathode / anode stack. Details of the 3E cell design are mentioned in the following prior art: Rudola et al., J. Electrochem. Soc., 2021, 168(11), 110534.

[0198] Cell test The cells were tested using constant-current (galvanostatic) charge-discharge cycling techniques. Generally, the cells were first charged in constant-current (CC) mode to a predetermined maximum voltage limit. Subsequently, as shown in the examples, the cells were subjected to a constant-voltage (CV) step at their maximum voltage limit for a predetermined time, or this CV step was sustained until the current dropped to a predetermined value. In some examples, the cells were subjected to a series of different CC modes to various voltage values ​​before undergoing a CV step at only the maximum voltage value. As shown, the discharge process was carried out in CC mode down to the lower cutoff voltage, or in constant-power (CP) mode.

[0199] A commercially available battery cycler from MTI Inc. (Richmond, CA, USA) or Maccor (Tulsa, OK, USA) was used. During charging, alkaline ions are inserted into the carbon-containing anode material. During discharge, alkaline ions are withdrawn from the cathode active material and reinserted.

[0200] All cells were subjected to charge-discharge cycle experiments at charge rates such as ±1C (sometimes written as ±C / 1), ±C / 5, or ±C / 10 (or other rates mentioned in each experiment). Rate performance tests also confirmed discharge rates of C / 5, C / 10, 1C, and 2C. All cells were rested for at least 4–24 hours before each charge-discharge cycle.

[0201] Experiment 0 (Control) - Charge / discharge cycle performance with sacrificial salt in the cathode The purpose of this experiment is to demonstrate the disadvantages of using one or more sacrificial sodium salts contained in the cathode, as in the prior art of pre-sodiumization.

[0202] In particular, the presence of one or more sacrificial sodium salts in the cathode is demonstrated to reduce the amount of cathode active material that can actually store sodium. Therefore, the mAh / g of the cell カソード活物質 Even if the amount increases, the actual mAh of the cell does not increase, and therefore this contradicts the purpose of this method. This can be explained by Experiment 0 conducted by the inventors of this application.

[0203] A 100mAh Na ion pouch cell was prepared. Details are shown in Table 0 below. The following samples were prepared: 1. (FPC211002,03) used 92% by weight of O3 / P2 oxide material as the cathode active material in the absence of one or more sacrificial sodium salts; 2. FPC210924 was a Na ion pouch cell in which the cathode contained 10% by weight of CH3COONa sacrificial salt and 82% by weight of O3 / P2 oxide cathode; 3. FPC210928 was a Na ion pouch cell in which the cathode contained 10% by weight of NaNO2 sacrificial salt and 82% by weight of O3 / P2 oxide cathode.

[0204] The cell underwent the following charge-discharge cycles: Cycles 1-2: ±C / 10 at 4.1-1V (to simulate the "formation" cycle) Cycles 3-10: +C / 5 charge for 4.05-1.8V; discharge for 2 cycles each at C / 5, C / 2, 1C, and 2C. From cycle 11 onwards: ±1C at 4.05~1.8V. Table 0 lists various indicators. The sacrificial salt is predicted to be completely oxidized after the first charge (excess Na). + This is to supply (the remainder is released as a gas and can be removed during the degassing step), so here "g" in mAh / g is based solely on the weight of the O3 / P2 oxide "active material", and therefore, after the first charging cycle, the cathode is expected to be lighter than 10 wt% (since 10 wt% was the weight of each sacrificial salt added). In Table 0, D1 refers to the first discharge capacity of a full cell with ±C / 10 in units of mAh / g, and the weight (grams, g) is the weight of the cathode active material.

[0205] "FCE" refers to the Coulomb efficiency of cycle 1 (i.e., the ratio of the cycle 1 discharge capacity to the cycle 1 charge capacity, expressed as a percentage).

[0206] D3 refers to the discharge capacity of the third cycle at ±C / 5, between 4.05 and 1.8V. D9 refers to the discharge capacity for the 9th cycle at 4.05~1.8V with C / 5 charge and 2C discharge.

[0207] Please refer to Table 0. As can be seen from Table 0, the mAh / g values ​​are for two types of sacrificial salt cathode base cells, FPC210924 and FPC210928. カソード活物質 The D1 capacity of cells FPC211002 and FPC211003 was comparable at slower C / 10 and C / 5 rates, but the actual cell capacity (mAh) of cells FPC210924 and FPC210928 was actually 9-15mAh lower than that of cells FPC211002 and FPC211003.

[0208] [Table 2]

[0209] Another problem related to this technique discovered by the inventors of the present application is that the integrity of the cathode is significantly impaired after the sacrificial salt is oxidized in the first charge. This is surprising in that it is significantly impaired due to the higher internal resistance induced in the cell, which is caused by the electrode microstructure affected by gas generation and void formation (these voids were previously occupied by the sacrificial salt).

[0210] This evidence is shown in Table 0 above: it can be observed that the 2C capacities of cell FPC210924 and cell FPC210928 were significantly lower (less than approximately 10 mAh / g) than the 2C capacities of cell FPC211002 and cell FPC211003 (even though the slow-rate capacities of the former were the same as / higher than those of the latter).

[0211] As demonstrated below, the present invention aims to alleviate or eliminate one or more of these drawbacks of the known prior art.

[0212] Experiment 1 - Charge-discharge cycle performance of cells using the electrolyte compositions of the present invention (i.e., TEL25, TEL25b, TEL25c, TEL25d, TEL25e, TEL25h, and TEL25g) Experiment 1 compares the charge-discharge cycle performance of sodium ion ~7 mAh (nominal capacity) pouch cells that underwent charge-discharge cycles using the electrolyte compositions of the present invention (i.e., TEL25, TEL25b, TEL25c, TEL25d, TEL25e, TEL25h, and TEL25g), against sodium ion ~7 mAh (nominal capacity) pouch cells that underwent charge-discharge cycles using the comparative electrolyte composition (i.e., TEL0).

[0213] In particular, each Na ion cell underwent charge-discharge cycles at ±C / 10 and 4.2-1V for 4 cycles (to simulate the formation cycle), followed by charge-discharge cycles at ±C / 2 and 4.2-1V from cycle 5 onwards. The performance indicators of these cells are shown in Table 2 below. Figure 1 also shows a graph of capacity versus number of cycles.

[0214] [Table 3]

[0215] As shown above in Table 2, D1 refers to the first discharge capacity of a full cell at ±C / 10 in units of mAh / g, and the weight (grams, g) is the weight of the cathode active material.

[0216] "FCE" refers to the Coulomb efficiency of cycle 1 (i.e., the ratio of the cycle 1 discharge capacity to the cycle 1 charge capacity, expressed as a percentage).

[0217] D5 refers to the first discharge capacity of the first cycle in C / 2 (the fifth discharge overall).

[0218] Furthermore, "cycle life" refers to the number of cycles until a 20% capacity reduction occurs (compared to D5).

[0219] analysis capacity: As shown in Table 2, when compared to Na ion cells that underwent charge-discharge cycling using a control sample (TEL0; APFC101), each Na ion cell that underwent charge-discharge cycling using the non-aqueous electrolyte composition according to the present invention (i.e., TEL25, TEL25b, TEL25c, TEL25d, TEL25e, TEL25h, and TEL25g) yielded a larger D1 discharge capacity and a larger D5 discharge capacity. For example, when compared to a cell (APFC101) that underwent charge-discharge cycling using the control sample TEL0, which had a D1 of 118.6 mAh / g, a cell (APFC132) that underwent charge-discharge cycling using TEL25 had a D1 of 128.5 mAh / g. Similarly, when compared to a cell (APFC101) that underwent charge-discharge cycling using the control sample TEL0, which had a D5 of 110.2 mAh / g, a cell (APFC136) that underwent charge-discharge cycling using TEL25b had a D5 of 115.9 mAh / g.

[0220] According to Table 2, the D1 of the cell using TEL25d (APFC150) was similar to that of the cell using the control sample TEL0 (APFC101) after charge-discharge cycling. However, Figure 1 shows that the second, third, and fourth discharge capacities of APFC150 were approximately 5 mAh / g higher than the corresponding capacities of APFC101 (as shown in Table 1, this approximately 5 mAh / g capacity increase corresponds to D5).

[0221] Sacrificial salt concentration: As shown in Table 1 above, the concentration of the sacrificial salt (NaSCN) decreased from 0.5 m in TEL25 to 0.015 m in TEL25 g. In fact, since NaSCN did not dissolve in the solvent mixture at a concentration of 1 m, it was not possible to perform charge-discharge cycles on the sodium ion cell containing sample TEL25a.

[0222] According to Table 2, as the sacrificial salt concentration decreased, the FCE of each Na ion cell gradually increased and then stabilized around the FCE value shown for cells that underwent charge-discharge cycles using the control sample TEL0. This is predicted to be because FCE is related to the irreversible oxidation of the sacrificial salt anions. As the sacrificial salt concentration increases, the amount of charge used to irreversibly oxidize the sacrificial salt also increases, thus decreasing FCE. At low concentrations of sacrificial salt in the electrolyte, the irreversibility caused by the oxidation of the sacrificial salt is due to the supplied excess Na +It is also possible that this is partially / completely offset, resulting in an FCE value similar to that of a control sample. Therefore, those skilled in the art will understand that a high FCE value is not a reasonable indicator for evaluating the performance of the present invention, since it is predicted that the sacrificial salt will be irreversibly oxidized once the cell is charged. Instead, the question is whether the present invention can provide an additional sodium source that can be contained in the anode in order to increase the capacity of the sodium ion cell. However, such additional capacity must also be compatible with the ability to maintain chemical and electrochemical stability, so that the sodium ion cell can be charged and discharged over many cycles.

[0223] As shown above, when compared with the electrolyte compositions of comparative examples, the discharge capacity of the sodium ion cell was increased using the electrolyte composition of the present invention, which has a pre-sodium treatment reagent containing one or more sacrificial sodium salts at a concentration of 0.5 mol / kg or less.

[0224] Furthermore, higher discharge capacity and improved charge-discharge cycle stability were obtained using the electrolyte composition of the present invention, which has a pre-sodium reagent containing one or more sacrificial sodium salts at a concentration of 0.025 mol / kg or less, particularly at a concentration of about 0.025 mol / kg to about 0.020 mol / kg.

[0225] For example, the capacity retention rate after 170 cycles of a cell (APFC157) charged and discharged using TEL25e was 91.9%. This value is comparable to the 91.6% after 170 cycles of a cell (APFC101) charged and discharged using the control sample TEL0. Similarly, compared to the 91.6% capacity retention rate after 170 cycles for the cell (APFC101) charged and discharged using the control sample TEL0, the capacity retention rate after 170 cycles of a cell (APFC209) charged and discharged using TEL25h was 92%. The basis for irreversible oxidation:

[0226] [Table 4]

[0227] Table 3 and Figure 2 reveal the differences in dQ / dV plots of separate 3E full cells filled with the non-aqueous electrolyte compositions according to the present invention (i.e., TEL25b, TEL25c, and TEL25d), as well as the control sample (TEL0).

[0228] Figure 2 shows the differential capacity curve (dQ / dV) of the cathode, with the x-axis representing the cathode potential relative to reference Na (i.e., V vs. Na / Na + ). Based on the dQ / dV plots of the 3E cells, as measured by the inflection points in the sacrificial salt-containing electrolytes, the sacrificial salt-containing electrolytes (TEL25b, TEL25c, TEL25d) can be observed to oxidize at 3.26 V vs. Na / Na + and 3.74 V vs. Na / Na + vicinity. It can also be observed that the discharge processes (reduction) of all four types of cells were identical. This makes the oxidation of the sacrificial salt irreversible and suitable for the intended use.

[0229] Conclusion Adding a sacrificial salt to the electrolyte according to the present invention surprisingly results in increased capacity in sodium-ion cells. At certain specific concentrations, the sacrificial salt also results in sodium-ion cells with increased cell cycle life, as demonstrated in the specific examples above.

[0230] Experiment 2: Alternating Voltage Range and Long-Term Charge-Discharge Cycles Figure 2 of the present invention shows that the oxidation of the sacrificial salt (i.e., NaSCN) was completed by approximately 3.74 V vs. Na / Na + . Accordingly, a 60 mAh Na-ion pouch cell was fabricated using TEL25b with C / A=2.87, subjected to charge-discharge cycles at 3.75 to 2.5 V, ±C / 5 for 3500 cycles, followed by ±C / 2 charge-discharge cycles.

[0231] As shown in Figure 3, cell FPC190415 retained more than 87% of its initial energy after 6900 cycles, demonstrating that sacrificial salts in the electrolyte concept can result in a lifetime of several thousand cycles.

[0232] Conclusion: Experiment 2 demonstrates that the sacrificial salt in the electrolyte concept can function effectively and measurably across a wide voltage range (data shown on a 60mAh scale, an order of magnitude higher than the cell shown in Experiment 1), resulting in a Na ion cell that can last for thousands of cycles, which is extremely important from an industrial application perspective.

[0233] Experiment 3: Increasing Rate Performance and Total Cell Capacity Table 4, Figure 4, and Figure 5 show data for approximately 6 mAh Na-ion pouch cells with a cathode composition of 92:04:04 wt / wt and an anode composition of 92:3.5:1.5 wt / wt. These cells underwent the following charge-discharge cycles: Cycles 1-2: ±C / 10 at 4.2-1V Cycles 3-10: Charge at +C / 5 to 4.1-1.8V; discharge for 2 cycles each at C / 5, C / 2, 1C, and 2C. From cycle 11 onwards: ±1C, 4.1~1.8V.

[0234] The relevant indicators for this experiment are shown in Table 4. Here, "2C:C / 5 ratio" refers to the capacity ratio obtained during discharge at the 2C rate (cycles 9-10) versus the C / 5 rate (cycles 3-4), and is expressed as a percentage. D11 represents the first discharge capacity at ±1C (the 11th discharge overall). For D1 and D11, the figures show mAh / g (weight based on cathode active material) and mAh (total charge stored by the cell in that cycle).

[0235] [Table 5]

[0236] Table 4 shows that UM2C63 using sacrificial salt-based TEL25e has a higher D1 (mAh / g) compared to TEL0-based UM2C52. カソード活物質 It can be observed that this method not only increased mAh / g (+2.6 mAh / g) but also resulted in a higher total cell capacity (mAh) (+0.3 mAh or a capacity increase of +5%). This experiment first reiterates that sacrificial salts in the electrolyte method can be adapted to various electrode formulations and binders. More importantly, this experiment also demonstrates that this method not only increases mAh / g but also actually increases the total cell capacity (mAh), a significant difference from the conventional method of adding sacrificial salts to the cathode, as exemplified by Experiment 0 disclosed herein.

[0237] Furthermore, the rate performance of UM2C63 is actually slightly better than that of the control UM2C52 cell: the 2C:C / 5 capacity ratio of UM2C63 was 88.9%, while that of UM2C52 was 88.6%. This improved rate performance is a significant advantage over the conventional method of adding sacrificial salt to the cathode, as exemplified by Experiment 0 disclosed herein. This is also evident in faster rate ±1C charge-discharge cycles: the D11 capacity improvement is +4.4 mAh / g (or +4.7%) and +0.3 mAh (or +6.7%) for TEL25e-based UM2C63 compared to TEL0-based UM2C52.

[0238] As shown in Figures 4 and 5, both cells demonstrated similar charge-discharge cycle stability over 450 cycles: in fact, after 450 cycles, not only was the charge-discharge cycle stability the same, but preferably UM2C63 was able to yield a higher specific capacity (82.9 mAh / g vs. 81.2 mAh / g) and a higher cell capacity (4.05 mAh vs. 3.86 mAh) compared to UM2C52.

[0239] Conclusion: According to Experiment 3, the charge-discharge cycle performance using one or more sacrificial salts in a non-aqueous electrolyte is improved when compared to the prior art method using one or more sacrificial salts contained in the cathode. The former not only results in a capacity increase in terms of mAh / g, but importantly, it can also result in a capacity increase in terms of total cell capacity (mAh), while the latter, considering the lower content of cathode active material in the cathode, cannot show a capacity increase in terms of total cell capacity. Furthermore, the former method actually yields similar rate performance and long-term charge-discharge cycle stability, while the latter method falls significantly short of expectations in both indicators.

[0240] Experiment 4: Demonstration of an alternative solvent mixture The use of one or more sacrificial salts in non-aqueous electrolytes was further investigated in different electrolyte compositions. In particular, this consisted of carbonate ester solvents (PC) and non-carbonate ester solvents (hydrofluoroether 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, also known in the prior art as "HFE-458" or sometimes as "TTE"). Table 5 (and Table 1) lists the control electrolytes and the sacrificial salt-based electrolytes according to the present invention.

[0241] [Table 6]

[0242] The two electrolytes described above were used in approximately 6 mAh Na-ion pouch cells with a cathode composition of 92:04:04 wt / wt and an anode composition of 92:3.5:1.5 wt / wt. These cells underwent the following charge-discharge cycles: Cycles 1-2: ±C / 10 at 4.2-1V Cycles 3-10: Charge at +C / 5 to 4.1-1.8V; discharge for 2 cycles each at C / 5, C / 2, 1C, and 2C. From cycle 11 onwards: ±1C, 4.1~1.8V.

[0243] The relevant indicators for this experiment are shown in Table 6.

[0244] [Table 7]

[0245] Table 6 shows that UM2C88 using the sacrificial salt-based TEL45c according to the present invention has a higher D1 (mAh / g) compared to the control TEL42d-based UM2C67. カソード活物質 It can be observed that this not only resulted in an increase of 2.5 mAh / g, but also a higher total cell capacity (mAh) (+0.3 mAh or a capacity increase of +4.9%). These conclusions are consistent with the conclusions of Experiment 3, which demonstrated the use of the composition according to the present invention that does not contain HFE-458.

[0246] Furthermore, the rate performance of the UM2C88 is indeed slightly better than that of the control UM2C67 cell: the 2C:C / 5 capacity ratio of the UM2C88 was 89.3%, while that of the UM2C67 was 88.7%. This better rate performance is also evident in faster ±1C charge / discharge cycles: the D11 capacity improvement is +4.4mAh / g (or +4.7%) and +0.27mAh (or +5.9%) for the TEL45c-based UM2C88 compared to the TEL42d-based UM2C67. As shown in Figures 6 and 7, both cells demonstrated similar charge-discharge cycle stability over 150 cycles: in fact, after 150 cycles, not only was the charge-discharge cycle stability the same, but preferably, UM2C88 was able to yield a higher specific capacity (93 mAh / g vs. 90.3 mAh / g) and a higher cell capacity (4.57 mAh vs. 4.35 mAh) compared to UM2C67.

[0247] Conclusion: According to Experiment 4, the present invention can be adapted to various salt-solvent combinations. Importantly, according to Experiment 4, the sacrificial salt in the electrolyte-based method can even perform well with non-carbonate ester electrolytes, such as hydrofluoroethers (e.g., HFE-458).

[0248] Further analysis of results from Experiment 1 Table 7 below shows data similar to Table 2 from Experiment 1. However, it further includes predicted volume increase values ​​based on the actual amount of sacrificial salt (NaSCN) content in the electrolyte that was actually added to the cell. In Table 7 below, "Added electrolyte" refers to the actual value of the electrolyte added to the cell. This value should have been approximately the same in each experiment (since the same electrolyte filler was used), but any slight discrepancies were within the range of what could be expected due to human error. In addition, this value (recorded) was used in the actual calculations, thus ensuring the accuracy of the results.

[0249] The weights (grams) of "D1 increase from NaSCN (mAh / g)", "D1 increase relative to TEL0 (mAh / g)", and "unexpected mAh / g increase" explain the weight of the cathode active material. Furthermore, in these calculations, the FCE of that cell is also explained by (e.g., "D1 increase from NaSCN (mAh / g)" = FCE * "Expected mAh from NaSCN" / (Cathode active material weight (g))).

[0250] [Table 8]

[0251] From Table 7, it can be seen that all cells containing the non-aqueous electrolyte according to the present invention (e.g., TEL25, TEL25b, TEL25c, TEL25d, TEL25e, TEL25h, TEL25g) yielded a higher volume increase than could be predicted simply by considering the amount of sacrificial salt added to the electrolyte in the cell. This occurs when one or more sacrificial sodium salts are present at concentrations of about 0.015 mol / kg to about 0.5 mol / kg.

[0252] Furthermore, this capacity increase becomes disproportionately high at slower concentrations of sacrificial salt (0.015m to 0.1m). It should be noted that for the APFC150 using TEL25d, the capacity increase was observed in cycles 2 to 4 (D2 to D4), and also from cycle 5 onwards in ±C / 2 charge-discharge cycles, indicating that an unexpected capacity increase actually occurred.

[0253] The prior art does not teach, suggest, or indicate the use of one or more sacrificial salts in non-aqueous electrolytes, much less the optimal concentrations disclosed herein. The prior art also does not mention the advantages of the non-aqueous electrolyte according to the present invention, which provide improved long-term charge-discharge cycles and / or increased capacity to electrochemical cells, particularly sodium ion cells. Therefore, those skilled in the art would not have considered the present invention without hindsight or inventive ability.

[0254] Experiment 5: Further charge-discharge cycle performance of cells using the electrolyte compositions of the present invention (i.e., TEL79c, TEL67Ra, TEL62a, TEL113a, TEL147a, TEL146a) Table 7 below shows the electrochemical performance of sodium ion cells with a rated capacity of 6–10 mAh using a layered oxide cathode / hard carbon anode configuration. These cells were fabricated following the general procedure for making sodium ion cells described above.

[0255] Table 7 shows the specific details of the test conditions, along with the relevant electrochemical performance (first discharge capacity of the cell).

[0256] [Table 9]

[0257] Table 7 shows that in all Examples 5a to 5f, the use of sacrificial salt electrolytes (TEL79c, TEL67Ra, TEL62a, TEL113a, TEL147a, and TEL146a) in sodium ion cells resulted in improved volume compared to the use of comparative compositions (TEL67a, TEL67Ra, TEL0c, TEL114, TEL147, and TEL146) in sodium ion cells, and this was the same in all cases except that the control electrolytes did not contain sacrificial salts. In particular, Example 5a demonstrates an increase in cell capacity using a PC-based electrolyte system containing NaPF6 as the main non-sacrificial salt, NaSO3CF3 as the sacrificial salt, and DEC as another carbonate-based cosolvent.

[0258] Figure 14 also shows dQ / dV plots of cells filled with the non-aqueous electrolyte composition according to the present invention (i.e., TEL79c) and a control sample (TEL67a). In particular, Figure 14 also shows the differential capacity curve (dQ / dV) of the cathode.

[0259] Based on the dQ / dV plot of the 2E cell, it can be observed that the sacrificial salt-containing electrolyte TEL79c oxidizes around 4.05V, as measured by the inflection point in the sacrificial salt-containing electrolyte.

[0260] Example 5b demonstrates an increase in cell capacity using a PC-based electrolyte system containing NaPF6 as the main non-sacrificial salt, NaPO2F2 as the sacrificial salt, and DEC as another carbonate-based cosolvent.

[0261] Figures 12 and 13 also show dQ / dV plots of cells filled with the non-aqueous electrolyte composition according to the present invention (i.e., TEL67Ra) and the control sample (TEL67). In particular, Figures 12 and 13 also show the differential capacity curves (dQ / dV) of the cathode.

[0262] Based on the dQ / dV plot of the 2E cell, the sacrificial salt-containing electrolyte TEL67Ra may be observed to oxidize around 4.05 V, as measured by the inflection point in the sacrificial salt-containing electrolyte.

[0263] Example 5c shows an increase in cell volume using the following: NaPF6 as the main non-sacrificial salt, NaBPh4 as the sacrificial salt, and a solvent system (EC:DEC:PC=1:2:1wt / wt) as the electrolyte.

[0264] Figures 10 and 11 also show dQ / dV plots of cells filled with the non-aqueous electrolyte composition according to the present invention (i.e., TEL62a) and the control sample (TEL0c). In particular, Figures 10 and 11 also show the differential capacity curves (dQ / dV) of the cathode.

[0265] Based on the dQ / dV plot of the 2E cell, it can be observed that the sacrificial salt-containing electrolyte TEL62a oxidizes around 4.05V to 4.2V, as measured by the inflection point in the sacrificial salt-containing electrolyte.

[0266] Example 5d shows an increase in cell volume using the following: NaFSI as the main non-sacrificial salt, NaSCN as the sacrificial salt, and a solvent system (EC:DEC:PC=1:2:1wt / wt) as the electrolyte.

[0267] Example 5e demonstrates an increase in cell capacity using NaPF6 as the main salt, NaSCN as the sacrificial salt, and a TEP+HFE+FEC solvent system as the electrolyte.

[0268] According to Example 5f, the sacrificial salt in the electrolyte concept is as follows: NaFSI as the main salt, NaSCN as the sacrificial salt, and a TEP+HFE+FEC solvent system as the electrolyte, which can demonstrate an increase in cell capacity. Experiment 6: Further Long-Term Charge / Discharge Cycle Performance This experiment provides long-term charge-discharge cycle data for Example 5a / Comparative Example 5a, as described in Experiment 5. The data is shown in Figure 8. In Figure 8, both cells UM2C108 (TEL67a) and UM2C121 (TEL79c) underwent two charge-discharge cycles at ±C / 10 between 4.2 and 1V, followed by a charge-discharge cycle at ±1C between 4.1 and 1V. Data over 1200 cycles is shown.

[0269] This experiment also provides long-term charge-discharge cycle data for Example 5f / Comparative Example 5f, as previously described in Experiment 5. The data is shown in Figure 9. In Figure 9, both cells F2400216 (TEL146) and F2400214 (TEL146a) underwent charge-discharge cycles at ±1C between 4.1 and 1V after two cycles at ±C / 10 and 4.1 to 1V. The data for the first 100 cycles is shown.

[0270] analysis Regarding Figure 8, it can be seen that cell UM2C121, using the electrolyte of the present invention (TEL79c), exhibited a cycle life of 1200 cycles until a 20% volume decrease. In contrast, comparative cell UM2C108, using TEL67a, showed a cycle life of only 885 cycles until a 20% volume decrease. Therefore, when used in a Na ion pouch cell, the electrolyte of the present invention (TEL79c) resulted in a 35.6% improvement in cycle life compared to another Na ion pouch cell that did not use the electrolyte of the present invention (TEL67a).

[0271] Regarding Figure 9, it can be seen that cell F2400214, using the electrolyte of the present invention (TEL146a), exhibited a volume retention rate of 93% after 100 cycles. For comparison, comparative cell F2400216, using TEL146, showed a volume retention rate of only 51.6% after 100 cycles. Therefore, when used in a Na ion pouch cell, the electrolyte of the present invention (TEL146a) resulted in an 80% improvement in volume retention rate compared to another Na ion pouch cell that did not use the electrolyte of the present invention (TEL146).

[0272] overview Experiments disclosed herein demonstrate that the non-aqueous electrolyte compositions according to the present invention provide increased capacity to electrochemical cells, particularly sodium ion cells. In some cases, the increased capacity is not only in terms of mAh / g but also in terms of total cell capacity (mAh), and importantly, is accompanied by similar / better rate performance and similar / better cycle life.

[0273] The experiments disclosed herein also demonstrate that they yield better performance indicators than the conventional methods used in the prior art, which employ a sacrificial salt in the cathode.

Claims

1. a) A solvent system comprising one or more organic carbonate-based solvents, b) One or more non-sacrificial sodium-containing salts, c) A pre-sodium reagent containing one or more sacrificial sodium salts at a concentration of less than 1.0 mol / kg A non-aqueous electrolyte composition for an electrochemical cell, comprising: One or more sacrificial sodium salts irreversibly supply sodium ions to the anode during the charging of the electrochemical cell. Nonaqueous electrolyte composition.

2. The non-aqueous electrolyte composition according to claim 1, wherein one or more sacrificial sodium salts comprise one or more anions that are oxidized during charging of an electrochemical cell.

3. The non-aqueous electrolyte composition according to claim 1 or 2, wherein one or more sacrificial sodium salts contain one or more anions, each containing at least one atom selected from the group consisting of sulfur atoms, nitrogen atoms, boron atoms, oxygen atoms, and fluorine atoms.

4. One or more sacrificial sodium salts include thiocyanate-containing compounds, cyanate-containing compounds, sulfonate-containing compounds, sulfite-containing compounds, periodate-containing compounds, fluorosilicate-containing compounds, fluoroferrate-containing compounds, alkoxide-containing compounds, boron-containing compounds, and compounds with the formula NaSb. ｍ X ｘ A non-aqueous electrolyte composition according to any one of claims 1 to 3, comprising one or more compounds selected from the group consisting of compounds, thiolate-containing compounds, thiosulfate-containing compounds, cyanamide-containing compounds (including dicyanamide-containing compounds), azide-containing compounds, carboxylate-containing compounds, ketone-containing compounds (including rhizonate-containing compounds), fluorotitanate-containing compounds, arene-containing compounds (including terephthalate-containing compounds), triflate-containing compounds, difluorophosphate-containing compounds, and tetraphenylborate-containing compounds.

5. A non-aqueous electrolyte composition according to any one of claims 1 to 4, wherein one or more sacrificial sodium salts have the general formula NaXCN [wherein X is a group 16 element, preferably selected from oxygen and sulfur].

6. The non-aqueous electrolyte composition according to claim 5, wherein one or more sacrificial sodium salts include sodium thiocyanate (NaSCN).

7. The non-aqueous electrolyte composition according to any one of claims 1 to 6, wherein the decomposition potential of one or more sacrificial sodium salts is about 2.75 V to about 4.3 V.

8. One or more sacrificial sodium salts are sodium triflate (NaSO4). ３ CF ３ ), sodium difluorophosphate (NaPO ２ F ２ ), and sodium tetraphenylborate (NaBPh ４ The non-aqueous electrolyte composition according to claim 4, comprising one or more of the following:

9. A non-aqueous electrolyte composition according to any one of claims 1 to 8, wherein one or more sacrificial sodium salts are present at a concentration of about 0.75 mol / kg or less.

10. The non-aqueous electrolyte composition according to claim 9, wherein one or more sacrificial sodium salts are present at a concentration of about 0.015 mol / kg to about 0.5 mol / kg.

11. The non-aqueous electrolyte composition according to any one of claims 1 to 10, wherein the solvent system comprises propylene carbonate (PC) and a further solvent selected from the group consisting of ethylene carbonate (EC), diethyl carbonate (DEC), and hydrofluoroalkyl ethers, such as 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE).

12. One or more non-sacrificial sodium-containing salts is sodium tetrafluoroborate (NaBF ４ ), sodium hexafluorophosphate (NaPF ６ ), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), and sodium bis(fluorosulfonyl)imide (NaFSI), selected from any one of claims 1 to 11, The non-aqueous electrolyte composition according to any one of claims 1 to 11.

13. One or more non-sacrificial sodium-containing salts, sodium hexafluorophosphate (NaPF) ６ The non-aqueous electrolyte composition according to claim 12, comprising ) or bis(fluorosulfonyl)imide sodium (NaFSI).

14. The non-aqueous electrolyte composition according to any one of claims 1 to 13, wherein one or more non-sacrificial sodium-containing salts do not substantially decompose at a voltage of 1V to 4.3V during charging of an electrochemical cell.

15. A non-aqueous electrolyte composition according to any one of claims 1 to 13, wherein one or more sacrificial sodium salts substantially decompose at a voltage of 1V to 4.3V during charging of an electrochemical cell.

16. The non-aqueous electrolyte composition according to any one of claims 1 to 15, further comprising one or more performance additives selected from one or more surfactants, one or more boron-containing compounds, and one or more sulfur-containing compounds, wherein the solvent system comprises one or more performance additives.

17. An electrochemical cell comprising the non-aqueous electrolyte composition according to any one of claims 1 to 16.

18. An electrochemical cell pre-sodiumized using the non-aqueous electrolyte composition according to any one of claims 1 to 16.

19. The electrochemical cell according to claim 17 or 18, which is a sodium ion cell.

20. An apparatus comprising an electrochemical cell according to any one of claims 17 to 19.

21. Use of the non-aqueous electrolyte composition according to any one of claims 1 to 16 in an electrochemical cell.

22. Use of the non-aqueous electrolyte composition according to any one of claims 1 to 16 for pre-sodiumization of an electrochemical cell.

23. A method for forming an electrochemical cell, (a) Providing an electrochemical cell with the non-aqueous electrolyte composition according to any one of claims 1 to 16, (b) A step of charging the electrochemical cell to a voltage of 4.5V or less. Methods that include...

24. The method according to claim 23, wherein the electrochemical cell is charged to a voltage exceeding 3V.

25. The method according to claim 23, wherein the electrochemical cell is charged to a voltage exceeding 3.5V.

26. The method according to claim 23, wherein the electrochemical cell is charged to a voltage exceeding 3.8V.

27. The method according to claim 23, wherein the electrochemical cell is charged to a voltage exceeding 4V.

28. An electrochemical cell manufactured by the method described in any one of claims 23 to 27.

Images