Multifunctional electrolyte for primary CFX / LI batteries.

Abstract

The present disclosure relates to a multifunctional electrolyte composition for primary CFx / Li batteries, the composition and preparation of such batteries, and their uses, including low- and high-temperature applications. The design of this electrolyte composition enables excellent discharge characteristics and robust use, even at temperatures as low as -70°C.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Patent Application No. 63 / 382,495, filed November 4, 2022, the entire contents of which are incorporated herein by reference.

[0002] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT This invention was made with government support under Grant 2021-21060200009 awarded by the Intelligence Advanced Research Projects Activity (IARPA). The government has certain rights in this invention.

[0003] The field of the present invention generally relates to electrolyte compositions for primary CFx / Li batteries and their uses. More specifically, the present invention relates to the use of LiBF4 in dimethyl sulfite as an electrolyte in primary CFx / Li batteries. [Background technology]

[0004] This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily made, nor should be construed, that any information disclosed herein constitutes prior art against the present invention.

[0005] Batteries in portable electronic devices, military applications, and implantable medical devices are placing increasingly stringent demands on them, driven by the upcoming push for space and deep-sea exploration. For example, recent missions to the Moon and Europa, conducted by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA), have placed requirements on primary lithium batteries that provide high specific energy (>700 Wh / kg), sustain low-temperature operation (below -40°C), and last for several weeks (approximately 480 hours). Furthermore, they are expected to provide both high energy density and high pulse power response as energy sources for intelligent logistics in situations such as unmanned aerial vehicles (UAVs) and unmanned electronic device applications. Among all known cathodes, fluorocarbon (CFx) cathodes offer the highest theoretical energy density of 2180 Wh / kg (based on a specific capacity of 865 mAh / g, x = 1) among all commercially available cathodes, including MnO2 (1005 Wh / kg), SO2 (1170 Wh / kg), and SOCl2 (1470 Wh / kg). They also have high reliability and a good safety record, indicating their great potential for use in the extreme environments mentioned above. Nevertheless, there is a large gap between the actual energy density of Li / CFx batteries and their theoretical value. Large-scale packaging produced by various suppliers, including Varta, USA Army, Eagle Picher, Yardney Electric, SAFT, QinetiQ, and Rayovac, delivers specific energies of 400–700 Wh / kg. Apart from this, power capability and low-temperature performance are also unsatisfactory, which is essentially related to the poor electrical conductivity of CFx due to the covalent bonding of the C–F bonds. Summary of the Invention [Problem to be solved by the invention]

[0006] To increase power and energy density, intense research has focused on the design of CFx electrode materials, including the synthesis of subfluorinated carbon and hybrid cathodes, optimization of carbon sources and nanostructures, blending with conductive additives, enhancing preparation methods, and surface modification. Although some progress has been made, obtaining the best of both worlds remains challenging and is also believed to be insufficient to improve the temperature resilience of Li / CFx batteries. Considering the cell reaction (Eq. 1) proposed by Watanable et al., where S is a solvent molecule, xLi + yS + CF → LixSyCF → yS + LiF + C (1), the thermodynamic and kinetic behavior of CFx cathodes strongly depends on the electrolyte, which has not received sufficient attention until now. For one, the Li + Lower solvation energy between the LiF and solvents such as fluorinated or methyl butyrate cosolvents may contribute to higher discharge voltages and lower charge transfer resistances. On the other hand, it has been demonstrated that LiF nucleation and crystal growth are influenced by the chemisorption energy of the solvent on the LiF crystal surfaces, resulting in different discharge capacities. In solid-state systems where the solvent is excluded, amorphous LiF nanoparticles form over time without agglomeration, making CFx partially rechargeable. Alternatives include modifying the geometry of the product layer, introducing anion receptors or BF3 additives to dissolve LiF, and allowing it to be assessed on a more active cathode surface and LiF. + This can also be achieved by reducing the diffusion resistance and thus providing high rate discharge even at low temperatures. As a result, although some initial tests have been conducted on CFx discharge performance below -40°C, discharge capacities are typically below 300 mAh / g. Furthermore, the introduction of catholytes such as SO2, SOCl2, and the newly emerging NF3 and SF6 is a promising method for generating energy. However, the toxicity of SO2 and safety concerns associated with pressurized SO2 or thermal runaway significantly limit the practical development of Li / SO2 and Li / SOCl2 batteries. While perfluorinated gases NF3 and SF6 are typically nontoxic and have attractive theoretical energy densities of 3922 Wh / kg, their commercial use remains a long way off due to the addition of an additional liquid-based electrolyte and complex thermodynamic, kinetic, and transport considerations resulting from the gas-solid conversion reaction. In contrast, bifunctional liquid electrolytes that directly act as both ionic conductors and cathode reactants can be successfully engineered. These electrolytes offer advantages over the conventional catholytes mentioned above and appear to be an easier way to contribute additional energy to Li / CFx batteries. However, such a revolution is hindered by catholytes' limited donable capacity (<300 mAh / g) and relatively low reaction potential (2.1 V). The electrolyte / electrode interface resulting from electrolyte decomposition is usually passivated, making it difficult to provide high additional capacity. Furthermore, commonly used salts or solvents have low reduction potentials, making it difficult to find ways to decompose them at high values. Therefore, an ideal functional electrolyte would have a closed reduction potential due to CFx defluorination, combined with non-passivating properties, to maximize the electrolyte's energy density and minimize its impact on power density and low-temperature performance. However, achieving this ideal is extremely difficult and requires significant innovation in electrolyte formulations.

[0007] The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein. [Brief explanation of the drawings]

[0008] [Figure 1]Figures 1a–d demonstrate the chemistry and energy density in coin cells. (a) Reduction activity of selected electrolytes on a copper current collector at a low current density of 5 × 10 mA cm . Discharge profiles of (b) Li / graphene and (c) Li / GCF cells using LiBF / DMS electrolyte as a function of concentration at 200 mA / g, and (d) comparison of the specific capacity and corresponding specific energy of GCF with 2.5 M DMS and commercial electrolytes at a current rate of 1 / 3 C (288 mA / g, 1 C = 865 mA / g). [Figure 2] Figures 2a-c show pulse discharge tests of Li / GCFx cells using DMS and commercial electrolytes. The cells were discharged to 15-20% and 75-85% DOD at 1 / 3C and pulsed at 5 / 3C for (a) 10 seconds and (b) 1 minute. (c) Comparison of corresponding pulse power densities. Note that 1C was calculated from the maximum capacity estimated by the researchers, which is therefore approximately 600 mA / g for the commercial electrolyte and 1730 mA / g for the DMS electrolyte. The capacities are based on actual values ​​in both cases. [Figure 3] Figures 3a–f show discharge performance and electrolyte properties at low temperatures. (a) Rate capacity of a Li / GCFx cell at -40 °C. (b) Discharge performance at different low temperatures (0 °C to -70 °C) compared with DMS electrolyte. Note that a lower concentration of 1 M is used below -40 °C, and a lower current rate of 5 mA / g is used at -70 °C. (c) Ionic conductivity of DMS and control electrolyte calculated from Nyquist plots from -65 °C to 25 °C. (d) EIS data collected from a Li / GCFx cell before and after discharge at -40 °C with 2.5 M DMS and (e) LiBF4 / PC:DME electrolytes, with a current rate of 80 mA / g. (f) 5 mV polarization curves and calculated Li+ transference numbers for DMS and control electrolytes. [Figure 4]Figure 4a-j shows the structural characterization of the reduction products of the 2.5M DMS electrolyte during discharge. (a) SEM images and corresponding EDS elemental maps showing F (cyan), O (blue), S (green), C (magenta), and B (red) obtained after partial discharge to 30% DOD and (b) full discharge to 0.5 V. (c, d) EELS mapping of the Li K-edge obtained at 30% DOD and (e, f) D0.5 V, as well as extracted spectra for (g) 30% DOD and (h) D0.5 V. A LiF standard with characteristic post-peaks at approximately 61.7 and 69.5 V was also included. (i) Comparative SAED patterns for 30% DOD and (j) D0.5 V. [Figure 5] Figures 5a–d show the chemical evolution of the SEI depth direction on a graphene electrode using 2.5 M DMS. (a) XPS C 1s, O 1s, F 1s, Li 1s, B 1s, and S 2p core level spectra at (b) 30% DOD and (c) 0.5 V. (c) Magnified image of a crater sputtered by a Ga+ ion beam at (d) 30% DOD and (e) 0.5 V, and the distribution of O, F, LiOH, and S in the sputtered cross section. [Figure 6] Figure 6a-d shows a unique solvation structure investigation of DMS electrolyte. (a, c) FTIR spectra (a, b) and Raman spectra (c, d) of LiBF dissolved in different solvents and (b, d) different salts dissolved in DMS solvent. Note that characteristic solvation behavior is marked with a square dotted box. [Figure 7] Figures 7a-d show (a) the self-discharge behavior of as-prepared cells in 2.5DMS-NO electrolyte tested under different storage time conditions. (b) the capacity and energy density of a single-layer pouch-type cell with limited electrolyte and lithium mass. (c) the estimated specific energy and energy density at different utilization levels (fraction of electrolyte reacted) based on physics-based modeling, and (d) the additive ratio compared to the case without electrolyte contribution. An electrolyte capacity of 1400 mAh / g was used at an average discharge voltage of 2 V. The ratios of CFx, carbon, and electrolyte in the cathode are 0.6, 0.1, and 0.3. [Figure 8] Figure 8 shows the reduction activity of selected electrolytes for stainless steel at a low current density of 5 × 10-3 mA cm-2. [Figure 9] Figure 9a-f shows the basic properties of the graphene used: (a) XRD pattern, (b) Raman spectrum, (c, d) SEM images, and (f) TEM image. [Figure 10] Figure 10a–c shows (a) the discharge profiles of Li / graphene cells with selected electrolytes at 200 mA / g and the rate capacities of (b) pure CFx and (c) GCFx electrodes with 2.5 M DMS electrolyte. [Figure 11] Figure 11a-d. Discharge profiles of Li / GCFx cells using (a) different salts in DMS solvent and (b) LiBF4 salt in different solvents. Similar discharge behavior of (c) graphene and (d) GCFx electrodes using other sulfite salts with DMS. The current rate is 200 mA / g. [Figure 12] Figure 12a-b: Discharge profiles of Li / GCFx cells with (a) commercial electrolyte at a current rate of 600 mA / g and (b) 2.5 M DMS at a current rate of 1730 mA / g. [Figure 13] Figures 13a-f show pulse discharge tests of Li / GCFx cells using DMS and commercial electrolytes. Method 2: (a) 10 s and (b) 1 min, 1 C = 865 mA / g, capacity based on actual values; and (c) corresponding pulse power density. Method 3: (d) 10 s and (e) 1 min, 1 C = 865 mA / g, capacity is 865 mAh / g; and (f) corresponding pulse power density. [Figure 14] Figure 14a-f shows the total pulse discharge curves tested by (a, b) Method 1, (c, d) Method 2, and (e, f) Method 3. [Figure 15] Figure 15a-c shows (a) discharge GITT (galvanostatic intermittent titration) curves and (b) equilibrium potentials of GCFx and pure CFx with DMS and commercial electrolytes, and (c) DLi calculated from the GITT data. The current rate is 100 mA / g for DMS electrolyte and 30 mA / g for commercial electrolyte. [Figure 16] Figure 16a-b: (a) DSC curves of DMS solvent and LiBF4 / DMS electrolyte (0.5 M, 1 M, and 2.5 M) with decreasing temperature. (b) Optical images of DMS solvent and electrolyte at -80 °C. [Figure 17] Figure 17a-d: Optimization of LiBF4 salt concentration at (a) -40 °C, (b) -60 °C, (c) -65 °C, and (d) -70 °C. [Figure 18] Figure 18a-b: (a) Nyquist plots obtained from electrochemical impedance spectroscopy studies for DMS and control electrolytes, (b) new Li / GCFx cells using the two electrolytes at different temperatures. [Figure 19] Figure 19a–c shows Nyquist plots before and after polarization used to calculate the Li+ transference numbers for (a) 2.5 M, (b) 0.5 M LiBF4 / PC:DME, and (c) 1 M LiPF6 / EC:DMC. [Figure 20] Figure 20a-b shows XRD spectra obtained after (a) partial discharge to 30% DOD and (b) full discharge to 0.5 V. Note: To gather clearer information about the discharged products, a thicker free-standing graphene film containing a PTFE binder was used. [Figure 21] FIG. 21 is an SEM image of another area at 30% DOD showing LiF aggregation with 2.5 M DMS electrolyte. [Figure 22] Figure 22a-b Quantitative analysis of graphene electrodes by EDS recovered from (a) 30% DOD and (b) 0.5 V using 2.5DMS electrolyte. [Figure 23] Figure 23a-b shows HRTEM images showing lattice fringes in the SEI formed in 2.5 M DMS electrolyte at (a) 30% DOD and (b) 0.5 V. LiF (PDF no. 45-1460), LiS (PDF no. 26-1188), and LiO (PDF no. 65-2972) nanoparticles were marked with cyan, yellow, and magenta solid ellipses, respectively. [Figure 24]Figure 24a-c shows the microscopic changes of the CFx electrode during discharge in 2.5 M DMS electrolyte. SEM images of the pure CFx electrode before discharge (a), discharged to 865 mAh / g (b), and discharged to 0.5 V (c). [Figure 25] Figure 25a-d: Structural characterization of reduction products during discharge using 0.5 M DMS electrolyte. SEM images of graphene electrodes recovered from (a) 30% DOD and (b) D0.5V, and corresponding EDS elemental maps showing F (cyan), O (blue), S (green), C (magenta), and B (red). Quantitative analysis of (c) 30% DOD and (d) D0.5V by DES. [Figure 26] Figure 26a-d: Structural characterization of reduction products during discharge using 6 M DMS electrolyte. SEM images of graphene electrodes recovered from (a) 30% DOD and (b) D0.5V, and corresponding EDS elemental maps showing F (cyan), O (blue), S (green), C (magenta), and B (red). Quantitative analysis of (c) 30% DOD and (d) D0.5V by DES. [Figure 27] Figure 27a-b: Comparative XRD spectra of the SEI characteristics formed on graphene electrodes using selected electrolytes: (a) after initial discharge to 30% DOD for LiBF4 / sulfite and salt / DMS electrolytes but 1.8 V for the others, and (b) after full discharge (0.5 V). [Figure 28] Figure 28a–d shows SEM images of the reduction products during discharge with LiBF4 / sulfite electrolyte, (a, b) ES, and (c, d) PS recovered from (a, c) 30% DOD and (b, d) 0.5 V, and the corresponding EDS elemental maps showing F (cyan), O (blue), S (green), C (magenta), and B (red). [Figure 29] Figure 29a–d shows SEM images of the reduction products during discharge with LiBF4 / sulfone electrolyte, (a, b) DMSO, and (c, d) SL recovered from (a, c) D1.8V and (b, d) D0.5V, and the corresponding EDS elemental maps showing F (cyan), O (blue), S (green), C (magenta), and B (red). [Figure 30]Figure 30a–d shows SEM images of the reduction products during discharge with LiBF4 / ether or carbonate electrolyte, (a, b) DME, and (c, d) EC:DMC recovered from (a, c) D1.8V and (b, d) D0.5V, and the corresponding EDS elemental maps showing F (cyan), O (blue), C (magenta), and B (red). [Figure 31] Figure 31a–d shows SEM images of the reduction products during discharge with LiPF6 or LiFSI dissolved in DMS electrolyte, (a, b) LiPF6 and (c, d) LiFSI recovered from (a, c) 30% DOD and (b, d) 0.5 V, and the corresponding EDS elemental maps showing F (cyan), O (blue), S (green), C (magenta), P (gray), and N (yellow). [Figure 32] Figure 32a-c shows the atomic composition ratios from XPS of the SEI layer formed on a graphene electrode in 2.5 M DMS electrolyte: (a) the surface and its change upon etching at (b) 30% DOD and (c) D0.5V. [Figure 33] Figure 33a-b: TOF-SIMS mass spectra of discharged graphene electrodes using 2.5 M DMS electrolyte with (a) negative polarity and (b) positive polarity. [Figure 34] Figure 34a-b: Unique solvation structure investigation for DMS electrolyte. FTIR spectra of (a) LiBF4 / DMS electrolyte at different concentrations and (b) LiBF4 / other sulfite electrolytes. Note that characteristic solvation behavior is marked with a square dotted box. [Figure 35] Figure 35. Reduction behavior of 1M LiNO3 / DME electrolyte on graphene electrode. [Figure 36] Figure 36a-f shows similar properties of 2.5 M DMS electrolyte with and without LiNO additive. Basic electrolyte properties of (a) FTIR spectrum, (b) ionic conductivity, and (c) Li+ transference number. Electrochemical performance of (d) reduction behavior, (e) pulse discharge curve tested by Method 1, and (f) discharge performance at -40 °C. [Figure 37] Figure 37. Voltage stability of Li / GCFx cells containing 2.5 M DMS-NO electrolyte over a 3-month period. [Figure 38] Figure 38a-b. Stability of Li surfaces in 2.5 M DMS-NO electrolyte: (a) fresh Li and (b) extracted after 5 months without discharge. [Figure 39] Figure 39. Self-discharge behavior after partial discharge with 2.5M DMS with and without LiNO3 additive and LiPON coating lithium, tested under intermittent conditions for 1 month. [Figure 40] FIG. 40. Pouch cell discharge performance versus applied pressure using a test fixture with an injection coefficient (electrolyte / CFx mass ratio) of 6:1. [Figure 41] Figure 41a-b. Characterization of reacted lithium after discharge in GCFx pouch cells with (a) commercial electrolyte and (b) 2.5 M DMS-NO electrolyte. [Figure 42] Figure 42a-b shows (a) the estimated specific energy and energy density for different amounts of reacted multifunctional electrolyte in the separator, based on an electrolyte utilization of 0.8. An electrolyte capacity of 1400 mAh / g was used at an average discharge voltage of 2 V. The ratios of CFx, carbon, and electrolyte in the cathode are 0.6, 0.1, and 0.3. [Figure 43] Figure 43a-c shows (a) a comparison of the average total capacity of the five electrodes based on the CFx weight, (b) the relative capacity contribution of each plateau to the total capacity, and (c) a comparison of the average total capacity of the five electrodes based on the total electrode weight. [Figure 44] Figure 44 shows a comparison of the average total capacity of the seven electrodes based on the total electrode weight. [Figure 45] Figure 45a-b: Discharge profiles of CFx / Li coin cells in 2.5 M LiBF4 DMS electrolyte with and without 0.25 M LiNO3 additive at 600 mA / gCFx after 16 h standing at (a) 25 °C and (b) 45 °C. [Figure 46] Figure 46 shows the discharge profile of a Li / CFx coin cell using SAFT electrodes in a 2.5M LiBF4 0.25M LiNO3 DMS electrolyte at 500 mA / g CFx. The red dots indicate the condition of the electrolyte when it was removed for mass spectrometry (MS) testing. [Figure 47] Figure 47 shows MS data of the electrolyte collected during the OCV state of the battery. [Figure 48] Figure 48 shows MS data of the electrolyte collected at 0.5 V (discharged state) of the battery. [Figure 49] Figure 49 MS data under Dart ESI+ mode for electrolytes collected from Li / CFx batteries as freshly prepared (2.5M, black) or in OCV (BL, red), 2V discharge (2V, green) and 0.5V discharge (0.5V, blue) states. [Figure 50] Figure 50. Li / CFx primary with multifunctional electrolyte. High energy and power density Li||CFx primary cell enabled by graphene-CFx cathode and multifunctional electrolyte that also contributes energy and power by forming a LiF-rich solid electrolyte interface at the same reduction potential of CFx. [Figure 51] FIG. 51. Discharge profiles of baseline 2.5 M LiBF4 / DMS multifunctional electrolyte on graphene electrode at 500 mA / g with different cell end capacities at 30% state of discharge (SOD) and 0.5 V voltage (D0.5V). [Figure 52] Figure 52a-d: SEM (a) and magnified SEM (b) images of graphene discharged at 30% SOD showing the formation of porous LiF particles on graphene in 2.5 M LiBF4-DMS. SEM images of 100% SOD discharge (c) and pristine graphene (d). [Figure 53] Figure 53a-c shows the discharge profiles of 2.5 M LiBF4 / different solvents (DMS, DME, EC:DME) and 2.5 M different lithium salts (LiPF6, LiFSI) / DMS electrolytes on freestanding graphene (graphene:PTFE = 8:2, 2 mg / cm2 loading) with marked 30% SOD and different cell end capacities at fully discharged states. (a) XRD profiles of discharged freestanding graphene electrodes extracted at a partial discharge state of 30% SOD near 1.8 V (D1.8 V) (b) and at a fully discharged state of D0.5 V (c), showing the formation of LiF phase (PDF#45-1460), compared to an undischarged pristine graphene electrode (Raw G). [Figure 54] Figure 54a-b High-resolution transmission electron microscope (HRTEM) images of discharged graphene in 2.5 M LiBF4 / DMS electrolyte with 30% SOD (a) and 100% SOD (b). [Figure 55] Figure 55 shows the discharge profiles of the designed multifunctional electrolyte (2.5 M LiBF-DMS) at 288 mA / g and the commercial LiPF / EC:DMC electrolyte at 200 mA / g. The electrolyte reduction plateau of the designed electrolyte can be divided into two reactions marked in red at 2.4 V and in green at a lower voltage. [Figure 56] Figure 56a-b Specific energy density of Li||CFx cells using multifunctional electrolyte at C / 10 rate compared to commercial LiPF6 / EC:DMC baseline electrolyte at C / 3 rate (a) and various temperature ranges from -40 to 60 °C (b). [Figure 57] Figure 57a-b shows the pulse power performance of the CFx electrode at 80% state of charge (SOC) and 15% SOC at 5 / 3C (a) during approximately C / 10 discharge for 10 seconds (green) and 1 minute (orange). [Figure 58] Figure 58a-c. Discharge profiles of Li||CFx batteries at 200 mA / g in 2.5 M different lithium salt / DMS electrolytes (a) and 2.5 M LiBF4 in different solvents (b). The asterisk indicates the 2.5 M LiBF4 / DMS multifunctional electrolyte. [Figure 59] Figure 59a-b. Measurement of the physical properties of the multifunctional electrolytes, including ionic conductivity (a) and Li+ transference number (b) at 25 °C, compared to a commercial low-temperature 0.5 M LiBF4 / PC:DME electrolyte and a commercial 1 M LiPF6 / EC / DMC electrolyte. [Figure 60] Figure 60a-c shows the discharge galvanostatic intermittent titration (GITT) curves (a) and equilibrium potentials (b) of GCFx and pure CFx with DMS and commercial electrolytes, and DLi+ (c) calculated from the GITT data. The current rates are 100 mA / g for DMS electrolyte and 30 mA / g for the commercial electrolyte. [Figure 61] Figure 61a-f shows the reduction behavior of 1 M LiNO3 / DME electrolyte on graphene electrode (a). Self-discharge behavior tested under different storage time conditions for as-prepared cells in 2.5 M DMS-NO electrolyte (b). Self-discharge behavior tested under intermittent conditions for 1 month after partial discharge with 2.5 M DMS with / without LiNO3 additive and LiPON coated lithium (c). Stability of Li surface in electrolyte with SEM images showing the surface of fresh Li (d) and Li extracted after 5 months without discharge with (e) no LiNO3 and (f) LiNO3 in the electrolyte. DETAILED DESCRIPTION OF THE INVENTION

[0009] 1.0 Definition For the purposes of promoting an understanding of the principles of the invention, reference will be made herein to particular embodiments and specific language will be used to describe the same. Nevertheless, it will be understood that no limitation of the scope of the invention is thereby intended, and that changes and modifications in the illustrated invention, and further applications of the principles of the invention as set forth therein, are contemplated herein as would normally occur to one skilled in the art to which the invention pertains.

[0010] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0011] For purposes of interpreting this specification, the following definitions shall apply, and where appropriate, terms used in the singular shall also include the plural and vice versa. In the event that any definition set forth below conflicts with the usage of that word in any other document, including any document incorporated herein by reference, the definition set forth below shall always control for purposes of interpreting this specification and its associated claims, unless a contrary meaning is clearly intended (e.g., in the document in which the term is first used).

[0012] The use of "or" means "and / or" unless otherwise stated.

[0013] The use of "a" or "an" herein means "one or more" unless otherwise specified or unless the use of "one or more" is clearly inappropriate.

[0014] The use of "comprise," "comprises," "comprising," "include," "includes," and "including" are interchangeable and are not intended to be limiting. Furthermore, when a description of one or more embodiments uses the term "comprising," those skilled in the art will understand that in some specific instances, one or more embodiments may alternatively be described using the terms "consisting essentially of" and / or "consisting of."

[0015] As used herein, the term "about" refers to a ±10% variation from the nominal value. It is to be understood that such a variation is always included in any given value provided herein, whether or not it is specifically referred to.

[0016] As used herein, the term "LiFSI" refers to lithium bis(trifluoromethylsulfonyl)imide.

[0017] As used herein, the term "LiDFOB" refers to lithium difluoro(oxalato)borate.

[0018] As used herein, the term "PVDF" refers to polyvinylidene fluoride.

[0019] As used herein, the term "PTFE" refers to polytetrafluoroethylene.

[0020] As used herein, the term "CMC" refers to carboxymethyl cellulose.

[0021] As used herein, the term "SBR" refers to styrene butadiene rubber.

[0022] As used herein, the term "DMS" refers to dimethyl sulfite.

[0023] As used herein, the term "DME" refers to 1,2-dimethoxyethane.

[0024] As used herein, the term "CFx" refers to fluorinated carbon, where x may be equal to 1 (also known as carbon monofluoride).

[0025] As used herein, the term "GCFx" refers to a mixture prepared by a method that includes combining CFx and graphene. The term also refers to a mixture prepared by a method that includes combining CFx, graphene, and a thermoplastic polymer material (e.g., a thermoplastic fluoropolymer such as PVDF).

[0026] The term "bare lithium metal" refers to lithium metal having a purity of at least about 99%, including lithium metal having a purity of about 99%, about 99.9%, or 100%.

[0027] 2.0 Multifunctional electrolyte

[0028] One aspect of the present invention relates to a multifunctional liquid catholyte comprising lithium tetrafluoroborate (LiBF4) in dimethyl sulfite (DMS), where the two components have been shown to interact at high potentials (2.4 V) on the cathode, creating a non-passivating interface and resulting in very high additional energy density. The inventors have demonstrated that the resulting electrolyte has a high transference number (t += 0.738) and low charge transfer resistance, resulting in dramatic improvements in pulse power and low-temperature performance. As a result, the specific capacity of CFx increased by approximately three times (from 900 mAh / g to 2700 mAh / g at a current rate of 1 / 3 C (288 mA / g, 1 C = 865 mA / g relative to CFx). CF ), which corresponds to a specific energy of 5689 Wh / kg, approximately three times higher than the commercial electrolyte. 2 When high pulse currents of 1000 W / kg are applied, the pulse power densities at 10-second and 1.0-minute DODs (depth of discharge) of 15-20% and 75-85% of the capacity of CFx (approximately 2000 mAh / g) are higher than 4000 W / kg. Surprisingly, we discovered that Li||CFx cells perform well at cryogenic temperatures, even at -70°C, delivering an unprecedented capacity of 1356 mAh / g at 1 / 175°C. Based on the actual additional capacity of 800-1400 mAh / g of electrolyte, the Li||CFx model predicts that the energy density of packaged pouch cells can be increased by 20%-30% by simply replacing the commercially available electrolyte with the multifunctional electrolyte. Finally, by adding a small amount of additive, the electrolyte can passivate the Li anode, thus extending the cell's shelf life (5 months). The extraordinary discharge performance recorded indicates great potential for practical use, especially in extreme environments.

[0029] 2.1 Non-Limiting Embodiments

[0030] One aspect of the present invention relates to a multifunctional electrolyte composition for a primary CFx / Li battery, the multifunctional electrolyte comprising a lithium salt dissolved in a solvent, the lithium salt may be selected from LiBF, LiDFOB, LiPF, LiFSI, and LiNO, or a combination thereof, and the solvent may be selected from dimethyl sulfite, ethylene sulfite, 1,2-propylene glycol sulfite, and diethyl sulfite, or a combination thereof. In some embodiments, the lithium salt may be LiBF. In further embodiments, the solvent may be dimethyl sulfite.

[0031] In some embodiments, the electrolyte has a concentration in the range of about 0.5 M to about 6 M, or in the range of about 1 M to about 6 M, or in the range of about 2.5 M to about 6 M, or in the range of about 1.5 M to about 3 M. In further embodiments, the electrolyte has a concentration of about 2.5 M.

[0032] Another aspect of the present invention relates to a primary CFx / Li battery comprising a cathode, an anode, and an electrolyte disclosed herein.

[0033] In some embodiments, the cathode material comprises CFx and a binder, optionally coated on an aluminum foil. Examples of binders include PVDF, PTFE, CMC, and SBR, or combinations thereof.

[0034] In some embodiments, the cathode material comprises CFx present in an amount of about 80 to about 99 wt% and a binder present in an amount of about 1 to about 20 wt%. In further embodiments, the cathode material comprises about 90 to about 99 wt% CFx and about 1 to about 10 wt% binder. In some embodiments, the cathode material comprises about 94.5 to about 98.5 wt% CFx and about 1.5 to about 5.5 wt% binder. In further embodiments, the cathode material comprises about 95 wt% CFx and about 5 wt% binder.

[0035] In some embodiments, the cathode material comprises CFx, a binder, and graphene. In further embodiments, the cathode material comprises CFx present in an amount ranging from about 60 to about 99 wt%, graphene present in an amount ranging from about 0.5 to about 20 wt%, and a binder present in an amount ranging from about 0.5 to about 20 wt%. In further embodiments, the cathode material comprises CFx in an amount ranging from about 80 to about 99 wt%, graphene in an amount ranging from about 0.5 to about 10 wt%, and a binder in an amount ranging from about 0.5 to about 10 wt%. In still further embodiments, the cathode material comprises CFx in an amount ranging from about 89 to about 97 wt%, graphene in an amount ranging from about 1.5 to about 5.5 wt%, and a binder in an amount ranging from about 1.5 to about 5.5 wt%. In a further embodiment, the cathode material comprises about 90% by weight of CFx, about 5% by weight of graphene, and about 5% by weight of a binder.

[0036] In some embodiments, the anode material comprises lithium. Examples of lithium that can be incorporated as the anode material include bare lithium metal, lithium metal plated on copper foil, lithium chips, and lithium foil, or combinations thereof. In some embodiments, the lithium chips have a thickness in the range of about 200 μm to about 700 μm, or in the range of about 200 μm to about 500 μm, or about 400 μm to about 600 μm, or about 500 μm. In further embodiments, the lithium foil has a thickness in the range of about 20 μm to about 50 μm. In some embodiments, the lithium foil has a thickness of about 50 μm.

[0037] In some embodiments, the electrolyte composition includes an additive. Examples of additives that can be incorporated into the electrolyte composition include LiNO3 in a solvent such as DME and a LiPON coating on lithium metal. In some embodiments, the molar ratio of LiNO3:LiBF4 in the electrolyte composition is about 1 to about 62.5. In some embodiments, the LiPON coating is about 10 nm thick.

[0038] In some embodiments, the primary CFx / Li battery is a coin cell battery. In further embodiments, the primary CFx / Li battery is a pouch cell battery.

[0039] In some embodiments, the operating temperature of the primary CFx / Li battery is in the range of about −90° C. to about 50° C., or in the range of about −70° C. to about 45° C., or in the range of about −40° C. to about 45° C., or in the range of about 0° C. to about 30° C.

[0040] A further aspect of the invention is a method of assembling such a primary CFx / Li battery, comprising stacking materials in the following order: cathode, electrolyte, and then anode, with a separator disposed between the cathode and anode, and the materials being mechanically sealed within a casing. In some embodiments, the materials are mechanically sealed within a coin cell. In other embodiments, the materials are mechanically sealed within a pouch cell.

[0041] Another aspect of the invention is a method of using the primary CFx / Li battery, wherein the battery, upon discharge, provides a voltage in the range of about 0 V to about 3 V. In some embodiments, the battery has a discharge voltage in the range of about 2 V to about 3 V. In further embodiments, the battery has a discharge voltage of about 2.4 V.

[0042] Enumeration of Embodiments The following is a list of non-limiting embodiments: 1. A multifunctional electrolyte composition for a primary CFx / Li battery, the multifunctional electrolyte comprising a lithium salt dissolved in a solvent, the lithium salt may be selected from LiBF, LiDFOB, LiPF, LiFSI, and LiNO, or a combination thereof, and the solvent may be selected from dimethyl sulfite, ethylene sulfite, 1,2-propylene glycol sulfite, and diethyl sulfite, or a combination thereof. 2. The composition of embodiment 1, wherein the lithium salt is LiBF4. 3. The composition of embodiment 1, wherein the solvent is dimethyl sulfite. 4. The composition of embodiment 1, wherein the electrolyte has a concentration ranging from about 0.5M to about 6M. 5. The composition of embodiment 1, wherein the electrolyte has a concentration ranging from about 1M to about 6M. 6. The composition of embodiment 1, wherein the electrolyte has a concentration ranging from about 2.5M to about 6M. 7. The composition of embodiment 1, wherein the electrolyte has a concentration ranging from about 1.5M to about 3M. 8. The composition of embodiment 1, wherein the electrolyte has a concentration of about 2.5 M. 9. A primary CFx / Li battery comprising a cathode, an anode, and an electrolyte, wherein the electrolyte is the electrolyte described in any of the previous embodiments. 10. The battery of embodiment 9, wherein the cathode comprises a cathode material comprising CFx and a binder. 11. The battery of embodiment 10, wherein the binder is coated on the aluminum foil. 12. The battery of embodiment 10, wherein the cathode material comprises CFx and a binder coated on a carbon-coated aluminum foil. 13. The battery of embodiment 10, wherein the binder is selected from PVDF, PTFE, CMC, and SBR, or a combination thereof. 14. The battery of embodiment 10, wherein the CFx is present in an amount of about 80 to 99 wt % and the binder is present in an amount of about 1 to about 20 wt %. 15. The battery of embodiment 10, wherein the CFx is present in an amount of about 90 to 99 wt. % CFx, and the binder is present in an amount of about 1 to about 10 wt. %. 16. The battery of embodiment 10, wherein the CFx is present in an amount of about 94.5 to 98.5 wt. % CFx, and the binder is present in an amount of about 1.5 to about 5.5 wt. %. 17. The battery of embodiment 10, wherein the CFx is present in an amount of about 95 wt% CFx, and the binder is present in an amount of about 5 wt%. 18. The battery of embodiment 10, wherein the battery further comprises graphene. 19. The battery of embodiment 18, wherein the battery comprises in the range of about 60 to about 99 wt.% of the CFx, the graphene in an amount of about 0.5 to about 20 wt.%, and the binder in an amount of about 0.5 to about 20 wt.%. 20. The battery of embodiment 19, wherein the CFx is present in an amount of 80 to about 99 wt %, the graphene is present in an amount of about 0.5 to about 10 wt %, and the binder is present in an amount of about 0.5 to about 10 wt %. 21. The battery of embodiment 19, wherein the CFx is present in the range of about 89 to about 97 wt. %, the graphene is present in an amount of about 1.5 to about 5.5 wt. %, and the binder is present in an amount of about 1.5 to about 5.5 wt. %. 22. The battery of embodiment 19, wherein the CFx is present in an amount of about 90 wt.%, the graphene is present in an amount of about 5 wt.% graphene, and the binder is present in an amount of about 5 wt.%. 23. The battery of embodiment 9, wherein the anode comprises a lithium metal anode material. 24. The battery of embodiment 9, wherein the anode material comprises lithium. 25. The battery of embodiment 24, wherein the lithium is present as bare lithium metal. 26. The battery of embodiment 24, wherein the lithium is present as lithium metal plated on a copper foil. 27. The battery of embodiment 24, wherein the lithium is present as lithium chips. 28. The battery of embodiment 24, wherein the anode material comprises lithium chips having a thickness in the range of about 200 μm to about 500 μm. 29. The battery of embodiment 24, wherein the anode material comprises lithium foil. 30. The anode material of embodiment 24, wherein the lithium foil has a thickness ranging from about 20 μm to about 50 μm, about 20 μm, or about 50 μm. 31. The anode material of embodiment 30, wherein the lithium foil has a thickness of 50 μm. 32. The electrolyte composition of any of the previous embodiments, wherein the electrolyte further comprises an additive. The additive is a lithium salt, for example, LiPON, LiNO 3)or LiBF4. In some examples, the additive may comprise a lithium salt in a solvent (e.g., LiNO disposed in a solvent such as DME). 3) ), for example, LiNO in DME. In some embodiments, the additive comprises a lithium salt coating. For example, the additive may be a composition comprising LiNO and LiBF. 33. The electrolyte composition of embodiment 32, wherein the additive comprises 1 M LiNO3 in a solvent such as DME. 34. The electrolyte composition of embodiment 32, wherein the additive comprises 1 M LiNO3 in a solvent such as DME, and the molar ratio of LiNO3:LiBF4 is in the range of about 1:40 to about 1:80, or in the range of about 1:50 to about 1:70, or about 1:65. 35. The electrolyte composition of embodiment 32, wherein the additive comprises a LiPON coating on the lithium metal having a thickness in the range of about 5 nm to about 50 nm, or in the range of about 5 nm to about 25 nm, or in the range of about 5 nm to about 15 nm, or about 10 nm. 36. The battery of embodiment 9, wherein the battery is a coin cell battery. 37. The battery of embodiment 9, wherein the battery is a pouch cell type battery. 38. The battery of embodiment 9, wherein the operating temperature of the battery is within the range of about -90°C to about 50°C. 39. The battery of embodiment 9, wherein the operating temperature of the battery is within the range of about -70°C to about 45°C. 40. The battery of embodiment 9, wherein the operating temperature of the battery is within the range of about -40°C to about 45°C. 41. The battery of embodiment 9, wherein the operating temperature of the battery is within the range of about 0°C to about 30°C. 42. A method for making a battery assembly, comprising preparing multiple layers of a cathode, an electrolyte, and an anode. 43. A method of assembling the battery of embodiment 9, comprising: - stacking a cathode, an electrolyte according to any of the previous claims and an anode to obtain multiple layers, the cathode then the electrolyte then the anode; disposing a separator between the cathode and the anode; The cathode, then the electrolyte, then the anode, and the separator are sealed (e.g., mechanically sealed) within a cell casing. A method comprising: 44. The method of embodiment 43, wherein the cathode, the electrolyte, the anode, and the separator are sealed in a coin cell. 45. The method of embodiment 43, wherein the cathode, the electrolyte, the anode, and the separator are sealed in a pouch cell. 46. ​​A method of supplying power, comprising using the battery of embodiment 9 to supply a voltage in the range of about 0 V to about 4 V, or a voltage in the range of about 0 V to about 3.5 V, or a voltage in the range of about 0 V to about 3 V, or about 3.5 V, when discharged. 47. The method of embodiment 46, wherein the battery provides a discharge voltage in the range of about 2V to about 3V. 48. The method of embodiment 46, wherein the battery provides a discharge voltage of about 2.4 V. 49. The method of embodiment 43, wherein the separator is selected from glass fibers of the types GF / A, GF / G, Celgard 2325, 2500, 2400, and cellulose having a thickness ranging from about 20 to about 80 μm or from about 30 to about 60 μm. [Example]

[0043] 3.0 Working Example The following examples are provided solely to illustrate the present invention and are not intended to limit the scope of the invention described herein.

[0044] Example 1 Coin Cell Proof of Concept

[0045] The reduction activity of selected electrolytes (Table 1) was evaluated on copper current collectors and stainless steel (Fig. 1a and Fig. 8). LiBF4 / DMS electrolyte was found to start decomposing at high potentials (>2.4 V) and to have non-passivating properties. This is due to the BF4 -This corresponds to the formation of a porous LiF-rich solid electrolyte interface (SEI) resulting from the reduction, as evidenced by both subsequent experimental and computational analysis. This is in stark contrast to the behavior of LiBF4 / DMS electrolyte, LiBF4 salt in other types of solvents, including ethers, carbonates, and sulfones, or other lithium salts, LiPF6 in DMS solvent, and lithium bis(fluorosulfonyl)imide (LiFSI), all of which exhibit self-limiting decomposition reactions at low potentials (<2 V). A unique interaction occurs in the LiBF4 / DMS electrolyte, resulting in a continuously growing interphase layer at approximately 2.4 V, forming Li|CF x This is expected to introduce a significant amount of additional energy into the battery. Therefore, we examined the capacity contribution of LiBF4 / DMS electrolyte to the graphene electrode (Figure 9 and Figure 1b) as a function of concentration. Noteworthy, the following electrochemical measurements were performed under an excess electrolyte volume (80 μL) per cell, using porous glass fiber as the separator. As shown in Figure 1b, due to the sufficient specific surface area of ​​the graphene electrode, a high achievable capacity of nearly 30,000 mAh / g was achieved in a 6 M LiBF4 / DMS electrolyte, based on the mass of graphene at an average voltage of 2.4 V. The small plateau below 2 V in the 1-4 M electrolyte can be assigned to the reduction of the DMS solvent, and its decomposition capacity and potential can be limited by high-potential LiF aggregation. Significantly, at a concentration as low as 0.5 M, BF4 - Due to the insufficient amount, the capacity at 2.1 V is mainly due to preferential DMS depletion, which is in good agreement with the cases of LiPF6 and LiFSI in DMS electrolyte (Fig. 10a).

[0046] [Table 1]

[0047] As is well known, the CFx cathode transforms into exfoliated graphite after electrochemical defluorination, forming a large bare surface ready to undergo electrolyte reduction reactions similar to those of graphene. Here, graphene (10% by mass) was uniformly dispersed throughout the CFx electrode to replace conventional conductive carbon black to enhance electronic conductivity and provide a continuous conductive network in the batter. Unless otherwise noted, the resulting electrode, referred to as GCFx, was used as the cathode in the following sections. When the electrolyte concentration is less than 4 M, the BF4 ion concentration increases due to the kinetic limitation caused by the scarcity of reactive sites on the defluorinated GCFx. - A more pronounced decomposition of DMS solvent was observed in GCFx than in that of the graphene electrode, corresponding to the incomplete reduction of DMS (Figure 1c). This also helps to soften the interpretation of the lowest capacity obtained with GCFx using 6 M electrolyte, in contrast to the graphene electrode. Considering both the electrolyte's contribution capacity and potential in GCFx, 2.5 M was selected for further study. Furthermore, the discharge performance of a pure CFx electrode without any conductive additive (CFx:PVDF = 95%:5%) was approximately 3200 mAh / g at a low rate of 50 mA / g, more than three times the theoretical capacity (865 mAh / g), as in the case of GCFx. CFx This still provided unprecedented capacity, reaffirming the effectiveness of the multifunctional electrolyte. However, as the current rate increased, the GCFx electrode became dominant (Figure 10b and c).

[0048] The discharge performance of GCFx in parallel with seven other salts in DMS solvent or LiBF4 salt in eight different solvents was then fully investigated (Figures 11a and 11b). Of these electrolytes, DMS-dominated reduction produces an additional plateau at approximately 2 V with the other salts, while LiBF4 provides an additional capacity of less than 1 V with other types of solvents. Considering identical experimental conditions, the exclusive interaction of LiBF4 with sulfite salts would result in the maximum energy density, at high potentials, as described below. -It was hypothesized that this would allow the decomposition of BF4 into a non-passivated LiF-rich layer. In this regard, two other sulfite solvents, ethylene sulfite (ES) and 1,2-propylene glycol sulfite (PS), were also employed on graphene and GCFx electrodes (Figures 11c and 11d). Similar decomposition voltages, but a smaller capacity contribution than that of DMS, were observed, suggesting that BF4 - Further evidence for the special interaction between the anions and the sulfite molecules was provided. As a result, the specific capacity and corresponding specific energy of GCFx increased almost threefold compared to the commercial electrolyte, LiPF6 / EC:DMC, from 900 mAh / g to 2700 mAh / g. CFx This corresponds to 1986 Wh / kg to 5689 Wh / kg, respectively, tested at a current rate of 1 / 3C (288 mA / g, 865 mA / g based on 1C = CFx). Such a breakthrough shows great promise for meeting the energy density demand (Figure 1d).

[0049] The inherent interaction between LiBF4 and DMS also contributes to the Li + This helps improve ion transport kinetics, which is desirable for high-rate pulse applications such as implantable medical devices, communication systems, and scientific payloads. As shown in Figures 2a and 2b, each specimen was discharged at a C / 3 rate and pulsed for 10 seconds or 1 minute at a 5 / 3C rate (defined as Method 1) at the initial (15-20%) and near-final (75-85%) depth of discharge (DOD, actual total capacity). 1C was calculated from its performance-estimated maximum capacity, thus approximately 600 mA / g for the commercial electrolyte and 1730 mA / g for the LiBF4 / DMS electrolyte (Figure 12), approximately 4 mA / cm, respectively. 2 (1000mA / g) and 11.5mA / cm 2This corresponds to a pulse current load of 2884 mA / g. Calculations show that in both specific test events, significantly higher pulse power densities of >4000 W / kg were achieved in the DMS electrolyte compared to the <2000 W / kg pulse power density in the commercial electrolyte (Figure 2c), demonstrating its high pulse power capability. To eliminate the effect of high pulse current from the electrolyte contribution, the same value of 5.7 mA / cm was used based on the typical CFx theoretical capacity of 865 mA / g. 2 The same pulse regime (defined as Method 2) identified above was further applied with the two electrolytes (Figures 13a-c). The DMS electrolyte still exhibited higher pulse power densities, except for the 10-second and 1-minute pulses at 75-85% DOD (actual total capacity), which appears to be due to the aggregation of abundant LiF products near the end of life. Furthermore, when the pulse rate was kept unchanged and the discharge state was calculated based on the theoretical value (865 mAh / g) (defined as Method 3), it still offers a measurable advantage over the commercial electrolyte (Figures 13d-f). The full pulse discharge curves tested with the three methods are shown in Figure 14. A voltage drop (pre-pulse - end pulse) was also concluded during the pulse (Table 2), which indicates a larger LiF charge. + Due to the diffusion coefficient, all cases showed a lower voltage delay in the early discharge state compared to the commercial electrolyte (Fig. 15), while the slightly higher values ​​near the final depth of discharge could be due to the accumulation of decomposition products or the higher current density used (Method 1).

[0050] [Table 2]

[0051] Moreover, the interaction is due to the Li +This allows for easy desolvation of the electrolyte, which appears to be one major factor facilitating low-temperature operation. Essentially, DMS solvent has a low melting point of -141 °C and a low viscosity of 0.87 mPa. We attempted to determine the freezing points of LiBF4-containing solutions (2.5 M, 1 M, and 0.5 M) by differential scanning calorimetry (DSC), but no exothermic peak was observed, implying that the investigated electrolytes have melting points below -90 °C (Figure 16a). Correspondingly, the electrolyte still maintained a liquid state at -80 °C in the environmental chamber, which ensures its feasibility at low temperatures (Figure 16b). Here, we selected the known electrolyte of 0.5 M LiBF4 / PC-DME, commonly used in low-temperature Li|CFx batteries, as a control. As shown in Figure 3a, at -40°C, the cell using the 2.5M LiBF4 / DMS electrolyte can deliver 1644 mAh / g of capacity at a current density of 80 mA / g, nearly 6.5 times that of the control electrolyte (247 mAh / g). Furthermore, adequate rate capacity further enhances the high-power advantage in certain environments. Next, we compared discharge performance at different low temperatures (0°C to -70°C) (Figure 3b). Accordingly, the voltage slightly decreased above -40°C, and up to 75% of the 0°C capacity was retained. When the temperature was below -40°C, the obviously reduced capacity could be improved by using a low-concentration current rate of 1M or less (Figure 17). As a result, even at the ultra-low temperature of -70°C, the cell was able to deliver a high capacity of 1356 mAh / g, as reported (Table 3).

[0052] [Table 3]

[0053] To clarify the origin of the superior low-temperature discharge performance obtained with the designed electrolyte compared to the reported ones, we first characterized the temperature-dependent ionic conductivity by electrochemical impedance spectroscopy (EIS) measurements using two symmetrically placed Pt plate electrodes (1 cm × 1 cm) in the electrolyte and an aqueous NaCl solution with an ionic conductivity of 1.413 mS / cm as the standard. As shown in Figure 3c, the control electrolyte has higher ionic conductivity than the designed electrolyte across the entire temperature range investigated (-65 °C to +25 °C) (Figure 18a and Table 4). However, the new Li|CFx cell using the control electrolyte was found to have dramatically higher resistance than that of the DMS electrolyte at all temperatures (Figure 18b). To further understand the electrode / electrolyte interface resistance in the two electrolytes, EIS data after partial and full discharge at -40 °C were collected for comparison (Figure 3d and Figure 3e). The commercial electrolyte outperformed the DMS electrolyte by two orders of magnitude, which is attributed to the desolvation process and the Li + The non-passivating SEI layer, which contains LiF, boron, and sulfur-containing compounds derived from LiBF4 and DMS, exhibits slow ion migration, thus limiting operation at low temperatures. + It is a better conductor of ions, which explains the low interfacial impedance. - The strong interaction between the solvent and the DMS solvent resulted in a surprisingly high Li + The transference number of the electrolyte can be increased by approximately twice that of commonly used electrolytes (Fig. 3f and Fig. 19), which essentially improves the Li + This observation suggests that the Li + This is recognized as a more important step, as it is clear that it improves mobility and electrode / electrolyte interfacial dynamics.

[0054] [Table 4]

[0055] Example 2 Characterization of the Unpassivated SEI

[0056] To gain insight into the discharge progression of DMS electrolytes unaffected by LiF formation due to CFx defluorination, detailed analysis of discharged graphene cathodes recovered from partial discharge cells (30% DOD at high voltage) and fully discharged cells (discharged to 0.5 V) was performed for solid-state analysis. X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) images were collected to determine the composition and morphology of the electrolyte reduction products (Figures 4 and 20). An additional peak from 30% DOD could be indexed as a crystalline LiF phase (PDF No. 45-1460). SEM images and energy-dispersive X-ray spectroscopy (EDS) elemental mapping revealed that large spherical particles with diameters ranging from 200 nm to 1 μm (Figure 4a) likely result from LiF aggregation due to the precise appearance of fluorine signals and the lack of carbon, oxygen, sulfur, and boron signals, and BF4. - This suggests a high-voltage reduction of BF4 (Fig. 21). Consistent with the semi-quantitative analysis by EDS (Fig. 22a), some smaller particles are also deposited with diameters of 50–200 nm, which may consist of multiple elements, resulting in an atomic ratio of C:F:O:S:B of 7:7:3:1:1. At fully discharged conditions (D 0.5 V), even more LiF particles are formed, agglomerated, and nearly cover the entire graphene surface. The extremely high F atomic ratio (1:10:2:0.2:1 C:F:O:S:B) compared to the others allows for the complete reduction of BF4 as long as there is sufficient surface area. -This indicates that reduction is possible and thermodynamically favorable (Figure 22b). Of course, several O-, S-, and C-containing species, likely solvent reduction products, are also observed (Figure 4b). The results are further verified by scanning transmission electron microscopy (STEM)-electron energy loss spectroscopy (EELS) combined with selected area electron diffraction (SAED) patterns and high-resolution TEM (HRTEM) images (Figures 4c-j and 23). The uniform Li distribution in the mapping images clearly indicates that the reduction products during discharge are Li-containing compounds (Figures 4c-f). The EELS Li K-edges obtained at 30% DOD are in perfect agreement with the LiF reference, and additional minor peaks attributed to LiO are also observed in the fully discharged state (Figures 4g and 4h). Further comparative SAED pattern analysis (Figures 4i and 4j) also helps prove that LiF primarily evolved at high voltages, while LiS and LiO newly appeared at 0.5 V, which is in good agreement with the X-ray photoelectron spectroscopy (XPS) results described later. Nanocrystals with lattice fringes attributed to LiF, LiS, and LiO crystal planes are marked in the HRTEM image, corresponding well to the diffraction rings (Figure 23). Together, the small amount of S-, O-, or C-containing species in the initial discharge state may be amorphous and originate from slight solvent reduction. This indicates that LiF aggregation likely predominates as the major component in the high-voltage state, which serves as a source for further 3D growth and thus less passivation. Meanwhile, the sparser particles allow for more available carbon surface, which is consistent with the ability to continue discharge and provide the highest capacity. Similarly, substantial electrolyte decomposition actually occurs in bare exfoliated graphite upon electrochemical defluorination of pure CFx (CFx) cathodes (Figure 24), providing substantially additional energy density. In contrast, when the LiBF4 concentration was decreased to 0.5 M, the smaller the multi-element particles in the initial discharge, the higher the S and O contents were compared with the F content at full discharge, which dominated the solvent reduction (Figure 25). On the other hand, when the concentration was increased to 6 M, the F content was still the highest and the S content was the lowest, even after discharge to 0.5 V. -This means that the decomposition dominates (Figure 26). To enhance its decomposition voltage and capacity, the BF4 content should be higher than 1 M, as determined from the discharge curve of graphene. - This indicates that concentration is necessary (Figure 1c).

[0057] To further clarify the special features of the DMS solvent, comparative XRD and SEM analyses were performed, focusing on the SEI characteristics formed in 2.5 M LiBF4 with different solvents (Figures 27-31). Similar crystallinity and morphology changes upon discharge were observable in other sulfite solvents (ES and PS), which were found to correspond to low-density, continuous features (Figures 27a and 28). Clearly different from sulfite, LiBF -4 Except for sparsely distributed small LiF particles, which are presumed to result from salt hydrolysis, no crystalline or large LiF particles were formed using ethers, carbonates, and sulfones at the initial discharge state (D 1.8 V) (Figures 27a, 29a, 29c, and 30a, 30c). Then, at the end of discharge (D 0.5 V), the size and quantity of the formed LiF nanoparticles increased, indicating the normal LiBF decomposition along with the solvent reduction products, resulting in the self-termination characteristics of the SEI and thus low discharge capacity (Figures 27b, 29b, 29d, and 30b, 30d). The significant solvent dependence implies that sulfite is very unique compared to other solvents and plays an important role in regulating LiBF reduction. For other salts, such as LiPF and LiFSI, DMS-dominated reduction was demonstrated, as evidenced by undetected LiF peaks in the XRD patterns and the greater deposition of S- or O-containing compounds (Figures 27 and 31). Overall, these findings reveal in unprecedented detail the microscopic origins that explain the unique discharge behavior of LiBF4 / DMS electrolyte.

[0058] Next, we utilized XPS to track the surface chemistry associated with the decomposition reaction of the LiBF4 / DMS electrolyte on the graphene cathode. The binding energies of all peaks were calibrated by SP2C at 284.8 eV. Figure 32a compares the atomic composition ratio of the SEI at two discharge states (30% DOD and D0.5V). Compared with the small amount of adsorbed O in the initial electrode (1.8%), a clear increase (14.0%) was determined at 30% DOD, mainly due to CO (533 eV) and SO / C=O (531.7 eV) species (Figure 5a). A small proportion (1.8%) of S signals appeared as different bonding environments, mainly located above 165 eV, attributable to SO-related bonds such as Li2SO3 (167.2 eV) and Li2SO4 (170 eV), while the others were Li2S / Li2S2 (160-163 eV) and Li2S. * The presence of -SO3 (165.0 eV) and other components below 165 eV indicates Li-S bonding. Considering the electrolyte composition, these results are a good indicator of the initial DMS decomposition and explain the O and S distribution from the SEM observations (Figure 4a). More importantly, the much higher F ratio (22.2%) is associated with LiBF4 decomposition. Deconvolution of the F1s spectrum reveals two components: LiF at 685.6 eV and the intermediate Li at 687.0 eV. x BF y The results are also identified in the Li 1s (56.7 eV) and B 1s (194 eV) spectra, respectively. Clearly, when fully discharged to 0.5 V, the higher F (34.5%) and Li (36.9%) and the decreased O and B ratios prove that LiF dominates in the SEI layer (Fig. 5b). Although the total S ratio (2.46%) is still low, the higher SO3 content is observed compared to that of the 30% DOD. 2- and SO4 2- As decreases, the lower order S2 - / S2 2- The intensity of sp increases, demonstrating a more fully reduced DMS solvent, corresponding to a small plateau <2 V in the discharge profile (Fig. 1c). From the C1s spectrum shown, sp 2The slight residual C peak is hypothesized to be due to the continuous deposition of SEI on the entire graphene electrode, thereby contributing to the high capacity. Furthermore, the intensity change of SEI species with depth of discharge directly reflects the potential dependence of electrolyte reduction.

[0059] XPS can be of limited use for providing an efficient microstructural distribution of the SEI due to its limited probe depth, as evidenced by the small decay of the atomic composition ratios during the entire 1200-second sputtering (Figures 32b and 32c). To overcome this issue, focused ion beam and scanning electron microscopy (FIB-SEM) with time-of-flight secondary ion mass spectrometry (TOF-SIMS) was performed complementary to investigate the spatial distribution of SEI species along the depth. The acquisition was performed on a 5 × 5 μm area at a sputter depth of approximately 1 μm. 2 Ga in both negative and positive ion modes covering the same field of view + The TOF-SIM spectrum showed a mass / electron charge (m / z) of 19 (F - ) and 7(Li + ) evidenced the predominant presence of LiF, whether in the initial or fully discharged state (Figure 33). Furthermore, 16(O - ), 32(S / O2 - ), 24(LiOH - The peaks recorded for O were derived from solvent reduction. This result is consistent with the XPS analysis. The spatial elemental mapping and corresponding depth profile distribution of these decomposition species were compared, as shown in Figures 5c and 5d. - , LiOH - and S - Both of them have weak cumulative signals under partial discharge conditions, but they are clearly spatially distributed locally. -The signal intensity continued to increase to a steady value at a depth of approximately 830 μm, corresponding to large spherical LiF particles (Figure 5c). Upon full discharge, a layered structure of the SEI layer was established, with unpassivated LiF predominating on the outside and partially reduced O and S species on the inside, with an estimated thickness of 500 μm (Figure 5d). The results confirm the dominance of LiF on the cathode, which is in good agreement with SEM and TEM observations.

[0060] Example 3 Reconstitution of the Solvated Sheath

[0061] Taken together, the multi-analytical approach provides comprehensive and reliable information on the composition and microstructure of the obtained films, so it will be essential to understand the underlying reasons why the LiBF / DMS electrolyte exhibits such special reduction behavior. Fourier transform infrared (FTIR) and Raman spectroscopy were first performed to investigate the ion-solvent interactions in the electrolyte. As shown in Figures 6 and 34, the ion-solvent interactions in the 1200-1100 cm -1 Li in the range + Besides the -DMS coordination, the orange dashed lines indicate two new peaks (1100 and 1060 cm) encountered at all salt concentrations or in the case of other sulfites (ES, PS, and diethyl sulfite (DES)). -1 ) indicates SL of 1060 cm -1 Except for the peak of , it is not observed in the LiBF4 solutions in DME, EC:DMC, and DMSO (Figures 6a and 34a, 34b). The peak is a characteristic stretching vibration of SO, which is probably due to the deformation vibration of sulfite, since the salt and concentration are the same. However, BF4 - This did not occur when using LiPF6 and LiFSI salts (Figure 6b), reflecting the inherent functionality of the anions. To clarify the differences between LiBF4 / DMS and the others, Raman spectra were further acquired for these electrolytes. - 765cm available for allocation (SSIP or CIP) -1The bands from the BF symmetric stretching mode of Li were clearly observed in DME and EC:DMC solvents. However, the peak intensity decreased in DMSO and SL solvents and completely disappeared in DMS or other sulfites (Figure 6c). However, the solvated Li + The peak is at 755 cm for LiPF in DMS electrolyte. -1 , 745 and 1221 cm for LiFSI -1 indicates the shoulders, and these are PF6 - and FSI - This is due to AGG or CIP (Fig. 6d). Again, this determination is consistent with the sulfite-associated BF4 - The special activity of BF4 - This is related to the favorable adsorption and subsequent depletion of Li, thus contributing to the main component of the SEI, which leads to high Li + This assumption helps to interpret the transfer numbers and low charge transfer resistance.

[0062] Example 4 Demonstration and prediction in pouch cells

[0063] Before proceeding further with the prototype cell, the self-discharge behavior was established. Experimental and theoretical results demonstrated that a small amount of polysulfides generated during the initial reduction process, which are known to react near the lithium interface, can lead to a decrease in open-circuit voltage and capacity after a long resting time. Inspired by the solution of Li-S batteries, by dissolving 1M LiNO3 as an additive in DME solvent, a protective film rich in inorganic NO compounds can be constructed in situ on the Li surface, with a decomposition potential of 1.8 V (vs Li + / Li) (Figure 35). Its small proportion in the LiBF4 / DMS electrolyte (volume ratio 1:25, corresponding to a molar ratio of LiNO3:LiBF4 = 1:62.5) resulted in unchanged ion-solvent interactions as verified by FTIR spectra, as well as similar ionic conductivity and Li +The transference number (Figures 36a-36c) and therefore the pulse power are barely affected at room temperature, and the discharge voltage and capacity are fully guaranteed, even though they are slightly reduced at low temperatures (-40°C) (Figures 36d-36f). As a result, a series of cells were assembled under identical conditions and stored for a period before discharge. The voltage monitored by the cell test equipment remained stable for the first 3 months, after which a slightly increased capacity was achieved (Figures 7a and 37). After up to 5 months, there was no significant capacity loss or potential degradation, meeting the need for a shelf life of several weeks. This can be attributed to the stability of the Li surface relative to the electrolyte, as demonstrated by the slight difference between fresh Li and that extracted after 5 months without discharge (Figures 38a and 38b). From a broader perspective, many programs for protecting Li anodes, either under development or yet to be considered, are worthwhile and will ensure a long shelf life. Here, a 10-nm-thick LiPON is generally used for Li x PO y N z and deposited on a Li anode that matches the GCFx cathode. The longer the plateau at about 2.4 V is maintained after one month of standing (Figure 39), the better the suppression of sulfur species formation and therefore the higher the potential for Li protection.

[0064] Pouch-type cells were then constructed to verify the energy density achievable with limited electrolyte and lithium mass. Here, to avoid excessive adsorption of graphene in the electrolyte, the mass ratios of graphene and PVDF were both reduced to 5%, thus resulting in 90% CFx active material. The resulting cathode had a mass of 3.3 mg / cm. 2The samples had a mass loading of 1000 sq. ft. (CFx) and were cut into 4 cm x 5 cm pieces, corresponding to thin Li foils (50 μm for DMS electrolyte and 20 μm for the commercial electrolyte) (Figure 7b). First, different mechanical pressures were applied by using a test fixture with a relatively high injection coefficient (electrolyte / CFx mass ratio) of 6:1 (Figure 40). A maximum capacity of 1818.5 mAh / gCFx was found to be achieved at a uniaxial pressure of approximately 440 kPa. Further lowering the injection coefficient to 3:1 under the same pressure retained a slightly reduced capacity of 1560 mAh / gCFx (0.5 V). The electrolyte and Li metal participated in the reduction process and acted as active materials, and their masses should be calculated. After discharge to 1.5 V, the 20 μm Li metal was almost completely consumed in the commercial electrolyte, as seen in the SEM images (Figure 41a). In the DMS-NO electrolyte, some lithium remained, but several reduction products were also observed (Figure 41b). Here, we assume that the entire 50 μm of Li is used up. Based on the total weight of the cathode, anode, and electrolyte actually consumed (see Table 5 for details), our LiBF / DMS+NO electrolyte delivers a specific energy of 676 Wh / kg, about 44% higher than that of the reference electrolyte LiPF / EC:DMC.

[0065] [Table 5]

[0066] Considering commercialization requirements, we established a multilayer pouch cell model with a capacity of approximately 3.7 Ah and estimated the package specific energy and energy density using our multifunctional electrolyte. This model shows the specifications for the materials, material properties, and dimensions of the cell repeat layers in our proposed cell in a fully charged state. The capacity of the electrolyte used is 1400 mAh / g. Because both the electrolyte in the CFx cathode and separator can partially contribute to the energy density, the respective proportions of reacted electrolyte were considered as adjustable factors to evaluate the final value. As predicted by the model, the energy contribution from the multifunctional electrolyte in the cathode increases with increasing utilization. At a value of 0.8, the specific energy and energy density can increase to 979 Wh / kg and 1672 Wh / L, respectively, which are 24% and 16% higher than those of a commercially available electrolyte Li||CFx cell (790 Wh / kg and 1440 Wh / L) (Figures 7c and 7d). Subsequently, the maximum fraction of electrolyte reacting in the separator is 0.5, ensuring pulse power density, especially at the end-of-discharge state. When the electrolyte in the separator reacts, both the specific energy and energy density increase, although the rate slightly decreases as the reacted fraction increases (Figure 42). For values ​​up to 0.5, the specific energy and energy density can be up to 1027 Wh / kg and 1730 Wh / L, respectively, corresponding to a 5% and 3.5% improvement compared to those without any contribution from the electrolyte when stored in the separator. Finally, assuming an 80% weight and 80% volume packing factor for the cell, the maximum specific energy and energy density using our multifunctional electrolyte are 889 Wh / kg and 1467 Wh / L, which actually meet current needs.

[0067] Example 5 Materials and Methods

[0068] Example 5.1 Materials

[0069] Lithium chips with a thickness of 550 μm and ultrathin Li foils with controlled thicknesses of approximately 20 or 50 μm coated on Cu foils were purchased from China Energy Lithium Company. CFx (x = 1) cathode powder was used as received from Daikin Industries, Ltd. Graphene powder was obtained from Sixth Element (Changzhou) Materials Technology Co., Ltd., China. Lithium tetrafluoroborate (LiBF4, >99.99%) and lithium hexafluorophosphate (LiPF6, >99.99%) were purchased from Gotion. Other salts, including lithium bis(fluorosulfonyl)imide (LiFSI >99.95%), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, 99.95%), lithium difluoro(oxalato)borate (LiDFOB, 99.9%), lithium nitrate (LiNO, 99.99%), lithium hexafluoroarsenate (LiAsF, 99.9%), lithium trifluoromethanesulfonate (LiOTf, 99.9%), and lithium trifluoroacetate (LiTFA, 99.9%), were purchased from Sigma-Aldrich. Dimethyl sulfite (DMS, >99.0%) and diethyl sulfite were used. Disodium EDTA (DES, >98.0%) was purchased from TCI. Ethylene sulfite (ES, >99.0%), 1,2-propylene glycol sulfite (PS, >98.0%), ethylene carbonate (EC, 99%), dimethyl carbonate (DMC, 99%), diethyl carbonate (DEC, 99%), propylene carbonate (PC, 99%), 1,2-dimethoxyethane (DME, 99%), and dimethyl sulfoxide (DMSO, 99.9%) were purchased from Sigma-Aldrich. Fluoroethylene carbonate (FEC, 99.9%) and sulfolane (SL, 99.9%) were provided by Army Research Lab. All solvents were dried overnight using molecular sieves (4 Å, Sigma-Aldrich) to ensure a water content of less than 10 ppm (Karl Fischer titration, Metrohm 899 Coulometer).For the preparation of differently concentrated LiBF / DMS electrolytes (0.5M / L to 6M / L), 0.0005, 0.001, 0.002, 0.0025, 0.003, 0.004, and 0.006 mol of LiBF were separately dissolved in 1 mL of DMS solvent. Similarly, 0.0025 mol of LiBF salt was separately dissolved in other solvents (1 mL), or 0.0025 mol of different salts was separately dissolved in 1 mL of DMS solvent to form comparative electrolytes.

[0070] GCFx cathode slurries were prepared by mixing CFx, graphene, and polyvinylidene fluoride (PVDF, 99.5%, Sigma Aldrich) binder in an 80 / 10 / 10 or 90 / 5 / 5 weight ratio in 1-methyl-2-pyrrolidinone (NMP, 99.5%, Sigma Aldrich) (additional NMP may be required to adjust the viscosity of the slurry). Pure CFx cathode slurries were prepared by mixing 95% by weight of CFx and 5% by weight of PVDF binder in NMP. Graphene thin-film electrodes were prepared by mixing graphene and PVDF binder in a 90 / 10 weight ratio in NMP. All slurries were cast onto copper or carbon-coated aluminum foil using a doctor blade and dried at 100 °C under vacuum for 24 hours. The areal loading of the GCFx and pure CFx electrodes was approximately 4 mg / cm for the graphene electrode. 2 and 0.4 mg cm 2 Thicker free-standing graphene electrodes (2 mg / cm) were obtained by rolling a mixture of graphene and polytetrafluoroethylene (PTFE) binder at a weight ratio of 8 / 2. 2 ) was prepared.

[0071] Example 5.2 Material Characterization

[0072] XRD patterns were collected on a Bruker D8 X-ray diffractometer using Cu Kα radiation (λ = 1.5418 Å) to determine the composition and crystallinity of the released products. Morphology characterization was performed using a Hitachi SU-70 field emission SEM equipped with an energy dispersive X-ray spectroscopy detector and a JEOL 2100F field emission TEM equipped with a Gatan Oneview camera operating at 200 kV. To further trace the surface chemistry associated with the electrolyte decomposition reaction, XPS was performed on a highly sensitive Kratos Axis 165 X-ray photoelectron spectrometer using Mg Kα radiation, and the binding energy of all peaks was determined to be SP at 284.8 eV. 2 Calibrated by C. Ga + The spatial elemental distribution in the depth direction was investigated using ToF-SIMS equipped with a focused ion beam (FIB) / scanning electron microscope (Tescan GAIA3). The accelerating voltage of the FIB / SEM was 30 kV. All samples for the above characterization were retrieved from partially / fully discharged batteries in a 2032 coin cell configuration. Before testing, the discharged electrodes were washed with corresponding solvents to remove residual salts and dried under vacuum. To demonstrate the Li-ion solvation structure, a deuterated triglycine sulfate detector, 4 cm -1 600-4000 cm using a resolution of 1000 mV and an average of 16 scans. -1 FTIR spectra of the electrolytes were obtained on a Thermo Nicolet NEXUS 670 FTIR between 3000 cm -1 ~100cm -1 Raman spectra were obtained on a Horiba Jobin Yvon Labram Aramis using a 532 nm diode-pumped solid-state laser. DSC curves of the electrolytes were obtained on a Discovery DSC 25 with Ar flowing over the samples at a freezing rate of 3 °C / min from 40 °C to -90 °C, with all samples sealed in a pan. The ionic conductivity of the electrolytes at different temperatures was measured using two platinum plate electrodes (1 cm) placed symmetrically in the electrolyte solution. 2 ), and calculated by EIS measurements using an aqueous NaCl solution used as a standard, whose ionic conductivity is 1.413 ms / cm.

[0073] Example 5.3 Electrochemical Measurements

[0074] All cell assembly / disassembly was performed in an Ar-filled glovebox with moisture and O2 contents below 0.1 ppm. Discharge tests (capacity, pulse power, and low-temperature capacity) were performed on CR2032 coin cells with GCFx (80 / 10 / 10) as the cathode, a 550 μm-thick Li chip as the anode, and a glass microfiber separator (GF / A, Whatman) as the separator. The electrolyte (2.5 M LiBF4 / DMS) volume per cell was 80 μL. Electrochemical performance was investigated using a Neware BTS-610 instrument at room temperature, a Land BT2000 battery test system at low temperature, and an Arbin instrument for high currents with a discharge voltage down to 0.5 V. Note that prior to constant-current discharge, the cells were held at the low test temperature for approximately 2 h to establish thermal equilibrium using a Tenney test chamber (JCR-A-F4T). EIS was performed on a Gamry 1000E electrochemical workstation (Gamry Instruments, USA). Li in different electrolytes was measured by applying a 5 mV voltage polarization to a Li||Li symmetric cell for 1 h. + The transference numbers were measured by constant current intermittent titration technique (GITT) measurements on a LAND CT-2001A battery test system at 100 mAg for DMS electrolyte. -1For 1M LiPF / EC:DMC electrolyte, the test was performed at a pulse current of 30 mA / g for 1 hour, followed by a 3-hour relaxation period. To better protect the Li anode, either a 1M LiNO / DME solution additive was added to the 2.5M LiBF / DMS solution at a volume ratio of 1:25, or a 10-nm-thick LiPON coating was applied to the lithium. Self-discharge behavior was evaluated by storing the cells for several months before discharge or by intermittent storage for 1 month after partial discharge. For pouch cells, a GCFx (90 / 5 / 5) cathode, a Li foil with a thickness of approximately 20 or 50 μm, a reduced electrolyte volume (containing LiNO additive), and a 25 μm PP / PE / PP trilayer separator (2325, Celgard) were combined and subjected to different mechanical pressures using a test fixture to evaluate the energy density.

[0075] Example 6 Electrode Modification

[0076] To further improve energy density, we optimized the electrode composition. Generally, only the active material (CFx) contributes to capacity, and minimizing the amount of conductive carbon and binder yields the highest capacity per total electrode weight. Therefore, maximizing the amount of active material clearly ensures the highest energy density. However, the multipurpose electrolyte is designed to include capacity not only from CFx but also from the electrolyte decomposition reaction. Because the additional capacity from the electrolyte decomposition reaction is strongly correlated with the conductive surface area, the opposite approach of increasing the carbon content can also result in higher energy density. Therefore, various electrode compositions were tested and compared to determine which composition maximizes capacity per total electrode weight.

[0077] First, five different electrode compositions were fabricated and tested using a 2.5 M LiBF4, 0.25 M LiNO3, and DMS electrolyte. The CFx cathodes had compositions of CFx:reduced graphene oxide:PVDF = 70:20:10, 75:20:5, 80:10:10, 85:10:5, and 90:5:5. The loading on all five electrodes was approximately 4 mg / cm. 2After standing for 12 hours, the cells were discharged under the same conditions at 600 mA / g at 25 °C. Overall, when considering only the capacity based on the CFx weight, electrodes with a higher conductive carbon ratio enabled higher capacities due to the facile electrolyte decomposition reaction (Figure 43a) and the higher second plateau capacity contribution associated with the electrolyte decomposition reaction (Figure 43b). However, the further increase in capacity was not significant. When comparing capacities based on the total electrode rather than the CFx weight, the highest capacity was obtained with the 90:5:5 electrode, where the CFx fraction was maximized (Figure 43c). This is because even electrodes with a low conductive carbon ratio are prone to electrolyte decomposition reactions due to the spontaneous formation of conductive carbon by CFx during the discharge process, according to the following equation: CFx+xLi + +xe - -->C+xLiF

[0078] Because primary battery systems involve only one discharge process, the role of the binder is less important than that of rechargeable battery systems. Therefore, further optimization was performed to achieve much higher energy density by minimizing the binder amount. To further minimize the binder amount, a CMC binder was incorporated instead of the PVDF binder. CMC binders are known to be advantageous due to their high adhesive properties, not to mention their water-processability. Thanks to the higher adhesive properties of CMC, electrodes with lower binder ratios of 93:5:2 and 95:3:2 compositions were successfully fabricated without delamination issues. Performance comparison in Figure 44 shows that, as expected, the 95:3:2 electrode composition using the CMC binder yielded the highest capacity. Specifically, the capacity of the 95:3:2 electrode was 1804.1 mAh / g based on the total electrode weight, a 20.6% increase compared to the conventional 80:10:10 electrode.

[0079] Example 7 Modified Electrolyte for Extended Shelf Life

[0080] No. 3 -It has previously been shown that anions can effectively extend the shelf life of CFx / Li cells by forming a smooth and dense passivation layer on the Li metal surface. Therefore, we investigated the protection of lithium anodes with LiNO3 additives.

[0081] When 0.25 M LiNO3 was added to a 2.5 M LiBF4-DMS baseline electrolyte, it was found that the additional 0.25 M LiNO3 had little effect on the plateau voltage or the capacity of the battery (Figure 45a). However, this modified electrolyte has a significant effect on Li metal protection. As shown in Figure 45b, the cells were allowed to stand at elevated temperature (45 °C) for 16 hours to accelerate self-discharge. It was found that the capacity of the battery without additive decreased significantly, while the capacity of the battery with LiNO3 protection remained unchanged.

[0082] Example 8 Mechanistic studies.

[0083] To better understand the mechanism of this Li / CFx battery system and to infer the specific reactions of electrolyte decomposition during discharge, the electrolyte was analyzed by mass spectrometry (MS). The electrolyte of the Li / CFx battery at open circuit potential (OCV) and 0.5 V discharge state (Figure 46) was first collected for MS testing.

[0084] Comparing the composition of the electrolyte collected at the two potentials, the electrolyte in the OCV was OCH3 - clusters (Figure 47, labeled in yellow), but in the fully discharged (0.5 V) state of the electrolyte (Figure 48), this material disappears and OCH3 - are intermediate products of electrolyte decomposition and are completely consumed after full discharge. Furthermore, it is clear that the electrolyte contains multiple ion clusters containing LiF, indicating that the electrolyte can dissolve LiF and that the dissolved LiF contributes to the formation of a porous SEI structure, ensuring the continuous decomposition of the electrolyte.

[0085] To fully characterize the organic products after electrolyte decomposition, we characterized the freshly prepared electrolyte using MS in the Dart ESI+ mode to measure the main components of the electrolyte at different potentials collected in a Li / CFx cell. As shown in Figure 49, 2.5M represents our freshly prepared electrolyte, while BL, 2V, and 0.5V represent the electrolyte composition curves in the cell at OCV, 2.0V, and 0.5V states, respectively. The electrolyte composition becomes increasingly diverse during discharge. A species with a mass of 149.11, representing an ionic cluster of LiOCH3, appeared in the BL sample. Interestingly, this peak increased in the 2V curve but disappeared at 0.5V, indicating that LiOCH3 is generated in the electrolyte at the beginning of discharge and consumed at voltages below 2V. This is consistent with our previous MS characterization results shown in Figures 47 and 48. Furthermore, as the discharge reaction progressed, BF4 - F in the anion - The group gradually becomes OCH3 - The replacement of functional groups can also be observed. According to the chemical formula, OCH3 is the product of the decomposition of the solvent DMS, indicating that the first decomposition platform of the electrolyte at approximately 2 V is the result of the joint decomposition of the salt and the solvent. Subsequently, in the electrolyte at a discharged voltage of 0.5 V, the formation of Li2S and Li2S6 species was observed, indicating that the solvent was further decomposed into sulfur-containing compounds.

[0086] A summary of the electrolyte components is shown in Table 6. In the freshly prepared electrolyte, BF2(OCH3) is present. After cell assembly, the electrolyte begins to decompose into LiOCH3, SOCH3, and BF3 upon contact with the CFx cathode and Li anode. In the first plateau above 2 V, the LiBF4 salt and DMS solvent decompose together to LiF, BF(OCH3)2, and B(OCH3)3. In the second plateau below 2 V, the electrolyte is completely reduced to Li2S and Li2O. Based on the MS results and previous characterization data, the updated electrolyte decomposition reaction can be described as follows: 2LiBF4+3C2H6O3S+18Li + +18e -→8LiF+2B(OCH3)3+3Li2S+3Li2O

[0087] (The theoretical capacity is 931.47mAh / g based on LiBF4, and C2H6O3S does not contain Li).

[0088] [Table 6]

[0089] Example 9 Design of multifunctional electrolytes to enhance the energy and power density of Li / CFx

[0090] Some steps to design a multifunctional electrolyte to enhance the energy and power density of Li / CFx primary batteries (Figure 50) include: designing the CFx electrode by replacing carbon black with graphene to enhance the rate and pulse power performance; replacing the inert electrolyte with a multifunctional electrolyte that can form porous LiF at the same potential as the CFx cathode to improve the specific energy of the cell; using a suitable electrolyte additive that can form a dense SEI on the Li anode and reduce it at potentials below 1.0 V to achieve long calendar life and low self-discharge rate; and improving the ionic conductivity and Li + and optimizing the multifunctional electrolyte to improve the transport number, reduce the interfacial resistance, and ensure good pulse power and sustained operation at low temperatures.

[0091] Example 10 Capacity of 2.5M LiBF4-DMS electrolyte

[0092] DMS has the following properties: density = 1.294 g / mL at 25°C, molecular weight = 110.3 g / mol. LiBF4 has a molecular weight of 93.75 g / mol. Table 7 shows the theoretical specific capacity at various concentrations of LiBF4-DMS. A graph of voltage vs. specific capacity for a CFx / Li cell with 2.5 M LiBF4-DMS electrolyte (Figure 55) shows two regions that determine whether the observed voltage is dominated by electrolyte reduction (region of reaction 1) or solvent reduction (region of reaction 2). The reactions are as follows: Response 1: 2LiBF4+3C2H6O3S+18Li + +18e - →8LiF+2B(OCH3)3+3Li2S+3Li2O Reaction 2: C2H6O3S+6Li + +6e - →2LiOCH3+Li2S+Li2O

[0093] [Table 7]

[0094] [Table 8]

[0095] All publications mentioned herein are incorporated by reference to the extent that they support the present invention.

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[0097] Several patents and publications are cited above in order to more fully describe and disclose the present invention and the state of the art to which it pertains. Full citations for these references are provided below. Each of these references is incorporated herein by reference in its entirety to the same extent as if each individual reference was specifically and individually indicated to be incorporated by reference.

Claims

1. A multifunctional electrolyte composition for a primary CFx / Li battery, the multifunctional electrolyte comprising a lithium salt dissolved in a solvent, the lithium salt being LiBF ４ , LiDFOB, LiPF ６ , LiFSI, and LiNO ３ or a combination thereof, and the solvent may be selected from dimethyl sulfite, ethylene sulfite, 1,2-propylene glycol sulfite, and diethyl sulfite, or a combination thereof.

2. The lithium salt is LiBF ４ The composition of claim 1 ,

3. The composition of claim 1 wherein the solvent is dimethyl sulfite.

4. 10. The composition of claim 1, wherein the electrolyte has a concentration ranging from about 0.5M to about 6M.

5. A primary CFx / Li battery comprising a cathode, an anode, and an electrolyte according to any one of claims 1 to 4.

6. 6. The battery of claim 5, wherein the cathode comprises a cathode material, the material comprising CFx and a binder.

7. 7. The battery of claim 6, wherein the cathode material comprises CFx and a binder.

8. 8. The battery of claim 7, wherein said binder is coated onto a carbon coated aluminum foil.

9. 9. The battery of claim 8, wherein the binder is selected from PVDF, PTFE, CMC, and SBR, or a combination thereof.

10. The battery of any one of claims 6 to 9, wherein the CFx is present in an amount of about 80 to 99 wt% and the binder is present in an amount of about 1 to about 20 wt%.

11. 10. The battery of claim 6, wherein the CFx is present in an amount of about 94.5 to 98.5 wt. % CFx and the binder is present in an amount of about 1.5 to about 5.5 wt. %.

12. 8. The battery of claim 7, wherein the battery further comprises graphene.

13. 13. The battery of claim 12, wherein the battery comprises the CFx in the range of about 60 to about 99 wt %, the graphene in an amount of about 0.5 to about 20 wt %, and the binder in an amount of about 0.5 to about 20 wt %.

14. 13. The battery of claim 12, wherein the CFx is present in the range of about 89 to about 97 wt%, the graphene is present in an amount of about 1.5 to about 5.5 wt%, and the binder is present in an amount of about 1.5 to about 5.5 wt%.

15. 6. The battery of claim 5, wherein the anode comprises a lithium metal anode material.

16. 17. The battery of claim 16, wherein the anode material comprises lithium.

17. Additives, such as LiNO ３ The electrolyte composition according to any one of claims 1 to 16, further comprising an additive.

18. The additive is about 1 M LiNO in a solvent (such as DME). ３ 18. The electrolyte composition of claim 17, comprising:

19. The additive is about 1 M LiNO in a solvent (such as DME). ３ LiNO ３ : LiBF ４ 20. The electrolyte composition of claim 18, wherein the molar ratio of is 1:62.

5.

20. 20. The battery of any one of claims 1 to 19, wherein the operating temperature of the battery ranges from about -90°C to about 50°C.

21. 21. The battery of any one of claims 1 to 20, wherein the operating temperature of the battery ranges from about 0°C to about 30°C.

22. 22. A method of supplying electrical power, comprising using a battery according to any one of claims 1 to 21 to supply a voltage in the range of about 0V to about 3V upon discharge.

23. 23. The method of claim 22, wherein the battery discharges to a voltage of about 2.4V.

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