Hybrid lithium-ion / lithium metal battery

Abstract

A lithium-ion electrochemical battery includes a housing, an anode (18), a cathode (22), a separator (24), and a nonaqueous organic electrolyte (26). According to another aspect, the cathode (22) includes lithium. According to yet another aspect, the anode (18) is carbonaceous and graphitized. According to a further aspect, an organic electrolyte (26) composition includes a lithium salt, a non-aqueous solvent, and a fluorinated cyclic carbonate co-solvent. In an aspect of the present battery (20), a capacity of a lithium-containing cathode (22) is greater than an intercalation storage limit of a carbonaceous anode (18), yielding a negative to positive ("N / P") ratio between the electrodes (26, 28) of about 0.01 to 0.999. The low N / P ratio and organic electrolyte (26) composition beneficially enables concurrent lithium-ion intercalation and controlled lithium-metal plating within the cell.

Description

HYBRID LITHIUM-ION / LITHIUM METAL BATTERYCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 539,855, filed on September 22, 2023, which is incorporated herein by reference.BACKGROUND AND SUMMARY

[0002] The present disclosure relates to a hybrid lithium-ion / lithium-metal battery, and more particularly to a battery with both lithium-ion intercalation and reversible lithium-metal plating capabilities.

[0003] The last several decades have witnessed a global increase in demand for portable consumer electronics including cell phones, tablets, and electric vehicles. In response, lithium-ion batteries have emerged as a frontrunner in the field of portable power technologies. However, there remains a significant need for higher energy densities, faster charging capabilities and increased safety across variable temperature ranges and operating conditions.

[0004] Conventionally, there is a gap between lithium-ion and lithium-metal technologies, largely due to uncontrolled formation of finger-like lithium dendrites on the battery anode surface in the presence of free lithium metal. These dendritic projections detrimentally consume free lithium inside the cell and ultimately grow until contact is made with the cathode, thereby shorting or destroying the cell’s electric conductivity. There have been traditional research attempts to the improvement of lithium-ion battery capabilities, but none have managed to resolve the discrepancy. See, for example, U.S. Patent Publication No. US2021 / 0408605 which was published on December 30, 2021 to Yang et aL, and U.S. Patent No. 6,506,524, issued on January 14, 2003 to McMillan et aL, both of which are incorporated by reference herein. Therefore, the present battery seeks to overcome these traditional problems by controlling the lithium-metal growth at the battery anode and utilizing an electrolyte composition which enables both lithium-ion intercalation and reversible lithium-metal plating mechanisms concurrently in a given cell.

[0005] In accordance with the present invention, a lithium-ion electrochemical battery includes a housing, an anode, a cathode, a separator, and a nonaqueous organic electrolyte. According to another aspect, the cathode includes lithium. According to yet another aspect, the anode is carbonaceous and graphitized. Accordingto a further aspect, an organic electrolyte composition includes a lithium salt, a nonaqueous solvent, and a fluorinated cyclic carbonate co-solvent. In an aspect of the present battery, a capacity of a lithium-containing cathode is greater than an intercalation storage limit of a carbonaceous anode, yielding a negative to positive (“N / P”) ratio between the electrodes of about 0.01 to 0.999. The low N / P ratio and organic electrolyte composition beneficially enables concurrent lithium-ion intercalation and controlled lithium-metal plating within the cell.

[0006] The present battery is advantageous over conventional devices. For example, the present battery construction simultaneously enables both lithium-ion and lithium-metal mechanisms within a single battery cell, unlike the conventional gap between the two technologies. Additionally, the electrolyte utilized by the present battery improves cycling and fast charging capabilities of existing commercialized lithium-ion cells. Additional advantageous features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.DRAWINGS

[0007] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

[0008] Figure 1 is a diagrammatic side view showing the present battery;

[0009] Figure 2 is an exploded, diagrammatic perspective view showing the present battery;

[0010] Figure 3 is a series of enlarged microphotographs depicting plating capability of the present battery in discharged and charged states;

[0011] Figure 4 is a graphical comparison of specific energy densities versus N / P ratios between cells prepared with different cathode thicknesses;

[0012] Figure 5 is a graphical comparison of specific energy densities versus N / P ratios between different battery cell types;

[0013] Figure 6 is a graphical comparison of discharge capacities versus cycle numbers between a conventional battery cell preparation and the preferred preparation of the present battery;

[0014] Figure 7 is a graphical comparison of discharge capacities versus cycle numbers further comparing different molar concentrations of the preferred preparation to a conventional preparation;

[0015] Figure 8 is a graphical comparison of discharge capacities versus cycle numbers further comparing different molar concentrations of the preferred preparation to a conventional preparation;

[0016] Figure 9 is a graphical comparison of discharge capacities versus cycle numbers between a conventional preparation and a 4M LiFSI electrolyte preparation of the present battery; and

[0017] Figures 10 and 11 are spider-chart comparisons of overall cell capabilities of a conventional cell preparation versus 2M and 4M preparations of the preferred electrolyte composition at different N / P ratios. Figures 12 and 13 are a graphical comparison of discharge capacity performance during fast-charging and high-energy modes in both cells prepared according to the present invention and commercially prepared cells at 25° C and 40° C, respectively.

[0018] Figures 14 and 15 are graphical comparisons of areal capacity over time in cells prepared according to the present invention and commercially prepared cells.

[0019] Figures 16 and 17 are graphical comparisons of lithium-ion capacity loss rates in cells of the present invention and commercially prepared cells.

[0020] Figures 18 and 19 are graphical comparisons of lithium-ion capacity and graphite capacity as cycle number increases in cells prepared according to the present invention as compared to commercially prepared cells.

[0021] Figure 20 is a graphical comparison of voltage potential versus areal capacity in commercially prepared cells and cells prepared according to the present invention.

[0022] Figure 21 is a graphical comparison of voltage versus time in both commercially prepared cells and cells prepared according to the present invention.

[0023] Figure 22 is a graphical comparison of the cycling performance during slow charging of the present invention and commercially prepared cells.

[0024] Figure 23 is a series of scanning electron microscopy images comparing dendrite growth in the present invention and commercially prepared cells.

[0025] Figure 24 is a graphical comparison of discharge capacity over time in both commercially prepared cells and cells prepared according to the present invention.

[0026] Figure 25 is a graphical comparison of coulombic efficiency over time in cells prepared according to the present invention and commercially prepared cells.

[0027] Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.DETAILED DESCRIPTION

[0028] Example embodiments will now be described more fully with reference to the accompanying drawings.

[0029] With reference to Figure 1 , a preferred embodiment of a hybrid lithium-ion battery 20 includes a cathode electrode 22, a separator 24, a non-aqueous organic electrolyte 26, and an anode electrode 28. The cathode 22 contains lithium such as LiNio.8Mno.1Coo.1O2 (LiNMC811 ) or another acceptable alternative. The separator 24 may be formed of a polymeric material such as polyethylene, or another acceptable alternative. The anode 18 is carbonaceous and is highly graphitized, being formed of graphene layers 30, and has an electrode preferably about 0.1 to 150 microns in thickness. A preferred embodiment of cathode 22 has a capacity greater than that of an intercalation storage limit of anode 28, which consists of graphite particles, yielding an N / P ratio of less than about 1 , and preferably between about 0.01 to 0.999.

[0030] Functionality of the present battery is divisible into two separate modes. During charging, lithium ions 32 pass from cathode 22 through non-aqueous organic electrolyte 26 and are intercalated between graphene layers 30 of anode 28. This intercalation process is a lithium-ion battery mode 34. Secondly, reversible plating of lithium metal 36 onto anode 28 surface, and within pores of the anode 28 and surrounding graphite particles is a process which is a lithium-metal mode 38. Throughout the charge and discharge process, negatively charged electrons 40 pass from an area of most negative charge to an area of most positive charge. The hybrid lithium-ion battery may be utilized in a variety of electronic devices 42 such as a cellular telephone, an automotive vehicle, a tablet, a medical device or the like.

[0031] With reference to Figure 2, an enhanced view of the plating mechanism is illustrated. Conventionally, free lithium metal in a secondary lithium-ion cell forms finger-like dendritic projections on the surface of an anode adversely affects the cycle life of the cell. The present battery, however, eliminates the formation of dendrites on a surface of anode 28 by enabling dense nodular lithium metal deposition 36 on and within anode 28. This is made possible by leveraging the high capacity of cathode 22against the lesser intercalation storage capacity of anode 28 to create the low cellular N / P ratio, while simultaneously employing the non-aqueous organic electrolyte 16. Electrolyte 16 is beneficially compatible with both lithium-metal and graphite, to form a solid electrolyte interphase (“SEI”) on the surface of the anode.

[0032] The non-aqueous organic electrolyte solution includes a lithium salt, a non-aqueous solvent, and a fluorinated cyclic carbonate co-solvent. In a preferred embodiment of the present invention, the lithium salt is LiFSI (Lithium bis(fluorosulfonyl)imide), but may be another suitable alternative including but without limitationLiPFe (Lithium hexafluorophosphate), LiDFOB (Lithium difluorooxalatoborate), or LiCIO4 (Lithium perchlorate), and is present in molar concentrations ranging from about 1 M to 4M by volume of total electrolyte. Most preferably, the molar concentration of the lithium salt is about 2M. The non-aqueous solvent is most preferably PC (propylene carbonate) but may be substituted by a suitable alternative including but without limitation DEC (diethyl carbonate), DEE (diethylether), and DME (dimethoxyethane). Furthermore, the preferred fluorinated cyclic carbonate is FEC (fluorinated ethylene carbonate) but may be substituted by a suitable alternative including but without limitation, such as DFEC (difluoroethylene carbonate), or TFPC (trifluoropropylene carbonate). Most preferably, the ratio of non-aqueous solvent to fluorinated cyclic carbonate is about 93:7, but may be 90:10 or another suitable ratio.

[0033] Turning now to Figure 3, images of the dense nodular lithium metal deposition in both a charged and discharged state are shown on the anode of both a conventionally prepared cell and an embodiment of the present invention. Figure 4 illustrates the effect of variable anode loading on the specific energy density of the cell. As the N / P ratio of the cell is decreased and cathode thickness is increased, the specific energy density of the cell also increases.

[0034] Figure 5 illustrates N / P ratios versus specific energy densities of variable cell types. “Anode-free” cells are displayed furthest to the right, having the lowest N / P ratio, and relatively high energy density. While achieving high energy density, anode- free cells often suffer from low Coulombic efficiency. Conventional lithium-ion batteries are depicted at the bottom left of the graph, having an N / P ratio greater than 1 , and relatively low specific energy densities. Conventional lithium-metal batteries, depicted at the top right of the graph, are capable of achieving high energy densities, but typically suffer from dendritic growth and safety issues under different temperatures and operating conditions. In contrast, the present hybrid lithium-ion battery exhibits anadvantageous balance of low N / P ratio to a relatively high specific energy density, and does not suffer from low Coulombic efficiency like anode-free cells, and eliminates the dendritic growth concerns presented by conventional lithium-ion batteries and lithium- metal batteries.

[0035] Figures 6-9 illustrate comparisons of expected discharge capacity over time in commercially prepared cells versus prepared cells of the present invention containing varying electrolyte concentrations. While the commercially prepared cells initially maintain a higher discharge capacity, the discharge capacity of the commercial cells quickly drop off as cycle number increases. Both the 2M and 4M preparations of the present battery far outperform the commercially prepared cell in both cycle length and maintained discharge capacity over time.

[0036] Turning to Figures 10 and 11 , a comparison of expected multiple efficiency variables in both traditionally prepared cells and the present 2M and 4M preparations are shown. Figure 10 illustrates the expected cell preparations at an N / P ratio of 1 .0, while Figure 11 illustrates the expected cells at an N / P ratio of 0.7. In both instances, the present battery preparations out-perform the conventional cells across multiple areas.

[0037] With reference to Figures 12 and 13, a comparison of fast-charging and high-energy modes between traditionally prepared cells and the present invention is shown. Figure 12 depicts the discharge capacity over time of traditionally prepared cells over time with an N / P ratio of 0.7 at 25° Celsius. Figure 13 depicts the same comparison of cells at 40° Celsius. At both temperatures, the preparations of the present battery maintain a higher discharge capacity over time than the commercially prepared cells.

[0038] Figures 14 and 15 illustrate a comparison of the high-energy mode areal capacity as cycle number increases of both the present invention and commercially prepared cells. Figure 14 demonstrates how the present invention maintains a higher areal capacity over time as compared to the commercially prepared cell of Figure 15.

[0039] Referencing Figures 16 and 17, the rates of Lithium-ion capacity loss as cycle number increases in both the present invention and commercially prepared cells are shown. A comparison of both graphs reveals a slower rate of Li-ion capacity loss in the present battery versus a higher rate of loss in the commercially prepared cells.

[0040] Turning to Figures 18 and 19, the Li-ion and graphite capacity of the present invention and commercially prepared cells as cycle number increases is shown.Figure 18 depicts how the Li-ion and graphite capacity remains higher over time in the cells of the present invention as compared to the commercially prepared cells shown in Figure 19.

[0041] With reference to Figures 20 and 21 , the nucleation of Li-ions in the present battery versus commercially prepared cells is shown. With specific reference to Figure 21 , a reduced overpotential in the present battery is shown as compared to a commercially prepared cell.

[0042] Figure 22 illustrates high discharge capacity as cycle number increases in cells prepared according to the present invention as compared to commercially prepared cells, indicating a higher level of cycling stability in the cells prepared according to the present invention.

[0043] Referencing Figure 23, comparisons of the amount of dendritic lithium between a preparation of the present invention and a commercially prepared electrolyte composition at 5 micrometers are shown. As seen in the images, cells prepared according to the present invention have minimal amounts of dendritic lithium as compared to commercially prepared cells.

[0044] With reference to Figures 24 and 25, discharge capacity and coulombic efficiency of the present invention and commercially prepared cells under fast charging conditions are shown. In both instances, the present battery outperforms the commercial preparation, maintaining a higher discharge capacity over time, and a higher coulombic capacity over time.

[0045] While various features of the present invention have been disclosed, it should be appreciated that other variations may be employed. For example, different cell types, quantities and / or shapes can be employed, although various advantages of the present system may not be realized. As another example, additional active materials can be added to either the anode or the cathode, and different concentrations of the electrolyte may be employed to achieve different levels of efficiency. Methods of using the present batteries are also envisioned. Features of each of the embodiments of the present invention may be interchanged and replaced with similar features of other embodiments, and all of the claims may be multiply dependent on each other in any combination. Variations are not to be regarded as a departure from the present disclosure, and all such modifications are intended to be included within the scope and spirit of the present invention.

[0046] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

CLAIMSWhat is claimed is:1 . A lithium-ion / lithium-metal electrochemical battery, comprising: a lithium-containing cathode; a separator; a carbonaceous anode having a surface and a plurality of pores; and an organic electrolyte composition comprising: (i) a lithium salt, (ii) a nonaqueous solvent, and (iii) a fluorinated cyclic carbonate co-solvent; wherein a capacity of the lithium-containing cathode is greater than that of the carbonaceous anode and is configured to yield a low N / P ratio of about 0.01 to 0.999, and wherein presence of both the organic electrolyte composition and the low N / P ratio causes both lithium-ion intercalation and reversible lithium-metal plating on the surface and within the plurality of pores of the carbonaceous anode.

2. The lithium-ion / lithium-metal electrochemical battery of Claim 1 , wherein a ratio of the non-aqueous solvent to the fluorinated cyclic carbonate is about 80:20 to 99:1.

3. The lithium-ion / lithium-metal electrochemical battery of Claim 2, wherein the non-aqueous solvent is propylene carbonate and the fluorinated cyclic carbonate is fluorinated ethylene carbonate.

4. The lithium-ion / lithium-metal electrochemical battery of Claim 3, wherein the ratio is 93:7.

5. The lithium-ion / lithium-metal electrochemical battery of Claim 1 , wherein the carbonaceous anode is at least partially formed of graphene layers.

6. The lithium-ion / lithium-metal electrochemical battery of Claim 5, wherein an electrode of the anode is between 0.1 and 150 microns in thickness.

7. The lithium-ion / lithium-metal electrochemical battery of Claim 1 , wherein a concentration of the lithium salt is about 1 M to 4M.

8. The lithium-ion / lithium-metal electrochemical battery of Claim 7, wherein the lithium salt is one of Lithium bis(fluorosulfonyl)imide, Lithium hexafluorophosphate, Lithium difluorooxalatoborate, or Lithium perchlorate.

9. The lithium-ion / lithium-metal electrochemical battery of Claim 1 , wherein the lithium-containing cathode is comprised of LiNiO.8MnO.1 CoO.102.

10. The lithium-ion / lithium-metal electrochemical battery of Claim 1 , wherein the non-aqueous solvent is one of propylene carbonate, diethyl carbonate, diethylether, or dimethoxyethane.11 . The lithium-ion / lithium-metal electrochemical battery of Claim 1 , wherein the fluorinated cyclic carbonate is one of fluorinated ethylene carbonate, difluoroethylene carbonate, or trifluoropropylene carbonate.

12. The lithium-ion / lithium-metal electrochemical battery of Claim 1 , wherein presence of the organic electrolyte composition causes formation of a solid-electrolyte interphase on the surface of the carbonaceous anode.

13. A lithium-ion / lithium-metal electrochemical battery, comprising: a lithium-containing cathode; a separator; a carbonaceous anode; and an organic electrolyte composition comprising: (i) a lithium salt, (ii) propylene carbonate, and (iii) fluorinated ethylene carbonate; wherein a ratio of propylene carbonate to fluorinated ethylene carbonate is about 80:20 to 99:1.

14. The lithium-ion / lithium-metal electrochemical battery of Claim 13, wherein the carbonaceous anode is at least partially formed of graphene layers, wherein the graphene layers further comprise a crystal structure.

15. The lithium-ion / lithium-metal electrochemical battery of Claim 14, wherein an electrode of the carbonaceous anode is between 0.1 to 150 microns in thickness.

16. The lithium-ion / lithium-metal electrochemical battery of Claim 13, wherein a capacity of the lithium-containing cathode is greater than that of the carbonaceous anode and is configured to yield a low N / P ratio of about 0.01 to 0.999.

17. The lithium-ion / lithium-metal electrochemical battery of Claim 16, wherein presence of both the organic electrolyte composition and the low N / P ratio causes both lithium-ion intercalation and reversible lithium-metal plating on a surface of and within a plurality of pores of the carbonaceous anode.

18. The lithium-ion / lithium-metal electrochemical battery of Claim 13, wherein the ratio of propylene carbonate to fluorinated ethylene carbonate in the organic electrolyte composition is 93:7.

19. The lithium-ion / lithium-metal electrochemical battery of Claim 13, wherein the lithium-containing cathode is comprised of LiNiO.8MnO.1 CoO.102.

20. The lithium-ion / lithium-metal electrochemical battery of Claim 13, wherein presence of the organic electrolyte composition causes formation of a solid-electrolyte interphase on a surface of the carbonaceous anode.

21. The lithium-ion / lithium-metal electrochemical battery of Claim 13, wherein the lithium salt is Lithium bis(fluorosulfonyl)imide in a concentration of about 1 M to 4M.

22. A method of making a lithium-ion / lithium metal electrochemical battery, the method comprising:(a) arranging a lithium-containing cathode opposite and spaced apart from a carbonaceous anode within a battery cell;(b) placing a polymeric separator between the cathode and the anode within the battery cell;(c) preparing an organic electrolyte composition comprising: (i) Lithium bis(fluorosulfonyl)imide in a concentration of about 1 M to 4M, and (ii) propylene carbonate and fluorinated ethylene carbonate, with a ratio of the propylene carbonate to the fluorinated ethylene carbonate being about 80:20 to 99:1 ; and(d) adding the organic electrolyte composition to the battery cell.

23. The method of Claim 22, wherein the battery is configured to pass lithium ions from the lithium-containing cathode through the organic electrolyte composition, which is a non-aqueous organic electrolyte, such that the passing lithium ions are intercalated between graphene layers of the carbonaceous anode.

24. The method of Claim 23, wherein the battery is configured to cause reversible plating of lithium metal onto and within the carbonaceous anode, and throughout a charge and discharge process, negatively charged electrons pass from an area of most negative charge to an area of most positive charge.

25. The method of Claim 20, wherein a capacity of the lithium-containing cathode is greater than that of the carbonaceous anode and is configured to yield an N / P ratio of about 0.01 to 0.999.

Images