Abstract
An electrochemical cell, including a first electrode, a first volume of electrolyte in contact with the first electrode, a second volume of electrolyte, a first separator positioned between the first volume and the second volume, a second electrode in contact with the second volume, and a third volume of electrolyte. A second separator is positioned between the second volume and the third volume. A lithium reservoir electrode is in contact with the third volume.
Claims
1. A method of producing a lithium ion battery, comprising: a) spacing a first electrode from a second electrode to define a first battery space therebetween; b) placing a first volume of lithium ion conducting electrolyte in the first battery space; c) spacing a third electrode from the first electrode to define a second battery space therebetween; and d) placing a second volume of lithium ion conducting electrolyte in the second battery space; e) connecting a switch in electric communication between the first and third electrodes; f) connecting a first switch in electric communication with the first electrode and the third electrode; g) connecting a second switch in electric communication with the first electrode and the second electrode; h) operating the lithium ion battery with the first switch open and the second switch closed, wherein the first electrode is an anode and the second electrode is a cathode; i) after h), operating the lithium ion battery with the first switch closed and the second switch open, wherein the first electrode is a cathode and the third electrode is an anode; and j) after i), operating the lithium ion battery with the first switch closed and the second switch open, wherein the first electrode is an anode and the second electrode is a cathode; wherein the third electrode is a lithium reservoir.
2. The method of claim 1 wherein lithium is replenished on the second electrode during j).
3. The method of claim 1 wherein the lithium ion battery does not experience voltage degradation over at least 100 cycles.
4. The method of claim 1 wherein the lithium ion battery does not experience voltage degradation over at least 200 cycles.
5. The method of claim 1 wherein the cathode does not experience lithium depletion over at least 100 cycles.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) FIG. 1A is a schematic illustration of a synchronized lithium and lithium-ion battery first embodiment of the present novel technology.
(2) FIG. 1B is a schematic illustration of the conventional cycling process of the synchronized lithium and lithium-ion battery.
(3) FIG. 1C is a schematic illustration of the reservoir replenishment process of the synchronized lithium and lithium-ion battery.
(4) FIG. 1D is a schematic illustration of the replenished cycling process of the synchronized lithium and lithium-ion battery.
(5) FIG. 2A graphically illustrates cell voltage vs. time for a synchronized lithium and lithium-ion battery operated sequentially in the conventional cycling, reservoir replenishment, and replenished cycling operations.
(6) FIG. 2B graphically illustrates cell voltage vs. capacity for a synchronized lithium and lithium-ion battery operated in the conventional cycling process.
(7) FIG. 2C graphically illustrates cell voltage vs. capacity for a synchronized lithium and lithium-ion battery operated in the reservoir replenishment process.
(8) FIG. 2D graphically illustrates cell voltage vs. capacity for a synchronized lithium and lithium-ion battery operated in the replenished cycling process.
(9) FIG. 2E graphically illustrates cell voltage vs. capacity for a synchronized lithium and lithium-ion battery operated cyclically.
(10) FIG. 3A graphically illustrates cell voltage vs. capacity for a synchronized lithium and lithium-ion battery operated at various voltages.
(11) FIG. 3B graphically illustrates cell voltage vs. capacity for a synchronized lithium and lithium-ion battery operated at various cycles.
(12) FIG. 3C graphically illustrates cell voltage vs. capacity for a synchronized lithium and lithium-ion battery, and the conventional full-cell operated at various voltages.
(13) FIG. 3D graphically illustrates cell voltage vs. capacity for a synchronized lithium and lithium-ion battery, and half-cell operated at various voltages.
(14) FIG. 3E graphically illustrates cell voltage vs. energy density for a synchronized lithium and lithium-ion battery, and the conventional full-cell.
(15) FIG. 3F graphically illustrates capacity vs. cycle number for a synchronized lithium and lithium-ion battery, conventional full cell, and half-cell for the charge-discharge cycle studies.
(16) FIG. 4A graphically illustrates cell voltage vs. capacity for a synchronized lithium and lithium-ion battery during 99.sup.th, 100.sup.th, 101.sup.st, and 102.sup.nd cycles.
(17) FIG. 4B graphically illustrates cell voltage vs. capacity for a synchronized lithium and lithium-ion battery and a full-cell during 101.sup.st and 102.sup.nd cycles.
(18) FIG. 4C graphically illustrates cell voltage vs. energy density for a synchronized lithium and lithium-ion battery and a full-cell during 99.sup.th, 100.sup.th, 101.sup.st and 102.sup.nd cycles.
(19) FIG. 4D graphically illustrates cell voltage vs. time for a synchronized lithium and lithium-ion battery operated sequentially in the conventional cycling, reservoir replenishment, and replenished cycling operations over the 100.sup.th and 101.sup.st cycles.
(20) FIG. 4E graphically illustrates energy density/cell capacity over time for a synchronized lithium and lithium-ion battery and a full-cell lithium ion battery.
(21) FIG. 4F graphically illustrates energy density over cycle number for a synchronized lithium and lithium-ion battery and a conventional full-cell battery.
(22) FIG. 5A schematically illustrates the synchronized lithium and lithium-ion battery of FIG. 1A switched for a reservoir reserve mode operation.
(23) FIG. 5B graphically illustrates cell voltage vs. capacity for the cell of FIG. 5A cycled over two cycles.
(24) FIG. 5C graphically illustrates experimental and fitted Nyquist plots for Li vs. MCMB and Li vs. LiFePO.sub.4 half-cells.
(25) FIG. 5D graphically illustrates experimental and fitted Nyquist plots for MCMB vs. LiFePO.sub.4 full cells.
(26) FIG. 5E graphically illustrates experimental and fitted Nyquist plots for synchronized lithium and lithium-ion battery for Li vs. MCMB and MCMB vs. LiFePO.sub.4.
(27) FIG. 5F graphically illustrates experimental and fitted Nyquist plots for synchronized lithium and lithium-ion battery for Li vs. LiFePO.sub.4.
(28) FIG. 6A graphically illustrates cell voltage vs. capacity over the first five stabilization cycles for MCMB vs. LiFePO.sub.4.
(29) FIG. 6B graphically illustrates cell voltage vs. capacity over the first 100 cycles for MCMB vs. LiFePO.sub.4.
(30) FIG. 7A graphically illustrates cell voltage vs. capacity over the first 100 cycles for Li vs. LiFePO.sub.4.
(31) FIG. 7B graphically illustrates capacity vs. cycle number over the first 100 cycles for Li vs. LiFePO.sub.4.
(32) FIG. 8A graphically illustrates cell voltage vs. capacity over the first 100 cycles for Li vs. MCMB.
(33) FIG. 8B graphically illustrates capacity vs. cycle number over the first 100 cycles for Li vs. MCMB.
(34) FIG. 9A graphically illustrates cyclic voltammograms of Li vs. LiFePO.sub.4 for the first five cycles.
(35) FIG. 9B graphically illustrates cyclic voltammograms of Li vs. MCMB for the first five cycles.
(36) FIG. 10A graphically illustrates cell voltage vs. capacity of Li vs. LiFePO.sub.4 half-cell for 100 cycles.
(37) FIG. 10B graphically illustrates capacity vs. cycle umber and cycle number vs. Coulombic efficiency for Li vs. LiFePO.sub.4.
(38) FIG. 11A graphically illustrates cell voltage vs. capacity of Li vs. MCMB half-cell for 100 cycles.
(39) FIG. 11B graphically illustrates capacity vs. cycle umber and cycle number vs. Coulombic efficiency for Li vs. MCMB.
(40) FIG. 12 graphically illustrates cell voltage vs. capacity of MCMB vs. LiFePO.sub.4 for 100 cycles.
DETAILED DESCRIPTION
(41) For the purposes of promoting an understanding of the principles of the invention and presenting its currently understood best mode process of operation, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, with such alterations and further modifications in the illustrated device and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
(42) To address the issue of Li.sup.+ ion consumption, different strategies have been explored such as loading excess cathode mass to provide 15-20% additional cathode capacity, providing a cathode having lithium additives, chemically blended cathodes, and pre-lithiation of graphite and film forming additives. All these cathode approaches contributed to changes in cell and electrode characteristics, particularly cell voltage, due to the presence of voids in an active LiFePO.sub.4 cathode, while pre-lithiation of graphite compensates completely the initial lithium consumption. Nevertheless, pre-lithiation process is one of the special techniques connected with complicated expensive process, which is not plausible for use in the large-scale applications. Indeed, there has been no known technique to achieve 100% specific full-cell capacity and energy density for lithium-ion battery full-cell, all of the above enumerated approve approaches have been enabled to minimize the irreversible capacity loss. Furthermore, continuous capacity fade in Li-ion full-cell, due to Li.sup.+ ion loss from the cathode and electrolyte, typically depletes LIBs as energy exhausted cells within 2-3 years. Hence, the enhancement of the lifetimes of current LIBs is most important for long-term EV applications by developing new strategies. Accordingly, the development of longer-lasting rechargeable batteries has enormous scope for EVs, HEVs and high-energy grid storage applications with extended lifetimes.
(43) As shown in FIGS. 1A-12, the present novel technology relates to a in-situ lithium replenishing of synchronized lithium and lithium-ion battery, 10, including a first anode electrode, 15, a second, spaced cathode electrode 20, and a reservoir-electrode 25, which acts as a booster for replenishing cycle Li.sup.+ ions consumed during SEI formation while also countering the energy reduction of the cell 10 due to capacity fading in cycle-sequence. The electrodes are immersed in an electrolyte 30 with a first separator 35 between the first and second electrodes 15, 20, and a second separator 40 between the first and third electrodes 15, 25. A first switch 45 is connected in electric communication between the first and third electrodes 15, 25, and a second switch 50 is connected in electric communication between the first and second electrodes 15, 20.
(44) The replenished MCMB vs LiFePO.sub.4 full-cell delivered the specific charge-discharge capacities of 147/145 mAh g.sup.−1 with renewed flat-voltage profiles at 3.3/3.2 V at 0.2 C and high-energy density 455 Wh/Kg. Eventually, reservoir replenishment and replenished cycling processes enable enhancement of cell capacity and energy densities for synchronized lithium and lithium-ion batteries with extended battery lifetimes approaching long lasting rechargeable batteries.
(45) Synchronized Lithium and Lithium-Ion Battery Design
(46) The synchronized lithium and lithium-ion battery geometry acts as a superseding configuration for LIBs and allows advancement towards EVs and high-power train transportation as schematized in FIGS. 1A-1D. Employing the instant synchronized lithium and lithium-ion battery configuration, in situ reservoir replenishment, and replenished cycling processes can be significantly improved battery lifetimes with an enhanced performance, particularly the specific full-cell capacity and energy densities. Thus, the ideal synchronized lithium and lithium-ion battery configuration as described in FIG. 1A, illustrate different mode operations such as conventional cycling (FIG. 1B), reservoir replenishment (FIG. 1C) and replenished cycling (FIG. 1D), executed by smart-grid line and switches connected externally. As schematized in FIG. 1A, the synchronized lithium and lithium-ion battery contains LiFePO.sub.4 cathode, MCMB anode, and thin lithium metal foil used as a lithium reservoir-electrode. These electrodes are connected via smart-grid line with switches to enjoy systematic cycling processes without external short-circuit. Significantly, the fabricated MCMB anode has the tendency of Li.sup.+ ion penetration from the reservoir-electrode to LiFePO.sub.4 cathode. With this outline, the synchronized lithium and lithium-ion battery may exhibit the conventional cycling charge-discharge process between MCMB vs LiFePO.sub.4 as given in FIG. 1B. During formation and stabilization cycles, an SEI passivation film formed and covered on the MCMB anode surface, simultaneously the Li.sup.+ ion loss occurred in LiFePO.sub.4 active particles and presented with (filled) and without Li.sup.+ ion (voids). As a result, the decreased Li.sup.+ ion concentration depleting LiFePO.sub.4 specific capacity with changes of cell voltage and introducing the term of rated cell capacity as 1 C (cell capacity determined in mAh). The synchronized lithium and lithium-ion battery operation changed to reservoir replenishment discharge-charge process between reservoir-electrode and MCMB as shown in FIG. 1C. The formation cycle Li.sup.+ ion loss can be completely compensated for by replenishment cycling charge-discharge process between MCMB anode and LiFePO.sub.4 cathode, as given in FIG. 1D. Such a reservoir replenishment process for lost Li.sup.+ ions was carried out without any other additional steps involved to recover 100% specific full-cell capacity and energy density of LiFePO.sub.4 using the synchronized lithium and lithium-ion battery configuration
(47) Reservoir Replenishment for Formation Cycles Li.sup.+ Ion Loss
(48) For the successful implementation of the novel automatic reservoir replenishment process to negate the effects of cycle Li.sup.+ ion loss in LIBs, MCMB and LiFePO.sub.4 materials are used in this example and characterized by powder X-ray diffraction pattern. All the diffraction peaks of MCMB and LiFePO.sub.4 could be well indexed with standard patterns and confirmed that no other impurity phase presented along with major phase. Consequently, the elemental mapping and energy dispersive X-ray (EDX) spectrum of MCMB shows that presence of C without any other elements, while LiFePO.sub.4 reveals presence of pronounced Fe, P and O elements. Then, the electrode materials exhibit polyhedral morphology with the average particle size in the range 3-5 μm for MCMB and 200-500 nm for LiFePO.sub.4. With this physical structural confirmation, the LiFePO.sub.4 and MCMB electrodes have been fabricated and assembled synchronized lithium and lithium-ion battery, exhibiting OCV of −0.032 V as depicted in FIGS. 2A-B. The complete in situ replenishment process, preceded by conventional cycling (SLLIB-MCMB vs LiFePO.sub.4), reservoir replenishment (SLLIB-Li vs MCMB) and the replenished cycling (SLLIB-MCMB vs LiFePO.sub.4) cycling processes are shown in FIG. 2A. The initial formation cycles were carried out with conventional cycling between MCMB vs LiFePO.sub.4 at 0.06 C rate (0.05 mA, blue) for 5 cycles as shown in FIG. 2A. From the Mode-1 results, the first formation cycle charge-discharge capacities are 172/87 mAh g.sup.−1 and its charge plateau comprising two kinds of slope-voltage profile (FIGS. 2A-B); specifically the initial slope-voltage region occurred below 2.5 V and was attributed to SEI formation and region between 2.8 to 3.5 V corresponding to electrochemically active Fe.sup.2+ redox species. The first formation cycle irreversible capacity loss was around 80 mAh g.sup.−1, which is almost 47% specific capacity loss for LiFePO.sub.4 (with respect to theoretical capacity 169 mAh g.sup.−1) as shown in FIG. 2B. The irreversible capacity loss was almost equal to the conventional full-cell irreversible capacity loss 67 mAh g.sup.−1, assembled with MCMB vs LiFePO.sub.4.
(49) The slightly excess irreversible capacity loss in synchronized lithium and lithium-ion battery can be associated with the double-sided SEI formation related to more Li.sup.+ ion consumption as the MCMB electrode has a the tendency for Li.sup.+ ion penetration through the electrode to both the reservoir-electrode and the LiFePO.sub.4 cathode. From the second cycle onward, the synchronized lithium and lithium-ion battery charge-discharge capacity of 90/85 mAh g.sup.−1 (2.5-3.5 V) was quite stable and typically matching with the stabilized charge-discharge capacity 91/88 mAh g.sup.−1 of conventional full-cell at 0.06 C (see FIGS. 6A and 6B). Also, the obtained slope-voltage profiles of the synchronized and conventional full-cells are completely different from the flat-voltage profile of LiFePO.sub.4 cathode for the reason of that reduced Li.sup.+ ion concentration with the presence of voids active particles at fully discharged state as shown in FIGS. 2B and 6A related to proposed schematic in FIG. 1C.
(50) In principle, decreased Li.sup.+ ion concentration has been associated with slope-voltage profile and unbalanced energy gradient between LiFePO.sub.4 and MCMB electrodes. Further, after formation cycles the stabilized charge-discharge capacities 90/85 mAh g.sup.−1 (rated capacity in mAh) at 0.06 C less than LiFePO.sub.4 half-cell cycling charge-discharge capacities 150/148 mAh g.sup.−1 (0.1 C, 3-4 V) as given in FIG. 7A-7F. Hence, after 5 cycles (conventional cycling of synchronized cell) the cycling process changed to reservoir replenishment operation between reservoir-electrode and MCMB at 0.1 C (0.300 mA) with measured OCV of 1.3 V and delivered stable discharge-charge capacities 396/392 mAh g.sup.−1 (1-3 cycles in FIG. 2B). The obtained results were exactly corroborated with the Li vs MCMB half-cell results, discharge-charge capacities 390/388 mAh g.sup.−1 (75.sup.th cycle) at 0.1 C between 0.01-1.5 V as given in FIG. 8A-8B. Importantly, 4.sup.th cycle discharge step (reservoir replenishment) was limited at 289 mAh g.sup.−1 to avoid complete Li.sup.+ ion intercalation into the MCMB anode. At this stage, the MCMB anode has been filled with more than required Li.sup.+ ions for the void's active particles, presented in LiFePO.sub.4 cathode. Accordingly, the synchronized cell operation was switched to replenished cycling process between MCMB vs LiFePO.sub.4 at 0.06 C rate (0.05 mA) for 1-6 cycles (sixth discharge only) with measured the OCV of 3.29 V. In replenished cycling, the synchronized lithium and lithium-ion battery delivered the charge-discharge capacities 157/152 mAh g.sup.−1 (second cycle, 0.06C, 2.5-3.5 V) with a renewed flat-voltage profile and was almost equal to the LiFePO.sub.4 half-cell cycling charge-discharge capacities of 150/148 mAh g.sup.−1 at 0.1 C between 3-4 V. Further, the rate of the replenished cycling process increased to 0.2 C and yielded charge-discharge capacities of 136/133 mAh g.sup.−1 in between 2.5-3.5 V with stable flat-voltage profile. From these results, the in situ reservoir-replenishment process was observed to complete compensate for Li.sup.+ ion loss, consumed to SEI formation, and almost 100% specific full-cell capacity of LiFePO.sub.4 cathode recovered, in lined with MCMB anode.
(51) Synchronized Lithium and Lithium-Ion Battery Performance with Renewed Electrode Characteristics
(52) The replenished synchronized cell enabled to replenished cycling (SLLIB-MCMB vs LiFePO.sub.4) charge-discharge cycling studies as shown in FIG. 3A between MCMB vs LiFePO.sub.4 at 0.2 C. It is noteworthy that the charge voltage profile at 0.2 C appeared as an incomplete process corresponding to the cut-off limit of 2.5-3.5 V. For this reason, upcoming cycling studies were carried out between 2.5-4.0 V as depicted in FIG. 3B. The obtained voltage profiles between 2.5-4.0 V were associated with complete intercalation/de-intercalation process, yielding charge-discharge capacities 147/145 mAh g.sup.−1 and comparable to with the charge-discharge capacities of 136/133 mAh g.sup.−1 obtained between 2.5-3.5 V at 0.2 C rate. The renewed flat-voltage profiles at 3.4 and 3.2 V corroborated with the pronounced oxidation and reduction peaks appearing at 3.6/3.22 V for LiFePO.sub.4 cathode and 0.25/0.16 V for MCMB anode at 0.1 mV S.sup.−1 in potentiostatic cyclic voltammetric half-cell studies as illustrated in FIGS. 9A,9B. The attained stable cycling flat-voltage profile of the synchronized cell associated with the half-cell cycling performance of LiFePO.sub.4 (FIGS. 7A,7B) and MCMB electrodes (FIGS. 8A, 8B) exhibiting flat-voltage profiles. Indeed, the delivered charge-discharge capacity of 147/145 mAh g.sup.−1 for the synchronized cell was higher than those of conventional full-cell (MCMB vs LiFePO.sub.4) charge-discharge capacity 88/86 mAh g.sup.−1 having slope-voltage profile (FIG. 3C) and closer to LiFePO.sub.4 half-cell results 142/143 mAh g.sup.−1 at 0.2 C as compared in FIG. 3D. Considerably, the slightly decreased voltage profile of synchronized cell from the half-cell voltage related to MCMB anode voltage, involved in the electrochemical cell reaction. Moreover, the discharge energy density 455 Wh Kg.sup.−1 of tri-electrode full-cell was higher an almost two-fold increase over the conventional full-cell energy density 275 Wh Kg.sup.−1 as shown in FIG. 3E. With this enhancement, the galvanostatic cycling performance of SLLIB-MCMB vs LiFePO.sub.4, MCMB vs LiFePO.sub.4 and Li vs LiFePO.sub.4 cells were carried out for 1-100 cycles and compared in terms of capacity vs cycle number as presented in FIG. 3F. From the results, the charge-discharge capacities of synchronized cell at 1.sup.st and 100.sup.th cycles were 147/145 mAh g.sup.−1 and 123/122 mAh g.sup.−1 respectively. It is pertinent to note that the performance of the synchronized cell exhibited gradual capacity fading upon cycling with the capacity retention of 84% and coulombic efficiency of 99% at 100.sup.th cycle. Still, the delivered capacity at 100.sup.th cycles were almost two-fold higher than conventional full-cell (MCMB vs LiFePO.sub.4) charge-discharge capacities 65/64 mAh g.sup.−1 and achieved closer to 125/124 mAh g.sup.−1 at 100.sup.th cycle for Li vs LiFePO.sub.4 half-cell performance as represented in FIG. 3F. Clearly, it is reasonable to infer that the two-fold capacity enhancement of synchronized lithium and lithium-ion battery is attributed by reservoir replenishing for SEI Li.sup.+ ion consumption.
(53) In Situ Reservoir Replenishment Repeated for Longer-Lasting Rechargeable Batteries
(54) The charge-discharge cycling studies of SLLIB-MCMB vs LiFePO.sub.4 showed depletion of Li.sup.+ ions and recovered by an additional in situ reservoir replenishment process, represented with the sloping voltage profile for 99.sup.th/100.sup.th cycles as compared to the 101.sup.st/102.sup.nd cycle at 0.2 C rate between 2.5-4.0 V, as shown in FIG. 4A. The obtained charge-discharge capacities 132/125 mAh g.sup.−1 are two-fold higher with recovered stable flat-voltage profile than conventional Li-ion full-cell, having slope-voltage profile and charge-discharge capacities 65/64 mAh g.sup.−1 at 101.sup.st cycles (FIG. 4B). The increased discharge energy density 390 Wh Kg.sup.−1 at 101.sup.st cycle than 369 Wh Kg.sup.−1 at 100.sup.th cycle corresponding to the 2.sup.nd reservoir replenishment (R-RM2) process for depleted Li.sup.+ ions during charge-discharge cycles (1-100). The obtained discharge energy density 390 Wh Kg.sup.−1 was almost two-fold higher than conventional energy density 201 Wh Kg.sup.−1 at 101.sup.st cycle as shown in FIG. 4C. The increased discharge energy density 390 Wh Kg.sup.−1 at 101.sup.st cycle over that of 369 Wh Kg.sup.−1 at 99/100.sup.th cycle corresponds the 2.sup.nd reservoir replenishment (R-RM2) process of SLLIB-Li vs MCMB and 2.sup.nd replenished cycling (R-CL2) of SLLIB-MCMB vs LiFePO.sub.4, as illustrated in FIG. 4D. The R-RM2 process was preceded by complete Li.sup.+ ion de-intercalation from the LiFePO.sub.4 cathode through conventional cycling process of SLLIB-MCMB vs LiFePO.sub.4 at 0.2 C (2.5-4.0 V) with 100.sup.th (123/122 mAh g.sup.−1) and 100a.sup.th cycle (123 mAh g.sup.−1), having only charge process as given in FIGS. 4D and 12. Consequently, the R-RM2 process Li vs MCMB has been performed for 4 cycles with an initial partial discharge capacity 168 mAh g.sup.−1 (R-RM2-0), started at 0.122 V (OCV). In the R-RM2-process, the SLLIB-Li vs MCMB yielded the stable discharge-charge capacities of 398/391 mAh g.sup.−1 for R-RM2-2.sup.nd to R-RM2-3.sup.rd, corroborated with MCMB half-cell studies at 0.1 C between 0.01-1.5 V, given in FIGS. 8A-8B. Then, the 4.sup.th cycle (R-RM2-4.sup.th) limited with the discharge capacity 247 mAh g.sup.−1 with respect to synchronized cell performance. With the refreshed intercalated Li.sup.+ ions into MCMB anode, the R-CL2 process (SLLIB-MCMB vs LiFePO.sub.4) started at 3.29 V (OCV) between MCMB and LiFePO.sub.4 cathode, and delivered the charge-discharge capacities 142/137 mAh g.sup.−1 (R-CL2-2.sup.nd, 0.1 C) and 132/125 mAh g.sup.−1 (101.sup.st, 0.2 C) with the stable flat-voltage profile. As discussed in half-cell studies, during cycling the internal resistance of pristine LiFePO.sub.4 cathode are increased and revealed with higher polarization between charge-discharge cycling profiles of synchronized cell for 1.sup.st and 101.sup.st cycles (FIGS. 3A-3B and 4A) related to considerable enhanced performance by the R-RM2 process. We performed the R-RM2 process using synchronized cell configuration and repeated for n-number of terms to minimize the capacity fade and enhanced capacity retention for extended battery lifetimes towards long lasting rechargeable batteries as schematized in FIG. 4E. The observed cycling performance has compared between the synchronized full-cell (SLLIB-MCMB vs LiFePO.sub.4) and conventional full-cell (MCMB vs LiFePO.sub.4) with respect to discharge energy density and cell specific capacity as given in FIG. 4F. As predicted, repeated replenishment processes were facilitated to reduce the capacity fade and enhanced capacity retention as demonstrated between 200-300 cycles for synchronized lithium and lithium-ion battery than conventional full-cell (MCMB vs LiFePO.sub.4) showed continuous capacity fade during cycling as depicted in FIG. 4F. From the obtained results, it is clear that the synchronized lithium and lithium-ion battery performance in terms of discharge energy density 343 Wh Kg.sup.−1 and specific charge-discharge capacities 114/113 mAh g.sup.−1 was superior to conventional full-cell performance 171 Wh Kg.sup.−1 and 56/55 mAh g.sup.−1 at 0.2 C for 200.sup.th cycle. The present technology addressed the issue of SEI Li.sup.+ ion loss for full-cell (MCMB vs LiFePO.sub.4. In view of this, the achieved higher performance by reservoir replenishment and replenished cycling establishes the synchronized lithium and lithium-ion battery as a practically ‘long lasting’ rechargeable battery with a much more stable cycling performance than the conventional full-cell. Thus, the the synchronized lithium and lithium-ion battery may be considered to be a ‘never ending’, or at least an extremely long lived, rechargeable battery having ample scope for EVs, HEVs and high-energy grid storage applications with extendable battery lifetimes.
(55) Reservoir Reserve Mode Cycling and Confirmation of Li.sup.+ Ion Diffusion Pathways
(56) Further, when the LIBs are used in specialized applications, the reserve mode cycling enables the issue of unexpected cell failure mechanism to be addressed. This, occurs either by SEI rupture, or full-cell over charging/discharging process or after extensive cycling. For applications, the unexpected failure prevention is critical, the synchronized lithium and lithium-ion battery would be preferred for the reserve mode operation involved, such as in space, medical and high-power applications. Hence, the reserve mode cycling process was examined (SLLIB-Li vs LiFePO.sub.4) at 0.2 C between 2.5-4.0 V as shown in FIG. 5A. It can be seen that the reserve mode cycling process delivered the charge-discharge capacities of 126/124 mAh g.sup.−1 and 124/122 mAh g.sup.−1 for first and second cycles (FIG. 5B).
(57) The discharge step shows a slightly slanting-voltage profile corresponding to the presence of a diffusion barrier for Li.sup.+ ion transportation between the reservoir-electrode and the LiFePO.sub.4 cathode. Therefore, the kinetic characteristics of intercalation/de-intercalation may be examined by electrochemical impedance spectroscopic (EIS) technique for half-cell, conventional full-cell and synchronized lithium and lithium-ion battery, as given in FIGS. 5C-F. The obtained Nyquist plots(experimental indicated in asterisk) were fitted (indicated in circle) with the equivalent circuit components (see FIG. 5). The Nyquist plot for Li vs MCMB and Li vs LiFePO.sub.4 half-cells shows similar high frequency semicircle (R.sub.ct˜75Ω; combination of R.sub.2 and Rd.sub.2) and low frequency Warburg Z.sub.w process attributed to high semi-infinite linear diffusion (FIG. 5C). It can be seen that the conventional full-cell (MCMB vs LiFePO.sub.4) EIS profile exhibits reduced R.sub.2˜25Ω and increased restricted diffusion Rd.sub.2˜131Ω (denoted in M.sub.2) as shown in FIG. 5D. Significantly, the synchronized lithium and lithium-ion battery EIS profiles of SLLIB-Li vs MCMB and SLLIB-Li vs LiFePO.sub.4 (FIG. 5E) shows analogous Nyquist plot related to MCMB half-cell and conventional MCMB vs LiFePO.sub.4 full-cell, comprising high frequency semicircle and low frequency Warburg process Z.sub.w with the fitted equivalent circuit R.sub.1+C.sub.2/(R.sub.2+M.sub.2)+W.sub.3. It can be seen that the EIS profile of TE-Li vs LiFePO.sub.4 (FIG. 5F) exhibited two semicircles at high frequency region and dominant restricted diffusion (Rd.sub.3˜180Ω), appearing along with low frequency Warburg process Z.sub.w. The entire impedance profile fitted with the equivalent circuit R.sub.1+C.sub.2/R.sub.2+C.sub.3/(R.sub.3+M.sub.3)+W.sub.4, having higher R.sub.ct˜230Ω corresponding to the additional resistor and capacitor. The additional resistance R.sub.3˜112Ω and capacitance C.sub.3˜11.44×10.sup.−6 may be attributed to the presence of MCMB electrode, presented as a diffusion barrier between reservoir and LiFePO.sub.4 cathode. This confirms that Li.sup.+ ion transportation between reservoir and LiFePO.sub.4 cathode through the MCMB electrode for reserve mode cycling of the synchronized lithium and lithium-ion battery. The warranted characteristics of reservoir replenishment, replenished cycling and reserve mode cycling operations are permitting the synchronized lithium and lithium-ion battery to approach ‘long lasting’ recharging battery. Therefore, synchronized cell have ample scope for the Li-ion, Na-ion and K-ion batteries in large-scale energy storage applications.
(58) The novel synchronized lithium and lithium-ion battery (Li vs MCMB vs LiFePO.sub.4) yields an extremely long lived rechargeable battery, taking advantage to renewed electrode characteristics through reservoir replenishment, replenished cycling and reserve mode cycling processes comprising conventional cycling (SLLIB-MCMB vs LiFePO.sub.4), reservoir replenishment (SLLIB-Li vs MCMB), replenished cycling (SLLIB-MCMB vs LiFePO.sub.4) and reserve mode cycling (SLLIB-Li vs LiFePO.sub.4) steps. By employing an inbuilt lithium reservoir-electrode, the intercalation and deintercalation of the lithium-ion battery may be successfully tuned to stimulate lithium regeneration and thus extend the battery lifetime. The inbuilt booster-electrode may be enabled to compensate for 45% Li.sup.+ ion loss as consumed in initial formation cycles, and to yield virtually 100% recovered charge-discharge capacities (147/145 mAh g.sup.−1) with a stable flat-voltage profile for synchronized lithium and lithium-ion battery analogous to half-cell results (145/144 mAh g.sup.−1) at 0.2 C. Consequently, higher discharge energy density 455 Wh Kg.sup.−1 may be achieved for a cell with a LiFePO.sub.4 cathode used in synchronized lithium and lithium-ion battery than conventional full-cell 275 Wh Kg.sup.−1. Particularly at the 200.sup.th cycle, two-fold increased discharge energy density 343 Wh Kg.sup.−1 (114/113 mAh g.sup.−1) was obtained for synchronized lithium and lithium-ion battery than conventional full-cell, and exceeding energy density 171 Wh Kg.sup.−1 (56/55 mAh g.sup.−1). The repeated reservoir replenishment process may be facilitated for minimized capacity fade and enhanced capacity retention in a Li-ion full-cell. Likewise, the issue of unexpected cell failure mechanism is addressed, the reserve mode cycling process has also been performed and obtained the charge-discharge capacities of 126/124 mAh g.sup.−1 at 0.2 C related to Li.sup.+ ion transportation from reservoir-electrode to LiFePO.sub.4 and confirmed with the Li.sup.+ ion diffusivity by EIS measurement. From these results, the novel synchronized lithium and lithium-ion battery advances the goal of creating a virtually ‘never ending’ rechargeable batteries having ample scope for EVs, HEVs and high-energy grid storage applications with extendable battery lifetimes.
(59) Methods
(60) Materials and Characterization
(61) Li-ion battery commercial-grade MCMB and LiFePO.sub.4 materials (MSE supplies) were preheated at 120° C. in a vacuum oven for 24 h and used with the preliminary characterization studies. Notably, the physical properties that phase purity and crystallinity of LiFePO.sub.4 and MCMB materials were investigated by powder X-ray diffraction analysis, recorded in 20, range between 10-80° using Rigaku diffractometer with Cu Kα X-ray source. To confirm the presence of elements in MCMB and LiFePO.sub.4 materials, the morphology and elemental mapping were examined with energy dispersive X-ray analysis via scanning electron microscopy. Further, particle agglomerations and size were inspected by high-resolution scanning electron microscopy.
(62) Electrode Preparation
(63) CR-2032 coin type cell configuration was used with LiFePO.sub.4 cathode (single side) and MCMB anodes (single side and double side). Single side electrodes of LiFePO.sub.4 and MCMB were fabricated by doctor-blade coating process using vacuum provided MTI laminate coater. The electrode slurry contained 80% active material, 10% Super carbon and 10% PVdF dissolved in N-methyl-2-pyrrolidone (NMP), homogenized by thinky planetary mixture, coated on aluminum foil (12 μm, thickness) for LiFePO.sub.4 cathode and copper foil (9 μm, thickness) for MCMB anode. The coated electrodes were dried at 80° C. in a vacuum oven for 12 h and roll pressed. The calendared LiFePO.sub.4/MCMB electrodes were punched with the average active material loading mass of ˜5.5/2.8 mg in 14 mm diameter. Then, the lithium metal foil with the loading weight of 12 mg and 14 mm diameter was used as reference electrode for half-cell studies as well as represented as a reservoir-electrode for reservoir replenishment, replenished cycling and reserve mode cycling in synchronized lithium and lithium-ion battery. Significantly, the double sided MCMB anode was fabricated with the capability of Li.sup.+ ion diffusion through the electrode, prepared by MCMB film connected with copper mesh. The double sided MCMB anode had a disc shape (14 mm diameter) with the active material loading mass of ˜8.5 mg and used in the synchronized lithium and lithium-ion battery.
(64) Cell Assembly
(65) In order to evaluate the electrochemical performance, the fabricated electrodes were used to assemble half-cells (Li vs LiFePO.sub.4 and Li vs MCMB), conventional full-cell (MCMB vs LiFePO.sub.4) and synchronized lithium and lithium-ion battery (Li vs MCMB vs LiFePO.sub.4) with the CR-2032 cell configuration. Lithium half-cells of LiFePO.sub.4 cathode and MCMB anode made-up by lithium metal foil (˜1 mm thickness were) used as reference. Further, conventional Li-ion full-cell MCMB vs LiFePO.sub.4 was assembled with the electrode mass ratio of negative and positive ˜1:2 (MCMB/LiFePO.sub.4) using 1 M LiPF.sub.6 electrolyte contains mixture of EC-DEC in 1:1 (v/v ratio) and polypropylene separator. The synchronized lithium and lithium-ion battery was fabricated using LiFePO.sub.4 cathode, double sided MCMB anode and reservoir-electrodes, externally connected with smart-grid line circuit and internally separated by polypropylene separator with 1 M LiPF.sub.6 electrolyte in EC-DEC (1:1, v/v). The double sided MCMB anode placed in between LiFePO.sub.4 cathode and reservoir-electrode to facilitate Li.sup.+ ion diffusion between LiFePO.sub.4 cathode and reservoir-electrode related to the intercalation and deintercalation process involved in the charge-discharge process preceded by conventional cycling (SLLIB-MCMB vs LiFePO.sub.4), reservoir replenishment (SLLIB-Li vs MCMB), replenished cycling (SLLIB-MCMB vs LiFePO.sub.4) and reserve mode (TE-Li vs LiFePO.sub.4) cycling process. All the electrochemical non-aqueous cells (half-cell, conventional full-cell and synchronized lithium and lithium-ion battery) were assembled using argon-filled glove-box with oxygen and moisture levels controlled at less than 0.5 ppm.
(66) Electrochemical Measurements
(67) The fabricated cells were used in electrochemical characterization techniques such as electrochemical impedance spectroscopic measurement (EIS), cyclic voltammograms (CV) and galvanostatic charge-discharge studies. Accordingly, EIS analysis was performed in the frequency range 1 MHz to 100 mHz to determine the kinetic characteristics of Li.sup.+ ion intercalation/de-intercalation and Li.sup.+ ion diffusion path through the electrode. Consequently, to confirm the Faradaic redox reaction corresponding to the full-cell voltage, CV was recorded to the fabricated half-cells at 0.1 mV s.sup.−1 in the voltage range 3.0 to 4.0 V (LiFePO.sub.4 cathode) and 0.01 to 1.5 V (MCMB anode) for 1-5 cycles. Eventually, galvanostatic charge-discharge studies have been carried out to all the fabricated cells using Arbin cycler at 25° C. with different voltage window and rates with respect to designed cell configuration. Thus, the Li vs LiFePO.sub.4 and Li vs MCMB half-cells were cycled between 3.0 to 4.0 V (LiFePO.sub.4 cathode) and 0.01 to 1.5 V (MCMB anode) respectively, at 0.1 C and 0.2 C rates. Subsequently, the conventional full-cell cycling studies were carried out in the voltage range 2.5 to 3.5 V at 0.06 C and 0.2 C rates. More importantly, the synchronized lithium and lithium-ion battery charge-discharge cycling studies were performed by conventional cycling (SLLIB-MCMB vs LiFePO.sub.4), reservoir replenishment (SLLIB-Li vs MCMB), replenished cycling (SLLIB-MCMB vs LiFePO.sub.4) and reserve mode (SLLIB-Li vs LiFePO.sub.4) cycling process with wide cell voltage range 0.01 to 4 V at different rates (0.06 C, 0.1 C and 0.2 C).
(68) While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character. It is understood that the embodiments have been shown and described in the foregoing specification in satisfaction of the best mode and enablement requirements. It is understood that one of ordinary skill in the art could readily make a nigh-infinite number of insubstantial changes and modifications to the above-described embodiments and that it would be impractical to attempt to describe all such embodiment variations in the present specification. Accordingly, it is understood that all changes and modifications that come within the spirit of the invention are desired to be protected.
