MXPA97005570A - Nickel oxide ases and coolant oxide deslitiadas and method to prepare mis - Google Patents

Abstract

The present invention relates to LiCoO2 and LiNiO2 totally electrochemically disrupted, using solid state electrolytic cells and oxidation-resistant electrolytes to give new, stable phases of CoO2 and Ni

Description

NICKEL OXIDE PHASES AND COBALT OXIDE PES ITI? PAS AND KETQPQ TO PREPARE THE SAME AMTECEDEWTES DE LA IHVBMCIOH The increased commercial importance of rechargeable lithium-ion battery cells has indicated a desire to identify and prepare cathode materials that are more capable of intercalating and reversibly deinterleaving lithium ions at higher voltages. There are three prominent reversible lithium intercalation compounds used for lithium ion rechargeable batteries: LiCoOa and LiNiOa compounds, as well as spinnaker LiMnaO «. The LiCo02 cells are of particular interest due to their ability to insert / disinsert lithium reversibly at voltages greater than 4V, resulting in batteries having an output voltage and energy density 3 times greater than Ni-Cd. The theoretical load capacity of LiCoO cells is large at approximately 275 Amp-hours / kilogram (A-h / kg). In practical application however, the maximum capacity obtainable for LiCoOa cells has been only about 140 Ah / kg corresponding to a maximum load voltage of about 4.2 V. Previous attempts to exceed this load cutoff voltage in LiCo03 cells has caused Poor cell performance manifested by severe loss of load capacity in subsequent load-unload cycles. The commonly held ratio for load limitation of 4.2 volts for cells REF: 25191 LiCo02 was that the electrochemical slide of LiCoOa on this voltage destabilizes the structure of the partially decayed LiCoO phase, deteriorating the lithium intercalation in subsequent charge-discharge cycles. Cobalt lithium oxide adopts a hexagonal structure consisting of CoOa layers separated by a Van der Waals space. The octahedral sites within the Van der Waals space are occupied by Li * ions. This results in the reversible intercalation of lithium. In these compounds, lithium acts as a cement or adhesive, screening out the repulsive interactions between the negatively charged Co02 layers. When the compound is LiCoOa completely lithiated, the screening effect is the largest. As the lithium is removed, the sieving effect is decreased and the repulsions between the two CoOa layers are improved resulting in an expansion space of the c-axis parameter. Due to the effect of lithium screening, it is considered that it was not possible to de-interleave the entire lithium to form CoOa. Ohzuku et al., J. Electrochem. Soc, Vol. 141, No. 11, November 1994, p. 2972, has succeeded in removing approximately 85% lithium. Their efforts reveal an onoclinical phase and question the existence of a CoOa phase.

In another theory, Reimers and Dahn, J. Electrochem. Soc. 139, 2091, (1992), declares that the excess of Co4 * destroys the crystallinity of the lithium cobalt oxide structure.

Apparently, it inhibits the formation of highly crystalline phases at low lithium contents. Wizansky, Rauch and DiSalvo, Journal of Solid State Chemistry, 81, 203-207 (1989), investigated the delineation of LiCoOa through the use of powerful oxidizing agents such as NOa "and MoF6." Their results showed that this approach simply decomposes LiCoOa LiNiOa is isostructural with LiCoOa and is commercially viable for use in secondary lithium ion batteries. has been able to obtain the layered NiOa phase Ohzuku et al, J. Electrochem Soc., Vol. 140, No. 7, July 1993, working with nickel oxide reported Li0.o6NiOa and approximately this was the final phase. secondary lithium batteries are generally recognized and described for example in the patent No. 5,296,318 issued to Gozdz et al., which is incorporated herein by reference in full. Lithium metal-free "rocking" batteries can thus be seen to comprise Two "sponges" of absorbent electrode of lithium-ion separated by an electrolyte containing lithium-ion, which usually comprises a Li * salt dissolved in a non-aqueous solvent or mixture of these solvents. Numerous of these salts and solvents are known in the art, as evidenced in Canadian Patent Publication No. 2,022,191, dated January 30, 1991. When cells comprising these previously available electrolytes are cycled to an even slightly higher voltage than 4.3 V, electrolyte oxidation occurs. Although small, this oxidation can injure the capacity, useful service life and safety of the battery cell. For example, the electrode oxidation reaction consumes part of the charge current, which can not be recovered when the cell is discharged. The result is a continuous loss in cell capacity over subsequent cycles. In addition, if a small part of the electrolyte is consumed during each charge, excess electrolyte must be included when the cell is assembled. The excess electrolyte reduces the amount of reactive material for a constant volume battery body, thus decreasing the initial capacity. In addition, the oxidation of the electrolyte often generates solid and gaseous by-products. The solid by-products build a passivating layer in the particles of the active material, essentially increasing the polarization of the cell and reusing the output voltage. Simultaneously and more importantly, the gaseous by-products increase the internal pressure of the cell, thereby increasing the risk of explosion and leading to unsafe and unacceptable operating conditions. The patent of the U.S.A. No. 5,192,629, which is incorporated herein by reference in its entirety, provides a class of electrolyte compositions that are exceptionally useful for minimizing electrolyte decomposition in secondary batteries comprising highly oxidizing positive electrode materials. These electrolytes in this way are unique able to improve cycle time and improve the temperature performance of "rocking" cells practices. These electrolyte compositions have an effective stability range extending to about 5.0 V at 55 ° C, as well as at room temperature (about 25 * C). Electrolytes that are substantially inert to oxidation include a 0.5M to 2M solution of LiPFß, or LiPF "with up to an equivalent amount of LiBF4 added, in a mixture of dimethylcarbonate (DMC) and ethylene carbonate (EC) within the range of weight percent ratio of approximately 95 DMC: 5 EC to 20 DMC: 80 EC. In a preferred electrolyte solution, the range of solvent ratios is approximately 80 DMC: 20 EC to 20 DMC: 80 EC. An optimum composition for operation at room temperature and below is a solution of approximately 1.5M LiPFβ in a solvent mixture of approximately 67 DMC: 33 EC. A battery operating at room temperature and above, for example in the 55 ° C range, optimally employs an electrolyte that essentially consists of a solution of approximately 1.5M LiPFβ in a solvent combination of approximately 33 DMC: 67 EC. A further useful electrolyte essentially consists of a solution of about 1M to 2M of equal parts of LiPFβ and LiBF 4 in a solvent mixture of about 50 DMC: 50 EC. Negligible current increases after reversible Li interleaves at voltages up to approximately 5 V against Li indicates this remarkable stability that allows improved cell capacity not only in the "rocking" cells comprising negative carbon electrodes, for example coke oil, but also in Li's negative electrode cells. This lithium metal cell using a LiCoOa positive electrode can reasonably be expected to achieve normal operating ranges of approximately 4.3 V to 5.1 V. With the aid of electrolytes that are substantially inert to oxidation and solid state electrolytic cells, totally lapsed phases of both CoOa and NiOa were obtained. In accordance with this, the present invention is directed to CoOa and NiOa metastable phases and their use as intercalation compounds for use in secondary lithium ion batteries. Characteristics and advantages of this invention are set forth in the description that follows, and will be apparent from the description or may be learned by practice of the invention. In one aspect, this invention relates to an electrochemical method for preparing a stable cobalt dioxide phase that includes preparing an electrolytic cell having an anode, an electrolyte substantially inert to oxidation, and a cathode that includes an oxide intercalating complex. cobalt lithium; and applying a voltage to the cell sufficient to completely de-interleave the lithium from the cobalt lithium oxide intercalating complex, thereby forming a stable cobalt dioxide phase at the cathode. In a further aspect, this invention relates to a stable cobalt dioxide phase prepared by the above method. In a further aspect, this invention relates to a stable cobalt dioxide phase having an x-ray diffraction pattern: L? L 4.30 ± 0.02 2.44 ± 0.02 2.12 + 0.02 dtAJ 1.61 ± 0.02 1.41 ± 0.02 1.34 ± 0.02 1.17 + 0.02 In a further aspect, this invention relates to an electrochemical method for preparing a stable nickel dioxide phase which includes providing an intercalated complex of nickel lithium dioxide having the formula LixNiOa wherein x is preferably 0.8 to 1.0, prepare an electrolytic cell having a cathode including the complex intercalated with nickel lithium dioxide and apply a voltage to the cell sufficient to completely disrupt the complex intercalated with nickel lithium dioxide. In a further aspect, this invention relates to a stable nickel dioxide phase prepared by the process described above. In a further aspect, this invention relates to a stable nickel dioxide phase having the diffraction pattern of ray-x: dl J 4.47 ± 0.02 2.40 ± 0.02 2.29 ± 0.02 1.97 ± 0.02 1.51 ± 0.02 d & 1.41 ± 0.02 1.38 ± 0.02 In a further aspect, the invention relates to a method for producing a secondary electrolytic cell which includes the stable phase CoOa or NiOa and the cell thus formed. The accompanying drawings that are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and with the description serve to explain the invention, its objectives, advantages and principles. BRIEF DESCRIPTION OF THE DRAWING The present invention will be described with reference to the accompanying drawing of which: Figure 1 is a series of X-ray diffraction diagrams that are taken during electrochemical cleavage of LiCoOa to form the CoOa phase; Figure 2 is a series of X-ray diffraction patterns taken during electrochemical lithium intercalation in the CoOa phase; Figure 3 plots discharge and charge voltage against lithium content for a cell using the CoOa phase; Figures 4 and 5 plot charge and discharge voltages against lithium content for a cell having a LiNiOs cathode that has been delineated to the NiO phase, according to the invention; Figure 6 traces heat of decomposition reaction against temperature for the CoOa and NiOa phase; Figures 7 and 8 are X-ray diffraction diagrams for the thermal decomposition products of the CoOa and NiOa phases; Figure 9 plots charge and discharge voltages against sodium content for a cell using the Co02 phase of this invention interspersed with sodium ions; Figure 10 is a X-ray diffraction diagram taken during electrochemical slipping of LiNiOa to form the Ni02 phase; and Figure 11 is an x-ray diffraction diagram illustrating the effect of atmospheric water on the Co02 phase. PBSCRIPCIQM OF THE INVBMCIPff An impediment to the achievement of the CoOa and NiOa phases of the present invention was eliminated by the development of electrolytes that are stable (inert to oxidation) at high voltages although necessary to achieve the phase Co02 lanced. These electrolytes are exemplified by those described in U.S. Pat. No. 5,192,629, the description of which is incorporated herein by reference. However, it was commonly considered that the Co02 phase was not reached due to the complete absence of lithium ions in the Van der Waals space between the negatively charged Co02 layers, the repulsive force between the layers would be too large, and a completely depleted CoOa phase. I would never be stable. The use of an electrolytic cell that incorporates a LiCo02 cathode material described here and a stable high voltage electrolyte, phase Co02 can be prepared by applying to the cell a charging voltage of 5.2 V, which will deintercalate substantially all the lithium of the LiCo02 cathode, formed in the CoOa phase. The Co02 phase is metastable and decomposes over 200 * C. Similarly, in an electrolytic cell that uses a stable high-voltage electrolyte and a LiNiOa cathode, a substantially complete slip to a Ni02 phase can be achieved by applying a charging voltage of 5.1 V. Once obtained, the CoOa and NiOa phases of the present invention can be re-invested with lithium or other ions such as hydrogen, sodium (Example 4), potassium or rubidium nuclei. The reintercalation of lithium or other ionic species in the CoOa and Ni02 phases can be achieved by electrochemical insertion or by transport in the vapor phase at temperatures below 200 * C. The vapor phase transport is described in a document by Tarascon et al., "Synthesis and peculiar properties of TlMOßSx-.Se * and HgyMoßS" _., SeÍIM (Synthesis and Peculiar Properties of InMoßSx_ ßSex,, Physical Review B, Vol. 31, No. 2, 1985, which is hereby incorporated by reference, following the re-interleaving, these phases can for example be cycled between 3 V and 4.2 V for the CoOa phase and 2.8 V and 4.1 V for the NiOa phase without Loss of cell capacity After formation of the CoOa phase, CoOOH can be formed by exposure of the phase to atmospheric water As can be seen from Figure 11, Co02 can be formed in situ in an electrochemical cell. About 30 minutes, two phases are present.After 3 days in air, CoOOH is formed due to an open circuit voltage >; 4 V the following reaction occurs: 2 H20 - 4 e "> 02 + 4 H * CoOa + x e" + xH * > H "CoOa CoOOH can be used as an electronic driver in another battery technology. This includes application in the Ni electrode or NiMeH, Ni-H or Ni-Cd batteries where cobalt is already used. As an alternative, once formed, these phases can be used in any variety of ways. In a preferred embodiment, the cathode of a plastic solid state cell is not laminated to the underlying electrolyte / anode structure, thereby allowing ease of removal of the Co02 or Ni02 phase in a plastic matrix. This plasticized phase can easily be transported to other environments. For the reasons discussed above, if the pure phase Co02 is desired, handling under inert (anhydrous) conditions is preferred. In another embodiment, this plasticized phase is placed in a cell containing, for example, an electrolyte containing sodium and a compatible electrolyte and then the nickel or cobalt oxide phase is reinterbed with the sodium ions. This re-interleaving can be stopped short before finishing and in that way, a second or subsequent ion can be added to the re-inlay metal oxide phase. In yet another embodiment, the cobalt or nickel oxide phase may be combined with an organic component to form, for example, either a composite polymer or an activated metal oxide carrier. The redox potential of this phase is high making it potentially useful in many areas. Advance applications include for example forming inorganic polymer structures and as a biochemical carrier. These applications will clearly be recognizable to the right-hander in the specialty. The following examples illustrate the practice of the present invention in the prior art. It will be appreciated by those skilled in the art that these examples are not to be construed as limiting the present invention.

Example 1 A plastic electrolytic cell is constructed comprising a matrix of polyvinylidene fluoride (PVdF) and hexafluoropropylene (HFP), which incorporates an electrolyte composition of 2 EC parts to a part of DMC and 1M LPFβ, which is inert to oxidation at high voltages. The cathode containing LiCo02 as an active material and the anode contains carbon. The solid state anode and electrolyte were laminated together and the cathode was placed on top. This cell was charged at 5.2 V at which point LiCoOa completely faded to form the CoOa phase. The existence of this phase is confirmed by the x-ray data illustrated in Figure 1. Figure 1 illustrates the diffraction pattern at the end of deintercalation of LiCo a starting approximately in the last known phase described in the previous literature, ie monoclinic (Li0,? BCoOa) and proceed to full delineated at a voltage of 5.2 V. X-ray diffraction patterns were obtained in situ through the use of an X-ray diffraction apparatus that allows the use of high voltages without corrosion of the beryllium window. The final x-ray diffraction pattern obtained at 5.2 V is the hexagonal structure associated with the CoOa phase. Furthermore, once it is obtained, the CoO phase is reconverted to the LiCo02 phase during cell discharge as illustrated by the series of x-ray diffraction patterns in Figure 2. After achieving the CoOa phase in the cathode and lithium re-intercalation to form the LiCo02 phase, this cell is cycled between 3 V and 4.2 V with little loss of carrying capacity, as seen in Figure 3. During the charging cycle of a partially-laden cobalt oxide , the reintegration of lithium forms a monoclinic phase; however, the reinsertion of lithium in the totally disrupted cobalt oxide results in a hexagonal structure, which is the same as the LiCoOa structure that was originally incorporated into the electrolytic cell. Example 2 A plastic electrolytic cell is constructed as in Example 1, incorporating an electrolyte composition inert to oxidation at high voltages and a cathode made from LiNiOa. This cell was charged at 5.1 V, at which voltage substantially all of the lithium is removed from the LiNi02 phase to form the NiOa phase. The existence of the NiOa phase is confirmed by the x-ray data illustrated in Figure 10. The cell is discharged at 200 Á, bringing 70% of the lithium back into the Ni02 structure as seen in Figure 4 The subsequent cycling of this cell between 2.8 V and 4.0 V without capacity fading confirmed that the reversible charge characteristics of LixNiOa were not destroyed by the achievement of the NiOa phase. Reducing the discharge current to 150 A resulted in interleaving all the lithium to form the LiNi02 phase. As illustrated in Figure 5, subsequent cycling of this cell between 2.8 V and 4.1 V resulted in high capacity (greater than 190 A-h / kg), with minimal polarization and slight irreversibility characteristic of LiNi02. These results show that the total lithium removal of LiNi02 results in a structure that remains electrochemically active. Example 3 A study of the thermal stability of the CoO phase, and the Ni02 phase, is carried out. Plastic electrodes of LiCoOa and LiNi0a lead to the CoOa phase and the NiOa phase in the forms described in Examples 1 and 2, respectively, were dissolved separately in a dilute acetone solvent at room temperature. The plastic portions of the electrodes dissolved in the solvent, and the soluble metal oxides were sedimented to the bottom of the containers. The metal oxides were separated from the solution and analyzed using differential scanning calorimetry (DSC) in ramp at 300 * C at 10'C / minute. As seen in Figure 6, a relatively strong exothermic reaction occurred at 200 ° C for both CoOa and NiOa phases.Analysis of the samples by X-ray diffraction after DSC revealed that both phases are reduced with accompanying oxygen loss of according to the reaction below the reaction M0a >; MO + 1/2 02 The X-ray diffraction patterns illustrated in Figures 7 and 8, confirm that the samples were transformed into mixed rock salt structures of CoO and NiO, which are known as electrochemically inactive to intercalation of lithium. Example 4 A cell is constructed as in Example 1. The Co02 phase was formed by sliding the plastic cell at 5.2 V for 15 hours. After the CoOa phase was formed, the plasticized Co02 was removed from the electrolyte / anode structure and then incorporated into a similarly constructed cell containing sodium. The new cell was constructed using the plastic cathode Co02, an electrolyte of NaC10 «and a sodium metal anode. Sodium is introduced to the CoOa phase when the cell is discharged at 2.2 V to insert the sodium. The cell is then cycled between 2.2 V and 4.1 V, as illustrated in Figure 9. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is the one that results clear of the present description of the invention.

Having described the invention as above, property is claimed as contained in the following:

Claims (1)

CLAIMS 1. A method for preparing a stable metal dioxide phase, characterized in that the method comprises: a) preparing an electrolytic cell having an anode, an electrolyte inert to oxidation and a cathode comprising a metal oxide selected from the group consists of an intercalated complex of lithium cobalt oxide and an intercalated lithium nickel oxide complex having the formula Li "Ni02 where x is 0.8 to 1.0; and b) applying a sufficiently high voltage to the cell to substantially de-interleave all of the lithium from the metal oxide. 2. A method according to claim 1, characterized in that the voltage exceeds approximately 5.0 V. 3. A method according to claim 2, characterized in that the electrolyte comprises a 0.5 solution. M to 2 M LiPFß or LiPF "with up to about an equal amount of" added LiBF, in a mixture of dimethylcarbonate (DMC) and ethylene carbonate (EC) within the range of weight percent ratio of approximately 95 DMC : 5 EC to 20 MDC: 80 EC. 4. A method according to claim 1, characterized in that it further comprises intercalating the stable metal dioxide phase with an element selected from the group consisting of lithium, sodium, potassium, rubidium and hydrogen. 5. A stable metal dioxide phase prepared according to the method of claim 1, characterized in that the metal is selected from the group consisting of cobalt and nickel. 6. A stable cobalt dioxide phase according to claim 5, characterized in that it has the x-ray diffraction pattern: ΔL ΔJ 4.30 ± 0.02 2.44 ± 0.02 2.12 ± 0.02 1.61 ± 0.02 1.41 ± 0.02 1.34 ± 0.02 1.17 ± 0.02 7. A stable nickel dioxide phase according to claim 5, characterized in that it has the x-ray diffraction pattern: dÜÜ 4.47 ± 0.02 2.40 ± 0.02 2.29 ± 0.02 1.97 ± 0.02 1.51 ± 0.02 1.41 ± 0.02

1. 38 ± 0.02 8. A secondary electrolytic cell that includes an anode as an electrolyte and a cathode, characterized in that the cathode comprises a stable metal dioxide phase in accordance with claim 5. 9. A secondary electrolytic cell in accordance with the claim 8, characterized in that the cathode further comprises an element selected from the group consisting of lithium, sodium, potassium, rubidium or hydrogen intercalated in the stable metal dioxide phase.