DE1935943C - - Google Patents

Description

The present invention relates to galvanic elements that act as primary and / or secondary elements are usable, with a negative lithium electrode and an electrolyte made of inert solvent, which contains lithium hexafluorophosphate.

Lithium and other light metals of groups IA and UA of the Periodic Table of the Elements attract as negative electrodes attract attention because they combine high potentials with low atomic weights. In the known literature, many elements have been suggested that are negative Contain high energy density electrodes; but few are entirely satisfactory for galvanic elements. One difficulty has been finding suitable, electrolytically compatible combinations, which meet the requirement that the electrolyte, including the solvent against the active type of negative (reducing agent) and the positive electrode (oxidizing agent) inert and a nonsolvent is. Such inertia is necessary so that the supply of active ingredient is not exhausted will or no impurities will be introduced into the electrolyte, which softens the service life shorten the element or intervene in its operation in some other way; it is also necessary with it the element is not short-circuited via the electrolyte through a direct chemical reaction.

In order to keep such difficulties to a minimum, considerations regarding external permeability Proposed selective subdivisions to separate the negative half-cell from the positive half-cell. However, this necessarily increases the cell resistance, which except for elements with lower Electricity delivery is a serious problem.

Since the elements belonging to the known state of the art have a high energy density in general difficult to charge once they are discharged or in terms of how often they are recharged are severely constrained, another problem was finding high-energy systems which are not only chemically inert to a high degree, but also electrochemically with high efficiency are reversible.

In one of the more relevant articles belonging to the known state of the art, namely B raeuer and Harvey, Power Sources Division - Electronics Components Laboratory, DA TASK ICO 14 501 A 34A-00-O1, US Army Electronics Command, May 1967, investigations are on Elements discloses the negative electrodes made from lithium and other metals including lithium electrodeposited onto aluminum, electrolytes made from alkali metal hexafluorophosphate salts (but not from lithium hexafluorophosphate) among other solutes in various solvents including dimethylformamide and Pro Have pylene carbonate, and various positive electrodes, including CuF ₁ and CuCi ₇ ,

Investigations on electrolytes made from lithium hexyfluorophosphate in dimethylformamide, acetonitrile and Propykncarbönat with various positive electrodes are carried out by Shaw, Remanick, and Radkey in “Electrochemical Characterization of Systems for Secondary Battery Application ", NASA, CR-72 181.17. February 1967, presented.

Galvanic elements with a negative electrode made of lithium, alloyed with a less active metal, which is immersed in lithium hexafluorophosphate solution, are known from French patent specification 1 515 724. So much of the electrolyte salt has to be dissolved that the conductivity of the electrolyte is sufficient. However, this patent specification does not specify which critical values must be adhered to so that a reversible galvanic element can be built up with such an electrode made of lithium alloyed with aluminum.

, o The subject of the invention is now a galvanic: Element with a lithium negative electrode, alloyed with a less active metal and an electric lytes from a practically neutral, inert solution medium, such as Ν, Ν-dimethylformamide, lithium hexa

fluorophosphate in sufficient concentration ent holds, which is characterized in that the Lithtun Electrode aluminum and 1 to 20 percent by weight Contains lithium and has a reduction potential ui at least 0.2 volts lower than that of lithium has metal.

The electrolyte from a practically neutral (i.e. the pH in water is about 6 to 8) inert. Solvent contains lithium hexafluorophosphate; one Amount that is sufficient to achieve a conductivity of

to be at least about 0.001 ″ ″ ″.

Preferably the positive electrode contains a reversibly reducible depolarizer from the group elemental sulfur and iron, nickel or copper compounds, their solubility in the electrolyte

solvent at 25 ° C less than 200 weight stiff per million, preferably copper (I) oxide, copper (II) oxide, copper (I) carbonate, basic copper (II) carbonate nat, copper (II) - ferroeyanid, copper (II) sulfide, copper fer (II) oxalate, copper (II) tartrate, copper (II) citrate, Wed

compounds of such copper compounds, nickel sulfide Nickel fluoride, nickel oxalate or iron (II) sulfide.

The positive electrode is preferably (1) a conductive paste made from (a) at least one of the depolaris Sators in particulate form, (b) particulate !, conductive carbon black and (c) a lithium hexafluorophos phat electrolytes and in contact with a conductive capable substance, (2) a porous, electrolyte-permeable sheet-like structure, which consists of a mixture of (a at least one of the depolarizers in particle form, (b) a particulate electrical conductor such as carbon black and (c) a normally solid, 'electrolyte' insoluble, electrochemically inert, polymeric filler material, such as polytetrafluoroethylene, in an amount sufficient to form a self-supporting sheet. with the sheet in electrical contact with a metal conductor, or (3) a self-supporting one Structure made of iron (II) sulfide.

These and other embodiments are further explained in detail below.

F i g. 1 is an exploded view of a typical assembly of a negative electrode and an electric hammer;

F i g. Figure 2 is an exploded view of a typical construction of a paste

like positive electrode, and

F i g. h is an exploded view of a typical structure of a sheet-like positive electrode. The present invention is based on the knowledge

never that a half-cell consists of a negative electrode made of a lithium-aluminum alloy and lithium hexafluorophosphate in a suitable, inert, practically neutral solvent especially linen

i 935 943

is an effective component for complete galvanic elements with high energy. Preferred complete elements and superior element performance and stability against self-discharge are obtained, if such half-cells with conductive positive electrode systems, d. H. Depolarizers (in electrical Contact with conductive materials if the depolarizer itself is insufficiently electrically conductive, to serve as a complete positive electrode), which are practically insoluble in the electrolyte are. However, the half-cells can be used in conjunction with any suitable positive electrode be used. If necessary, membrane can separate the half-cell and the positive electrode can be applied.

Such combinations, when used together with reversible lithium negative electrodes (e.g. Lithium deposited on aluminum, and more preferably those described below Lithium-aluminum alloys) can be used. Elements of high energy that turn out to be desirable Wise recharge. For example, they typically show voltages with the open Circuit around 3 volts, can be recharged ten times or more, showing total discharge lifetimes to the 1.0 volt level for at least 150 minutes and discharge / charge Coulomb benefits of at least 50%. In other words, such elements according to the invention are suitable as secondary elements.

In contrast, the use of (a) other alkali metal hexafluorophosphates and other lithium salts as dissolved substances, (b) other metal compounds (metal halides ^ as oxidizing agents, (c) less neutral solvents (acetic anhydride, isopropylamine) and other lithium anodes (mainly lithium) Secondary elements with much poorer performance.

The electrolyte

Lithium hexafluorophosphate, LiPF ₆ , is commercially available and can be used as received. It can also be obtained by mixing lithium fluoride and phosphorus pentafluoride in a suitable solvent, e.g. B. the solvents defined above and described more fully below by means of examples. If desired, the LiPF ₆ can be prepared in situ in the electrolyte solvent. Although the dissolved lithium substance is critical for the reversibility of the element, smaller proportions (of for example up to 10 mol percent) of other alkali metal hexafluorophosphates, hexafluoroarsenates, perchlorates, thiocyanates and the like can also be present, although these compounds are preferably essentially absent are.

The electrolyte solvent can vary widely, provided that it has enough lithium hexafluorophosphate for practical conductivity values, essentially a nonsolvent for lithium metal, and (being the material of the positive electrode, chemically modified from the above-mentioned electrochemical reactants and other components of the element and is practically electrochemically inert during operation of the element, that is, it does not oxidize or reduce during the discharging and charging of the element. Conductivities are desirably at least 0.001 ohms " ¹ cm" ¹ and the greater the conductivity the better so that the internal resistance and the accumulation of heat within the elements are kept to a minimum.

Representative solvents which are suitably inert and neutral, i. H. in the mixture result in a pH value of not lower than 6 and not higher than 8 with water, include N, N-dimethyl-

formamide, Ν, Ν-dimethyl-acetamide, acetonitrile, propylene carbonate, Dimethyl sulfoxide and the like compounds. To other solvents that can be used include butyrolactone, nitromethane, dimethyl carbonate, methyl acetate, methyl formate and diethylene glycol dimethyl ether.

Not included are protic ones that react with lithium Solvents such as water or alcohol, basic solvents such as ammonia and the alkylamines, and acid solvents such as the carboxylic acids and their anhydrides.

LiPF ₆ in dimethylformamide (DMF) is the preferred electrolyte because of its high conductivity and its contribution to the discharge efficiency and the reversibility of the overall element.

LiPF ₆ shows high solubility in DMF (up to 37 percent by weight at around 25C). Preferred concentrations range from about 15 to 24 percent by weight, where the conductivity is at least 1 χ 10 ³ ohnT'cm ¹ , and more preferably the concentration

tration about 20%. where the conductivity is about 2 χ 10 ~ ² ohnr'cm ~ '.

The positive electrode

The depolarizer can vary widely, especially

exposed to being the oxidizing member of an electrochemically reversible redox couple; that is, the oxidized portion, e.g. B. Cu ", Cu ¹ , Fe", Ni "or S ⁰ , can be reversibly reduced to the lower-valued portion, eg Cu ¹ , Cu ⁰ , Fe ⁰ , Ni ⁰ or S ⁼ , and oxidatively regenerated therefrom The anions added to the cations given above are not critical, provided they are inert towards the rest of the system

is avoided when the positive electrode materials and the depolarizer are insoluble. the Electrolyte solubilities of the metallic electrode materials should be less than 200 parts by weight per million and / preferably less than 100 parts by weight each

so be a million. The lithium salts of the depolarizer anions should preferably also be less soluble than 0.5 percent by weight (it is even better if they are soluble to less than 0.2%), so that an addition of unnecessary, dissolved substances in the electrolyte

is avoided. The solubility is not so critical in the case of elemental sulfur as a depolarizer.

The specially used copper electrode JKSepolari Sator largely depends on the electrolyte solution medium. To representative copper compounds that

Particularly satisfactory for use with the preferred LiPF ₆ -DMF electrolyte include copper (I> oxide, copper (I) oxide, copper (I) carbonate, basic copper (H> carbonate, copper (I)) ferrocyanide, copper (I) sulfide , Copper sulfide and

$ 6 mixes of these. Particularly preferred are Kup * ferfJtVsulnd, copper (I) oxide and basic copper * !!) * carbonate. Electrolyte-insoluble, organic copper (I) and (! ^ Compounds with the above

beds, desirable properties can be used, t. Copper (II) salts, such as copper (II) oxalate and salts of such polybasic, hydroxyl carboxylic acids, such as tartaric acid, citric acid and sugar syrups. Such copper (II) compounds must be insoluble in the electrolyte solvent and act as depolaf Isators may be satisfactorily reducible. Copper salts of polymeric acids, such as carboxylic acid and sulfuric acid type exchange resins, can also be used. Non-copper compounds such as fisendl sulfide, nickel sulfide, nickel fluoride, nickel oxalate, and elemental sulfur are also very effective, useful depolarizers.

It goes without saying that the possible depolarizer t $ Exchange products, namely the hexafluorophosphates of copper. Iron and nickel, also used Can be. Such products can be made by reacting lithium hexafluorophosphate with either the depolarizer used at the beginning or its lower quality discharge product can be produced in situ. As the discharged element electrolyte contains practically no metal, it seems. that the hexamiorophosphates. when they are formed, practical are insoluble in it.

If H * «Oiydans Id h the depolarizer) itself Is insufficiently electrically conductive. to serve as the full-term positive electrode, it is used in combination with a conductive carbon or a other conductors, such as copper. Iron. Nickel or another conductive, inert metal is used. the positive electrodes can be in the form of pastes or composite masses, which may contain inert fillers or binders, and they can be produced by known methods. Such structures should, as is well known in the art is. be sufficiently porous that the electrolyte in the Location is. to come into intimate contact with the oxidant, and at the same time they should be sufficiently compressed so that a good electrical contact / between the Oxydans and the conductor is guaranteed. the in essentially serves to absorb and release electrons from and into the outer circle.

Paste electrodes are expediently produced by the particulate depolarizer, em particulate conductor and the electrolyte in for the Providing a leavenable paste are mixed in sufficient proportions and the mixture is pressed onto a load-bearing grid, which is a may or may not be an electrical conductor. If necessary, excess electrolyte solvent can e.g. B. removed by evaporation so that the desired paste consistency is obtained. In general, the depolarizer and the Ladder each to at least 1% of the paste weight and together make up 50%. while the electrolyte solution makes up 50 to 90 percent by weight.

Sheet electrodes are made using about 15 to 25 percent by volume polytetrafluoroethylene or one other plastic that can be molded under pressure, 30 to 75 percent by volume carbon black or another conductive solid, and 5 to 35 volume percent of the depolarizer are mixed and the mixture with an inert, volatile solvent such as naphtha, wetted intimately, for example in one Waring mixer, mixed and filtered to give a wet filter cake. The filter cake is processed on a rubber mill for compaction, with rollers to make a defiber avoid, at temperature above the phases' Transition temperature of the polymer (53 ° C for poly ' tetrafluoroethylene). The sheet is grind, and the roller opening is gradually reduced as the solvent evaporates and the sheet gains structural strength. Usually, when grinding, the Walzon opening is initially twice the desired final thickness. The sheet finally obtained is folded and the Mill opening is set to double the final thickness of the sheet and for each new pass progressively reduced by halving the roller opening. In order to give the polytetrafluoroethylene sheet additional tensile strength, the roller temperature is increased to 165 ° C. and the sheet after Milled procedure described above until the final thickness is 0.05 to 0.1 cm. To further increase the tensile strength, the sheet can be sintered at 340 to 360 ° C for 45 to 60 minutes.

Preferably, the positive electrode is, which Composition whatever it may have. on its side facing away from the negative electrode in electrical contact with a metal or another learned substance. For copper electrode depolarizers, a copper sheet or grid is the preferred positive conductor electrode. For ironOD-suIrtd is an iron sheet or grid is useful; however, platinum, stainless steel or a similar inert material is preferable. It is evident that there is no support plate or grid is necessary. since FeS is itself a conductor (i.e., a porous, rigid sheet of ferrous sulfide itself is appropriate). Nickel compounds are preferably used together with nickel mesh or sheet used. Elemental sulfur can be mixed with carbon black (the paste is made up as described above) and on an iron plate or grid, graphitized ^ Cloth or similar conductive material be brought.

The negative electrode

To operate as a primary element, “Inactive negative electrode only needs lithium m. «I ^ although it is itself conductive. in contact with another conductor, such as aluminum. Tungsten, stainless Steel. Platinum. Nickel or silver, in the form of a bla ·· «·« or lattice that serves to counteract the negative Electrically connect electrode to the external circuit structure. However, the lithium hexafluorophosphate metal electrode system according to the invention is specially calculated for use with rechargeable lithium negative electrodes. Preferably negative lithium electrodes are made with Aluminum alloyed lithium is used, which is 1 to about 20 and preferably 5 to 16 percent by weight Contain lithium. The alloys can be made by melting lithium and aluminum together, or they can be made electrochemically by adding lithium ions Electrolytically reduced except for the positive aluminum electrode. The electrolyte for the galvanic Deposition can be any inert solvent! being. z. B. one of the for use as an electrolyte described in the present invention. The anion of the lithium salt Liihiumquelle is expediently one that is present on the negative electrode is oxidized, while lithium is deposited reductively on the positive electrode. In one

In such systems, the positive electrode and the negative electrode are separated from one another by an ion-permeable membrane or a porous electrolyte septum, so that the anodic oxidation product is prevented from coming into contact with the lithium deposit. Containing Ν, Ν-dimethylformamide containing about 10 weight percent lithium bromide, is particularly satisfactory for a galvanic deposition at current densities of up tu about IO mA / cm ^2. The aluminum sheet substrate can be a plate or foil, but it should not be too thin. Thin sheets may be prone to crumbling during electrodeposition due to the formation of a Li-Al alloy. Satisfactory results are obtained with sheets 0.025 to 0.05 cm thick. Thicker sheets can be used if desired. Electroplating is typically continued until the thickness of the lithium deposit is at least about 0.001 cm (preferably at least 0.005 cm), and usually no more than about 0.05 cm.

It appears that the electrodeposited lithium is not merely physically attached to the aluminum adheres, but is actually alloyed with it. What is proven by the fact that the reduction potential of lithium electrodeposited on aluminum is consequently lower than that of pure lithium metal. This difference in the reduction potential reflects the binding energy between the lithium and aluminum.

At 25 C and in an electrolyte consisting of 20 percent by weight lithium hexafluorophosphate in N.N-dimethylformamide, the preferred is galvanic deposited lithium-aluminum negative electrode by at least about 0.2 volts less than reducing Lithium metal when these two negative electrodes are rated against a saturated calomel electrode will.

When considering the electrochemical reactants, the overall reaction in element I requires up to 2 lithium atoms per oxidant (depolarizer). At least 1.5 lithium atoms are preferred for each valence level of the oxidant. Therefore, 3 lithium atoms become Cu ". Fe". Ni "and S ° preferred, while 1.5 ^{are preferred for Cu 1.} Such a lithium to oxidant atomic ratio, although not critical, preferably does not exceed 10: 1. In general, both the negative electrode and the positive electrode project same electrode area.

Element dividing devices, such as ion-permeable membranes or electrolyte-porous partitions, although they are not necessary in the elements according to the invention, can sometimes be included Advantageously, for example, to avoid the contact between the active components of the negative tive electrode and the positive electrode through the common electrolyte to further reduce.

Drawings - manufacture of the element

The invention can be further explained with reference to the drawings. The dimensions given are not critical; its purpose is to illustrate a distinctive embodiment.

The F i g. 1 shows a typical structure of the lithium negative electrode and an electrolyte chamber. rw *. outer plate 10 is expediently made of Aluminum (0.32 12.7 12.7 cm). The negative elec trodeliisteinAluminiUfflblechCO.ÖSbisöitO χ ί2.7 χ 12.7 Gfli), which is 0.0025 to 0.0050 cm thick «, galvanic lithium deposit is coated. The sealing washer 14 (0.64 12.7 χ 12.7 cm) is in typically silicone rubber, but can be any inert, insulating and sealing material such as polyethylene, polytetrafluoroethylene or non-conductive neoprene. The sealing washer 14 serves to the t ithiurrl-Elektrndenoberflächen 16 in To keep distance from the positive electrode structure (described in FIGS. 2 and 3) and towards it and isolate the electrolyte chamber 18 (0.64 χ 10.2 χ 10.2 cm). A polyethylene braid made from two layers of strands with a diameter of 1 mm (2.4 strands to the centimeter), wherein the strands cross at an angle of 90 "and form a uniform network, expediently serves as a spacer 20, the size of which is sized to fit into chamber 18 and is so constructed. that it prevents the surface of the positive electrode (described below) in contact with the surface 16 of the negative electrode comes.

The one shown in FIG. The structure of the positive electrode shown in Fig. 2 thus prepared. that he is a capable one Electrode paste (not shown) in chamber 30 comprises sealing washer 32 (identical to sealing washer 14 of FIG. I). one Mesh 34 (identical to spacer 20 of FIG. I). a copper plate 36. the one with the plate 38 (Identical to the plate 10 of Fig. It is laminated and which forms the conductive back wall of the electrode paste chamber, and the grid 40. a nylon mesh with openings of O.f <43 cm, which is porous to the electrolyte and serves to support the Retain electrode paste in chamber 30.

The in F i g. The structure of the positive electrode shown in FIG. 3 is the same as that of FIG. 2. only that the positive sheet electrode 50 replaces grid 40. grid 34 and sealing washer 32. The positive electrode 50 typically contains a mixture of particulate! Depolarizer, particulate !, conductive carbon and particulate polytetrafluoroethylene which was processed on a rubber mill to give the electrically conductive, electrolyte-porous, sheet-like structure described above.

V ie in the f i g. 1. Shown 2 and 3, each contains the Items 10, 12, 14, 40, 32. 36. 38 and 50 have twelve pigeon holes (denoted as 22) that are perimetric are arranged so that they can accommodate machine screw sets, suitably provided with threaded, insulating plastic screws and nuts (not shown).

To assemble the element, the one shown in FIG. 1 shown negative electrode-electrolyte chamber system with a structure of the positive electrode according to FIG. 2 in the order 10,12,14.20.40. 34, 32, 36 and 38 (electrode paste element) or with a structure of the positive electrode according to FIG. 3 in the order 12/10/14, 20 ', 50, 36 and 38 (electrode sheet element) coupled and the whole thing is screwed together with the Kunststorrmuttern and -screws to single-chamber elements according to the invention. Instead, the cell elements also clamped, glued or otherwise held together by suitable means.

9 νΓ ίο

In the following examples, which charge the invention until the element voltage drops to 1.5 volts *

Describe in more detail, all parts are that were covered. The item was then immediately at 200 HiA

unless otherwise stated, weight parts. charged again until a final voltage of

3.5 volts had been reached, whereupon the discharge took place

Ö e i s ρ i e 1 1 5 at 200 rnA up to the final voltage of 1.5 volts

ti ««. * ». ·« ,, a ** «-« »!"<«« tsu ^ n- ^ A * was repeated. This was the first charge * un-

Production of the negat.ven electrode end of the charge cycle, which in this example is about

A 0.33 12.7 12.7 "cm aluminum sheet required 60 minutes. This process was carried out by means of an electrode in one exchange cycle (" Amfioti "C <310 > Mernbra «repeated until the period of time to carry out a complete charge · discharge cycle from a JO weight percent solution of LiBr in a complete charge · discharge cycle shorter than dimethylformamide at 10 mA / cm ^{J for} 1 hour with 2 minutes. Characteristic results are lithium coated. The from the electrolyte * listed in the table below: the coated electrode taken was stored in a, -.. dry argon atmosphere., _s charge-discharge power;

r> : i *, t icj ei t .. λ Li / LiPF ₆ ■ DMF / CuS element Positive copper sulfide paste electrode

75 parts of a 20 weight percent solution of open circuit voltage, volts 3.00

LiPF ₆ (lithium hexafluorophosphate) in dimethyl oraminal number of charge-discharge

formamide were stirred and dried under dry » „ f? * '? ⁿ 1 ° [. ^d ? ^{m Ver9a} S «j ....... 3 t

Nitrogen, to a mixture of 12 parts of copper ^mte ° ^ _t Emladungszeit during the

sulfide powder and 12 parts of a conductive furnace black ^{STm Ladun} Es-Discharge-Zyk-

given to form a paste which is then placed on a _r ™ ' ¹ T ¹ I ¹ "??,« ·.

Polyethylene grille with the cycle benefit effect used in the description of the ^C ° V £ ^mb The dimensions given has been spread out. "" Ϊ́ ^ ϊίΗΙΤίίίίΤΤ! 78. Assembly and filling of the element maximum. % 93

The negative electrode described above and these results show that the paste positive electrode of the present invention was discharged and repeatedly charged in a dry element in a practical discharge current-strength argon atmosphere with other elements, such as at 30 th. the F i g. I and 2 described, assembled. The solubility of copper / ID sulfide in dimethyl-A 20 weight percent solution of LiPF ₆ in diformamide was 71 parts per million of methylformamide as follows. 14 parts (the conductivity is determined to be 2 χ: a sample, the amount of which is significantly above 10 ohms 'cm'). was on the way over half of the solubility value given above. Injection syringe through the wall of the sealing 35 was vigorously moved for 20 hours in a closed Rt disk 14 to complete the galvanic holder with 100 ml of the solvent. <K element introduced into chamber 18. Alternatively, mix dun under the action of gravity. h, two glass tubes of Whatman No. 5 filter paper are filtered to fill the element and the filtrate is introduced through the wall of the sealing washer 14. and the copper content is colorimetrically Ijstimrn! one for introducing the electrolyte and the other 40 The element according to the invention combines well ·· '* to displace the atmosphere of the element cycle groove / effect with the ability to restore itself during filling. The tubes become after the electrolyte has been filled for a relatively long time. locked. Discharge cycle life, the average Be _{F1 mpnt} i _pi "..__ ^s P ^'el' is 1200 31 = 39 minutes recurrent lackn to let ^g 45th

The element produced in this way shows a stress at B e i s ρ i e I e 2 to 6

open circuit of 3.00 V and the following Ent- elements were essentially as in the Ba-

Charging and recharging features described in game I, only that the copper! You-

following conditions referring to the examination of the secondary sulfide by the same weight of another

element efficiency: 50 copper compound as an oxidant of the positive elec-

The element was under stress when a con- trode was replaced. The results are below

constant discharge current of 200 mA as long as it is compiled in the form of a table:

example

Oiydans of the positive electrode and Solubility in DMF

(Parts per million I

Copper (II) ferrocyanide. Cu ₂ Fe (CN) ₆ (29) ...

Basic copper (H) carbonate. CuCO ₃ ■ Cu (OH) ₂ (0.7) .. copper D-sulfide, Cu ₂ S (53) ... copper (I> oxide, Cu ₂ O (2) ... copper (II) -OHd, CuO (3) ...

Total service life Ladunes EntiadunK discharge Cycle efficiency Cycles Minutes % 161 673 79 144 1895 90 51 838 60 55 1110 85 132 1704 86

In addition to the copper compounds mentioned in Examples 2 to 6, copper (II) hydroxide and copper (II) metaborate Cu (BO ₂ J _{2) are} useful depolarizers.

11 (\ 12th

Examples 7 to

Elements were prepared essentially as described in Example 1, except that the dimethylformamide was used has been replaced by the solvents listed in the table below:

example solvent

discharge Minutes

Total service life Cycle utility flexes

Cycles

7 N.N-dimethylacetamide

8 dimethyl sulfoxide

9 acetonitrile

Example IO

A positive sheet electrode element was assembled as follows: A 0.1 cm thick positive filate electrode (the production of which is described below, and which contains 11 percent by weight copper / merryanide, 32% polytetrafluoroethylene and 32% carbon black and an active electrode surface of 100 cm ² has), a 0.32 cm lamination sheet made of aluminum and an O.Sl-em copper contact sheet, the skins as shown in FIG. 3 were provisionally assembled by inserting a nylon machine screw into each hole. The construction of the positive electrode was placed Γη a storage chamber under an argon atmosphere, while a lithium-on-aluminum negative electrode. as described in example 1. was produced. After the plating was complete, the plating electrolyte was displaced from the plating element by argon and this was poured into the argon together with an aluminum plate, a silicone rubber sealing washer and a polyethylene screen (all of which had the dimensions described in FIG. I). Chamber broke with the construction of the positive electrode. The electroplating element was disassembled in the argon atmosphere, the negative electrode was wiped dry, and the components were in the order 10, 12, 16, 14, 20, SO. 36 and 37 with reference to FIGS. and 3 arranged. The element was assembled by screwing and removed from the argon chamber. A solution of 4.1 g of lithium hexafluorophosphate in 16.2 cm ^{3 of} dimethylformamide was injected into the electrolyte chamber by inserting a syringe needle through the wall of the sealing washer. At the same time the argon atmosphere of the element was displaced into a second empty syringe, which in the same way penetrated the wall of the sealing washer. This element had an open circuit potential of 3.0 volts and a closed circuit potential of X5 volts after a 4 mm discharge at 200 mA. The element was recharged in 4 minutes at 200 mA to a closed circuit potential of 3.6 volts; it was left open circuit (3.25 volts) for 4 minutes and then subjected to 69 cycles at 200 mA comprising 1 minute charging and 1 minute discharging, during which time the minimum discharge voltage was 2 and the maximum was 3.8 volts . These cycles were followed by deeper discharge cycles between 0.8VoIt (when discharged) and 4VoIt (when charged) at 200 mA, as described below: The element was 22.5 Mi- 257 284 167

65 85 63

59 43 50

discharged for a long time, charged for 20.2 minutes, Discharge again for 17.3 minutes and in 14.0 minutes with a mean Coulomb cycle efficiency recharged by 85%.

The positive sheet electrode used in this example was prepared as follows: 10 parts by weight of a powdered polytetrafluoroethylene wire coating resin with an average particle size of 500 ± 150 microns, which melted at 327 ± 10 ° C, were mixed with 90 parts by weight of a granular polytetrafluoroethylene - Compression and extrusion resin mixed with a particle size of about 35 microns. This mixture (18.9 percent by volume) was then mixed in a Waring blender with the conductive furnace black of Example 1 (70.5 percent by volume). Copper (II) ferrocyanide (10.9 percent by volume) and Stoddard solvent (in sufficient amount to give a wet filter cake) mixed and filtered. The filter cake was transferred to a rubber mill and ground with rollers heated to 55X. The roller opening of the mill was progressively reduced until practically all of the naphtha had evaporated and the ground mass formed a coherent skin. The hide was removed, folded and ground with an initial roller opening setting of 0.2 cm. The skin was removed again, folded and passed through the mill, the roller opening being slightly reduced. This was repeated until the fur was 0.1 cm thick. The rollers were then heated to 165 ° C. and the leaf mass was ground again as before, assuming an opening of 0.2 cm and then progressively reducing the size of the opening until the skin thickness was 0.1 cm. ^{The fur was then heated to 340 to 360 °} C. for 1 hour in an oven.

At game 11 (Organic copper salts as a depolarizer)

Elements were essentially as in Example 1 described, manufactured, only that the same weight amount of a copper salt of a polycarboxylic acid ah depolarizer was used.

Total service life Cylindrical
benefit Charge Oxydans of the positive % Development
loading Electrode and Solubility 86 Cycles m DMF discharge 88 63 (Parts per million) Minutes 90 120 Copper (II) oxa] ate (6) .. 1630 86 Copper (II) citrate (5) .. 2220 Copper (II) tartrate (35) 2339

I 935

Oxydans of the positive
Electrode and Solubility

(Parts per million |

Iron (I!) - siilfid Nickel oxate (70) Nickel fluoride '

Nickel sulfide (44) ¹ ) ... sulfur (2000) ² )

Sulfur (2000) ³ )

Total service life

discharge
Minutes

626

167

570

3080

2300

2740

Cycle efficiency

95 80 80 96 90 90

Charge

Loading cycles

220

23

23

459

730

685

Example 13 (DMF is replaced by propylene carbonate)

electrolyte discharge
Minutes cycle
use effect Charge
Development
charge
Cycles Propylene carbonate
+20 percent by weight
LlPF ₈ ¹ ) 236 > 95 42

The above items are both in terms of discharge and recharge similar to the element of example 1.

Example 12

(FeS, NiS, Ni (COO) ₂ and S ⁰
as depolarizers)

Positive paste electrodes made of iron (II) sulphide, nickel sulphide, Nickel oxate and elemental sulfur became essentially like the copper sulfide positive paste electrode of Example 1, except that the conductor plates or grids are made of iron, nickel or platinum was. The elements produced as in Example 1 showed the following results:

electrolyte

discharge

Minutes

IO 3260

Cycle usage ffcki

91

Charge

Loading cycles

1830

') In these elements, the end voltages at maximum charge were 2.7 door FeS and NiF ₂ and 3.0 door NiS: the discharge end voltages were 0.8 and 1.0 volts, respectively. For good electrical resistance with FeS, NiF ₂ and NiS oxidants, it was found necessary to have terminal voltages that were smaller than the more common 3.5 and 1.5 volts.
² ) Weight ratio of powdered sulfur to carbon black as I: 1

') Weight ratio of powdered sulfur to soot like 4: 1.

The results given above show that depolarizers other than copper compounds also work very well are effective.

45

The elements were made essentially as the element of Example 1, except that the Ν, Ν-dimethylformamide was replaced by propylene carbonate and by propylene carbonate diluted with benzene.

') Gm Nylongllier the Pig. 2 was replaced by a polyester frame, the dimensions of which were basically the same as the Nyfongftten · Pure »Pfopyleneaftmnal attacks nylon.

Propylene carbonate

(58 percent by weight),

benzene
(28 percent by weight),

LiPF ₆
(15 percent by weight)

Methyl acetate and methyl formate can also be used effectively as solvents for electrolyte salts will.

Claims (5)

Patent claims: 1. Galvanic element with a negative lithium electrode, alloyed with a less active metal, and an electrolyte made from a practically neutral, inert solvent such as NN-dimethylformamide. contains the lithium hexafluorophosphate in sufficient concentration, characterized in that the lithium electrode consists of aluminum and 1 to 20 percent by weight lithium and has a reduction potential of at least 0.2 volts lower than that of lithium metal. 2. Galvanic element according to claim 1, characterized in that the positive electrode a reversibly reducible depolarizer from the group of elemental sulfur and iron. Nickel or copper compounds, their solubility in the electrolyte solvent at 25 ° C is less than 200 parts by weight per million, preferably copper (I) oxide, copper! II) oxide, copper (I) carbonate, basic copper (II) carbonate. Copper (II) ferrocyanide, copper (II) sulfide, copper (II) oxalate, copper (II) tartrate, copper (II) citrate. Mixtures of such copper compounds, nickel sulfide. Nickel fluoride. Contains nickel oxate or iron (II) sulfide. 3. Galvanic element according to claim 2, characterized in that the positive electrode an electrically conductive paste composed of (a) at least one of the depolarizers in particulate form, (b) particulate! conductive carbon black and (c) one Lithium hexafluofophosphorus electrolyte and is in contact with a conductive material. 4. Galvanic element according to claim 2, characterized in that the positive electrode a porous, electrolyte-permeable, sheet-like structure int. which consists of a mixture of (a) at least one of the depolarizers in particle form, (b) a particulate electrical conductor such as carbon black and (C) a normally solid electrolyte insoluble, electrochemically inert, polymeric filler, such as polytetrafluoroethylene, in an amount which is sufficient to form a self-supporting sheet, the sheet in electrical Is in contact with a metal conductor. 5. Galvanic element according to claim 2, since * characterized in that the positive electrode is a self-supporting structure made of iron (ll> sulfld. 1 sheet of drawings