EP3105804A1

EP3105804A1 - Galvanic cells and (partially) lithiated lithium battery anodes with increased capacity, and method for producing synthetic graphite intercalation connections

Info

Publication number: EP3105804A1
Application number: EP15706396.7A
Authority: EP
Inventors: Ulrich Wietelmann; Vera NICKEL; Stefan Scherer; Ute Emmel; Thorsten Buhrmester; Steffen Haber; Gerd Krämer
Original assignee: Rockwood Lithium GmbH
Current assignee: Albemarle Germany GmbH
Priority date: 2014-02-13
Filing date: 2015-02-13
Publication date: 2016-12-21
Also published as: KR102411555B1; CN106663775A; JP6738276B2; KR20160121564A; JP2017513177A; US20160351893A1; BR112016018582B1; CN106663775B; WO2015121391A1; CA2939157A1; BR112016018582A2; DE102015202611A1

Abstract

The invention relates to a galvanic cell containing a cathode, a lithium-conductive electrolyte separator system, and a synthetic graphite-containing anode. In the manufacture of the cell ( i.e. prior to the first charging cycle), the anode contains or consists of a (partially) lithiated graphite powder which is produced from synthetic graphite and lithium powder in a non-electrochemical manner. The invention also relates to a method for (partially) lithiating synthetic graphite in an electroless manner. The invention is characterized in that the particulate synthetic graphite is (partially) lithiated in an electroless manner after mixing with particulate lithium metal powder and by means of a mixing and/or milling process, thereby forming Li graphite intercalates of the composition LiCx (mit x = 6 –600).

Description

Galvanic cells and increased capacity lithium ion battery (lithiated) lithiated anodes and methods of making syngraphite intercalation compounds

Electrochemical cells for lithium-ion batteries are built by default in the discharged state. This has the advantage that both electrodes are in air and water stable form. The electrochemically active lithium is introduced exclusively in the form of the cathode material. The cathode material contains lithium metal oxides such as lithium cobalt oxide (LiCo0 ₂ ) as an electrochemically active component. The anode material in the currently commercial batteries contains in the discharged state as active material a graphitic material with a theoretical electrochemical capacity of 372 Ah / kg. It is usually completely lithium free. In future designs, (also lithium-free) materials with higher specific capacitance, for example alloy anodes, often silicon- or tin-based, can be used.

In real battery systems, part of the lithium introduced with the cathode material is lost by irreversible processes, especially during the first charge-discharge process. In addition, the classic lithium-ion battery design with lithium-free graphite as anode has the disadvantage that lithium-free potential cathode materials (eg Mn0 ₂ ) are not usable.

In the case of graphite, it is believed that, in particular, oxygen-containing surface groups react irreversibly with lithium during the first battery charging process to form stable salts. This part of the lithium is lost for the subsequent electrochemical charge / discharge processes, since the salts formed are electrochemically inactive. It is similar in the case of alloy anodes, for example, silicon or tin anode materials. Oxidic impurities consume lithium according to:

M0 ₂ + 4 Li + M + 2 Li ₂ 0 (1)

(M = Sn, Si and others)

The bound in the form of Li ₂ 0 lithium is no longer electrochemically active. When using anode materials with a potential <about 1.5 V, a further part of the lithium is irreversibly consumed for the formation of a passivation layer (so-called solid electrolyte interface, SEI) on the negative electrode. In the case of graphite go in this way between a total of about 7 and 20 wt .-% of the positive mass (ie the cathode material) lost lithium. In the case of tin or silicon anodes, these losses are usually even higher. The following equation (2) entlithiierte, "remaining" transition metal oxide (for example, Co0 ₂₎ may lack active lithium do not contribute to reversible electrochemical capacity of the galvanic cell:

2n LiCo0 ₂ + MO _n - »n Li ₂ 0 + M + 2n Co0 ₂ (2)

(M = Si, Sn, etc., n = 1 or 2)

There are many studies aimed at minimizing or even eliminating these irreversible losses of the first charge / discharge cycle. The limitation can be overcome by introducing additional lithium in metallic form, for example as a stabilized metal powder ("SLMP") into the battery cell (eg US2008283155A1, B. Meyer, F. Cassel, M. Yakovleva, Y. Gao, G. Au , Proc. Power Sourc., Conf., 2008, 43rd, 105-108), but this has the disadvantage that the usual methods for producing battery electrodes for lithium-ion batteries can not be carried out, according to the prior art, passivated lithium reacts with the main air constituents Oxygen and Nitrogen Although the kinetics of this reaction are very much slower compared to non-stabilized lithium, prolonged exposure to air, even under dry-room conditions, does not allow for a change in surface area or a decrease in metal content is the extremely violent reaction of Li metal powder often used for electrode preparation solvent to evaluate N-methylpyrrolidone (NMP). While significant progress towards safer handling has been made by providing stabilized or coated lithium powder, the stability of the prior art stabilized lithium powder is often insufficient to allow safe use of passivated lithium powder in practice in NMP-based electrode fabrication processes ( Suspension procedure). While uncoated or poorly coated metal powders can react vigorously (thermal run away) with NMP already after a short induction time even at room temperature, this process only takes place at elevated temperatures (for example 30 or 80 ° C.) in the case of coated lithium powder. For example, it is described in US2008 / 0283155 that the phosphoric acid-coated lithium powder from Example 1 reacts extremely vigorously immediately after mixing together at 30 ° C., while a powder additionally coated with a wax is stable at 30 ° C. in NMP for at least 24 h is. The lithium powders coated according to WO2012 / 052265 are kinetically stable up to about 80 ° C. in NMP, they but decompose at temperatures beyond exothermic, mostly under runaway-like phenomena. For mainly this reason, the use of lithium powders as a lithium reservoir for lithium-ion batteries or for the prelithiation of electrode materials has not been able to prevail commercially.

Alternatively, additional electrochemically active lithium can also be introduced by the addition of graphite lithium intercalation compounds (LiC _x ) to the anode in a lithium electrochemical cell. Such Li intercalation compounds can be prepared either electrochemically or chemically.

The electrochemical production takes place automatically when charging conventional lithium-ion batteries. By this process, materials with lithium: carbon stoichiometries of at most 1: 6.0 can be obtained (see, for example, N. Imanishi, "Development of the Carbon Anode in Lithium Ion Batteries", in: M. Wakihara and O. Yamamoto (ed Lithium Ion Batteries, Wiley-VCH, Weinheim 1998.) The partially or completely lithiated material prepared in this way can in principle be taken from a charged lithium-ion cell under a protective gas atmosphere (argon) and, after appropriate conditioning (washing and drying with suitable solvents), for new battery cells Because of the high associated costs, this procedure is chosen only for analytical investigation purposes and the method has no practical relevance for economic reasons.

Furthermore, there are chemical-preparative ways for Lithiierung of graphite materials. It is known that lithium vapor reacts with graphite at temperatures of 400 ° C to lithium intercalation compounds (lithium intercalates). When exceeding 450 ° C, however, undesirable lithium carbide Li ₂ C _{2 forms} . The incorporation reaction works well with highly oriented graphite (HOPG = Highly Oriented Pyrolytic Graphite). When using liquid lithium even a temperature of 350 ° C is sufficient (R. Yazami, J. Power Sources 43-44 (1993) 39-46). The use of high temperatures is generally unfavorable for energetic reasons. In the case of lithium, the high reactivity and corrosiveness of the alkali metal is added. Therefore, this production variant also has no commercial significance.

When using extremely high pressures (2 GPa, corresponding to 20,000 atm), the lithium intercalation can be achieved even at room temperature (D.Guard, A. Herold, CR Acad., Ser. C, 275 (1972) 571). Such high pressures can be only in very specific reach hydraulic presses, which are suitable only for the production of smallest laboratory quantities. Thus, it is not a technically-industrially suitable method for producing commercial quantities of lithium-graphite intercalation compounds.

Finally, the production of lithiated natural graphite (Ceylon graphite) by high energy milling in a ball mill has been described. For this purpose, the predominantly hexagonally structured natural graphite from present day Sri Lanka was treated with lithium powder (170 μηη average particle size) in the Li: C ratios of 1: 6; 1: 4 and 1: 2 implemented. Complete lithiation to the final molar ratio LiC ₆ could only be achieved with the molar ratio 1: 2 (R. Janot, D. Guerard, Progr. Mat. Sci. 50 (2005) 1 -92). This synthesis variant is technically-commercially disadvantageous. On the one hand, a very high lithium excess is needed to achieve sufficient or complete lithiation. The majority of the lithium is lost (in the mill and on the grinding balls) or it is not intercalated (so it is still in elemental form). On the other hand, no unconditioned natural graphites are generally used for the production of anodes for lithium-ion batteries. The mechanical integrity of natural graphites is namely due to sogn. Exfoliation irreversibly destroyed by the intercalation of solvated lithium ions during battery cycling, s. P. Kurzweil, K. Brandt, "Secondary Batteries - Lithium Rechargeable Systems" in Encyclopedia of Electrochemical Power Sources, J. Garche (ed.), Elsevier Amsterdam 2009, Vol. 5, pp. 1-26) Such synthetic graphites are less crystalline and have a lower degree of graphitization Finally, the long milling times required for natural graphite, preferably 12 hours (page 29), are detrimental For the reasons set out above, the described process has not been commercialized.

Janot and Guerard's publication also describes the application properties of lithiated Ceylon graphite (Chapter 7). The electrode production takes place by simply pressing the graphite onto a copper net. The counter and reference electrodes are lithium bands, and the electrolyte used is a 1 M LiClO ₄ solution in EC / DMC. The type of electrode preparation by simple pressing is not the prior art, as it is used in the commercial battery electrode production. Simple compression without binder and if necessary addition of conductivity additives does not lead to stable electrodes, since the volume changes taking place during charging / discharging must inevitably lead to crumbling of the electrodes, whereby the functionality of the battery cell is destroyed. The invention has for its object to show a partially or completely lithiated anode graphite for lithium battery cells and to provide a built-lithium cell available whose capacity is increased by the additional lithium reservoir over the prior art.

Furthermore, a method for achieving this goal should be specified. This procedure should

1 . starting from inexpensive, marketable materials, in particular from synthesis graphites,

2. use the lithium in high yield and

3. the usual manufacturing methods, i. In particular, anode production using solvent-based dispersion casting techniques allows the use of common solvents in anode production, e.g. by NMP, should be possible without danger.

The object is achieved in that a lithium battery cell is used, the lithiated in the anode before the first charging cycle partially or fully lithiated to the thermodynamically stable boundary stoichiometry LiC ₆ (hereinafter referred to as "(partially) lithiated") contains synthetic graphite or the (That is, the anode) consists thereof and wherein the lithiation of the synthetic graphite was effected by non-electrochemical means under normal pressure or a slight pressure of <about 10 bar.

Synthetic anode graphites are offered by a number of manufacturers, including: SGL Carbon, Hitachi and Timcal. These products are particularly important for use as anode materials for lithium-ion batteries. For example, the synthesis graphite SLP 30 from Timcal consists of particles having an average particle size of 31.5 μηη and has an irreversible capacity of 43 mAh / g (based on the reversible capacity of 365 mAh / g corresponds to about 12%) C. Decaux et al., Electrochim. Acta 86 (2012) 282).

The (partially) lithiated synthesis graphite powders according to the invention are prepared by mixing a powdered synthetic graphite with lithium metal powder and by stirring, grinding and / or pressing at pressures of <10 bar to form Li-graphite intercalates of the composition LiC _x (where x = 6 - 600) is reacted. Depending on desired end stoichiometry, the two said raw materials in the molar ratio Li: C of 1: at least 3 to 1: 600 maximum used, preferably 1: at least 5 and 1: at most 600. The introduced via the Grenzstöchiometrie LiC ₆ lithium is presumably in finely divided form the graphite surface.

The reaction takes place in the temperature range between 0 and 180 ° C, preferably 20 to 150 ° C either in vacuo or under an atmosphere whose components are not or only slowly acceptable with metallic lithium and / or lithium graphite intercalation react. This is preferably either dry air or a noble gas, more preferably argon. The Lithiierungsvorgang takes place at normal or only moderately elevated ambient pressures (maximum 10 bar).

The lithium is in powder form, consisting of particles having an average particle size between about 5 and 500 μηη, preferably 10 and 200 μηη used. Both coated powders, e.g. a stabilized metal powder offered by FMC (Lectromax powder 100, SLMP) having a lithium content of at least 97% by weight or, for example, an alloying element-coated powder having metal contents of at least 95% by weight (WO2013 / 104787A1). Particular preference is given to using uncoated lithium powders having a metal content of> 99% by weight. For use in the battery sector, the purity with respect to metallic impurities must be very high. Among other things, the sodium content must not be> 200 ppm. The Na content is preferably <100 ppm, particularly preferably <80 ppm.

As synthesis graphite come all powdered graphite grades, which are industrially produced and not obtained from natural resources (mines) in question. Starting materials for synthesis graphites are graphitizable carbon carriers, such as petroleum coke, needle coke, industrial carbon black, plant wastes, etc., as well as graphitizable binders, in particular coal tar pitch or thermosetting synthetic resins. The synthesis graphites used are characterized by average particle sizes in the range of about 1 to 200 μηη, preferably 10 to 100 μηη. The synthesis graphites used generally have a lower degree of graphitization or order (and a lower crystallinity) than typical natural graphites, for example the graphite from Ceylon / Sri Lanka. The degree of graphitization of a graphitic material can be characterized by accurate measurement of the coherent domain diameter L _a (ie, the in-plane crystallite diameter) by X-ray or (more simply) by Raman spectroscopic measurements. Graphites exhibit typical Raman absorption at about 1575-1581 cm ^"1 (" G-band "). This absorption is due to in-plane vibration vibrations (E _2g G-mode) of the sp ² -bonded carbons of the undisturbed lattice. In the case of polycrystalline or disordered graphites, Raman peaks are typically added at 1355 cm ^-1 (A _1g ) and (at lower intensities) at 1620, 1500 and 1550 cm ^-1 (see also "D band", D = defect). From the signal ratio between the intensities of D-band and G-band 1 _D : IG, the domain diameter L _a can be calculated, which describes the degree of crystallinity and thus the degree of graphitization (AC Ferrari and J. Robertson, Phys. Rev. B, Rhim et al., Carbon 48 (2010) 1012-1024) Highly crystalline graphite (HOPG) and well-ordered natural graphites have a 1: _D _G ratio of 0 - ca Guoping et al., Solid State Ionics 176 (2005) 905-909) The natural graphite from Ceylon / Sri Lanka has an ID: IG ratio of about 0.1 (corresponding to a domain diameter L _a of about 40 nm, s. MR Ammar, carboxylic -Amer. carbon SOC print ed. 61 1 -2, 2000). in contrast, at T <1000 ° C annealed synthetic graphites significantly higher l _D : IG ratios of typically 1 to (corresponds to L _a = ca. 4 nm, S. Bhardwaj et al., Carbon Lett. 8 (2007) 285-291). Although the domain diameter L _a can be increased by high temperature annealing, this process increases the irreversible loss of the first charge / discharge cycle when used as the anode material. Therefore, synthetic anode graphites require a surface treatment that improves the electrochemical properties. For example, WO2013 / 149807 describes that a synthetic graphite with L _a = 40 nm (1 _D : IG = approx. 0.15) reduces the L _a diameter to 15 nm by aftertreatment with oxygen (I _D : l _G = approx. 0.39). The irreversible losses fall from 27 to 1 1, 5%.

According to the invention, preference is given to those synthesis graphites which have a L _D : I _G ratio of at least 0.2, more preferably at least 0.5 (corresponding to domain diameter L _a of not more than 29 nm, particularly preferably not more than 12 nm).

The reaction (ie the (partial) lithiation) takes place during mixing or grinding of the two components lithium powder and graphite powder. In the laboratory, the grinding can be done by mortar and pestle. The reaction preferably takes place in a mill, for example a rod, vibration or ball mill. Particularly advantageously, the reaction is carried out in a planetary ball mill. For example, the planetary ball mill Pulverisette 7 premium line from Fritsch can be used on a laboratory scale. When using planetary ball mills can surprisingly very short reaction times of <10 h, often even <1 h realize. The mixture of lithium and graphite powder is preferably ground in the dry state. However, it is also possible to add a fluid which is inert to both substances up to a maximum weight ratio of 1: 1 (total Li + C: fluid). The inert fluid is preferably an anhydrous hydrocarbon solvent, eg a liquid alkane or alkane mixture or an aromatic solvent. The addition of solvents dampens the severity of the grinding process and less grazes the graphite particles.

The grinding time depends on different requirements and process parameters:

• Weight ratio of grinding balls to product mixture

Type of grinding balls (e.g., hardness and density)

• Intensity of the grinding (rotation frequency of the grinding plate)

Reactivity of lithium powder (e.g., type of coating)

• Weight ratio Li: C

• Product-specific material properties

• desired particle size etc.

The appropriate conditions can be found by those skilled in the art by simple optimization experiments. In general, the milling times vary between 5 minutes and 24 hours, preferably 10 minutes and 10 hours.

The (according to the method described above) (partially) lithiated synthesis graphite powder against environmental conditions (air and water) and many functionalized solvents and liquid electrolyte solutions still "active", ie it can react for extended periods, but not usually violently or even run-away When stored in normal air, the lithium contained slowly reacts to form stable salts such as lithium hydroxide, lithium oxide and / or lithium carbonate, which can be eliminated or at least further mitigated by a coating process reacted with a gaseous or liquid coating agent in a suitable manner ("passivated"). Suitable coating agents contain reactive functional groups or molecular components in relation to metallic lithium and lithium graphite intercalation compounds and therefore react with the surface-available lithium. It finds an implementation of the lithium-containing surface zone to form no or little air-reactive (ie thermodynamically stable) lithium salts (such as lithium carbonate, lithium fluoride, lithium hydroxide, lithium alcoholates, lithium carboxylates etc) instead. In this coating process, most of the lithium not present on the particle surface (eg the intercalated portion) remains in active form, ie with an electrochemical potential of <approximately 1 V vs.. Li / Li ^" * ^" received. Such coating agents are known from the lithium-ion battery technology as in situ film former (also referred to as SEI-formers) for the negative electrode and described, for example, in the following review article: A. Lex-Balducci, W. Henderson, S. Passerini, Electrolytes for Lithium Ion Batteries, in Lithium Ion Batteries, Advanced Materials and Technologies, X. Yuan, H. Liu, and J. Zhang (eds.), CRC Press Boca Raton, 2012, p. 147-196. In the following, suitable coating agents are exemplified , As gases are N _2, C0 _2, CO, 0 _2, N ₂ 0, NO, N0 _2, HF, F _2, PF _3, PF _5, etc. POF ₃ Suitable liquid coating agents are, for example: carbonic acid esters (eg vinylene carbonate (VC), vinyl ethylene carbonate (VEC), ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC)); Lithium chelatoborate solutions (eg lithium bis (oxalato) borate (LiBOB); lithium bis (salicylato) borate (LiBSB); lithium bis (malonato) borate (LiBMB); lithium difluorooxalatoborate (LiDFOB), as solutions in organic solvents, preferably selected from: oxygen-containing Heterocycles such as tetrahydrofuran (THF), 2-methyl-tetrahydrofuran (2-methyl-THF), dioxolane, carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and / or ethylmethyl carbonate, nitriles such as acetonitrile, glutarodinitrile, carboxylic acid esters such as ethyl acetate, butyl formate and ketones such Acetone, butanone); sulfur organic compounds (eg, sulfites (vinyl ethylene sulfite, ethylene sulfite), sulfones, sultones and the like); N-containing organic compounds (eg pyrrole, pyridine, vinylpyridine, picolines, 1-vinyl-2-pyrrolidinone), phosphoric acid, organic phosphorus-containing compounds (eg vinylphosphonic acid), fluorine-containing organic and inorganic compounds (eg partially fluorinated hydrocarbons, PF ₃ , PF ₅ , LiPF ₆ , LiBF ₄ , the latter two compounds dissolved in aprotic solvents), silicon-containing compounds (eg silicone oils, alkylsiloxanes), inter alia

The coating not only improves handling properties and safety in electrode (generally anode) fabrication, but also application properties in the electrochemical battery cell. The use of precoated anode materials eliminates the formation of an SEI (solid electrolyte interface) during contact of the (partially) lithiated graphite anode material with the liquid electrolyte of the battery cell. The trained outside the electrochemical cell stabilizing coating layer corresponds in its properties to a so-called artificial SEI. Ideally, the necessary prior art forming process of the electrochemical cell is eliminated or it is at least simplified.

When using liquid coating agents, the coating process is generally carried out under inert gas atmosphere (e.g., argon protective atmosphere) at temperatures between 0 and 150 ° C. In order to increase the contact between the coating agent and the (partially) lithiated synthesis graphite powder, mixing or stirring conditions are advantageous. The necessary contact time between coating agent and (partially) lithiated synthesis graphite powder depends on the reactivity of the coating agent, the prevailing temperature and other process parameters. In general, times between 1 minute and 24 hours make sense. The gaseous coating agents are used either in pure form or, preferably, in admixture with a carrier gas, e.g. a noble gas such as argon.

The (partially) lithiated (and optionally pre-coated) synthesis graphite powder can be used to make battery electrodes by the method described above. This is done under inert or dry space conditions with at least one binder material and optionally one or more further powdery lithium-storable material (s) with an electrochemical potential <2 V vs Li / Li ^" * ^" and also optionally with a conductivity-improving additive (eg carbon blacks or nickel powder ) and an organic solvent and homogenized and this dispersion is applied by a coating method (casting method, spin coating or air-brush method) on a current collector and dried. The (partially) lithiated graphite powder produced by the process according to the invention is surprisingly only moderately reactive toward N-methylpyrrolidone (NMP). When using highly reactive solvents such as NMP, uncoated (partially) lithiated graphite powders with a stoichiometric molar C: Li ratio of min. 6, preferably min. 12 used. In the case of the coating (partially) lithiated graphite powder stabilized by a coating, lower molar C: Li ratios (ie higher Li contents) of up to min. 3 are used. By adhering to these restrictions, the (partially) lithiated graphite powders can be processed into a castable or sprayable dispersion without any problems with NMP and the binder material PVdF (polyvinylidene difluoride). Alternatively, the solvents N-ethylpyrrolidone, dimethyl sulfoxide, cyclic ethers (eg tetrahydrofuran, 2-methyltetrahydrofuran), ketones (eg acetone, butanone) and / or lactones (eg γ-butyrolactone) can be used. Further examples of suitable binder materials are: carboxymethylcellulose (CMC), alginic acid, polyacrylates, Teflon and polyisobutylene (for example Oppanol from BASF When using polyisobutylene binders, preference is given to using hydrocarbons (aromatics, for example toluene or saturated hydrocarbons, eg hexane, cyclohexane, heptane, octane).

The optionally used further pulverulent lithium-storable material is preferably selected from the groups graphites, graphene, layer-structured lithium transition metal nitrides (eg Li _2.6 Co ₀ , 4N, LiMoN ₂ , Li ₇ MnN ₄ , Li _2,7 Fe ₀ , 3N), with lithium alloyable metal powder (eg, Sn, Si, Al, Mg, Ca, Zn or mixtures thereof), main group metal oxides with a metal which in reduced form (ie as metal) with lithium alloyed (eg Sn0 ₂ , Si0 ₂ , SiO, Ti0 ₂ ), metal hydrides (eg MgH ₂ , LiH, TiNiH _x , AlH ₃ , L1AlH ₄ , LiBH ₄ , Li ₃ AlH _6, LiNiH ₄ , TiH ₂ , LaNi _4.25 Mno, 75H5, Mg ₂ NiH _3.7 ), lithium amide , lithium imide, Tetralithiumnitridhydrid, black phosphorus and transition metal oxides that can react with lithium to a conversion mechanism by absorbing lithium (eg C03O4, CoO, FeO, Fe ₂ 0 _3, Mn ₂ 0 _3, Mn ₃ 0 _4, MnO, Mo0 _3, Mo0 ₂ , CuO, Cu ₂ 0). An overview of usable anode materials can be found in the review article by X. Zhang et al., Energy & Environ. Be. 201 1, 4, 2682, are taken. The anode dispersion prepared according to the invention containing a non-electrochemical (partially) lithiated synthesis graphite powder is applied to a current collector foil preferably consisting of a thin copper or nickel sheet, dried and preferably calendered. The anode foil produced in this way can be produced by combination with a lithium-conducting electrolyte separator system and a suitable cathode foil containing a lithium compound with a potential of> 2 V vs. Li / Li ^" * ^" (eg lithium metal oxides such as LiCoO ₂ , LiMn ₂ O ₄ , LiNi _{0, 5} Mn _{1 5} O ₂ or sulfides such as Li ₂ S, FeS ₂ ) to a lithium battery with respect to the prior art increased capacity combine. The technical production of such galvanic cells (but without the use of the (partially) lithiated synthesis graphite powder according to the invention) is well known and described, for example P. Kurzweil, K. Brandt, Secondary Batteries, Lithium Rechargeable Systems: Overview, in: Encyclopedia of Electrochemical Power Sources, ed. J. Garche, Elsevier, Amsterdam 2009, Vol. 5, p. 1 -26).

The invention relates in detail:

Process for the production of lithium battery anodes, in which a powdered (partially) lithiated synthesis graphite prepared by an electroless process is treated under inert or dry space conditions with at least one binder material and optionally one or more further powdery lithium-storable material (s) with an electrochemical potential <2 V vs Li / Li + and also optionally mixed with a conductivity-improving additive and a solvent and homogenized and this dispersion is applied by a coating process on a Stromabieiterfolie and dried.

Method in which the synthesis graphite has an ID: IG ratio determined by Raman spectroscopy of min. 0.2 particularly preferred min. 0.5.

Process in which the optionally used further powdery lithium-insertable material is preferably selected from the groups graphites, graphene, layered lithium transition metal nitrides, lithium alloyable metal powders, main group metal oxides with a metal which alloys with lithium in reduced form (ie as metal), metal hydrides , Lithium amide, lithium imide, tetralithium nitride hydride, black phosphorus, as well as transition metal oxides that can react with lithium according to a lithium conversion mechanism.

- Process in which the electroless (partial) lithiation of the powdered synthetic graphite is carried out after mixing with powdered lithium metal powder and by stirring, grinding and / or pressing to form Li-graphite intercalates of the composition LiCx (with x = 6 - 600) is brought about ,

Process in which the molar ratio of the two atomic species Li: C is between 1: at least 3 and 1: maximum 600, preferably between 1: at the most 5 and 1: maximum 600.

- Process in which the Lithiierungsprozeß is carried out at a surrounding pressure of 10 bar maximum.

- Process in which the lithiation process in the temperature range between 0 and 180 ° C is performed.

- Process in which a gecoatetes or preferably a ungeecoatetes lithium powder having average particle sizes between 5 and 500 μηι is used.

Process wherein the uncoated lithium metal powder has a purity (i.e., a proportion of metallic lithium) of at least 99% by weight.

- Process in which the grinding of the lithium powder with the synthetic graphite powder takes place in the dry state.

Method in which the grinding of the lithium powder with the synthetic graphite powder takes place in the presence of an inert fluid, the proportion by weight of the fluid not exceeding that of the solids (that is to say a maximum of 1: 1 w: w). - Process in which the Na content of the Li powder is not more than 200 ppm, preferably not more than 100 ppm, more preferably not more than 80 ppm.

- Process in which the electroless (partially) lithiated synthetic graphite in a subsequent step to improve the handling and further reduction of irreversible losses with substances that are able to form an artificial SEI on the graphite surface, is coated.

Method in which the coating agents are selected from: N ₂ , CO ₂ , CO, O ₂ , N ₂ O, NO, NO ₂ , HF, F ₂ , PF ₃ , PF ₅ , POF ₃ , carbonic acid esters, lithium chelatoborate solutions, sulfur organic compounds, nitrogen-containing organic compounds, phosphoric acid, organic phosphorus-containing compounds, fluorine-containing organic and inorganic compounds, silicon-containing compounds.

Use of the (partially) lithiated graphite powder prepared by the process according to the invention as constituent / active material of lithium battery electrodes.

Galvanic cell containing a cathode, a lithium-conductive electrolyte separator system and a synbium-containing anode, wherein the anode contains or consists of a (partially) lithiated graphite powder produced from synthesis graphite and lithium powder by non-electrochemical means during cell production (i.e., prior to the first charge cycle).

Galvanic cell in which the synthesis graphite used for the lithiation has an ID: IG ratio of at least 0.2, more preferably at least 0.5, determined by Raman spectroscopy.

Galvanic cell at which the molar ratio between graphite (C) and electrochemically active lithium (Li) min. 3: 1 and max. 600: 1.

Examples

Example 1: Preparation of LiC _x (x = about 6) from synthesis graphite SLP 30 and uncoated lithium in a planetary ball mill

Under a protective gas atmosphere (argon-filled glove box) 5.00 g of SLP30 synthesis graphite powder from Timcal and 0.529 g ungecoatetes lithium powder with an average particle size of D ₅₀ = 123 were μηι (measurement method: laser reflection, device Lasentec FBRM of Company Mettler Toledo) filled and mixed with a spatula. Then about 27 g of zirconia grinding balls (ball diameter 3 mm) were filled. The mixture was milled in a planetary ball mill (Pulverisette 7 premium line from Fritsch) for 15 minutes at a rotation frequency of 800 rpm.

The milled product was sieved in the glove box and 4.6 g of a black, gold shimmering and flowable powder were obtained.

It can be shown by X-ray diffractometry that a uniform product with a stoichiometry of C: intercalated Li of approximately 12: 1 has formed. Metallic lithium can no longer be detected.

Example 2: Preparation of LiC _x (x = 6 - 12) from synthesis graphite SLP 30 and silicon-coated lithium in a planetary ball mill

In a protective gas atmosphere (argon-filled glove box) 5.00 g of SLP30 synthesis graphite powder from Timcal and 0.529 g of Si-coated lithium powder (preparation according to WO2013 / 104787A1) having an average particle size of D ₅₀ = 56 μm were introduced into a 50 ml zirconium oxide grinding bowl (Measuring method: laser reflection, device Lasentec FBRM from Mettler Toledo) filled and mixed with a spatula. Then about 27 g of zirconia grinding balls (ball diameter 3 mm) were filled. The mixture was milled in a planetary ball mill (Pulverisette 7 premium line from Fritsch) for 15 minutes at a rotation frequency of 800 rpm.

The milled product was sieved in the glove box and 4.9 g of a black, flowable powder was obtained.

It can be shown by X-ray diffractometry that the lithium intercalation occurred; but it can still be seen unchanged graphite. In contrast, no elemental or metallic lithium can be seen more.

Example 3: Stability of the lithiated synthesis graphite from Example 1 in contact with NMP and EC / EMC

The investigation of the thermal stability was carried out with the aid of an apparatus from Systag, Switzerland, the Radex system. For this purpose, the substances or substance mixtures to be investigated are weighed into steel autoclaves with a capacity of about 3 ml and heated. From temperature measurements of the furnace and vessel thermodynamic data can be derived. In the present case, 0.1 g of Li / C mixture or compound was weighed with 2 g of EC / EMC under inert gas conditions and heated to a final furnace temperature of 250 ° C. Only when exceeding about 190 ° C, the mixture of inventive LiC _x - material and EC / EMC begins to decompose.

When mixing the Li / C compound of Example 1 with NMP, a spontaneous but weak reaction (without run-away phenomena) is noted. In the subsequent Radex experiment, no significant exothermal effect is noted up to a final temperature of 250 ° C. The thermolyzed mixture is still liquid.

Comparative Example 1 Stability of Mixtures of Uncoated and Coated Lithium Metal Powder and Synthetic Graphite (molar ratio 1: 5) in NMP and EC / EMC

As in Example 3, blends of 0.09 g graphite powder SLP30 and 0.01 g lithium powder with 2 g solvents were weighed into the 3 ml steel autoclave and examined for thermal events.

Both mixtures with the highly reactive solvent NMP show clear decomposition-runoff with peak temperatures of 1 10-120 ° C. The mixture with the uncoated powder reacts even at significantly lower temperatures than the one with the coated powder.

The thermolyzed mixtures are predominantly solid or polymerized. Even the analogous mixture of uncoated lithium powder with a 1: 1 mixture of EC / EMC reacts violently when it exceeds about 170 ° C.

Example 4 Coating of a Lithiated Synthetic Graphite Powder According to the Invention Produced by Stoichiometry LiC ₆ Using a LiBOB Solution in EC / EMC

4.5 g of a prepared according to Example 1 lithiated synthesis graphite powder under argon atmosphere in a glass flask with 10 ml of a 1% LiBOB solution (LiBOB = lithium bis (oxalato) borate) in anhydrous EC / EMC (1: 1 wt / wt ) and stirred for 2 hours at room temperature. The dispersion was filtered with exclusion of air, washed three times with dimethyl carbonate and once each with diethyl ether and hexane. After 3 hours Vacuum drying at room temperature, 4.3 g of a gold shimmering dark powder were obtained.

Example 6 Stability of the Coated Product of Example 4 in EC / EMC and NMP

The coated material from Example 5 and a sample of the untreated lithiated graphite powder (prepared analogously to Example 1) were investigated in the Radex apparatus for thermal stability in the presence of an EC / EMC mixture.

The uncoated material begins to decompose already from about 130 ° C, while the coated powder reacts exothermally above about 170 ° C.

When mixed with NMP, no reaction is noticed at room temperature. In the Radex experiment very weak exotherms are registered at> 90 ° C.

The mixture remains liquid.

Example 7: Preparation of LiCx (x = 12) from synthesis graphite SLP 30 and silicon-coated lithium in a planetary ball mill and stability in NMP

In the mill described in Example 1, 5.00 g of synthesis graphite SLP 30 and 0.26 g of uncoated lithium powder were milled at 800 rpm for 30 minutes. There was obtained 4.8 g of a black, flowable powder. When mixed with NMP, no significant events are recorded in the DSC experiment with the Radex apparatus.

Claims

claims

1 . Process for the preparation of (partially) lithiated synthesis graphite, characterized in that an electroless (partial) lithiation of powdered synthetic graphite with lithium metal powder by stirring, grinding and / or pressing at ambient pressures of max. 10 bar to form Li-graphite intercalates of composition LiC _x (with x = 6 - 600) is brought about.

2. The method according to claim 1, characterized in that synthesis graphites are used with a determined by Raman spectroscopy l _D : l _G - ratio of at least 0.2, more preferably at least 0.5.

3. The method according to claim 1 or 2, characterized in that the molar ratio of the two types of atoms Li: C between 1: at least 3 and 1: a maximum of 600, preferably between 1: at least 5 and 1: a maximum of 600.

4. The method according to claim 1 to 3, characterized in that the Lithiierungsprozeß in the temperature range between 0 and 180 ° C, preferably 20-150 ° C is performed.

5. The method according to claim 1 to 4, characterized in that a gecoatetes or preferably a ungeecoatetes lithium powder having average particle sizes between 5 and 500 μηη is used.

A process according to claims 1 to 5, characterized in that the uncoated lithium metal powder has a purity (i.e., a proportion of metallic lithium) of at least 99% by weight.

7. The method according to claim 1 to 6, characterized in that the grinding of the lithium powder with the synthetic graphite powder takes place in the dry state.

8. The method according to claim 1 to 7, characterized in that the grinding of the lithium powder with the synthetic graphite powder takes place in the presence of an inert fluid, wherein the weight fraction of the fluid does not exceed that of the solids (ie a maximum of 1: 1 w: w).

9. The method of claim 1 to 8, characterized in that the Na content of the Li powder is not more than 200 ppm, preferably at most 100 ppm, more preferably at most 80 ppm.

10. The method of claim 1 to 9, characterized in that the electroless (partially) lithiated synthetic graphite in a subsequent step to improve the handling and further reduction of irreversible losses with substances that are able to form an artificial SEI on the graphite surface, is coated.

1 1. The method of claim 1 to 10, characterized in that the coating agents are selected from the group consisting of: N ₂ , C0 ₂ , CO, 0 ₂ , N ₂ 0, NO, N0 ₂ , HF, F ₂ , PF ₃ , PF ₅ , POF ₃ , carbonic acid esters, Lithiumchelatoboratlösungen, organosulfur compounds, nitrogen-containing organic compounds, phosphoric acid, organic phosphorus-containing compounds, fluorine-containing organic and inorganic compounds, silicon-containing compounds.

12. Use of (partially) lithiated graphite powder obtained according to claim 1 to 1 1 as a constituent / active material of lithium battery electrodes.

13. Use according to claim 12, characterized in that it takes place in a galvanic cell containing a cathode, a lithium-conductive electrolyte separator system and a graphite-containing anode, wherein the anode during cell production (ie before the first charge cycle) on a non-electrochemical way and then coated (partially) lithiated graphite powder is added.

14. Galvanic cell containing in the charged state a (partially) lithiated graphite powder prepared according to claim 1 to 1 1, characterized in that the synthesis graphite used for the lithiation a determined by Raman spectroscopy l _D : l _G - ratio of at least 0.2 , preferably at least 0.5.

15. Galvanic cell obtaining a (partially) lithiated graphite powder prepared according to claim 1 to 1 1, characterized in that the molar ratio between graphite (C) and electrochemically active lithium (Li) is at least 3: 1 and at most 600: 1.

16. A process for the preparation of Lithiumbatterieanoden, characterized in that powdered produced by an electroless process (partially) lithiated synthesis graphite under inert or dry space conditions with at least one binder material and optionally one or more further powdery lithium einlagerungsfähigen material (s) with an electrochemical potential <2 V vs. Li / Li ^" * ^" and optionally mixed with a conductivity-improving additive and a non-aqueous solvent and homogenized and this dispersion is applied by a coating process on a Stromabieiterfolie and dried.

17. The method according to claim 16, characterized in that the further pulverulent lithium-storable material is selected from the groups consisting of: graphite, graphene, layer-structured lithium transition metal nitrides, with lithium alloyable metal powder, main group metal oxides with a metal in a reduced form (ie as Metal having zero oxidation state) with lithium, metal hydrides, lithium amide, lithium imide, tetralithium nitride hydride, black phosphorus, and transition metal oxides capable of reacting with lithium by a lithium conversion mechanism.

18. The method according to claim 16 to 17, characterized in that the non-aqueous solvent is preferably selected from hydrocarbons, N-methylpyrrolidone, N-ethylpyrrolidone, dimethyl sulfoxide, ketones, lactones and / or cyclic ethers.

19. The method according to claim 16 to 18, characterized in that the binder is preferably selected from polyvinylidene difluoride, Teflon, polyacrylates and polyisobutenes.