DE102020134700A1 - NMC MEMORY MATERIALS WITH POLYMER COATING - Google Patents

Abstract

The present invention relates to surface-coated NMC memory materials (ONMC), in which an NMC memory material (NMC) has a surface coating of a polymer which contains at least one lithium phosphonate group, and methods for producing such ONMC memory materials, their use as cathodes in lithium Batteries or electrochemical cells and such cathodes, cells and batteries.

Description

Introduction:

The present invention relates to surface-coated NMC memory materials (ONMC), wherein an NMC memory material (NMC) has a surface coating of a polymer containing at least one lithium phosphonate group. The present invention also relates to methods for producing such ONMC storage materials and their use as cathodes in lithium batteries or electrochemical cells and such cathodes, cells and batteries. A further aspect of the invention relates to the use of a polymer which has at least one lithium phosphonate group for the surface coating of NMC storage materials for the purposes described herein.

Background:

Layered nickel-containing lithium transition metal oxides, derivatives of LiCoO ₂ , are particularly suitable materials for the development of improved cathode materials due to their higher capacity, lower cost, better environmental compatibility and improved stability compared to LiCoO ₂ .

Lithium-ion batteries are already the technology of choice for a wide range of applications, such as portable electronic devices (e.g. laptops, mobile phones, camcorders, etc.), electrically powered vehicles (e.g. bicycles, scooters, automobiles, etc.) and stationary energy storage. Against this background, they are becoming increasingly important in economic terms, combined with the ever-increasing numbers of items being produced and sold. There is an increasing need to develop improved batteries with higher capacity and energy density, particularly for a range of applications including all-electric vehicles (EVs), hybrid electric vehicles (HEFs), and plug-in hybrid electric vehicles (PHEFs). However, in order to enable a further increase in the implementation of lithium-ion batteries, for example in electrically powered vehicles, further improvement in terms of safety and performance is imperative.

In order to meet the demanding requirements in this area, improvements in cycle stability, discharge rates, and improved thermal and structural stability of the electrodes are particularly desirable. Side reactions between electrode and electrolyte can lead to increased electrode/electrolyte interface resistance and dissolution of transition metals, especially at elevated temperatures and high terminal voltages. These problems can increase with increasing Ni content.

One way to increase the energy density is to use alternative active materials that enable improved energy and/or power densities or similar energy and power densities with increased safety.

For the positive electrode (cathode), one focus is on the development of nickel-rich LiNi _1-xy Mn _x Co _y O ₂ (NMC) storage materials.

However, due to the high Ni content and a potentially higher terminal voltage, these materials are increasingly exposed to aggressive reactions with the electrolyte at the particle/electrolyte interface, leading to increased electrolyte decomposition and structural degradation of the NMC memory materials at their surface and thus ultimately leads to a relatively poor cycle stability.

State of the art:

It is fundamentally known to subject cathode materials to a surface modification in order to improve the cycle stability, the discharge rate or the thermal stability.

Examples of known inorganic surface coatings of cathodes are described in WO2019141981A1 or the publications mentioned therein US6921609 and Cho, W. et al.; Electrochim. Acta 2016, 198, 77-83.

• L.-P. Wang et al.; Adv. Energy Mater. 2018, 8, 1801528 beschreiben NMC₆₂₂ Speichermaterialien mit einer Beschichtung von Poly(acrylonitril-co-butadien) in Kombination mit einem Poly(ether-acrylat)-basiertem Elektrolyten.
• Q. Gan et al.; ACS Appl. Mater. Interfaces 2019, 11, 12594 beschreiben NMC₈₁₁ Speichermaterialien mit einer Beschichtung von Polyvinylpyrrolidon und Polyanilin.
• E.-H. Lee et al.; J. Power Sources 2013, 244, 389 beschreiben NMC₁₁₁ Speichermaterialien mit einer Beschichtung eines Poly(tris(2-(acryloyloxy)ethyl)phosphat Gelpolymer Elektrolyten.
• S. H. Ju et al.; ACS Appl. Mater. Interfaces 2014, 6, 2546 beschreiben NMC₆₂₂ Speichermaterialien mit einer Beschichtung von Poly(3,4-ethylendioxythiophen)-copoly(ethylenglycol).
• H. Wang et al.; ACS Appl. Mater. Interfaces 2016, 8, 18439 beschreiben NMC₆₂₂ Speichermaterialien mit einer Ethoxy-funktionalisierten Polysiloxan Beschichtung.
• S. Chen et al.; ACS Appl. Mater. Interfaces 2017, 9, 29732 beschreiben NMC₈₁₁ Speichermaterialien mit einer Beschichtung von Li₃PO₄ (2 wt%) und Polypyrrol (3 wt%).
• Y. Cao et al.; ACS Appl. Mater. Interfaces 2018, 10, 18270 beschreiben NMC₈₁₁ Speichermaterialien mit einer Beschichtung von Polyanilin und Poly(ethylenglycol).
• G.-L. Xu et al.; Nat. Energy 2019, 4, 484 beschreiben verschiedene NMC-Speichermaterialien mit einer Beschichtung von Poly(3,4-ethylendioxythiophen).

A number of NMC materials with different polymer coatings are also known from the literature:

• L.-P. Wang et al.; Adv. Energy Mater. 2018, 8, 1801528 describe NMC ₆₂₂ storage materials with a coating of poly(acrylonitrile-co-butadiene) in combination with a poly(ether-acrylate)-based electrolyte.
• Q.Gan et al.; ACS Appl. mater Interfaces 2019, 11, 12594 describe NMC ₈₁₁ storage materials with a coating of polyvinylpyrrolidone and polyaniline.
• E.-H. Lee et al.; J. Power Sources 2013, 244, 389 describe NMC ₁₁₁ storage materials with a coating of a poly(tris(2-(acryloyloxy)ethyl) phosphate gel polymer electrolyte.
• SH Ju et al.; ACS Appl. mater Interfaces 2014, 6, 2546 describe NMC ₆₂₂ memory materials with a coating of poly(3,4-ethylenedioxythiophene)-copoly(ethylene glycol).
• H.Wang et al.; ACS Appl. mater Interfaces 2016, 8, 18439 describe NMC ₆₂₂ memory materials with an ethoxy-functionalized polysiloxane coating.
• S. Chen et al.; ACS Appl. mater Interfaces 2017, 9, 29732 describe NMC ₈₁₁ storage materials with a coating of Li ₃ PO ₄ (2 wt%) and polypyrrole (3 wt%).
• Y. Cao et al.; ACS Appl. mater Interfaces 2018, 10, 18270 describe NMC ₈₁₁ memory materials with a coating of polyaniline and poly(ethylene glycol).
• G.-L. Xu et al.; nat. Energy 2019, 4, 484 describes various NMC storage materials with a coating of poly(3,4-ethylenedioxythiophene).

• • einfache Prozessierung ohne aufwendige und kostenintensive Verfahren,
• • geringer Polymer-Anteil, um die Gesamtkapazität und somit die Energiedichte der Zelle nicht allzu sehr zu beeinträchtigen,
• • hohe Coulomb-Effizienz im ersten Zyklus,
• • hohe Zyklenstabilität, insbesondere bei Raumtemperatur (23 °C ± 3 °C) und höheren Temperaturen,
• • hohe Ent-/Laderaten,
• • Kompatibilität mit allgemein verwendeten flüssigen Elektrolyten,
• • verbesserte Sicherheit, beispielsweise gekennzeichnet durch eine geringere Wärmeentwicklung,
• • hohe thermische Stabilität,
• • hohe strukturelle Stabilität.

None of the known solutions combines the following characteristics, which are important for commercialization, in an advantageous manner:

• • simple processing without complex and cost-intensive procedures,
• • low polymer content in order not to affect the overall capacity and thus the energy density of the cell too much,
• • high Coulomb efficiency in the first cycle,
• • high cycle stability, especially at room temperature (23 °C ± 3 °C) and higher temperatures,
• • high discharge/charge rates,
• • Compatibility with commonly used liquid electrolytes,
• • improved safety, characterized for example by less heat generation,
• • high thermal stability,
• • high structural stability.

Task:

The object of the present invention was to provide improved electrode materials which do not have the disadvantages of the known materials. In particular, the object of the present invention was to provide improved electrode materials which have one or more of the aforementioned advantages.

Another aspect includes the task of providing a method for producing such improved electrode materials.

These objects have been achieved by the embodiments and aspects of the invention described in detail in the claims and below.

Description of the invention:

1. [1] Oberflächenbeschichtete NMC-Speichermaterialien (ONMC), umfassend ein NMC-Speichermaterial (NMC) mit einer Oberflächenbeschichtung eines Polymers, welches mindestens eine Lithiumphosphonat-Gruppe aufweist.
2. [2] ONMC gemäß [1], worin das Polymer ein Polyarylethersulfon mit mindestens einer Lithiumphosphonatgruppe ist.
3. [3] ONMC gemäß [1] oder [2], worin als NMC-Speichermaterial Partikel eines Lithium-Übergangsmetalloxids gemäß der allgemeinen Formel (I) ausgewählt sind Li_aNi_xM_yM'_zO_2+b (I) mit M = Co, Mn und Kombinationen davon; M' = Mg, AL, V, Ti, B, Zr, Sr, Ca, Cu, Zn, Nb, Mo, W, Ta und Kombinationen davon; $$\mathrm{0,8}\le \text{a}\le \mathrm{1,2};$$
   
   $$\mathrm{0,2}\le \text{x}\le 1;$$
   
   $$0<\text{y}\le \mathrm{0,8};$$
   
   $$0\le \text{z}\le \mathrm{0,2};$$
   
   und $$-\mathrm{0,2}\le \text{b}\le \mathrm{0,2.}$$
   
4. [4] ONMC gemäß einem der vorhergehenden Aspekte [1] bis [3], worin als NMC-Speichermaterial Partikel eines Lithium-Übergangsmetalloxids gemäß der allgemeinen Formel (II) oder (III) ausgewählt sind

LiNi_1-x-yCO_xMn_yO₂ LiNi_xCo_yMn_1-x-yO₂ (II) (III) mit mit 1-x-y ≥ 0,6; x ≥ 0,8.

1. [5] ONMC gemäß einem der vorhergehenden Aspekte [1] bis [4], worin als NMC-Speichermaterial NMC₈₁₁, NMC₁₁₁, NMC₅₃₂ oder NMC₆₂₂, bevorzugt NMC₈₁₁ (LiNi_0,8Co_0,1Mn_0,1O₂) ausgewählt wird.
2. [6] ONMC gemäß einem der vorhergehenden Aspekte [1] bis [5], worin das Polymer ein Polyarylethersulfon mit mindestens einer Lithiumphosphonatgruppe gemäß einer der folgenden Formeln (A) oder (B) ist
   
   
3. [7] ONMC gemäß einem der vorhergehenden Aspekte [1] bis [6], worin die Oberflächenbeschichtung eine kontinuierliche Oberflächenbeschichtung ist und eine Dicke im Bereich von 0,5 nm bis 100 nm, bevorzugt im Bereich von 1 nm bis 50 nm, besonders bevorzugt im Bereich von 2 nm bis 25 nm aufweist.
4. [8] Verfahren zur Herstellung der oberflächenbeschichteten NMC-Speichermaterialien (ONMC) gemäß einem der vorhergehenden Aspekte [1] bis [7], umfassend die Schritte
   1. (i) Lösen des Polymers, welches mindestens eine Lithiumphosphonat-Gruppe aufweist, in einem geeigneten Lösungsmittel;
   2. (ii) Zugabe der NMC-Partikel und Herstellung einer Dispersion der NMC-Partikel in einem geeigneten Lösungsmittel;
   3. (iii) Abtrennen des Lösungsmittels.
5. [9] Kathode für eine Lithium-Batterie oder eine elektrochemische Zelle, umfassend das oberflächenbeschichtete NMC-Speichermaterial (ONMC) gemäß einem der vorhergehenden Aspekte [1] bis [7].
6. [10] Eine Batterie oder elektrochemische Zelle, umfassend eine Kathode gemäß [9].
7. [11] Eine Batterie oder elektrochemische Zelle gemäß [10], umfassend ferner einen Polymerelektrolyten umfassend mindestens ein organisches Lösungsmittel und mindestens ein aromatisches lonomer mit alternierenden ionischen und nichtionischen Segmenten, umfassend mindestens nichtionische aromatische Wiederholungseinheiten UAr1 und mindestens eine ionische Wiederholungseinheit UI1 gemäß der Formel (I)
   
   mit der folgenden Bedeutung:

M ist ein Alkalimetallkation, ein Erdalkalimetallkation, ein Übergangsmetallkation oder ein Ammoniumkation mit einer Valenz m, mit 1 ≤ m ≤ 3, wobei m eine ganze Zahl ist; A^a- ist ein Anion, ausgewählt aus einem Sulfonatanion, einem Sulfonimidanion der Formel -SO₂-N-SO₂R, einem von einem Sulfonimidanion abgeleiteten Anion, das mindestens zwei negative Ladungen trägt, und einem Carbanion der Formel -SO₂-C'R'R'', mit 1 ≤ a ≤ 3, wobei a eine ganze Zahl ist; R repräsentiert: - ein Fluoratom, - eine Fluor- oder Perfluoralkylgruppe mit 1 bis 8 Kohlenstoffatomen, - eine Fluor- oder Perfluoralkoxygruppe mit 1 bis 8 Kohlenstoffatomen, - eine Thiocyanatgruppe (-SCN), - eine Phenylgruppe, die gegebenenfalls mit einer elektronenziehenden Gruppe X substituiert ist, - eine Nitrilgruppe, - eine Gruppe -NR¹ ausgewählt aus einem gesättigten Heterozyklus mit 3 bis 6 Kohlenstoffatomen und einem ungesättigten Heterozyklus mit 4 bis 6 Kohlenstoffatomen, - eine Dicyanamidgruppe -N(CN)₂, - eine Tricyanomethylgruppe -C(CN)₃, wobei R' und R'' unabhängig voneinander ausgewählt sind aus den folgenden einwertigen Gruppen: - einem Fluoratom, - einer Thiocyanatgruppe, - einer Nitrilgruppe, - einer Nitrogruppe, - einer Sulfoxidgruppe der Formel -SOR², worin R² eine Fluor- oder Perfluoralkylgruppe mit 1 bis 5 Kohlenstoffatomen oder eine Fluor- oder Perfluordialkylethergruppe mit 1 bis 5 Kohlenstoffatomen ist, - einer Sulfonylgruppe der Formel -SO₂R³, worin R³ ein Fluoratom, eine Thiocyanatgruppe, eine Nitrilgruppe, eine Fluor- oder Perfluoralkoxygruppe mit 1 bis 5 Kohlenstoffatomen, eine Fluor- oder Perfluoralkylgruppe mit 1 bis 5 Kohlenstoffatomen, oder eine Fluor- oder Perfluordialkylethergruppe mit 1 bis 5 Kohlenstoffatomen ist, - einer Carbonsäureestergruppe der Formel -COOR⁴, worin R⁴ eine Alkylgruppe mit 1 bis 5 Kohlenstoffatomen ist, - einer gegebenenfalls substituierten Phenylgruppe, und - einer gegebenenfalls substituierten Phenoxygruppe; wobei R' und R'' divalente Gruppen sind, so dass der resultierende Carbanion-Rest -C-R'R'' einen aromatischen Ring mit 5 bis 6 Kohlenstoffatomen und gegebenenfalls einem oder mehreren Heteroatomen O oder N bildet, wobei der aromatische Ring gegebenenfalls mit einer oder mehreren Nitrilgruppen substituiert ist; W ist ein Sauerstoffatom, ein Schwefelatom oder eine Gruppe -NR''', worin R''' H oder eine (C₁-C₃)-Alkylgruppe ist; 1 ≤ n ≤ 4, wobei n eine ganze Zahl ist; 1 ≤ n' ≤ 2, wobei n' eine ganze Zahl ist; Z¹ ist ausgewählt aus einer Einfachbindung, einem Sauerstoffatom, einem Schwefelatom, einer Gruppe -S(=O)-, einer Gruppe -S((=O)₂)- und einer Phenylgruppe, die gegebenenfalls in der ortho-Position relativ zu einer der Funktionen (CF₂)_n oder (CF₂)_n' substituiert ist; Z² ist ausgewählt aus einer Einfachbindung, einem Sauerstoffatom, einem Schwefelatom, einer Gruppe -S(=O)-, einer Gruppe -S((=O)₂)- und einer Gruppe -C(=O)-, und E ist eine aromatische Gruppe mit 5 bis 20 Kohlenstoffatomen, die 1 oder 2 aromatische Ringe umfasst.

1. [12] Eine Batterie oder elektrochemische Zelle gemäß [11], worin das aromatische lonomer des Polymerelektrolyten ein Multiblock-Copolymer der folgenden Formel (i) ist:
   
   mit $$\text{n}=8\text{bis}\mathrm{50,}$$
   
   $$\text{m}=4\text{bis}\mathrm{50,}$$
   
   und $$\text{x}=2\text{bis}12.$$
   
2. [13] Eine Batterie oder elektrochemische Zelle gemäß [11], worin das aromatische lonomer des Polymerelektrolyten ein Multiblock-Copolymer der folgenden Formel (ii) ist:
   
   mit $$\text{n}=8\text{bis}\mathrm{50,}$$
   
   $$\text{m}=4\text{bis}\mathrm{50,}$$
   
   und $$\text{p}=2\text{bis}12.$$
   
3. [14] Eine Batterie oder elektrochemische Zelle gemäß [11], worin das aromatische lonomer des Polymerelektrolyten ein Multiblock-Copolymer der folgenden Formel (iii) ist:
   
   mit $$\text{n}=8\text{bis}\mathrm{50,}$$
   
   $$\text{m}=4\text{bis}\mathrm{50,}$$
   
   und $$\text{p}=2\text{bis}12.$$
   
4. [15] Verwendung eines Polymers, welches mindestens eine Lithiumphosphonat-Gruppe aufweist, zur Oberflächenbeschichtung von NMC-Speichermaterialien.
5. [16] Verwendung gemäß [15], worin das Polymer ein Polyarylethersulfon gemäß einer der folgenden Formeln (A) oder (B) ist
   
   

The present invention is described in more detail below and includes in particular the following aspects:

1. [1] Surface-coated NMC memory materials (ONMC), comprising an NMC memory material (NMC) with a surface coating of a polymer which has at least one lithium phosphonate group.
2. [2] ONMC according to [1], wherein the polymer is a polyarylethersulfone having at least one lithium phosphonate group.
3. [3] ONMC according to [1] or [2], wherein particles of a lithium transition metal oxide according to the general formula (I) are selected as NMC storage material Li _a Ni _x M _y M' _z O _2+b (I) with M = Co, Mn and combinations thereof; M' = Mg, AL, V, Ti, B, Zr, Sr, Ca, Cu, Zn, Nb, Mo, W, Ta and combinations thereof; $$0.8\le \text{a}\le 1.2;$$
   
   $$0.2\le \text{x}\le 1;$$
   
   $$0<\text{y}\le 0.8;$$
   
   $$0\le \text{e.g}\le 0.2;$$
   
   and $$-0.2\le \text{b}\le 0.2$$
   
4. [4] ONMC according to one of the preceding aspects [1] to [3], wherein particles of a lithium transition metal oxide according to the general formula (II) or (III) are selected as NMC storage material

LiNi _1-xy CO _x Mn _y O ₂ LiNi _x Co _y Mn _1-xy O ₂ (ii) (III) With With 1-xy ≥ 0.6; x ≥ 0.8.

1. [5] ONMC according to one of the preceding aspects [1] to [4], wherein as NMC storage material NMC ₈₁₁ , NMC ₁₁₁ , NMC ₅₃₂ or NMC ₆₂₂ , preferably NMC ₈₁₁ (LiNi _0.8 Co _0.1 Mn _0.1 O ₂ ) is selected.
2. [6] ONMC according to any one of the preceding aspects [1] to [5], wherein the polymer is a polyarylethersulfone having at least one lithium phosphonate group according to one of the following formulas (A) or (B).
   
   
3. [7] ONMC according to any one of the preceding aspects [1] to [6], wherein the surface coating is a continuous surface coating and a thickness in the range from 0.5 nm to 100 nm, preferably in the range from 1 nm to 50 nm, particularly preferred in the range of 2 nm to 25 nm.
4. [8] Method for producing the surface-coated NMC memory materials (ONMC) according to one of the preceding aspects [1] to [7], comprising the steps
   1. (i) dissolving the polymer having at least one lithium phosphonate group in a suitable solvent;
   2. (ii) adding the NMC particles and preparing a dispersion of the NMC particles in a suitable solvent;
   3. (iii) separating off the solvent.
5. [9] A cathode for a lithium battery or an electrochemical cell, comprising the surface-coated NMC storage material (ONMC) according to any one of the preceding aspects [1] to [7].
6. [10] A battery or electrochemical cell comprising a cathode according to [9].
7. [11] A battery or electrochemical cell according to [10], further comprising a polymer electrolyte comprising at least one organic solvent and at least one aromatic ionomer having alternating ionic and nonionic segments, comprising at least nonionic aromatic repeating units UAr1 and at least one ionic repeating unit UI1 according to the formula ( i)
   
   with the following meaning:

M is an alkali metal cation, an alkaline earth metal cation, a transition metal cation, or an ammonium cation having a valence m, with 1 ≤ m ≤ 3, where m is an integer; A ^a- is an anion selected from a sulfonate anion, a sulfonimide anion of the formula -SO ₂ -N-SO ₂ R, an anion derived from a sulfonimide anion bearing at least two negative charges, and a carbanion of the formula -SO ₂ -C'R'R'', with 1 ≤ a ≤ 3, where a is an integer; R represents: - a fluorine atom, - a fluoro or perfluoroalkyl group having from 1 to 8 carbon atoms, - a fluoro or perfluoroalkoxy group having from 1 to 8 carbon atoms, - a thiocyanate group (-SCN), - a phenyl group optionally substituted with an electron-withdrawing group X, - a nitrile group, - a group -NR ¹ chosen from a saturated heterocycle having 3 to 6 carbon atoms and an unsaturated heterocycle having 4 to 6 carbon atoms, - a dicyanamide group -N(CN) ₂ , - a tricyanomethyl group -C(CN) ₃ , whereby R' and R'' are independently selected from the following monovalent groups: - a fluorine atom, - a thiocyanate group, - a nitrile group, - a nitro group, - a sulfoxide group of formula -SOR ² in which R ² is a fluoro or perfluoroalkyl group having 1 to 5 carbon atoms or a fluoro or perfluorodialkyl ether group having 1 to 5 carbon atoms, - a sulfonyl group of formula -SO ₂ R ³ in which R ³ represents a fluorine atom, a thiocyanate group, a nitrile group, a fluorine or perfluoroalkoxy group having 1 to 5 carbon atoms, a fluorine or perfluoroalkyl group having 1 to 5 carbon atoms, or a fluorine or is a perfluorodialkyl ether group having 1 to 5 carbon atoms, - a carboxylic acid ester group of the formula -COOR ⁴ where R ⁴ is an alkyl group having 1 to 5 carbon atoms, - an optionally substituted phenyl group, and - an optionally substituted phenoxy group; whereby R' and R'' are divalent groups such that the resulting carbanion moiety -C-R'R'' forms an aromatic ring having 5 to 6 carbon atoms and optionally one or more heteroatoms O or N, the aromatic ring optionally having substituted by one or more nitrile groups; W is an oxygen atom, a sulfur atom or a group -NR''', wherein R''' is H or a (C ₁ -C ₃ )alkyl group; 1 ≤ n ≤ 4, where n is an integer; 1 ≤ n' ≤ 2, where n' is an integer; Z ¹ is selected from a single bond, an oxygen atom, a sulfur atom, a group -S(=O)-, a group -S((=O) ₂ )- and a phenyl group optionally in the ortho position relative to one of the functions (CF ₂ ) _n or (CF ₂ ) _n' is substituted; Z ² is selected from a single bond, an oxygen atom, a sulfur atom, a group -S(=O)-, a group -S((=O) ₂ )- and a group -C(=O)-, and E is an aromatic group of 5 to 20 carbon atoms, comprising 1 or 2 aromatic rings.

1. [12] A battery or electrochemical cell according to [11], wherein the aromatic ionomer of the polymer electrolyte is a multiblock copolymer of the following formula (i):
   
   With $$\text{n}=\mathrm{8th}\text{until}\mathrm{50,}$$
   
   $$\text{m}=4\text{until}\mathrm{50,}$$
   
   and $$\text{x}=2\text{until}12.$$
   
2. [13] A battery or electrochemical cell according to [11], wherein the aromatic ionomer of the polymer electrolyte is a multiblock copolymer of the following formula (ii):
   
   With $$\text{n}=\mathrm{8th}\text{until}\mathrm{50,}$$
   
   $$\text{m}=4\text{until}\mathrm{50,}$$
   
   and $$\text{p}=2\text{until}12.$$
   
3. [14] A battery or electrochemical cell according to [11], wherein the aromatic ionomer of the polymer electrolyte is a multiblock copolymer of the following formula (iii):
   
   With $$\text{n}=\mathrm{8th}\text{until}\mathrm{50,}$$
   
   $$\text{m}=4\text{until}\mathrm{50,}$$
   
   and $$\text{p}=2\text{until}12.$$
   
4. [15] Use of a polymer which has at least one lithium phosphonate group for the surface coating of NMC storage materials.
5. [16] Use according to [15], wherein the polymer is a polyarylethersulfone represented by one of the following formulas (A) or (B).
   
   

Surprisingly, it was found that the coating of the NMC storage materials described here with the polymers described here leads to significantly improved cycle stability, in particular at high discharge/charge rates and higher temperatures. Surprisingly, the polymer coating results in a stabilization of the interface and substantially reduces the decomposition of the electrolyte while at the same time suppressing harmful structural changes on the surface of the NMC storage material particles.

• • die Oberflächenbeschichtung ist einfach und erfordert keine komplexen Verfahrensschritte;
• • die Zyklenstabilität wird deutlich verbessert, insbesondere bei Raumtemperatur und höheren Temperaturen;
• • die Coulomb-Effizienz im ersten Zyklus liegt sowohl bei Raumtemperatur als auch bei höheren Temperaturen wie 40 °C oder 60 °C bei Werten ≥ 90,0%;
• • die Ladungsleistung wird nicht beeinträchtigt;
• • die Sicherheit wird verbessert, da weniger Wärme frei wird bei hohen Temperaturen, was wiederum weitere Zersetzungsreaktionen mildert.

The polymer coating according to the invention of the NMC storage materials according to the invention allows the realization of the above characteristics:

• • the surface coating is simple and does not require complex processing steps;
• • the cycle stability is significantly improved, especially at room temperature and higher temperatures;
• • the Coulomb efficiency in the first cycle is ≥ 90.0% both at room temperature and at higher temperatures such as 40 °C or 60 °C;
• • charging performance is not affected;
• • Safety is improved as less heat is released at high temperatures, which in turn mitigates further decomposition reactions.

Detailed description of the invention:

The term "NMC" storage materials is generally known and refers to the group of lithium-nickel-manganese-cobalt oxides known under it, also abbreviated as Li-NMC, LNMC, NMC or NCM. NMCs are mixed oxides of lithium, nickel, manganese and cobalt. They have the general formula Li _a Ni _x Mn _y Co _z 0 ₂ . The most important representatives have a composition with x + y + z = 1. The NMCs are closely related to lithium cobalt(III) oxide (LiCoO ₂ ) and, like this, have a layered structure. NMCs are among the most important storage materials for lithium ions in lithium ion batteries. They are used on the "positive pole side", which forms the cathode during the discharge process. An accumulator that uses NMC is accordingly called an NMC accumulator.

The term "cathode" according to the invention denotes the "positive pole" and is used here in accordance with the usual usage of the term in the present technical field for the positive electrode in the discharge process.

Polymers are macromolecules of a substance that are made up of one or more structurally identical or similar units, the so-called constitutional repeating units or repeating units. In principle, polymers in the context of the present invention can be made up of at least 2, preferably more, repeating units. Usually, polymers with short chain lengths of up to about 8 repeat units are also referred to as "oligomers". The term "polymer" as used herein The invention encompasses both short-chain and longer-chain polymers, so that oligomers are encompassed by the term “polymer(s)” used according to the invention.

$$\mathrm{0,2}\le \text{x}\le 1;$$

$$0<\text{y}\le \mathrm{0,8};$$

$$0\le \text{z}\le \mathrm{0,2};$$

und $$-\mathrm{0,2}\le \text{b}\le \mathrm{0,2.}$$

NMC storage materials (NMC) according to the invention include, in particular, NMC particles of a lithium transition metal oxide of the general formula (I) Li _a Ni _x M _y M' _z O _2+b (I)
With
M = Co, Mn and combinations thereof;
M' = Mg, AL, V, Ti, B, Zr, Sr, Ca, Cu, Zn, Nb, Mo, W, Ta and combinations thereof; $$0.8\le \text{a}\le 1.2;$$

$$0.2\le \text{x}\le 1;$$

$$0<\text{y}\le 0.8;$$

$$0\le \text{e.g}\le 0.2;$$

and $$-0.2\le \text{b}\le 0.2$$

NMC particles of a lithium transition metal oxide of the general formula (II) or (III) are preferably selected LiNi _1-xy CO _x Mn _y O ₂ LiNi _x Co _y Mn _1-xy O ₂ (ii) (iii) With With 1-xy ≥ 0.6; x ≥ 0.8.

Abbreviations are common for important NMC variants, which indicate the ratio of nickel, manganese and cobalt. For example, LiNi _0.333 Mn _0.333 Co _0.333 O ₂ is referred to as NMC ₁₁₁ or NMC ₃₃₃ for short, LiNi _0.5 Mn _0.3 Co _0.2 O ₂ is referred to as NMC ₅₃₂ (or NMC ₅₂₃ ), LiNi _{0, 6} Mn _0.2 Co _0.2 O ₂ is referred to as NMC ₆₂₂ and LiNi _0.8 Mn _0.1 Co _0.1 O ₂ as NMC ₈₁₁ .

According to the invention, the NMC material can be selected from NMC ₈₁₁ , NMC ₁₁₁ , NMC ₅₃₂ or NMC ₆₂₂ . NMC ₈₁₁ (LiNi _0.8 Co _0.1 Mn _0.1 O ₂ ) is particularly preferred.

In a preferred aspect of the invention, the surface coating according to the invention is applied in particular to Ni-rich NMC materials, since Ni-rich NMCs have an increased tendency to mechanical degradation of the surface structure and thus lower cycle stability, which can be significantly improved by the polymer coating according to the invention.

The oxides Li _a Ni _x Mn _y Co _z O ₂ with a > 1 are called lithium-rich. In a further aspect of the invention, the surface coating according to the invention is applied to lithium-rich NMC materials, since lithium-rich NMCs also tend to mechanical degradation of the surface structure after a large number of charging cycles, which can be reduced by the polymer coating according to the invention.

The aforementioned problems with cycle stability include surface changes, such as surface restructuring and mechanical degradation of the surfaces of the electrode materials (NMC particles), undesirable surface reactions, and reduced thermal stability. The structural changes and surface degradation are expressed, for example, in the formation of a remodeling of the surface layers with an increase in such remodeled surface layers after several charging cycles and/or in contact with the electrolytes used. The occurrence of cracks due to anisotropic volume expansions and contractions is also observed. Side reactions with humid air lead to the formation of electrochemically inactive LiOH and Li ₂ CO ₃ .

The surface changes described and the formation of the undesired surface layers can lead to an increased release of oxygen, particularly at elevated temperatures, which has an adverse effect on the safety of the systems and is one of the reasons for the poor thermal stability.

These effects are particularly pronounced in the case of Ni-rich NMCs (with a Ni content >0.8), which is why the present invention is particularly suitable for improving Ni-rich NMCs.

The aforementioned undesired side reactions can be suppressed and reduced by the surface coatings applied according to the invention, since this creates a physical separation between the NMC material and the electrolyte (in particular liquid electrolyte) and moist air.

The surface-coated NMC (storage) materials according to the invention are also referred to as ONMC.

Surprisingly, it was found that lithium-containing polymers are particularly suitable as a coating material for solving the aforementioned problems.

Polymers which have at least one lithium phosphonate group have proven to be particularly suitable surface coating materials for the NMC storage materials.

A particularly preferred polymer is a polyarylethersulfone having at least one lithium phosphonate group. Polyarylethersulfone cause a particularly good (as far as possible) complete "coverage" (coating) of the active material, which has a positive effect on the thermal stability of the surface-coated NMC materials. Particularly preferred polymers for the surface coating of the NMCs are polyarylethersulfones of the following formula (A) or (B):

Polyaryl ether sulfones of the formula (A) are also referred to as PP10-Li and polyaryl ether sulfones of the formula (B) are also referred to as PP1510-Li.

In order to achieve high thermal stability, a particularly good, i.e. as complete, uniform and homogeneous (continuous) surface coating of the active material (NMC) as possible is advantageous. The surface coating of the ONMC according to the invention is therefore preferably a continuous surface coating. It is further preferred that the surface coating has a thickness in the range from 0.5 nm to 100 nm, preferably in the range from 1 nm to 50 nm, particularly preferably in the range from 2 nm to 25 nm.

The cycle stability and the efficiency of the electrode materials can be significantly improved with the surface coatings according to the invention. For example, for the preferred NMC material NMC ₈₁₁ , first cycle coulombic efficiencies of >93.0% at 20°C, >95.0% at 40°C, and/or >93% at 60°C can be achieved.

1. (i) Lösen des für die Oberflächenbeschichtung gewählten Polymers, welches mindestens eine Lithiumphosphonat-Gruppe aufweist, in einem geeigneten Lösungsmittel;
2. (ii) Zugabe der NMC-Partikel und Herstellung einer Dispersion der NMC-Partikel in einem geeigneten Lösungsmittel;
3. (iii) Abtrennen des Lösungsmittels.

A further aspect of the invention relates to a method for producing the surface-coated NMC memory materials (ONMC) described herein, comprising the steps

1. (i) dissolving the polymer selected for the surface coating, which has at least one lithium phosphonate group, in a suitable solvent;
2. (ii) adding the NMC particles and preparing a dispersion of the NMC particles in a suitable solvent;
3. (iii) separating off the solvent.

In principle, all known solvents that are compatible with the NMC particles dispersed therein and do not attack them in any way (e.g. chemically) can be used. Organic solvents and water are preferred. Examples of suitable solvents include dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), toluene, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and corresponding derivatives these solvents and mixtures thereof. Likewise, water or mixtures of water and the aforementioned solvents can be used for dissolving, and water can also be used as a (co)solvent for dispersing the NMC particles.

The preparation of the dispersion of the NMC particles in the suitable solvent can be carried out using conventional methods, e.g. by stirring, mixing, dispersing, slurrying, etc.

Depending on the solvent used, the organic solvent can be separated off by suitable conventional methods, including, for example, vaporization, evaporation, decantation, filtration, azeotropic rectification and, if appropriate, subsequent drying, etc.

The ONMCs of the present invention are particularly useful as cathodes or cathode materials (i.e., positive electrode in the discharge process) for lithium batteries or electrochemical cells. A further aspect of the invention thus relates to cathodes/cathode materials for a lithium battery or electrochemical cell, comprising one or more of the surface-coated NMC storage materials (ONMC) described herein.

A further aspect of the invention relates to batteries or electrochemical cells comprising one or more of the surface-coated NMC storage materials (ONMC) described herein or a cathode/a cathode material comprising the same.

It has also been shown that the advantageous effects of the ONMCs according to the invention can be additionally enhanced or further positively influenced if they are combined with special electrolytes which are in the WO2019/243529A1 are described in detail and the disclosure content of which is hereby fully encompassed.

mit der folgenden Bedeutung: M ist ein Alkalimetallkation, ein Erdalkalimetallkation, ein Übergangsmetallkation oder ein Ammoniumkation mit einer Valenz m, mit 1 ≤ m ≤ 3, wobei m eine ganze Zahl ist; A^a- ist ein Anion, ausgewählt aus einem Sulfonatanion, einem Sulfonimidanion der Formel -SO₂-N-SO₂R, einem von einem Sulfonimidanion abgeleiteten Anion, das mindestens zwei negative Ladungen trägt, und einem Carbanion der Formel -SO₂-C'R'R'', mit 1 ≤ a ≤ 3, wobei a eine ganze Zahl ist; R repräsentiert: - ein Fluoratom, - eine Fluor- oder Perfluoralkylgruppe mit 1 bis 8 Kohlenstoffatomen, - eine Fluor- oder Perfluoralkoxygruppe mit 1 bis 8 Kohlenstoffatomen, - eine Thiocyanatgruppe (-SCN), - eine Phenylgruppe, die gegebenenfalls mit einer elektronenziehenden Gruppe X substituiert ist, - eine Nitrilgruppe, - eine Gruppe -NR¹ ausgewählt aus einem gesättigten Heterozyklus mit 3 bis 6 Kohlenstoffatomen und einem ungesättigten Heterozyklus mit 4 bis 6 Kohlenstoffatomen, - eine Dicyanamidgruppe -N(CN)₂, - eine Tricyanomethylgruppe -C(CN)₃, wobei R' und R'' unabhängig voneinander ausgewählt sind aus den folgenden einwertigen Gruppen: - einem Fluoratom, - einer Thiocyanatgruppe, - einer Nitrilgruppe, - einer Nitrogruppe, - einer Sulfoxidgruppe der Formel -SOR², worin R² eine Fluor- oder Perfluoralkylgruppe mit 1 bis 5 Kohlenstoffatomen oder eine Fluor- oder Perfluordialkylethergruppe mit 1 bis 5 Kohlenstoffatomen ist, - einer Sulfonylgruppe der Formel -SO₂R³, worin R³ ein Fluoratom, eine Thiocyanatgruppe, eine Nitrilgruppe, eine Fluor- oder Perfluoralkoxygruppe mit 1 bis 5 Kohlenstoffatomen, eine Fluor- oder Perfluoralkylgruppe mit 1 bis 5 Kohlenstoffatomen, oder eine Fluor- oder Perfluordialkylethergruppe mit 1 bis 5 Kohlenstoffatomen ist, - einer Carbonsäureestergruppe der Formel -COOR⁴, worin R⁴ eine Alkylgruppe mit 1 bis 5 Kohlenstoffatomen ist, - einer gegebenenfalls substituierten Phenylgruppe, und - einer gegebenenfalls substituierten Phenoxygruppe; wobei R' und R'' divalente Gruppen sind, so dass der resultierende Carbanion-Rest -C-R'R'' einen aromatischen Ring mit 5 bis 6 Kohlenstoffatomen und gegebenenfalls einem oder mehreren Heteroatomen O oder N bildet, wobei der aromatische Ring gegebenenfalls mit einer oder mehreren Nitrilgruppen substituiert ist; W ist ein Sauerstoffatom, ein Schwefelatom oder eine Gruppe -NR''', worin R''' H oder eine (C₁-C₃)-Alkylgruppe ist; 1 ≤ n ≤ 4, wobei n eine ganze Zahl ist; 1 ≤ n' ≤ 2, wobei n' eine ganze Zahl ist; Z¹ ist ausgewählt aus einer Einfachbindung, einem Sauerstoffatom, einem Schwefelatom, einer Gruppe -S(=O)-, einer Gruppe -S((=O)₂)- und einer Phenylgruppe, die gegebenenfalls in der ortho-Position relativ zu einer der Funktionen (CF₂)_n oder (CF₂)_n' substituiert ist; Z² ist ausgewählt aus einer Einfachbindung, einem Sauerstoffatom, einem Schwefelatom, einer Gruppe -S(=O)-, einer Gruppe -S((=O)₂)- und einer Gruppe -C(=O)-, und E ist eine aromatische Gruppe mit 5 bis 20 Kohlenstoffatomen, die 1 oder 2 aromatische Ringe umfasst. The present invention thus also includes a battery or electrochemical cell as described above, which further comprises a polymer electrolyte according to WO2019/243529A1 includes. Such a polymer electrolyte comprises at least one organic solvent and at least one aromatic ionomer having alternating ionic and nonionic segments comprising
at least non-ionic aromatic repeating units UAr1 and
at least one ionic repeating unit UI1 according to the formula (I)

with the following meaning: M is an alkali metal cation, an alkaline earth metal cation, a transition metal cation, or an ammonium cation having a valence m, with 1 ≤ m ≤ 3, where m is an integer; A ^a- is an anion selected from a sulfonate anion, a sulfonimide anion of the formula -SO ₂ -N-SO ₂ R, an anion derived from a sulfonimide anion bearing at least two negative charges, and a carbanion of the formula -SO ₂ -C'R'R'', with 1 ≤ a ≤ 3, where a is an integer; R represents: - a fluorine atom, - a fluoro or perfluoroalkyl group having from 1 to 8 carbon atoms, - a fluoro or perfluoroalkoxy group having from 1 to 8 carbon atoms, - a thiocyanate group (-SCN), - a phenyl group optionally substituted with an electron-withdrawing group X, - a nitrile group, - a group -NR ¹ chosen from a saturated heterocycle having 3 to 6 carbon atoms and an unsaturated heterocycle having 4 to 6 carbon atoms, - a dicyanamide group -N(CN) ₂ , - a tricyanomethyl group -C(CN) ₃ , whereby R' and R'' are independently selected from the following monovalent groups: - a fluorine atom, - a thiocyanate group, - a nitrile group, - a nitro group, - a sulfoxide group of formula -SOR ² in which R ² is a fluoro or perfluoroalkyl group having 1 to 5 carbon atoms or a fluoro or perfluorodialkyl ether group having 1 to 5 carbon atoms, - a sulfonyl group of formula -SO ₂ R ³ in which R ³ represents a fluorine atom, a thiocyanate group, a nitrile group, a fluorine or perfluoroalkoxy group having 1 to 5 carbon atoms, a fluorine or perfluoroalkyl group having 1 to 5 carbon atoms, or a fluorine or is a perfluorodialkyl ether group having 1 to 5 carbon atoms, - a carboxylic acid ester group of the formula -COOR ⁴ where R ⁴ is an alkyl group having 1 to 5 carbon atoms, - an optionally substituted phenyl group, and - an optionally substituted phenoxy group; whereby R' and R'' are divalent groups such that the resulting carbanion moiety -C-R'R'' forms an aromatic ring having 5 to 6 carbon atoms and optionally one or more heteroatoms O or N, the aromatic ring optionally having substituted by one or more nitrile groups; W is an oxygen atom, a sulfur atom or a group -NR''', wherein R''' is H or a (C ₁ -C ₃ )alkyl group; 1 ≤ n ≤ 4, where n is an integer; 1 ≤ n' ≤ 2, where n' is an integer; Z ¹ is selected from a single bond, an oxygen atom, a sulfur atom, a group -S(=O)-, a group -S((=O) ₂ )- and a phenyl group optionally in the ortho position relative to one of the functions (CF ₂ ) _n or (CF ₂ ) _n' is substituted; Z ² is selected from a single bond, an oxygen atom, a sulfur atom, a group -S(=O)-, a group -S((=O) ₂ )- and a group -C(=O)-, and E is an aromatic group of 5 to 20 carbon atoms, comprising 1 or 2 aromatic rings.

mit $$\text{n}=8\text{bis}\mathrm{50,}$$

$$\text{m}=4\text{bis}\mathrm{50,}$$

und $$\text{x}=2\text{bis}12;$$

oder ein Multiblock-Copolymer der folgenden Formel (ii):

mit $$\text{n}=8\text{bis}\mathrm{50,}$$

$$\text{m}=4\text{bis}\mathrm{50,}$$

und $$\text{p}=2\text{bis}12;$$

oder ein Multiblock-Copolymer der folgenden Formel (iii):

mit $$\text{n}=8\text{bis}\mathrm{50,}$$

$$\text{m}=4\text{bis}\mathrm{50,}$$

und $$\text{p}=2\text{bis}12;$$

oder Mischungen davon.The aromatic ionomer of such a polymer electrolyte is preferably a multiblock copolymer of the following formula (i):

With $$\text{n}=\mathrm{8th}\text{until}\mathrm{50,}$$

$$\text{m}=4\text{until}\mathrm{50,}$$

and $$\text{x}=2\text{until}12;$$

or a multiblock copolymer of the following formula (ii):

With $$\text{n}=\mathrm{8th}\text{until}\mathrm{50,}$$

$$\text{m}=4\text{until}\mathrm{50,}$$

and $$\text{p}=2\text{until}12;$$

or a multiblock copolymer of the following formula (iii):

With $$\text{n}=\mathrm{8th}\text{until}\mathrm{50,}$$

$$\text{m}=4\text{until}\mathrm{50,}$$

and $$\text{p}=2\text{until}12;$$

or mixtures thereof.

The organic solvent of this polymer electrolyte is a plasticizing solvent with a boiling point greater than 100°C and an electrochemical stability window of at least 2V. Examples include ethylene carbonate (EC), propylene carbonate (PC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (FZEC), fluoropropylene carbonate , glymes, dinitriles, sulfones (linear and cyclic), sulfides, sulfites, vinylene carbonate (VC), propane sultone, propene sultone, adiponitrile, dimethyl sulfoxide (DMSO), and mixtures thereof. Ethylene carbonate (EC), propylene carbonate (PC), adiponitrile and mixtures thereof are preferred.

A further aspect of the invention relates to the use of a polymer which has at least one lithium phosphonate group, as described herein, for the surface coating of NMC storage materials.

The polymer therein is preferably a polyarylethersulfone according to one of the following formulas (A) or (B):

character list

• 1 Diffraction pattern of an ONMC according to the invention according to production example 1 in comparison to the NMC base material used.
• 2 Cyclic voltammetry results for NCM ₈₁₁ - and ONCM ₈₁₁ -based cells at a scan rate of 0.01 mV s ^-1 ; both cells show high reversibility after the first cycle.
• 3 (a) Cycling NCM ₈₁₁ - and ONCM ₈₁₁ -based cells at different C rates from 0.1C to 10C and then cycling at 1C for several hundred cycles. (b,c) Cycle stability over several hundred cycles for (b) 3C and (c) 5C of NCM ₈₁₁ - and ONCM ₈₁₁ - based cells. Regardless of the applied C rate, ONCM ₈₁₁ -based cells achieve significantly higher cycling stability and lifetime (defined as the number of cycles up to a capacity of 80% of the original capacity), ie 459 cycles (3C) and 377 cycles (5C) im In contrast to 387 cycles (3C) and 358 cycles (5C) for NCM ₈₁₁ -based cells. The increased cycle stability after the PP10-Li polymer coating is not only given at low, but also at high C rates.
• 4 Comparison of (a) the cycling stability at a C rate of 3C and a temperature of 40 °C and (b) the rate performance at varying C rates from 0.1C to 10C and subsequent cycling stability at a C rate of 1C and a temperature of 60 °C of NCM ₈₁₁ - and ONCM ₈₁₁ -based electrodes. The electrochemical performance at elevated temperatures, ie 40 and 60 °C, of the two NCM ₈₁₁ - and ONCM ₈₁₁ -based electrodes is in 4a or. 4b shown. At 40 °C, both cells could deliver higher capacities than at room temperature, which can be attributed to the improved Li ⁺ diffusion at elevated temperatures. As in 4a shown, the NCM ₈₁₁ -based cell delivered a higher capacity than the ONCM ₈₁₁ -based cell (e.g., 191.8 vs. 179.6 mAh g ^-1 ) after three formation cycles at a rate of 0.1C. However, due to the more pronounced side reactions promoted by the elevated temperatures, the NCM ₈₁₁ -based cell showed a rapid capacity drop after about 130 cycles, resulting in a 20% capacity drop after only 176 cycles, while the ONCM ₈₁₁ -based cell showed this Limit only reached after 221 cycles. 4b compares the rate performance and cycling stability of the two cells at 60 °C. The general trend in rate performance at 60°C is similar to that at 20°C, ie the NCM ₈₁₁ -based cell delivers slightly higher capacity than the ONCM ₈₁₁ -based cell. Nevertheless, the capacities that can be delivered for both cells at 60 °C are significantly higher. More than 180 mAh g ^-1 capacity could be achieved even at 10C, which is comparable to the capacities achieved at 1C and 20 °C. There is a clear difference between NCM ₈₁₁ - and ONCM ₈₁₁ -based cells with regard to the subsequent cycle stability at 1C. The latter achieves a lifespan of 180 cycles, while the former barely lasts 15 cycles in sharp contrast. The drastic drop in capacity of the NCM ₈₁₁ -based cells suggests very strong side reactions that occur at 60 °C. With ONCM ₈₁₁ , however, these side reactions are greatly reduced thanks to the polymer coating, which ultimately leads to greatly improved cycle stability.

examples

experimental part

1. Chemicals

4,4'-Difluorodiphenylsulfone (DFDPS, >98%) and 4,4'-Biphenol (BP, 99%) purchased from Alfa Aesar were recrystallized from isopropanol prior to use. Toluene, potassium carbonate (K ₂ CO ₃ , 99%), calcium hydride (CaH ₂ , 98%), methanol, hydrochloric acid (HCl 36.5% by weight), lithium hydroxide monohydrate (LiOH-H ₂ O, 98%), purchased from Alfa Aesar, used as received with no further cleaning. Dichloromethane (DCM), purchased from Sigma Aldrich, was freshly distilled from CaH ₂ before use. Hexafluorobenzene (HFB, 99%), anhydrous dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP, >99%), bromine (Br ₂ , 99.99%), anhydrous acetic acid (CH ₃ COOH, 99.8 %), palladium acetate (Pd(OAc) ₂ , >99.9), triphenylphosphine (TPP, 99%), diethyl phosphite (DEP, 98%), dicyclohexylmethylamine (DCHMA, 97%) purchased from Sigma Aldrich were used as received .

2. Synthesis of PP10-Li polymer

2.1 Synthesis of HFB-Endcapped Aromatic Polymers 10 kg/mol (PES10)

PES10 polymers were synthesized by modification of a one-pot, two-reaction procedure. A 100 mL three-necked round-bottom flask equipped with a mechanical stirrer, condenser, argon inlet/outlet, and Dean-Stark trap was charged with DFDPS (4.000 g, 15.732 mmol), BP (3.052 g, 16.388 mmol) filled. DMAc (28 mL) was added to give a solids concentration of 25% (w/v). The mixture was dissolved, then K ₂ CO ₃ (6.79 g, 0.0492 mol) and 14 mL of toluene were added as an azeotrope. The ratio of DMAc to toluene (v/v) was 2:1. The reaction bath was heated to 150°C and maintained at that temperature for 4 hours to dehydrate the system. Then the bath temperature was slowly increased to 160°C during the controlled withdrawal of toluene. Thereafter, the temperature of the reaction bath was lowered to 120°C and the polymerization was continued at that temperature for 24 hours. Then the reaction temperature was adjusted to 70°C and 2.44 g (13.11 mmol) of HFB was added (the molar ratio of HFB/PES is 20). The reaction was continued at this temperature for 12 hours. When HFB was introduced, the argon purge was stopped at this point due to its low boiling point. The reaction mixture was then precipitated in 2 L aqueous 1M HCl solution with magnetic stirring for 8 h and then filtered and rinsed with distilled water until neutral pH. The white powder was dried under vacuum at 80°C for 24 h to obtain the final product (Mn = 10,600 g/mol, polydispersity = 2.0).

2.2 Synthesis of the Brominated PES10 Intermediate (BPES10)

The bromination of the PES10 polymer was carried out at room temperature using bromine as the brominating agent in the presence of acetic acid. 5.000 g (12.10 mmol biphenyl moiety) of PES10 polymer was placed in a 250 mL three-necked round bottom flask equipped with a mechanical stirrer, condenser, argon inlet and addition funnel. Then 90 mL of DCM distilled from CaH ₂ and 9 mL (10% v/v to DCM) of acetic acid were added. After the polymer was completely dissolved, 9.36 mL (0.182 mol) of bromine (Br ₂ ) was added dropwise into the reaction mixture, followed by vigorous stirring. The reaction was carried out at room temperature for 16 hours. The reaction mixture was precipitated into 1000 mL of methanol, washed three times with methanol to remove excess bromine and stirred for 16 h. Thereafter, the polymer was filtered and carefully rinsed with methanol until the bromine was completely removed. The final product was dried under vacuum at 80°C for 24 h.

2.3 Synthesis of PES10 Polymers with Lithium Phosphonate Functions (PP10-Li)

The phosphonate functions were attached to the polymer backbone by a palladium-catalyzed coupling reaction. BPES10 intermediate (2.00 g, 7.19 mmol Br), Pd(OAc) ₂ (80.7 mg, 0.36 mmol), TPP (0.283 g, 1.08 mmol) and anhydrous DMAc (40 mL) was placed in a 100 mL two-necked round-bottomed flask equipped with an argon inlet/outlet and a magnetic bar. The reaction mixture was heated to 95°C with vigorous stirring to dissolve the solid. Then DEP (4.6 mL, 36.0 mmol) and DCHMA (4.6 mL, 21.6 mmol) were added and the reaction was continued at this temperature for 48 h. The reaction mixture was precipitated in ethanol, washed several times with ethanol and filtered to give a white solid which was dried under vacuum at 80°C for 24 h to give the ethyl phosphonate form of the product (namely PP10-Et, 95% yield). receive. The PP10-Et polymer (1.00 g, 2.98 mmol of the -PO(OC2H5)2 function) was boiled in 36.5% aqueous HCl solution for 4 h and washed several times with distilled water to remove the Remove trace of HCl and obtain the PES10 polymer bearing phosphonic acid functionalities (designated PP10-H). Finally, the acidic polymer was neutralized with 0.5 M LiOH aqueous solution, washed several times with distilled water, filtered and dried under vacuum at 80 °C for 24 h to obtain the target PP10-Li compound (93% yield) .

2.4. Synthesis of PP10-Li polymer-coated Li[Ni _0.8 Co _0.1 Mn _0.1 ]O ₂ (ONCM ₈₁₁ )

2.4.1. Preparation of the PP10 Li polymer in NMP solution

First, 0.1 g of PP10-Li polymer was placed in a 50 mL single-necked round bottom flask equipped with a magnetic bar and magnetic stirrer. 10.0 mL of N-methyl-2-pyrrolidone (NMP) was added and the mixture heated to 120°C. Then 4.0 mL of deionized water (DIW) was added dropwise until the polymer was completely dissolved. Thereafter, water was removed by azeotropic distillation. 10 mL of toluene was added to the flask, to which a Dean-Stark trap containing 25 mL of toluene was attached. The mixture was heated to 160°C and refluxed overnight. Then all the water and toluene in the system were removed in a controlled manner and the PP10-Li polymer solution in NMP was obtained.

2.4.2 Manufacture of ONCM ₈₁₁

1 g of Li[Ni _0.8 C0 _0.1 Mn _0.1 ]O ₂ powder was added into 2 mL of the above solution, which was then slowly stirred at 80°C. The ONCM811 was maintained until all of the NMP solution had evaporated.

3. Electrode manufacture and cell construction

The ONCM ₈₁₁ (or NCM ₈₁₁ ) electrodes were prepared by dispersing NCM ₈₁₁ (92 wt%), C-NERGY Super C65 (TIMCAL, 4 wt%) and poly(vinylidene difluoride) (PVdF 6020, Solvay, 4 wt%) in NMP (Aldrich) at a solids to liquid ratio of 1:1 (w/w). The intimately mixed slurries were then applied to Al foils using the doctor blade technique. The wet electrodes were pre-dried at 60°C to remove the NMP. The electrodes were then punched and subjected to a further vacuum drying process (glass oven B-585 Drying, Büchi) at 100° C. for 12 h. The mean active material loading density of both electrodes was ~2.2 ± 0.2 mg cm ^-2 . All processes were carried out in a dry room with a dew point below -60 °C and a room temperature of 20 °C.

Electrochemical characterization was performed in 2032 button cells. The coin cells contain an electrode based on NCM ₈₁₁ (or ONMC ₈₁₁ ) as working electrode, metallic lithium (Honjo, battery grade) as counter electrode, 1M LiPF ₆ dissolved in ethyl carbonate diethyl carbonate (EC-DEC) (1:1 w/w ) with 1% by weight of vinylene carbonate (VC) as the electrolyte (BASF) and a single-layer polyethylene membrane (ASAHI KASEI, Hipore SV718) as the separator. All button cells were mounted in an argon-filled glove box (with O ₂ <0.1 ppm and H ₂ O <0.1 ppm).

Electrochemical characterization:

All galvanostatic tests were performed in a voltage range of 3.0-4.3 V using a battery tester (Maccor 4000 series). The tests at different temperatures (20, 40 and 60 °C) were carried out using a climatic chamber (Binder GmbH). For the long-term cycling, cells were always activated with three formation cycles at 0.1C before being cycled at higher C rates, ie, 3C and 5C. The cyclic voltammetry experiments for both the NCM ₈₁₁ - and the ONCM ₈₁₁ -based electrodes were recorded with a multichannel potentiostat (VMP, Bio-Logic). The voltage range was set at 3.0-4.3 V and the temperature was controlled at 20 °C. The scan rate was 0.01 mV s ^-1 .

Example 1 - Example of preparation

Step (i):

100 mg PP10-Li (polymer according to formula (A)) are added to 10 mL NMP. The temperature is then increased to 120° C. and 4 mL of water are added dropwise. In a next step, the water is removed by azeotroprectification, 10 mL toluene is added and then removed again so that only PP10-Li is dissolved in NMP.

Step (ii):

1 g of NMC ₈₁₁ particles are added to 2 mL of the solution from step (i) with constant, slow stirring and dispersed therein at 80°C.

Step (iii):

Subsequently, the organic solvent (NMP) is removed by evaporation and the ONMC particles according to the invention are thus obtained, in which NMC ₈₁₁ is surface-coated with a polymer of the formula (A) (ONMC ₈₁₁ ).

1 shows that the diffraction pattern of the ONMC ₈₁₁ obtained is identical to that of the NMC ₈₁₁ base material used. A slightly reduced peak intensity of the ONMC ₈₁₁ results from the applied PP10-Li polymer layer.

This shows that the bulk structure of the NCM storage material used (NMC ₈₁₁ ) is not affected by the polymer coating.

Example 2 - Example of preparation

Production example 1 is carried out analogously using a polymer PP1510-Li according to the formula (B) for the surface coating of NMC ₈₁₁ .

Example 3 - Examination of the ONMC ₈₁₁ from production example 1

A) Morphology

The ONMC ₈₁₁ obtained according to Preparation Example 1 was analyzed by electron microscopy with regard to morphology and surface structure.

A uniform coating (thickness of the coating 7-12 nm) with PP10-Li was found on the NMC ₈₁₁ material.

B) Elements distribution

Analysis of the element distribution using energy-dispersive X-ray spectroscopy showed that the elements C, S, P and F (representing PP10-Li) are distributed homogeneously on the NMC ₈₁₁ particle surface, which speaks for a uniform and even (continuous) coating .

C) Surface examination

Examination of the ONMC ₈₁₁ surfaces by X-ray photoelectron spectroscopy showed a substantially low amount of LiOH and Li ₂ CO ₃ and a high LiF content close to the NMC ₈₁₁ base material. This suggests that the polymeric surface coating suppresses a surface lithium impurity phase in favor of a LiF layer.

D) Thermal stability

The investigation of the thermal stability was carried out by means of dynamic differential scanning calorimetry.

The thermal stability of the delithiated NCM ₈₁₁ and ONCM ₈₁₁ electrodes soaked in the electrolyte was investigated using differential scanning calorimetry. Although the decomposition onset temperature for these two samples is quite similar, the ONCM ₈₁₁ electrode generates a significantly lower amount of heat (ie, 1139.0 J g ^-1 ) than the NCM ₈₁₁ electrode (1321.7 J g ^-1 ). On the other hand, the PP10-Li oligomer shows no signs of exothermic degradation but shows a glass transition temperature and an endothermic peak at -230°C and -274°C, respectively. The thermal stability of the PP10-Li oligomer coating prevents direct contact of the active material with the electrolyte, resulting in an improved thermal stability of ONCM ₈₁₁ , which plays an important role in practical application.

From this it can be seen that for the ONMC ₈₁₁ according to the invention significantly less heat is released when the ambient temperature is increased, due to the suppressed side reactions between the lithiated cathode and the electrolyte, with the onset of decomposition temperature being more or less the same as for the uncoated NMC used ₈₁₁ base material.

E) Electrochemical behavior

• Elektrodenzusammensetzung: NMC₈₁₁
• Super C65: PVdF = 92:4:4
• Elektrolyt: LP30+1 Gew.% Vinylencarbonat (1M LiPF₆ in Ethylencarbonat : DMC 1:1, v/v) Spannungsbereich: 3,0-4,3 V gegen Li⁺/Li

The investigation of the electrochemical behavior was initially carried out using cyclic voltammetry under the following conditions:

• Electrode composition: NMC ₈₁₁
• Super C65: PVdF = 92:4:4
• Electrolyte: LP30+1 wt% vinylene carbonate (1M LiPF ₆ in ethylene carbonate: DMC 1:1, v/v) Voltage range: 3.0-4.3 V vs. Li ⁺ /Li

The result shows 2 .

This shows that the ONMC ₈₁₁ according to the invention has a lower polarization and a slightly higher apparent Li ⁺ diffusion coefficient of 9.7 × 10 ^-8 and 3.9 × 10 ^-8 cm ² s ^-1 compared to the uncoated NMC ₈₁₁ used Base material with 8.3 x 10 ^-8 and 3.4 x 10 ^-8 cm ² s ^-1 .

F) Electrochemical performance / cycling stability

Electrochemical performance and cycling stability were investigated using galvanostatic cycling.

The results show 3 and 4 .

This shows that cells based on the ONMC ₈₁₁ according to the invention have a de facto comparable specific capacity (if only the amount of active material is considered) as well as a better discharge rate (load capacity) and a significantly increased cycle stability, especially at elevated temperatures (40 ° C and 60 °C).

In addition, surface examinations after several charging cycles showed that the applied PP10-Li coating was still detectable even after 540 charging cycles and led to the formation of thinner CEI layers (Cathode Electrolyte Interphase). In addition, the crystal structure of the NMC ₈₁₁ active material remains intact on the surface, while significant degradation processes can be seen using electron microscopy for the uncoated sample. These observations support the high stability of the polymer coatings according to the invention and are also supported by the high cycle stability that can be achieved with them.

G) Summary of results

• • die Zyklenstabilität verbessert,
• • die Entladungsraten erhöht,
• • bessere thermische Stabilität bewirkt,
• • unerwünschte Oberflächenmodifikationen verringert, sowie
• • einfach und kostengünstig herstellbar ist.

On the ONMC according to the invention from production example 1 (ONMC ₈₁₁ ), it was shown by way of example that the surface modification according to the invention of the NMC storage materials described herein

• • improved cycle stability,
• • increased discharge rates,
• • causes better thermal stability,
• • Reduced unwanted surface modifications, as well
• • is easy and inexpensive to produce.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• WO 2019141981 A1 [0009]
• US6921609 [0009]
• WO 2019/243529 A1 [0044, 0045]

Claims (10)

Surface-coated NMC memory materials (ONMC), comprising an NMC memory material (NMC) with a surface coating of a polymer which has at least one lithium phosphonate group. ONMC according to claim 1 wherein the polymer is a polyarylethersulfone having at least one lithium phosphonate group. ONMC according to claim 1 or 2 , wherein particles of a lithium transition metal oxide according to the general formula (I) are selected as NMC storage material Li _a Ni _x M _y M' _z O _2+b (I) with M = Co, Mn and combinations thereof; M' = Mg, AL, V, Ti, B, Zr, Sr, Ca, Cu, Zn, Nb, Mo, W, Ta and combinations thereof; $$0.8\le \text{a}\le 1.2;$$

$$0.2\le \text{x}\le 1;$$

$$0<\text{y}\le 0.8;$$

$$0\le \text{e.g}\le 0.2;$$

and $$-0.2\le \text{b}\le 0.2$$

ONMC according to one of the preceding claims, wherein particles of a lithium transition metal oxide according to the general formula (II) or (III) are selected as the NMC storage material LiNi _1-xy CO _x Mn _y O ₂ LiNi _x Co _y Mn _1-xy O ₂ (ii) (iii) With With 1-xy ≥ 0.6; x ≥ 0.8. ONMC according to any one of the preceding claims, wherein the polymer is a polyarylethersulphone according to one of the following formulas (A) or (B).

Method for producing the surface-coated NMC memory materials (ONMC) according to any one of the preceding claims, comprising the steps (iv) dissolving the polymer having at least one lithium phosphonate group in an organic solvent; (v) adding the NMC particles and making a dispersion of the NMC particles in the organic solvent; (vi) Separating the organic solvent. A cathode for a lithium battery or an electrochemical cell, comprising the surface-coated NMC storage material (ONMC) according to any one of Claims 1 until 6 . A battery or electrochemical cell comprising a cathode according to claim 7 . A battery or electrochemical cell according to claim 8 , further comprising a polymer electrolyte comprising at least one organic solvent and at least one aromatic ionomer with alternating ionic and nonionic segments, comprising at least nonionic aromatic repeating units UAr1 and at least one ionic repeating unit UI1 according to the formula (I)

with the following meaning: M is an alkali metal cation, an alkaline earth metal cation, a transition metal cation, or an ammonium cation having a valence m, with 1 ≤ m ≤ 3, where m is an integer; A ^a- is an anion selected from a sulfonate anion, a sulfonimide anion of the formula -SO ₂ -N-SO ₂ R, an anion derived from a sulfonimide anion bearing at least two negative charges, and a carbanion of the formula -SO ₂ -C'R'R'', with 1 ≤ a ≤ 3, where a is an integer; R represents: - a fluorine atom, - a fluoro or perfluoroalkyl group having from 1 to 8 carbon atoms, - a fluoro or perfluoroalkoxy group having from 1 to 8 carbon atoms, - a thiocyanate group (-SCN), - a phenyl group optionally substituted with an electron-withdrawing group X, - a nitrile group, - a group -NR ¹ chosen from a saturated heterocycle having 3 to 6 carbon atoms and an unsaturated heterocycle having 4 to 6 carbon atoms, - a dicyanamide group -N(CN) ₂ , - a tricyanomethyl group -C(CN) ₃ , whereby R' and R'' are independently selected from the following monovalent groups: - a fluorine atom, - a thiocyanate group, - a nitrile group, - a nitro group, - a sulfoxide group of formula -SOR ² in which R ² is a fluoro or perfluoroalkyl group having 1 to 5 carbon atoms or a fluoro or perfluorodialkyl ether group having 1 to 5 carbon atoms, - a sulfonyl group of formula -SO ₂ R ³ in which R ³ represents a fluorine atom, a thiocyanate group, a nitrile group, a fluorine or perfluoroalkoxy group having 1 to 5 carbon atoms, a fluorine or perfluoroalkyl group having 1 to 5 carbon atoms, or a fluorine or is a perfluorodialkyl ether group having 1 to 5 carbon atoms, - a carboxylic acid ester group of the formula -COOR ⁴ where R ⁴ is an alkyl group having 1 to 5 carbon atoms, - an optionally substituted phenyl group, and - an optionally substituted phenoxy group; wherein R' and R" are divalent groups such that the resulting carbanion moiety -C-R'R" forms an aromatic ring having 5 to 6 carbon atoms and optionally one or more heteroatoms O or N, which aromatic ring is optionally is substituted with one or more nitrile groups; W is an oxygen atom, a sulfur atom or a group -NR''', wherein R''' is H or a (C ₁ -C ₃ )alkyl group; 1 ≤ n ≤ 4, where n is an integer; 1 ≤ n' ≤ 2, where n' is an integer; Z ¹ is selected from a single bond, an oxygen atom, a sulfur atom, a group -S(=O)-, a group -S((=O) ₂ )- and a phenyl group optionally in the ortho position relative to one of the functions (CF ₂ ) _n or (CF ₂ ) _n' is substituted; Z ² is selected from a single bond, an oxygen atom, a sulfur atom, a group -S(=O)-, a group -S((=O) ₂ )- and a group -C(=O)-, and E is an aromatic group of 5 to 20 carbon atoms, comprising 1 or 2 aromatic rings. Use of a polymer which has at least one lithium phosphonate group for the surface coating of NMC storage materials, in particular a polymer according to one of the following formulas (A) or (B)

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