METHOD FOR THE PRODUCTION OF TWO-PHASE UNICROYABLE POSITIVE ELECTRODE MATERIALS FOR LITHIUM ION CYCLING BATTERIES

Abstract

A process for producing a positive electrode for a lithium-ion cycling battery, as well as a battery containing the positive electrode, are disclosed. In the disclosed process, a single-crystal precursor particle is brought into contact with an aqueous solution. The precursor particle contains a lithium-rich manganese-based transition metal oxide (LRMO) with a layered crystal structure, and the aqueous solution contains exchangeable cations. When the precursor particle is brought into contact with the aqueous solution, lithium ions are removed from an outer surface section of the precursor particle, and the LRMO in the outer surface section of the precursor particle is converted into a lithium-poor manganese-based oxide (LDMO).The precursor particle is then heated so that the LDMO in the outer surface section of the precursor particle undergoes a phase transition and is converted into a lithium manganese-based transition metal oxide with spinel crystal structure (spinel LMO).

Description

INTRODUCTION

[0001] The information contained in this section serves to present the general context of the disclosure. Works of the inventors mentioned herein, insofar as they are described in this section, as well as aspects of the description that might not otherwise be considered prior art at the time of filing, are neither expressly nor implicitly admitted as prior art against the present disclosure.

[0002] The present disclosure relates to a process for producing a positive electrode for a battery that cycles lithium ions, and in particular to a process for producing positive electrodes comprising single-crystal, lithium-rich manganese-based transition metal oxides.

[0003] Layered lithium-rich manganese-based oxides (LRMO) are desirable electroactive materials for the positive electrodes of lithium-ion cycling batteries due to their relatively high capacity (e.g., >250 mAh / g), thermal stability, and relatively low cost. However, during activation, LRMO can undergo an irreversible phase transition from a layered to a spinel structure, leading to a voltage drop and potentially affecting the long-term cycling performance of the LRMO. Using single-crystal LRMO particles instead of polycrystalline particles can slow down this undesirable phase transition process. However, single-crystal LRMO particles may exhibit a low initial coulombic efficiency, which can limit the maximum utilization of their capacity.

[0004] Known methods for producing a positive electrode for a battery that cycles lithium ions are described, for example, in DE 10 2023 131 742 A1, US 2002 / 0 182 502 A1, US 2012 / 0 028 114 A1 and US 2023 / 0 024 868 A1. SUMMARY

[0005] Not according to the invention, a method for producing a positive electrode for a lithium-ion cycling battery is described, comprising contacting a single-crystal precursor particle with an aqueous solution. The precursor particle comprises a lithium-rich manganese-based transition metal oxide (LRMO) with a layered crystal structure. The aqueous solution comprises exchangeable cations. The precursor particle is contacted with the aqueous solution such that lithium ions are removed from an outer surface section of the precursor particle and the LRMO in the outer surface section of the precursor particle is converted into a lithium-poor manganese-based oxide (LDMO).The precursor particle is then heated so that the LDMO in the outer surface section of the precursor particle undergoes a phase transition and is converted into a lithium manganese-based transition metal oxide with spinel crystal structure (spinel LMO).

[0006] In some cases, the aqueous solution may contain an aqueous ammonium solution, and the exchangeable cations may include ammonium (NH4). + )-ions.

[0007] In other cases, the aqueous solution may comprise an aqueous citric acid solution, and the exchangeable cations may include hydrogen ions (H₂). + ).

[0008] The amount of exchangeable cations in the aqueous solution, relative to the amount of LRMO in the aqueous solution, can be greater than or equal to 0.1 millimoles per gram of LRMO and less than or equal to 2 millimoles per gram of LRMO.

[0009] The precursor particle can be brought into contact with the aqueous solution at a temperature greater than or equal to 50 degrees Celsius and less than or equal to 100 degrees Celsius for a duration of more than or equal to 2 hours and less than or equal to 24 hours.

[0010] The precursor particle can be heated at a temperature greater than or equal to 400 degrees Celsius and less than or equal to 700 degrees Celsius for a duration of more than or equal to 1 hour and less than or equal to 24 hours.

[0011] The LRMO can have a composition that can be described by the formula Li y Mn x Me 1-x O2, is represented where: y is greater than 1 and less than or equal to 1.4, x is greater than 0.5 and less than 1, and Me includes Ni, Co or a combination thereof.

[0012] Spinel LMO can have a composition described by the formula Li(Mn x Me 1-x)2O4 is represented where: x is greater than 0.5 and less than 1 and Me includes Ni, Co or a combination thereof.

[0013] A method for producing a positive electrode for a lithium-ion cycling battery, according to the present invention, comprises contacting a single-crystal precursor particle with an aqueous ammonium solution. The precursor particle comprises a lithium-rich manganese-based transition metal oxide (LRMO) with a layered crystal structure. The aqueous ammonium solution comprises ammonium (NH4) +The precursor particle is brought into contact with the aqueous ammonium solution such that lithium ions are removed from an outer surface section of the precursor particle, and the LRMO in the outer surface section is converted into a lithium-poor manganese-based oxide (LDMO). The precursor particle is brought into contact with the aqueous ammonium solution at a temperature greater than or equal to 50°C and less than or equal to 100°C for a duration of more than or equal to 2 hours and less than or equal to 24 hours. The precursor particle is then heated such that the LDMO in the outer surface section undergoes a phase transition and is converted into a lithium-manganese-based transition metal oxide with a spinel crystal structure (spinel LMO), forming a two-phase single-crystal particle (2P-SC particle).The 2P-SC particles have a core and a shell surrounding the core. The core is defined by a remaining portion of the LRMO in the precursor particle, and the shell by the spinel LMO. The precursor particle is heated to a temperature greater than or equal to 400 degrees Celsius and less than or equal to 700 degrees Celsius for a duration of more than or equal to 1 hour and less than or equal to 24 hours.

[0014] The aqueous ammonium solution may comprise at least one ammonium salt selected from the group consisting of ammonium persulfate, ammonium molybdate and ammonium phosphate.

[0015] The amount of NH4 + The concentration of ions in the aqueous ammonium solution relative to the amount of LRMO in the aqueous ammonium solution can be greater than or equal to 0.1 millimoles of NH4. + per gram of LRMO and less than or equal to 2 millimoles of NH4 + per gram of LRMO.

[0016] The LRMO can have a composition that can be described by the formula Li y Mn x Me 1-x O2 is represented where: y is greater than 1 and less than or equal to 1.4, x is greater than 0.5 and less than 1, and Me includes Ni, Co or a combination thereof.

[0017] Spinel LMO can have a composition described by the formula Li(Mn x Me 1-x )2O4 is represented where: x is greater than 0.5 and less than 1 and Me includes Ni, Co or a combination thereof.

[0018] The LRMO can have a composition that can be described by the formula Li 1,2 Mn x Ni 1-x O2 is represented, where x is greater than or equal to 0.6 and less than or equal to 0.9.

[0019] The 2P-SC particle can have a particle diameter greater than or equal to 0.5 micrometers and less than or equal to 5 micrometers.

[0020] The shell can have a thickness greater than or equal to 1 nanometer and less than or equal to 20 nanometers.

[0021] The process may further include: mixing the 2P-SC particle with a polymer binder, optionally an electrically conductive material and a solvent to form a slurry; applying the slurry to a substrate; and subsequently removing the solvent from the slurry.

[0022] A battery that cycles lithium ions is described according to the invention. The battery comprises a positive electrode comprising an electroactive material that includes a two-phase single-crystal particle (2P-SC particle) with a core and a shell surrounding the core. The core of the 2P-SC particle comprises a lithium-rich, manganese-based transition metal oxide (LRMO) with a layered crystal structure. The shell of the 2P-SC particle comprises a lithium-manganese-based transition metal oxide with a spinel crystal structure (spinel-LMO). The shell is formed in situ along an outer surface section of the 2P-SC particle by performing a cation exchange process followed by a calcination process on a single-crystal precursor particle comprising the LRMO. During the cation exchange process, the precursor particle is treated with an aqueous ammonium solution containing ammonium (NH4). +The precursor particle, containing lithium ions, is brought into contact such that lithium ions are removed from an outer surface section of the precursor particle, and the LRMO in the outer surface section of the precursor particle is converted into a lithium-poor, manganese-based oxide (LDMO). Then, during the calcination process, the precursor particle is heated such that the LDMO in the outer surface section of the precursor particle undergoes a phase transition and is converted into the spinel LMO, forming the 2P-SC particle, where the core is defined by a remaining section of the LRMO in the precursor particle and the shell by the spinel LMO.

[0023] Further applications of the present disclosure will become apparent from the detailed description, the claims, and the drawings. The detailed description and the specific examples serve only for illustration and are not intended to limit the scope of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present disclosure is better understood from the detailed description and the accompanying drawings; the following applies: Fig. Figure 1 is a schematic perspective view of a motor vehicle powered by a battery pack with multiple battery modules. Fig. Figure 2 is a schematic cross-sectional view of a section of one of the battery modules of Fig. 1, wherein the battery module contains multiple electrochemical cells or batteries that cycle lithium ions. Fig. Figure 3 is a schematic cross-sectional view of a battery that cycles lithium ions, wherein the battery comprises a positive electrode, a negative electrode, a porous separator and an electrolyte that infiltrates the positive and negative electrodes and the porous separator. Fig. Figure 4 is a schematic cross-sectional view of an electroactive positive electrode material in the form of a two-phase single-crystal particle (2P-SC particle) comprising a core and a shell surrounding the core. Fig. Figure 5 is a scanning electron microscope image of single crystal particles made of lithium-rich manganese-based transition metal oxide (SC-LRMO particles). Fig. 6 and Fig. Figure 7 are scanning electron micrographs of 2P-SC particles formed according to embodiments of the present disclosure. Fig. Figure 8 is a diagram of the differential capacity dQ / dV (mAh / V) versus the voltage (V versus Li / Li+) for the first cycle of: (i) a half cell comprising SC-LRMO particles as electroactive materials (solid line) and (ii) a half cell comprising 2P-SC particles as electroactive materials (dashed line). Fig. Figure 9 is an enlarged view of the diagram of Fig. 8 from rectangle 9. Fig. Figure 10 is a diagram of the Coulomb efficiency 300 (%) versus the relative ammonium content 400 (mmol NH4). + / g SC-LRMO) for the first cycle of: (i) half-cells comprising 2P-SC particles formed using aqueous ammonium persulfate solutions for the ion exchange process (solid line) and (ii) half-cells comprising 2P-SC particles formed using aqueous ammonium molybdate solutions for the ion exchange process (dashed line).

[0025] Reference numbers can be used repeatedly in the drawings to identify similar and / or identical elements. DETAILED DESCRIPTION

[0026] The single-crystal LRMO particles disclosed herein have a two-phase structure and can be used as electroactive positive electrode materials in lithium-ion cycling batteries to increase their first-cycle coulombic efficiency compared to batteries containing single-crystal LRMO particles without the disclosed two-phase structure. The disclosed two-phase single-crystal (2P-SC) LRMO particles can be produced using a controlled surface reconstruction process in which single-crystal LRMO particles with a layered structure undergo an ion-exchange treatment followed by a calcination treatment to effectively convert an outer surface region of the LRMO particles from a layered structure to a spinel structure.It is assumed that the thin spinel shell on the 2P-SC-LRMO particles contributes to increasing the coulombic efficiency of the first cycle by, for example, facilitating the penetration of lithium ions into the surface of the particles and their diffusion within it.

[0027] Fig. Figure 1 represents a motor vehicle 2 powered by an electric motor 4, which draws power from a battery pack 6 with one or more battery modules 8. The battery modules 8 can be connected electrically in series and / or parallel to meet the desired capacity and power requirements of the electric motor 4. The vehicle 2 can be a purely electric vehicle powered exclusively by the electric motor 4, or the vehicle 2 can be a hybrid electric vehicle powered by the electric motor 4 and an internal combustion engine (not shown).

[0028] As in Fig. As shown in Figure 2, each battery module 8 contains one or more electrochemical cells or batteries 10 that cycle lithium ions. In practice, the batteries 10 in the battery module 8 are often assembled as a stack of layers, including negative electrode layers 12, negative electrode current collectors 13, positive electrode layers 14, positive electrode current collectors 15, and separator layers 16. Each battery 10 is defined by a negative electrode layer 12 and a positive electrode layer 14, separated from each other by a separator layer 16. In practice, the separator layer 16 can be infiltrated with an electrolyte that provides a medium for the conduction of lithium ions between the negative electrode layer 12 and the positive electrode layer 14, or the separator layer 16 itself can act as the electrolyte.The layers 12 of the negative electrode are arranged on the current collectors 13 of the negative electrode and are electrically connected to them, and the layers 14 of the positive electrode are arranged on the current collectors 15 of the positive electrode and are electrically connected to them. As in . Fig. As shown in Figure 2, for efficiency reasons the layers can be stacked such that some of the current collectors 13 of the negative electrode and some of the current collectors 15 of the positive electrode are double-sided, with layers 12 of the negative electrode or layers 14 of the positive electrode on each side. In this arrangement, adjacent layers 12 of the negative electrode and layers 14 of the positive electrode each share a single current collector 13 of the negative electrode or a current collector 15 of the positive electrode.

[0029] Fig. Figure 3 represents an electrochemical cell or battery 20 that cycles lithium ions. The battery 20 can generate an electric current during discharge, which can be used to supply power to a consumer device (e.g., the electric motor 4), and can be recharged by connecting it to a power source. Like the batteries 10, which are in Fig. 1 and Fig. As shown in Figure 2, in some cases the battery 20 can be used to supply power to an electric motor 4 of a motor vehicle 2. Additionally or alternatively, the battery 20 can also be used in other transportation applications (e.g., motorcycles, boats, tractors, buses, motorhomes, caravans, tanks, and aircraft) and to power stationary and / or portable electronic devices, components, and equipment used in a wide variety of other industries and applications, such as, but not limited to, industrial, residential, and commercial buildings, consumer goods, industrial plants and machinery, agricultural machinery and equipment, and heavy machinery.

[0030] The battery 20 comprises a negative electrode 22, a positive electrode 24, a separator 26, and an electrolyte 28, which provides a medium for the conduction of lithium ions between the negative electrode 22 and the positive electrode 24. The negative electrode 22 is arranged on a main surface of a current collector 30 of the negative electrode, and the positive electrode 24 is arranged on a main surface of a current collector 32 of the positive electrode. In practice, the current collector 30 of the negative electrode and the current collector 32 of the positive electrode are electrically connected to a power source or a load 34 (e.g., the electric motor 4) via an external circuit 36. The negative electrode 22 and the positive electrode 24 are configured such that an electrochemical potential difference is established between the negative electrode 22 and the positive electrode 24 when the battery 20 is at least partially charged.During the discharge of battery 20, the electrochemical potential that arises between the negative electrode 22 and the positive electrode 24 leads to spontaneous reduction and oxidation reactions (redox reactions) within battery 20 and to the release of lithium ions and electrons from the negative electrode 22. The released lithium ions migrate from the negative electrode 22 to the positive electrode 24 through the separator 26 and the electrolyte 28, while the electrons migrate from the negative electrode 22 to the positive electrode 24 via the external circuit 36, which generates an electric current.Once the lithium in the negative electrode 22 is partially or completely depleted, the battery 20 can be charged by connecting the negative electrode 22 and the positive electrode 24 to the power source 34. This causes non-spontaneous redox reactions within the battery 20 and the release of lithium ions and electrons from the positive electrode 24. The repeated discharging and recharging of the battery 20 can be referred to as "cycling," with one complete charge followed by one complete discharge constituting a full cycle.

[0031] The positive electrode 24 comprises an electroactive material (positive electrode electroactive material) capable of storing and releasing lithium ions by undergoing a reversible redox reaction with lithium at a higher electrochemical potential than that of the negative electrode 22, such that an electrochemical potential difference exists between the negative electrode 22 and the positive electrode 24. The positive electrode electroactive material 24 is particulate, and particles of the positive electrode electroactive material may be mixed with a polymeric binder and optionally an electrically conductive material within the positive electrode 24. The positive electrode 24 may be in the form of a continuous porous layer arranged on the main surface of the current collector 32 of the positive electrode.

[0032] With the following reference to Fig. 4 At least one of the electroactive material particles of the positive electrode 24 is a two-phase single-crystal particle (2P-SC) 40 with a core 42 and a shell 44 surrounding the core 42. The 2P-SC particle 40 comprises a lithium- and manganese-containing oxide; however, the composition and crystal structure of the core 42 differ from that of the shell 44. The 2P-SC particle 40 can have a particle diameter greater than or equal to 0.5 micrometers and less than or equal to 5 micrometers. The at least one 2P-SC particle 40 can constitute more than or equal to 80%, optionally more than or equal to 90%, or optionally more than or equal to 95% and less than or equal to 99% of the positive electrode 24 by weight.

[0033] The core 42 of the 2P-SC particle 40 comprises a lithium-rich, manganese-based transition metal oxide (LRMO) with a layered crystal structure. The LRMO of core 42 has a composition described by the formula Li y Mn x Me 1-x O2 is represented where y is greater than 1, optionally greater than or equal to 1.1, optionally greater than or equal to 1.2 and less than or equal to 1.4, or optionally less than or equal to 1.33; x is greater than 0.5, optionally greater than or equal to 0.6, or optionally greater than or equal to 0.7 and less than 1, optionally less than or equal to 0.9, or optionally less than or equal to 0.8; and Me is a transition metal (e.g., Co, Ni, Fe, Al, V, or a combination thereof). In certain cases, Me may include Ni and / or Co. In some aspects, for example, the LRMO of core 42 may include a lithium nickel manganese oxide (LNMO), represented by the formula Li 1,2 Mn x Ni 1-×O2 is represented where x is greater than 0.5 or optionally greater than or equal to 0.6 and less than 1 or optionally less than or equal to 0.9.

[0034] The shell 44 of the 2P-SC particle 40 comprises a lithium-manganese-based transition metal oxide with a spinel crystal structure (spinel LMO). The spinel LMO of shell 44 can have a composition described by the formula Li(Mn x Me 1-x)2O4 is represented, where x is greater than 0.5, optionally greater than or equal to 0.6 or optionally greater than or equal to 0.7 and less than 1, optionally less than or equal to 0.9 or optionally less than or equal to 0.8, and Me is a transition metal. In some cases, Me may include Ni and / or Co. For example, in some cases, the spinel LMO of shell 44 may include a lithium nickel manganese oxide. The shell 44 of the 2P-SC particles 40 may have a thickness greater than or equal to 1 nanometer and less than or equal to 20 nanometers. The shell 44 of the 2P-SC particle 40 is formed in situ by a controlled surface reconstruction process and not by depositing material onto the core 42. Like the core 42, the shell 44 is not an agglomerate of particles.

[0035] In addition to the 2P-SC particle 40, the electroactive material of the positive electrode 24 can further comprise: a layered lithium transition metal oxide, represented by the formula LiMeO2 and / or Li2MeO3, a layered lithium-rich transition metal oxide, represented by the formula Li 1+x Me 1-xO2 (where 0 < x ≤ 0.33), an olivine-type lithium transition metal oxide represented by the formula LiMePO4, a monoclinic-type lithium transition metal oxide represented by the formula Li3Me2(PO4)3, a spinel-type lithium transition metal oxide represented by the formula LiMe2O4, a tavorite represented by one or both of the following formulas LiMeSO4F or LiMePO4F, or a combination thereof, where Me is a transition metal (e.g., Co, Ni, Mn, Fe, Al, V, or a combination thereof). The electroactive material of the positive electrode 24 can constitute, by weight, more than or equal to 80%, optionally more than or equal to 90%, or optionally more than or equal to 95% and less than or equal to 99% of the positive electrode 24.

[0036] The polymer binder is electrochemically inactive and may be included in the positive electrode 24 to provide structural integrity to the positive electrode 24 and / or to assist the positive electrode 24 in adhering to the main surface of the current collector 32 of the positive electrode. Examples of polymer binders include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), ethylene propylene diene monomer (EPDM) rubber, styrene-butadiene rubber (SBR), carboxymethylcellulose (CMC), nitrile butadiene rubber (NBR), styrene-butadiene rubber (SBR), styrene-ethylene-butylene-styrene copolymer (SEBS), polyacrylates, alginates, polyacrylic acid, and combinations thereof. The polymer binder can constitute, based on weight, more than or equal to 1% or optionally more than or equal to 5% and less than or equal to 10% of the positive electrode 24.

[0037] The optional electrically conductive material is electrochemically inert and can be included in the positive electrode 24 to impart electrical conductivity to the positive electrode 24. Examples of electrically conductive materials include carbon-based materials, metals (e.g., nickel), and / or electrically conductive polymers. Examples of electrically conductive carbon-based materials are carbon black (CB) (e.g., acetylene black), graphite, graphene (e.g., graphene nanoplatelets, GNP), graphene oxide, carbon nanotubes (CNTs), and / or carbon fibers (e.g., carbon nanofibers). Examples of electrically conductive polymers include polyaniline, polythiophene, polyacetylene, and / or polypyrrole.If the optional electrically conductive material is included in the positive electrode 24, it can constitute, based on weight, more than 0%, optionally more than or equal to 1%, or optionally more than or equal to 5% and less than or equal to 10% of the positive electrode 24.

[0038] The negative electrode 22 comprises an electroactive material designed to participate directly in the electrochemical reactions that store and release energy from the battery 20. It can take the form of a continuous porous or non-porous layer of material arranged on a major surface of the current collector 30 of the negative electrode. The electroactive material of the negative electrode 22 can be lithium and / or a material designed to store and release lithium ions by undergoing a reversible redox reaction with lithium during the charging and discharging of the battery 20. Examples of electroactive materials of the negative electrode that can store and release lithium include carbon-based materials (e.g., graphite), silicon, silicon-based materials (e.g., silicon-lithium alloys), and silicon dioxide (SiO₂). x), silicon oxide-based materials (e.g., lithium silicon oxide, LiSiO₂) x ), lithium oxide-based materials (e.g., lithium titanate) and combinations thereof. Like the electroactive material of the positive electrode, the electroactive material of the negative electrode can also be a particulate material, and the particles of the electroactive material of the negative electrode 22 can be mixed with a polymeric binder and optionally an electrically conductive material.

[0039] The separator 26 physically separates the negative electrode 22 and the positive electrode 24 from each other and electrically insulates them while allowing lithium ions to pass through. The separator 26 has an open microporous structure and can comprise an organic and / or inorganic material. For example, the separator 26 can comprise a polymer.

[0040] The electrolyte 28 is ionically conductive and provides a medium for the conduction of lithium ions between the negative electrode 22 and the positive electrode 24. The electrolyte 28 can comprise a non-aqueous aprotic organic solvent and a lithium salt (e.g., LiPF6) in the organic solvent. Non-restrictive examples of non-aqueous aprotic organic solvents are cyclic carbonates (e.g., ethylene carbonate (EC), propylene carbonate (PC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC)), linear carbonates (e.g., dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC)), and combinations thereof.

[0041] The current collector 30 of the negative electrode and the current collector 32 of the positive electrode are electrically conductive, electrochemically inert, and provide an electrical connection between the external circuit 36 ​​and the negative electrode 22 and the positive electrode 24, respectively. The current collector 30 of the negative electrode and the current collector 32 of the positive electrode can each be made of metal or another suitable electrically conductive material. Proceedings

[0042] The 2P-SC particle 40 can be prepared by a cation exchange process followed by calcination with a single-crystal precursor particle. The following description refers to the preparation of a single 2P-SC particle 40 from a single single-crystal precursor particle. However, the procedures described herein can be used to simultaneously prepare a multitude of 2P-SC particles from a multitude of single-crystal precursor particles, as would be apparent to the average person with expertise in the field.

[0043] The precursor particle can have essentially the same composition and crystal structure as the core 42 of the 2P-SC particle 40. For example, the precursor particle can have a layered crystal structure and comprise a lithium-rich manganese-based transition metal oxide (LRMO). The precursor particle can have essentially the same size as the 2P-SC particle 40. For example, the precursor particles can have a particle diameter greater than or equal to 0.5 micrometers and less than or equal to 5 micrometers. In embodiments in which the methods disclosed herein are used to produce a plurality of 2P-SC particles, the plurality of single-crystal precursor particles can have a mean particle diameter greater than or equal to 0.5 micrometers and less than or equal to 5 micrometers.

[0044] LRMO is described as "lithium-rich" because it contains a greater than stoichiometric amount of lithium compared to the amount required for the formula LiMeO₂. The layered crystal structure of LRMO comprises a repeating transition metal layer (TM layer), an oxygen layer (O layer), and a lithium layer (Li layer). The TM layer contains transition metal (Me) ions (e.g., Mn and Ni ions), and the O layer contains oxygen anions (O₂). 2- Since the LRMO contains a stoichiometric excess of Li, the TM layer also includes Li. + -ions.

[0045] A cation exchange process is carried out on the precursor particle by bringing it into contact with an aqueous solution containing a variety of exchangeable cations, such that a portion of the lithium ions in the LRMO in an outer surface region of the precursor particle are removed and replaced by the exchangeable cations. The removal of lithium ions from the LRMO in the outer surface region of the precursor particle alters the chemical composition of the material in this region. Specifically, the removal of lithium ions from the LRMO transforms the LRMO in the outer surface region of the precursor particle into a lithium-poor, manganese-based oxide (LDMO).LDMO is described as "low in lithium" because it contains less than the stoichiometric amount of lithium compared to the amount of lithium required to meet the formula LiMeO2.

[0046] In certain embodiments, the aqueous solution used to carry out the cation exchange process may comprise an aqueous ammonium solution, and the exchangeable cations may be ammonium ions (NH4). + The aqueous ammonium solution may comprise at least one ammonium salt selected from the group consisting of ammonium persulfate, ammonium molybdate, and ammonium phosphate. In other embodiments, the aqueous solution used to carry out the cation exchange process may comprise an aqueous citric acid solution, and the exchangeable cations may be hydrogen (H₂). + include )-ions.

[0047] The aqueous solution is such that it allows an exchange between the cations dissolved in the aqueous solution and the Li + -ions are promoted in the LRMO and the dissolution and / or removal of transition metals from the LRMO during the cation exchange process is prevented or inhibited. Preventing or inhibiting the dissolution and / or removal of transition metals from the LRMO during the cation exchange process can contribute to the 2P-SC particle 40 having a single-crystal structure and consisting essentially or entirely of two phases: the layered LRMO in the core 42 and the spinel LMO in the shell 44.

[0048] For example, the ammonium salts contained in the aqueous ammonium solution are preferably selected such that Li is produced during the cation exchange process. +-ions are effectively removed from the crystal structure of the LRMO in the outer surface section of the precursor particle without removing transition metals (e.g., Mn and / or Ni). Furthermore, the ammonium salts contained in the aqueous ammonium solution are preferably selected such that Li is released during the cation exchange process. + -ions are extracted only from the outer surface section of the precursor particle and not from a remaining main part of the precursor particle.

[0049] The amount of exchangeable cations in the aqueous solution can be selected based on the amount of precursor particles in the aqueous solution and modified and / or adjusted based on the cation exchange rate in the aqueous solution. Furthermore, the amount of exchangeable cations in the aqueous solution can be chosen to achieve a desired balance between increasing the coulombic efficiency of the first cycle of battery 20 due to the formation of the spinel LMO and reducing the cycle life of battery 20 due to the removal of active lithium from the LRMO.In some cases, the amount of exchangeable cations in the aqueous solution, relative to the amount of precursor particle in the aqueous solution, may be greater than or equal to 0.1 millimoles (mmol), optionally greater than or equal to 0.5 mmol, or optionally greater than or equal to 0.8 mmol and less than or equal to 2 mmol, optionally less than or equal to 1.5 mmol, or optionally less than or equal to 1.2 mmol per gram of precursor particle in the aqueous solution. For example, in some cases where the aqueous solution includes an aqueous ammonium solution, the moles of NH4 may be greater than or equal to 0.1 millimoles (mmol). + -Ions in the aqueous solution in relation to the grams of precursor particle in the aqueous solution greater than or equal to 0.1 mmol, optionally greater than or equal to 0.5 mmol or optionally greater than or equal to 0.8 mmol and less than or equal to 2 mmol, optionally less than or equal to 1.5 mmol or optionally less than or equal to 1.2 mmol per gram of precursor particle in the aqueous solution.

[0050] In some cases, the concentration of the precursor particle in the aqueous solution, based on weight, can be greater than or equal to 0.1%, optionally greater than or equal to 0.5%, or optionally greater than or equal to 1% and less than or equal to 50%, optionally less than or equal to 10%, or optionally less than or equal to 5%, based on the total weight of the aqueous solution. This can mean that the concentration of exchangeable cations in the aqueous solution is greater than or equal to 0.5 millimolar (mM), optionally greater than or equal to 1 mM, optionally greater than or equal to 2 mM, or optionally greater than or equal to 5 mM and less than or equal to 20 mM, optionally less than or equal to 15 mM, or optionally less than or equal to 10 mM.

[0051] During the cation exchange process, the precursor particle is brought into contact with the aqueous solution containing the exchangeable cations at a temperature greater than or equal to 50 degrees Celsius (°C) and less than or equal to 100 °C for a duration of more than or equal to 2 hours and less than or equal to 24 hours. In some cases, the cation exchange process can be carried out at a temperature of approximately 80 °C for about 15 hours.

[0052] In some cases, the cation exchange process can be carried out as a batch process, and the precursor particles and the aqueous solution can be mixed during the cation exchange process, e.g., in a stirred tank reactor. Additionally or alternatively, the cation exchange process can be carried out as a continuous process, and the precursor particles can be in contact with a stream of the aqueous solution, e.g., in a fixed-bed reactor.

[0053] After completion of the cation exchange process, the precursor particle can be separated from the aqueous solution, e.g. by filtration, and washed with water or with an additional amount of the aqueous solution.

[0054] After the precursor particle is separated from the aqueous solution, it undergoes a calcination process to form the 2P-SC particle 40. During the calcination process, the precursor particle is heated to such an extent that the LDMO in the outer surface region of the precursor particle undergoes a phase transition and is converted into a lithium-manganese-based transition metal oxide with a spinel crystal structure (spinel LMO), thus forming the 2P-SC particle 40. In the 2P-SC particle 40, the core 42 is defined by a remaining portion of the LDMO, and the shell 44 by the spinel LMO. The phase transition that occurs in the outer surface region of the precursor particle during the calcination process is triggered by the lithium deficiency in the LDMO.During the calcination process, the precursor particle is heated in air at a temperature greater than or equal to 400 °C and less than or equal to 700 °C for a duration of 1 hour to 24 hours.

[0055] Although the calcination process transforms the structure of the oxide material in the outer surface region of the precursor particle from a layered structure to a spinel structure, the precursor particle itself is not transformed into a polycrystalline material by the calcination process. The resulting 2P-SC particle 40 is a single-crystal particle with two phases: a layered phase in the core 42 and a spinel phase in the shell 44.

[0056] After completion of the calcination process, the 2P-SC particles 40 can be used as electroactive positive electrode materials in batteries that cycle lithium ions, such as the battery 20. Positive electrodes containing the 2P-SC particles 40 can be produced by mixing the 2P-SC particles 40 with a polymer binder, optionally an electrically conductive material, and a solvent to form a slurry, applying the slurry to a substrate and then removing the solvent. Try

[0057] In the example, 2P-SC particles were produced using single-crystal particles of lithium-rich manganese-based transition metal oxide (SC-LRMO) with a layered crystal structure and a composition of the formula Li 1,2 Mn x Ni1. x O2 is produced, where x≈0.7. Fig. Figure 5 is a scanning electron micrograph of a variety of SC-LRMO particles, taken prior to the performance of the following experiments.

[0058] Six different aqueous ammonium solutions were prepared by dissolving ammonium persulfate ((NH4)2S2O8, MW=228.2 g / mol) (APS) or ammonium molybdate ((NH4)2MoO4, MW=1163.9 g / mol) (AMB) in water. The concentration of ammonium ions (NH4) + The concentration in each of the aqueous ammonium solutions thus prepared is listed in Table 1 below. Table 1. Lös.Nr. Wasser(mL) APS(g) AMB(g) mmol NH4 + pro Liter(mM) 1 300 0,06 - 1,75 2 300 0,3 - 8,76 3 300 0,6 - 17,53 4 300 - 0,06 1,03 5 300 - 0,3 5,16 6 300 - 0,6 10,31

[0059] Three grams of the SC-LRMO particles were added to each of the aqueous ammonium solutions thus prepared to produce NH4 + To form / SC-LRMO mixtures. Details on the formulations of NH4 + / SC-LRMO mixtures are listed in Table 2 below. Table 2. Gemisch Nr. Wasser (mL) SC-LRMO (g) APS(g) AMB(g) g APS / g SC-LRMO(%) g AMB / g SC-LRMO (%) mmolNH4 + / gSC-LRMO 1 300 3 0,06 - 2 - 0,18 2 300 3 0,3 - 10 - 0,88 3 300 3 0,6 - 20 - 1,75 4 300 3 - 0,06 - 2 0,10 5 300 3 - 0,3 - 10 0,52 6 300 3 - 0,6 - 20 1,03

[0060] The NH4 +SC-LRMO mixtures were stirred in a stirred tank reactor at a temperature of about 80 °C for a duration of about 15 hours to induce an ion exchange between the lithium ions in an outer surface section of the SC-LRMO particles and the NH4 + to effect the formation of ions in the ammonium solutions. After completion of the ion exchange process, the SC-LRMO particles were separated from their respective ammonium solutions by filtration and washed with water to remove byproducts of the ion exchange process. The ion-exchanged SC-LRMO particles were calcined in air at a temperature of approximately 450 °C for about 2 hours to form 2P-SC particles.

[0061] Fig. Figure 6 is a scanning electron microscope image of 2P-SC particles taken using NH4 + / SC-LRMO mixture no. 6 (1.03 mmol NH4 + / g SC-LRMO) were formed for the ion exchange process. Fig. Figure 7 is a scanning electron micrograph of 2P-SC particles taken using NH4 + / SC-LRMO mixture no. 3 (1.75 mmol NH4 + / g SC-LRMO) were formed for the ion exchange process. As shown, the ion exchange and calcination had no visible effect on the surface morphology of the 2P-SC particles compared to that of the SC-LRMO particles, suggesting that the layer-to-spinel transformation only takes place in some surface layers of the particles.

[0062] Positive electrodes were fabricated using the 2P-SC particles thus formed as electroactive materials. The 2P-SC particles used to fabricate the positive electrodes were derived from NH4. + / SC-LRMO mixtures No. 1, 2, 3, 4, and 5 were prepared for the ion exchange process. For comparison, positive electrodes were also prepared using SC-LRMO particles as the electroactive materials. The positive electrodes were prepared by mixing the SC-LRMO particles or the 2P-SC particles with a polymeric binder, an electrically conductive material, and a solvent to form a slurry, applying the slurry to a substrate, and then removing the solvent. The positive electrodes thus prepared were assembled into half-cells and investigated by cyclic voltammetry. The half-cells contained an electrolyte consisting of 1.2 molar LiPF6 in a mixture of FEC and DEC (FEC:DEC = 1:4 vol / vol) with 1 wt% bis(trimethylsilyl)phosphite and lithium metal as the counter electrode.

[0063] During the first formation cycle, the cells were charged to 4.6 V at a C / 20 rate and then discharged to 2.0 V at a C / 20 rate. Fig. Figure 8 is a diagram of the differential capacity, dQ / dV, (mAh / V) 100 versus the voltage (V versus Li / Li+) 200 for the first formation cycle of: (i) a cell containing SC-LRMO particles as electroactive materials (solid line) and (ii) a cell containing 2P-SC particles using NH4 + / SC-LRMO mixture no. 5 for the ion exchange process were formed (dashed line). How best to in Fig. Figure 9 shows that the local minimum at about 2.75 volts in the dQ / dV curve for the cell with the 2P-SC particles (dashed line) is evidence for the formation of the spinel LMO phase in the shells of the 2P-SC particles.

[0064] Fig. Figure 10 is a diagram of the Coulomb efficiency 300 (%) against the relative ammonium content 400 (mmol NH4). + / g SC-LRMO) for the first formation cycle of: (i) cells containing 2P-SC particles produced using NH4 + (1) / SC-LRMO mixtures No. 1, 2 and 3 were formed for the ion exchange process (solid line) and (ii) cells containing 2P-SC particles formed using the NH4 + / SC-LRMO mixtures No. 4 and 5 were formed for the ion exchange process (dashed line).

[0065] The terminology used herein serves only to describe exemplary embodiments and is not to be understood as restrictive. As used herein, the singular forms "a," "an," and "the" can also include the plural forms unless the context clearly indicates otherwise. The terms "includes," "comprehensive," "contain," and "exhibit" are inclusive and therefore specify the presence of specified features, elements, compositions, steps, integers, processes, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, processes, elements, components, and / or groups thereof.Although the open terms "comprises," "comprising," "including," and "having" are to be understood as non-restrictive terms used to describe and claim various embodiments set forth herein, in some cases these terms may alternatively be understood as more restrictive terms, such as "consisting of" or "essentially consisting of." Therefore, for each given embodiment that specifies compositions, materials, components, elements, ingredients, features, integers, operations, and / or process steps, the present disclosure expressly includes embodiments that consist of, or essentially consist of, such specified compositions, materials, components, elements, ingredients, features, integers, operations, and / or process steps.In the case of "consisting of", the alternative embodiment excludes all additional compositions, materials, components, elements, ingredients, features, integers, operations and / or process steps, whereas in the case of "essentially consisting of", all additional compositions, materials, components, elements, ingredients, features, integers, operations and / or process steps that significantly affect the basic and novel properties are excluded from such an embodiment, but all compositions, materials, components, elements, ingredients, features, integers, operations and / or process steps that do not significantly affect the basic and novel properties may be included in the embodiment.

[0066] As used here, the expression “A, B and / or C” should be interpreted using a non-exclusive logical “OR” conjunction as logical (A OR-connected with B OR-connected with C), and not as “at least one of A, at least one of B and at least one of C”.

[0067] As used herein, the terms “composition” and “material” are used interchangeably to refer generally to a substance containing at least the preferred chemical constituents, elements, or compounds, but which may also include additional elements, compounds, or substances, including trace impurities, unless otherwise specified. An “X-based” composition or “X-based” material generally refers to compositions or materials in which “X” is the largest single constituent of the composition or material by weight percent (%). This may include compositions or materials with a weight percentage of X greater than 50% as well as compositions or materials with a weight percentage of X less than 50%, as long as X is the largest single constituent of the composition or material by weight.When a composition or material is described as “essentially free” from a substance, the composition or material may contain less than 5%, optionally less than 3%, optionally less than 1%, or optionally less than 0.1% of the substance.

Claims

[1] Method for producing a positive electrode for a lithium ion cycling battery, comprising: Contacting a single-crystal precursor particle comprising a lithium-rich manganese-based transition metal oxide (LRMO) with a layered crystal structure with an aqueous ammonium solution containing ammonium (NH4). + )-ions, such that lithium ions are removed from an outer surface section of the precursor particle and the LRMO in the outer surface section of the precursor particle is converted into a lithium-poor manganese-based oxide (LDMO), wherein the contact between the precursor particle and the aqueous ammonium solution is carried out at a temperature greater than or equal to 50 degrees Celsius and less than or equal to 100 degrees Celsius for a duration of more than or equal to 2 hours and less than or equal to 24 hours; and Heating the precursor particle such that the LDMO in the outer surface section of the precursor particle undergoes a phase transition and is transformed into a lithium manganese-based transition metal oxide with a spinel crystal structure (spinel-LMO), thereby forming a two-phase single-crystal particle (2P-SC) with a core and a shell surrounding the core, wherein the core is defined by a remaining section of the LRMO in the precursor particle and the shell is defined by the spinel-LMO. wherein the precursor particle is heated to a temperature greater than or equal to 400 degrees Celsius and less than or equal to 700 degrees Celsius for a duration of more than or equal to 1 hour and less than or equal to 24 hours. [2] Method according to claim 1, wherein the aqueous ammonium solution comprises at least one ammonium salt selected from the group consisting of ammonium persulfate, ammonium molybdate and ammonium phosphate. [3] Method according to claim 1, wherein the amount of NH4 + -ions in the aqueous ammonium solution in relation to the amount of LRMO in the aqueous ammonium solution greater than or equal to 0.1 millimoles of NH4 + per gram of LRMO and less than or equal to 2 millimoles of NH4 + per gram of LRMO. [4] Method according to claim 1, wherein The LRMO has a composition that can be described by the formula Li y Mn x Me 1-x O2 is represented, where: y is greater than 1 and less than or equal to 1.4, x is greater than 0.5 and less than 1, and Me Ni, Co or a combination thereof includes; and The spinel LMO has a composition that can be described by the formula Li(Mn x Me 1-x )2O4 is represented, where: x is greater than 0.5 and less than 1, and Me Ni, Co or a combination thereof. [5] The method of claim 1, wherein the LRMO has a composition defined by the formula Li 1,2 Mn x Ni 1-× O2 is represented, where x is greater than or equal to 0.6 and less than or equal to 0.

9. [6] Method according to claim 1, wherein the 2P-SC particle has a particle diameter greater than or equal to 0.5 micrometers and less than or equal to 5 micrometers. [7] Method according to claim 6, wherein the shell has a thickness greater than or equal to 1 nanometer and less than or equal to 20 nanometers. [8] Method according to claim 1, further comprising: Mixing the 2P-SC particles with a polymeric binder, optionally an electrically conductive material and a solvent to form a slurry; Applying the slurry to a substrate; and Removing the solvent from the slurry.

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