Composite negative electrode material and electrochemical cell comprising the same

Abstract

Composite negative electrode materials and electrochemical cells containing the same are disclosed. A negative electrode for an electrochemical cell for cycling lithium ions includes a particulate component embedded in a polymeric matrix component, the polymeric matrix component including polytetrafluoroethylene. The particulate component includes a plurality of composite material particles, wherein each of the composite material particles has a core and a selective barrier layer disposed on a surface of the core. The core of each of the composite material particles includes an electroactive negative electrode material. The selective barrier layer of each of the composite material particles is formulated to prevent or inhibit an electrochemical reaction between lithium stored in the electroactive negative electrode material of the core and the polytetrafluoroethylene in the polymeric matrix component.

Description

Technical Field

[0001] This invention relates to composite negative electrode materials and electrochemical cells containing the same. Background Technology

[0002] This section provides background information relating to this disclosure, which is not necessarily prior art.

[0003] This disclosure relates to electrodes for secondary lithium-ion battery packs, and more specifically to composite negative electrodes comprising electrochemically active material particles embedded in a polymer binder.

[0004] A battery pack typically comprises one or more electrochemical cells that convert chemical energy into electrical energy through electrochemical reduction-oxidation (redox) reactions. In secondary or rechargeable battery packs, these electrochemical reactions are reversible, allowing the pack to undergo multiple charge and discharge cycles.

[0005] A secondary lithium-ion battery pack's electrochemical cell includes a negative electrode, a positive electrode, and an electrolyte that provides the medium for lithium-ion conduction between the negative and positive electrodes. A porous polymer separator is typically sandwiched between the negative and positive electrodes, physically separating and electrically isolating them from each other within the electrochemical cell. Externally, the negative and positive electrodes are electrically connected to each other via an external circuit. The negative and positive electrodes are configured such that an electrochemical potential is established between them when the electrochemical cell is at least partially charged. During discharge, the electrochemical potential established between the negative and positive electrodes drives spontaneous redox reactions within the cell and the release of lithium ions and electrons at the negative electrode. Lithium ions released from the negative electrode diffuse through the electrolyte to the positive electrode, while electrons simultaneously travel from the negative electrode to the positive electrode via the external circuit, generating a current. After the negative electrode has been partially or completely depleted of lithium, the electrochemical cell can be recharged by connecting both the negative and positive electrodes to an external power source, which drives non-spontaneous redox reactions within the cell and the release of lithium ions and electrons from the positive electrode.

[0006] In practice, the electrochemical cells of secondary lithium-ion battery packs are typically assembled into a stack of layers, where each of the negative and positive electrodes is deposited as a thin porous layer on a metal current collector. The negative and positive electrode layers can exhibit a composite structure containing a mixture of electrochemically active material particles embedded in a polymer binder. Summary of the Invention

[0007] This section provides a general overview of this disclosure and is not a full disclosure of its entire scope or all its features.

[0008] This disclosure relates to a negative electrode for an electrochemical battery used in cycling lithium-ion batteries. The negative electrode comprises a polymer matrix component and a particulate component embedded in the polymer matrix component. The polymer matrix component comprises polytetrafluoroethylene (PTFE). The particulate component comprises a plurality of composite material particles, each of which has a core and a selective barrier layer disposed on the surface of the core. The core of each of the composite material particles comprises an electroactive negative electrode material. The selective barrier layer of each of the composite material particles is formulated to prevent or inhibit electrochemical reactions between lithium stored in the electroactive negative electrode material of the core and the PTFE in the polymer matrix component.

[0009] The selective barrier layer may comprise polymer-based materials, ceramic-based materials, nitride-based materials, halide-based materials, borate-based materials, or combinations thereof.

[0010] In some aspects, the selective barrier layer may comprise poly(acrylonitrile), poly(ethylene oxide), poly(ethylene glycol), polyethylene carbonate, poly(trimethylene carbonate), poly(propylene carbonate), polyvinylidene fluoride-copolymer-hexafluoropropylene, or combinations thereof.

[0011] In some aspects, the selective barrier layer may comprise garnet-type lithium, lanthanum, and zirconium oxides; perovskite-type lithium oxides; lithium-containing nitride-based materials; lithium-containing halide-based materials; lithium-containing borate-based materials; or combinations thereof.

[0012] For each of the composite material particles, the selective barrier layer may constitute greater than or equal to about 0.01% by weight to less than or equal to about 10% by weight of the composite material particles.

[0013] In some respects, the selective barrier layer may be disposed on the surface of the core in the form of a discontinuous layer that does not completely encapsulate the core.

[0014] In some respects, the selective barrier layer may be disposed on the surface of the core in the form of a continuous layer that completely encapsulates the core.

[0015] The electroactive negative electrode material in the core of each of the composite material particles may include at least one of silicon, tin, carbon, metal oxides, or metal sulfides.

[0016] The polymer matrix component may constitute a negative electrode at a rate of greater than or equal to about 0.5% by weight and less than or equal to about 10% by weight.

[0017] The polymer matrix component may contain more than or equal to about 90% by weight of polytetrafluoroethylene.

[0018] The particulate component may also contain multiple electrochemically inert conductive particles.

[0019] An electrochemical battery for cycling lithium ions is disclosed. The electrochemical battery includes a positive electrode, a negative electrode physically spaced apart from the positive electrode, and a non-aqueous electrolyte providing an ion conduction pathway for lithium ion transport between the positive and negative electrodes. The negative electrode comprises a polymer matrix component and a particulate component embedded in the polymer matrix component. The polymer matrix component comprises polytetrafluoroethylene (PTFE), and the particulate component comprises a plurality of composite material particles. Each of the composite material particles has a core and a selective barrier layer disposed on the surface of the core. The core of each of the composite material particles contains an electroactive negative electrode material. The selective barrier layer of each of the composite material particles is formulated to prevent or inhibit electrochemical reactions between lithium stored in the electroactive negative electrode material in the core and the PTFE in the polymer matrix component.

[0020] The selective barrier layer may comprise polymer-based materials, ceramic-based materials, nitride-based materials, halide-based materials, borate-based materials, or combinations thereof.

[0021] For each of the composite material particles, the selective barrier layer may constitute greater than or equal to about 0.01% by weight to less than or equal to about 10% by weight of the composite material particles.

[0022] In some respects, the selective barrier layer may be disposed on the surface of the core in the form of a discontinuous layer that does not completely encapsulate the core.

[0023] In some respects, the selective barrier layer may be disposed on the surface of the core in the form of a continuous layer that completely encapsulates the core.

[0024] The electroactive negative electrode material in the core of each of the composite material particles may include at least one of silicon, tin, carbon, metal oxides, or metal sulfides.

[0025] For each of the composite material particles, the electroactive negative electrode material may constitute greater than or equal to about 90% by weight of the core.

[0026] The polymer matrix component may contain more than or equal to about 90% by weight of polytetrafluoroethylene.

[0027] The polymer matrix component may constitute a negative electrode at a rate of greater than or equal to about 0.5% by weight and less than or equal to about 10% by weight.

[0028] The electrochemical cell may further include a porous separator disposed between the negative electrode and the positive electrode, a negative electrode current collector having a main surface, and a positive electrode current collector having a main surface. The negative electrode may be disposed on the main surface of the negative electrode current collector, and the positive electrode may be disposed on the main surface of the positive electrode current collector.

[0029] The positive electrode may contain an electrochemically active material that can undergo a reversible redox reaction with lithium at a higher electrochemical potential than that of the electrochemically active negative electrode material in the core of each of the composite material particles.

[0030] The present invention discloses the following embodiments.

[0031] 1. A negative electrode for an electrochemical cell used in cycling lithium ions, said negative electrode comprising: Polymer matrix component containing polytetrafluoroethylene; and The particulate component embedded in the polymer matrix component comprises a plurality of composite material particles, each of which has a core and a selective barrier layer disposed on the surface of the core. The core of each of the composite material particles contains an electroactive negative electrode material, and The selective barrier layer of each of the composite material particles is formulated to prevent or inhibit the electrochemical reaction between lithium stored in the electroactive negative electrode material of the core and polytetrafluoroethylene in the polymer matrix component.

[0032] 2. The negative electrode according to embodiment 1, wherein the selective barrier layer comprises a polymer-based material, a ceramic-based material, a nitride-based material, a halide-based material, a borate-based material, or a combination thereof.

[0033] 3. The negative electrode according to embodiment 1, wherein the selective barrier layer comprises poly(acrylonitrile), poly(ethylene oxide), poly(ethylene glycol), polyethylene carbonate, poly(trimethylene carbonate), poly(propylene carbonate), polyvinylidene fluoride-copolymer-hexafluoropropylene, or a combination thereof.

[0034] 4. The negative electrode according to embodiment 1, wherein the selective barrier layer comprises a garnet-type lithium, lanthanum and zirconium oxide; a perovskite-type lithium oxide; a lithium-containing nitride-based material; a lithium-containing halide-based material; a lithium-containing borate-based material; or a combination thereof.

[0035] 5. The negative electrode according to embodiment 1, wherein for each of the composite material particles, the selective barrier layer constitutes a composite material particle of greater than or equal to about 0.01% by weight and less than or equal to about 10% by weight.

[0036] 6. The negative electrode according to embodiment 1, wherein for each of the composite material particles, the selective barrier layer is disposed on the surface of the core in the form of a discontinuous layer that does not completely encapsulate the core.

[0037] 7. The negative electrode according to embodiment 1, wherein for each of the composite material particles, the selective barrier layer is disposed on the surface of the core in the form of a continuous layer that completely encapsulates the core.

[0038] 8. The negative electrode according to embodiment 1, wherein the electroactive negative electrode material in the core of each of the composite material particles comprises at least one of silicon, tin, carbon, metal oxide or metal sulfide.

[0039] 9. The negative electrode according to embodiment 1, wherein the polymer matrix component constitutes a negative electrode of greater than or equal to about 0.5% by weight and less than or equal to about 10% by weight.

[0040] 10. The negative electrode according to embodiment 1, wherein the polymer matrix component comprises more than or equal to about 90% by weight of polytetrafluoroethylene.

[0041] 11. The negative electrode according to embodiment 1, wherein the particulate component further comprises a plurality of electrochemically inert conductive particles.

[0042] 12. An electrochemical battery for cycling lithium ions, said electrochemical battery comprising: Positive electrode; A negative electrode physically spaced apart from the positive electrode; and A non-aqueous electrolyte that provides an ion conduction path for lithium-ion transport between the positive and negative electrodes. The negative electrode comprises a polymer matrix component and a particulate component embedded in the polymer matrix component. The polymer matrix component comprises polytetrafluoroethylene (PTFE), and the particulate component comprises a plurality of composite material particles, each of which has a core and a selective barrier layer disposed on the surface of the core. The core of each of the composite material particles contains an electroactive negative electrode material, and The selective barrier layer of each of the composite material particles is formulated to prevent or inhibit the electrochemical reaction between lithium stored in the electroactive negative electrode material of the core and polytetrafluoroethylene in the polymer matrix component.

[0043] 13. The electrochemical battery according to embodiment 12, wherein the selective barrier layer comprises a polymer-based material, a ceramic-based material, a nitride-based material, a halide-based material, a borate-based material, or a combination thereof.

[0044] 14. The electrochemical cell according to embodiment 13, wherein for each of the composite material particles, the selective barrier layer constitutes a composite material particle of greater than or equal to about 0.01% by weight and less than or equal to about 10% by weight.

[0045] 15. The electrochemical cell according to embodiment 12, wherein for each of the composite material particles, the selective barrier layer is disposed on the surface of the core in the form of a discontinuous layer that does not completely encapsulate the core.

[0046] 16. The electrochemical cell according to embodiment 12, wherein for each of the composite material particles, the selective barrier layer is disposed on the surface of the core in the form of a continuous layer that completely encapsulates the core.

[0047] 17. The electrochemical battery according to embodiment 12, wherein the electroactive negative electrode material in the core of each of the composite material particles comprises at least one of silicon, tin, carbon, metal oxide or metal sulfide, and wherein for each of the composite material particles, the electroactive negative electrode material constitutes more than or equal to about 90% by weight of the core.

[0048] 18. The electrochemical cell according to embodiment 12, wherein the polymer matrix component comprises greater than or equal to about 90% by weight of polytetrafluoroethylene, and wherein the polymer matrix component constitutes greater than or equal to about 0.5% by weight to less than or equal to about 10% by weight of the negative electrode.

[0049] 19. The electrochemical cell according to embodiment 12 further includes: A porous insulating member disposed between the negative electrode and the positive electrode; Negative electrode current collector with main surface; and Positive electrode current collector with main surface, The negative electrode is disposed on the main surface of the negative electrode current collector, and the positive electrode is disposed on the main surface of the positive electrode current collector.

[0050] 20. The electrochemical battery according to embodiment 12, wherein the positive electrode comprises an electrochemically active material that can undergo a reversible redox reaction with lithium at a higher electrochemical potential than that of the electrochemically active negative electrode material in the core of each of the composite material particles.

[0051] Further applicability will become apparent from the description provided herein. The descriptions and specific examples in this invention are intended for illustrative purposes only and are not intended to limit the scope of this disclosure. Attached Figure Description

[0052] The accompanying drawings described herein are for illustrative purposes only for selected embodiments and not all possible implementations, and are not intended to limit the scope of this disclosure.

[0053] Figure 1 This is a schematic side cross-sectional view of the electrochemical cell of a secondary lithium-ion battery pack, wherein the negative electrode of the electrochemical cell comprises a polymer matrix component and a plurality of composite material particles embedded in the polymer matrix component, and wherein each of the composite material particles has a core-shell structure defined by a core and a selective barrier layer disposed on the surface of the core.

[0054] Figure 2 yes Figure 1 A schematic cross-sectional view of one of the composite material particles, depicting a core and a selective barrier layer, wherein the selective barrier layer is in the form of a basic continuous layer that completely encapsulates the core.

[0055] Figure 3 This is a schematic cross-sectional view of another composite material particle having a core-shell structure defined by a core and a selective barrier layer disposed on the surface of the core, wherein the selective barrier layer is in the form of a discontinuous layer extending on and surrounding the core but not completely enclosing the core.

[0056] Several views are shown throughout the accompanying drawings, with corresponding reference numerals indicating the respective parts. Detailed Implementation

[0057] Exemplary embodiments are provided to make this disclosure thorough and to fully convey the scope to those skilled in the art. Numerous specific details, such as examples of specific compositions, components, apparatuses, and methods, are set forth to provide a thorough understanding of embodiments of this disclosure. It will be apparent to those skilled in the art that specific details are not required, that exemplary embodiments may be embodied in many different forms, and that none of them should be construed as limiting the scope of this disclosure. In some exemplary embodiments, well-known methods, well-known apparatus structures, and well-known techniques are not described in detail.

[0058] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” as used herein are intended to include the plural forms as well. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore specify the presence of the stated features, elements, compositions, steps, integers, operations, and / or components, but do not exclude the presence or inclusion of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. While the open-ended term “comprising” should be understood as a non-limiting term used to describe and claim the various embodiments described herein, in some respects it may be alternatively understood as a more restrictive and binding term, such as “consisting of” or “substantially consisting of.” Thus, for any given embodiment recounting compositions, materials, components, elements, features, integers, operations, and / or process steps, this disclosure also specifically includes embodiments consisting of or substantially consisting of such recounted compositions, materials, components, elements, features, integers, operations, and / or process steps. In the case of “consisting of…”, the alternative embodiments exclude any additional compositions, materials, components, elements, features, integers, operations and / or process steps, while in the case of “essentially composed of…”, any additional compositions, materials, components, elements, features, integers, operations and / or process steps that substantially affect the essential and novel characteristics are excluded from such embodiments, but such embodiments may include any compositions, materials, components, elements, features, integers, operations and / or process steps that do not substantially affect the essential and novel characteristics.

[0059] Any methods, procedures, and operations described herein should not be construed as requiring them to be performed in the order discussed or illustrated, unless expressly specified otherwise. It should also be understood that additional or alternative steps may be used unless otherwise stated.

[0060] When a component, element, or layer is referred to as being "located on," "engaged to," "connected to," or "coupled to" another element or layer, it may be directly located on, engaged to, connected to, or coupled to that other component, element, or layer, or there may be intermediate elements or layers present. In contrast, when an element is referred to as being "directly located on," "directly engaged to," "directly connected to," or "directly coupled to" another element or layer, there may be no intermediate elements or layers present. Other terms used to describe relationships between elements should be interpreted in a similar manner (e.g., "between" vs. "directly between," "adjacent" vs. "directly adjacent," etc.). As used herein, the term "and / or" includes combinations of one or more of the relevant enumerations.

[0061] Although the terms first, second, third, etc., may be used herein to describe various steps, elements, components, regions, layers, and / or sections, these steps, elements, components, regions, layers, and / or sections should not be limited by these terms unless otherwise specified. These terms may be used only to distinguish one step, element, component, region, layer, or section from another. Unless the context clearly indicates otherwise, terms such as “first,” “second,” and other numerical terms used herein do not imply order or sequence. Therefore, a first step, element, component, region, layer, or section discussed below may be referred to as a second step, element, component, region, layer, or section without departing from the teachings of the exemplary embodiments.

[0062] For ease of description, spatially or temporally relative terms such as “before,” “after,” “inside,” “outside,” “below,” “below,” “lower,” “above,” “upper,” etc., may be used herein to describe the relationship of one element or feature as shown in the accompanying drawings to other elements or features(s). In addition to the orientations depicted in the accompanying drawings, spatially or temporally relative terms may be intended to cover different orientations of the apparatus or system in use or operation.

[0063] Throughout this disclosure, numerical values ​​represent approximate measurements or range limits and encompass minor deviations from a given value and embodiments having approximately the mentioned value as well as embodiments having the exact mentioned value. Except for the working examples provided at the end of the detailed description, all numerical values ​​of parameters (e.g., quantities or conditions) in this specification (including the appended claims) should be understood to be modified in all cases by the term “about,” regardless of whether “about” actually precedes the numerical value. “About” means that the numerical value allows for a certain degree of slight imprecision (approaching the exact value to a certain extent; approximating the value roughly or reasonably; almost). If the imprecision provided by “about” is not otherwise understood in the art in this ordinary sense, then “about” as used herein refers to a deviation that is at least likely to result from common methods of measuring and using such parameters. For example, “about” may include deviations of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in some respects optionally less than or equal to 0.1%.

[0064] In addition, the disclosure of the range includes the disclosure of all values ​​within the entire range and the disclosure of further subdivisions of the range, including the endpoints and subranges given for that range.

[0065] Unless otherwise specified, as used herein, the terms “composition” and “material” are used interchangeably to refer generally to a substance containing at least preferred chemical components, elements, or compounds, but may also contain additional elements, compounds, or substances, including trace impurities. “X-based” composition or material generally refers to a composition or material in which “X” is the single largest component based on weight percentage (%). This can include compositions or materials having more than 50% by weight X, and compositions or materials having less than 50% by weight X, provided that X is the single largest component of the composition or material.

[0066] Exemplary embodiments will now be described more fully with reference to the accompanying drawings.

[0067] This disclosure relates to the negative electrode of a secondary lithium-ion battery pack, exhibiting a composite structure comprising a particulate component embedded in and dispersed throughout a polymer matrix component. The polymer matrix component contains a polytetrafluoroethylene (PTFE) binder. The particulate component comprises a plurality of composite material particles having a core-shell structure defined by a core and a selective barrier layer disposed on the surface of the core. The core of each composite material particle contains an electroactive negative electrode material. The selective barrier layer extends around the core of each composite material particle and is formulated to prevent or inhibit electrochemical reactions between lithium stored in the electroactive negative electrode material in the core and the PTFE binder in the polymer matrix component. The selective barrier layer helps prevent the loss of active lithium during battery pack cycling, which could otherwise occur due to parasitic reactions between lithium stored in the core of the composite material particle and the surrounding PTFE binder in the polymer matrix component.

[0068] Figure 1 An electrochemical cell 10 is depicted that can be included in a battery pack for cycling lithium-ion batteries (e.g., a secondary lithium-ion battery pack). The electrochemical cell 10 includes a negative electrode 12, a positive electrode 14, a porous separator 16 disposed between the negative electrode 12 and the positive electrode 14, and an ion-conducting electrolyte 18 that wets the negative electrode 12, the positive electrode 14, and the porous separator 16. The negative electrode 12 is disposed on the main surface of a negative electrode current collector 20, and the positive electrode 14 is disposed on the main surface of a positive electrode current collector 22. In practice, the negative electrode current collector 20 and the positive electrode current collector 22 can be electrically connected to a load or an external power source 24 via an external circuit 26.

[0069] Electrochemical battery 10 can be used as a secondary lithium-ion battery pack for vehicle or automotive transportation applications (e.g., motorcycles, boats, tractors, buses, motorcycles, mobile homes, campervans, and tanks), as well as a wide variety of other industrial and applications. As non-limiting examples, these include aerospace components, consumer products, devices, buildings (e.g., houses, offices, factories, and warehouses), office equipment and furniture, as well as industrial equipment machinery, agricultural or farm equipment, or heavy machinery. In some respects, electrochemical battery 10 can be used as a secondary lithium-ion battery pack for hybrid electric vehicles (HEVs) and / or electric vehicles (EVs).

[0070] The negative electrode 12 and the positive electrode 14 are configured such that an electrochemical potential difference is established between the negative electrode 12 and the positive electrode 14 when the electrochemical cell 10 is at least partially charged. During the discharge of the electrochemical cell 10, the electrochemical potential established between the negative electrode 12 and the positive electrode 14 drives a spontaneous redox reaction within the electrochemical cell 10 and releases lithium ions and electrons at the negative electrode 12. The released lithium ions travel from the negative electrode 12 through the porous separator 16 and the ion-conducting electrolyte 18 to the positive electrode 14, and electrons travel from the negative electrode 12 to the positive electrode 14 via the external circuit 26, which generates a current. After the negative electrode 12 has been partially or completely depleted of lithium, the electrochemical cell 10 can be recharged by connecting the negative electrode 12 and the positive electrode 14 to an external power source 24, which drives a non-spontaneous redox reaction within the electrochemical cell 10 and releases lithium ions and electrons from the positive electrode 14. The repeated charging and discharging of the electrochemical cell 10 can be referred to as a “cycle” in this paper, where a complete charge event followed by a complete discharge event is considered a complete cycle.

[0071] The negative electrode 12 may be in the form of a continuous porous material layer deposited on the main surface of the negative electrode current collector 20. The negative electrode 12 is configured to store and release lithium ions to facilitate the charging and discharging of the electrochemical cell 10, respectively. The negative electrode 12 may have a thickness greater than or equal to about 20 micrometers to less than or equal to about 100 micrometers defined between the main surface of the negative electrode current collector 20 and the separator 16.

[0072] The negative electrode 12 is a composite material and comprises a polymer matrix component 28 and a particulate component embedded in the polymer matrix component 28. The particulate component comprises composite material particles 30 distributed throughout the polymer matrix component 28 and optional conductive particles 32.

[0073] The polymer matrix component 28 is formulated as the negative electrode 12 to provide structural integrity, for example, by generating cohesive forces between the composite material particles 30 and optional conductive particles 32. The polymer matrix component 28 comprises polytetrafluoroethylene (PTFE). The polymer matrix component 28 may contain more than about 50% by weight, more than about 75% by weight, or more than about 90% by weight of PTFE. In some aspects, the polymer matrix component 28 may consist substantially of PTFE or be entirely composed of PTFE. The polymer matrix component 28 may constitute more than or equal to about 0.5% by weight and less than or equal to about 10% by weight of the negative electrode 12, more than or equal to about 0.5% by weight and less than or equal to about 5% by weight of the negative electrode 12, or more than or equal to about 0.5% by weight and less than or equal to about 2.5% by weight of the negative electrode 12. In some aspects, the polymer matrix component 28 may constitute about 1% by weight of the negative electrode 12.

[0074] like Figure 2 As best shown, each of the composite material particles 30 has a core-shell structure defined by a core 34 and a selective barrier layer 36 disposed on the surface 38 of the core 34.

[0075] The core 34 of each of the composite material particles 30 is configured to store and release lithium ions during the charging and discharging processes of the electrochemical cell 10. To achieve this, the core 34 of each of the composite material particles 30 in the negative electrode 12 comprises one or more electrochemically active (electroactive) materials that can promote the storage and release of lithium ions in the negative electrode 12 by undergoing a reversible redox reaction with lithium during the charging and discharging processes of the electrochemical cell 10. For example, the core 34 of each of the composite material particles 30 may comprise a lithium intercalation host material, a material reversibly alloyable with lithium (lithium alloying material), and / or a conversion material that can reversibly react with lithium through a phase transition or a change in crystal structure accompanied by a change in oxidation state during the charging and discharging processes of the electrochemical cell 10. Examples of lithium intercalation host materials, lithium alloying materials, and conversion materials used for core 34 include: carbon-based materials (e.g., graphite, graphene, and / or carbon nanotubes), silicon-based materials (e.g., silicon (Si) and / or Si alloys), tin-based materials (e.g., tin (Sn) and / or Sn alloys), metal oxides (e.g., V₂O₅ and / or Co₃O₄), and / or metal sulfides (e.g., FeS). In some aspects, the electroactive material may constitute greater than or equal to about 90% by weight, greater than or equal to about 95% by weight, or greater than or equal to about 99% by weight of core 34.

[0076] The core 34 of each of the composite particles 30 may have a diameter in the range of about 1 micrometer to about 40 micrometers.

[0077] Unintentionally, it is believed that parasitic side reactions may occur between the polytetrafluoroethylene in the polymer matrix component 28 and the lithium stored in the electrochemical active material of the core 34 of the composite particle 30 during the cycling of the electrochemical cell 10. Such parasitic side reactions are believed to consume active lithium and thereby reduce the overall capacity of the electrochemical cell 10.

[0078] A selective barrier layer 36 is formulated and disposed on the surface 38 of the core 34 in a manner that effectively prevents or inhibits the electrochemical reaction between lithium stored in the electroactive material of the core 34 and the polytetrafluoroethylene in the polymer matrix component 28. Simultaneously, the selective barrier layer 36 is ion-conducting and allows lithium ions to pass through it during the charging and discharging of the electrochemical cell 10. The selective barrier layer 36 may comprise an ion-conducting material that chemically and / or physically isolates the lithium stored in the core 34 of the composite particle 30 from the surrounding polytetrafluoroethylene in the polymer matrix component 28. In some aspects, the selective barrier layer 36 may comprise a polymer-based material, a ceramic-based material, a nitride-based material, a halide-based material, a borate-based material, or a combination thereof. Examples of polymer-based materials include poly(acrylonitrile) (PAN), poly(ethylene oxide) (PEO), poly(ethylene glycol) (PEG), polyethylene carbonate (PEC), poly(trimethylene carbonate) (PTMC), poly(propylene carbonate) (PPC), polyvinylidene fluoride-copolymer-hexafluoropropylene (PVdF-HFP), and combinations thereof. Examples of ceramic-based materials include garnet-type lithium, lanthanum, and zirconium-containing oxides, perovskite-type lithium-containing oxides, and combinations thereof. Examples of garnet-type lithium, lanthanum, and zirconium-containing oxides include Li7La3Zr2O. 12 (LLZO), Li 6.2 Ga 0.3 La 2.95 Rb 0.05 Zr2O 12 Li 6.85 La 2.9 Ca 0.1 Zr 1.75 Nb 0.25 O 12 Li 6.25 Al 0.25 La3Zr2O 12 Li 6.75 La3Ca 0.1 Zr 1.75 Nb 0.25 O 12 and their combinations. Examples of perovskite-type lithium-containing oxides include Li. 3.3 La 0.53 TiO3, LiSr 1.65 Zr 1.3 Ta1.7 O9, Li 2x-y Sr 1-x Ta y Zr 1-y O3 (where x=0.75y and 0.60<y<0.75), Li 3 / 8 Sr 7 / 16 Nb 3 / 4 Zr 1 / 4 O3, Li 3x La (2 / 3-x) TiO3 (where 0<x<0.25) and combinations thereof. Examples of lithium-containing nitride-based materials include Li3N, Li7PN4, LiSi2N3 and combinations thereof. Examples of lithium-containing halide-based materials include LiI, Li3InCl6, Li2CdCl4, Li2MgCl4, LiCdI4, Li2ZnI4, Li3OCl, Li3YCl6, Li3YBr6 and combinations thereof. Examples of lithium-containing borate-based materials include Li2B4O7, Li2O-B2O3-P2O5 and combinations thereof.

[0079] In Figure 2 , the selective barrier layer 36 is disposed on the surface 38 of the core 34 in the form of a substantially continuous material layer that completely encapsulates the core 34.

[0080] Referring now to Figure 3 , in some aspects, the negative electrode 12 may include composite material particles 130 having a core-shell structure defined by a core 134 and a selective barrier layer 136 disposed on the surface 138 of the core 134. The composite material particles 130 are similar in many respects to the composite material particles 30 discussed above with reference to Figure 1 and 2 , and descriptions of common subject matter may not be repeated herein. In Figure 3 , the selective barrier layer 136 is disposed on the surface 138 of the core 134 in the form of a discontinuous layer that extends over the surface 138 and surrounds the core 134 but does not completely encapsulate the core 134. As shown in Figure 3 , in some aspects, the selective barrier layer 136 may be defined by a plurality of lands 140 and a plurality of pores 142. The lands 140 may be physically spaced apart and isolated from each other by the pores 142, or the lands 140 may define an interconnected network surrounding the core 134. The size of the pores 142 may be set to selectively exclude polytetrafluoroethylene in the surrounding polymer matrix component 28 while allowing lithium ions to pass therethrough.

[0081] The selective barrier layers 36, 136 may have a thickness greater than or equal to about 1 nanometer to less than or equal to about 100 nanometers.

[0082] In each of the composite material particles 30 and 130, the core 34 and 134 may constitute greater than or equal to about 90% by weight and less than or equal to about 99.99% by weight of the composite material particles 30 and 130. In some aspects, the core 34 and 134 may constitute greater than or equal to about 99% by weight and less than or equal to about 99.95% by weight of the composite material particles 30 and 130. The selective barrier layers 36 and 136 may constitute greater than or equal to about 0.01% by weight and less than or equal to about 10% by weight of the composite material particles 30 and 130. In some aspects, the selective barrier layers 36 and 136 may constitute greater than or equal to about 0.05% by weight and less than or equal to about 2.0% by weight of the composite material particles 30 and 130. For example, in some aspects, the selective barrier layers 36 and 136 may constitute about 1.3% by weight of the composite material particles 30 and 130.

[0083] Optional conductive particles 32 are formulated as the negative electrode 12 to provide high conductivity, for example, by forming a robust conductive network throughout the negative electrode 12. The conductive particles 32 are electrochemically inert and do not reversibly react with lithium during the charging and discharging of the electrochemical cell 10. The conductive particles 32 may comprise particles of carbon-based materials, metal particles, and / or conductive polymers. Examples of conductive carbon-based materials include carbon black (e.g., acetylene black), graphite, graphene (e.g., graphene nanosheets), carbon nanotubes (e.g., single-walled carbon nanotubes), and / or carbon fibers (e.g., carbon nanofibers). Examples of conductive metal particles include powdered copper, nickel, aluminum, silver, and / or alloys thereof. Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, and / or polypyrrole. Optional conductive particles 32 may have an average particle size greater than or equal to about 2 nanometers to less than or equal to about 20 micrometers and may constitute greater than 0% by weight to less than or equal to about 10% by weight of the negative electrode 12. For example, the conductive particles 32 may account for more than or equal to about 0.5% by weight to less than or equal to about 5% by weight of the negative electrode 12. In some aspects, the conductive particles 32 may account for about 2% by weight of the negative electrode 12.

[0084] The positive electrode 14 may be in the form of a continuous porous material layer and may contain one or more electrochemically active materials. These electrochemically active materials can undergo a reversible redox reaction with lithium at a higher electrochemical potential than that of the electrochemically active material of the negative electrode 12, resulting in an electrochemical potential difference between the negative electrode 12 and the positive electrode 14. For example, the positive electrode 14 may contain a lithium intercalation host material capable of reversible lithium ion insertion or intercalation, a material reversibly alloyed with lithium (lithium alloying material), and / or a conversion material that can reversibly react with lithium through a phase transition or a change in crystal structure accompanied by a change in oxidation state during the charging and discharging of the electrochemical cell 10. Examples of lithium intercalation host materials for the positive electrode 14 include layered oxides represented by the formula LiMeO2, olivine-type oxides represented by the formula LiMePO4, spinel-type oxides represented by the formula LiMe2O4, tavorites represented by one or both of the following formulas LiMeSO4F or LiMePO4F, and combinations thereof, wherein Me is a transition metal (e.g., Co, Ni, Mn, Fe, Al, V, or combinations thereof). Examples of conversion materials for the positive electrode 14 include sulfur, selenium, tellurium, iodine, halides (e.g., fluorides or chlorides), sulfides, selenides, tellurides, iodides, phosphides, nitrides, oxides, oxysulfides, oxyfluorides, sulfur-fluorides, sulfur-oxyfluorides, lithium and / or metal compounds of any of the above, and combinations thereof. Examples of metals included in the conversion material of the positive electrode 14 include iron, manganese, nickel, copper, and cobalt.

[0085] The electrochemically active material of the positive electrode 14 may be a particulate material, and the particles of the electrochemically active material of the positive electrode 14 may be mixed with a polymer binder to provide structural integrity to the positive electrode 14. Examples of polymer binders include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), ethylene propylene diene monomer (EPDM), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), nitrile butadiene rubber (NBR), styrene-butadiene rubber (SBR), polyacrylate, alginate, polyacrylic acid, and mixtures thereof. The positive electrode 14 may optionally contain particles of an electrochemically inert conductive material. Examples of conductive materials include carbon-based materials, metal particles, and / or particles of conductive polymers. Examples of conductive carbon-based materials include carbon black (e.g., acetylene black), graphite, graphene (e.g., graphene nanosheets), carbon nanotubes (e.g., single-walled carbon nanotubes), and / or carbon fibers (e.g., carbon nanofibers). Examples of conductive metal particles include powdered copper, nickel, aluminum, silver, and / or alloys thereof. Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, and / or polypyrrole.

[0086] The porous separator 16 electrically isolates the negative electrode 12 and the positive electrode 14 from each other, and can be in the form of a microporous ion-conducting and electrically insulating film or a nonwoven material, such as an artificial sheet, mesh, or pad of oriented or randomly oriented fibers. In some aspects, the porous separator 16 may comprise a microporous polymeric material, such as a microporous polyolefin-based membrane or film. For example, the porous separator 16 may comprise a single polyolefin or a combination of polyolefins, such as polyethylene (PE), polypropylene (PP), polyamide (PA), poly(tetrafluoroethylene) (PTFE), polyvinylidene fluoride (PVdF), and / or poly(vinyl chloride) (PVC). In some aspects, the porous separator 16 may comprise a laminate of one or more polymeric materials, such as a laminate of PE and PP.

[0087] Electrolyte 18 provides a medium for the conduction of lithium ions through electrochemical cell 10 between negative electrode 12 and positive electrode 14, and may be in the form of a liquid, solid, or gel. In some aspects, electrolyte 18 may comprise a non-aqueous liquid electrolyte solution containing one or more lithium salts dissolved in a non-aqueous aprotic organic solvent or a mixture of non-aqueous aprotic organic solvents. Examples of lithium salts include lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrachloroaluminate (LiAlCl4), lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium tetrafluoroborate (LiBF4), lithium tetraphenylborate (LiB(C6H5)4), lithium bis(oxalate)borate (LiB(C2O4)2) (LiBOB), lithium difluorooxalate borate (LiBF2(C2O4)), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethane)sulfonylimide (LiN(CF3SO2)2), lithium bis(fluorosulfonyl)imide (LiN(FSO2)2) (LiSFI), and combinations thereof. Examples of non-aqueous aprotic organic solvents include alkyl carbonates, such as cyclic carbonates (e.g., ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), fluoroethylene carbonate (FEC)), linear carbonates (e.g., dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC)), aliphatic carboxylic acid esters (e.g., methyl formate, methyl acetate, methyl propionate), γ-lactones (e.g., γ-butyrolactone, γ-valerolactone), chain ethers (e.g., 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane), cyclic ethers (e.g., tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane), sulfur compounds (e.g., sulfolane), and combinations thereof. In the case where the electrolyte 18 is in solid form, the electrolyte 18 can function as both an electrolyte and a separator, eliminating the need for a discrete separator 16.

[0088] Negative electrode current collector 20 and positive electrode current collector 22 are conductive and provide an electrical connection between external circuit 26 and their respective negative electrodes 12 and positive electrodes 14. In some aspects, negative electrode current collector 20 and positive electrode current collector 22 may be in the form of non-porous metal foil, perforated metal foil, porous metal mesh, or combinations thereof. Negative electrode current collector 20 may be made of copper, nickel, or alloys thereof, stainless steel, or other suitable conductive materials. Positive electrode current collector 22 may be made of aluminum (Al) or other suitable conductive materials.

[0089] Composite particles 30, 130 can be manufactured by depositing selective barrier layers 36, 136 onto surfaces 38, 138 of cores 34, 134 using a wet or dry deposition process. For example, selective barrier layers 36, 136 can be deposited onto surfaces 38, 138 of cores 34, 134 by the following steps: forming a slurry comprising a mixture of selective barrier layer materials dissolved or dispersed in a solvent, depositing the slurry onto surfaces 38, 138 of cores 34, 134, and then removing the solvent. As another example, a melt-coating process can be used to deposit selective barrier layers 36, 136 onto surfaces 38, 138 of cores 34, 134.

[0090] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or limiting of this disclosure. Independent elements or features of a particular embodiment are generally not limited to that embodiment, but are interchangeable where applicable and can be used in selected embodiments, even if not specifically shown or described. They can also be varied in many ways. Such variations should not be considered as departing from this disclosure, and all such modifications are intended to be included within the scope of this disclosure.

Claims

1. A negative electrode for an electrochemical cell used in cycling lithium ions, the negative electrode comprising: Polymer matrix component containing polytetrafluoroethylene; and The particulate component embedded in the polymer matrix component comprises a plurality of composite material particles, each of which has a core and a selective barrier layer disposed on the surface of the core. The core of each of the composite material particles contains an electroactive negative electrode material. The electroactive negative electrode material comprises carbon, and the carbon constitutes 90% or more by weight of the core. The selective barrier layer comprises a ceramic-based material, a nitride-based material, a halide-based material, a borate-based material, or a combination thereof, and The selective barrier layer of each of the composite material particles is formulated to prevent or inhibit the electrochemical reaction between lithium stored in the electroactive negative electrode material of the core and polytetrafluoroethylene in the polymer matrix component.

2. The negative electrode according to claim 1, wherein the selective barrier layer comprises a garnet-type lithium, lanthanum and zirconium oxide; a perovskite-type lithium oxide; a lithium-containing nitride-based material; a lithium-containing halide-based material; a lithium-containing borate-based material; or a combination thereof.

3. The negative electrode of claim 1, wherein for each of the composite material particles, the selective barrier layer constitutes a percentage of the composite material particles of greater than or equal to 0.01% by weight and less than or equal to 10% by weight.

4. The negative electrode according to claim 1, wherein for each of the composite material particles, the selective barrier layer is disposed on the surface of the core in the form of a discontinuous layer that does not completely encapsulate the core.

5. The negative electrode of claim 1, wherein for each of the composite material particles, the selective barrier layer is disposed on the surface of the core in the form of a continuous layer that completely encapsulates the core.

6. The negative electrode according to claim 1, wherein the polymer matrix component constitutes a negative electrode of greater than or equal to 0.5% by weight and less than or equal to 10% by weight.

7. The negative electrode according to claim 1, wherein the polymer matrix component comprises greater than or equal to 90% by weight of polytetrafluoroethylene.

8. The negative electrode according to claim 1, wherein the particulate component further comprises a plurality of electrochemically inert conductive particles.

9. An electrochemical battery for cycling lithium ions, said electrochemical battery comprising: Positive electrode; A negative electrode that is physically separated from the positive electrode; and A non-aqueous electrolyte that provides an ion conduction path for lithium-ion transport between the positive and negative electrodes. The negative electrode comprises a polymer matrix component and a particulate component embedded in the polymer matrix component. The polymer matrix component comprises polytetrafluoroethylene (PTFE), and the particulate component comprises a plurality of composite material particles, each of which has a core and a selective barrier layer disposed on the surface of the core. The core of each of the composite material particles contains an electroactive negative electrode material. The electroactive negative electrode material comprises carbon, and the carbon constitutes 90% or more by weight of the core. The selective barrier layer comprises a ceramic-based material, a nitride-based material, a halide-based material, a borate-based material, or a combination thereof, and The selective barrier layer of each of the composite material particles is formulated to prevent or inhibit the electrochemical reaction between lithium stored in the electroactive negative electrode material of the core and polytetrafluoroethylene in the polymer matrix component.

10. The electrochemical cell of claim 9, wherein for each of the composite material particles, the selective barrier layer constitutes a percentage of the composite material particles of greater than or equal to 0.01% by weight and less than or equal to 10% by weight.

11. The electrochemical cell of claim 9, wherein for each of the composite material particles, the selective barrier layer is disposed on the surface of the core in the form of a discontinuous layer that does not completely encapsulate the core.

12. The electrochemical cell of claim 9, wherein for each of the composite material particles, the selective barrier layer is disposed on the surface of the core in the form of a continuous layer that completely encapsulates the core.

13. The electrochemical cell of claim 9, wherein the polymer matrix component comprises greater than or equal to 90% by weight of polytetrafluoroethylene, and wherein the polymer matrix component constitutes greater than or equal to 0.5% by weight to less than or equal to 10% by weight of the negative electrode.

14. The electrochemical battery according to claim 9, further comprising: A porous insulating member disposed between the negative electrode and the positive electrode; A negative electrode current collector with a main surface; and Positive electrode current collector with main surface, The negative electrode is disposed on the main surface of the negative electrode current collector, and the positive electrode is disposed on the main surface of the positive electrode current collector.

15. The electrochemical battery according to claim 9, wherein the positive electrode comprises an electrochemically active material, the electrochemically active material being capable of undergoing a reversible redox reaction with lithium at a higher electrochemical potential than that of the electrochemically active negative electrode material in the core of each of the composite material particles.

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