Blended cathode materials for secondary batteries

Abstract

The present disclosure relates to blended cathode materials for use as positive electrode materials for rechargeable electrochemical cells (or secondary cells), such as lithium-ion secondary cells, and also to secondary cells comprising cathodes having blended cathode materials. In particular, a blend of lithium vanadium fluorophosphate (LVPF) or a derivative thereof with one or more conventional cathode active materials in certain weight ratios is disclosed.

Description

background Technical Field

[0001] This disclosure relates to blended cathode materials intended for use as positive electrode materials (or cathode materials) in rechargeable electrochemical batteries (or secondary batteries) (e.g., lithium-ion secondary batteries), and also to secondary batteries including cathodes having blended cathode materials. In particular, this disclosure relates to blended cathode materials that provide one or more benefits such as improved determination of state of charge (SOC), energy density, cycle life, coating quality, adhesion, safety, and electrode density.

[0002] Description of related technologies

[0003] In secondary batteries, active materials are materials that participate in electrochemical reactions to generate electrical energy during battery discharge.

[0004] Many materials are commonly known as cathode active materials for secondary batteries, such as NCA, NMC, LFP, LMP, LFMP, LCP, LCO, LNO, LMO and LNMO (which are described in detail below).

[0005] Lithium vanadium fluorophosphate (e.g., LiVPO4F and its derivatives) (LVPF) is a known cathode active material with relatively high energy density (compared to many conventionally used cathode materials), due to its high efficiency for Li- ionization. + / Li(V 4+ / V 3+ The redox pair (corresponding to lithium ion insertion and extraction, respectively) has a charge and discharge plateau of approximately 4.2V.

[0006] However, it has been established that using LVPF as the cathode active material may have some drawbacks. For example, the very flat charge / discharge plateau of LVPF has been identified, which may make it difficult for the battery management system (or BMS) to monitor the state of charge (or SOC), thus making it difficult to accurately predict the remaining energy available for further utilization.

[0007] Therefore, there remains a need for cathode active materials for secondary batteries that offer one or more of the following advantages: high energy density, high cycle life, improved rate performance, and improved ease of use with BMS. Invention Overview

[0009] Some embodiments of this disclosure overcome the aforementioned disadvantages and / or other disadvantages not described above. However, aspects of the embodiments do not need to overcome the aforementioned disadvantages, and aspects of the embodiments may not be able to overcome any of the aforementioned disadvantages.

[0010] Implementations of this disclosure relate to blended cathode materials comprising lithium vanadium fluorophosphate.

[0011] More specifically, the blended cathode material according to the present disclosure comprises a blend of a first active material which is lithium vanadium fluorophosphate (LVPF) or a derivative thereof and a second active material, which is a conventionally used cathode active material other than LVPF. The second active material and / or the amount thereof may be selected for the purpose of generating a voltage slope at the start of charging and the end of discharging. The first active material (LVPF or a derivative thereof) may also be blended with the second active material for the purpose of achieving one or more of higher energy density, improved cycle life, and / or improved rate performance. Alternatively, the first active material (LVPF or a derivative thereof) may be added to the second active material to improve the processability of the second active material (for example, LFMP).

[0012] According to one embodiment, the present disclosure provides a positive electrode active material for a secondary battery, the positive electrode active material comprising:

[0013] a first active material, the first active material being selected from lithium vanadium fluorophosphate (LVPF) represented by the following formula (1) or a LVPF derivative represented by the following formula (2):

[0014] Li 1+x VPO4F Formula (1),

[0015] wherein, in formula (1), 0≤x≤0.15,

[0016] Li 1+x V 1-y M y PO4F z Formula (2),

[0017] wherein, in formula (2), 0≤x≤0.15; 0<y≤0.5; 0.8≤z≤1.2; and M is selected from Ti, Al, Y, Cr, Cu, Mg, Mn, Fe, Co, Ni or Zr; and

[0018] a second active material,

[0019] wherein the weight ratio of the first active material to the second active material is r:(1-r), wherein 0<r<1; and

[0020] the second active material is represented by one of the following formulas (A) to (D) or a blend thereof:

[0021] Li 1+x M1 a X b PO4 Formula (A),

[0022] In formula (A), M1 is at least one selected from Fe, Mn, or Co; X is at least one transition metal selected from Ni, V, Y, Mg, Ca, Ba, Al, Sc, or Nd; 0 ≤ x ≤ 0.15; a > 0; b ≥ 0; and optionally a + b = 1;

[0023] Li 1+x Ni a M2 d M3 e O2 formula (B),

[0024] In formula (B), M2 is at least one selected from Co, Al, or Mn; M3 is at least one of B, Mg, Si, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, Sr, Ce, Ga, Ta, or a mixture thereof; 0 ≤ x ≤ 0.15; a > 0; d > 0; e ≥ 0; and optionally a + d + e = 1;

[0025] Li 1+x Mn2O4 formula (C),

[0026] In equation (C), 0 ≤ x ≤ 0.15;

[0027] Li 1+x CoO2 formula (D),

[0028] In equation (D), 0 ≤ x ≤ 0.15.

[0029] In this document, the general use of both the term "LVPF" alone and the term "LVPF or derivative" generally refers to the combination of LVPF according to formula (1) and LVPF derivative according to formula (2). Furthermore, the general use of the term "LMO" refers to formula (C), and the general use of the term "LCO" refers to formula (D).

[0030] In any aspect of this disclosure, for the weight ratio (r:(lr)) of the blend of the first active material and the second active material, the value r corresponding to the weight of the first active material can be any value greater than 0 and less than 1. For example, in some embodiments, the value of r can be 0.1≤r≤0.9, 0.2≤r≤0.9, 0.3≤r≤0.9, 0.4≤r≤0.9, 0.5≤r≤0.9, 0.6≤r≤0.9, 0.7≤r≤0.9, or 0.8≤r≤0.9.

[0031] In one aspect of this disclosure, the second active material is represented by a known cathode active material or a blend thereof selected from LFP, LMP, LCP, (optionally doped) LFMP, NMC, LNMO, NCA, NMCA, LMO or LCO.

[0032] In one aspect of this disclosure, the second active material is represented by one of the following formulas (A1) to (A4) or a blend thereof:

[0033] Li 1+x FePO4 formula (A1),

[0034] In equation (A1), 0 ≤ x ≤ 0.15;

[0035] Li 1+x MnPO4 formula (A2),

[0036] In equation (A2), 0 ≤ x ≤ 0.15;

[0037] Li 1+x CoPO4 formula (A3),

[0038] In equation (A3), 0 ≤ x ≤ 0.15;

[0039] Li 1+x Fe y Mn z X b PO4 formula (A4),

[0040] In formula (A4), X is at least one transition metal selected from Ni, V, Y, Mg, Ca, Ba, Al, Sc or Nd; 0 ≤ x ≤ 0.15; y > 0; z > 0; b ≥ 0; and optionally y + z + b = 1.

[0041] In this document, the general term “LFP” refers to formula (A1), the general term “LMP” refers to formula (A2), the general term “LCP” refers to formula (A3), and the general term “optionally doped LFMP” or “LFMP” refers to formula (A4).

[0042] In one aspect of this disclosure, the second active material is represented by one of the following formulas (B1) to (B4) or a blend thereof:

[0043] Li w (Ni x Mn y Co z M t O2 formula (B1),

[0044] In equation (B1), 0.9 ≤ w ≤ 1.1; x > 0; y > 0; z > 0; t ≥ 0; M is at least one of Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, Sr, Ce, Ga, Ta, or a mixture thereof; and optionally x + y + z + t = 1.

[0045] Li 1+x Ni a Mn b O2 formula (B2),

[0046] In equation (B2), 0 ≤ x ≤ 0.15; a > 0; b > 0; and a + b = 1.

[0047] Li w (Ni x Co y Al z M t O2 formula (B3),

[0048] In equation (B3), 0.9 ≤ w ≤ 1.1; x > 0; y > 0; z > 0; t ≥ 0; M is at least one of B, Mg, Si, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, Sr, Ce, Ga, Ta, or a mixture thereof; and optionally x + y + z + t = 1.

[0049] Li 1+x Ni a Mn b Co c Al d O2 formula (B4),

[0050] In equation (B4), 0 ≤ x ≤ 0.15; a > 0; b > 0; c > 0; d > 0; and arbitrarily a + b + c + d = 1.

[0051] In this document, the general term “NMC” refers to formula (B1), the general term “LNMO” refers to formula (B2), the general term “NCA” refers to formula (B3), and the general term “NMCA” refers to formula (B4).

[0052] In some aspects of this disclosure, the second active material represented by formula (B1)(NMC) is represented by the following formula (B1'):

[0053] Li w (Ni x Mn y Co z O2 formula (B1'),

[0054] In equation (B1'), 0.9 ≤ w ≤ 1.1; x > 0; y > 0; z > 0; and optionally x + y + z = 1.

[0055] In one aspect of this disclosure, the second active material represented by formula (B1) is selected from: LiNi 0.33 Mn 0.33 Co 0.33 O2, LiNi 0.5 Mn 0.3 Co 0.2 O2, LiNi 0.6 Mn 0.2 Co 0.2 O2 or LiNi 0.8 Mn 0.1 Co 0.1 O2.

[0056] In some aspects of this disclosure, the second active material represented by formula (B3)(NCA) is represented by the following formula (B3'):

[0057] Li w (Ni x Co y Al z O2 formula (B3'),

[0058] In equation (B3), 0.9 ≤ w ≤ 1.1; x > 0; y > 0; z > 0; and optionally x + y + z = 1.

[0059] In one aspect of this disclosure, the second active material is represented by a blend of formula (A) and formula (B).

[0060] In one aspect of this disclosure, the second active material is represented by a blend of the following formula (A4) and the following formula (B1):

[0061] Li 1+x Fe y Mn z X b PO4 formula (A4),

[0062] In equation (A4), X is at least one transition metal selected from Ni, V, Y, Mg, Ca, Ba, Al, Sc, or Nd; 0 ≤ x ≤ 0.15; y > 0; z > 0; b ≥ 0; and optionally y + z + b = 1, Li w (Ni x Mn y Co z M t O2 formula (B1),

[0063] wherein, in formula (B1), 0.9≤w≤1.1; x>0; y>0; z>0; t≥0; M is at least one selected from Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, Sr, Ce, Ga, Ta or a mixture thereof; and optionally x+y+z+t=1.

[0064] In one aspect of the present disclosure, the weight ratio of formula (A4) to formula (B1) is m:(1-m), wherein 0<m<1.

[0065] In one aspect of the present disclosure, the second active material is represented by a blend of the following formula (A4) and the following formula (B3):

[0066] Li 1+x Fe y Mn z X b PO4 Formula (A4),

[0067] wherein, in formula (A4), X is at least one transition metal selected from Ni, V, Y, Mg, Ca, Ba, Al, Sc or Nd; 0≤x≤0.15; y>0; z>0; b≥0; and optionally y+z+b=1; Li w (Ni x Co y Al z M t )O2 Formula (B3),

[0068] wherein, in formula (B3), 0.9≤w≤1.1; x>0; y>0; z>0; t≥0; M is at least one selected from B, Mg, Si, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, Sr, Ce, Ga, Ta or a mixture thereof; and optionally x+y+z+t=1.

[0069] In one aspect of the present disclosure, the weight ratio of formula (A4) to formula (B3) is m:(1-m), wherein 0<m<1.

[0070] In one aspect, formula (A4) (corresponding to optionally doped LFMP) may be blended with formula (B1) (NMC), wherein the weight ratio of formula (A4) to formula (B1) is a:(1-a), and the value a is any value greater than 0 and less than 1 (i.e., 0<a<1). For example, the value a may be 0.1≤a≤0.9, 0.2≤a≤0.8, 0.3≤a≤0.7, or 0.4≤a≤0.6.

[0071] In another aspect, Formula (A4) (optionally doped LFMP) may be blended with Formula (B3) (NCA), wherein the weight ratio of Formula (A4) to Formula (B3) is b:(1-b), and the value b is any value greater than 0 and less than 1 (i.e., 0<b<1). For example, the value b may be 0.1≤b≤0.9, 0.2≤b≤0.8, 0.3≤b≤0.7, or 0.4≤b≤0.6.

[0072] In another aspect, for the benefit of improved safety without significantly sacrificing energy density, 20 wt% to 40 wt% of LVPF (0.2≤r≤0.4) is blended with a non-phosphate cathode material (such as NMC, NCA, LCO, LNMO, etc.).

[0073] In one aspect of the present disclosure, the positive electrode material comprises a binder material and / or a conductive material.

[0074] In another embodiment, the present disclosure provides a secondary battery using one of the cathode material blends according to the present disclosure.

[0075] In one aspect, the secondary battery is a lithium ion secondary battery.

[0076] In one aspect, the secondary battery at least comprises: a cathode comprising the positive electrode material according to the present disclosure; an anode comprising a negative electrode active material; and an electrolyte solution comprising a supporting salt and an organic solvent. When the battery is a lithium ion secondary battery, the supporting salt may be a well-known lithium salt.

[0077] In another embodiment, the present disclosure provides a battery system comprising a plurality of electrically connected secondary batteries according to the present disclosure.

[0078] In one aspect, the battery system comprises: a plurality of secondary batteries according to the present disclosure, the plurality of batteries being electrically connected; and a battery management system configured to monitor the state of charge of the plurality of batteries based on the voltage of one or more of the plurality of batteries.

[0079] In one aspect, the blended cathode material of one or more of the plurality of batteries in the battery system is selected to generate a voltage slope that occurs at the start of charging and the end of discharging.

[0080] Additional features and advantages of the present disclosure are described further below. This Summary section is only intended to exemplify certain features of the present disclosure, and is not intended to limit the scope of the present disclosure in any way. The absence of discussion of specific features or embodiments of the present disclosure in this Summary section, or the inclusion of one or more features, shall not be construed as limiting the claims. Brief Description of the Drawings

[0081] This application contains at least one color-drawn figure. Upon request and payment of the necessary fees, the official authority will provide a copy of this patent application disclosure with color drawings.

[0082] Any accompanying figures included in this article are provided as examples only and not as limitations.

[0083] Figure 1 To illustrate the voltage (V) (for Li) versus SOC of the battery prepared in Example 1 during charging.

[0084] Figure 2 To illustrate the voltage (V) (for Li) versus DOD of the battery prepared in Example 1 during discharge.

[0085] Figure 3 A graph showing the rate performance (capacity retention (%) vs. C-rate) of the battery prepared in Example 1.

[0086] Figure 4 A graph showing the capacity retention (%) versus cycle number of the battery prepared in Example 1.

[0087] Figure 5 A graph showing the capacity retention rate (%) versus C-rate of the battery prepared in Example 2. Detailed Implementation

[0088] It should be understood that the foregoing general description and the following detailed description are exemplary and intended to provide further clarification of the claims. Therefore, various changes, modifications, and equivalents of the methods, apparatus, and / or systems described herein will be apparent to those skilled in the art. Furthermore, for clarity and conciseness, descriptions of well-known functions and structures may be omitted.

[0089] The terminology used in this specification is intended to describe embodiments only and is by no means limiting. Unless expressly used otherwise, singular expressions include the meaning of plural forms. In this specification, expressions such as “comprising” or “including” are intended to specify features, numbers, steps, operations, elements, components, or combinations thereof, and should not be construed as excluding any presence or possibility of one or more other features, numbers, steps, operations, elements, components, or combinations thereof.

[0090] Any range should be understood to encompass and disclose the discrete points and subranges within that range.

[0091] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure, as it is understood that modifications and variations are encompassed within the spirit and scope of the present disclosure.

[0092] As used herein, "about", "approximately", "substantially" and "significantly" are understood by those of ordinary skill in the art, and will vary to some extent depending on the context in which they are used. If the usage of a term is not clear to those of ordinary skill in the art in view of the context in which the term is used, "about" and "approximately" mean ±10% of the specified term, and "substantially" and "significantly" mean more than ±10% of the specified term. "Comprising" and "consisting essentially of" have their customary meanings in the art.

[0093] The blended cathode material of the present disclosure comprises a blend of a first active material which is lithium vanadium fluorophosphate (LVPF) or a derivative thereof, and a second active material which is a conventional cathode active material other than LVPF.

[0094] LVPF — First Active Material

[0095] The first active material is selected from lithium vanadium fluorophosphate (LVPF) represented by the following formula (1) or an LVPF derivative represented by the following formula (2):

[0096] Li 1+x VPO₄F Formula (1),

[0097] wherein, in formula (1), 0≤x≤0.15,

[0098] Li 1+x V 1-y M y PO₄F z Formula (2),

[0099] wherein, in formula (2), 0≤x≤0.15; 0<y≤0.5; 0.8≤z≤1.2; and M is selected from Ti, Al, Cu, Mg, Mn, Fe, Co, Y, Cr, Ni or Zr.

[0100] In some embodiments, the first active material may be a blend of formula (1) and formula (2). When both LVPF and the LVPF derivative are used, the weight ratio of formula (1) to formula (2) may be s:(1-s), where 0<s<1. In some embodiments, the value of s may be, for example, 0.1≤s≤0.9, 0.2≤s≤0.8, 0.3≤s≤0.7, or 0.4≤s≤0.6.

[0101] Among the LVPF derivatives according to Formula (2), LiY x V 1-x PO4F (0<x≤0.5), LiCr x V 1-x PO4F (0<x≤0.5), LiCo x V 1-x PO4F (0<x≤0.5), LiMn x V 1-x PO4F (0<x≤0.5), LiTi x V 1-x PO4F (0<x≤0.5), LiFe x V 1-x PO4F (0<x≤0.5) are considered particularly preferred.

[0102] Second Active Material

[0103] The second active material may be any known cathode active material other than LVPF. In some embodiments, the second active material is one of the well-known materials NCA, NMC, LFP, LMP, optionally doped LFMP, LCP, LCO, LNO, LMO or LNMO, or a blend thereof. The second active material may generally be represented by one or more of the following Formulas (A) to (D).

[0104] Formula (A) (e.g., LFP, LMP, LCP and optionally doped LFMP)

[0105] The second active material may be represented by the following Formula (A):

[0106] Li 1+x M1 a X b PO4 Formula (A),

[0107] wherein in Formula (A), M1 is at least one selected from Fe, Mn and Co; X is at least one transition metal selected from Ni, V, Y, Mg, Ca, Ba, Al, Sc or Nd; 0≤x≤0.15; a>0; b≥0; and optionally a+b=1.

[0108] More specifically, the second active material according to Formula (A) may be one of the following Formula (A1) (i.e., LFP), Formula (A2) (i.e., LMP), Formula (A3) (i.e., LCP) or Formula (A4) (i.e., optionally doped LFMP), or a blend thereof:

[0109] Li 1+x FePO4 Formula (A1),

[0110] In equation (A1), 0 ≤ x ≤ 0.15;

[0111] Li 1+x MnPO4 formula (A2),

[0112] In equation (A2), 0 ≤ x ≤ 0.15;

[0113] Li 1+x CoPO4 formula (A3),

[0114] In equation (A3), 0 ≤ x ≤ 0.15;

[0115] Li 1+x Fe y Mn z X b PO4 formula (A4),

[0116] In formula (A4), X is at least one transition metal selected from Ni, V, Y, Mg, Ca, Ba, Al, Sc or Nd; 0 ≤ x ≤ 0.15; y > 0; z > 0; b ≥ 0; and optionally y + z + b = 1.

[0117] As stated above, the general term “LFP” refers to formula (A1), the general term “LMP” refers to formula (A2), the general term “LCP” refers to formula (A3), and the general term “optionally doped LFMP” or “LFMP” alone refers to formula (A4).

[0118] Formula (B) (e.g., NMC, LNMO, NCA, and NMCA)

[0119] The second active material can be represented by the following formula (B):

[0120] Li 1+x Ni a M2 d M3 e O2 formula (B),

[0121] In formula (B), M2 is at least one selected from Co, Al or Mn; M3 is at least one of B, Mg, Si, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, Sr, Ce, Ga, Ta or a mixture thereof; 0 ≤ x ≤ 0.15; a > 0; d > 0; e ≥ 0; and optionally a + d + e = 1.

[0122] More specifically, the second active material according to formula (A) can be one of the following formulas (B1) to (B4):

[0123] Li w (Nix Mn y Co z M t O2 formula (B1),

[0124] In equation (B1), 0.9 ≤ w ≤ 1.1; x > 0; y > 0; z > 0; t ≥ 0; M is at least one of Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, Sr, Ce, Ga, Ta, or a mixture thereof; and optionally x + y + z + t = 1;

[0125] Li 1+x Ni a Mn b O2 formula (B2),

[0126] In equation (B2), 0 ≤ x ≤ 0.15; a > 0; b > 0; and optionally a + b = 1.

[0127] Li w (Ni x Co y Al z M t O2 formula (B3),

[0128] In equation (B3), 0.9 ≤ w ≤ 1.1; x > 0; y > 0; z > 0; t ≥ 0; M is at least one of B, Mg, Si, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, Sr, Ce, Ga, Ta, or a mixture thereof; and optionally x + y + z + t = 1;

[0129] Li 1+x Ni a Mn b Co c Al d O2 formula (B4),

[0130] In equation (B4), 0 ≤ x ≤ 0.15; a > 0; b > 0; c > 0; d > 0; and arbitrarily a + b + c + d = 1.

[0131] Specific examples of Equation (B) include, for example, NMC (see Equation B1), LNMO (see Equation B2), NCA (see Equation B3), and NMCA (see Equation B4).

[0132] As described above, the general term “NMC” is interpreted as (B1), the general term “LNMO” as (B2), the general term “NCA” as (B3), and the general term “NMCA” as (B4).

[0133] Specific examples of formula (B1) include, for example, LiNi 0.33 Mn 0.33 Co 0.33 O2 (NMC 111), LiNi 0.5 Mn 0.3 Co 0.2 O2 (NMC532), LiNi 0.6 Mn 0.2 Co 0.2 O2 (NMC622) or LiNi 0.8 Mn 0.1 Co 0.1 O2 (NMC811).

[0134] Formula (C) (LMO)

[0135] The second active material may be represented by the following formula (C):

[0136] Li 1+x Mn2O4 Formula (C),

[0137] wherein, in formula (C), 0≤x≤0.15.

[0138] As described above, the general term "LMO" means formula (C).

[0139] Formula (D) (LCO)

[0140] The second active material may be represented by the following formula (D):

[0141] Li 1+x CoO2 Formula (D),

[0142] wherein, in formula (D), 0≤x≤0.15.

[0143] As described above, the general term "LCO" means formula (D).

[0144] Exemplary Blends and Amounts

[0145] As described above, the weight ratio of the first active material (i.e., LVPF or a derivative) to the second active material is r:(1-r), where 0<r<1. In other words, when the total of the first active material and the second active material is considered as 100%, the term "r" corresponds to the weight percentage of the first active material. For example, when r is 0.9, this corresponds to 90 wt% of the first active material and 10 wt% of the second active material.

[0146] In the weight ratio r:(1-r), r can be any value greater than 0 and less than 1, and r does not need to be an integer (for example, r can be 0.75 to 0.85). In certain embodiments, the value of r can be, for example, 0.1≤r≤0.9, 0.2≤r≤0.9, 0.3≤r≤0.9, 0.4≤r≤0.9, 0.5≤r≤0.9, 0.6≤r≤0.9, 0.7≤r≤0.9, 0.8≤r≤0.9, etc.

[0147] The following exemplary blended cathode materials of the blend of the first active material and the second active material are specifically mentioned.

[0148] In an exemplary embodiment, the first active material (LVPF) is blended with the formula (A4) (LFMP) as the second active material at a weight ratio of r:(1-r) to produce a sloped discharge curve, which facilitates the determination of SOC. For example, the second plateau (about 3.5V) of LFMP during discharge can serve as an excellent SOC indicator. In this embodiment, r is not particularly limited. However, in certain aspects, r is preferably 0.4≤r≤0.6.

[0149] In a modification of this exemplary embodiment, formula (A4) (LFMP) can be blended with formula (B1) (NMC) as the second active material, wherein the weight ratio of LFMP to NMC in this blend is a:(1-a) (i.e., LVPF r (LMFP a NMC 1-a ) 1-r ), where the value a is any value greater than 0 and less than 1 (i.e., 0<a<1). For example, the value a can be 0.1≤a≤0.9, 0.2≤a≤0.8, 0.3≤a≤0.7, or 0.4≤a≤0.6.

[0150] In another modification of this exemplary embodiment, formula (A4) (LFMP) can be blended with formula (B3) (NCA) as the second active material, wherein the weight ratio of LFMP to NCA in this blend is b:(1-b) (i.e., LVPF r (LMFP b NCA 1-b ) 1-r ), where the value b is any value greater than 0 and less than 1 (i.e., 0<b<1). For example, the value b can be 0.1≤b≤0.9, 0.2≤b≤0.8, 0.3≤b≤0.7, or 0.4≤b≤0.6.

[0151] In another exemplary embodiment, the first active material (LVPF) is blended with Formula (B1) (NMC (e.g., NMC111, NMC532, NMC622, NMC811, etc.)) as the second active material at a weight ratio of r:(1-r). In this exemplary embodiment, the value of r is preferably 0.4≤r≤0.6.

[0152] In another exemplary embodiment, the first active material (LVPF) is blended with Formula (B3) (NCA) as the second active material at a weight ratio of r:(1-r). In this exemplary embodiment, r is preferably 0.4≤r≤0.6.

[0153] In another exemplary embodiment, for the purpose of improving one or both of the capacity retention and processability of LFMP, LVPF is added to Formula (A4) (LFMP) as the second active material at a weight ratio of r:(1-r). In this exemplary embodiment, r may be 0.1≤r≤0.6. In this exemplary embodiment, the second active material may comprise another second active material combined with LFMP as follows: LVPF x (LFMP a Z b ) y , wherein a+b=1, 0<a≤1, 0≤b<1, x+y=1; 0<x<1, 0<y<1, and "Z" is any one of the additional second active materials disclosed herein (e.g., NCA, LCO, LNO, LMO, etc.).

[0154] In another exemplary embodiment, it has also been found that blending LVPF into non-phosphate cathode materials (e.g., NMC, NCA, LCO, LNMO, etc.) can improve battery safety. For example, without being bound by any theory, blending LVPF can suppress oxygen release from non-phosphate cathode materials during cycling, reduce exothermic reactions during thermal runaway or abuse, and / or increase decomposition temperature, etc. It has been found that by adding 10 wt% LVPF (i.e., r = 0.1) to the cathode material blend, the blended cathode material begins to show these safety benefits, and it has been shown that by adding 20 wt% or more LVPF, the benefits become significant. In summary, it has been found that increasing the amount of LVPF in the blended cathode material provides a correspondingly increased safety improvement. On the other hand, increasing the amount of LVPF may reduce the energy density, as the energy density of LVPF is lower than that of some NMC cathode materials, such as NMC811. Therefore, in this exemplary embodiment, in order to achieve the benefit of improved safety without significantly sacrificing energy density, a blended cathode material wherein 20% to 40% by weight of LVPF (0.2 ≤ r ≤ 0.4) is blended with a non-phosphate cathode material (e.g., NMC, NCA, LCO, LNMO, etc.) is specifically disclosed.

[0155] Secondary batteries

[0156] This disclosure also provides a secondary battery comprising a cathode, an anode, and an electrolyte solution, including a positive electrode active material (blended cathode material) having the present disclosure. A separator may be disposed between the anode and the cathode.

[0157] The individual electrochemical cells disclosed herein can be of any known type, such as cylindrical cells, button cells, prismatic cells, and pouch cells.

[0158] cathode

[0159] There are no particular limitations on the structure of the cathode, except that the cathode includes at least the positive electrode active material (blended cathode material) disclosed herein on the current collector. The cathode material may also contain one or more binder materials and one or more conductive materials.

[0160] There are no particular limitations on the current collector, and known materials and designs can be used. In a preferred embodiment, the current collector is a two-dimensional conductive support, such as a solid or perforated sheet based on carbon or metals such as aluminum, nickel, steel, stainless steel, or carbon-coated aluminum.

[0161] There are no particular limitations on the adhesive material, and known materials used for this function can be used. For example, the adhesive material may contain one or more of the following components: polyvinylidene fluoride (PVdF) and its copolymers; polytetrafluoroethylene (PTFE); polyacrylonitrile (PAN); polymethyl methacrylate or polybutyl methacrylate; polyvinyl chloride (PVC); polyvinyl alcohol formaldehyde; polyester and polyether block amides; polymers of acrylic acid, methacrylic acid, acrylamide, itaconic acid, sulfonic acid; and their derivatives with lithium salt elastomers and cellulose compounds.

[0162] Among the elastomers that may be used are ethylene / propylene / diene terpolymers (EPDM), styrene / butadiene copolymers (SBR), acrylonitrile / butadiene copolymers (NBR), styrene / butadiene / styrene block copolymers (SBS) or styrene / acrylonitrile / styrene block copolymers (SIS), styrene / ethylene / butene / styrene copolymers (SEBS), styrene / butadiene / vinylpyridine terpolymers (SBVR), polyurethanes (PU), neopentadiene, polyisobutylene (PIB), butyl rubber, and mixtures thereof.

[0163] Cellulose compounds can be, for example, carboxymethyl cellulose (CMC), hydroxypropyl methyl cellulose (HPMC), hydroxypropyl cellulose (HPC), hydroxyethyl cellulose (HEC), or other cellulose derivatives.

[0164] There are no particular restrictions on the conductive material, and any known conductive material can be used. For example, the conductive material can be selected from graphite, carbon black, acetylene black (AB), carbon nanotubes (CNT), carbon fiber (CF), soot, or mixtures thereof.

[0165] Methods for manufacturing cathodes are well known. For example, cathode material can be combined with binder material and / or conductive material by known methods and applied to a current collector. For example, particles containing cathode material can be formed by known methods and pressed onto a current collector, or a slurry containing cathode material and solvent can be coated onto a current collector by known methods and then dried.

[0166] There are no particular limitations on the amount of binder, conductive material and other additives, and suitable ratios are known in the art. When the total weight of the positive electrode material is considered to be 100% by weight, the amount of conductive material is preferably 1% to 20% by weight (or any amount within this range, for example 4% to 18% by weight), and the amount of binder is preferably 1% to 20% by weight (or any amount within this range, for example 1% to 7% by weight).

[0167] anode

[0168] There are no particular restrictions on the structure of the negative electrode (or anode), and known anode active materials can be used, as long as the material can function as the negative electrode active material in a lithium-ion battery. For example, the anode active material can include carbon-based negative electrode active materials such as graphite and coke, alloy-based negative electrode active materials such as Si and / or Sn, SiOx, lithium metal, lithium titanate oxide (LTO), or blends thereof. The anode active material can also include particles of one of these materials coated with a layer of conductive carbon (e.g., graphitic carbon) (e.g., particles of SiOx coated with carbon).

[0169] Similar to the cathode, the anode material may comprise an anodic active material and a binder, and the anode material may be applied to the current collector. In a preferred embodiment, the anodic active material of this disclosure may comprise 50% to 99% by weight of the anode material (or any amount within that range, such as 95% to 99% by weight, or 97% to 99% by weight of the anode material).

[0170] Electrolyte solution

[0171] The electrolyte solution can be a known non-aqueous electrolyte solution containing a supporting salt (e.g., a lithium salt) dissolved in a solvent.

[0172] There are no particular limitations on the lithium salt, and known lithium salts used in non-aqueous lithium-ion batteries can be used. In a preferred embodiment, the electrolyte salt may include one or more of the following: lithium bis(fluorosulfonyl)imide (“LiFSI”), lithium bis(trifluoromethanesulfonyl)imide (“LiTFSI”), LiBF4, lithium bis(oxalate)borate (“LiBOB”), LiClO4, LiAsF6, LiPF6, LiCF3SO3, LiAlCl4, lithium 4,5-dicyano-2-(trifluoromethyl)imidazolium (“LiTDI”), LiPO2F2, etc.

[0173] In a preferred embodiment, the lithium salt concentration in the electrolyte solution is greater than 0.8M, greater than 1.0M, greater than 1.2M, greater than 1.4M, greater than 1.5M, greater than 1.6M, greater than 1.7M, greater than 1.8M, or greater than 2.0M. In a preferred embodiment, the salt concentration is less than 4.0M, less than 3.6M, less than 3.2M, less than 2.8M, less than 2.4M, less than 2.0M, less than 1.6M, or less than 1.2M.

[0174] There are no particular restrictions on the solvent, and known solvents used in non-aqueous lithium-ion batteries can be used. The solvent can be a single solvent or a mixture of several solvents. The solvent can be selected from common organic solvents, particularly saturated cyclic carbonates; unsaturated cyclic carbonates; acyclic (or linear) carbonates; alkyl esters, such as formate, acetate, propionate, or butyrate; ethers; lactones, such as γ-butyrolactone; tetrahydrothiophene dioxide; nitrile solvents; and mixtures thereof. Among such saturated cyclic carbonates, specific examples include ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), and mixtures thereof. Among unsaturated cyclic carbonates, specific examples include vinylene carbonate (VC), its derivatives, and mixtures thereof. Among acyclic carbonates, specific examples include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dipropyl carbonate (DPC), and mixtures thereof. Among alkyl esters, specific examples include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, and mixtures thereof. Among ethers, examples include dimethyl ether (DME) or diethyl ether (DEE), and mixtures thereof. Known fluorinated solvents may also be used, including, for example, fluorinated benzenes (such as hexafluorobenzene, pentafluorobenzene, 1,2,3,4-tetrafluorobenzene, etc.), fluorinated linear carbonates, etc.

[0175] The electrolyte solution may contain known additives used in non-aqueous lithium-ion batteries.

[0176] One type of additive that can be included in the electrolyte solution is a gas generator for implementing a pressure-type current interruption device (CID). Exemplary gas generators include cyclohexylbenzene (CHB), biphenyl, and fluorinated biphenyl, which have oxidation potentials lower than the oxidation potentials of the solvent in the electrolyte solution. When the lithium-ion battery reaches an overcharged state, the compound reacts to generate gas before the electrolyte solution decomposes. When included, the amount of the gas generator is preferably from 0.01% to 10% by weight (or any amount within that range, e.g., 0.1% to 5% by weight; or 1% to 3% by weight).

[0177] Specific mention may also be made of the use of known film-forming additives for forming solid electrode interface (SEI) films on the anode or cathode. For example, one such additive includes a fluorinated compound additive, such as fluorinated ethylene carbonate (FEC). When included, FEC (and / or another additive) may be added to the solvent in an amount from 0.1% to 20% by weight based on the total weight of the solvent, or in any amount within that range, such as 1% to 10% by weight, 2% to 9% by weight, 3% to 8% by weight, 4% to 7% by weight, 5% to 6% by weight, 1% to 5% by weight, 1% to 4% by weight, 1% to 3% by weight, 1% to 2% by weight, 2% to 3% by weight, or 0.1% to 1% by weight.

[0178] Separator

[0179] There are no particular restrictions on the use of the separator, and known separators for secondary batteries can be used. The separator is placed between the two electrodes and typically exhibits high ionic conductivity (e.g., allowing cations (e.g., Li) to pass through). + (Through) mechanical stability and thermal stability. Separators that prevent dendrite growth are also known.

[0180] Conventional types of separators include microporous membranes, nonwoven membranes, electrospun membranes, membranes with modified outer surfaces, composite membranes, and polymer blends. In one embodiment, the separator is a microporous membrane made of a polyolefin-based material, such as a microporous membrane made of polyethylene (PE), polypropylene (PP), etc.

[0181] In some implementations, the battery does not include an electrolyte solution and a separator. Instead, a solid electrolyte layer (i.e., a solvent-free electrolyte) that functions as both a separator and an electrolyte solution can be used, such as a solid ion-conducting polymer in contact with both the negative and positive electrodes. Solid electrolytes rely on ions hopping across a rigid structure. Solid electrolytes can also be referred to as fast ion conductors or superion conductors. Solid electrolytes can also be used to electrically insulate the positive and negative electrodes of the battery while allowing ions, such as Li, to hop across the structure. + Conducted via electrolytes. In this case, the solid electrolyte layer can also be referred to as a solid electrolyte separator.

[0182] There are no particular restrictions on the use of solid electrolyte separators. Known solid electrolytes include polymer-based materials (e.g., polyethylene oxide (PEO), PEO-based materials (e.g., PEO-PPO, PEO-epoxychloropropane, methyleneoxy-PEO, PEO-PAAM, PEO-PMHS (polymethylhydrosiloxane), etc.), ceramic-based materials, and cellulose-based materials.

[0183] Battery modules, battery packs and battery systems

[0184] According to this disclosure, a battery module is a structure comprising multiple secondary batteries arranged side-by-side in a common housing; a battery pack is a structure comprising a plurality of electrically connected battery modules; and a battery system is a structure comprising a plurality of electrically connected single cells or battery modules. A battery module or battery pack may include one or more control systems (e.g., a battery management system).

[0185] How to electrically connect secondary batteries in series and parallel is well known and understood. Several techniques for assembling multiple electrochemical cells and modules are disclosed, for example, in U.S. Publication No. 2019 / 0123315 ('315 application) and U.S. Publication No. 2019 / 0165584 ('584 application), the disclosures of which are incorporated herein by reference. Furthermore, battery systems may include additional structures, including a battery management system (BMS) and a cooling system.

[0186] Charging status

[0187] Determining the state of charge (SOC) of a secondary battery based on its voltage is well known in the art, and battery management systems (BMS) configured to determine SOC based on battery voltage are also well known. Methods for battery monitoring and balancing are also well known in the art. For example, such methods are discussed in U.S. Publication No. 2010 / 0253277 ('277 application) and U.S. Publication No. 2015 / 0115736 ('736 application), and their discussions of battery monitoring and balancing (including the hardware and programming used to implement this function) are incorporated herein by reference.

[0188] The battery modules and / or battery systems of this disclosure may include known BMS configured with, for example, known procedures (e.g., algorithms) for determining State of Charge (SOC). Alternatively, the battery modules and systems of this disclosure may be configured to be operated and / or monitored by an external BMS.

[0189] Example

[0190] In the following, although embodiments of the present disclosure are described in more detail by way of examples, the present disclosure is not limited thereto.

[0191] Example 1

[0192] In Example 1, a single-layer pouch cell with the following configuration was prepared. For each cell, LVPF (LiVPO4F) as the first active material and NMC622 (LiNi) as the second active material were used. 0.6 Mn 0.2 Co 0.2The cathode is manufactured by blending the first active material with the second active material in a weight ratio (i.e., r:(1-r)) of 0.1:0.9 to 1:0 (i.e., the weight ratio of the battery ranges from 10% LVPF to 100% LVPF); the anode is Li metal; and the electrolyte is 1M LiPF6 in an organic solvent blend of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (with a volume ratio (EC / EMC / DMC) of 1:1:1). The configurations of the batteries of Example 1 are summarized in Table 1 below.

[0193] Table 1

[0194]

[0195] The prepared battery was tested as follows.

[0196] State of charge and depth of discharge (DOD)

[0197] As mentioned above, LVPFs are found to have a very flat voltage plateau for state of charge (SOC) or depth of discharge (DOD), making it difficult (if not impossible) for BMS to detect SOC or DOD by voltage. This is, for example, in... Figure 1 and Figure 2 As shown in the diagram. To generate... Figure 1 and Figure 2 The curve in the figure shows that the prepared battery was charged at a constant rate (0.1C) at a temperature of approximately 25°C. Figure 1 ) or discharge ( Figure 2 ).

[0198] like Figure 1 and Figure 2 As shown, battery 1A, containing only LVPF, exhibits a very flat voltage for both SOC during charging and DOD during discharging. However, batteries 1B to 1E demonstrate that blending LVPF with NMC as a second active material produces a slope at the start of charging and the end of discharging. This allows the BMS to detect either SOC or DOD via voltage.

[0199] Ratio performance

[0200] The rate performance of the prepared battery was also tested (specific capacity retention (%) at different current (C) rates). The results are shown in... Figure 3 As shown, LVPF significantly improves the rate performance of NMC, especially at higher C rates.

[0201] Capacity retention

[0202] The capacity retention of the prepared battery was also tested. The results are shown in... Figure 4As shown, blending these cathode materials improved the cycle life of both LVPF and NMC. For example, the best capacity retention was achieved in cell 1D (r = 0.4 (LVPF 40 wt%; NMC 60 wt%)) and cell 1C (r = 0.7 (LVPF 70 wt%; NMC 30 wt%)), while the worst capacity retention was achieved in cell 1A (r = 1 (LVPF 100 wt%)) and cell 1E (r = 0.1 (LVPF 10 wt%; NMC 90 wt%)).

[0203] Example 2

[0204] In Example 2, a single-layer pouch cell with the same configuration as in Example 1 was prepared, except that the second active material was LFMP (LiFe2+). 0.22 Mn 0.78 PO4). The battery configuration is summarized in Table 2 below.

[0205] Table 2

[0206]

[0207] The prepared battery was tested as follows.

[0208] Ratio performance

[0209] The rate performance of the prepared battery was tested (the retention rate of specific capacity (%) at different current (C) rates). The results are shown in... Figure 5 As shown, LVPF significantly improves the rate performance of LFMP, especially at higher C rates.

[0210] The addition of LVPF also improved the processability of LFMP, demonstrating that LVPF has excellent processability. For example, it was found that blending LVPF with LFMP made the slurry more stable over time and easier to coat, thus making both the slurry preparation process and the electrode coating process more controllable and robust.

[0211] Various modifications and alternatives are readily possible within this disclosure, and specific embodiments thereof are described in detail herein. However, it should be understood that this disclosure is not limited to the specific embodiments or methods disclosed, but rather, this disclosure covers all modifications, equivalents, and alternatives falling within the spirit and scope of the claims.

Claims

1. A positive electrode material for a secondary battery, the positive electrode material comprising: a first active material, the first active material being selected from lithium vanadium fluorophosphate represented by the following formula (1) and lithium vanadium fluorophosphate derivatives represented by the following formula (2): Li 1+x VPO4F Formula (1), in, in formula (1), 0≤x≤0.15, Li 1+x V 1-y M y PO4F z Formula (2), wherein, in formula (2), 0≤x≤0.15; 0<y≤0.5; 0.8≤z≤1.2; and M is one or more selected from Ti, Al, Mg, Mn, Fe, Co, Y, Cr, Cu, Ni and Zr; and a second active material, wherein the weight ratio of the first active material to the second active material is r:(1-r), where 0.6≤r≤0.9; and the second active material is represented by the following: - formula (B1) or - formula (B3) or - a blend of formula (A4) and formula (B1), or - a blend of formula (A4) and formula (B3), Equation (B1) is Li w (Ni x Mn y Co z M t O2, wherein, in formula (B1), 0.9≤w≤1.1; x>0; y>0; z>0; t≥0; M is one or more selected from Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, Sr, Ce, Ga and Ta; and optionally x+y+z+t=1, Equation (B3) is Li w (Ni x Co y Al z M t O2, wherein, in formula (B3), 0.9≤w≤1.1; x>0; y>0; z>0; t≥0; M is one or more selected from B, Mg, Si, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, Sr, Ce, Ga and Ta; and optionally x+y+z+t=1, Equation (A4) is Li 1+x Fe y Mn z X b PO4, wherein, in formula (A4), X is at least one transition metal selected from Ni, V, Y, Mg, Ca, Ba, Al, Sc and Nd; 0≤x≤0.15; y>0; z>0; b≥0; and optionally y+z+b=1.

2. The positive electrode material according to claim 1, wherein the second active material represented by formula (B1) is selected from: LiNi 0.33 Mn 0.33 Co 0.33 O2, LiNi 0.5 Mn 0.3 Co 0.2 O2, LiNi 0.6 Mn 0.2 Co 0.2 O2 and LiNi 0.8 Mn 0.1 Co 0.1 O2.

3. The positive electrode material according to claim 1, wherein the weight ratio of formula (A4) to formula (B1) is m:(1-m), where 0<m<1.

4. The positive electrode material according to claim 1, wherein the weight ratio of formula (A4) to formula (B3) is m:(1-m), where 0<m<1.

5. The positive electrode material according to claim 1, further comprising a binder material and a conductive material.

6. A lithium-ion secondary battery, the battery comprising: a cathode comprising the positive electrode material according to claim 1; an anode comprising a negative electrode active material; and an electrolyte solution comprising a lithium salt and an organic solvent.

7. A battery system, comprising: a plurality of the batteries according to claim 6, the plurality of batteries being electrically connected; and a battery management system, the battery management system being configured to monitor the state of charge of the plurality of batteries based on the voltage of one or more batteries among the plurality of batteries.

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