Battery cell and manufacturing method therefor, and battery and electric apparatus

Abstract

Provided in the present application are a battery cell and a manufacturing method therefor, and a battery and an electric apparatus. The battery cell comprises a positive electrode sheet and an electrolyte. The electrolyte solution contains a non-aqueous solvent and electrolyte salt, wherein the electrolyte salt contains lithium salt and metal Me salt, the ionic radius of Me positive ions is greater than the ionic radius of lithium ions, and the weight content of the lithium ions in the electrolyte is denoted as w1, and the weight content of the Me positive ions in the electrolyte is denoted as w2, both of which are based on the total weight of the electrolyte. In a charge and discharge test of a battery cell, the total discharge capacity of the battery cell is denoted as Q1, and the discharge capacity of the battery cell with a discharge voltage of 3.6 V is denoted as Q2, and the unit of the discharge capacities is mAh. When the remaining capacity of the battery cell is greater than 90%, 0.8≤(Q2 / Q1) / [w2 / (w1+w2)]≤8.5 is satisfied.

Description

Battery monomer and preparation method thereof, battery and power-using device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202310775706.4, filed on June 28, 2023, entitled “Battery Cell and Method for Making Same, Battery and Electrical Device,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to a battery cell and a preparation method thereof, a battery and an electrical device. Background Art

[0004] In recent years, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. As an important component of the battery, the performance of the positive electrode active material will affect the performance of the battery. At present, a single positive electrode active material that can meet the requirements of low cost, high gram capacity and few side reactions has not yet been developed, so the positive electrode plate often includes two or more different types of positive electrode active materials at the same time. However, when different types of positive electrode active materials are mixed, the internal resistance increases rapidly during the battery cycle, which causes the power performance of the battery to decay more significantly and the capacity retention rate to decay faster in the later stage of use, thereby affecting the use of the battery. The above statements are only used to provide background technical information related to this application and do not necessarily constitute prior art.

[0005] Summary of the Invention

[0006] The present application provides a battery cell and a preparation method thereof, a battery and an electrical device, which can improve the cycle performance of the battery.

[0007] A first aspect of the present application provides a battery cell comprising a positive electrode plate and an electrolyte.

[0008] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material, the positive electrode active material includes a first positive electrode active material and a second positive electrode active material, the first positive electrode active material and the second positive electrode active material can extract and embed lithium ions, the first positive electrode active material and the second positive electrode active material have different crystal forms, the second positive electrode active material has a one-dimensional ion transport channel, and the ionic conductivity of the first positive electrode active material is greater than the ionic conductivity of the second positive electrode active material.

[0009] The electrolyte includes a non-aqueous solvent and an electrolyte salt, the electrolyte salt includes a lithium salt and a metal Me salt, the lithium salt dissociates into lithium ions and a first anion in the electrolyte, the metal Me salt dissociates into Me cations and a second anion in the electrolyte, the ionic radius of the Me cation is larger than the ionic radius of the lithium ion, the weight content of the lithium ion in the electrolyte is recorded as w1, and the weight content of the Me cation in the electrolyte is recorded as w2, both based on the total weight of the electrolyte.

[0010] In the charge and discharge test of the battery cell, the total discharge capacity of the battery cell is recorded as Q1, and the discharge capacity of the battery cell at a discharge voltage below 3.6V is recorded as Q2, both in mAh.

[0011] When the remaining capacity of the battery cell is greater than 90%, the following condition is satisfied: 0.8≤(Q2 / Q1) / [w2 / (w1+w2)]≤8.5.

[0012] The charge and discharge test of the battery cell was carried out under the following conditions: the test temperature was 25° C., the battery cell was fully charged at 0.5C, and after standing for 5 minutes, the battery cell was fully discharged at 0.33C.

[0013] The inventors discovered that by including a metal Me salt in the electrolyte whose cations have an ionic radius larger than that of lithium ions, the Me cations in the electrolyte become embedded in the surface layer of the first positive electrode active material during battery discharge. Because the Me cations have an ionic radius larger than that of lithium ions, they become trapped in the transport channels of the first positive electrode active material used for lithium ion extraction and insertion during battery discharge, thereby stabilizing the surface structure of the first positive electrode active material.

[0014] The inventors further discovered that when the battery cell satisfies 0.8≤(Q2 / Q1) / [w2 / (w1+w2)]≤8.5, the battery can have a lower internal resistance growth rate, a long cycle life, and good power performance.

[0015] In any embodiment, 1.1≤(Q2 / Q1) / [w2 / (w1+w2)]≤6.8, optionally, 1.7≤(Q2 / Q1) / [w2 / (w1+w2)]≤3.9. This allows the amount of Me cations in the electrolyte to better match the discharge capacity of the battery at a discharge voltage below 3.6V, thereby further reducing the battery internal resistance growth rate and further improving the battery's cycle performance and power performance.

[0016] In any embodiment, 0.29≤Q2 / Q1≤0.42, optionally, 0.31≤Q2 / Q1≤0.40.

[0017] In any embodiment, 0.05≤w2 / (w1+w2)≤0.35, optionally, 0.05≤w2 / (w1+w2)≤0.30. When w2 / (w1+w2) is within the above range, the stability of the negative electrode interface can be improved, thereby improving the high-temperature performance of the battery.

[0018] In any embodiment, the Me element includes one or more elements selected from the group consisting of alkali metal elements and alkaline earth metal elements.

[0019] Optionally, the alkali metal element includes one or more of Na and K.

[0020] Optionally, the alkaline earth metal elements include one or more of Ca and Mg.

[0021] In any embodiment, the first anion comprises PF6 - 、ClO4 - 、AsF6 - 、BF4 - 、N(CF3SO2)2 - CF3SO3 - 、N(FSO2)2 - 、C(SO2CF3)3 - PO2F2 - , one or more of difluorooxalatoborate ion, dioxalatoborate ion, difluorooxalatophosphate ion, and tetrafluorooxalatophosphate ion.

[0022] In any embodiment, the second anion comprises PF6 - 、ClO4 - 、AsF6 - 、BF4 - 、N(CF3SO2)2 - CF3SO3 - 、N(FSO2)2 - 、C(SO2CF3)3 - PO2F2 - , one or more of difluorooxalatoborate ion, dioxalatoborate ion, difluorooxalatophosphate ion, and tetrafluorooxalatophosphate ion.

[0023] In any embodiment, the first anion is the same as the second anion, thereby further reducing the growth rate of the battery internal resistance and better improving the cycle performance and power performance of the battery.

[0024] In any embodiment, based on the total weight of the positive electrode active material, the weight proportion W1 of the first positive electrode active material is 10%-90%, and optionally 70%-90%.

[0025] In any embodiment, based on the total weight of the positive electrode active material, the weight proportion W2 of the second positive electrode active material is 10%-90%, and optionally 10%-30%.

[0026] This enables the battery to better balance high energy density and long cycle life.

[0027] In any embodiment, the specific surface area of ​​the first positive electrode active material is 0.5-1 m 2 / g, optional 0.6-0.9m 2 / g.

[0028] In any embodiment, the specific surface area of ​​the second positive electrode active material is 10-20 m 2 / g, optional 12-16m 2 When the specific surface area of ​​the second positive electrode active material is within the above range, the battery has a lower internal resistance growth rate and a longer cycle life.

[0029] In any embodiment, the first positive active material includes a lithium-containing layered oxide.

[0030] In any embodiment, the first positive electrode active material comprises a compound represented by formula (I). a A 1 b Ni c Co d B 1 e C 1 f O g D 1 h (I)

[0031] A 1 It includes one or more elements selected from Group IA, Group IIA, Group VIII, Group VIB, and Group IIB, and may optionally include one or more elements selected from Na, K, Mg, Rb, Zn, and Zr; B 1 including Mn and / or Al; C 1comprising one or more elements selected from Group IA, Group IIA, Group IIIA, Group IVA, Group VA, Group VIA, Group IB, Group IIB, Group IIIB, Group IVB, Group VB, Group VIB, and Group VIII, optionally comprising one or more elements selected from Al, Mg, Ca, Na, Ti, W, Zr, Sr, Cr, Fe, Zn, Cu, Ba, Mo, V, Ce, Nb, Sb, Ta, Ge, Nb, Sc, Ba, B, S, and Y, more optionally comprising one or more elements selected from Mg, Ti, W, Zr, Cr, Fe, Zn, Cu, V, Nb, Sr, Sb, and Y; D 1 It includes one or more elements selected from Group VIA and Group VIIA, and can be optionally selected from one or more elements selected from N, S, F, Cl and Br, and can be further optionally selected from S and / or F; a is selected from the range of 0.75 to 1.2, and can be optionally selected from the range of 0.9 to 1.1; b is selected from the range of 0 to 0.2, and can be optionally selected from the range of 0 to 0.1; c is selected from the range of 0.001 to 0.990, and can be optionally selected from the range of 0.500 to 0.990; d is selected from the range of 0 to 0.990, and can be optionally selected from the range of 0 to 0.100; e is selected from the range of 0.001 to 0.990, and can be optionally selected from the range of 0.005 to 0.450; f is selected from the range of 0 to 0.1, and can be optionally selected from the range of 0.001 to 0.05; g is selected from the range of 1.0 to 2.0, and can be optionally selected from the range of 1.9 to 2.0; h is selected from the range of 0 to 1.0, and can be optionally selected from the range of 0.01 to 0.1.

[0032] In any embodiment, c+d+e+f=1.

[0033] In any embodiment, g+h=2.

[0034] In any embodiment, the first positive electrode active material includes a first core and a first shell covering the first core, wherein the first core includes a compound represented by formula (I); the first shell includes one or more coating layers, each coating layer having ionic conductivity and / or electronic conductivity.

[0035] In any embodiment, the one or more coating layers independently include one or more selected from phosphate, pyrophosphate, carbon, doped carbon, oxide, and fast ion conductor, and can optionally include one or more selected from phosphate, pyrophosphate, and oxide.

[0036] In any embodiment, the coating amount of the first shell is 0.005-1 wt %, optionally 0.01-0.5 wt %, based on the weight of the first core.

[0037] In any embodiment, the thickness of the first shell is 2 nm to 200 nm, optionally 5 nm to 50 nm.

[0038] In any embodiment, the second positive active material includes a lithium-containing phosphate.

[0039] In any embodiment, the second positive electrode active material comprises a compound represented by formula (II). m1 A 2 x1 Mn 1-y1 B 2 y1 P 1-z1 C 2 z1 O 4-n1 D 2 n1 (II)

[0040] A 2 It includes one or more elements selected from Group IA, Group IIA, Group IIIA, Group IIB, Group VB, and Group VIB, and may optionally include one or more elements selected from Rb, Cs, Be, Ca, Sr, Ba, Ga, In, Cd, V, Ta, Cr, Zn, Al, Na, K, Mg, Nb, Mo, and W, and may further include one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo, and W; B 2 The invention comprises one or more elements selected from Group IA, Group IIA, Group IIIA, Group IVA, Group VA, Group IIB, Group IVB, Group VB, Group VIB and Group VIII, and may optionally include one or more elements selected from the group consisting of Rb, Cs, Be, Ca, Sr, Ba, In, Pb, Bi, Cd, Hf, Ta, Cr, Ru, Rh, Pd, Os, Ir, Pt, Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge, and may further include one or more elements selected from the group consisting of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge; C 2 including one or more elements selected from Group IIIA, Group IVA, Group VA, and Group VIA, and optionally including one or more elements selected from B, S, Si, and N; D 2It includes one or more elements selected from Group VIA and Group VIIA, and can be optionally selected from one or more elements selected from S, F, Cl and Br; m1 is selected from the range of 0.85 to 1.15, can be optionally selected from the range of 0.9 to 1.1, and can be more optionally selected from the range of 0.97 to 1.01; x1 is selected from the range of 0 to 0.1, can be optionally selected from the range of 0.001 to 0.1, and can be more optionally selected from the range of 0.001 to 0.005; y1 is selected from the range of 0.001 to 0.999, can be selected from the range of 0.001 to 0.5, and can be more optionally selected from the range of 0.2 to 0.5; z1 is selected from the range of 0 to 0.5, can be selected from the range of 0.001 to 0.1, and can be more optionally selected from the range of 0.001 to 0.005; n1 is selected from the range of 0 to 0.5, can be selected from the range of 0 to 0.1, and can be more optionally selected from the range of 0.001 to 0.005.

[0041] By doping LiMnPO4 with specific elements in specific amounts at the Mn position and optionally at the Li, P and / or O positions, improved rate performance can be obtained while reducing the dissolution of Mn and the doping elements at the Mn position, thereby achieving improved cycle performance and / or high-temperature stability, and the gram capacity and compaction density of the material are also improved.

[0042] In any embodiment, A 2 The present invention includes any one element selected from the group consisting of Zn, Al, Na, K, Mg, Nb, Mo, and W, and may optionally include any one element selected from the group consisting of Mg and Nb.

[0043] In any embodiment, B 2 It includes one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge, and can be optionally included at least two elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge, and can be more optionally included at least two elements selected from Fe, Ti, V, Ni, Co and Mg, and can further be optionally included at least two elements selected from Fe, Ti, V, Co and Mg, and can further be optionally included Fe and one or more elements selected from Ti, V, Co and Mg.

[0044] In any embodiment, C 2 Includes any one element selected from B, S, Si and N, and S is optional.

[0045] In any embodiment, D 2 It includes any one element selected from S, F, Cl and Br, and F is optional.

[0046] In any embodiment, x1 is 0, z1 is 0, and n1 is 0; or, x1 is 0, z1 is selected from the range of 0.001 to 0.5, and n1 is selected from the range of 0.001 to 0.1; or, x1 is selected from the range of 0.001 to 0.1, z1 is 0, and n1 is selected from the range of 0.001 to 0.1; or, x1 is selected from the range of 0.001 to 0.1, z1 is selected from the range of 0.001 to 0.5, and n1 is 0; or, x1 is 0, z1 is 0, and n1 is selected from the range of 0.001 to 0.1; or, x1 is 0, z1 is 0, and n1 is selected from the range of 0.001 to 0.1; or, x1 is 0, z1 is selected from the range of 0.001 to 0.5, and n1 is 0; or, x1 is selected from the range of 0.001 to 0.1, z1 is selected from the range of 0.001 to 0.5, and n1 is 0.

[0047] By doping a specific element in a specific amount at the Mn position of LiMnPO4 and optionally at the Li position, P position and / or O position, especially doping a specific element in a specific amount at the Mn position and P position of LiMnPO4 or at the Li position, Mn position, P position and O position of LiMnPO4, the rate performance can be improved, the dissolution of Mn and the doping element at the Mn position can be reduced, the cycle performance and / or high temperature stability can be improved, and the gram capacity and compaction density of the second positive electrode active material can be increased.

[0048] In any embodiment, y1:z1 is selected from the range of 0.002 to 999, and can be selected from the range of 0.025 to 999 or the range of 0.002 to 500, and can be further selected from the range of 0.2 to 600. In this way, defects of the second positive electrode active material can be reduced, and the integrity of the framework structure of the second positive electrode active material can be improved, thereby effectively improving the structural stability of the second positive electrode active material and further improving the cycle stability of the battery.

[0049] In any embodiment, z1:n1 is selected from the range of 0.002 to 500, optionally from the range of 0.2 to 100, and more optionally from the range of 0.2 to 50. In this way, defects of the second positive electrode active material can be further reduced, the integrity of the framework structure of the second positive electrode active material can be further improved, the structural stability of the second positive electrode active material can be effectively improved, and the cycle stability of the battery can be improved.

[0050] In any embodiment, A 2 including one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo and W; B 2 including one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge; C 2 including one or more elements selected from B, S, Si and N; D 2It includes one or more elements selected from S, F, Cl and Br; m1 is selected from the range of 0.9 to 1.1, x1 is selected from the range of 0.001 to 0.1, y1 is selected from the range of 0.001 to 0.5, z1 is selected from the range of 0.001 to 0.1, and n1 is selected from the range of 0.001 to 0.1.

[0051] By doping specific elements at specific amounts at the Li, Mn, P, and O positions of LiMnPO4 simultaneously, improved rate performance can be obtained, while reducing the dissolution of Mn and the doping elements at the Mn position, thereby achieving improved cycle performance and / or high-temperature stability, and the gram capacity and compaction density of the second positive electrode active material can also be improved.

[0052] In any embodiment, B 2 including one or more elements selected from the group consisting of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and optionally including one or more elements selected from the group consisting of Zn, Fe, Ti, V, Ni, Co, and Mg; C 2 It includes one or more elements selected from B, Si, N and S; m1 is selected from the range of 0.9 to 1.1, x1 is 0, y1 is selected from the range of 0.001 to 0.5, z1 is selected from the range of 0.001 to 0.1, and n1 is 0.

[0053] By doping specific elements at specific amounts at both the Mn and P sites of LiMnPO4, the rate performance can be improved, the dissolution of Mn and the doping elements at the Mn site can be reduced, the cycle performance and / or high-temperature stability can be improved, and the gram capacity and compaction density of the second positive electrode active material can be increased.

[0054] In any embodiment, (1-y1):y1 is in the range of 0.1-999, optionally in the range of 0.1-10 or in the range of 0.67-999, more optionally in the range of 1 to 10, further optionally in the range of 1 to 4, and further optionally in the range of 1.5 to 3.

[0055] In any embodiment, a1:x1 is in the range of 1 to 1200, optionally in the range of 9 to 1100, and more optionally in the range of 190-998.

[0056] In any embodiment, z1:(1-z1) is 1:9 to 1:999, and can be optionally 1:499 to 1:249. When the above conditions are met, the energy density and cycle performance of the second positive electrode active material can be further improved.

[0057] In any embodiment, the second positive electrode active material comprises a compound represented by formula (III). m2 A3 x2 Fe 1-y2 B 3 y2 P 1-z2 C 3 z2 O 4-n2 D 3 n2 (III)

[0058] A 3 It includes one or more elements selected from Group IA, Group IIA, Group IIIA, Group IIB, Group VB, and Group VIB, and may optionally include one or more elements selected from Rb, Cs, Be, Ca, Sr, Ba, Ga, In, Cd, V, Ta, Cr, Zn, Al, Na, K, Mg, Nb, Mo, and W, and may further include one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo, and W; B 3 The invention comprises one or more elements selected from Group IA, Group IIA, Group IIIA, Group IVA, Group VA, Group IIB, Group IVB, Group VB, Group VIB and Group VIII, and may optionally include one or more elements selected from the group consisting of Rb, Cs, Be, Ca, Sr, Ba, In, Pb, Bi, Cd, Hf, Ta, Cr, Ru, Rh, Pd, Os, Ir, Pt, Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Ni, Co, Ga, Sn, Sb, Nb and Ge, and may further include one or more elements selected from the group consisting of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Ni, Co, Ga, Sn, Sb, Nb and Ge; C 3 including one or more elements selected from Group IIIA, Group IVA, Group VA, and Group VIA, and optionally including one or more elements selected from B, S, Si, and N; D 3 It includes one or more elements selected from Group VIA and Group VIIA, and can be optionally selected from one or more elements selected from S, F, Cl and Br; m2 is selected from the range of 0.85 to 1.15, can be optionally selected from the range of 0.9 to 1.1, and can be more optionally selected from the range of 0.97 to 1.01; x2 is selected from the range of 0 to 0.1, and can be optionally selected from the range of 0.001 to 0.005; y2 is selected from the range of 0 to 0.5, can be optionally selected from the range of 0.001 to 0.2, and can be more optionally selected from the range of 0.005 to 0.1; z2 is selected from the range of 0 to 0.5, can be optionally selected from the range of 0.001 to 0.1, and can be more optionally selected from the range of 0.001 to 0.005; n2 is selected from the range of 0 to 0.5, can be optionally selected from the range of 0 to 0.1, and can be more optionally selected from the range of 0.001 to 0.005.

[0059] In any embodiment, the second positive electrode active material includes a second core and a second shell coating the second core, wherein the second core includes the compound represented by formula (II) or the compound represented by formula (III); the second shell includes one or more coating layers; each coating layer has ionic conductivity and / or electronic conductivity. By providing a coating layer having ionic conductivity and / or electronic conductivity on the surface of the second core, a second positive electrode active material having a core-shell structure is provided. When the second positive electrode active material is used in a battery, the high-temperature cycling performance, cycling stability, and high-temperature storage performance of the battery can be improved.

[0060] In any embodiment, the one or more coating layers each independently include one or more selected from pyrophosphate, phosphate, carbon, doped carbon, oxide, boride, and polymer.

[0061] In any embodiment, the second shell comprises a coating layer; optionally, the coating layer comprises one or more selected from pyrophosphate, phosphate, carbon, doped carbon, oxide, boride, and polymer. Using such materials can provide a coating layer having ionic and / or electronic conductivity, thereby improving the high-temperature cycling performance, cycling stability, and high-temperature storage performance of the battery.

[0062] In any embodiment, the second shell includes a first coating layer covering the second core and a second coating layer covering the first coating layer; optionally, the first coating layer and the second coating layer each independently include one or more selected from pyrophosphate, phosphate, carbon, doped carbon, oxide, boride, and polymer; more optionally, the first coating layer includes one or more selected from pyrophosphate, phosphate, oxide, and boride, and the second coating layer includes one or more selected from carbon and doped carbon. Using a first coating layer and a second coating layer of a specific material can further improve rate performance and further reduce the dissolution of Mn and Mn-site doping elements, thereby improving the battery's cycling performance and / or high-temperature stability.

[0063] In any embodiment, the second shell includes a first coating layer covering the second inner core, a second coating layer covering the first coating layer, and a third coating layer covering the second coating layer; optionally, the first coating layer, the second coating layer, and the third coating layer each independently include one or more selected from pyrophosphate, phosphate, carbon, doped carbon, oxide, boride, and polymer; more optionally, the first coating layer includes pyrophosphate, the second coating layer includes one or more selected from phosphate, oxide, and boride, and the third coating layer includes one or more selected from carbon and doped carbon. The use of a first coating layer, a second coating layer, and a third coating layer of a specific material further improves rate performance, further reduces the dissolution of Mn and Mn-site doping elements, thereby improving the battery's cycling performance and / or high-temperature stability, and further increases the gram capacity and compaction density of the second positive electrode active material.

[0064] In any embodiment, the pyrophosphate is M i (P2O7) j and / or,

[0065] The phosphate is X p (PO4) q and / or,

[0066] The doping element in the doped carbon includes one or more elements selected from Group IIIA, Group VA, Group VIA and Group VIIA; and / or,

[0067] The oxide is M' k O l and / or,

[0068] The boride is Z v B w and / or,

[0069] The polymer includes one or more selected from polysaccharides and their derivatives, and polysiloxanes;

[0070] M, X, and Z each independently comprise one or more elements selected from Group IA, Group IIA, Group IIIA, Group IB, Group IIB, Group IVB, Group VB, Group VIIB, and Group VIII;

[0071] i is selected from the range of 1 to 4;

[0072] j is selected from the range of 1 to 6;

[0073] p is selected from the range of 1 to 2;

[0074] q is selected from the range of 1 to 4;

[0075] M′ comprises one or more elements selected from alkali metals, alkaline earth metals, transition metals, Group IIIA elements, Group IVA elements, lanthanides, and Sb;

[0076] k is greater than 0 and less than or equal to 2;

[0077] l is greater than 0 and less than or equal to 5;

[0078] v is selected from the range of 1 to 7;

[0079] w is selected from the range of 1 to 2.

[0080] By using the above materials as the coating layer, the dissolution of Mn and Mn-doping elements can be further reduced, the gram capacity and compaction density of the second positive electrode active material can be further increased, and the battery's rate performance, high-temperature cycle performance and high-temperature storage performance can be further improved.

[0081] In any embodiment, M, X and Z each independently include one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, Mn and Al; and / or,

[0082] The doping element in the doped carbon includes one or more elements selected from nitrogen, phosphorus, sulfur, boron and fluorine; and / or,

[0083] M′ comprises one or more elements selected from the group consisting of Li, Be, B, Na, Mg, Al, Si, P, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, W, La, and Ce, and may optionally comprise one or more elements selected from the group consisting of Mg, Al, Si, Zn, Zr, and Sn; and / or

[0084] The polysiloxane is selected from one or more of linear polysiloxane and cyclic polysiloxane; and / or,

[0085] The polysaccharide is selected from one or more of plant polysaccharides and marine polysaccharides.

[0086] By using the above-mentioned specific material as the coating layer, the dissolution of Mn and Mn-doping elements can be further reduced, and the high-temperature cycle performance and high-temperature storage performance of the battery can be further improved.

[0087] In any embodiment, the second positive electrode active material includes a second core and a second shell covering the second core, wherein the second core includes Li m1 Mn 1-y1 B 2 y1P 1-z1 C 2 z1 O4, m1 is selected from the range of 0.9 to 1.1, y1 is selected from the range of 0.001 to 0.5, z1 is selected from the range of 0.001 to 0.1, B 2 including one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge, C 2 The lithium manganese phosphate (LMP) comprises one or more elements selected from B, S, Si, and N. The second shell comprises a first coating layer covering the second core and a second coating layer covering the first coating layer. The first coating layer comprises pyrophosphate MP2O7 and phosphate XPO4, and M and X each independently comprise one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al. The second coating layer comprises carbon. By doping the LMP with specific elements and coating its surface, Mn dissolution during the lithiation process can be effectively reduced while promoting lithium ion migration, thereby improving the battery's rate capability, cycling performance, and high-temperature performance.

[0088] In any embodiment, the second positive electrode active material includes a second core and a second shell covering the second core, wherein the second core includes Li m1 Mn 1-y1 B 2 y1 P 1-z1 C 2 z1 O4, m1 is selected from the range of 0.9 to 1.1, y1 is selected from the range of 0.001 to 0.5, z1 is selected from the range of 0.001 to 0.1, B 2 including one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge, C 2 The second shell includes a first coating layer covering the second core, a second coating layer covering the first coating layer, and a third coating layer covering the second coating layer, wherein the first coating layer includes pyrophosphate Li r QP2O7 and / or Q s (P2O7) t , 0≤r≤2, 1≤s≤4, 1≤t≤6, the pyrophosphate Li r QP2O7 and / or Q s (P2O7) tQ in the second coating layer independently comprises one or more elements selected from the group consisting of Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al; the second coating layer comprises crystalline phosphate XPO4, and X comprises one or more elements selected from the group consisting of Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al; and the third coating layer comprises carbon. Thus, the second positive electrode active material can improve the specific capacity and cycle performance of the battery.

[0089] In any embodiment, the one or more coating layers in the second shell that are furthest from the second core each independently comprise one or more selected from polysiloxanes, polysaccharides, and polysaccharide derivatives. This improves coating uniformity and effectively blocks interfacial side reactions caused by high voltage, thereby enhancing the high-temperature cycling and storage performance of the second positive electrode active material. Furthermore, the coating layer exhibits good ionic conductivity, contributing to an increase in the specific capacity of the second positive electrode active material while reducing heat generation in the battery.

[0090] In any embodiment, the polysiloxane comprises a structural unit represented by formula (i).

[0091] R1 and R2 are independently selected from H, -COOH, -OH, -SH, -CN, -SCN, amino, phosphate, carboxylate, amide, aldehyde, sulfonyl, polyether segment, C1-C20 aliphatic, C1-C20 halogenated aliphatic, C1-C20 heteroaliphatic, C1-C20 halogenated heteroaliphatic, C6-C20 aromatic, C6-C20 halogenated aromatic, C2-C20 heteroaromatic and C2-C20 halogenated heteroaromatic; optionally, R1 and R2 are independently selected from H, amino, phosphate, polyether segment, C1-C8 alkyl, C1-C8 halogenated alkyl, C1-C8 heteroalkyl, C1-C8 halogenated heteroalkyl, C2-C8 alkenyl and C2-C8 halogenated alkenyl.

[0092] In any embodiment, the polysiloxane further comprises an end-capping group, wherein the end-capping group comprises one or more of the following functional groups: polyether, C1-C8 alkyl, C1-C8 haloalkyl, C1-C8 heteroalkyl, C1-C8 haloheteroalkyl, C2-C8 alkenyl, C2-C8 haloalkenyl, C6-C20 aromatic hydrocarbon group, C1-C8 alkoxy, C2-C8 epoxy, hydroxyl, C1-C8 hydroxyalkyl, amino, C1-C8 aminoalkyl, carboxyl, C1-C8 carboxylalkyl.

[0093] In any embodiment, the polysiloxane comprises a polysiloxane selected from polydimethylsiloxane, polydiethylsiloxane, polymethylethylsiloxane, polymethylvinylsiloxane, polyphenylmethylsiloxane, polymethylhydrogensiloxane, carboxyl functionalized polysiloxane, epoxy-terminated polysiloxane, methoxy-terminated polydimethylsiloxane, hydroxypropyl-terminated polydimethylsiloxane, polymethylchloropropylsiloxane, hydroxy-terminated polydimethylsiloxane, polymethyltrifluoropropylsiloxane, perfluorooctylmethylpolysiloxane, aminoethylaminopropyl polydimethylsiloxane, terminal polyether polydimethylsiloxane, side chain aminopropyl polysiloxane. , aminopropyl-terminated polydimethylsiloxane, side chain phosphate grafted polydimethylsiloxane, side chain polyether grafted polydimethylsiloxane, 1,3,5,7-octamethylcyclotetrasiloxane, 1,3,5,7-tetrahydro-1,3,5,7-tetramethylcyclotetrasiloxane, cyclopentapolydimethylsiloxane, 2,4,6,8-tetramethylcyclotetrasiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, cyclic polymethylvinylsiloxane, hexadecylcyclooctasiloxane, tetradecamethylcycloheptasiloxane, and one or more of cyclic polydimethylsiloxane.

[0094] In any embodiment, the number average molecular weight of the polysiloxane, the polysaccharide and the polysaccharide derivative is independently below 300,000, optionally 10,000 to 200,000, more optionally 20,000 to 120,000, further optionally 400 to 80,000.

[0095] In any embodiment, the mass percentage of the polar functional groups in the polysiloxane is α, 0≤α<50%, optionally, 5%≤α≤30%.

[0096] In any embodiment, the substituents attached to the sugar units in the polysaccharide and the polysaccharide derivatives each independently include one or more of the group consisting of the following functional groups: -OH, -COOH and its salts, -R-OH, -SO3H and its salts, -R-OH, -R-SO3H and its salts, sulfate, alkoxy, R represents an alkylene group, optionally represents a C1-C5 alkylene group; optionally, the substituents attached to the sugar units in the polysaccharide and the polysaccharide derivatives each independently include one or more of the group consisting of the following functional groups: -OH, -COOH, -COOLi, -COONa, -COOK, -SO3H, -SO3Li, -SO3Na, -SO3K, -CH2-SO3H, -CH2-SO3Li, -CH2-SO3Na, -CH2-SO3K, methoxy, ethoxy.

[0097] In any embodiment, the polysaccharide comprises one or more selected from pectin, carboxymethyl starch, hydroxypropyl starch, dextrin, cellulose ether, carboxymethyl chitosan, hydroxyethyl cellulose, carboxymethyl cellulose, carboxypropyl methyl cellulose, guar gum, sesbania gum, gum arabic, lithium alginate, sodium alginate, potassium alginate, fucoidan, agar, carrageenan, carrageenan, xanthan gum and fenugreek gum.

[0098] In any embodiment, the weight percentage of the substituents attached to the sugar units in the polysaccharide and the polysaccharide derivative is independently 20% to 85%, optionally 30% to 78%.

[0099] In any embodiment, the lattice mismatch between the material of the second core and the material of the second shell is less than 10%, thereby ensuring good contact between the second core and the second shell (or coating layer) to prevent the second shell (or coating layer) from falling off.

[0100] In any embodiment, based on the total weight of the second positive electrode active material, the manganese content is in the range of 10-35 weight %, optionally in the range of 13.3-33.2 weight %, more optionally in the range of 15-30 weight %, and further optionally in the range of 17-20 weight %.

[0101] In any embodiment, the content of phosphorus is in the range of 12-25 weight %, optionally in the range of 15-20 weight %, and more optionally in the range of 16.8-19.5 weight %.

[0102] In any embodiment, the weight ratio of manganese element to phosphorus element ranges from 0.71 to 1.85, optionally from 0.90 to 1.25, and more optionally from 0.95 to 1.20.

[0103] Limiting the manganese content within the above range can further improve the stability and density of the second positive electrode active material, thereby improving the battery's cycling, storage, and compaction performance; and can maintain a higher voltage platform, thereby improving the battery's energy density.

[0104] Limiting the phosphorus content within the above range can effectively reduce the influence of small polaron conductivity on the conductivity of the second positive electrode active material, further improve the stability of the lattice structure, and thus enhance the overall stability of the second positive electrode active material.

[0105] Limiting the weight ratio of manganese to phosphorus within the above range can further reduce manganese dissolution, improve the stability and gram capacity of the second positive electrode active material, and improve the cycle performance and storage performance of the battery; it can also reduce impurities, enable the second positive electrode active material to maintain a higher discharge voltage platform, and enable the battery to have a high energy density.

[0106] In any embodiment, the surface of the second positive electrode active material is coated with one or more of carbon and doped carbon; optionally, the surface of the second positive electrode active material is coated with carbon, thereby improving the conductivity of the second positive electrode active material.

[0107] In any embodiment, the doping element in the doped carbon includes one or more elements selected from nitrogen, phosphorus, sulfur, boron and fluorine.

[0108] In any embodiment, the coating amount of the second shell is 0.1-6 weight percent based on the weight of the second core. The coating amount of the coating layer is preferably within the above range, which can fully coat the second core and further improve the kinetic performance of the battery without sacrificing the gram capacity of the second positive electrode active material.

[0109] In any embodiment, the coating amount of the first coating layer is greater than 0 and less than or equal to 7 weight%, optionally greater than 0 and less than or equal to 6 weight%, more optionally greater than 0 and less than or equal to 5.5 weight% or 4-5.6 weight%, further optionally greater than 0 and less than or equal to 2 weight%, based on the weight of the second core; and / or, the coating amount of the second coating layer is greater than 0 and less than or equal to 6 weight%, optionally greater than 0 and less than or equal to 5.5 weight%, more optionally 2-4 weight% or 3-5 weight%, based on the weight of the second core; and / or, the coating amount of the third coating layer is greater than 0 and less than or equal to 6 weight%, optionally greater than 0 and less than or equal to 5.5 weight%, more optionally greater than 0 and less than or equal to 2 weight%, based on the weight of the second core.

[0110] In any embodiment, the second shell further includes a fourth coating layer coating the third coating layer and a fifth coating layer coating the fourth coating layer; the coating amounts of the fourth coating layer and the fifth coating layer are each independently 0.01-10 weight%, optionally 0.05-10 weight%, more optionally 0.1-5 weight%, and further 0.1-2 weight%, based on the weight of the second core.

[0111] In any embodiment, the second shell is located on 40% to 90% of the surface of the second core, and optionally on 60% to 80% of the surface, thereby fully covering the second core and improving the dynamic performance of the battery.

[0112] In any embodiment, the second shell has a thickness of 1-15 nm.

[0113] In any embodiment, the thickness of the first cladding layer is 1-10nm, optionally 2-10nm; and / or the thickness of the second cladding layer is 2-25nm, optionally 2-15nm, more optionally 3-15nm; and / or the thickness of the third cladding layer is 2-25nm, optionally 5-25nm.

[0114] In any embodiment, the one or more coating layers independently include one or more selected from pyrophosphate, phosphate and oxide, and one or more selected from the pyrophosphate, phosphate and oxide is crystalline; optionally, the crystallinity of the pyrophosphate, the phosphate and the oxide is independently 10% to 100%, and more optionally 50% to 100%.

[0115] Pyrophosphate and phosphate with a certain degree of crystallinity are not only conducive to giving full play to the pyrophosphate coating layer's ability to reduce manganese dissolution and the phosphate coating layer's excellent lithium ion conductivity and the function of reducing interface side reactions, but also enable the pyrophosphate coating layer and the phosphate coating layer to better lattice match, thereby achieving a close bond between the coating layers.

[0116] In any embodiment, in the second shell, the weight ratio of the pyrophosphate to the phosphate and the weight ratio of the pyrophosphate to the oxide are each independently 1:3 to 3:1, and can be optionally 1:3 to 1:1. Thus, by having the pyrophosphate to the phosphate or the pyrophosphate to the oxide in a suitable weight ratio range, manganese dissolution can be effectively reduced, the surface impurity lithium content can be effectively reduced, and interfacial side reactions can be reduced, thereby improving the high-temperature storage performance and high-temperature cycling performance of the battery.

[0117] In any embodiment, the one or more coating layers independently comprise carbon, and the carbon is a mixture of SP2 carbon and SP3 carbon. Optionally, the molar ratio of the SP2 carbon to the SP3 carbon is any value in the range of 0.07-13, more preferably any value in the range of 0.1-10, and further preferably any value in the range of 2.0-3.0. By selecting the carbon morphology in the carbon coating layer, the overall electrical performance of the battery is improved.

[0118] In any embodiment, the one or more coating layers independently include doped carbon, and the weight content of the doping element in the doped carbon is less than 30%; alternatively, the weight content of the doping element in the doped carbon is less than 20%. The doping element within the above content range can not only fully improve the conductivity of the pure carbon layer, but also effectively avoid excessive surface activity caused by excessive doping of the doping element, thereby effectively controlling interfacial side reactions caused by excessive doping of the coating layer.

[0119] In any embodiment, the one or more coating layers independently include doped carbon, wherein the doping element in the doped carbon is nitrogen and / or sulfur, and the weight content of the doping element in the doped carbon is 1% to 15%; or, the doping element is phosphorus, boron, and / or fluorine, and the weight content of the doping element in the doped carbon is 0.5% to 5%. Optionally, the doping element is nitrogen, phosphorus, sulfur, boron, or fluorine.

[0120] In any embodiment, the one or more coating layers independently include pyrophosphate, the interplanar spacing of the pyrophosphate is in the range of 0.293-0.470nm, optionally 0.297-0.462nm or 0.293-0.326nm, more optionally 0.300-0.310nm, and the angle range of the crystal direction (111) is 18.00°-32.57°, optionally 18.00°-32.00° or 26.41°-32.57°, more optionally 19.211°-30.846°, and further optionally 29.00°-30.00°.

[0121] In any embodiment, the one or more coating layers independently include phosphate, the interplanar spacing of the phosphate is in the range of 0.244-0.425nm, optionally 0.345-0.358nm, and the angle of the crystal direction (111) is in the range of 20.00°-37.00°, optionally 24.25°-26.45°.

[0122] In any embodiment, the first coating layer or the second coating layer comprises phosphate.

[0123] In this way, the impurity phase in the coating layer can be effectively reduced, thereby improving the material's specific capacity, cycle performance and rate performance.

[0124] In any embodiment, the lattice change rate of the second positive electrode active material before and after complete lithium deintercalation is 50% or less, optionally 9.8% or less, more optionally 8.1% or less, further optionally 7.5% or less, further optionally 6% or less, further optionally 4% or less, further optionally 3.8% or less, and further optionally 2.0%-3.8%, thereby improving the rate performance of the battery.

[0125] In any embodiment, the Li / Mn antisite defect concentration of the second positive electrode active material is 5.3% or less, optionally 5.1% or less, more optionally 4% or less, further optionally 2.2% or less, further optionally 2% or less, further optionally 1.5%-2.2% or 0.5% or less. By reducing the Li / Mn antisite defect concentration, the specific capacity and rate performance of the second positive electrode active material are improved.

[0126] In any embodiment, the surface oxygen valence state of the second positive electrode active material is -1.55 or less, optionally -1.82 or less, more optionally -1.88 or less, further optionally -1.90 or less, or -1.98 to -1.88, further optionally -1.98 to -1.89, further optionally -1.98 to -1.90. By reducing the surface oxygen valence state, the interfacial side reactions between the second positive electrode active material and the electrolyte can be reduced, thereby improving the cycle performance and high temperature stability of the battery.

[0127] In any embodiment, the battery cell further includes a negative electrode plate and a separator.

[0128] The second aspect of the present application provides a method for preparing a battery cell according to the first aspect of the present application, comprising the following steps: providing a battery container containing a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises a positive electrode active material, wherein the positive electrode active material comprises a first positive electrode active material and a second positive electrode active material, wherein the first positive electrode active material and the second positive electrode active material are capable of extracting and inserting lithium ions, wherein the first positive electrode active material and the second positive electrode active material have different crystal forms, wherein the second positive electrode active material has a one-dimensional ion transport channel, and wherein the first positive electrode active material comprises a first positive electrode active material and a second positive electrode active material ... The ionic conductivity of the active material is greater than the ionic conductivity of the second positive electrode active material; a non-aqueous solvent and an electrolyte salt are uniformly mixed to obtain an electrolyte, the electrolyte salt includes a lithium salt and a metal Me salt, the lithium salt dissociates into lithium ions and a first anion in the electrolyte, the metal Me salt dissociates into Me cations and a second anion in the electrolyte, the ionic radius of the Me cations is greater than the ionic radius of the lithium ions, the weight content of the lithium ions in the electrolyte is recorded as w1, and the weight content of the Me cations in the electrolyte is recorded as w2, both based on the total weight of the electrolyte; the obtained electrolyte is injected into the battery container to obtain a battery cell.

[0129] In the charge and discharge test of the battery cell, the total discharge capacity of the battery cell is recorded as Q1, and the discharge capacity of the battery cell at a discharge voltage below 3.6V is recorded as Q2, both in mAh.

[0130] When the remaining capacity of the battery cell is greater than 90%, the following condition is satisfied: 0.8≤(Q2 / Q1) / [w2 / (w1+w2)]≤8.5.

[0131] The battery cell charge and discharge test was conducted under the following conditions: the test temperature was 25° C., the battery cell was fully charged at 0.5C, and after standing for 5 minutes, the battery cell was fully discharged at 0.33C.

[0132] A third aspect of the present application provides a battery, comprising the battery cell of the first aspect of the present application or the battery cell prepared by the method of the second aspect of the present application.

[0133] A fourth aspect of the present application provides an electrical device comprising the battery of the third aspect of the present application.

[0134] The electric device of the present application includes the battery provided by the present application, and thus has at least the same advantages as the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0135] To more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on the drawings without inventive effort.

[0136] FIG1 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0137] FIG. 2 is an exploded schematic diagram of an embodiment of the battery cell of FIG. 1 .

[0138] FIG3 is a schematic diagram of an embodiment of a battery module of the present application.

[0139] FIG4 is a schematic diagram of an embodiment of a battery pack of the present application.

[0140] FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4 .

[0141] FIG6 is a schematic diagram of an embodiment of an electric device including the battery of the present application as a power source.

[0142] FIG7 is a discharge curve of the battery prepared in Example 2.

[0143] In the accompanying drawings, which are not necessarily drawn to scale, reference numerals are as follows: 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 battery cell, 51 housing, 52 electrode assembly, 53 cover plate. DETAILED DESCRIPTION

[0144] Below, the battery cell and its preparation method, battery and electric device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0145] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0146] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0147] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0148] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0149] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0150] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0151] If not otherwise specified, in this application, the terms "first", "second", etc. are used to distinguish different objects rather than to describe a specific order or a primary-secondary relationship.

[0152] In this application, the terms "plurality" and "multiple" refer to two or more.

[0153] Throughout this specification, substituents of compounds are disclosed in groups or ranges. It is expressly intended that such descriptions include each individual subcombination of the members of these groups and ranges. For example, it is expressly intended that the term "C1-C6 alkyl" individually discloses C1, C2, C3, C4, C5, C6, C1-C6, C1-C5, C1-C4, C1-C3, C1-C2, C2-C6, C2-C5, C2-C4, C2-C3, C3-C6, C3-C5, C3-C4, C4-C6, C4-C5, C5-C6 alkyl.

[0154] Unless otherwise specified, the terms used in this application have the common meanings that are commonly understood by those skilled in the art.

[0155] Unless otherwise stated, the numerical values ​​of the various parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise stated, the test temperature of each parameter is 25°C.

[0156] Unless otherwise specified, all ratio parameters involved in this application are compared in the same unit. For example, the ratio of the mass of A to that of B is 1:1, in which case the units of the mass of A and B are the same.

[0157] The battery mentioned in the embodiments of the present application may be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery cell, a battery module, or a battery pack.

[0158] A battery cell is the smallest unit of a battery, independently capable of charging and discharging. A battery cell can be cylindrical, rectangular, or have other shapes, though this is not a limitation in the present invention. Figure 1 shows a battery cell 5 with a rectangular structure as an example.

[0159] When there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in mixed series via a busbar. In some embodiments, the battery may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery may be a battery pack, which includes a housing and battery cells, with the battery cells or battery modules housed in the housing. In some embodiments, the housing may serve as part of the vehicle's chassis structure. For example, a portion of the housing may form at least a portion of the vehicle's floor, or a portion of the housing may form at least a portion of the vehicle's crossbeam or longitudinal beam.

[0160] In some embodiments, the battery may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0161] A battery cell generally includes an electrode assembly. The electrode assembly generally includes a positive electrode sheet and a negative electrode sheet. The electrode assembly can be a wound structure or a stacked structure, which is not limited in the present embodiment.

[0162] The battery cell may also include an outer packaging, which can be used to encapsulate the electrode assembly and electrolyte. The outer packaging can be a hard shell, such as a hard plastic shell, aluminum shell, steel shell, etc. The outer packaging can also be a soft package, such as a bag-type soft package. The soft package can be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0163] In some embodiments, as shown in Figure 2, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, which together form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening, thereby sealing the receiving cavity. The electrode assembly 52 is enclosed in the receiving cavity. The number of electrode assemblies 52 contained in a battery cell 5 can be one or more, and can be adjusted according to needs.

[0164] In some embodiments, battery cells can be assembled into a battery module. The number of battery cells contained in a battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. Figure 3 is a schematic diagram of a battery module 4 as an example. As shown in Figure 3, in the battery module 4, multiple battery cells 5 can be arranged in sequence along the length of the battery module 4. Of course, they can also be arranged in any other manner. The multiple battery cells 5 can further be fixed by fasteners.

[0165] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0166] In some embodiments, the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0167] Figures 4 and 5 are schematic diagrams of an exemplary battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a housing and multiple battery modules 4 disposed within the housing. The housing comprises an upper housing 2 and a lower housing 3. The upper housing 2 covers the lower housing 3 and forms an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 may be arranged in any manner within the housing.

[0168] The battery cell provided in the embodiment of the present application includes a positive electrode plate and an electrolyte, and the battery cell also includes a negative electrode plate and a separator.

[0169] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material. The positive electrode active material includes a first positive electrode active material and a second positive electrode active material. The first positive electrode active material and the second positive electrode active material are capable of extracting and inserting lithium ions. The first positive electrode active material and the second positive electrode active material have different crystal forms. The second positive electrode active material has a one-dimensional ion transport channel. The ionic conductivity of the first positive electrode active material is greater than that of the second positive electrode active material.

[0170] The electrolyte includes a non-aqueous solvent and an electrolyte salt. The electrolyte salt includes a lithium salt and a metal Me salt. The lithium salt dissociates into lithium ions and a first anion in the electrolyte, and the metal Me salt dissociates into Me cations and a second anion in the electrolyte. The ionic radius of the Me cations is larger than that of the lithium ions. The weight content of lithium ions in the electrolyte is denoted as w1, and the weight content of Me cations in the electrolyte is denoted as w2, both based on the total weight of the electrolyte.

[0171] During the battery cell charge and discharge test, the total discharge capacity of the battery cell is recorded as Q1, and the discharge capacity of the battery cell at a discharge voltage below 3.6V is recorded as Q2. Both units are expressed in mAh. The battery cell charge and discharge test was conducted under the following conditions: the test temperature was 25°C, the battery cell was fully charged at 0.5C, allowed to rest for 5 minutes, and then fully discharged at 0.33C.

[0172] When the remaining capacity of the battery cell is greater than 90%, the following condition is satisfied: 0.8≤(Q2 / Q1) / [w2 / (w1+w2)]≤8.5.

[0173] The battery cell with a remaining capacity greater than 90% may be a fresh battery cell, such as a battery cell that has just been shipped and has not been used, or may be a battery cell that has been used but has a remaining capacity greater than 90%.

[0174] The remaining capacity of a battery cell can be characterized by the state of health (SOH) of the battery cell, which indicates the percentage of the discharge capacity of the battery cell after it is fully discharged to the initial capacity of the battery cell. The initial capacity of a battery cell has a meaning well known in the art and can be measured by equipment and methods known in the art. Typically, after the battery cell is prepared, the initial capacity of the battery cell is measured and marked on the battery cell product. Therefore, the initial capacity of the battery cell can be determined by the marking of the battery cell. The discharge capacity of the battery cell after it is fully discharged can be measured according to the charge and discharge test conditions as described above.

[0175] The positive electrode active material in the positive electrode sheet includes a first positive electrode active material and a second positive electrode active material, and the ionic conductivity of the first positive electrode active material is greater than the ionic conductivity of the second positive electrode active material. The inventors have found that during the use of the battery, due to the large difference in ionic conductivity between the first positive electrode active material and the second positive electrode active material (for example, greater than 4 orders of magnitude), the first positive electrode active material is easily overused, thereby destroying its surface structure, and further causing the internal resistance to continue to increase during the battery cycle. In particular, the internal resistance of the battery is larger in the later stage of use, resulting in more obvious attenuation of the battery cycle performance and power performance.

[0176] The inventors discovered that by including a metal Me salt in the electrolyte whose cations have an ionic radius larger than that of lithium ions, the Me cations in the electrolyte become embedded in the surface layer of the first positive electrode active material during battery discharge. Because the Me cations have an ionic radius larger than that of lithium ions, they become trapped in the transport channels of the first positive electrode active material used for lithium ion extraction and insertion during battery discharge, thereby stabilizing the surface structure of the first positive electrode active material.

[0177] The inventors further discovered that when the battery cell satisfies 0.8≤(Q2 / Q1) / [w2 / (w1+w2)]≤8.5, the battery can have a lower internal resistance growth rate, a long cycle life, and good power performance.

[0178] The first cathode active material contributes almost no capacity below 3.6V. Therefore, the battery's discharge capacity below 3.6V is primarily provided by the second cathode active material. The second cathode active material has a one-dimensional ion transport channel. When the battery's discharge capacity ratio Q2 / Q1 below 3.6V is low, and the weight ratio of Me cations in the cations w2 / (w1+w2) is high, the amount of Me cations does not match the battery's discharge capacity below 3.6V. During battery discharge, excess Me cations are easily trapped in the ion transport channels of the second cathode active material, blocking the ion transport channels and affecting the battery's cycle performance and power performance. When the discharge capacity ratio Q2 / Q1 of the battery below the discharge voltage of 3.6V is high, and the weight ratio w2 / (w1+w2) of Me cations in the cations is low, the amount of Me cations does not match the discharge capacity of the battery below the discharge voltage of 3.6V. During the battery discharge process, there are not enough Me cations in the electrolyte to stabilize the surface structure of the first positive electrode active material, which leads to a rapid increase in the internal resistance of the battery, and poor power performance and cycle performance.

[0179] (Q2 / Q1) / [w2 / (w1+w2)] can be 0.8, 0.85, 0.97, 1.1, 1.3, 1.5, 1.7, 2.0, 2.4, 2.8, 3.1, 3.4, 3.9, 4.2, 5.0, 6.0, 6.8, 8.0, 8.5, or a range consisting of any two of the above values. In some embodiments, 1.1≤(Q2 / Q1) / [w2 / (w1+w2)]≤6.8, optionally, 1.7≤(Q2 / Q1) / [w2 / (w1+w2)]≤3.9. This can better match the amount of Me cations in the electrolyte with the discharge capacity of the battery at a discharge voltage below 3.6V, thereby further reducing the battery internal resistance growth rate and better improving the battery's cycle performance and power performance.

[0180] In some embodiments, 0.29≤Q2 / Q1≤0.42, for example, 0.29, 0.31, 0.34, 0.36, 0.39, 0.40, 0.42, or a range consisting of any two of the above values. Optionally, 0.31≤Q2 / Q1≤0.40.

[0181] In some embodiments, 0.05≤w2 / (w1+w2)≤0.35, for example, 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25, 0.28, 0.30, 0.32, 0.35, or a range consisting of any two of the foregoing values. Alternatively, 0.05≤w2 / (w1+w2)≤0.30.

[0182] When w2 / (w1+w2) is within the above range, the stability of the negative electrode interface can be improved, thereby facilitating the improvement of the high-temperature performance of the battery.

[0183] The components and their contents in the electrolyte can be determined by methods known in the art, for example, by gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), and the like.

[0184] In some embodiments, the lithium ions and Me cations in the electrolyte can be quantitatively tested using an ion chromatograph, and w2 / (w1+w2) can be calculated. The testing standard can be referenced to GB / T36240-2018.

[0185] The ionic radius of the Me cation is larger than the ionic radius of the lithium ion. In some embodiments, the Me element includes one or more elements selected from the group consisting of alkali metal elements and alkaline earth metal elements.

[0186] Optionally, the alkali metal element includes one or more of Na and K.

[0187] Optionally, the alkaline earth metal elements include one or more of Ca and Mg.

[0188] In some embodiments, the first anion may include PF6 - 、ClO4 - 、AsF6 - 、BF4 - 、N(CF3SO2)2 - (TFSI - ), CF3SO3 - 、N(FSO2)2 - (FSI - )、C(SO2CF3)3 - PO2F2 -, difluorooxalatoborate ion (DFOB - ), dioxalatoborate ion (BOB - ), difluorobis(oxaloyl)phosphate ion (DFOP - ), tetrafluorooxalophosphate ion (TFOP - )

[0189] In some embodiments, the second anion may include PF6 - 、ClO4 - 、AsF6 - 、BF4 - 、N(CF3SO2)2 - (TFSI - ), CF3SO3 - 、N(FSO2)2 - (FSI - )、C(SO2CF3)3 - PO2F2 - , difluorooxalatoborate ion (DFOB - ), dioxalatoborate ion (BOB - ), difluorobis(oxaloyl)phosphate ion (DFOP - ), tetrafluorooxalophosphate ion (TFOP - )

[0190] In some embodiments, the first anion and the second anion may be the same, thereby further reducing the growth rate of the battery's internal resistance and better improving the battery's cycle performance and power performance.

[0191] In some embodiments, the non-aqueous solvent may include one or more of cyclic carbonates, linear carbonates, and carboxylic acid esters. As an example, the non-aqueous solvent may include one or more of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0192] In some embodiments, the electrolyte may further optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives capable of improving certain battery properties, such as additives that improve battery overcharge performance, or additives that improve battery high or low temperature performance, etc., although this is not limited in the present embodiment.

[0193] The electrolyte solution can be prepared according to conventional methods in the art. For example, the non-aqueous solvent, electrolyte salt, and optional additives can be uniformly mixed to obtain the electrolyte solution. The order of adding the materials is not particularly limited. For example, the electrolyte salt, optional additives, and other components can be added to the non-aqueous solvent and uniformly mixed to obtain the electrolyte solution.

[0194] The different crystal forms of the first and second cathode active materials refer to different crystal systems of the first and second cathode active materials. In some embodiments, the first cathode active material may include a lithium-containing layered oxide, and the second cathode active material may include a lithium-containing phosphate.

[0195] The second positive electrode active material includes a lithium-containing phosphate, which has a one-dimensional ion transport channel and is generally an olivine structure. The second positive electrode active material has high stability and generally low production cost, which can reduce the cost of the battery and facilitate large-scale production. However, the compaction density of the second positive electrode active material is generally small, which makes it difficult to meet the use of high energy density batteries. The first positive electrode active material includes a lithium-containing layered oxide, which has a two-dimensional ion transport channel and also has a high gram capacity and a high voltage platform, which is conducive to improving the energy density of the battery.

[0196] Therefore, the combined use of the first positive electrode active material and the second positive electrode active material is advantageous for obtaining a low-cost and high-energy-density battery.

[0197] The first positive electrode active material and the second positive electrode active material may have regular morphologies, such as spherical or quasi-spherical, or irregular morphologies, which are not limited in the embodiments of the present application.

[0198] In some embodiments, based on the total weight of the positive electrode active material, the weight proportion W1 of the first positive electrode active material is 10%-90%, optionally 50%-90%, or 70%-90%.

[0199] In some embodiments, based on the total weight of the positive electrode active material, the weight proportion W2 of the second positive electrode active material is 10%-90%, optionally 10%-50%, or 10%-30%.

[0200] This enables the battery to better balance high energy density and long cycle life.

[0201] In some embodiments, the specific surface area of ​​the first positive electrode active material is 0.5-1 m 2 / g, optional 0.6-0.9m 2 / g.

[0202] In some embodiments, the specific surface area of ​​the second positive electrode active material is 10-20 m2 / g, optional 12-16m 2 / g.

[0203] When the specific surface area of ​​the second cathode active material is small, its kinetic and cycling performance are poor, which can easily lead to overuse of the first cathode active material. When the specific surface area of ​​the second cathode active material is large, it can increase battery side reactions, thereby also affecting the battery's cycling performance. Therefore, when the specific surface area of ​​the second cathode active material is within the above range, it is beneficial for the battery to have a lower internal resistance growth rate and a longer cycle life.

[0204] The specific surface area of ​​a material (such as a first positive electrode active material, a second positive electrode active material, etc.) is a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, it can be tested with reference to GB / T 19587-2017 using a nitrogen adsorption specific surface area analysis test method and calculated using the BET (Brunauer Emmett Teller) method. The testing instrument can be a Tri-Star 3020 specific surface area pore size analyzer from Micromeritics, USA. Before testing, the material powder can be placed in a vacuum oven and dried at 200°C for more than 2 hours, and the sampling mass of the material powder can be more than 20g.

[0205] In some embodiments, the powder compaction density P1 of the first positive electrode active material at 30000N is 3.0 g / cm 3 Above, 3.2g / cm2 can be selected 3 Above, 3.3g / cm2 is optional 3 Above, further optional 3.4g / cm 3 Above, further optional 3.5g / cm 3 above.

[0206] In some embodiments, the powder compaction density P2 of the second positive electrode active material at 30000N is 1.89 g / cm 3 Above, 1.95g / cm2 is optional 3 Above, 1.98g / cm2 is optional 3 Above, further optional 2.0g / cm 3 Above, further optional 2.2g / cm 3 Above, further optionally 2.2g / cm 3 Above and 2.8g / cm 3 Below or 2.2g / cm 3 Above and 2.65g / cm 3 the following.

[0207] The higher the powder compaction density, the greater the weight of the material per unit volume, which is beneficial for increasing the compaction density of the positive electrode sheet and the volumetric energy density of the battery. Powder compaction density can be measured according to GB / T 24533-2009.

[0208] [First positive electrode active material]

[0209] In some embodiments, the first positive electrode active material comprises a compound represented by formula (I). a A 1 b Ni c Co d B 1 e C 1 f O g D 1 h (I)

[0210] A 1 including one or more elements selected from Group IA, Group IIA, Group VIII, Group VIB, and Group IIB; B 1 including Mn and / or Al; C 1 comprising one or more elements selected from Group IA, Group IIA, Group IIIA, Group IVA, Group VA, Group VIA, Group IB, Group IIB, Group IIIB, Group IVB, Group VB, Group VIB, and Group VIII; D 1 Including one or more elements selected from Group VIA and Group VIIA; a is selected from the range of 0.75 to 1.2; b is selected from the range of 0 to 0.2; c is selected from the range of 0.001 to 0.990; d is selected from the range of 0 to 0.990; e is selected from the range of 0.001 to 0.990; f is selected from the range of 0 to 0.1; g is selected from the range of 1.0 to 2.0; h is selected from the range of 0 to 1.0.

[0211] Unless otherwise specified, in the above chemical formulas, when A 1 When there are two or more elements, the above-mentioned limitation on the value range of b is not only for each element as A 1 The stoichiometric number of the elements is also limited to each element as A 1 The sum of the stoichiometric numbers of the elements is limited. For example, when A 1 Two or more elements A 1 1. A 1 2……A 1 When n, A 1 1. A 1 2……A 1The stoichiometric numbers b1, b2, ..., bn of each of n must each fall within the numerical range specified for b in this application, and the sum of b1, b2, ..., bn must also fall within this numerical range.

[0212] Similarly, for B mentioned in the examples of this application 1 、C 1 、D 1 、A 2 、B 2 、C 2 、D 2 、A 3 、B 3 、C 3 、D 3 When M, M′, X, Z, P, Q, etc. are two or more elements, the numerical range of their stoichiometric numbers in this application also has a similar meaning as above.

[0213] In some embodiments, c+d+e+f=1.

[0214] In some embodiments, g+h=2.

[0215] In some embodiments, A 1 It includes one or more elements selected from Na, K, Mg, Rb, Zn, and Zr.

[0216] In some embodiments, C 1 Includes one or more elements selected from Al, Mg, Ca, Na, Ti, W, Zr, Sr, Cr, Fe, Zn, Cu, Ba, Mo, V, Ce, Nb, Sb, Ta, Ge, Nb, Sc, Ba, B, S and Y, and optionally includes one or more elements selected from Mg, Ti, W, Zr, Cr, Fe, Zn, Cu, V, Nb, Sr, Sb, Y

[0217] In some embodiments, D 1 The invention comprises one or more elements selected from N, S, F, Cl and Br, and may optionally comprise S and / or F.

[0218] In some embodiments, a is selected from the range of 0.9 to 1.1.

[0219] In some embodiments, b is selected from the range of 0 to 0.1.

[0220] In some embodiments, c is selected from the range of 0.250 to 0.990, and optionally selected from the range of 0.500 to 0.990.

[0221] When the content of Ni element in the first active material is higher, its gram capacity is higher; however, at this time, the stability of the surface structure of the first positive electrode active material itself will be poor. By making the electrolyte contain an appropriate content of Me cations, the cycle performance of the battery can be better improved, and the energy density of the battery can be increased.

[0222] In some embodiments, d is selected from the range of 0 to 0.320, and optionally selected from the range of 0 to 0.100.

[0223] When the content of Co element in the first active material is low, the material cost can be reduced; however, at this time, the stability of the surface structure of the first positive electrode active material itself will be poor. By making the electrolyte contain an appropriate content of Me cations, the cycle performance of the battery can be better improved, and the manufacturing cost of the battery can be reduced.

[0224] In some embodiments, e is selected from the range of 0.001 to 0.450, and optionally selected from the range of 0.005 to 0.450.

[0225] In some embodiments, f is selected from the range of 0.001 to 0.1, and can be optionally selected from the range of 0.001 to 0.05.

[0226] In some embodiments, g is selected from the range of 1.9 to 2.0, and optionally selected from the range of 1.95 to 1.99.

[0227] In some embodiments, h is selected from the range of 0 to 0.1, and optionally selected from the range of 0.01 to 0.05.

[0228] In some embodiments, the first positive electrode active material includes a first core and a first shell covering the first core, wherein the first core includes the compound represented by formula (I) above; and the first shell includes one or more coating layers. Each coating layer has ionic conductivity and / or electronic conductivity.

[0229] In some embodiments, the one or more coating layers in the first shell each independently include one or more selected from phosphate, pyrophosphate, carbon, doped carbon, oxide, and fast ion conductor, and may optionally include one or more selected from phosphate, pyrophosphate, and oxide.

[0230] In some embodiments, the first shell comprises a coating layer; optionally, the coating layer comprises one or more selected from phosphates, pyrophosphates, and oxides.

[0231] In some embodiments, the first shell includes a first coating layer coating the inner core and a second coating layer coating the first coating layer; optionally, the first coating layer and the second coating layer each independently include one or more selected from phosphates, pyrophosphates, and oxides; more optionally, the first coating layer includes one or more selected from phosphates and oxides, and the second coating layer includes one or more selected from pyrophosphates and oxides.

[0232] In some embodiments, the coating amount of the first shell is 0.005-1 wt %, optionally 0.01-0.5 wt %, based on the weight of the first core.

[0233] In some embodiments, the thickness of the first shell is 2 nm to 200 nm, optionally 5 nm to 50 nm.

[0234] [Second positive electrode active material]

[0235] In some embodiments, the second positive electrode active material comprises a compound represented by formula (II). m1 A 2 x1 Mn 1-y1 B 2 y1 P 1-z1 C 2 z1 O 4-n1 D 2 n1 (II)

[0236] A 2 including one or more elements selected from Group IA, Group IIA, Group IIIA, Group IIB, Group VB, and Group VIB; 2 including one or more elements selected from Group IA, Group IIA, Group IIIA, Group IVA, Group VA, Group IIB, Group IVB, Group VB, Group VIB, and Group VIII; C 2 including one or more elements selected from Group IIIA, Group IVA, Group VA, and Group VIA; D 2 It includes one or more elements selected from Group VIA and Group VIIA; m1 is selected from the range of 0.85 to 1.15; x1 is selected from the range of 0 to 0.1; y1 is selected from the range of 0.001 to 0.999; z1 is selected from the range of 0 to 0.5; and n1 is selected from the range of 0 to 0.5.

[0237] The compound represented by formula (II) is obtained by doping lithium manganese phosphate LiMnPO4 with elements, A 2 、B 2 、C 2 and D 2The elements doped at the Li, Mn, P and O positions of LiMnPO4 are respectively. Without being limited by theory, it is now believed that the performance improvement of lithium manganese phosphate is related to reducing the lattice change rate of lithium manganese phosphate during the lithium insertion and extraction process and reducing the surface activity. Reducing the lattice change rate can reduce the lattice constant difference between the two phases at the grain boundary, reduce the interfacial stress, and enhance the Li + The transport capacity at the interface improves the rate performance of the second positive electrode active material. However, high surface activity can easily lead to serious side reactions at the interface, exacerbating gas production, electrolyte consumption and interface damage, thereby affecting the cycle performance of the battery. The lattice change rate can be reduced by doping with Li and / or Mn. Mn doping can also effectively reduce surface activity, thereby reducing Mn dissolution and side reactions at the interface between the second positive electrode active material and the electrolyte. P-site doping makes the change rate of the Mn-O bond length faster, reduces the migration barrier of small polarons in the material, and is beneficial to improving electronic conductivity. O-site doping has a good effect on reducing side reactions at the interface. P-site and / or O-site doping also affects the Mn dissolution and kinetic properties of antisite defects. Therefore, doping reduces the concentration of antisite defects in the material, improves the kinetic properties and specific capacity of the material, and can also change the morphology of the particles, thereby improving the compaction density. The inventors unexpectedly discovered that by doping specific elements in specific amounts at the Mn position of LiMnPO4 and optionally at the Li position, P position and / or O position, improved rate performance can be obtained, while reducing the dissolution of Mn and the doping elements at the Mn position, obtaining improved cycle performance and / or high-temperature stability, and the gram capacity and compaction density of the material are also improved.

[0238] In some embodiments, A 2 Includes one or more elements selected from Rb, Cs, Be, Ca, Sr, Ba, Ga, In, Cd, V, Ta, Cr, Zn, Al, Na, K, Mg, Nb, Mo and W, and can optionally include one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo and W.

[0239] In some embodiments, B 2 Includes one or more elements selected from Rb, Cs, Be, Ca, Sr, Ba, In, Pb, Bi, Cd, Hf, Ta, Cr, Ru, Rh, Pd, Os, Ir, Pt, Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge, and can optionally include one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge.

[0240] In some embodiments, C 2 Includes one or more elements selected from B, S, Si and N.

[0241] In some embodiments, D 2 It includes one or more elements selected from S, F, Cl and Br.

[0242] In some embodiments, A 2 including any one element selected from Zn, Al, Na, K, Mg, Nb, Mo and W, and optionally including any one element selected from Mg and Nb; and / or,

[0243] B 2 comprising one or more elements selected from the group consisting of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge, optionally comprising at least two elements selected from the group consisting of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge, more optionally comprising at least two elements selected from the group consisting of Fe, Ti, V, Ni, Co, and Mg, further optionally comprising at least two elements selected from the group consisting of Fe, Ti, V, Co, and Mg, and further optionally comprising Fe and one or more elements selected from the group consisting of Ti, V, Co, and Mg; and / or,

[0244] C 2 including any one element selected from B, S, Si and N, optionally S; and / or,

[0245] D 2 It includes any one element selected from S, F, Cl and Br, and F is optional.

[0246] By selecting the Li-site doping element within the above range, the lattice change rate during the delithiation process can be further reduced, thereby further improving the rate performance of the battery.

[0247] By selecting the Mn-site doping element within the above range, the electronic conductivity can be further improved and the lattice change rate can be further reduced, thereby improving the rate performance and gram capacity of the battery.

[0248] By selecting the P-site doping element within the above range, the rate performance of the battery can be further improved.

[0249] By selecting the O-site doping element within the above range, the side reactions at the interface can be further reduced and the high-temperature performance of the battery can be improved.

[0250] In some embodiments, m1 is selected from the range of 0.9 to 1.1, and optionally selected from the range of 0.97 to 1.01.

[0251] In some embodiments, x1 is selected from the range of 0.001 to 0.1, and optionally selected from the range of 0.001 to 0.005.

[0252] In some embodiments, y1 is selected from the range of 0.001 to 0.5, optionally selected from the range of 0.01 to 0.5, and more optionally selected from the range of 0.2 to 0.5.

[0253] In some embodiments, z1 is selected from the range of 0.001 to 0.5, optionally selected from the range of 0.001 to 0.1, and more optionally selected from the range of 0.001 to 0.005.

[0254] In some embodiments, n1 is selected from the range of 0 to 0.1, and may be optionally selected from the range of 0.001 to 0.005.

[0255] By selecting the value of y1 within the above range, the gram capacity and rate performance of the second positive electrode active material can be further improved.

[0256] By selecting the value of x1 within the above range, the kinetic performance of the second positive electrode active material can be further improved.

[0257] By selecting the z1 value within the above range, the rate performance of the battery can be further improved.

[0258] By selecting the n1 value within the above range, the high-temperature performance of the battery can be further improved.

[0259] In some embodiments, y1 is selected from the range of 0.001 to 0.999, and x1 is 0, z1 is 0, and n1 is 0.

[0260] In some embodiments, y1 is selected from the range of 0.001 to 0.999, x1 is 0, z1 is selected from the range of 0.001 to 0.5, and n1 is selected from the range of 0.001 to 0.1; or, y1 is selected from the range of 0.001 to 0.999, x1 is selected from the range of 0.001 to 0.1, z1 is 0, and n1 is selected from the range of 0.001 to 0.1; or, y1 is selected from the range of 0.001 to 0.999, x1 is selected from the range of 0.001 to 0.1, z1 is 0, and n1 is selected from the range of 0.001 to 0.5 , n1 is 0; or, y1 is selected from the range of 0.001 to 0.999, x1 is 0, z1 is 0, and n1 is selected from the range of 0.001 to 0.1; or, y1 is selected from the range of 0.001 to 0.999, x1 is 0, z1 is selected from the range of 0.001 to 0.5, and n1 is 0; or, y1 is selected from the range of 0.001 to 0.999, x1 is selected from the range of 0.001 to 0.1, z1 is selected from the range of 0.001 to 0.5, and n1 is selected from the range of 0.001 to 0.1.

[0261] Thus, by doping a specific element in a specific amount at the Mn position of LiMnPO4 and optionally at the Li position, P position and / or O position, especially doping a specific element in a specific amount at the Mn position and P position of LiMnPO4 or at the Li position, Mn position, P position and O position of LiMnPO4, the rate performance can be improved, the dissolution of Mn and the doping element at the Mn position can be reduced, the cycle performance and / or high temperature stability can be improved, and the gram capacity and compaction density of the second positive electrode active material can be increased.

[0262] In some embodiments, y1:z1 is selected from the range of 0.002 to 999, and may be selected from the range of 0.025 to 999 or the range of 0.002 to 500, and may be further selected from the range of 0.2 to 600, such as 0.2, 0.25, 1, 2, 3, 4, 5, 6, 8, 10, 12, 13, 15, 17, 20, 70, 80, 84, 67, 91, 100, 134, 150, 182, 200, 250, 300, 320, 350, 400, 420, 450, 500, 600, 999, or a range consisting of any two of the above values. Thus, the defects of the second positive electrode active material can be reduced, and the integrity of the framework structure of the second positive electrode active material can be improved, thereby effectively improving the structural stability of the second positive electrode active material, and thus improving the cycle stability of the battery.

[0263] In some embodiments, z1:n1 is selected from the range of 0.002 to 500, optionally from the range of 0.2 to 100, and more optionally from the range of 0.2 to 50, such as 0.2, 0.8, 1, 1.25, 4, 5, 50, or a range consisting of any two of the foregoing values. Thus, defects in the second positive electrode active material can be further reduced, the integrity of the framework structure of the second positive electrode active material can be further improved, the structural stability of the second positive electrode active material can be effectively improved, and the cycle stability of the battery can be improved.

[0264] In some embodiments, (1-y1):y1 is in the range of 0.1-999, optionally in the range of 0.1-10 or in the range of 0.67-999, more optionally in the range of 1 to 10, further optionally in the range of 1 to 4, and further optionally in the range of 1.5 to 3.

[0265] In some embodiments, a1:x1 is in the range of 1 to 1200, optionally in the range of 9 to 1100, and more optionally in the range of 190-998.

[0266] Here, y1 represents the sum of the stoichiometric ratios of the doping elements at the Mn site. When the above conditions are met, the energy density and cycle performance of the second positive electrode active material can be further improved.

[0267] In some embodiments, z1:(1-z1) is 1:9 to 1:999, and can be 1:499 to 1:249. When the above conditions are met, the energy density and cycle performance of the second positive electrode active material can be further improved.

[0268] In some embodiments, A 2 including one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo and W; B 2 including one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge; C 2 including one or more elements selected from B, S, Si and N; D 2 It includes one or more elements selected from S, F, Cl and Br; m1 is selected from the range of 0.9 to 1.1, x1 is selected from the range of 0.001 to 0.1, y1 is selected from the range of 0.001 to 0.5, z1 is selected from the range of 0.001 to 0.1, and n1 is selected from the range of 0.001 to 0.1.

[0269] By doping specific elements at specific amounts at the Li, Mn, P, and O positions of LiMnPO4 simultaneously, improved rate performance can be obtained, while reducing the dissolution of Mn and the doping elements at the Mn position, thereby achieving improved cycle performance and / or high-temperature stability, and the gram capacity and compaction density of the second positive electrode active material can also be improved.

[0270] In some embodiments, B 2 including one or more elements selected from the group consisting of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and optionally including one or more elements selected from the group consisting of Zn, Fe, Ti, V, Ni, Co, and Mg; C 2 It includes one or more elements selected from B, Si, N and S; m1 is selected from the range of 0.9 to 1.1, x1 is 0, y1 is selected from the range of 0.001 to 0.5, z1 is selected from the range of 0.001 to 0.1, and n1 is 0.

[0271] By doping specific elements at specific amounts at both the Mn and P sites of LiMnPO4, the rate performance can be improved, the dissolution of Mn and the doping elements at the Mn site can be reduced, the cycle performance and / or high-temperature stability can be improved, and the gram capacity and compaction density of the second positive electrode active material can be increased.

[0272] In some embodiments, the second positive electrode active material includes a second core and a second shell coating the second core, wherein the second core includes a compound represented by formula (II). The second shell includes one or more coating layers. The coating layers have ionic conductivity and / or electronic conductivity. In practice, each coating layer may be fully or partially coated.

[0273] By arranging a coating layer with ionic conductivity and / or electronic conductivity on the surface of the second inner core, a second positive electrode active material with a core-shell structure is provided. Applying the second positive electrode active material to the battery can improve the high-temperature cycle performance, cycle stability and high-temperature storage performance of the battery.

[0274] In some embodiments, the one or more coating layers each independently comprise one or more selected from the group consisting of pyrophosphate, phosphate, carbon, doped carbon, oxide, boride, and polymer.

[0275] In some embodiments, the second shell comprises a coating layer; optionally, the coating layer comprises one or more selected from pyrophosphate, phosphate, carbon, doped carbon, oxide, boride, and polymer.

[0276] The above materials can be used to obtain a coating layer with ionic conductivity and / or electronic conductivity, thereby improving the high-temperature cycle performance, cycle stability and high-temperature storage performance of the battery.

[0277] In some embodiments, the second shell includes a first coating layer coating the second core and a second coating layer coating the first coating layer; optionally, the first coating layer and the second coating layer each independently include one or more selected from pyrophosphate, phosphate, carbon, doped carbon, oxide, boride and polymer.

[0278] Using the above materials as the materials for the coating layer and providing two coating layers can further improve the high-temperature cycle performance, cycle stability and high-temperature storage performance of the battery.

[0279] In some embodiments, the first coating layer includes one or more selected from pyrophosphate, phosphate, oxide, and boride, and the second coating layer includes one or more selected from carbon and doped carbon.

[0280] The use of a first coating layer of a specific material and a second coating layer of a specific material can further improve rate performance and further reduce the dissolution of Mn and Mn-doping elements, thereby improving the cycle performance and / or high-temperature stability of the battery.

[0281] In some embodiments, the second shell includes a first coating layer coating the second inner core, a second coating layer coating the first coating layer, and a third coating layer coating the second coating layer; optionally, the first coating layer, the second coating layer and the third coating layer each independently include one or more selected from pyrophosphate, phosphate, carbon, doped carbon, oxide, boride and polymer.

[0282] Using the above materials as the coating layer material and providing three coating layers can further reduce the dissolution of Mn and Mn-doping elements, and further improve the high-temperature cycle performance, cycle stability and high-temperature storage performance of the battery.

[0283] In some embodiments, the first coating layer includes pyrophosphate, the second coating layer includes one or more selected from phosphates, oxides, and borides, and the third coating layer includes one or more selected from carbon and doped carbon.

[0284] The use of a first coating layer of a specific material, a second coating layer of a specific material, and a third coating layer of a specific material further improves the rate performance, further reduces the dissolution of Mn and Mn-doping elements, thereby improving the cycle performance and / or high-temperature stability of the battery, and further increases the gram capacity and compaction density of the second positive electrode active material.

[0285] In some embodiments, the pyrophosphate is i (P2O7) j M includes one or more elements selected from Group IA, Group IIA, Group IIIA, Group IB, Group IIB, Group IVB, Group VB, Group VIIB, and Group VIII; i is selected from the range of 1 to 4, and j is selected from the range of 1 to 6.

[0286] In some embodiments, the phosphate is X p (PO4) q X includes one or more elements selected from Group IA, Group IIA, Group IIIA, Group IB, Group IIB, Group IVB, Group VB, Group VIIB, and Group VIII; p is selected from the range of 1 to 2; and q is selected from the range of 1 to 4.

[0287] In some embodiments, the doping element in the doped carbon includes one or more elements selected from Group IIIA, Group VA, Group VIA, and Group VIIA.

[0288] In some embodiments, the oxide is M' k O l M′ includes one or more elements selected from alkali metals, alkaline earth metals, transition metals, Group IIIA elements, Group IVA elements, lanthanides, and Sb; k is greater than 0 and less than or equal to 2; and l is greater than 0 and less than or equal to 5.

[0289] In some embodiments, the boride is Z v B w Z includes one or more elements selected from Group IA, Group IIA, Group IIIA, Group IB, Group IIB, Group IVB, Group VB, Group VIIB, and Group VIII; v is selected from the range of 1 to 7, and w is selected from the range of 1 to 2.

[0290] In some embodiments, the polymer includes one or more selected from polysaccharides and their derivatives, and polysiloxanes.

[0291] By using the above materials as the coating layer, the dissolution of Mn and Mn-doping elements can be further reduced, the gram capacity and compaction density of the second positive electrode active material can be further increased, and the battery's rate performance, high-temperature cycle performance and high-temperature storage performance can be further improved.

[0292] In some embodiments, M, X and Z each independently include one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, Mn and Al; and / or the doping element in the doped carbon includes one or more elements selected from nitrogen, phosphorus, sulfur, boron and fluorine; and / or M′ includes one or more elements selected from Li, Be, B, Na, Mg, Al, Si, P, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, W, La and Ce, and may optionally include one or more elements selected from Mg, Al, Si, Zn, Zr and Sn; and / or the polysiloxane is selected from one or more of linear polysiloxanes and cyclic polysiloxanes; and / or the polysaccharide is selected from one or more of plant polysaccharides and marine polysaccharides.

[0293] By using the above-mentioned specific material as the coating layer, the dissolution of Mn and Mn-doping elements can be further reduced, and the high-temperature cycle performance and high-temperature storage performance of the battery can be further improved.

[0294] In some embodiments, the second positive active material includes a second core and a second shell covering the second core.

[0295] The second core includes Li m1 Mn 1-y1 B 2 y1 P 1-z1 C 2 z1 O4, m1 is selected from the range of 0.9 to 1.1, y1 is selected from the range of 0.001 to 0.5, z1 is selected from the range of 0.001 to 0.1, B 2including one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge, C 2 Includes one or more elements selected from B, S, Si and N.

[0296] The second shell includes a first coating layer coating the second core and a second coating layer coating the first coating layer, the first coating layer includes pyrophosphate MP2O7 and phosphate XPO4, M and X each independently include one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al; the second coating layer contains carbon.

[0297] The second positive electrode active material may be a core-shell structure with two coating layers, and the element B is doped at the manganese position of the lithium manganese phosphate. 2 It helps to reduce the lattice change rate of lithium manganese phosphate during the process of lithium insertion and removal, improve the structural stability of the second positive electrode active material, greatly reduce the dissolution of manganese and reduce the oxygen activity on the particle surface. 2 It helps to change the difficulty of the change in the Mn-O bond length, thereby reducing the lithium ion migration barrier, promoting lithium ion migration, and improving the battery's rate performance. The first coating layer of the second positive electrode active material includes pyrophosphate and phosphate. Since the migration barrier of transition metals in pyrophosphate is relatively high (>1eV), the dissolution of transition metals can be effectively reduced. Phosphate has excellent lithium ion conductivity and can reduce the surface impurity lithium content. In addition, since the second coating layer is a carbon-containing layer, it can effectively improve the conductivity and desolvation ability of LiMnPO4. In addition, the "barrier" effect of the second coating layer can further reduce the migration of manganese ions into the electrolyte and reduce the corrosion of the electrolyte on the second active material. Therefore, by performing specific element doping and surface coating on lithium manganese phosphate, the dissolution of Mn during the lithium insertion process can be effectively reduced, while promoting the migration of lithium ions, thereby improving the battery's rate performance, cycle performance and high temperature performance.

[0298] In some embodiments, the second positive active material includes a second core and a second shell covering the second core.

[0299] The second core includes Li m1 Mn 1-y1 B 2 y1 P 1-z1 C 2 z1 O4, m1 is selected from the range of 0.9 to 1.1, y1 is selected from the range of 0.001 to 0.5, z1 is selected from the range of 0.001 to 0.1, B 2including one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge, C 2 Includes one or more elements selected from B, S, Si and N.

[0300] The second shell includes a first covering layer covering the second inner core, a second covering layer covering the first covering layer, and a third covering layer covering the second covering layer.

[0301] The first coating layer includes Li pyrophosphate r QP2O7 and / or Q s (P2O7) t , 0≤r≤2, 1≤s≤4, 1≤t≤6, pyrophosphate Li r QP2O7 and / or Q s (P2O7) t Each Q in the above-mentioned ions independently comprises one or more elements selected from the group consisting of Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al.

[0302] The second coating layer includes crystalline phosphate XP04, where X includes one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al.

[0303] The third coating layer includes carbon.

[0304] Therefore, the second positive electrode active material can improve the specific capacity and cycle performance of the battery.

[0305] The second positive electrode active material is a core-shell structure, wherein the manganese site and phosphorus site of the second core are doped with element B respectively. 2 and element C 2 , which can not only effectively reduce manganese dissolution, thereby reducing manganese ions migrating to the negative electrode, reducing the electrolyte consumed due to SEI film decomposition, and improving the battery's cycle performance, but also promote Mn-O bond adjustment, reduce the lithium ion migration barrier, promote lithium ion migration, and improve the battery's rate performance; by coating the second core with a first coating layer including pyrophosphate, the migration resistance of manganese can be further increased, its dissolution can be reduced, and the surface impurity lithium content can be reduced, and the contact between the second core and the electrolyte can be reduced, thereby reducing interfacial side reactions, reducing gas production, and improving the battery's high-temperature storage performance and cycle performance; by further coating with a phosphate coating layer with excellent lithium ion conductivity, the interfacial side reactions on the surface of the second positive electrode active material can be effectively reduced, thereby improving the battery's high-temperature cycle and storage performance; by further coating with a carbon layer as the third coating layer, the battery's kinetic performance can be further improved. In addition, in the second core, the element B doped at the manganese position 2It also helps to reduce the lattice change rate of lithium manganese phosphate during the process of lithium insertion and removal, improve the structural stability of the second positive electrode active material, greatly reduce the dissolution of manganese and reduce the oxygen activity on the particle surface; the element C doped at the phosphorus position 2 It also helps to change the difficulty of the Mn-O bond length change, thereby improving electronic conductivity and reducing the lithium ion migration barrier, promoting lithium ion migration, and improving the battery's rate performance.

[0306] Furthermore, maintaining electrical neutrality throughout the entire second core system minimizes defects and impurities in the second cathode active material. If the second cathode active material contains an excess transition metal (e.g., manganese), due to the inherently stable structure of the material system, the excess transition metal is likely to precipitate as a single element or form impurities within the crystal lattice. Maintaining electrical neutrality minimizes these impurities. Furthermore, maintaining electrical neutrality can, in some cases, create lithium vacancies within the material, thereby enhancing the kinetic performance of the second cathode active material.

[0307] In some embodiments, the one or more coating layers in the second shell that are farthest from the second core each independently comprise one or more selected from polysiloxane, polysaccharide, and polysaccharide derivatives.

[0308] As a result, the uniformity of the coating can be improved, and the interfacial side reactions caused by high voltage can be effectively blocked, thereby improving the high-temperature cycle performance and high-temperature storage performance of the second positive electrode active material; and the coating layer has good ionic conductivity, which helps to improve the gram capacity of the second positive electrode active material while reducing the heat generation of the battery.

[0309] In some embodiments, the polysiloxane comprises a structural unit represented by formula (i).

[0310] R1 and R2 are independently selected from H, -COOH, -OH, -SH, -CN, -SCN, amino, phosphate, carboxylate, amide, aldehyde, sulfonyl, polyether segment, C1-C20 aliphatic, C1-C20 halogenated aliphatic, C1-C20 heteroaliphatic, C1-C20 halogenated heteroaliphatic, C6-C20 aromatic, C6-C20 halogenated aromatic, C2-C20 heteroaromatic and C2-C20 halogenated heteroaromatic.

[0311] Optionally, R1 and R2 are independently selected from H, amino, phosphate, polyether segment, C1-C8 alkyl, C1-C8 haloalkyl, C1-C8 heteroalkyl, C1-C8 haloheteroalkyl, C2-C8 alkenyl and C2-C8 haloalkenyl.

[0312] In some embodiments, the polysiloxane further comprises an end-capping group, which includes one or more of the following functional groups: polyether, C1-C8 alkyl, C1-C8 haloalkyl, C1-C8 heteroalkyl, C1-C8 haloheteroalkyl, C2-C8 alkenyl, C2-C8 haloalkenyl, C6-C20 aromatic hydrocarbon group, C1-C8 alkoxy, C2-C8 epoxy, hydroxyl, C1-C8 hydroxyalkyl, amino, C1-C8 aminoalkyl, carboxyl, C1-C8 carboxylalkyl.

[0313] In some embodiments, the polysiloxane comprises a polysiloxane selected from polydimethylsiloxane, polydiethylsiloxane, polymethylethylsiloxane, polymethylvinylsiloxane, polyphenylmethylsiloxane, polymethylhydrogensiloxane, carboxyl functionalized polysiloxane, epoxy-terminated polysiloxane, methoxy-terminated polydimethylsiloxane, hydroxypropyl-terminated polydimethylsiloxane, polymethylchloropropylsiloxane, hydroxy-terminated polydimethylsiloxane, polymethyltrifluoropropylsiloxane, perfluorooctylmethylpolysiloxane, aminoethylaminopropyl polydimethylsiloxane, terminal polyether polydimethylsiloxane, side chain aminopropyl polysiloxane, One or more of aminopropyl-terminated polydimethylsiloxane, side chain phosphate-grafted polydimethylsiloxane, side chain polyether-grafted polydimethylsiloxane, 1,3,5,7-octamethylcyclotetrasiloxane, 1,3,5,7-tetrahydro-1,3,5,7-tetramethylcyclotetrasiloxane, cyclopentasiloxane, 2,4,6,8-tetramethylcyclotetrasiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, cyclic polymethylvinylsiloxane, hexadecylcyclooctasiloxane, tetradecamethylcycloheptasiloxane, and cyclic polydimethylsiloxane.

[0314] In some embodiments, the number average molecular weight of polysiloxane, polysaccharide, and polysaccharide derivative is independently less than 300,000, optionally 10,000 to 200,000, more optionally 20,000 to 120,000, and further optionally 400 to 80,000.

[0315] The number average molecular weight of polysiloxane, polysaccharide and polysaccharide derivatives can be measured by methods known in the art, such as gel permeation chromatography (GPC), using a PL-GPC 220 high temperature gel permeation chromatograph.

[0316] In some embodiments, the mass percentage of polar functional groups in the polysiloxane is α, 0≤α<50%, optionally, 5%≤α≤30%.

[0317] The "mass percentage of polar functional groups in the polysiloxane" refers to the mass proportion of polar functional groups in R1, R2, and end-capping groups in the polysiloxane. Polar functional groups include one or more of -COOH, -OH, -SH, -CN, -SCN, amino groups (including -NH2 and -NH-), phosphate groups, carboxylate groups (-COO-), amide groups (-CONH-), aldehyde groups (-CHO), sulfonyl groups (-S(=O)2-), polyether segments, halogen groups, alkoxy groups, and epoxy groups. When the aforementioned polar functional groups are directly attached to silicon atoms, α represents the mass fraction of these polar functional groups in the polysiloxane. When the aforementioned polar functional groups are not directly attached to silicon atoms, α represents the sum of the mass fractions of the polar functional groups and the divalent to tetravalent methyl groups (e.g., -CH2, -CH-, -C-, etc.) directly attached to them in the polysiloxane. Here, "divalent to tetravalent methyl groups" refers to the carbon atoms directly attached to the polar functional groups and located between the polar functional groups and the silicon atoms, as well as other non-polar functional groups attached to the carbon atoms. For example, in polymethyltrifluoropropylsiloxane, α refers to the mass percentage of -CF3, excluding the ethylene group; in polymethylchloropropylsiloxane, α refers to the mass percentage of -CH2Cl, excluding the ethylene group; in hydroxypropyl-terminated polydimethylsiloxane, α refers to the mass percentage of -CH2OH. The mass percentage of the polar functional groups in the polysiloxane can be determined by methods known in the art, such as titration (eg, acid-base titration, redox titration, precipitation titration), infrared spectroscopy, and nuclear magnetic resonance spectroscopy.

[0318] In some embodiments, the substituents attached to the sugar units in the polysaccharides and polysaccharide derivatives each independently include one or more of the group consisting of the following functional groups: -OH, -COOH and salts thereof, -R-OH, -SO3H and salts thereof, -R-OH, -R-SO3H and salts thereof, sulfate, alkoxy, R represents an alkylene group, optionally representing a C1-C5 alkylene group.

[0319] Optionally, the substituents attached to the sugar units in the polysaccharide and polysaccharide derivatives each independently include one or more of the group consisting of the following functional groups: -OH, -COOH, -COOLi, -COONa, -COOK, -SO3H, -SO3Li, -SO3Na, -SO3K, -CH2-SO3H, -CH2-SO3Li, -CH2-SO3Na, -CH2-SO3K, methoxy, ethoxy.

[0320] The term "substituents attached to the sugar unit" includes all groups attached to the sugar unit backbone.

[0321] In some embodiments, the polysaccharide comprises one or more selected from pectin, carboxymethyl starch, hydroxypropyl starch, dextrin, cellulose ether, carboxymethyl chitosan, hydroxyethyl cellulose, carboxymethyl cellulose, carboxypropyl methyl cellulose, guar gum, sesbania gum, gum arabic, lithium alginate, sodium alginate, potassium alginate, fucoidan, agar, carrageenan, carrageenan, xanthan gum, and fenugreek gum.

[0322] In some embodiments, the weight percentage of substituents attached to the sugar units in the polysaccharide and polysaccharide derivatives is independently 20% to 85%, and optionally 30% to 78%. The weight percentage of substituents attached to the sugar units in the polysaccharide and polysaccharide derivatives can be determined by methods known in the art, such as titration (e.g., acid-base titration, redox titration, precipitation titration), infrared spectroscopy, and nuclear magnetic resonance spectroscopy.

[0323] In some embodiments, the lattice mismatch between the material of the second core and the material of the second shell is less than 10%, thereby ensuring good contact between the second core and the second shell (or coating layer) to prevent the second shell (or coating layer) from falling off.

[0324] In some embodiments, based on the weight of the positive electrode active material, the manganese content is in the range of 10-35 wt %, optionally in the range of 13.3-33.2 wt %, more optionally in the range of 15-30 wt %, and further optionally in the range of 17-20 wt %.

[0325] In some embodiments, based on the weight of the positive electrode active material, the content of phosphorus is in the range of 12-25 wt %, optionally in the range of 15-20 wt %, and more optionally in the range of 16.8-19.5 wt %.

[0326] In some embodiments, based on the weight of the positive electrode active material, the weight ratio of manganese element to phosphorus element is in the range of 0.71-1.85, optionally 0.90-1.25, and more optionally 0.95-1.20.

[0327] In the case where manganese is contained only in the second core of the second positive active material, the content of manganese may correspond to the content of the second core.

[0328] Limiting the manganese content within the above range can further improve the stability and density of the second positive electrode active material, thereby improving the battery's cycling, storage, and compaction performance; and can maintain a higher voltage platform, thereby improving the battery's energy density.

[0329] Limiting the phosphorus content within the above range can effectively reduce the influence of small polaron conductivity on the conductivity of the second positive electrode active material, further improve the stability of the lattice structure, and thus enhance the overall stability of the second positive electrode active material.

[0330] Limiting the weight ratio of manganese to phosphorus within the above range can further reduce manganese dissolution, improve the stability and gram capacity of the second positive electrode active material, and improve the cycle performance and storage performance of the battery; it can also reduce impurities, enable the second positive electrode active material to maintain a higher discharge voltage platform, and enable the battery to have a high energy density.

[0331] Manganese and phosphorus can be measured using conventional techniques in the art. Specifically, the following method is used to determine the manganese and phosphorus contents: the material is dissolved in dilute hydrochloric acid (concentration 10-30%), the content of each element in the solution is measured using ICP, and then the manganese content is measured and converted to obtain its weight percentage.

[0332] In some embodiments, the surface of the second positive electrode active material is coated with one or more of carbon and doped carbon; alternatively, the surface of the second positive electrode active material is coated with carbon, thereby improving the conductivity of the second positive electrode active material.

[0333] In some embodiments, the doping element in the doped carbon layer includes one or more elements selected from nitrogen, phosphorus, sulfur, boron, and fluorine, so as to facilitate control of the properties of the doped carbon layer.

[0334] In some embodiments, the coating amount of the second shell (which is only one coating layer) is 0.1-6 weight percent based on the weight of the second core. The coating amount of the coating layer is preferably within the above range to fully coat the second core while further improving the kinetic performance of the battery without sacrificing the gram capacity of the second positive electrode active material.

[0335] In certain embodiments, the coating amount of the first coating layer is greater than 0 and less than or equal to 7 weight %, can be optionally greater than 0 and less than or equal to 6 weight %, can be more optionally greater than 0 and less than or equal to 5.5 weight % or be 4-5.6 weight %, can further be optionally greater than 0 and less than or equal to 2 weight %, based on the weight meter of the second kernel; and / or, the coating amount of the second coating layer is greater than 0 and less than or equal to 6 weight %, can be optionally greater than 0 and less than or equal to 5.5 weight %, can be more optionally 2-4 weight % or 3-5 weight %, based on the weight meter of the second kernel; and / or, the coating amount of the 3rd coating layer is greater than 0 and less than or equal to 6 weight %, can be optionally greater than 0 and less than or equal to 5.5 weight %, can more optionally be greater than 0 and less than or equal to 2 weight %, based on the weight meter of the second kernel.

[0336] In some embodiments, the second shell further includes a fourth cladding layer covering the third cladding layer and a fifth cladding layer covering the fourth cladding layer.

[0337] The coating amounts of the fourth coating layer and the fifth coating layer are each independently 0.01-10 wt %, optionally 0.05-10 wt %, more optionally 0.1-5 wt %, further 0.1-2 wt %, based on the weight of the second core.

[0338] In the second positive electrode active material with a core-shell structure of the present application, the coating amount of each coating layer is preferably within the above range, thereby being able to fully coat the second inner core and at the same time further improve the battery's kinetic performance without sacrificing the gram capacity of the second positive electrode active material.

[0339] In some embodiments, the second shell is located on 40% to 90% of the surface of the second core, and optionally on 60% to 80% of the surface, thereby fully covering the second core and improving the dynamic performance of the battery.

[0340] In some embodiments, the second shell (which is only one coating layer) has a thickness of 1-15 nm.

[0341] In some embodiments, the thickness of the first cladding layer is 1-10 nm, optionally 2-10 nm; and / or the thickness of the second cladding layer is 2-25 nm, optionally 2-15 nm, more optionally 3-15 nm; and / or the thickness of the third cladding layer is 2-25 nm, optionally 5-25 nm.

[0342] In some embodiments, the thickness of the first cladding layer can be about 2 nm, about 3 nm, about 4 nm, about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, about 10 nm, or any range thereof.

[0343] In some embodiments, the thickness of the second coating layer may be about 2 nm, about 3 nm, about 4 nm, about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, about 10 nm, about 11 nm, about 12 nm, about 13 nm, about 14 nm, about 15 nm, or any range of any of the above values.

[0344] In some embodiments, the thickness of the third coating layer may be about 2 nm, about 3 nm, about 4 nm, about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, about 10 nm, about 11 nm, about 12 nm, about 13 nm, about 14 nm, about 15 nm, about 16 nm, about 17 nm, about 18 nm, about 19 nm, about 20 nm, about 21 nm, about 22 nm, about 23 nm, about 24 nm, about 25 nm, or any range within the above range.

[0345] The first coating layer has a thickness within the above range, which can further reduce the adverse effects on the kinetic properties of the second positive electrode active material.

[0346] The second coating layer has the above-mentioned thickness range, so that the surface structure of the second coating layer is stable and the side reaction with the electrolyte is small, thereby effectively reducing the interface side reaction and improving the high temperature performance of the battery.

[0347] The third coating layer has the above-mentioned thickness range, which can enhance the electrical conductivity of the second positive electrode active material and improve the compaction density of the positive electrode sheet prepared using the second positive electrode active material.

[0348] The thickness test of the coating layer is mainly carried out by FIB. The specific method may include the following steps: randomly selecting a single particle from the second positive electrode active material powder to be tested, cutting a thin slice with a thickness of about 100nm from the middle position or near the middle position of the selected particle, and then performing TEM testing on the thin slice to measure the thickness of the coating layer, measuring 3-5 positions and taking the average value.

[0349] In some embodiments, the one or more coating layers each independently include one or more selected from pyrophosphate, phosphate, and oxide, and the one or more selected from pyrophosphate, phosphate, and oxide are crystalline.

[0350] Optionally, the crystallinity of the pyrophosphate, phosphate, and oxide are each independently from 10% to 100%, more preferably from 50% to 100%.

[0351] Herein, crystalline means a crystallinity of 50% or more, i.e., 50%-100%. That is, when the crystalline pyrophosphate and crystalline phosphate of the present application appear, it means a crystallinity of 50% to 100%.

[0352] Pyrophosphate and phosphate with a certain degree of crystallinity are not only conducive to giving full play to the pyrophosphate coating layer's ability to reduce manganese dissolution and the phosphate coating layer's excellent lithium ion conductivity and the function of reducing interface side reactions, but also enable the pyrophosphate coating layer and the phosphate coating layer to better lattice match, thereby achieving a close bond between the coating layers.

[0353] It should be noted that the crystallinity can be adjusted, for example, by adjusting the process conditions of the sintering process, such as sintering temperature, sintering time, etc. The crystallinity can be measured by methods known in the art, such as X-ray diffraction, density method, infrared spectroscopy, differential scanning calorimetry, and nuclear magnetic resonance absorption method. A specific method for testing the crystallinity of the second positive electrode active material by X-ray diffraction method may include the following steps:

[0354] Take a certain amount of the second positive electrode active material powder and measure the total scattering intensity by X-ray. It is the sum of the scattering intensities of the entire space matter and is only related to the intensity of the primary rays, the chemical structure of the second positive electrode active material powder, and the total number of electrons participating in the diffraction, that is, the mass, but has nothing to do with the order state of the sample; then separate the crystalline scattering and the non-crystalline scattering from the diffraction pattern, and the crystallinity is the ratio of the scattering of the crystalline part to the total scattering intensity.

[0355] In some embodiments, in the second shell, the weight ratio of the pyrophosphate to the phosphate and the weight ratio of the pyrophosphate to the oxide are each independently 1:3 to 3:1, and may be 1:3 to 1:1. Thus, by having the pyrophosphate to the phosphate or the pyrophosphate to the oxide in a suitable weight ratio range, manganese dissolution can be effectively reduced, the surface lithium content can be effectively reduced, and interfacial side reactions can be reduced, thereby improving the high-temperature storage performance and high-temperature cycling performance of the battery.

[0356] In some embodiments, one or more coating layers independently include carbon, and the carbon is a mixture of SP2 carbon and SP3 carbon. Optionally, the molar ratio of SP2 carbon to SP3 carbon in the carbon is any value in the range of 0.07-13, more preferably any value in the range of 0.1-10, and further preferably any value in the range of 2.0-3.0.

[0357] In some embodiments, the molar ratio of sp2 carbon to sp3 carbon can be about 0.1, about 0.2, about 0.3, about 0.4, about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, about 1, about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, about 10, or any range thereof.

[0358] In this application, "about" a numerical value represents a range, which means a range of ±10% of the numerical value.

[0359] By selecting the carbon morphology in the carbon coating, the overall electrical performance of the battery is improved. Specifically, by using a mixture of SP2 carbon and SP3 carbon and limiting the ratio of SP2 carbon to SP3 carbon to a certain range, the following situations can be avoided: if the carbon in the coating is all amorphous SP3, the conductivity is poor; if it is all graphitized SP2, although the conductivity is good, there are few lithium ion pathways, which is not conducive to lithium intercalation and deintercalation. In addition, limiting the molar ratio of SP2 carbon to SP3 carbon to the above range can achieve good conductivity and promote the transport of lithium ions, which is beneficial to the realization of battery functions and its cycle performance.

[0360] The mixing ratio of the SP2 and SP3 carbon forms can be controlled by sintering conditions, such as temperature and time. The molar ratio of SP2 to SP3 carbon can be determined by Raman spectroscopy. The Raman spectrum is separated to obtain the peak intensity of the SP3 carbon form (Id / Ig), where Id represents the peak intensity of the SP3 carbon form and Ig represents the peak intensity of the SP2 carbon form. This allows the molar ratio of the two to be determined.

[0361] In some embodiments, one or more coating layers independently include doped carbon, and the weight content of the doping element in the doped carbon is less than 30%; alternatively, the weight content of the doping element in the doped carbon is less than 20%. The doping element within the above content range can not only fully improve the conductivity of the pure carbon layer, but also effectively avoid excessive surface activity caused by excessive doping of the doping element, thereby effectively controlling interfacial side reactions caused by excessive doping of the coating layer.

[0362] In some embodiments, one or more coating layers each independently include doped carbon, in which the doping elements are nitrogen and / or sulfur, and the mass content of the doping elements in the doped carbon is 1% to 15%; or, the doping elements are phosphorus, boron and / or fluorine, and the mass content of the doping elements in the doped carbon is 0.5% to 5%.

[0363] Optionally, the doping element is nitrogen, phosphorus, sulfur, boron or fluorine.

[0364] Since nitrogen atoms and sulfur atoms are closer in atomic radius to carbon atoms and are less likely to destroy the carbon skeleton, when the doping amount of nitrogen atoms and sulfur atoms is within the above relatively wide range, the conductivity of the doped carbon layer can be fully exerted, and the lithium ion transport and lithium ion desolvation capabilities can be promoted.

[0365] Since the atomic radius of phosphorus atoms, boron atoms and / or fluorine atoms is different from that of carbon atoms, excessive doping can easily destroy the carbon skeleton. Therefore, when the doping amount of phosphorus atoms, boron atoms and / or fluorine atoms is within the above-mentioned relatively small range, it can not only fully exert the conductivity of the doped carbon layer, but also promote lithium ion transmission and lithium ion desolvation capabilities.

[0366] In some embodiments, one or more coating layers independently include pyrophosphate, the interplanar spacing of the pyrophosphate is in the range of 0.293-0.470 nm, optionally 0.297-0.462 nm or 0.293-0.326 nm, more optionally 0.300-0.310 nm, and the angle range of the crystal direction (111) is 18.00°-32.57°, optionally 18.00°-32.00° or 26.41°-32.57°, more optionally 19.211°-30.846°, and further optionally 29.00°-30.00°.

[0367] In some embodiments, one or more coating layers independently include phosphate, the interplanar spacing of the phosphate ranges from 0.244-0.425 nm, optionally from 0.345-0.358 nm, and the angle of the crystal orientation (111) ranges from 20.00°-37.00°, optionally from 24.25°-26.45°.

[0368] In some embodiments, the first coating layer or the second coating layer comprises a phosphate.

[0369] The first and second coating layers of the second positive electrode active material are both crystalline, with their interplanar spacing and angles falling within the aforementioned ranges. This effectively reduces impurity phases in the coating layers, thereby improving the material's specific capacity, cycle performance, and rate capability.

[0370] In some embodiments, the lattice change rate of the second positive electrode active material before and after complete deintercalation of lithium is less than 50%, optionally less than 9.8%, more optionally less than 8.1%, further optionally less than 7.5%, further optionally less than 6%, further optionally less than 4%, further optionally less than 3.8%, and further optionally between 2.0% and 3.8%.

[0371] By reducing the lattice change rate, Li ion transport can be facilitated, that is, the mobility of Li ions in the second positive electrode active material is stronger, which is beneficial to improving the rate performance of the battery. The lattice change rate can be measured by methods known in the art, such as X-ray diffraction (XRD).

[0372] In some embodiments, the Li / Mn antisite defect concentration of the second positive electrode active material is less than 5.3%, optionally less than 5.1%, more optionally less than 4%, further optionally less than 2.2%, further optionally less than 2%, further optionally less than 1.5%-2.2% or less than 0.5%.

[0373] The so-called Li / Mn antisite defect refers to the Li + With Mn 2+ The positions of Li / Mn are interchanged. The Li / Mn antisite defect concentration refers to the concentration of Li / Mn in the second positive electrode active material. 2+ Li exchange occurs + Occupy + The percentage of total antisite defect Mn 2+ Will hinder Li + The transport of Li / Mn antisite defects can improve the specific capacity and rate performance of the second positive electrode active material by reducing the concentration of Li / Mn antisite defects. The concentration of Li / Mn antisite defects can be measured by methods known in the art, such as XRD.

[0374] In some embodiments, the surface oxygen valence state of the second positive electrode active material is below -1.55, optionally below -1.82, more optionally below -1.88, further optionally below -1.90 or -1.98 to -1.88, further optionally -1.98 to -1.89, further optionally -1.98 to -1.90.

[0375] By reducing the surface oxygen valence state, the interfacial side reactions between the second cathode active material and the electrolyte can be reduced, thereby improving the cycle performance and high temperature stability of the battery. The surface oxygen valence state can be measured by methods known in the art, such as electron energy loss spectroscopy (EELS).

[0376] In some embodiments, the second positive electrode active material comprises a compound represented by formula (III). m2 A 3 x2 Fe 1-y2 B 3 y2 P 1-z2 C 3 z2 O 4-n2 D 3 n2 (III)

[0377] A 3 including one or more elements selected from Group IA, Group IIA, Group IIIA, Group IIB, Group VB, and Group VIB; 3 including one or more elements selected from Group IA, Group IIA, Group IIIA, Group IVA, Group VA, Group IIB, Group IVB, Group VB, Group VIB, and Group VIII; C 3 including one or more elements selected from Group IIIA, Group IVA, Group VA, and Group VIA; D 3 It includes one or more elements selected from Group VIA and Group VIIA; m2 is selected from the range of 0.85 to 1.15; x2 is selected from the range of 0 to 0.1; y2 is selected from the range of 0 to 0.5; z2 is selected from the range of 0 to 0.5; and n2 is selected from the range of 0 to 0.5.

[0378] In some embodiments, A 3 Includes one or more elements selected from Rb, Cs, Be, Ca, Sr, Ba, Ga, In, Cd, V, Ta, Cr, Zn, Al, Na, K, Mg, Nb, Mo and W, and can optionally include one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo and W.

[0379] In some embodiments, B3 Includes one or more elements selected from Rb, Cs, Be, Ca, Sr, Ba, In, Pb, Bi, Cd, Hf, Ta, Cr, Ru, Rh, Pd, Os, Ir, Pt, Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Ni, Co, Ga, Sn, Sb, Nb and Ge, and can optionally include one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Ni, Co, Ga, Sn, Sb, Nb and Ge.

[0380] In some embodiments, C 3 Includes one or more elements selected from B, S, Si and N.

[0381] In some embodiments, D 3 It includes one or more elements selected from S, F, Cl and Br.

[0382] In some embodiments, m2 is selected from the range of 0.9 to 1.1, and optionally selected from the range of 0.97 to 1.01.

[0383] In some embodiments, x2 is selected from the range of 0.001 to 0.005.

[0384] In some embodiments, y2 is selected from the range of 0.001 to 0.2, and can be optionally selected from the range of 0.005 to 0.1.

[0385] In some embodiments, z2 is selected from the range of 0.001 to 0.1, and more preferably, is selected from the range of 0.001 to 0.005.

[0386] In some embodiments, n2 is selected from the range of 0 to 0.1, and more preferably, is selected from the range of 0.001 to 0.005.

[0387] The compound represented by formula (III) is obtained by doping elements in lithium iron phosphate LiFePO4, A 3 、B 3 、C 3 and D 3 They are the elements doped at the Li, Fe, P and O sites of LiFePO4 respectively.

[0388] In some embodiments, the second positive electrode active material includes a second core and a second shell covering the second core, the second core includes the compound represented by the above formula (III), and the second shell includes one or more coating layers; each coating layer has ionic conductivity and / or electronic conductivity.

[0389] The second shell covering the compound represented by the above formula (III) is the same as the second shell covering the compound represented by the above formula (III), and will not be described again here.

[0390] The element contents of the first positive electrode active material and the second positive electrode active material can be detected by inductively coupled plasma emission spectroscopy (ICP).

[0391] The first positive electrode active material and the second positive electrode active material can be prepared by a sintering method. When the first positive electrode active material and the second positive electrode active material have a shell, the shell of each of the first positive electrode active material and the second positive electrode active material can be prepared by a liquid phase coating method.

[0392] The positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is arranged on either one or both of the two opposite surfaces of the positive electrode current collector.

[0393] In some embodiments, the total content of the positive electrode active material in the positive electrode film layer is 50-99.5 wt %, optionally 90-99.5 wt %, or 95-99.5 wt %, based on the total weight of the positive electrode film layer.

[0394] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0395] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. As an example, the positive electrode binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0396] In some embodiments, the positive electrode film layer may further include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0397] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the first positive electrode active material, the second positive electrode active material, the positive electrode conductive agent, the positive electrode binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0398] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0399] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0400] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0401] In some embodiments, the negative electrode active material may be a material known in the art. As an example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0402] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. As an example, the negative electrode binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0403] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. For example, the negative electrode conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0404] In some embodiments, the negative electrode film layer may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC)).

[0405] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the negative electrode conductive agent, the negative electrode binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0406] In some embodiments, the negative electrode plate may not include a negative electrode active material capable of intercalating and deintercalating lithium ions. For example, the negative electrode plate may include a lithium plate or a lithium alloy plate; or, the negative electrode plate may include a three-dimensional skeleton layer in a network or foam form; or, the negative electrode plate may include a negative electrode current collector and a lithium-containing layer disposed on at least one surface of the negative electrode current collector.

[0407] The present application does not impose any particular restrictions on the type of isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected. In some embodiments, the isolation membrane includes a porous substrate. The material of the porous substrate may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polyester, and polyimide. The porous substrate can be a single-layer film or a multi-layer composite film, without particular restrictions. When the porous substrate is a multi-layer composite film, the materials of each layer can be the same or different, without particular restrictions.

[0408] In some embodiments, the isolation membrane may further include a coating layer located on at least one surface of the porous substrate. Optionally, the coating layer includes one or more of inorganic heat-resistant particles and organic heat-resistant particles.

[0409] Preparation method

[0410] The embodiments of the present application also provide a method for preparing the above-mentioned battery cell.

[0411] The method comprises the following steps: providing a battery container containing a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises a positive electrode active material, wherein the positive electrode active material comprises a first positive electrode active material and a second positive electrode active material, wherein the first positive electrode active material and the second positive electrode active material are capable of extracting and inserting lithium ions, wherein the first positive electrode active material and the second positive electrode active material have different crystal forms, wherein the second positive electrode active material has a one-dimensional ion transport channel, and wherein the ion conductivity of the first positive electrode active material is large. The ionic conductivity of the second positive electrode active material is improved; a non-aqueous solvent and an electrolyte salt are uniformly mixed to obtain an electrolyte, the electrolyte salt includes a lithium salt and a metal Me salt, the lithium salt dissociates into lithium ions and a first anion in the electrolyte, the metal Me salt dissociates into Me cations and a second anion in the electrolyte, the ionic radius of the Me cations is larger than the ionic radius of the lithium ions, the weight content of the lithium ions in the electrolyte is recorded as w1, and the weight content of the Me cations in the electrolyte is recorded as w2, both based on the total weight of the electrolyte; the obtained electrolyte is injected into a battery container to obtain a battery cell.

[0412] The method provided in the embodiment of the present application can prepare the above-mentioned battery cell. Other parameters of the battery cell can refer to the battery cell described above in the present application and will not be repeated here.

[0413] In some embodiments, the battery container further includes a separator.

[0414] In some embodiments, the method may further include the following steps: forming an electrode assembly by winding the positive electrode sheet, the separator and the negative electrode sheet through a winding process and / or a lamination process, and placing the electrode assembly in a battery container.

[0415] The battery container can be an outer packaging. The outer packaging can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging can also be a soft package, such as a bag-type soft package. The soft package can be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0416] In some embodiments, after the obtained electrolyte is injected into a battery container, it may further undergo processes such as standing, formation, aging, and capacity testing to obtain a battery cell.

[0417] Multiple battery cells can be further connected in series, parallel, or hybrid to form a battery module. Multiple battery modules can also be connected in series, parallel, or hybrid to form a battery pack. In some embodiments, multiple battery cells can also be directly connected to form a battery pack.

[0418] The present application also provides an electrical device, which includes a battery provided in the present application. The battery can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0419] The electrical device can select the type of battery according to its usage requirements, such as a battery cell, a battery module or a battery pack.

[0420] Figure 6 is a schematic diagram of an exemplary electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of this device, a battery pack or battery module may be used.

[0421] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0422] Example

[0423] The following examples describe the present disclosure in more detail and are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further processing, and all instruments used in the examples are commercially available.

[0424] Examples 1-25 and Comparative Examples 1-3 were prepared according to the following method.

[0425] Preparation of positive electrode

[0426] The positive electrode active material, positive electrode conductive agent carbon black, and positive electrode binder polyvinylidene fluoride (PVDF) shown in Table 1 were thoroughly stirred and mixed in an appropriate amount of solvent NMP at a weight ratio of 90:5:5 to form a uniform positive electrode slurry; the positive electrode slurry was evenly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained.

[0427] The positive electrode active material includes a first positive electrode active material and a second positive electrode active material. In Table 1, the weight contents of the first positive electrode active material and the second positive electrode active material are both based on the total weight of the positive electrode active material.

[0428] Preparation of negative electrode sheet

[0429] The negative electrode active material graphite, the negative electrode binder styrene-butadiene rubber (SBR), the negative electrode thickener sodium carboxymethyl cellulose (CMC-Na), and the negative electrode conductive agent carbon black (Super P) are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 90:3:2:5 to form a uniform negative electrode slurry; the negative electrode slurry is evenly coated on the surface of the negative electrode current collector copper foil, and after drying and cold pressing, the negative electrode sheet is obtained.

[0430] Isolation film

[0431] A porous polyethylene (PE) film is used as the separator.

[0432] Preparation of electrolyte

[0433] Ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 1:1:1 to prepare a non-aqueous solvent. The lithium salts and metal Me salts listed in Table 1 were dissolved in the non-aqueous solvent, and then FEC was added to prepare an electrolyte solution. The total concentration of the electrolyte salts was 1 mol / L, and the FEC content was 5% based on the total weight of the electrolyte solution.

[0434] In Table 1, w2 / (w1+w2) represents the mass ratio of Me cations to the mixture of lithium ions and Me cations.

[0435] Battery preparation

[0436] The positive electrode sheet, separator, and negative electrode sheet are made into an electrode assembly according to a Z-shaped stacking structure, and then vacuum dried at 90°C for 12 hours. After that, the tabs are welded (the positive electrode uses aluminum tabs, the negative electrode uses nickel tabs, and the positive and negative tabs are located at the same end of the electrode assembly). The electrode assembly after welding the tabs is placed in an aluminum-plastic film of appropriate size for top and side sealing. After that, the battery is obtained through processes such as liquid filling, standing, formation, aging, exhaust, secondary sealing, and capacity testing.

[0437] Test section

[0438] (1) Chemical molar ratio test of Ni and Co in the first positive electrode active material

[0439] Take about 0.4g (accurate to 0.0001g) of the first positive electrode active material in a 25ml beaker, add 2-5ml of nitric acid and let it sit overnight, then place the beaker on a hot plate and heat at about 100°C (the input voltage can be adjusted to control the temperature with a voltage regulator transformer) until the first positive electrode active material is digested, then add 0.5ml of perchloric acid and heat to digest at about 140°C until the white smoke is gone. The residue should be white, otherwise nitric acid and perchloric acid should be added again to repeat the digestion, and finally the extraction solution is dissolved with 7% (volume %) hydrochloric acid. After that, the obtained solution is diluted to an appropriate volume and tested using an inductively coupled plasma optical emission spectrometer ICP-OES, and the chemical molar ratio of Ni and Co in the first positive electrode active material is calculated.

[0440] (2) Q2 / Q1 test

[0441] Under a constant temperature environment of 25°C, the prepared battery was charged at a constant current of 0.5C to 4.4V, then charged at a constant voltage at 4.4V to a current ≤0.05C, allowed to stand for 5 minutes, and then discharged at a constant current of 0.33C to 2.5V to obtain the total discharge capacity Q1. The total discharge capacity below 3.6V on the discharge curve was obtained and recorded as Q2.

[0442] (3) 25℃ cycle performance test

[0443] At a constant temperature of 25°C, the prepared battery was charged at a constant current of 0.5C to 4.4V, then charged at a constant voltage of 4.4V to a current of ≤0.05C, allowed to rest for 5 minutes, and then discharged at a constant current of 1C to 2.5V. This constituted one cycle of charge and discharge. The discharge capacity at this point was recorded as the first cycle discharge capacity. The battery was subjected to cyclic charge and discharge tests according to the above method, and the discharge capacity after each cycle was recorded until the battery's discharge capacity decayed to 80% of the first cycle discharge capacity. The number of cycles at this point was used to characterize the battery's cycling performance. The higher the number of cycles, the better the cycling performance.

[0444] (4) Battery internal resistance growth rate test after 500 cycles

[0445] Under a constant temperature environment of 25°C, the prepared battery was charged at a constant current of 0.5C to 4.4V, and then charged at a constant voltage at 4.4V to a current ≤ 0.05C, and allowed to stand for 30 minutes. At this time, the voltage of the battery was recorded as V1; the battery was discharged at a constant current of 1C for 30 seconds, and the voltage at the end of discharge was recorded as V2. The internal resistance DCR of the battery before cycling was recorded, DCR = (V1-V2) / 1C.

[0446] The battery was cycled 500 times according to the above cycle performance test method, and the internal resistance DCR of the battery after 500 cycles was tested according to the above method.

[0447] The internal resistance growth rate of the battery after 500 cycles = (internal resistance after 500 cycles / internal resistance before the cycle) - 1.

[0448] The test results are shown in Table 1.

[0449] Figure 7 is a discharge curve of the battery prepared in Example 2. As shown in Figure 2, the Q2 / Q1 of the battery prepared in Example 2 is 0.34.

[0450] It can be seen from the test results in Table 1 that by making the electrolyte include a metal Me salt whose cation ionic radius is larger than the ionic radius of the lithium ion, and making the battery satisfy 0.8≤(Q2 / Q1) / [w2 / (w1+w2)]≤8.5, the battery can have a lower internal resistance growth rate and a longer cycle life.

[0451] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, comprising a positive electrode plate and an electrolyte, wherein: The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprises a first positive electrode active material and a second positive electrode active material, the first positive electrode active material and the second positive electrode active material are capable of extracting and inserting lithium ions, the first positive electrode active material and the second positive electrode active material have different crystal forms, the second positive electrode active material has a one-dimensional ion transport channel, and the ion conductivity of the first positive electrode active material is greater than the ion conductivity of the second positive electrode active material; The electrolyte includes a non-aqueous solvent and an electrolyte salt, the electrolyte salt includes a lithium salt and a metal Me salt, the lithium salt dissociates into lithium ions and a first anion in the electrolyte, the metal Me salt dissociates into Me cations and a second anion in the electrolyte, the ionic radius of the Me cations is greater than the ionic radius of the lithium ions, the weight content of the lithium ions in the electrolyte is recorded as w1, and the weight content of the Me cations in the electrolyte is recorded as w2, both based on the total weight of the electrolyte; In the charge and discharge test of the battery cell, the total discharge capacity of the battery cell is recorded as Q1, and the discharge capacity of the battery cell at a discharge voltage below 3.6V is recorded as Q2, both in mAh; When the remaining capacity of the battery cell is greater than 90%, the following conditions are met: 0.8≤(Q2 / Q1) / [w2 / (w1+w2)]≤8.

5. The charge and discharge test of the battery cell was carried out under the following conditions: the test temperature was 25° C., the battery cell was fully charged at 0.5C, and after standing for 5 minutes, the battery cell was fully discharged at 0.33C.

2. The battery cell according to claim 1, wherein: 1.1≤(Q2 / Q1) / [w2 / (w1+w2)]≤6.8, optionally, 1.7≤(Q2 / Q1) / [w2 / (w1+w2)]≤3.

9.

3. The battery cell according to claim 1 or 2, wherein: 0.29≤Q2 / Q1≤0.42, optionally, 0.31≤Q2 / Q1≤0.40; and / or, 0.05≤w2 / (w1+w2)≤0.35, optionally, 0.05≤w2 / (w1+w2)≤0.

30.

4. The battery cell according to any one of claims 1 to 3, wherein: Me elements include one or more elements of alkali metal elements and alkaline earth metal elements. Optionally, the alkali metal element includes one or more of Na and K; and / or, Optionally, the alkaline earth metal element includes one or more of Ca and Mg.

5. The battery cell according to any one of claims 1 to 4, wherein: The first anion includes PF6 - 、ClO4 - 、AsF6 - 、BF4 - 、N(CF3SO2)2 - CF3SO3 - 、N(FSO2)2 - 、C(SO2CF3)3 - PO2F2 - , one or more of difluorooxalatoborate ion, dioxalatoborate ion, difluorooxalatophosphate ion, tetrafluorooxalatophosphate ion; and / or, The second anion includes PF6 - 、ClO4 - 、AsF6 - 、BF4 - 、N(CF3SO2)2 - CF3SO3 - 、N(FSO2)2 - 、C(SO2CF3)3 - PO2F2 - , one or more of difluorooxalatoborate ion, dioxalatoborate ion, difluorooxalatophosphate ion, and tetrafluorooxalatophosphate ion.

6. The battery cell according to any one of claims 1 to 5, wherein: The first anion is the same as the second anion.

7. The battery cell according to any one of claims 1 to 6, wherein: Based on the total weight of the positive electrode active material, the weight proportion W1 of the first positive electrode active material is 10%-90%, and can be 70%-90%; and / or, Based on the total weight of the positive electrode active material, the weight proportion W2 of the second positive electrode active material is 10%-90%, and can be 10%-30%; and / or, The specific surface area of ​​the first positive electrode active material is 0.5-1 m 2 / g, optional 0.6-0.9m 2 / g; and / or, The specific surface area of ​​the second positive electrode active material is 10-20 m 2 / g, optional 12-16m 2 / g.

8. The battery cell according to any one of claims 1 to 7, wherein: The first positive electrode active material includes a layered oxide containing lithium; Optionally, the first positive electrode active material comprises a compound represented by formula (I), Li a A 1 b Ni c Co d B 1 e C 1 f O g D 1 h (I), A 1 It includes one or more elements selected from Group IA, Group IIA, Group VIII, Group VIB, and Group IIB, and may optionally include one or more elements selected from Na, K, Mg, Rb, Zn, and Zr; B 1 Includes selected from Mn and / or Al; C 1 The invention comprises one or more elements selected from Group IA, Group IIA, Group IIIA, Group IVA, Group VA, Group VIA, Group IB, Group IIB, Group IIIB, Group IVB, Group VB, Group VIB and Group VIII, and may be selected from Al, Mg, Ca, Na, Ti, W, Zr, Sr, Cr, Fe, Zn, Cu, Ba, Mo, V, Ce, Nb, Sb, Ta, Ge, Nb, Sc, Ba, B, S and Y, and may be selected from Mg, Ti, W, Zr, Cr, Fe, Zn, Cu, V, Nb, Sr, Sb and Y. D 1 It includes one or more elements selected from Group VIA and Group VIIA, and may optionally include one or more elements selected from N, S, F, Cl and Br, and may further optionally include S and / or F; a is selected from the range of 0.75 to 1.2, and can be selected from the range of 0.9 to 1.1; b is selected from the range of 0 to 0.2, and may be selected from the range of 0 to 0.1; c is selected from the range of 0.001 to 0.990, and may be selected from the range of 0.500 to 0.990; d is selected from the range of 0 to 0.990, and may be selected from the range of 0 to 0.100; e is selected from the range of 0.001 to 0.990, and can be selected from the range of 0.005 to 0.450; f is selected from the range of 0 to 0.1, and may be selected from the range of 0.001 to 0.05; g is selected from the range of 1.0 to 2.0, and may be selected from the range of 1.9 to 2.0; h is selected from the range of 0 to 1.0, and may be selected from the range of 0.01 to 0.1; Optionally, c+d+e+f=1; and / or, Optionally, g+h=2.

9. The battery cell according to claim 8, wherein: The first positive electrode active material includes a first core and a first shell covering the first core. The first core comprises a compound represented by formula (I); The first shell comprises one or more coating layers, each coating layer having ionic conductivity and / or electronic conductivity; Optionally, the one or more coating layers each independently include one or more selected from phosphate, pyrophosphate, carbon, doped carbon, oxide, and fast ion conductor, and more optionally include one or more selected from phosphate, pyrophosphate, and oxide.

10. The battery cell according to claim 9, wherein: The coating amount of the first shell is 0.005-1% by weight, and optionally 0.01-0.5% by weight, based on the weight of the first core; and / or, The thickness of the first shell is 2 nm to 200 nm, and can be 5 nm to 50 nm.

11. The battery cell according to any one of claims 1 to 10, wherein: The second positive electrode active material includes a lithium-containing phosphate, Optionally, the second positive electrode active material comprises a compound represented by formula (II), Li m1 A 2 x1 Mn 1-y1 B 2 y1 P 1-z1 C 2 z1 O 4-n1 D 2 n1 (II), A 2 It includes one or more elements selected from Group IA, Group IIA, Group IIIA, Group IIB, Group VB and Group VIB, and may be selected from one or more elements selected from Rb, Cs, Be, Ca, Sr, Ba, Ga, In, Cd, V, Ta, Cr, Zn, Al, Na, K, Mg, Nb, Mo and W, and may be selected from one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo and W; B 2 The invention comprises one or more elements selected from Group IA, Group IIA, Group IIIA, Group IVA, Group VA, Group IIB, Group IVB, Group VB, Group VIB and Group VIII, and may be selected from one or more elements selected from Rb, Cs, Be, Ca, Sr, Ba, In, Pb, Bi, Cd, Hf, Ta, Cr, Ru, Rh, Pd, Os, Ir, Pt, Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge, and may be selected from one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge; C 2 It includes one or more elements selected from Group IIIA, Group IVA, Group VA and Group VIA, and may optionally include one or more elements selected from B, S, Si and N; D 2 It includes one or more elements selected from Group VIA and Group VIIA, and may optionally include one or more elements selected from S, F, Cl and Br; m1 is selected from the range of 0.85 to 1.15, and may be selected from the range of 0.9 to 1.1, and may be selected from the range of 0.97 to 1.01; x1 is selected from the range of 0 to 0.1, and may be selected from the range of 0.001 to 0.1, and may be further selected from the range of 0.001 to 0.005; y1 is selected from the range of 0.001 to 0.999, and may be selected from the range of 0.001 to 0.5, and may be further selected from the range of 0.2 to 0.5; z1 is selected from the range of 0 to 0.5, and may be selected from the range of 0.001 to 0.1, and may be further selected from the range of 0.001 to 0.005; n1 is selected from the range of 0 to 0.5, and may be selected from the range of 0 to 0.1, and may be further selected from the range of 0.001 to 0.

005.

12. The battery cell according to claim 11, wherein: A 2 comprising any one element selected from Zn, Al, Na, K, Mg, Nb, Mo and W, and optionally comprising any one element selected from Mg and Nb; and / or, B 2 comprising one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge, and optionally comprising at least two elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge, and more optionally comprising at least two elements selected from Fe, Ti, V, Ni, Co and Mg, and further optionally comprising at least two elements selected from Fe, Ti, V, Co and Mg, and further optionally comprising Fe and one or more elements selected from Ti, V, Co and Mg; and / or, C 2 comprising any one element selected from B, S, Si and N, optionally S; and / or, D 2 The element comprises any one element selected from S, F, Cl and Br, and F is optional.

13. The battery cell according to any one of claims 11 to 12, wherein: x1 is 0, z1 is 0, and n1 is 0; or, x1 is 0, z1 is selected from the range of 0.001 to 0.5, and n1 is selected from the range of 0.001 to 0.1; or, x1 is selected from the range of 0.001 to 0.1, z1 is 0, and n1 is selected from the range of 0.001 to 0.1; or, x1 is selected from the range of 0.001 to 0.1, z1 is selected from the range of 0.001 to 0.5, and n1 is 0; or, x1 is 0, z1 is 0, and n1 is selected from the range of 0.001 to 0.1; or, x1 is 0, z1 is selected from the range of 0.001 to 0.5, and n1 is 0; or, x1 is selected from the range of 0.001 to 0.1, z1 is selected from the range of 0.001 to 0.5, and n1 is 0.

14. The battery cell according to any one of claims 11 to 12, wherein: y1:z1 is selected from the range of 0.002 to 999, and may be selected from the range of 0.025 to 999 or the range of 0.002 to 500, and may be further selected from the range of 0.2 to 600; and / or, z1:n1 is selected from the range of 0.002 to 500, can be selected from the range of 0.2 to 100, and can be further selected from the range of 0.2 to 50.

15. The battery cell according to any one of claims 11 to 14, wherein: A 2 comprising one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo and W; B 2 Includes one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge; C 2 including one or more elements selected from B, S, Si and N; D 2 It includes one or more elements selected from S, F, Cl and Br; m1 is selected from the range of 0.9 to 1.1, x1 is selected from the range of 0.001 to 0.1, y1 is selected from the range of 0.001 to 0.5, z1 is selected from the range of 0.001 to 0.1, and n1 is selected from the range of 0.001 to 0.

1.

16. The battery cell according to any one of claims 11 to 14, wherein: B 2 It includes one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge, and may be one or more elements selected from Zn, Fe, Ti, V, Ni, Co and Mg; C 2 It includes one or more elements selected from B, Si, N and S; m1 is selected from the range of 0.9 to 1.1, x1 is 0, y1 is selected from the range of 0.001 to 0.5, z1 is selected from the range of 0.001 to 0.1, and n1 is 0.

17. The battery cell according to any one of claims 11 to 16, wherein: (1-y1): y1 is in the range of 0.1-999, and may be in the range of 0.1-10 or in the range of 0.67-999, and may be in the range of 1 to 10, and may be in the range of 1 to 4, and may be in the range of 1.5 to 3; and / or, a1:x1 is in the range of 1 to 1200, and may be in the range of 9 to 1100, and may be in the range of 190-998; and / or, z1: (1-z1) is 1:9 to 1:999, and can be optionally 1:499 to 1:

249.

18. The battery cell according to any one of claims 1 to 10, wherein: The second positive electrode active material includes a compound represented by formula (III), Li m2 A 3 x2 Fe 1-y2 B 3 y2 P 1-z2 C 3 z2 O 4-n2 D 3 n2 (III) A 3 It includes one or more elements selected from Group IA, Group IIA, Group IIIA, Group IIB, Group VB and Group VIB, and may be selected from one or more elements selected from Rb, Cs, Be, Ca, Sr, Ba, Ga, In, Cd, V, Ta, Cr, Zn, Al, Na, K, Mg, Nb, Mo and W, and may be selected from one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo and W; B 3 The invention comprises one or more elements selected from Group IA, Group IIA, Group IIIA, Group IVA, Group VA, Group IIB, Group IVB, Group VB, Group VIB and Group VIII, and may be selected from one or more elements selected from Rb, Cs, Be, Ca, Sr, Ba, In, Pb, Bi, Cd, Hf, Ta, Cr, Ru, Rh, Pd, Os, Ir, Pt, Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Ni, Co, Ga, Sn, Sb, Nb and Ge, and may be selected from one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Ni, Co, Ga, Sn, Sb, Nb and Ge; C 3 It includes one or more elements selected from Group IIIA, Group IVA, Group VA and Group VIA, and may optionally include one or more elements selected from B, S, Si and N; D 3 It includes one or more elements selected from Group VIA and Group VIIA, and may optionally include one or more elements selected from S, F, Cl and Br; m2 is selected from the range of 0.85 to 1.15, and may be selected from the range of 0.9 to 1.1, and may be selected from the range of 0.97 to 1.01; x2 is selected from the range of 0 to 0.1, and may be selected from the range of 0.001 to 0.005; y2 is selected from the range of 0 to 0.5, and may be selected from the range of 0.001 to 0.2, and may be selected from the range of 0.005 to 0.1; z2 is selected from the range of 0 to 0.5, and may be selected from the range of 0.001 to 0.1, and may be further selected from the range of 0.001 to 0.005; n2 is selected from the range of 0 to 0.5, and may be selected from the range of 0 to 0.1, and may be further selected from the range of 0.001 to 0.

005.

19. The battery cell according to any one of claims 11 to 18, wherein: The second positive electrode active material includes a second core and a second shell covering the second core, The second core comprises the compound represented by the formula (II) or the compound represented by the formula (III); The second shell comprises one or more coating layers; each coating layer has ionic conductivity and / or electronic conductivity; Optionally, the one or more coating layers each independently include one or more selected from pyrophosphate, phosphate, carbon, doped carbon, oxide, boride and polymer.

20. The battery cell according to claim 19, wherein: The second shell comprises a coating layer; optionally, the coating layer comprises one or more selected from pyrophosphate, phosphate, carbon, doped carbon, oxide, boride and polymer.

21. The battery cell according to claim 19, wherein: The second shell includes a first coating layer covering the second core and a second coating layer covering the first coating layer; Optionally, the first coating layer and the second coating layer each independently include one or more selected from pyrophosphate, phosphate, carbon, doped carbon, oxide, boride and polymer; More optionally, the first coating layer includes one or more selected from pyrophosphate, phosphate, oxide and boride, and the second coating layer includes one or more selected from carbon and doped carbon.

22. The battery cell according to claim 19, wherein: The second shell includes a first coating layer covering the second core, a second coating layer covering the first coating layer, and a third coating layer covering the second coating layer; Optionally, the first coating layer, the second coating layer and the third coating layer each independently include one or more selected from pyrophosphate, phosphate, carbon, doped carbon, oxide, boride and polymer; More optionally, the first coating layer includes pyrophosphate, the second coating layer includes one or more selected from phosphates, oxides and borides, and the third coating layer includes one or more selected from carbon and doped carbon.

23. The battery cell according to any one of claims 19 to 22, wherein: The pyrophosphate is M i (P2O7) j and / or, The phosphate is X p (PO4) q and / or, The doping element in the doped carbon includes one or more elements selected from Group IIIA, Group VA, Group VIA and Group VIIA; and / or, The oxide is M' k O l and / or, The boride is Z v B w and / or, The polymer includes one or more selected from polysaccharides and their derivatives, and polysiloxanes; M, X and Z each independently include one or more elements selected from Group IA, Group IIA, Group IIIA, Group IB, Group IIB, Group IVB, Group VB, Group VIIB and Group VIII; i is selected from the range of 1 to 4; j is selected from the range of 1 to 6; p is selected from the range of 1 to 2; q is selected from the range of 1 to 4; M′ comprises one or more elements selected from alkali metals, alkaline earth metals, transition metals, Group IIIA elements, Group IVA elements, lanthanides and Sb; k is greater than 0 and less than or equal to 2; l is greater than 0 and less than or equal to 5; v is selected from the range of 1 to 7; w is selected from the range of 1 to 2.

24. The battery cell according to claim 23, wherein: M, X and Z each independently include one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, Mn and Al; and / or, The doping element in the doped carbon includes one or more selected from nitrogen, phosphorus, sulfur, boron and fluorine; and / or, M′ comprises one or more elements selected from Li, Be, B, Na, Mg, Al, Si, P, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, W, La and Ce, and may optionally comprise one or more elements selected from Mg, Al, Si, Zn, Zr and Sn; and / or The polysiloxane is selected from one or more of linear polysiloxane and cyclic polysiloxane; and / or, The polysaccharide is selected from one or more of plant polysaccharides and marine polysaccharides.

25. The battery cell according to claim 19, wherein: The second positive electrode active material includes a second core and a second shell covering the second core, The second core includes Li m1 Mn 1-y1 B 2 y1 P 1-z1 C 2 z1 O4, m1 is selected from the range of 0.9 to 1.1, y1 is selected from the range of 0.001 to 0.5, z1 is selected from the range of 0.001 to 0.1, B 2 Including Ti, V, Zr, Fe, Ni, Mg, Co, One or more elements of Ga, Sn, Sb, Nb and Ge, C 2 including one or more elements selected from B, S, Si and N; The second shell includes a first coating layer coating the second inner core and a second coating layer coating the first coating layer, the first coating layer includes pyrophosphate MP2O7 and phosphate XPO4, M and X each independently include one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al; the second coating layer contains carbon.

26. The battery cell according to claim 19, wherein: The second positive electrode active material includes a second core and a second shell covering the second core, The second core includes Li m1 Mn 1-y1 B 2 y1 P 1-z1 C 2 z1 O4, m1 is selected from the range of 0.9 to 1.1, y1 is selected from the range of 0.001 to 0.5, z1 is selected from the range of 0.001 to 0.1, B 2 It includes one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge, C 2 including one or more elements selected from B, S, Si and N; The second shell includes a first coating layer covering the second core, a second coating layer covering the first coating layer, and a third coating layer covering the second coating layer. The first coating layer includes pyrophosphate Li r QP2O7 and / or Q s (P2O7) t , 0≤r≤2, 1≤s≤4, 1≤t≤6, the pyrophosphate Li r QP2O7 and / or Q s (P2O7) t wherein Q independently comprises one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al; The second coating layer comprises crystalline phosphate XPO4, wherein X comprises one or more elements selected from the group consisting of Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al; The third coating layer includes carbon.

27. The battery cell according to any one of claims 19 to 24, wherein: The one or more coating layers in the second shell that are farthest from the second core each independently include one or more selected from polysiloxane, polysaccharide and polysaccharide derivatives.

28. The battery cell according to any one of claims 23 to 24 and 27, wherein: The polysiloxane comprises a structural unit represented by formula (i), R1 and R2 are independently selected from H, -COOH, -OH, -SH, -CN, -SCN, amino, phosphate, carboxylate, amide, aldehyde, sulfonyl, polyether segment, C1-C20 aliphatic, C1-C20 halogenated aliphatic, C1-C20 heteroaliphatic, C1-C20 halogenated heteroaliphatic, C6-C20 aromatic, C6-C20 halogenated aromatic, C2-C20 heteroaromatic and C2-C20 halogenated heteroaromatic; Optionally, R1 and R2 are independently selected from H, amino, phosphate, polyether segment, C1-C8 alkyl, C1-C8 haloalkyl, C1-C8 heteroalkyl, C1-C8 haloheteroalkyl, C2-C8 alkenyl and C2-C8 haloalkenyl.

29. The battery cell according to any one of claims 23-24, 27-28, wherein: The polysiloxane further comprises an end-capping group, which comprises one or more of the following functional groups: polyether, C1-C8 alkyl, C1-C8 haloalkyl, C1-C8 heteroalkyl, C1-C8 haloheteroalkyl, C2-C8 alkenyl, C2-C8 haloalkenyl, C6-C20 aromatic hydrocarbon group, C1-C8 alkoxy, C2-C8 epoxy, hydroxyl, C1-C8 hydroxyalkyl, amino, C1-C8 aminoalkyl, carboxyl, C1-C8 carboxylalkyl.

30. The battery cell according to any one of claims 23-24, 27-29, wherein: The polysiloxane comprises polydimethylsiloxane, polydiethylsiloxane, polymethylethylsiloxane, polymethylvinylsiloxane, polyphenylmethylsiloxane, polymethylhydrogensiloxane, carboxyl functionalized polysiloxane, epoxy-terminated polysiloxane, methoxy-terminated polydimethylsiloxane, hydroxypropyl-terminated polydimethylsiloxane, polymethylchloropropylsiloxane, hydroxy-terminated polydimethylsiloxane, polymethyltrifluoropropylsiloxane, perfluorooctylmethylpolysiloxane, aminoethylaminopropyl polydimethylsiloxane, terminal polyether polydimethylsiloxane, side-chain aminopropyl polysiloxane, aminopropyl One or more of end-capped polydimethylsiloxane, side chain phosphate grafted polydimethylsiloxane, side chain polyether grafted polydimethylsiloxane, 1,3,5,7-octamethylcyclotetrasiloxane, 1,3,5,7-tetrahydro-1,3,5,7-tetramethylcyclotetrasiloxane, cyclopentapolydimethylsiloxane, 2,4,6,8-tetramethylcyclotetrasiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, cyclic polymethylvinylsiloxane, hexadecylcyclooctasiloxane, tetradecamethylcycloheptasiloxane, and cyclic polydimethylsiloxane.

31. The battery cell according to any one of claims 23 to 24, 27 to 30, wherein: The number average molecular weight of the polysiloxane, the polysaccharide and the polysaccharide derivative is independently below 300,000, and may be 10,000 to 200,000, more preferably 20,000 to 120,000, and further preferably 400 to 80,000.

32. The battery cell according to any one of claims 23 to 24, 27 to 31, wherein: The mass percentage of the polar functional groups in the polysiloxane is α, 0≤α<50%, optionally, 5%≤α≤30%.

33. The battery cell according to any one of claims 23 to 24 and 27 to 32, wherein: The substituents attached to the sugar units in the polysaccharide and the polysaccharide derivatives each independently include one or more of the group consisting of the following functional groups: -OH, -COOH and salts thereof, -R-OH, -SO3H and salts thereof, -R-OH, -R-SO3H and salts thereof, sulfate, alkoxy, R represents an alkylene group, optionally representing a C1-C5 alkylene group; Optionally, the substituents attached to the sugar units in the polysaccharide and the polysaccharide derivatives each independently include one or more of the group consisting of the following functional groups: -OH, -COOH, -COOLi, -COONa, -COOK, -SO3H, -SO3Li, -SO3Na, -SO3K, -CH2-SO3H, -CH2-SO3Li, -CH2-SO3Na, -CH2-SO3K, methoxy, ethoxy.

34. The battery cell according to any one of claims 23 to 24 and 27 to 33, wherein: The polysaccharide includes one or more selected from pectin, carboxymethyl starch, hydroxypropyl starch, dextrin, cellulose ether, carboxymethyl chitosan, hydroxyethyl cellulose, carboxymethyl cellulose, carboxypropyl methyl cellulose, guar gum, sesbania gum, gum arabic, lithium alginate, sodium alginate, potassium alginate, fucoidan, agar, carrageenan, carrageenan, xanthan gum and fenugreek gum.

35. The battery cell according to any one of claims 23 to 24, 27 to 34, wherein: The mass percentage of the substituents attached to the sugar units in the polysaccharide and the polysaccharide derivatives is independently 20% to 85%, and optionally 30% to 78%.

36. The battery cell according to any one of claims 19 to 35, wherein: The lattice mismatch between the material of the second core and the material of the second shell is less than 10%.

37. The battery cell according to any one of claims 11 to 36, wherein: Based on the total weight of the second positive electrode active material, The manganese content is in the range of 10-35 wt %, optionally in the range of 13.3-33.2 wt %, more optionally in the range of 15-30 wt %, further optionally in the range of 17-20 wt %; and / or, The phosphorus content is in the range of 12-25 wt %, optionally in the range of 15-20 wt %, and more preferably in the range of 16.8-19.5 wt %; and / or, The weight ratio of manganese element to phosphorus element ranges from 0.71 to 1.85, and can be selected from 0.90 to 1.25, and more preferably from 0.95 to 1.

20.

38. The battery cell according to any one of claims 1 to 18, wherein: The surface of the second positive electrode active material is coated with one or more of carbon and doped carbon; optionally, the surface of the second positive electrode active material is coated with carbon.

39. The battery cell according to claim 38, wherein: The doping elements in the doped carbon include one or more selected from nitrogen, phosphorus, sulfur, boron and fluorine.

40. The battery cell according to any one of claims 19-20, 23-24, 27-39, wherein: The coating amount of the second shell is 0.1-6 wt % based on the weight of the second core.

41. The battery cell according to any one of claims 19, 21-37, wherein: The coating amount of the first coating layer is greater than 0 and less than or equal to 7% by weight, and can be greater than 0 and less than or equal to 6% by weight, and can be greater than 0 and less than or equal to 5.5% by weight or 4-5.6% by weight, and can be further greater than 0 and less than or equal to 2% by weight, based on the weight of the second core; and / or, The coating amount of the second coating layer is greater than 0 and less than or equal to 6% by weight, optionally greater than 0 and less than or equal to 5.5% by weight, and more optionally 2-4% by weight or 3-5% by weight, based on the weight of the second core; and / or, The coating amount of the third coating layer is greater than 0 and less than or equal to 6% by weight, optionally greater than 0 and less than or equal to 5.5% by weight, and more optionally greater than 0 and less than or equal to 2% by weight, based on the weight of the second core.

42. The battery cell according to any one of claims 19, 22-24, 26-37, and 41, wherein: The second shell further includes a fourth coating layer covering the third coating layer and a fifth coating layer covering the fourth coating layer; The coating amounts of the fourth coating layer and the fifth coating layer are independently 0.01-10 wt %, optionally 0.05-10 wt %, more optionally 0.1-5 wt %, further 0.1-2 wt %, based on the weight of the second core.

43. The battery cell according to any one of claims 19 to 42, wherein: The second shell is located on 40% to 90% of the surface of the second core, optionally 60% to 80% of the surface.

44. The battery cell according to any one of claims 19-20, 23-24, 27-40, 43, wherein: The thickness of the second shell is 1-15 nm.

45. The battery cell according to any one of claims 19, 21-37, 41-43, wherein: The thickness of the first coating layer is 1-10 nm, and can be 2-10 nm; and / or, The thickness of the second coating layer is 2-25 nm, optionally 2-15 nm, more optionally 3-15 nm; and / or, The thickness of the third coating layer is 2-25 nm, and can be optionally 5-25 nm.

46. ​​The battery cell according to any one of claims 19 to 45, wherein: The one or more coating layers each independently include one or more selected from pyrophosphate, phosphate and oxide, and the one or more selected from the pyrophosphate, phosphate and oxide are crystalline; Optionally, the crystallinity of the pyrophosphate, the phosphate and the oxide is each independently 10% to 100%, more preferably 50% to 100%.

47. The battery cell according to any one of claims 19 to 46, wherein: In the second shell, the weight ratio of the pyrophosphate to the phosphate and the weight ratio of the pyrophosphate to the oxide are each independently 1:3 to 3:1, and may be 1:3 to 1:

1.

48. The battery cell according to any one of claims 19 to 47, wherein: The one or more coating layers each independently include carbon, and the carbon is a mixture of SP2 carbon and SP3 carbon; Optionally, in the carbon, the molar ratio of the SP2 carbon to the SP3 carbon is any value in the range of 0.07-13, more preferably any value in the range of 0.1-10, and further preferably any value in the range of 2.0-3.

0.

49. The battery cell according to any one of claims 19 to 48, wherein: The one or more coating layers each independently include doped carbon, and the mass content of the doping element in the doped carbon is less than 30%; optionally, the mass content of the doping element in the doped carbon is less than 20%.

50. The battery cell according to any one of claims 19 to 49, wherein: The one or more coating layers each independently include doped carbon, in which: The doping element is nitrogen and / or sulfur, and the mass content of the doping element in the doped carbon is 1% to 15%; or, The doping element is phosphorus, boron and / or fluorine, and the mass content of the doping element in the doped carbon is 0.5% to 5%; Optionally, the doping element is nitrogen, phosphorus, sulfur, boron or fluorine.

51. The battery cell according to any one of claims 19 to 50, wherein: The one or more coating layers independently include pyrophosphate, the interplanar spacing of the pyrophosphate is in the range of 0.293-0.470nm, optionally 0.297-0.462nm or 0.293-0.326nm, more optionally 0.300-0.310nm, and the angle of the crystal direction (111) is in the range of 18.00°-32.57°, optionally 18.00°-32.00° or 26.41°-32.57°, more optionally 19.211°-30.846°, and further optionally 29.00°-30.00°; and / or, The one or more coating layers independently include phosphate, the interplanar spacing of the phosphate is in the range of 0.244-0.425 nm, optionally 0.345-0.358 nm, and the angle of the crystal direction (111) is in the range of 20.00°-37.00°, optionally 24.25°-26.45°; Optionally, the first coating layer or the second coating layer comprises phosphate.

52. The battery cell according to any one of claims 11 to 51, wherein: The lattice change rate of the second positive electrode active material before and after complete lithium deintercalation is 50% or less, optionally 9.8% or less, more optionally 8.1% or less, further optionally 7.5% or less, further optionally 6% or less, further optionally 4% or less, further optionally 3.8% or less, further optionally 2.0%-3.8%; and / or, The Li / Mn antisite defect concentration of the second positive electrode active material is 5.3% or less, optionally 5.1% or less, more optionally 4% or less, further optionally 2.2% or less, further optionally 2% or less, further optionally 1.5%-2.2% or 0.5% or less; and / or, The surface oxygen valence state of the second positive electrode active material is -1.55 or less, optionally -1.82 or less, more optionally -1.88 or less, further optionally -1.90 or less or -1.98 to -1.88, further optionally -1.98 to -1.89, further optionally -1.98 to -1.

90.

53. The battery cell according to any one of claims 1 to 52, wherein: The battery cell further comprises a negative electrode plate and a separator.

54. A method for preparing the battery cell according to any one of claims 1 to 53, comprising the following steps: A battery container containing a positive electrode sheet and a negative electrode sheet is provided, wherein: The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprises a first positive electrode active material and a second positive electrode active material, the first positive electrode active material The first positive electrode active material and the second positive electrode active material are capable of extracting and inserting lithium ions, the first positive electrode active material and the second positive electrode active material have different crystal forms, the second positive electrode active material has a one-dimensional ion transport channel, and the ion conductivity of the first positive electrode active material is greater than the ion conductivity of the second positive electrode active material; The non-aqueous solvent and the electrolyte salt are uniformly mixed to obtain an electrolyte, wherein the electrolyte salt comprises a lithium salt and a metal Me salt, the lithium salt dissociates into lithium ions and a first anion in the electrolyte, the metal Me salt dissociates into Me cations and a second anion in the electrolyte, the ionic radius of the Me cations is greater than the ionic radius of the lithium ions, the weight content of the lithium ions in the electrolyte is recorded as w1, and the weight content of the Me cations in the electrolyte is recorded as w2, both based on the total weight of the electrolyte; injecting the obtained electrolyte into the battery container to obtain a battery cell; In the charge and discharge test of the battery cell, the total discharge capacity of the battery cell is recorded as Q1, and the discharge capacity of the battery cell at a discharge voltage below 3.6V is recorded as Q2, both in mAh; When the remaining capacity of the battery cell is greater than 90%, the following conditions are met: 0.8≤(Q2 / Q1) / [w2 / (w1+w2)]≤8.

5. The battery cell charge and discharge test was carried out under the following conditions: the test temperature was 25° C., the battery cell was fully charged at 0.5C, and after standing for 5 minutes, the battery cell was fully discharged at 0.33C.

55. A battery, wherein: A battery cell comprising the battery cell according to any one of claims 1 to 53 or a battery cell prepared by the method according to claim 54.

56. An electrical device comprising the battery according to claim 55.

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