Secondary battery having improved cycle storage performance, and electric device

Abstract

The present application provides a secondary battery having improved cycle storage performance, and an electric device. The secondary battery comprises a positive electrode sheet, a negative electrode sheet and a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises an additive, the additive comprising a first additive, which is a cyclic organic base additive; and the positive electrode sheet comprises a positive electrode active material. The positive electrode active material comprises: an inner core and a carbon coating layer, wherein the inner core is lithium iron manganese phosphate, and the carbon coating layer at least covers part of the surface of the inner core. In the present invention, by introducing the organic base additive, which captures protons, into the electrolyte of the secondary battery, in which lithium iron manganese phosphate serves as a positive electrode active material, the interaction effect of protons is reduced, thereby realizing the long service life of a cell.

Description

Cycling performance improved secondary battery and power consuming device

[0001] Cross-reference to related applications

[0002] This application is based on and claims priority to CN application No. 202410881074.4, filed on July 2, 2024, the contents of which are incorporated herein in their entirety. TECHNICAL FIELD

[0003] The present application relates to the technical field of batteries, in particular to a secondary battery and a power consuming device. BACKGROUND

[0004] Lithium ion batteries have become the most popular energy storage system due to their high operating potential, long service life, and environmental friendliness, and have been widely used in pure electric vehicles, hybrid electric vehicles, smart grids, and other fields. At the same time, with the rapid development of new energy vehicles in recent years, the market has also put forward higher demands on the service life and capacity of lithium ion batteries.

[0005] Researchers have obtained higher capacity density batteries by improving the specific capacity of positive and negative electrode materials and the average voltage of positive electrode materials. However, with the increase of energy density and voltage, the electrolyte limits the improvement of battery life. For lithium ion batteries, the capacity reduction during high-temperature cycling and storage is a serious performance degradation problem, and the side reactions caused by the degradation of electrolyte at high temperature are one of the causes of the above problems. HF generated by the degradation of solvents and fluorine-containing electrolytes (such as LiPF6) can destroy the solid electrolyte interface film (SEI film) on the positive and negative electrode surfaces, and further deteriorate the cycle and storage life.

[0006] Lithium manganese iron phosphate has the advantages of high voltage platform and large capacity, and is widely used as a positive active material in lithium batteries. However, due to the high specific surface area of lithium manganese iron phosphate positive material, the electrolyte degradation caused by high voltage of lithium manganese iron phosphate battery is more serious. In particular, as a positive electrode with high voltage, lithium manganese iron phosphate will promote the dehydrogenation of solvents at high temperature, and the removed proton hydrogen will further induce the decomposition of fluorine-containing lithium salt, and then form HF. On the one hand, HF will attack the SEI film on the negative side during cycling and storage, causing the SEI to partially dissolve into the electrolyte, resulting in a loose and porous SEI. On the other hand, HF will increase the dissolution of manganese in the positive electrode, and the dissolved manganese will be reduced in the negative electrode, destroying the stability of the SEI. The instability of the SEI will cause the electrolyte to directly contact the negative electrode, thereby causing the electrolyte to decompose and increasing the consumption of active lithium, and further deteriorating the cycle and storage life of the battery. SUMMARY

[0007] In view of the problems in the background art, the purpose of the present application is to provide a secondary battery with improved cycle storage performance, which reduces proton interaction by introducing a proton-capturing organic base additive into the electrolyte of a secondary battery containing lithium manganese iron phosphate.

[0008] The present application provides a secondary battery and a power consumption device to solve the above problems.

[0009] The first aspect of the present application provides a secondary battery, comprising a positive electrode sheet, a negative electrode sheet and a non-aqueous electrolyte, wherein the non-aqueous electrolyte contains an additive; the additive contains a first additive, which is a cyclic organic base additive; the positive electrode sheet contains a positive electrode active material, which comprises an inner core and a carbon coating layer, the inner core is lithium manganese iron phosphate, and the carbon coating layer covers at least part of the surface of the inner core.

[0010] Since the BET of the manganese iron phosphate positive electrode material is significantly larger than that of lithium iron phosphate, and the use voltage is higher than that of lithium iron phosphate, the oxidation and decomposition of the electrolyte to generate acidic substances is more likely to occur in the battery. On the one hand, this byproduct increases the manganese dissolution of the positive electrode, and on the other hand, it also damages the SEI film at the negative electrode, causing the negative electrode to react more severely with the electrolyte, resulting in capacity decay during the cycle storage process. In order to solve this problem, an electrolyte containing an alkaline additive is used in the battery, which captures protons in the electrolyte using an alkaline additive, reduces the acidity of the electrolyte, and reduces the dissolution of transition metals. At the same time, the alkaline additive can reduce the destructive effect of protons on the negative electrode, thereby prolonging the life of the battery.

[0011] In some embodiments, the cyclic organic base is an aromatic ring organic base or a non-aromatic ring organic base (e.g., a saturated or unsaturated non-aromatic ring organic base). In some embodiments, the cyclic organic base is a monocyclic or fused bicyclic ring containing 5-12 ring atoms.

[0012] In some embodiments, the cyclic organic base additive includes any one or more of compound 1 represented by general formula (I), compound 2 represented by general formula (II), compound 3 represented by general formula (IV), compound 4 represented by general formula (IV) or general formula (V), and compound 5 represented by general formula (V).

[0013] In general formula (I), Y 1 , Y 2 are the same or different, Y 1 , Y 2 are each independently selected from CH, N; R 11 , R 12 , R 13each independently selected from the group consisting of H, C1-C6 alkyl, C2-C6 alkenyl (e.g., allyl (H2C=CH-CH2-)), C2-C6 alkynyl (e.g., propargyl (-CH2CºCH)), halogen (e.g., F, Cl, Br, or I), -R 14 OH, -R 15 NR 16 R 17 , -R 18 -O-R 19 , C3-C5 cycloalkyl, wherein R 14 , R 15 , R 18 each independently selected from the group consisting of nothing, C1-C6 alkylene, C2-C6 alkenylene, R 16 , R 17 , R 19 each independently selected from the group consisting of hydrogen, halogen, C1-C6 alkyl, C1-C6 haloalkyl, and as R 16 , R 17 , R 19 any carbon atom in R 16 , R 17 and the nitrogen atom to which both are attached together form a 5-6 membered nitrogen-containing heterocyclic ring;

[0014] In general formula (III), W 1 and W 2 are the same or different, W 1 is selected from C, N, O, S, W 2 is selected from C, N, and W 1 and W 2 at least one of which is N; R 21 , R 22 , R 23 , R 24 each independently selected from the group consisting of H, C1-C6 alkyl, C2-C6 alkenyl (e.g., allyl (H2C=CH-CH2-)), C2-C6 alkynyl (e.g., propargyl (-CH2CºCH)), halogen (e.g., F, Cl, Br, or I), -R 25 OH, -R 26 N R 27 R 28 , -R 29 -O-R 30 , C3-C5 cycloalkyl, wherein R 25 , R 26 , R 29 each independently selected from the group consisting of nothing, C1-C6 alkylene, C2-C6 alkenylene, R27 , R 28 , R 30 each independently is selected from a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group;

[0015] In general formula (IV), A 1 , A 2 , A 3 , A 4 , A 5 , A 6 , A 7 may be the same or different, each independently is C or N, and A 1 , A 2 , A 3 , A 4 and A 5 at least one (e.g., 1, 2, 3, or 4) of A 31 , R 32 , R 33 , R 34 , R 35 , R 36 , R 37 each independently is selected from the group consisting of H, C1-C6 alkyl, C2-C6 alkenyl (e.g., allyl (H2C=CH-CH2-)), C2-C6 alkynyl (e.g., propargyl (-CH2CºCH)), halogen (e.g., F, Cl, Br, or I), -OH, -R 38 NR 39 R 40 , C1-C6 alkoxy, C3-C5 cycloalkyl, wherein R 38 is absent or selected from C1-C6 alkylene, C2-C6 alkenylene, R 39 , R 40 each independently is selected from a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group;

[0016] In general formula (V), X 1 , X 2 , X 3 each independently is C or N, and at least one of X 1 , X 2 , X 3 is N, in general formula (V’), X 1 , X 3 each independently is C or N, and at least one of X 1 , X 3 is N,

[0017] In general formula (V) and (V'), a, b are each independently selected from 0, 1, 2, 3, c is selected from 1, 2, 3, 4, 5, 6, 7, 8, each R 41 each independently selected from H, C1-C6 alkyl, C2-C6 alkenyl (e.g. allyl (H2C=CH-CH2-)), C2-C6 alkynyl (e.g. propargyl (-CH2CºCH)), halogen (e.g. F, CI, Br or I), -R 42 OH, -R 43 NR 44 R 45 , -R 46 -O-R 47 , C3-C5 cycloalkyl, wherein R 42 , R 43 , R 46 each independently selected from: nothing, C1-C6 alkylene, C2-C6 alkenylene, R 44 , R 45 , R 47 each independently selected from hydrogen, halogen, C1-C6 alkyl, C1-C6 haloalkyl;

[0018] In general formula (VI), V 1 , V 2 , V 3 each independently C or N, and at least one of V 1 , V 2 , V 3 is N, d is selected from 0, 1, 2, 3, e is selected from 1, 2, 3, 4, 5, 6, each R 51 each independently selected from H, C1-C6 alkyl, C2-C6 alkenyl (e.g. allyl (H2C=CH-CH2-)), C2-C6 alkynyl (e.g. propargyl (-CH2CºCH)), halogen (e.g. F, CI, Br or I), -R 52 OH, -R 53 N R 54 R 55 , -R 56 -O-R 57 , C3-C5 cycloalkyl, wherein R 52 , R 53 , R 56 each independently selected from: nothing, C1-C6 alkylene, C2-C6 alkenylene, R 54 , R 55 , R 57 each independently selected from a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group.

[0019] In some embodiments, in general formula (II), Y1 , Y 2 are both N, or, Y 1 , Y 2 is N and the other is CH.

[0020] In some embodiments, in general formula (II), the R 11 , R 12 , R 13 are each independently selected from the group consisting of hydrogen, halogen, C1-C4 alkyl, C3-C5 alkenyl, C3-C5 alkynyl, -R 14 OH, -R 15 N R 16 R 17 , -R 18 -O-R 19 , wherein R 14 , R 15 , R 18 are each independently selected from the group consisting of nothing, C1-C3 alkylene, R 16 , R 17 , R 19 are each independently selected from the group consisting of hydrogen, halogen, C1-C3 alkyl, C1-C3 haloalkyl, and as the R 16 , R 17 , R 19 C1-C3 alkyl groups, any carbon atom can be substituted with one or more heteroatoms, which are N atoms, optionally, R 16 , R 17 and the nitrogen atom to which both are attached together form a 5-6 membered nitrogen-containing heterocycle.

[0021] In some embodiments, in general formula (II), the R 11 , R 12 , R 13 are each independently selected from the group consisting of hydrogen, halogen, methyl, ethyl, n-propyl, i-propyl, t-butyl, allyl, propargyl, -OH, -CH2OH, -NH2, -CH2NH2, -N(CH3)2, -O-CH3, In some embodiments, the R 11 , R 12 , R 13 are each independently selected from the group consisting of hydrogen, fluorine, methyl, t-butyl, -CH2OH, -CH2NH2, -N(CH3)2, -O-CH3, any one of the group consisting of.

[0022] In some embodiments, the compound having the structure according to general formula (II) is selected from any one or more of the following compounds:

[0023] In some embodiments, in Formula (III), W 1 and W 2 are both N, or one of W 1 , W 2 is N and the other is CH.

[0024] In some embodiments, in Formula (III), each of R 21 , R 22 , R 23 , R 24 is independently selected from hydrogen, halogen, C1-C4 alkyl, C3-C5 alkenyl, C3-C5 alkynyl, -R 25 OH, -R 26 NR 27 R 28 , -R 29 -O-R 30 , C3-C5 cycloalkyl, wherein each of R 25 , R 26 , R 29 is independently selected from absent, C1-C4 alkylene, R 27 , R 28 , R 30 is independently selected from hydrogen, halogen, C1-C4 alkyl, C1-C4 haloalkyl.

[0025] In some embodiments, in Formula (III), each of R 21 , R 22 , R 23 , R 24 is independently selected from hydrogen, fluorine, methyl, ethyl, propyl, cyclopropyl, allyl, propargyl, -OH, -CH3OH, -NH2, -NHCH3, -CH2NH2, -N(CH3)2, -O-CH3. In some embodiments, each of R 21 , R 22 , R 23 , R 24 is independently selected from hydrogen, fluorine, methyl, cyclopropyl, allyl, -CH3OH, -NHCH3.

[0026] In some embodiments, the compound having the structure according to Formula (III) is selected from any one or more of the following compounds:

[0027] In some embodiments, in Formula (IV), A 1 is N, A 2 , A 3 , A 4 , A 5 , A6 , A 7 each independently C or N. In some embodiments, A 1 is N, and A 5 is C.

[0028] In some embodiments, in general formula (IV), R 31 , R 32 , R 33 , R 34 , R 35 , R 36 , R 37 each independently is selected from any one of hydrogen, C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, -OH, -R 38 NR 39 R 40 , C1-C4 alkoxy, R 38 is absent or selected from C1-C3 alkylene, R 39 , R 40 each independently is selected from any one of hydrogen, halogen, C1-C3 alkyl, C1-C3 haloalkyl. In some embodiments, R 31 , R 32 , R 33 , R 34 , R 35 , R 36 , R 37 each independently is selected from any one of hydrogen, methyl, ethyl, allyl, propargyl, -OH, -NH2, -CH2NH2, -N(CH3)2, -O-CH3. In some embodiments, R 31 , R 32 , R 33 , R 34 , R 35 , R 36 , R 37 each independently is selected from any one of hydrogen, methyl, -O-CH3.

[0029] In some embodiments, in general formula (IV), R 32 , R 33 , R 34 , R 35 , R 36 , R 37 are all hydrogen. In some embodiments, R 31 is selected from any one of hydrogen, methyl, ethyl, allyl, propargyl, -OH, -NH2, -CH2NH2, -N(CH3)2, -O-CH3. In some embodiments, R 31 is selected from any one of hydrogen, methyl, -O-CH3.

[0030] In some embodiments, the compound having the structure of Formula (IV) is selected from any one or more of the following compounds:

[0031] In some embodiments, in Formula (V), X 1 is N, X 2 , X 3 are each independently C or N. In some embodiments, X 2 is N. In some embodiments, X 3 is C. In some embodiments, X 1 , X 3 are each N.

[0032] In some embodiments, in Formula (V), a, b, c are each independently 1, 2, or 3. In some embodiments, a is 2. In some embodiments, b is 1, 2, or 3. In some embodiments, c is 1 or 2.

[0033] In some embodiments, in Formula (V’), a is 0 or 1, and c is 1 or 2.

[0034] In some embodiments, Formula (V) is (V-1):

[0035] wherein a, b, X 1 , X 2 , X 3 are as defined above.

[0036] In some embodiments, Formula (V’) is (V’-1):

[0037] wherein a, X 1 , X 3 are as defined above.

[0038] In some embodiments, in Formula (V), (V’), (V-1), or (V’-1), each R 41 is each independently selected from hydrogen, halogen, C1-C4 alkyl, C3-C5 alkenyl, C3-C5 alkynyl, -R 42 OH, -R 43 NR 44 R 45 , -R 46 -O-R 47 , R 42 , R 43 , R 46 is each independently selected from: nothing, C1-C3 alkylene, R 44 , R 45 , R47 each R is independently selected from hydrogen, halogen, C1-C4 alkyl, C1-C4 haloalkyl. In some embodiments, each R 41 each R is independently selected from hydrogen, halogen, C1-C4 alkyl, C1-C4 haloalkyl. In some embodiments, each R 41 each R is independently selected from hydrogen, halogen, C1-C4 alkyl, C1-C4 haloalkyl. In some embodiments, each R

[0039] In some embodiments, the compound having the structure of Formula (V) is selected from any one or more of the following compounds:

[0040] In some embodiments, in Formula (VI), d is 0 or 1.

[0041] In some embodiments, in Formula (VI), each R 51 each R is independently selected from hydrogen, halogen, C1-C4 alkyl, C3-C5 alkenyl, C3-C5 alkynyl, -R 52 OH, -R 53 NR 54 R 55 , -R 56 -O-R 57 , R 52 , R 53 , R 56 each R is independently selected from: nothing, C1-C3 alkylene, R 54 , R 55 , R 57 each R is independently selected from hydrogen, halogen, C1-C4 alkyl, C1-C4 haloalkyl. In some embodiments, each R 51 each R is independently selected from hydrogen, halogen, C1-C4 alkyl, C1-C4 haloalkyl. In some embodiments, each R 51 each R is independently selected from hydrogen, halogen, C1-C4 alkyl, C1-C4 haloalkyl. In some embodiments, each R

[0042] In some embodiments, the compound having the structure of Formula (VI) is selected from any one or more of the following compounds:

[0043] In some embodiments, the mass percentage of the first additive in the non-aqueous electrolyte is W1, W1 satisfies 0.001%≤W1≤20%, and optionally 0.1%≤W1≤2%. W1 within the above range is conducive to reducing the gas production while ensuring the fast charging performance, and improving the cycle performance and storage performance of the battery.

[0044] In some embodiments, W1 is 0.001% to 0.05%, 0.05% to 0.1%, 0.1% to 0.5%, 0.5% to 1%, 1% to 2%, 2% to 5%, 5% to 12%, 12% to 20%, or 20% to 22%.

[0045] In some embodiments, the non-aqueous electrolyte of the secondary battery of the present application further comprises a second additive, which optionally includes one or more of a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive capable of improving battery performance.

[0046] In some embodiments, the positive active material of the secondary battery of the present application comprises a lithium manganese iron phosphate having a chemical formula of Li m A a Fe x Mn b D d P y E e O z G g , the A includes at least one element of Al, Na, K, or Mg; the D includes at least one element of Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, Ti, or V; the E includes at least one element of B, S, Si, or N; the G includes at least one element of S, F, Cl, or Br; the m is selected from a range of 0.95 to 1.15; the a is selected from a range of 0 to 0.1; the x is selected from a range of 0.1 to 1; the b is selected from a range of 0.1 to 0.9; the d is selected from a range of 0 to 0.1; the y is selected from a range of 0.95 to 1; the e is selected from a range of 0 to 0.1; the z is selected from a range of 3.5 to 4; and the g is selected from a range of 0 to 0.1.

[0047] The core of the present application includes Li m A a Fe x Mn b D d P y E e O z G gwherein the manganese site doping element D helps to reduce the lattice change rate of lithium manganese phosphate during lithium deintercalation, improve the structural stability of the positive electrode active material, greatly reduce the dissolution of manganese and reduce the oxygen activity on the surface of the particles; the phosphorus site doping element E also helps to change the difficulty of the Mn-O bond length change, thereby improving the electronic conductivity and reducing the lithium ion migration barrier, promoting lithium ion migration and improving the rate performance of the secondary battery. The size of m is affected by the valence state of A, D, E and G and the size of a, d, e and g to ensure that the entire system is electrically neutral. If the value of m is too small, it will reduce the lithium content of the entire core and affect the specific capacity of the positive electrode active material. The value of d will limit the total amount of all doping elements, and if d exceeds 0.1, it will result in less Mn and Fe content in the system, affecting the voltage platform of the positive electrode active material. The E element is doped at the P position, and because the P-O tetrahedron is relatively stable, a too large value of e will affect the stability of the positive electrode active material. Therefore, by doping specific elements at the Li site, Fe / Mn site, P site and / or O site of the compound, the dissolution of transition metals can be significantly reduced, and the cycle performance and high temperature stability can be significantly improved.

[0048] In some embodiments, a, d, e, g are all 0, and the lithium manganese iron phosphate has a chemical formula of Li m Fe x Mn b P y O z wherein m, x, b, y, z are as defined above. In some embodiments, the lithium manganese iron phosphate has a chemical formula selected from the group consisting of: Li 0.5 Fe 0.5 PO4, Li 0.6 Fe 0.4 PO4, Li 0.7 Fe 0.3 PO4, Li 0.8 Fe 0.2 PO4;

[0049] In some embodiments, d, e, g are all 0, and the lithium manganese iron phosphate has a chemical formula of Li m A a Fe x Mn b PO z wherein A, a, m, x, b, y, z are as defined above. In some embodiments, A is Mg; and optionally, the lithium manganese iron phosphate has a chemical formula selected from the group consisting of: Li 0.60 Fe 0.395 Mg 0.005 PO4;

[0050] In some embodiments, a, e, g are all 0, and the lithium manganese iron phosphate has a chemical formula of Lim Fe x Mn b D d P y O z wherein m, x, b, D, d, y, z are as defined above. In some embodiments, D is selected from one or more elements of V, Ni. In some embodiments, the lithium manganese iron phosphate has a chemical formula of Li 0.60 Fe 0.395 V 0.002 Ni 0.003 PO4;

[0051] In some embodiments, a is 0, and the lithium manganese iron phosphate has a chemical formula of Li m Fe x Mn b D d P y E e O, wherein m, x, b, D, d, E, e, y, z are as defined above. In some embodiments, D is selected from one or more elements of V, Co. In some embodiments, E is selected from one or more elements of S, Si. In some embodiments, the lithium manganese iron phosphate has a chemical formula selected from: Li 0.997 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.997 S 0.003 O4, Li 1.001 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.999 Si 0.001 O4.

[0052] In some embodiments, the thickness of the carbon coating layer in the positive electrode active material is 0.5 nm to 10 nm. In some embodiments, the thickness of the carbon coating layer is 4 nm to 8 nm. Transition metals in the positive electrode active material can be dissolved into the electrolyte during structural degradation in the cycle process, and the transition metals can be reduced to elements after migrating to the negative electrode, which can damage the SEI, causing the SEI to thicken, and then increasing the lithium consumption and the impedance, and deteriorating the cycle storage life. By controlling the formation of a thin carbon coating layer on the surface of the core, on the one hand, the conductivity of the positive electrode active material can be improved, and on the other hand, the structural degradation of the positive electrode material during use can be improved, the dissolution of manganese can be reduced, and the damage to the SEI after the transition metal migrates to the negative electrode can be reduced, thereby reducing the capacity attenuation during the cycle storage process. When the thickness of the carbon coating layer is greater than 10 nm, a carbon coating layer containing larger pores is more likely to be formed, which can increase the possibility of water absorption and storage of the carbon coating layer. The water stored in the carbon layer can cause decomposition of the electrolyte at high temperatures, thereby deteriorating the cycle storage performance. In addition, a too thick carbon coating layer can affect the extraction and embedding of lithium ions in the core, which can significantly reduce the specific capacity of the positive electrode active material, and is not conducive to the further application of the material. When the thickness of the carbon coating layer is too small, the improvement in structural stability may not be significant. Therefore, when the carbon coating layer is in the above range, the cycle performance and high-temperature stability can be significantly improved.

[0053] The third aspect of the present application provides a power utilization device including a secondary battery, and the secondary battery includes any of the embodiments of the second aspect. BRIEF DESCRIPTION OF DRAWINGS

[0054] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the drawings.

[0055] FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0056] FIG. 2 is an exploded view of the secondary battery according to an embodiment of the present application shown in FIG. 1.

[0057] FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0058] FIG. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0059] FIG. 5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 4.

[0060] FIG. 6 is a schematic diagram of a power utilization device using the secondary battery according to an embodiment of the present application as a power source.

[0061] In the drawings, the figures are not necessarily drawn to scale.

[0062] BRIEF DESCRIPTION OF DRAWINGS 1: battery pack; 2: upper case; 3: lower case; 4: battery module; 5: secondary battery cell; 51: case; 52: electrode assembly; 53: top cap assembly. DETAILED DESCRIPTION

[0063] The embodiments of the present application will be described in further detail below with reference to the accompanying drawings and examples. The following detailed description of the examples and the accompanying drawings are provided to illustrate the principles of the present application, but are not intended to limit the scope of the present application, i.e., the present application is not limited to the described examples.

[0064] Hereinafter, specific embodiments of the non-aqueous electrolyte secondary battery, the secondary battery, and the electric device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there are cases where unnecessary detailed description is omitted. For example, there are cases where detailed description of matters well known, repeated description of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying 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 recited in the claims.

[0065] The "ranges" disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this manner can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. In addition, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise stated, a numerical range "a-b" represents a shorthand manner of describing each and every numerical value that is contained in the range between "a" and "b," wherein "a" and "b" are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed herein, and "0-5" is merely a shorthand manner of describing each and every numerical value that is contained in the range between "0" and "5." In addition, when it is stated that a parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0066] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0067] All the technical features and optional technical features of the present application can be combined with each other to form new technical solutions, if there is no special description.

[0068] All the steps of the present application can be performed in sequence or randomly, preferably in sequence, if there is no special description. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method can further comprise step (c), which means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0069] The terms "comprise" and "contain" mentioned in the present application mean open type, if there is no special description. For example, the "comprise" and "contain" can mean that other components not listed can also be included or contained.

[0070] The term "or" in the present application is inclusive, if there is no special description. For example, any of the following conditions satisfies the condition "A or B": 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 A and B are both true (or exist).

[0071] The term "linear carboxylate" refers to a linear or branched organic compound containing an -O-C(=O)- group.

[0072] The term "cyclic organic base" refers to a basic compound having a cyclic structure composed of one or more nitrogen atoms and carbon atoms.

[0073] The term "alkyl" means a straight-chain or branched hydrocarbon group obtained by removing one hydrogen atom from an alkane, for example, "C 1-20 The term "alkyl", "C 1-10 The term "alkyl", "C 1-6 The term "alkyl", "C 1-4 The term "alkyl", "C 1-3 The term "alkyl", "C

[0074] The term "alkylene" refers to a divalent straight or branched chain alkyl group consisting solely of carbon and hydrogen atoms, containing no degree of unsaturation, and connected to the rest of the molecule by two single bonds, including but not limited to methylene, etc. For example, "C 1-6 alkylene" refers to a saturated divalent straight or branched chain hydrocarbon group comprising 1 to 6 carbon atoms.

[0075] The term "alkenyl" refers to a straight or branched chain hydrocarbon group containing at least one carbon-carbon double bond, including for example "C 2-6 alkenyl", "C 2-4 alkenyl", and the like. Examples include, but are not limited to: ethenyl, 1- propenyl, 2-propenyl, 1-butenyl, 2-butenyl, 1,3-buten-yl, 1-pentenyl, 2-pentenyl, 3- pentenyl, 1,3-pentadienyl, 1,4-pentadienyl, 1-hexenyl, 2-hexenyl, 3-hexenyl, 1,4- hexadienyl, and the like.

[0076] The term "alkenylene" refers to a divalent straight or branched chain alkyl group consisting solely of carbon and hydrogen atoms, containing at least one double bond, and connected to the rest of the molecule by two single bonds, including but not limited to etc. For example, "C2-6alkenylene" refers to a divalent straight or branched chain hydrocarbon group comprising 2 to 6 carbon atoms and having at least 1 carbon-carbon double bond (>C=C<).

[0077] The term "alkynyl" refers to a straight or branched chain hydrocarbon group containing at least one carbon-carbon triple bond. Including for example "C 2- 6alkynyl", "C 4-6 alkynyl", and the like. Examples include, but are not limited to: ethynyl, 1- propynyl, 2-propynyl, 1-butynyl, 2-butynyl, 1,3-butadiynyl, 1-pentynyl, 2-pentynyl, 3- pentynyl, 1,3-pentadiynyl, 1,4-pentadiynyl, 1-hexynyl, 2-hexynyl, 3-hexynyl, 1,4- hexadiynyl, and the like.

[0078] The term "heterocyclyl" or "heterocycle" refers to saturated or partially saturated, monocyclic or polycyclic (such as bicyclic) non-aromatic ring structures whose ring atoms are composed of carbon atoms and at least one (e.g., 1, 2, or 3) heteroatom selected from nitrogen, oxygen, and sulfur. A heterocyclyl group can be attached to the rest of the molecule through any one of the ring atoms, if valence permits. The term "5-6 membered nitrogen-containing heterocycle" as used herein refers to a heterocycle having 5 to 6 ring atoms, at least one (e.g., 1, 2, or 3) of which is a nitrogen atom. Common heterocyclyl groups include, but are not limited to, azetidinyl, oxetanyl, tetrahydrofuryl, pyrrolidinyl, pyrrolidinonyl, imidazolidinyl, pyrazolidinyl, tetrahydropyranyl, piperidinyl, piperazinyl, morpholinyl. The heterocyclyl groups in the present application can optionally be fused to one or more aromatic or non-aromatic rings.

[0079] The term "cycloalkyl" refers to monocyclic or polycyclic groups comprising saturated or partially unsaturated (e.g., containing 1 or 2 double bonds). "Monocycloalkyl" is preferably a 3-10 membered monocycloalkyl, more preferably a 3-8 membered monocycloalkyl, for example: cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl, cyclododecyl, cyclohexenyl. "Polycycloalkyl" includes "bridged cycloalkyl," "fused cycloalkyl," and "spirocycloalkyl." "Bridged cycloalkyl" refers to a monocycloalkyl group in which any two non-adjacent carbon atoms are connected by an alkylene bridge of one or more (e.g., 1-3) additional carbon atoms (i.e., -(CH2)t- where t is, for example, 1, 2, or 3). "Fused cycloalkyl" comprises a cycloalkyl ring fused to a phenyl, monocycloalkyl, monocycloheteroalkyl, or monocycloheteroaryl. "Spirocycloalkyl" refers to a bicyclic group formed from two cycloalkyl groups sharing a single carbon atom. Polycycloalkyl groups can be 5-18 membered, preferably 6-15 membered, more preferably 6-12 membered. The polycycloalkyl group is preferably bicyclic. t

[0080] The term "aromatic ring" includes all-carbon monocyclic rings having a conjugated pi-electron system as well as heteroaromatic rings. The term "heteroaromatic ring" refers to a monocyclic or polycyclic aromatic ring system having, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14 ring atoms, particularly 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms, and which includes one or more (e.g., 1, 2, 3, or 4) heteroatoms (e.g., oxygen, nitrogen, or sulfur) which can be the same or different. ​

[0081] The term "alkoxy" refers to a group having the structure "alkyl-O-," wherein alkyl is defined above. For example, methoxy, ethoxy, n-propyloxy, isopropyloxy, n-butyloxy, isobutyloxy, t-butyloxy, pentyloxy, hexyloxy, and the like. Alkoxy groups in the present application are optionally substituted with one or more substituents described herein. 1-6 alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl, heteroaryl, heterocyclyl, alkoxy, C 1-4 alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl, heteroaryl, heterocyclyl, alkoxy, C 1-3 alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl, heteroaryl, heterocyclyl, alkoxy, C 1-2 alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl, heteroaryl, heterocyclyl, alkoxy, C

[0082] The term "halo" or "halogen" is defined to include F, CI, Br, or I.

[0083] The term "substituted" means that one or more hydrogens, for example 1, 2, 3, 4, or 5, on the designated compound or structural fragment are replaced with a substituent, provided that the designated atom's normal valence is not exceeded, and that the substitution results in a stable compound. Combinations of substituents and / or variables are permissible only if such combinations result in stable compounds.

[0084] As used herein, the term "one or more" means 1 or more than 1, for example 2, 3, 4, 5, or 10, under reasonable conditions.

[0085] The term "independently" means that the range of values for at least two groups (or ring systems) in a structure that are the same or similar can have the same or different meanings under the particular circumstances. For example, substituent X and substituent Y are each independently hydrogen, halogen, hydroxyl, cyano, alkyl, or aryl, then when substituent X is hydrogen, substituent Y can be either hydrogen or halogen, hydroxyl, cyano, alkyl, or aryl; similarly, when substituent Y is hydrogen, substituent X can be either hydrogen or halogen, hydroxyl, cyano, alkyl, or aryl.

[0086] Unless otherwise indicated, as used herein, the point of attachment of a substituent can be from any suitable position on the substituent, unless otherwise indicated.

[0087] As described in the background, the lithium iron manganese phosphate as a positive electrode with higher voltage can promote the dehydrogenation of the solvent at high temperature, and the hydrogen of the removed proton can further induce the decomposition of the lithium salt containing fluorine, and then form HF. On the one hand, HF can attack the SEI film on the negative side during the cycle storage process, so that part of the components of the SEI are dissolved into the electrolyte again, causing the SEI to be loose and porous. On the other hand, HF can increase the manganese dissolution of the positive electrode, and the dissolved manganese is reduced at the negative electrode, which destroys the stability of the SEI. The instability of the SEI can cause the electrolyte to directly contact the negative electrode, thereby causing the electrolyte to decompose and increasing the consumption of active lithium, thereby deteriorating the cycle storage life of the battery. In order to solve this problem, the application provides a secondary battery and a power device.

[0088] [Secondary battery]

[0089] The secondary battery is also called a rechargeable battery or a storage battery, which refers to a battery that can continue to be used by activating the active material through charging after the battery is discharged.

[0090] Generally, the secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte. During the charging and discharging process of the battery, active ions (such as lithium ions) are inserted and removed between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the short circuit of the positive and negative electrodes, and can also allow the active ions to pass through. The electrolyte is between the positive electrode sheet and the negative electrode sheet, mainly to conduct the active ions.

[0091] The first embodiment of the application provides a secondary battery, which comprises a positive electrode sheet, a negative electrode sheet and a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises an additive; the additive comprises a first additive, and the first additive is a cyclic organic base additive; the positive electrode sheet comprises a positive electrode active material, and the positive electrode active material comprises an inner core and a carbon coating layer, the inner core is lithium iron manganese phosphate, and the carbon coating layer covers at least part of the surface of the inner core.

[0092] Because the BET of the lithium iron manganese phosphate positive electrode material is significantly larger than that of the lithium iron phosphate, and the use voltage is higher than that of the lithium iron phosphate, the electrolyte is more likely to be oxidized and decomposed to generate acidic substances in the battery. The by-products can increase the manganese dissolution of the positive electrode on the one hand, and can also damage the SEI film at the negative electrode on the other hand, so that the reaction between the negative electrode and the electrolyte is intensified, causing the capacity attenuation during the cycle storage process. In order to improve this problem, an electrolyte containing an alkaline additive is used in the battery, the alkaline additive is used to capture the protons in the electrolyte, reduce the acidity of the electrolyte, and reduce the dissolution of transition metals. At the same time, the alkaline additive can reduce the damage of the protons to the negative electrode, thereby prolonging the life of the battery.

[0093] The cyclic organic base additive useful in the present application can be an aromatic ring organic base or a non-aromatic ring organic base (e.g., a saturated or unsaturated non-aromatic ring organic base). Exemplary aromatic ring organic bases can be found in compounds represented by general formula (II), (III), or (IV). Exemplary saturated non-aromatic ring organic bases can be found in compounds represented by general formula (VI). Exemplary unsaturated non-aromatic ring organic bases can be found in compounds represented by general formula (V) or (V’).

[0094] In some embodiments, the cyclic organic base is a monocyclic or fused bicyclic ring containing 5-12 (e.g., 5, 6, 7, 8, 9, 10, 11, or 12) ring atoms. In some embodiments, the cyclic organic base is a nitrogen-containing heteroaromatic monocyclic ring, a nitrogen-containing saturated monocyclic heterocycle, or a nitrogen-containing unsaturated monocyclic heterocycle containing 5, 6, 7, or 8 ring atoms. In some embodiments, the cyclic organic base is a nitrogen-containing heteroaromatic fused bicyclic ring, a nitrogen-containing saturated fused heterocycle, or a nitrogen-containing unsaturated fused heterocycle containing 7, 8, 9, 10, 11, or 12 ring atoms.

[0095] The present application employs a cyclic organic base as an electrolyte additive. Compared with non-cyclic organic bases, the alkyl group of the heteroatom on the cyclic organic base has a smaller bond angle due to the effect of the ring, fully exposing the lone pair of electrons on the heteroatom, so the heteroatom generally has stronger nucleophilic ability and stronger ability to capture free protons in the electrolyte, reducing the damage of SEI to the negative electrode.

[0096] In some embodiments, the cyclic organic base additive includes any one or more of compound 1 represented by general formula (III), compound 2 represented by general formula (IV), compound 3 represented by general formula (IV), compound 4 represented by general formula (V) or (V’), and compound 5 represented by general formula (VI),

[0097] In general formula (III), Y 1 , Y 2 are the same or different, Y 1 , Y 2 are each independently selected from CH, N; R 11 , R 12 , R 13 are each independently selected from the following groups: H, C1-C6 alkyl, C2-C6 alkenyl (e.g., allyl (H2C=CH-CH2-)), C2-C6 alkynyl (e.g., propargyl (-CH2C≡CH)), halogen (e.g., F, Cl, Br, or I), -R 14 OH, -R 15 NR 16 R 17 , -R 18 -O-R 19 , C3-C5 cycloalkyl, wherein R14 R 15 R 18 Each is independently selected from: non-existent, C1-C6 alkylene, C2-C6 alkenyl, R 16 R 17 R 19 Each is independently selected from hydrogen, halogen, C1-C6 alkyl, and C1-C6 haloalkyl, and is R 16 R 17 R 19 Any carbon atom in the C1-C6 alkyl group may optionally be substituted by one or more heteroatoms, said heteroatoms being N, S, or P atoms; optionally, R 16 R 17 Together with the nitrogen atoms attached to both, they form a 5-6 member nitrogen-containing heterocycle;

[0098] In general formula (II), W 1 and W 2 Same or different, W 1 Selected from C, N, O, S, W 2 Selected from C, N, and W 1 and W 2 At least one of them is N; R 21 R 22 R 23 R 24 Each group is independently selected from the following groups: H, C1-C6 alkyl, C2-C6 alkenyl (e.g., allyl (H2C=CH-CH2-)), C2-C6 alkynyl (e.g., propargyl (-CH2C≡CH)), halogen (e.g., F, Cl, Br or I), -R 25 OH, -R 26 NR 27 R 28 -R 29 -OR 30 C3-C5 cycloalkyl, wherein R 25 R 26 R 29 Each is independently selected from: non-existent, C1-C6 alkylene, C2-C6 alkenyl, R 27 R 28 R 30 Each is independently selected from hydrogen atoms, halogen atoms, C1-C6 alkyl groups, and C1-C6 haloalkyl groups;

[0099] In general formula (IV), A 1 A 2 A 3 A 4 A 5 A6 , A 7 may be the same or different, each independently C or N, and A 1 , A 2 , A 3 , A 4 and at least one (e.g. 1, 2, 3 or 4) of A 5 , R 31 , R 32 , R 33 , R 34 , R 35 , R 36 , R 37 each independently is selected from the group consisting of H, C1-C6 alkyl, C2-C6 alkenyl (e.g. allyl (H2C=CH-CH2-)), C2-C6 alkynyl (e.g. propargyl (-CH2CºCH)), halogen (e.g. F, CI, Br or I), -OH, -R 38 NR 39 R 40 , C1-C6 alkoxy, C3-C5 cycloalkyl, wherein R 38 is absent or selected from C1-C6 alkylene, C2-C6 alkenylene, R 39 , R 40 each independently is selected from the group consisting of a hydrogen atom, a halogen atom, C1-C6 alkyl, C1-C6 haloalkyl;

[0100] In general formula (V), X 1 , X 2 , X 3 each independently is C or N, and at least one of X 1 , X 2 , X 3 is N, in general formula (V’), X 1 , X 3 each independently is C or N, and at least one of X 1 , X 3 is N,

[0101] In general formula (V) and (V’), a, b each independently is selected from 0, 1, 2, 3, c is selected from 1, 2, 3, 4, 5, 6, 7, 8, each R 41 each independently is selected from the group consisting of H, C1-C6 alkyl, C2-C6 alkenyl (e.g. allyl (H2C=CH-CH2-)), C2-C6 alkynyl (e.g. propargyl (-CH2CºCH)), halogen (e.g. F, CI, Br or I), -R 42 OH, -R 43 NR 44 R 45 , -R46 -O-R 47 C3-C5 cycloalkyl, wherein R 42 R 43 R 46 each independently is selected from the group consisting of: nothing, C1-C6 alkylene, C2-C6 alkenylene, R 44 R 45 R 47 each independently is selected from the group consisting of hydrogen, halogen, C1-C6 alkyl, C1-C6 haloalkyl;

[0102] In general formula (VI), V 1 V 2 V 3 each independently is C or N, and at least one of V 1 V 2 V 3 is N, d is selected from 0, 1, 2, 3, e is selected from 1, 2, 3, 4, 5, 6, and each R 51 each independently is selected from the group consisting of H, C1-C6 alkyl, C2-C6 alkenyl (e.g., allyl (H2C=CH-CH2-)), C2-C6 alkynyl (e.g., propargyl (-CH2CºCH)), halogen (e.g., F, Cl, Br, or I), -R 52 OH, -R 53 N R 54 R 55 , -R 56 -O-R 57 C3-C5 cycloalkyl, wherein R 52 R 53 R 56 each independently is selected from the group consisting of: nothing, C1-C6 alkylene, C2-C6 alkenylene, R 54 R 55 R 57 each independently is selected from the group consisting of hydrogen atom, halogen atom, C1-C6 alkyl, C1-C6 haloalkyl.

[0103] In some embodiments, in general formula (II), Y 1 Y 2 are both N, or, one of Y 1 Y 2 is N and the other is CH.

[0104] In some embodiments, in general formula (II), the R 11 R 12 R 13 each independently is selected from the group consisting of hydrogen, halogen, C1-C4 alkyl, C3-C5 alkenyl, C3-C5 alkynyl, -R 14 OH, -R15 N R 16 R 17 , -R 18 -O-R 19 , -O-R 14 , -O-R 15 , -O-R 18 each independently is selected from the group consisting of absent, C1-C3 alkylene, R 16 , R 17 , R 19 each independently is selected from the group consisting of hydrogen, halogen, C1-C3 alkyl, C1-C3 haloalkyl, and as said R 16 , R 17 , R 19 any carbon atom in said C1-C3 alkyl group of R 16 , R 17 and the nitrogen atom to which both are attached together form a 5-6 membered nitrogen containing heterocyclic ring.

[0105] In some embodiments, in general formula (II), each R 11 , R 12 , R 13 is independently selected from the group consisting of hydrogen, halogen, methyl, ethyl, n-propyl, i-propyl, t-butyl, allyl, propargyl, -OH, -CH2OH, -NH2, -CH2NH2, -N(CH3)2, -O-CH3, In some embodiments, each R 11 , R 12 , R 13 is independently selected from the group consisting of hydrogen, fluorine, methyl, t-butyl, -CH2OH, -CH2NH2, -N(CH3)2, -O-CH3, any one of the group consisting of:

[0106] In some embodiments, the compound having the structure according to general formula (II) is selected from any one or more of the following compounds:

[0107] In some embodiments, in general formula (III), W 1 and W 2 are both N, or one of W 1 , W 2 is N and the other is CH.

[0108] In some embodiments, in general formula (III), each R 21 , R 22 , R 23 , R 24each independently selected from the group consisting of hydrogen, halogen, C1-C4alkyl, C3-C5alkenyl, C3-C5alkynyl, -R 25 OH, -R 26 NR 27 R 28 , -R 29 -O-R 30 , C3-C5cycloalkyl, wherein R 25 , R 26 , R 29 each independently selected from the group consisting of nothing, C1-C4alkylene, R 27 , R 28 , R 30 each independently selected from the group consisting of hydrogen, halogen, C1-C4alkyl, C1-C4haloalkyl.

[0109] In some embodiments, in general formula (III), the R 21 , R 22 , R 23 , R 24 each independently selected from the group consisting of hydrogen, fluorine, methyl, ethyl, propyl, cyclopropyl, allyl, propargyl, -OH, -CH3OH, -NH2, -NHCH3, -CH2NH2, -N(CH3)2, -O-CH3. In some embodiments, the R 21 , R 22 , R 23 , R 24 each independently selected from the group consisting of hydrogen, fluorine, methyl, cyclopropyl, allyl, -CH3OH, -NHCH3.

[0110] In some embodiments, the compound having a structure according to general formula (III) is selected from any one or more of the following compounds:

[0111] In some embodiments, in general formula (IV), A 1 is N, A 2 , A 3 , A 4 , A 5 , A 6 , A 7 each independently is C or N. In some embodiments, A 1 is N, and A 5 is C.

[0112] In some embodiments, in general formula (IV), the R 31 , R 32 , R 33 , R 34 , R 35 , R 36 , R37 each independently selected from the group consisting of hydrogen, C1-C4alkyl, C2-C4alkenyl, C2-C4alkynyl, -OH, -R 38 NR 39 R 40 , C1-C4alkoxy, R 38 is absent or selected from C1-C3alkylene, R 39 , R 40 each independently selected from the group consisting of hydrogen, halogen, C1-C3alkyl, C1-C3haloalkyl. In some embodiments, R 31 , R 32 , R 33 , R 34 , R 35 , R 36 , R 37 each independently selected from the group consisting of hydrogen, methyl, ethyl, allyl, propargyl, -OH, -NH2, -CH2NH2, -N(CH3)2, -O-CH3. In some embodiments, R 31 , R 32 , R 33 , R 34 , R 35 , R 36 , R 37 each independently selected from the group consisting of hydrogen, methyl, -O-CH3.

[0113] In some embodiments, in general formula (IV), R 32 , R 33 , R 34 , R 35 , R 36 , R 37 are all hydrogen. In some embodiments, R 31 is selected from the group consisting of hydrogen, methyl, ethyl, allyl, propargyl, -OH, -NH2, -CH2NH2, -N(CH3)2, -O-CH3. In some embodiments, R 31 is selected from the group consisting of hydrogen, methyl, -O-CH3.

[0114] In some embodiments, the compound having the structure according to general formula (IV) is selected from any one or more of the following compounds:

[0115] In some embodiments, in general formula (V), X 1 is N, X 2 , X 3 each independently is C or N. In some embodiments, X 2 is N. In some embodiments, X 3 is C. In some embodiments, X 1, X 3 are each N.

[0116] In some embodiments, in general formula (V), a, b, c are each independently 1, 2, or 3. In some embodiments, a is 2. In some embodiments, b is 1, 2, or 3. In some embodiments, c is 1 or 2.

[0117] In some embodiments, in general formula (V’), a is 0 or 1, and c is 1 or 2.

[0118] In some embodiments, the general formula (V) is (V-1):

[0119] wherein a, b, X 1 , X 2 , X 3 are as defined above.

[0120] In some embodiments, the general formula (V’) is (V’-1):

[0121] wherein a, X 1 , X 3 are as defined above.

[0122] In some embodiments, in general formula (V), (V’), (V-1), or (V’-1), each R 41 is each independently selected from hydrogen, halogen, C1-C4 alkyl, C3-C5 alkenyl, C3-C5 alkynyl, -R 42 OH, -R 43 NR 44 R 45 , -R 46 -O-R 47 , R 42 , R 43 , R 46 is each independently selected from: nothing, C1-C3 alkylene, R 44 , R 45 , R 47 is each independently selected from hydrogen, halogen, C1-C4 alkyl, C1-C4 haloalkyl. In some embodiments, each R 41 is each independently selected from hydrogen, fluorine, methyl, ethyl, hydroxyl, -NH2, -N(CH3)2. In some embodiments, each R 41 is each independently selected from hydrogen, methyl, -N(CH3)2.

[0123] In some embodiments, the compound having the structure of general formula (V) is selected from any one or more of the following compounds:

[0124] In some embodiments, in general formula (VI), d is 0 or 1.

[0125] In some embodiments, in general formula (VI), each R 51 each independently selected from hydrogen, halogen, C1-C4 alkyl, C3-C5 alkenyl, C3-C5 alkynyl, -R 52 OH, -R 53 NR 54 R 55 , -R 56 -O-R 57 , R 52 , R 53 , R 56 each independently selected from: nothing, C1-C3 alkylene, R 54 , R 55 , R 57 each independently selected from hydrogen, halogen, C1-C4 alkyl, C1-C4 haloalkyl. In some embodiments, each R 51 each independently selected from hydrogen, fluorine, methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, hydroxyl, -NH2, -N(CH3)2. In some embodiments, each R 51 each independently selected from hydrogen, fluorine, methyl, ethyl, isopropyl, t-butyl.

[0126] In some embodiments, the compound having the structure represented by general formula (VI) is selected from any one or more of the following compounds:

[0127] In some embodiments, the mass proportion of the first additive in the non-aqueous electrolyte is W1, W1 satisfies 0.001%≤W1≤20%. In some embodiments, W1 satisfies 0.1%≤W1≤2%. W1 within the above range is conducive to reducing the gas production while ensuring the fast charging performance, and improving the cycle performance and storage performance of the battery.

[0128] In some embodiments, W1 is 0.001%-0.05%, 0.05%-0.1%, 0.1%-0.5%, 0.5%-1%, 1%-2%, 2%-5%, 5%-12%, 12%-20%, or 20%-22%.

[0129] The non-aqueous solvent of the non-aqueous electrolyte of the secondary battery of the present application is not particularly limited and can be selected according to the actual needs. Optionally, the non-aqueous solvent includes any one or more of cyclic carbonates, chain carbonates, nitrile solvents, ketone solvents, and sulfone solvents; further optionally, the non-aqueous solvent includes one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl 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, butyrolactone, dimethyl sulfone, methyl ethyl sulfone, diethyl sulfone, tetrahydrofuran, glyme, dioxolane, acetone, acetonitrile, and butyronitrile. The above non-aqueous solvents can be used alone or in a mixture of two or more, such as a mixture of cyclic carbonates and chain carbonates to improve the load characteristics and low-temperature characteristics of the secondary battery. When the non-aqueous electrolyte of the present application is applied to a solid-state battery, a solid solvent such as dimethyl sulfone can be used. In some embodiments, the organic solvent is a combination of ethylene carbonate (EC) and methyl ethyl carbonate (EMC).

[0130] In some embodiments, the non-aqueous electrolyte of the present application further optionally includes a second additive. As an example, the second additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain properties of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, and the like. In some embodiments, the second additive is selected from at least one of a cyclic carbonate compound containing an unsaturated bond, a halogen-substituted cyclic carbonate compound, a sulfate compound, a sulfite compound, a sulfonolactone compound, a disulfonic acid compound, a nitrile compound, an aromatic compound, an isocyanate compound, a phosphazene compound, a cyclic anhydride compound, a phosphite compound, a phosphate compound, a borate compound, and a carboxylate compound.

[0131] The non-aqueous electrolyte used in the present application also includes an electrolyte, and any electrolyte commonly used in non-aqueous electrolytes can be considered for application to the non-aqueous electrolyte of the present application. Those skilled in the art can select the electrolyte according to the battery system to which the non-aqueous electrolyte is applied, such as a conventional electrolyte suitable for a secondary battery. In some embodiments, the electrolyte includes an alkali metal salt electrolyte; optionally, the electrolyte includes a lithium salt; optionally, the lithium salt includes one or more selected from the group consisting of lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, and lithium bis-trifluoromethanesulfonimide. The above lithium salts can be used alone or in a mixture of two or more. In some embodiments, the lithium salt can be selected from LiN(C x F 2x+1 SO2)(Cy F 2y+1 SO2), LiPF6, LiBF4, LiBOB, LiAsF6, Li(FSO2)2N, LiCF3SO3, and LiClO4, wherein x, y are natural numbers, and optionally, m and n are each independently a natural number up to 9.

[0132] The content of the electrolyte in the non-aqueous electrolyte can refer to the content of the electrolyte in a conventional non-aqueous electrolyte. In some embodiments, the concentration of the lithium salt ranges from 0.2 M to 2.2 M, for example, from 0.2 M to 0.8 M, from 0.8 M to 1 M, from 1 M to 1.5 M, or from 1.5 M to 2 M.

[0133] [Positive electrode sheet]

[0134] The positive electrode sheet generally 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 including a positive electrode active material.

[0135] As an example, the positive electrode current collector has two surfaces opposite in the thickness direction thereof, and the positive electrode film layer is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0136] In the secondary battery of the present application, the positive electrode sheet contains a positive electrode active material, the positive electrode active material including: an inner core, the inner core being lithium iron manganese phosphate, and a carbon coating layer, the carbon coating layer covering at least part of the surface of the inner core.

[0137] In some embodiments, the lithium iron manganese phosphate has a chemical formula Li m A a Fe x Mn b D d P y E e O z G g , the A includes at least one element of Al, Na, K, or Mg; the D includes at least one element of Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, Ti, or V; the E includes at least one element of B, S, Si, or N; the G includes at least one element of S, F, Cl, or Br; the m is selected from the range of 0.95 to 1.15; the a is selected from the range of 0 to 0.1; the x is selected from the range of 0.1 to 1; the b is selected from the range of 0.1 to 0.9; the d is selected from the range of 0 to 0.1; the y is selected from the range of 0.95 to 1; the e is selected from the range of 0 to 0.1; the z is selected from the range of 3.5 to 4; and the g is selected from the range of 0 to 0.1.

[0138] The inner core of the present application includes Lim A a Fe x Mn b D d P y E e O z G g wherein the manganese site doping element D helps to reduce the lattice change rate of lithium manganese phosphate during the lithium deintercalation process, improve the structural stability of the positive electrode active material, greatly reduce the dissolution of manganese and reduce the oxygen activity on the particle surface; the phosphorus site doping element E also helps to change the difficulty of the Mn-O bond length change, thereby improving the electronic conductivity and reducing the lithium ion migration barrier, promoting lithium ion migration and improving the rate performance of the secondary battery. The size of m is affected by the valence state of A, D, E and G and the size of a, d, e and g to ensure that the entire system is electrically neutral. If the value of m is too small, it will reduce the lithium content of the entire core and affect the specific capacity of the positive electrode active material. The value of d will limit the total amount of all doping elements, and if d exceeds 0.1, it will result in less Mn and Fe content in the system, affecting the voltage platform of the positive electrode active material. The E element is doped at the P position, and since the P-O tetrahedron is relatively stable, a too large value of e will affect the stability of the positive electrode active material. Therefore, by doping specific elements in specific amounts at the Li site, Fe / Mn site, P site and / or O site of the compound, the dissolution of transition metals can be significantly reduced, and the cycle performance and high temperature stability can be significantly improved.

[0139] In some embodiments, A is a Mg element.

[0140] In some embodiments, D includes one or two elements of Co, Ni or V.

[0141] In some embodiments, G is a S element.

[0142] In some embodiments, m is selected from 0.95-0.997, 0.997-1, 1-1.001, 1.001-1.15.

[0143] In some embodiments, a is selected from 0-0.005, 0.005-0.01, 0.01-0.05, 0.05-0.1.

[0144] In some embodiments, x is selected from 0.1-0.2, 0.2-0.3, 0.3-0.4 (e.g. 0.395, 0.393), 0.4-0.5, 0.5-0.6, 0.6-0.7, 0.7-0.8, 0.8-0.9, 0.9-1.

[0145] In some embodiments, b is selected from 0.1-0.2, 0.2-0.3, 0.3-0.4 (e.g., 0.395, 0.393), 0.4-0.5, 0.5-0.6, 0.6-0.7, 0.7-0.8, 0.8-0.9.

[0146] In some embodiments, d is selected from 0-0.002, 0.002-0.003, 0.003-0.004, 0.004-0.005, 0.005-0.006, 0.006-0.007, 0.007-0.008, 0.008-0.009, 0.009-0.01, 0.01-0.05, 0.05-0.1.

[0147] In some embodiments, y is selected from 0.95-0.997, 0.997-0.999, 0.999-1.

[0148] In some embodiments, e is selected from 0-0.001, 0.001-0.002, 0.002-0.003, 0.003-0.004, 0.004-0.005, 0.005-0.006, 0.006-0.007, 0.007-0.008, 0.008-0.009, 0.009-0.01, 0.01-0.05, 0.05-0.1.

[0149] In some embodiments, a, d, e, g are all 0, and the lithium manganese iron phosphate has the chemical formula Li m Fe x Mn b P y O z wherein m, x, b, y, z are as defined above. In some embodiments, the lithium manganese iron phosphate has a chemical formula selected from the group consisting of: LiMn 0.5 Fe 0.5 PO4, LiMn 0.6 Fe 0.4 PO4, LiMn 0.7 Fe 0.3 PO4, LiMn 0.8 Fe 0.2 PO4.

[0150] In some embodiments, d, e, g are all 0, and the lithium manganese iron phosphate has the chemical formula Li m A a Fe x Mn b PO z wherein A, a, m, x, b, y, z are as defined above. In some embodiments, A is Mg. In some embodiments, the lithium manganese iron phosphate has a chemical formula selected from the group consisting of: LiMn0.60 Fe 0.395 Mg 0.005 PO4.

[0151] In some embodiments, a, e, g are all 0, and the lithium iron manganese phosphate has a chemical formula of Li m Fe x Mn b D d P y O z wherein m, x, b, D, d, y, z are as defined above. In some embodiments, D is selected from one or more elements of V, Ni. In some embodiments, the lithium iron manganese phosphate has a chemical formula selected from: Li 0.60 Fe 0.395 V 0.002 Ni 0.003 PO4.

[0152] In some embodiments, a, g are all 0, and the lithium iron manganese phosphate has a chemical formula of Li m Fe x Mn b D d P y E e O z wherein m, x, b, D, d, E, e, y, z are as defined above. In some embodiments, D is selected from one or more elements of V, Co. In some embodiments, E is selected from one or more elements of S, Si. In some embodiments, the lithium iron manganese phosphate has a chemical formula selected from: Li 0.997 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.997 S 0.003 O4, Li 1.001 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.999 Si 0.001 O4.

[0153] Compared with lithium iron phosphate, the high voltage characteristics of manganese make the lithium iron manganese phosphate have a higher voltage platform, which also leads to a higher energy density at the same specific capacity. Under the same conditions, the energy density is 10-20% higher than that of lithium iron phosphate, but the disadvantage is that the introduction of manganese significantly reduces the electrical conductivity of the material. Carbon coating can effectively improve the electrical conductivity of the lithium iron manganese phosphate material.

[0154] In some embodiments, the thickness of the carbon coating layer of the positive electrode material is 0.5 nm to 10 nm; optionally, the thickness of the carbon coating layer is 4 nm to 8 nm. Transition metals in the positive electrode active material will be dissolved into the electrolyte with structural deterioration during the cycle process, and the transition metals will be reduced into elements after migrating to the negative electrode, which will destroy the SEI and cause the SEI to thicken, and then increase the lithium consumption and increase the impedance, and deteriorate the cycle storage life. By controlling the formation of a thin carbon coating layer on the surface of the core, on the one hand, the conductivity of the positive electrode active material can be improved, and on the other hand, the structural deterioration of the positive electrode material during use can be improved, the manganese dissolution is reduced, the damage to the SEI after the transition metal migrates to the negative electrode is reduced, and thus the capacity attenuation during the cycle storage process is reduced. When the thickness of the carbon coating layer is greater than 10 nm, it is easier to form a carbon coating layer containing larger pores, which can increase the possibility of water absorption and storage of the carbon coating layer. The water stored in the carbon layer can cause the electrolyte to decompose at high temperatures, thereby deteriorating the cycle storage performance. In addition, a too thick carbon coating layer will affect the extraction and embedding of lithium ions in the core, which will significantly reduce the gram capacity of the positive electrode active material, and is not conducive to the further application of the material. When the thickness of the carbon coating layer is too small, the improvement in structural stability may not be great. Therefore, when the carbon coating layer is in the above range, the cycle performance and high-temperature stability can be significantly improved.

[0155] In some embodiments, the thickness of the carbon coating layer is 0.5 nm to 1 nm, 1 nm to 4 nm, 4 nm to 8 nm, 8 nm to 9 nm, 9 nm to 10 nm, 10 nm to 15 nm. The thickness of the carbon coating layer can be tested by the following method: a thin slice with a thickness of about 100 nm is cut from the middle of a single particle of the positive electrode active material by FIB, and then the thin slice is subjected to TEM testing to obtain a TEM test original picture, and the original picture format (xx.dm3) is saved. The above TEM test original picture is opened in Digital Micrograph software, and the carbon coating layer is identified by lattice spacing and angle information, and the thickness of the carbon coating layer is measured. The thickness at three positions of the selected particle is measured, and the average value is taken.

[0156] The carbon-coated lithium manganese iron phosphate used in the present application can be prepared by a method comprising the following steps: providing a core; forming a carbon coating layer on at least part of the surface of the core. In this way, the aforementioned carbon-coated lithium manganese iron phosphate can be obtained by a relatively simple method.

[0157] In some embodiments, forming the carbon coating layer on at least part of the surface of the core includes: forming a pre-carbon coating layer on the surface of the core by a carbon source to obtain a pre-coated positive electrode active material, and performing a sintering treatment on the pre-coated positive electrode active material in an inert gas atmosphere to form the carbon coating layer, so as to obtain the positive electrode active material, wherein the carbon source includes a first carbon source and a second carbon source. In this way, the carbon coating layer with higher graphitization degree can be formed on the surface of the core.

[0158] In some embodiments, forming the carbon coating layer on at least part of the surface of the core includes: mixing the core with a first carbon source, and obtaining a first coated positive electrode active material by a first sintering treatment, mixing the first coated positive electrode active material with a second carbon source, and obtaining the positive electrode active material by a second sintering treatment. In this way, the carbon coating layer with higher graphitization degree can be formed on the surface of the core.

[0159] In some embodiments, when the first carbon source is a polymer, the molecular weight of the first carbon source is not less than 1000, and preferably, the molecular weight of the first carbon source is 2000-5000. In some embodiments, the temperature of the sintering treatment is 650-800°C, and the time of the sintering treatment is 6-12h. In some embodiments, the temperature of the first sintering treatment is 350-800°C, and the time of the first sintering treatment is 6-12h. In some embodiments, the temperature of the second sintering treatment is 650-850°C, and the time of the second sintering treatment is 6-24h. In this way, the carbon coating layer with higher graphitization degree can be formed on the surface of the core.

[0160] In any embodiment, the synthesis method of the core material is not specifically limited. The core material can be prepared by a method for preparing lithium iron manganese phosphate in the prior art, including but not limited to spray drying method, high temperature solid phase method, coprecipitation method, sol-gel method, hydrothermal / solvothermal method, etc.

[0161] In any embodiment, the thickness of the carbon layer is mainly controlled by the change of carbon content. When the coating conditions are certain, the effect of carbon layer coating can be adjusted by controlling the proportion of the carbon source. In addition, the coating thickness is affected by the type of carbon source, the coating effect, the sintering temperature, etc., and the specific method is not specifically limited in the present application.

[0162] The source of element D can be selected from at least one of elemental D, oxide, phosphate, oxalate, carbonate and sulfate of element D. The source of manganese can be a manganese-containing substance known in the art that can be used to prepare lithium manganese phosphate, for example the source of manganese can be selected from one or a combination of elemental manganese, manganese dioxide, manganese phosphate, manganese oxalate, manganese carbonate. The source of iron can be selected from at least one of elemental iron, oxide, phosphate, oxalate, carbonate and sulfate of iron. The acid can be selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, organic acid such as oxalic acid and the like, for example can be oxalic acid. The source of element E can be selected from at least one of sulfate, borate, nitrate and silicate of element E, and the source of element G can be selected from at least one of elemental G and ammonium salt of element G.

[0163] The preparation method of compound Li 0.997 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.997 S 0.003 The preparation method of compound Li

[0164] Step S1 : 689.6 g of manganese carbonate, 455.27 g of ferrous carbonate, 4.65 g of cobalt sulfate, and 4.87 g of vanadium dichloride were added into a mixer and mixed for 6 h. Then the obtained mixture was transferred into a reaction kettle, 5 L of deionized water and 1260.6 g of oxalic acid dihydrate were added, heated to 80 °C, and stirred at a speed of 500 rpm for 6 h until the reaction was complete and no bubbles were generated, to obtain a manganese oxalate suspension co-doped with Fe, Co, and V. Then the suspension was filtered, dried at 120 °C, and subjected to sand milling to obtain Fe, Co, V and S co-doped manganese oxalate particles with a particle size of 100 nm.

[0165] Step S2: 1793.1 g of the manganese oxalate prepared in step S1, 368.3 g of lithium carbonate, 1146.6 g of ammonium dihydrogen phosphate, and 4.9 g of dilute sulfuric acid were added into 20 L of deionized water and stirred well, and then uniformly mixed and reacted at 80 °C for 10 h to obtain a slurry. The slurry was transferred into a spray drying device for spray drying and granulation to obtain a powder. The powder was sintered in a roller kiln at 700 °C for 4 h in a protective atmosphere (90% nitrogen and 10% hydrogen) to obtain the inner core Li 0.997 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.997 S 0.003 O4.

[0166] Step S3: PEG-1000 is selected as the first carbon source, 58.2 g of PEG-1000 is dissolved in 500 g of deionized water, and then stirred and fully dissolved to obtain an aqueous solution. 1571.9 g of the above-mentioned core material is added to the solution, and stirred and mixed together for 6 h until uniformly mixed, and then subjected to first sintering treatment, the first sintering treatment temperature is 600°C, the first sintering treatment time is 9 h, so as to obtain the first coated positive electrode active material through the first sintering treatment;

[0167] Step S4: glucose is selected as the second carbon source, 37.3 g of glucose is dissolved in 500 g of deionized water, and then stirred and fully dissolved to obtain a glucose aqueous solution. 1603.3 g of the first coated positive electrode active material obtained in step S3 is added to the above-mentioned glucose solution, and stirred and mixed together for 6 h until uniformly mixed, and then subjected to second sintering treatment, the second sintering treatment temperature is 750°C, the second sintering treatment time is 20 h, so as to obtain the positive electrode active material through the second sintering treatment.

[0168] In some embodiments, the positive electrode sheet of the secondary battery of the present application further comprises other kinds of positive electrode active materials, which can optionally include at least one of the following materials: lithium-containing phosphate with olivine structure, lithium transition metal oxide and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials can also be used. These positive electrode active materials can be used alone or in combination with two or more kinds. Among them, examples of lithium transition metal oxides can include but are not limited to lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2(also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2(also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2(also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1O2(also can be referred to as NCM 811 LiNi 0.85 Co 0.15 Al 0.05 O2) and modified compounds thereof. Examples of the olivine-structured lithium-containing phosphate can include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4(also can be referred to as LFP)), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite of lithium manganese iron phosphate and carbon.

[0169] The battery will be accompanied by Li de-intercalation and consumption during charging and discharging, and the molar content of Li is different when the battery is discharged to different states. In the enumeration of the positive electrode material in the present application, the molar content of Li is the initial state of the material, i.e. the state before feeding, and the positive electrode material is applied to the battery system. After charging and discharging cycle, the molar content of Li will change.

[0170] In the enumeration of the positive electrode material in the present application, the molar content of O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will appear to float.

[0171] When the secondary battery is a sodium-ion secondary battery, as an example, the positive active material of the sodium-ion secondary battery can include at least one of the following materials: at least one of sodium transition metal oxide, polyanion compound and Prussian blue compound. However, the present application is not limited to these materials, and other conventional and well-known materials that can be used as positive active materials for sodium-ion batteries can also be used.

[0172] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. The sodium transition metal oxide is, for example, Na x MO2, wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0

[0173] As an optional technical solution of the present application, the polyanion compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- anion units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y can be at least one of P, S and Si; and n represents the valence state of (YO4) n- .

[0174] The polyanion compound can also be a compound having sodium ions, transition metal ions, tetrahedral (YO4)n- Anionic units and halogen anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, n represents the valence of (YO4) n- ; and the halogen can be at least one of F, Cl, and Br.

[0175] The polyanionic compound can also be a compound having sodium ions, tetrahedral (YO4) n- anionic units, polyhedral (ZO y ) m+ ; and optional halogen anions. Y can be at least one of P, S, and Si, n represents the valence of (YO4) n- ; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, m represents the valence of (ZO y ) m+ ; and the halogen can be at least one of F, Cl, and Br.

[0176] The polyanionic compound can be at least one of NaFeP04, Na3V2(P04)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(P04)2(P207), NaM’P04F (M’ is one or more of V, Fe, Mn, and Ni), and Na3(VO y )2(P04)2F 3-2y (0≤y≤1).

[0177] The Prussian blue compound can be a compound having sodium ions, transition metal ions, and cyanide ions (CN ). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The Prussian blue compound can be, for example, Na a Me b Me’ c (CN)6, where Me and Me’ are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0 < a < 2, 0 < b < 1, and 0 < c < 1.

[0178] In some embodiments, the positive electrode film layer can also optionally include a binder. As an example, the binder can include at least one 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.

[0179] In some embodiments, the positive electrode film layer can also optionally include a conductive agent. As an example, the conductive agent can include at least one of super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0180] In some embodiments, the positive electrode current collector can employ a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be employed. The composite current collector can 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 can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0181] In some embodiments, the positive electrode tab can be prepared by dispersing the above-described components for preparing the positive electrode tab, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and subjecting to a drying, cold-pressing, or the like process to obtain the positive electrode tab.

[0182] [Negative electrode tab]

[0183] The negative electrode tab includes a negative electrode current collector and a negative electrode active material coating layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material coating layer including a negative electrode active material.

[0184] As an example, the negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode film layer is disposed on either one or both of the two opposite surfaces of the negative electrode current collector.

[0185] In some embodiments, the negative electrode current collector can employ a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0186] In some embodiments, the negative active material can employ a negative active material for a battery known in the art. As an example, the negative active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, mesocarbon microbeads, carbon fiber, carbon nanotube, silicon-based material, tin-based material, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can be selected from at least one of elemental tin, tin oxide compound, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative active material for a battery can also be used. These negative active materials can be used alone or in combination of two or more.

[0187] In some embodiments, the negative active material coating layer can further optionally include a binder. As an example, the binder can be selected from at least one 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).

[0188] In some embodiments, the negative active material coating layer can further optionally include a conductive agent. As an example, the conductive agent can be selected from at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dot, carbon nanotube, graphene, and carbon nanofiber.

[0189] In some embodiments, the negative active material coating layer can further optionally include other auxiliary agents, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na)), etc.

[0190] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-described components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry, coating the negative electrode slurry on a negative electrode current collector, and then drying, cold-pressing, etc.

[0191] [Separator]

[0192] In some embodiments, the secondary battery further includes a separator. The type of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0193] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0194] In some embodiments, the positive electrode tab, the negative electrode tab, and the separator film can be made into an electrode assembly through a winding process or a stacking process.

[0195] In some embodiments, the secondary battery includes a secondary battery cell, or includes a battery module and a battery pack.

[0196] In some embodiments, the secondary battery can include an outer package. The outer package can be used to package the electrode assembly and the electrolyte described above.

[0197] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, and polybutylene succinate, etc. can be listed.

[0198] The shape of the secondary battery cell is not particularly limited in the present application, and it can be cylindrical, square, or any other shape. For example, FIG. 1 is a secondary battery cell 5 of a square structure as an example.

[0199] In some embodiments, referring to FIG. 2, the outer package can include a shell 51 and a top cover assembly 53. The shell 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can be provided on the opening to close the receiving cavity. The positive electrode tab, the negative electrode tab, and the separator film can be made into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the secondary battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific actual needs.

[0200] In some embodiments, the secondary battery cell can be assembled into a battery module, and the number of secondary battery cells contained in the battery module can be one or more, which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0201] FIG. 3 is a battery module 4 as an example. Referring to FIG. 3, in the battery module 4, a plurality of secondary battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be made. Further, the plurality of secondary battery cells 5 can be fixed by fasteners.

[0202] Optionally, the battery module 4 can also include a housing having a receiving space, and the plurality of secondary battery cells 5 are received in the receiving space.

[0203] In some embodiments, the above battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0204] Figs. 4 and 5 are a battery pack 1 as an example. Referring to Figs. 4 and 5, a battery case and a plurality of battery modules 4 disposed in the battery case can be included in the battery pack 1. The battery case includes an upper case 2 and a lower case 3, and the upper case 2 can be disposed on the lower case 3 and form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery case in any manner.

[0205] In addition, the application also provides a power utilization device, which comprises the secondary battery provided by the application. The secondary battery can be used as a power supply of the power utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device (such as a mobile phone, a notebook 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 and a satellite, an energy storage system, etc., but is not limited thereto.

[0206] As the power utilization device, the secondary battery monomer, the battery module or the battery pack can be selected according to the use requirement thereof.

[0207] Fig. 6 is a power utilization device as an example. The power utilization device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the secondary battery for the power utilization device, the battery pack or the battery module can be used.

[0208] [Embodiment]

[0209] Hereinafter, the embodiments of the application will be described. The embodiments described below are exemplary and are only used to explain the application, and cannot be understood as a limitation of the application. If the specific technology or condition is not indicated in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. If the reagent or instrument used is not indicated by the manufacturer, it is a conventional product that can be obtained by market purchase.

[0210] Preparation of positive active material

[0211] For example, the preparation method of compound Li 0.997 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.997 S 0.003 The preparation method of compound Li

[0212] Step S1 : 689.6 g of manganese carbonate, 455.27 g of ferrous carbonate, 4.65 g of cobalt sulfate, and 4.87 g of vanadium dichloride were added into a mixer and mixed for 6 h. Then the obtained mixture was transferred into a reactor, 5 L of deionized water and 1260.6 g of oxalic acid dihydrate were added, heated to 80 °C, and stirred at a speed of 500 rpm for 6 h until the reaction was completed and no bubbles were generated, to obtain a Fe, Co, and V co-doped manganese oxalate suspension. Then the suspension was filtered, dried at 120 °C, and sand-milled to obtain Fe, Co, V, and S co-doped manganese oxalate particles with a particle size of 100 nm.

[0213] Step S2: 1793.1 g of the manganese oxalate prepared in step S1, 368.3 g of lithium carbonate, 1146.6 g of ammonium dihydrogen phosphate, and 4.9 g of dilute sulfuric acid were added into 20 L of deionized water, stirred well, and uniformly mixed at 80 °C for 10 h to obtain a slurry. The slurry was transferred into a spray drying device for spray drying and granulation to obtain a powder. The powder was sintered in a roller kiln at 700 °C for 4 h in a protective atmosphere (90% nitrogen and 10% hydrogen) to obtain the inner core Li 0.997 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.997 S 0.003 O4.

[0214] Step S3: PEG-1000 was selected as the first carbon source, 58.2 g of PEG-1000 was dissolved in 500 g of deionized water, and then stirred and dissolved completely to obtain an aqueous solution. 1571.9 g of the inner core material was added into the solution, and stirred and mixed for 6 h until uniformly mixed. After spray drying, first sintering treatment was performed, the first sintering treatment temperature was 600 °C, and the first sintering treatment time was 9 h, so as to obtain the first coated positive electrode active material through the first sintering treatment.

[0215] Step S4: glucose was selected as the second carbon source, 37.3 g of glucose was dissolved in 500 g of deionized water, and then stirred and dissolved completely to obtain a glucose aqueous solution. 1603.3 g of the first coated positive electrode active material obtained in step S3 was added into the above glucose solution, and stirred and mixed for 6 h until uniformly mixed. After spray drying, second sintering treatment was performed, the second sintering treatment temperature was 750 °C, and the second sintering treatment time was 20 h, so as to obtain the positive electrode active material through the second sintering treatment.

[0216] The lithium ion batteries of the comparative examples and the examples were prepared according to the following method

[0217] (1) Preparation of the positive electrode sheet

[0218] LiMn 0.7 Fe 0.3 PO4, a binder polyvinylidene fluoride (PVDF), and a conductive agent acetylene black were dissolved in a solvent N-methyl pyrrolidone (NMP) at a mass ratio of 97:2:1, and after being fully stirred and mixed uniformly, a positive electrode slurry was obtained; then the positive electrode slurry was uniformly coated on a positive electrode current collector, and after drying, cold pressing, and slitting, a positive electrode sheet was obtained.

[0219] (2) Preparation of the negative electrode sheet

[0220] An active substance artificial graphite, a binder styrene-butadiene rubber (SBR), a thickening agent sodium carboxymethyl cellulose (CMC), and a conductive agent acetylene black were dissolved in a solvent deionized water at a mass ratio of 96.5:2:1:0.5, and after being uniformly mixed with the solvent deionized water, a negative electrode slurry was prepared; then the negative electrode slurry was uniformly coated on a negative electrode current collector copper foil, and after drying, a negative electrode film was obtained, and then the negative electrode film was subjected to cold pressing and slitting to obtain a negative electrode sheet.

[0221] (3) Preparation of the electrolyte

[0222] In an argon atmosphere glove box (H2O <0.1 ppm, O2 <0.1 ppm), 1 mol / L LiPF6 was dissolved in an organic solvent (EC / EMC = 3 / 7), and after being stirred uniformly, a corresponding electrolyte was obtained, as shown in Table 1.

[0223] (4) Preparation of the separator film: a conventional polypropylene film was used as the separator film.

[0224] (5) Preparation of the lithium ion battery

[0225] The positive electrode sheet, the separator film, and the negative electrode sheet were stacked in order, with the separator film between the positive electrode sheet and the negative electrode sheet to play a separating role, and then an electrode assembly was obtained by winding; the electrode assembly was placed in a battery shell, and after drying, an electrolyte was injected, and then the lithium ion battery was prepared by processes such as formation and standing.

[0226] Next, the test methods of the physical parameters and performance parameters mentioned in the embodiments of the present application are briefly introduced.

[0227] 1. Test method of the thickness of the carbon coating layer

[0228] A thin slice of about 100 nm thickness is cut from the middle of a single particle of the positive electrode active material by FIB, and then the slice is subjected to TEM testing to obtain a TEM test original picture, which is saved in an original picture format (xx.dm3). The original picture obtained by the above TEM testing is opened in Digital Micrograph software, and the carbon coating layer is identified by the lattice spacing and the included angle information, and the thickness of the carbon coating layer is measured. The thickness at three positions of the selected particle is measured, and the average value is taken.

[0229] 2. Test method for positive electrode doping

[0230] In the present application, the doping component of the positive electrode active material is determined by inductively coupled plasma (ICP) spectrometry, for example, reference can be made to the standards YS / T1006.2-2014, GB / T23367.2-2009 or YS / T1028.5-2015. Specifically, according to the embodiments of the present application, an inductively coupled plasma emission spectrometer can be used to measure according to the instructions of the corresponding equipment.

[0231] 3. 45°C cycle performance test

[0232] At 45°C, the lithium ion battery is charged at 1C constant current to 4.1V, then charged at 4.1V constant voltage to current ≤0.02C, and after standing for 2min, the lithium ion battery is discharged at 1C constant current to voltage 2.0V, which is one charge and discharge cycle process, and the discharge capacity of this time is the discharge capacity of the first cycle. The lithium ion battery is subjected to multiple cycle charge and discharge tests according to the above method until the discharge capacity of the lithium ion secondary battery decays to 80%, and the cycle number of the lithium ion battery is recorded.

[0233] The capacity retention rate (%) of the battery after 45°C cycle N times = (the discharge capacity of the battery in the Nth cycle / the discharge capacity of the battery in the first cycle) x 100%.

[0234] 4. 45°C storage performance test

[0235] At 45°C, the prepared lithium ion secondary battery is first charged to 4.1V at a constant current of 0.33C, then further charged to a current of 0.05C at a constant voltage of 4.1V, and then discharged to 2V at a constant current of 0.33C, and the discharge capacity C0 of this time is the discharge capacity before high temperature storage of the lithium ion secondary battery; then the lithium ion secondary battery is charged to 4.1V at a constant current of 0.33C, and charged to a current of 0.05C at a constant voltage of 4.1V, and the lithium ion battery is fully charged. The battery is placed in a 45°C oven for 90 days, and then taken out and placed in a 25°C environment, and discharged at 0.33C, and the discharge capacity is recorded as C1; the capacity retention rate = (C1 / C0) x 100%

[0236] 5.45℃ cycle 500 times after the transition metal ion dissolution content test

[0237] Take a certain 45℃ cycle 500 times after the battery, ethylene glycol dimethyl ether washing, drying, adding 1+1 aqua regia microwave digestion (high temperature and high pressure ~ 200℃) 6h, by inductively coupled plasma emission spectrometer (ICP), the determination of the various transition metal content contained in the cathode.

[0238] Battery preparation parameters and battery test results are shown in Table 1.

[0239] As can be seen from Example 1, Example 51-Example 54, by doping specific elements in specific amounts at the Li site, Fe / Mn site, P site and / or O site of the compound, the dissolution of transition metals can be significantly reduced, and the cycle performance and high temperature stability can be significantly improved.

[0240] As can be seen from Example 1, Example 55-Example 57, the thickness of the carbon coating layer of lithium manganese iron phosphate is 4nm-9nm, which can improve the cycle and storage performance of the battery.

[0241] Although the present application has been described with reference to the preferred embodiments, various modifications can be made to it without departing from the scope of the application, and equivalent components can be substituted therefor. In particular, the technical features mentioned in each embodiment can be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A secondary battery comprising a positive electrode sheet, a negative electrode sheet, and a nonaqueous electrolyte, wherein, The non-aqueous electrolyte comprises an additive; the additive comprises a first additive, the first additive being a cyclic organic base additive; the positive electrode plate comprises a positive electrode active material, the positive electrode active material comprising: an inner core and a carbon coating layer, the inner core being lithium iron manganese phosphate, and the carbon coating layer covering at least part of the surface of the inner core.

2. The secondary battery according to claim 1, wherein the cyclic organic base is an aromatic ring organic base or a non-aromatic ring organic base (optionally a saturated or unsaturated non-aromatic ring organic base); optionally, the cyclic organic base is a monocyclic or fused bicyclic ring containing 5-12 ring atoms. Optionally, the cyclic organic base additive includes any one or more of compound 1 of general formula (I), compound 2 of general formula (II), compound 3 of general formula (IV), compound 4 of general formula (V) or (V’), and compound 5 of general formula (VI), In general formula (III), Y 1 , Y 2 are identical or different, Y 1 , Y 2 are each independently selected from CH, N; R 11 , R 12 , R 13 are each independently selected from the group consisting of H, Ci-C6-alkyl, C2-C6-alkenyl, C2-C6-alkynyl, halogen, -R 14 OH, -R 15 NR 16 R 17 , -R 18 -O-R 19 , C3-C5-cycloalkyl, wherein, R 14 , R 15 , R 18 are each independently selected from the group consisting of: nothing, C1-C6alkylene, C2-C6alkenylene, R 16 , R 17 , R 19 are each independently selected from the group consisting of hydrogen, halogen, C1-C6alkyl, C1-C6haloalkyl, and as R 16 , R 17 , R 19 any carbon atom in the C1-C6alkyl group of R 16 , R 17 and the nitrogen atom to which both are attached together form a 5-6 membered nitrogen containing heterocyclic ring; In general formula (II), W 1 and W 2 are the same or different, W 1 is selected from C, N, O, S, W 2 is selected from C, N, and W 1 at least one of W 2 and W 21 is N; R 22 , R 23 , R 24 are each independently selected from the following groups: H, C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, halogen, -R 25 OH, -R 26 NR 27 R 28 , -R 29 -O-R 30 , C3-C5 cycloalkyl, wherein R 25 , R 26 , R 29 are each independently selected from: nothing, C1-C6 alkylene, C2-C6 alkenylene, R 27 , R 28 , R 30 are each independently selected from a hydrogen atom, a halogen atom, C1-C6 alkyl, C1-C6 haloalkyl; In general formula (IV), A 1 , A 2 , A 3 , A 4 , A 5 , A 6 , A 7 may be the same or different, each independently C or N, and A 1 , A 2 , A 3 , A 4 and A 5 at least one of A 31 , R 32 , R 33 , R 34 , R 35 , R 36 , R 37 each independently is selected from the group consisting of H, C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, halogen, -OH, -R 38 NR 39 R 40 , C1-C6 alkoxy, C3-C5 cycloalkyl, wherein R 38 is absent or selected from C1-C6 alkylene, C2-C6 alkenylene, R 39 , R 40 each independently is selected from the group consisting of a hydrogen atom, a halogen atom, C1-C6 alkyl, C1-C6 haloalkyl; In general formula (V), X 1 , X 2 , X 3 are each independently C or N, and at least one of X 1 , X 2 , X 3 is N, in general formula (V’), X 1 , X 3 are each independently C or N, and at least one of X 1 , X 3 is N, In general formula (V) and (V’), a, b are each independently selected from 0, 1, 2, 3, c is selected from 1, 2, 3, 4, 5, 6, 7, 8, each R 41 is each independently selected from H, C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, halogen, -R 42 OH, -R 43 NR 44 R 45 , -R 46 -O-R 47 , C3-C5 cycloalkyl, wherein R 42 , R 43 , R 46 is each independently selected from: nothing, C1-C6 alkylene, C2-C6 alkenylene, R 44 , R 45 , R 47 is each independently selected from hydrogen, halogen, C1-C6 alkyl, C1-C6 haloalkyl; In general formula (VI), V 1 , V 2 , V 3 are each independently C or N, and at least one of V 1 , V 2 , V 3 is N, d is selected from 0, 1, 2, 3, e is selected from 1, 2, 3, 4, 5, 6, each R 51 is independently selected from H, C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, halogen, -R 52 OH, -R 53 NR 54 R 55 , -R 56 -O-R 57 , C3-C5 cycloalkyl, wherein R 52 , R 53 , R 56 are each independently selected from: nothing, C1-C6 alkylene, C2-C6 alkenylene, R 54 , R 55 , R 57 are each independently selected from a hydrogen atom, a halogen atom, C1-C6 alkyl, C1-C6 haloalkyl.

3. The secondary battery according to claim 2, wherein In general formula (II), Y 1 , Y 2 are both N, or one of Y 1 , Y 2 is N and the other is CH.

4. The secondary battery according to claim 2 or 3, wherein In general formula (II), the R 11 , R 12 , R 13 each independently is selected from the group consisting of hydrogen, halogen, C1-C4 alkyl, C3-C5 alkenyl, C3-C5 alkynyl, -R 14 OH, -R 15 NR 16 R 17 , -R 18 -O-R 19 , wherein R 14 , R 15 , R 18 each independently is selected from the group consisting of nothing, C1-C3 alkylene, R 16 , R 17 , R 19 each independently is selected from the group consisting of hydrogen, halogen, C1-C3 alkyl, C1-C3 haloalkyl, and any carbon atom of the C1-C3 alkyl as the R 16 , R 17 , R 19 may be substituted with one or more heteroatoms, which are N atoms, optionally, R 16 , R 17 and the nitrogen atom to which both are attached together form a 5-6 membered nitrogen-containing heterocyclic ring.

5. The secondary battery according to any one of claims 2 to 4, wherein R 11 , R 12 , R 13 are each independently selected from the group consisting of hydrogen, halogen, methyl, ethyl, n-propyl, i-propyl, t-butyl, allyl, propargyl, -OH, -CH2OH, -NH2, -CH2NH2, -N(CH3)2, -O-CH3, R 11 , R 12 , R 13 are each independently selected from the group consisting of hydrogen, fluorine, methyl, t-butyl, -CH2OH, -CH2NH2, -N(CH3)2, -O-CH3, any of the above.

6. The secondary battery according to any one of claims 2 to 5, wherein The compound having the structure of general formula (II) is selected from any one or more of the following compounds: Compound 2-1; Compound 2-2; Compound 2-3; Compound 2-4; Compound 2-5; Compounds 2-6; Compounds 2-7; Compounds 2-8; Compounds 2-9; Compound 2-10; Compound 2-11; Compound 2-12.

7. The secondary battery according to claim 2, in general formula (III), W 1 and W 2 are each N, or one of W 1 , W 2 is N and the other is CH.

8. The secondary battery according to claim 2 or 7, the R 21 , R 22 , R 23 , R 24 each independently is selected from the group consisting of hydrogen, halogen, Ci-C4-alkyl, C3-C5-alkenyl, C3-C5-alkynyl, -R 25 OH, -R 26 NR 27 R 28 , -R 29 -O-R 30 , C3-C5-cycloalkyl, wherein, R 25 , R 26 , R 29 are each independently selected from the group consisting of: nothing, C1-C4alkylene, R 27 , R 28 , R 30 are each independently selected from the group consisting of hydrogen, halogen, C1-C4alkyl, C1-C4haloalkyl.

9. The secondary battery according to claim 2, 7 or 8, wherein said R 21 , R 22 , R 23 , R 24 are each independently selected from the group consisting of hydrogen, fluorine, methyl, ethyl, propyl, cyclopropyl, allyl, propargyl, -OH, -CH3OH, -NH2, -NHCH3, -CH2NH2, -N(CH3)2, -O-CH3; optionally, said R 21 , R 22 , R 23 , R 24 are each independently selected from the group consisting of hydrogen, fluorine, methyl, cyclopropyl, allyl, -CH3OH, -NHCH3.

10. The secondary battery according to any one of claims 2 or 7-9, wherein, The compound having the structure of general formula (III) is selected from any one or more of the following compounds: Compound 3-1; Compound 3-2; Compound 3-3; Compound 3-4; Compound 3-5; Compound 3-6; Compound 3-7; Compound 3-8; Compound 3-9.

11. The secondary battery according to claim 2, in the general formula (IV), A 1 is N, A 2 , A 3 , A 4 , A 5 , A 6 , A 7 each independently is C or N; Optionally, A 1 is N, and A 5 is C.

12. The secondary battery according to claim 2 or 11, wherein R 31 32 33 34 35 36 37 each independently is selected from any one of hydrogen, C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, -OH, -R 38 39 R 40 , C1-C4 alkoxy, R 38 is absent or selected from C1-C3 alkylene, R 39 40 each independently is selected from hydrogen, halogen, C1-C3 alkyl, C1-C3 haloalkyl;​​​​​​​​​​​​​ Optionally, R 31 , R 32 , R 33 , R 34 , R 35 , R 36 , R 37 each independently is selected from the group consisting of hydrogen, methyl, ethyl, allyl, propargyl, -OH, -NH2, -CH2NH2, -N(CH3)2, -O-CH3; Optionally, R 31 , R 32 , R 33 , R 34 , R 35 , R 36 , R 37 are each independently selected from the group consisting of hydrogen, methyl, -O-CH3.

13. The secondary battery according to any one of claims 2 or 10-12, wherein in the general formula (IV), R 32 R 33 R 34 R 35 R 36 R 37 All are hydrogen; Optionally, R 31 is selected from hydrogen, methyl, ethyl, allyl, propargyl, -OH, -NH2, -CH2NH2, -N(CH3)2, -O-CH3; Optionally, R 31 is selected from hydrogen, methyl, -O-CH3.

14. The secondary battery according to any one of claims 2 or 10-13, wherein, The compound having the structure of general formula (IV) is selected from any one or more of the following compounds: Compound 4-1; Compound 4-2; Compound 4-3; Compound 4-4; Compound 4-5; Compound 4-6; Compound 4-7; Compound 4-8; Compound 4-9; Compound 4-10.

15. The secondary battery according to claim 2, in the general formula (V), X 1 is N, X 2 , X 3 are each independently C or N; optionally, X 2 is N; optionally, X 3 is C; In the general formula (V), X 1 , X 3 are each N.

16. The secondary battery according to claim 2 or 15, wherein in the general formula (V), a, b, c are each independently 1, 2 or 3; optionally, a is 2; optionally, b is 1, 2 or 3; optionally, c is 1 or 2. In the general formula (V’), a is 0 or 1, and c is 1 or 2.

17. The secondary battery according to claim 2, 15 or 16, wherein the general formula (V) is (V-1): ###00019### wherein a, b, X 1 , X 2 , X 3 as defined in claim 2, 15 or 16; The general formula (V) is (V-1): wherein a, X 1 , X 3 as defined in claim 2, 15 or 16.

18. The secondary battery according to any one of claims 2 or 15-17, in the general formula (V), (V'), (V-1) or (V'-1), each R 41 each independently selected from the group consisting of hydrogen, halogen, Ci-C4-alkyl, C3-C5-alkenyl, C3-C5-alkynyl, -R 42 OH, -R 43 NR 44 R 45 , -R 46 -O-R 47 , R 42 , R 43 , R 46 each independently selected from the group consisting of nothing, Ci-C3-alkylene, R 44 , R 45 , R 47 each independently selected from the group consisting of hydrogen, halogen, Ci-C4-alkyl, Ci-C4-haloalkyl; Optionally, each R 41 Each is independently selected from hydrogen, fluorine, methyl, ethyl, hydroxyl, -NH2, -N(CH3)2; Optionally, each R 41 each independently is selected from hydrogen, methyl, -N(CH3)2.

19. The secondary battery according to any one of claims 2 or 15-18, wherein, The compound having the structure of general formula (V) is selected from any one or more of the following compounds: Compound 5-1a; Compound 5-1; Compound 5-2; Compound 5-3; Compound 5-4; Compound 5-5; Compound 5-6.

20. The secondary battery according to claim 2, wherein in the general formula (VI), d is 0 or 1.

21. The nonaqueous electrolyte according to claim 2 or 20, wherein each R 51 each is independently selected from the group consisting of hydrogen, halogen, C1-C4 alkyl, C3-C5 alkenyl, C3-C5 alkynyl, -R 52 OH, -R 53 NR 54 R 55 , -R 56 -O-R 57 , wherein, R 52 , R 53 , R 56 are each independently selected from the group consisting of: nothing, C1-C3 alkylene, R 54 , R 55 , R 57 are each independently selected from the group consisting of hydrogen, halogen, C1-C4 alkyl, C1-C4 haloalkyl; Optionally, each R 51 Each is independently selected from hydrogen, fluorine, methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, hydroxyl, -NH2, -N(CH3)2; Optionally, each R 51 each independently is selected from hydrogen, fluorine, methyl, ethyl, isopropyl, tert-butyl.

22. The secondary battery according to any one of claims 2, 20 or 21, wherein, The compound having the structure of general formula (VI) is selected from any one or more of the following compounds: Compound 6-1; Compound 6-2; Compound 6-3; Compound 6-4; Compound 6-5; Compound 6-6; Compound 6-7; Compound 6-8.

23. The secondary battery according to any one of claims 1-22, wherein, The mass proportion of the first additive in the non-aqueous electrolyte is W1, W1 satisfying 0.001%≤W1≤20%, optionally 0.1%≤W1≤2%.

24. The secondary battery according to any one of claims 1-23, wherein the additive further comprises a second additive, optionally, the second additive comprises one or more of a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive capable of improving battery performance.

25. The secondary battery of any one of claims 1-24, the lithium iron manganese phosphate having a chemical formula Li m A a Fe x Mn b D d P y E e O z G g , the A comprising at least one element of Al, Na, K, or Mg; the D comprising at least one element of Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, Ti, or V; the E comprising at least one element of B, S, Si, or N; the G comprising at least one element of S, F, Cl, or Br; the m selected from a range of 0.95 to 1.15; the a selected from a range of 0 to 0.1; the x selected from a range of 0.1 to 1; the b selected from a range of 0.1 to 0.9; the d selected from a range of 0 to 0.1; the y selected from a range of 0.95 to 1; the e selected from a range of 0 to 0.1; the z selected from a range of 3.5 to 4; the g selected from a range of 0 to 0.

1. Optionally, a, d, e, g are all 0, and said lithium iron manganese phosphate has a chemical formula Li m Fe x Mn b P y O z wherein m, x, b, y, z are as defined above; optionally, said lithium iron manganese phosphate has a chemical formula selected from the group consisting of: LiMn 0.5 Fe 0.5 PO4, LiMn 0.6 Fe 0.4 PO4, LiMn 0.7 Fe 0.3 PO4, LiMn 0.8 Fe 0.2 PO4; Optionally, d, e, g are all 0, and said lithium iron manganese phosphate has a chemical formula Li m A a Fe x Mn b PO z wherein A, a, m, x, b, y, z are as defined above; optionally, A is Mg; optionally, said lithium iron manganese phosphate has a chemical formula selected from the group consisting of: LiMn 0.60 Fe 0.395 Mg 0.005 PO4; Optionally, a, e, g are each 0, and the lithium iron manganese phosphate has the chemical formula Li m Fe x Mn b D d P y O z wherein m, x, b, D, d, y, z are as defined above; optionally, D is selected from one or more elements of V, Ni; optionally, the lithium iron manganese phosphate has the chemical formula Li 0.60 Fe 0.395 V 0.002 Ni 0.003 PO4; Optionally, a is 0, said lithium iron manganese phosphate has a chemical formula Li m Fe x Mn b D d P y E e O, wherein m, x, b, D, d, E, e, y, z are as defined above; optionally, D is selected from one or more elements of V, Co; optionally, E is selected from one or more elements of S, Si; optionally, said lithium iron manganese phosphate has a chemical formula selected from: Li 0.997 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.997 S 0.003 O4, Li 1.001 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.999 Si 0.001 O4.

26. The secondary battery according to any one of claims 1-25, wherein in the positive electrode active material, the thickness of the carbon coating layer is 0.5-10 nm; optionally, the thickness of the carbon coating layer is 4-8 nm.

27. An electrically powered device comprising a secondary battery, wherein The secondary battery comprises the secondary battery according to any one of claims 1-26.

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