Battery and electric device

Abstract

The invention provides a battery cell combination, a battery and a power utilization device. The battery cell combination comprises first battery cells and second battery cells, the number of the first battery cells is larger than or equal to that of the second battery cells, and each of the first battery cells and the second battery cells comprises a positive pole piece and a negative pole piece; the battery core combination meets the following conditions: NPA1 is greater than or equal to 0.7 and less than or equal to 1.05 NPB1 and NPA1 < lt >; 1, or 0.75 < = NPA2 < = 1.05 NPB2 and NPA2lt; 1.2; when the state of charge of the single-cell battery comprising the second cell is in a range of 95% to 100%, the voltage change of the second cell is correspondingly greater than 5mV every time the state of charge of the single-cell battery is changed by 1%. The battery cell combination improves the safety performance and the cycle life of the battery.

Description

[0001] This application is a divisional application of the patent application filed on April 27, 2023, with application number 202380061017.5 and entitled "Cell Assembly, Battery and Electrical Device". Technical Field

[0002] This application relates to the field of secondary battery technology, and more particularly to a battery and an electrical device. Background Technology

[0003] In recent years, with the increasingly wide range of applications, rechargeable batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. Due to the significant development of rechargeable batteries, higher requirements have been placed on their cycle performance and safety performance. Summary of the Invention

[0004] This application was made in view of the above-mentioned problems, and its object is to provide a battery and an electrical device. Using the battery of this application helps to reduce the occurrence of battery overcharging, improves battery safety performance, and extends battery cycle life.

[0005] To achieve the above objectives, the first aspect of this application provides a battery, including a cell assembly, the cell assembly including a first cell and a second cell, the number of the first cell being greater than or equal to the number of the second cell, and both the first cell and the second cell including a positive electrode and a negative electrode.

[0006] Furthermore, the cell assembly satisfies:

[0007] 0.7≤ NP A1 ≤1.05 NP B1 And NP A1 <1, or 0.75≤ NP A2 ≤1.05 NP B2 And NP A2 <1.2;

[0008] Among them, NP A1 NP is the ratio of the initial lithium insertion capacity of the negative electrode to the initial lithium extraction capacity of the positive electrode in the first cell. B1 NP is the ratio of the initial lithium insertion capacity of the negative electrode to the initial lithium extraction capacity of the positive electrode in the second cell. A2 NP is the ratio of the non-first lithium insertion capacity of the negative electrode to the non-first lithium extraction capacity of the positive electrode in the first cell. B2It is the ratio of the non-first lithium insertion capacity of the negative electrode to the non-first lithium removal capacity of the positive electrode in the second cell;

[0009] When the state of charge of a single-cell battery including the second cell is in the range of 95% to 100%, for every 1% change in the state of charge of the single-cell battery, the voltage of the second cell changes by more than 5mV.

[0010] Designing the cell's NP to be less than 1 helps reduce the amount of negative electrode active material used, lowering costs. The space saved can also be used to further increase capacity. However, this will cause the state of charge (SOC) of a single cell to approach saturation. When the SOC of a single cell changes by 1%, the corresponding voltage change of the cell is very small, which can easily lead to overcharging of the single cell and pose a safety hazard.

[0011] This application defines a cell combination in which the number of first cells is greater than or equal to the number of second cells. It further defines a configuration where, when the SOC of a single second cell approaches saturation, for every 1% change in the SOC of a single cell, the corresponding voltage change of the second cell is greater than 5mV. Additionally, it defines NP... A1 Numerical values ​​and their relationship with NP B1 Relationship, or restriction of NP A2 Numerical values ​​and their relationship with NP B2 This relationship helps reduce battery overcharging, improves battery safety, and extends battery cycle life.

[0012] In any embodiment, when the state of charge of a single-cell battery including the first cell is in the range of 95% to 100%, for every 1% change in the state of charge of the single-cell battery, the voltage change of the first cell is less than or equal to 5mV.

[0013] When the first cell reaches its design limit, the first cell satisfies the voltage change characteristics described above.

[0014] In any implementation, the cell assembly satisfies:

[0015] 0.08≤ (1.1-NP A1 ) / (NP B1 -1) ≤20;

[0016] Preferably, 0.1 ≤ (1.1 - NP) A1 ) / (NP B1 -1) ≤15.

[0017] Therefore, when the above relationship is met, the battery capacity requirement is satisfied while the initial voltage of the battery is limited, so that the battery can form a stable and dense SEI film in a lower voltage range, thereby extending the cycle life of the battery.

[0018] In any implementation, the cell assembly satisfies:

[0019] 0.95≤C B / C A ≤1.4, can be replaced with 1.0≤C B / C A ≤1.3;

[0020] Among them, C A C represents the widest voltage range capacity across the entire lifecycle of the first battery cell. B This represents the widest voltage range capacity for the second battery cell throughout its entire lifecycle.

[0021] Therefore, by matching the capacity design of the first and second cells, this application satisfies the lifespan matching of the battery throughout its entire life cycle, thereby extending the battery's cycle life and improving its safety performance throughout its entire life cycle.

[0022] In any embodiment, the positive electrode in the first battery cell includes a first positive electrode active material, the first positive electrode active material comprising the compound Li. a A x Mn 1-y B y P 1-z C z O 4-n D n ;

[0023] Wherein, A includes one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo, and W; B includes one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; C includes one or more elements selected from B (boron), S, Si, and N; D includes one or more elements selected from S, F, Cl, and Br; a is 0.85-1.15; x is 0-0.1; y is 0.001-1; z is 0-0.5; and n is 0-0.5.

[0024] In any embodiment, the first positive electrode active material includes a core and a coating layer covering the core; wherein the core comprises the compound Li. a A x Mn 1-y B y P 1-z C z O 4-n D n The coating layer contains carbon.

[0025] Therefore, this application uses the aforementioned first positive electrode active material to achieve the maximum NP of the first cell, which is beneficial to improving the energy density of the first cell.

[0026] In any embodiment, the positive electrode in the second cell includes a second positive electrode active material; the second positive electrode active material comprises the compound LiNi. b Co d Mn e M f O2;

[0027] Wherein, M includes one or more elements selected from Mn, Al, Mg, Ca, Na, Ti, W, Zr, Sr, Cr, Zn, Ba, B, S, and Y, and may optionally include Mg and / or Al; b is 0.314-0.970; d is 0-0.320, and may optionally be 0.047-0.320; e is 0.006-0.390; and the sum of b, d, e, and f is 1 and f is greater than 0.

[0028] In any embodiment, the positive electrode in the second battery cell further includes a third positive electrode active material; the third positive electrode active material includes a core and a shell covering the core, the shell including a first coating layer covering the core, a second coating layer covering the first coating layer, and a third coating layer covering the second coating layer; the core contains the compound Li. 1+g Mn 1-h E h P 1-i R i O4, the first coating layer contains crystalline pyrophosphate Li j GP2O7 and / or G k (P2O7) r The second coating layer contains crystalline phosphate X t PO4, the third coating layer contains carbon;

[0029] Wherein, E includes one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and may optionally include one or more elements selected from Fe, V, Ni, and Co; R includes one or more elements selected from B, Si, N, and S, and may optionally include one or more elements selected from Si, N, and S; the crystalline pyrophosphate Li j GP2O7 and G k (P2O7) rEach of the G elements independently includes one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, and may optionally include one or more elements selected from Fe, Co, Ti, and Al; each of the X elements includes one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, and may optionally include one or more elements selected from Li, Fe, Ag, and Al; g is -0.100 to 0.100; h is 0.001 to 0.600; i is 0.001 to 0.100; j is greater than 0 and less than or equal to 2; k is 1 to 4; r is 1 to 3; and t is greater than 0 and less than or equal to 2.

[0030] Therefore, the second cell of this application uses the aforementioned second positive electrode active material and an optional third positive electrode active material, which improves the compaction density of the second cell, enhances the thermal stability of the battery, and extends the cycle life of the battery.

[0031] In any embodiment, in the positive electrode sheet of the second battery cell, the mass of the second positive electrode active material accounts for 5%-100% of the total mass of the second positive electrode active material and the third positive electrode active material, and can be selected as 5%-95%.

[0032] This further improves the compaction density of the second cell, further enhances the thermal stability of the battery, and further extends the cycle life of the battery.

[0033] In any embodiment, the upper limit voltage of the second cell during the 90th-110th charge-discharge cycle of the battery is greater than the upper limit voltage of the second cell during the first charge-discharge cycle of the battery.

[0034] Therefore, while meeting the battery capacity requirements, the lower upper limit voltage of the second cell in the early stage limits the initial voltage of the battery, allowing the battery to form a stable and dense SEI film in a lower voltage range, thereby extending the cycle life of the battery after widening in the later stage.

[0035] A second aspect of this application also provides an electrical device, including the battery of the first aspect of this application. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0037] Figure 2 yes Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0038] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0039] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0040] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0041] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0042] Explanation of reference numerals in the attached figures:

[0043] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0044] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the cell assembly, secondary battery, battery module, battery pack, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0045] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, 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 specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0046] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0047] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0048] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0049] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0050] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0051] [Rechargeable Battery]

[0052] Secondary batteries, also known as rechargeable batteries or storage batteries, are batteries that can be recharged after being discharged to activate the active materials and continue to be used.

[0053] Typically, a secondary battery consists of a cell or a cell assembly, which includes a positive electrode, a negative electrode, a separator, and an electrolyte. During charging and discharging, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing active ions to pass through. The electrolyte, also positioned between the positive and negative electrodes, mainly serves to conduct active ions.

[0054] An embodiment of this application provides a battery including a cell assembly, the cell assembly including a first cell and a second cell, the number of the first cell being greater than or equal to the number of the second cell, and both the first cell and the second cell including a positive electrode and a negative electrode.

[0055] Furthermore, the cell assembly satisfies:

[0056] 0.7≤ NP A1 ≤1.05 NP B1 And NP A1 <1, or 0.75≤ NP A2 ≤1.05 NP B2 And NP A2 <1.2;

[0057] Among them, NP A1 NP is the ratio of the initial lithium insertion capacity of the negative electrode to the initial lithium extraction capacity of the positive electrode in the first cell. B1 NP is the ratio of the initial lithium insertion capacity of the negative electrode to the initial lithium extraction capacity of the positive electrode in the second cell. A2 NP is the ratio of the non-first lithium insertion capacity of the negative electrode to the non-first lithium extraction capacity of the positive electrode in the first cell. B2 It is the ratio of the non-first lithium insertion capacity of the negative electrode to the non-first lithium removal capacity of the positive electrode in the second cell;

[0058] When the state of charge of a single-cell battery including the second cell is in the range of 95% to 100%, for every 1% change in the state of charge of the single-cell battery, the voltage of the second cell changes by more than 5mV.

[0059] Designing the cell's NP to be less than 1 helps reduce the amount of negative electrode active material used, lowering costs. The space saved can also be used to further increase capacity. However, this will cause the state of charge (SOC) of a single cell to approach saturation. When the SOC of a single cell changes by 1%, the corresponding voltage change of the cell is very small, which can easily lead to overcharging of the single cell and pose a safety hazard.

[0060] Although the mechanism is not yet clear, the applicant unexpectedly discovered that by using a cell combination in which the number of first cells is greater than or equal to the number of second cells, this application limits the voltage change of the second cell to more than 5mV for every 1% change in the SOC of a single cell battery when it is close to saturation, and limits the NP... A1 Numerical values ​​and their relationship with NP B1 Relationship, or restriction of NP A2 Numerical values ​​and their relationship with NP B2This relationship helps reduce battery overcharging, improves battery safety, and extends battery cycle life.

[0061] In some implementations, when the state of charge of a single-cell battery including the first cell is in the range of 95% to 100%, for every 1% change in the state of charge of the single-cell battery, the voltage change of the first cell is less than or equal to 5mV.

[0062] When the first cell reaches its design limit, the first cell satisfies the voltage change characteristics described above.

[0063] In some implementations, when the state of charge (SOC) of a single-cell battery is in the range of 95% to 100%, the voltage change of the first or second cell is determined by conventional methods in the art for every 1% change in the SOC of the single-cell battery; for example, the specific method is to assemble the first or second cell into a single-cell battery according to conventional methods. In a constant temperature environment of 25℃, the battery is left to stand for 10 minutes, then discharged at a constant current of 0.1C to the cutoff voltage. After standing for 10 minutes, it is charged at a constant current of 0.04C to the target voltage. After standing for 10 minutes, it is discharged at a constant current of 0.04C to the cutoff voltage. After standing for 10 minutes, it is charged at a constant current of 0.04C to the target voltage. The charging capacity at this time is recorded as 100% SOC. After standing for 10 minutes, it is discharged at a constant current of 0.04C to the cutoff voltage. Plot the charging capacity of the last charging process as the y-axis and the voltage as the x-axis. From the graph, the voltage Vm corresponding to 95% SOC and the voltage Vn corresponding to 100% SOC are obtained. When the state of charge of the battery is in the range of 95% to 100%, for every 1% change in the state of charge of the battery, the voltage change of the first cell or the second cell is (Vn-Vm) / 5.

[0064] In some embodiments, the initial lithium insertion capacity and non-initial lithium insertion capacity of the negative electrode, and the initial lithium extraction capacity and non-initial lithium insertion capacity of the positive electrode are determined using conventional methods in the art. For example, the method for determining the initial lithium extraction capacity and non-initial lithium insertion capacity of the positive electrode is as follows: a coin cell is fabricated by combining the positive electrode and the counter electrode lithium sheet. The battery is charged at a constant current of 0.1C to 4.35V in a constant temperature environment of 25°C, and then discharged at 0.1C to 2.8V. The discharge capacity of the first cycle is recorded. The initial lithium extraction capacity of the positive electrode is obtained by dividing the initial discharge capacity by the mass of the positive active material in the positive electrode. The coin cell is then charged and discharged twice more in the same manner, for a total of three charge-discharge cycles. The capacity of the second charge-discharge cycle is recorded as the non-initial discharge capacity. The non-initial discharge capacity is then divided by the mass of the positive active material in the positive electrode to obtain the non-initial lithium extraction capacity of the positive electrode. For example, the method for determining the initial lithium insertion capacity and non-initial lithium insertion capacity of the negative electrode is as follows: A coin cell is fabricated by combining the negative electrode and the counter electrode lithium sheet. In a constant temperature environment of 25°C, it is charged at a constant current of 0.1C to 2.0V, and then discharged at 0.1C to 0V. The discharge capacity of the first cycle is recorded. The initial lithium insertion capacity of the negative electrode is obtained by dividing the initial discharge capacity by the mass of the negative electrode active material in the negative electrode. The coin cell is then charged and discharged twice more in the same manner, for a total of three charge-discharge cycles. The capacity of the second charge-discharge cycle is recorded as the non-initial discharge capacity. The non-initial discharge capacity is obtained by dividing the non-initial discharge capacity by the mass of the negative electrode active material in the negative electrode.

[0065] In some implementations, the cell assembly satisfies:

[0066] 0.08≤ (1.1-NP A1 ) / (NP B1 -1) ≤20;

[0067] Preferably, 0.1 ≤ (1.1 - NP) A1 ) / (NP B1 -1) ≤15; for example (1.1-NP A1 ) / (NP B1 -1) is a range consisting of 0.2, 0.3, 0.6, 0.8, 1, 2, 3, 5, 7, 8, 10, 12, 14, 16, 17, 18, 19 and any of the above values.

[0068] Therefore, when the above relationship is met, the battery capacity requirement is satisfied while the initial voltage of the battery is limited, so that the battery can form a stable and dense SEI film in a lower voltage range, thereby extending the cycle life of the battery.

[0069] In some implementations, the cell assembly satisfies:

[0070] 0.95≤CB / C A ≤1.4;

[0071] The value can be 1.0≤C B / C A ≤1.3, for example, C B / C A The range is composed of 1.1, 1.2, 1.25, and any of the above values;

[0072] Among them, C A C represents the widest voltage range capacity across the entire lifecycle of the first battery cell. B This represents the widest voltage range capacity for the second battery cell throughout its entire lifecycle.

[0073] Therefore, by matching the capacity design of the first and second cells, this application satisfies the lifespan matching of the battery throughout its entire life cycle, thereby extending the battery's cycle life and improving its safety performance throughout its entire life cycle.

[0074] In some embodiments, the positive electrode in the first cell includes a first positive active material, the first positive active material comprising the compound Li. a A x Mn 1-y B y P 1-z C z O 4-n D n ;

[0075] Wherein, A includes one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo, and W; B includes one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge, optionally including Ti and / or Fe; C includes one or more elements selected from B (boron), S, Si, and N; D includes one or more elements selected from S, F, Cl, and Br; a is 0.85-1.15, for example, 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, 1.15, and any range of the above values; x is 0-0.1, optionally 0, for example, 0, 0. The range of values ​​is 0.1, 0.02, 0.03, 0.04, 0.05, 0.06, 0.08, 0.09, 0.1, and any of the above values; y is 0.001-1, for example, 0.005, 0.008, 0.01, 0.03, 0.05, 0.08, 0.1, 0.3, 0.5, 0.7, 0.8, 0.9, 0.95, 1, and any of the above values; z is 0-0.5, for example, 0, 0.1, 0.2, 0.3, 0.4, 0.5, and any of the above values; n is 0-0.5, for example, 0, 0.1, 0.2, 0.3, 0.4, 0.5, and any of the above values.

[0076] In some embodiments, the first positive electrode active material includes a core and a coating layer covering the core; wherein the core comprises the compound Li. a A x Mn 1-y B y P 1-z C z O 4-n D n The coating layer contains carbon.

[0077] Therefore, this application uses the aforementioned first positive electrode active material to achieve the maximum NP of the first cell, which is beneficial to improving the energy density of the first cell.

[0078] In some embodiments, the positive electrode in the second cell includes a second positive electrode active material; the second positive electrode active material comprises the compound LiNi. b Co d Mn e M f O2;

[0079] Wherein, M includes one or more elements selected from Mn, Al, Mg, Ca, Na, Ti, W, Zr, Sr, Cr, Zn, Ba, B, S, and Y, and may optionally include Mg and / or Al; b is 0.314-0.970, for example, 0.4, 0.5, 0.55, 0.6, 0.7, 0.8, 0.9, and any combination of the above values; d is 0-0.320, and may optionally be 0.047-0.320, for example, 0.050, 0.060, 0.080, 0.100, 0.120, 0.141, 0.160, 0... The range of values ​​including 0.180, 0.200, 0.250, 0.270, 0.300, 0.310, and any of the above values; where e is 0.006-0.390, for example, 0.010, 0.020, 0.050, 0.080, 0.100, 0.130, 0.170, 0.200, 0.220, 0.230, 0.249, 0.260, 0.280, 0.300, 0.320, 0.350, 0.370, 0.380, and any of the above values; and the sum of b, d, e, and f is 1 and f is greater than 0.

[0080] In some embodiments, the positive electrode in the second cell further includes a third positive electrode active material; the third positive electrode active material includes a core and a shell covering the core, the shell including a first coating layer covering the core, a second coating layer covering the first coating layer, and a third coating layer covering the second coating layer; the core contains the compound Li. 1+g Mn 1-h E h P 1-i R i O4, the first coating layer contains crystalline pyrophosphate Li j GP2O7 and / or G k (P2O7) r The second coating layer contains crystalline phosphate X t PO4, the third coating layer contains carbon;

[0081] Wherein, E includes one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and optionally includes one or more elements selected from Fe, V, Ni, and Co, and more preferably includes one or more elements selected from Fe, V, and Co; R includes one or more elements selected from B, Si, N, and S, and optionally includes one or more elements selected from Si, N, and S, and more preferably includes Si; the crystalline pyrophosphate Li j GP2O7 and G k (P2O7)r The G in each element independently includes one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, and may optionally include one or more elements selected from Fe, Co, Ti, and Al, more preferably including Fe; the X in each element includes one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, and may optionally include one or more elements selected from Li, Fe, Ag, and Al, more preferably including Li and / or Fe; the g is in the range of -0.100 to 0.100, for example, -0.05, -0.01, 0, 0.001, 0.005, 0.01. The range of values ​​is defined as follows: 0.02, 0.05, 0.07, 0.08, 0.09, and any of the above values; h is 0.001-0.600, for example, 0.005, 0.01, 0.03, 0.05, 0.07, 0.1, 0.2, 0.3, 0.4, 0.5, and any of the above values; i is 0.001-0.100, for example, 0.001, 0.003, 0.007, 0.01, 0.04, 0.06, 0.08, 0.1, and any of the above values; j is greater than 0 and less than or equal to 2; k is 1-4; r is 1-3; t is greater than 0 and less than or equal to 2.

[0082] Therefore, the second cell of this application uses the aforementioned second positive electrode active material and an optional third positive electrode active material, which improves the compaction density of the second cell, enhances the thermal stability of the battery, and extends the cycle life of the battery.

[0083] In some implementations, Li a A x Mn 1-y B y P 1-z C z O 4-n D n LiNi b Co d Mn e M f O2, Li 1+g Mn 1-h E h P 1-i R i O4, Li j GP2O7, G k (P2O7) r and X t PO4 is all electrically neutral.

[0084] In some embodiments, the mass of the second positive electrode active material in the positive electrode sheet of the second battery cell accounts for 5%-100% of the total mass of the second positive electrode active material and the third positive electrode active material, and can be selected as 5%-95%, such as 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and any range of the above values.

[0085] This further improves the compaction density of the second cell, further enhances the thermal stability of the battery, and further extends the cycle life of the battery.

[0086] In some embodiments, the preparation method of the first positive electrode active material of this application includes the following steps:

[0087] (1) Dissolve and stir the manganese source, the source of element B and the acid in a solvent to generate a suspension of manganese salt doped with element B. Filter the suspension and dry the filter cake to obtain manganese salt doped with element B.

[0088] (2) The lithium source, phosphorus source, source of element A, source of element C and source of element D, solvent and manganese salt doped with element B obtained in step (1) are added to the reaction vessel, ground and mixed to obtain a slurry;

[0089] (3) The slurry obtained in step (2) is transferred to a spray drying equipment for spray drying and granulation to obtain granules;

[0090] (4) The particles obtained in step (3) are sintered.

[0091] In some embodiments, the source of element A is selected from at least one of elemental form, oxide, phosphate, oxalate, carbonate, and sulfate; the source of element B is selected from at least one of elemental form, oxide, phosphate, oxalate, carbonate, and sulfate; the source of element C is selected from at least one of sulfate, borate, nitrate, and silicate of element C; and the source of element D is selected from at least one of elemental form and ammonium salt of element D. By selecting the source of each dopant element, the uniformity of the dopant element distribution can be improved, thereby improving the material performance.

[0092] In some embodiments, the acid is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and organic acids such as oxalic acid, for example, oxalic acid. In some embodiments, the acid is a dilute acid with a concentration of 60% by weight or less.

[0093] In some embodiments, the manganese source may be a manganese-containing substance known in the art that can be used to prepare lithium manganese phosphate, such as one or a combination of elemental manganese, manganese dioxide, manganese phosphate, manganese oxalate, and manganese carbonate.

[0094] In some embodiments, the lithium source may be a lithium-containing material known in the art that can be used to prepare lithium manganese phosphate, such as lithium carbonate, lithium hydroxide, lithium phosphate, lithium dihydrogen phosphate, or a combination thereof.

[0095] In some embodiments, the phosphorus source may be a phosphorus-containing substance known in the art that can be used to prepare lithium manganese phosphate, such as one or a combination of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, and phosphoric acid.

[0096] The amount of source added for each of elements A, B, C, and D depends on the target doping amount, and the ratio of the amount of lithium source, manganese source, and phosphorus source used conforms to the stoichiometric ratio.

[0097] In some embodiments, the solvents described in steps (1) and (2) may each be a solvent commonly used by those skilled in the art in the preparation of manganese salts and lithium manganese phosphate, for example, each may be independently selected from at least one of ethanol, water (e.g., deionized water).

[0098] In some embodiments, the preparation method of the third positive electrode active material includes the following steps:

[0099] The steps for providing the core material: the core has the chemical formula Li 1+g Mn 1-h E h P 1-i R i O4, wherein the definitions of E, R, g, h, and i are as described above;

[0100] First coating step: Dissolve the source of element G, phosphorus source, acid, and optionally lithium source in a solvent to obtain a first coating layer suspension; thoroughly mix the core obtained in the core step with the first coating layer suspension obtained in the first coating step, dry, and then sinter to obtain the material coated by the first coating layer.

[0101] Second coating step: Dissolve the source of element X, phosphorus source and acid in solvent to obtain a second coating layer suspension; mix the material coated by the first coating layer obtained in the first coating step with the second coating layer suspension obtained in the second coating step, dry, and then sinter to obtain a material coated by two coating layers.

[0102] The third coating step: dissolve the carbon source in a solvent to obtain a third coating layer solution; then add the material coated by the two coating layers obtained in the second coating step to the third coating layer solution, mix evenly, dry, and then sinter to obtain a material coated by the three coating layers.

[0103] In some embodiments, the upper limit voltage of the second cell in the 90th to 110th charge-discharge cycles (e.g., 92, 95, 96, 97, 98, 100 cycles and any range of the above values) is greater than the upper limit voltage of the second cell in the first charge-discharge cycle of the battery.

[0104] Therefore, while meeting the battery capacity requirements, the lower upper limit voltage of the second cell in the early stage limits the initial voltage of the battery, allowing the battery to form a stable and dense SEI film in a lower voltage range, thereby extending the cycle life of the battery after widening in the later stage.

[0105] [Positive electrode plate]

[0106] A positive electrode typically includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0107] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0108] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0109] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0110] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0111] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0112] [Negative electrode plate]

[0113] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0114] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0115] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0116] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0117] In some embodiments, the negative electrode film layer may optionally include a binder. As an example, the binder may 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).

[0118] In some embodiments, the negative electrode film may optionally include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0119] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0120] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0121] [Electrolytes]

[0122] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0123] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0124] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0125] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0126] In some embodiments, the electrolyte may optionally include additives. As examples, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0127] [Isolation membrane]

[0128] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0129] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0130] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0131] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the aforementioned electrode assembly and electrolyte.

[0132] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0133] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 5.

[0134] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0135] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0136] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0137] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0138] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0139] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0140] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0141] As an electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0142] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0143] [Example]

[0144] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0145] Example 1

[0146] (I) Preparation of the first battery cell

[0147] (1) Preparation of the first positive electrode active material:

[0148] Using iron phosphate, lithium carbonate, and titanium dioxide as raw materials, and according to a stoichiometric ratio of FePO4:Li2CO3:TiO2 = 0.996:0.498:0.004, iron phosphate, lithium carbonate, and titanium dioxide were mixed, and glucose and polyethylene glycol (mass ratio of glucose to polyethylene glycol 1:1, carbon source accounting for 6% of the total mass of raw materials) were added as carbon source and reducing agent. Then, water was added as a solvent for wet grinding to obtain a mixed slurry. The obtained slurry was spray-dried, and the dried product was then sintered in a roller furnace at 500℃ in the absence of air for 20 hours. After natural cooling to a material temperature <80℃, the material was discharged to obtain calcined material. The calcined material was crushed, sieved, and demagnetized to obtain lithium iron phosphate substrate LiFe. 0.998 Ti 0.002 PO4, doped with approximately 0.3% carbon. The above substrate was sintered in a roller furnace under a nitrogen atmosphere, while simultaneously spraying with acetone solution. Sintering was carried out at a constant temperature of 600℃ for 10 hours. After the material naturally cooled to below 80℃, it was discharged, crushed, and sieved. The material was then placed back into the roller furnace and sprayed with acetone solution again, sintering at a constant temperature of 780℃ for 10 hours. After the material naturally cooled to below 80℃, it was discharged. The product from the second sintering was then subjected to air jet milling to obtain carbon-coated LiFe. 0.998 Ti 0.002 PO4.

[0149] (2) Preparation of the positive electrode sheet:

[0150] The first positive electrode active material, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black were dissolved in the solvent N-methylpyrrolidone (NMP) at a mass ratio of 96:2:2. After thorough stirring and mixing, a positive electrode slurry was prepared. The positive electrode slurry was uniformly coated on the positive electrode current collector aluminum foil, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0151] (3) Preparation of negative electrode sheet:

[0152] Artificial graphite (anode active material), acetylene black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC-Na) (thickener) were dissolved in deionized water at a mass ratio of 96:2:1:1 and thoroughly mixed to prepare a cathode slurry. The cathode slurry was then coated onto copper foil (anode current collector), and subsequently dried, cold-pressed, and slit to obtain the cathode sheet.

[0153] (4) Separation membrane: Polypropylene membrane is used.

[0154] (5) Fabrication of the first battery cell:

[0155] The positive electrode, separator, and negative electrode are stacked and wound in sequence to obtain the first battery cell. The first battery cell has a maximum voltage range capacity C throughout its entire life cycle. A Designed for 100 Ah.

[0156] (II) Preparation of the second battery cell

[0157] (1) Preparation of the second positive electrode active material:

[0158] Prepare a mixed solution by adding water to NiSO4, CoSO4 and MnSO4 in a molar ratio of 0.55:0.141:0.249, wherein the concentration of NiSO4 in the mixed solution is 2 mol / L; prepare a 5 mol / L NaOH solution.

[0159] 50 L of mixed solution was introduced into the reactor, followed by 50 L of NaOH solution and an appropriate amount of 0.5 mol / L ammonia solution, to adjust the pH of the reactor to 9.0-12.0. The reaction temperature was 40℃-80℃, and the reaction was carried out for 60 h with stirring at a speed of 300-1000 r / min. After the reaction was completed, the precipitate was filtered out and washed. The washed precipitate was then vacuum dried at 120℃ for 24 h to obtain the precursor.

[0160] Li₂CO₃, precursor, Al₂O₃, and MgO were mixed, with the molar ratio of Li₂CO₃ (based on the molar amount of Li), precursor (based on the total molar amount of Ni, Co, and Mn in the mixed solution), Al₂O₃ (based on the molar amount of Al) to MgO being 1.05:0.94:0.04:0.02. The mixture was then ball-milled in a ball mill at 300 r / s for 2 h. Afterward, it was placed in a chamber furnace and pre-calcined at 950 °C for 12 h in an air atmosphere at a heating rate of 1 °C / min. The temperature was then decreased to 600 °C at a rate of 1 °C / min and held for 8 h for sintering. After sintering, the temperature was decreased to 300 °C at a rate of 1 °C / min and allowed to cool naturally to room temperature. Finally, the mixture was passed through an air jet mill at 3000 r / min and a 500 m³ / min flow rate. 3The material is pulverized at an airflow rate of / h for 0.5h, then sieved through a 500-mesh filter to obtain the second positive electrode active material, LiNi. 0.55 Co 0.141 Mn 0.249 Al 0.04 Mg 0.02 O2.

[0161] (2) Preparation of the positive electrode sheet:

[0162] The second positive electrode active material, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black were dissolved in the solvent N-methylpyrrolidone (NMP) at a mass ratio of 96:2:2. After thorough stirring and mixing, a positive electrode slurry was prepared. The positive electrode slurry was uniformly coated on the positive electrode current collector aluminum foil, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0163] (3) Preparation of negative electrode sheet:

[0164] Artificial graphite (anode active material), acetylene black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC-Na) (thickener) were dissolved in deionized water at a mass ratio of 96:2:1:1 and thoroughly mixed to prepare a negative electrode slurry. The negative electrode slurry was then coated onto copper foil (anode current collector), and subsequently dried, cold-pressed, and slit to obtain the negative electrode sheet.

[0165] (4) Separation membrane: Polypropylene membrane is used.

[0166] (5) Preparation of the second battery cell:

[0167] The positive electrode, separator, and negative electrode are stacked and wound in sequence to obtain the second cell. The second cell has a maximum voltage range capacity C throughout its entire life cycle. B Designed for 100 Ah.

[0168] (III) Preparation of electrolyte:

[0169] Ethyl carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1. LiPF6 was then uniformly dissolved in this solution to obtain the electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L.

[0170] (iv) Preparation of secondary batteries:

[0171] Three first cells and two second cells are assembled into an electrode assembly; the electrode assembly is placed in a housing, the electrolyte prepared above is added, and after processes such as encapsulation, settling, formation, and aging, a secondary battery is obtained.

[0172] Examples 2-24 and Comparative Examples 1-3 are similar to the secondary battery preparation methods in Example 1, with different product parameters detailed in Table 1.

[0173] The NP is adjusted by changing the ratio of the coating mass of the positive electrode paste on the positive electrode current collector to the coating mass of the negative electrode paste on the negative electrode current collector in the first battery cell. A1 and NP A2 .

[0174] The NP is adjusted by modifying the ratio of the coating mass of the positive electrode paste on the positive electrode current collector to the coating mass of the negative electrode paste on the negative electrode current collector in the second battery cell. B1 and NP B2 .

[0175] By using different sized housings, the widest voltage range capacity C across the entire lifecycle of the first or second cell can be achieved. A Or C B Design requirements.

[0176] Comparative Example 3 uses 5 first cells. The first positive electrode active material in Examples 2-24 and Comparative Examples 1-3 is a carbon-coated core material.

[0177] Preparation method of the first positive electrode active material in Example 24

[0178] Step S1: Preparation of co-doped manganese oxalate

[0179] 689.6 g of manganese carbonate, 455.3 g of ferrous carbonate, 4.7 g of cobalt sulfate, and 4.7 g of vanadium dichloride were added to a mixer and mixed thoroughly for 6 h. The resulting mixture was then transferred to a reaction vessel, and 5 L of deionized water and 1260.6 g of oxalic acid dihydrate were added. The mixture was heated to 80°C and stirred thoroughly at 500 rpm for 6 h until homogeneous mixing and the reaction was terminated without bubble formation, yielding a Fe, Co, and V co-doped manganese oxalate suspension. The suspension was then filtered, dried at 120°C, and milled to obtain manganese oxalate particles with a particle size of 100 nm.

[0180] Step S2: Prepare the kernel

[0181] 1793.1 g of the prepared manganese oxalate, 369.8 g of lithium carbonate, 1148.9 g of ammonium dihydrogen phosphate, and 0.8 g of silicic acid were added to 20 L of deionized water and stirred thoroughly. The mixture was then uniformly mixed and reacted at 80 °C for 10 h to obtain a slurry. The slurry was transferred to a spray dryer for spray drying and granulation, and dried at 250 °C to obtain a powder. Under a protective atmosphere (90% nitrogen and 10% hydrogen), the powder was sintered in a roller kiln at 700 °C for 4 h to obtain carbon-coated Li. 1.001 Mn0.60 Fe 0.393 V 0.004 Co 0.003 P 0.999 Si 0.001 O4.

[0182] Preparation methods of the third positive electrode active material in Examples 8-12 and 21

[0183] Step S1: Preparation of Fe, Co, V and S co-doped manganese oxalate

[0184] 689.6 g of manganese carbonate, 455.3 g of ferrous carbonate, 4.7 g of cobalt sulfate, and 4.9 g of vanadium dichloride were added to a mixer and mixed thoroughly for 6 h. The resulting mixture was then transferred to a reaction vessel, and 5 L of deionized water and 1260.6 g of oxalic acid dihydrate were added. The mixture was heated to 80 °C and stirred thoroughly at 500 rpm for 6 h until homogeneous mixing and the reaction was terminated without bubble generation, yielding a Fe, Co, and V co-doped manganese oxalate suspension. The suspension was then filtered, dried at 120 °C, and milled to obtain manganese oxalate particles with a particle size of 100 nm.

[0185] Step S2: Prepare the kernel

[0186] Take 1793.1 g of manganese oxalate, 369.8 g of lithium carbonate, 1148.9 g of ammonium dihydrogen phosphate, and 0.8 g of silicic acid prepared in (1), add them to 20 L of deionized water, stir thoroughly, and react uniformly at 80℃ for 10 h to obtain a slurry. Transfer the slurry to a spray drying equipment for spray drying and granulation, and dry at 250℃ to obtain a powder. In a protective atmosphere (90% nitrogen and 10% hydrogen), sinter the powder in a roller kiln at 700℃ for 4 h to obtain the core material. Use inductively coupled plasma atomic emission spectrometry (ICP) to detect the elemental content of the core material to obtain the core.

[0187] Step S3: Preparation of the first coating layer suspension

[0188] Preparation of Li2FeP2O7 solution: 7.4g lithium carbonate, 11.6g ferrous carbonate, 23.0g ammonium dihydrogen phosphate and 12.6g oxalic acid dihydrate were dissolved in 500mL deionized water, and the pH was controlled at 5. The mixture was then stirred and reacted at room temperature for 2h to obtain a solution. The solution was then heated to 80℃ and maintained at this temperature for 4h to obtain the first coating layer suspension.

[0189] Step S4: Coating with the first coating layer

[0190] The 1571.9g of doped lithium manganese phosphate core material obtained in step S2 was added to the first coating layer suspension (coating material content of 15.7g) obtained in step S3. The mixture was stirred and mixed thoroughly for 6 hours. After being mixed evenly, the mixture was dried in an oven at 120℃ for 6 hours and then sintered at 650℃ for 6 hours to obtain the pyrophosphate coated material.

[0191] Step S5: Preparation of the second coating layer suspension

[0192] 3.7 g lithium carbonate, 11.6 g ferrous carbonate, 11.5 g ammonium dihydrogen phosphate and 12.6 g oxalic acid dihydrate were dissolved in 1500 mL deionized water, stirred and reacted for 6 h to obtain a solution. The solution was then heated to 120 °C and maintained at this temperature for 6 h to obtain a second coating layer suspension.

[0193] Step S6: Coating with the second coating layer

[0194] The 1586.8g of pyrophosphate-coated material obtained in step S4 was added to the second coating suspension (coating material content of 47.1g) obtained in step S5. The mixture was stirred and mixed thoroughly for 6 hours. After mixing evenly, the mixture was dried in an oven at 120℃ for 6 hours and then sintered at 700℃ for 8 hours to obtain the two-layer coated material.

[0195] Step S7: Preparation of the third coating layer aqueous solution

[0196] Dissolve 37.3g of sucrose in 500g of deionized water, then stir and dissolve completely to obtain a sucrose aqueous solution.

[0197] Step S8: Coating with the third coating layer

[0198] 1633.9g of the two-layer coated material obtained in step S6 was added to the sucrose solution obtained in step S7 and stirred together for 6 hours. After mixing evenly, the mixture was placed in a 150°C oven and dried for 6 hours. Then, it was sintered at 700°C for 10 hours to obtain the third positive electrode active material with three layers.

[0199] Table 1: Parameter results of Examples 1-24 and Comparative Examples 1-3

[0200] In the above table:

[0201] a: When the state of charge of a single-cell battery, including the first cell, is in the range of 95% to 100%, the voltage of the first cell changes accordingly for every 1% change in the state of charge of the single-cell battery.

[0202] b: When the state of charge of a single-cell battery, including the second cell, is in the range of 95% to 100%, the voltage of the second cell changes accordingly for every 1% change in the state of charge of the single-cell battery.

[0203] c: The mass percentage of the second positive electrode active material in the first and second positive electrode active materials;

[0204] condition : 0.7 ≤ NPA1 ≤ 1.05 NPB1 and NPA1 < 1; condition : 0.75 ≤ NPA2 ≤ 1.05 NPB2 and NPA2 < 1.2

[0205] Battery test

[0206] (1) When the state of charge (SOC) of a single-cell battery is in the range of 95% to 100%, the voltage change of the first or second cell is measured for every 1% change in the SOC of the single-cell battery:

[0207] Assemble the first or second cell into a single-cell battery according to item (iv) above.

[0208] Single-cell battery test of the first cell: In a constant temperature environment of 25℃, the battery was left to stand for 10 minutes, then discharged at a constant current of 0.1C to the cutoff voltage of 2.8V. After standing for 10 minutes, it was charged at a constant current of 0.04C to the target voltage of 3.65V. After standing for 10 minutes, it was discharged at a constant current of 0.04C to the cutoff voltage of 2.8V. After standing for 10 minutes, it was charged at a constant current of 0.04C to the target voltage of 3.65V. The charging capacity at this time was recorded as 100% SOC. After standing for 10 minutes, it was discharged at a constant current of 0.04C to the cutoff voltage of 2.8V. The charging capacity of the last charging process was plotted on the y-axis and the voltage on the x-axis. The voltage Vm corresponding to 95% SOC and the voltage Vn corresponding to 100% SOC were obtained from the graph. When the state of charge of the battery is in the range of 95% to 100%, the voltage change of the first cell is (Vn1-Vm1) / 5 for every 1% change in the state of charge of the battery. The target voltage for the first cell in Example 24 is 4.25V.

[0209] Single-cell battery test of the second cell: In a constant temperature environment of 25℃, the battery was left to stand for 10 minutes, then discharged at a constant current of 0.1C to the cutoff voltage of 2.8V. After standing for 10 minutes, it was charged at a constant current of 0.04C to the target voltage of 4.25V. After standing for 10 minutes, it was discharged at a constant current of 0.04C to the cutoff voltage of 2.8V. After standing for 10 minutes, it was charged at a constant current of 0.04C to the target voltage of 4.25V. The charging capacity at this time was recorded as 100% SOC. After standing for 10 minutes, it was discharged at a constant current of 0.04C to the cutoff voltage of 2.8V. The charging capacity of the last charging process was plotted on the y-axis and the voltage on the x-axis. The voltage Vm corresponding to 95% SOC and the voltage Vn corresponding to 100% SOC were obtained from the graph. When the state of charge of the battery is in the range of 95% to 100%, the voltage change of the second cell is (Vn2-Vm2) / 5 for every 1% change in the state of charge of the battery.

[0210] (2) Testing of the lithium delithiation capacity of the positive electrode and the lithium insertion capacity of the negative electrode:

[0211] The positive electrode and negative electrode are respectively made into a coin cell with a counter electrode lithium sheet.

[0212] Testing of the coin cell with positive electrode: In a constant temperature environment of 25℃, charge at a constant current of 0.1C to 4.35V, and then discharge at 0.1C to 2.8V. Record the discharge capacity of the first cycle. Divide the discharge capacity of the first cycle by the mass of the positive active material in the positive electrode to obtain the first lithium removal capacity of the positive electrode. Continue to charge and discharge the coin cell twice in the above manner, for a total of three charge and discharge cycles. Record the capacity of the second charge and discharge cycle as the discharge capacity of the non-first cycle. Divide the discharge capacity of the non-first cycle by the mass of the positive active material in the positive electrode to obtain the non-first lithium removal capacity of the positive electrode.

[0213] Testing of the coin cell with negative electrode: In a constant temperature environment of 25℃, charge at a constant current of 0.1C to 2.0V, and then discharge at 0.1C to 0V. Record the discharge capacity of the first cycle. Divide the discharge capacity of the first cycle by the mass of the negative electrode active material in the negative electrode to obtain the initial lithium insertion capacity of the negative electrode. Continue to charge and discharge the coin cell twice in the above manner, for a total of three charge and discharge cycles. Record the capacity of the second charge and discharge cycle as the discharge capacity of the non-first cycle. Divide the discharge capacity of the non-first cycle by the mass of the negative electrode active material in the negative electrode to obtain the non-initial lithium insertion capacity of the negative electrode.

[0214] (3) Determine whether the upper limit voltage of the second cell has increased:

[0215] In a constant temperature environment of 25℃, the battery is discharged at 0.33C to the lower cutoff voltage limit of 2.8V, left to stand for 10 minutes, and then charged at a constant current of 0.33C to the upper cutoff voltage limit of 5V. Finally, it is charged at a constant voltage to ≤0.05C, and the resulting charging capacity is recorded as the nominal capacity. During the charging process, the voltage data of the second cell is monitored to obtain the upper limit voltage of the second cell corresponding to the nominal capacity. This discharge-charge cycle is repeated 100 times. During the last charging cycle, the voltage data of the second cell is monitored to obtain the upper limit voltage of the second cell in the last cycle. If the upper limit voltage of the second cell in the last cycle minus the upper limit voltage of the second cell corresponding to the nominal capacity is greater than 0.05V, then the upper limit voltage of the second cell is considered to have increased; otherwise, its upper limit voltage has not increased.

[0216] (4) Overcharge protection test:

[0217] In a constant temperature environment of 25℃, the battery is charged at 0.1C to the upper limit of the cutoff voltage, and then discharged at 0.33C to the lower limit of the cutoff voltage. The values ​​of the upper and lower cutoff voltages are shown in Table 2. The battery is charged and discharged 200 times in the above manner. The battery is disassembled. If the lithium plating area (excluding corner positions) on the negative electrode sheet accounts for more than 1 / 5 of the total area of ​​the negative electrode sheet, it is considered to have failed the overcharge protection test and is marked as NG. Otherwise, it is considered to have passed the overcharge protection test and is marked as OK.

[0218] (5) Cycle life test:

[0219] In a constant temperature environment of 25℃, the battery was left to stand for 10 minutes, then discharged at 0.33C to 2.8V; after standing for 10 minutes, it was charged at a constant current of 0.1C to 4.3V, then charged at a constant voltage until the current ≤0.05C, and after standing for 10 minutes, discharged at 0.33C to 2.8V. The discharge capacity of the battery in the first cycle was recorded as D1. The above charging and discharging operation was repeated, and the discharge capacity of each cycle was recorded as D. n (n=2, 3...); Calculate the cell's state of health (SOH) according to the following formula, and record the number of cycles n when the state of health reaches 90% SOH.

[0220] Cell degradation rate = 100% × D n / D3.

[0221] Table 2: Performance test results of Examples 1-24 and Comparative Examples 1-3

[0222] Based on the above results, we can conclude that:

[0223] Compared with Comparative Examples 1-3, the batteries of Examples 1-24 of this application have higher safety and longer cycle life.

[0224] Compared with Examples 5-7, 17, and 19-22, the batteries of Examples 1-4, 8-16, and 23-24 of this application have a longer cycle life.

[0225] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery comprising a cell assembly, the cell assembly including a first cell and a second cell, the number of the first cells being greater than or equal to the number of the second cells, and both the first cell and the second cell including a positive electrode and a negative electrode; Furthermore, the cell assembly satisfies: 0.7≤ NP A1 ≤1.05 NP B1 And NP A1 <1, or 0.75≤ NP A2 ≤1.05 NP B2 And NP A2 <1.2; in, NP A1 NP is the ratio of the initial lithium insertion capacity of the negative electrode to the initial lithium extraction capacity of the positive electrode in the first cell. B1 NP is the ratio of the initial lithium insertion capacity of the negative electrode to the initial lithium extraction capacity of the positive electrode in the second cell. A2 NP is the ratio of the non-first lithium insertion capacity of the negative electrode to the non-first lithium extraction capacity of the positive electrode in the first cell. B2 It is the ratio of the non-first lithium insertion capacity of the negative electrode to the non-first lithium removal capacity of the positive electrode in the second cell; When the state of charge of a single-cell battery including the second cell is in the range of 95% to 100%, for every 1% change in the state of charge of the single-cell battery, the voltage of the second cell changes by more than 5mV.

2. The battery according to claim 1, wherein, When the state of charge of a single-cell battery including the first cell is in the range of 95% to 100%, for every 1% change in the state of charge of the single-cell battery, the voltage change of the first cell is less than or equal to 5mV.

3. The battery according to claim 1 or 2, wherein it satisfies: 0.08 ≤ (1.1-NP A1 ) / (NP B1 -1) ≤20; Preferably, 0.1 ≤ (1.1 - NP) A1 ) / (NP B1 -1) ≤15.

4. The battery according to any one of claims 1 to 3, wherein it satisfies: 0.95≤C B / C A ≤1.4, can be replaced with 1.0≤C B / C A ≤1.3; in, C A C represents the widest voltage range capacity across the entire lifecycle of the first battery cell. B This represents the widest voltage range capacity for the second battery cell throughout its entire lifecycle.

5. The battery according to any one of claims 1 to 4, wherein, The positive electrode in the first battery cell includes a first positive active material, which contains the compound Li. a A x Mn 1-y B y P 1-z C z O 4-n D n ; Wherein, A includes one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo, and W; B includes one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; C includes one or more elements selected from B (boron), S, Si, and N; D includes one or more elements selected from S, F, Cl, and Br; a is 0.85-1.15; x is 0-0.1; y is 0.001-1; z is 0-0.5; and n is 0-0.

5.

6. The battery according to claim 5, wherein, The first positive electrode active material includes a core and a coating layer covering the core; wherein the core contains the compound Li. a A x Mn 1-y B y P 1-z C z O 4-n D n The coating layer contains carbon.

7. The battery according to any one of claims 1 to 6, wherein, The positive electrode in the second cell includes a second positive electrode active material; the second positive electrode active material contains the compound LiNi. b Co d Mn e M f O2; Wherein, M includes one or more elements selected from Mn, Al, Mg, Ca, Na, Ti, W, Zr, Sr, Cr, Zn, Ba, B, S, and Y, and may optionally include Mg and / or Al; b is 0.314-0.970; d is 0-0.320, and may optionally be 0.047-0.320; e is 0.006-0.390; and the sum of b, d, e, and f is 1 and f is greater than 0.

8. The battery according to claim 7, wherein, The positive electrode in the second cell further includes a third positive electrode active material; the third positive electrode active material includes a core and a shell covering the core, the shell including a first coating layer covering the core, a second coating layer covering the first coating layer, and a third coating layer covering the second coating layer; the core contains the compound Li. 1+g Mn 1-h E h P 1-i R i O4, the first coating layer contains crystalline pyrophosphate Li j GP2O7 and / or G k (P2O7) r The second coating layer contains crystalline phosphate X t PO4, the third coating layer contains carbon; Wherein, E includes one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and may optionally include one or more elements selected from Fe, V, Ni, and Co; R includes one or more elements selected from B, Si, N, and S, and may optionally include one or more elements selected from Si, N, and S; the crystalline pyrophosphate Li j GP2O7 and G k (P2O7) r Each of the G elements independently includes one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, and may optionally include one or more elements selected from Fe, Co, Ti, and Al; each of the X elements includes one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, and may optionally include one or more elements selected from Li, Fe, Ag, and Al; g is -0.100 to 0.100; h is 0.001 to 0.600; i is 0.001 to 0.100; j is greater than 0 and less than or equal to 2; k is 1 to 4; r is 1 to 3; and t is greater than 0 and less than or equal to 2.

9. The battery according to claim 8, wherein, In the positive electrode of the second cell, the mass of the second positive electrode active material accounts for 5%-100% of the total mass of the second positive electrode active material and the third positive electrode active material, and can be selected as 5%-95%.

10. The battery according to any one of claims 1 to 9, wherein, The upper limit voltage of the second cell during the 90th-110th charge-discharge cycle of the battery is greater than the upper limit voltage of the second cell during the first charge-discharge cycle of the battery.

11. An electrical device comprising the battery as described in any one of claims 1 to 10.

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