A lithium battery and a powered vehicle

Abstract

The application provides a lithium battery and a power vehicle. The lithium battery uses a lithium-containing phosphate material and a lithium transition metal oxide as a positive electrode active material, and links the mass proportion of the lithium transition metal oxide, the content of vinylene carbonate in a battery electrolyte, the discharge capacity of the lithium battery at 25 DEG C under 0.33C discharge and the direct current internal resistance, and controls them to meet certain conditions, so that the battery containing vinylene carbonate has good low-temperature rate performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a lithium battery and a power vehicle. BACKGROUND

[0002] Lithium ion batteries have been widely used in portable electronic devices (such as mobile phones, tablets, etc.), new energy vehicles and other fields. In particular, with the popularization of new energy vehicles in recent years, people have higher requirements for the safety performance, cycle performance and other performances of lithium ion batteries. The battery using lithium-containing phosphate (such as lithium iron phosphate) as the positive active material has high safety and low price, and is more widely used in new energy vehicles.

[0003] Among them, adding a film-forming additive to the electrolyte is one of the effective means to improve the cycle energy of the battery. Vinyl carbonate (VC) is one of the commonly used negative film-forming additives for lithium ion batteries, but the low-temperature rate performance of lithium batteries with VC is usually poor. Therefore, for lithium batteries with VC in the electrolyte, how to control the battery to have good low-temperature rate performance is a problem that needs to be solved at present. SUMMARY

[0004] In view of this, the lithium transition metal oxide is introduced into the lithium battery system with the positive electrode containing the lithium-containing phosphate material, and the mass ratio of the lithium transition metal oxide in the lithium-containing phosphate material and the VC content in the electrolyte, the discharge capacity of the lithium battery at 25℃ with 0.33C discharge and the direct current internal resistance are linked, and they are controlled to meet certain conditions, which can ensure that the lithium battery with VC in the electrolyte has good low-temperature rate performance.

[0005] In the first aspect, the present application provides a lithium battery, comprising a positive electrode sheet, a negative electrode sheet and an electrolyte, the positive electrode sheet comprises a positive electrode current collector and a positive electrode material layer arranged on at least one side surface of the positive electrode current collector, wherein the electrolyte contains vinyl carbonate (VC), and the mass ratio of VC in the electrolyte is α%; the positive electrode active material contained in the positive electrode material layer comprises a lithium-containing phosphate material and a lithium transition metal oxide; the mass ratio of the lithium transition metal oxide to the sum of the mass of the lithium-containing phosphate material and the lithium transition metal oxide is A%;

[0006] The lithium battery satisfies: 0.01≤DCIR×C0×α×A≤30;

[0007] Wherein, C0 is the discharge capacity of the lithium battery at 25℃ with 0.33C discharge, unit: Ah; DCIR is the direct current internal resistance of the lithium battery measured based on C0, unit: mΩ.

[0008] The lithium phosphate positive electrode material and the lithium transition metal oxide are used as the positive active material of the lithium battery, the good water absorption of the lithium transition metal oxide can reduce the damage degree of the SEI film caused by the residual moisture of the electrolyte, and the mass ratio A% of the lithium transition metal oxide in the sum of the lithium phosphate material and the lithium transition metal oxide is related to the mass content a% of VC in the electrolyte, the discharge capacity C0 of the battery at 0.33C at 25℃, and the direct current internal resistance DCIR, and the DCIRxC0xaxA is controlled in the range of 0.01-30, so that the lithium battery containing VC has good low-temperature rate performance.

[0009] In a second aspect, the embodiments of the present application also provide a power vehicle with the lithium battery of the first aspect of the present application.

[0010] Due to the use of the above-mentioned lithium battery with excellent performance, the market competitiveness of the power vehicle is outstanding. DETAILED DESCRIPTION

[0011] The embodiments of the present application provide a lithium battery, which comprises a positive electrode sheet, a negative electrode sheet and an electrolyte, the positive electrode sheet comprises a positive electrode current collector and a positive electrode material layer arranged on at least one side surface of the positive electrode current collector, wherein the electrolyte contains vinylene carbonate (VC), and the mass content of VC in the electrolyte is a%; the positive electrode active material contained in the positive electrode material layer comprises a lithium phosphate material and a lithium transition metal oxide; the mass of the lithium transition metal oxide accounts for A% of the sum of the mass of the lithium phosphate material and the lithium transition metal oxide;

[0012] The lithium battery satisfies 0.01≤DCIRxC0xaxA≤30;

[0013] Wherein, C0 is the discharge capacity of the lithium battery at 0.33C at 25℃, and the unit is Ah; DCIR is the direct current internal resistance of the lithium battery measured based on C0, and the unit is mΩ.

[0014] The lithium phosphate positive electrode material and the lithium transition metal oxide are used as the positive active material of the lithium battery, the good water absorption of the lithium transition metal oxide can reduce the damage degree of the SEI film caused by the residual moisture of the electrolyte, and the mass ratio A% of the lithium transition metal oxide in the sum of the lithium phosphate material and the lithium transition metal oxide is related to the mass content a% of VC in the electrolyte, the discharge capacity C0 of the battery at 0.33C at 25℃, and the direct current internal resistance etc., and the DCIRxC0xaxA is controlled in the range of 0.01-30, so that the battery containing VC has good low-temperature rate performance.

[0015] For the convenience of expression, DCIRxC0xαx A can be represented by the letter X. X represents the degree of influence of the lithium transition metal oxide on the low-temperature rate performance of the battery with VC added. X is in the range of 0.01-30, which can ensure that the battery has high discharge capacity and good rate performance at low temperature. Exemplarily, X can be specifically 0.01, 0.05, 0.08, 0.1, 0.15, 0.2, 0.3, 0.5, 0.6, 0.8, 1, 2, 3, 5, 8, 9, 10, 12, 15, 20, 25, 28, 29 or 29.5, etc.

[0016] The above VC-containing lithium battery provided by the embodiments of the present application can have good low-temperature rate performance when the above conditions are met, and can provide a thought / reference standard for manufacturing a battery with excellent performance.

[0017] In the above parameters, C0 and DCIR are measured for a full-pack lithium battery. The shape of the lithium battery is not particularly limited and can be square, cylindrical, etc. C0 is specifically the discharge capacity of the lithium battery after 0.33C charging and discharging for 3 times at 25°C, and C0 can be referred to as the calibrated discharge capacity of the lithium battery at room temperature. The specific test method of DCIR can be referred to the description hereinafter.

[0018] The mass percentage of VC in the electrolyte of the lithium battery is α%, which can be obtained by analyzing and determining the composition of the electrolyte after disassembling the lithium battery. The above mass percentage A% of the lithium transition metal oxide can be obtained by analyzing and determining the composition of the positive active material in the positive electrode sheet after disassembling the lithium battery.

[0019] In some embodiments of the present application, the above X is in the range of 0.05-30. When X is in this range, the above lithium battery can have good low-temperature rate performance while having good high-temperature cycle performance. That is, the lithium battery can better balance the low-temperature rate performance and the high-temperature cycle performance.

[0020] In some embodiments of the present application, the above α is in the range of 0.05-3, for example, specifically 0.06, 0.08, 0.1, 0.2, 0.5, 0.8, 1, 1.2, 1.3, 1.5, 2, 2.2, 2.5, 2.9, etc.

[0021] In the present application, in the system composed of the lithium phosphate material and the lithium transition metal oxide, the mass percentage of the lithium transition metal oxide is A%, and the mass percentage of the lithium phosphate material is B%, wherein A+B=100. It can be understood that the positive active material of the present application can also include other active materials in addition to the lithium phosphate material and the lithium transition metal oxide. In some embodiments of the present application, the above-mentioned A is in the range of 5-50. That is, the mass of the lithium transition metal oxide accounts for 5%-50% of the sum of the mass of the lithium phosphate material and the lithium transition metal oxide, for example, specifically 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 15%. The lithium transition metal oxide is introduced in an appropriate proportion, which can ensure that the residual moisture in the electrolyte is fully absorbed, reduce the probability of damage to the SEI film, and ensure that the low-temperature performance of the above-mentioned lithium battery is good, while the safety performance of the battery is not significantly reduced.

[0022] In the present application, the lithium phosphate material includes a phosphate containing lithium and transition metal elements. The lithium phosphate material includes LiM 1 PO4, M 1 includes transition metal elements. Wherein M 1 includes at least one or more of Fe and Mn. In some embodiments, M 1 In addition to including one or more of Fe and Mn, at least one of Ti, Zr, V, Cr, Al is also included. Wherein when M 1 is two or more elements, the sum of the subscripts of each element is 1, that is, the sum of the moles of each element is equal to the Li element.

[0023] In some embodiments, the lithium phosphate material includes LiFe 1-a Mn a PO4, 0≤a≤1, preferably 0≤a≤0.8. Wherein when a=0, the lithium phosphate material is specifically a lithium iron phosphate material (abbreviated as LFP); when a=1, the lithium phosphate material is specifically a lithium manganese phosphate material; when 0

[0024] Optionally, the surface of the lithium phosphate material can also have a conductive coating layer (such as a conductive carbon layer) to improve its conductivity.

[0025] In the present application, the lithium transition metal oxide is an oxide containing lithium element and transition metal element. The type of transition metal element contained in the lithium transition metal oxide can be one or more. In addition, the lithium transition metal oxide can further include other metal elements (such as main group metal elements) in addition to the transition metal element.

[0026] In the present application, the lithium transition metal oxide includes LiNi x Co y M 3 z O2, wherein x≥0, y≥0, z≥0, x+y+z=1; M 3 may be selected from one or more of Mn, Al, Mg, Sr, V, Fe, Cr, Ni, Cu, Zn, Zr, Ti, Y and W, and when M 3 x and y are not simultaneously 0 when M is at least one of main group metal elements Al, Mg, Sr. Preferably, x>0, 0<y<1. The lithium transition metal oxide at this time can be referred to as "a nickel-cobalt-containing ternary positive electrode material". In some embodiments, 0.33≤x≤0.98. Optionally, 0.01≤y≤0.33. 0.01≤z≤0.33. When x takes a higher value, the lithium transition metal oxide has higher basicity and better water absorption. Preferably, 0.70≤x≤0.98, further preferably, 0.80≤x≤0.90, further preferably, 0.83≤x≤0.88. In some embodiments, M 3 may be selected from at least one of Mn and Al.

[0027] In the present application, the positive electrode material layer can be disposed on one side surface or opposite two side surfaces of the positive electrode current collector. The positive electrode material layer contains, in addition to the positive electrode active material, a binder and a conductive agent. Among them, the types and contents of the binder and the conductive agent are conventional choices in the battery field. Exemplarily, the binder can be selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polyimide (PI), polyacrylic acid (PAA), polyacrylate, polyolefins (such as polyethylene, polypropylene, polystyrene), styrene butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), sodium alginate, etc. The conductive agent can be selected from at least one of conductive carbon black (such as acetylene black, ketjen black), carbon nanotubes (CNT), graphene, carbon fibers, graphite, etc., but is not limited thereto. In addition, the positive electrode current collector can include, but is not limited to, a metal film material, a foamed metal mesh, etc., and for example, can be specifically an aluminum foil, an aluminum foil with a conductive layer on the surface (carbon-coated aluminum foil), etc. The solvent in the positive electrode slurry used to form the positive electrode material layer can be selected from one or more of N-methyl pyrrolidone (NMP), dimethylformamide (DMF), diethylformamide (DEF), water, and alcohols, and preferably, the solvent includes NMP. The content of the solvent in the positive electrode slurry is not particularly limited, and can be sufficient to satisfy the flowability and uniformity of the positive electrode slurry coating.

[0028] The present application does not limit the area density and compaction of the above-mentioned positive electrode sheet, and can be designed according to the specific electrochemical system. In some embodiments, the positive electrode sheet of the present application is a double-sided positive electrode sheet with an area density of 300-500 g / m 2 , and the compaction density thereof can be 2.40-3.3 g / cm 3 .

[0029] In the present application, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side surface of the negative electrode current collector, and the negative electrode active material layer contains a negative electrode active material, a binder, and optionally a conductive agent. Among them, the negative electrode active material can include, but is not limited to, one or more of carbon materials, silicon-based materials, tin-based materials, and lithium titanate. Among them, the carbon material includes one or more of soft carbon, hard carbon, graphitized carbon microspheres, and graphite (such as natural graphite or artificial graphite). The silicon-based material can include one or more of elemental silicon, silicon alloy, silicon oxide, silicon-carbon composite material, and silicon carbide. The tin-based material can include one or more of elemental tin, tin oxide, tin-based alloy, and tin-carbon compound. In some embodiments, the negative electrode active material includes graphite, and specifically can be natural graphite or artificial graphite. Similarly, the binder and the conductive agent in the negative electrode active material layer can be selected from the ranges described above for the positive electrode sheet. The negative electrode current collector can include, but is not limited to, a metal film material, a foamed metal mesh, etc., and for example, can be specifically a copper foil, a carbon-coated copper foil, etc.

[0030] The electrolyte of the present application contains electrolyte lithium salt, organic solvent and film-forming additive. The film-forming additive at least includes vinylene carbonate (VC). In some embodiments, the film-forming additive can also include at least one of vinyl ethylene carbonate (VEC), phenyl ethylene carbonate (PhEC), phenyl vinyl carbonate (PhVC), fluoroethylene carbonate (FEC) and the like. The organic solvent can include one or more of carbonate solvents, carboxylate solvents. The carboxylate solvent can include cyclic carbonate and / or linear carbonate. The specific composition of the electrolyte in the present application is not limited, which can be the conventional selection in the field of batteries. Generally, the injection coefficient of the electrolyte is generally 2.0-4.5 g / Ah.

[0031] The positive electrode sheet and the negative electrode sheet are separated by a separator to maintain the insulation between the two and the liquid retention property; the separator and the positive electrode sheet and the negative electrode sheet together constitute the battery cell, which is accommodated in the battery shell (such as aluminum plastic film), and the electrolyte is injected into the battery shell, i.e. the cell is soaked in the electrolyte. The separator of the present application is not particularly limited, which can be various separators commonly used in lithium batteries, including but not limited to single-layer PP (polypropylene) film, single-layer PE (polyethylene) film, double-layer PP / PE, double-layer PP / PP and triple-layer PP / PE / PP and the like.

[0032] The present application also provides a preparation method of a lithium battery, comprising the following steps:

[0033] The positive electrode slurry containing positive electrode active material is coated on at least one side surface of the positive electrode current collector to form a positive electrode sheet with a positive electrode material layer on the surface through drying and rolling; wherein the positive electrode active material includes lithium-containing phosphate material and lithium transition metal oxide, and the mass of the lithium transition metal oxide accounts for A% of the sum of the mass of the lithium-containing phosphate material and the lithium transition metal oxide;

[0034] The positive electrode sheet, the separator, the negative electrode sheet and the electrolyte containing vinylene carbonate are assembled into a lithium battery; wherein the mass fraction of vinylene carbonate in the electrolyte is α%;

[0035] The lithium battery satisfies 0.01≤DCIR×C0×α×A≤30;

[0036] Wherein, C0 is the discharge capacity of the lithium battery at 25℃ with 0.33C discharge, unit Ah; DCIR is the battery direct current resistance measured based on C0, unit mΩ.

[0037] The assembling process of the lithium battery includes: sequentially stacking the positive electrode sheet, the separator and the negative electrode sheet to make an electric core; containing the electric core in a battery shell, injecting electrolyte, and then sealing the battery shell to obtain the lithium battery. Generally, after the shell is sealed, before the battery is shipped, formation, aging and distribution processes can be performed to preliminarily activate and stabilize the battery.

[0038] The preparation method of the lithium battery can be used to prepare the lithium battery of the first aspect of the application. The parameters involved herein are as described above, and will not be repeated here.

[0039] The embodiment of the application also provides a power vehicle which can be provided with the lithium battery described above.

[0040] Since the lithium battery described above is used, it can provide power for the power vehicle for a long time at low temperature, so that the power vehicle has a long cruising range and high safety.

[0041] Since the power vehicle uses the lithium battery with excellent low-temperature rate performance, the battery can provide power for the power vehicle for a long time at low temperature, so that the power vehicle has a long cruising range, good charge-discharge tolerance and high safety, and the market competitiveness of the power vehicle is outstanding.

[0042] The technical solutions of the embodiments of the application will be further described below in combination with multiple specific embodiments.

[0043] Embodiment 1

[0044] Preparation of a lithium battery:

[0045] (1) Preparation of a positive electrode sheet:

[0046] Preparation of a positive electrode slurry: mix the positive electrode active material, the carbon nanotube CNT conductive agent and the carbon black SP conductive agent, the binder PVDF and the solvent NMP in a mass ratio of 100:12:0.3:2.5:55, and uniformly disperse to obtain the positive electrode slurry. The positive electrode active material specifically includes a mixture of lithium iron phosphate (LiFePO4, abbreviated as LFP) and lithium transition metal oxide (specifically single-crystal lithium nickel cobalt manganese oxide, with a general structure formula of LiNi 0.7 Co 0.1 Mn 0.2 O2, abbreviated as NCM). The particle size D50 of the LFP is 0.8-1.4 μm, and the gram capacity of the LFP is 142 mAh / g. The particle size D50 of the NCM is 3.5-5 μm, and the gram capacity of the NCM is 189 mAh / g.

[0047] Take 12 μm aluminum foil as the positive current collector, coat the above positive electrode slurry on one side surface of the aluminum foil, dry to form a positive electrode material layer; then, in the same way, coat the positive electrode slurry on the other side surface of the aluminum foil to form a positive electrode material layer, to obtain a double-sided positive electrode sheet; and roll, cut and die cut the double-sided positive electrode sheet to obtain a double-sided positive electrode sheet with a surface density of about 400 g / m 2 .

[0048] (2) Preparation of the negative electrode sheet:

[0049] Mix natural graphite, binder CMC, binder SBR and water in a mass ratio of 100:1.5:3:130 to obtain a negative electrode slurry; uniformly coat the negative electrode slurry on both side surfaces of a 8 μm thick copper foil, form negative electrode active material layers on both sides of the copper foil after baking at 110°C to remove water, and then roll, cut and die cut to obtain a double-sided negative electrode sheet.

[0050] (3) Assembly of the full battery:

[0051] Stack the above double-sided positive electrode sheet, negative electrode sheet and PP separator in a Z-shaped manner to assemble a one-way cell, accommodate the heat-pressed cell in a battery shell, inject an electrolyte containing VC (the electrolyte contains common lithium salt LiPF6, common organic solvent and VC) under vacuum according to an injection coefficient of 3.2 g / Ah, then seal the shell, and after high-temperature aging, formation, aging and capacity distribution, vacuum seal to obtain a square aluminum shell battery with a length of 80 mm, a width of 60 mm, a height of 7 mm and a capacity of 2.13 Ah.

[0052] The full battery of Example 1 was subjected to the following performance tests. The relevant results are also summarized in Table 1 below.

[0053] a) Discharge capacity test of the battery at 25°C with 0.33C: at 25°C, each battery was charged to 4.3V at 0.33C constant current and constant voltage, and then rested for 30 min; then discharged to 2.0V at 0.33C constant current, and then rested for 30 min; the above charging and discharging steps were repeated 3 times, and the capacity discharged in the 3rd time was recorded as C0, in Ah.

[0054] b) DCIR test: each battery was subjected to 3 times of charging and discharging at 0.33C at 25°C, with a voltage range of 2.0-4.3V, and the discharge capacity C0 discharged in the 3rd time was recorded; then each battery was charged to a cutoff current of 0.5C0 at 0.33C0 at 25°C, rested for 20 min and recorded the battery voltage V1 at the end of the rest; then discharged at 1.5C0 for 30 s and recorded the battery voltage V2 at the end of the discharge, wherein DCIR=(V1-V2) / 1.5C0, in mΩ.

[0055] c) -10°C low temperature discharge ratio test: at 25°C, the full battery is charged and discharged at 0.33C for 3 times, the voltage range is 2.0-4.3V, and the 3rd discharge capacity is recorded as C0 (i.e., C1-25°C 0.33C). Then the battery is placed in an environment at -10°C for 4h, and then charged and discharged at 0.33C for 3 times, the voltage range is 2.0-4.3V, and the 3rd discharge capacity C' is recorded. The ratio of C' to C0 is the low temperature discharge ratio γ of the battery. In other words, γ is the ratio of the discharge capacity of the lithium battery after being charged and discharged at 0.33C for 3 times at -10°C to the discharge capacity after being charged and discharged at 0.33C for 3 times at 25°C.

[0056] d) High temperature 45°C cycle performance test: at 25°C, the full battery is charged and discharged for 3 times, the voltage range is 2.0-4.3V, and the discharge capacity of the 3rd discharge is calibrated as the battery capacity C0. Then at 45°C, the battery is charged at 1C0 constant current and constant voltage to 4.3V, the cutoff current is 0.05C0, and then it is placed for 30min; then it is discharged at 1C0 constant current to 2.0V, and then it is placed for 30min. The above steps are repeated for 500 times, and the ratio of the capacity after 500 cycles at 45°C to the first discharge capacity at 45°C is the cycle capacity retention rate β.

[0057] e) The content of VC in the electrolyte measured from the disassembled battery: at 25°C, a suitable solvent (EP (specifically ethyl propionate) is injected into the battery cell; the battery cell injected with EP is sealed, and then shaken on a shaker for 24h until the pole piece is fully soaked, then the battery cell is disassembled, the liquid is taken out and tested by gas chromatography-mass spectrometry (GC-MS), and the composition and content of the solvent and additives in the electrolyte can be measured. The mass percentage of VC in the electrolyte is α%.

[0058] f) Test the composition of the positive active material in the positive pole piece of the disassembled battery: disassemble the above batteries and take out the positive pole piece, scrape off the powder, and analyze the composition of the collected powder material by inductively coupled plasma spectrometer (ICP). It is found by testing that the positive active material in the positive pole piece is a mixture of LFP with a mass percentage of B% and lithium transition metal oxide with a mass percentage of A%, A+B=100; the specific values of A and B are listed in Table 1.

[0059] In addition, the positive electrode sheets and lithium batteries of the remaining examples and comparative examples were prepared according to the parameters listed in Table 1, and the test results are also summarized in Table 1 below. Among them, the lithium transition metal oxides in Examples 2-8 and Comparative Examples 4-5 are NCMs, the same as in Example 1. The lithium transition metal oxide used in Example 9 is lithium nickelate (LNO, LiNiO2), and the lithium transition metal oxide used in Example 10 is lithium cobaltate (LiCoO2, LCO).

[0060] Part of the parameters and test results of each example and comparative example in Table 1

[0061]

[0062]

[0063] Note: Taking Example 2 as an example, α = 0.1, and parameter X = 0.143 x 0.1 x 5 = 0.07.

[0064] By comparing Examples 1-5 with Comparative Example 1 in Table 1, which have similar VC contents in the electrolyte, it can be seen that the positive electrode of Comparative Example 1 does not contain a lithium transition metal oxide (i.e., A is 0) that has better rate capability and low-temperature performance than the LFP material, so the value of parameter X is not within the range of 0.01-30 required by the present application, and the -10°C low-temperature discharge rate γ of the battery is only 62.4%. In addition, because there is no lithium transition metal oxide in the battery of Comparative Example 1 to adsorb the residual water in the system in advance, the HF produced by the hydrolysis of the fluorine-containing lithium salt in the electrolyte can damage the SEI film, and the high-temperature cycle performance of the battery (reflected by β in Table 1) is also poor. However, the X values of Examples 1-5, which have similar VC contents in the electrolyte as Comparative Example 1, are all within the range required by the present application, and the low-temperature discharge rates of the batteries are significantly better than that of Comparative Example 1, all of which are above 70%. Similarly, the comparison between Example 6 and Comparative Example 2, which has a positive electrode without a lithium transition metal oxide, also has similar rules as described above.

[0065] Similarly to Comparative Examples 1-2, the X value of the battery of Comparative Example 3, which has a positive electrode without a lithium transition metal oxide, is 0, which is not within the range required by the present application, and the -10°C low-temperature discharge rate of the battery is very low. Although the X values of the batteries of Comparative Examples 4-5 are not 0 (i.e., the positive electrode contains a lithium transition metal oxide), the X values are not within the range required by the present application (0.01≤X≤30), and the discharge rates of the batteries at -10°C are significantly reduced, and the low-temperature discharge performance is poor.

[0066] In summary, the battery provided by the embodiments of the present application introduces lithium transition metal oxide as a supplement of lithium-containing phosphate material, and controls the above-mentioned mass ratio A of lithium transition metal oxide and the content of VC in the electrolyte to meet the aforementioned definition parameter X in the range of 0.01-30, so as to ensure that the battery has good low-temperature rate performance. The comparative battery with or without lithium transition metal oxide in the positive electrode does not meet the aforementioned definition parameter X in the range of 0.01-30, and the low-temperature rate performance of the battery is poor. In addition, it can be known from the above Table 1 that when the types of positive electrode active materials contained in the positive electrode of the battery are the same (for example, Example 1 and Examples 2-8), the value of X is greater than 0.01, for example, in the range of 0.05-30, the high-temperature cycle performance of the lithium battery is better, and the battery can better balance the low-temperature rate performance and the high-temperature cycle performance.

[0067] The above-described embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent of the present application. It should be pointed out that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A lithium battery comprising a positive electrode sheet, a negative electrode sheet, and an electrolyte, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode material layer disposed on at least one side of the positive electrode current collector, characterized in that: The electrolyte contains vinylene carbonate, and the mass proportion of the vinylene carbonate in the electrolyte is α%. The positive electrode active material contained in the positive electrode material layer includes a lithium-containing phosphate material and a lithium transition metal oxide, and the mass of the lithium transition metal oxide accounts for A% of the sum of the mass of the lithium-containing phosphate material and the lithium transition metal oxide; The lithium battery satisfies: 0.01≤DCIR×C0×α×A≤30; Wherein, C0 is the discharge capacity of the lithium battery at 0.33C at 25° C., in Ah; DCIR is the DC internal resistance of the lithium battery measured based on C0, in mΩ.

2. The lithium battery according to claim 1, wherein 0.05≤DCIR×C0×α×A≤30.

3. The lithium battery according to claim 1, wherein The α is in the range of 0.05-3.

4. The lithium battery according to claim 1, wherein The A is in the range of 5-50.

5. The lithium battery according to any one of claims 1 to 4, wherein: The lithium phosphate material includes LiM 1 PO4, where M 1 Including transition metal elements.

6. The lithium battery according to claim 5, wherein The M 1 Contains at least one of Fe and Mn.

7. The lithium battery according to claim 5, wherein The surface of the lithium phosphate material further has a conductive coating layer.

8. The lithium battery according to any one of claims 1 to 4, wherein: The lithium transition metal oxide includes LiNi x Co y M 3 z O2, where x≥0, y≥0, z≥0, x+y+z=1; M 3 One or more selected from Mn, Al, Mg, Sr, V, Fe, Cr, Ni, Cu, Zn, Zr, Ti, Y and W, and when M 3 In the case of Al, Mg, or Sr, x and y are not 0 at the same time.

9. The lithium battery according to claim 8, wherein 0.33≤x≤0.98,0 <y<1。 10. A powered vehicle, characterized in that: The power vehicle is provided with a lithium battery as claimed in any one of claims 1 to 9.

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