A battery

Abstract

The application provides a battery, which comprises an electrolyte and a negative electrode; the electrolyte comprises an additive B with the structure of formula I; the negative electrode comprises a negative electrode active material layer; the powder conductivity of the negative electrode active material layer is a, with the unit of S / cm; the mass content of the additive B is b% based on the mass of the electrolyte; a and b satisfy the relationship formula: 6.5<=a / b<=550. In the application, only the additive B with the structure of formula I is added in the electrolyte, and the powder conductivity of the negative electrode active material layer in the negative electrode satisfies a certain relationship formula. When the relationship formula is satisfied, the degree of the electrolyte side reaction is low, the battery gas generation in the use process is reduced, and the fast charging performance and the high-temperature cycle life of the battery are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and particularly relates to a battery. BACKGROUND

[0002] Lithium ion batteries develop rapidly, and a lithium battery with higher energy density has become a future trend. While pursuing a lithium ion battery with higher energy density, the requirement for cycle performance also becomes higher and higher.

[0003] As the requirement for cycle performance becomes higher and higher, the voltage of the battery needs to be improved. However, with the increase of the voltage, the side reactions of solvents, additives and other components in the electrolyte are accelerated, which leads to serious gas production of the battery, and also produces hydrofluoric acid, thereby reducing the cycle performance of the ion battery and seriously affecting the performance of the ion battery. SUMMARY

[0004] Therefore, the purpose of the application is to provide a battery, and the battery assembled with the electrolyte has excellent cycle performance.

[0005] The application provides a battery, which comprises an electrolyte and a negative electrode.

[0006] The electrolyte comprises an additive B with the structure of formula I:

[0007]

[0008] R1, R2 and R3 are independently selected from -H or -C p H 2p+1 , wherein 1≤p≤4.

[0009] R4, R5 and R6 are independently selected from a vinyl group, an allyl group, an oxyvinyl group, an oxyallyl group, an oxyallyl group, an acetylenic ethyl group, an acetylenic propyl group, an oxyacetylenic ethyl group or an oxyacetylenic propyl group.

[0010] R7, R8 and R9 are independently selected from -H, -CH3 or -CH2CH3.

[0011] The negative electrode comprises a negative electrode active material layer.

[0012] The powder conductivity of the negative electrode active material layer is a S / cm.

[0013] The mass content of the additive B is b% based on the mass of the electrolyte, and a and b satisfy the following relationship:

[0014] 6.5≤a / b≤550.

[0015] The battery provided by the application has the following advantages: by adding only the additive B with the structure of formula I into the electrolyte, the mass content of the additive B is b% based on the mass of the electrolyte, and the powder conductivity a of the negative active material layer in the negative electrode satisfies the following relationship: 6.5≤a / b≤550, when the relationship is satisfied, the degree of electrolyte side reaction is low, the gas production of the battery during use is reduced, and thus the fast charging performance and high-temperature cycle life of the battery are improved. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The cycle capacity retention rate curve of the battery prepared for the example 1 and the comparative example 7 of the application at 60℃ is shown in the figure. DETAILED DESCRIPTION

[0017] The application provides a battery, which comprises an electrolyte and a negative electrode.

[0018] The electrolyte comprises an additive B with the structure of formula I:

[0019]

[0020] R1, R2 and R3 are independently selected from -H or -C p H 2p+1 wherein 1≤p≤4.

[0021] R4, R5 and R6 are independently selected from a vinyl group, an allyl group, an oxyvinyl group, an oxyallyl group, an oxyallyl group, an acetylenic ethyl group, an acetylenic propyl group, an oxyacetylenic ethyl group or an oxyacetylenic propyl group.

[0022] R7, R8 and R9 are independently selected from -H, -CH3 or -CH2CH3.

[0023] The negative electrode comprises a negative active material layer.

[0024] The powder conductivity of the negative active material layer is a, in S / cm.

[0025] The mass content of the additive B is b% based on the mass of the electrolyte, and a and b satisfy the following relationship:

[0026] 6.5≤a / b≤550.

[0027] In the application, only the additive B with the structure of formula I is added into the electrolyte, and the powder conductivity of the negative active material layer in the negative electrode satisfies a certain relationship, so that the degree of electrolyte side reaction is low, the gas production of the battery during use is reduced, and thus the fast charging performance and high-temperature cycle life of the battery are improved.

[0028] In the application, R1, R2 and R3 are all selected from -H, and R4, R5 and R6 are independently selected from an acetylenic ethyl group, an acetylenic propyl group, an oxyacetylenic ethyl group or an oxyacetylenic propyl group.

[0029] R1, R2 and R3 are each selected from -C p H 2p+1 R4, R5 and R6 are independently selected from vinyl or oxyethylene.

[0030] The powder conductivity of the negative active material layer in the present application is a, the mass content of the additive B is b%, a and b satisfy the relationship: 0.1≤a / b≤40; the addition of the additive B can effectively reduce the gas production of the electrolyte under high voltage, improve the high voltage resistance of the electrolyte, thereby improving the high temperature life of the battery; at the same time, due to the relationship between the powder conductivity of the negative active material and the addition amount of the additive B, the higher powder conductivity of the negative active material can improve the conductivity of the negative active material layer, thereby controlling the DCR of the whole battery system within a reasonable range, and the battery has excellent fast charging capacity.

[0031] The powder conductivity a of the negative active material layer in the present application is 5-20 S / cm, preferably 8-18 S / cm. In specific embodiments, the powder conductivity is 13.41 S / cm, 17.95 S / cm, 8.02 S / cm, 8.01 S / cm, 10.45 S / cm, 7.9 S / cm, 18.12 S / cm, 17.88 S / cm, 10.21 S / cm, 8.21 S / cm, 11.21 S / cm, 18.97 S / cm, 5.03 S / cm, 6.05 S / cm, 19.68 S / cm, 12.61 S / cm, 12.89 S / cm, 13.22 S / cm, 12.51 S / cm, 13.23 S / cm, 8.02 S / cm, 9.13 S / cm, 10.34 S / cm, 12.75 S / cm, 11.98 S / cm, 8.01 S / cm, 9.02 S / cm, 11.03 S / cm, 12.71 S / cm, 11.41 S / cm, 12.23 S / cm or 14.41 S / cm.

[0032] The mass content of the additive B in the present application is b% based on the mass of the electrolyte, 0.01%≤b≤3%, preferably 0.1%-1.5%. In specific embodiments of the present application, the mass content b of the additive B is 0.85%, 1.491%, 0.841%, 0.105%, 0.102%, 1.121%, 1.452%, 1.521%, 0.112%, 0.913%, 0.105%, 2.330%, 0.711%, 0.011%, 2.995%, 0.750%, 0.122%, 0.812%, 0.332%, 1.492%, 1.495%, 0.102%, 0.824%, 0.354%, 1.491% or 1.413%.

[0033] The relation formula satisfied by a and b in the application is 6.5<=a / b<=550, preferably 9.5~102.5; in specific embodiments, the value of a / b is 15.78, 12.04, 9.54, 76.29, 102.45, 65.29, 12.48, 11.76, 91.16, 8.99, 106.76, 8.14, 7.07, 550, 6.57, 16.81, 17.19, 17.63, 16.68, 17.64, 65.74, 11.24, 31.14, 8.55, 8.01, 78.53, 10.95, 31.16, 8.52, 8.08, 16.31 or 19.21.

[0034] The additive B having the structure of formula I provided by the application has a number of double bonds n, and the value range of n is 1~5; n is a positive integer; it can be 1, 2, 3, 4 or 5; preferably 2~3. When the double bond content of additive B is in this content range, the effect achieved is that a compact SEI can be formed after the negative electrode is reduced to play a role in protecting the negative electrode interface, and the electrolyte will not have a large impedance, which will not affect the kinetic performance of the battery.

[0035] The specific structure of formula I in the application includes formula (I1)~formula (I21):

[0036]

[0037]

[0038] The battery provided by the application further comprises a positive electrode;

[0039] The positive electrode comprises a positive electrode main material, a binder and a conductive agent;

[0040] The positive electrode main material is lithium iron phosphate or a ternary material or lithium manganese iron phosphate.

[0041] The mass ratio of the positive electrode main material, the binder and the conductive agent in the positive electrode of the application is (97~98):(1~1.5):(0.8~1.2); in specific embodiments, the mass ratio of the main material, the binder and the conductive agent in the positive electrode is 97.8:1.2:1.

[0042] In the application, the structure formula of the ternary material used in the positive electrode main material is LiNi x1 Co y Mn 1-x1-y O2(0<x1<1, 0<y<1). The structure formula of the lithium manganese iron phosphate used is LiMn x2 Fe (1-x2) PO4(0<x2<1). In specific embodiments, the ternary material is LiNi 0.4 Co 0.2 Mn0.4 O2; the lithium manganese iron phosphate is LiMn 0.4 Fe 0.6 PO4.

[0043] The battery provided by the application further comprises a negative electrode,

[0044] The negative electrode comprises a negative electrode main material, a binder and a conductive agent,

[0045] The particle size Dv50 of the negative electrode main material ranges from 5 to 20 μm; and the negative electrode main material is selected from one or more of natural graphite, artificial graphite, mesocarbon microbeads, hard carbon, soft carbon, silicon-oxygen, silicon-carbon and Li4Ti5O 12 .

[0046] The mass ratio of the negative electrode main material, the binder and the conductive agent in the negative electrode is (96-98.5):(1.0-2.5):(0.5-1.5); in a specific embodiment, the mass ratio of the negative electrode main material, the binder and the conductive agent in the negative electrode is 97.5:1.2:1.3.

[0047] The preparation method of the positive electrode sheet in the application is as follows:

[0048] The positive electrode main material, the binder and the conductive agent are dispersed in N-methyl pyrrolidone (NMP) according to a mass ratio of (95.5-98.2):(1-2.0):(0.8-2.5); the positive electrode slurry is coated on an aluminum foil to obtain an aluminum foil coated with the positive electrode slurry, and then rolling and cutting are performed to obtain the positive electrode sheet.

[0049] In a specific embodiment, the mass ratio of the positive electrode main material, the binder and the conductive agent is 97.8:1.2:1.

[0050] The positive electrode main material is lithium iron phosphate (particle size Dv50 ranging from 0.1 to 2 μm), lithium nickel cobalt manganese oxide (particle size Dv50 ranging from 3 to 15 μm) or any one of LiNi x1 Co y Mn 1-x1-y O2(0 x2 Fe (1-x2) PO4(0

[0051] When the positive electrode material is lithium iron phosphate, the single-sided compaction density of the positive electrode sheet is 2.2-2.6 g / cm 3 ; when the positive electrode material is lithium nickel cobalt manganese oxide, the single-sided compaction density of the positive electrode sheet is 3.2-3.8 g / cm 3 ; and when the positive electrode material is lithium manganese iron phosphate, the single-sided compaction density of the positive electrode sheet is 2.4-2.8 g / cm 3 .

[0052] The binder is selected from polytetrafluoroethylene or PVDF.

[0053] The conductive agent is selected from one or more of conductive carbon black, acetylene black and carbon nanotubes.

[0054] The preparation method of the negative electrode sheet in the present application:

[0055] The negative electrode main material, the binder and the conductive agent are dispersed in deionized water according to a mass ratio of (96-98.5):(1.0-2.5):(0.5-1.5), and the negative electrode slurry is coated on a copper foil; then rolling, sheet cutting are performed to obtain a negative electrode sheet;

[0056] The compaction density of the negative electrode sheet is 1.4-1.8 g / cm 3 ; in the embodiment, the compaction density of the negative electrode sheet is 1.6 g / cm 3 .

[0057] The negative electrode main material is selected from one or more of natural graphite, artificial graphite, mesocarbon microbeads, hard carbon, soft carbon, silicon-oxygen, silicon-carbon and Li4Ti5O 12 ; the negative electrode main material in the negative electrode sheet of the present application is selected from one or more of natural graphite, artificial graphite, mesocarbon microbeads, hard carbon, soft carbon, silicon-oxygen, silicon-carbon and Li4Ti5O 12 ; in a specific embodiment, the negative electrode main material is artificial graphite. The Dv50 of the negative electrode main material is 5-20 μm, and the Dv50 can be specifically 5 μm, 5.5 μm, 6.0 μm, 6.5 μm, 7.0 μm, 7.5 μm, 8.0 μm, 8.5 μm, 9.0 μm, 9.5 μm, 10.0 μm, 10.5 μm, 11.0 μm, 11.5 μm, 12.0 μm, 12.5 μm, 13.0 μm, 13.5 μm, 14.0 μm, 14.5 μm, 15.0 μm, 15.5 μm, 16.0 μm, 16.5 μm, 17.0 μm, 17.5 μm, 18.0 μm, 18.5 μm, 19.0 μm, 19.5 μm or 20 μm. In a specific embodiment, the Dv50 of the negative electrode active material is 10.5 μm, 7.6 μm, 17.2 μm, 17.1 μm, 12.2 μm, 17.4 μm, 7.3 μm, 7.7 μm, 12.8 μm, 10.5 μm, 6.4 μm, 19.8 μm, 18.3 μm, 5.2 μm, 11.4 μm, 11.2 μm, 10.9 μm, 11.6 μm, 15.1 μm, 12.3 μm, 11.3 μm, 12 μm, 17.2 μm, 15.2 μm, 12.4 μm, 11.3 μm, 12.1 μm, 11.6 μm or 9.4 μm, and the negative electrode main material is artificial graphite.

[0058] The binder is selected from one or more of polyacrylic acid (PAA), styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC);

[0059] The conductive agent is selected from one or more of conductive carbon black and carbon nanotubes.

[0060] The preparation method of the electrolyte in the application is as follows:

[0061] The solvent is mixed with the lithium salt to prepare a mixed solution with a lithium salt concentration of 0.5-1.5 mol / L, and the additive B is added and mixed to obtain the electrolyte.

[0062] The solvent includes but is not limited to at least one of ethylene carbonate (EC), methylene methanesulfonate (MMDS), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), propylene carbonate (PC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE). In a specific embodiment, the solvent is obtained by mixing ethylene carbonate and methyl ethyl carbonate at a mass ratio of 3:7.

[0063] The lithium salt includes but is not limited to at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate borate (LiDFOB), lithium difluorophosphate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorophosphate borate (LiDFOP) and lithium tetrafluorophosphate borate (LiTFOP). In a specific embodiment, the concentration of the lithium salt is 1 mol / L.

[0064] The separator in the application is selected from one of PP, PE and PP / PE.

[0065] The above battery is preferably prepared according to the following method:

[0066] The positive electrode sheet and the negative electrode sheet are prepared respectively;

[0067] The solvent is mixed with the lithium salt to prepare a mixed solution with a lithium salt concentration of 0.5-1.5 mol / L, and the additive B is added and mixed to obtain the electrolyte.

[0068] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in sequence and wound to obtain a bare battery cell;

[0069] The bare battery cell is placed in an outer packaging shell, electrolyte is injected after drying, and a lithium ion battery is obtained through vacuum packaging, injection, standing, formation, and constant volume.

[0070] The present application is not particularly limited to the processes of vacuum packaging, injection, standing, formation, and constant volume, and any method known to those skilled in the art can be used.

[0071] To further illustrate the present application, a battery provided by the present application is described in detail below in conjunction with examples, but they should not be construed as limiting the scope of protection of the present application.

[0072] Examples 1-30 and Comparative Examples 1-4

[0073] Referring to the values of the types and parameters of the raw materials in Table 1 and Table 2:

[0074] The method for preparing the battery comprises:

[0075] 1) Preparation of the positive electrode sheet:

[0076] The positive electrode main material lithium iron phosphate, the binder PVDF, and the conductive agent SP are dispersed in N-methyl pyrrolidone (NMP), the positive electrode slurry is coated on an aluminum foil to obtain an aluminum foil coated with a positive electrode slurry on the surface, and then rolling and cutting are performed to obtain a positive electrode sheet, with the compaction density of one side of the positive electrode sheet controlled at 2.3 g / cm 3 .

[0077] 2) Preparation method of the negative electrode sheet:

[0078] The negative electrode main material artificial graphite, the binder SBR, and the conductive agent SP are dispersed in deionized water, the negative electrode slurry is coated on a copper foil to obtain a copper foil coated with a negative electrode slurry on the surface, and a negative electrode sheet is obtained, with the compaction density of one side of the negative electrode sheet controlled at 1.6 g / cm 3 .

[0079] 3) Preparation method of the electrolyte:

[0080] The solvent is mixed with the lithium salt to prepare a mixed solution with a lithium salt concentration of 1 mol / L, the additive B is added, and the electrolyte is obtained by mixing;

[0081] The solvent is obtained by mixing ethylene carbonate and methyl ethyl carbonate at a mass ratio of 3:7; the lithium salt is lithium hexafluorophosphate.

[0082] 4) Separator: PP is selected as the separator;

[0083] The above positive electrode sheet, separator, and negative electrode sheet are stacked in order and wound to obtain a bare cell;

[0084] The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum packaging, injection, standing, formation, and constant volume, a lithium ion battery is obtained.

[0085] Example 31

[0086] Compared with Example 1, the differences include, in addition to those listed in Table 1, that the positive electrode main material used is ternary LiNi 0.4 Co 0.2 Mn 0.4 O2; the compaction density of the positive electrode sheet on one side is 3.3 g / cm 3 .

[0087] Example 32

[0088] Compared with Example 1, the differences include, in addition to those listed in Table 1, that the positive electrode main material used is lithium manganese iron phosphate LiMn 0.4 Fe 0.6 PO4; the compaction density of the positive electrode sheet on one side is 2.6 g / cm 3 .

[0089] Comparative Example 5

[0090] Compared with Comparative Example 1, the differences include, in addition to those listed in Table 2, that the positive electrode main material used is ternary LiNi 0.4 Co 0.2 Mn 0.4 O2; the compaction density of the positive electrode sheet on one side is 3.3 g / cm 3 .

[0091] Comparative Example 6

[0092] Compared with Comparative Example 1, the differences include, in addition to those listed in Table 2, that the positive electrode main material used is lithium manganese iron phosphate LiMn 0.4 Fe 0.6 PO4; the compaction density of the positive electrode sheet on one side is 2.6 g / cm 3 .

[0093] Comparative Example 7

[0094] Compared with Example 1, no additive B is added, and the rest is the same as Example 1. The performance results of the batteries prepared in the above examples and comparative examples are shown in Table 3:

[0095] Table 1

[0096]

[0097] Table 2

[0098]

[0099] Table 3

[0100]

[0101]

[0102] Test method:

[0103] 1. Test method of additive B content:

[0104] The battery is subjected to emptying electricity treatment using a battery charge-discharge device. The discharge condition is: current 0.3C, cut-off voltage 2.5V. After recording the battery number / barcode, the battery is disassembled in a glove box (H2O≤0.1ppm, O2≤0.1ppm) to collect the electrolyte.

[0105] There are two methods for collecting electrolyte: after disassembling the battery cover plate, ① if there is free electrolyte, use a pipette to collect the electrolyte into a 5mL sample tube, and use sealing glue to seal to prevent electrolyte leakage. ② If there is no free electrolyte, a hydraulic machine (FY-30 hydraulic machine from Beijing Hengao Technology Co., Ltd.) can be used to continuously press until free electrolyte appears, and the electrolyte is collected into a sample tube and sealed.

[0106] The collected electrolyte sample is injected into an Agilent Intuvo 9000 gas chromatograph-mass spectrometer for content testing:

[0107] ① Obtaining MS standard curve and LC peak area-concentration curve: EMC solutions of formula I1 to formula I21 with different concentrations are prepared and injected into the above liquid chromatograph-mass spectrometer, respectively, to obtain MS spectra and LC spectra of standard substances, respectively, and the peak areas in the LC spectra are integrated (routine processing of test data by test software) to obtain the peak areas. The peak areas of different concentrations of standard substances and the concentrations are plotted to obtain the standard LC peak area-concentration curve.

[0108] ② Type determination: the electrolyte to be tested is injected into the above liquid chromatograph-mass spectrometer to obtain the LC spectrum and MS spectrum of the electrolyte to be tested. The MS spectrum of the electrolyte to be tested is compared with the standard MS spectrum to determine whether the electrolyte to be tested contains additives of formula I1 to formula I21 (for example, if the MS spectrum of the electrolyte to be tested has a peak corresponding to the position of the peak of formula I1 in the standard spectrum, it is determined that the electrolyte to be tested contains additive B of formula I1, and other components are determined in the same way).

[0109] ③ Mass content determination:

[0110] The peak area is obtained by integrating the peaks in the LC chromatogram of the test electrolyte. According to the standard LC peak area-concentration curve, the concentration of the test substance can be obtained when the peak area is known.

[0111] 2. Test method for the number of double bonds in additive B:

[0112] The battery is subjected to emptying and electrical treatment using a battery charge and discharge device. The discharge conditions are: current 0.3C, cut-off voltage 2.5V. After recording the battery number / barcode, the battery is disassembled in a glove box (H2O≤0.1ppm, O2≤0.1ppm) to collect the electrolyte.

[0113] There are two methods for collecting the electrolyte: after the battery cover plate is removed, ① if there is free electrolyte, use a pipette to collect the electrolyte into a 5mL sample tube, and use sealing glue to seal the tube to prevent electrolyte leakage. ② If there is no free electrolyte, use a hydraulic machine (FY-30 hydraulic machine from Beijing Hengao Technology Co., Ltd.) to continuously press until free electrolyte appears, collect the electrolyte into a sample tube and seal it.

[0114] Experimental process:

[0115] 1) Weigh an appropriate amount of electrolyte sample into a 250ml iodometric flask, add 20g of deionized water, then add 5ml of acetone, shake well to dissolve. Continue to add 10ml of potassium bromide-potassium bromate solution and 5ml of hydrochloric acid solution, cover the flask with a cap and place it in the dark for 20 minutes, then add 10ml of potassium iodide solution, tightly cap the flask and place it for 20 minutes.

[0116] 2) The blank sample is the same as step 1 above, but without adding the test electrolyte sample

[0117] 3) Use the sodium thiosulfate standard solution to titrate the samples obtained in steps 1 and 2, respectively. After the sample color turns light yellow, add 2-3 drops of starch indicator, and then titrate to colorless. Record the amount of sodium thiosulfate standard solution used for titrating the sample obtained in step 1, denoted as V; record the amount of sodium thiosulfate standard solution used for titrating the sample obtained in step 2, denoted as V0.

[0118] Calculate the number of double bonds in the additive in the electrolyte sample according to formula (1):

[0119]

[0120] Where n: the number of double bonds contained in additive B;

[0121] c: the concentration of Na2S2O3, unit mol / L;

[0122] V: the amount of Na2S2O3 required for titrating m grams of electrolyte sample, unit L;

[0123] V0: The amount of Na2S2O3 required for titration of the blank sample, unit L;

[0124] m: The mass of the electrolyte sample, unit g;

[0125] b: The amount of additive B added in the electrolyte sample, unit %.

[0126] Preparation of the required solution:

[0127] 0.09 mol / L potassium bromate-potassium bromide solution (i.e. the concentration of potassium bromide is 0.09 mol / L): potassium bromate 2.8 g, potassium bromide 10 g, dissolved in a small amount of deionized water, diluted to 1000 mL;

[0128] 0.1 mol / L sodium thiosulfate standard solution (the most affected by the experiment, standard sample titration or purchase);

[0129] 10% potassium iodide solution: 10 g of potassium iodide is dissolved in 90 g of deionized water;

[0130] 1% starch indicator: 1 g of soluble starch is dissolved in 99 g of deionized water, heated to boiling and clarified, and after cooling, 0.125 g of benzoic acid is added for preservation;

[0131] 1:1 hydrochloric acid: deionized water mixed with 36% hydrochloric acid in equal volume;

[0132] 3. Test method of powder conductivity of negative electrode active material layer:

[0133] 1) Open circuit voltage: After recording the battery number / barcode, use the battery charge and discharge equipment to process the open circuit voltage of the battery, discharge conditions: current 0.3C, cut-off voltage 2.5V;

[0134] 2) Disassembly and cleaning: disassemble the battery in a room with dew point control, take out the negative electrode sheet, immerse the negative electrode sheet in a polytetrafluoroethylene box containing DMC solvent for 24 h, then take out the negative electrode sheet, and bake the cleaned electrode sheet at 60°C for 4 h to remove the residual DMC solvent, obtaining the electrode sheet to be tested;

[0135] 3) Powder scraping: scrape the electrode sheet, and gently grind the scraped powder in a mortar to eliminate clumps in the powder, and collect the powder for testing;

[0136] 4) Test: load the collected powder sample into the sample cell of YK22-FT-300II powder conductivity meter to test the conductivity, obtaining the powder conductivity of the negative electrode active material layer.

[0137] 4. Test method of negative electrode particle size

[0138] 1) Open-circuit voltage: After recording the battery number / barcode, the battery is subjected to open-circuit voltage treatment using a battery charge-discharge device, and the discharge conditions are: current 0.3C, cut-off voltage 2.5V;

[0139] 2) Disassembly and cleaning: The battery is disassembled in a room with dew point control, and the negative electrode sheet is taken out. The negative electrode sheet is soaked in a polytetrafluoroethylene box containing DMC solvent for 24h, and then the negative electrode sheet is taken out. The cleaned electrode sheet is baked to remove the residual DMC solvent, and the measured electrode sheet is obtained;

[0140] 3) Powder scraping: The electrode sheet is subjected to powder scraping treatment, and the scraped powder is gently ground using a mortar to eliminate the agglomerates in the powder. The powder is collected for measurement;

[0141] 4) Test: The particle size of the above negative electrode particles is tested using a scanning electron microscope detector.

[0142] 5. Fast charging performance test method

[0143] After recording the battery number / barcode, the battery is subjected to open-circuit voltage treatment using a battery charge-discharge device, and the discharge conditions are: current 0.33C, cut-off voltage 2.5V. Then, 0.33C is used for charge-discharge cycling, and the lower and upper limits of the voltage are 2.5V and 3.65V, respectively. The capacity is determined by charging and discharging 3 times, and the discharge capacity of the third cycle is taken as the capacity of the battery. Then, after charging to 5% SOC at 0.33C, fast charging test is performed, specifically: charging to 10% SOC at 1.5C, recording the charging time as t1; charging to 20% SOC at 1.5C, recording the charging time as t2; standing for 5 min; charging to 30% SOC at 1.5C, recording the charging time as t3; standing for 5 min; charging to 40% SOC at 1.5C, recording the charging time as t4; standing for 5 min; charging to 50% SOC at 1.5C, recording the charging time as t5; standing for 5 min; then charging to 60% SOC at 1.2C, recording the charging time as t6; standing for 5 min; charging to 70% SOC at 1.2C, recording the charging time as t7; standing for 5 min; charging to 80% SOC at 1.2C, recording the charging time as t8; standing for 5 min. Fast charging time t = t1+t2+t3+t4+t5+t6+t7+t8, the smaller the fast charging time, the better the fast charging performance of the battery.

[0144] 6. Test method for cycle capacity retention rate at 60°C

[0145] The lithium ion battery is tested for cycle performance by using a LAND system, the temperature of the LAND system is adjusted to be 60 DEG C, the battery is charged to 3.65V at a charge rate of 0.5C, the current is cut off at 0.05C, after standing for 10 minutes, the battery is discharged to 2.5V at a discharge rate of 1C, after standing for 10 minutes, the battery is cycled for 280 times under the above conditions, the discharge capacity of the first cycle Q1 and the discharge capacity of the 280th cycle Q2 are recorded, and the capacity retention rate of the battery after 280 cycles is calculated according to the formula Q2 / Q1*100%.

[0146] From the above examples, it can be seen that the battery provided by the present application has the following advantages: only the additive B with the structure of formula I is added in the electrolyte, the mass content of the additive B is b% based on the mass of the electrolyte, and the powder conductivity a of the negative active material layer in the negative electrode satisfies the following relationship: 6.5≤a / b≤550, when the relationship is satisfied, the degree of electrolyte side reaction is low, the gas production of the battery during use is reduced, and the fast charging performance and high temperature cycle life of the battery are improved. The experimental results show that the fast charging time of the battery is 22-29 minutes, the capacity retention rate of the lithium ion battery is 80-89% after 280 cycles under the conditions of 0.5C / 1C charge-discharge rate, 0.05C current cut-off and voltage range of 2.5-3.65V at 60 DEG C.

[0147] The above only describes the preferred embodiments of the present application, and it should be noted that, for those skilled in the art, some improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A battery comprising an electrolyte and a negative electrode; The electrolyte includes additive B having the structure of Formula I: Formula I; R1, R2, and R3 are independently selected from -H or -C. p H 2p+1 ,in, 1≤p≤4； R4, R5 and R6 are independently selected from vinyl, allyl, oxyvinyl, oxyallyl, ethynyl ethyl, ethynyl propargyl, oxyethynyl ethyl or oxyethynyl propargyl; R7, R8, and R9 are independently selected from -H, -CH3, or -CH2CH3; The negative electrode includes a negative electrode active material layer; The powder conductivity of the negative electrode active material layer is a, in S / cm; 5≤a≤20; Based on the mass of the electrolyte, the mass content of additive B is b%, 0.01%≤b%≤3%; a and b satisfy the following relationship: 6.5≤a / b≤550.

2. The battery according to claim 1, characterized in that, The value of a ranges from 8 to 18.

3. The battery according to claim 1, characterized in that, The value of b% ranges from 0.1% to 1.5%.

4. The battery according to claim 1, characterized in that, 9.5≤a / b≤102.

5.

5. The battery according to claim 1, characterized in that, R1, R2, and R3 are all selected from -H, and R4, R5, and R6 are independently selected from ethyl alkynyl, propynyl alkynyl, ethyl alkynyl, or propynyl alkynyl.

6. The battery according to claim 1, characterized in that, R1, R2, and R3 are all selected from -C p H 2p+1 R4, R5, and R6 are independently selected from vinyl or oxyvinyl groups.

7. The battery according to claim 1, characterized in that, The specific structural formulas (Ⅰ1) to (Ⅰ21) of Formula I are as follows: 。 8. The battery according to claim 1, characterized in that, The additive B having the structure of Formula I has n double bonds, and the value of n ranges from 1 to 5.

9. The battery according to claim 8, characterized in that, The value of n is in the range of 2 to 3, and 8.5 ≤ a / b ≤ 31.

2.

10. The battery according to claim 1, characterized in that, The negative electrode active material layer includes a negative electrode main material, the particle size Dv50 of which ranges from 5 to 20 μm; the negative electrode main material is selected from natural graphite, artificial graphite, mesophase carbon microspheres, hard carbon, soft carbon, silicon oxide, silicon carbon, and Li4Ti5O. 12 One or more of them.

11. The battery according to claim 1, characterized in that, The electrolyte includes a solvent selected from at least one of ethylene carbonate, methylene disulfonate, ethyl methyl carbonate, diethyl carbonate, propylene 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.

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