Non-aqueous electrolyte composition, lithium ion battery and electric equipment

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a non-aqueous electrolyte composition, a lithium ion battery and electric equipment. The non-aqueous electrolyte composition provided by the invention comprises a primary liquid injection electrolyte and a secondary liquid injection electrolyte, the primary liquid injection electrolyte comprises heterocyclic lithium carboxylate and a first solvent, and the first solvent comprises an ether solvent. According to the invention, full film formation can be ensured through cooperation of the components in the one-time injection electrolyte, a high-stability conductive ion SEI / CEI interface film is formed, the problems of impedance increase, capacity loss and the like caused by damage to negative electrode SEI due to deterioration of the structural stability of a high-nickel positive electrode material are relieved, and the electrolyte still has good performance under high voltage; according to the present invention, the secondary injection electrolyte is not specifically limited, is the conventional electrolyte, and has high conductivity, such that the film forming performance and the conductivity performance of the non-aqueous electrolyte composition can be considered through the cooperation of the secondary injection electrolyte so as to improve the comprehensive performance of the battery.

Description

Technical Field

[0001] The present application belongs to the technical field of lithium ion batteries, and specifically relates to a non-aqueous electrolyte composition, a lithium ion battery and an electrical device. Background Art

[0002] Layered nickel-cobalt-manganese ternary material (NCM) has become one of the mainstream positive electrode materials for current power lithium battery applications due to its high gram capacity, excellent rate performance and low-temperature performance. As the market demand for high energy density continues to grow, NCM materials are driven to develop towards higher Ni content and higher upper limit voltage, but some characteristic problems that come with it limit its actual application and development.

[0003] Among them, the more prominent key problem is that the increase in Ni content leads to poor structural stability of the positive electrode material, and Li / Ni mixing is more likely to occur during the charge and discharge process, resulting in changes in the positive electrode structure and more serious dissolution of transition metal ions. The dissolution and deposition of transition metal ions will induce various positive and negative electrode crosstalk side reactions, especially the destruction of the negative electrode SEI, which will lead to the consumption and decomposition of the electrolyte and active lithium, resulting in a significant increase in impedance and serious capacity loss. The above problems will be further aggravated under high voltage. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present application is to overcome the defects of the high-nickel positive electrode material in the prior art, such as poor structural stability, increased impedance and capacity loss of lithium-ion batteries, and further aggravation of the above problems under high pressure, thereby providing a non-aqueous electrolyte composition, a lithium-ion battery and an electrical device.

[0005] To this end, this application provides the following technical solutions:

[0006] According to one aspect of the present application, a non-aqueous electrolyte composition is provided, comprising a primary injection electrolyte and a secondary injection electrolyte,

[0007] Wherein, the primary injection electrolyte includes heterocyclic carboxylic acid lithium and a first solvent, and the first solvent includes an ether solvent.

[0008] In some optional embodiments, the heterocyclic lithium carboxylate has a structure represented by any of the following general formulas:

[0009]

[0010] Wherein, R1 is selected from one of O and S, R2 and R5 are independently selected from one of hydrogen, alkyl, halogenated alkyl, amino and phenyl; R3 is selected from one of C and N; R4 is selected from one of a connecting bond, C1-C4 alkylene or C1-C4 halogenated alkylene;

[0011] Optionally, the alkyl group includes a C1-C4 alkyl group, and the haloalkyl group includes a C1-C4 haloalkyl group;

[0012] Further optionally, the heterocyclic carboxylic acid lithium is selected from any of the following structures:

[0013]

[0014]

[0015] In some optional embodiments, the concentration of the heterocyclic carboxylic acid lithium in the primary injection electrolyte is 0.3 to 2 mol / L, optionally 0.5 to 1.5 mol / L;

[0016] And / or, the mass m of the primary injection electrolyte and the mass n of the secondary injection electrolyte satisfy the following relationship: 0.2≤m / (m+n)≤0.7.

[0017] In some optional embodiments, the ether solvent includes at least one of an unsubstituted ether solvent or a halogenated ether solvent;

[0018] Optionally, the ether solvent includes at least one of ethylene glycol dimethyl ether, tetrahydrofuran, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, 2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,2-tetrafluoroethyl methyl ether, 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane, difluoromethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, and hexafluoroisopropyl methyl ether.

[0019] In some optional embodiments, based on the total mass of the primary injection electrolyte, the primary injection electrolyte further comprises 0.5% to 10% of a functional additive; optionally, the functional additive comprises a positive and negative electrode film-forming additive;

[0020] And / or, the secondary injection electrolyte comprises an organic solvent, a lithium salt and a functional additive; optionally, the concentration of the lithium salt in the secondary injection electrolyte is 0.5-1.5 mol / L, and the mass percentage of the functional additive is 0.5%-10%.

[0021] According to another aspect of the present application, a lithium ion battery is provided, comprising the non-aqueous electrolyte composition described above.

[0022] In some optional embodiments, the mass m of the primary injection electrolyte, the mass n of the secondary injection electrolyte, and the capacity C of the lithium-ion battery satisfy the following relationship: 2g / Ah≤(m+n) / C≤6g / Ah.

[0023] In some optional embodiments, the method for injecting the non-aqueous electrolyte includes:

[0024] Inject the primary injection electrolyte into the uninjected battery cell, form it, inject the secondary injection electrolyte, and let it stand.

[0025] In some optional embodiments, the formation includes standing at 25 to 60° C. for 8 to 48 hours, charging to 50% to 100% SOC at a current of 0.05C to 0.2C;

[0026] And / or, after the second injection, the standing temperature is 25 to 60° C. and the standing time is 8 to 48 hours.

[0027] According to another aspect of the present application, there is provided an electrical device comprising the above-mentioned lithium-ion battery.

[0028] The technical solution of this application has the following advantages:

[0029] The non-aqueous electrolyte composition provided by the present application includes a primary injection electrolyte and a secondary injection electrolyte, wherein the primary injection electrolyte includes a heterocyclic carboxylic acid lithium and a first solvent, and the first solvent includes an ether solvent. The non-aqueous electrolyte composition provided by the present application can ensure sufficient film formation through the coordination between the components in the primary injection electrolyte to form a highly stable ion-conducting SEI / CEI interface film, which alleviates the problems of increased impedance and capacity loss caused by the damage to the negative electrode SEI due to the poor structural stability of the high-nickel positive electrode material, and still has good performance under high pressure; at the same time, the present application does not specifically limit the secondary injection electrolyte, which is a conventional electrolyte with high conductivity. Through the coordination of the primary injection electrolyte and the secondary injection electrolyte, the film-forming performance and conductivity performance of the non-aqueous electrolyte composition can be achieved, and the comprehensive performance of the battery can be improved. Specifically, the single-injection electrolyte in the present application has both excellent electrode wettability and interface film forming function. By selecting a lithium salt containing a heterocyclic carboxylate anion, the composition and structure of the anion-derived interface film can be optimized to form a highly stable ion-conducting SEI / CEI interface film rich in inorganic substances; the weakly solvated unsubstituted ether solvent has a weak effect on lithium ions, so that more anions in the heterocyclic carboxylate lithium salt participate in the lithium ion solvation shell. During the charge and discharge process, redox reactions can occur preferentially as the lithium ions migrate to the electrode surface to form an anion-derived interface film; at the same time, the first solvent has excellent wettability with the positive and negative electrodes, so that the single-injection electrolyte can fully wet the electrode surface in a shorter time, thereby improving the wetting efficiency and ensuring more sufficient film formation.

[0030] The non-aqueous electrolyte composition provided in the present application can further improve various performances of the electrolyte by limiting the structure of the heterocyclic lithium carboxylate.

[0031] The non-aqueous electrolyte composition provided in the present application can ensure uniform film formation and moderate thickness of the electrode sheet and ensure the wettability of the electrode sheet by limiting the relationship between the mass m of the primary injection electrolyte and the mass n of the secondary injection electrolyte. If the mass m of the primary injection electrolyte is small, the electrode cannot be fully wetted and the film formation is uneven; when m is high, the film formation is thicker, the impedance is larger, and the secondary injection electrolyte cannot fully wet.

[0032] The non-aqueous electrolyte composition provided by the present application further comprises functional additives in the primary injection electrolyte. The functional additives can further optimize and regulate the various properties of the electrolyte, especially the positive and negative electrode film-forming additives, which can adjust the composition and structure of the anion-derived interface film of the primary injection electrolyte and optimize the ion conductivity and stability of the interface film.

[0033] The lithium-ion battery provided in the present application, by limiting the filling coefficient, ensures that the electrolyte can fully infiltrate the battery cell while avoiding the increase in gas production and cell volume expansion caused by the continuous decomposition of excessive residual electrolyte during long-term aging. In addition, the limitation of the filling coefficient can also enable the battery to have both high energy density and low cost.

[0034] The lithium-ion battery provided in the present application, through the limitation of the specific injection method, can quickly wet the electrode and form an inorganic-rich SEI / CEI interface film dominated by anion salt decomposition after one injection, through the limitation of the specific injection method, because the primary injection electrolyte has both excellent electrode wettability and interface film forming function, combined with a specific injection method, and has excellent stability and low impedance performance after the first injection, which can improve the cycle and storage stability of the battery; after the second injection, it is allowed to stand still, so that the secondary injection electrolyte can fully infiltrate the electrode, improve the conductivity, and achieve the improvement of the overall performance of the battery.

[0035] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. DETAILED DESCRIPTION

[0036] The following examples are provided for a better understanding of the present application, but are not limited to the best implementation mode described, and do not limit the content and protection scope of the present application. Any product identical or similar to the present application obtained by anyone under the inspiration of the present application or by combining the features of the present application with other prior arts shall fall within the protection scope of the present application.

[0037] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0038] In the description of the present application, it should be noted that the terms "first", "second", "first", "secondary", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0039] In order to overcome the problems in the prior art that the high-nickel positive electrode material has poor stability, which will cause the lithium-ion battery impedance to increase and capacity to lose, and the above problems will be further aggravated under high voltage, the present application provides the following technical solutions:

[0040] According to one aspect of the present application, a non-aqueous electrolyte composition is provided, comprising a primary injection electrolyte and a secondary injection electrolyte.

[0041] Wherein, the primary injection electrolyte includes heterocyclic carboxylic acid lithium and a first solvent, and the first solvent includes an ether solvent.

[0042] The non-aqueous electrolyte composition provided in the present application can ensure sufficient film formation through the coordination between the components to form a highly stable ion-conducting SEI / CEI interface film, thereby alleviating the problems of increased impedance and capacity loss caused by the damage to the negative electrode SEI due to the deterioration of the structural stability of the high-nickel positive electrode material, and still has good performance under high pressure; at the same time, the present application does not make any specific limitations on the secondary injection electrolyte, which is a conventional electrolyte with high conductivity. Through the coordination of the primary injection electrolyte and the secondary injection electrolyte, it is possible to achieve a balance between the film-forming performance and the conductivity performance of the non-aqueous electrolyte composition, thereby improving the overall performance of the battery. Specifically, the single-injection electrolyte in the present application has both excellent electrode wettability and interface film forming function. By selecting a lithium salt containing a heterocyclic carboxylate anion, the composition and structure of the anion-derived interface film can be optimized to form a highly stable ion-conducting SEI / CEI interface film rich in inorganic substances; the weakly solvated unsubstituted ether or fluoroether solvent has a weak effect on lithium ions, so that more anions in the heterocyclic carboxylate lithium salt participate in the lithium ion solvation shell. During the charge and discharge process, redox reactions can occur preferentially as the lithium ions migrate to the electrode surface to form an anion-derived interface film; at the same time, the first solvent has excellent wettability with the positive and negative electrodes, so that the single-injection electrolyte can fully wet the electrode surface in a shorter time, thereby improving the wetting efficiency and ensuring more sufficient film formation.

[0043] In some optional embodiments, the heterocyclic lithium carboxylate has a structure represented by any of the following general formulas:

[0044]

[0045] Wherein, R1 is selected from one of O and S, R2 and R5 are independently selected from one of hydrogen, alkyl, halogenated alkyl, amino and phenyl; R3 is selected from one of C and N; R4 is selected from one of a connecting bond, C1-C4 alkylene or C1-C4 halogenated alkylene;

[0046] Optionally, the alkyl group includes a C1-C4 alkyl group, and the haloalkyl group includes a C1-C4 haloalkyl group;

[0047] Further optionally, the heterocyclic carboxylic acid lithium is selected from any of the following structures:

[0048]

[0049] The non-aqueous electrolyte composition provided by the present application can further improve the various properties of the electrolyte by limiting the structure of the heterocyclic carboxylic acid lithium. By introducing alkyl / halogenated alkylene / aromatic ring / aliphatic ring into the heterocyclic carboxylic acid lithium structure, the electron distribution of the organic carboxylate anion can be adjusted to balance its binding force with the lithium ion. When dissociating in the solvent, a certain degree of ion dissociation can be guaranteed, and it can be distributed in the first shell of lithium ion solvation to participate in SEI / CEI film formation. At the same time, the components and structure of the anion-derived SEI / CEI can be adjusted to make it have better flexibility and stability.

[0050] In some optional embodiments, the concentration of the heterocyclic carboxylic acid lithium in the primary injection electrolyte is 0.5 to 1.5 mol / L.

[0051] As an example, the molar concentration of the lithium salt is 0.5mol / L, 0.8mol / L, 0.9mol / L, 1.0mol / L, 1.1mol / L, 1.2mol / L, 1.3mol / L, 1.4mol / L, 1.5mol / L, or within the range of any of the above values. The present application limits the concentration of lithium salts so that the lithium ion solvation structure has a suitable anion ratio, so that an anion-induced SEI / CEI stable interface film can be formed on the surface of the positive and negative electrodes during the charge and discharge process, while maintaining a relatively high ionic conductivity; when the lithium salt concentration is low, the number of dissociable lithium ions is limited, the ionic conductivity is reduced, and the anion ratio in the lithium ion solvation structure is reduced, which will make the ion conduction and stability of the SEI / CEI film formed worse; when the lithium salt concentration is high, it is difficult to fully dissolve and increase the viscosity of the electrolyte, reducing the wettability and ion conduction ability of the electrolyte.

[0052] In some optional embodiments, the mass m of the primary injection electrolyte and the mass n of the secondary injection electrolyte satisfy the following relationship: 0.2≤m / (m+n)≤0.7. As an example, the value of m / (m+n) can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or within the range of any of the above values.

[0053] In this application, by limiting the proportional relationship between the mass m of the primary injection electrolyte and the mass n of the secondary injection electrolyte, it is possible to ensure that the electrode is formed uniformly and with a moderate thickness, thereby ensuring the wettability of the electrode. If the mass m of the primary injection electrolyte is small, the electrode cannot be fully wetted, and the film is uneven; when m is high, the film is thicker, the impedance is larger, and the secondary injection electrolyte cannot fully wet.

[0054] In some optional embodiments, the ether solvent includes at least one of an unsubstituted ether solvent or a halogenated ether solvent;

[0055] Optionally, the ether solvent includes at least one of ethylene glycol dimethyl ether, tetrahydrofuran, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, 2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,2-tetrafluoroethyl methyl ether, 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane, difluoromethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, and hexafluoroisopropyl methyl ether.

[0056] In some optional embodiments, based on the total mass of the single-injection electrolyte, the single-injection electrolyte also includes 0.5% to 10% of functional additives; as an example, the mass percentage of the functional additives is 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or within the range of any of the above values.

[0057] In some optional embodiments, the functional additives in the primary injection electrolyte include positive and negative electrode film-forming additives, including at least one of additives containing S or double bonds or F or B or P or CN or lithium salt additives.

[0058] As an example, the S-containing additive includes at least one of PS (1,3-propane sultone), PST (propenyl-1,3-sultone), DTD (vinyl sulfate), and MMDS (methylene disulfonate); the double bond-containing additive includes at least one of VC (vinyl carbonate), VEC (vinyl ethylene carbonate), and TAP (triallyl phosphate); the F-containing additive includes at least one of FEC (fluoroethylene carbonate) and TTFP (tris (2,2,2-trifluoroethyl) phosphite); the B-containing additive includes LiBOB (dioxalyl borate) The P-containing additive includes at least one of TMSP (tri(trimethylsilyl)phosphate), TMSPi (tri(trimethylsilyl)phosphite), LiPO2F2 (lithium difluorophosphate), and LiODFP (lithium difluorobis(oxalatephosphate); the CN-containing additive includes at least one of HTCN (hexanetrinitrile), SN (succinonitrile), ADN (adiponitrile), DENE (1,2-bis(cyanoethoxy)ethane), and TCP (tricyanoethoxypropane).

[0059] It can be understood that the use of functional additives in the present application can further optimize and regulate the various properties of the electrolyte, especially the positive and negative electrode film-forming additives, which can adjust the composition and structure of the anion-derived interface film of the single-injection electrolyte and optimize the ion conductivity and stability of the interface film; by limiting the amount of functional additives, the film stability, film thickness and film impedance can be balanced.

[0060] And / or, the secondary injection electrolyte comprises an organic solvent, a lithium salt and a functional additive; optionally, the concentration of the lithium salt in the secondary injection electrolyte is 0.5-1.5 mol / L, and the mass percentage of the functional additive is 0.5%-10%.

[0061] In the present application, the lithium salt in the secondary injection electrolyte includes at least one of LiPF6, LiClO4, LiBF4, LiAsF6, LiBOB, LiODFB, LiFSI, LiTFSI, and LiTDI; as an example, the mass percentage of the lithium salt can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or within the range of any of the above values. The present application limits the concentration of lithium salts so that the lithium ion solvation structure has a suitable anion ratio, so that an anion-induced SEI / CEI stable interface film can be formed on the surface of the positive and negative electrodes during the charge and discharge process, while maintaining a relatively high ionic conductivity; when the lithium salt concentration is low, the number of dissociable lithium ions is limited, the ionic conductivity is reduced, and the anion ratio in the lithium ion solvation structure is reduced, which will make the ion conduction and stability of the SEI / CEI film formed worse; when the lithium salt concentration is high, it is difficult to fully dissolve and increase the viscosity of the electrolyte, reducing the wettability and ion conduction ability of the electrolyte.

[0062] In some optional embodiments, the mass percentage of the functional additive is 0.5% to 10% based on the total mass of the secondary injection electrolyte. As an example, the mass percentage of the functional additive is 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or within the range of any of the above values. It can be understood that the use of functional additives in this application can further optimize and regulate the various properties of the electrolyte, especially the positive and negative electrode film-forming additives, which can adjust the composition and structure of the anion-derived interface film of the secondary injection electrolyte and optimize the ion conductivity and stability of the interface film; by limiting the amount of functional additives, the film stability, film thickness and film impedance can be balanced.

[0063] In some optional embodiments, the functional additives in the secondary injection electrolyte include positive and negative electrode film-forming additives, including at least one of additives containing S or double bonds or F or B or P or CN or lithium salt additives.

[0064] As an example, the S-containing additive includes at least one of PS (1,3-propane sultone), PST (propenyl-1,3-sultone), DTD (vinyl sulfate), and MMDS (methylene disulfonate); the double bond-containing additive includes at least one of VC (vinyl carbonate), VEC (vinyl ethylene carbonate), and TAP (triallyl phosphate); the F-containing additive includes at least one of FEC (fluoroethylene carbonate) and TTFP (tris (2,2,2-trifluoroethyl) phosphite); the B-containing additive includes LiBOB (dioxalyl borate) The P-containing additive includes at least one of TMSP (tri(trimethylsilyl)phosphate), TMSPi (tri(trimethylsilyl)phosphite), LiPO2F2 (lithium difluorophosphate), and LiODFP (lithium difluorobis(oxalatephosphate); the CN-containing additive includes at least one of HTCN (hexanetrinitrile), SN (succinonitrile), ADN (adiponitrile), DENE (1,2-bis(cyanoethoxy)ethane), and TCP (tricyanoethoxypropane).

[0065] In some optional embodiments, the organic solvent includes at least one of a carbonate solvent or a carboxylate solvent. As an example, the carbonate solvent includes at least one of ethylene carbonate (EC), propylene carbonate, dimethyl carbonate, diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and various fluorinated cyclic and linear carbonates, and the carboxylate solvent includes at least one of methyl acetate, ethyl acetate, methyl propionate, ethyl propionate and various fluorinated cyclic and linear carboxylates.

[0066] According to another aspect of the present application, a lithium ion battery is provided, comprising the above-mentioned non-aqueous electrolyte composition. The lithium ion battery exhibits good cycle stability and high voltage performance due to the use of the above-mentioned non-aqueous electrolyte composition.

[0067] In some optional embodiments, the mass m of the primary injection electrolyte, the mass n of the secondary injection electrolyte, and the capacity C of the lithium-ion battery satisfy the following relationship (ie, injection coefficient): 2g / Ah≤(m+n) / C≤6g / Ah.

[0068] This application limits the injection coefficient, ensuring that the electrolyte can fully infiltrate the battery cell while avoiding the increase in gas production and battery cell volume expansion caused by the continuous decomposition of excess residual electrolyte during long-term aging. In addition, the limitation of the injection coefficient can also make the battery have both high energy density and low cost. In this application, the capacity C of the lithium-ion battery is the design capacity of the battery cell, which can be calculated by the following formula: (positive electrode gram capacity × positive electrode surface density × positive electrode active material content × positive electrode electrode sheet coating area × number of positive electrode sheets).

[0069] In some optional embodiments, the method for injecting the non-aqueous electrolyte includes:

[0070] Inject the primary injection electrolyte into the uninjected battery cell, form it, inject the secondary injection electrolyte, and let it stand.

[0071] In some optional embodiments, the formation includes standing at 25-60°C for 8-48 hours, and charging to 50%-100% SOC with a current of 0.05C-0.2C; as an example, the standing temperature can be 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, or within the range of any of the above values; the standing time can be 8h, 12h, 16h, 18h, 20h, 24h, 28h, 32h, 36h, 40h, 44h, 48h, or within the range of any of the above values. The charging current can be 0.05C, 0.08C, 0.1C, 0.13C, 0.15C, 0.17C, 0.2C, or within the range of any of the above values; charged to 50% SOC, 55% SOC, 60% SOC, 65% SOC, 70% SOC, 75% SOC, 80% SOC, 85% SOC, 90% SOC, 95% SOC, 100% SOC, or within the range of any of the above values.

[0072] And / or, the standing temperature after the secondary injection is 25-60°C, and the standing time is 8-48h. As an example, the standing temperature after the secondary injection can be 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, or within the range of any of the above values; the standing time can be 8h, 12h, 16h, 18h, 20h, 24h, 28h, 32h, 36h, 40h, 44h, 48h, or within the range of any of the above values.

[0073] This application defines a specific injection method. Since the primary injection electrolyte has both excellent electrode wettability and interface film forming function, combined with a specific injection method, after the first injection, it can quickly wet the electrode and form an inorganic-rich SEI / CEI interface film dominated by anion salt decomposition, which has excellent stability and low impedance performance, and can improve the battery's cycle and storage stability; after the second injection, it is allowed to stand to achieve full infiltration of the electrode by the secondary injection electrolyte. In this application, the standing temperature and time will affect the stability of the electrolyte and the degree of electrolyte wetting of the battery cell; the formation current and cut-off SOC will affect the film-forming components and thickness as well as the overall formation efficiency. By limiting the formation parameters (including temperature, standing time, formation current, and cut-off SOC), it can be ensured that the formed interface film has the best comprehensive performance.

[0074] It is understood by those skilled in the art that the lithium-ion battery provided in the present application, in addition to the non-aqueous electrolyte composition and the above-mentioned injection method, also includes a positive electrode sheet, a negative electrode sheet, and a separator. During the battery charging and discharging process, lithium ions are embedded and removed back and forth between the positive electrode sheet and the negative electrode sheet, the electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet, and the separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing lithium ions to pass through.

[0075] As an example, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer is arranged on any one or both of the two opposite surfaces of the positive electrode current collector. The material, composition and manufacturing method of the positive electrode sheet used in the lithium ion secondary battery of the present application may include any technology disclosed in the prior art.

[0076] As an example, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is arranged on any one or both of the two opposite surfaces of the negative electrode current collector. The material, composition and manufacturing method of the negative electrode sheet used in the lithium ion secondary battery of the present application may include any technology disclosed in the prior art.

[0077] The steps of the positive / negative electrode preparation method are as follows: add active materials, conductive agents, binders and dispersants in a certain mass ratio to an appropriate amount of solvent and stir them thoroughly, and obtain a uniform mixed slurry by controlling the solid content. Then, the formed material is coated on the current collector foil, and is formed by rolling and die-cutting after drying.

[0078] The material and shape of the separator used in the lithium ion secondary battery of the present application are not particularly limited, and may include any technology disclosed in the prior art. As an example, the separator in the present application may be a commercial polyolefin separator.

[0079] According to another aspect of the present application, there is provided an electric device, comprising the above-mentioned lithium-ion battery. The advantages of the electric device and the above-mentioned lithium-ion battery over the prior art are the same, which will not be described in detail here.

[0080] In the present application, the lithium-ion battery can be used as a power source for the electrical equipment, or as an energy storage unit for the electrical equipment. The electrical equipment can be, 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.

[0081] The present application is described below with reference to specific examples and comparative examples. It should be noted that these examples are merely illustrative and do not limit the present application in any way. In all examples and comparative examples of the present application, the unit % represents the mass percentage content.

[0082] Example 1

[0083] This embodiment provides a non-aqueous electrolyte composition and a lithium ion battery, wherein the non-aqueous electrolyte composition comprises a primary injection electrolyte and a secondary injection electrolyte, wherein the primary injection electrolyte comprises: a lithium heterocyclic carboxylate represented by structural formula I, with a concentration of 1 mol / L, a solvent of 1,1,2,2-tetrafluoroethyl ether, and 1% of an additive VC;

[0084] The secondary injection electrolyte comprises: 1 mol / L LiPF6, 2% DTD and 1% PS in terms of mass percentage, and the composition of the organic solvent is EC / EMC / DEC in a volume ratio of 30:50:20.

[0085] The specific composition and preparation method of the lithium ion battery are as follows:

[0086] Positive electrode sheet preparation: The positive electrode active material Li (Ni 0.9 Co 0.05 Mn 0.05 )O2, conductive agent (SP), single-walled carbon nanotube (SWNT) and binder polyvinylidene fluoride (PVDF) were added to an appropriate amount of N-methyl-2-pyrrolidone (NMP) solvent in a mass ratio of 96:2:1:1 and stirred thoroughly. The solid content was controlled to 68% to prepare a positive electrode mixture slurry. Thereafter, the formed positive electrode slurry was coated on aluminum foil and rolled and die-cut to form a positive electrode sheet (double-sided surface density of 400g / m 2 ).

[0087] Preparation of negative electrode sheet: Graphite, conductive agent (SP), thickener CMC, and adhesive SBR were added to an appropriate amount of deionized water in a mass ratio of 95:2:1:2 and stirred thoroughly. The solid content was controlled to 55% to prepare a negative electrode mixture slurry. Afterwards, the formed negative electrode slurry was coated on copper foil and rolled and die-cut to form a negative electrode sheet (double-sided surface density of 160g / m 2 ).

[0088] Battery assembly: positive electrode sheet, negative electrode sheet and separator, stacking the negative electrode, separator and positive electrode in order, then welding the tabs and encapsulating with aluminum plastic film to obtain a soft package dry cell, and finally injecting the non-aqueous electrolyte prepared in each embodiment and comparative example into the cell to prepare a lithium ion battery with a capacity of 5Ah;

[0089] Wherein, the liquid injection step comprises:

[0090] 7.5 g of the above-mentioned primary injection electrolyte was injected into the obtained soft-pack dry battery cell, allowed to stand at 45°C for 24 hours, and charged to 70% SOC at a low rate current of 0.05C; 7.5 g of the above-mentioned secondary injection electrolyte was injected, allowed to stand at 45°C for 24 hours, and then fully infiltrated to obtain a lithium-ion battery with a capacity of 5Ah.

[0091] Example 2

[0092] This embodiment provides a non-aqueous electrolyte composition and a lithium ion battery, which are different from the embodiment 1 only in that the injection amount of the primary injection electrolyte is 1.5 g, and the injection amount of the secondary injection electrolyte is 13.5 g.

[0093] Example 3

[0094] This embodiment provides a non-aqueous electrolyte composition and a lithium ion battery, which are different from the embodiment 1 only in that the injection amount of the primary injection electrolyte is 13.5 g, and the injection amount of the secondary injection electrolyte is 1.5 g.

[0095] Example 4

[0096] This embodiment provides a non-aqueous electrolyte composition and a lithium ion battery, which are different from the embodiment 1 only in that the injection amount of the primary injection electrolyte is 3 g, and the injection amount of the secondary injection electrolyte is 12 g.

[0097] Example 5

[0098] This embodiment provides a non-aqueous electrolyte composition and a lithium ion battery, which are different from the embodiment 1 only in that the injection amount of the primary injection electrolyte is 10.5 g, and the injection amount of the secondary injection electrolyte is 4.5 g.

[0099] Example 6

[0100] This embodiment provides a non-aqueous electrolyte composition and a lithium ion battery, which are different from the embodiment 1 only in that the heterocyclic carboxylate lithium in the primary injection electrolyte has a structure shown in structural formula II.

[0101] Example 7

[0102] This embodiment provides a non-aqueous electrolyte composition and a lithium ion battery, which are different from the embodiment 1 only in that the heterocyclic carboxylate lithium in the primary injection electrolyte has a structure shown in structural formula III.

[0103] Example 8

[0104] This embodiment provides a non-aqueous electrolyte composition and a lithium ion battery, which are different from the embodiment 1 only in that the heterocyclic carboxylate lithium in the primary injection electrolyte has a structure shown in structural formula IV.

[0105] Example 9

[0106] This embodiment provides a non-aqueous electrolyte composition and a lithium ion battery, which are different from the embodiment 1 only in that the heterocyclic carboxylate lithium in the primary injection electrolyte has a structure shown in structural formula V.

[0107] Example 10

[0108] This embodiment provides a non-aqueous electrolyte composition and a lithium ion battery, which are different from the embodiment 1 only in that the heterocyclic carboxylate lithium in the primary injection electrolyte has a structure shown in structural formula VI.

[0109] Embodiment 11

[0110] The present embodiment provides a non-aqueous electrolyte composition and a lithium-ion battery, which differs from the embodiment 1 only in that the operating parameters of the injection step are different, specifically: 7.5 g of the above-mentioned primary injection electrolyte is injected into the obtained soft-pack dry battery cell, left to stand at 60°C for 8 hours, and charged to 70% SOC at a low rate current of 0.05C; 7.5 g of the above-mentioned secondary injection electrolyte is injected, left to stand at 60°C for 8 hours, and then fully infiltrated to obtain a lithium-ion battery with a capacity of 5Ah.

[0111] Example 12

[0112] The present embodiment provides a non-aqueous electrolyte composition and a lithium-ion battery, which differs from the embodiment 1 only in that the operating parameters of the injection step are different, specifically: 7.5 g of the above-mentioned primary injection electrolyte is injected into the obtained soft-pack dry battery cell, left to stand at 45°C for 24 hours, and charged to 80% SOC with a low rate current of 0.1C; 7.5 g of the above-mentioned secondary injection electrolyte is injected, left to stand at 45°C for 24 hours, and then fully infiltrated to obtain a lithium-ion battery with a capacity of 5Ah.

[0113] Example 13

[0114] This embodiment provides a non-aqueous electrolyte composition and a lithium ion battery. Compared with the embodiment 1, the difference is only that the composition of the non-aqueous electrolyte composition is different, wherein the primary injection electrolyte comprises: a lithium heterocyclic carboxylate represented by the structural formula I, with a concentration of 0.8 mol / L, a solvent of 1,1,2,2-tetrafluoroethyl methyl ether, and 2% of an additive VC;

[0115] The secondary injection electrolyte comprises: 1 mol / L lithium salt LiFSI, 2% DTD and 1% PS in terms of mass percentage, and the composition of the organic solvent is EC / EMC / DEC in a volume ratio of 30:50:20.

[0116] Embodiment 14

[0117] This embodiment provides a non-aqueous electrolyte composition and a lithium ion battery. Compared with the embodiment 1, the difference is only that the composition of the non-aqueous electrolyte composition is different, wherein the primary injection electrolyte comprises: a lithium heterocyclic carboxylate represented by structural formula I, with a concentration of 1 mol / L, a solvent of 1,1,2,2-tetrafluoroethyl methyl ether, and also comprises 2% of an additive FEC;

[0118] The secondary injection electrolyte comprises: 1 mol / L lithium salt LiFSI, 1.5% DTD and 1.5% PS by mass percentage, and the composition of the organic solvent is EC / EMC / DEC with a volume ratio of 30:50:20.

[0119] Embodiment 15

[0120] This embodiment provides a non-aqueous electrolyte composition and a lithium ion battery, which is different from the embodiment 3 only in that the concentration of the heterocyclic carboxylic acid lithium in the primary injection electrolyte is 0.3 mol / L.

[0121] Example 16

[0122] This embodiment provides a non-aqueous electrolyte composition and a lithium ion battery, which is different from the embodiment 3 only in that the concentration of the heterocyclic carboxylic acid lithium in the primary injection electrolyte is 2 mol / L.

[0123] Comparative Example 1

[0124] This comparative example provides a non-aqueous electrolyte composition and a lithium-ion battery, which differs from Example 1 only in that the primary injection electrolyte and the secondary injection electrolyte are interchanged, that is, the composition of the primary injection electrolyte in this comparative example is the same as the secondary injection electrolyte in Example 1, and the composition of the secondary injection electrolyte is the same as the primary injection electrolyte in Example 1.

[0125] Comparative Example 2

[0126] This comparative example provides a non-aqueous electrolyte composition and a lithium ion battery, which are different from Example 1 only in that the composition of the primary injection electrolyte is the same as the secondary injection electrolyte in Example 1, that is, the secondary injection electrolyte is used in both injections.

[0127] Comparative Example 3

[0128] This comparative example provides a non-aqueous electrolyte composition and a lithium ion battery, which differs from Example 1 only in that the primary injection electrolyte and the secondary injection electrolyte are mixed in a mass ratio of 1:1;

[0129] The difference between the injection operation and that of Example 1 is that 7.5 g of the mixed electrolyte is injected each time.

[0130] Comparative Example 4

[0131] This comparative example provides a non-aqueous electrolyte composition and a lithium ion battery, which are different from Example 1 only in that the composition of the secondary injection electrolyte is the same as the primary injection electrolyte in Example 1, that is, the primary injection electrolyte is used in both injections.

[0132] Comparative Example 5

[0133] This comparative example provides a non-aqueous electrolyte composition and a lithium ion battery, which are different from Example 3 only in that an equimolar amount of lithium salt LiFSI is used in the primary injection electrolyte to replace the heterocyclic carboxylic acid lithium shown in structural formula I.

[0134] Comparative Example 6

[0135] This comparative example provides a non-aqueous electrolyte composition and a lithium ion battery, which are different from Example 3 only in that the first solvent 1,1,2,2-tetrafluoroethyl ether is replaced by solvent EC / EMC (volume ratio of 30 / 70) in the primary injection electrolyte.

[0136] Test Case

[0137] The performance of the lithium-ion batteries provided in each embodiment and comparative example was tested, and the specific testing method is as follows:

[0138] (1) Conventional voltage high temperature cycle test: At 45°C, the battery was cycled after capacity division (3 cycles of charge and discharge at 0.33C) with a test voltage range of 2.7V-4.3V. It was charged to 4.3V at 1C constant current, and then charged at constant voltage until the current reached 0.05C. After standing for half an hour, it was discharged to 2.7V at 1C constant current to obtain the initial capacity of the first cycle of the battery and recorded as C1. Thereafter, the first week of CCCV / DC charging and discharging cycles were repeated. The capacity after the 600th cycle of discharge was recorded as C600. The capacity retention rate after 600 cycles of high temperature cycling (%) = C600 / C1×100%. Before and after the high temperature cycling of the battery cell, the DC internal resistance DCR value of the battery cell at 50% SOC was tested and recorded by the following current pulse method.

[0139] (2) DCR test: At 25°C, charge the cell before or after high temperature cycling at a constant current of 0.5C to 4.3V, charge at a constant voltage to a current of 0.05C, leave it for 1 hour, then discharge it at 0.5C for 1 hour (50% SOC), leave it for another 1 hour, and record the voltage V1 at the end; then discharge it at 2C for 10 seconds, and record the voltage V2 at the end. The DCR of the cell before or after cycling = (V1-V2) / (I 1C -I 0.1C ), the DCR before the cycle is the initial DCR, the unit is mΩ, and the DCR growth rate after the cycle is (DCR 循环后 -DCR 循环前 ) / DCR 循环前 ×100%.

[0140] (3) High-voltage and high-temperature cycle test: The test method and process are the same as (1) conventional voltage and high-temperature cycle test, except that the test voltage range is adjusted to 2.7-4.4V.

[0141] (4) Storage gas production test: The divided battery cells are charged to 4.3V at 0.33C constant current and constant voltage, and the battery reaches 100% SOC. Then the fully charged battery is placed in a 60°C oven for storage for 30 days. At 25°C, the battery volume is tested by the drainage method before and after high-temperature storage. The specific operation is as follows: Place a container containing deionized water on an electronic scale, use a fixing clip to fix the pole ear at the upper end of the soft-pack battery, immerse the soft-pack battery completely in water, and record the weight change displayed on the electronic scale. The volume of the soft-pack battery can be calculated by measuring the change in the volume of deionized water after the soft-pack battery is immersed in deionized water. The specific calculation formula is: V = (m1-m2) / ρ, where m1 is the weight of the soft-pack battery after it is completely immersed in deionized water, m2 is the weight of the soft-pack battery when it is not immersed in deionized water, and ρ is the density of deionized water (1g / mL). The volume V before storage was measured respectively. 存储前 and the volume after storage V 存储后, the cycle gas production is calculated by the following formula: (V 存储后- V 存储前 ) / V 存储前 ×100%.

[0142] The specific test results are shown in the table below:

[0143] Table 1

[0144]

[0145]

[0146] From the data in the above table, it can be seen that compared with Comparative Examples 1 to 4, Examples 1-16 have lower initial DCR, less high-temperature storage gas production, higher cycle capacity retention rate and smaller cycle DCR growth rate. It can be seen that the non-aqueous electrolyte composition defined in the present application can effectively improve the comprehensive performance of lithium-ion batteries. Compared with Comparative Examples 5 to 6, Example 3 has better comprehensive performance, indicating that the type of lithium salt and the type of solvent are preferred in the single-injection electrolyte; when the solvent or lithium salt of the single-injection electrolyte is a substance within an unrestricted range, it will cause the solvation structure of lithium ions to change, and it will not be possible to form an anion-rich lithium ion solvation shell, thereby affecting the molecular orbital energy level of the anion, making it difficult for the anion to preferentially decompose on the positive and negative electrode surfaces, and thus it is impossible to form an anion-derived inorganic-rich high-conductivity stable interface film. From the comparison between Examples 2 and 3 and Examples 4 and 5, and the comparison between Examples 15 and 16 and Example 1, it can be seen that the limitation on the dosage relationship between the primary injection electrolyte and the secondary injection electrolyte and the preference for the concentration of heterocyclic lithium carboxylate in the primary injection electrolyte can further improve the comprehensive performance of lithium-ion batteries.

[0147] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A non-aqueous electrolyte composition, characterized in that: Including primary injection electrolyte and secondary injection electrolyte, Wherein, the primary injection electrolyte includes heterocyclic carboxylic acid lithium and a first solvent, and the first solvent includes an ether solvent.

2. The non-aqueous electrolyte composition according to claim 1, characterized in that The heterocyclic carboxylate lithium has a structure shown in any of the following general formulas: Wherein, R1 is selected from one of O and S, R2 and R5 are independently selected from one of hydrogen, alkyl, halogenated alkyl, amino and phenyl; R3 is selected from one of C and N; R4 is selected from one of a connecting bond, C1-C4 alkylene or C1-C4 halogenated alkylene; Optionally, the alkyl group includes a C1-C4 alkyl group, and the haloalkyl group includes a C1-C4 haloalkyl group; Further optionally, the heterocyclic carboxylic acid lithium is selected from any of the following structures:

3. The non-aqueous electrolyte composition according to claim 1, characterized in that The concentration of the heterocyclic carboxylic acid lithium in the primary injection electrolyte is 0.3 to 2 mol / L, and optionally 0.5 to 1.5 mol / L; And / or, the mass m of the primary injection electrolyte and the mass n of the secondary injection electrolyte satisfy the following relationship: 0.2≤m / (m+n)≤0.

7.

4. The non-aqueous electrolyte composition according to claim 1, characterized in that The ether solvent includes at least one of an unsubstituted ether solvent or a halogenated ether solvent; Optionally, the ether solvent includes at least one of ethylene glycol dimethyl ether, tetrahydrofuran, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, 2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,2-tetrafluoroethyl methyl ether, 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane, difluoromethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, and hexafluoroisopropyl methyl ether.

5. The non-aqueous electrolyte composition according to any one of claims 1 to 4, characterized in that: Based on the total mass of the primary injection electrolyte, the primary injection electrolyte further comprises 0.5% to 10% of functional additives; optionally, the functional additives include positive and negative electrode film-forming additives; And / or, the secondary injection electrolyte comprises an organic solvent, a lithium salt and a functional additive; optionally, the concentration of the lithium salt in the secondary injection electrolyte is 0.5-1.5 mol / L, and the mass percentage of the functional additive is 0.5%-10%.

6. A lithium ion battery, characterized in that: The non-aqueous electrolyte composition comprises the non-aqueous electrolyte composition according to any one of claims 1 to 5.

7. The lithium-ion battery according to claim 6, characterized in that: The mass m of the primary injection electrolyte, the mass n of the secondary injection electrolyte, and the capacity C of the lithium-ion battery satisfy the following relationship: 2g / Ah≤(m+n) / C≤6g / Ah.

8. The lithium-ion battery according to claim 7, characterized in that: The non-aqueous electrolyte injection method comprises: Inject the primary injection electrolyte into the uninjected battery cell, form it, inject the secondary injection electrolyte, and let it stand.

9. The lithium-ion battery according to claim 8, characterized in that: The formation comprises standing at 25 to 60° C. for 8 to 48 hours, and charging to 50% to 100% SOC at a current of 0.05C to 0.2C; And / or, after the second injection, the standing temperature is 25 to 60° C. and the standing time is 8 to 48 hours.

10. An electrical device, characterized in that: A lithium ion battery comprising any one of claims 6 to 9.

Images