A non-aqueous electrolyte composition, a lithium-ion battery, and an electrical device.

Abstract

This application belongs to the field of lithium-ion battery technology, specifically relating to a non-aqueous electrolyte composition, a lithium-ion battery, and an electrical device. The non-aqueous electrolyte composition provided in this application includes a primary electrolyte and a secondary electrolyte. The primary electrolyte comprises lithium heterocyclic carboxylate and a first solvent, the first solvent being an ether solvent. This application ensures sufficient film formation through the coordination of the components in the primary electrolyte, forming a highly stable ion-conducting SEI / CEI interface film. This alleviates problems such as increased impedance and capacity loss caused by the deterioration of the negative electrode SEI due to the poor structural stability of the high-nickel cathode material, and maintains excellent performance under high voltage. The secondary electrolyte is not specifically limited and is a conventional electrolyte with high conductivity. Through the coordination of the two electrolytes, both film-forming performance and conductivity of the non-aqueous electrolyte composition are achieved, improving the overall battery performance.

Description

Technical Field

[0001] This application belongs to the field of lithium-ion battery technology, specifically relating to a non-aqueous electrolyte composition, a lithium-ion battery, and an electrical device. Background Technology

[0002] Layered nickel-cobalt-manganese ternary materials (NCM) have become one of the mainstream cathode materials for current power lithium battery applications due to their high specific capacity, excellent rate performance and low temperature performance. As the market demand for high energy density continues to grow, NCM materials are being developed towards higher Ni content and higher upper limit voltage. However, some characteristic problems brought about by this have limited their practical application and development.

[0003] One of the more prominent key issues is that the increased Ni content leads to a decrease in the structural stability of the cathode material, making it more prone to Li / Ni mixing during charging and discharging. This results in changes in the cathode structure and more severe dissolution of transition metal ions. The dissolution and deposition of transition metal ions induce various crosstalk side reactions between the cathode and anode, especially the damage to the SEI of the anode, which leads to the consumption and decomposition of the electrolyte and active lithium, resulting in a significant increase in impedance and severe capacity loss. Under high voltage, these problems will be further aggravated. Summary of the Invention

[0004] Therefore, the technical problem to be solved by this application is to overcome the defects in the prior art, such as the poor structural stability of high nickel cathode materials, which will cause the lithium-ion battery to increase impedance and capacity loss, and the above problems will be further aggravated under high voltage, so as to provide a non-aqueous electrolyte composition, lithium-ion battery and electrical device.

[0005] Therefore, this application provides the following technical solution:

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

[0007] The primary electrolyte solution includes lithium heterocyclic carboxylate and a first solvent, wherein the first solvent includes an ether solvent.

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

[0009]

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

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

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

[0013]

[0014]

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

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

[0017] In some alternative embodiments, the ether solvent includes at least one of unsubstituted ether solvents or halogenated ether solvents;

[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 hexafluoroisopropylmethyl ether.

[0019] In some optional embodiments, the primary electrolyte further includes 0.5% to 10% functional additives based on the total mass of the primary electrolyte; optionally, the functional additives include positive and negative electrode film-forming additives.

[0020] And / or, the secondary electrolyte includes an organic solvent, a lithium salt, and a functional additive; optionally, the concentration of the lithium salt in the secondary 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 this application, a lithium-ion battery is provided, comprising the above-described non-aqueous electrolyte composition.

[0022] In some alternative embodiments, the mass m of the primary electrolyte injection, the mass n of the secondary electrolyte injection, and the lithium-ion battery capacity C 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 a first-stage electrolyte into the unfilled cell, form it, inject a second-stage electrolyte, and let it stand.

[0025] In some alternative 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;

[0026] And / or, after the second injection, the standing temperature is 25-60℃, and the standing time is 8-48h.

[0027] According to another aspect of this application, an electrical device is provided, including the aforementioned lithium-ion battery.

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

[0029] The non-aqueous electrolyte composition provided in this application includes a primary electrolyte and a secondary electrolyte. The primary electrolyte comprises lithium heterocyclic carboxylate and a first solvent, the first solvent being an ether solvent. The non-aqueous electrolyte composition provided in this application, through the coordination of the components in the primary electrolyte, ensures sufficient film formation, forming a highly stable ion-conducting SEI / CEI interface film. This alleviates problems such as increased impedance and capacity loss caused by the deterioration of the negative electrode SEI due to the poor structural stability of the high-nickel cathode material, and maintains excellent performance under high voltage. Simultaneously, this application does not specifically limit the secondary electrolyte; it uses a conventional electrolyte with high conductivity. Through the coordination of the primary and secondary electrolytes, a balance between the film-forming performance and conductivity of the non-aqueous electrolyte composition can be achieved, improving the overall battery performance. Specifically, the primary electrolyte in this application possesses both excellent electrode wettability and interfacial film formation capabilities. By selecting lithium salts containing heterocyclic carboxylic acid anions, the composition and structure of the anion-derived interfacial film can be optimized, forming a highly stable ion-conducting SEI / CEI interfacial film rich in inorganic matter. The weakly solvated unsubstituted ether solvent has a weak effect on lithium ions, allowing more anions from the heterocyclic carboxylic acid lithium salt to participate in the lithium ion solvation shell. During charging and discharging, these anions migrate to the electrode surface with the lithium ions and preferentially undergo redox reactions to form an anion-derived interfacial film. Simultaneously, the primary solvent has excellent wettability with both the positive and negative electrodes, enabling the primary electrolyte to fully wet the electrode surface in a short time, improving wetting efficiency and ensuring more complete film formation.

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

[0031] The non-aqueous electrolyte composition provided in this application, by limiting the relationship between the mass m of the primary electrolyte and the mass n of the secondary electrolyte, can ensure uniform and moderate film formation on the electrode, thus guaranteeing the wettability of the electrode. If the mass m of the primary electrolyte is too small, the electrode cannot be sufficiently wetted, and the film formation will be uneven and insufficient; when m is too large, the film will be too thick, the impedance will be too high, and the secondary electrolyte will not be able to fully wet the electrode.

[0032] The non-aqueous electrolyte composition provided in this application further includes functional additives in the primary electrolyte solution. These functional additives can further optimize and control various properties of the electrolyte, particularly the positive and negative electrode film-forming additives, which can adjust the composition and structure of the anion-derived interfacial film in the primary electrolyte solution, thereby optimizing the ion conductivity and stability of the interfacial film.

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

[0034] The lithium-ion battery provided in this application, by limiting the specific electrolyte injection method, allows the primary electrolyte injection to rapidly wet the electrodes and form an inorganic-rich SEI / CEI interface film dominated by anion salt decomposition after the first injection, due to the excellent electrode wettability and interfacial film formation function of the primary electrolyte injection. This film exhibits excellent stability and low impedance performance, improving the battery's cycle and storage stability. After the second injection, the electrolyte injection is allowed to stand, enabling the secondary electrolyte injection to fully wet the electrodes, improving conductivity and enhancing the overall performance of the battery.

[0035] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Detailed Implementation

[0036] The following embodiments are provided to better understand this application and are not limited to the preferred embodiments described herein. They do not constitute a limitation on the content and scope of protection of this application. Any product that is the same as or similar to this application, derived by anyone under the guidance of this application or by combining features of this application with other prior art, falls within the scope of protection of this application.

[0037] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

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

[0039] To overcome the problems in existing technologies, such as increased impedance and capacity loss in lithium-ion batteries due to the poor stability of high-nickel cathode materials, which are further exacerbated under high voltage, this application provides the following technical solution:

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

[0041] The primary electrolyte solution includes lithium heterocyclic carboxylate and a first solvent, wherein the first solvent includes an ether solvent.

[0042] The non-aqueous electrolyte composition provided in this application can ensure sufficient film formation through the coordination between its components, forming a highly stable ion-conducting SEI / CEI interface film. This alleviates problems such as increased impedance and capacity loss caused by the deterioration of the negative electrode SEI due to the poor structural stability of the high-nickel cathode material, and still exhibits excellent performance under high voltage. At the same time, this application does not specifically limit the secondary electrolyte, but uses a conventional electrolyte with high conductivity. By combining the primary and secondary electrolytes, the film-forming performance and conductivity performance of the non-aqueous electrolyte composition can be balanced, thereby improving the overall battery performance. Specifically, the primary electrolyte in this application possesses both excellent electrode wettability and interfacial film formation capabilities. By selecting lithium salts containing heterocyclic carboxylic acid anions, the composition and structure of the anion-derived interfacial film can be optimized, forming a highly stable ion-conducting SEI / CEI interfacial film rich in inorganic matter. The weakly solvated unsubstituted ether or fluorinated ether solvents have a weaker effect on lithium ions, allowing more anions from the heterocyclic carboxylic acid lithium salt to participate in the lithium ion solvation shell. During charging and discharging, these anions migrate to the electrode surface with the lithium ions and preferentially undergo redox reactions to form an anion-derived interfacial film. At the same time, the primary solvent has excellent wettability with both the positive and negative electrodes, enabling the primary electrolyte to fully wet the electrode surface in a short time, improving wetting efficiency and ensuring more complete film formation.

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

[0044]

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

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

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

[0048]

[0049] The non-aqueous electrolyte composition provided in this application, by defining the structure of the heterocyclic lithium carboxylate, can further improve the various properties of the electrolyte. By introducing alkyl / haloalkylene / aromatic / aliphatic rings into the structure of the heterocyclic lithium carboxylate, the electron distribution of the organic carboxylate anion can be adjusted, balancing its binding force with lithium ions. During dissociation in the solvent, a certain degree of ion dissociation can be ensured, and the anion can be distributed in the first shell of lithium ion solvation to participate in SEI / CEI film formation. At the same time, the composition and structure of the anion-derived SEI / CEI can be adjusted, giving it better flexibility and stability.

[0050] In some alternative embodiments, the concentration of lithium heterocyclic carboxylate in the primary electrolyte is 0.5–1.5 mol / L.

[0051] As an example, the molar concentration of the lithium salt is 0.5 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, or within any range of the above values. By limiting the lithium salt concentration, this application allows for a suitable anion ratio in the lithium-ion solvation structure, thereby forming an anion-induced stable SEI / CEI interface film on the positive and negative electrode surfaces during charging and discharging, while maintaining relatively high ionic conductivity. When the lithium salt concentration is low, the number of dissociable lithium ions is limited, resulting in decreased ionic conductivity and a reduced anion ratio in the lithium-ion solvation structure, which deteriorates the ion conduction and stability of the SEI / CEI film. When the lithium salt concentration is high, it is difficult to fully dissolve and increases the electrolyte viscosity, reducing the wettability and ion conduction capacity of the electrolyte.

[0052] In some alternative embodiments, the mass m of the primary electrolyte and the mass n of the secondary 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 any range of the above values.

[0053] In this application, by limiting the ratio between the mass m of the primary electrolyte and the mass n of the secondary electrolyte, it is possible to ensure that the electrode film is uniform and of moderate thickness, thus guaranteeing the wettability of the electrode. If the mass m of the primary electrolyte is too small, the electrode cannot be sufficiently wetted, and the film formation will be uneven and insufficient; if m is too large, the film will be too thick, the impedance will be too high, and the secondary electrolyte will not be able to fully wet the electrode.

[0054] In some alternative embodiments, the ether solvent includes at least one of unsubstituted ether solvents or halogenated ether solvents;

[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 hexafluoroisopropylmethyl ether.

[0056] In some alternative embodiments, the primary electrolyte may further include 0.5% to 10% of functional additives based on the total mass of the primary electrolyte; as an example, the mass percentage of the functional additives may be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or within any of the above values.

[0057] In some optional embodiments, the functional additives in the primary 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-propanesulfonate lactone), PST (propenyl-1,3-sulfonate lactone), 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 (tracelyl phosphate); the F-containing additive includes at least one of FEC (fluorovinyl carbonate) and TTFP (tris(2,2,2-trifluoroethyl) phosphite); and the B-containing additive includes LiBOB (boronic acid dioxalate). The additives include at least one of lithium, LiODFB (lithium difluorooxalatoborate), and TMSB (tris(trimethylsilane)borate); the P-containing additives include at least one of TMSP (tris(trimethylsilane)phosphate), TMSPi (tris(trimethylsilane)phosphite), LiPO2F2 (lithium difluorophosphate), and LiODFP (lithium difluorooxalatophosphate); the CN-containing additives include at least one of HTCN (hexanetrionitrile), SN (butadionitrile), ADN (adiponitrile), DENE (1,2-bis(cyanoethoxy)ethane), and TCP (tricyanoethoxypropane).

[0059] It is understood that the use of functional additives in this application can further optimize and control 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 electrolyte and optimize the ion conductivity and stability of the interface film; by limiting the amount of functional additives, the film-forming stability, film-forming thickness and film-forming impedance can be balanced.

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

[0061] In this application, the lithium salt in the secondary 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 any range of these values. By limiting the lithium salt concentration, this application allows for a suitable anion ratio in the lithium-ion solvation structure, thereby forming an anion-induced stable SEI / CEI interface film on the positive and negative electrode surfaces during charging and discharging, while maintaining relatively high ionic conductivity. When the lithium salt concentration is low, the number of dissociable lithium ions is limited, resulting in decreased ionic conductivity and a reduced anion ratio in the lithium-ion solvation structure, which degrades the ion conduction and stability of the SEI / CEI film. When the lithium salt concentration is high, it is difficult to fully dissolve the electrolyte and increases its viscosity, reducing its wettability and ion conduction capacity.

[0062] In some optional embodiments, the functional additive is present in a mass percentage of 0.5% to 10% of the total mass of the secondary electrolyte. For example, the mass percentage of the functional additive is 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any range thereof. It is understood that the use of functional additives in this application can further optimize and control 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 interfacial film in the secondary electrolyte, optimizing the ion conductivity and stability of the interfacial film; by limiting the amount of functional additives, film stability, film thickness, and film impedance can be balanced.

[0063] In some optional embodiments, the functional additives in the secondary 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-propanesulfonate lactone), PST (propenyl-1,3-sulfonate lactone), 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 (tracelyl phosphate); the F-containing additive includes at least one of FEC (fluorovinyl carbonate) and TTFP (tris(2,2,2-trifluoroethyl) phosphite); and the B-containing additive includes LiBOB (boronic acid dioxalate). The additives include at least one of lithium, LiODFB (lithium difluorooxalatoborate), and TMSB (tris(trimethylsilane)borate); the P-containing additives include at least one of TMSP (tris(trimethylsilane)phosphate), TMSPi (tris(trimethylsilane)phosphite), LiPO2F2 (lithium difluorophosphate), and LiODFP (lithium difluorooxalatophosphate); the CN-containing additives include at least one of HTCN (hexanetrionitrile), SN (butadionitrile), ADN (adiponitrile), DENE (1,2-bis(cyanoethoxy)ethane), and TCP (tricyanoethoxypropane).

[0065] In some alternative embodiments, the organic solvent includes at least one of carbonate solvents or carboxylic acid ester solvents. As examples, 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; the carboxylic acid ester solvent includes at least one of methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, and various fluorinated cyclic and linear carboxylic acid esters.

[0066] According to another aspect of this application, a lithium-ion battery is provided, comprising the above-described non-aqueous electrolyte composition. Because the lithium-ion battery uses the above-described non-aqueous electrolyte composition, it exhibits better cycle stability and high-voltage performance.

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

[0068] This application, by limiting the electrolyte injection coefficient, ensures that the electrolyte can fully wet the cell while avoiding increased gas production and cell volume expansion caused by the continuous decomposition of excess residual electrolyte during long-term aging. Furthermore, limiting the electrolyte injection coefficient allows the battery to achieve both high energy density and low cost. In this application, the lithium-ion battery capacity C is the cell design capacity, which can be calculated using the following formula: (specific capacity of positive electrode × areal density of positive electrode × content of positive electrode active material × coating area of ​​positive electrode × number of positive electrode sheets).

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

[0070] Inject a first-stage electrolyte into the unfilled cell, form it, inject a second-stage electrolyte, and let it stand.

[0071] In some alternative embodiments, the formation includes resting 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 resting temperature can be 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, or any range of the above values; the resting time can be 8 hours, 12 hours, 16 hours, 18 hours, 20 hours, 24 hours, 28 hours, 32 hours, 36 hours, 40 hours, 44 hours, 48 ​​hours, or any range 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 any range of the above values; charging to 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% SOC, or within any range of the above values.

[0072] And / or, the settling temperature after the second injection is 25–60°C, and the settling time is 8–48 hours. As an example, the settling temperature after the second injection can be 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, or any value within the range above; the settling time can be 8 hours, 12 hours, 16 hours, 18 hours, 20 hours, 24 hours, 28 hours, 32 hours, 36 hours, 40 hours, 44 hours, 48 ​​hours, or any value within the range above.

[0073] This application, by defining specific electrolyte injection methods, ensures that the primary electrolyte injection, possessing both excellent electrode wettability and interfacial film formation capabilities, can rapidly wet the electrodes and form an inorganic-rich SEI / CEI interfacial film dominated by anion salt decomposition after the first injection formation. This film exhibits excellent stability and low impedance performance, improving the battery's cycle and storage stability. A second injection followed by a settling period allows for thorough wetting of the electrodes by the secondary electrolyte injection. In this application, the settling temperature and time affect the electrolyte's stability and its wettability on the cell; the formation current and cutoff SOC affect the film composition, thickness, and overall formation efficiency. By limiting formation parameters (including temperature, settling time, formation current, and cutoff SOC), the formed interfacial film can be guaranteed to have optimal overall performance.

[0074] Those skilled in the art will understand that the lithium-ion battery provided in this application, in addition to including the aforementioned non-aqueous electrolyte composition and the aforementioned electrolyte injection method, also includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process, lithium ions repeatedly insert and extract between the positive and negative electrode. The electrolyte acts as a conductor between the positive and negative electrode. The separator, disposed between the positive and negative electrode, primarily serves to prevent short circuits between the positive and negative electrodes while allowing lithium ions to pass through.

[0075] As an example, the positive electrode sheet includes a positive current collector and a positive active material layer. The positive current collector has two opposing surfaces in its own thickness direction, and the positive active material layer is disposed on either or both of the opposing surfaces of the positive current collector. The materials, composition, and manufacturing methods of the positive electrode sheet used in the lithium-ion secondary battery of this application may include any techniques 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 opposing surfaces in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the opposing surfaces of the negative electrode current collector. The materials, composition, and manufacturing methods of the negative electrode sheet used in the lithium-ion secondary battery of this application may include any techniques disclosed in the prior art.

[0077] The general steps for preparing positive / negative electrode sheets are as follows: Active materials, conductive agents, binders, and dispersants are added to an appropriate amount of solvent in a certain mass ratio and stirred thoroughly. By controlling the solid content, a uniform slurry is obtained. Subsequently, the formed material is coated onto a current collector foil and then dried and die-cut into shape using a roll press.

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

[0079] According to another aspect of this application, an electrical device is provided, including the aforementioned lithium-ion battery. The advantages of the described electrical device over the prior art are the same as those of the lithium-ion battery described above, and will not be repeated here.

[0080] In this application, the lithium-ion battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., 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 will now be described with reference to specific embodiments and comparative examples. It should be noted that these embodiments are merely descriptive and do not limit the present application in any way. In all embodiments 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. The non-aqueous electrolyte composition includes a primary electrolyte and a secondary electrolyte. The primary electrolyte includes: lithium heterocyclic carboxylate of structural formula I, with a concentration of 1 mol / L, and 1,1,2,2-tetrafluoroethyl ether as the solvent. It also includes 1% additive VC.

[0084] The secondary electrolyte composition includes: 1 mol / L LiPF6, and by mass percentage, 2% DTD, 1% PS, and the organic solvent composition 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 preparation: The positive electrode active material Li(Ni) is prepared... 0.9 Co 0.05 Mn 0.05 O2, conductive agent (SP), single-walled carbon nanotubes (SWNT), and binder polyvinylidene fluoride (PVDF) were added to an appropriate amount of N-methyl-2-pyrrolidone (NMP) solvent at a mass ratio of 96:2:1:1 and stirred thoroughly until the solid content was controlled to 68%, thus obtaining a positive electrode mixture slurry. Subsequently, the formed positive electrode slurry was coated onto aluminum foil, and after drying, it was roll-cut to form a positive electrode sheet (double-sided areal density of 400 g / m²). 2 ).

[0087] Negative electrode preparation: Graphite, conductive agent (SP), thickener CMC, and binder SBR were added to an appropriate amount of deionized water in a mass ratio of 95:2:1:2 and stirred thoroughly until the solid content was controlled to 55%, thus obtaining a negative electrode mixture slurry. Subsequently, the formed negative electrode slurry was coated onto copper foil, and after drying, it was roll-cut to form a negative electrode sheet (double-sided areal density of 160 g / m²). 2 ).

[0088] Battery assembly: The positive electrode, negative electrode and separator are stacked in the order of negative electrode, separator and positive electrode, and then the tabs are welded and the cells are encapsulated with aluminum-plastic film to obtain a soft-pack dry cell. Finally, the non-aqueous electrolyte prepared in each embodiment and comparative example is injected into the cell to prepare a lithium-ion battery with a capacity of 5Ah.

[0089] The injection process includes:

[0090] 7.5g of the first-fill electrolyte was injected into the obtained soft-pack dry cell, and the cell was left to stand at 45°C for 24 hours. It was then charged to 70% SOC with a low-rate current of 0.05C. 7.5g of the second-fill electrolyte was injected, and the cell was left to stand at 45°C for 24 hours to fully impregnate it, resulting in 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. The only difference from Example 1 is that the amount of electrolyte injected in the first injection is 1.5g, and the amount of electrolyte injected in the second injection is 13.5g.

[0093] Example 3

[0094] This embodiment provides a non-aqueous electrolyte composition and a lithium-ion battery. The only difference from Example 1 is that the amount of electrolyte injected in the first injection is 13.5g, and the amount of electrolyte injected in the second injection is 1.5g.

[0095] Example 4

[0096] This embodiment provides a non-aqueous electrolyte composition and a lithium-ion battery. The only difference from Example 1 is that the amount of electrolyte injected in the first injection is 3g, and the amount of electrolyte injected in the second injection is 12g.

[0097] Example 5

[0098] This embodiment provides a non-aqueous electrolyte composition and a lithium-ion battery. The only difference from Example 1 is that the amount of electrolyte injected in the first injection is 10.5g, and the amount of electrolyte injected in the second injection is 4.5g.

[0099] Example 6

[0100] This embodiment provides a non-aqueous electrolyte composition and a lithium-ion battery. The only difference from Example 1 is that the heterocyclic lithium carboxylate in the primary electrolyte has the structure shown in Formula II.

[0101] Example 7

[0102] This embodiment provides a non-aqueous electrolyte composition and a lithium-ion battery. The only difference from Example 1 is that the heterocyclic lithium carboxylate in the primary electrolyte has the structure shown in Formula III.

[0103] Example 8

[0104] This embodiment provides a non-aqueous electrolyte composition and a lithium-ion battery. The only difference from Example 1 is that the heterocyclic lithium carboxylate in the primary electrolyte has the structure shown in Formula IV.

[0105] Example 9

[0106] This embodiment provides a non-aqueous electrolyte composition and a lithium-ion battery. The only difference from Example 1 is that the heterocyclic lithium carboxylate in the primary electrolyte has the structure shown in formula V.

[0107] Example 10

[0108] This embodiment provides a non-aqueous electrolyte composition and a lithium-ion battery. The only difference from Example 1 is that the heterocyclic lithium carboxylate in the primary electrolyte has the structure shown in structural formula VI.

[0109] Example 11

[0110] This embodiment provides a non-aqueous electrolyte composition and a lithium-ion battery. The only difference from Embodiment 1 is the operating parameters of the electrolyte injection step. Specifically, 7.5g of the first-injection electrolyte is injected into the obtained soft-pack dry cell, and it is left to stand at 60°C for 8 hours. It is then charged to 70% SOC at a low rate current of 0.05C. 7.5g of the second-injection electrolyte is injected, and after standing at 60°C for 8 hours, it is fully soaked to obtain a lithium-ion battery with a capacity of 5Ah.

[0111] Example 12

[0112] This embodiment provides a non-aqueous electrolyte composition and a lithium-ion battery. The only difference from Embodiment 1 is the operating parameters of the electrolyte injection step. Specifically, 7.5g of the first-injection electrolyte is injected into the obtained soft-pack dry cell, and it is left to stand at 45°C for 24 hours. It is then charged to 80% SOC at a low rate current of 0.1C. 7.5g of the second-injection electrolyte is injected, and after standing at 45°C for 24 hours, it is fully soaked 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 Example 1, the only difference is the composition of the non-aqueous electrolyte composition. The primary electrolyte includes: lithium heterocyclic carboxylate of structural formula I with a concentration of 0.8 mol / L, 1,1,2,2-tetrafluoroethyl methyl ether as solvent, and 2% additive VC.

[0115] The secondary electrolyte composition includes: 1 mol / L lithium salt LiFSI, and by mass percentage, 2% DTD, 1% PS, and an organic solvent composition of EC / EMC / DEC volume ratio of 30:50:20.

[0116] Example 14

[0117] This embodiment provides a non-aqueous electrolyte composition and a lithium-ion battery. Compared with Example 1, the only difference is the composition of the non-aqueous electrolyte composition. The primary electrolyte includes: lithium heterocyclic carboxylate of structural formula I with a concentration of 1 mol / L, 1,1,2,2-tetrafluoroethyl methyl ether as solvent, and 2% additive FEC.

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

[0119] Example 15

[0120] This embodiment provides a non-aqueous electrolyte composition and a lithium-ion battery. The only difference from Example 3 is that the concentration of heterocyclic lithium carboxylate in the primary electrolyte is 0.3 mol / L.

[0121] Example 16

[0122] This embodiment provides a non-aqueous electrolyte composition and a lithium-ion battery. The only difference from Example 3 is that the concentration of heterocyclic lithium carboxylate in the electrolyte during the first injection is 2 mol / L.

[0123] Comparative Example 1

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

[0125] Comparative Example 2

[0126] This comparative example provides a non-aqueous electrolyte composition and a lithium-ion battery. The only difference from Example 1 is that the composition of the primary electrolyte is the same as that of the secondary electrolyte in Example 1, that is, the secondary electrolyte is used for both the primary and secondary electrolyte 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 electrolyte and the secondary electrolyte are mixed at a mass ratio of 1:1.

[0129] The difference between the injection procedure and Example 1 is that 7.5g of the above-mentioned 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. The only difference from Example 1 is that the composition of the secondary electrolyte is the same as that of the primary electrolyte in Example 1, that is, the primary electrolyte is used for both the first and second electrolyte injections.

[0132] Comparative Example 5

[0133] This comparative example provides a non-aqueous electrolyte composition and a lithium-ion battery. The only difference from Example 3 is that an equimolar amount of lithium salt LiFSI is used instead of the heterocyclic carboxylic acid lithium shown in Formula I in the primary electrolyte injection.

[0134] Comparative Example 6

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

[0136] Test case

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

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

[0139] (2) DCR Test: At 25℃, the cell is charged at a constant current of 0.5C to 4.3V before or after high-temperature cycling, then charged at a constant voltage to a current of 0.05C. After resting for 1 hour, it is discharged at 0.5C for 1 hour (50% SOC), and then rested for another hour. The voltage V1 at the end is recorded. Then, it is discharged at 2C for 10 seconds, and the voltage V2 at the end is recorded. Then, the DCR of the cell before or after cycling is (V1-V2) / (I 1C -I 0.1C The initial DCR before the cycle is given by the value in mΩ. The DCR growth rate after the cycle is given by the value in mΩ. 循环后 -DCR 循环前 ) / DCR 循环前 ×100%.

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

[0141] (4) Gas generation test during storage: The cells after capacity testing were charged to 4.3V at a constant current and constant voltage of 0.33C, reaching 100% SOC. The fully charged cells were then stored in a 60℃ oven for 30 days. At 25℃, the cell volume before and after high-temperature storage was tested using the water displacement method. The specific operation was as follows: A container filled with deionized water was placed on an electronic scale. The tabs at the top of the pouch battery were fixed using clamps. The pouch battery was completely immersed in water, and the weight change displayed on the scale was recorded. By measuring the change in the volume of deionized water after immersion, the volume of the pouch battery could be calculated. The specific calculation formula is: V=(m1-m2) / ρ, where m1 is the weight of the pouch battery after complete immersion in deionized water, m2 is the weight of the pouch battery before immersion, and ρ is the density of deionized water (1g / mL). The volume V before storage was measured separately. 存储前 and the volume V after storage 存储后The gas production in the cycle is calculated using 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] As can be seen from the data in the table above, compared with Comparative Examples 1-4, Examples 1-16 exhibit lower initial DCR, less high-temperature storage gas generation, higher cycle capacity retention, and a smaller cycle DCR growth rate. This demonstrates that the non-aqueous electrolyte composition defined in this application can effectively improve the overall performance of lithium-ion batteries. Compared with Comparative Examples 5-6, Example 3 shows superior overall performance, indicating that the primary electrolyte has a preference for the type of lithium salt and solvent. When the solvent or lithium salt in the primary electrolyte is not within the defined range, it leads to a change in the solvation structure of lithium ions, making it impossible to form an anion-rich lithium-ion solvation shell. This affects the molecular orbital energy levels of anions, making it difficult for anions to preferentially decompose on the positive and negative electrode surfaces, thus preventing the formation of anion-derived, inorganic-rich, high-conductivity, stable interface films. The comparison between Examples 2 and 3 and Examples 4 and 5, and the comparison between Examples 15 and 16 and Example 1, show that limiting the amount of primary and secondary electrolytes and optimizing the concentration of lithium heterocyclic carboxylate in the primary electrolyte can further improve the overall performance of lithium-ion batteries.

[0147] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A non-aqueous electrolyte composition, characterized in that, Includes primary injection electrolyte and secondary injection electrolyte. The primary electrolyte solution includes lithium heterocyclic carboxylate and a first solvent, wherein the first solvent includes an ether solvent. The heterocyclic lithium carboxylate has the structure shown in the following general formula: R2 and R5 are independently derived from one of hydrogen, alkyl, haloalkyl, amino, and phenyl; R3 is derived from one of C and N; and R4 is derived from one of a linking bond, a C1-C4 alkylene group, or a C1-C4 haloalkylene group.

2. The non-aqueous electrolyte composition according to claim 1, characterized in that, The alkyl group includes C1-C4 alkyl groups, and the haloalkyl group includes C1-C4 haloalkyl groups.

3. The non-aqueous electrolyte composition according to claim 2, characterized in that, The lithium heterocyclic carboxylate is selected from any of the following structures:

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

7.

5. The non-aqueous electrolyte composition according to claim 1, characterized in that, The concentration of heterocyclic lithium carboxylate in the primary electrolyte is 0.5~1.5 mol / L; And / or, the ether solvent includes at least one of unsubstituted ether solvents or halogenated ether solvents.

6. The non-aqueous electrolyte composition according to claim 5, characterized in that, The ether solvents include 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 hexafluoroisopropylmethyl ether.

7. The non-aqueous electrolyte composition according to any one of claims 1 to 6, characterized in that, The electrolyte, based on the total mass of the electrolyte injected once, also includes 0.5% to 10% functional additives. And / or, the secondary electrolyte includes an organic solvent, a lithium salt, and functional additives.

8. The non-aqueous electrolyte composition according to claim 7, characterized in that, The functional additives include positive and negative electrode film-forming additives; And / or, the concentration of lithium salt in the secondary electrolyte is 0.5~1.5 mol / L, and the mass percentage of functional additives is 0.5%~10%.

9. A lithium-ion battery, characterized in that, Includes the non-aqueous electrolyte composition according to any one of claims 1-8.

10. The lithium-ion battery according to claim 9, characterized in that, The mass m of the primary electrolyte injection, the mass n of the secondary electrolyte injection, and the lithium-ion battery capacity C satisfy the following relationship: 2g / Ah≤(m+n) / C≤6g / Ah.

11. The lithium-ion battery according to claim 10, characterized in that, The method for injecting the non-aqueous electrolyte includes: Inject a first-stage electrolyte into the unfilled cell, form it, inject a second-stage electrolyte, and let it stand.

12. The lithium-ion battery according to claim 11, characterized in that, The formation process includes standing at 25~60℃ for 8~48h and charging to 50%~100% SOC with a current of 0.05C~0.2C; And / or, after the second injection, the standing temperature is 25~60℃, and the standing time is 8~48h.

13. An electrical appliance, characterized in that, Including the lithium-ion battery according to any one of claims 9 to 12.

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