A high-voltage electrolyte additive, electrolyte and lithium ion battery
By using high-voltage electrolyte additives and mixed lithium salts to form a composite SEI film in lithium-ion batteries, the interface stability and safety issues of high-voltage lithium-ion batteries are solved, and the cycle life and high-temperature performance of the batteries are improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- 东莞维科电池有限公司
- Filing Date
- 2022-12-16
- Publication Date
- 2026-05-19
AI Technical Summary
In high-voltage lithium-ion batteries, problems such as pulverization of the positive electrode material, increased internal resistance, dissolution of transition metal ions, accelerated electrolyte consumption, damage to the SEI film of the negative electrode, and gas generation in the battery lead to shortened battery life and reduced safety.
High-voltage electrolyte additives are used, including positive electrode protection additives adiponitrile and 1,3,6-hexanetrionitrile, negative electrode film-forming additives vinylene carbonate, fluoroethylene carbonate and ethylene sulfate, and mixed lithium salts lithium hexafluorophosphate and lithium bis(oxalato)borate, to form an organic-inorganic composite SEI film, which suppresses side reactions and improves interface stability.
It improves the cycle performance, high-temperature performance and safety of lithium-ion batteries, extends battery life, reduces gas formation and electrolyte consumption, and enhances the electrochemical performance of batteries.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-ion battery technology, specifically to a high-voltage electrolyte additive, an electrolyte, and a lithium-ion battery. Background Technology
[0002] Compared to other batteries, lithium-ion batteries have attracted widespread attention due to their advantages such as light weight, small size, high energy density, and long cycle life, leading to rapid development in mobile phones, digital devices, electric vehicles, electric bicycles, power tools, and energy storage. As the capacity requirements of electrical devices continue to increase, expectations for improving the energy density of lithium-ion batteries are rising. This is especially true for portable devices such as smartphones, tablets, and laptops, which place higher demands on lithium-ion batteries for smaller size and longer standby time. Therefore, developing high-energy-density lithium-ion batteries is a crucial research direction for the lithium battery industry. Increasing the positive electrode voltage to improve the specific capacity of the material is currently one of the effective ways to improve the energy density of lithium-ion batteries.
[0003] However, as the voltage increases, problems gradually emerge. In high-voltage systems, the lithium cobalt oxide cathode material undergoes excessive lithium-ion removal, leading to particle interface pulverization, increased internal resistance, and reduced battery capacity. High-temperature cycling also makes it prone to rapid capacity loss. Simultaneously, the dissolution of transition metal ions in the cathode material catalyzes the decomposition of the electrolyte, accelerating electrolyte consumption. These transition metal ions can easily migrate with the charge and enter the anode, damaging the SEI film and causing anode failure. Furthermore, the cathode material is prone to cracking during charging and discharging, easily causing gas generation during battery use or storage, shortening battery life. In addition, the decomposition of lithium hexafluorophosphate and unstable components in the electrolyte under high-temperature conditions accelerates the damage to the electrolyte and interface film, further leading to battery failure. Summary of the Invention
[0004] In view of this, it is necessary to provide a high-voltage electrolyte additive, electrolyte, and lithium-ion battery to address the above problems and improve the cycle performance, high-temperature performance, and safety of lithium-ion batteries.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] In a first aspect, the present invention provides a high-voltage electrolyte additive, comprising additive A, wherein additive A comprises one or more of the following compounds:
[0007]
[0008] In a second aspect, the present invention provides an electrolyte comprising an organic solvent, a lithium salt, and additives; the additives include a positive electrode protection additive, a negative electrode film-forming additive, and the above-mentioned high-voltage electrolyte additives.
[0009] Furthermore, the positive electrode protective additive includes adiponitrile (ADN) and 1,3,6-hexanetrionitrile (HTCN); the negative electrode film-forming additive includes at least two of vinylene carbonate (VC), fluoroethylene carbonate (FEC), and vinyl sulfate (DTD).
[0010] Preferably, the positive electrode protective additive is adiponitrile (ADN) and 1,3,6-hexanetrionitrile (HTCN); the negative electrode film-forming additive is vinylene carbonate (VC), fluoroethylene carbonate (FEC) and vinyl sulfate (DTD).
[0011] Furthermore, the mass of the positive electrode protective additive is 2 to 10 wt% of the total mass of the electrolyte.
[0012] Furthermore, the mass of the negative electrode film-forming additive is 2 to 15 wt% of the total mass of the electrolyte.
[0013] Furthermore, the mass of the high-voltage electrolyte additive is 0.2% to 2% of the total mass of the electrolyte.
[0014] Furthermore, the lithium salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium difluorobis(oxalato)borate (DFOB), and lithium bis(oxalato)borate (BOB).
[0015] Preferably, the lithium salt is lithium hexafluorophosphate (LiPF6), lithium difluorobis(oxalato)borate (DFOB), or lithium bis(oxalato)borate (BOB).
[0016] Furthermore, the mass of the lithium salt is 12-20 wt% of the total mass of the electrolyte.
[0017] Furthermore, the organic solvent includes one or more of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and propyl propionate (PP).
[0018] Preferably, the organic solvent is a mixture of EC, PC, PP and DEC; the mass ratio of which is EC:PC:PP:DEC = 2:2:4:2.
[0019] Thirdly, the present invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and the electrolyte described above.
[0020] Furthermore, the active materials in the positive electrode include, but are not limited to, lithium cobalt oxide and ternary materials.
[0021] Furthermore, the active materials in the negative electrode include, but are not limited to, graphite and silicon carbide.
[0022] Beneficial effects
[0023] 1. The high-voltage electrolyte additive A provided by this invention can form a passivation layer at both the negative and positive electrode interfaces, suppressing the side reactions between the active material and the electrolyte. Furthermore, it can form a dense SEI film at the negative electrode interface, constructing an organic-inorganic composite SEI film with mixed lithium salts, thereby improving the stability of the negative electrode interface, slowing down the continuous consumption of negative electrode film-forming additives and gas formation during the use of lithium-ion batteries, and enhancing the cycle performance and high-temperature performance of lithium-ion batteries.
[0024] 2. The nitrogen-containing structure in additive A of the high-voltage electrolyte provided by the present invention can adsorb trace amounts of HF and water in the electrolyte, inhibit the decomposition of lithium hexafluorophosphate, and reduce damage to active materials and electrolyte; the halogen atom F it contains can improve the safety of the electrolyte.
[0025] 3. The electrolyte provided by this invention uses a unique combination of mixed lithium salts, reducing the amount of unstable LiPF6 added and replacing it with highly stable and conductive ODFB and BOB to improve high-temperature performance. These two lithium salts can also participate in film formation, thereby improving the battery's cycle performance. The negative electrode film-forming additive added to the electrolyte protects the negative electrode, preventing damage from metal leaching from the positive electrode and other electrolyte decomposition products, thus improving the battery's cycle life. The positive electrode protection additive added to the electrolyte works synergistically with high-voltage electrolyte additive A to protect the positive electrode and improve cycle and high-temperature performance.
[0026] 4. The high-voltage lithium-ion battery provided by this invention meets the requirements for high-temperature cycle life, while improving the battery's high-temperature storage performance and safety performance, thereby improving the electrochemical performance of the lithium-ion battery. Detailed Implementation
[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be further described clearly and completely below in conjunction with the embodiments of this invention. It should be noted that the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0028] It should be noted that the preparation method of compound 1 provided in the embodiments of the present invention is not intended to limit the compound of the present invention. Other conventional chemical methods can also be used to synthesize the compound, as long as the compound structure described in the present invention is satisfied.
[0029] In the description of this invention, it should be noted that unless specific conditions are specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available products.
[0030] Example 1
[0031] 1. Preparation of electrolyte
[0032] Ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and propyl propionate (PP) were mixed uniformly in a mass ratio of 20:20:40:20 to obtain an organic solvent. 14 wt% LiPF6, 1 wt% DFOB, and 0.5 wt% BOB were added to the organic solvent and stirred until completely dissolved. Then, a positive electrode protection additive, a negative electrode film-forming additive, and a high-voltage electrolyte additive were added and mixed uniformly. The positive electrode protection additive consisted of 2 wt% AND and 3 wt% HTCN; the negative electrode film-forming additive consisted of 0.5 wt% VC, 5 wt% FEC, and 2 wt% DTD; and the high-voltage electrolyte additive consisted of 0.5 wt% compound 1.
[0033] The mass percentages (wt%) mentioned in the examples refer to the percentage of the mass of each added substance relative to the total mass of the electrolyte.
[0034] The preparation method of compound 1 is as follows:
[0035] Raw material 1 is reacted at a controlled reaction temperature of 300-400℃ for 1-48 hours to obtain material 2; material 2 is then subjected to halogen atom F substitution at a temperature of 10-200℃ to obtain compound 1.
[0036]
[0037] 2. Preparation of the positive electrode: In a dry environment, the positive electrode active material lithium cobalt oxide, conductive agent acetylene black, carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are thoroughly mixed in an N-methylpyrrolidone solvent system at a mass ratio of 97:1:1:1. The mixture is then coated onto aluminum foil, dried, rolled, and slit to obtain the positive electrode sheet with a compacted density of 4.15 g / cm³. 3 .
[0038] 3. Preparation of negative electrode: The negative electrode active material graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are thoroughly mixed in a deionized water solvent system at a mass ratio of 96.3:1:1.5:1.2. The mixture is then coated onto copper foil, dried, rolled, and slit to obtain the negative electrode sheet.
[0039] 4. Preparation of 4.5V lithium-ion batteries
[0040] Using (7μm) polyethylene (PE) as the base film, and coating it with an alumina coating (2μm) and (1μm) PVDF as the separator; the above-mentioned positive electrode, separator and negative electrode are stacked in sequence, so that the separator is placed between the positive electrode and the negative electrode to play a role in isolation, and then placed in the outer packaging foil, and the electrolyte is injected into the dried battery. After vacuum sealing, standing, formation and shaping and other processes, the lithium-ion battery is completed.
[0041] Comparative Example 1
[0042] The difference from Example 1 is that the lithium salt in this comparative example is 14 wt% LiPF6 and 1 wt% LiBF4, the positive electrode protective agent is 2 wt% ADN + 3 wt% succinate (SN), the negative electrode film-forming additive is 5 wt% FEC + 0.5 wt% fluorinated ether (D2), and it does not contain compound 1, but all other aspects are the same.
[0043] Comparative Example 2
[0044] The difference from Example 1 is that the lithium salt in this comparative example is 14 wt% LiPF6 and 1 wt% ODFB, the positive electrode protective agent is 2 wt% ADN + 3 wt% SN, the negative electrode film-forming additive is 5 wt% FEC + 0.5 wt% D2, and it does not contain compound 1, while the rest are the same.
[0045] Comparative Example 3
[0046] The difference from Example 1 is that the lithium salt in this comparative example is 14 wt% LiPF6, 1 wt% ODFB and 0.5 wt% BOB, the positive electrode protective agent is 2 wt% ADN + 3 wt% SN, the negative electrode film-forming additive is 5 wt% FEC + 0.5 wt% fluorinated ether D2, and it does not contain compound 1, but all other aspects are the same.
[0047] Comparative Example 4
[0048] The difference from Example 1 is that the lithium salt in this comparative example is 14 wt% LiPF6, 1 wt% ODFB and 0.5 wt% BOB, the positive electrode protective agent is 2 wt% ADN + 3 wt% HTCN, the negative electrode film-forming additive is 5 wt% FEC + 0.5 wt% fluorinated ether D2, and it does not contain compound 1, but all other aspects are the same.
[0049] Comparative Example 5
[0050] The difference from Example 1 is that this comparative example does not contain 2 wt% DTD and 0.5 wt% compound 1, but all other contents are the same.
[0051] Comparative Example 6
[0052] The difference from Example 1 is that this comparative example does not contain 0.5 wt% of compound 1, but all other aspects are the same.
[0053] Comparative Example 7
[0054] The difference from Example 1 is that the lithium salt in this comparative example is 10 wt% LiPF6, 0.5 wt% ODFB, and 0.3 wt% BOB; the positive electrode protective agent is 1 wt% ADN and 0.5 wt% HTCN; the negative electrode film-forming additive is 0.5 wt% VC, 1 wt% FEC, and 0.2 wt% DTD; and the high-voltage electrolyte additive is 0.1 wt% of Compound 1. All other aspects are the same.
[0055] Comparative Example 8
[0056] The difference from Example 1 is that the lithium salt in this comparative example is 10 wt% LiPF6, 0.5 wt% ODFB and 0.3 wt% BOB, the positive electrode protective agent is 5 wt% ADN and 6 wt% HTCN, the negative electrode film-forming additive is 0.5 wt% VC, 1 wt% FEC and 0.2 wt% DTD, and the high-voltage electrolyte additive is 0.1 wt% of Compound 1. All other aspects are the same.
[0057] Comparative Example 9
[0058] The difference from Example 1 is that the lithium salt in this comparative example is 10 wt% LiPF6, 0.5 wt% ODFB and 0.3 wt% BOB, the positive electrode protective agent is 5 wt% ADN and 6 wt% HTCN, the negative electrode film-forming additive is 3 wt% VC, 15 wt% FEC and 1 wt% DTD, and the high-voltage electrolyte additive is 0.1 wt% of Compound 1. All other aspects are the same.
[0059] Comparative Example 10
[0060] The difference from Example 1 is that the lithium salt in this comparative example is 10 wt% LiPF6, 0.5 wt% ODFB and 0.3 wt% BOB, the positive electrode protective agent is 5 wt% ADN and 6 wt% HTCN, the negative electrode film-forming additive is 3 wt% VC, 15 wt% FEC and 1 wt% DTD, and the high-voltage electrolyte additive is 3 wt% of Compound 1. All other aspects are the same.
[0061] Comparative Example 11
[0062] The difference from Example 1 is that the lithium salt in this comparative example is 16 wt% LiPF6, 3 wt% ODFB and 2 wt% BOB, the positive electrode protective agent is 1 wt% ADN and 0.5 wt% HTCN, the negative electrode film-forming additive is 0.5 wt% VC, 1 wt% FEC and 0.2 wt% DTD, and the high-voltage electrolyte additive is 0.1 wt% of Compound 1. All other aspects are the same.
[0063] Comparative Example 12
[0064] The difference from Example 1 is that the lithium salt in this comparative example is 16 wt% LiPF6, 3 wt% ODFB and 2 wt% BOB, the positive electrode protective agent is 5 wt% ADN and 6 wt% HTCN, the negative electrode film-forming additive is 0.5 wt% VC, 1 wt% FEC and 0.2 wt% DTD, and the high-voltage electrolyte additive is 0.1 wt% of Compound 1. All other aspects are the same.
[0065] Comparative Example 13
[0066] The difference from Example 1 is that the lithium salt in this comparative example is 16 wt% LiPF6, 3 wt% ODFB and 2 wt% BOB, the positive electrode protective agent is 5 wt% ADN and 6 wt% HTCN, the negative electrode film-forming additive is 3 wt% VC, 15 wt% FEC and 1 wt% DTD, and the high-voltage electrolyte additive is 0.1 wt% of Compound 1. All other aspects are the same.
[0067] Comparative Example 14
[0068] The difference from Example 1 is that the lithium salt in this comparative example is 16 wt% LiPF6, 3 wt% ODFB and 2 wt% BOB, the positive electrode protective agent is 5 wt% ADN and 6 wt% HTCN, the negative electrode film-forming additive is 3 wt% VC, 15 wt% FEC and 1 wt% DTD, and the high-voltage electrolyte additive is 3 wt% of Compound 1. All other aspects are the same.
[0069] Lithium-ion battery performance testing
[0070] The 4.5V lithium-ion batteries prepared in Comparative Examples 1-2 and Example 1 were subjected to room temperature cycling performance tests, high temperature cycling performance tests, high temperature storage performance tests, and thermal abuse performance tests, respectively. The test methods are as follows:
[0071] 1. Room temperature cycling performance:
[0072] Under normal temperature (25±2℃) conditions, a 4.5V lithium-ion battery was charged to 4.5V at a constant current and constant voltage of 1C, with a cutoff current of 0.05C; it was then allowed to rest for 5 minutes, followed by constant current discharge at 1C to 3.0V, and then allowed to rest for 5 minutes. This charge-discharge cycle was repeated until the cycle capacity reached 80% of the initial capacity, at which point the battery's cycle life was recorded. The test results are shown in Table 1.
[0073] 2. High-temperature cycling performance
[0074] Under high temperature (45±2℃) conditions, a 4.5V lithium-ion battery was charged to 4.5V at 1C constant current and constant voltage with a cutoff current of 0.05C; it was then allowed to rest for 5 minutes, followed by constant current discharge at 1C to 3.0V, and then allowed to rest for 5 minutes. This charge-discharge cycle was repeated until the battery reached 80% of its initial capacity, at which point the cycle life was recorded. The test results are shown in Table 1.
[0075] 3. High-temperature storage performance
[0076] Under normal temperature (25±2℃), a 4.5V lithium-ion battery was subjected to one 1C / 1C charge and discharge cycle (discharge capacity denoted as C0). The initial thickness was recorded as D0, and the initial internal resistance as R0. Then, the battery was charged to 4.5V under 1C constant current and constant voltage conditions. The fully charged lithium-ion battery was stored in a 60℃ high-temperature chamber for 21 days. Immediately after removal, the thickness was measured as D1, and the internal resistance as R1. Under normal temperature conditions, a 1C discharge test was performed to maintain the capacity (discharge capacity denoted as C1). Then, a 1C / 1C charge and discharge test was performed under normal temperature conditions to recover the capacity (discharge capacity denoted as C2). The thickness change rate, internal resistance change rate, capacity retention rate, and capacity recovery rate of the battery were calculated using the following formulas. The test results are shown in Table 2.
[0077] Thickness change rate % = (D1 - D0) / D0 * 100%
[0078] Internal resistance change rate % = (R1 - R0) / R0 * 100%
[0079] Capacity retention rate % = (C1 - C0) / C0 * 100%
[0080] Capacity recovery rate % = (C2 - C0) / C0 * 100%
[0081] 4. Thermal abuse performance
[0082] Under normal temperature (25±2℃) conditions, the lithium-ion battery was fully charged to 4.5V; the fully charged lithium-ion battery was placed in a high temperature chamber and heated to 130±2℃ at a rate of (5±2℃) / min, and kept at that temperature for 60min. The battery was observed to see if it caught fire or exploded. The test results are shown in Table 3.
[0083] Table 1
[0084]
[0085] Table 2
[0086]
[0087] Table 3
[0088]
[0089]
[0090] As can be seen from the comparison between Example 1 and Comparative Example 6, when the lithium-ion battery electrolyte contains additive A provided by the present invention, the lithium-ion battery exhibits better high-temperature cycle life, high-temperature storage performance, electrochemical performance, and safety performance. This is because additive A can form a passivation layer at both the negative and positive electrode interfaces, inhibiting side reactions between the active material and the electrolyte; and additive A can form a dense SEI film at the negative electrode interface, constructing an organic-inorganic composite SEI film with mixed lithium salts, improving the stability of the negative electrode interface and slowing down the continuous consumption of negative electrode film-forming additives and gas formation during battery use; the fluorine-containing structure of additive A can effectively improve the safety performance of the electrolyte, and the nitrogen-containing structure can adsorb trace amounts of HF and moisture in the electrolyte, inhibiting the decomposition of lithium hexafluorophosphate and reducing damage to the active material and electrolyte.
[0091] As shown in Examples 1 and Comparative Examples 1-6, the battery exhibits the best overall performance when the lithium salts are lithium hexafluorophosphate (LiPF6), lithium difluorobis(oxalato)borate (DFOB), and lithium bis(oxalato)borate (BOB); the positive electrode protective additives are adiponitrile (ADN) and 1,3,6-hexanetrionitrile (HTCN); and the negative electrode film-forming additives are vinylene carbonate (VC), fluoroethylene carbonate (FEC), and ethylene sulfate (DTD). Adding 0.5 wt% of Compound 1 further enhances the battery's overall performance.
[0092] As can be seen from the comparison of Example 1 and Comparative Examples 7-14, lithium salt, positive electrode protective agent, negative electrode film-forming agent and high voltage electrolyte additive can effectively improve the overall performance of the battery only when they are within the range defined by the present invention. Too much or too little addition will not achieve good technical results.
[0093] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.
Claims
1. An electrolyte, characterized in that, The high-voltage electrolyte additive includes additive A, which comprises one or more of the following compounds: .
2. The electrolyte according to claim 1, characterized in that, The electrolyte comprises an organic solvent, a lithium salt, and additives; the additives include a positive electrode protection additive, a negative electrode film-forming additive, and the high-voltage electrolyte additive as described in claim 1.
3. The electrolyte according to claim 2, characterized in that, The positive electrode protective additive includes adiponitrile (ADN) and 1,3,6-hexanetrionitrile (HTCN); the negative electrode film-forming additive includes at least two of vinylene carbonate (VC), fluoroethylene carbonate (FEC), and vinyl sulfate (DTD).
4. The electrolyte according to claim 2, characterized in that, The mass of the positive electrode protective additive is 2 to 10 wt% of the total mass of the electrolyte.
5. The electrolyte according to claim 2, characterized in that, The mass of the negative electrode film-forming additive is 2-15 wt% of the total mass of the electrolyte.
6. The electrolyte according to claim 2, characterized in that, The mass of the high-voltage electrolyte additive is 0.2 to 2 wt% of the total mass of the electrolyte.
7. The electrolyte according to claim 2, characterized in that, The lithium salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium difluorobis(oxalato)borate (DFOB), and lithium bis(oxalato)borate (BOB); the mass of the lithium salt is 12-20 wt% of the total mass of the electrolyte.
8. The electrolyte according to claim 2, characterized in that, The organic solvent includes one or more of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and propyl propionate (PP).
9. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and the electrolyte as described in any one of claims 2 to 8.
10. The lithium-ion battery according to claim 9, wherein the active material in the positive electrode includes, but is not limited to, lithium cobalt oxide and ternary materials; and the active material in the negative electrode includes, but is not limited to, graphite and silicon carbon.