Semi-solid electrolyte and lithium ion battery

Abstract

The invention belongs to the technical field of lithium ion battery materials, and discloses a semi-solid electrolyte and a lithium ion battery. The semi-solid electrolyte comprises an anhydrous solvent, a lithium salt, a functional additive and a polymer gel network, the polymer gel network is obtained by carrying out polymerization reaction on the following monomers in percentage by mass: 40 to 70 percent of acrylate monomer, 30 to 50 percent of polyether monomer and 1 to 10 percent of anthraquinone modified crosslinking monomer; the anthraquinone modified crosslinking monomer has a structural formula as shown in a formula (1). The anthraquinone modified crosslinking monomer is adopted to modify a polymer gel network of the semi-solid electrolyte, so that the ionic conductivity of the semi-solid electrolyte can be remarkably improved, meanwhile, the impedance with an electrode interface can be remarkably reduced, and a lithium ion transmission path is improved. Therefore, the electrochemical performance of the semi-solid lithium ion battery is obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material technology, specifically relating to a semi-solid electrolyte and a lithium-ion battery. Background Technology

[0002] In recent years, with the rapid development of the electric vehicle and energy storage industries, higher requirements have been placed on the energy density, cost, cycle life, and safety of secondary batteries, represented by lithium-ion batteries. Traditional liquid electrolytes have safety issues such as leakage, fire, and explosion, which seriously hinder the further development of lithium-ion batteries.

[0003] Solid-state batteries were proposed to improve upon and replace traditional liquid electrolytes, fundamentally solving safety issues. In all-solid-state batteries, thermally stable solid polymer electrolytes or inorganic solid electrolytes are used instead of liquid electrolytes, helping to avoid electrolyte leakage and combustion / explosion. However, all-solid-state batteries still have some problems, such as poor contact between the electrolyte and electrodes, high interfacial impedance, and limited lithium-ion transport, leading to poor battery performance. To address these issues, constructing semi-solid-state batteries through in-situ polymerization technology is considered one of the most promising solutions for improving the safety performance of lithium-ion batteries.

[0004] Polymer gel semi-solid electrolytes combine the advantages of liquid electrolytes and solid polymer electrolytes, exhibiting good ionic conductivity and interfacial compatibility. They typically consist of a polymer network and an electrolyte solution; the polymer network provides mechanical support and stability, while the electrolyte solution provides ion transport channels. However, conventional polymer gels still present some obstacles to ion transport pathways, and the polymer film formed on the electrode surface creates interfaces with high impedance. These factors all contribute to reduced performance of semi-solid lithium-ion batteries. Summary of the Invention

[0005] To address the problems of high impedance and poor cycle performance in existing semi-solid lithium-ion batteries, the present invention aims to provide a semi-solid electrolyte and a lithium-ion battery.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A semi-solid electrolyte comprises an anhydrous solvent, a lithium salt, functional additives, and a polymer gel network; the polymer gel network is obtained by polymerization of monomers in the following mass ratios:

[0008] Acrylic ester monomers 40-70%, polyether monomers 30-50%, anthraquinone-modified crosslinking monomers 1-10%;

[0009] The anthraquinone-modified crosslinking monomer has the following structural formula:

[0010] In the formula, R is Linking groups or Linking group.

[0011] Preferably, the anhydrous solvent is one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate.

[0012] Preferably, the lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium dioxaborate, lithium difluorooxaborate, lithium trifluoromethanesulfonate, lithium bisfluorosulfonylimide, and lithium bistrifluoromethanesulfonylimide.

[0013] Preferably, the functional additive is one or more of vinylene carbonate, fluoroethylene carbonate, 1,3-propanesulfonate lactone, methyl vinyl sulfone, and vinyl sulfate.

[0014] Preferably, the acrylate monomer is one or more of acrylic acid, methacrylic acid, methyl methacrylate, ethyl acrylate, butyl acrylate, isooctyl acrylate, hydroxyethyl acrylate, and hydroxyethyl methacrylate.

[0015] Preferably, the polyether monomer is an allyl polyoxyethylene ether with a molecular weight of 400 to 1000.

[0016] Preferably, the semi-solid electrolyte comprises the following components by mass percentage: 60-86% anhydrous solvent, 8-15% lithium salt, 1-5% functional additives, and 5-20% polymer gel network.

[0017] A method for preparing a semi-solid electrolyte includes the following steps:

[0018] (1) Acryloyloxyethyl isocyanate was mixed with 2,6-diaminoanthraquinone or 2,6-dihydroxyanthraquinone in an organic solvent and reacted. The product was separated to obtain anthraquinone-modified crosslinking monomer.

[0019] (2) Add acrylate monomer, polyether monomer, anthraquinone modified crosslinking monomer, initiator and lithium salt and functional additive to anhydrous solvent and mix evenly. Then inject into the battery cell, let it stand to wet and then heat to polymerize to obtain a semi-solid electrolyte.

[0020] The organic solvent mentioned in step (1) is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and dimethyl sulfoxide.

[0021] The molar ratio of acryloyloxyethyl isocyanate to 2,6-diaminoanthraquinone or 2,6-dihydroxyanthraquinone in step (1) is 2:1.

[0022] The synthetic route for the anthraquinone-modified crosslinking monomer described in step (1) is shown below:

[0023]

[0024] The above reaction has extremely high reactivity and can spontaneously proceed at room temperature or under simple heating conditions, and the preparation method is simple.

[0025] A lithium-ion battery includes a positive electrode, a negative electrode, a separator, and the aforementioned semi-solid electrolyte.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] (1) Anthraquinones, due to the easy reduction and oxidation of their carbonyl groups, exhibit excellent electrochemical activity and outstanding electronic conductivity, making them excellent electron transport carriers. This invention uses anthraquinone-modified crosslinking monomers to modify the polymer gel network of a semi-solid electrolyte, which can significantly improve the ionic conductivity of the semi-solid electrolyte while significantly reducing the impedance at the electrode interface. Furthermore, the carbonyl groups of anthraquinones have a strong coordination ability with lithium ions, enabling them to synergistically promote the dissociation of lithium salts with the polyether chains, thereby enhancing lithium-ion transport. Finally, the anthraquinone-modified crosslinking monomers of this invention possess a highly sterically hindered polycyclic structure, which, while improving the stability of the crosslinking structure, can spontaneously adjust the crosslinking network density and uniformity, thereby reducing the obstruction of the crosslinking network to the ion transport path. Through these combined effects, the impedance of the semi-solid lithium-ion battery is significantly reduced, and the cycle performance is improved.

[0028] (2) The anthraquinone modified crosslinking monomer preparation method used in this invention is simple. It can spontaneously react at room temperature or under simple heating conditions, and the industrialization difficulty is low. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0030] Example 1

[0031] A semi-solid electrolyte and a semi-solid lithium-ion battery are disclosed, and their preparation method is as follows:

[0032] (1) Acryloyloxyethyl isocyanate and 2,6-diaminoanthraquinone were added to N,N-dimethylformamide solvent after nitrogen deoxygenation and dehydration at a molar ratio of 2:1 and mixed and dissolved. The mixture was heated to 40°C in a water bath and reacted for 2 hours to complete the reaction. The solvent was removed by flash evaporation of the reaction mixture to obtain the anthraquinone modified crosslinking monomer.

[0033] (2) Weigh each raw material according to the mass fraction. Add 54 parts of butyl acrylate monomer, 40 parts of allyl polyoxyethylene ether monomer with a molecular weight of 600, 6 parts of anthraquinone modified crosslinking monomer, 0.5 parts of azobisisobutyronitrile initiator, 120 parts of lithium hexafluorophosphate, and 30 parts of 1,3-propanesulfonate lactone to 750 parts of a mixed solvent of methyl ethyl carbonate and ethylene carbonate with a volume ratio of 1:1 and mix evenly. Then inject it into a lithium-ion battery cell containing a positive electrode (composed of 96 wt% lithium nickel cobalt manganese oxide, 2.5% conductive carbon black and 1.5% binder), a negative electrode (composed of 95 wt% graphite, 3% conductive carbon black and 2% binder) and a separator (vacuum baking to remove oxygen and water before use). After standing at room temperature for 12 h to soak, heat to 65℃ for 4 h to polymerize to obtain a semi-solid electrolyte and a semi-solid lithium-ion battery.

[0034] The DC impedance (DCIR) value of the semi-solid-state lithium-ion battery obtained in this embodiment was tested. The battery was placed in a 25°C environment and discharged at a constant current of 1C to a cutoff voltage of 2.0V. After resting for 5 minutes, it was charged at a constant current and constant voltage of 1C to the upper limit voltage of 4.0V, with a cutoff current of 0.05C. It was then discharged at a constant current of 1C for 30 minutes. The battery, adjusted to 50% SOC, was placed at 25°C and rested for 5 minutes. It was then discharged at a constant current of 2C for 30 seconds, with the discharge current during 2C discharge being I²C. The initial voltage was recorded. The voltage V0 and the voltage V1 after 30 seconds of discharge are given. The formula for calculating the DC internal resistance at 50% SOC is as follows: DCIR (Ω) = (V0 - V1) / I²C. Cycle performance is also assessed (the battery is charged at 25°C with a constant current of 1C to 4.0V, then charged at a constant voltage of 4.0V to a cutoff current of 0.05C, and then discharged at 1C for 600 cycles. The discharge capacity of the 600th cycle is recorded and divided by the discharge capacity of the 1st cycle to obtain the capacity retention rate). Its DCIR value is 42.6Ω, and the capacity retention rate is 94.3%.

[0035] Example 2

[0036] A semi-solid electrolyte and a semi-solid lithium-ion battery are disclosed, and their preparation method is as follows:

[0037] (1) Acryloyloxyethyl isocyanate and 2,6-diaminoanthraquinone were added to N,N-dimethylformamide solvent after nitrogen deoxygenation and dehydration at a molar ratio of 2:1 and mixed and dissolved. The mixture was heated to 40°C in a water bath and reacted for 2 hours to complete the reaction. The solvent was removed by flash evaporation of the reaction mixture to obtain the anthraquinone modified crosslinking monomer.

[0038] (2) Weigh each raw material according to the mass parts, add 45 parts of butyl acrylate monomer, 45 parts of allyl polyoxyethylene ether monomer with a molecular weight of 800, 10 parts of anthraquinone modified crosslinking monomer, 0.5 parts of azobisisobutyronitrile initiator, 120 parts of lithium hexafluorophosphate, and 30 parts of 1,3-propanesulfonate lactone to 750 parts of a mixed solvent of methyl ethyl carbonate and ethylene carbonate with a volume ratio of 1:1 and mix evenly. Then inject it into a lithium-ion battery cell containing a positive electrode (composed of 96wt% lithium nickel cobalt manganese oxide, 2.5% conductive carbon black and 1.5% binder), a negative electrode (composed of 95wt% graphite, 3% conductive carbon black and 2% binder) and a separator (vacuum baking to remove oxygen and water before use), let it stand at room temperature for 12h to soak, and then heat it to 65℃ for 4h to polymerize, to obtain a semi-solid electrolyte and a semi-solid lithium-ion battery.

[0039] The DC impedance (DCIR) of the semi-solid-state lithium-ion battery obtained in this embodiment was tested to be 41.2Ω, and the capacity retention rate was 94.6%.

[0040] Example 3

[0041] A semi-solid electrolyte and a semi-solid lithium-ion battery are disclosed, and their preparation method is as follows:

[0042] (1) Acryloyloxyethyl isocyanate and 2,6-diaminoanthraquinone were added to N,N-dimethylformamide solvent after nitrogen deoxygenation and dehydration at a molar ratio of 2:1 and mixed and dissolved. The mixture was heated to 40°C in a water bath and reacted for 2 hours to complete the reaction. The solvent was removed by flash evaporation of the reaction mixture to obtain the anthraquinone modified crosslinking monomer.

[0043] (2) Weigh each raw material according to the mass parts, add 65 parts of butyl acrylate monomer, 30 parts of allyl polyoxyethylene ether monomer with a molecular weight of 400, 5 parts of anthraquinone modified crosslinking monomer, 0.5 parts of azobisisobutyronitrile initiator, 120 parts of lithium hexafluorophosphate, and 30 parts of 1,3-propanesulfonate lactone to 750 parts of a mixed solvent of ethyl methyl carbonate and ethylene carbonate with a volume ratio of 1:1 and mix evenly. Then inject it into a lithium-ion battery cell containing a positive electrode (composed of 96 wt% lithium nickel cobalt manganese oxide, 2.5% conductive carbon black and 1.5% binder), a negative electrode (composed of 95 wt% graphite, 3% conductive carbon black and 2% binder) and a separator (vacuum baking to remove oxygen and water before use), let it stand at room temperature for 12 h to soak, and then heat it to 65℃ for 4 h to polymerize, to obtain a semi-solid electrolyte and a semi-solid lithium-ion battery.

[0044] The DC impedance (DCIR) of the semi-solid-state lithium-ion battery obtained in this embodiment was tested to be 45.1Ω, and the capacity retention rate was 92.8%.

[0045] Example 4

[0046] A semi-solid electrolyte and a semi-solid lithium-ion battery are disclosed, and their preparation method is as follows:

[0047] (1) Acryloyloxyethyl isocyanate and 2,6-dihydroxyanthraquinone were added to N,N-dimethylformamide solvent after nitrogen deoxygenation and dehydration at a molar ratio of 2:1 and mixed and dissolved. The mixture was heated to 80°C in a water bath and reacted for 6 hours to complete the reaction. The solvent was removed by flash evaporation of the reaction mixture to obtain the anthraquinone modified crosslinking monomer.

[0048] (2) Weigh each raw material according to the mass parts, add 50 parts of butyl acrylate monomer, 40 parts of allyl polyoxyethylene ether monomer with a molecular weight of 600, 10 parts of anthraquinone modified crosslinking monomer, 0.5 parts of azobisisobutyronitrile initiator, 120 parts of lithium hexafluorophosphate, and 30 parts of 1,3-propanesulfonate lactone to 750 parts of a mixed solvent of methyl ethyl carbonate and ethylene carbonate with a volume ratio of 1:1 and mix evenly. Then inject it into a lithium-ion battery cell containing a positive electrode (composed of 96wt% lithium nickel cobalt manganese oxide, 2.5% conductive carbon black and 1.5% binder), a negative electrode (composed of 95wt% graphite, 3% conductive carbon black and 2% binder) and a separator (vacuum baking to remove oxygen and water before use), let it stand at room temperature for 12h to soak, and then heat it to 65℃ for 4h to polymerize, to obtain a semi-solid electrolyte and a semi-solid lithium-ion battery.

[0049] The DC impedance (DCIR) of the semi-solid-state lithium-ion battery obtained in this embodiment was tested to be 42.7Ω, and the capacity retention rate was 93.6%.

[0050] Example 5

[0051] A semi-solid electrolyte and a semi-solid lithium-ion battery are disclosed, and their preparation method is as follows:

[0052] (1) Acryloyloxyethyl isocyanate and 2,6-dihydroxyanthraquinone were added to N,N-dimethylformamide solvent after nitrogen deoxygenation and dehydration at a molar ratio of 2:1 and mixed and dissolved. The mixture was heated to 80°C in a water bath and reacted for 6 hours to complete the reaction. The solvent was removed by flash evaporation of the reaction mixture to obtain the anthraquinone modified crosslinking monomer.

[0053] (2) Weigh each raw material according to the mass fraction. Add 60 parts of butyl acrylate monomer, 38 parts of allyl polyoxyethylene ether monomer with a molecular weight of 1000, 2 parts of anthraquinone modified crosslinking monomer, 0.5 parts of azobisisobutyronitrile initiator, 120 parts of lithium hexafluorophosphate, and 30 parts of 1,3-propanesulfonate lactone to 750 parts of a mixed solvent of methyl ethyl carbonate and ethylene carbonate with a volume ratio of 1:1 and mix evenly. Then inject it into a lithium-ion battery cell containing a positive electrode (composed of 96wt% lithium nickel cobalt manganese oxide, 2.5% conductive carbon black and 1.5% binder), a negative electrode (composed of 95wt% graphite, 3% conductive carbon black and 2% binder) and a separator (vacuum baking to remove oxygen and water before use). After standing at room temperature for 12h to soak, heat to 65℃ for 4h to polymerize to obtain a semi-solid electrolyte and a semi-solid lithium-ion battery.

[0054] The DC impedance (DCIR) of the semi-solid-state lithium-ion battery obtained in this embodiment was tested to be 49.5Ω, and the capacity retention rate was 90.7%.

[0055] Comparative Example 1

[0056] A semi-solid electrolyte and a semi-solid lithium-ion battery, compared with Example 1, use an equal amount of polyethylene glycol diacrylate crosslinking monomer to replace the anthraquinone modified crosslinking monomer, and the rest are the same.

[0057] The DC impedance (DCIR) of the semi-solid-state lithium-ion battery obtained in this comparative test was 62.5Ω, and the capacity retention rate was 81.7%.

[0058] The results above demonstrate that the polymer gel network semi-solid electrolyte and semi-solid lithium-ion battery prepared using anthraquinone-modified crosslinked monomers exhibit significantly improved electrochemical performance. This is because the introduction of the anthraquinone crosslinked structure enhances the ionic conductivity of the gel electrolyte, improves the lithium-ion transport pathway, and significantly reduces the impedance at the electrode interface.

[0059] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A semi-solid electrolyte, characterized in that, It includes anhydrous solvent, lithium salt, functional additives, and a polymer gel network; the polymer gel network is obtained by polymerization of monomers in the following mass ratios: Acrylic ester monomers 40-70%, polyether monomers 30-50%, anthraquinone-modified crosslinking monomers 1-10%; The anthraquinone-modified crosslinking monomer has the following structural formula: In the formula, R is Linking groups or Linking group.

2. The semi-solid electrolyte according to claim 1, characterized in that, The anhydrous solvent is one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate; the lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium dioxaborate, lithium difluorooxaborate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

3. The semi-solid electrolyte according to claim 1, characterized in that, The functional additive is one or more of vinylene carbonate, fluoroethylene carbonate, 1,3-propanesulfonate lactone, methyl vinyl sulfone, and vinyl sulfate.

4. The semi-solid electrolyte according to claim 1, characterized in that, The acrylate monomer is one or more of acrylic acid, methacrylic acid, methyl methacrylate, ethyl acrylate, butyl acrylate, isooctyl acrylate, hydroxyethyl acrylate, and hydroxyethyl methacrylate.

5. The semi-solid electrolyte according to claim 1, characterized in that, The polyether monomer is an allyl polyoxyethylene ether with a molecular weight of 400 to 1000.

6. The semi-solid electrolyte according to claim 1, characterized in that, The semi-solid electrolyte comprises the following components by mass percentage: 60-86% anhydrous solvent, 8-15% lithium salt, 1-5% functional additives, and 5-20% polymer gel network.

7. A method for preparing a semi-solid electrolyte, characterized in that, Includes the following steps: (1) Acryloyloxyethyl isocyanate was mixed with 2,6-diaminoanthraquinone or 2,6-dihydroxyanthraquinone in an organic solvent and reacted. The product was separated to obtain anthraquinone-modified crosslinking monomer. (2) Add acrylate monomer, polyether monomer, anthraquinone modified crosslinking monomer, initiator and lithium salt and functional additive to anhydrous solvent and mix evenly. Then inject into the battery cell, let it stand to wet and then heat to polymerize to obtain a semi-solid electrolyte.

8. The method for preparing a semi-solid electrolyte according to claim 7, characterized in that, The organic solvent mentioned in step (1) is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and dimethyl sulfoxide.

9. The method for preparing a semi-solid electrolyte according to claim 7, characterized in that, The molar ratio of acryloyloxyethyl isocyanate to 2,6-diaminoanthraquinone or 2,6-dihydroxyanthraquinone in step (1) is 2:

1.

10. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and the semi-solid electrolyte as described in any one of claims 1 to 6.

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