Crosslinked polyether composite solid polymer electrolyte as well as preparation method and application thereof
By utilizing the three-dimensional network structure of cross-linked polyether composite solid polymer electrolyte and functional additives, the problems of lithium dendrite growth and cathode structure collapse under high voltage were solved, achieving high conductivity and high stability lithium metal battery performance.
Patent Information
- Application Number
- CN202510786521.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-12
- Publication Date
- 2025-10-17
AI Technical Summary
During long-term operation, high-voltage solid-state lithium metal batteries suffer from insufficient electrolyte Li+ conductivity and oxidation stability, leading to lithium dendrite growth and cathode structure collapse, which affects battery capacity and lifespan.
A cross-linked polyether composite solid polymer electrolyte is adopted, which forms a three-dimensional network structure through an epoxy cross-linking agent. Combined with functional additives, the vacancy in the positive electrode lattice is dynamically filled, thereby improving the conductivity and mechanical properties of the electrolyte and stabilizing the positive electrode electrolyte interface.
It significantly improves the electrolyte conductivity and lithium-ion transference number, suppresses lithium dendrite growth, extends battery life, and maintains good capacity retention under high voltage.
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Figure CN120809945A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of lithium battery electrolyte materials, and mainly relates to a method for forming a solid-state polymer electrolyte by cross-linking between long polyether chains through the addition of an epoxy cross-linking agent and dynamically doping and stabilizing a positive electrode by adding a functional additive. BACKGROUND
[0002] High safety, long cycle life and high energy / power density are the key performance indicators guiding the development of the next generation of energy storage devices. The battery composed of lithium (Li) metal anode (LMA), high-voltage (>4.4V) cathode (such as high-nickel layered oxide (such as LiNi 0.8 Co 0.1 Mn 0.1 O2, NCM811) and solid-state electrolyte (SSE) shows great potential due to its high theoretical energy density and inherent safety. However, such high-voltage solid-state lithium metal batteries (LMB) have the problem of rapid capacity decline during long-time operation. Key reasons include insufficient Li + conductivity and oxidation stability of the electrolyte, unstable solid electrolyte interface (SEI) leading to lithium dendrite growth, and unstable cathode electrolyte interface (CEI).
[0003] As a solution to these problems, in-situ polymerized (quasi-)SSE has emerged and has become effective due to their in-situ formation of solid from liquid inside the battery, thereby achieving tight interfacial contact and significantly reducing interfacial resistance. Among various in-situ polymerized systems, polyether-based electrolytes (PE), such as polymerized 1,3-dioxolane (PDOL)-based electrolytes, have attracted extensive attention due to their excellent ionic conductivity at room temperature at the level of 1 mS / cm and good compatibility with LMA. However, the following two shortcomings severely limit the application of polyether-based electrolytes at high voltage. First, the polyether long-chain structure is prone to decomposition at high voltage, and severe side reactions occur on the cathode surface, leading to the formation of an unstable cathode electrolyte interface (CEI), which cannot match high-capacity high-voltage cathodes (such as nickel-cobalt-manganese ternary materials and lithium cobaltate, etc.). Second, the dissolution of transition metals from the cathode leads to degradation and structural collapse of the cathode at high voltage, thereby causing battery capacity attenuation during cycling. In this work, a new in-situ polymerized polyether electrolyte for high-voltage quasi-solid-state batteries is developed to solve the problem of low electrochemical stability of polyether-based solid-state polymer electrolytes, which is difficult to apply under high-voltage conditions. SUMMARY
[0004] The present application aims to provide a cross-linked polyether composite solid-state polymer electrolyte and a preparation method and application thereof, a three-dimensional network structure and aggregated ions in the electrolyte are formed by adding an epoxy cross-linking agent, and the solvent molecules are highly phase-separated, so that the ion conductivity, lithium ion transference number and mechanical properties are improved, and a functional additive is added to dynamically fill the lattice vacancies generated by the dissolution of transition metals in the positive electrode, so that a stable positive electrode electrolyte interface is formed, thereby solving the problem that the existing polyether network structure has low electrochemical stability and is difficult to match with a high-voltage positive electrode.
[0005] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:
[0006] A cross-linked polyether composite solid-state polyether electrolyte is prepared from an electrolyte including a polymer monomer with an epoxy alkyl functional group, an epoxy cross-linking agent, a lithium salt and a functional additive, the epoxy cross-linking agent and the polymer monomer with the epoxy alkyl functional group are in-situ polymerized to form a three-dimensional network structure, and the lithium salt and the functional additive are filled in the three-dimensional network structure.
[0007] The functional additive can release metal ions in the charging and discharging process, dynamically fill the lattice vacancies generated by the dissolution of transition metals in the positive electrode, and inhibit the lattice strain of the positive electrode, and the functional additive includes but is not limited to one or more of copper phthalocyanine, cobalt phthalocyanine, iron phthalocyanine, nickel phthalocyanine, manganese phthalocyanine, ferrocene hexafluorophosphate, cobaltocene hexafluorophosphate, decamethylferrocene hexafluorophosphate, ferrocene tetrafluoroborate, and titaniumocene hexafluorophosphate.
[0008] Specifically, the volume ratio of the polymer monomer with the epoxy alkyl functional group, the epoxy cross-linking agent and the functional additive is 1-2:0.1-1:0.001-1.
[0009] The polymer monomer with the epoxy alkyl functional group first undergoes a cationic ring-opening polymerization reaction to form a polyether backbone, and the epoxy cross-linking agent then connects different polyether backbones to form a three-dimensional network structure. The polymer monomer with the epoxy alkyl functional group includes but is not limited to one or more of 1,3-dioxolane (DOL), 1,2-epoxybutane, diglycidyl ether (DGE), polyethylene glycol diglycidyl ether (PEGDGE), propylene oxide, ethylene oxide, 1,4-dioxane, 1,2-epoxycyclopentene and 3,4-epoxy-1-butene. The epoxy cross-linking agent includes but is not limited to one or more of glycerol triglycidyl ether, 1,4-butanediol diglycidyl ether, pentaerythritol glycidyl ether, neopentyl glycol diglycidyl ether, neopentyl glycol diglycidyl ether, isocyanuric acid (S, S, S)-triglycidyl ester and 2,2'-(2,2,3,3,4,4,5,5-octafluorohexane-1,6-diyl) bis(oxirane).
[0010] The lithium salt can initiate cationic ring-opening polymerization of the polymer monomer with an epoxy alkyl functional group, and also provide ionic conductivity of the electrolyte as a cation and anion supplier. The lithium salt includes, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluoro(oxalato)borate (LiDFOB), aluminum triflate (Al(OTF)3), tin triflate (Sn(OTF)3), tin difluoride (SnF2), lithium bis(trifluorosulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium triflate (LiOTf). The concentration of the lithium salt in the electrolyte is 1.1 mmol / L to 4 mol / L.
[0011] Further, the electrolyte further includes a solvent which can improve the solubility of the lithium salt in the electrolyte, thereby improving the ionic conductivity of the electrolyte. The solvent is selected as needed to be added or not. The solvent includes, but is not limited to, one or more of dimethoxymethane (DMM), ethylene glycol dimethyl ether (DME), 1,2-diethoxyethane (DEE), 1,2-dimethoxypropane (DMP), and diphenyloxymethane (DH). The volume ratio of the polymer monomer with an epoxy alkyl functional group to the solvent is 1 to 2: 0 to 2.
[0012] A preparation method of a cross-linked polyether composite solid-state polymer electrolyte, under an inert atmosphere, a polymer monomer with an epoxy alkyl functional group, an epoxy cross-linking agent, a lithium salt, and a functional additive are stirred at room temperature to form a uniform electrolyte, and the electrolyte is in-situ polymerized to generate the cross-linked polyether composite solid-state polymer electrolyte.
[0013] Preferably, the in-situ polymerization temperature is 20 to 120°C, and the time is 60 to 300 min.
[0014] A solid-state lithium battery includes a positive electrode and a negative electrode, and a cross-linked polyether composite solid-state polymer electrolyte between the positive electrode and the negative electrode. The cross-linked polyether composite solid-state polymer electrolyte is applied in a high-voltage lithium battery, and the high-voltage range is 4.4 to 4.7 V.
[0015] The positive electrode comprises active material, conductive agent and binder, the active material, conductive agent and binder are ground, dissolved in a solvent, mixed uniformly and coated on the positive electrode sheet, wherein the active material comprises but is not limited to one of lithium cobalt oxide (LCO), lithium nickel cobalt aluminum oxide (NCA), ternary material (NCM), lithium iron phosphate (LiFePO4) and lithium nickel manganese oxide (LNMO), the conductive agent comprises but is not limited to one or more of conductive carbon black (Super P), conductive graphite, acetylene black, ketjen black, carbon nanotube, graphene, the binder comprises but is not limited to one of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), styrene butadiene rubber (SBR), polyvinyl alcohol (PVA), and the solvent comprises but is not limited to one or more of N-methyl pyrrolidone (NMP), deionized water, ethanol, isopropyl alcohol. The negative electrode is lithium metal, monocrystalline silicon, silicon monoxide or silicon-carbon composite material.
[0016] Compared with the prior art, the present application has the following beneficial effects:
[0017] (1) The epoxy crosslinking agent is crosslinked with the polyether chain to form a three-dimensional network structure to construct a rigid skeleton, and the strong coordination of lithium ions and lithium salt anions is utilized to form an internal flexible solvation structure, thereby improving the electrical conductivity, Li + ion transference number and electrochemical window of the electrolyte.
[0018] (2) The three-dimensional network structure formed by the present application has higher mechanical strength and effectively inhibits the penetration of lithium dendrites from the perspective of physical barrier, and the Li + ion transference number of 0.85 can ensure more uniform Li + deposition, greatly reducing the influence of concentration polarization caused by the migration of anions together (low transference number), inhibiting lithium dendrites from the perspective of chemical reaction, solving the problem of short circuit caused by the growth of negative electrode dendrites to pierce the separator in traditional lithium metal batteries, and prolonging the service life of the battery.
[0019] (3) The functional additive used in the present application releases metal ions during the charging and discharging process, dynamically fills the lattice vacancies generated by the dissolution of transition metals in the positive electrode, and inhibits the lattice strain of the positive electrode. The NCM811||Li battery assembled under the present application has a capacity retention rate of 82.5% after more than 300 cycles at a high cut-off voltage of 4.6V, and is also suitable for a variety of other types of high-voltage positive electrodes. BRIEF DESCRIPTION OF DRAWINGS
[0020] Figure 1 The ion conductivity and Li + ion transference number of the solid-state polymer electrolyte in Example 1 and Comparative Examples 1 and 2 are shown in the following figures.
[0021] Figure 2 The electrochemical window of the solid-state polymer electrolyte in Example 1 and Comparative Examples 1 and 2 is shown in the following figures.
[0022] Figure 3 Lithium metal surface morphology map after cycling of Li||Li battery prepared for example 1 and comparative examples 1, 2.
[0023] Figure 4 Cycling performance map of lithium metal NCM811 full battery prepared for example 1 and comparative examples 1, 2. DETAILED DESCRIPTION
[0024] The application will be described in further detail below with reference to the drawings and specific embodiments.
[0025] Example 1
[0026] (1) Preparation of electrolyte: DOL, 2,2'-(2,2,3,3,4,4,5,5-octafluoro-hexane-1,6-diyl) bis(oxymethylene), DME, copper phthalocyanine were mixed uniformly in a glove box according to the volume ratio of 1:0.5:2:0.003, and then 1 mol / L of LiDFOB and 1 mol / L of LiTFSI (the concentration is the final concentration in the electrolyte) were added. The uniform electrolyte solution was formed at room temperature under continuous stirring.
[0027] (2) Assembly of symmetrical battery: lithium metal sheet was selected as the positive and negative electrode, and the electrolyte solution of step (1) was used for battery assembly.
[0028] (3) Assembly of full battery:
[0029] (301) Preparation of battery positive electrode: NCM811, Super P, PVDF were weighed and ground and mixed uniformly, and then added to NMP and stirred uniformly to obtain a slurry, which was uniformly coated on an aluminum foil. The coated electrode sheet was transferred to an oven for drying, cut into a 10mm diameter disc and stored in a glove box for standby.
[0030] (302) CR2032 button cell was assembled according to the assembly sequence of positive electrode shell, positive electrode, step (1) electrolyte, separator, step (1) electrolyte, negative electrode (lithium metal sheet), gasket, spring and negative electrode shell.
[0031] (4) Heat curing: the batteries obtained in steps (2) and (3) were heated and cured at 60°C for 300 min to obtain cross-linked polyether composite solid-state polymer electrolyte and corresponding batteries.
[0032] Comparative Example 1
[0033] Comparative Example 1 is the same as Example 1 except for step (1). Step (1) is specifically:
[0034] (1) DOL and DME were mixed in a glove box at a volume ratio of 1:2, and then 1 mol / L LiDFOB and 1 mol / L LiTFSI were added and stirred continuously at room temperature to form a uniform electrolyte solution.
[0035] Comparative Example 2
[0036] Except for step (1), the other steps of this comparative example 1 are the same as those of example 1. Step (1) is specifically as follows:
[0037] (1) DOL, 2,2'-(2,2,3,3,4,4,5,5-octafluorohexane-1,6-diyl)bis(ethylene oxide), and DME were mixed in a glove box at a volume ratio of 1:0.5:2, and then 1 mol / L LiDFOB and 1 mol / L LiTFSI were added and stirred continuously at room temperature to form a uniform electrolyte solution.
[0038] 1. Ionic conductivity and Li + Number of migrations
[0039] The ionic conductivity of Example 1 and Li + Migration number Figure 1 As shown, an ionic conductivity greater than 2 mS / cm and a Li + The ionic conductivity of Comparative Example 1 is less than 1 mS / cm at room temperature. + The migration number is only 0.29, while the ionic conductivity of Example 2 reaches 1 mS / cm at room temperature, indicating that the formed cross-linked polyether composite polymer electrolyte provides a faster lithium ion migration channel and lower interface impedance.
[0040] 2. Electrochemical Window
[0041] like Figure 2 As shown, the electrochemical window of Example 1 reaches 5.1 V, while that of Comparative Example 1 is only 4.7 V and that of Comparative Example 2 is only 4.9 V, indicating that the formed cross-linked polyether composite polymer electrolyte has higher redox properties.
[0042] 3. Scanning electron microscope (SEM) and optical images of lithium metal surface after cycling
[0043] At 0.2 mA cm -2 After 100 hours of cycling at a current density of 100, the lithium sheet was removed from the Li||Li battery and the lithium salt on the surface was cleaned with DME solvent for sample preparation and observation. The macroscopic and microscopic appearances were as follows: Figure 3 As shown in the figure, it can be seen that the surface morphology of Example 1 is smoother and flatter than that of Comparative Examples 1 and 2, indicating that the formed cross-linked polyether polymer electrolyte can inhibit the growth and deposition of lithium dendrites.
[0044] 4. NCM811||Li battery cycle performance test
[0045] The charge-discharge performance of the above-mentioned assembled button cell was tested at room temperature by using a Land CT3002A battery test system.
[0046] Figure 4 is a lithium metal battery cycle performance chart. The NCM811||Li battery of Example 1 was cycled more than 320 times at a cutoff voltage of 4.6 V, and the capacity retention rate was 82.5%. However, Comparative Example 1 and Comparative Example 2 both short-circuited after 10 cycles and 50 cycles, respectively. This indicates that Example 1 can be matched with a high-voltage positive electrode and has higher high-voltage resistance than Comparative Examples 1 and 2.
[0047] Example 2
[0048] (1) Preparation of electrolyte: 1,2-epoxybutane, glycerol triglycidyl ether, DEE, and ferrocene tetrafluoroborate were weighed and mixed in a glove box according to a volume ratio of 1.5:0.5:1:0.01, 0.5 mol / L LiPF6 and 1.5 mol / L LiFSI were added, and the obtained precursor solution was continuously stirred at room temperature for 0.5 hours to form a uniform electrolyte solution.
[0049] (2) Preparation of battery positive electrode: LiNi0.5Mn1.5O4, carbon nanotubes, and PAA were weighed and mixed uniformly, an appropriate amount of NMP was added and stirred uniformly to obtain a slurry, which was uniformly coated on an aluminum foil. Then the coated electrode was transferred to an oven for drying, cut into a 10 mm diameter disc and stored in a glove box for standby.
[0050] (3) Assembly of full battery: CR2032 button cells were assembled according to the assembly sequence of positive electrode shell, positive electrode, step (1) electrolyte, separator, step (1) electrolyte, negative electrode (lithium metal sheet), gasket, spring, and negative electrode shell.
[0051] (4) Heat curing: the battery obtained in step (3) was heated and cured at 60°C for 150 min.
[0052] The LNMO full battery of this example was cycled more than 300 times at a high cutoff voltage of 4.7 V, and the capacity retention rate was 82.7%, which had good high-voltage resistance.
[0053] Example 3
[0054] (1) Preparation of electrolyte: propylene oxide, 1,4-butanediol diglycidyl ether, DMM, iron phthalocyanine were weighed and mixed in a glove box according to the volume ratio of 1.7:0.3:1:0.1, 0.5mol / L LiBF4 and 2mol / L LiTFSI were added, and the obtained precursor solution was continuously stirred at room temperature for 1 hour to form a uniform electrolyte solution.
[0055] (2) Preparation of battery positive electrode: LiCoO2, carbon nanotube, PAA were weighed and mixed uniformly, and then a proper amount of NMP was added and stirred uniformly to obtain a slurry, which was uniformly coated on an aluminum foil. Then the coated electrode was transferred to an oven for drying, cut into a 10mm diameter disc and stored in a glove box for standby.
[0056] (3) Assembly of full battery: CR2032 button cell was assembled according to the assembly order of positive electrode shell, positive electrode, electrolyte of step (1), separator, electrolyte of step (1), negative electrode (lithium metal sheet), gasket, spring and negative electrode shell.
[0057] (4) Heat curing: the battery obtained in step (3) was heated and cured at 60℃ for 150min.
[0058] The LiCoO2 full battery of the present embodiment has a capacity retention rate of 80.66% after more than 300 cycles at a high cut-off voltage of 4.6V, and has good high voltage resistance.
Claims
1. A cross-linked polyether composite solid polyether electrolyte, characterized in that: The invention is prepared from an electrolyte including a polymer monomer having an alkylene oxide functional group, an epoxy crosslinking agent, a lithium salt, and a functional additive. The epoxy crosslinking agent and the polymer monomer having an alkylene oxide functional group in the electrolyte are in situ polymerized to form a three-dimensional network structure. The lithium salt and the functional additive are filled in the three-dimensional network structure. The functional additive includes one or more of copper phthalocyanine, cobalt phthalocyanine, iron phthalocyanine, nickel phthalocyanine, manganese phthalocyanine, ferrocene hexafluorophosphate, cobaltocene hexafluorophosphate, decamethylferrocene hexafluorophosphate, ferrocene tetrafluoroborate, and titanocene hexafluorophosphate.
2. The cross-linked polyether composite solid polyether electrolyte according to claim 1, characterized in that The volume ratio of the polymer monomer having an alkylene oxide functional group, the epoxy crosslinking agent, and the functional additive is 1 to 2: 0.1~1:0.001~1, the concentration of lithium salt in the electrolyte is 1.1mmol / L~4mol / L.
3. The cross-linked polyether composite solid polyether electrolyte according to claim 1, characterized in that The polymer monomers having an alkylene oxide functional group include one or more of 1,3-dioxolane, 1,2-butylene oxide, diglycidyl ether, polyethylene glycol diglycidyl ether, propylene oxide, ethylene oxide, 1,4-dioxane, 1,2-epoxycyclopentene, and 3,4-epoxy-1-butene; the epoxy crosslinking agent includes one or more of glycerol triglycidyl ether, 1,4-butanediol diglycidyl ether, pentaerythritol glycidyl ether, neopentyl glycol diglycidyl ether, neopentyl glycol diglycidyl ether, (S,S,S)-triglycidyl isocyanurate, and 2,2'-(2,2,3,3,4,4,5,5-octafluorohexane-1,6-diyl)bis(ethylene oxide).
4. The cross-linked polyether composite solid polyether electrolyte according to claim 1, characterized in that The lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorooxalatoborate, aluminum trifluoromethanesulfonate, tin trifluoromethanesulfonate, tin difluoride, lithium bis(trifluorosulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium trifluoromethanesulfonate (LiOTf).
5. The cross-linked polyether composite solid polyether electrolyte according to claim 1, characterized in that The electrolyte also includes a solvent, which includes one or more of dimethoxymethane, ethylene glycol dimethyl ether, 1,2-diethoxyethane, 1,2-dimethoxypropane and diphenoxymethane, and the volume ratio of the polymer monomer having an alkylene oxide functional group to the solvent is 1-2:0-2.
6. A method for preparing the cross-linked polyether composite solid polymer electrolyte according to any one of claims 1 to 5, characterized in that: Under an inert atmosphere, a polymer monomer having an alkylene oxide functional group, an epoxy crosslinking agent, a lithium salt, and a functional additive are stirred at room temperature to form a uniform electrolyte, and the electrolyte undergoes an in-situ polymerization reaction to generate a cross-linked polyether composite solid polymer electrolyte.
7. The method for preparing the cross-linked polyether composite solid polymer electrolyte according to claim 6, characterized in that: The in-situ polymerization reaction temperature is 20-120° C., and the reaction time is 60-300 min.
8. Use of the cross-linked polyether composite solid polymer electrolyte according to claim 1 in lithium batteries.
9. Use of the cross-linked polyether composite solid polymer electrolyte according to claim 1 in a high-voltage lithium battery, wherein the high voltage range is 4.4-4.7V.