Novel sodium ion battery electrolyte and sodium ion battery
By adding phosphorous acid groups to the sodium ion battery electrolyte to form a carbonaceous protective layer and a silicon dioxide layer, the problem of sodium ion batteries being easily flammable at high temperatures is solved, and the safety of the battery is improved.
Patent Information
- Application Number
- CN202510796122.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-16
- Publication Date
- 2025-09-12
AI Technical Summary
Sodium-ion batteries generate a lot of heat in large-scale energy storage systems, and the electrolyte is easily decomposed at high temperatures, leading to the risk of battery combustion. Traditional carbonate electrolytes are easily decomposed at high temperatures, leading to the risk of battery combustion.
Phosphite groups are added to the electrolyte as additives. The phosphite groups form a carbonaceous protective layer at high temperatures, which absorbs heat, cools down and isolates the electrolyte from contact with air. The silicon dioxide layer isolates the electrode from the electrolyte, consumes hydrogen radicals and hydroxyl radicals, and inhibits the combustion reaction.
It effectively reduces the electrolyte temperature, forms a protective layer to isolate the active substances inside the battery, prevents battery combustion, and improves battery safety.
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of transformers, and specifically provides a novel sodium ion battery electrolyte and a sodium ion battery. Background Art
[0002] Sodium-ion batteries (SIBs) have garnered widespread attention in the energy storage field in recent years due to their low raw material costs, abundant sodium resources (approximately 2.3% in the Earth's crust, far exceeding lithium's 0.0017%), and environmental friendliness. They are considered a potential alternative to lithium-ion batteries (LIBs), particularly suitable for large-scale energy storage systems (such as grid storage and renewable energy storage). All batteries generate heat during operation, and larger batteries generate more heat.
[0003] The electrolyte is the medium for ion migration within the battery. Traditional electrolytes are significantly affected by temperature and are prone to decomposition at high temperatures, leading to thermal runaway. For example, traditional carbonate electrolytes are prone to thermal decomposition at high temperatures, causing solvent oxidation (on the positive electrode side) or reduction (on the negative electrode side), generating gases such as CO2 and CH4, which can cause battery bulging and even thermal runaway, and in severe cases, even combustion. When sodium-ion batteries are used in large-scale energy storage systems, they generate even more heat and pose a greater risk of battery combustion, making battery safety issues an urgent issue to address. Summary of the Invention
[0004] The present invention provides a novel sodium ion battery electrolyte and a sodium ion battery, which are used to solve the battery safety problems such as higher heat generation and greater battery combustion risk when sodium ion batteries are used in large-scale energy storage systems.
[0005] The technical solutions of the present invention are as follows:
[0006] A novel sodium ion battery electrolyte comprises a sodium salt, a solvent and an additive, wherein the sodium salt and the additive are dissolved in the solvent, and the additive comprises a phosphite group, which is used to undergo a cross-linking reaction or a polymerization reaction under high temperature conditions and form a carbonaceous protective layer. The carbonaceous protective layer absorbs heat during the reaction process to achieve cooling, and after formation, the carbonaceous protective layer isolates the active substances inside the battery.
[0007] In this solution, the electrolyte contains an additive with a phosphite group, and the phosphite group in the additive forms high-temperature protection for the electrolyte. The phosphite group undergoes polymerization or cross-linking reaction under high temperature environment, thereby forming a carbonaceous protective layer on the electrode surface or the electrolyte interface. In the process of forming the carbonaceous protective layer, heat is absorbed to cool the electrolyte, which plays a role in preventing the electrolyte temperature from rising. In addition, the carbonaceous protective layer formed by the phosphite group has certain mechanical properties and thermal stability, which can prevent the electrolyte from contacting with the air, avoid further reaction of the electrolyte with the air, and play an effect of preventing further reaction of the electrolyte, avoiding battery combustion, and improving the safety of the battery.
[0008] Preferably, the additive further includes a trimethylsilyl group, which is used to oxidize in a high temperature environment to generate silicon dioxide. The generated silicon dioxide forms a silicon dioxide layer on the electrode surface or electrolyte interface, and the silicon dioxide layer is used for heat insulation and isolation of the electrolyte from contact with oxygen.
[0009] In this scheme, the electrolyte can be isolated by a silicon dioxide layer, thereby isolating the electrode and the electrolyte, preventing the electrolyte from contacting and reacting with oxygen in a high-temperature environment, which can cause tissue combustion.
[0010] Preferably, the additive is bis(trimethylsilyl)phosphite. Bis(trimethylsilyl)phosphite decomposes into phosphate radicals and trimethylsiloxy radicals under high temperature conditions. The phosphate radicals and trimethylsiloxy radicals react with hydrogen radicals and hydroxyl radicals decomposed from the electrolyte, consuming the hydrogen radicals and hydroxyl radicals in the electrolyte, reducing the proportion of combustibles in the electrolyte, and inhibiting combustion of the electrolyte.
[0011] In this scheme, bis(trimethylsilyl)phosphite contains both phosphite groups and trimethylsilyl groups, and can decompose into phosphate radicals and trimethylsiloxy radicals under high temperature conditions. It can consume the hydrogen radicals and hydroxyl radicals decomposed in the electrolyte through reaction, reduce the concentration of combustibles in the electrolyte, and inhibit electrolyte combustion.
[0012] Preferably, the additive accounts for 0.5wt%-5wt% of the total mass of the electrolyte.
[0013] In this solution, the additive in this mass ratio can form a protective layer with a thickness of less than 30 nm when the battery is at high temperature and about to burn, preventing the electrolyte in the battery from continuing to react and causing combustion.
[0014] Preferably, the sodium salt accounts for 10 wt% to 30 wt% of the total mass of the electrolyte, and the organic solvent accounts for 70 wt% to 90 wt% of the total mass of the electrolyte.
[0015] In order to reduce the rate of the electrolyte combustion reaction and facilitate the suppression of the combustion intensity of the electrolyte in a high-temperature environment, the additive decomposes trimethylsiloxyl radicals and phosphate radicals in a high-temperature environment. The electrolyte will decompose hydrogen radicals and hydroxyl radicals in a high-temperature environment. The phosphate radicals react with the hydrogen radicals to generate hydrogen phosphate, and the trimethylsiloxyl radicals react with the hydroxyl radicals to generate siloxane. The combustion of the electrolyte is suppressed by consuming the hydrogen radicals and hydroxyl radicals through the reaction.
[0016] In this scheme, because the electrolyte will decompose into hydrogen radicals and hydroxyl radicals in a high-temperature environment, hydrogen radicals and hydroxyl radicals are important components in the combustion chain during combustion, and trimethylsiloxy radicals and phosphate radicals can capture hydroxyl radicals and hydrogen radicals respectively, thereby cutting off the hydroxyl radicals and hydrogen radicals in the combustion chain of the electrolyte, preventing hydroxyl radicals and hydrogen radicals from participating in combustion, thereby inhibiting the combustion of the electrolyte.
[0017] The sodium salt includes one or more of sodium hexafluorophosphate, anhydrous sodium perchlorate, sodium bis(oxalatoborate), sodium 2,3,4,5-tetracyanopyrrole, sodium difluorooxalatoborate, sodium pentacyanopropylene, sodium bis(fluorosulfonyl)imide, sodium bis(trifluorosulfonyl)imide, sodium (fluorosulfonyl) (perfluorobutylsulfonyl)imide, and sodium fluorosulfonyl-(trifluoromethylsulfonyl)imide.
[0018] The organic solvent includes cyclic carbonates, chain carbonates, cyclic carboxylates and chain carboxylates, wherein the cyclic ester is one or more selected from ethylene carbonate, propylene carbonate, fluoroethylene carbonate, fluoropropylene carbonate, chloroethylene carbonate and chloropropylene carbonate; the chain carbonate is one or more selected from dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate and methyl propyl carbonate.
[0019] The present invention also provides a new sodium ion battery, comprising the above-mentioned electrolyte, and also comprising a positive electrode, a negative electrode and a diaphragm, one end of the positive electrode is inserted into the electrolyte, one end of the negative electrode is inserted into the electrolyte, the diaphragm is located between the positive electrode and the negative electrode, the diaphragm prevents direct contact between the positive electrode and the negative electrode through mechanical isolation, the material of the positive electrode is sodium iron pyrophosphate, the material of the negative electrode is hard carbon, and the diaphragm is a polypropylene diaphragm.
[0020] Beneficial effects of the present invention:
[0021] The present invention adds an additive containing a phosphite group to the electrolyte, utilizes the phosphite group to undergo an endothermic reaction in a high-temperature environment to lower the temperature of the electrolyte, and forms a carbonaceous protective layer after the reaction. The carbonaceous protective layer isolates the active substances inside the battery, preventing the active substances inside the battery from continuing to react, thereby achieving a flame retardant effect. DETAILED DESCRIPTION
[0022] The technical solution of the present invention is clearly and completely described through the specific implementation methods of the embodiments of the present invention.
[0023] Example 1:
[0024] This embodiment provides a novel sodium ion battery electrolyte, including sodium salt, solvent and additives, wherein:
[0025] The additives account for 0.5-5% of the total mass of the electrolyte, and the rest is sodium salt and solvent. Sodium salt accounts for 10-30% of the total mass of the electrolyte, and organic solvent accounts for 70-90% of the total mass of the electrolyte.
[0026] The additives include any one or more of trimethyl phosphate, triethyl phosphate, tributyl phosphate, and dimethyl methyl phosphate.
[0027] All of these additives can undergo polymerization or cross-linking reactions at high temperatures, forming a protective carbon layer. This carbon layer has a certain degree of thermal stability and mechanical strength, effectively isolating the active substances inside the battery from direct contact with oxygen, thereby inhibiting the combustion reaction.
[0028] The carbonization process can also absorb some heat, lower the internal temperature of the battery, and further suppress the thermal runaway of the battery.
[0029] Therefore, the above additives can inhibit battery combustion by forming a carbonaceous protective layer to isolate the air and absorb heat.
[0030] Sodium salts include one or more of sodium hexafluorophosphate, anhydrous sodium perchlorate, sodium bis(oxalatoborate), sodium 2,3,4,5-tetracyanopyrrole, sodium difluorooxalatoborate, sodium pentacyanopropylene, sodium bis(fluorosulfonyl)imide, sodium bis(trifluorosulfonyl)imide, sodium (fluorosulfonyl) (perfluorobutylsulfonyl)imide, and sodium fluorosulfonyl-(trifluoromethylsulfonyl)imide;
[0031] The solvent includes cyclic carbonates, chain carbonates, cyclic carboxylates and chain carboxylates, wherein the cyclic ester is one or more selected from ethylene carbonate, propylene carbonate, fluoroethylene carbonate, fluoropropylene carbonate, chloroethylene carbonate and chloropropylene carbonate; the chain carbonate is one or more selected from dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate and methyl propyl carbonate.
[0032] Example 2:
[0033] The second embodiment provides a novel sodium ion battery electrolyte. The difference from the first embodiment is that the additive used in the second embodiment is bis(trimethylsilyl)phosphite.
[0034] Bis(trimethylsilyl)phosphite contains a trimethylsilyl group. Under high temperature conditions, bis(trimethylsilyl)phosphite will decompose. When bis(trimethylsilyl)phosphite decomposes, the trimethylsilyl group will be oxidized to form silicon dioxide, thereby forming a silicon dioxide layer on the battery electrode surface or electrolyte interface, preventing the electrolyte from contacting the electrode and air, and avoiding further contact with air and combustion of the electrolyte.
[0035] The additive used is bis(trimethylsilyl)phosphite. Under high temperatures, bis(trimethylsilyl)phosphite decomposes into trimethylsiloxy radicals (·SiO) and phosphate radicals (·PO). The electrolyte decomposes into hydrogen radicals (·H) and hydroxyl radicals (·OH) at high temperatures. These hydrogen and hydroxyl radicals are key components of the electrolyte combustion chain and participate in the combustion chain reaction, causing violent combustion.
[0036] Trimethylsiloxyl radicals can capture hydrogen radicals in the electrolyte and react with them to form relatively stable trimethylsilanol (SiO·H). Trimethylsiloxyl radicals can also capture hydroxyl radicals in the electrolyte and react with them to form silanol (SiO·OH), thus interrupting the chain combustion reaction between hydrogen and hydroxyl radicals.
[0037] Phosphate radicals can react with hydrogen radicals to form hydrogen phosphate; they can also react with hydroxyl radicals to form phosphoric acid. This also reduces the concentration of hydrogen and hydroxyl radicals in the electrolyte, thus inhibiting combustion.
[0038] The technical solution of the second embodiment of the present invention suppresses the combustion of the electrolyte from two aspects. First, the electrolyte can be isolated by forming a silicon dioxide layer and a carbonaceous protective layer on the electrode surface or electrolyte interface of the battery. When the battery is punctured, the electrolyte can be prevented from contacting the air. At the same time, the silicon dioxide layer and the carbonaceous protective layer will inhibit the decomposition of the electrolyte, reducing the gas decomposed by the electrolyte, thereby preventing the problem of excessive gas decomposition from causing battery bulging. In a high temperature environment, trimethylsilyl will decompose before the solvent, producing a small amount of chemically stable gas while producing a silicon dioxide layer, reducing the oxygen concentration exposed to the electrolyte and reducing the possibility of combustion. Because the content of trimethylsilyl in the electrolyte is low and the amount of gas produced is small, when the decomposition of the electrolyte is suppressed, the effect of preventing the amount of gas produced from being large and causing battery bulging can be achieved. Second, it can react with the hydrogen free radicals and hydroxyl free radicals in the electrolyte to generate relatively stable substances, reducing the important components in the electrolyte combustion reaction chain, and playing the role of suppressing electrolyte combustion.
[0039] Example 3:
[0040] This embodiment 3 provides a novel sodium ion battery, using the electrolyte of embodiment 1 or embodiment 2, and further comprising a positive electrode, a negative electrode, and a separator. The positive electrode is made of sodium iron pyrophosphate, the negative electrode is made of hard carbon, and the separator is a polypropylene separator.
[0041] The positive electrode is prepared as follows:
[0042] Sodium ferric pyrophosphate, acetylene black, and PVDF were thoroughly mixed in N-methylpyrrolidone at a mass ratio of 8:1:1 to obtain a positive electrode slurry. The slurry was evenly applied to aluminum foil and dried to obtain a positive electrode.
[0043] Comparative Example 1:
[0044] This comparative example 1 provides a sodium ion battery. The difference from Example 3 is that this comparative example 1 uses a different electrolyte.
[0045] The electrolyte used in this comparative example 1 is a conventional carbonate electrolyte.
[0046] The electrolytes of Example 1 and Example 2 were compared with the electrolyte of Comparative Example 1.
[0047] Comparison: Three identical flammable polypropylene separators were immersed in the electrolyte of Example 1, the electrolyte of Example 2, and the electrolyte of Comparative Example 1 for the same soaking time. The polypropylene separators were then removed and a portion of the separators were placed in a heat source for heating. After the separators began to burn, the separators were removed from the heat source or the heat source was turned off.
[0048] The comparison results show that the polypropylene diaphragm soaked in the electrolyte of Example 1 continues to burn after leaving the heat source, resulting in that part of the polypropylene diaphragm, in addition to the heated part, still burns.
[0049] The polypropylene diaphragm soaked in the electrolyte of Example 2 did not continue to burn after leaving the heat source. In the absence of continuous heating from an external heat source, the polypropylene diaphragm did not continue to burn, demonstrating that the electrolyte of Example 2 has good thermal safety.
[0050] After the polypropylene diaphragm in Comparative Example 1 leaves the heat source, the polypropylene diaphragm continues to burn, and the polypropylene diaphragm is eventually basically burned out.
[0051] By comparison, it can be seen that the electrolyte in Example 2 has the best flame retardant effect and the highest thermal safety.
Claims
1. A novel sodium ion battery electrolyte, characterized in that: The method comprises a sodium salt, a solvent and an additive, wherein the sodium salt and the additive are dissolved in the solvent, and the additive comprises a phosphorous acid group. The phosphite group is used to undergo a cross-linking reaction or a polymerization reaction under high temperature conditions and form a carbonaceous protective layer. The temperature is lowered by absorbing heat during the reaction process of the carbonaceous protective layer. After the carbonaceous protective layer is formed, the active substances inside the battery are isolated.
2. A novel sodium ion battery electrolyte according to claim 1, characterized in that: The additive also includes a trimethylsilyl group, which is used to oxidize in a high-temperature environment to generate silicon dioxide. The generated silicon dioxide forms a silicon dioxide layer on the electrode surface or the electrolyte interface, and the silicon dioxide layer is used for heat insulation and isolation of the electrolyte from contact with oxygen.
3. A novel sodium ion battery electrolyte according to claim 2, characterized in that: The additive is bis(trimethylsilyl)phosphite, which decomposes into phosphate free radicals and trimethylsiloxy free radicals under high temperature environment. The phosphate free radicals and trimethylsiloxy free radicals react with hydrogen free radicals and hydroxyl free radicals decomposed from the electrolyte, consume the hydrogen free radicals and hydroxyl free radicals in the electrolyte, reduce the proportion of combustibles in the electrolyte, and inhibit electrolyte combustion.
4. A novel sodium ion battery electrolyte according to claim 3, characterized in that: The additive accounts for 0.5wt%-5wt% of the total mass of the electrolyte.
5. A novel sodium ion battery electrolyte according to claim 4, characterized in that: The sodium salt accounts for 10wt%-30wt% of the total mass of the electrolyte, and the organic solvent accounts for 70wt%-90wt% of the total mass of the electrolyte.
6. A novel sodium ion battery electrolyte according to claim 2, characterized in that: The additive decomposes into trimethylsiloxyl radicals and phosphate radicals in a high-temperature environment. The electrolyte decomposes into hydrogen radicals and hydroxyl radicals in a high-temperature environment. The phosphate radicals react with the hydrogen radicals to generate hydrogen phosphate, and the trimethylsiloxyl radicals react with the hydroxyl radicals to generate siloxane. The combustion of the electrolyte is suppressed by consuming the hydrogen radicals and hydroxyl radicals through the reaction.
7. A novel sodium ion battery electrolyte according to claim 1, characterized in that: The sodium salt includes one or more of sodium hexafluorophosphate, anhydrous sodium perchlorate, sodium bis(oxalatoborate), sodium 2,3,4,5-tetracyanopyrrole, sodium difluorooxalatoborate, sodium pentacyanopropylene, sodium bis(fluorosulfonyl)imide, sodium bis(trifluorosulfonyl)imide, sodium (fluorosulfonyl)(perfluorobutylsulfonyl)imide, and sodium fluorosulfonyl-(trifluoromethylsulfonyl)imide.
8. A novel sodium ion battery electrolyte according to claim 1, characterized in that: The organic solvent includes cyclic carbonates, chain carbonates, cyclic carboxylates and chain carboxylates, wherein the cyclic ester is one or more selected from ethylene carbonate, propylene carbonate, fluoroethylene carbonate, fluoropropylene carbonate, chloroethylene carbonate and chloropropylene carbonate; the chain carbonate is one or more selected from dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate and methyl propyl carbonate.
9. A novel sodium ion battery, characterized in that: The electrolyte comprising the electrolyte according to any one of claims 1 to 9.
10. A novel sodium ion battery according to claim 9, characterized in that: It also includes a positive electrode, a negative electrode and a diaphragm. One end of the positive electrode is inserted into the electrolyte, one end of the negative electrode is inserted into the electrolyte, and the diaphragm is located between the positive electrode and the negative electrode. The diaphragm prevents direct contact between the positive electrode and the negative electrode through mechanical isolation. The material of the positive electrode is sodium iron pyrophosphate, the material of the negative electrode is hard carbon, and the diaphragm is a polypropylene diaphragm.