An electrolyte for all-weather battery with high nickel positive electrode material

Abstract

The present invention relates to an electrolyte for a full-climate battery with a high-nickel cathode material, which solves the problems that lithium-ion batteries with layered high-nickel oxides as the cathode material face aggravated deterioration of the high-temperature interface, resulting in a decline in performance stability and potential safety hazards, and more importantly, it cannot overcome the technical bottleneck of electrochemical performance such as discharge capacity, Coulomb efficiency, and cycle life at both room temperature and low temperature of the battery. The working temperature of the lithium-ion battery with a high-nickel cathode material is extended to -60°C to 55°C. Through the component design of a sulfone-based high-concentration electrolyte and the introduction of a lithium salt additive LiClO4, the solvation sheath structure is changed, the HOMO of the system of organic solvent dipoles and ions is reduced, and the basic composition and structural characteristics of the CEI on the surface of the high-nickel cathode material are further regulated, forming an interfacial layer that is dense, firm, and has a low desolvation energy. The battery maintains excellent interfacial stability and capacity retention rate during high-temperature storage and high-temperature cycling, and still releases a high specific capacity and excellent cycling performance at low temperature.

Description

Technical field:

[0001] The present invention belongs to the technical field of energy storage and conversion, and more specifically relates to an electrolyte for an all-weather battery using a high-nickel positive electrode material. Background technology:

[0002] High nickel layered metal oxides have become the mainstream positive electrode material system for power batteries with high theoretical specific capacity (>250mAh / g) and high operating voltage (~3.65V). When high nickel positive electrode materials are charged to high voltage, they can theoretically increase the Li + The utilization rate (i.e. reversible capacity) of Li + Excessive deintercalation and high oxide Ni appears on the positive electrode surface 4+ , the reaction activity of the electrolyte and the positive electrode surface is enhanced, and the battery performance is irreversibly attenuated. Especially under high temperature conditions, the side reactions between commercial carbonate electrolytes and electrodes are intensified, producing gas and releasing a large amount of heat, causing potential hazards such as thermal runaway and explosion. In addition, commercial carbonate electrolytes inevitably solidify at -20°C and below, the ionic conductivity of the electrolyte decreases, and the desolvation barrier on the electrode surface increases sharply, limiting the operation of the battery at low temperatures. However, with the rapid promotion of electric vehicles and various electronic devices in many fields, there is an urgent need to broaden the application temperature range of batteries, design and develop wide temperature range high-voltage electrolytes, to ensure the application of high-nickel positive electrode materials in high-energy density batteries, and to improve the safety and reliability of high-energy density batteries in the full climate temperature range and excellent discharge performance.

[0003] Due to the different mechanisms of electrolyte / electrode interface degradation and even damage under high or low temperature conditions, the requirements for electrolyte indicators are not the same, and the technical difficulty of taking into account a wide temperature range is very high. An excellent low-temperature electrolyte needs to have a wide liquid range, and at the same time adsorb and react at the electrode interface to form a stable interface passivation film CEI, and is required to have a low interface desolvation energy, thereby reducing the interface barrier and facilitating the migration of lithium ions. However, low-temperature electrolytes usually have poor chemical stability and thermal stability at room temperature / high temperature, and it is difficult to form a dense and solid CEI at the positive electrode interface, and the cycle stability and storage performance of the battery deteriorate, and the safety is reduced. At the same time, the high-nickel positive electrode material itself has high reaction activity under charge and discharge conditions, and the electrochemical stability of the interface with the electrolyte is extremely challenging. Therefore, the current research and development of electrolytes matching high-nickel positive electrode materials mainly focuses on solving the use problems at low and normal temperatures, or taking into account both high temperature and normal temperature usage scenarios. Patent CN113675474A provides a phosphorus-containing electrolyte additive, which forms a stable CEI film on the positive electrode surface, inhibits gas production, improves flame retardancy, and greatly improves the high-temperature cycle performance of high-nickel ternary lithium-ion batteries. The invention patent CN113764737A discloses an additive containing a cyclic unsaturated double bond of silicon, which polymerizes at the positive electrode interface. The formed interface film can reduce the surface activity of the positive electrode and inhibit the oxidative decomposition of the electrolyte, mainly improving the high-temperature performance of the ternary battery. The invention patent CN114142086A provides a low-temperature resistant electrolyte containing a sulfonic acid silane potassium salt compound as an additive, including: lithium salt, organic solvent, film-forming additive, low-temperature resistant additive, and the low-temperature stability of the battery is improved. The invention patent CN113823837A provides a non-aqueous electrolyte containing a solvent, a lithium salt, an organic silicon nitrile additive A and an oxazolone additive B. When applied to a ternary lithium-ion battery, it can maintain a stable cycle at a high temperature of 45°C, and can also achieve normal operation at a low temperature of -10°C. For batteries that use high-nickel positive electrode materials, it is necessary to find a wide-temperature range high-voltage electrolyte system that has both low-temperature, high-temperature and room-temperature performance, and to continue to expand to lower temperatures (-60°C) and higher temperatures (55°C). There are huge technical challenges in designing all-weather batteries. Summary of the invention:

[0004] The present invention is an electrolyte for an all-weather battery with a high-nickel positive electrode material, which solves the problem that the interface of lithium-ion batteries with high-nickel oxide as the positive electrode material deteriorates aggravatedly at high temperatures, causing reduced stability and potential safety hazards, and cannot take into account the electrochemical properties of the battery such as discharge capacity, coulomb efficiency and cycle life at room and low temperatures. The operating temperature of the battery with a high-nickel positive electrode material is extended to -60°C to 55°C.

[0005] The electrolyte of a high-nickel cathode material all-climate battery of the present invention comprises at least the following components: sulfone-based solvent, fluorinated ether, sulfonic acid-based lithium salt, and LiClO4. It is characterized in that the molar ratio of the sulfonic acid-based lithium salt to the sulfone-based solvent is 2 to 4, the molar ratio of the sulfonic acid-based lithium salt to LiClO4 is 0.01 to 0.0125, and the mass ratio of the sulfone-based solvent to the fluorinated ether is 0.5 to 2; the high-nickel cathode material is LiNi x M y O2, where M is at least one of Al, Mn, Co, and Mg, 0.5 ≤ x ≤ 0.98, 0 ≤ y ≤ 0.2, 0 < x + y ≤ 1, and LiNi x M y O2 is in the R-3m space group.

[0006] The sulfone-based solvent is one of dimethyl sulfone, methyl ethyl sulfone, diethyl sulfone, phenyl ethyl sulfone, diphenyl sulfone, sulfolane, bisphenol, dimethyl sulfoxide, diethyl sulfoxide, and benzyl phenyl sulfoxide.

[0007] The sulfone-based solvent is preferably at least one of sulfolane, dimethyl sulfoxide, and diethyl sulfoxide.

[0008] The fluorinated ether is one or two of 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl nonafluorobutyl ether, 2,2,2-trifluoroethyl ether, 1,1,5-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, and 2,2,2-trifluoroethyl-1,1,1-2,2-pentafluoroethyl ether.

[0009] The sulfonic acid-based lithium salt is one of lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, 2-trifluoromethylbenzenesulfonyl lithium, o-sulfonylbenzoic acid imide lithium, lithium bis(pentafluoroethylsulfonyl)imide, and lithium bis(hexafluoroisopropoxy) sulfonyl imide.

[0010] A battery composed of the electrolyte of a high-nickel cathode material all-climate battery can operate at -60°C to 55°C.

[0011] The advantages and technical advantages of the electrolyte of the present invention are as follows:

[0012] (1) Through the design of the electrolyte components and the addition of lithium perchlorate LiClO4, the interaction between cations and anions inside the first solvation sheath of the electrolyte is enhanced, the proportion of ion aggregates is increased, the solvation sheath structure is fundamentally changed, and the lithium ion transference number is significantly increased; the highest occupied molecular orbital HOMO of the organic solvent dipole-ion interaction system is reduced, and the overall oxidation potential is increased.

[0013] (2) The electrolyte of the present invention changes the original oxidation reaction at the interface of the high-nickel positive electrode material. The overall number of anions participating in the oxidation is reduced, but the proportion of defluorination is increased, so that the passivation layer CEI is thinner and stronger, which inhibits the repeated occurrence of side reactions at the interface between the high-nickel positive electrode material and the electrolyte, reduces the interface resistance, and ensures the stability and safety of the battery at room temperature and high temperature.

[0014] (3) The electrolyte of the present invention has low desolvation energy at the interface of high-nickel positive electrode materials, which significantly reduces the Li + The main barrier in the interface diffusion dynamics effectively promotes the interface transport of lithium ions at low temperatures, ensuring good discharge capacity at low temperatures even at -60°C and stable cycle performance at -20°C.

[0015] (4) The electrolyte of the present invention starts from the regulation of the solvation sheath, a key factor that determines the performance of the electrolyte and even the battery, and optimizes Li + The first solvation layer structure changes the redox reaction path of the electrode surface, realizes the joint regulation of the bulk and interface properties of the electrolyte, and achieves the technical goal of taking into account the high temperature, room temperature and low temperature performance of high nickel positive electrode materials. Description of the drawings:

[0016] Figure 1 It is the differential scanning calorimetry DSC graph of the electrolyte of Example 1.

[0017] Figure 2 1 is a conductivity diagram of the electrolyte of Example 1 at different temperatures.

[0018] Figure 3 It is the solvation sheath structure of the electrolyte in Example 2. Molecular dynamics is used to simulate the configuration distribution between particles inside the electrolyte.

[0019] Figure 4 The electrolyte of Example 3 matches Li||LiNi 0.8 Co 0.15 Al 0.05 O2 battery, charge and discharge cycle test chart at 55°C.

[0020] Figure 5 The electrolyte of Example 4 is Li|LiNi 0.8 Mn 0.1 Co 0.1 The O2 battery was charged at 0.3C at room temperature and left to stand at -60℃ for 6 hours, and then discharged at 0.1C at -60℃.

[0021] Figure 6 The electrolyte of Example 4 is Li||LiNi 0.8 Mn 0.1 Co0.1 Cycling curves of the O2 battery during charge and discharge at -20°C. Specific implementation method:

[0022] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] The high-nickel cathode material described in the following embodiments is LiNi x M y O2, where M is at least one of Al, Mn, Co, and Mg, 0.5 ≤ x ≤ 0.98, 0 ≤ y ≤ 0.2, 0 < x + y ≤ 1, and LiNi x M y O2 is in the R-3m space group.

[0024] Example 1:

[0025] An electrolyte for a high-nickel cathode material all-climate battery, comprising the following components: dimethyl sulfoxide, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, lithium bis(fluorosulfonyl)imide, and LiClO4, where the molar ratio of lithium bis(fluorosulfonyl)imide to dimethyl sulfoxide is 3, the molar ratio of lithium bis(fluorosulfonyl)imide to LiClO4 is 0.012, and the mass ratio of dimethyl sulfoxide to 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether is 0.5.

[0026] The electrolyte maintains a good flow state in a wide temperature range. After differential scanning calorimetry analysis, as Figure 1 shown, the electrolyte does not undergo a phase change in a wide temperature range and will not condense into a solid state even at -80°C; moreover, it has a high conductivity in the range of -60 to 55°C, as Figure 2 shown.

[0027] Example 2:

[0028] An electrolyte for a high-nickel cathode material all-climate battery, comprising the following components: sulfolane, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, lithium trifluoromethanesulfonate, and LiClO4, where the molar ratio of lithium trifluoromethanesulfonate to sulfolane is 4, the molar ratio of lithium trifluoromethanesulfonate to LiClO4 is 0.0125, and the mass ratio of sulfolane to 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether is 1.5.

[0029] According to molecular dynamics simulation, the electrolyte shows a network structure of anions and cations, and the solvation sheath structure is as follows: Figure 3 As shown. After density functional theory calculation, the oxidation potential of the coordination structure corresponding to the first solvation layer rich in ion aggregates increases, it becomes difficult for the electrolyte to react and release electrons, the number of anions oxidized and decomposed on the electrode surface decreases, and the electrode interface reaction path is changed, so that a thin and strong passivation layer CEI is formed on the positive electrode surface.

[0030] Embodiment 3:

[0031] An electrolyte for an all-weather battery with a high-nickel cathode material, comprising the following components: diethyl sulfoxide, 1,1,2,2-tetrafluoroethyl ether, lithium bistrifluoromethylsulfonyl imide and LiClO4, wherein the molar ratio of lithium bistrifluoromethylsulfonyl imide to diethyl sulfoxide is 4, the molar ratio of lithium bistrifluoromethylsulfonyl imide to LiClO4 is 0.01, and the mass ratio of diethyl sulfoxide to 1,1,2,2-tetrafluoroethyl ether is 1.0; the high-nickel cathode material is LiNi5Mn3Co2O2, and is of R-3m space group;

[0032] Electrolyte matching LiNi 0.8 Co 0.15 Al 0.05 O2(LiNi x M y O2, where M is Co and Al, x = 0.8, y = 0.2, x + y = 1, and LiNi 0.8 Co 0.15 Al 0.05 O2 is R-3m space group) for charge and discharge cycle test. The discharge performance at 55℃ is as follows Figure 4 As shown, it is indicated that the electrolyte of the high nickel positive electrode material proposed in the present invention has excellent high temperature cycle stability.

[0033] Embodiment 4:

[0034] An electrolyte for an all-weather battery with a high-nickel positive electrode material comprises the following components: methyl ethyl sulfone, 1,1,5-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, 2-trifluoromethylbenzenesulfonyl lithium and LiClO4, wherein the molar ratio of 2-trifluoromethylbenzenesulfonyl lithium to methyl ethyl sulfone is 3.5, the molar ratio of 2-trifluoromethylbenzenesulfonyl lithium to LiClO4 is 0.011, and the mass ratio of methyl ethyl sulfone to 1,1,5-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether is 1.5; the high-nickel positive electrode material is LiNi 0.8 Mn 0.1 Co 0.1 O2(LiNi x M yO2, where M is Mn and Co, x = 0.8, y = 0.2, x + y = 1, and LiNi 0.8 Mn 0.1 Co 0.1 O2 is R-3m space group).

[0035] Using the above electrolyte and lithium sheet, LiNi 0.8 Mn 0.1 Co 0.1 O2 positive electrode, low temperature discharge at -60℃. Figure 5 As shown in the figure, the battery can release 110mAh / g capacity at -60℃. Moreover, after 200 cycles at -20℃, the discharge capacity can be maintained at around 150mAh / g, showing excellent low-temperature cycle performance. Figure 6 It shows that the electrolyte of the present invention can not only ensure the high temperature performance of high nickel positive electrode materials, but also has excellent electrochemical performance at low temperatures, and provides an electrolyte for the design of all-weather batteries with high nickel positive electrode materials.

Claims

1. An electrolyte for a high nickel cathode material all-weather battery, characterized in that: It contains at least the following components: sulfone-based solvent, fluorinated ether, lithium sulfonate salt and LiClO4. The molar ratio of the lithium sulfonate salt to the sulfone-based solvent is 2 to 4, the molar ratio of the lithium sulfonate salt to LiClO4 is 0.01 to 0.0125, and the mass ratio of the sulfone-based solvent to the fluorinated ether is 0.5 to 2; the high-nickel cathode material is LiNi x M y O2, where M is at least one of Al, Mn, Co, and Mg, 0.5 ≤ x ≤ 0.98, 0 ≤ y ≤ 0.2, 0 < x + y ≤ 1, and LiNi x M y O2 is in the R-3m space group; The sulfone-based solvent is one of dimethyl sulfone, methyl ethyl sulfone, diethyl sulfone, phenethyl sulfone, diphenyl sulfone, cyclopentane, bisphenol, dimethyl sulfoxide, diethyl sulfoxide, and benzyl phenyl sulfoxide; The fluorinated ether is one or two of 1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl nonafluorobutyl ether, 2,2,2-trifluoroethyl ether, 1,1,5-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, and 2,2,2-trifluoroethyl-1,1,1-2,2-pentafluoroethyl ether; The sulfonate lithium salt is one of trifluoromethylsulfonyl lithium, bisfluorosulfonyl imide lithium, bistrifluoromethylsulfonyl imide lithium, 2-trifluoromethylbenzenesulfonyl lithium, o-sulfonylbenzoic acid imide lithium, bispentafluoroethylsulfonyl imide lithium, and bishexafluoroisopropoxysulfonyl imide lithium.

2. The electrolyte of the high nickel positive electrode material all-weather battery according to claim 1, characterized in that: The sulfone-based solvent is one of sulfolane, dimethyl sulfoxide and diethyl sulfoxide.

3. An electrolyte for a high nickel cathode material all-weather battery according to any one of claims 1-2, characterized in that: The composed battery works at -60℃-55℃.

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