Secondary battery and electrochemical device

Abstract

The present application provides a secondary battery and an electrochemical device to improve the cycle and rate performance of the secondary battery. The secondary battery comprises a positive pole piece, electrolyte and a negative pole piece, wherein the negative pole piece comprises a negative current collector and a negative material layer arranged on at least one side surface of the negative current collector; wherein the negative electrode material layer comprises a negative electrode active material and a solid electrolyte, the solid electrolyte comprises an element F, based on the mass of the solid electrolyte, the mass ratio a of the element F is greater than or equal to 0.23% and less than or equal to 1.13%, the electrolyte comprises a fluorine-containing additive, and based on the mass of the electrolyte, the mass ratio a of the element F is greater than or equal to 0.23% and less than or equal to 1.13%. The mass ratio w1 of the fluorine-containing additive is more than or equal to 0.5% and less than or equal to 4%.

Description

Technical Field

[0001] This application relates to the field of energy storage technologies, and in particular, to a secondary battery and an electrochemical device. Background Art

[0002] With the development of clean energy, lithium-ion batteries are widely used in portable electronic products, new energy vehicles, eVTOL (electric Vertical Take-off and Landing), national defense and military industries due to their advantages such as high energy density, light weight, small volume, and no memory effect. To improve the electrochemical performance of lithium-ion batteries, it is common to increase the compaction density of the positive electrode sheet or the compaction density of the negative electrode sheet. However, the cycle performance of lithium-ion batteries still needs to be improved. Summary of the Invention

[0003] This application provides a secondary battery and a device to improve its cycle performance and rate performance.

[0004] In a first aspect, an embodiment of this application provides a secondary battery, including a positive electrode sheet, an electrolyte, and a negative electrode sheet. The negative electrode sheet includes a negative current collector and a negative electrode material layer provided on at least one surface of the negative current collector; wherein, the negative electrode material layer includes a negative electrode active material and a solid electrolyte,

[0005] the solid electrolyte includes element F, and based on the mass of the solid electrolyte, the mass percentage a of element F satisfies: 0.23% ≤ a ≤ 1.13%,

[0006] the electrolyte includes a fluorine-containing additive, and based on the mass of the electrolyte, the mass percentage w of the fluorine-containing additive 1 satisfies: 0.5% ≤ w 1 ≤ 4%.

[0007] In one embodiment, the secondary battery satisfies at least one of the following conditions:

[0008] (1) 0.45% ≤ a ≤ 1%;

[0009] (2) w 1 ≤ 3%;

[0010] (3) 0.23 ≤ a / w 1 ≤ 0.68.

[0011] In one embodiment, 0.45% ≤ a ≤ 1%.

[0012] In one embodiment, w 1 ≤ 3%.

[0013] In one embodiment, 0.23 ≤ a / w 1 ≤ 0.68.

[0014] In one embodiment, the fluorine-containing additive includes at least one of lithium difluorophosphate, lithium bis(oxalato) difluorophosphate, lithium tetrafluorooxalate phosphate, lithium tetrafluoroborate, and lithium difluoro(oxalato) borate.

[0015] In one embodiment, at room temperature, the ionic conductivity of the solid electrolyte is 1×10 -4 S / cm to 1×10 -2 S / cm;

[0016] At room temperature, the electronic conductivity of the solid electrolyte is 1×10 -14 S / cm to 1×10 -8 S / cm.

[0017] In one embodiment, the solid electrolyte includes at least one crystal structure type of NASICON structure, cubic garnet-type structure, and perovskite structure;

[0018] Among them, the NASICON structure includes Li 1.1 Al 0.3 Ti 1.7 P 3 O 11.8 F 0.1 、Li 1.1 Al 0.3 Ti 1.7 P 3 O 11.8 F 0.2 At least one of; the cubic garnet-type structure includes Li 6.5 La 3 Zr 2 O 11.5 F 0.5 、Li 6.6 La 3 Zr 2 O 11.6 F 0.4 、Li 6.7 La 3 Zr 2 O 11.7 F 0.3 、Li 6.8 La 3 Zr 2 O 11.8 F 0.2 、Li 6.9 La 3 Zr 2 O 11.9 F0.1 and Li 6.2 La 3 Zr 1.5 Ta 0.5 O 11.7 F 0.3 at least one of; the perovskite structure includes Li 0.27 La 0.56 TiO 2.94 F 0.06 、Li 0.3 La 0.56 TiO 2.97 F 0.03 at least one of. Wherein, the solid electrolyte further includes a doping element, and the doping element includes at least one of Zn, Cl, Co, Ge, Ca, Mg, La, and Si.

[0019] In one embodiment, the solid electrolyte satisfies at least one of the following conditions:

[0020] (1) The solid electrolyte includes the element Ti, and based on the mass of the solid electrolyte, the mass fraction b of the element Ti satisfies: 18% ≤ b ≤ 32%;

[0021] (2) Based on the mass of the solid electrolyte, the ratio between a and the mass fraction b of the element Ti in the solid electrolyte satisfies: 0.020 ≤ a / b ≤ 0.260;

[0022] (3) The solid electrolyte includes the element La, and based on the mass of the solid electrolyte, the mass fraction c of the element La satisfies: 40% ≤ c ≤ 50%;

[0023] (4) Based on the mass of the solid electrolyte, the ratio between a and the mass fraction c of the element La in the solid electrolyte satisfies: 0.005 ≤ a / c ≤ 0.273;

[0024] (5) The solid electrolyte includes the element Zr, and based on the mass of the solid electrolyte, the mass fraction d of the element Zr satisfies: 18% ≤ d ≤ 32%;

[0025] (6) Based on the mass of the solid electrolyte, the ratio between a and the mass fraction d of the element Zr in the solid electrolyte satisfies: 0.010 ≤ a / d ≤ 0.128.

[0026] In one embodiment, the solid electrolyte includes the element Ti, and based on the mass of the solid electrolyte, the mass fraction b of the element Ti satisfies: 18% ≤ b ≤ 32%.

[0027] In one embodiment, based on the mass of the solid electrolyte, the ratio between a and the mass fraction b of element Ti in the solid electrolyte satisfies: 0.020 ≤ a / b ≤ 0.260.

[0028] In one embodiment, the solid electrolyte includes element La. Based on the mass of the solid electrolyte, the mass fraction c of element La satisfies: 40% ≤ c ≤ 50%.

[0029] In one embodiment, based on the mass of the solid electrolyte, the ratio between a and the mass fraction c of element La in the solid electrolyte satisfies: 0.005 ≤ a / c ≤ 0.273.

[0030] In one embodiment, the solid electrolyte includes element Zr. Based on the mass of the solid electrolyte, the mass fraction d of element Zr satisfies: 18% ≤ d ≤ 32%.

[0031] In one embodiment, based on the mass of the solid electrolyte, the ratio between a and the mass fraction d of element Zr in the solid electrolyte satisfies: 0.010 ≤ a / d ≤ 0.128.

[0032] In one embodiment, the D v 50 of the solid electrolyte is 300 nm to 800 nm, and the D v 90 is 800 nm to 5000 nm;

[0033] The average particle size of the negative electrode active material is 8 to 15 μm.

[0034] In one embodiment, based on the mass of the negative electrode material layer, the mass fraction e of the solid electrolyte satisfies: 0.8% ≤ e ≤ 10%.

[0035] In one embodiment, the negative electrode sheet satisfies at least one of the following conditions:

[0036] (1) The porosity of the negative electrode sheet is 15% to 55%;

[0037] (2) The tap density of the negative electrode sheet is 1.0 to 1.95 g / cm 3 .

[0038] In one embodiment, the electrolyte includes a sulfur-containing additive; based on the mass of the electrolyte, the mass fraction w 2 of the sulfur-containing additive satisfies: 0.1% ≤ w 2 ≤ 5%.

[0039] In one embodiment, the sulfur-containing additive includes at least one of methylene methanedisulfonate, 1,3-propane sultone, allyl-1,3-sultone, and ethylene sulfate.

[0040] In one embodiment, the electrolyte includes a cyclic carbonate additive; based on the mass of the electrolyte, the mass percentage w of the cyclic carbonate additive 3 satisfies: 0.1% ≤ w 3 ≤ 5%.

[0041] In one embodiment, the cyclic carbonate additive includes at least one of vinylene carbonate, ethylene vinylene carbonate, fluoroethylene carbonate, and difluoroethylene carbonate.

[0042] In a second aspect, an embodiment of the present application provides an electrochemical device, including:

[0043] The secondary battery according to the first aspect and any possible implementation manner.

[0044] One or more technical solutions provided in the embodiments of the present application have at least the following beneficial effects:

[0045] In the secondary battery provided in the embodiment of the present application, a strongly electronegative element F is introduced into the solid electrolyte in the negative electrode material layer to improve the storage capacity of alkali metal active ions (Li + , Na + ) through the solid electrolyte, and at the same time, promote the desolvation of alkali metal ions through stronger electrostatic forces to improve the cycling performance of the secondary battery. On this basis, the cooperation between element F in the solid electrolyte and the fluorine-containing additive in the electrolyte can effectively reduce the unstable components in the SEI film (for example, Li 2 O, Li 2 CO 3 ), and significantly increase the generation amount of LiF at the interface, thereby effectively reducing the accumulation of by-products at the negative electrode interface, promoting the reduction of the interface impedance, and effectively improving the stability of the SEI film, so that the cycling performance and rate performance of the secondary battery are further improved.

[0046] Other features and advantages of the present application will be described in the following specification, and part of them will be obvious from the specification, or will be understood by implementing the present application. The objectives and other advantages of the present application can be achieved and obtained by the structures specifically pointed out in the written specification and claims. It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present disclosure. Detailed Embodiments

[0047] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of this application. The embodiments described herein are illustrative in nature and are provided to provide a basic understanding of this application. The embodiments of this application should not be construed as limiting this application.

[0048] The terms "first" and "second" in the description and claims of this application are used to distinguish different objects, rather than to describe a specific order.

[0049] For the sake of brevity, only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and similarly any upper limit can be combined with any other upper limit to form a range not explicitly recited. In addition, each individually disclosed point or single numerical value itself can be used as a lower limit or upper limit and combined with any other point or single numerical value or combined with other lower limits or upper limits to form a range not explicitly recited.

[0050] In the description herein, unless otherwise specified, "above" and "below" include the recited number.

[0051] Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values of the various parameters mentioned in this application can be measured using various commonly used measurement methods in the art (for example, they can be tested according to the methods given in the embodiments of this application).

[0052] The list of items connected by the terms "at least one of", "at least one of", "at least one kind of" or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A can include a single component or multiple components. Item B can include a single component or multiple components. Item C can include a single component or multiple components.

[0053] To improve the cycling performance of a secondary battery, an embodiment of this application provides a secondary battery. The secondary battery may include a positive electrode plate, an electrolyte, and a negative electrode plate. The negative electrode plate includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector.

[0054] Wherein, the negative electrode material layer includes a negative electrode active material and a solid electrolyte.

[0055] The solid electrolyte includes element F. Based on the mass of the solid electrolyte, the mass fraction a of element F satisfies: 0.23% ≤ a ≤ 1.13%. Exemplarily, the value of a can be 0.23%, 0.28%, 0.33%, 0.38%, 0.43%, 0.45%, 1.00%, 1.13% or a range composed of any two values.

[0056] The electrolyte includes a fluorine-containing additive. Based on the mass of the electrolyte, the mass fraction w of the fluorine-containing additive 1 satisfies: 0.5% ≤ w 1 ≤ 4%. Exemplarily, the value of w 1 can be 0.5%, 3.0%, 3.5%, 4.0% or a range composed of any two values.

[0057] In the above secondary battery, element F in the solid electrolyte has the characteristic of strong electronegativity. Therefore, on the one hand, its interaction with Li and Na is stronger, promoting the desolvation of active ions (such as Li + , Na + ) on the surface of the negative electrode material layer; on the other hand, it can promote the formation of LiF at the negative electrode interface between the negative electrode material layer and the electrolyte, thereby effectively reducing the content of unstable components such as Li 2 O and Li 2 CO 3 in the SEI film at the negative electrode interface, and further effectively reducing the decomposition amount of the electrolyte at the SEI at the negative electrode interface, thereby effectively alleviating the accumulation of by-products at the negative electrode interface.

[0058] On this basis, element F in the solid electrolyte can cooperate with the fluorine provided by the fluorine-containing additive in the electrolyte to improve the stability of the SEI.

[0059] In one embodiment, 0.45% ≤ a ≤ 1%. Exemplarily, the value of a can be 0.45%, 0.50%, 0.55%, 0.60%, 0.65%, 0.70%, 0.75%, 0.80%, 0.85%, 0.90%, 0.95%, 1.00% or a range composed of any two values.

[0060] In one embodiment, w 1 ≤ 3%. Exemplarily, the value of w 1 can be 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0% or a range composed of any two values.

[0061] To avoid the problem of excessive battery kinetics caused by too high interface impedance of the SEI, in one embodiment, 0.23 ≤ a / w 1≤0.68, thereby improving the rate performance and cycle performance of the secondary battery; and it can effectively avoid the aggravation of side reactions at the negative electrode interface caused by the decomposition of the electrolyte catalyzed by transition metal ions on the surface of the electrode sheet, which instead leads to a decrease in the stability of the SEI and thus a decrease in the cycle performance of the secondary battery.

[0062] Exemplarily, a / w 1 The value can be 0.23, 0.28, 0.33, 0.38, 0.43, 0.48, 0.53, 0.58, 0.63, 0.68 or taken from the range composed of any two values.

[0063] In one embodiment, the fluorine-containing additive includes at least one of lithium difluorophosphate, lithium difluoro(oxalato)phosphate, lithium tetrafluoro(oxalato)phosphate, lithium tetrafluoroborate, and lithium difluoro(oxalato)borate.

[0064] To further promote the conduction of active ions (Li + , Na + ) by the solid electrolyte to improve the kinetic performance of the negative electrode material layer, in one embodiment, at room temperature, the ionic conductivity of the solid electrolyte is 1×10 -4 S / cm to 1×10 -2 S / cm.

[0065] And, at room temperature, the electronic conductivity of the solid electrolyte is 1×10 -14 S / cm to 1×10 -8 S / cm.

[0066] The above room temperature condition means that the ambient temperature under standard atmospheric pressure is 25°C.

[0067] To further improve the chemical stability and / or electrochemical stability of the electrode sheet, in one embodiment, the above solid electrolyte includes at least one crystal structure type of NASICON structure, cubic garnet-type structure, and perovskite structure.

[0068] In one embodiment, the molecular structural formula of the solid electrolyte with NASICON structure can be Li 1.1 Al 0.3 Ti 1.7 P 3 O 11.8 F 0.1 , Li 1.1 Al 0.3 Ti 1.7 P 3 O 11.8 F 0.2 .

[0069] In one embodiment, the molecular structural formula of the solid electrolyte with cubic garnet-type structure can be Li6.5 La 3 Zr 2 O 11.5 F 0.5 , Li 6.6 La 3 Zr 2 O 11.6 F 0.4 , Li 6.7 La 3 Zr 2 O 11.7 F 0.3 , Li 6.8 La 3 Zr 2 O 11.8 F 0.2 , Li 6.9 La 3 Zr 2 O 11.9 F 0.1 and Li 6.2 La 3 Zr 1.5 Ta 0.5 O 11.7 F 0.3 .

[0070] In one embodiment, the molecular formula of the perovskite structured solid electrolyte may be Li 0.27 La 0.56 TiO 2.94 F 0.06 , Li 0.3 La 0.56 TiO 2.97 F 0.03 .

[0071] In one embodiment, the solid electrolyte further includes at least one of the doping elements Zn, Cl, Co, Ge, Ca, Mg, La, and Si.

[0072] In one embodiment, the solid electrolyte includes the element Ti, and based on the mass of the solid electrolyte, the mass proportion b of the element Ti satisfies: 18%≤b≤32%. Exemplarily, b can be 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, or a range consisting of any two values ​​thereof.

[0073] Preferably, 0.020≤a / b≤0.260. For example, a / b may be 0.020, 0.070, 0.120, 0.170, 0.220, 0.260, or a range consisting of any two values ​​thereof.

[0074] In one embodiment, the above solid electrolyte includes the element La. Based on the mass of the solid electrolyte, the mass fraction c of the element La satisfies: 40% ≤ c ≤ 50%. Exemplarily, c can be 40%, 42%, 44%, 46%, 48%, 50% or a range composed of any two of these values.

[0075] Preferably, 0.005 ≤ a / c ≤ 0.273. Exemplarily, a / c can be 0.005, 0.010, 0.050, 0.100, 0.150, 0.200, 0.250, 0.273 or a range composed of any two of these values.

[0076] In one embodiment, based on the mass of the solid electrolyte, the mass fraction d of the element Zr satisfies: 18% ≤ d ≤ 32%. Exemplarily, d can be 18%, 20%, 23%, 26%, 29%, 32% or a range composed of any two of these values.

[0077] Preferably, 0.010 ≤ a / d ≤ 0.128. Exemplarily, a / d can be 0.010, 0.040, 0.070, 0.100, 0.128 or a range composed of any two of these values.

[0078] To avoid the solid electrolyte having too large a specific surface area due to too small a particle size, resulting in too large a contact area with the electrolyte and exacerbating the interfacial side reactions; or, the solid electrolyte having too large a particle size, which affects the uniformity of lithium ion insertion and extraction on the negative electrode side, resulting in lithium plating. In one embodiment, the D v 50 of the solid electrolyte is 300 nm to 800 nm, and the D v 90 is 800 nm to 5000 nm. The average particle size of the negative electrode active material is 8 to 15 μm.

[0079] The above negative electrode active material includes at least one of artificial graphite, natural graphite, silicon-carbon material, and silicon-oxygen material.

[0080] Based on the mass of the negative electrode material layer, the mass fraction e of the solid electrolyte satisfies: 0.8% ≤ e ≤ 10%. Exemplarily, e can be 0.8%, 1%, 1.8%, 2.6%, 3.4%, 4.2%, 5%, 5.8%, 6.6%, 7.2%, 8%, 8.8%, 10% or a range composed of any two of these values.

[0081] Based on the mass of the negative electrode material layer, the mass fraction p of the negative electrode active material satisfies: 90% ≤ p ≤ 99.2%. Exemplarily, p can be 90%, 93%, 96%, 99.2 or a range composed of any two of these values.

[0082] To further reduce the side reactions between the transition metal elements on the surface of the solid electrolyte and the electrolyte, in one embodiment, the aforementioned electrolyte includes a sulfur-containing additive to synergistically form an SEI film rich in sulfur and fluorine elements with the fluorine-containing additive, further enhance the stability of the SEI film, reduce the side reactions of the electrolyte on the surface of the negative electrode sheet, and improve the storage stability of the battery cell. Specifically, based on the mass of the electrolyte, the mass ratio w 2 satisfies: 0.1% ≤ w 2 ≤ 5%. Exemplarily, w 2 can be 0.1%, 1%, 2%, 4%, 5% or a range composed of any two of them.

[0083] In one embodiment, the above sulfur-containing additive is at least one of methylene methanedisulfonate, 1,3-propane sultone, allyl-1,3-sultone, and vinylene sulfate.

[0084] To further enhance the stability of the SEI film at the negative electrode interface and improve the cycling performance of the secondary battery, in one embodiment, the above electrolyte includes a cyclic carbonate additive to crosslink the cyclic carbonate additive on the surface of the negative electrode material layer, thereby wrapping the surface of the negative electrode material layer, effectively alleviating the side reactions at the interface, and achieving the improvement of the stability of the SEI film at the negative electrode interface.

[0085] Based on the mass of the electrolyte, the mass ratio w 3 of the cyclic carbonate additive satisfies: 0.1% ≤ w 3 ≤ 5%, thus avoiding the problem of deterioration of the interface impedance and resulting in a decline in the cycling performance. Exemplarily, w 3 can be 0.1%, 1%, 2%, 4%, 5% or a range composed of any two of them.

[0086] In one embodiment, the above cyclic carbonate additive includes at least one of vinylene carbonate, ethylene vinylene carbonate, fluoroethylene carbonate, and difluoroethylene carbonate.

[0087] Furthermore, the above positive electrode sheet includes a positive electrode current collector and a positive electrode material layer provided on at least one surface of the positive electrode current collector, and the positive electrode material layer includes a positive electrode active material. The positive electrode active material can be a positive electrode active material for a lithium-ion battery, such as lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium cobalt oxide, lithium iron phosphate, lithium manganate, Prussian blue, etc. The positive electrode active material can also be a positive electrode active material for a sodium-ion battery. For example, it can be Prussian white.

[0088] Furthermore, the secondary battery described above may further include a separator. The separator is located between the negative electrode sheet and the positive electrode sheet. The material of the separator may include, but is not limited to, at least one of polyethylene (PE), polypropylene (PP), polyolefin (PO) membranes mainly composed of polytetrafluoroethylene, polyester membranes (such as polyethylene terephthalate (PET) membranes), cellulose membranes, polyimide membranes (PI), polyamide membranes (PA), spandex or aramid membranes, etc. The type of the separator may include, but is not limited to, at least one of woven membranes, non-woven membranes (non-woven fabrics), microporous membranes, composite membranes, rolled membranes or spun membranes, etc.

[0089] The separator may include a porous layer provided on at least one surface of the separator. The porous layer includes inorganic particles and a binder. The inorganic particles may include at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate. The binder may include at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene. In the embodiments of the present application, there is no particular limitation on the size of the pore diameter of the porous layer. The pore diameter may be, for example, 0.01 μm to 1 μm. In the embodiments of the present application, the thickness of the separator is not particularly limited. For example, the thickness may be 5 μm to 500 μm.

[0090] In one embodiment, the secondary battery of the present application may include, but is not limited to: lithium-ion batteries or sodium-ion batteries.

[0091] Based on the same inventive concept, the embodiments of the present application provide an electrochemical device, which includes the aforementioned secondary battery.

[0092] The electrochemical device may include, but is not limited to, laptop computers, pen input computers, mobile computers, e-book players, mobile phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, minidiscs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, motorized bicycles, bicycles, lighting appliances, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.

[0093] Taking a lithium-ion battery as an example below, it will be described in detail through examples and comparative examples:

[0094] The following examples describe more specifically the disclosure of the present invention. These examples are for illustrative purposes only, as various modifications and variations within the scope of the present invention disclosure are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized by conventional methods and can be used directly without further treatment, and all instruments used in the examples are commercially available.

[0095] (I) Test Methods and Equipment

[0096] (1) Content Test of Elements

[0097] Discharge the lithium-ion battery to 3.0 V and disassemble it to separate the negative electrode sheet. Cut the negative electrode sheet along the thickness direction to obtain a cut surface of the negative electrode sheet with a size of 1 cm × 1 cm. Then use argon plasma polishing technology to polish the cut surface of the negative electrode sheet to prepare a cross-section sample of the negative electrode sheet.

[0098] Observe the cross-section sample of the negative electrode sheet with a scanning electron microscope, and randomly select three solid electrolyte particles in the cross-section sample of the negative electrode sheet. Test the weight percentage content of F, Ti, La, and Zr elements in the selected particles by energy-dispersive X-ray analysis, calculate the mass ratio of each element in each particle, calculate the arithmetic mean value, and obtain a, b, c, and d respectively.

[0099] The content of each additive in the electrolyte can be obtained by testing with GC-MS (Gas Chromatography-Mass Spectrometry).

[0100] (2) Solid Electrolyte Particle Size Test:

[0101] Add about 0.02 g of the powder sample of the solid electrolyte to a 50 mL clean beaker, add about 20 mL of deionized water, and then add 1 mL of 1 wt% surfactant P40 to completely disperse the powder in water. Ultrasonic for 5 min in a 120 W ultrasonic cleaner, and use a MasterSizer 2000 to test the particle size distribution to obtain Dv50 and Dv90 of the solid electrolyte.

[0102] (3) Negative Electrode Active Material Particle Size Test:

[0103] Discharge the lithium-ion battery to 3.0 V and disassemble it to separate the negative electrode sheet. Use a cross-section polishing instrument (model IB-09010CP) to perform high-energy ion beam cutting and polishing on the negative electrode sheet, place the obtained cross-section sample under a scanning electron microscope (SEM) for observation, and take an SEM image at a magnification of 1000 times.

[0104] Use image processing software to observe the SEM image, randomly select 30 negative electrode active material particles, measure their respective perimeters, and calculate the equivalent diameter of each negative electrode active material particle respectively, then calculate the average value to obtain the average particle size of the negative electrode active material particles.

[0105] The equivalent diameter d of the negative electrode active material particles eq =(4A / π)^0.5, where A is the cross-sectional area.

[0106] (4) Porosity test:

[0107] Punch the negative electrode sheet into small round pieces with a diameter D of 14 mm, measure the thickness H of the small round pieces, measure the weight m of the small round pieces, put the above small round pieces into a true density meter (model AccupycⅡ1340) for testing, and measure the true density of the small round pieces as V 2 , and then calculate the apparent density V of the small round pieces through the diameter D and thickness H 1 , V 1 =m / [π×(D / 2) 2 ×H].

[0108] The porosity V of the negative electrode sheet 0 =(V 1 -V 2 ) / V 1 ×100%.

[0109] (5) Compaction density test of the negative electrode sheet:

[0110] Punch the negative electrode sheet into small round pieces with a diameter D of 14 mm, and measure the thickness of the small round pieces as H 1 cm and the mass as M 1 g, then wipe off the negative electrode material layer with alcohol, clean it, and obtain the negative electrode current collector. Measure the thickness of the negative electrode current collector as H 2 cm and the mass as M 2 g. According to the following formula, the compaction density A of the negative electrode sheet can be calculated:

[0111] A=(M 1 -M 2 ) / [π×(D / 2) 2 ×(H 1 -H 2 )], with the unit of g / cm 3 .

[0112] (6) Ionic conductivity test:

[0113] The solid electrolyte was prepared into a high-density ceramic sheet (density 0.96) by cold pressing, and gold was sprayed on both ends of the ceramic sheet to make a blocking electrode. The prepared blocking electrode was subjected to an AC impedance test with a frequency range of 1 MHz to 10 Hz and a disturbance amplitude of 10 mV. The ionic conductivity σ of the solid electrolyte was calculated as follows: σ = d / Re×S;

[0114] Where d is the thickness of the sample under test (in cm); Re is the body impedance of the sample under test (in Ω), which can be obtained from the intersection of the semicircle arc and the oblique line in the Nyquist diagram of the electrochemical impedance spectroscopy; S is the effective area of ​​the electrode (in cm 2 ).

[0115] (7) Electronic conductivity test:

[0116] The electronic conductivity of the solid electrolyte was tested using a resistivity tester (Suzhou Jingge Electronics, model ST-2255A).

[0117] Take 5g of solid electrolyte powder and use an electronic press to compress the solid electrolyte powder into tablets. The electronic press is pressed to 5000kg and maintained for 20s to obtain a solid electrolyte sample. The solid electrolyte sample is placed between the electrodes of a resistivity tester for testing. The electronic conductivity of the solid electrolyte is δ = h / (S×R) / 1000.

[0118] Wherein, the unit of δ is S / m, h is the height of the solid electrolyte sample (in cm), R is the resistance of the solid electrolyte sample (in KΩ), S is the area of ​​the solid electrolyte sample, S = 3.14 cm 2 .

[0119] (8) DC resistance (DCR) test:

[0120] At 25℃, charge the lithium-ion battery to 3.65V at 0.1C constant current, charge to 0.025C at constant voltage, and let it stand for 10min; then discharge to 2.5V at 0.1C constant current, and let it stand for 10min; then charge to 3.65V at 0.1C constant current, charge to 0.025C at constant voltage, and let it stand for 10min; continue to discharge at 0.1C constant current for 5h (the lithium-ion battery is 50% charged at this time), and then discharge at 1C constant current for 1s. The voltage before the above 1C constant current discharge is V 0 , the voltage after the above 1C constant current discharge is V 1 , the current of the above 1C constant current discharge is A, and the DC resistance DCR corresponding to the 50% state of charge (SOC) of the lithium-ion battery is calculated as:

[0121] DCR = (V 0 - V 1 ) / A.

[0122] (9) Cycling performance test

[0123] The test temperature was 25 °C. Each lithium-ion battery was charged at a constant current of 0.5C to 4.45V, then charged at a constant voltage to 0.025C, allowed to stand for 5 minutes, and then discharged at a constant current of 0.5C to 3.0V. The capacity obtained in this step was taken as the initial capacity, and cyclic tests were carried out with 0.5C charge / 0.5C discharge. The ratio of the capacity of each step to the initial capacity was used to obtain the capacity attenuation curve.

[0124] The cycling performance was characterized by the number of cycles corresponding to a capacity retention rate of 80%. The more cycles, the better the cycling performance.

[0125] (10) Rate performance test

[0126] The test temperature was 25 °C. Each lithium-ion battery was charged at a constant current of 0.5C to 4.45V, charged at a constant voltage of 4.45V to 0.025C, allowed to stand for 5 minutes, and then discharged at a constant current of 0.5C to 3.0V; the capacity obtained in this step was taken as the reference capacity.

[0127] Each lithium-ion battery was charged at a constant current of 5C to 4.45V, charged at a constant voltage of 4.45V to 0.025C, allowed to stand for 5 minutes, and then discharged at a constant current of 5C to 3.0V; the capacity obtained in this step was taken as the 5C capacity.

[0128] Rate capacity retention rate CRR2 (%) = 5C capacity / reference capacity × 100%.

[0129] (II) Preparation

[0130] Example 1

[0131] (1) Preparation of the positive electrode sheet

[0132] S11. The positive electrode active material lithium nickel cobalt manganese oxide (molecular formula LiNi 0.5 Co 0.2 Mn 0.3 O 2 ), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF, weight average molecular weight of 5 × 10 5 ) were mixed in a weight ratio of 94:3:3 to obtain a positive electrode mixture.

[0133] S12. The positive electrode mixture was added to an N-methylpyrrolidone (NMP) solvent and stirred evenly under the action of a vacuum mixer to obtain a positive electrode slurry with a solid content of 75 wt%.

[0134] S13. Uniformly coat the positive electrode slurry on the surface of the positive electrode current collector aluminum foil with a thickness of 6 μm, dry the coated aluminum foil at 90 °C, then perform cold pressing and slitting, and dry it under vacuum conditions to obtain the positive electrode sheet. The compaction density of the positive electrode sheet after cold pressing is 2 g / cm 3 .

[0135] (2) Prepare the negative electrode sheet

[0136] S21. Mix artificial graphite, the negative electrode active material with an average particle size of 12 μm, a solid electrolyte (Li 6.9 La 3 Zr 2 O 11.9 F 0.1 , D v 50 is 700 nm, D v 90 is 2 μm), conductive agent Super P, thickening agent sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) in a weight ratio of 95:1:2:0.8:1.2, add deionized water, and obtain the negative electrode slurry under the action of a vacuum mixer, where the solid content of the negative electrode slurry is 54 wt%.

[0137] Among them, the ionic conductivity of Li 6.9 La 3 Zr 2 O 11.9 F 0.1 is 1.7×10 -3 S / cm, and the electronic conductivity is 5×10 -10 S / cm.

[0138] S22. Uniformly coat the negative electrode slurry on the negative electrode current collector copper foil; dry the coated copper foil at 85 °C, then perform cold pressing, blanking, and slitting, and dry it under vacuum conditions to obtain the negative electrode sheet. The porosity of the negative electrode sheet is 22%, and the compaction density is 1.7 g / cm 3 .

[0139] (3) Prepare the electrolyte

[0140] S31. In a dry (water content < 10 ppm) argon atmosphere glove box, mix the solvents ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) in a mass ratio of 5:10:35 to obtain a pre-solvent.

[0141] S32. Add a fluorine-containing additive, a sulfur-containing additive, a cyclic carbonate compound, and LiPF 6 to the pre-solvent, dissolve it, and stir well to obtain the electrolyte.

[0142] Among them, based on the mass of the final electrolyte as a reference, the mass ratio of the fluorine-containing additive is 2 wt%, the mass ratio of the sulfur-containing additive is 3 wt%, the mass ratio of the cyclic carbonate compound is 3 wt%, and the mass ratio of LiPF 6 is 12.5 wt%;

[0143] Among them, the fluorine-containing additive is lithium tetrafluoroborate (LiBF 4 ), the sulfur-containing additive is 1,3-propane sultone (PS), and the cyclic carbonate compound is fluoroethylene carbonate (FEC).

[0144] (4) Preparation of separator

[0145] Select polyethylene (PE) with a thickness of 8 μm and a porosity of 55% as the base film, and distribute and coat PVDF slurry and inorganic particle (flake boehmite and Al 2 O 3 with a mass ratio of 70:30) slurry on both surfaces of the base film, and dry it to obtain a separator. The coating thickness on each surface of the separator is 3 μm.

[0146] (5) Preparation of lithium-ion battery

[0147] S51. Stack the positive electrode, separator, and negative electrode in sequence, so that the separator is located between the positive and negative electrodes to play a role in isolation. After welding the tabs, wind them to obtain a bare battery cell.

[0148] S52. Place the bare battery cell in an outer packaging aluminum-plastic film, remove the moisture at 80 °C, and then inject the above electrolyte.

[0149] S53. After vacuum packaging, standing, forming, and shaping, a soft-pack lithium-ion battery is obtained.

[0150] Among them, the forming steps are: at a temperature of 25 °C, charge at 0.1C to 4.3V; then charge at a constant voltage of 4.3V until the current is less than or equal to 0.02C, stand for 6h, and then charge at a constant voltage of 4.3V again until the current is less than or equal to 0.01C; then discharge at 0.1C to 2.7V.

[0151] Examples 2 to 5

[0152] The difference from Example 1 is only that: in step S21, the solid electrolyte Li 6.9 La 3 Zr 2 O 11.9 F 0.1 is replaced by Li 6.8 La 3 Zr 2 O 11.8 F 0.2 、Li6.7 La 3 Zr 2 O 11.7 F 0.3 、Li 6.6 La 3 Zr 2 O 11.6 F 0.4 、Li 6.5 La 3 Zr 2 O 11.5 F 0.5 。 The rest is the same as in Example 1. Among them, Li 6.8 La 3 Zr 2 O 11.8 F 0.2 、Li 6.7 La 3 Zr 2 O 11.7 F 0.3 、Li 6.6 La 3 Zr 2 O 11.6 F 0.4 、Li 6.5 La 3 Zr 2 O 11.5 F 0.5 have ionic conductivities of 1.8×10 -3 S / cm, 2.31×10 -3 S / cm, 1.82×10 -3 S / cm, 1.58×10 -3 S / cm, respectively, and the electronic conductivities are all between 1×10 -10 S / cm and 1×10 -8 S / cm.

[0153] Examples 6 to 10

[0154] The difference from Example 3 is only that in step S32, based on the mass of the final electrolyte, the mass percentage of the fluorine-containing additive in the electrolyte is replaced with 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, the mass percentage of the sulfur-containing additive is 0 wt%, the mass percentage of the cyclic carbonate compound is 0 wt%, and the mass percentage of LiPF 6 is 12.5 wt%. The rest is the same as in Example 3.

[0155] Examples 11 to 16

[0156] The difference from Example 3 is only that: in step S32, based on the mass of the final electrolyte, the mass percentage of the fluorine-containing additive in the electrolyte is replaced with 2 wt%, the mass percentage of the sulfur-containing additive is replaced with 0.1 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%; the mass percentage of the cyclic carbonate compound is 0 wt%, LiPF 6 has a mass percentage of 12.5 wt%. The rest is the same as in Example 3.

[0157] Examples 17 to 22

[0158] The difference from Example 3 is only that: in step S32, based on the mass of the final electrolyte, the mass percentage of the fluorine-containing additive in the electrolyte is replaced with 2 wt%, the mass percentage of the sulfur-containing additive is 3 wt%, the mass percentage of the cyclic carbonate compound is replaced with 0.1 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, LiPF 6 has a mass percentage of 12.5 wt%. The rest is the same as in Example 3.

[0159] Examples 23 to 25

[0160] The difference from Example 1 is only that: in step S21, the solid electrolyte Li 6.9 La 3 Zr 2 O 11.9 F 0.1 is replaced with Li 1.1 Al 0.3 Ti 1.7 P 3 O 11.8 F 0.2 , Li 6.2 La 3 Zr 1.5 Ta 0.5 O 11.7 F 0.3 , Li 0.27 La 0.56 TiO 2.94 F 0.06 . The rest is the same as in Example 1.

[0161] Among them, in Examples 23 to 25, the solid electrolytes Li 1.1 Al 0.3 Ti 1.7 P 3 O 11.8 F 0.2 , Li 6.2 La 3 Zr 1.5 Ta 0.5 O11.7 F 0.3 ,Li 0.27 La 0.56 TiO 2.94 F 0.06 The ionic conductivities of -3 are 1.98×10 -3 S / cm, 1.78×10 -3 S / cm, 1.82×10 -3 S / cm, 1.99×10 - 10 S / cm, respectively, and the electronic conductivities of each solid electrolyte are all between 1×10 -8 S / cm and 1×10

[0162] Example 26

[0163] The difference from Example 3 is only that: in S21, the weight ratio of artificial graphite as the negative electrode active material, solid electrolyte, conductive agent Super P, thickening agent sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) is 95.5:0.5:2:0.8:1.2.

[0164] Example 27

[0165] The difference from Example 3 is only that: in S21, the weight ratio of artificial graphite as the negative electrode active material, solid electrolyte, conductive agent Super P, thickening agent sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) is 95.2:0.8:2:0.8:1.2.

[0166] Example 28

[0167] The difference from Example 3 is only that: in S21, the weight ratio of artificial graphite as the negative electrode active material, solid electrolyte, conductive agent Super P, thickening agent sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) is 93:3:2:0.8:1.2.

[0168] Example 29

[0169] The difference from Example 3 is only that: in S21, the weight ratio of artificial graphite as the negative electrode active material, solid electrolyte, conductive agent Super P, thickening agent sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) is 89:7:2:0.8:1.2.

[0170] Example 30

[0171] The difference from Example 3 is only that: in S21, the weight ratio of artificial graphite as the anode active material, solid electrolyte, conductive agent Super P, thickening agent sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) is 86:10:2:0.8:1.2.

[0172] Example 31

[0173] The difference from Example 3 is only that: in S21, the weight ratio of artificial graphite as the anode active material, solid electrolyte, conductive agent Super P, thickening agent sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) is 84:12:2:0.8:1.2.

[0174] Example 32

[0175] The difference from Example 3 is only that: in S32, the fluorine-containing additive is lithium difluoro(oxalato)phosphate. The rest is the same as Example 3.

[0176] Example 33

[0177] The difference from Example 3 is only that: in S32, the fluorine-containing additives are lithium difluoro(oxalato)phosphate and lithium tetrafluoroborate; based on the mass of the final electrolyte, the mass percentages of lithium difluoro(oxalato)phosphate and lithium tetrafluoroborate each account for 1 wt%. 。

[0178] The rest is the same as Example 3.

[0179] Example 34

[0180] The difference from Example 3 is only that: in S32, the sulfur-containing additive is vinylene sulfate. The rest is the same as Example 3.

[0181] Example 35

[0182] The difference from Example 3 is only that: in S32, the cyclic carbonate additive is ethylene carbonate. The rest is the same as Example 3.

[0183] Comparative Example 1

[0184] The difference from Example 1 is only that: in step S21, the solid electrolyte Li 6.9 La 3 Zr 2 O 11.9 F 0.1 is replaced with Li 7 La 3 Zr 2 O 12; In step S32, the addition amounts of the sulfur-containing additive and the cyclic carbonate compound in the electrolyte are 0. The rest is the same as in Example 1.

[0185] Comparative Example 2

[0186] The difference from Example 1 is only that: in step S21, the solid electrolyte Li 6.9 La 3 Zr 2 O 11.9 F 0.1 is replaced with Li 7 La 3 Zr 2 O 12 ; In step S32, the addition amounts of the fluorine-containing additive and the cyclic carbonate compound in the electrolyte are 0. The rest is the same as in Example 1.

[0187] Comparative Example 3

[0188] The difference from Example 1 is only that: in step S21, the solid electrolyte Li 6.9 La 3 Zr 2 O 11.9 F 0.1 is replaced with Li 7 La 3 Zr 2 O 12 ; In step S32, the addition amounts of the fluorine-containing additive and the sulfur-containing additive in the electrolyte are 0. The rest is the same as in Example 1.

[0189] Comparative Example 4

[0190] The difference from Example 1 is only that: in step S21, the solid electrolyte Li 6.9 La 3 Zr 2 O 11.9 F 0.1 is replaced with Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 . The rest is the same as in Example 1.

[0191] Comparative Example 5

[0192] The difference from Example 1 is only that: in step S21, the solid electrolyte Li 6.9 La 3 Zr 2 O 11.9 F 0.1 is replaced with Li 6.5 La 3 Zr1.5 Ta 0.5 O 12 The rest is the same as that of Example 1.

[0193] Comparative Example 6

[0194] The difference from Example 1 is only that: in step S21, the solid electrolyte Li 6.9 La 3 Zr 2 O 11.9 F 0.1 is replaced by Li 0.33 La0 .56 TiO 3 The rest is the same as that of Example 1.

[0195] Comparative Example 7

[0196] The difference from Example 1 is only that: in step S21, the solid electrolyte Li 6.9 La 3 Zr 2 O 11.9 F 0.1 is replaced by Li 6.4 La 3 Zr 2 O 11.4 F 0.6 The rest is the same as that of Example 1.

[0197] Comparative Example 8

[0198] The difference from Example 3 is only that: in step S32, the mass percentage of the fluorine-containing additive in the electrolyte is replaced by 5 wt%. The rest is the same as that of Example 3.

[0199] Test the lithium-ion batteries in each example and comparative example according to the foregoing test methods and equipment.

[0200] Summarize the molecular structural formula of the solid electrolyte in Table 1; and, based on the mass of the solid electrolyte, the mass percentage a of element F, the mass percentage b of element Ti, and the mass percentage c of element Zr in the solid electrolyte.

[0201] Table 1

[0202]

[0203]

[0204]

[0205] Based on the mass of the negative electrode material on the surface of the negative electrode current collector, the mass content e of the solid electrolyte. Based on the mass of the electrolyte, the mass ratio w of the fluorine-containing additive in the electrolyte 1 , the mass ratio w of the sulfur-containing additive 2 , the mass ratio w of the cyclic carbonate additive 3 , and for the test data of the DCR, cycle performance, and rate capacity retention rate of the secondary battery, see Table 2.

[0206] Table 2

[0207]

[0208]

[0209]

[0210]

[0211] As can be seen from Table 1 - Table 2, compared with the comparative examples, since the negative electrode material of the lithium-ion battery provided in the examples includes a fluorine-containing solid electrolyte with an appropriate content, it can form a synergistic effect with the fluorine-containing additive in the electrolyte, promoting the improvement of both the cycle performance and rate performance of the lithium-ion battery.

[0212] When 0.23 ≤ a / w in the examples 1 ≤ 0.68, the synergistic effect between the element F in the solid electrolyte and the fluorine-containing additive in the electrolyte is further highlighted, prompting the lithium-ion battery to exhibit good cycle performance and rate performance.

[0213] Continuing to compare with Comparative Example 7 and Comparative Example 8, it can be seen that when a is greater than 1.13%, or w 1 is greater than 4%, the rate performance of the lithium-ion battery, especially the cycle performance, both show a significant decline.

[0214] Obviously, those skilled in the art can make various changes and modifications to this application without departing from the scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalent technologies, this application also intends to include these changes and modifications.

Claims

1. A secondary battery, characterized in that: The invention comprises a positive electrode sheet, an electrolyte and a negative electrode sheet, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode material layer arranged on at least one side of the negative electrode current collector; wherein the negative electrode material layer comprises a negative electrode active material and a solid electrolyte, The solid electrolyte includes an element F. Based on the mass of the solid electrolyte, the mass proportion a of the element F satisfies: 0.23%≤a≤1.13%. The electrolyte includes a fluorine-containing additive. Based on the mass of the electrolyte, the mass proportion of the fluorine-containing additive is w1, which satisfies: 0.5%≤w1≤4%.

2. The secondary battery according to claim 1, wherein: The secondary battery satisfies at least one of the following conditions: (1)0.45％≤a≤1％； (2)w1≤3％； (3)0.23≤a / w1≤0.

68.

3. The secondary battery according to claim 1 or 2, characterized in that: The fluorine-containing additive includes at least one of lithium difluorophosphate, lithium difluorobisoxalate phosphate, lithium tetrafluorooxalate phosphate, lithium tetrafluoroborate and lithium difluorooxalate borate.

4. The secondary battery according to claim 1, wherein: At room temperature, the ionic conductivity of the solid electrolyte is 1×10 -4 S / cm to 1×10 -2 S / cm; At room temperature, the electronic conductivity of the solid electrolyte is 1×10 -14 S / cm to 1×10 -8 S / cm.

5. The secondary battery according to claim 1, wherein: The solid electrolyte comprises at least one crystal structure type of a NASICON structure, a cubic garnet structure and a perovskite structure; Wherein, the NASICON structure includes Li 1.1 Al 0.3 Ti 1.7 P3O 11.8 F 0.1 , Li 1.1 Al 0.3 Ti 1.7 P3O 11.8 F 0.2 At least one of; the cubic garnet structure includes Li 6.5 La3Zr2O 11.5 F 0.5 , Li 6.6 La3Zr2O 11.6 F 0.4 , Li 6.7 La3Zr2O 11.7 F 0.3 , Li 6.8 La3Zr2O 11.8 F 0.2 , Li 6.9 La3Zr2O 11.9 F 0.1 and Li 6.2 Ln3Z 1.5 Ta 0.5 O 11.7 F 0.3 At least one of; the perovskite structure includes Li 0.27 La 0.56 TiO 2.94 F 0.06 , Li 0.3 La 0.56 TiO 2.97 F 0.03 , at least one of the following.

6. The secondary battery according to any one of claims 1 to 2, 4 to 5, characterized in that: The solid electrolyte satisfies at least one of the following conditions: (1) The solid electrolyte includes the element Ti, and based on the mass of the solid electrolyte, the mass proportion b of the element Ti satisfies: 18%≤b≤32%; (2) Based on the mass of the solid electrolyte, the ratio of a to the mass proportion b of the element Ti in the solid electrolyte satisfies: 0.020≤a / b≤0.260; (3) The solid electrolyte includes the element La, and based on the mass of the solid electrolyte, the mass proportion c of the element La satisfies: 40%≤c≤50%; (4) Based on the mass of the solid electrolyte, the ratio of a to the mass proportion c of the element La in the solid electrolyte satisfies: 0.005≤a / c≤0.273; (5) The solid electrolyte includes the element Zr, and the mass proportion d of the element Zr, based on the mass of the solid electrolyte, satisfies: 18%≤d≤32%; (6) Based on the mass of the solid electrolyte, the ratio of a to the mass proportion d of the element Zr in the solid electrolyte satisfies: 0.010≤a / d≤0.

128.

7. The secondary battery according to claim 1, wherein: The solid electrolyte D v 50 is 300nm~800nm, D v 90 is 800nm~5000nm; The average particle size of the negative electrode active material is 8 to 15 μm.

8. The secondary battery according to claim 1, wherein: Based on the mass of the negative electrode material layer, the mass proportion e of the solid electrolyte satisfies: 0.8%≤e≤10%.

9. The secondary battery according to claim 1, wherein: The electrolyte includes a sulfur-containing additive; based on the mass of the electrolyte, the mass proportion w2 of the sulfur-containing additive satisfies: 0.1%≤w2≤5%.

10. The secondary battery according to claim 9, characterized in that The sulfur-containing additive includes at least one of methylene methanedisulfonate, 1,3-propane sultone, propenyl-1,3-sultone and vinyl sulfate.

11. The secondary battery according to any one of claims 1, 2, 4, 5, 7 to 10, characterized in that: The electrolyte includes a cyclic carbonate additive; based on the mass of the electrolyte, the mass proportion w3 of the cyclic carbonate additive satisfies: 0.1%≤w3≤5%.

12. The secondary battery according to claim 11, wherein: The cyclic carbonate additive includes at least one of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate and bisfluoroethylene carbonate.

13. An electrochemical device, characterized in that: include: The secondary battery according to any one of claims 1 to 12.

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