73results about How to "Reduce energy density" patented technology

The invention provides a positive electrode active material, positive electrode slurry, a positive plate, a battery and a vehicle, and belongs to the technical field of batteries, the positive electrode active material comprises lithium manganese iron phosphate and nickel cobalt lithium manganate; wherein the mass ratio of the lithium manganese iron phosphate to the nickel cobalt lithium manganate is (50-95): (5-50); the chemical general formula of the nickel cobalt lithium manganate is LiNiaCobMn (1-a-b) O2, a is more than or equal to 0.6 and less than 1, b is more than 0 and less than 0.5, and a + b is more than 0 and less than 1. According to the present invention, the lithium manganese iron phosphate and the nickel cobalt lithium manganate are compounded to serve as the positive electrode active material, and the mass ratio of the lithium manganese iron phosphate to the nickel cobalt lithium manganate is controlled within the range of (50-95): (5-50), such that when the positive electrode active material is applied to the battery, the high safety performance can be provided while the high energy density is provided so as to improve the comprehensive performance.

The invention provides a positive electrode material and a preparation method thereof, a positive electrode plate, a battery and an electric device. The preparation method of the positive electrode material comprises the following steps: preparing a layered oxide internal core material, wherein the layered oxide internal core material is a layered oxide containing sodium and transition metal; preparing a polyanion external coating material, wherein the polyanion external coating material comprises sodium ferromanganese pyrophosphate; and fusing the layered oxide internal core material and the polyanion external coating material in a mechanical fusion manner to obtain the positive electrode material with the layered oxide and polyanion compounded core-shell structure. The positive electrode material comprises a layered oxide internal core material and a polyanion external coating material; the core material in the layered oxide comprises Na1 + xMO2, X is more than or equal to-0.3 and less than or equal to 0.2, and M comprises at least one of Fe, Ni, Cu, Zn, Co, Ti and Mn; and the external coating material of the polyanion system comprises Na < 4 > Fe < 3-y > Mn < y > (PO4) < 2 > P < 2 > O < 7 > / C.

The invention discloses a flexible self-supporting porous pole piece for an ion battery, a membrane module and a preparation method, the porous pole piece is a porous positive pole piece or a porous negative pole piece, the overall thickness is 9-150 microns, the porous pole piece comprises a supporting framework, an active material and a conductive agent, the supporting framework is a porous fiber membrane made of ultra-high molecular weight polyethylene, and the active material is a porous fiber membrane made of ultra-high molecular weight polyethylene. Active materials and conductive agents are distributed on the surface of the supporting framework. The membrane assembly comprises a porous pole piece and a diaphragm layer which are connected and form an integrated structure, and the number of the diaphragm layer is one, and the number of the porous pole piece is one or two. The preparation method comprises the following steps: preparing a porous pole piece in an extrusion-stretching manner, or preparing a membrane assembly in a co-extrusion-stretching manner, and performing high-temperature annealing after extraction to obtain the high-performance porous pole piece or membrane assembly. The porous pole piece and the membrane assembly have good flexibility, the performance of the porous pole piece and the membrane assembly is not changed after the porous pole piece and the membrane assembly are folded for multiple times, meanwhile, the expansion problem of the porous pole piece and the membrane assembly in the charge-discharge process is effectively avoided, and the thermal stability is high.

The invention relates to the technical field of lithium ion batteries, in particular to a composite positive pole piece, a preparation method of the composite positive pole piece and a lithium ion battery, the composite positive pole piece comprises a positive current collector, a negative current collector, a positive electrode and a negative electrode, and the positive current collector is provided with two opposite surfaces; the positive electrode active material layer is arranged on at least one surface of the positive electrode current collector; and the solid electrolyte layer is arranged on the positive electrode active material layer. According to the lithium ion battery, the solid electrolyte layer is arranged on the positive active material layer, so that the battery can pass needling, overcharge and short-circuit test inspection, and the use safety of the lithium ion battery is comprehensively improved.

The invention belongs to the field of scramjet engines, and particularly relates to an ammonia-hydrogen power wide-speed-range scramjet engine and a combustion method thereof. The ammonia-hydrogen power wide-speed-range scramjet engine comprises a combustion chamber, a liquid ammonia storage device and a hydrogen storage device; a concave cavity is formed in the combustion chamber, a fuel injection section upstream injection hole is formed in a fuel injection section of the concave cavity, the concave cavity is located at the downstream of the fuel injection section, a fuel injection section upstream micro-jet injection hole is formed in the upstream of the fuel injection section upstream injection hole, and a concave cavity inner micro-jet injection hole is formed in the concave cavity; the liquid ammonia storage device is connected with an upstream injection hole of the fuel injection section through a cooling structure; and the hydrogen storage device is connected with the upstream micro-jet injection hole of the fuel injection section and the micro-jet injection hole in the concave cavity. According to the invention, liquid ammonia and hydrogen are introduced as fuels to realize wide-range combustion organization, so that wide-range efficient combustion is realized, the fuel heat absorption requirement of high-Mach-number active cooling thermal protection is met, and zero carbon emission can be realized in the whole process.

The invention provides a composite positive plate, a lithium ion battery and a preparation method, and relates to the technical field of lithium ion batteries, the composite positive plate comprises a current collector, a ternary material layer and a quinone polyimide layer; the ternary material layer is located between the current collector and the quinone polyimide layer; the quinonoid polyimide layer comprises quinonoid polyimide and a lithium supplement agent. According to the invention, the ternary material and the quinonoid polyimide are matched, the foil is coated with the ternary layer and the quinonoid polyimide layer at the same time by using a double-layer coating technology, and then the foil is dried and cut to prepare the novel double-layer positive plate, so that the safety performance of the battery can be improved while the relatively good electrochemical performance of the ternary material is maintained.

The invention relates to the technical field of batteries, in particular to a battery and an electric device comprising the battery, the battery comprises a shell and a battery cell arranged in the shell, the material of the shell comprises steel, the steel comprises Ti, Nb and Cr, based on the total mass of the steel, the mass percentage content of Cr is larger than or equal to 16 wt.%, and based on the total mass of the steel, the mass percentage content of Nb is larger than or equal to 20 wt.%. The shell comprises a side wall and end walls, the end walls comprise a first end wall and a second end wall located at the two ends of the side wall, and the two ends of the battery cell comprise a first end face close to the first end wall and a second end face close to the second end wall; the shell satisfies the following relational expression: 0.15 < = a / [d * (b + c)] < = 300. By controlling the sum a of the distances between the end walls at the two ends of the shell and the end faces at the two ends of the battery cell, the thickness d of the first end wall and the relation between the content b and the content c of Ti and Nb, the processability of the shell in the forming process and the capacity of the shell for resisting the deformation risk caused by battery cell expansion are balanced.

The invention belongs to the field of batteries, and particularly relates to an electrolyte and a battery. The electrolyte comprises a lithium salt, a solvent and a lithium salt additive; and the lithium salt additive is one or a mixture of Li F, Li2O, Li2CO3, Li3N and L i NO3. The lithium salt additive contained in the electrolyte has the following characteristics: 1, an L < i + > weak solvation environment can be created by reducing Li < + >-solvent molecule coordination and increasing Li < + >-anion coordination in the electrolyte; 2, the decomposition of solvent molecules in the electrolyte can be inhibited, and inorganic-rich and organic-poor SEIs are formed on the surface of the negative electrode; and 3, the transmission of Li < + > in SE I s can be promoted, and the growth of lithium dendrites is inhibited. And thus, the charge-discharge efficiency, the cycle stability and the safety performance of the battery are improved.

The invention provides a mixed positive electrode material, positive electrode slurry, a preparation method of the positive electrode slurry, a positive electrode plate and application. The mixed positive electrode material comprises the following components in parts by weight: 95-98 parts of an active substance, 1-5 parts of a conductive agent, 1-5 parts of a binder and 0-0.5 part of a dispersing agent, the active substance comprises lithium manganese iron phosphate and lithium manganate, and the weight ratio of the lithium manganese iron phosphate to the lithium manganate is (7-8): (3-2). According to the mixed positive electrode material, the minimum energy density can be increased to 190 wh / kg or above and the rate capability can be greatly improved through the ratio of the lithium manganese iron phosphate to the lithium manganate being (7-8): (3-2); meanwhile, the lithium manganese iron phosphate is large in specific surface area and small in compaction density, and the lithium manganate is small in specific surface area and large in compaction density, so that the use amount of a dispersing agent in a homogenizing section is reduced, the surface density fluctuation of a coating section is reduced, and the compaction density is increased to 2.6 kg / m < 3 > or above.

The invention belongs to the technical field of battery safety, and particularly relates to a phase change heat insulation baffle, a preparation method and application thereof, and a soft package battery module. The invention provides a phase-change heat-insulation barrier plate. The phase-change heat-insulation barrier plate comprises a phase-change heat-insulation material and a packaging film for packaging the phase-change heat-insulation material, the phase-change thermal insulation material comprises a substrate material, and a phase-change material and a flame-retardant material which are adsorbed on the substrate material, the substrate material comprises a silicon dioxide nanofiber felt and a supporting material; the phase-change material comprises one or more of silica sol, alumina sol and a saturated calcium chloride solution, and the flame-retardant material comprises a phosphorus-containing flame retardant. The phase-change thermal insulation material contains the phase-change material and the thermal insulation substrate, has a very high phase-change enthalpy value, plays a good role in blocking heat spreading through thermal insulation of the thermal insulation material and phase-change energy consumption of the phase-change material during thermal runaway, and can delay the heat spreading time or inhibit the heat spreading.

The invention discloses a lithium ion battery non-combustible electrolyte and a preparation method and application thereof, and relates to the technical field of electrolyte preparation. The electrolyte comprises an organic solvent, a lithium salt, fluorophosphate and a film-forming additive, wherein the film-forming additive is aluminum isopropoxide. The preparation method disclosed by the invention is simple, mild in condition, low in cost and suitable for large-scale industrial production, not only meets the requirements of the existing market on non-combustible and high-safety performance of the electrolyte, but also has relatively wide application and production prospects. The problem that an existing electrolyte is poor in safety performance is solved.

The invention relates to the technical field of combustors, in particular to an ultra-low nitrogen oil-gas dual-purpose combustor which comprises a supporting plate and a shell fixedly arranged on the supporting plate, an oil supply pipe, a gas supply pipe and a blast assembly are arranged in the shell, a first control valve is arranged at one end of the oil supply pipe, and a second control valve is arranged on the gas supply pipe; a fixed sleeve is fixedly arranged on the side face of the shell, and a rotational flow disc and an ignition assembly are fixedly arranged in the fixed sleeve. An oil outlet pipe, an oil return pipe and a plurality of air outlet pipes are fixedly arranged in the fixed sleeve; according to the combustor, jet flow kinetic energy, wind speed kinetic energy and flame kinetic energy of fuel are fully utilized, and smoke recirculation can be conducted in the combustion head in combination with special inner air duct arrangement and fuel spray gun arrangement of the combustion head, so that the energy density of the fuel and the oxygen density of combustion-supporting wind can be reduced, and the combustion efficiency is improved. Therefore, smoke is extracted from the rear portion of the boiler instead of the outside, and NOx emission can be directly smaller than 30 mg / m < 3 > * or 50 mg / m < 3 > *.

The invention discloses a processing method for a copper-clad ceramic substrate, which relates to the technical field of copper-clad ceramic substrate processing, and comprises the following steps of: taking a pre-treated copper-clad ceramic substrate, introducing nitrogen, and carrying out layered progressive micropore processing on an exposed aluminum oxide ceramic substrate of the pre-treated copper-clad ceramic substrate through picosecond laser to form micropores; each micropore is divided into an inlet layer, a middle layer and an outlet layer from top to bottom; the layer number of the micropores, the thickness of each layer of the micropores and the pulse width are controlled, and a light spot and long-focal-depth lens is adopted; adjusting monopulse energy and frequency parameters of picosecond laser, and punching an inlet layer; adjusting monopulse energy and frequency parameters of picosecond laser, and punching the middle layer; and adjusting monopulse energy and frequency parameters of the picosecond laser, and punching the outlet layer to obtain the copper-clad ceramic substrate. In the middle layer, the monopulse energy is gradually increased, and it is ensured that the material is evenly removed; at the inlet layer and the outlet layer, energy is reduced, and cracks caused by stress generated instantly when the material is punctured are avoided.

The invention discloses a lithium metal negative electrode with volume expansion adaptivity as well as a preparation method and application thereof, belongs to the technical field of lithium metal batteries, and provides a preparation method of the lithium metal negative electrode with volume expansion adaptivity, which comprises the following steps: soaking a carbon felt in a mixed solution of metal salt and a sulfur source, performing hydrothermal treatment, and cooling, thereby obtaining the lithium metal negative electrode with volume expansion adaptivity. Pre-treated carbon felt is obtained; washing with deionized water, and drying to obtain a sulfurized carbon felt; taking a piece of lithium foil and two pieces of carbon sulfide felts, respectively covering the upper part and the lower part of the lithium foil with the carbon sulfide felts, and rolling to obtain a carbon sulfide felt and lithium metal compound; and heating and reacting to obtain the lithium metal negative electrode. One or more sulfides grow on the commercial carbon felt, lithium metal is modified through simple rolling, the lithium metal electrode is obtained, the strength of the electrode is higher than that of the lithium metal, and the electrode has good mechanical performance; the phenomena of non-uniform deposition and dendritic crystal growth of lithium metal are retarded, and the volume expansion self-adaptive capacity of the battery is improved.

The invention discloses a preparation method of a square lithium iron phosphate battery capable of improving cycle performance and the square lithium iron phosphate battery, a diaphragm is a polyethylene coated ceramic layer diaphragm, double surfaces of the diaphragm are coated with ceramic layers, the total thickness of the ceramic layers is 1-3 microns, the ceramic layers can improve the liquid retention capacity and contribute to improving the cycle capacity, and the ceramic layers are too thick, so that the cycle performance of the lithium iron phosphate battery is improved. The system energy density is reduced. The process is simplified, and mass production control is easy; the cycle performance is improved, the cycle attenuation trend is reduced, and the user experience is improved.

The application discloses a metal part plasma detonation treatment device, which comprises a capacitive induction power supply, a reaction chamber and a detonation gun. The capacitive induction power supply comprises a ring-shaped cathode electrode, a ring-shaped anode electrode and a center electrode. The center electrode is fixedly connected with the anode electrode. The reaction chamber is a ring-shaped cavity surrounding the anode electrode. The reaction chamber separates the cathode electrode from the anode electrode. The detonation gun is connected with a detonation gun ring chamber and is used for introducing combustible gas and performing periodic detonation. The nozzle is connected with the ring-shaped cavity and is used for introducing alloy elements. The metal part plasma detonation treatment device improves the hardening effect of the device on the metal surface, improves the uniform distribution of the alloy elements, and improves the modification quality and productivity of the workpiece surface.

The invention relates to the technical field of laser treatment, and particularly discloses a laser needle and a hand tool, the laser needle comprises a needle body and a light guide fiber, the needle body is provided with a hollow channel, the side wall of the far end of the needle body is provided with a light transmitting part, the light guide fiber is located in the hollow channel, and the far end of the light guide fiber extends to the light transmitting part. The far end of the light-guide fiber is provided with at least two light-emitting surfaces, the light-emitting surfaces are obliquely arranged relative to the axial direction of the light-guide fiber, and at least part of laser beams guided out through the light-emitting surfaces are emitted through the light-transmitting part; the end face of the light-guide fiber is made into at least two light-emitting surfaces which are inclined relative to the axial direction of the light-guide fiber, so that a laser beam in the light-guide fiber can be divided into two or more beams to be emitted from the side face of the needle body, and the wavelength of the divided laser beam is not changed while the energy density is reduced; therefore, the risk of skin burn caused by excessively concentrated energy of the laser beams can be avoided, meanwhile, the laser beams can irradiate a wider area, the efficiency and safety of laser treatment are remarkably improved, and the treatment time is shortened.

The invention relates to the technical field of display, and discloses a light source system and projection equipment, in the light source system, a light source and a lens group are off-axis, that is, when light generated by the light source passes through a light guide element or avoids the light guide element and directly enters the lens group, the optical axis of a light spot and the optical axis of the lens group are spaced by a certain distance; after being focused by the lens group, the light is used as exciting light of the wavelength conversion area, so that the loss of the first colored light and the excited second colored light on the light guide element can be reduced; when the excited second color light finally enters the dodging element, formed light spots are oval and correspond to the long and short edges of the dodging element, and the light utilization rate is increased; the brightness of the projection equipment can be improved.

An irradiation probe system is, for example, an irradiation probe system including: an irradiation probe having a core and first cladding surrounding the core; at least one light source; and a coupling portion that couples light output by the at least one light source, to at least one of the core and the first cladding; the core includes a first input end portion at one end of an axis of the core, and an output end portion at the other end of the axis; and the first cladding includes a second input end portion at one end of the axis, and a leakage portion that is provided at a position separate from the second input end portion and leaks, radially outward, light transmitted inside the first cladding, from an outer peripheral surface of the first cladding.

A method of producing a liquid organic hydrogen carrier (LOHC). The method includes delivering a hydrocarbon feed stream rich in aromatic hydrocarbons to a thermal treatment unit to convert olefin compounds to heavier compounds by a dimerization reaction and generate a dimerized feed stream; delivering the dimerized feed stream to a fractionation unit to form a light fraction stream and a heavy fraction stream at a cut point of 115°C to 150°C; and delivering the light fraction stream to an aromatic hydrocarbon extraction unit to form an aromatic compound stream and a non-aromatic compound stream. The method also includes delivering the aromatic compound stream and an input hydrogen stream to a hydrogenation unit to form a hydrotreated effluent stream; and delivering the hydrotreated effluent stream to a separator to remove unsaturated compounds, thereby isolating a saturated compound as a LOHC stream.

The invention discloses a preparation method of a positive and negative electrode insulation isolation layer of a solar cell. The preparation method comprises the following steps: S1, placing the back surface of a back contact solar cell on an ink-jet printing platform deck; s2, arranging an insulation isolation area in parallel on a metal auxiliary grid line on the back surface of the back contact solar cell and a welding contact area; carrying out insulation ink-jet printing in the insulation isolation area; and curing the solar cell after ink-jet printing of the insulation isolation area under an ultraviolet lamp. According to the invention, the graph is digitally printed, and the manufacturing time is shortened from several weeks to several hours; the film forming thickness of 1-50 microns can be realized through one-time ink-jet printing, and the problem of bubbles can be solved at the same time; precision of ink-jet printing graph capable of being controlled within range

The present invention discloses a component bidirectional gradient energetic charge liner charging structure, the energetic charge liner charging structure includes a component bidirectional gradient charge liner, the energy density and ductility of the component bidirectional gradient charge liner bidirectionally gradient along the generatrix direction and the wall thickness direction, along the direction from the liner top to the liner mouth and from the outer surface to the inner surface, the energy density of the material constituting the charge liner gradually increases and the ductility gradually decreases; the material properties close to the liner top and the outer surface are biased towards the inert charge liner; the material properties away from the liner top and the outer surface are biased towards the energetic charge liner, and the explosive mainly forms an energetic pestle after detonation, which breaks into a large amount of fragment clouds and releases chemical energy after the jet penetrates the target plate. The above energetic charge liner charging structure combines the advantages of the energetic charge liner and the traditional inert charge liner, and can effectively improve the damage aftereffect of the armor-piercing warhead on the basis of retaining the high penetration depth performance.

The application discloses a battery pack and a battery cell thereof, which comprises a battery shell and an electric core, the electric core is placed in the battery shell, an explosion-proof valve is arranged on the battery shell, the explosion-proof valve comprises a weak part, a blocking part is arranged on the battery shell, the blocking part is arranged at the periphery of the weak part, the thickness of the blocking part is greater than the thickness of the weak part, the blocking part comprises a blocking main structure, the area surrounded by the weak part is S1, the area surrounded by the outer edge of the blocking part is S2, S1 and S2 satisfy 0.03*10 4 ≤S1*(S2‑S1) / (Q*h1 / h2)≤20*10 4 Wherein, Q is the battery capacity, h1 is the thickness of the shell where the explosion-proof valve is arranged, and h2 is the thickness sum of the battery shell and the blocking main structure; the blocking main structure comprises a blocking platform. The battery pack and the battery cell thereof reduce the probability of the situation that the battery cell on fire spreads to the adjacent battery cell when the battery cell is in thermal runaway, and reduce the occurrence of heat spread when the battery is in thermal runaway.

This invention provides a battery module. A battery module includes: a laminate formed by stacking multiple battery cells; a pair of first components respectively disposed at both ends of the laminate along its stacking axis, clamping the laminate; and a pair of end plates respectively disposed at both ends of the laminate along its stacking axis, the first components being single-layer components including an elastomer, and configured in contact with the battery cells and the end plates.

A lithium secondary battery according to the present invention includes a positive electrode including a positive electrode active material layer and a negative electrode including a negative electrode active material layer, wherein the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material consists of silicon, and in a graph of capacity-voltage measured by manufacturing a half-cell including the positive electrode and a lithium metal electrode and then discharging the half-cell at a constant current of 0.1 C, an inflection point appears in a region in which a voltage is 3.3 V to 3.7 V, and the capacity of the positive electrode at the inflection point is 3% to 25% of the capacity of the positive electrode at a final charge voltage.

The invention belongs to but is not limited to the technical field of electrochemical containers, and particularly relates to a double-hybrid electrochemical capacitor and a preparation method thereof, the double-hybrid electrochemical capacitor comprises a hybrid positive electrode and a hybrid negative electrode, and the hybrid positive electrode and the hybrid negative electrode simultaneously comprise two energy storage mechanism active materials of double-electric-layer electrostatic energy storage and Faraday quasi-capacitance energy storage. An active material of the double-electrode-layer electrostatic energy storage mechanism is open-pore activated carbon, the port aperture of the open-pore activated carbon is smaller than or equal to 0.2 nm, and the pore web size is 1-1.5 nm. In the manufacturing process of the capacitor, the electrochemical principle is utilized, the positive electrode and the negative electrode are subjected to electrochemical hybridization design at the same time, on one hand, the upper limit of the working voltage of the electrochemical capacitor is increased to 4.4 V from 2.7 V through introduction of a Faraday quasi-capacitor energy storage mechanism active material at the positive electrode end, and therefore effective energy storage of the capacitor is greatly enhanced; the volume energy density is greatly improved; and on the other hand, high-power output characteristic matching of the system is simultaneously introduced and maintained at the positive electrode end and the negative electrode end through a double-electric-layer electrostatic energy storage mechanism active material.

The invention discloses a shared power bank solid hydrogen power supply system, which relates to the technical field of shared power banks and comprises a solid hydrogen storage unit, a power supply unit, an electric energy distribution unit, an energy storage unit, a battery monitoring unit and an automatic energy supply unit. The solid hydrogen power supply system is adopted as a power supply of the shared power bank, the solid hydrogen power supply system has high energy density, more energy can be stored in a small space, the power supply system is made to be smaller in size and lighter in weight, only water vapor is generated after hydrogen reaction, no gas pollutant is discharged, environmental pollution is reduced, and energy is saved. The storage form of solid hydrogen is safer and more portable than that of liquid hydrogen, a hydrogen source can be quickly replaced, dependence on an external power supply is reduced, charging service can be provided in a place without a traditional power grid, the flexibility and environmental sustainability of the shared power bank pile are improved, the operation efficiency of the shared power bank pile can be improved, and the cost of the shared power bank pile is reduced. And the idle time of the equipment caused by charging is reduced.

The utility model relates to the technical field of batteries, in particular to a battery device, which comprises a plurality of batteries stacked along the Z direction and at least comprising an accommodating space; the pressure relief structure is arranged in the accommodating space and corresponds to the step surface, and the pressure relief structure is used for puncturing the step surface to realize pressure relief under the condition that the interior of the first battery reaches bursting pressure; a pole of the second battery is arranged in the accommodating space and is positioned on the second surface; in the Z direction, a first distance h is arranged between the surface, close to the first face, of the pole and the first face, and the range of the first distance h is 1 mm < = h < = 24 mm. The first distance is controlled within a certain range, the enough distance between the first surface and the pole is ensured, and when the pressure relief structure punctures the first surface to perform pressure relief blasting, the accommodating space has enough space for buffering, so that the impact of gas-liquid substances sprayed out by pressure relief on the pole can be reduced as much as possible, the influence of battery blasting on adjacent batteries is reduced, and the service life of the batteries is prolonged. And short circuit of adjacent batteries is avoided.

The present application provides a positive electrode sheet, a secondary battery, a battery module, a battery pack, and an electrical apparatus; the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer having a single-layer structure or a multi-layer structure provided on at least one surface thereof; when the positive electrode film layer is of a single-layer structure, at least one positive electrode film layer comprises both a first positive electrode active material and a second positive electrode active material; and / or, when the positive electrode film layer is of a multi-layer structure, at least one layer of the at least one positive electrode film layer comprises both a first positive electrode active material and a second positive electrode active material; the first positive electrode active material comprises an inner core containing Li1+xMn1-yAyP1-zRzO4, a first coating layer containing pyrophosphate MP2O7 and phosphate XPO4 and covering the inner core, and a second coating layer containing carbon element and covering the first coating layer. The secondary battery prepared with the positive electrode sheet of the present application has high energy density, high battery cell rate performance, good dynamic performance and low temperature performance, good cycling performance and high safety.

A battery pack includes a battery module and a pack case. The battery module includes a plurality of cylindrical batteries each including, at one end in a specified direction, a battery exhaust valve that opens in response to an increase in internal pressure; and a battery holder including a plurality of housing parts for the one ends of the cylindrical batteries in the specified direction to be inserted. The pack case houses the battery module and internally includes an exhaust passage for gas exhausted from at least one of the plurality of cylindrical batteries to be exhausted out of the pack case. Each of the plurality of housing parts includes a lid part facing the battery exhaust valve of a corresponding cylindrical battery. The lid part includes an opening cover part that creates a larger holder opening with a greater outside diameter than the battery exhaust valve, and the opening cover part includes a ring-shaped or incomplete ring-shaped outer periphery that is defined by a weak part with less strength than a part external to the opening cover part.