350 results about "Cell impedance" patented technology

The invention provides a positive electrode material and a preparation method thereof, a positive electrode plate and a battery, the positive electrode material comprises lithium manganese iron phosphate particles, a first shell layer and a second shell layer, the first shell layer and the second shell layer sequentially coat the surfaces of the lithium manganese iron phosphate particles, the material of the first shell layer comprises nanoscale SiO2 particles, and the material of the second shell layer comprises nanoscale TiO2 particles. The surfaces of the lithium manganese iron phosphate particles are sequentially coated with the SiO2 layer and the TiO2 layer, so that the contact between the lithium manganese iron phosphate particles and an electrolyte can be reduced, the side reaction between the lithium manganese iron phosphate particles and the electrolyte in the electrochemical reaction process is reduced, the cycle life attenuation of the battery is relieved, the dissolution of Mn element is reduced, and the service life of the battery is prolonged. Therefore, the battery impedance increase caused by deposition of Mn < 2 + > on the negative electrode in the circulation process is relieved.

A method for battery power management based on battery nonlinearity characterization and compensation using a nonlinear resistor-capacitor (RC) equivalent circuit model (ECM) may include: measuring a current, a terminal voltage, and a temperature of a battery; implementing the nonlinear RC ECM comprising fixed, logarithmically spaced time constants and current dependent resistances and capacitances; constraining resistances of the nonlinear RC ECM to be nonnegative and performing a nonlinearity characterization procedure using the nonlinear RC ECM configured to characterize variations of a battery impedance with current amplitudes over a range of frequencies and create ECM parameter variations with current amplitudes by fitting impedance variations by nonlinear RC ECMs; performing online estimation of the nonlinear RC ECM using a battery current and a terminal voltage of the battery over time; and modifying the online estimated nonlinear RC ECM using ECM parameter variations to compensate for nonlinearity of the battery.

An impedance measurement apparatus is provided for measuring impedance of a secondary battery. The impedance measurement apparatus includes a measurement unit and a switching unit. The measurement unit is capable of measuring the impedance of the secondary battery using a plurality of measurement modes differing in measurement condition. The switching unit is configured to switch between the plurality of measurement modes based on a comparison between a correlating parameter, which correlates with the impedance of the secondary battery, and a threshold value.

The invention relates to a multi-dimensional testing method and device for a golf cart battery. The method comprises the following steps: carrying out standard working condition operation data acquisition on a golf cart battery, and constructing an electrochemical-thermal-mechanical coupling theoretical model to obtain a battery multi-dimensional coupling theoretical matrix; the method comprises the following steps: arranging a temperature sensor and a strain gauge on the surface of a golf cart battery, executing real-time data synchronous acquisition to obtain multi-dimensional actual measurement data of the battery, and carrying out electrochemical impedance spectroscopy test on the battery to obtain a battery impedance characteristic vector; dispersing the battery volume into control volume units and carrying out thermal-mechanical coupling iterative solution to obtain a battery thermal-mechanical coupling characteristic matrix; and performing battery performance evaluation based on the battery impedance characteristic vector, the battery thermal coupling characteristic matrix and the battery multi-dimensional measured data to obtain a battery performance evaluation result. According to the invention, the interaction among the physical fields in the battery can be comprehensively captured, and the real-time monitoring and quick response of the multi-dimensional physical quantity of the battery are realized.

Understanding a health status and expected remaining lifetime of an EV (electric vehicle) battery is important before repurposing the battery for second life applications. A device for connecting to an unopened EV battery pack via operable coupling to signal and power wiring is disclosed. The device enables access to diagnostic information from the unopened EV battery. The device measures cell and / or module voltages and currents within the battery pack for several different depths of discharge. A self-learning algorithm implemented by the diagnostic device, which uses historical data and diagnostic information from the battery pack, determines a condition of the battery and provide recommended operational conditions for future use of the battery. For example, a degradation slope and expected capacity loss over time can be determined based on measured variations of cell and / or modular voltages and subsequently used, with cell impedance data, to recommend an operational C-rate for the battery pack.

The invention provides a cell fault early warning method and system based on dynamic impedance fitting, and the method comprises the steps: carrying out the impedance test of a target battery, obtaining an impedance value at an initial moment, and charging the target battery; performing impedance recording on the target battery at each time point through the excitation current with the preset frequency to obtain a real-time impedance observation value; constructing an exponential decay model and performing impedance fitting prediction on the real-time impedance observation value at each time point to obtain a real-time impedance prediction value; and carrying out residual error fitting and deviation analysis on the real-time impedance observation value and the real-time impedance prediction value to obtain battery abnormal change monitoring data, and sending out early warning when the target battery cell has a fault. The problem that in the prior art, in the battery charging and discharging process, the battery impedance change cannot be detected in real time, and the battery fault cannot be early warned in time, so that the safety of the battery cell is poor is solved. According to the invention, the impedance abnormal change time can be fed back in time and early warning can be made, so that the safety of the battery cell is improved.

The invention provides a battery state prediction method and system, computer equipment and a storage medium, and the method comprises the steps: randomly selecting a preset proportion of batteries from a target batch of batteries as a test sample set; performing current switching cycle life test on each battery sample to obtain a plurality of groups of current sudden change data comprising current time sequence data, voltage time sequence data and battery health state corresponding to the preset charge state segment point sequence; obtaining a current abrupt change point battery impedance spectrum according to the current time sequence data and the voltage time sequence data in each group of current abrupt change data, and constructing a battery state prediction model according to all the current abrupt change point battery impedance spectrums and the corresponding battery health states; and obtaining a battery state prediction value according to the obtained current mutation battery impedance spectrum of the to-be-evaluated battery and the battery state prediction model. According to the invention, the high efficiency, accuracy and operation convenience of online monitoring of the health state of the battery can be effectively improved under the low-cost condition of not additionally adding measuring equipment.

The invention discloses a Fourier transform and S transform combined battery impedance spectroscopy measurement method and device, and aims to improve the precision, speed and reliability of impedance measurement of a battery energy storage system. According to the method, a multi-frequency component excitation signal is generated through a controllable current source, and current and voltage response signals of a battery are synchronously acquired and are respectively input into a Fourier transform module and an S transform module for frequency domain analysis. The Fourier transform module extracts impedance spectrums of low and medium frequency bands, and the S transform module extracts impedance spectrums of medium and high frequency bands through Gaussian window time-frequency analysis. And a data fusion algorithm is adopted to perform composite processing on results of the two modules, including a direct selection method, an arithmetic average method, an amplitude and phase calibration method and a weighted average method, so that smooth transition and optimization between frequency bands are realized, and finally the electrochemical impedance spectrum is generated. Through collaborative analysis of Fourier transform and S transform, parameter optimization and a fusion algorithm, the efficiency and accuracy of impedance spectroscopy measurement are remarkably improved, and the method is suitable for rapid monitoring and diagnosis of the battery state.

The invention relates to the field of lithium ion batteries, and discloses a positive electrode lithium supplement additive, a preparation method thereof, a positive plate and a lithium ion battery. The lithium supplement additive for the positive electrode comprises a lithium-containing compound, and a first coating layer and a second coating layer which sequentially coat the surface of the lithium-containing compound, wherein the first coating layer comprises at least one of lithium aluminum titanium phosphate, lithium lanthanum zirconium oxide and lithium lanthanum titanium oxide; the second coating layer includes at least one of a Ga-containing compound, a Sm-containing compound, a Si-containing compound, an Al-containing compound, a V-containing compound, a Nb-containing compound, a Mg-containing compound, a Zr-containing compound, and a Zn-containing compound. The first coating layer improves the stability in the processing process, prevents side reaction, ensures the structural stability of the positive electrode lithium supplement additive, and improves the cycle performance of the battery; and the second coating layer provides an effective smooth channel for lithium ions, so that the impedance of the battery can be effectively reduced, and the capacity and the cycle performance of the battery are improved.

Understanding a health status and expected remaining lifetime of an EV (electric vehicle) battery is important before repurposing the battery for second life applications. A device for connecting to an unopened EV battery pack via operable coupling to signal and power wiring is disclosed. The device enables access to diagnostic information from the unopened EV battery. The device measures cell and / or module voltages and currents within the battery pack for several different depths of discharge. A self-learning algorithm implemented by the diagnostic device, which uses historical data and diagnostic information from the battery pack, determines a condition of the battery and provide recommended operational conditions for future use of the battery. For example, a degradation slope and expected capacity loss over time can be determined based on measured variations of cell and / or modular voltages and subsequently used, with cell impedance data, to recommend an operational C-rate for the battery pack.

The invention provides an EIS on-line detection system and method for a high-power fuel cell system, a main loop of the EIS on-line detection system adopts two Boost type converter topological structures which are connected in parallel, and small signal excitation injection is carried out through an auxiliary DC / DC converter 2; the control system comprises a sampling system, a PWM drive circuit, a communication module and an embedded controller. Establishing a battery equivalent circuit model; when a high-power fuel cell system runs, a multi-frequency sine periodic signal optimized by a non-dominated sorting genetic algorithm improved based on Tent chaotic mapping is injected into an output current of an auxiliary DC / DC converter 2; sampling the voltage of a single body or a galvanic pile, measuring current data, calculating the voltage drop corresponding to the internal resistance of the current data, converting a time domain signal into a frequency domain signal, and obtaining the battery impedance information in the corrected Foouquet equivalent circuit model; importing the characteristic parameter data into a least square support vector machine (LSSVM) for training and testing, and performing in-situ detection and fault diagnosis on line; according to the invention, a new way can be provided for active diagnosis and early warning of faults.

A lithium supplement, a preparation method therefor, a positive electrode sheet and a secondary battery. The lithium supplement comprises a first material phase and a second material phase, the first material phase comprising a lithium-rich material, and the second material phase comprising a reducing agent. The reducing agent can combine with active oxygen to inhibit a gas-producing reaction caused by the active oxygen, and the reducing agent can also combine with oxygen to reduce the gas output of a battery, thereby effectively improving the safety performance, the electrochemical performance and the stability of the battery. In addition, the reduction in the gas output of the battery reduces the battery impedance, helping to improve electron and ion conductivity and thus increasing the deintercalation rate of lithium ions during charging processes. Moreover, the reducing agent combining with the oxygen to generate a stable substance can avoid oxygen deintercalation again, thereby ensuring the reliability of the reducing agent for reducing the battery gas output.

The invention belongs to the related technical field of fuel cells, and particularly relates to a fuel cell impedance spectroscopy rapid measurement system and method, the system is divided into an excitation current injection part, a data acquisition part and an upper computer, the upper computer adopts a DIBS signal with an excellent peak value inhibition capability and a flexible amplitude-frequency design capability as test excitation, and the test excitation part is connected with the data acquisition part; an electronic load is used as an excitation source. The upper computer can control the electronic load to generate a current excitation waveform used for impedance testing based on a DIBS signal, the electronic load injects excitation current into output current of a tested galvanic pile, the upper computer can also read sampling data of the data acquisition part, fast Fourier transform is carried out on the acquired excitation current and response voltage data, and the impedance of the tested galvanic pile is tested. And obtaining an electrochemical impedance spectrum. According to the method, the impedance measurement efficiency is improved, the hardware structure is simple, the method has a good field application prospect, a measured object can be expanded to other electrochemical systems including an electrolytic tank, and the method has good expansibility.

The invention relates to the technical field of lithium ion batteries, in particular to a non-aqueous electrolyte and a lithium ion battery. The non-aqueous electrolyte comprises an organic solvent, a lithium salt, difluorophosphate ions, tris (trimethylsilyl) phosphate and a first additive; the lithium salt comprises lithium hexafluorophosphate; the non-aqueous electrolyte satisfies the following conditions: 0.05 < = a / b < = 20, 0.03 < = a / c < = 15, 0.05 < = c * d / b < = 20, 0.01 < = a < = 1, 0.01 < = b < = 1.2, 0.01 < = c < = 0.8, and 1.1 < = d < = 1.3. According to the non-aqueous electrolyte disclosed by the invention, the advantages of tris (trimethylsilyl) phosphate that the impedance of a battery is reduced and a high-stability LiF-rich interfacial film is formed can be fully exerted, meanwhile, the defect that tris (trimethylsilyl) phosphate catalyzes decomposition of lithium salt to generate unfavorable byproducts is greatly inhibited, and relatively low initial impedance and excellent high-temperature quick-charge cycle performance can be considered on the battery level; and the problem of rapid increase of impedance under high-temperature rapid charging circulation is inhibited.

The invention relates to the technical field of electric energy storage systems, in particular to a mathematical model-based vehicle-mounted charger component parameter optimization method and system. The method comprises the following steps: performing multi-physical field joint modeling according to a vehicle-mounted charger switching device to obtain a vehicle-mounted charger component simulation model; performing dynamic sensitivity analysis according to the vehicle-mounted charger component simulation model to obtain dynamic sensitivity matrix data; performing layered MINLP solution on the dynamic sensitivity matrix data to obtain battery impedance change curve data; and on-line parameter reconstruction is carried out according to the battery impedance change curve data to obtain vehicle-mounted charger component parameter optimization data. The adaptive capacity of the system to different working conditions is enhanced while the charging efficiency is improved, and the overall performance, stability and reliability of the vehicle-mounted charger are remarkably improved.

The invention provides an intelligent battery sorting method integrating impedance characteristics and deep learning. The method comprises the following steps: acquiring battery impedance data through an electrochemical workstation, drawing an electrochemical impedance spectroscopy (EIS), and extracting impedance characteristics of a medium-frequency region; a 25-dimensional impedance coupling feature space is innovatively constructed, a dual-network differentiated feature selection strategy (IC-GRU) is adopted, a main network selects 12 features with the highest correlation, a boundary expert network selects 10 features with the highest correlation and additionally constructs 5 boundary sensitive features, and finally, the main network selects 12 features with the highest correlation. And establishing an impedance coupling sensing gating circulation unit network to realize accurate prediction of the state of health (SOH). And performing four-stage sorting on the SOH result predicted by the IC-GRU through a random forest algorithm (RF). According to the method, more accurate SOH prediction is realized through deep learning guided by a physical mechanism, the battery pack health state sorting precision and consistency are improved, and an intelligent solution is provided for new energy automobile battery life management.

The present invention relates to the technical field of power battery measurement. Disclosed are an offline measuring method for available capacity of a power battery, a device, and a storage medium. A circuit initial model is established by means of pulse working conditions, actual charging data is used to train the initial model, data of the battery in a constant-current charging state is used as negative feedback to correct battery model parameters, then a battery end voltage is simulated by means of the corrected model, and calculation is performed to obtain the actual available capacity of the battery and the state of health of the battery. According to the present invention, on the basis of existing voltages and Coulomb counting algorithms, a dynamic learning mechanism of battery parameters is added, reducing model prediction errors, enabling a predicted voltage to be closest to an actual voltage, solving the problem of the impedance of a battery changing over time, rapidly measuring the available capacity of the battery, and obtaining the state of health of the battery.

A control method for impedance spectrum measurement of a battery is disclosed. The battery outputs a power via a DC-DC converter. The control method includes (i) sending a first signal, wherein the first signal indicates a conduction mode of the DC-DC converter to be set, and the conduction mode includes a discontinuous conduction mode or a critical conduction mode, (ii) receiving a current measurement value and a voltage measurement value at an output end of the battery, and (iii) calculating an impedance spectrum of the battery based on the received current measurement value and the received voltage measurement value. A control device and a system for impedance spectrum measurement of a battery, a computer-readable storage medium, a computer program product, a vehicle electronic control unit, and a vehicle is also disclosed.

The invention provides a positive electrode, a lithium battery and a device. The positive electrode comprises a positive electrode current collector and a lithium supplement layer and a positive electrode material layer which are sequentially stacked on at least one side of the positive electrode current collector, the lithium supplement layer contains a first positive electrode lithium supplement agent, the positive electrode material layer contains a positive electrode active material and a second positive electrode lithium supplement agent, the first coulombic efficiency of the first positive electrode lithium supplement agent is less than 30%, and the second coulombic efficiency of the second positive electrode lithium supplement agent is less than 30%. And the second positive electrode lithium supplement agent can be decomposed to generate gas. The first positive electrode lithium supplement agent and the second positive electrode lithium supplement agent are simultaneously introduced into the positive electrode and are arranged in a layered manner, so that the power performance of the battery can be improved while the impedance of the battery is not obviously increased.

The invention provides a secondary battery electrolyte additive and a preparation method thereof. The additive is obtained by bonding oxygen atoms of four hydroxyl groups on R1-R5 groups in a compound as shown in a structural formula I with a group A and a group B through any one of the following modes: (1) bonding with two groups A; (2) bonding with two B groups; (3) bonding with one A group and one B group: # imgabs0 # wherein n is 0 or 1; r1 to R5 are independently selected from H, alkoxy of C1 to C5, hydroxyl and alkyl of C1 to C5 substituted by hydroxyl, and at least four hydroxyl are contained in R1 to R5; * represents a bonding position. The additive can form a stable, cross-linked and tough SEI film, and battery impedance is further reduced. The additive is cheap and easily available in preparation raw materials, low in cost, short in reaction route, simple in purification process, high in production efficiency and wide in application prospect in the secondary battery electrolyte.

The invention relates to a non-aqueous electrolyte and a lithium secondary battery. In order to solve the problems of poor cycle performance, high impedance and serious gas production of a lithium secondary battery, the invention provides a non-aqueous electrolyte, the non-aqueous electrolyte comprises an organic solvent, a lithium salt and additives, the additives comprise a first additive, a second additive and a third additive, the first additive is selected from one or more of compounds shown in a formula I, and the third additive is selected from one or more of compounds shown in a formula II; the formula I is # imgabs0; the second additive is selected from a compound shown in a formula II and / or a formula III; the formula II is # imgabs 1 #, the formula III is # imgabs 2 #, and the third additive is selected from one or more of double-bond-containing cyclic carbonate, halogen-containing cyclic carbonate, sulfonate, sulfate, sulfite, anhydride, a benzene compound, a fluorobenzene compound, a nitrile compound, phosphate, phosphite, a boron compound, an amine compound, a silicon-containing compound and a heterocyclic compound. Through the synergistic effect of the three additives, the cycle performance of the battery is improved, the impedance of the battery is reduced, and the gas production of the battery is reduced.

The invention provides a negative pole piece, a preparation method thereof and a battery, the negative pole piece comprises a negative current collector and a negative active material layer, and the negative active material layer comprises a negative active material, a conductive agent and a binder; the negative pole piece meets the following relational expressions: 0.1 < = SV / SL < = 1.0, R / W < = 10%, 0.1% < = R < = 0.5%, 1.0% < = W < = 5.0%; wherein SL is the area of the active particles corresponding to the included angle theta between the orientation of the negative electrode active material and the negative electrode current collector being less than 45 degrees, and Sv is the area of the active particles corresponding to theta being greater than or equal to 45 degrees; r is the range of the distributed mass percentage content of the binder; w0 is the total mass percentage content of the binder; the distribution range R of the binder and the orientation SV / SL of the active particles are controlled through the novel manufacturing process, the phenomenon that the binder is not uniformly distributed in the solvent evaporation process can be reduced, the orientation degree of the active substance particles on the pole piece in the rolling process can be reduced, the battery impedance is reduced, and the battery performance is improved. The electrochemical performance of the battery is improved.

The embodiment of the invention discloses a method and a device for controlling charging, charging equipment and a computer readable storage medium, which are used for performing electrochemical impedance spectroscopy analysis by using a second charging protocol and controlling charging through a power management integrated circuit, so that the precision of the electrochemical impedance spectroscopy analysis can be improved. The method comprises the steps of receiving a first communication frame sent by power supply equipment under the condition of detecting that the power supply equipment is inserted and charging is performed by using a first charging protocol; when it is determined that the second charging protocol is used for charging, a first instruction is sent to the power supply equipment according to the first communication frame; acquiring a plurality of first voltage values and a plurality of first current values for charging by using a second charging protocol, wherein the plurality of first voltage values form a first voltage sequence and the plurality of first current values form a first current sequence; and under the condition that at least one of the first voltage sequence and the first current sequence meets a step response condition, calculating a first battery impedance value, and sending a second instruction to the power supply equipment.

The present invention relates to the technical field of lithium ion battery manufacturing, and in particular to an in-situ gel polymer electrolyte and its preparation method and application. It includes: dissolving lithium salt in a mixed organic solvent of 1,3-dioxolane and carbonate organic matter, stirring and mixing evenly under the conditions of room temperature, inert gas protection and a rotation speed of 100 to 1000 rpm; dissolving additives in an electrolyte, stirring under the conditions of room temperature, inert gas protection and a rotation speed of 100 to 1000 rpm; adding an initiator, stirring under the conditions of room temperature, inert gas protection and a rotation speed of 100 to 1000 rpm to obtain an in-situ gel polymer electrolyte. The advantages are: the initiator triggers the in-situ polymerization of 1,3-dioxolane, forms a gel polymer electrolyte in situ in the battery, improves the compatibility of the interface, and reduces the battery impedance; forms a stable interface film, improves the stability of the electrode interface, and improves the room temperature rate performance and low temperature performance of the battery.

The invention relates to an electric energy meter battery fault detection method and device, computer equipment, a computer readable storage medium and a computer program product. The method comprises the following steps: establishing communication connection with a to-be-detected electric energy meter, and reading operation state information and battery data of the to-be-detected electric energy meter through the communication connection; according to the operation state information and the battery data, determining a battery fault preliminary judgment result of the to-be-detected electric energy meter; under the condition that the battery fault preliminary judgment result is that the battery is suspected to be abnormal, acquiring battery impedance data of the to-be-detected electric energy meter through communication connection; and obtaining a battery fault detection result of the to-be-detected electric energy meter according to the battery impedance data and a pre-trained electric energy meter battery fault detection model. The method can improve the battery fault detection efficiency of the electric energy meter.

The invention discloses a working condition monitoring method for a sodium ion battery sodium precipitation behavior based on battery impedance analysis. The core principle of the method is based on the following points: when sodium precipitation occurs, sodium metal is deposited on the surface of hard carbon, so that the physical and chemical properties of the surface of the hard carbon can be changed; the conductivity of sodium metal is obviously different from that of a hard carbon material, so that the charge transfer resistance of hard carbon is obviously changed. In addition, the appearance of the sodium metal also causes the change of the electric double layer capacitance on the hard carbon surface; therefore, whether sodium metal begins to be separated out or not can be accurately judged by detecting the change of the charge transfer resistance and the electric double-layer capacitance on the hard carbon surface; according to the scheme, in-situ monitoring of sodium metal precipitation can be achieved under the condition that the battery structure is not damaged, the sodium metal precipitation situation of the sodium ion battery in the half-battery discharging process can be sensitively captured, and sodium metal deposition of the half battery, the full battery and the soft package battery under the actual operation condition can be monitored in real time.

The invention discloses a battery health state assessment method and device, electronic equipment and a storage medium, and belongs to the technical field of battery state assessment, and the method comprises the steps: determining a time constant corresponding to each peak value in a time domain distribution diagram of a sample battery impedance spectrum; determining a frequency point corresponding to the peak value according to the time constant, and obtaining dynamic impedance corresponding to the frequency point in the charging and discharging process of the sample battery; constructing a neural network model by taking the dynamic impedance of the battery as input and the residual capacity of the battery as output, and performing iterative training on the neural network model according to the dynamic impedance and the residual capacity of the sample battery to obtain a target neural network model; and performing health state evaluation on the to-be-tested battery based on the target neural network model. According to the method, the frequency point is determined through the time constant corresponding to the peak value of the time domain distribution diagram of the impedance spectrum, the health state of the battery is evaluated according to the dynamic impedance corresponding to the frequency point in the charging and discharging process, and accurate and efficient evaluation of the health state of the battery is achieved.

The invention provides a positive pole piece, a lithium battery and a device. The positive pole piece comprises a positive current collector as well as a bottom coating and a positive coating which are sequentially stacked on at least one side of the positive current collector, the bottom coating contains a first positive lithium supplement agent, the positive coating contains a positive active material and a second positive lithium supplement agent, the first coulombic efficiency of the first positive lithium supplement agent is less than 30%, and the second coulombic efficiency of the second positive lithium supplement agent is less than 30%. And the second positive electrode lithium supplement agent can be decomposed to generate gas at a voltage greater than the lithium removal potential thereof. The first positive electrode lithium supplement agent and the second positive electrode lithium supplement agent are simultaneously introduced into the positive electrode plate and are arranged in a layered manner, so that many problems caused by independent use of the first positive electrode lithium supplement agent and the second positive electrode lithium supplement agent can be reduced, the lithium supplement utilization rates of the positive electrode plate and the second positive electrode lithium supplement agent are improved, the battery impedance is not obviously increased, and the battery power performance is improved.

The invention belongs to the technical field of batteries, and particularly relates to a sodium ion battery monomer, a positive pole piece, a preparation method thereof and a related device. The sodium ion battery monomer comprises a positive pole piece, the positive pole piece comprises a positive active material and a solid electrolyte interface film at least combined on the surface of the positive active material, and the solid electrolyte interface film comprises one or more cations of Na < + >, Li < + >, K < + > and Ca < 2 + >. The solid electrolyte interface film combined on the surface of the positive electrode active material contains cations such as Na < + >, Li < + >, K < + > and Ca < 2 + >, and the cations can participate in electrochemical reaction of the sodium ion battery, so that reversible capacity is provided, capacity loss generated after the positive electrode active material is passivated is made up, and the cycle performance of the battery is improved. Meanwhile, the solid electrolyte interfacial film containing the cations is beneficial to reducing the impedance of the battery, so that the cycle performance of the battery is further improved.

To measure battery performance by a simple method.SOLUTION: A control unit 16 causes a damping vibration circuit 12 to generate a damping vibration current by controlling a switch SW. The control unit 16 acquires a damping vibration signal related to the time waveform of the damping vibration current from a signal detector 14 and obtains a real part of impedance of a battery 10. The control unit 16 acquires each sample value at a plurality of sample times obtained by operation of a calibration mode from the time waveform indicated by the damping vibration signal, and obtains the real part of impedance of the battery 10 on the basis of each sample value. The control unit 16 operating in the calibration mode causes the damping vibration circuit 12 to generate the damping vibration current by controlling the switch SW. The control unit 16 acquires a damping vibration signal for calibration related to the time waveform of the damping vibration current and obtains a plurality of positions on the time axis at which the time waveform indicated by the damping vibration signal for calibration becomes maximum, or a plurality of positions on the time axis at which the same becomes minimum, as the plurality of sample times.SELECTED DRAWING: Figure 1