Experimental investigation of the lithium-ion battery impedance characteristic at various conditions and aging states and its influence on the application

Temperature dependent ageing mechanisms in Lithium-ion batteries – A Post-Mortem study

Influence of the Discretization Methods on the Distribution of Relaxation Times Deconvolution: Implementing Radial Basis Functions with DRTtools

https://iopscience.iop.org/article/10.1149/2.026304jes/pdf

Electrochemical Impedance Spectroscopy Study of a Lithium/Sulfur Battery: Modeling and Analysis of Capacity Fading

A lumped-parameter electro-thermal model for cylindrical batteries

Studies on LiFePO4 as cathode material using impedance spectroscopy

Lithium iron phosphate is a promising candidate material for Li-Ion batteries. In this study, the rate determining processes are assessed in more detail in order to separate performance limiting factors. Electrochemical impedance spectroscopy (EIS) data of experimental LiFePO4/Lithium-cells are deconvoluted by the method of distribution of relaxation times (DRT), what necessitates a pre-processing of the capacitive branch. This results in a separation into cathode and anode polarization processes and in a proposition of a physically motivated equivalent circuit model. We identify three different polarization processes of the LiFePO4-cathode (i) solid state diffusion, (ii) charge transfer (cathode/electrolyte) and (iii) contact resistance (cathode/current collector). Our model is then applied to EIS data sets covering varied temperature (0° to 30°C) and state of charge (10% to 100%). Activation energy, polarization resistance and frequency range are determined separately for all cathode processes involved. Finally, the tape-casted LiFePO4–cathode sheet is modified in porosity, thickness and contact area between cathode/electrolyte and cathode/current collector by a calendering process. Charge transfer resistance and contact resistance respond readily in polarization and relaxation frequency.

https://iopscience.iop.org/article/10.1149/2.030207jes/pdf

Separation of Charge Transfer and Contact Resistance in LiFePO4-Cathodes by Impedance Modeling

Lithium iron phosphate is a promising cathode material for the use in lithium-ion batteries meeting the demands of good stability during cycling and safe operation due to reduced risk of thermal runaway. However, slow solid state diffusion and poor electrical conductivity reduce power capability. For further improvement, the identification of the rate determining processes is necessary. Electrochemical impedance spectroscopy (EIS) has proven to be a powerful tool for the characterization of electrochemical systems. In this contribution a deconvolution of the impedance with the distribution of relaxation times (DRT) is used to obtain a better resolution in frequency domain. Therewith, the cathodic and anodic polarization processes are identified and an impedance model for the cell is proposed. Introduction The demand for high energy density rechargeable batteries for electric and hybrid electrical vehicle systems has rised particular interest in lithium-ion batteries in recent times. Many kinds of material are in consideration as the cathode material to meet the requirements of a satisfying cathode performance (1). In 1997, Lithium iron phosphate (LiFePO4) was proposed by John B. Goodenough’s group for the first time (2). It has been investigated as a promising candidate for cathode material in lithium-ion batteries due to its high theoretical capacity (170 mAh/g) compared with other iron-based compounds (3), its good thermal stability leading to high safety (3;4), and its cycling stability (5). One major drawback of lithium iron phosphate is its poor conductivity (ionic and electronic), which generally causes capacity losses at higher charge–discharge currents (6;7). Recently, many studies on lithium iron phosphate have been published, mainly focused on the understanding and improvement of lithium-ion conduction in the active material (8;9;10). However, there are other loss processes which influence the performance of LiFePO4-cells (11). Their identification and physical interpretation according to literature is not consistent. EIS has proven to be a powerful tool for the characterization of electrochemical systems (3;11;12). In general, physio-chemical processes with different time constants can be distinguished in the EIS spectra. However, the identification of these processes remains ambiguous as they overlap in the frequency domain. ECS Transactions, 28 (30) 3-17 (2010) 10.1149/1.3505456 © The Electrochemical Society

Studies on LiFePO4 as Cathode Material in Li-Ion Batteries

Lithium iron phosphate is a promising cathode material for the use in lithium-ion batteries meeting the demands of good stability during cycling and safe operation due to reduced risk of thermal runaway. However, slow solid state diffusion and poor electrical conductivity reduce power capability. For further improvement, all rate determining electrode processes have to be quantified. Electrochemical impedance spectroscopy (EIS) has proven to be a powerful tool for the characterization of electrochemical systems. In recent publications (1,2), a physical interpretation for the impedance response of LiFePO4/Li-cells was given and an equivalent circuit model was proposed. In this contribution, the proposed equivalent circuit is used to quantify the predominant electrode processes depending on temperature (0°C…30°C), SoC (10% … 100%) and microstructure characteristics (porosity).

Evaluation of the Rate Determining Processes for LiFePO4 as Cathode Material in Lithium-Ion-Batteries

Lithium iron phosphate is a cathode candidate material for Li-ion-batteries, which provides (i) stability during cycling and (ii) reduced risk of thermal runaway. However, disadvantages as (i) slow solid state diffusion and (ii) poor electrical conductivity reduce power capability. Improvement requires identification of the rate determining process. Electrochemical impedance spectroscopy (EIS) has proven to be a powerful tool for the exploration of electrochemical systems. The resolution of electrochemical processes can be enhanced in the frequency domain by applying the DRT-method (distribution of relaxation times). The DRT-method was developed and demonstrated for high-temperature fuel cells [1, 2]. For the first time, the benefits will be presented for the exploration of Li-ion-batteries. Measurements in a wide frequency range (10 mHz to 1 MHz) have been conducted on experimental LiFePO4cells with metallic lithium as anode (half cell). The study covers a variation of temperature (0 to 40 °C) and state of charge (10 to 90 %).

http://ma.ecsdl.org/content/MA2010-01/3/144.full.pdf

Thorsten Chrobak

Papers

Studies on LiFePO4 as cathode material using impedance spectroscopy

Separation of Charge Transfer and Contact Resistance in LiFePO4-Cathodes by Impedance Modeling

Studies on LiFePO4 as Cathode Material in Li-Ion Batteries

Evaluation of the Rate Determining Processes for LiFePO4 as Cathode Material in Lithium-Ion-Batteries

Studies on LiFePO4 as Cathode Materials in Lithium-Ion-Batteries