Degradation and Dependence Analysis of a Lithium-Ion Battery Pack in the Unbalanced State

Wang, Xiaohong; Li, Shixiang; Wang, Lizhi; Sun, Yaning; Wang, Zhongxing

doi:10.3390/en13225934

Cited by 9 publications

(3 citation statements)

References 35 publications

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“…It is of utmost importance to enable a uniform temperature distribution on both cell and pack level, as uneven temperature distribution leads to non-uniform and accelerated degradation [73]. An unbalanced system restricts the optimum performance and decreases the lifetime of a battery severely [74]. The magnitude of the overall heat generation of the battery under load dictates the size and design of the cooling system needed [75].…”

Section: Thermal Managementmentioning

confidence: 99%

Temperature, Ageing and Thermal Management of Lithium-Ion Batteries

2021

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Heat generation and therefore thermal transport plays a critical role in ensuring performance, ageing and safety for lithium-ion batteries (LIB). Increased battery temperature is the most important ageing accelerator. Understanding and managing temperature and ageing for batteries in operation is thus a multiscale challenge, ranging from the micro/nanoscale within the single material layers to large, integrated LIB packs. This paper includes an extended literature survey of experimental studies on commercial cells investigating the capacity and performance degradation of LIB. It compares the degradation behavior in terms of the influence of operating conditions for different chemistries and cell sizes. A simple thermal model for linking some of these parameters together is presented as well. While the temperature appears to have a large impact on ageing acceleration above room temperature during cycling for all studied cells, the effect of SOC and C rate appear to be rather cell dependent.Through the application of new simulations, it is shown that during cell testing, the actual cell temperature can deviate severely from the reported temperature depending on the thermal management during testing and C rate. It is shown, that the battery lifetime reduction at high C rates can be for large parts due to an increase in temperature especially for high energy cells and poor cooling during cycling studies. Measuring and reporting the actual battery (surface) temperature allow for a proper interpretation of results and transferring results from laboratory experiments to real applications.

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Section: Thermal Managementmentioning

confidence: 99%

Temperature, Ageing and Thermal Management of Lithium-Ion Batteries

2021

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“…While total current measurement is achievable using Hall sensors and current shunt resistors, measuring individual currents in parallel branches proves challenging due to space constraints and specific mounting requirements. The branch circuit electrical signals, especially current, are clearly the most effective in reflecting the operational state of a battery pack [2] . Therefore, precise parallel branches' current measurement plays a crucial role in elevating the level of battery management.…”

Section: Introductionmentioning

confidence: 99%

Research on the application of fiber-optical current sensor in power battery

Qiu,

Li,

Wang

et al. 2024

J. Phys.: Conf. Ser.

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Compared with the total current, the current in each parallel branch will help to achieve better battery management for new energy vehicles. However, today, accurate measurement of branch current is very difficult because the space between branches in the power battery pack is very limited. In this study, the fiber-optic current mini-sensor is used to meet this challenge. A saddle-sensing fiber structure has been designed to achieve surface measurement in response to the specific interconnection of circuitry in battery packs. A computer simulation was used to validate the feasibility, and experimental testing showed positive results. The specific experiments confirmed that the relative error between the saddle fiber-optic current sensor and conventional fiber-optic loop current sensor does not exceed 0.0119%. It meets the requirements of the automotive industry standards.

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“…However, the SoC of each cell in the module can vary during charge-discharge operations because of variations in manufacturing tolerance or an inhomogeneous operating temperature gradient. 16 Although a battery management system (BMS), which approximates the cells in the module as one equivalent cell, has been widely adopted to estimate either capacity fade or resistance increase to understand the degree of deterioration for the module, BMS cannot determine capacity and power fading at the cell level. BMS only approximates the capacity and power fading as an equivalent single value for the whole battery stack.…”

mentioning

confidence: 99%

Degradation Behavior of Graphite–Nickel Cobalt Aluminum Oxide Lithium Ion Cells with Series Connections Including an Overcharged Cell

Yokoshima¹,

Togasaki²

2022

J. Electrochem. Soc.

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Cycle life of series-connected lithium-ion battery (LIB) modules in the presence or absence of an overcharged cell is reported, and degradation behavior is characterized by electrochemical impedance spectroscopy (EIS) and differential voltage analysis (DVA). Three-stage capacity decay is solely observed in modules in the presence of an overcharged cell, which is exposed to a state of charge (SoC) of ≥105% during cycling. The module without overcharged cells or with an overcharged cell at an SoC of <103% exhibits capacity decay as a function of the square root of cycle numbers. EIS and DVA analyses confirmed that the overcharged cell with an SoC of ≥105% in the module deteriorates more harshly than the other cells and that deterioration occurs especially at the cathode. Cycle dependence of the charge/discharge cutoff voltage of LIBs revealed that the cell capacity of the overcharged cell shrinks with the end point on charge as a fulcrum, thereby decreasing the lower cutoff voltage as cycling progresses. Such a voltage change of an overcharged cell directly affects module capacity, leading to three-stage capacity decay. This study reveals a potential risk in series-connected cells using a wide SoC range and provides critical insights for safe operation without balance circuits.

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Degradation and Dependence Analysis of a Lithium-Ion Battery Pack in the Unbalanced State

Cited by 9 publications

References 35 publications

Temperature, Ageing and Thermal Management of Lithium-Ion Batteries

Temperature, Ageing and Thermal Management of Lithium-Ion Batteries

Research on the application of fiber-optical current sensor in power battery

Degradation Behavior of Graphite–Nickel Cobalt Aluminum Oxide Lithium Ion Cells with Series Connections Including an Overcharged Cell

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