Copper dissolution refers to the undesirable electrochemical reaction in lithium-ion batteries where copper from the anode current collector dissolves into the electrolyte, typically during over-discharge or low-voltage abuse conditions.
Prevention Strategies:
Robust BMS protection to avoid deep discharge
Safe SoC storage windows (e.g., >20%)
Anode coatings or alternative current collectors (e.g., carbon-coated copper)
Cell design with anti-overdischarge protection fuses or circuits
Coulomb (symbol: C, Chinese: coulomb) is the SI unit of electric charge, used to measure the amount of electric charge. In the field of batteries, Coulomb is an important unit for expressing the amount of charge charged and discharged by batteries: 1 Coulomb is equal to the amount of charge passed by 1 ampere in 1 second (1 C = 1 A × 1 s).
Coulomb counting is an algorithm commonly used to estimate the state of charge (SOC) of a battery. Its basic principle is to calculate the remaining battery power by integrating the changes in the battery’s charge and discharge current over time.
Current refers to the rate at which charge flows over time. It is an important parameter for measuring the speed of electron flow during the battery’s charge and discharge process. Its unit is ampere (A).
In the battery industry, “Cycle” refers to a complete charge and discharge process of the battery. Specifically, a cycle includes a charge (battery energy is input from the outside) and a discharge (battery energy is output to the outside). A cycle does not necessarily mean charging from 0% to 100% and then discharging to 0%, but refers to the total charge and discharge capacity reaching the nominal capacity of the battery.
The number of cycles is one of the important indicators for measuring battery life. After a battery has gone through multiple cycles, its capacity and performance will gradually decay, so “cycle life” is usually used to indicate the number of cycles a battery can complete before its capacity drops to a certain percentage (such as 80%) of its initial value.
Cyclic aging refers to the phenomenon that the performance of batteries gradually degrades during repeated charge and discharge (i.e. multiple cycles). As the battery goes through more and more cycles, its capacity, voltage stability and energy efficiency will decrease. This process
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Mechanical damage to electrode material structure
The electrolyte decomposition produces side reactions;
The SEI film (solid electrolyte interface) breaks and rebuilds repeatedly;
Lithium deposition or loss of active lithium.
Cylindrical cell refers to a battery cell structure with a cylindrical appearance. It is currently the most widely used battery form and is widely used in power tools, electric vehicles, energy storage systems, consumer electronics and other fields.
Advantages:
High degree of standardization : high automated production efficiency and good quality consistency
Good heat dissipation performance : large cylindrical convection surface, conducive to thermal management
Strong mechanical stability : better pressure resistance than soft pack batteries
Cost maturity : large-scale mass production system has been formed
Data analysis refers to a systematic approach to analyzing the performance of batteries during manufacturing, testing, operation or retirement.
Common analysis methods:
Descriptive statistics (mean, variance, box plots, etc.)
Trend analysis (such as capacity attenuation curves, resistance change trends)
Anomaly detection (determining the existence of over-temperature, over-voltage, and abnormal welding of terminals, etc.)
Regression modeling and prediction (predicting SOH or RUL)
Clustering and classification (identifying different usage patterns or fault types)
Machine learning/deep learning methods (for intelligent diagnosis and control optimization)
Data-driven models refer to predictive or discriminative models established based on a large amount of historical or real-time data, using statistical methods, machine learning, or artificial intelligence. These models can model battery behavior without the need for explicit physical mechanism expressions. In the battery industry, such models are widely used in performance prediction, health assessment, safety monitoring, and intelligent control.
Direct current (DC) is the flow of electric current in a circuit in a single direction.A form of electrical energy whose voltage remains constant or changes slowly. It is widely used in battery systems, electric vehicles, energy storage devices and electronics.
Roles in Batteries:
All batteries inherently output DC current
The direction of electron flow produced by the battery chemical reaction is fixed , so it naturally produces DC output
In the energy storage system, the inverter (DC-AC inverter) is responsible for converting direct current into alternating current to adapt to the grid.
DCR , or DC internal resistance , refers to the resistance value corresponding to the voltage loss caused by the internal materials, electrolyte, electrode interface, etc. of the battery under the action of constant DC current . It is one of the important electrical parameters to measure battery performance and health status.
Note:
DCR is closely related to temperature and state of charge (SoC), and standardized test conditions are required
Unlike AC internal resistance (ACR), which measures the impedance behavior of the battery under high-frequency signals, DCR is closer to the performance under actual workload.
The growth of dendrites refers to the phenomenon where metal ions (especially lithium, zinc, or sodium) deposit unevenly on the surface of the negative electrode during the battery charging process, forming metal structures similar to tree branches or needles. This process is particularly common in lithium metal batteries or overcharged lithium-ion batteries.
The causes of dendrite formation: overcharging (high rate), charging under low temperature conditions, surface defects or uneven distribution of activity on the negative electrode material, improper composition of the electrolyte or poor stability of the SEI film, overcharging or abnormal cycling strategies.
The depth of discharge (DoD) is the ratio of the used battery capacity to the rated total capacity, indicating how much energy the battery has discharged during a single discharge cycle. DoD is an important indicator for evaluating the battery’s usage status, cycle life, and degradation of life.
Digital Commissioning refers to the process of remote verification, testing, optimization, and configuration validation of the system before and after the delivery of battery systems or energy storage systems, utilizing digital models, sensor data, simulation platforms, and automation tools. This concept is the digital upgrade of the traditional ‘on-site debugging’ and is particularly suitable for large-scale battery energy storage systems (BESS), grid integration projects, and intelligent manufacturing.
Digital twin is a data-driven virtual model that maps the state and behavior of real-world systems in real time. It connects physical entities (such as batteries, battery systems, or energy storage power stations) with the digital world, creating a ‘digital copy’ that can simulate, monitor, predict, and optimize the entire lifecycle of its operation.
The discharge profile is a graphical or data set that describes the voltage, current, time, and temperature change behavior of a battery during the discharge process. It reflects the performance of the battery under specific working conditions and is a key indicator for evaluating the battery’s capacity, internal resistance, state of health (SOH), and thermal characteristics.
Discharging refers to the process in which the chemical energy stored in the battery is converted into electrical energy while the battery is providing electrical energy to the external circuit. This process is conducted through an external load, allowing electrons to flow from the negative pole to the positive pole, thereby driving the operation of the device.
Caution: Overdischarge (Overdischarge) can cause irreversible capacity loss, deposition of copper foil on the negative electrode, internal short circuits, and even thermal runaway; Uneven discharge will exacerbate the imbalance between cells, affecting the overall lifespan; High-rate discharge will accelerate heat accumulation, requiring a good heat dissipation system.
The driving range refers to the maximum distance an electric vehicle can travel continuously on a full charge, usually expressed in kilometers (km) or miles (mi). It is one of the core indicators for measuring the performance and energy efficiency of electric vehicles (EVs).
Battery Capacity (kWh) The larger the energy stored in the battery, the longer the potential driving range.
Energy Consumption Efficiency (Wh/km) The lower the energy required per kilometer, the longer the driving range.
Durability refers to the ability of batteries or energy storage systems to maintain performance and structural integrity during long-term operation, covering their performance stability, lifespan performance, and fault resistance after experiencing multiple charge-discharge cycles, environmental stresses, and load changes.
Factors affecting durability:
anode/cathode/electrolyte) Determines the stability of the reaction and the rate of formation of side reactions
Charging and discharging strategy (C-rate, DoD) High-frequency or deep charging and discharging accelerates aging
The Eastern Interconnection is one of the main power transmission grids in the United States (as well as parts of Canada), covering about 2/3 of the population in North America. It is one of the four major interconnection systems in the North American power system, which are physically connected to other interconnection systems (such as Western Interconnection, ERCOT, Quebec Interconnection) through a small number of direct current (DC) interconnection lines.
