We all know the feeling unboxing a new phone and enjoying the hours of battery life. New phones charge quickly, and discharge slowly. But eventually, the tides turn. After normal use, our batteries eventually begin to charge slowly and discharge quickly. Eventually, we carry pocket chargers or ask “do you have a charger” just to make it through a normal day.
This article will explain how battery degradation happens and why. It will provide information about what you can do to circumvent this inevitable decline in performance and introduce some technologies on the horizon that are poised to solve this problem.
The cornerstone of modern devices like phones, e-scooters, and electric cars lies in their battery systems. Some view this as planned obsolescence, especially in phones where non-removable batteries often lead consumers to upgrade to new devices rather than replace batteries. Similarly, for electric vehicles (EVs) and cars, the battery represents a significant portion of the overall cost, sometimes up to half. This phenomenon, known as battery degradation, poses challenges in understanding why it occurs, requiring a grasp of how lithium-ion batteries function.
Lithium Ion Battery
Lithium-ion batteries operate through the movement of positively charged ions between the positive (anode) and negative (cathode) electrodes, facilitated by an electrolyte. This process creates an electric potential, driving electrons through the device being powered. Importantly, this process is reversible, known as intercalation, where lithium ions move back and forth across the electrolyte bridge. Lithium’s atomic properties make it ideal for battery usage due to its light-weight nature and energy storage capabilities, dependent on the number of lithium ions that can fit into the anode and cathode spaces.
Battery degradation is a critical issue that affects the performance and lifespan of lithium-ion batteries used in various devices. To comprehend why degradation occurs, it’s essential to grasp the fundamental workings of these batteries.
All batteries consist of positive and negative electrodes separated by an electrolyte. During operation, positively charged ions move between the electrodes, creating an electric potential and driving electrons through the device being powered. This process, known as intercalation, is reversible for lithium-ion batteries, where lithium ions move back and forth across the electrolyte bridge, determining the battery’s energy storage capacity.
Lithium is particularly favored for batteries due to its lightweight nature and high energy-to-weight ratio. However, the number of lithium ions that can fit into the electrode spaces determines the battery’s capacity. For instance, while graphite anodes require six carbon atoms to store a single lithium ion, silicon can store more lithium ions, significantly increasing battery capacity. However, this comes with drawbacks, such as significant volume expansion during charging, which stresses the battery and damages the electrode material over repeated cycles.
Battery designers strive to maximize energy density without compromising longevity. However, degradation occurs due to various factors, including changes in electrode coatings and the formation of the solid electrolyte interface (SEI) layer during initial charging. While the SEI layer is initially protective, it can grow beyond its intended thin coating, permanently trapping lithium ions and hindering further reactions with the electrolyte.
Factors like charging rate, temperature, and cycling frequency also impact degradation rates. For example, lower temperatures decrease chemical activity, slowing down degradation but also reducing the battery’s ability to store energy. Nascent, a battery company, experienced significant capacity loss due to inadequate thermal management, highlighting the importance of temperature control in battery performance.
Cycling the battery through charge and discharge states contributes significantly to degradation, as it provides opportunities for the SEI layer to grow. Minimizing the number of cycles and maintaining ideal voltage levels can extend battery life. However, these measures must be balanced with the need for energy density and operational efficiency.
In essence, while lithium-ion batteries offer impressive energy storage capabilities, managing factors like electrode degradation and SEI layer formation is crucial to prolonging battery life and optimizing performance.
Charging
When charging a lithium-ion battery, the process occurs in several stages. Initially, the charging rate is relatively high, allowing for rapid replenishment of the battery’s charge. However, as the battery approaches higher states of charge, particularly around 80% and above, the rate of charge slows down significantly.
One reason for this slowdown is to prevent overheating and ensure battery safety. As the battery reaches higher charge levels, the internal resistance increases, making it more difficult for the charging current to penetrate the cell. This increased resistance generates heat, which can lead to thermal runaway and pose safety risks if not managed properly. To mitigate this risk, charging currents are typically reduced as the battery approaches full capacity to prevent excessive heat buildup.
Additionally, the charging process becomes more complex as the battery nears full capacity. At higher charge levels, the lithium ions must be inserted into increasingly packed electrode structures, which requires more precise control of the charging process to avoid damaging the battery. This precise control often involves slowing down the charging rate and carefully monitoring voltage and current levels to prevent overcharging or overvoltage conditions.
Furthermore, modern battery management systems (BMS) often incorporate algorithms that optimize charging patterns to enhance battery longevity and performance. These algorithms may prioritize slower charging rates at higher charge levels to minimize stress on the battery and prolong its lifespan.
Overall, while slower charging times at higher charge levels may seem inconvenient, they are essential for maintaining battery safety, longevity, and performance. By balancing the need for efficient charging with safety considerations and battery health, manufacturers can ensure that lithium-ion batteries remain reliable and durable power sources for various electronic devices.
Battery Packs – Charging in Series
Most larger battery systems are comprised of multiple smaller battery cells. Imagine thousands of AA batteries comprising an EV’s battery pack.
Charging batteries arranged in series or in parallel presents unique challenges compared to charging individual cells. In a series configuration, multiple battery cells are connected end-to-end, forming a chain where the voltage of each cell adds up cumulatively. While this setup allows for higher voltages and greater energy storage capacity, it also introduces complexities during the charging process.
One significant issue with charging batteries in series is that the charging current must pass through each cell sequentially. This means that the first cells in the series receive the charging current initially, while the subsequent cells receive their share only after the preceding cells reach their maximum charge capacity. As a result, the first cells tend to reach a state of maximum charge earlier than the cells further down the series, leading to an uneven distribution of energy within the battery pack.
This uneven charging process prolongs the overall charging time, as the entire battery pack cannot reach full capacity until each cell in the series has been adequately charged. Additionally, the cells at the beginning of the series may experience higher temperatures due to the concentrated charging current, increasing the risk of thermal runaway and potential battery degradation.
BMS systems monitor and control the charging process for each individual cell, ensuring that charging currents are distributed evenly across the series to prevent overcharging of certain cells. Additionally, temperature sensors may be integrated into the battery pack to monitor cell temperatures and implement thermal management strategies, such as reducing charging currents or activating cooling mechanisms, to maintain safe operating conditions.
Despite these precautions, charging batteries in series remains a complex process that requires careful management to optimize charging efficiency, prevent overcharging, and minimize the risk of battery degradation. By employing sophisticated BMS systems and implementing appropriate thermal management techniques, manufacturers can ensure the reliable and safe operation of series-configured battery packs in various applications.
Battery Packs – Charging in Parallel
Charging battery packs configured in parallel poses different challenges compared to series configurations, primarily related to balancing the charging currents and ensuring uniform charging across all cells.
In a parallel configuration, multiple battery cells are connected side by side, with the positive terminals connected together and the negative terminals connected together. This setup allows for increased capacity and higher discharge currents while maintaining the same voltage as a single cell. During charging, each cell within the parallel configuration receives the same charging current simultaneously.
One challenge with parallel charging is ensuring that each cell receives an equal share of the charging current to prevent overcharging or undercharging. If one cell receives a higher current than the others, it may reach full capacity before the rest, leading to an imbalance in the battery pack. This imbalance can reduce overall battery capacity, decrease efficiency, and potentially cause safety issues.
To address this challenge, sophisticated battery management systems (BMS) are employed in parallel-configured battery packs as well. These BMS systems monitor the voltage and state of charge of each individual cell and adjust the charging currents accordingly to ensure uniform charging. Additionally, active cell balancing circuits may be used to redistribute charge between cells during charging, helping to maintain balance and maximize battery performance.
While parallel charging does not inherently suffer from the same issues as series charging, ensuring proper balancing and uniform charging across all cells is essential for optimizing battery performance, longevity, and safety. By implementing advanced BMS systems and cell balancing techniques, manufacturers can effectively manage parallel-configured battery packs and maintain their reliability and efficiency in various applications.
Solid State Graphene Battery Systems
Solid-state battery packs and those incorporating graphene offer promising advancements in battery technology, with the potential to address many of the challenges associated with traditional lithium-ion batteries.
Solid-state batteries replace the liquid electrolyte found in conventional lithium-ion batteries with a solid electrolyte material. This solid-state design offers several advantages, including increased energy density, improved safety, and enhanced lifespan. Solid-state batteries are less prone to leakage, thermal runaway, and other safety issues associated with liquid electrolytes, making them potentially safer for use in various applications, including electric vehicles and consumer electronics.
Graphene, a two-dimensional carbon material with exceptional electrical conductivity and mechanical strength, has also attracted considerable attention for its potential applications in battery technology. Graphene-based batteries promise higher energy density, faster charging rates, and longer lifespan compared to traditional lithium-ion batteries. Graphene’s high surface area and conductivity enable efficient electron transport and ion diffusion, leading to improved battery performance.
Moreover, graphene-based batteries exhibit excellent thermal stability, reducing the risk of overheating and thermal runaway during charging and discharging cycles. This thermal stability is particularly crucial for electric vehicle applications, where safety is paramount.
However, despite these promising characteristics, solid-state batteries and graphene-based batteries still face several challenges that must be overcome before widespread commercialization. These challenges include manufacturing scalability, cost-effectiveness, and optimizing the performance of solid electrolytes and graphene materials in practical battery applications.
Nonetheless, ongoing research and development efforts continue to advance solid-state battery and graphene-based battery technologies, driving progress toward more efficient, safer, and longer-lasting energy storage solutions. As these technologies mature, they hold the potential to revolutionize various industries, from transportation to renewable energy storage, ushering in a new era of sustainable energy utilization.
