The ultimate guide to battery technology
- Without a doubt, our modern world would not be possible without the humble battery.
- These seemingly inconspicuous energy storage devices have quietly revolutionized how we live, work, and play.
- But how much do you know about them?
Since the earliest discoveries of electricity, batteries have evolved into the backbone of modern technology, with cutting-edge innovations continuing to emerge today. Batteries have enabled the electrification of the world, revolutionizing industries and unlocking technological potential.
But what are they, and how do they work? How have they changed throughout history? What will they be like in the future? Let's take a look.
Introduction to battery technology
Simply put, the modern world as we know it would not be possible without batteries. From life-sustaining devices like pacemakers to the cellphone, batteries power the many portable electronic devices all around you.
They have also found applications in recent decades in electric vehicles and are touted as a "silver bullet" for the future of renewable energy storage systems. They provide a convenient and portable source of electrical energy, allowing us to stay connected, work efficiently, and could make a more sustainable future possible when recharged with renewable energy.
Their utility comes from their ability to store and provide electrical energy on demand. This allows us to use devices and equipment even in places without consistent power supply. In addition, batteries are crucial for off-grid usage as they make it possible to supply electricity in isolated areas. They are vital in disaster response as they provide alternative power sources for important facilities such as hospitals, communication systems, and emergency lighting.
Innovations in battery technology are driving progress in various industries. Experts constantly strive to improve battery performance by increasing energy density, reducing charging time, and extending overall lifespan. The progress made in this field has numerous advantages, such as improving electronic devices for customers, facilitating electric automobiles, and incorporating renewable energy sources into the power network.
Before the invention of "true" batteries in the mid-18th century, experimenters used "Leyden jars" to store electrical charge. These jars were an early version of capacitors, which stored their charge physically and released it all at once, unlike electrochemical cells. To increase the strength of the charge, experimenters connected many of the jars together.
One such experimenter was Benjamin Franklin, an inventor from colonial America who may have coined the term "electrical battery" to describe his devices—a play on the military term for weapons functioning together.
However, it would take a few more years before real battery technology would begin to coalesce. In the late 18th century, Luigi Galvani and Alessandro Volta conducted experiments with "Voltaic Piles," which are generally considered the first recognized battery. These were made by alternating layers of zinc and copper discs with layers of brine-soaked cardboard, producing a continuous flow of electricity. Volta's invention paved the way for the development of batteries that could store and deliver electrical energy.
During the early 1800s, John Frederic Daniell created an innovative battery called the "Daniell cell." This battery used separate electrolyte solutions with copper and zinc electrodes, significantly reducing internal resistance, improving stability, and increasing efficiency. It proved a reliable power source for telegraph networks, making long-distance communication possible.
In 1859, Gaston Planté created a groundbreaking invention in the history of batteries - the now ubiquitous lead-acid battery. The first rechargeable battery in the world, this utilized lead and lead dioxide electrodes that were submerged in a sulfuric acid electrolyte. This invention was revolutionary in energy storage, opening doors for the extensive use of batteries in different fields. These included early electric vehicles, as well as stationary power systems.
Between the late 1800s and early 1900s, there were great strides made in the development of battery technology. Thomas Edison's nickel-iron battery proved to be more durable and longer-lasting than lead-acid batteries. Despite this, it could not keep up with the emergence of internal combustion engines in the automobile industry, resulting in limited usage.
In the middle of the 20th century, there was a growing need for compact and dependable batteries to power emerging electronic devices. Lewis Urry developed the alkaline battery to meet this demand, which the Eveready Battery Company later introduced as the widely used alkaline-manganese dioxide battery.
During the latter half of the 20th century, lithium-based batteries introduced a major change in portable power technology. Sony's commercializing of lithium-ion batteries in the early-1990s provided a greater energy density, lighter weight, and longer lifespan than previous battery models. These technological improvements led to the widespread use of portable electronics, including smartphones, laptops, and digital cameras.
Recently, there has been a renewed focus on researching and developing battery technology. This is mainly because of the growing need for sustainable forms of energy storage for electric vehicles and other renewable energy sources. Lithium-ion batteries have seen significant advancements in their manufacturing processes and in the use of new materials, leading to higher energy densities and faster charging capabilities.
In addition, there is ongoing research into alternative battery chemistries, such as solid-state and lithium-sulfur batteries, which offer promising potential for further advancements in the future. These technologies seek to overcome existing limitations in current battery systems, including issues related to energy density, safety, and environmental impact. But, more on that later.
Major types of batteries
As we are sure you are more than aware, battery technology comes in various forms. However, it is important to first distinguish between the two main umbrella categories of batteries. These are what are termed "primary" and "secondary" batteries.
What are primary batteries?
A primary battery is a simple and convenient power source for portable devices like lights, cameras, watches, toys, and radios. However, they cannot be recharged and must be discarded after use. In short, these batteries can only discharge once "powered up" and cannot be recharged.
Primary batteries are cost-effective, lightweight, and require little maintenance. They are mainly used in household appliances and typically consist of a single cylindrical cell, although they can be made in various shapes and sizes. These include older batteries like alkaline, zinc-carbon, and mercury-containing batteries.
What are secondary batteries?
A secondary battery, also known as a rechargeable battery, can be recharged electrically after discharge. By passing a current through the cells in the opposite direction of their discharge, the electrochemical cells can be returned to their original status.
Secondary batteries can be used in two ways:
- The first is as energy storage devices. In this application, they are electrically connected to a main energy source, charged by it, and then supply energy when required. Examples include Hybrid Electric Vehicles (HEV) and Uninterrupted Power Supplies (UPS). These are a vital component of the move to renewable energy.
- The other category of secondary battery applications includes using the battery as a primary battery until it is almost fully discharged. At this point, it can be recharged with an appropriate mechanism instead of discarded. Modern portable electronics such as mobile phones, laptops, and electric vehicles are examples of such applications.
Secondary batteries have lower energy density but offer high power density, flat discharge curves, high discharge rates, and good low-temperature performance.
There are many types of secondary batteries, but the five most common include, but are not limited to:
- Lead–acid batteries
- Nickel–cadmium batteries
- Nickel–metal hydride batteries
- Lithium-ion batteries
- Sodium-ion batteries
We'll discuss each of these in more detail in the next section.
1. Lithium-ion batteries: the dominant player in portable electronics and electric vehicles
Lithium batteries are widely used due to their high energy density, storing more energy than alkaline batteries and other cell types. Like most batteries, they are lightweight and ideal for heavy usage. They also tend to perform well in extremes of temperature and have a shelf life of around a decade. However, they are potentially highly flammable and require specialist disposal at life's end.
Lithium batteries have higher milliampere-hour (mAh) ratings than other non-rechargeable batteries and are available in AA, AAA, and 9V sizes. With a range of 2,700-3,400+ mAh, a single AA lithium battery can last a long time, even with heavy use. Other types, specifically lithium-ion (Li-ion), are also rechargeable.
Li-ion batteries have an extremely high energy density and do not require regular maintenance. However, they are unavailable in consumer sizes due to the risk of explosion if charged with a regular device. Instead, a specific lithium-ion charge device is necessary.
2. Lead-acid batteries: widely used in automotive and backup power applications
Lead-acid batteries are the most widely used rechargeable batteries, a successful product for over a century. They come in various configurations ranging from small sealed cells with a capacity of 1 Ah to large cells with a capacity of 12,000 Ah.
Lead-acid batteries have multiple applications, including as starting, light, and ignition (SLI) batteries for the automotive industry, energy storage, emergency power, electric and hybrid vehicles, communication systems, and emergency lighting systems.
The wide range of applications for lead-acid batteries is due to their wide voltage ranges, various shapes and sizes, low cost, and easy maintenance.
Lead-acid batteries are the least expensive option compared to other secondary battery technologies and provide excellent performance. The electrical efficiency of lead-acid batteries is typically between 75% and 80%, making them suitable backup for for energy storage (Uninterrupted Power Supplies - UPS) and electric vehicles.
3. Nickel-cadmium batteries: known for their reliability and durability
NiCd batteries, nickel-cadmium, are commonly used in toys, digital cameras, flashlights, and other high-drain devices like power drills. They are available in standard AA, AAA, C, and 9V sizes. Unlike alkaline batteries, NiCd batteries maintain a consistent voltage until fully depleted.
They tend to be inexpensive to buy, discharge quickly and can deliver at full capacity. On the downside, they do not tend to store well over a long period and require full discharge before recharging. They also contain toxic metals and require specialist disposal.
Although NiCd batteries have a low voltage of 1.2V per cell, they compensate with powerful delivery.
4. Nickel-metal hydride batteries (NiMH): hybrid vehicles and portable devices
Although NiMH batteries have a high energy density, they may not be the best choice for applications like smoke alarms, TV remotes, or clocks because they can only be recharged about 500 times before their cycle life is reduced.
NiMH tends to have a relatively high energy-to-volume ratio, is generally considered relatively environmentally friendly, and can deliver at full capacity. They tend to ship discharged, so they require a full charge before first use, and overcharging can reduce the battery capacity.
These devices use minimal energy, and NiMH batteries are best when used within 30 to 60 days. Like NiCd batteries, NiMH batteries maintain full capacity until almost completely discharged.
5. Sodium-ion batteries: an emerging technology
A sodium-ion battery is similar to a lithium-ion battery but uses sodium ions (Na+) as charge carriers instead of lithium ions (Li+). The working principles and cell construction are virtually identical, but sodium compounds are used instead of lithium.
Sodium-ion batteries are emerging as a potential alternative to lithium-ion technology due to their lower cost, higher availability, and reduced environmental impact. They use cheap and abundant sodium and aluminum instead of lithium and copper.
Main battery components
Batteries consist of an anode, cathode, and electrolyte, with a separator to prevent contact. They are typically also encased for storage and safety. Both the anode and cathode are types of electrodes. Electrodes are conductors through which electricity enters or leaves a component in a circuit.
Electrons flow out of the anode in a circuit when conventional current flows into it. In a battery, an anode and electrolyte reaction builds up electrons that want to move to the cathode but can't pass through the electrolyte or separator until the circuit is completed.
Electrons flow into the cathode through an external circuit in a device. In batteries, the cathode undergoes a chemical reaction using electrons produced in the anode.
The electrolyte is a substance that transports ions between the anode and cathode while inhibiting electron flow so they easily pass through the external circuit instead.
The electrolyte is essential to the functioning of a battery. As electrons can't pass through it, they travel through electrical conductors in a circuit that connects the anode to the cathode.
Separators prevent the anode and cathode from touching and causing a short circuit. They can be made from cotton, nylon, polyester, cardboard, or synthetic polymer films. Ions in the electrolyte can have positive or negative charges and different sizes. Specific separators can selectively allow ion passage.
Most batteries require a casing to contain their chemical components. Casings, also known as "housings" or "shells," are mechanical structures designed to hold the battery's internal components. They can be made of plastic, steel, soft polymer laminate pouches, and other materials. Some batteries use a conducting steel casing that is electrically connected to one of the electrodes, such as the cathode of a common AA alkaline cell.
Main principles of operation
As we've seen, the principal parts of a battery are the anode (positive electrode), cathode (negative electrode), and electrolyte. But how do these bits work together to make a battery work?
1. Electrochemical reactions: how batteries generate and store energy
The operation of a battery is based on redox reactions, short for reduction-oxidation reactions. These are chemical reactions involving a transfer of electrons from one molecule (or atom) to another.
In the context of a battery:
- Anode (discharging): At the anode, oxidation occurs where electrons are released. For example, in a classic zinc-carbon battery, zinc metal at the anode is oxidized to zinc ions.
- Cathode (discharging): These electrons then flow to the cathode through an external circuit, providing electrical energy. At the cathode, a reduction process occurs where positive ions gain electrons. In the same zinc-carbon battery, the incoming electrons reduce manganese dioxide at the cathode.
The electrolyte in the battery allows ions to move between the electrodes while preventing direct electron flow between the electrodes inside the battery. This movement of ions maintains charge neutrality within the battery. The battery then generates energy by converting chemical energy into electrical energy through electrochemical reactions.
2. Charging and discharging processes: understanding the flow of electrons and ions
The discharging process is explained above, i.e., converting stored chemical energy into electrical energy. When the battery is connected to a device (like a flashlight or a smartphone), the electrons flow from the anode to the cathode through the device, powering it.
The process of charging a battery is essentially the reverse of discharging. The flow of electrons is reversed by providing electrical energy to the battery, driving the reduction reaction at the anode and oxidation at the cathode. This replenishes the chemical potential in the battery, storing energy. Notably, this process applies to rechargeable batteries like lead-acid and lithium-ion batteries.
3. Capacity, voltage, and energy density: key performance metrics of batteries
Capacity measures the total charge stored in the battery, often expressed in milliampere-hours (mAh) or ampere-hours (Ah). The capacity of a battery gives us an idea of how long a battery can provide a certain current. For example, a battery with a capacity of 2000 mAh should be able to provide a current of 2000 mA for one hour.
Voltage represents the electric potential difference between the battery's two electrodes, measured in volts (V). The voltage is essentially the 'pressure' driving the flow of electrons from the anode to the cathode. The nominal voltage of a battery cell is determined by its chemistry. For example, a lithium-ion cell has a nominal voltage of about 3.6V.
Energy density measures the energy a battery can store per unit volume, often expressed in watt-hours per liter (Wh/L). Energy density is a key indicator of how much energy a battery can store for its size or weight. Batteries with high energy densities are desirable for portable devices such as electric vehicles and smartphones, as they can store more energy in less space.
In summary, batteries operate based on redox electrochemical reactions that convert chemical energy into electrical energy. The charging process stores energy by reversing these reactions, while discharging provides energy.
Main performance factors
Regarding batteries, several main performance factors need to be considered. Let's take a look at each of these in order.
The cycle life of a battery is the number of charge-discharge cycles before its capacity falls to a specified percentage of the initial rated capacity (often 80%). Cycle life defines battery lifespan, influenced by depth of discharge (DoD) - how much of the battery's capacity is used before recharging. Batteries have longer cycle life when DoD is low.
Energy efficiency in batteries refers to the amount of energy retrieved from a battery relative to the amount of energy put into it during charging. Inefficiencies can be caused by internal resistance, leading to energy loss in heat during charging and discharging. Chemical processes inside the battery can also contribute to energy loss, which may not be 100% reversible.
When a battery is not in use, it naturally loses its charge, a process known as self-discharge. High temperatures can worsen this rate. Different batteries have different self-discharge rates, with lithium-ion batteries having lower rates than nickel-based batteries.
Temperature can have a significant impact on battery performance and safety. Chemical reactions within the battery may slow down at low temperatures, reducing capacity and power output. Conversely, high temperatures can speed up these reactions, temporarily enhancing performance but also leading to accelerated aging, increased self-discharge, and in severe cases, thermal runaway and safety risks.
Aging and degradation
With use, batteries degrade and lose capacity due to physical and chemical changes such as solid electrolyte interphase (SEI) layer formation, electrolyte decomposition, and more. These factors are also influenced by conditions like temperature and charging rates, limiting their lifespan.
Optimizing battery design and operation is critical for enhancing performance and lifespan. Scientists and engineers continually research new materials, designs, management systems, and charging strategies.
Batteries have various applications, from consumer electronics like smartphones and laptops to electric vehicles, grid energy storage systems, aerospace and defense equipment, and critical medical devices. These applications each have unique requirements, necessitating different types of batteries and continuous technological advancements.
Let's look at some of the most common applications in turn.
Consumer electronics like smartphones, laptops, and wearables rely on batteries to function. Lithium-ion batteries are widely utilized due to their high energy density and rechargability, allowing for integrating features like mobile internet, high-definition screens, and sophisticated computing. These attributes have become essential for modern-day technologies and have transformed the way we interact with these devices.
Electric vehicles (EVs)
Batteries are crucial for sustainable transportation, powering everything from electric cars to buses and trucks. High energy and power densities are necessary for long driving ranges, fast charging, and acceleration. Therefore, EV battery development focuses on cost reduction and safety enhancement while improving these key features.
Renewable energy storage (RES)
As the usage of renewable energy sources like wind and solar continues to rise in the energy mix, there is an increasing demand for energy storage solutions to balance the supply and demand on the grid. Batteries can store excess power produced during periods of high renewable generation, such as sunny or windy periods, and then provide that power to the grid during periods of high demand or when renewable generation is low, like at night or during calm weather. Grid energy storage systems, ranging from small residential-scale systems to large utility-scale battery installations, are used for this purpose.
Aerospace and defense
In the aerospace industry, batteries are crucial in starting aircraft engines and powering onboard electrical systems. These batteries are also used in space applications such as satellites and rovers, where they store energy generated by solar panels. In addition, they are used in defense applications to power military equipment and vehicles. Due to the nature of these applications, batteries need to be reliable, safe, and capable of operating in extreme conditions.
Batteries are essential for operating various medical devices, including portable devices like hearing aids and insulin pumps, and larger equipment like defibrillators. Additionally, batteries are used in implantable devices such as pacemakers and neurostimulators, which require very high reliability and longevity. In these applications, battery performance can directly impact patient health and safety.
Applications require different batteries based on energy density, power, safety, reliability, cost, and lifetime. Better batteries can catalyze advancements in all fields.
Advancements in technology
As the reliance on batteries continues to grow, their performance, sustainability, and the exploration of new technologies will remain at the forefront of research and development. So, what kind of promising battery technologies are in the pipeline?
Solid-state batteries represent a promising evolution in battery technology. Unlike traditional liquid or gel electrolytes, these use a solid electrolyte, ceramic, glass, or solid polymer. This change potentially leads to several benefits, including higher energy density (enabling longer range for electric vehicles or longer life for electronics) and improved safety, as the solid electrolytes are generally more stable and less likely to lead to thermal runaway.
Despite these benefits, challenges remain, including manufacturing complexities and ensuring long cycle life. However, numerous companies and research institutions are working to overcome these hurdles and commercialize solid-state batteries.
Flow batteries offer a unique solution for large-scale, long-duration energy storage. These store chemical energy in external tanks, converted to electricity in electrochemical cells that can be independently scaled. This characteristic separates the energy and power capacities, allowing for flexible design based on the application needs. Flow batteries typically have lower energy densities than lithium-ion batteries. However, their potential for long operational lifetimes with minimal capacity loss and their ability to discharge power over extended periods makes them attractive for grid storage applications.
While lithium-ion batteries currently dominate the rechargeable battery market, there is considerable research into alternative materials and chemistries to overcome their limitations and meet the growing demand for energy storage. These technologies include sodium-ion, magnesium-ion, zinc-ion, and lithium-sulfur batteries.
Each alternative has potential advantages, such as lower cost, higher safety, or increased energy density, but it also faces challenges. Continued research and development are essential to bring these promising technologies to market.
Battery recycling and sustainability
As the demand for batteries grows, so does the need for sustainable production and end-of-life management practices. Battery recycling can help to recover valuable materials, reducing the environmental impact of mining the materials needed to produce the batteries, and promote a more sustainable and circular economy.
However, current recycling rates are low, especially for lithium-ion batteries. To address this, advancements are being made in recycling technologies, and regulations are being implemented to promote battery collection. Moreover, research is also being conducted into the design of more sustainable batteries, such as those using abundant, non-toxic, and easily recyclable materials.
Challenges and future outlook
The field of battery technology is rapidly evolving due to consumer demand, environmental needs, and technological advancements. Improvements in battery technology are essential for achieving net zero, from improving everyday electronic devices' efficiency to driving the shift towards electric mobility and renewable energy.
These advancements address critical aspects such as cost reduction, safety, performance enhancement, and integration with smart grids and IoT devices, which are pivotal in global energy transition and decarbonization efforts. Let's examine some of the most critical factors influencing future battery research and development.
Battery cost and manufacturing scalability
Due to the increasing demand in the EV sector, there has been a significant focus on reducing battery costs and increasing manufacturing scalability. Major advances have been made in improving production efficiency and developing more cost-effective and abundant materials.
Economies of scale have also played a role in cost reduction. For instance, the cost of lithium-ion batteries has dropped substantially over the last decade due to improvements in production processes and increased demand.
Safety concerns and mitigation strategies
Battery safety is a significant concern, especially in electric vehicles (EVs) and energy storage. Researchers are developing various strategies to enhance safety, such as the use of more stable electrode materials, solid-state electrolytes, advanced Battery Management Systems (BMS), and thermal management systems. Solid-state batteries are a promising technology with potentially improved safety characteristics compared to traditional lithium-ion batteries.
Enhanced battery performance
Numerous research and development efforts are enhancing battery performance through new materials (such as lithium-rich cathodes), advanced cell designs (like Tesla's 4680 cells), and alternative batteries (like solid-state batteries, lithium-sulfur batteries, sodium-ion, magnesium-ion, etc.). Research is also ongoing in developing technologies like metal-air and flow batteries.
One promising area of battery research is the combination of robotics and artificial intelligence to rapidly prototype new chemistries and technologies. This could prove to be very fruitful in the future.
Integration of batteries into smart grids and the Internet of Things (IoT)
Advancements in small-scale batteries and energy harvesting techniques enable a new generation of connected IoT devices. Additionally, the development of advanced battery management systems allows for better integration and battery management in these systems, contributing to the transition to renewable energy sources and improving grid stability.
Implications of battery technology on energy transition and decarbonization efforts
As we've seen above, advancements in battery technology are crucial for the global transition to sustainable energy and efforts toward decarbonization. They support the shift to electric mobility and renewable energy, both critical components of a low-carbon economy.
Battery cost, performance, and safety improvements make electric vehicles more competitive with traditional vehicles, accelerating the transition to sustainable transportation. Likewise, progress in grid-scale batteries allows for greater penetration of variable renewable energy sources like wind and solar.
And that is your lot for today.
Battery technology forms the backbone of many pivotal shifts in modern life, from personal electronics to electric vehicles, renewable energy, and more. But the technology is far from done yet.
As we have seen, it constantly evolves, pushing the boundaries of what's possible. As we move towards a sustainable future, progress in this critical domain will continue to spark transformative changes, and future developments will likely be as alien to us today as the humble AA battery would be to our ancestors.