Wang Chaoyang: Battery technology scientist, member of the National Academy of Inventors, and chair professor at Pennsylvania State University.
Hello everyone! I'm Wang Chaoyang from Pennsylvania State University, and I'd like to share my thoughts on the future of batteries and energy storage.
A battery is a device that stores chemical energy. When in use, it directly converts the energy into electrical energy, and when recharged, it converts the electrical energy back into chemical energy for storage. The 2019 Nobel Prize in Chemistry was awarded to three scientists from the United States and Japan for their scientific contributions to lithium-ion batteries.
As we all know, batteries are closely related to our lives. They are ubiquitous, from 3C digital products to electric vehicles and aerospace. Moreover, battery technology often determines the rise of new industries. For example, without lithium batteries, there would be no smartphones, let alone e-commerce and 5G communication, and there would be no revolution in new energy vehicles.
Humanity is currently facing an increasingly severe climate change crisis, making energy transition imperative. Vigorously developing renewable energy and achieving carbon peaking and carbon neutrality is a shared responsibility of the entire human society. Renewable energy sources such as solar and wind power are intermittent energy sources, and their value only lies in energy storage. Therefore, energy storage technology is a key core technology for achieving dual-carbon goals and an energy revolution, and it has significant strategic importance.
The vast and profound impact of battery energy storage applications also means that it faces enormous challenges in multiple dimensions. It requires abundant and inexpensive raw materials, extremely high safety to protect people's lives and property, high energy density, high power, fast charging, and long lifespan. Furthermore, regardless of hot or cold regions, batteries must maintain good performance, lifespan, and safety across the entire temperature range.
For nearly 100 years, improvements in battery technology have primarily stemmed from material innovation. The mainstream batteries we are familiar with have evolved from lead-acid batteries to nickel-metal hydride batteries, and then to today's lithium-ion batteries. Lead-acid batteries are most commonly found in electric bicycles or as starter batteries in gasoline-powered vehicles. A well-known example of nickel-metal hydride batteries is the Toyota Prius hybrid. Of course, lithium-ion batteries are now ubiquitous, but even the latest lithium-ion battery technology has been developing for 30 years. In today's rapidly evolving technological landscape, we often feel that battery technology is lagging behind, developing too slowly to meet our rapidly evolving application scenarios, and even failing to fulfill some of people's small desires, such as a phone that only needs charging once a week, or an electric car that never spontaneously combusts.
To address these questions and accelerate the development of battery technology, scientists have been asking: Besides materials innovation, is it possible to overturn the battery structure that has remained unchanged for over 200 years? Is there a better working environment that allows battery materials to unleash their greater potential and propel battery technology forward by leaps and bounds?
Before answering this fundamental scientific question, let's look at the battery structure that has remained unchanged for over 200 years. It consists of three materials: a negative electrode material, a positive electrode material, and an electrolyte separating them. This structure naturally creates two interfaces: one between the positive electrode material and the electrolyte, and the other between the negative electrode material and the electrolyte. The potential difference between these two interfaces gives the battery voltage. For lithium batteries, this voltage is approximately 4 volts. Clearly, the reaction interface within the battery is always present and constantly functioning, regardless of whether we use the battery or not. For example, if we park an electric car in a garage and turn off the car, the battery is not in use, but we can still measure its maximum voltage. This demonstrates that the reaction interface within the battery still exists and is actively working. This ever-present reaction interface is precisely the root cause of battery safety hazards and aging.
Imagine if a short-circuited conductor accidentally existed between these two interfaces. Under voltage, there would be a huge short-circuit current that could ignite the battery. Simple energy balance calculations show that if an internal short circuit caused the battery to release 100% of its charge, the battery temperature would rise to 1500 degrees Celsius—a truly terrifying consequence.
Let's look at another example to fully appreciate the drawbacks of this perpetually existing reaction interface. In winter, say at -30 degrees Celsius, lithium batteries are extremely sensitive to cold, losing 9 to 10 times their power. This is why we often hear about electric vehicles breaking down in winter. Worse still, batteries cannot be charged in cold weather, meaning we cannot recover the braking energy. This braking energy can account for 20-25% of the driving range, which is a considerable amount of energy. This creates a very awkward situation. On the one hand, automakers want drivers to avoid using the heater in winter, saving electricity by wearing thick coats. On the other hand, the battery cannot recover the enormous energy generated during braking; instead, it is wasted on the brake pads. This is a very imperfect product.
Our electrochemists and battery engineers have come up with many material solutions, such as adding a large amount of highly volatile and flammable linear carbonate to the electrolyte. This can greatly reduce the freezing temperature of the electrolyte and indeed improve low-temperature performance. However, it has also given lithium battery electrolytes a bad reputation for being flammable. We often hear in the media that battery electrolytes are flammable. This is the side effect of solving the low-temperature problem.
Alternatively, high-surface-area electrode materials can be used to increase activity, or high-energy electrode materials can be used. For example, ternary materials perform better than lithium iron phosphate in winter. In this way, we can construct such a battery using highly active materials, which can indeed solve the winter problem. However, a battery composed of highly active materials will not be able to resist thermal runaway in the hot summer. This is because we have made the electrolyte highly volatile and flammable and made the electrode materials thermally unstable. In summer, the battery is prone to fire or even explosion, causing huge losses. A recent vehicle recall with economic losses of 1.8 billion US dollars is a good warning.
So, regarding the safety of the battery cells, our engineers said there are solutions. These flammable and explosive cells can be encapsulated in containers with strong copper and iron walls, reinforced with firewalls, and covered with fire extinguishing materials. They might even install a water-based fire suppression system. This would ensure the safety of the battery system. We collectively call these measures a management system. However, all these management measures do not add energy but rather increase the weight, volume, and cost of the battery, immediately leading to a decrease in the overall energy density of the battery system and an increase in unit cost. Thus, while we solved a low-temperature problem, two new problems arose: decreased energy density and increased cost.
Electrochemists and battery engineers make painful choices about compromises every day. The fundamental reason is that the reaction interface within a battery is always present, and battery materials themselves cannot simultaneously satisfy high activity at low temperatures and stability at high temperatures. In other words, making a material highly active at low temperatures and stable at high temperatures seems like an almost unsolvable problem. So, an interesting idea arises regarding this problem: Is there a battery where we can partially shut down the reaction interface when not in use to improve safety, and then increase and intensify the interface when in use to deliver the high power required for operation?
For over a decade, my team has been searching for and exploring batteries with adjustable interfaces. We've indeed found a thermal regulation method: by using instantaneous thermal stimulation—consuming approximately 1% to 3% of the battery's capacity in 10-30 seconds—we can amplify and intensify the electrochemical interface. With this quick and low-energy thermal stimulation method, we can manufacture batteries using the most stable and safest materials. When not in use, the chemical interface within the battery remains at a minimum, ensuring absolute safety and a minimal aging rate. During operation, thermal stimulation can instantly amplify and intensify the reaction interface to supply high-power fast charging capabilities, maintaining excellent performance even in low-temperature environments. After the battery has finished operating, natural cooling can lower the battery temperature to below 40 degrees Celsius within 5 minutes, returning the battery to its original, safe, stable, or rather, low-temperature state.
So what is the range of thermal regulation? Let's look at some experimental data. The vertical axis of the graph uses measurable battery internal resistance to inversely characterize battery activity; internal resistance and activity are inversely proportional. We see that thermal regulation can reduce the battery's internal resistance from 1000 ohms square centimeters to 15 ohms square centimeters, meaning it increases the battery's activity by 60 times. This indicates that the range of thermal regulation can be adjusted within 60 times. Even more excitingly, the graph shows that experiments have proven our thermal regulation mechanism is applicable to all chemical and material systems, whether lithium-ion batteries, metal batteries, or all-solid-state batteries. We can achieve a 60-fold adjustment range. Therefore, we now have a fast, low-energy-consumption method for adjusting the interface with a large range, allowing us to invent and create new types of batteries.
To address the low-temperature challenge mentioned earlier, we invented the all-weather battery. This is achieved without altering the hazardous nature of the battery materials—that is, without increasing the flammability of the electrolyte or changing the thermal stability of the electrode materials. Instead, we implant a 10-micrometer-thick nickel foil inside the battery as a heating element. This thickness is only 1/10 the thickness of a human hair. Therefore, it adds almost no increase to the battery's size and weight.
With a heating element and utilizing the battery's own energy, plus a switch, we can freely control the battery's activity. Even a battery frozen solid at -30 degrees Celsius can be self-heated back to above zero degrees Celsius and operate normally in just 30 seconds. Therefore, the advantages of this all-weather battery are:
1. Deliver high power quickly within 30 seconds
2. It can be self-heating and does not require other energy sources.
Third, and most importantly, it does not compromise battery safety; it does not alter the activity or safety of the materials, thus achieving the goal of ensuring the battery functions normally at extremely low temperatures.
From scientific discovery in the laboratory to product commercialization is a difficult process. I would like to thank our partners and participating companies. They spent three years, from 2018 to 2020, conducting field vehicle tests in Hailar, Northeast China, to fully verify the functionality, performance and lifespan of the all-weather battery, providing a strong guarantee for the deployment of the all-weather battery at next year's Winter Olympics.
The principle of thermal regulation has enabled us to invent a 10-minute fast-charging battery. The scientific requirement for fast charging is that the battery has high enough activity and that lithium ions are transferred quickly enough between the two electrodes. Our thermal regulation mechanism allows the battery to achieve these things. So in the future, when electric vehicles arrive at a fast-charging station, we can give the battery a 30-second thermal stimulus and then charge it with a large current within 10 minutes.
The best we can currently achieve is 200Wh/kg of energy in 10 minutes of charging, which can then be charged thousands of times without damage. The application and promotion of 10-minute fast-charging batteries will be a significant milestone for electric vehicles, as it provides a fast and convenient way to replenish energy, which will inevitably trigger revolutionary changes in electric vehicles and many application scenarios. For example, where electric vehicles previously required 80 kWh of electricity to eliminate range anxiety, this can now be reduced to 40 kWh. Although the driving range is only 300 kilometers, with fast charging anytime and anywhere, 10 minutes can provide another 300 kilometers of range, eliminating range anxiety. In doing so, we reduce the cost of onboard batteries by half and save 50% on raw material consumption. In other words, the battery from one vehicle can be used in two vehicles, truly putting the philosophy of "less is more" into practice.
Fast-charging battery technology is also the most important prerequisite for the commercialization of flying cars in the future. Flying cars are my personal dream. I hope to drive a flying car to work before I retire, so that I can avoid ground traffic congestion. However, flying cars have very high requirements for batteries. The most promising vertical takeoff and landing flying cars or air taxis in the world at present must have their batteries quickly recharged immediately after each landing. Therefore, we must have fast-charging batteries to make flying cars a reality.
Our current experimental results have confirmed the feasibility and economic viability of using 10-minute fast-charging batteries in flying cars. This naturally leads us to ask: can we use the principle of interface control to develop a safe battery that never spontaneously combusts, and which not only has high safety but also high energy density? This is where our invention, the Shuoan Battery, comes in.
"Shuo" refers to high specific energy. Shuoan batteries use simple electrolyte additives to further passivate the electrochemical interface in the battery. The key here is passivation—passivating the electrochemical interface. Our experiments found that adding just 1.5% triallyl phosphate can reduce the battery's activity by 4 times. Imagine a battery where 3/4 of the reaction interface is shut down, leaving only 1/4—isn't that incredibly safe?
Indeed, we conducted the most rigorous nail penetration test on this passivated battery. Even with the highest energy density cell, 290 Wh/kg, and using the most unstable ternary 811 material, the highest nail penetration temperature did not exceed 55 degrees Celsius. This is lower than the 60-degree nail penetration temperature of lithium iron phosphate batteries. In other words, we can make ternary batteries with extremely high energy density safer than ordinary lithium iron phosphate batteries.
So here's your question: how can a passivated battery, which only has 1/4 of its reaction interface remaining, be made to exhibit high power output during operation?
Using the same thermal stimulation method, we can heat the passivated battery from room temperature to 60 degrees Celsius before operation, which can generate 1.7 times the power of a comparable battery. This is the unique design principle of "passivated battery, heated for use". We have also discovered a thermally regulated lithium iron phosphate battery that overcomes the three major pain points of the original lithium iron phosphate battery: First, it solves the problem of poor low-temperature performance. Because of the thermal stimulation function, we no longer rely on the low-temperature performance of the lithium iron phosphate material itself. For example, in winter, we can rapidly raise the battery temperature to above 0 degrees Celsius within 30 seconds, thereby outputting normal high power.
Secondly, we can achieve 10-minute fast charging, which is very significant because 10 minutes of quick and convenient charging allows lithium iron phosphate to directly avoid its relatively low energy density. At this point, range anxiety is no longer a problem, because you can conveniently charge anytime, anywhere.
Thirdly, it allows us to use non-flammable electrolytes, further enhancing the safety of lithium iron phosphate batteries. In continued research, we have developed a second-generation thermally regulated lithium iron phosphate battery. Currently, in the laboratory, we have achieved an energy density of 300 watt-hours per kilogram, and the cost is expected to drop to 35 cents per watt-hour. This new achievement, combined with the other advantages of the first generation, such as 10-minute fast charging, cold resistance, and the absence of cobalt (a strategic metal), and the lack of a thermal management system, makes this a near-final battery that can meet the needs of most applications.
Let's summarize: Batteries and energy storage are among the most important foundational technologies for the new energy era and intelligent society. I believe that the next decade will bring tremendous opportunities for innovation, because we will not only continue to innovate in materials, but also scientifically reveal the possibility of controllable reaction interfaces. This controllable working ecosystem will open new doors for materials innovation.
The all-weather battery, 10-minute fast-charging battery, Shuoan battery, and low-cost thermally regulated lithium iron phosphate battery that I mentioned earlier are just the beginning of our invention and innovation. We sincerely invite you to join us in exploring new types of batteries that are actively regulated and actively stimulated, so that battery materials can shine to their fullest potential.
Finally, I'd like to briefly share three insights from my personal research career:
First, as a scientist, one must have the courage and perseverance to tread paths no one has ever walked before, and not care too much about the thoughts and opinions of others, because innovation is always a solitary endeavor.
Secondly, simplicity is beauty. Scientific discoveries that have practical value are generally exquisitely simple.
Third, honest energy. Before making scientific discoveries and technological inventions, and even before independently considering the work of others, we must first remember that energy is conserved.
