Are solid-state batteries the solution to the next generation of electric vehicle batteries?

Lithium-ion batteries in electric vehicles plague the electric vehicle industry

The development of electric vehicles relies on batteries to provide continuous power, and batteries are the key to the future of electric vehicles. However, the development of lithium-ion batteries for more than 30 years has hardly changed. Current electric vehicles are powered by lithium-ion batteries, which are similar to those used in laptop computers, mobile phones and other consumer electronics. They contain a liquid electrolyte inside, which makes them heavy and prone to instability at high temperatures. Lithium-ion batteries are relatively heavier and bulkier than solid-state batteries; at the same time, the main problems of liquid electrolytes are leakage and high flammability. Over time, the compounds in the liquid will corrode the internal components of the battery, and will experience degradation or accumulation of solid substances inside, both of which will cause the battery capacity and overall performance to decrease. In addition, the metals and raw materials in lithium-ion batteries, especially graphite, cobalt and high-purity nickel, may cause serious pollution and increase carbon dioxide emissions during mining and refining.

The innovation of battery technology has appeared urgency

On average, electric cars are still 30% more expensive than traditional cars, but they cannot provide performance far exceeding the high endurance provided by internal combustion engines. In addition, the charging time is also longer, and it takes 20-30 minutes to fully charge the battery at the fastest, and the endurance is mostly between 300 and 400 kilometers. Market research companies predict that electric vehicles will replace internal combustion engine vehicles and become the mainstream of the automotive industry. The driving range of electric vehicles should be similar to that of current internal combustion engine vehicles, so it is very important to increase the battery capacity of electric vehicle batteries. The way to increase capacity is to increase the number of batteries. But in this case, the price of the battery rises, and the battery takes up a lot of space in the vehicle. In addition, half of the weight of electric vehicles comes from batteries, making the body heavier than fuel vehicles. If the weight of the battery is reduced by half, the endurance of the vehicle can be increased by 25%. The limitations of battery technology have brought some problems that may slow down the pace of substantial adoption of electric vehicles. In order to reduce the cost of electric vehicles, and improve the endurance and efficiency, battery technology must have a breakthrough. To this end, scientists put forward the idea of ​​a “solid-state battery”. The electrolyte is removed and stacked in an all-solid state, which will not cause the positive and negative electrodes to contact short-circuit explosion due to the breakage of the separator. The energy density is also increased, and the energy density is increased at minus 25°C to 60°C. It can operate normally in the temperature range of ℃. The power source of solid-state batteries has a thin layer of solid electrolyte, which can replace the flammable liquid solution in current lithium-ion batteries and can store energy more densely. The electrolyte can also be used as a battery separator. The separator is a necessary component in a lithium-ion battery. Using an electrolyte as a separator can reduce the risk of fire and reduce the amount of raw materials required.

Why don’t we all drive cars with solid-state batteries?

Like other emerging technologies, solid-state batteries are expensive, partly due to development costs, but they are also difficult to produce on a large scale; although they have advantages over liquids. The main reason why solid-state batteries are not seen on the market is that there are many technical problems to be broken through. For example, the conductivity of solid electrolytes is not as good as that of liquid electrolytes. In addition to the immature technology, the manufacturing cost is still high, which is not conducive to large-scale manufacturing and popularization. The solid electrolyte is looking for the right material. Conductive chalcogenide glass is an excellent candidate material, and its conductivity is 10-100 times that of its oxide counterpart. Several solid-state batteries have been developed that include lithium conductive chalcogenide glass or glass ceramic as the solid electrolyte. However, designers have encountered high cost and various technical challenges, such as the expansion and contraction of solid-state batteries during charging and discharging. However, the research organization Bloomberg NEF estimates that if solid-state batteries can be produced on a large scale, the cost will be only 40% of that of lithium batteries, and they have the opportunity to become the mainstream of electric vehicle batteries.

Next-generation power source-solid state battery

In solid-state designs, solid materials replace liquids or gels. This material, sometimes ceramic, can still allow lithium ions to pass through. Solid-state batteries have a higher energy density than lithium-ion batteries that use liquid electrolyte solutions. It has no risk of explosion or fire, so no safety components are needed, which saves more space. In this way, we have more space to place more active materials, thereby increasing the battery capacity of the battery. Solids take up less space than liquids, which results in batteries that are smaller, lighter, and can pack more energy into each unit volume.

Solid-state batteries are expected to become a viable alternative to lithium-ion batteries that use liquid electrolyte solutions. This innovation will reduce the risk of fire and increase energy density. If solid-state battery developers can afford mass-production technology, the result will be longer battery life and shorter charging times than the most common batteries currently available. Since solid-state batteries are cooler and less flammable than some current lithium-ion designs, they will also have safety advantages.

Solid-state batteries can increase the energy density per unit area because only a small number of batteries are needed. Therefore, solid-state batteries are very suitable for manufacturing EV battery systems that require high-capacity modules and battery packs. Compared with lithium-ion batteries of the same weight and volume, solid-state batteries can store 80% more energy. Lithium metal with higher energy density can replace graphite and help reduce the weight and volume of the battery. The lithium metal anode realized by the solid-state separator can not only solve the energy density problem, but also solve many other limitations of conventional lithium-ion batteries.

It takes about 10 minutes to charge an electric car equipped with a solid-state battery, which reduces the charging time by two-thirds. The battery can extend the driving distance of a compact electric vehicle while maintaining leg room. Samsung Electronics Technology Research Institute demonstrated the results of a solid-state battery that can be charged 1,000 times and can travel 800 kilometers per charge. This technology can extend life cycle and safety, and reduce the size of solid-state batteries by half. Toyota plans to become the first company to sell electric vehicles equipped with solid-state batteries in the early 2020s. Under the same conditions, the driving distance of an electric car developed by Toyota will be more than twice that of a car running on a traditional lithium-ion battery.