With the release of the Zhiji L6, aside from the apology news, the topic of solid-state batteries has once again been pushed to the forefront of trending searches, and related solid-state battery concept stocks have also experienced a surge in popularity. In fact, the concept of solid-state batteries has been around for quite some time. As early as 2021, NIO had already begun to hype the integration of solid-state batteries, and Li Bin completed his long-distance live broadcast last year. On the 12th of this month, GAC will also be launching an all-solid-state battery.

I am not here to advertise for GAC, but please pay attention to the term "all-solid-state," which is very prominent. Let me first provide a brief introduction to the concept of solid-state batteries.

The batteries we currently use contain the "four great kings," which are: cathode, anode, separator, and electrolyte, with the electrolyte accounting for about 25wt%.

Advertisement

"Solid-state batteries" are generally classified into three types: semi-solid, quasi-solid, and all-solid, which can all be collectively referred to as solid-state batteries. The difference lies in their liquid content, which is 5-10wt%, 0-5wt%, and 0wt%, respectively.

What are the advantages of solid-state batteries?

Without a doubt, the all-solid-state battery is the ultimate goal, currently in the research and development phase, with an estimated commercialization timeline around 2030. However, based on current information, it does not seem to be on track as expected. You might ask, why does it take such a long time? What are the advantages and disadvantages of all-solid-state batteries? Where exactly are the difficulties?

The biggest limiting factor in the batteries we currently use is the liquid electrolyte, which is composed of organic solvents, lithium salts, and some additives. It serves to transport ions and conduct electric current. However, these organic solvents have issues with solubility, corrosion resistance, and poor oxidative stability. Their presence cannot solve the problem of lithium dendrites. Once crystallization occurs, it may pierce the separator, causing direct contact between the anode and cathode, leading to thermal runaway.

Furthermore, the presence of the electrolyte also limits the use of anode and cathode materials. The batteries we are currently using generally employ graphite anodes, which you can think of as a container. When lithium ions arrive, it's like they are housed in a structure. Due to the framework constraint provided by graphite, the SEI (solid electrolyte interphase) on the surface of the "house" becomes controllable. The theoretical energy density limit we currently see for ternary lithium batteries is approximately 250-300wh/kg.

If a solid medium is used to replace the liquid, the separator can be completely eliminated, and there is no longer a need to worry about short circuits due to direct contact between the anode and cathode. This is because the solid medium can completely physically isolate the anode and cathode materials, and the issue of lithium dendrites piercing the barrier can essentially be resolved, providing better safety assurance. Therefore, solid-state batteries are safer, with a lower probability of thermal runaway.

Additionally, the selection of anode and cathode materials becomes more diverse, allowing for compatibility with high-capacity anode and cathode materials, significantly increasing the battery capacity. For example, for anode materials, one could even use all-lithium: the "container" can be completely eliminated because the solid medium will not react with metallic lithium, allowing for more lithium to be stored. Moreover, it can suppress the growth of lithium dendrites. Due to the hard interface, it can forcibly level the anode surface, which is also one of the reasons for its higher energy density. Theoretically, the energy density of all-solid-state batteries can reach 500wh/kg, resulting in smaller batteries and longer endurance.The Disadvantages of Solid-State Batteries

While solid-state batteries boast numerous advantages, they also have significant drawbacks that have not yet been fully resolved (which makes me curious about how GAC's solid-state batteries have managed to achieve this). For instance, we see issues such as low ionic conductivity, poor cycle life, and high costs that hinder commercial progress.

In the previous text, we mentioned various solid media, and from the information we have gathered, these solid media generally fall into four categories: oxides, sulfides, halides, and polymers. Due to the contact between solids, its ionic conductivity is certainly not as high as that of liquids, so the battery requires increased pressure to ensure tight contact between these three materials. However, a problem arises: as the battery operates and heats up, different materials expand differently upon heating, and under the combined pressure of internal and external forces, the battery can expand and become damaged. According to an interview with Zeng Yuqun, Chairman of Contemporary Amperex Technology Co., Ltd. (CATL), "It cannot withstand many charge and discharge cycles; perhaps it might fail after just 10 cycles."

The most challenging issue to resolve is the high cost of materials. Since the solid-state battery media are difficult to thin, many rare metals are used, and some materials are quite expensive. According to estimates by Ganfeng Lithium, the current cost of a 350 Wh/kg system sulfide solid-state battery is about 40 yuan/Wh. You can imagine how high the cost of a 1000Wh battery would be.

Semi-Solid Batteries as a Compromise

Since we cannot reach the end goal immediately, let's find a middle ground, or what can be considered an intermediate technology—semi-solid batteries.

As a compromise, its properties are almost in between fully solid and fully liquid. Semi-solid batteries reduce the content of liquid electrolyte and increase the solid electrolyte. There are two approaches here: one is solid plus a small amount of liquid electrolyte, which actually still requires the addition of liquid, and the other uses a polymer base to carry the electrolyte, making its properties more similar to a gel (like a child's fever patch), which is also the most common solution, often seen in mobile phone batteries.

So, its advantages are quite summarized: higher safety, higher energy density, longer life, wider temperature range, better pressure resistance, higher ionic conductivity, and costs significantly lower than solid-state batteries. It can leverage the current lithium battery manufacturing processes to achieve easier mass production and lower costs, with only about 20% of the processes being different. Therefore, in terms of economic viability and the speed of industrialization, it currently appears to be the best option.

In terms of safety and energy density, since the electrolyte in the middle is a gel, even lithium dendrites find it difficult to penetrate this medium, so its safety is also better. There will be no hard-to-hard issues between the positive and negative electrodes and the electrolyte, and the conductivity and expansion problems have been well resolved.

In addition, there will be more choices in the selection of positive and negative electrode materials. For example, for the negative electrode materials mentioned earlier, in addition to graphite, it is also possible to "dope silicon and replenish lithium," which greatly increases the capacity of the container and improves the energy density of the battery. For instance, NIO's 150kWh semi-solid battery has an energy density as high as 360Wh/kg, and the battery pack energy density is as high as 261Wh/kg, which is definitely leading the field. The overall weight of the battery pack is only about 575 kilograms, which is similar to the weight of a traditional 100kWh battery. Even the semi-solid battery just released by Zhiji has an energy density of 300Wh/kg, with a battery pack energy density of around 215Wh/kg.The Significance of Solid-State Batteries

Does solid-state battery technology truly hold significance?

Why would such a question arise? Common sense dictates that advancements in technology will invariably lead to positive outcomes.

However, during a recent live broadcast, Li Bin, CEO of NIO, stated, "The symbolic value of a 150kWh battery pack in daily life outweighs its practical significance." The rationale is straightforward: no one would drive an electric vehicle (EV) to traverse a thousand kilometers continuously, as it is meaningless to do so. No one would undertake such a journey, as charging stations are readily available on highways. Thus, he believes that this type of battery would only address 1% of user scenarios.

From this perspective, it may seem as if Li Bin is undermining his own company, but in reality, he is considering the matter from the consumer's point of view. Indeed, no one would carry such a large battery for continuous driving. Even with long-distance needs, considering a break every four hours, a practical range of around 500 kilometers is more than sufficient. The battery itself is not light, and carrying it daily would increase electricity consumption, making it unnecessary.

The author believes that the development of solid-state batteries could likely bring about positive changes in the layout of electric vehicles. Li Bin's view that large batteries are meaningless to consumers stems from the fact that NIO's adoption of battery swapping technology greatly restricts the shape and size of the batteries. All NIO batteries have the same dimensions, so as battery technology advances, the capacity of NIO's batteries will only increase, potentially reaching an unreasonable level.

But what if we could reduce the battery size, even fitting it under the seat? Wouldn't the vehicle layout become much more flexible? Could the chassis be lowered by another two centimeters?

Therefore, let's allow the situation to unfold for a while longer and see what GAC's all-solid-state battery will bring to us.