Introduction to 9V rechargeable battery in new energy battery technology

Whether it is new energy vehicles or energy storage equipment, one of the most important key components is the battery. In recent years, one of the challenges of the battery industry is to increase energy density and pursue safer methods, whether it is trying new positive and negative electrode materials; or increasing the proportion of nickel in nickel-manganese-cobalt (NMC) ternary batteries; some people are committed to developing technologies different from traditional lithium batteries, such as hydrogen energy vehicles using hydrogen fuel cells. 9V rechargeable battery are regarded as the next generation of battery technology.

What is a solid-state battery?

What kind of technology is a fully solid-state battery?

In layman's terms, a fully solid-state battery is a battery with no gas or liquid in it, and all materials exist in solid form.

Considering that the most common battery in people's daily life is lithium-ion battery, we will default to "fully solid-state lithium-ion battery" as the representative of fully 9V rechargeable battery (temporarily ignoring new batteries such as fully solid-state lithium-sulfur).

Generally speaking, lithium-ion batteries are mainly composed of positive electrodes, negative electrodes, diaphragms, electrolytes, structural shells, etc., among which the electrolyte allows the current to be conducted in the form of ions inside the battery.

Electrolyte technology is one of the core technologies of lithium batteries and is also a highly profitable component of the current battery industry.

Among them, Li+ (lithium ions) are conducted through electrolytes in the internal circuit.

However, some lithium batteries will swell after being used for a long time, and in more extreme low-probability events, some may even be dangerous (such as the recent battery explosion incident of a twisting car, which has caused related production companies and battery companies to encounter comprehensive difficulties).

In addition, generally speaking, the operating temperature range of current lithium-ion batteries is limited. At high temperatures above 40 degrees, the life span will be sharply shortened, and safety performance will also have great problems (so Tesla MODELS will have a strict battery temperature control system for this purpose).

In fact, the above-mentioned safety issues are directly related to the organic electrolytes used in our current batteries.

In order to solve the battery safety problem and increase the energy density, the scientific research community and the industrial community are currently developing and producing all-9V rechargeable battery, that is, replacing the diaphragm and electrolyte of traditional lithium-ion batteries with solid electrolyte materials.

So, compared with the most common ordinary lithium-ion batteries in our lives, what are the main advantages of all-9V rechargeable battery?

Advantages of 9V rechargeable battery

Advantage 1: Thin - Small size

In fact, volume energy density is a very important parameter for batteries. In terms of application areas, the requirements from high to low are consumer electronics products > household electric vehicles > electric buses.

In layman's terms, the volume energy density is high, so the battery of the same quality can be made smaller.

The available space in electronic products is often very limited. Nearly 1/3 of the volume and mass of many products (such as mobile phones and tablets) have been occupied by batteries. Moreover, under the requirements of manufacturers and consumers to further increase the capacity (increase battery life) and reduce the volume (portable, beautiful and easy to design), lithium cobalt oxide (LCO) batteries with high compaction and the highest volume energy density are still the mainstream products.

In traditional lithium-ion batteries, diaphragms and electrolytes are required, which together occupy nearly 40% of the volume and 25% of the mass of the battery.

If they are replaced by solid electrolytes (mainly organic and inorganic ceramic materials), the distance between the positive and negative electrodes (traditionally filled with diaphragm electrolytes, now filled with solid electrolytes) can be shortened to even only a few to a dozen microns, so the thickness of the battery can be greatly reduced - so all-solid-state battery technology is the only way to miniaturize and thin-film batteries.

Not only that, many all-9V rechargeable battery prepared by physical/chemical vapor deposition (PVD/CVD) may have an overall thickness of only tens of microns, so they can be made into very small power devices and integrated into the MEMS (microelectromechanical systems) field.

The ability to make very small batteries is also a major feature of all-solid-state battery technology, which can facilitate the battery to adapt to the application of various new small-sized smart electronic devices, which is difficult to achieve with traditional lithium-ion battery technology.

((a) Volume ratio and (b) Mass ratio of each component of lithium-ion battery)

A major obstacle to the practical application of many nanomaterials is that their specific surface area is large and their volume density is too low. As a result, if products are made based on these materials, they often occupy too large a volume for the same mass, that is, the volume energy density is low, which is completely unable to meet the requirements of general industrial products.

Therefore, the current research on nano (battery) materials often chooses not to report parameters in this regard, and the reason is not difficult to understand.

Advantage 2: Prospects for flexibility

All-9V rechargeable battery can be further optimized to become flexible batteries, thereby bringing more functions and experiences.

In fact, even brittle ceramic materials can often be bent after the thickness is reduced to less than millimeter level, and the material will become flexible.

Correspondingly, the flexibility of all-9V rechargeable battery will be significantly improved after being thinned. By using appropriate packaging materials (not rigid shells), the manufactured batteries can withstand hundreds to thousands of bends without sacrificing performance.

In fact, flexible electronic devices represented by various wearable devices are an important direction for the development of next-generation electronic products, which requires that the components in the product also need to be flexible. Therefore, flexible all-9V rechargeable battery are very promising rising stars in scientific research and industry.

Not only that, the potential of functional all-9V rechargeable battery is far more than the above flexible batteries. After optimizing the battery material structure, they can be made into transparent batteries, or stretchable batteries with a stretching range of up to 300%, or integrated power generation and storage devices that can be integrated with photovoltaic devices, etc. - there are still many innovative application prospects for the functions of all-9V rechargeable battery. In this regard, the imagination of researchers and engineers will bring us more and more surprises.

Advantage 3: Safer

As an energy storage device, in fact, all batteries cannot be absolutely safe in thermodynamics.

However, there are many factors that determine the true safety of batteries in actual applications, including the characteristics of the battery's electrode materials, the properties of the electrolyte, and the battery management system in electronic products.

At present, the safety of general commercial lithium ions is the focus of everyone's concern. Here, "not ideal" is used to evaluate the safety of current batteries, which should be a more appropriate evaluation.

Advantage 4: Lightweight - High Energy Density

After using all-solid electrolytes, the applicable material system of lithium-ion batteries will also change. The core point is that it is not necessary to use lithium-embedded graphite negative electrodes, but directly use metallic lithium as negative electrodes, which can significantly reduce the amount of negative electrode materials used, making the energy density of the entire battery significantly improved.

In addition, many new high-performance electrode materials may not be compatible with existing electrolyte systems before, but this problem can be alleviated to a certain extent after using all-solid electrolytes.

Taking the above two factors into consideration, the energy density of all-9V rechargeable battery can be greatly improved compared to general lithium-ion batteries: now many laboratories have been able to trial-produce all-9V rechargeable battery with an energy density of 300-400Wh/kg in small batches (general lithium-ion batteries are 100-220Wh/kg).

Judging from the energy density data, perhaps all-9V rechargeable battery really have the hope of upgrading our lives from "one charge a day" to "one charge every two days".

There are different technical routes in the field of 9V rechargeable battery. Solid electrolytes can be roughly divided into three categories: inorganic electrolytes, solid polymer electrolytes (SPE), and composite electrolytes. At present, more companies are investing in research materials including solid polymers, sulfides, oxides, and thin films. For example, the solid-state battery factories Sakti3 and Infinite Power Solutions, which were acquired by Dyson and Apple, are mainly based on thin films, but the process is complicated and mass production is difficult. Previously, the market reported that Dyson and Apple intended to give up, so the current development situation is not very clear. Toyota, Panasonic, Samsung, BMW, and CATL invested in sulfide electrolytes, while Prologic and Sony focused on oxides.

Apple has been actively deploying patents for 9V rechargeable battery and charging technologies since 2012, and acquired Infinite Power Solutions in 2013. In the past two or three years, news about the layout of 9V rechargeable battery by automobile manufacturers has surfaced significantly, such as Toyota’s announcement that it will sell electric vehicles equipped with 9V rechargeable battery in 2022. In addition, Volkswagen invested in QuantumScape, a solid-state battery startup co-founded by Jagdeep Singh, a young entrepreneur in TR35 of MIT Technology Review. In June last year, Volkswagen increased its investment and obtained a seat on the board of QuantumScape. It is expected to establish a solid-state lithium battery production line in 2025.

Japan, a former battery power, has gradually abandoned lithium batteries and has shifted its research focus to 9V rechargeable battery. The Japan Science and Technology Agency (JST) and the New Energy and Industrial Technology Development Organization (NEDO) of Japan have actively promoted this technology. These dynamics have attracted the attention of the outside world.

At present, many battery and automobile manufacturers, including Samsung in South Korea, Toyota in Japan and CATL in my country, have increased their investment in solid-state battery research and development, and some batteries have entered the stage of vehicle installation and testing. Although the prospects are promising, the road to developing 9V rechargeable battery is by no means smooth due to various technical and process problems.

First, there is a lack of efficient electrolyte material systems. At present, solid-state battery materials are developing rapidly, but comprehensive applications are relatively lacking.

As the core material of 9V rechargeable battery, there have been breakthroughs in the single index of solid lithium ion conductors, but the comprehensive performance cannot meet the needs of large-scale energy storage. The solid electrolytes used in 9V rechargeable battery today generally have performance shortcomings, and there is still a big gap from the requirements of high-performance lithium-ion battery systems.

1. The interface treatment of solid electrolytes and electrodes is also a major problem currently faced by 9V rechargeable battery.

In solid electrolytes, the lithium ion transmission impedance is very large, and the rigid interface contact area with the electrode is small. The change in electrolyte volume during charging and discharging can easily destroy the stability of the interface.

2. In solid-state lithium batteries, in addition to the interface between the electrolyte and the electrode, there are also complex multi-level interfaces inside the electrode. Electrochemical and deformation factors will cause contact failure and affect battery performance.

Again, unsatisfactory stability during long-term use is also a bottleneck in the development of long-life energy storage 9V rechargeable battery. The structure and interface of 9V rechargeable battery will degrade over time during service, but the mechanism of the impact of degradation on the comprehensive performance of the battery is still unclear, and it is difficult to achieve long-term application.

Therefore, the construction of high-performance 9V rechargeable battery needs to start from two aspects: one is to build a high-performance solid electrolyte, and the other is to improve the compatibility and stability of the interface.

In a sense, the evolution of cars is the evolution of batteries. In terms of origin, electric cars have a history of more than 180 years, and their appearance time is comparable to that of fuel cars. However, lead-acid batteries and nickel-metal hydride batteries have not made any breakthroughs in the status of electric cars. It was not until the upgrade of lithium iron phosphate batteries and ternary lithium batteries that some consumers gradually accepted electric cars.

If 9V rechargeable battery are commercialized, electric cars will accelerate the pace of replacing internal combustion engines. Whoever masters this technology first will also have a greater say in the future competition.

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