The structure, advantages and disadvantages of solid-state lithium-ion batteries

Infineon / Mitsubishi / Fuji / Semikron / Eupec / IXYS

The structure, advantages and disadvantages of solid-state lithium-ion batteries

Posted Date: 2024-02-01

The so-called solid-state lithium-ion battery is that both the electrode and the electrolyte are in solid form. Currently, the lithium-ion batteries commonly used on the market use liquid or polymer electrolyte materials.

The solid lithium film secondary battery is prepared into a film on a substrate in the order of anode, electrolyte, and cathode, and is packaged into a battery. During the preparation process, appropriate techniques are used to prepare each thin film layer of the battery. Generally speaking, the negative electrode mostly uses metallic lithium and is prepared by vacuum thermal deposition (VD) technology. The electrolyte and positive electrode, including the oxide negative electrode, can use a variety of sputtering technologies, such as radio frequency sputtering (RFS), radio frequency magnetron sputtering (RFMS), etc.

Structure of solid-state lithium-ion battery

From a macro perspective, solid-state lithium batteries are also composed of solid positive electrode materials, solid electrolytes, and solid negative electrode materials. Their working principles are similar to liquid lithium batteries.

The positive electrode material of the solid-state battery is an active material, and its function is to collect lithium cations in large quantities; under the action of chemical potential, the positive ions lose electrons, and the electrons flow from the external circuit to the negative electrode; the lithium ions that have lost their electrons are free to the negative electrode through the solid electrolyte; The function of the solid negative electrode material is to embed a large number of lithium ions that have lost their electrons. After the negative electrode combines with the electrons, the positive ions that have lost their electrons will then dissociate toward the positive electrode. The function of the solid electrolyte is to allow lithium ions to move between the positive and negative electrodes. conducts smoothly. Simply put, solid-state lithium batteries only rely on the movement of lithium ions between the positive and negative electrodes to achieve the charge and discharge process.

The picture above is the basic structure of the current solid-state lithium battery. The buffer layer is used to make the solid electrode and solid electrolyte effectively compatible and combined; the isolation layer is set up to prevent the internal positive and negative electrodes from short-circuiting. If the technology If you make further progress, you can remove the isolation layer. Simply put, solid lithium batteries and liquid lithium batteries are the same in terms of macrostructure. The fundamental difference is that the electrolyte is solid.

The one shown above with an isolation layer is called a quasi-solid-state battery, and the one without an isolation layer is called an all-solid-state battery. Currently, we are developing and producing quasi-solid-state batteries, which are referred to as solid-state batteries in this article.

Of course, the advantages of solid-state lithium batteries compared with liquid lithium batteries are:

① It completely eliminates the potential safety hazards of electrolyte corrosion and leakage, has higher thermal stability, and will not cause explosion problems;

②The voltage of the battery cell can reach more than 5V, the energy density is also high, and it can match high-voltage electrode materials;

③The solid electrolyte is a single ion conductor, there are no side reactions, and the battery has a longer service life.

④The battery is assembled from solid functional blocks, which not only reduces weight but also reduces production costs.

It is precisely because of the solid electrolyte that solid-state lithium batteries have created new requirements in terms of material selection and processing:

① "Solid electrolyte" requires high conductivity and electrochemical stability at room temperature;

② The positive and negative electrode materials are required to meet high energy density and have good thermal stability;

③The interface between solid electrode and solid electrolyte requires good conductivity and compatibility.

Advantages and disadvantages of solid-state lithium-ion batteries

Solid-state lithium-ion batteries have the following advantages compared to traditional liquid lithium-ion batteries:

1. Improved safety: Solid electrolytes have excellent thermal stability and chemical corrosion resistance, making solid lithium-ion batteries safer and more reliable under extreme conditions such as high temperatures and external impacts. In contrast, traditional liquid batteries have safety hazards such as liquid electrolyte leakage and combustion and explosion.

2. Improved energy density: Solid-state batteries use lithium metal as the negative electrode material. Compared with traditional carbon-based negative electrode materials, they can achieve higher energy density and provide longer cruising range.

3. Faster charging: Solid electrolytes have higher ionic conductivity and can support faster charging. This means that solid-state lithium-ion batteries can be fully charged in less time, improving charging efficiency and user experience.

4. Excellent cold resistance: Solid electrolytes have better ionic conductivity in low-temperature environments than liquid electrolytes, making solid-state lithium-ion batteries perform better in extremely cold areas or low-temperature application scenarios.

However, solid-state lithium-ion batteries still face some challenges and shortcomings:

1. High cost: The manufacturing cost of solid-state batteries is relatively high, including high-purity materials, complex production processes and equipment requirements. This leads to certain challenges in the commercial application of solid-state lithium-ion batteries.

2. Interface issues: The interface stability of solid-state batteries plays a key role in battery performance and life. Current solid-state batteries also face problems such as interface instability and electrode capacity fading, which require further research and improvement.

3. Lifespan and cycle performance: The lifespan and cycle performance of solid-state batteries still need to be further improved. At present, solid-state lithium-ion batteries may have problems such as electrode polarization and increased ionic interface impedance during long-term cycling.

As the next generation battery technology, solid-state lithium-ion batteries have broad application prospects and many advantages, but further research and development and improvements are still needed to overcome existing technical challenges.

In terms of preparation process, due to the poor elasticity of the current solid-state electrolyte membrane, solid-state battery assembly is more prone to delamination than the winding process, but the subdivision process is unknown. In terms of manufacturing equipment, although solid-state batteries are very different from traditional lithium-ion batteries, apart from the need for customized equipment during painting, packaging and other processes, and the manufacturing environment having to be carried out in a drying room with higher requirements, there are no Essentially different.

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