Differences Between Polymer Batteries and Lithium Batteries: Which Is Better?
Overview of Polymer Lithium Batteries
Lithium-ion batteries are categorized into liquid lithium-ion batteries and polymer lithium-ion batteries (or plastic lithium-ion batteries) based on the electrolyte material used. Both types use the same positive and negative electrode materials: positive electrodes include lithium cobalt oxide, lithium manganese oxide, ternary materials, or lithium iron phosphate, while the negative electrode is typically graphite. The working principles are fundamentally the same. The primary difference lies in the electrolyte: liquid lithium-ion batteries use a liquid electrolyte, whereas polymer lithium-ion batteries use a solid polymer electrolyte, which can be either “dry” or “gel-like.” Currently, most polymer lithium-ion batteries employ a gel polymer electrolyte.
Classification
- Solid Polymer Electrolyte Lithium-Ion Battery: The electrolyte is a mixture of polymer and salt, offering high ionic conductivity at room temperature, making it suitable for ambient use.
- Gel Polymer Electrolyte Lithium-Ion Battery: Additives like plasticizers are incorporated into the solid polymer electrolyte to enhance ionic conductivity, enabling use at room temperature.
Compared to liquid lithium-ion batteries, polymer lithium-ion batteries, which use a solid electrolyte, offer advantages such as thinner profiles, customizable shapes, and variable sizes. They can be encased in aluminum-plastic composite films, improving specific capacity. Additionally, polymer lithium-ion batteries can use polymers as positive electrode materials, potentially increasing specific energy by over 20% compared to current liquid lithium-ion batteries. These batteries are characterized by miniaturization, thinness, and lightweight design, leading to their growing market share.
Caratteristiche
Polymer lithium-ion batteries have the following characteristics:
- Flexible shaping
- Higher specific energy (3x that of Ni-MH batteries)
- Wide electrochemical stability window (up to 5V)
- Excellent safety and reliability
- Longer cycle life with minimal capacity loss
- High volume efficiency
Polymer Lithium Battery Principle
Lithium-ion batteries are divided into liquid lithium-ion batteries (LIB) and polymer lithium-ion batteries (PLB). Liquid lithium-ion batteries use Li+ intercalation compounds as positive and negative electrodes. The positive electrode typically uses lithium compounds like LiCoO2, LiNiO2, or LiMn2O4, while the negative electrode uses lithium-carbon intercalation compounds (LixC6). A typical battery system is: (-) C | LiPF6—EC+DEC | LiCoO2 (+)
Positive Electrode Reaction (Reduction): Li1-xCoO2 + xLi+ + xe- = LiCoO2 (2.1) Negative Electrode Reaction (Oxidation): LixC6 – xe- = 6C + xLi+ (2.2) Overall Battery Reaction: Li1-xCoO2 + LixC6 = LiCoO2 + 6C (2.3)
The principle of polymer lithium-ion batteries is identical to that of liquid lithium-ion batteries, with the main difference being the electrolyte. A polymer lithium-ion battery uses a solid or gel-like polymer electrolyte or an organic electrolyte. Liquid or gel electrolytes in traditional lithium-ion batteries require robust secondary packaging to contain flammable active components, increasing weight and limiting size flexibility.
Next-generation polymer lithium-ion batteries can be made ultra-thin (as thin as 0.5mm, equivalent to a card’s thickness), with customizable shapes and sizes, greatly enhancing design flexibility. This allows manufacturers to tailor batteries to specific product requirements, optimizing performance. Polymer lithium-ion batteries also offer a 20% improvement in energy density compared to standard lithium-ion batteries, along with enhancements in capacity and environmental performance.
Differences Between Polymer Batteries and Lithium Batteries: Which Is Better?
Polymer batteries are generally superior, as traditional lithium batteries are nearly obsolete. Lithium batteries use metallic lithium as the negative electrode, with the earliest being lithium-manganese dioxide batteries, operating via a redox reaction: Li + MnO2 = LiMnO2. Lithium metal batteries typically have a voltage of around 3.0-3.6V, depending on the positive electrode material. Today, lithium metal batteries are primarily used in button cells, as they have been largely replaced by polymer lithium-ion or liquid lithium-ion batteries. Lithium is a highly reactive metal, even more so than sodium, readily losing electrons and undergoing oxidation. In air, lithium reacts almost instantly, and historically, lithium batteries were used to start fires in the wilderness by breaking them open, as the lithium reacts with air to release significant heat, highlighting their inherent danger.
Unlike lithium batteries, lithium-ion batteries do not contain metallic lithium. They rely on lithium ions moving between the positive and negative electrodes to function. During charging, Li+ ions deintercalate from the positive electrode and embed into the negative electrode, which becomes lithium-rich; during discharge, the process reverses. Polymer batteries are a type of lithium-ion battery, sharing the same principle but using a solid or gel polymer electrolyte instead of a liquid one. This makes them safer and allows for smaller, more flexible designs.
Which Is Better?
Polymer lithium-ion batteries are superior due to their safety, flexibility, higher energy density, and longer cycle life. Their solid or gel electrolytes eliminate the risks associated with liquid electrolytes, such as leakage or flammability, and enable thinner, customizable shapes. While lithium metal batteries are now limited to niche applications like button cells due to their reactivity and safety concerns, polymer lithium-ion batteries are the preferred choice for modern applications, offering improved performance and design versatility.
