The basics and status of rechargeable battery

The basics and status of rechargeable battery

A battery that can be called a rechargeable battery must have the characteristics of the negative and positive electrodes that can be recharged and discharged. The electrode structure must remain stable during the process of ion deintercalation, during which the electrolyte acts as a medium for ion transmission. The charging diagram of the lithium rechargeable battery is shown in the figure below.

The basics and status of rechargeable battery
The migration of Li+ in the electrolyte and the insertion/extraction of Li+ in the electrode in the lithium rechargeable battery

When the ions flowing into the electrode and the electrons entering the electrode through the conductor meet, charge neutralization occurs, so that electric energy is stored in the electrode through a medium. In addition, when ions quickly enter the electrode from the electrolyte, the reaction rate increases. In other words, the total reaction time of the battery depends largely on the ion migration between the electrolyte and the electrode. The number of ions embedded in the electrode under the charge neutralization condition determines the electrical energy storage capacity. Fundamentally speaking, the types of ions and materials are the main factors that affect the electrical energy storage capacity of materials. Lithium-ion (Li+)-based batteries are what we know as lithium rechargeable batteries.

Lithium is the lightest among all metals and has the lowest standard reduction potential. It can generate a working voltage above 3V. Lithium metal has become an ideal choice for anode materials with high specific energy and energy density. Since the operating voltage of lithium rechargeable batteries is higher than the decomposition voltage of water, organic electrolytes must be used instead of aqueous solutions. Materials capable of Li+ deintercalation can be used as electrodes.
Lithium rechargeable batteries use transition metal oxides as the positive electrode and carbon as the negative electrode. Liquid lithium ion batteries (LIB) use organic solvents for electrolyte, while polymer lithium ion batteries (LIPB) use solid polymer composite materials.

The basics and status of rechargeable battery
Different shapes of lithium ion rechargeable batteries: a) cylindrical, b) button type, c) square, d) soft pack type

As shown in the figure above, commercial lithium rechargeable batteries can be classified according to the shape and composition of the battery. Different forms of batteries include cylindrical notebook batteries, prismatic batteries for portable devices, button batteries, and soft-pack batteries packed in aluminum-plastic composite materials.

The table shows the main components of lithium rechargeable batteries, and their materials can be described as shown in the table. Since lithium is extracted from the crystal lattice into ions, a stable transition oxide can be used as a positive electrode. The negative electrode material must have a reduction potential close to that of lithium to fix the released ions and provide a high electromotive force. The electrolyte is composed of a lithium salt dissolved in an organic solvent, which can maintain electrochemical stability and thermal stability within the operating voltage range. In addition, the separator made of polymer or ceramic has high-temperature melt integrity and can prevent short circuits caused by electrical contact between the positive electrode and the negative electrode.

electrodePositive electrode active materialTransition metal oxide/battery capacityLiCoO2、LiMn2O4、LiNiO2、LiFePO4
ElectrodeAnode active materialCarbon/non-carbon alloy/electrode reversible reactionGraphite, hard (soft) carbon, Li, Si, Sn, lithium alloy
ElectrodeConductive agentCarbon/electronic conductivityAcetylene Black
ElectrodeBinderPolymer/adhesive propertiesPolyvinylidene chloride (PVdF), SBB/CMC
ElectrodeCurrent collectorMetal foil/as pole plateCu(-), AI(+)
ElectrolyteDiaphragmPolymer/isolated positive and negative electrodes to prevent short circuitsPolyethylene (PE), Polypropylene (PP), PVdF
ElectrolyteLithium saltOrganic and inorganic lithium compounds/ion conductivityLiPF6、LiAsF6、LiClO4、LiCF3SO3、Li(CF3SO2)2N
ElectrolyteElectrolyte solventNon-aqueous organic solvent/dissolved lithium saltEthylene carbonate (EC). Propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC)
ElectrolyteadditiveOrganic compound/SEI film formation and overcharge protectionVinylene carbonate (VC), biphenyl (BP)
otherLugMetal/electrode connectionAl(+)、Ni(-)
othershellBattery protection, moldingMolybdenum-rich stainless steel, aluminum plastic shell
otherSecure elementOvercharge and overdischarge protection, safety deviceSafety valve, positive temperature coefficient (PTC) device, protection circuit module (PCM)
Characteristics and examples of main components in lithium rechargeable batteries

Nowadays, the development of lithium rechargeable batteries focuses on energy storage batteries, consumer batteries and power lithium batteries.

On the basis of these achievements, lithium rechargeable batteries have reached new applications, such as green energy and wireless charging.

In the future applications of lithium rechargeable batteries, medium-sized batteries and large-sized batteries have shown great potential. Energy storage systems are regarded as key components of the next-generation smart grid technology, including batteries for electric vehicles and robots or high-performance lithium rechargeable batteries that can store alternative energy sources such as solar, wind and tidal energy.
Among the commercial rechargeable batteries on the market, the mainstream batteries are still lithium batteries, and lithium-ion batteries have the highest specific energy. Because lithium-ion batteries have high volumetric specific energy and mass specific energy, they are rechargeable and pollution-free, and have the current battery industry development. The three required characteristics, so the demand for lithium batteries in developed countries has a relatively rapid growth. With the development of new energy vehicles, lithium batteries continue to attract worldwide attention.

Today, lithium-ion batteries have become the most important power source for electric vehicles in the development process, and this development has also experienced three generations (first generation: lithium cobalt oxide cathode, second generation: lithium manganate and lithium iron phosphate, and third Generation: ternary technology). With the development of positive and negative materials in the direction of higher gram capacity and the gradual maturity and perfection of safety technology, higher energy density battery cell technology is moving from the laboratory to industrialization and applied to more scenarios to provide future life. A more convenient, cleaner, environmentally friendly and smart life.

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