lithium-ion technology | Lithium-ion battery

A lithium-ion battery (sometimes Li-ion battery or LIB) is a member of a family of rechargeable battery types in which lithium ions move from the anode to the cathode during discharge and back when charging. Li-ion batteries use an intercalated lithium compound as the electrode material, compared to the metallic lithium used in non-rechargeable lithium battery.
Lithium-ion batteries are common in consumer electronics. They are one of the most popular types of rechargeable battery for portable electronics, with one of the best energy densities, no memory effect (note, however, that new studies have shown signs of memory effect in lithium-ion batteries), and only a slow loss of charge when not in use. Beyond consumer electronics, LIBs are also growing in popularity for military, electric vehicle and aerospace applications. For example, Lithium-ion batteries are becoming a common replacement for the lead acid batteries that have been used historically for golf carts and utility vehicles. Instead of heavy lead plates and acid electrolyte, the trend is to use a lightweight lithium/carbon anode and lithium iron phosphate cathode. Lithium-ion batteries can provide the same voltage as lead-acid batteries, so no modification to the vehicle's drive system is required.
Chemistry, performance, cost and safety characteristics vary across LIB types. Handheld electronics mostly use LIBs based on lithium cobalt oxide (LiCoO
2), which offers high energy density, but present safety risks, especially when damaged. Lithium iron phosphate (LFP), lithium manganese oxide (LMO) and lithium nickel manganese cobalt oxide (NMC) offer lower energy density, but longer lives and inherent safety. Such batteries are widely used for electric tools, medical equipment and other roles. NMC in particular is a leading contender for automotive applications. Lithium nickel cobalt aluminum oxide (NCA) and lithium titanate (LTO) are specialty designs aimed at particular niche roles.
Lithium-ion batteries can be dangerous under some conditions and can pose a safety hazard since they contain, unlike other rechargeable batteries, a flammable electrolyte and are also kept pressurized. This makes the standards of these batteries high, and it consists of many safety features. There have been many reported accidents as well as recalls done by some companies.

                                     History

Lithium batteries were first proposed by M. S. Whittingham, now at Binghamton University, while working for Exxon in the 1970s. Whittingham used titanium(IV) sulfide and lithium metal as the electrodes.
Reversible intercalation in graphite and intercalation into cathodic oxides was discovered in the 1970s by J. O. Besenhard at TU Munich. Besenhard proposed its application in lithium cells. Electrolyte decomposition and solvent co-intercalation into graphite were severe early drawbacks for battery life.
Primary lithium batteries with metallic lithium anodes pose safety issues. As a result, lithium-ion batteries were developed in which both electrodes are made of a material containing lithium ions.
At Oxford University, England, in 1979, John Goodenough and Koichi Mizushima demonstrated a rechargeable cell with voltage in the 4 V range using lithium cobalt oxide (LiCoO
2) as the positive electrode and lithium metal as the negative electrode. This innovation provided the cathode material that made LIBs possible. LiCoO
2 is a stable positive electrode material which acts as a donor of lithium ions, which means that it can be used with a negative electrode material other than lithium metal. By enabling the use of stable and easy-to-handle negative electrode materials, LiCoO
2 opened a whole new range of possibilities for novel rechargeable battery systems.
In 1977, Samar Basu demonstrated electrochemical intercalation of lithium in graphite at the University of Pennsylvania. This led to the development of a workable lithium intercalated graphite electrode at Bell Labs (LiC
6)  to provide an alternative to the lithium metal electrode battery.
In 1980, Rachid Yazami demonstrated the reversible electrochemical intercalation of lithium in graphite. The organic electrolytes available at the time would decompose during charging with a graphite anode, slowing the development of a rechargeable lithium/graphite battery. Yazami used a solid electrolyte to demonstrate that lithium could be reversibly intercalated in graphite through an electrochemical mechanism. The graphite electrode discovered by Yazami is currently the most commonly used electrode in commercial lithium ion batteries.
In 1983, Michael M. Thackeray, Goodenough, and coworkers identified manganese spinel as a cathode material. Spinel showed great promise, given its low-cost, good electronic and lithium ion conductivity, and three-dimensional structure, which gives it good structural stability. Although pure manganese spinel fades with cycling, this can be overcome with chemical modification of the material. As of 2013 manganese spinel was used in commercial cells.

In 1985, Akira Yoshino assembled a prototype cell using carbonaceous material into which lithium ions could be inserted as one electrode, and lithium cobalt oxide (LiCoO
2), which is stable in air, as the other. By using materials without metallic lithium, safety was dramatically improved. LiCoO
2) enabled industrial-scale production and represents the birth of the current lithium-ion battery.
In June 2012 John Goodenough, Rachid Yazami and Akira Yoshino received the 2012 IEEE Medal for Environmental and Safety Technologies for developing the lithium ion battery.

                             Modern batteries

In 1989, Goodenough and Arumugam Manthiram of the University of Texas at Austin showed that cathodes containing polyanions, e.g., sulfates, produce higher voltages than oxides due to the induction effect of the polyanion.
In 1991, Sony and Asahi Kasei released the first commercial lithium-ion battery.
In 1996, Goodenough, Akshaya Padhi and coworkers proposed lithium iron phosphate (LiFePO
4) and other phospho- (lithium metal phosphates with the same structure as mineral olivine) as cathode materials.
In 2002, Yet-Ming Chiang and his group at MIT showed a substantial improvement in the performance of lithium batteries by boosting the material's conductivity by doping itwith aluminium, niobium and zirconium. The exact mechanism causing the increase became the subject of widespread debate.
In 2004, Chiang again increased performance by utilizing iron phosphate particles of less than 100 nanometers in diameter. This decreased particle density almost one hundredfold, increased the cathode's surface area and improved capacity and performance. Commercialization led to a rapid growth in the market for higher capacity LIBs, as well as a patent infringement battle between Chiang and Goodenough.
As of 2011, lithium-ion batteries accounted for 66% of all portable secondary (i.e., rechargeable) battery sales in Japan.

                                  Construction

The three primary functional components of a lithium-ion battery are the anode, cathode and electrolyte. Generally, the anode of a conventional lithium-ion cell is made from carbon. The cathode is a metal oxide, and the electrolyte is a lithium salt in an organic solvent. The electrochemical roles of the electrodes reverse between anode and cathode, depending on the direction of current flow through the cell.

The most commercially popular anode is graphite. The cathode is generally one of three materials: a layered oxide (such as lithium cobalt oxide), a polyanion (such as lithium iron phosphate) or a spinel (such as lithium manganese oxide).
The electrolyte is typically a mixture of organic carbonates such as ethylene carbonate or diethyl carbonate containing complexes of lithium ions. These non-aqueous electrolytes generally use non-coordinating anion salts such as lithium hexafluorophosphate (LiPF
6), lithium hexafluoroarsenate monohydrate (LiAsF
6), lithium perchlorate (LiClO
4), lithium tetrafluoroborate (LiBF
4) and lithium triflate (LiCF
3SO
3).
Depending on materials choices, the voltage, energy density, life and safety of a lithium-ion battery can change dramatically. Recently, novel architectures using nanotechnology have been employed to improve performance.
Pure lithium is highly reactive. It reacts vigorously with water to form lithium hydroxide and hydrogen gas. Thus, a non-aqueous electrolyte is typically used, and a sealed container rigidly excludes moisture from the battery pack.
Lithium ion batteries are more expensive than NiCd batteries but operate over a wider temperature range with higher energy densities. They require a protective circuit to limit peak voltage.
For notebooks or laptops, lithium-ion cells are supplied as part of a battery pack with temperature sensors, voltage converter/regulator circuit, voltage tap, battery charge state monitor and the main connector. These components monitor the state of charge and current in and out of each cell, capacities of each individual cell (drastic change can lead to reverse polarities which is dangerous), temperature of each cell and minimize the risk of short circuits

                                         Formats

Li-ion cells are available in various form factors, which can generally be divided into four groups:

• Small cylindrical (solid body without terminals, such as laptop batteries)
• Large cylindrical (solid body with large threaded terminals)
• Pouch (soft, flat body, such as those used in cell phones)
• Prismatic (semi-hard plastic case with large threaded terminals, such as vehicles' traction packs)

The absence of a case gives pouch cells the highest energy density; however, pouch cells (and prismatic cells) require an external means of containment to prevent expansion when their state-of-charge (SOC) level is high.

                                                            Electrolytes

 

The cell voltages given in the Electrochemistry section are larger than the potential at which aqueous solutions can electrolyze. Given lithium's high reactivity to water, nonaqueous or aprotic solutions are used.
Liquid electrolytes in lithium-ion batteries consist of lithium salts, such as LiPF
6, LiBF
4 or LiClO
4 in an organic solvent, such as ethylene carbonate, dimethyl carbonate, and diethyl carbonate. A liquid electrolyte acts as a carrier between the cathode and the anode when current flows through an external circuit. Typical conductivities of liquid electrolyte at room temperature (20 °C (68 °F)) are in the range of 10 mS/cm (1 S/m), increasing by approximately 30–40% at 40 °C (104 °F) and decreasing slightly at 0 °C (32 °F)
Organic solvents easily decompose on anodes during charging. However, when appropriate organic solvents are used as the electrolyte, the solvent decomposes on initial charging and forms a solid layer called the solid electrolyte interphase (SEI), which is electrically insulating yet provides significant ionic conductivity. The interphase prevents decomposition of the electrolyte after the second charge. For example, ethylene carbonate is decomposed at a relatively high voltage, 0.7 V vs. lithium, and forms a dense and stable interface.
Composite electrolytes based on POE (poly(oxyethylene)) developed by Syzdek et al., provide a relatively stable interface. It can be either solid (high molecular weight) and be applied in dry Li-polymer cells, or liquid (low molecular weight) and be applied in regular Li-ion cells.
Room temperature ionic liquids (RTILs)are another approach to limiting the flammability and volatility of organic electrolytes.