John Wang

Bio: John Wang is an academic researcher from HRL Laboratories. The author has contributed to research in topics: Battery (electricity) & Lithium. The author has an hindex of 21, co-authored 45 publications receiving 8302 citations. Previous affiliations of John Wang include University of California, Los Angeles & Amazon.com.

Methods and systems for improved battery performance

Abstract: Systems, methods, and computer-readable media are disclosed for improved battery performance. The systems, methods, and computer-readable media described herein may improve user experiences and prolong the battery's life. In an example method described herein, a battery may be placed within a clamp or housing that applies configurable pressure to the battery. In turn, the applied pressure may counter the swelling pressure of the battery and improve the battery's power output, reduce the internal resistance or impedance, and improve the life cycle of the battery.

Thermomagnetic temperature sensing

Abstract: A thermomagnetic sensor includes a thermomagnetic probe that includes a ferromagnetic material having a temperature-dependent magnetic permeability characterized by a maximum magnetic permeability value at a temperature below a Curie temperature of the ferromagnetic material. The thermomagnetic sensor further includes an alternating magnetic field source to produce an alternating magnetic field in a vicinity of the thermomagnetic probe to facilitate a measurement of the temperature-dependent magnetic permeability as function of temperature remotely using a thermomagnetic effect. A predetermined relationship between the temperature-dependent magnetic permeability and temperature in a range between the maximum magnetic permeability value and the Curie temperature provides a measurement of a temperature local to the thermomagnetic probe. A battery-temperature measurement system includes the thermomagnetic probe in a battery, a magnetic field coil to apply the alternating magnetic field, and a magnetic permeability measurement apparatus to measure the temperature-dependent magnetic permeability.

Batteries with replenishable storage capacities

Abstract: This invention provides batteries with improved calendar and cycle lifetimes. A rechargeable battery comprises an additional electrode that includes active ions, such as lithium ions. Cell capacity of the battery can be increased by supplying these active ions to the anode or the cathode. In some variations, this invention provides a lithium-ion battery comprising an anode, a cathode, an electrolyte, and an additional lithium-containing electrode, wherein the additional lithium-containing electrode is capable of supplying lithium ions to the anode or the cathode in the presence of an electrical current.

Method for operation of device using battery state of health

Abstract: A system and method for operating a portable electronic device are presented. The device includes a battery and a controller. The controller is configured to execute instructions for determining a first resistance value for the battery during a first power cycle of the battery, and determining a second resistance value for the battery during a second power cycle of the battery. The second power cycle is after the first power cycle. The controller is configured to execute instructions for determining that a first difference equal to the first resistance value subtracted from the second resistance value is less than a first predetermined threshold value, and electrically isolating the battery. In an embodiment, the first resistance value and the second resistance values are determined at the same state of charge for the battery.

Methods for online estimation of battery capacity and state of health

Abstract: In some variations, a method of real-time monitoring of battery capacity comprises correlating electrode open-circuit voltage with electrode state of charge for a selected electrode; compiling a look-up table to correlate the electrode open-circuit voltage with the electrode capacity at different values of the active-material capacity; during real-time operation, identifying first and second times at which battery terminal voltages are approximated as battery open-circuit voltages; and calculating battery capacity based on the difference in battery open-circuit voltages at the first and second times, current integration, and the look-up table. No reference electrode is needed, and a complete battery charge/discharge is not necessary to determine the capacity. This technique can therefore be implemented on-board and in real time to provide reliable capacity estimation even as the battery ages. The methods are applicable to various metal-ion secondary battery systems, including lithium-ion batteries, with different material chemistries.

Two‐Dimensional Nanocrystals Produced by Exfoliation of Ti 3 AlC 2

Abstract: Currently, however, there are relatively few such atomically layered solids. [ 2–5 ] Here, we report on 2D nanosheets, composed of a few Ti 3 C 2 layers and conical scrolls, produced by the room temperature exfoliation of Ti 3 AlC 2 in hydrofl uoric acid. The large elastic moduli predicted by ab initio simulation, and the possibility of varying their surface chemistries (herein they are terminated by hydroxyl and/or fl uorine groups) render these nanosheets attractive as polymer composite fi llers. Theory also predicts that their bandgap can be tuned by varying their surface terminations. The good conductivity and ductility of the treated powders suggest uses in Li-ion batteries, pseudocapacitors, and other electronic applications. Since Ti 3 AlC 2 is a member of a 60 + group of layered ternary carbides and nitrides known as the MAX phases, this discovery opens a door to the synthesis of a large number of other 2D crystals. Arguably the most studied freestanding 2D material is graphene, which was produced by mechanical exfoliation into single-layers in 2004. [ 1 ] Some other layered materials, such as hexagonal BN, [ 2 ] transition metal oxides, and hydroxides, [ 4 ] as well as clays, [ 3 ] have also been exfoliated into 2D sheets. Interestingly, exfoliated MoS 2 single layers were reported as early as in 1986. [ 5 ] Graphene is fi nding its way to applications ranging from supercapacitor electrodes [ 6 ] to reinforcement in composites. [ 7 ] Although graphene has attracted more attention than all other 2D materials combined, its simple chemistry and the weak van der Waals bonding between layers in multilayer structures limit its use. Complex, layered structures that contain more than one element may offer new properties because they

Interface engineering of highly efficient perovskite solar cells

Abstract: Advancing perovskite solar cell technologies toward their theoretical power conversion efficiency (PCE) requires delicate control over the carrier dynamics throughout the entire device. By controlling the formation of the perovskite layer and careful choices of other materials, we suppressed carrier recombination in the absorber, facilitated carrier injection into the carrier transport layers, and maintained good carrier extraction at the electrodes. When measured via reverse bias scan, cell PCE is typically boosted to 16.6% on average, with the highest efficiency of ~19.3% in a planar geometry without antireflective coating. The fabrication of our perovskite solar cells was conducted in air and from solution at low temperatures, which should simplify manufacturing of large-area perovskite devices that are inexpensive and perform at high levels.

Carbon-based Supercapacitors Produced by Activation of Graphene

Abstract: Supercapacitors, also called ultracapacitors or electrochemical capacitors, store electrical charge on high-surface-area conducting materials. Their widespread use is limited by their low energy storage density and relatively high effective series resistance. Using chemical activation of exfoliated graphite oxide, we synthesized a porous carbon with a Brunauer-Emmett-Teller surface area of up to 3100 square meters per gram, a high electrical conductivity, and a low oxygen and hydrogen content. This sp 2 -bonded carbon has a continuous three-dimensional network of highly curved, atom-thick walls that form primarily 0.6- to 5-nanometer-width pores. Two-electrode supercapacitor cells constructed with this carbon yielded high values of gravimetric capacitance and energy density with organic and ionic liquid electrolytes. The processes used to make this carbon are readily scalable to industrial levels.

Advanced Materials for Energy Storage

Abstract: [Liu, Chang; Li, Feng; Ma, Lai-Peng; Cheng, Hui-Ming] Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, Shenyang 110016, Peoples R China.;Cheng, HM (reprint author), Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, 72 Wenhua Rd, Shenyang 110016, Peoples R China;cheng@imr.ac.cn