What happens inside a Mobile battery right before it explodes?

The first thing we need to understand is how exactly the lithium-ion battery in your phone works. The name gives us a hint — electricity is carried from one electrode to another using charged lithium ions.

Lithium-ion batteries store, transfer and release energy because of natural chemical reactions. The battery has two electrodes — an anode and a cathode. The cathode is connected to the positive (+) connection on the battery and holds positively charged ions, and the anode is connected to the negative (-) connection and holds (you guessed it) negatively charged ions.

Between the two electrodes is what's called an electrolyte. The electrolyte in a lithium battery is (usually) an organic solvent paste that has a very large number of metallic salts (in most cases, that metal is lithium) as part of its makeup. This makes it electrically conductive — electricity can pass through it. The anode and the cathode are in the electrolyte and separated by a physical barrier so they can't touch.

When you discharge the battery (when you're using your phone and not charging it) the cathode pushes its positively charged ions away and the negatively charged anode attracts them. Electricity flows out from the anode, through your device, then back to the cathode. Yes, electricity travels through a loop and isn't "used up" by the thing being powered. When you charge your phone, the reverse happens and ions travel from the cathode through the electrolyte to the anode.

Lithium is the perfect element for rechargeable batteries: It's lightweight, easy to recharge and holds a charge for a long time.

When these ions come in contact with the charged atoms in an electrode, an electrochemical reaction called oxidation-reduction (redox) frees the charged electrons to travel out through the battery contacts, which are connected to the electrodes. This continues to charge the lithium ions in the electrolyte until there aren't enough left that can hold a positive charge that's strong enough to move through the electrolyte paste, and your battery will no longer charge.

Lithium is the lightest metal — number three on the periodic table. It's also very excitable, making it easy to create a powerful chemical reaction. This makes it a near-perfect metal to use in a portable rechargeable battery. It's lightweight, easy to recharge and continues to hold a charge for a long time.

 From the fiery Note 7 debacles to exploding hoverboards, lithium-ion batteries aren't doing so hot lately. A new study helps to explain how these popular power sources can turn into safety hazards.

In the paper, published in the Journal of the Electrochemical Society, scientists at the Canadian Light Source (CLS) synchrotron looked inside an overworked battery. In this case, they drained a battery until its voltage was below a critical level.

Overcharging or overworking deforms the insides of a battery. (A) shows the inside of a battery before it was misused. (B) shows how misuse causes the original design defects to become even more warped. (C) highlights the areas where warping got worse.
Toby Bond, Canadian Light Source

When we overcharge or overheat lithium ion batteries, the materials inside start to break down and produce bubbles of oxygen, carbon dioxide, and other gasses. Pressure builds up, and the hot battery swells from a rectangle into a pillow shape. Sometimes the phone involved will operate afterward. Other times it will die. And occasionally—kapow!

To see what's happening inside the battery when it swells, the CLS team used an x-ray technique called computed tomography.

Inside the battery is an electrode that spirals out from a central point like a jellyroll. The x-ray scan revealed that the bubbles produced during overheating warped and dented this electrode.

Intriguingly, the study authors found that the worst deformation from the gas buildup occurred in areas that had slight defects before the battery was ever over-drained. The authors note that doing more studies like this, on a larger variety of batteries, would improve understanding of how these batteries respond to gas evolution, which could lead to better designs.

As New Scientist notes, it's not clear whether the Samsung Note 7 catastrophes included pillowing or this type of deformation.

[Journal of the Electrochemical Society via New Scientist]

 www.popsci.com.

Vacuum tube (old technology to make Electronics to get a whole lot faster without semiconductors )

Researchers are re purposing decades-old technology to build faster gadgets for the future, creating nano scale

Researchers are re purposing decades-old technology to build faster gadgets for the future, creating nano scale vacuum tubes that could dramatically improve the speed and efficiency of personal electronics and solar panels.

Vacuum tubes were originally used in the earliest digital electronic computers back in the 1930s and 1940s, before being replaced by transistors composed of semiconductors, which can can be manufactured much smaller, making today's computers, smartphones, and tablets possible.

that could dramatically improve the speed and efficiency of personal electronics and solar panels.

Vacuum tubes were originally used in the earliest digital electronic computers back in the 1930s and 1940s, before being replaced by transistors composed of semiconductors, which can can be manufactured much smaller, making today's computers, smartphones, and tablets possible.

But transistors have their limits in size and speed too, and we're getting closer than ever to reaching them. Now scientists from UC San Diego have gone back to the vacuum tube idea - and this time they've made them at tiny sizes and with far more efficient technology.

"This certainly won’t replace all semiconductor devices, but it may be the best approach for certain specialty applications, such as very high frequencies or high power devices," says lead researcher and electrical engineer, Dan Sievenpiper.

While transistors remain one of the most important inventions of the 20th century - and much smaller and more energy-efficient than the original vacuum tubes - scientists are now struggling to make them any tinier or more powerful than they already are.

What's more, electron flow through transistor semiconductor materials like silicon is slowed as electrons collide with atoms, and semiconductors also have what's called a band gap - where a boost of external energy is needed to get electrons moving.

The main advantage new nanoscale vacuum tubes have over semiconductor-based transistors is that they carry currents through air, rather than a solid material, and could be be much faster as a result.

 

The vacuum tube design (left), electric field enhancement (middle), and electric field distribution (right) of the new nanoscale structure. Credit: UC San Diego   

Freeing up electrons to carry currents through the air normally takes a large voltage or a powerful laser, both of which are difficult to do at the nanoscale, and which hampered the progress of early vacuum tubes.

To solve this problem, the team created a layer of special mushroom-style structures made of gold - known as an electromagnetic metasurface - and placed it on top of a layer of silicon dioxide and a silicon wafer.

When a low-powered voltage (less than 10 volts) and a low-powered laser are applied to this metasurface, it creates 'hot spots' with high-intensity electric fields, giving the structure enough energy to free the electrons from the metal.

In testing, this enabled the researchers to achieve a 1,000 percent (or 10-fold) increase in conductivity compared with nanoscale vacuum tubes without the metasurface. 

Right now, it's just a proof-of-concept demonstration, and there's a lot more work to be done to make the system practical for use in actual devices. But in the future, different metasurfaces could be designed to meet specific needs, such as new kinds of solar panels, the researchers suggest.

"Next we need to understand how far these devices can be scaled and the limits of their performance," says Sievenpiper.

Here's the team explaining their findings: Thanks: fossbytes.com and sciencealert.com

 

Electronics References Sheet

Electronics is more than just schematics and circuits. By using various components, such as resistors and capacitors, electronics allows you to bend electric current to your will to create an infinite variety of gizmos and gadgets. In exploring electronics, use this handy reference for working with Ohm’s, Joule’s, and Kirchhoff’s Laws; making important calculations; determining the values of resistors and capacitors according to the codes that appear on their casings; and using a 555 timer and other integrated circuits (ICs).

Important Formulas in Electronics

With just a handful of basic mathematical formulas, you can get pretty far in analyzing the goings-on in electronic circuits and in choosing values for electronic components in circuits you design.

Ohm’s Law and Joule’s Law

Ohm’s Law and Joule’s Law are commonly used in calculations dealing with electronic circuits. These laws are straightforward, but when you’re trying to solve for one variable or another, it is easy to get them confused. The following table presents some common calculations using Ohm’s Law and Joule’s Law. In these calculations:
V = voltage (in volts)
I = current (in amps)
R = resistance (in ohms)
P = power (in watts)

Unknown Value	Formula
Voltage	V = I x R
Current	I = V/R
Resistance	R = V/I
Power	P = V x I or P = V2/R or P = I2R

Equivalent resistance and capacitance formulas

Electronic circuits may contain resistors or capacitors in series, parallel, or a combination. You can determine the equivalent value of resistance or capacitance using the following formulas:
Resistors in series:

Resistors in parallel:

or

Capacitors in series:

or

Capacitors in parallel:

Kirchhoff’s Current and Voltage Laws

Kirchhoff’s Circuit Laws are commonly used to analyze what’s going on in a closed loop circuit. Based on the principle of conservation of energy, Kirchhoff’s Current Law (KCL) states that, at any node (junction) in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node, and Kirchhoff’s Voltage Law (KVL) states that the sum of all voltage drops around a circuit loop equals zero.
For the circuit shown, Kirchhoff’s Laws tells you the following:
KCL: I = I₁ + I₂
KVL: V_battery – V_R – V_LED = 0, or V_battery = V_R + V_LED

Calculating the RC time constant

In a resistor-capacitor (RC) circuit, it takes a certain amount of time for the capacitor to charge up to the supply voltage, and then, once fully charged, to discharge down to 0 volts.

Circuit designers use RC networks to produce simple timers and oscillators because the charge time is predictable and depends on the values of the resistor and the capacitor. If you multiply R (in ohms) by C (in farads), you get what is known as the RC time constant of your RC circuit, symbolized by T:

A capacitor charges and discharges almost completely after five times its RC time constant, or 5RC. After the equivalent of one time constant has passed, a discharged capacitor will charge to roughly two-thirds its capacity, and a charged capacitor will discharge nearly two-thirds of the way.

Electronics: Reading Resistor and Capacitor Codes

Electronics can sometimes be difficult to decipher. By decoding the colorful stripes sported by many resistors and the alphanumeric markings that appear on certain types of capacitors, you can determine the nominal value and tolerance of the specific component.

Resistor color codes

Many resistor casings contain color bands that represent the nominal resistance value and tolerance of the resistor. You translate the color and position of each band into digits, multipliers, and percentages.

The table that follows outlines the meaning of the resistor color bands.

Color	1st Digit	2nd Digit	Multiplier	Tolerance
Black	0	0	x1	±20%
Brown	1	1	x10	±1%
Red	2	2	x100	±2%
Orange	3	3	x1,000	±3%
Yellow	4	4	x10,000	±4%
Green	5	5	x100,000	n/a
Blue	6	6	x1,000,000	n/a
Violet	7	7	x10,000,000	n/a
Gray	8	8	x100,000,000	n/a
White	9	9	n/a	n/a
Gold	n/a	n/a	x0.1	±5%
Silver	n/a	n/a	x0.01	±10%

Capacitor value reference

In electronic circuits, the value of a capacitor can be determined by a two- or three-digit code that appears on its casing. The following table outlines values for some common capacitors.

Marking	Value
nn (a number from 01 to 99) or nn0	nn picofarads (pF)
101	100 pF
102	0.001 µF
103	0.01 µF
104	0.1 µF
221	220 pF
222	0.0022 µF
223	0.022 µF
224	0.22 µF
331	330 pF
332	0.0033 µF
333	0.033 µF
334	0.33 µF
471	470 pF
472	0.0047 µF
473	0.047 µF
474	0.47 µF

Capacitor tolerance codes

In electronic circuits, the tolerance of capacitors can be determined by a code that appears on the casing. The code is a letter that often follows a three-digit number, for instance, the Z in 130Z. The following table outlines common tolerance values for capacitors. Note that the letters B, C, and D represent tolerances in absolute capacitance values, rather than percentages. These three letters are used on only very small (pF range) capacitors.

Code	Tolerance
B	± 0.1 pF
C	± 0.25 pF
D	± 0.5 pF
F	± 1%
G	± 2%
J	± 5%
K	± 10%
M	± 20%
Z	+80%, –20%

Electronics: Integrated Circuit (IC) Pinouts

The pins on an IC chip provide connections to the tiny integrated circuits inside of your electronics. To determine which pin is which, you look down on the top of the IC for the clocking mark, which is usually a small notch in the packaging but might instead be a little dimple or a white or colored stripe. By convention, the pins on an IC are numbered counterclockwise, starting with the upper-left pin closest to the clocking mark. So, for example, with the clocking notch orienting the chip at the 12 o’clock position, the pins of a 14-pin IC are numbered 1 through 7 down the left side and 8 through 14 up the right side.

Electronics: 555 Timer as an Astable Multivibrator

The 555 can behave as an astable multivibrator, or oscillator. By connecting components to the chip in your electronics, you can configure the 555 to produce a continuous series of voltage pulses that automatically alternate between low (0 volts) and high (the positive supply voltage, V_CC).

You can calculate the low and high timing intervals using the formulas that follow: