5 ms·

Something makes me suspect this article is missing part of the truth, similar to sites that claim we don't know how bees can fly (we do).

46Bit 14y ago
I agree. I've only high school electrochemistry to draw on, but questioning this sort of thing becomes much easier if we focus on the exact claim: * When reduced, ethylene carbonate forms a dense material that lithium cations can pass through but solvent molecules can't. * Propylene carbonate does not form this/similar material. * Using propylene carbonate therefore allows the solvent to come into contact with and weaken the graphite anode. * Nobody knows the chemical process that forms the material for ethylene carbonate but does not for propylene carbonate.
semenko 14y ago
Yeah, this piece is a little misleading. The author is referring to a nuanced difference between ethylene carbonate (EC) and propylene carbonate (PC) in the formation of a protective film around anodes. See this (paywalled) review of electrolyte chemistry: http://pubs.acs.org/doi/abs/10.1021/cr030203g http://pubs.acs.org/doi/abs/10.1021/cr030203g http://www.ncbi.nlm.nih.gov/pubmed/15669157 http://www.ncbi.nlm.nih.gov/pubmed/15669157 """ The unique position of EC as a lithium battery electrolyte was established in 1990 when Dahn and co-workers reported the fundamental difference between EC and PC in their effects on the reversibility of lithium ion intercalation/deintercalation with graphitic anodes.36 Despite the seemingly minute difference in molecular structure between the two, EC was found to form an effective protective film (SEI) on a graphitic anode that prevented any sustained electrolyte decomposition on the anode, while this protection could not be realized with PC and the graphene structure eventually disintegrated in a process termed “exfoliation” because of PC cointercalation. The reason for the effectiveness of the SEI has incited a lot of research interest in the past decade but remains an unsolved mystery, although it is generally believed that EC undergoes a reduction process on the carbonaceous anode via a similar path to that shown in Scheme 1. Because of the important role this SEI plays in lithium ion chemistry, the research efforts on this topic will be reviewed in a dedicated section (section 6). """
- runn1ng 14y ago
  So still, the main claim sort of stands - there are unsolved mysteries in every day's life, which we still don't understand fully, but that we use anyway. (I know nothing about electrochamistry or batteries :( )
- kragen 14y ago
  What do you think is misleading about the linked LJ post? The abstract you've quoted here seems to back up every word in it.
mossplix 14y ago
it took a while though ... http://www.livescience.com/528-scientists-finally-figure-bees-fly.html http://www.livescience.com/528-scientists-finally-figure-bee...
- JoeAltmaier 14y ago
  Now find the one explaining why when you sit around a campfire, the smoke always comes right at you?
  - dmd 14y ago
    Confirmation bias, selection bias.
  - sp332 14y ago
    Because you suck all the air out of the room.
  - InclinedPlane 14y ago
    Some people attribute this to confirmation bias (and there is a reply here doing just that) but it is a real phenomenon due to several causes. The simplest is the fact that if you consider all of the directions the wind might blow when you are standing next to a fire you are blocking the wind that would blow the wind directly away from you. This gives a slight bias toward the smoke being blown toward you when you stand near a fire. However, when you are standing "upwind" of the fire you don't simply block the wind, you create a recirculation zone of turbulent air in front of you. If you are close enough to a fire then this recirculation zone will be able to suck in the smoke from the fire, towards you. Additionally, the heat of a fire will create a convective flow, with air flowing upward (due to the heat) and being replaced from all sides laterally. So even if there is no wind there will still be a convective airflow which gives rise to that turbulent recirculation zone in between you and the fire. Thus you have a situation where only in the case where there is a wind blowing substantially sideways relative to the line between you and the fire will the smoke not be attracted to you if you are close enough to the fire. This can be avoided simply by standing far enough away from the fire to avoid these various effects.

46Bit 14y ago

I agree. I've only high school electrochemistry to draw on, but questioning this sort of thing becomes much easier if we focus on the exact claim: * When reduced, ethylene carbonate forms a dense material that lithium cations can pass through but solvent molecules can't. * Propylene carbonate does not form this/similar material. * Using propylene carbonate therefore allows the solvent to come into contact with and weaken the graphite anode. * Nobody knows the chemical process that forms the material for ethylene carbonate but does not for propylene carbonate.

semenko 14y ago

Yeah, this piece is a little misleading. The author is referring to a nuanced difference between ethylene carbonate (EC) and propylene carbonate (PC) in the formation of a protective film around anodes. See this (paywalled) review of electrolyte chemistry: http://pubs.acs.org/doi/abs/10.1021/cr030203g http://pubs.acs.org/doi/abs/10.1021/cr030203g http://www.ncbi.nlm.nih.gov/pubmed/15669157 http://www.ncbi.nlm.nih.gov/pubmed/15669157 """ The unique position of EC as a lithium battery electrolyte was established in 1990 when Dahn and co-workers reported the fundamental difference between EC and PC in their effects on the reversibility of lithium ion intercalation/deintercalation with graphitic anodes.36 Despite the seemingly minute difference in molecular structure between the two, EC was found to form an effective protective film (SEI) on a graphitic anode that prevented any sustained electrolyte decomposition on the anode, while this protection could not be realized with PC and the graphene structure eventually disintegrated in a process termed “exfoliation” because of PC cointercalation. The reason for the effectiveness of the SEI has incited a lot of research interest in the past decade but remains an unsolved mystery, although it is generally believed that EC undergoes a reduction process on the carbonaceous anode via a similar path to that shown in Scheme 1. Because of the important role this SEI plays in lithium ion chemistry, the research efforts on this topic will be reviewed in a dedicated section (section 6). """

runn1ng 14y ago
So still, the main claim sort of stands - there are unsolved mysteries in every day's life, which we still don't understand fully, but that we use anyway. (I know nothing about electrochamistry or batteries :( )
kragen 14y ago
What do you think is misleading about the linked LJ post? The abstract you've quoted here seems to back up every word in it.

mossplix 14y ago

it took a while though ... http://www.livescience.com/528-scientists-finally-figure-bees-fly.html http://www.livescience.com/528-scientists-finally-figure-bee...

JoeAltmaier 14y ago
Now find the one explaining why when you sit around a campfire, the smoke always comes right at you?
- dmd 14y ago
  Confirmation bias, selection bias.
- sp332 14y ago
  Because you suck all the air out of the room.
- InclinedPlane 14y ago
  Some people attribute this to confirmation bias (and there is a reply here doing just that) but it is a real phenomenon due to several causes. The simplest is the fact that if you consider all of the directions the wind might blow when you are standing next to a fire you are blocking the wind that would blow the wind directly away from you. This gives a slight bias toward the smoke being blown toward you when you stand near a fire. However, when you are standing "upwind" of the fire you don't simply block the wind, you create a recirculation zone of turbulent air in front of you. If you are close enough to a fire then this recirculation zone will be able to suck in the smoke from the fire, towards you. Additionally, the heat of a fire will create a convective flow, with air flowing upward (due to the heat) and being replaced from all sides laterally. So even if there is no wind there will still be a convective airflow which gives rise to that turbulent recirculation zone in between you and the fire. Thus you have a situation where only in the case where there is a wind blowing substantially sideways relative to the line between you and the fire will the smoke not be attracted to you if you are close enough to the fire. This can be avoided simply by standing far enough away from the fire to avoid these various effects.