15 Energy Applications I Batteries Battery types Primary

15. Energy Applications I: Batteries

Battery types: Primary Battery: Non reversible chemical reactions (no recharge) Secondary Battery: Rechargeable Common characteristics Electrode complex coposite of powders of active material and conductive diluent, polymer matrix to bind the mix typically 30% porosity, with complex surface throughout the material allows current production to be uniform in the structure Current distribution primary – cell geometry secondary – production sites within the porous electrode parameters affecting the secondarycurrent distribution are conductivity of diluent (matrix) electrolyte conductivity, exchange current diffusion characteristics of reactants and products total current flow porosity, pore size, and tortuosisity What are Batteries, Fuel Cells, and Supercapacitors, Chem Rev, 2004, 104, 4245, Martin Winter and Ralph J. Brodd

We will briefly look at: Lead and Lithium insertion What are Batteries, Fuel Cells, and Supercapacitors, Chem Rev, 2004, 104, 4245, Martin Winter and Ralph J. Brodd

What are Batteries, Fuel Cells, and Supercapacitors, Chem Rev, 2004, 104, 4245, Martin Winter and Ralph J. Brodd

Require very good conductivity Throughout the system Which tends to lower the energy Content of the system In the lead acid system a significant amount Of the weight Is in the grids required To hold the paste What are Batteries, Fuel Cells, and Supercapacitors, Chem Rev, 2004, 104, 4245, Martin Winter and Ralph J. Brodd

Equivalent Circuit for a Battery External Resistance, Rext Terminals, Resistance To current flow of, RM Capacitance of electrode Internal Discharge Rate (e. t. ) Resistance of electrolyte

Basic requirements for a battery 1. chemical energy stored near the electrode ( if too far away current will be controlled by time to get to electrode) 2. The chemical form coating the electrode must allow ion transport, or better yet, electronic conduction 3. The chemical form of the energy must be mechanically robust 4. The chemical form of the energy should generate a large voltage ad Acid Battery

The capacity of the battery depends on The type of material present. Fitch lead book Support grids

One possible mechanism: . simultaneous dissolution of Pb. O 2 and introduction of 2 e Requires electronic conductivity of Pb. O 2 and pore space for motion of wat 1. 2. 3. 4. 5. 6. 7. Add e, H+ and OH- to Pb. O 2 Add 2 nd e to reduce valence of Pb Add 3 rd e to reduce valence while r Pb. O is more soluble than Pb. O 2 so Initiate formation of Pb. SO 4, nuclea Pb. SO 4 structure is rhombic which Therefore need to control the alletr

Beta Pb. O 2 is formed under acid and can be compressed to shorten bonds overlap induces semiconductor behavior which increases the performance Of the battery Add antiomony To drive reaction To beta phase Alpha forms when Pb metal Corrodes – reduces lifetime of Battery, is more compressible.

Lead Acid battery a. What is the potential associated with a lead acid battery with the overall reaction: at the following concentration: [H 2 SO 4] = 4. 5 M

Vo 1. 69 -0. 35 1. 69 -(-0. 35) 2. 04

Lead Acid battery energy

c. What is the free energy associated with the lead acid battery?

Dendrites are Good: porous (makes more Of possible energy available) Bad: fragile, break and fall from underlying electrode = NO CURRENT e No e

The type of structure that forms depends upon the rate of crystallization which Depends upon rate of reaction which depends upon: Loss/production of products (current) Which depends also upon the rate constant (potential dependent)

One way to “image” the various processes described above is by an Equivalent Circuit

In a simplified system As the battery is discharged the discharge voltage is the Difference between what we started with and the remaining Voltage in the battery

Lead acid batteries can be valve regulated to control the pressure associated With No pressure 1. 29 V 1. 38 V Suggests higher Degree of interparticle Contact under pressure Lower CT resistance Under pressure pressurized

Insulating layer which can conduct only protons and lead Solubility Diffusion Et at conducting Pb. O 2

Solubility Diffusion Et at conducting Pb. O 2 Modeled effect of diffusion

Solubility Diffusion Et at conducting Pb. O 2 Modeled effect of proton conc

Solubility Diffusion Et at conducting Pb. O 2 Different magnitude of discharge Changes the solubility and proton conc As well as the conductivity of the film

Based on V. S. Bagotsky text, Fundamentals of Electrochemistry

For the simplified model

Monitor structural changes at electrode as a function of the discharge power

Charge transfer resistance Decreases due formation of more porous Pb. O 2 High charge transfer Resistance due to insulating Pb. SO 4 layer Increasing Charge transfer Resistance due To layer of Pb. SO 4 Small diameter Of impedance Circle here indic The fast et kine O 2 reaction.

Reaction Li++e K+ + e Na+ + e NCl 3_4 H+ + 6 e 2 H 2 O + 2 e Fe 2+ + 2 e Pb 2+ + 2 e 2 H+ + 2 e N 2(g) + 8 H+ + 6 e Cu 2+ + 2 e O 2 + 2 H 2 O + 4 e O 2 + 2 H+ + 2 e Ag+ + e NO 3 - + 4 H+ + 3 e Br 2 + 2 e 2 NO 3 - + 12 H+ + 10 e Cl 2 + 2 e Au+ + e F 2 + 2 e Li K Na 3 Cl- + NH 4+ H 2 + 2 OHFe Pb H 2(gas) 2 NH 4+ Cu 4 OHH 2 O 2 Ag NO(g) +2 H 2 O 2 Br. N 2(g) +6 H 2 O 2 Cl. Au 2 F- Vo -3. 0 -2. 95 -2. 71 -1. 37 -0. 828 -0. 44 -0. 13 0 0. 275 0. 34 0. 40 0. 68 0. 799 0. 957 1. 09 1. 246 1. 36 1. 83 2. 87 7 g/mol 207 g/mol

Lithium oxidation proceeds a little too uncontrollably Lithium reduction does not result in good attachment back to the lithium metal Forms dendrites which can grow to Short circuit Lithium intercalated in graphite is close to metallic, formal potential differs by only 0. 1 to. 3 V = -2. 7 to -2. 9 V

Anode – Solid electroactive metal salt (Can change overall charge so that it can electrostatically stabilize & localize Li+ Potential should be very positive (far from -2. 5 V for Li/C reaction Solid should conduct charge throughout Solid should allow ion motion Should have fast kinetics (open and porous) Should be stable (does not convert to alleotropes) Low cost Environmentally benign M. Stanley Whittingham, Lithium Batteries and Cathode Materials, Chem. Rev. 2004, 104, 4271 -4301

Group III Spinels M. Stanley Whittingham, Lithium Batteries and Cathode Materials, Chem. Rev. 2004, 104, 4271 -4301

Smooth galvanostatic curve indicates That there are no sites nucleating Alleotropes of the compound. Single phase Went to market Allotropes would alter the structure, Light weight In the late 1970 s Porosity, and the ease of intercalation, Conducting, but not Potential, and conductivity Reactive (oxidised or reduced) Li ion intercalates in response to double layer charging M. Stanley Whittingham, Lithium Batteries and Cathode Materials, Chem. Rev. 2004, 104, 4271 -4301

Indicates various crystal forms octahedral Lithium ion inserts in response To reduction of vanadium 2 nd is tetrahedral Different phases of VSe 2 have similar structures So the distortion is not great M. Stanley Whittingham, Lithium Batteries and Cathode Materials, Chem. Rev. 2004, 104, 4271 -4301

Group II M. Stanley Whittingham, Lithium Batteries and Cathode Materials, Chem. Rev. 2004, 104, 4271 -4301

Major phase changes in Lix. V 2 O 5 (x<0. 01) is well ordered Є ( 0. 35<x<0. 7)is more puckered (x=1) shifting of layers (x>1) results in permanent structural change ω (x>>1) is a rock salt form

Sol gel processes of the V 2 O 5 materials

Group III Spinels These materials have a major change in Unit cell dimensions when Mn changes Oxidation state (see B). Need to keep the Lattice parameter less than 8. 23 A for good Cycling, which 1. Keeps Mn in higher oxidation state, therefore less soluble 2. Prevents distortion in the coordination of oxygen (Jahn-Teller) around the manganese. These distortions will alter the oxidation and reduction potential as seen in the next slide M. Stanley Whittingham, Lithium Batteries and Cathode Materials, Chem. Rev. 2004, 104, 4271 -4301

M. Stanley Whittingham, Lithium Batteries and Cathode Materials, Chem. Rev. 2004, 104, 4271 -4301