Issue 983 half cell

[brosaplanella]

Description

Basic DFN model for a half-cell. This is an experimental functionality which doesn't support all PyBaMM features (e.g. experiments) and which will be integrated into the submodel structure in the future.

Fixes #983

Type of change

Please add a line in the relevant section of CHANGELOG.md to document the change (include PR #) - note reverse order of PR #s. If necessary, also add to the list of breaking changes.

• New feature (non-breaking change which adds functionality)

Key checklist:

• No style issues: $ flake8
• All tests pass: $ python run-tests.py --unit
• The documentation builds: $ cd docs and then $ make clean; make html

You can run all three at once, using $ python run-tests.py --quick.

Further checks:

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[codecov]

Codecov Report

Merging #1121 into develop will increase coverage by 0.02%.
The diff coverage is 99.48%.

@@             Coverage Diff             @@
##           develop    #1121      +/-   ##
===========================================
+ Coverage    97.87%   97.90%   +0.02%     
===========================================
  Files          245      246       +1     
  Lines        13382    13572     +190     
===========================================
+ Hits         13098    13287     +189     
- Misses         284      285       +1     

Impacted Files	Coverage Δ
...m/models/full_battery_models/base_battery_model.py	99.65% <ø> (ø)
..._battery_models/lithium_ion/basic_dfn_half_cell.py	99.20% <99.20%> (ø)
pybamm/expression_tree/binary_operators.py	95.51% <100.00%> (+0.27%)	⬆️
...mm/expression_tree/operations/convert_to_casadi.py	95.09% <100.00%> (+0.30%)	⬆️
pybamm/expression_tree/symbol.py	97.46% <100.00%> (+0.01%)	⬆️
pybamm/expression_tree/unary_operators.py	100.00% <100.00%> (ø)
...models/full_battery_models/lithium_ion/__init__.py	100.00% <100.00%> (ø)
pybamm/simulation.py	96.80% <100.00%> (+0.02%)	⬆️
pybamm/solvers/base_solver.py	100.00% <100.00%> (ø)

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[valentinsulzer]

Thanks @ferranbrosa , the model looks good. There should be a test that the half-cell DFN can be solved (without Simulation)

[TomTranter]

Hi Ferran, I've run the code and checked the plots for positive and negative and seems fine. I think as this is a work in progress we should merge - it would be nice to have this fully integrated into the modelling framework so we can add thermal models etc and look at changes in entropy on the half cells. I think actually a lot of microstructure models are just done on half cells so it would be a really useful feature and we should think about how to do it by just flexibly specifying what each electrode is. I don't know if that would cause too many headaches

[valentinsulzer]

Looks good to me once the tests are fixed!