Using MAPI to retrieve materials' voltages

Hi all!
I was wondering whether the MP API also supports access to battery-related entities like electrodes’ voltages.
Querying with a simple

with MPRester(key) as mpr:
    query = mpr.query(criteria, ['average_voltage'])

does not appear to retrieve any voltage value. Am I simply fetching a wrong string or is the battery analysis tool not available through API?

Hi @acarnevali, the electrodes data is indeed accessible via the API. I would suggest using the new client to get the latest data release. See Materials Project - API.

You can search the data using:

from mp_api import MPRester

with MPRester(key) as mpr:
    docs = mpr.insertion_electrodes.search_electrode_docs(...)

Thank you for your help! Currently though I am getting the following error:

MPRestError: REST query returned with error status code 401 on URL with message:
Response {
  "message":"Invalid authentication credentials"

is there any further authentication required to access these data?
Moreover, in the API docs the “See the InsertionElectrodeDoc schema for a full list of fields returned by this route.” voice is not linked to any insertion electrodes documentation. Where can I find that?
Lastly, I see that this method is limited to 1000 entries per query: how can one retrieve all the data present in the DB?

Edit: the same happens after generating a new API key associated to my account

Hi @acarnevali,

You will need an API key from the new website. Make sure you are using the one from here: Materials Project - Dashboard

There are a couple of ways to see the available fields. One is to print the available_fields property:


The second is to consult the document schema which can be found here: Materials Project API - ReDoc

Specifically, you can look at the fields to project, or you can take a look at the sample data response on the right. If reading code is easier for you, you can also directly take a look at the data model here:

When using the search method, it will by default retrieve all available data in the DB matching a query in 1000 document chunks. This should happen automatically, and will only return less documents if num_chunks is set to a number.

– Jason

Hello Munrojm,
I have tried to retrieve electrodes data with different working ions. I keep getting errors, please you assist me over come this error.
This is the code i used

from mp_api import MPRester
battery_list2 = pd.DataFrame()
with MPRester(“11111111111111111111111”) as mpr:
battery_list = mpr.insertion_electrodes.search_electrode_docs(“Li”, all_fields=True)
battery_list2 = battery_list2.append(battery_list, ignore_index=True)

@mukhtar, can you post the errors you are getting?

This is the error I get. Thank you for your prompt reply.

ValidationError Traceback (most recent call last)
2 battery_list2 = pd.DataFrame()
3 with MPRester(“11111111111111111111111”) as mpr:
----> 4 battery_list = mpr.insertion_electrodes.search_electrode_docs(“Li”, all_fields=True)
5 battery_list2 = battery_list2.append(battery_list, ignore_index=True)
6 battery_list2.head()

~\AppData\Roaming\Python\Python37\site-packages\mp_api\routes\electrodes\ in search_electrode_docs(self, working_ion, formula,
elements, exclude_elements, max_delta_volume, average_voltage, capacity_grav, capacity_vol, energy_grav, energy_vol, fracA_charge,
fracA_discharge, stability_charge, stability_discharge, num_steps, max_voltage_step, sort_fields, num_chunks, chunk_size, all_fields, fields)
109 }
→ 111 return super().search(**query_params)

~\AppData\Roaming\Python\Python37\site-packages\mp_api\core\ in search(self, num_chunks, chunk_size, all_fields, fields, **kwargs)
436 fields=fields,
437 chunk_size=chunk_size,
→ 438 num_chunks=num_chunks,
439 )

~\AppData\Roaming\Python\Python37\site-packages\mp_api\core\ in _get_all_documents(self, query_params, all_fields, fields, chunk_size, num_chunks)
459 query_params[“limit”] = chunk_size
→ 461 results = self._query_resource(query_params, fields=fields,)
463 # if we have all the results in a single page, return directly

~\AppData\Roaming\Python\Python37\site-packages\mp_api\core\ in _query_resource(self, criteria, fields, suburl, use_document_model)
281 # the client does not handle this in a particularly smart way currently
282 if self.document_model and use_document_model:
→ 283 data[“data”] = [self.document_model.parse_obj(d) for d in data[“data”]] # type: ignore
285 return data

~\AppData\Roaming\Python\Python37\site-packages\mp_api\core\ in (.0)
281 # the client does not handle this in a particularly smart way currently
282 if self.document_model and use_document_model:
→ 283 data[“data”] = [self.document_model.parse_obj(d) for d in data[“data”]] # type: ignore
285 return data

~\SoftwaresInstalled\Anaconda\envs\tf1\lib\site-packages\pydantic\main.cp37-win_amd64.pyd in pydantic.main.BaseModel.parse_obj()

~\SoftwaresInstalled\Anaconda\envs\tf1\lib\site-packages\pydantic\main.cp37-win_amd64.pyd in pydantic.main.BaseModel.init()

ValidationError: 1 validation error for InsertionElectrodeDoc
value is not a valid dict (type=type_error.dict)

@mukhtar, it looks like you might have an older version of the API client. Try updating with pip install mp_api --upgrade and re-running.

– Jason

@munrojm , i have updated it now, it still gives the same error.

Please update emmet-core with pip install emmet-core --upgrade.

If you still are getting an error, please post the versions of mp-api and emmet-core you are using.

– Jason

this are the versions.
emmet-core in /usr/local/lib/python3.7/dist-packages (0.21.3)
mp_api in /usr/local/lib/python3.7/dist-packages (0.18.0)

I still face the same error.


Please try updating to emmet-core v0.21.20 and mp-api v0.20.6.

– Jason

Thank you very much Jason. But there is no mp_api v0.20.6 version available
pip install mp_api==0.20.6 ERROR: Could not find a version that satisfies the requirement mp_api==0.20.6 (from versions: 0.2.1, 0.2.2, 0.2.3, 0.3.0, 0.4.0, 0.4.1, 0.5.0, 0.5.1, 0.6.0, 0.6.1, 0.7.0, 0.7.1, 0.8.0, 0.9.0, 0.9.1, 0.10.0, 0.10.1, 0.10.2, 0.11.0, 0.11.1, 0.11.2, 0.11.3, 0.11.4, 0.12.0, 0.12.1, 0.12.2, 0.13.0, 0.14.0, 0.14.1, 0.15.0, 0.15.1, 0.16.0, 0.16.1, 0.16.2, 0.16.3, 0.16.4, 0.16.5, 0.17.0, 0.18.0)

You will need to update your python version.

– Jason

Hello Mr.munrojm,

I tried to take the voltage profile after DFT calculation for MgxCr2O4 by Pymatgen,
Can you show me any code for calculation and take the plot as samilar with bellow figure,
Hình 1

Thank so much for helping!

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