Conditionally format openxlsx numbers stored as text - r

Question

I am trying to format a mixed class vector in an xlsx output using openxlsx.
The code produces the excel file desired, but the numeric values are stored as test, how do I go about conditionally formatting the numbers?
wb <- openxlsx::createWorkbook() # create workbook
openxlsx::addWorksheet(wb, sheetName = 'data') # add sheet
openxlsx::writeData(wb, sheet ='data',
x=df, xy=c(1, 1),withFilter = T) # write data on workbook
# convert square brackets to superscript in xlsx output
for(i in grep("\\_\\[([A-z0-9\\s]*)\\]", wb$sharedStrings)){
# if empty string in superscript notation, then just remove the superscript notation
if(grepl("\\_\\[\\]", wb$sharedStrings[[i]])){
wb$sharedStrings[[i]] <- gsub("\\_\\[\\]", "", wb$sharedStrings[[i]])
next # skip to next iteration
}
# insert additioanl formatting in shared string
wb$sharedStrings[[i]] <- gsub("<si>", "<si><r>", gsub("</si>", "</r></si>", wb$sharedStrings[[i]]))
# find the "_[...]" pattern, remove brackets and udnerline and enclose the text with superscript format
wb$sharedStrings[[i]] <- gsub("\\_\\[([A-z0-9\\s]*)\\]",
"</t></r><r><rPr><vertAlign val=\"superscript\"/></rPr><t xml:space=\"preserve\">\\1</t></r><r><t xml:space=\"preserve\">",
wb$sharedStrings[[i]])
}
# write excel file
openxlsx::saveWorkbook(wb, file="test.xlsx",
overwrite = TRUE)
The output has the error triangles saying "Number stored as Text".
I tried adding, but no luck.
openxlsx::writeData(wb, sheet = 'data', names(df)[i], startCol = i, startRow = 1)
icol <- df[[i]]
for(j in seq_along(icol)){
x <- icol[[j]]
openxlsx::writeData(wb, sheet = 'data', x, startCol = i, startRow = j + 1)
}
}