Positive Electrode Plate Coating for Manganese Dissolution Control

The patent employs a composite conductive undercoat layer comprising multiple components including conductive polymers (such as polyaniline, polythiophene, or their derivatives), carbon materials (such as carbon black, carbon nanotubes, or graphene), and binding agents. This composite structure provides both electrical conductivity and mechanical adhesion functionality, resolving the contradiction by integrating multiple functions into a single layered component rather than requiring separate systems.

The conductive undercoat layer serves as an intermediary between the positive electrode active material (lithium manganese phosphate) and the current collector (aluminum foil). It mediates the interface by providing electrical conductivity where the active material itself is insufficiently conductive, while also providing mechanical adhesion to prevent delamination during cycling. This intermediary layer resolves the contradiction by creating a functional buffer zone that addresses both electrical and mechanical requirements.

The patent specifies precise compositional parameters for the doping elements at manganese and phosphorus sites, with defined concentration ranges (e.g., 0.01-0.5 mol ratio for manganese-site dopants, 0.01-0.3 mol ratio for phosphorus-site dopants). By establishing these quantitative parameter ranges, the patent transforms the manufacturing challenge into a controllable parameter optimization problem, where precision is defined in terms of measurable compositional variables rather than qualitative descriptions.

The doping strategy applies different elements at different crystallographic sites within the lithium manganese phosphate structure - specifically at manganese sites (octahedral positions) and phosphorus sites (tetrahedral positions). This local quality approach targets the specific locations where doping provides maximum benefit for reducing manganese dissolution and enhancing structural stability, rather than uniform doping throughout the material.

The patent employs a multi-layer composite coating structure where each layer is composed of specific materials designed to address different aspects of interfacial stability. The layers include phosphate-based coatings (such as Li3PO4 or AlPO4), pyrophosphate coatings (such as Li2SiO3 or Li2GeO3), and carbon coatings. Each material in the composite structure provides specific functionality - phosphate layers for chemical stability, pyrophosphate layers for structural protection, and carbon layers for electrical conductivity and additional barrier properties.

The coating structure is segmented into multiple distinct layers rather than applying a single thick coating. This segmentation allows each layer to be optimized for its specific function and provides a gradient transition from the active material core to the external environment. The segmented structure also facilitates controlled application processes where each layer can be deposited and cured independently, managing the complexity through staged manufacturing.

The patent implements protective measures beforehand by applying the multi-layer coating structure (phosphate, pyrophosphate, and carbon layers) and conducting element doping before the battery undergoes deep charging and discharging cycles. These pre-applied protective layers act as cushioning barriers that prevent manganese dissolution during subsequent high-power operation, allowing the battery to achieve high power output without suffering from the typical manganese dissolution problems associated with deep cycling.

The protective system uses composite materials combining phosphate-based coatings, pyrophosphate-based coatings, and carbon materials. This composite approach provides multiple mechanisms of protection simultaneously - chemical stability from phosphate, structural integrity from pyrophosphate, and conductive protection from carbon - enabling the battery to withstand deep charging and discharging conditions that would otherwise cause significant manganese dissolution.