Birnessite Manganese Dioxide Cathode with Bismuth Stabilization
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Solution Overview
Problem
Manganese dioxide-based primary batteries are not easily convertible to rechargeable secondary cells due to their crystal structure and side reactions, leading to limited cycle life and capacity loss, and existing attempts at rechargeable alkaline batteries have not achieved widespread adoption due to rapid depth of discharge and high carbon content requirements that are economically and practically impractical.
Innovation Solution
A secondary alkaline battery using a mixed cathode material comprising birnessite-phase manganese dioxide, a bismuth compound, and a copper compound, with optional conductive carbon and binder, allowing for galvanostatic cycling and achieving high energy density and long cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If manganese dioxide is used as cathode material for rechargeable alkaline batteries, then the theoretical capacity can reach 617mAh/g based on two-electron redox reaction, but the crystal structure undergoes stressful phase transformations and chemical reactions that lead to breakdown and loss of rechargeable material
Solution Approach 1:
The patent uses a composite cathode material consisting of birnessite-phase manganese dioxide combined with bismuth and lead compounds. This composite structure allows the MnO2 to achieve high theoretical capacity (617mAh/g) while the bismuth and lead components stabilize the crystal structure during charge-discharge cycling, preventing breakdown and maintaining reliability over thousands of cycles.
Solution Approach 2:
The patent incorporates bismuth and lead specifically at certain locations within the cathode structure to stabilize the manganese dioxide crystal lattice. These dopants are positioned to control lattice dilations and prevent phase transformations that would otherwise lead to material breakdown, allowing local structural reinforcement without compromising overall capacity.
2Reliability
If bismuth and lead are incorporated into manganese dioxide crystal structure to control lattice dilations, then rechargeability characteristics are improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent combines the synthesis of birnessite-phase manganese dioxide with the incorporation of bismuth and lead into a single integrated process. By merging the phase formation and dopant incorporation steps, the patent achieves complex compositional control without requiring separate manufacturing operations, thereby maintaining ease of manufacture while achieving reliable rechargeability.
Solution Approach 2:
The patent utilizes parameter changes in the synthesis process (such as pH, temperature, and precursor ratios) to simultaneously control the formation of birnessite-phase MnO2 and the incorporation of bismuth and lead. By adjusting these parameters, the patent achieves precise compositional control and stable rechargeability characteristics through a relatively simple manufacturing process.
3Duration of action of stationary object
If prior art methods are used to achieve high cycle life, then excessive carbon content (about 10 times more than MnO2 loading) is required, but this results in poor energy density that is economically and practically impractical
Solution Approach 1:
The patent changes the compositional parameters of the cathode material by using a balanced ratio of manganese dioxide to bismuth and lead compounds, eliminating the need for excessive carbon content. This parameter optimization achieves both high cycle life and practical energy density, making the battery economically and practically viable.
Solution Approach 2:
The patent replaces the carbon-heavy composite structure of prior art with a bismuth and lead-doped manganese dioxide composite. This new composite material provides structural stability for long cycle life without requiring excessive carbon, thereby achieving high energy density that is economically and practically practical.
4Quantity of substance
If manganese dioxide batteries are designed for high depth of discharge, then capacity utilization increases, but the crystal structure breakdown accelerates and cycle life decreases
Solution Approach 1:
The patent incorporates bismuth and lead compounds beforehand into the manganese dioxide crystal structure to cushion against the stresses of high depth of discharge. These dopants are positioned in advance to prevent lattice breakdown during aggressive charge-discharge cycling, allowing high capacity utilization without sacrificing cycle life.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The battery achieves stable discharge capacity over 3700 cycles with high coulombic efficiency and maintains energy density, overcoming previous limitations of manganese dioxide batteries by enabling full second electron capacity utilization and prolonged cycle life.
Implementation Method 1
The theoretical capacity that a manganese dioxide crystal can discharge is 617mAh/g, which is based on the incorporation of two electrons in the redox reaction
Implementation Method 2
bismuth plays a role in lattice stabilization and in avoiding the electrochemical inactive phase of hausmannite (Mn3O4) during cycling
Implementation Method 3
A secondary alkaline battery using a mixed cathode material comprising birnessite-phase manganese dioxide, a bismuth compound, and a copper compound
Data Source
Figure 1~3A
Figure 3B~4A
Figure 4B~4C
AI summary
A secondary alkaline battery using manganese dioxide is described. The battery includes a mixed cathode material with birnessite-phase manganese dioxide or electrolytic manganese dioxide (EMD), a bismuth compound and a copper compound selected from the group consisting of elemental copper and a copper salt. In some embodiments, a conductive carbon and/or a binder may also be included.