Negative Battery Plates Research Articles

Understanding Function and Performance of Carbon Additives in Lead-Acid Batteries

While the low cost and strong safety record of lead-acid batteries make them an appealing option compared to lithium-ion technologies for stationary storage, they can be rapidly degraded by the extended periods of high rate, partial state-of-charge operation required in such applications. Degradation occurs primarily through a process called hard sulfation, where large PbSO4 crystals are formed on the negative battery plates, hindering charge acceptance and reducing battery capacity. Various researchers have found that the addition of some forms of excess carbon to the negative active mass in lead-acid batteries can mitigate hard sulfation, but the mechanism through which this is accomplished is unclear. In this work, the effect of carbon composition and morphology was explored by characterizing four discrete types of carbon additives, then evaluating their effect when added to the negative electrodes within a traditional valve-regulated lead-acid battery design. The cycle life for the carbon modified cells was significantly larger than an unmodified control, with cells containing a mixture of graphitic carbon and carbon black yielding the greatest improvement. The carbons also impacted other electrochemical aspects of the battery (e.g., float current, capacity, etc.) as well as physical characteristics of the negative active mass, such as the specific surface area.

Influence of carbons on the structure of the negative active material of lead-acid batteries and on battery performance

It has been established that addition of carbon additives to the lead negative active material (NAM) of lead-acid batteries increase battery charge acceptance in hybrid electric vehicle mode of operation. The present work studies three types of activated carbons and two types of carbon blacks with the aim to evaluate their efficiency in improving the charge acceptance of lead-acid batteries. It has been established that the size of carbon particles and their affinity to lead are essential. If carbon particles are of nanosizes, they are incorporated into the bulk of the skeleton branches of NAM and may thus increase the latter's ohmic resistance. Their content in NAM should not exceed 0.2–0.5 wt.%. At this loading level, carbon grains are adsorbed only on the surface of NAM contributing to the increase of its specific surface area and thus improving its charge acceptance. When carbon particles are of micron sizes and have high affinity to lead, they are integrated into the skeleton structure of NAM as a structural component and act as super-capacitors, i.e. electric charges are concentrated in them and then the current is distributed along the adjacent branches of the lead skeleton with the lowest ohmic resistance. This eventually improves the charge acceptance of the negative battery plates.

Electrodeposited, dispersion-hardened, lightweight grids for lead–acid batteries

Abstract We report a novel processing route to produce battery grids by electrocodeposition of lead with dispersed particles. The grid thickness and design can be chosen within a wide range. This permits us to minimise grid weight and to optimise grid design for current density distribution. The process development has reached a state of maturity permitting us to produce test quantities for battery tests. The grid properties have been investigated thoroughly. Hardness can be adjusted in the range of 4–25 HV units by choice of particle size and volume fraction of dispersoid (oxides or Cu). Creep resistance is excellent. Corrosion tests indicate that grid corrosion is similar to that of Pb–Ca–Sn grids. Such grids were used to make several hundred positive and negative battery plates and eventually test cells and batteries. First test results have been very promising and have shown clearly that the new grid type allows us to make batteries of high specific energy. The process is, also, suitable for the production of lead alloy foil for alternative battery designs. The new manufacturing process can be combined with a hydrometallurgical process for the recycling of battery grids and paste such that a fully integrated processing route from the treatment of battery scrap to the production of new battery grids for batteries featuring significantly higher specific energy is now available.

Effect of hydrogen and oxygen on stability of expanders and performance of lead/acid batteries

Expanders are organic additives to the negative active mass that increase plate capacity, expecially at low temperatures. They operate under constant hydrogen and oxygen attack at strongly negative potentials as a result of which they undergo degradation. This leads to changes in plate capacity, which may limit the life of the battery. The aims of the present work are: (i) to suggest a method for determining the effect of hydrogen, oxygen and the potential on the stability of expanders; (ii) to identify some of the structural group in organic compounds that exert an efficient expander action. The influence of Velex, Mimosa, Quebraco, Syntan NK (SNK) and EZE-Skitan on the electrochemical characteristics and the life of negative battery plates has been investigated. It is established that structural groups of the pyrocatechin type (Quebraco and EZE-Skitan) have effective expander action. Quebraco increases the plate capacity during the first cycles. EZE-Skitan increases the capacity of the plates after 50 to 60 charge/discharge cycles, when disintegration of its structure, probably to pyrocatechin groups, proceeds. By applying a new method for determining the expander stability, it is found that expanders containing pyrocatechin structural groups are more easily oxidized than hydrogenated. It is concluded that the most effective expander should be a combination of several compounds with different stabilities to oxidation and reduction. Appropriate expanders should be selected for each type of battery.

The Deposition of Antimony on Negative Battery Plates

The Deposition of Antimony on Negative Battery Plates